{"language": "en", "segments": [{"text": " So I was looking for a thesis topic.", "start": 1.8800000000000008, "stop": 3.54, "id": 0}, {"text": " And that's sometimes a hard thing.", "start": 5.900000000000001, "stop": 7.68, "id": 1}, {"text": " And that's sometimes why people take so long to get their graduate school, to", "start": 7.76, "stop": 10.92, "id": 2}, {"text": " find what are you going to do?", "start": 10.92, "stop": 13.24, "id": 3}, {"text": " You only do that on thesis, and it's kind of a big deal.", "start": 13.34, "stop": 15.38, "id": 4}, {"text": " And part of the problems with finding a thesis topic is that I was being", "start": 16.38, "stop": 18.78, "id": 5}, {"text": " distracted by all sorts of things, including ham radio, which I was getting more", "start": 18.78, "stop": 23.96, "id": 6}, {"text": " and more involved in the ham radio club.", "start": 23.96, "stop": 25.72, "id": 7}, {"text": " And what they were doing was hidden transmitter hunting.", "start": 28.459999999999994, "stop": 31.02, "id": 8}, {"text": " And I was running around wasting time looking for a hidden transmitter that", "start": 31.5, "stop": 35.0, "id": 9}, {"text": " kept getting hidden in the Boston area.", "start": 35.0, "stop": 36.72, "id": 10}, {"text": " And I was also getting distracted by other fantasies.", "start": 39.26, "stop": 42.36, "id": 11}, {"text": " I was having technical fantasies to build things and do neat things.", "start": 43.26, "stop": 46.86, "id": 12}, {"text": " And I was sort of in a computer science, more oriented graduate program.", "start": 47.08, "stop": 50.52, "id": 13}, {"text": " And one of the things that always frustrated me was the fact that I had to walk", "start": 51.12, "stop": 54.18, "id": 14}, {"text": " across campus to go back to freshman year.", "start": 54.18, "stop": 57.22, "id": 15}, {"text": " I had a 300-bit per second dial-up in my room.", "start": 57.34, "stop": 59.26, "id": 16}, {"text": " I'd have to walk across campus to get the real useful connection to the computer", "start": 60.16, "stop": 64.26, "id": 17}, {"text": " in the net, which was a 9,600-bit per second 2480 VT100.", "start": 64.26, "stop": 68.34, "id": 18}, {"text": " But by the time I was in graduate school, I had the 9,600", "start": 69.0, "stop": 71.22, "id": 19}, {"text": "-bit per second modem in my room.", "start": 71.22, "stop": 72.72, "id": 20}, {"text": " But it wasn't useful because I'd walk across campus.", "start": 73.48000000000002, "stop": 76.5, "id": 21}, {"text": " And by then I had an office where I had a microvax2 running x-window system.", "start": 76.64, "stop": 80.76, "id": 22}, {"text": " And it was on the net.", "start": 80.76, "stop": 81.58, "id": 23}, {"text": " And on 10-megabit Ethernet, well hooked to the internet.", "start": 82.85999999999999, "stop": 85.52, "id": 24}, {"text": " And frustration, why can't I have the net at home?", "start": 85.88, "stop": 88.84, "id": 25}, {"text": " And so I'd always been scheming on how to do this.", "start": 89.32, "stop": 91.54, "id": 26}, {"text": " Actually, one of the buildings I lived in was the building which had the 10", "start": 91.66, "stop": 95.7, "id": 27}, {"text": "-megabit microwave for the near net, which was the Boston area internet.", "start": 95.7, "stop": 100.88, "id": 28}, {"text": " And actually, I lived on the 8th floor.", "start": 101.44, "stop": 102.94, "id": 29}, {"text": " And up on the 26th floor was all the equipment.", "start": 103.06, "stop": 105.04, "id": 30}, {"text": " And they had routers and everything.", "start": 105.04, "stop": 106.18, "id": 31}, {"text": " And there was actually fiber, only six feet from my room, where it was the trunk.", "start": 106.28, "stop": 112.44, "id": 32}, {"text": " And it's like.", "start": 112.6, "stop": 112.94, "id": 33}, {"text": " And I still had to dial in with my 8600-bit per second.", "start": 117.28, "stop": 120.06, "id": 34}, {"text": " Frustration, frustration.", "start": 120.34, "stop": 121.54, "id": 35}, {"text": " This is a frustration I had, I think, a better part of a decade.", "start": 121.72, "stop": 124.64, "id": 36}, {"text": " And so then I moved.", "start": 125.7, "stop": 126.82, "id": 37}, {"text": " And I looked.", "start": 127.02, "stop": 127.66, "id": 38}, {"text": " And the building they had my office in, I could see", "start": 127.88, "stop": 131.54, "id": 39}, {"text": " many windows in that building.", "start": 131.54, "stop": 133.08, "id": 40}, {"text": " Not my own, but I could see many windows in that building out my window.", "start": 133.08, "stop": 136.78, "id": 41}, {"text": " I don't remember the exact distance.", "start": 137.84, "stop": 139.72, "id": 42}, {"text": " There's one or two kilometers.", "start": 139.72, "stop": 140.78, "id": 43}, {"text": " I ought to be able to do something.", "start": 141.84, "stop": 142.74, "id": 44}, {"text": " And I started thinking free space optical", "start": 142.92, "stop": 144.4, "id": 45}, {"text": " links, which actually there are a few of those around.", "start": 144.4, "stop": 146.14, "id": 46}, {"text": " But of course, they were very expensive", "start": 146.26, "stop": 148.02, "id": 47}, {"text": " for a graduate student budget in those days.", "start": 148.02, "stop": 149.74, "id": 48}, {"text": " So I started having other fantasies.", "start": 149.88, "stop": 151.3, "id": 49}, {"text": " Like maybe I could build a pair of radios.", "start": 151.48, "stop": 153.04, "id": 50}, {"text": " And actually, optics has a problem that you have to get lenses.", "start": 153.5, "stop": 155.6, "id": 51}, {"text": " And you have to line it up.", "start": 155.68, "stop": 156.56, "id": 52}, {"text": " And it doesn't work when it rains.", "start": 156.58, "stop": 157.5, "id": 53}, {"text": " So I started thinking about radio.", "start": 158.24, "stop": 159.28, "id": 54}, {"text": " The problem with radio is, well, you need a license.", "start": 159.4, "stop": 161.0, "id": 55}, {"text": " Well, I already have a hand license.", "start": 161.18, "stop": 162.02, "id": 56}, {"text": " But there's this content problem that you can't just go read all your email,", "start": 162.2, "stop": 167.74, "id": 57}, {"text": " because you never know what anybody has sent you.", "start": 168.44, "stop": 169.98, "id": 58}, {"text": " So you can't take responsibility for it.", "start": 170.12, "stop": 171.96, "id": 59}, {"text": " So I thought, well, I need something.", "start": 172.16, "stop": 173.3, "id": 60}, {"text": " And besides, I sort of wanted to be able to let my friends do this.", "start": 173.44, "stop": 176.44, "id": 61}, {"text": " And most of them didn't have licenses.", "start": 176.54, "stop": 177.66, "id": 62}, {"text": " And so what I wanted was a loophole.", "start": 177.96, "stop": 180.0, "id": 63}, {"text": " So I actually went off and I sat down in the small", "start": 180.22, "stop": 187.14, "id": 64}, {"text": " law library at the business school at MIT.", "start": 187.14, "stop": 189.9, "id": 65}, {"text": " And I actually sat down and I started reading 47 CFR in general, and particularly", "start": 190.36, "stop": 196.64, "id": 66}, {"text": " 47 CFR 15, which is the place I expected I'd find a loophole.", "start": 196.64, "stop": 201.3, "id": 67}, {"text": " That's what people call 15.", "start": 201.46, "stop": 202.62, "id": 68}, {"text": " This is sort of what a lawyer's would call part 10.", "start": 202.74, "stop": 205.86, "id": 69}, {"text": " This is volume 47 of the Code of Federal Regulations, which are the regulations", "start": 206.0, "stop": 210.74, "id": 70}, {"text": " that are written by the bureaucrats, not the laws that are made", "start": 210.74, "stop": 212.92, "id": 71}, {"text": " by the legislative process.", "start": 212.92, "stop": 214.86, "id": 72}, {"text": " Anyway, this is with the part 15 unlicensed authorization that I discovered.", "start": 215.92, "stop": 220.36, "id": 73}, {"text": " And this was probably late in 91.", "start": 220.56, "stop": 222.48, "id": 74}, {"text": " I'm reading along, looking at each of the things you can do in part 15.", "start": 224.06, "stop": 226.86, "id": 75}, {"text": " And I'm like, wow, you can do a watt as long as your", "start": 226.86, "stop": 231.06, "id": 76}, {"text": " antenna gain is at most 6 dVI.", "start": 231.06, "stop": 232.94, "id": 77}, {"text": " So sort of an arp of 4 watts in three different bands, the widest of which is", "start": 233.4, "stop": 238.96, "id": 78}, {"text": " 125 megahertz wide.", "start": 238.96, "stop": 240.46, "id": 79}, {"text": " But this regulation required that you use spread spectrum with at least 10 dB", "start": 241.28000000000003, "stop": 246.3, "id": 80}, {"text": " of processing gain in the receiver.", "start": 246.3, "stop": 247.8, "id": 81}, {"text": " Most people are ignoring this requirement that you actually demonstrate the", "start": 250.10000000000002, "stop": 254.16, "id": 82}, {"text": " system of 10 dB of processing gain in the receiver these days.", "start": 254.16, "stop": 256.72, "id": 83}, {"text": " But anyway, sitting there reading the FCC regulations is", "start": 257.6, "stop": 261.4, "id": 84}, {"text": " like, what's the spread spectrum?", "start": 261.4, "stop": 263.6, "id": 85}, {"text": " And what's the processing gain?", "start": 264.32, "stop": 265.92, "id": 86}, {"text": " And I had sort of gone through the computer science curriculum, so I hadn't had", "start": 266.74, "stop": 271.68, "id": 87}, {"text": " all the modulation and that sort of theory.", "start": 271.68, "stop": 274.96, "id": 88}, {"text": " So that sent me off studying, looking in the library.", "start": 275.38, "stop": 278.96, "id": 89}, {"text": " And I started thinking, oh, yeah, that's something I could do.", "start": 280.14, "stop": 282.5, "id": 90}, {"text": " And I started having fantasies of building up, here's me.", "start": 282.5, "stop": 287.24, "id": 91}, {"text": " Here's the building I want to get to.", "start": 287.6, "stop": 288.86, "id": 92}, {"text": " I want that.", "start": 291.06, "stop": 291.96, "id": 93}, {"text": " And that'd be neat.", "start": 295.91999999999996, "stop": 297.16, "id": 94}, {"text": " And of course, any time you go to the trouble of spinning some boards and", "start": 297.42, "stop": 301.26, "id": 95}, {"text": " populating them, you don't build just two boards.", "start": 301.26, "stop": 305.86, "id": 96}, {"text": " You actually get a dozen boards made and maybe a prototype.", "start": 306.02, "stop": 310.44, "id": 97}, {"text": " And then you figure out how to really make them.", "start": 310.62, "stop": 312.28, "id": 98}, {"text": " And then you sell them to your friends.", "start": 312.28, "stop": 313.44, "id": 99}, {"text": " And I had all these friends in grad school.", "start": 314.04, "stop": 315.3, "id": 100}, {"text": " And I thought, they're all over the place.", "start": 315.48, "stop": 317.74, "id": 101}, {"text": " And they're all going to want this, too.", "start": 317.92, "stop": 319.44, "id": 102}, {"text": " They're just like me, sort of.", "start": 319.56, "stop": 321.34, "id": 103}, {"text": " And I started thinking, yeah, this would be really neat.", "start": 321.94, "stop": 325.42, "id": 104}, {"text": " But the internet wasn't just a, by this point, the internet was not just", "start": 328.94, "stop": 333.4, "id": 105}, {"text": " something that all the computer science students were addicted to.", "start": 333.4, "stop": 337.68, "id": 106}, {"text": " Even the biology graduate students were addicted to the internet.", "start": 337.9, "stop": 341.5, "id": 107}, {"text": " They couldn't go a day without reading their email.", "start": 341.5, "stop": 343.28, "id": 108}, {"text": " And they probably wanted it home, as well.", "start": 345.2, "stop": 347.76, "id": 109}, {"text": " This is sort of before the web.", "start": 347.88, "stop": 349.0, "id": 110}, {"text": " Or the web was just getting started then, anyway.", "start": 350.56, "stop": 352.48, "id": 111}, {"text": " So I realized it's not going to necessarily just be this.", "start": 353.32, "stop": 356.72, "id": 112}, {"text": " It might be other groups around the campus or around the area", "start": 358.2, "stop": 363.08, "id": 113}, {"text": " might want to do this, as well.", "start": 363.08, "stop": 364.72, "id": 114}, {"text": " And it's like, oh, that's interesting.", "start": 364.92, "stop": 366.26, "id": 115}, {"text": " Well, maybe their community looks like that.", "start": 367.62, "stop": 370.5, "id": 116}, {"text": " There's this little network of me and my friends here.", "start": 370.5, "stop": 372.54, "id": 117}, {"text": " But maybe everybody else distributed and", "start": 372.72, "stop": 374.4, "id": 118}, {"text": " tried to use the same things to get here.", "start": 374.4, "stop": 376.08, "id": 119}, {"text": " And I'm having fantasies of selling these things as kits or maybe even a product.", "start": 376.18, "stop": 381.12, "id": 120}, {"text": " Full of fantasy.", "start": 382.86, "stop": 383.34, "id": 121}, {"text": " But then I spent a lot of time just thinking about this sort of stuff.", "start": 383.56, "stop": 388.1, "id": 122}, {"text": " And I realized that it's probably not right to have a hub system, but to actually", "start": 388.22, "stop": 392.86, "id": 123}, {"text": " just view it as you've got all these stations.", "start": 392.86, "stop": 394.58, "id": 124}, {"text": " And what you really want to do is get them all connected together in a network.", "start": 395.16, "stop": 398.36, "id": 125}, {"text": " And I was also thinking at the time.", "start": 398.9, "stop": 400.54, "id": 126}, {"text": " And I realized that you need to not hop over intermediate stations", "start": 400.64, "stop": 406.14, "id": 127}, {"text": " or the system cannot scale.", "start": 406.14, "stop": 407.94, "id": 128}, {"text": " And that was sort of the beginning of me thinking about how can this scale.", "start": 408.72, "stop": 412.82, "id": 129}, {"text": " And then I actually realized that, oh, it's not just the biology graduate", "start": 412.96, "stop": 416.24, "id": 130}, {"text": " students who want to get on the internet as well.", "start": 416.24, "stop": 417.84, "id": 131}, {"text": " It's also the entire population.", "start": 418.18, "stop": 420.5, "id": 132}, {"text": " At that point, I think I sort of realized that the internet is something that", "start": 420.76, "stop": 426.66, "id": 133}, {"text": " eventually the whole population is going to be on one way or another.", "start": 426.66, "stop": 430.26, "id": 134}, {"text": " And being behind a modem is not really on the", "start": 432.1, "stop": 434.38, "id": 135}, {"text": " net, at least from my point of view.", "start": 434.38, "stop": 437.42, "id": 136}, {"text": " So I started thinking about, well, how can this scale?", "start": 437.48, "stop": 439.58, "id": 137}, {"text": " To maybe 100 stations or maybe 1,000 stations.", "start": 440.32, "stop": 443.64, "id": 138}, {"text": " And then I thought, oh, no.", "start": 444.9, "stop": 445.9, "id": 139}, {"text": " Well, if actually how many houses are there in the Metro Boston area?", "start": 446.08, "stop": 449.1, "id": 140}, {"text": " Or Metro Beijing?", "start": 450.6, "stop": 451.88, "id": 141}, {"text": " Or whatever.", "start": 453.3, "stop": 454.06, "id": 142}, {"text": " And I was thinking about, I was reading packet radio research reading propagation", "start": 454.32, "stop": 459.62, "id": 143}, {"text": " stuff in the library, trying to understand, well, what is the propagation model?", "start": 459.62, "stop": 463.58, "id": 144}, {"text": " And how can you design a packet radio stuff?", "start": 465.5, "stop": 467.36, "id": 145}, {"text": " And by this time, I'm reading some of the real packet radio research that's been", "start": 467.5, "stop": 470.36, "id": 146}, {"text": " funded by DARPA starting around 1970.", "start": 470.36, "stop": 472.18, "id": 147}, {"text": " There's about 25 years worth of literature in the library.", "start": 472.46, "stop": 474.62, "id": 148}, {"text": " You can actually spend the time to go look through it all.", "start": 475.14, "stop": 476.94, "id": 149}, {"text": " I was trying to understand it.", "start": 477.52, "stop": 479.26, "id": 150}, {"text": " A lot of the packet radio research model, their model", "start": 480.64, "stop": 483.04, "id": 151}, {"text": " is done by computer scientists.", "start": 483.04, "stop": 485.04, "id": 152}, {"text": " And their model of a radio system is a transmitter and a receiver.", "start": 485.04, "stop": 490.54, "id": 153}, {"text": " And it has some range.", "start": 490.74, "stop": 491.68, "id": 154}, {"text": " And if you're inside that range, it works.", "start": 492.1, "stop": 493.58, "id": 155}, {"text": " And if you're outside that range, it doesn't work.", "start": 493.7, "stop": 495.38, "id": 156}, {"text": " And if there's another station transmitting, well, if you're inside", "start": 496.8, "stop": 499.26, "id": 157}, {"text": " his range, then he interferes with you.", "start": 499.26, "stop": 500.82, "id": 158}, {"text": " And if you're outside his range, then he doesn't interfere with you.", "start": 500.82, "stop": 503.22, "id": 159}, {"text": " And sort of a very determined transmission radius.", "start": 503.46, "stop": 506.16, "id": 160}, {"text": " And you can actually go find papers talking about, well, what is the right", "start": 507.2, "stop": 510.54, "id": 161}, {"text": " transmission range to set your transmitter to?", "start": 510.54, "stop": 512.88, "id": 162}, {"text": " To let the packet radio scale.", "start": 513.5600000000001, "stop": 515.94, "id": 163}, {"text": " And this wasn't making too much sense to me, because I was out", "start": 517.08, "stop": 519.86, "id": 164}, {"text": " hidden transmitter hunting at the time.", "start": 519.86, "stop": 521.44, "id": 165}, {"text": " And Radio Prop Free Space is 1 over r squared.", "start": 523.0600000000001, "stop": 525.38, "id": 166}, {"text": " And if you go behind a hill, it's different stuff.", "start": 525.6, "stop": 527.86, "id": 167}, {"text": " Some of the more serious land mobile propagation stuff", "start": 529.14, "stop": 531.76, "id": 168}, {"text": " talked about 1 over r to the fourth.", "start": 531.76, "stop": 533.28, "id": 169}, {"text": " And I'm just now starting to understand where some of these numbers come from.", "start": 535.34, "stop": 539.84, "id": 170}, {"text": " But then actually, about this time, I went to Albuquerque New Mexico for some of", "start": 539.98, "stop": 546.06, "id": 171}, {"text": " my sisters-in-law's big Thanksgiving gathering.", "start": 546.06, "stop": 547.96, "id": 172}, {"text": " And I was visiting them for Thanksgiving that year.", "start": 548.2, "stop": 550.42, "id": 173}, {"text": " And I arrived in Albuquerque late at night, was shown up to an upstairs room,", "start": 550.6, "stop": 554.08, "id": 174}, {"text": " looked out the window the next morning when I woke up.", "start": 554.1, "stop": 557.08, "id": 175}, {"text": " And I believed I could see every rooftop in", "start": 557.3, "stop": 560.9, "id": 176}, {"text": " Albuquerque, New Mexico, from where I was.", "start": 560.9, "stop": 562.7, "id": 177}, {"text": " And it occurred to me that, at least in my naive understanding at the time, that", "start": 563.58, "stop": 567.94, "id": 178}, {"text": " it would probably be effectively free-space path loss between all pairs of", "start": 567.94, "stop": 572.3, "id": 179}, {"text": " rooftops in that area.", "start": 572.3, "stop": 574.06, "id": 180}, {"text": " And that that is the most challenging to scaling, is if it is free-space.", "start": 574.62, "stop": 579.46, "id": 181}, {"text": " Because free-space is 1 over r squared.", "start": 579.88, "stop": 582.06, "id": 182}, {"text": " And most of the other models indicate that you get more attenuation than that.", "start": 582.2, "stop": 585.14, "id": 183}, {"text": " And I realized that if I can figure out how to make it scale in the free-space", "start": 585.68, "stop": 591.64, "id": 184}, {"text": " case, then it can scale in any other propagation model that anybody", "start": 591.64, "stop": 594.9, "id": 185}, {"text": " thinks is reasonable.", "start": 594.9, "stop": 596.96, "id": 186}, {"text": " The free-space propagation is the hard case for scaling.", "start": 597.38, "stop": 601.48, "id": 187}, {"text": " So that's the one to solve.", "start": 601.8, "stop": 603.44, "id": 188}, {"text": " So at that point, I was off.", "start": 605.6800000000001, "stop": 607.24, "id": 189}, {"text": " And I was actually thinking, well, how about a million", "start": 607.38, "stop": 609.12, "id": 190}, {"text": " stations in a metropolitan area?", "start": 609.12, "stop": 610.64, "id": 191}, {"text": " And packet radio networks, all the stations are the same.", "start": 613.1400000000001, "stop": 618.42, "id": 192}, {"text": " It's not like a cellular system where you've got a base station in the thing.", "start": 618.5, "stop": 621.4, "id": 193}, {"text": " And actually, I don't really, I mean, I'm thinking of a fixed packet radio", "start": 621.48, "stop": 625.7, "id": 194}, {"text": " network where all the stations are fixed.", "start": 625.7, "stop": 627.28, "id": 195}, {"text": " Maybe I can figure out how to add mobility later.", "start": 628.0, "stop": 629.62, "id": 196}, {"text": " But I didn't really care about that.", "start": 629.74, "stop": 630.72, "id": 197}, {"text": " I just wanted to get the internet out to the houses.", "start": 630.8, "stop": 632.3, "id": 198}, {"text": " And so by base stations, I mean no cell sites.", "start": 633.26, "stop": 636.02, "id": 199}, {"text": " They're sort of all base stations.", "start": 637.04, "stop": 637.98, "id": 200}, {"text": " They're all peers.", "start": 638.06, "stop": 638.62, "id": 201}, {"text": " They're all the same.", "start": 638.76, "stop": 639.3, "id": 202}, {"text": " They form this mesh-not work.", "start": 639.4, "stop": 640.66, "id": 203}, {"text": " It needs to be multi-hop routing.", "start": 641.34, "stop": 642.72, "id": 204}, {"text": " I had some intuition to that at the time that I really believed in.", "start": 643.32, "stop": 646.14, "id": 205}, {"text": " And I want a single-channel system.", "start": 646.8, "stop": 648.26, "id": 206}, {"text": " These stations are just people by them.", "start": 649.7199999999999, "stop": 652.04, "id": 207}, {"text": " They put them on top of their house.", "start": 652.08, "stop": 653.38, "id": 208}, {"text": " And they don't have to point them.", "start": 654.52, "stop": 656.38, "id": 209}, {"text": " They don't have to think about whatever that should just work.", "start": 656.5, "stop": 659.66, "id": 210}, {"text": " So I was thinking on the antennas.", "start": 660.32, "stop": 661.88, "id": 211}, {"text": " And I wanted to make it scale to millions of stations in the metro area while", "start": 666.0400000000001, "stop": 672.86, "id": 212}, {"text": " maintaining reasonable per user", "start": 672.86, "stop": 674.82, "id": 213}, {"text": " performance, whatever those traffic they're doing.", "start": 674.82, "stop": 677.34, "id": 214}, {"text": " And I don't really know what the traffic load on this net's going to be.", "start": 677.44, "stop": 679.84, "id": 215}, {"text": " I don't know who's going to talk to who.", "start": 679.88, "stop": 681.12, "id": 216}, {"text": " So it needs to be sort of a general purpose net.", "start": 681.62, "stop": 683.34, "id": 217}, {"text": " Kind of like when you install an ethernet, you usually don't worry", "start": 684.64, "stop": 687.24, "id": 218}, {"text": " about what the traffic matrix is going to be.", "start": 687.24, "stop": 688.74, "id": 219}, {"text": " You just kind of string it everywhere.", "start": 688.86, "stop": 689.82, "id": 220}, {"text": " And if it gets too busy, then you start thinking about it.", "start": 690.14, "stop": 692.16, "id": 221}, {"text": " So the real concern is my original goal was just to get my one link.", "start": 694.52, "stop": 698.58, "id": 222}, {"text": " But if there were millions of these, is mine still going to work?", "start": 700.3, "stop": 702.86, "id": 223}, {"text": " Maybe actually there's some point to where it falls over as you scale it.", "start": 704.28, "stop": 707.24, "id": 224}, {"text": " And my question is, is there a way to design these", "start": 707.58, "stop": 709.88, "id": 225}, {"text": " things so that it all still works?", "start": 709.88, "stop": 711.96, "id": 226}, {"text": " It works with my two, and then it works after a million more have been sold.", "start": 712.06, "stop": 717.62, "id": 227}, {"text": " So this is all thinking.", "start": 722.1399999999999, "stop": 723.64, "id": 228}, {"text": " At some point along the way, I realized, oh, this is my thesis topic.", "start": 724.52, "stop": 728.16, "id": 229}, {"text": " So I actually wound up talking a committee into actually", "start": 728.24, "stop": 731.8, "id": 230}, {"text": " letting me do this as a thesis topic.", "start": 731.8, "stop": 733.32, "id": 231}, {"text": " What?", "start": 735.24, "stop": 735.68, "id": 232}, {"text": " The ECS department?", "start": 736.18, "stop": 736.72, "id": 233}, {"text": " Well, it's an ECS department.", "start": 737.1, "stop": 739.58, "id": 234}, {"text": " [...] and actually, if you think about who is computer science faculty,", "start": 739.58, "stop": 745.82, "id": 235}, {"text": " well, they were double the graduate students because there was no computer", "start": 746.46, "stop": 749.58, "id": 236}, {"text": " science when they went through grad school.", "start": 749.58, "stop": 751.72, "id": 237}, {"text": " They kind of remember this stuff.", "start": 752.08, "stop": 753.18, "id": 238}, {"text": " I taught my particular supervisor didn't know much about", "start": 753.54, "stop": 755.82, "id": 239}, {"text": " radio except the courses he'd taken.", "start": 755.82, "stop": 757.36, "id": 240}, {"text": " And I wound up teaching him a lot, which is kind of neat about radios.", "start": 758.14, "stop": 762.1, "id": 241}, {"text": " He knows a lot about systems.", "start": 762.5, "stop": 763.66, "id": 242}, {"text": " Anyway, so I think there are two important things that come out of the thesis.", "start": 764.02, "stop": 769.56, "id": 243}, {"text": " And this is the most important thing.", "start": 769.74, "stop": 773.38, "id": 244}, {"text": " And actually, I'm going to be talking about this pretty soon here.", "start": 773.72, "stop": 775.82, "id": 245}, {"text": " And then I've got a way of scheduling the packets so that you can", "start": 777.4, "stop": 784.34, "id": 246}, {"text": " send the packet to your nearby neighbor without having", "start": 784.34, "stop": 787.8, "id": 247}, {"text": " to worry about whether or not it got there.", "start": 787.8, "stop": 789.42, "id": 248}, {"text": " So it'd be nice if you're going across a thousand station network per hop", "start": 789.96, "stop": 793.7, "id": 249}, {"text": " acknowledgment is going to be a lot of stuff.", "start": 793.7, "stop": 795.52, "id": 250}, {"text": " It'd be nice if you could just use end-to-end", "start": 795.9799999999999, "stop": 797.9, "id": 251}, {"text": " acknowledgments across the whole network.", "start": 797.9, "stop": 799.52, "id": 252}, {"text": " Can you say those words I keep?", "start": 799.54, "stop": 800.88, "id": 253}, {"text": " Oh, this says understanding of noise growth of a large system and decentralized", "start": 802.9, "stop": 808.98, "id": 254}, {"text": " collision-free channel access method.", "start": 808.98, "stop": 810.66, "id": 255}, {"text": " So this understanding of the noise growth of a large", "start": 813.94, "stop": 815.94, "id": 256}, {"text": " system that I think is the most important thing.", "start": 815.94, "stop": 817.64, "id": 257}, {"text": " I've come up with a particular way of doing the decentralized collision", "start": 818.02, "stop": 821.06, "id": 258}, {"text": "-free channel access.", "start": 821.06, "stop": 822.82, "id": 259}, {"text": " And that MIT filed for a patent on.", "start": 822.82, "stop": 826.66, "id": 260}, {"text": " And I have not yet figured out how to invent around it.", "start": 828.04, "stop": 830.26, "id": 261}, {"text": " But actually, I think math paper yesterday suggests to me", "start": 830.34, "stop": 834.56, "id": 262}, {"text": " that actually there may be a way.", "start": 834.56, "stop": 836.12, "id": 263}, {"text": " Anyway, onward forward.", "start": 839.1999999999999, "stop": 840.46, "id": 264}, {"text": " OK, now how to understand.", "start": 840.92, "stop": 842.16, "id": 265}, {"text": " Oh, question.", "start": 842.78, "stop": 843.3, "id": 266}, {"text": " You mentioned that.", "start": 843.54, "stop": 844.08, "id": 267}, {"text": " Did you indicate to MIT that the graduate student at MIT shared the patents?", "start": 844.24, "stop": 847.28, "id": 268}, {"text": " MIT owns the rights to the patents and all", "start": 848.24, "stop": 851.08, "id": 269}, {"text": " decisions about licensing and everything.", "start": 851.08, "stop": 852.6, "id": 270}, {"text": " And so some sense I have no control that if they ever actually do manage to make", "start": 852.9, "stop": 857.14, "id": 271}, {"text": " money off of it, which is not likely in general.", "start": 857.14, "stop": 860.8, "id": 272}, {"text": " Only one in 10 patents ever gets a license.", "start": 861.3, "stop": 863.9, "id": 273}, {"text": " They chose to go ahead and do it because they thought it was", "start": 866.54, "stop": 869.58, "id": 274}, {"text": " worth the gamble given what it was.", "start": 869.58, "stop": 871.1, "id": 275}, {"text": " But I think I get some 10% or 15% of whatever license fees they bring in.", "start": 871.26, "stop": 876.14, "id": 276}, {"text": " I'm not ever expecting that to produce any money.", "start": 878.2799999999999, "stop": 881.44, "id": 277}, {"text": " Patents aren't really about producing money.", "start": 882.96, "stop": 884.46, "id": 278}, {"text": " They're this legal game that companies play chicken game.", "start": 884.88, "stop": 889.36, "id": 279}, {"text": " Companies play chicken with each other about perhaps going into", "start": 889.56, "stop": 893.22, "id": 280}, {"text": " court and whatever.", "start": 893.22, "stop": 894.84, "id": 281}, {"text": " But it was kind of neat.", "start": 895.02, "stop": 896.14, "id": 282}, {"text": " I got to see what it's like to apply for a patent.", "start": 897.46, "stop": 900.24, "id": 283}, {"text": " I mean, they hired a patent attorney and stuff.", "start": 900.44, "stop": 901.76, "id": 284}, {"text": " I didn't really want to- [...] a name.", "start": 902.18, "stop": 904.16, "id": 285}, {"text": " Yeah.", "start": 904.82, "stop": 905.18, "id": 286}, {"text": " Yeah, it was written by the lawyer.", "start": 906.28, "stop": 907.54, "id": 287}, {"text": " The lawyer read my thesis and understood it.", "start": 907.86, "stop": 909.76, "id": 288}, {"text": " I was very impressed.", "start": 909.92, "stop": 910.64, "id": 289}, {"text": " He had been a double e undergrad before he went to law school.", "start": 911.88, "stop": 914.2, "id": 290}, {"text": " So OK.", "start": 918.66, "stop": 919.38, "id": 291}, {"text": " My first concern is what happens as the thing", "start": 920.3, "stop": 927.04, "id": 292}, {"text": " scales to the radio channel if these are all one single channel system.", "start": 927.04, "stop": 930.36, "id": 293}, {"text": " I'm here.", "start": 934.1, "stop": 934.94, "id": 294}, {"text": " I've got a nearby neighbor that's trying to send me something.", "start": 935.18, "stop": 937.3, "id": 295}, {"text": " There's some signal there.", "start": 937.7, "stop": 938.62, "id": 296}, {"text": " And there's a whole bunch of other stations out there using the same channel.", "start": 939.72, "stop": 943.52, "id": 297}, {"text": " Does it work?", "start": 945.12, "stop": 945.78, "id": 298}, {"text": " And actually, I was trying to place", "start": 949.7, "stop": 956.6, "id": 299}, {"text": " this in the context of the packet radio literature.", "start": 956.6, "stop": 959.06, "id": 300}, {"text": " If I'm talking to a computer scientist who's read some of this packet radio", "start": 959.22, "stop": 964.14, "id": 301}, {"text": " literature and it's published, I need to explain what I'm doing that's different.", "start": 964.14, "stop": 970.4, "id": 302}, {"text": " And in those systems, the signal is something that's either there or not.", "start": 970.76, "stop": 973.72, "id": 303}, {"text": " And transmitters have a range.", "start": 974.52, "stop": 975.74, "id": 304}, {"text": " And they design on this transmission radius thing.", "start": 976.42, "stop": 979.04, "id": 305}, {"text": " So just in general, you can look at any of these models", "start": 979.46, "stop": 983.38, "id": 306}, {"text": " for what a packet radio network is like.", "start": 983.38, "stop": 985.2, "id": 307}, {"text": " They've got some idea of what is a signal and what is propagation and what", "start": 985.7, "stop": 990.82, "id": 308}, {"text": " criteria are there on successfully capturing a packet that's been sent to you.", "start": 990.82, "stop": 996.14, "id": 309}, {"text": " And other systems have other answers to those three questions.", "start": 996.92, "stop": 1000.06, "id": 310}, {"text": " But in my case, the signal at the receiver has a power level, which", "start": 1000.42, "stop": 1005.72, "id": 311}, {"text": " is a function of a whole bunch of stuff.", "start": 1005.72, "stop": 1007.38, "id": 312}, {"text": " It's a continuum.", "start": 1007.52, "stop": 1008.6, "id": 313}, {"text": " And radio signals propagate to the end of the universe with some free space path", "start": 1009.36, "stop": 1014.82, "id": 314}, {"text": " loss or perhaps the attenuating media in between or whatever.", "start": 1014.82, "stop": 1018.12, "id": 315}, {"text": " And by propagation, there's an attenuation.", "start": 1019.06, "stop": 1021.32, "id": 316}, {"text": " It's the model I use in all the work I did.", "start": 1022.56, "stop": 1025.94, "id": 317}, {"text": " Actually, in general, if you have two antennas in the world and you assume that", "start": 1026.88, "stop": 1033.12, "id": 318}, {"text": " the world between the antennas is linear and time invariant, then", "start": 1033.12, "stop": 1039.82, "id": 319}, {"text": " with those two assumptions, then the most general model of what's between", "start": 1040.8, "stop": 1045.04, "id": 320}, {"text": " the antennas is an impulse response.", "start": 1045.04, "stop": 1046.68, "id": 321}, {"text": " That captures all of the multipath between those antennas.", "start": 1047.54, "stop": 1050.58, "id": 322}, {"text": " And then you could do the Fourier transform of that and understand what", "start": 1051.52, "stop": 1054.72, "id": 323}, {"text": " is the filter between the two antennas.", "start": 1054.72, "stop": 1056.82, "id": 324}, {"text": " And it's one with a lot of attenuation and everything.", "start": 1057.0, "stop": 1059.54, "id": 325}, {"text": " And what I did is I dropped the impulse response and said, well, I'm going to", "start": 1060.64, "stop": 1064.02, "id": 326}, {"text": " ignore the multipath for now because in a multipath, you can design", "start": 1064.02, "stop": 1068.2, "id": 327}, {"text": " modulation schemes around that.", "start": 1068.2, "stop": 1069.74, "id": 328}, {"text": " And any problem that the multipath gives you is probably just going to be you can", "start": 1072.9, "stop": 1077.56, "id": 329}, {"text": " design around it.", "start": 1077.56, "stop": 1079.34, "id": 330}, {"text": " I wanted to wave my hands here and get beyond that.", "start": 1079.36, "stop": 1081.2, "id": 331}, {"text": " But you can design around that.", "start": 1081.32, "stop": 1083.2, "id": 332}, {"text": " And it affects you by some small factor in how many bits you can get through.", "start": 1083.22, "stop": 1086.54, "id": 333}, {"text": " So for the purposes of understanding noise growth system, between every", "start": 1088.1999999999998, "stop": 1093.52, "id": 334}, {"text": " pair of stations, there's some attenuation.", "start": 1093.52, "stop": 1095.16, "id": 335}, {"text": " It's the path loss between those two things.", "start": 1095.42, "stop": 1098.02, "id": 336}, {"text": " And it's actually I think of this as a path gain,", "start": 1098.02, "stop": 1104.88, "id": 337}, {"text": " which is 1 over the path loss.", "start": 1105.98, "stop": 1107.68, "id": 338}, {"text": " So it's a small number.", "start": 1109.0, "stop": 1110.18, "id": 339}, {"text": " So you take the power at the station you're transmitting ascending.", "start": 1110.34, "stop": 1114.96, "id": 340}, {"text": " And this term here is this is the power at station k.", "start": 1116.24, "stop": 1122.76, "id": 341}, {"text": " And this term here is the attenuation between the two stations.", "start": 1123.24, "stop": 1127.8, "id": 342}, {"text": " It's probably symmetric.", "start": 1128.34, "stop": 1129.66, "id": 343}, {"text": " And so you multiply that times the power they're sending.", "start": 1131.18, "stop": 1133.54, "id": 344}, {"text": " And that tells you how much signal you're getting from that station.", "start": 1133.66, "stop": 1136.46, "id": 345}, {"text": " And then for all the other stations, in fact, this term here is to sum up the", "start": 1136.98, "stop": 1141.4, "id": 346}, {"text": " power that everybody else is transmitting times how much", "start": 1141.4, "stop": 1147.24, "id": 347}, {"text": " attenuation you're getting from them.", "start": 1147.24, "stop": 1149.18, "id": 348}, {"text": " And if I just did this over this, it would be signal to signal plus noise", "start": 1149.84, "stop": 1154.24, "id": 349}, {"text": " ratio in power.", "start": 1154.24, "stop": 1155.82, "id": 350}, {"text": " And if I subtract out this term, then I get signal to noise.", "start": 1157.4599999999998, "stop": 1161.8, "id": 351}, {"text": " Because this is the signal.", "start": 1162.24, "stop": 1163.36, "id": 352}, {"text": " This term includes the signal and the noise.", "start": 1163.6, "stop": 1166.0, "id": 353}, {"text": " And I'm treating all of the other, what's coming", "start": 1166.46, "stop": 1168.24, "id": 354}, {"text": " from all the other stations, as noise.", "start": 1168.24, "stop": 1169.88, "id": 355}, {"text": " I'm lumping that in.", "start": 1170.5, "stop": 1171.26, "id": 356}, {"text": " Sometimes people say signal to noise plus interference.", "start": 1171.38, "stop": 1174.38, "id": 357}, {"text": " And they actually put an explicit i over there.", "start": 1174.6, "stop": 1176.22, "id": 358}, {"text": " I'm lumping all of the interference into noise.", "start": 1176.28, "stop": 1178.34, "id": 359}, {"text": " Because this is sort of going to be spread spectrum like.", "start": 1179.7, "stop": 1182.06, "id": 360}, {"text": " And maybe everybody's using random codes.", "start": 1182.06, "stop": 1183.96, "id": 361}, {"text": " So by propagation, what you can understand that", "start": 1186.58, "stop": 1190.64, "id": 362}, {"text": " there's propagation from every station.", "start": 1190.64, "stop": 1192.86, "id": 363}, {"text": " And what you care about in order to understand whether you've gotten a successful", "start": 1193.0, "stop": 1196.32, "id": 364}, {"text": " reception is whether the signal to noise ratio is sufficient.", "start": 1196.32, "stop": 1199.62, "id": 365}, {"text": " And sort of my criteria for successful reception, what I've done is I've taken", "start": 1200.3, "stop": 1204.6, "id": 366}, {"text": " Shannon's capacity theorem and solved it for signal to noise ratio.", "start": 1204.6, "stop": 1209.24, "id": 367}, {"text": " Remember your algebra, you can do that.", "start": 1210.3799999999999, "stop": 1212.22, "id": 368}, {"text": " And I've thrown in, and I chose a log base 2 so", "start": 1212.62, "stop": 1216.22, "id": 369}, {"text": " that I'm measuring information in bits.", "start": 1216.22, "stop": 1217.74, "id": 370}, {"text": " And then say you have the bit rate you want to communicate at and the bandwidth.", "start": 1218.76, "stop": 1222.42, "id": 371}, {"text": " And here it's 2 to that power.", "start": 1222.58, "stop": 1224.84, "id": 372}, {"text": " Subtract 1.", "start": 1225.46, "stop": 1226.08, "id": 373}, {"text": " And then it's got a fudge factor here, which is all of that.", "start": 1226.44, "stop": 1230.56, "id": 374}, {"text": " This is my abstraction of a radio engineer, a good communication engineer.", "start": 1231.02, "stop": 1235.54, "id": 375}, {"text": " You need the fudge factor.", "start": 1236.32, "stop": 1237.26, "id": 376}, {"text": " And probably needs a fudge factor of somewhere between 3 and 10.", "start": 1237.26, "stop": 1241.18, "id": 377}, {"text": " Or maybe with fancy turbo code, the only needs a", "start": 1241.56, "stop": 1243.76, "id": 378}, {"text": " fudge factor of 1.5 or something.", "start": 1243.76, "stop": 1245.34, "id": 379}, {"text": " And actually, I'm waving my hands a little bit here because when you're sending", "start": 1246.04, "stop": 1249.84, "id": 380}, {"text": " packets, you have to synchronize.", "start": 1249.84, "stop": 1252.0, "id": 381}, {"text": " And so how do you build a burst modem that actually approaches the Shannon limit?", "start": 1252.46, "stop": 1255.06, "id": 382}, {"text": " Well, that's tough.", "start": 1255.18, "stop": 1255.82, "id": 383}, {"text": " My answer to that is, well, actually, it doesn't have to just be a burst modem", "start": 1257.92, "stop": 1260.62, "id": 384}, {"text": " because if you've been swapping packets with this other station multiple times", "start": 1260.62, "stop": 1266.32, "id": 385}, {"text": " per second, then perhaps you can maintain some timing information and not", "start": 1266.32, "stop": 1271.1, "id": 386}, {"text": " actually have to start from scratch on every", "start": 1271.1, "stop": 1273.2, "id": 387}, {"text": " packet to get everything synchronized up.", "start": 1273.2, "stop": 1274.88, "id": 388}, {"text": " So actually, I think some of the commercial Part 15 radios that give you point-to", "start": 1276.56, "stop": 1280.42, "id": 389}, {"text": "-point data links, the radios go like this.", "start": 1280.42, "stop": 1282.76, "id": 390}, {"text": " And they actually maintain spreading code synchronization across the, yeah,", "start": 1283.18, "stop": 1289.72, "id": 391}, {"text": " so they don't have to actually go hunt.", "start": 1290.1, "stop": 1291.7, "id": 392}, {"text": " And so they're not really trying to build burst modems.", "start": 1291.7, "stop": 1294.6, "id": 393}, {"text": " But anyway, so this is my criteria for successful reception.", "start": 1295.38, "stop": 1298.28, "id": 394}, {"text": " Now, what about scaling?", "start": 1302.3600000000001, "stop": 1304.08, "id": 395}, {"text": " The concern is here that my neighbor is here near me.", "start": 1306.02, "stop": 1310.52, "id": 396}, {"text": " And I want to hear him.", "start": 1311.44, "stop": 1313.14, "id": 397}, {"text": " And I want to decode his packet.", "start": 1313.3, "stop": 1314.68, "id": 398}, {"text": " And whether or not I'm going to be able to do that depends on how", "start": 1315.54, "stop": 1318.56, "id": 399}, {"text": " much other stuff is out there.", "start": 1318.56, "stop": 1320.16, "id": 400}, {"text": " And that depends on how far we've scaled.", "start": 1321.74, "stop": 1324.7, "id": 401}, {"text": " And the most general thing to do is, well, what if... there's an", "start": 1325.48, "stop": 1331.4, "id": 402}, {"text": " unlimited number of stations out there.", "start": 1331.4, "stop": 1333.22, "id": 403}, {"text": " And I started thinking about that.", "start": 1333.92, "stop": 1336.04, "id": 404}, {"text": " And I started thinking about that problem.", "start": 1336.52, "stop": 1338.82, "id": 405}, {"text": " I had some friends who were like physicists and astronomers.", "start": 1338.96, "stop": 1341.3, "id": 406}, {"text": " And I went rambling to them, and they said, oh, that's just like Olver's Paradox.", "start": 1342.2, "stop": 1346.18, "id": 407}, {"text": " And Olver's Paradox is something in astronomy.", "start": 1346.94, "stop": 1350.24, "id": 408}, {"text": " Here's a question.", "start": 1352.3, "stop": 1352.84, "id": 409}, {"text": " How bright is the sky at night?", "start": 1353.1, "stop": 1354.22, "id": 410}, {"text": " Well, we can figure this out.", "start": 1354.6, "stop": 1356.0, "id": 411}, {"text": " We live in an infinitely old universe, perhaps.", "start": 1357.04, "stop": 1360.8, "id": 412}, {"text": " And the universe is infinite in extent.", "start": 1361.76, "stop": 1363.48, "id": 413}, {"text": " And there's a uniform finite density of galaxies throughout the", "start": 1364.38, "stop": 1368.32, "id": 414}, {"text": " universe, this density rho.", "start": 1368.32, "stop": 1370.08, "id": 415}, {"text": " And each galaxy radiates at some average power level.", "start": 1370.94, "stop": 1374.36, "id": 416}, {"text": " I'm kind of waving your hand about how evenly distributed", "start": 1375.46, "stop": 1378.3, "id": 417}, {"text": " there are, but we really don't care about that.", "start": 1378.3, "stop": 1379.92, "id": 418}, {"text": " And then you assume that, oh, and you look up at the sky at", "start": 1380.44, "stop": 1382.58, "id": 419}, {"text": " night, and it's electromagnetic radiation.", "start": 1382.58, "stop": 1384.36, "id": 420}, {"text": " It's all free space, path lost to the eye.", "start": 1384.54, "stop": 1386.26, "id": 421}, {"text": " And then you do the integral out to an infinite bound.", "start": 1386.7, "stop": 1389.92, "id": 422}, {"text": " Actually, I've screwed up in the interval a little bit here.", "start": 1391.0400000000002, "stop": 1393.58, "id": 423}, {"text": " And I was still thinking 2D when I made this slide.", "start": 1393.98, "stop": 1397.04, "id": 424}, {"text": " And I don't have the constants right, but I've got all the important terms.", "start": 1397.52, "stop": 1399.86, "id": 425}, {"text": " There's 1 over r squared in here.", "start": 1399.96, "stop": 1401.38, "id": 426}, {"text": " And as you're integrating from here out to infinity distance, you pick up a r", "start": 1402.08, "stop": 1408.36, "id": 427}, {"text": " squared dr thing.", "start": 1408.36, "stop": 1410.94, "id": 428}, {"text": " And you do the integral to ask, and the result of the integral is going to tell", "start": 1411.48, "stop": 1414.72, "id": 429}, {"text": " you how much power is impinging on your eye.", "start": 1414.72, "stop": 1416.68, "id": 430}, {"text": " And the integral diverges.", "start": 1417.02, "stop": 1418.2, "id": 431}, {"text": " So it should be an unbounded infinite amount of power", "start": 1419.5, "stop": 1422.36, "id": 432}, {"text": " on your eye when you look up at the sky at night.", "start": 1422.84, "stop": 1424.48, "id": 433}, {"text": " Well, you're not actually looking at the whole sky.", "start": 1424.6, "stop": 1425.94, "id": 434}, {"text": " You're only looking at a piece of it.", "start": 1425.96, "stop": 1427.02, "id": 435}, {"text": " But a piece of infinity is still infinity.", "start": 1427.02, "stop": 1428.46, "id": 436}, {"text": " And there's something wrong here.", "start": 1430.86, "stop": 1432.68, "id": 437}, {"text": " And there's probably something wrong with one of these", "start": 1433.14, "stop": 1435.96, "id": 438}, {"text": " assumptions, or more than one.", "start": 1435.96, "stop": 1438.32, "id": 439}, {"text": " And some astronomers, their standard model for the universe", "start": 1439.0, "stop": 1441.7, "id": 440}, {"text": " is that it's actually not infinitely old.", "start": 1441.7, "stop": 1443.36, "id": 441}, {"text": " And light travels at a finite speed.", "start": 1443.48, "stop": 1445.14, "id": 442}, {"text": " So the universe that we can see is finite in extent.", "start": 1445.8, "stop": 1449.04, "id": 443}, {"text": " And that's why the sky is dark at night, maybe.", "start": 1450.54, "stop": 1452.94, "id": 444}, {"text": " They're just theories, mysteries of the universe.", "start": 1453.42, "stop": 1456.98, "id": 445}, {"text": " But anyway, but for packet radio networks, we live on an infinite flat Earth.", "start": 1456.98, "stop": 1463.5, "id": 446}, {"text": " And if we have a uniform finite density of transmitters throughout, and each", "start": 1464.08, "stop": 1467.72, "id": 447}, {"text": " transmitter radiates at a given average power, alpha is measured.", "start": 1467.72, "stop": 1473.54, "id": 448}, {"text": " And I'm just sort of in order to make, what I've actually got on the integral", "start": 1473.96, "stop": 1477.5, "id": 449}, {"text": " here is I've got power as observed by a receiver at a distance.", "start": 1477.5, "stop": 1481.44, "id": 450}, {"text": " That's the power coming out of a thing.", "start": 1481.66, "stop": 1483.48, "id": 451}, {"text": " And you do that integral.", "start": 1483.58, "stop": 1484.46, "id": 452}, {"text": " And because two-dimensional space is smaller than three-dimensional", "start": 1485.0, "stop": 1487.6, "id": 453}, {"text": " space, the noise shouldn't grow as rapidly.", "start": 1487.6, "stop": 1490.0, "id": 454}, {"text": " And hopefully, this integral will not diverge.", "start": 1490.28, "stop": 1492.34, "id": 455}, {"text": " Unfortunately, it diverges as well.", "start": 1494.08, "stop": 1495.92, "id": 456}, {"text": " You get the integral of 1 over r squared r dr, which", "start": 1496.0, "stop": 1498.94, "id": 457}, {"text": " turns into an integral of 1 over r dr.", "start": 1498.94, "stop": 1500.44, "id": 458}, {"text": " And that's log of r.", "start": 1501.56, "stop": 1502.94, "id": 459}, {"text": " And you evaluate the indefinite integral of log r.", "start": 1503.24, "stop": 1507.22, "id": 460}, {"text": " And then you plug in the infinite bound.", "start": 1507.56, "stop": 1509.42, "id": 461}, {"text": " And log of infinity is still infinity.", "start": 1509.6, "stop": 1511.08, "id": 462}, {"text": " What?", "start": 1512.32, "stop": 1512.48, "id": 463}, {"text": " Yeah.", "start": 1514.98, "stop": 1515.58, "id": 464}, {"text": " So the initial integral diverges as well.", "start": 1517.2800000000002, "stop": 1519.78, "id": 465}, {"text": " This had me depressed for a couple months.", "start": 1519.88, "stop": 1522.22, "id": 466}, {"text": " At this point, I had decided to do this as a thesis project.", "start": 1524.6000000000001, "stop": 1527.98, "id": 467}, {"text": " And I was convinced that it all was lost, because packet radio networks cannot", "start": 1528.18, "stop": 1532.1, "id": 468}, {"text": " scale arbitrarily by this result.", "start": 1532.1, "stop": 1536.94, "id": 469}, {"text": " But then I learned something.", "start": 1540.34, "stop": 1541.64, "id": 470}, {"text": " We do not live on an infinite flat Earth.", "start": 1542.86, "stop": 1544.92, "id": 471}, {"text": " But does that really change anything?", "start": 1546.18, "stop": 1547.84, "id": 472}, {"text": " We have a finite horizon.", "start": 1549.9, "stop": 1551.24, "id": 473}, {"text": " Very good.", "start": 1552.14, "stop": 1552.52, "id": 474}, {"text": " So I'm going to do this calculation again.", "start": 1552.7, "stop": 1555.64, "id": 475}, {"text": " But I'm going to twist different knobs this time.", "start": 1556.9199999999998, "stop": 1560.74, "id": 476}, {"text": " I'm going to say that there's a sixth radius.", "start": 1561.04, "stop": 1563.02, "id": 477}, {"text": " This is where my receiver is.", "start": 1563.34, "stop": 1564.68, "id": 478}, {"text": " There's some sort of unit circle distance.", "start": 1564.78, "stop": 1566.5, "id": 479}, {"text": " And that's where the guy, that's the distance to the guy I'm trying to listen to.", "start": 1566.68, "stop": 1570.34, "id": 480}, {"text": " He's sort of out here at one unit distance or something.", "start": 1570.34, "stop": 1573.98, "id": 481}, {"text": " I'm going to get to that in just a moment in more detail.", "start": 1574.1, "stop": 1576.74, "id": 482}, {"text": " But at this radius, beyond this radius, they've dropped over the horizon.", "start": 1577.42, "stop": 1582.56, "id": 483}, {"text": " And I don't hear them at all.", "start": 1582.76, "stop": 1583.66, "id": 484}, {"text": " Or there's enough attenuation that I can neglect it.", "start": 1583.7, "stop": 1585.78, "id": 485}, {"text": " So that's fixed.", "start": 1587.68, "stop": 1588.66, "id": 486}, {"text": " And what I'm going to do is I've got this m is the number of stations.", "start": 1589.42, "stop": 1593.42, "id": 487}, {"text": " I didn't use the letter n, because that's signal to noise and signal to noise.", "start": 1593.54, "stop": 1596.38, "id": 488}, {"text": " This radius is fixed.", "start": 1598.58, "stop": 1599.84, "id": 489}, {"text": " And m is my knob.", "start": 1600.06, "stop": 1600.88, "id": 490}, {"text": " I'm going to turn it up.", "start": 1600.96, "stop": 1601.7, "id": 491}, {"text": " I'm going to start out with my two stations.", "start": 1601.78, "stop": 1603.3, "id": 492}, {"text": " And I'm going to think about 10 stations, 100", "start": 1603.48, "stop": 1605.66, "id": 493}, {"text": " stations, 1,000 stations, and go on.", "start": 1605.66, "stop": 1607.68, "id": 494}, {"text": " Now, if we assume this many stations are sort of uniformly distributed through", "start": 1609.0399999999997, "stop": 1613.38, "id": 495}, {"text": " the circle, then you take the number of", "start": 1613.38, "stop": 1617.52, "id": 496}, {"text": " stations divided by the area of the circle.", "start": 1617.52, "stop": 1619.32, "id": 497}, {"text": " And that sort of gives you the density, number of stations per unit area.", "start": 1619.42, "stop": 1623.58, "id": 498}, {"text": " Now, this r sub 0, this is kind of a trick.", "start": 1624.6799999999998, "stop": 1629.72, "id": 499}, {"text": " What I've done here is I said, well, how far away is that nearby neighbor?", "start": 1631.12, "stop": 1634.5, "id": 500}, {"text": " Well, that kind of depends on how many stations there are.", "start": 1635.06, "stop": 1638.48, "id": 501}, {"text": " And I'm thinking stations that are just randomly placed, or everybody puts them", "start": 1639.64, "stop": 1643.9, "id": 502}, {"text": " on their houses, and they are over their houses.", "start": 1643.9, "stop": 1645.82, "id": 503}, {"text": " But I need some measure of how far away that nearby neighbor is.", "start": 1645.94, "stop": 1649.0, "id": 504}, {"text": " So if you take density, which is number per unit area, which is numbers per meter", "start": 1649.66, "stop": 1654.48, "id": 505}, {"text": " squared or something, if you invert that and take a square root,", "start": 1654.48, "stop": 1658.1, "id": 506}, {"text": " you get something that has units of length.", "start": 1658.18, "stop": 1659.74, "id": 507}, {"text": " And I think of that as the character.", "start": 1661.08, "stop": 1662.3, "id": 508}, {"text": " Given a density of stations, that's kind of a characteristic length.", "start": 1662.56, "stop": 1665.9, "id": 509}, {"text": " And if you like to think about probability problems, and you take a circle of", "start": 1666.84, "stop": 1672.68, "id": 510}, {"text": " this radius, if you have stations randomly distributed at this density, and you", "start": 1672.68, "stop": 1677.08, "id": 511}, {"text": " think about a circle of this radius r sub 0, which is the", "start": 1677.08, "stop": 1682.52, "id": 512}, {"text": " density raised to the minus 1 half power.", "start": 1682.52, "stop": 1685.1, "id": 513}, {"text": " You invert it.", "start": 1685.24, "stop": 1686.4, "id": 514}, {"text": " That's 1 over the density square root.", "start": 1686.64, "stop": 1688.5, "id": 515}, {"text": " That's 1 over the square root of the density.", "start": 1688.86, "stop": 1690.38, "id": 516}, {"text": " If you take a circle of that radius in an area that you've got randomly stations,", "start": 1691.68, "stop": 1695.74, "id": 517}, {"text": " then ask, what is the expected number of stations", "start": 1695.96, "stop": 1697.94, "id": 518}, {"text": " that I'm going to find inside this circle?", "start": 1697.94, "stop": 1699.64, "id": 519}, {"text": " That's pi stations.", "start": 1699.98, "stop": 1701.0, "id": 520}, {"text": " And if you double that radius, you'd expect to find 4 pi stations, about a dozen", "start": 1701.98, "stop": 1707.44, "id": 521}, {"text": " in a circle.", "start": 1707.44, "stop": 1709.4, "id": 522}, {"text": " So I'm going to use this distance here to represent how far is it to a nearby", "start": 1709.8799999999999, "stop": 1714.84, "id": 523}, {"text": " neighbor for the purposes of this calculation.", "start": 1714.84, "stop": 1717.22, "id": 524}, {"text": " And then there's another factor to throw in here, which is the duty cycle.", "start": 1717.94, "stop": 1722.34, "id": 525}, {"text": " Not all the stations are going to be transmitting at once.", "start": 1722.94, "stop": 1725.44, "id": 526}, {"text": " Maybe only half, or a third, or 10%.", "start": 1725.58, "stop": 1727.84, "id": 527}, {"text": " So there's going to be some duty cycle.", "start": 1728.6, "stop": 1730.14, "id": 528}, {"text": " So I'm going to carry this duty cycle through all the analysis as well.", "start": 1730.24, "stop": 1733.96, "id": 529}, {"text": " So how much signal is there?", "start": 1734.82, "stop": 1736.88, "id": 530}, {"text": " Well, that depends on the transmitter power and", "start": 1737.34, "stop": 1743.08, "id": 531}, {"text": " all sorts of constants and stuff.", "start": 1743.08, "stop": 1744.9, "id": 532}, {"text": " You can go read about your antenna and feed line books.", "start": 1745.04, "stop": 1747.42, "id": 533}, {"text": " And you've got a feed line attenuation and", "start": 1747.84, "stop": 1750.44, "id": 534}, {"text": " perhaps the antenna gain and everything.", "start": 1750.44, "stop": 1752.18, "id": 535}, {"text": " But I'm assuming all the stations are using the same thing.", "start": 1752.32, "stop": 1754.58, "id": 536}, {"text": " And so all of the sources of the interference are the same.", "start": 1754.68, "stop": 1756.82, "id": 537}, {"text": " So I'm going to use this constant alpha to collect all that detail.", "start": 1758.26, "stop": 1765.04, "id": 538}, {"text": " And what's important is that the signal goes as 1 over the distance r squared.", "start": 1765.52, "stop": 1770.98, "id": 539}, {"text": " I've got the lambda squared term in here, but it's all in one band.", "start": 1771.52, "stop": 1774.52, "id": 540}, {"text": " What's important is that this alpha comes in again.", "start": 1775.14, "stop": 1777.32, "id": 541}, {"text": " I'm neglecting all the thermal noise.", "start": 1777.6, "stop": 1779.42, "id": 542}, {"text": " I'm assuming this is a self-interference limited system.", "start": 1779.52, "stop": 1781.72, "id": 543}, {"text": " So all the interference comes from similar stations.", "start": 1783.4, "stop": 1786.12, "id": 544}, {"text": " So I'm going to have the same alpha down here.", "start": 1786.24, "stop": 1787.64, "id": 545}, {"text": " Anyway, you take alpha and 1 over r squared.", "start": 1788.1, "stop": 1791.38, "id": 546}, {"text": " Now, if you square this r sub 0, which is 1 over the square root of the density,", "start": 1791.68, "stop": 1797.96, "id": 547}, {"text": " when you square that, you get this alpha times the density", "start": 1798.18, "stop": 1801.46, "id": 548}, {"text": " because this is in the denominator.", "start": 1802.28, "stop": 1803.8, "id": 549}, {"text": " So the signal is proportional to the density.", "start": 1804.34, "stop": 1806.02, "id": 550}, {"text": " And this rho is a function.", "start": 1809.48, "stop": 1811.84, "id": 551}, {"text": " The only thing that's really a variable in this thing is this capital M, which", "start": 1812.1, "stop": 1817.3, "id": 552}, {"text": " on the previous slide.", "start": 1817.3, "stop": 1819.26, "id": 553}, {"text": " And this rho is defined as a function of density as well.", "start": 1819.4, "stop": 1821.7, "id": 554}, {"text": " And I'm going to do some substitution in a moment.", "start": 1821.76, "stop": 1823.52, "id": 555}, {"text": " The noise is the same integral again.", "start": 1823.92, "stop": 1826.4, "id": 556}, {"text": " It's the Olders paradox integral.", "start": 1826.54, "stop": 1827.72, "id": 557}, {"text": " And I'm only going to integrate out to my fixed radius.", "start": 1828.22, "stop": 1831.02, "id": 558}, {"text": " And this r, this rho is also a function of r.", "start": 1831.36, "stop": 1834.76, "id": 559}, {"text": " So I've only got one variable to sim, but I can't.", "start": 1834.92, "stop": 1838.82, "id": 560}, {"text": " This r is constant.", "start": 1843.24, "stop": 1844.5, "id": 561}, {"text": " This rho is a function of both the number of stations", "start": 1844.76, "stop": 1846.92, "id": 562}, {"text": " and this fixed radius as well.", "start": 1846.92, "stop": 1848.54, "id": 563}, {"text": " So I integrate out only to r.", "start": 1853.1999999999998, "stop": 1855.44, "id": 564}, {"text": " Now, I have another problem.", "start": 1855.5, "stop": 1856.44, "id": 565}, {"text": " What do I choose for a lower bound of the integral?", "start": 1856.68, "stop": 1858.44, "id": 566}, {"text": " And I have to hand wave here again.", "start": 1859.14, "stop": 1860.58, "id": 567}, {"text": " What's your question?", "start": 1860.74, "stop": 1861.06, "id": 568}, {"text": " That's what I was just going to ask.", "start": 1861.4, "stop": 1862.22, "id": 569}, {"text": " This is only talking about the only integrating from the range", "start": 1862.42, "stop": 1865.4, "id": 570}, {"text": " of the desired station, the top.", "start": 1865.4, "stop": 1867.04, "id": 571}, {"text": " But what about other stations?", "start": 1867.44, "stop": 1868.66, "id": 572}, {"text": " That might be closer.", "start": 1868.9, "stop": 1869.7, "id": 573}, {"text": " Exactly.", "start": 1870.1, "stop": 1870.5, "id": 574}, {"text": " Now, why not just drop this to 0?", "start": 1871.1, "stop": 1873.08, "id": 575}, {"text": " This integral also diverges at 0.", "start": 1873.86, "stop": 1876.06, "id": 576}, {"text": " It flows up there as well, because log of 0 is another problem.", "start": 1876.6, "stop": 1882.58, "id": 577}, {"text": " So I couldn't go all the way to 0.", "start": 1883.48, "stop": 1885.08, "id": 578}, {"text": " I had to pick some number.", "start": 1885.26, "stop": 1886.28, "id": 579}, {"text": " The reason I picked r sub 0 is because it makes the algebra work well.", "start": 1886.84, "stop": 1889.6, "id": 580}, {"text": " But I claim it's reasonable, because I've said the number of stations you expect", "start": 1892.86, "stop": 1896.78, "id": 581}, {"text": " to find in here are only pi.", "start": 1896.78, "stop": 1898.98, "id": 582}, {"text": " So there's only three other guys that I'm neglecting here.", "start": 1899.12, "stop": 1902.02, "id": 583}, {"text": " Or maybe there's five.", "start": 1902.6, "stop": 1903.5, "id": 584}, {"text": " But they're all right next to you.", "start": 1903.5, "stop": 1905.29, "id": 585}, {"text": " It doesn't matter.", "start": 1910.54, "stop": 1911.68, "id": 586}, {"text": " I'll get the simulation results.", "start": 1912.78, "stop": 1914.08, "id": 587}, {"text": " And hopefully by the end of the day, you won't be worried about this.", "start": 1914.32, "stop": 1916.32, "id": 588}, {"text": " Those guys are clearly local.", "start": 1917.9, "stop": 1919.22, "id": 589}, {"text": " And maybe we can do some other.", "start": 1919.5, "stop": 1920.78, "id": 590}, {"text": " That's a different issue.", "start": 1921.32, "stop": 1922.32, "id": 591}, {"text": " Anyway, you do the integral.", "start": 1923.6, "stop": 1924.88, "id": 592}, {"text": " And you plug in.", "start": 1925.24, "stop": 1925.96, "id": 593}, {"text": " And I'm skipping over a bunch of algebra here.", "start": 1926.02, "stop": 1927.64, "id": 594}, {"text": " But you do some simplification.", "start": 1928.18, "stop": 1930.18, "id": 595}, {"text": " And you get a term for the noise.", "start": 1930.18, "stop": 1931.58, "id": 596}, {"text": " And then you take the ratio of signal to noise.", "start": 1931.94, "stop": 1933.9, "id": 597}, {"text": " And everything drops out almost, leaving only this capital M", "start": 1935.5400000000002, "stop": 1941.74, "id": 598}, {"text": " and the duty cycle and a few constants.", "start": 1941.74, "stop": 1944.62, "id": 599}, {"text": " And this is sort of a remarkable result.", "start": 1946.22, "stop": 1948.2, "id": 600}, {"text": " What's sort of stunning to me when I first saw this was that", "start": 1950.3600000000001, "stop": 1954.44, "id": 601}, {"text": " the scale length drops out.", "start": 1954.44, "stop": 1956.22, "id": 602}, {"text": " I was surprised by that.", "start": 1956.96, "stop": 1958.34, "id": 603}, {"text": " After thinking, I realized I shouldn't have been surprised by that.", "start": 1958.8, "stop": 1961.22, "id": 604}, {"text": " Because if you're an interference limited system and you bring everybody together", "start": 1961.46, "stop": 1964.62, "id": 605}, {"text": " by a factor of 2, then everything goes up by a factor of 4 in", "start": 1964.62, "stop": 1970.64, "id": 606}, {"text": " power, both noise and signal.", "start": 1970.64, "stop": 1973.2, "id": 607}, {"text": " So it really shouldn't be surprising.", "start": 1973.58, "stop": 1974.92, "id": 608}, {"text": " So this is something that's true at any scale length.", "start": 1977.08, "stop": 1980.2, "id": 609}, {"text": " So the signal to noise ratio depends only on this number of stations.", "start": 1982.7, "stop": 1985.68, "id": 610}, {"text": " So it's 1 over the log of how many stations you've got.", "start": 1985.88, "stop": 1989.08, "id": 611}, {"text": " Actually, it's 1 over the duty cycle times pi times the log", "start": 1989.72, "stop": 1992.78, "id": 612}, {"text": " of the number of stations divided by pi.", "start": 1992.78, "stop": 1994.4, "id": 613}, {"text": " So the thesis is actually on the web.", "start": 1995.44, "stop": 2001.82, "id": 614}, {"text": " There's a sitcom paper on the web.", "start": 2002.28, "stop": 2003.66, "id": 615}, {"text": " And the thesis of the PostScript file is actually put up for FTP.", "start": 2004.32, "stop": 2007.72, "id": 616}, {"text": " And somebody at Tapper, before I even really knew what Tapper was three years", "start": 2008.78, "stop": 2013.4, "id": 617}, {"text": " ago, took the PostScript file that I had made available, converted it to a PDF", "start": 2013.4, "stop": 2019.12, "id": 618}, {"text": " file, and put it on the Tapper FTP server.", "start": 2019.12, "stop": 2021.04, "id": 619}, {"text": " So there's been a PDF file of my whole thesis.", "start": 2021.22, "stop": 2023.08, "id": 620}, {"text": " It's only about 80 pages, single spaced.", "start": 2023.28, "stop": 2026.24, "id": 621}, {"text": " It's available on the Tapper website.", "start": 2028.06, "stop": 2029.98, "id": 622}, {"text": " And it actually, yeah, it doesn't skip all the algebra.", "start": 2030.22, "stop": 2033.82, "id": 623}, {"text": " So you can actually try and check my algebra.", "start": 2034.02, "stop": 2035.7, "id": 624}, {"text": " Go ahead.", "start": 2043.06, "stop": 2044.02, "id": 625}, {"text": " The question is, although you derive it based on circle text, it's now", "start": 2044.02, "stop": 2048.72, "id": 626}, {"text": " pretty independent of the one in the case.", "start": 2048.72, "stop": 2050.74, "id": 627}, {"text": " A square is almost a circle, I mean, if you're standing in the middle of it.", "start": 2051.62, "stop": 2054.6, "id": 628}, {"text": " [...]", "start": 2054.64, "stop": 2055.38, "id": 629}, {"text": " Yeah.", "start": 2056.04, "stop": 2056.48, "id": 630}, {"text": " Well, this calculation is in the circle, because", "start": 2057.0, "stop": 2060.12, "id": 631}, {"text": " that's where the pi's and stuff come from.", "start": 2060.12, "stop": 2061.98, "id": 632}, {"text": " If it's not a circle, maybe this isn't pi.", "start": 2062.1, "stop": 2064.14, "id": 633}, {"text": " Maybe it's 2 or something.", "start": 2064.7, "stop": 2065.84, "id": 634}, {"text": " Would it get real messy to try and introduce some randomness of height, the", "start": 2066.48, "stop": 2070.12, "id": 635}, {"text": " concept of height gain, and the fact of topology, real topology?", "start": 2070.12, "stop": 2073.24, "id": 636}, {"text": " Well, I was trying for a worst case.", "start": 2073.24, "stop": 2075.28, "id": 637}, {"text": " Anything, any real world propagation phenomena are going to cut down distant", "start": 2075.72, "stop": 2080.32, "id": 638}, {"text": " guys and help you improve.", "start": 2080.32, "stop": 2082.06, "id": 639}, {"text": " So this is how bad can it get.", "start": 2082.88, "stop": 2084.74, "id": 640}, {"text": " Now, I've got a plot of this for a bunch of interesting values.", "start": 2088.3199999999997, "stop": 2091.38, "id": 641}, {"text": " So what I've got on the next slide, I don't have two projectors, so I", "start": 2091.54, "stop": 2094.08, "id": 642}, {"text": " can't show you both at the same time.", "start": 2094.08, "stop": 2095.64, "id": 643}, {"text": " But what I'm going to show you is signal to noise ratio as a function of the", "start": 2095.66, "stop": 2099.04, "id": 644}, {"text": " number of stations for a few different values of duty cycle.", "start": 2099.04, "stop": 2102.96, "id": 645}, {"text": " [...]", "start": 2103.78, "stop": 2104.26, "id": 646}, {"text": " Let me.", "start": 2105.76, "stop": 2106.12, "id": 647}, {"text": " One factor that strikes my mind is there's obviously a horizontal plane", "start": 2106.18, "stop": 2112.56, "id": 648}, {"text": " with which stations can be.", "start": 2112.56, "stop": 2114.24, "id": 649}, {"text": " There's also a possibility of a vertical plane.", "start": 2114.88, "stop": 2117.02, "id": 650}, {"text": " I neglected that.", "start": 2117.28, "stop": 2118.1, "id": 651}, {"text": " That was correct.", "start": 2118.32, "stop": 2118.9, "id": 652}, {"text": " But we haven't built skyscrapers arbitrarily high.", "start": 2120.4, "stop": 2124.06, "id": 653}, {"text": " And if you're in a big building like that, you", "start": 2124.48, "stop": 2125.78, "id": 654}, {"text": " probably just don't have one station on the roof anyway.", "start": 2125.78, "stop": 2127.42, "id": 655}, {"text": " Actually, I'm trying to get to the suburbs, not to the downtown.", "start": 2128.02, "stop": 2131.62, "id": 656}, {"text": " Do you have a low energy road on a lot of times?", "start": 2131.98, "stop": 2133.82, "id": 657}, {"text": " [...]", "start": 2134.96, "stop": 2135.36, "id": 658}, {"text": " Yeah.", "start": 2135.88, "stop": 2136.12, "id": 659}, {"text": " Well, because the building attenuates.", "start": 2137.42, "stop": 2138.84, "id": 660}, {"text": " I neglected all that.", "start": 2139.22, "stop": 2140.0, "id": 661}, {"text": " This is still thinking about stations in the flat plane of the finite circle.", "start": 2140.16, "stop": 2143.58, "id": 662}, {"text": " So here's the plot for signal to noise ratio on this axis.", "start": 2144.14, "stop": 2147.4, "id": 663}, {"text": " Actually, I've got two copies of this plot.", "start": 2148.62, "stop": 2149.98, "id": 664}, {"text": " This one I wrote all over.", "start": 2150.08, "stop": 2151.08, "id": 665}, {"text": " I'm going to use it.", "start": 2154.6, "stop": 2155.94, "id": 666}, {"text": " I've got it labeled in dB, but then I took a pin.", "start": 2156.8799999999997, "stop": 2159.2, "id": 667}, {"text": " And this is the 5 dB signal to noise ratio, or a 3 to 1 ratio.", "start": 2159.62, "stop": 2163.58, "id": 668}, {"text": " This is like a 1 to 1 ratio.", "start": 2163.82, "stop": 2164.9, "id": 669}, {"text": " This is 0 dB minus 5 minus 10 minus 15 minus 20.", "start": 2165.06, "stop": 2168.24, "id": 670}, {"text": " So this would be a 1 part in 100 signal to noise ratio.", "start": 2168.88, "stop": 2171.58, "id": 671}, {"text": " And on the x-axis, I have number of stations. 10 to the 2, 10 to the 3, 4,", "start": 2172.78, "stop": 2178.6, "id": 672}, {"text": " 5, or in other words, this is 1,000.", "start": 2178.68, "stop": 2180.34, "id": 673}, {"text": " That's a million.", "start": 2180.66, "stop": 2181.22, "id": 674}, {"text": " This is a billion.", "start": 2181.84, "stop": 2182.54, "id": 675}, {"text": " And over here would be 10 to the 12.", "start": 2183.4, "stop": 2184.84, "id": 676}, {"text": " Stations.", "start": 2185.62, "stop": 2186.14, "id": 677}, {"text": " And this curve is 100% duty cycle.", "start": 2187.96, "stop": 2191.4, "id": 678}, {"text": " This is a 50% duty cycle, 20%.", "start": 2191.54, "stop": 2193.68, "id": 679}, {"text": " And actually, this just moves in dB, whatever this factor is.", "start": 2193.68, "stop": 2197.46, "id": 680}, {"text": " So we can just look at the 100% duty cycle.", "start": 2198.04, "stop": 2200.0, "id": 681}, {"text": " All the curves have the same shape.", "start": 2201.02, "stop": 2202.36, "id": 682}, {"text": " And so the thing to observe is that this flattens,", "start": 2204.68, "stop": 2209.1, "id": 683}, {"text": " seems to sort of flatten out here.", "start": 2209.16, "stop": 2210.82, "id": 684}, {"text": " Which means if you build the station, if you build the, if you designed", "start": 2211.22, "stop": 2216.02, "id": 685}, {"text": " to cope with 1 part in 100 signal to noise ratios, it would work", "start": 2217.78, "stop": 2223.06, "id": 686}, {"text": " here, it would work here.", "start": 2223.06, "stop": 2224.72, "id": 687}, {"text": " And then as you got to larger numbers of stations, it could continue to work.", "start": 2224.88, "stop": 2229.36, "id": 688}, {"text": " And this flattens out.", "start": 2231.34, "stop": 2232.76, "id": 689}, {"text": " I mean, this 100% line doesn't not cross the minus 21 dB", "start": 2233.02, "stop": 2239.74, "id": 690}, {"text": " line, I believe it was, until you get to 10 to the 18 stations.", "start": 2239.74, "stop": 2242.56, "id": 691}, {"text": " [...]", "start": 2243.14, "stop": 2243.36, "id": 692}, {"text": " And this ended my two month depression about the scaling problem.", "start": 2247.08, "stop": 2251.28, "id": 693}, {"text": " This made me think, yes, it can scale to everybody having one on their roof.", "start": 2251.76, "stop": 2256.22, "id": 694}, {"text": " No, they eventually go to zero signal to noise ratio.", "start": 2261.0, "stop": 2267.14, "id": 695}, {"text": " They get there extremely slowly.", "start": 2269.72, "stop": 2272.34, "id": 696}, {"text": " Do they go to minus infinity?", "start": 2272.38, "stop": 2274.42, "id": 697}, {"text": " Yeah, there's actually, after I finished the thesis, I did some reading.", "start": 2275.66, "stop": 2278.96, "id": 698}, {"text": " And I think in one of, James Gluck wrote a biography of Richard", "start": 2279.16, "stop": 2284.06, "id": 699}, {"text": " Feynman, which I highly recommend.", "start": 2284.06, "stop": 2285.8, "id": 700}, {"text": " And there's actually, in the middle of the book, there's this quote about talking", "start": 2287.82, "stop": 2290.66, "id": 701}, {"text": " about when Feynman realized that a log of infinity is not infinity", "start": 2290.66, "stop": 2293.88, "id": 702}, {"text": " in practical sense.", "start": 2293.88, "stop": 2295.84, "id": 703}, {"text": " I mean, mathematically, it is.", "start": 2295.84, "stop": 2298.04, "id": 704}, {"text": " But any time, because they were solving some problem in physics, and he just", "start": 2298.44, "stop": 2301.88, "id": 705}, {"text": " says, well, what if we just neglect that term, and then they made progress?", "start": 2301.88, "stop": 2304.32, "id": 706}, {"text": " That's kind of neat.", "start": 2307.02, "stop": 2307.82, "id": 707}, {"text": " And so logs grow very slowly.", "start": 2309.14, "stop": 2312.22, "id": 708}, {"text": " The reason is because we're taking the log of the number of stations.", "start": 2313.18, "stop": 2318.38, "id": 709}, {"text": " And once you logarithm, you have to.", "start": 2318.64, "stop": 2320.74, "id": 710}, {"text": " So this is neat.", "start": 2323.68, "stop": 2324.58, "id": 711}, {"text": " This, I've got the words on this slide.", "start": 2327.8599999999997, "stop": 2329.84, "id": 712}, {"text": " The conclusion is you can hear your nearby neighbor.", "start": 2329.96, "stop": 2334.44, "id": 713}, {"text": " And it depends only on the log and the number of stations.", "start": 2335.52, "stop": 2338.06, "id": 714}, {"text": " And it falls very slowly.", "start": 2338.58, "stop": 2339.9, "id": 715}, {"text": " And it only gets to about minus 20 dB.", "start": 2341.94, "stop": 2343.7, "id": 716}, {"text": " And that's just 100% 3D cycle.", "start": 2343.84, "stop": 2345.4, "id": 717}, {"text": " At 50% 3D cycle, things are 3 dB better.", "start": 2345.84, "stop": 2348.1, "id": 718}, {"text": " At a 10% 3D cycle, things are 10 dB better.", "start": 2348.76, "stop": 2350.94, "id": 719}, {"text": " It's just greater than the network you can just change.", "start": 2354.92, "stop": 2357.76, "id": 720}, {"text": " It depends on the cycle of energy.", "start": 2358.04, "stop": 2359.32, "id": 721}, {"text": " Or you can just design to, I mean, yeah.", "start": 2361.38, "stop": 2364.04, "id": 722}, {"text": " That's absolutely possible.", "start": 2365.04, "stop": 2366.18, "id": 723}, {"text": " There are many possibilities now.", "start": 2366.7, "stop": 2368.02, "id": 724}, {"text": " And this made me think there are many possibilities now.", "start": 2368.2, "stop": 2371.26, "id": 725}, {"text": " And I went on.", "start": 2371.38, "stop": 2371.74, "id": 726}, {"text": " When you say you have more processes, does that mean you can have more processes?", "start": 2371.86, "stop": 2374.66, "id": 727}, {"text": " [...]", "start": 2375.14, "stop": 2376.88, "id": 728}, {"text": " No, you don't actually.", "start": 2378.58, "stop": 2379.52, "id": 729}, {"text": " It's a, it turns out, it's a, the duty cycle issue, it turns out it's a wash.", "start": 2380.5, "stop": 2384.54, "id": 730}, {"text": " If you double the duty cycle, if you cut the duty cycle in half, you get three,", "start": 2385.38, "stop": 2389.3, "id": 731}, {"text": " you can only transmit half the time.", "start": 2389.62, "stop": 2391.32, "id": 732}, {"text": " But you can get twice as many vistas times.", "start": 2391.9, "stop": 2393.88, "id": 733}, {"text": " So it's a wash.", "start": 2394.1, "stop": 2394.6, "id": 734}, {"text": " You don't gain anything by cutting back on duty cycle.", "start": 2394.9, "stop": 2396.98, "id": 735}, {"text": " [...]", "start": 2397.08, "stop": 2399.1, "id": 736}, {"text": " Yeah.", "start": 2399.44, "stop": 2399.84, "id": 737}, {"text": " I didn't come to understand that until later.", "start": 2400.58, "stop": 2402.22, "id": 738}, {"text": " But yes.", "start": 2403.06, "stop": 2403.36, "id": 739}, {"text": " The question was, well, what's the right way to place the design of the system?", "start": 2404.58, "stop": 2407.58, "id": 740}, {"text": " I didn't plan on mentioning this now.", "start": 2407.66, "stop": 2409.04, "id": 741}, {"text": " But something I figured out.", "start": 2409.6, "stop": 2412.12, "id": 742}, {"text": " It's like, well, what duty cycle should you run the system at?", "start": 2412.12, "stop": 2414.22, "id": 743}, {"text": " Well, in a noise-limited environment, the capacity is roughly proportionate.", "start": 2414.36, "stop": 2420.9, "id": 744}, {"text": " This is something Matt Aitouz had on the slide yesterday.", "start": 2420.94, "stop": 2422.84, "id": 745}, {"text": " And actually, I realized I should make that slide.", "start": 2423.06, "stop": 2424.94, "id": 746}, {"text": " It says that the bits per second that you can get through in a noise-limited", "start": 2425.74, "stop": 2430.22, "id": 747}, {"text": " system, in other words, with a signal-to-noise", "start": 2430.22, "stop": 2431.8, "id": 748}, {"text": " ratio, is noticeably less than one.", "start": 2431.8, "stop": 2433.46, "id": 749}, {"text": " It's proportional to the signal-to-noise ratio.", "start": 2434.36, "stop": 2436.26, "id": 750}, {"text": " So if you do a fifth, if say you move from a 20% duty cycle to a 10% duty cycle,", "start": 2437.42, "stop": 2442.5, "id": 751}, {"text": " you've improved the signal-to-noise ratio sort of", "start": 2442.84, "stop": 2445.62, "id": 752}, {"text": " throughout the system by a factor of 2.", "start": 2445.62, "stop": 2447.24, "id": 753}, {"text": " So you can go twice as fast, but you're only spending half the time transmitting", "start": 2448.74, "stop": 2454.34, "id": 754}, {"text": " the two or the four, which means that nothing's changed.", "start": 2454.34, "stop": 2459.04, "id": 755}, {"text": " So it's a wash as to where you actually design the system on here.", "start": 2459.76, "stop": 2462.5, "id": 756}, {"text": " And in a little while, I'll be suggesting that you", "start": 2463.72, "stop": 2466.48, "id": 757}, {"text": " should spend more than half the time transmitting.", "start": 2466.48, "stop": 2468.06, "id": 758}, {"text": " No, I'm sorry, what?", "start": 2473.94, "stop": 2476.94, "id": 759}, {"text": " Yeah, I've lost my design.", "start": 2481.7000000000003, "stop": 2483.16, "id": 760}, {"text": " You're relaying for people too, so.", "start": 2484.92, "stop": 2486.72, "id": 761}, {"text": " So this slide actually covers a lot of ground.", "start": 2488.98, "stop": 2493.2, "id": 762}, {"text": " I can't talk about the entire thesis today.", "start": 2494.68, "stop": 2496.74, "id": 763}, {"text": " I'm going to have to skip over some details.", "start": 2496.76, "stop": 2500.76, "id": 764}, {"text": " But I've still got a lot to talk about.", "start": 2500.76, "stop": 2503.9, "id": 765}, {"text": " I think I'm only going to talk about, well, I need to explain all of this, but", "start": 2504.2, "stop": 2509.58, "id": 766}, {"text": " I'm going to hand wave my way all the way through this", "start": 2509.58, "stop": 2512.58, "id": 767}, {"text": " slide to try to give you the whole picture.", "start": 2512.58, "stop": 2514.9, "id": 768}, {"text": " And I'm going to come back and expand on things and try to", "start": 2515.28, "stop": 2517.98, "id": 769}, {"text": " illustrate, and hopefully it will all gel.", "start": 2517.98, "stop": 2519.84, "id": 770}, {"text": " What I've just showed you is that you can scale a spread second with sufficient", "start": 2521.0, "stop": 2524.84, "id": 771}, {"text": " processing gain is what lets this thing scale.", "start": 2524.84, "stop": 2527.32, "id": 772}, {"text": " And you can't, and I understood that it seems to me that you have to not try to", "start": 2529.52, "stop": 2535.98, "id": 773}, {"text": " skip over people, that you need to route over short hops.", "start": 2535.98, "stop": 2538.28, "id": 774}, {"text": " And if somebody shows up between you and where you were going, you should start", "start": 2538.62, "stop": 2541.34, "id": 775}, {"text": " routing through them for the purposes of letting the system scale.", "start": 2541.34, "stop": 2544.24, "id": 776}, {"text": " And I'm going to come back and hopefully plant some more intuition about", "start": 2546.04, "stop": 2550.24, "id": 777}, {"text": " this right towards the end of my talk.", "start": 2550.24, "stop": 2551.76, "id": 778}, {"text": " But I was sort of going with this on intuition at this point.", "start": 2553.06, "stop": 2556.4, "id": 779}, {"text": " Every station I expect will have one transmitter.", "start": 2558.16, "stop": 2561.92, "id": 780}, {"text": " When I was thinking through this, I've got other ideas", "start": 2564.06, "stop": 2566.74, "id": 781}, {"text": " for actually how to really do this.", "start": 2566.74, "stop": 2568.32, "id": 782}, {"text": " But for now, think of every station as having one transmitter, one on the", "start": 2568.56, "stop": 2573.54, "id": 783}, {"text": " antenna, using that same antenna for receive, and cannot", "start": 2573.54, "stop": 2579.8, "id": 784}, {"text": " hear while its transmitters on.", "start": 2579.8, "stop": 2582.08, "id": 785}, {"text": " So when the transmitter comes on, the station is deaf.", "start": 2582.2, "stop": 2584.1, "id": 786}, {"text": " So you can't, you have to somehow avoid stomping on", "start": 2585.3399999999997, "stop": 2589.32, "id": 787}, {"text": " yourself on your own reception.", "start": 2589.32, "stop": 2590.98, "id": 788}, {"text": " And I'm going to talk in detail about that.", "start": 2591.78, "stop": 2593.82, "id": 789}, {"text": " But there's the problem of what if two people try to", "start": 2594.78, "stop": 2596.68, "id": 790}, {"text": " send you a packet at the same time?", "start": 2596.68, "stop": 2598.18, "id": 791}, {"text": " Well, with spread spectrum, you can run multiple of these", "start": 2598.42, "stop": 2600.34, "id": 792}, {"text": " spreading channels and capture them both.", "start": 2600.34, "stop": 2601.84, "id": 793}, {"text": " And so, for now, I'm going to say multiple of these spreading channels.", "start": 2604.0199999999995, "stop": 2608.24, "id": 794}, {"text": " In fact, we'll put in however many we need.", "start": 2608.36, "stop": 2610.1, "id": 795}, {"text": " I haven't really, I haven't come up with the exact", "start": 2610.65, "stop": 2614.28, "id": 796}, {"text": " argument for what we really need.", "start": 2614.28, "stop": 2615.88, "id": 797}, {"text": " But this is how you solve the problem of two people sending", "start": 2616.08, "stop": 2618.64, "id": 798}, {"text": " you packets at the same time.", "start": 2618.64, "stop": 2620.26, "id": 799}, {"text": " A lot of literature on packet rate, like Macaw, MACA, and then all of the follow", "start": 2620.66, "stop": 2626.74, "id": 800}, {"text": " on, the MACAW and the FANA stuff that's all been done just", "start": 2626.74, "stop": 2631.0, "id": 801}, {"text": " on the last eight or so years.", "start": 2631.0, "stop": 2632.84, "id": 802}, {"text": " Starting with Phil Carnes paper, which was a DCC paper in 1990, I think.", "start": 2633.06, "stop": 2636.86, "id": 803}, {"text": " I'm not really thinking about Indian", "start": 2636.86, "stop": 2641.22, "id": 804}, {"text": " protocols, I'm just trying to get communication working.", "start": 2641.22, "stop": 2643.16, "id": 805}, {"text": " But the, Is there some of these issues of, you know, propagation delay with", "start": 2643.24, "stop": 2648.24, "id": 806}, {"text": " driving protocols and propagation delay?", "start": 2648.24, "stop": 2651.0, "id": 807}, {"text": " Well, propagation is five microseconds per mile.", "start": 2651.16, "stop": 2654.0, "id": 808}, {"text": " And I sort of neglect that.", "start": 2655.02, "stop": 2656.3, "id": 809}, {"text": " You have also got issue of protocol acknowledgment delays.", "start": 2657.16, "stop": 2659.78, "id": 810}, {"text": " Well, I'm thinking I want to do end to end protocols.", "start": 2660.4, "stop": 2663.04, "id": 811}, {"text": " So I'm going to, I'd like to be able to engineer the system so that the per hop", "start": 2664.16, "stop": 2667.84, "id": 812}, {"text": " reliability is high enough so that we can just build the reliability on the end", "start": 2667.84, "stop": 2672.28, "id": 813}, {"text": " end things like the rest of the internet works.", "start": 2672.28, "stop": 2675.4, "id": 814}, {"text": " So I'd like to, when a packet is transmitted by a station, I'd like it to be", "start": 2676.96, "stop": 2682.14, "id": 815}, {"text": " received by that receiver almost certainly.", "start": 2682.14, "stop": 2684.98, "id": 816}, {"text": " So I don't need to do any hop by hop acknowledgment, any feedback.", "start": 2685.3, "stop": 2688.42, "id": 817}, {"text": " And so you can just go on.", "start": 2688.86, "stop": 2690.0, "id": 818}, {"text": " And then do that, you have to get rid of any packet loss", "start": 2690.9, "stop": 2693.74, "id": 819}, {"text": " due to what people think of as collisions.", "start": 2693.74, "stop": 2695.32, "id": 820}, {"text": " Collisions, I think are a misleading term because, you know, it's all signal to", "start": 2696.74, "stop": 2700.76, "id": 821}, {"text": " noise ratios and all depends on, you know, whether you had enough to decode it.", "start": 2700.76, "stop": 2704.92, "id": 822}, {"text": " And if you're in the middle of a sea of a million stations, then the real issue", "start": 2705.12, "stop": 2710.0, "id": 823}, {"text": " is if you have enough processing gain and, you know, whether the signal noise", "start": 2710.0, "stop": 2714.54, "id": 824}, {"text": " ratio or decoding, what was the probability of decoding that packet?", "start": 2714.54, "stop": 2718.46, "id": 825}, {"text": " But I'd like to engineer that to be reliable.", "start": 2718.46, "stop": 2720.6, "id": 826}, {"text": " And I don't really think about the real", "start": 2721.22, "stop": 2723.3, "id": 827}, {"text": " problem that I'm trying to solve as collisions.", "start": 2723.3, "stop": 2724.8, "id": 828}, {"text": " I didn't come at this from a collisions problem.", "start": 2724.94, "stop": 2726.36, "id": 829}, {"text": " But if we want to think about collisions for a second, there's three cases.", "start": 2726.42, "stop": 2729.36, "id": 830}, {"text": " I don't have the slide for this, but a little picture in the thesis.", "start": 2729.52, "stop": 2732.22, "id": 831}, {"text": " There's a, I don't remember what number, what order I put", "start": 2733.04, "stop": 2736.94, "id": 832}, {"text": " them in the thesis, but there's a couple possibilities.", "start": 2736.94, "stop": 2738.52, "id": 833}, {"text": " There's like, I'm trying to receive a packet from a guy over here, and then", "start": 2738.78, "stop": 2744.4, "id": 834}, {"text": " there's a guy over here trying to send a packet to somebody else.", "start": 2744.4, "stop": 2746.58, "id": 835}, {"text": " And so I get a signal from him, and I'm getting interference from this", "start": 2746.58, "stop": 2750.3, "id": 836}, {"text": " transmission for going over there.", "start": 2750.3, "stop": 2752.66, "id": 837}, {"text": " That's one type of collision.", "start": 2753.04, "stop": 2754.2, "id": 838}, {"text": " And with spread spectrum, I mean, I've already like", "start": 2754.92, "stop": 2756.8, "id": 839}, {"text": " included like all the other transmissions.", "start": 2756.8, "stop": 2758.56, "id": 840}, {"text": " And so if this is a sort of a type one collision, I'm not really worried about", "start": 2759.26, "stop": 2763.28, "id": 841}, {"text": " that because I'm sort of solving that with spread spectrum.", "start": 2763.28, "stop": 2765.1, "id": 842}, {"text": " The second case would be two people sending packets at the same time to me.", "start": 2765.56, "stop": 2769.14, "id": 843}, {"text": " And that's what this multiple de-spreading channels issue is about.", "start": 2769.2, "stop": 2772.56, "id": 844}, {"text": " And another type of collision is somebody's trying to send a packet to me, and at", "start": 2772.56, "stop": 2776.78, "id": 845}, {"text": " the same time I'm transmitting a packet to somebody else.", "start": 2776.78, "stop": 2778.86, "id": 846}, {"text": " And that is still a problem because I'm completely deaf when my transmitter's on", "start": 2779.22, "stop": 2783.8, "id": 847}, {"text": " because the most performance you can get out of a duplexer for", "start": 2783.8, "stop": 2786.58, "id": 848}, {"text": " an antenna is about 20 dB isolation.", "start": 2786.58, "stop": 2788.08, "id": 849}, {"text": " And the difference between a transmitted signal level up the antenna and what", "start": 2788.72, "stop": 2792.22, "id": 850}, {"text": " comes down at the other end is on the order of 100 dB.", "start": 2792.22, "stop": 2794.7, "id": 851}, {"text": " So you can only get about 20 dB of isolation on the same frequency.", "start": 2797.1, "stop": 2801.2, "id": 852}, {"text": " Yeah.", "start": 2802.66, "stop": 2803.06, "id": 853}, {"text": " Well, the old cards are getting senior, you know, 90, but that's the likelihood.", "start": 2804.2, "stop": 2808.16, "id": 854}, {"text": " Well, in separate antennas.", "start": 2808.98, "stop": 2810.16, "id": 855}, {"text": " They're not using the same feed line for that.", "start": 2810.96, "stop": 2813.04, "id": 856}, {"text": " Well, you can't get any separation.", "start": 2813.5, "stop": 2815.42, "id": 857}, {"text": " You can get about 20 dB on the same feed line, but only 20 and you need about", "start": 2816.18, "stop": 2819.72, "id": 858}, {"text": " 100, so you're about 80 dB short.", "start": 2819.72, "stop": 2821.26, "id": 859}, {"text": " There are some short order systems for dB, but they're very narrow banded.", "start": 2821.34, "stop": 2824.5, "id": 860}, {"text": " And probably extensive.", "start": 2824.68, "stop": 2825.46, "id": 861}, {"text": " So, wait a minute.", "start": 2825.46, "stop": 2827.6, "id": 862}, {"text": " If you go back to that 100% duty cycle, is everybody's transmitting 100%?", "start": 2827.84, "stop": 2834.26, "id": 863}, {"text": " [...] do you detect only everybody's deaf?", "start": 2834.66, "stop": 2836.36, "id": 864}, {"text": " That's right.", "start": 2837.06, "stop": 2837.46, "id": 865}, {"text": " So people are going to...", "start": 2838.16, "stop": 2839.6, "id": 866}, {"text": " What?", "start": 2839.6, "stop": 2839.88, "id": 867}, {"text": " No, it has to be less.", "start": 2840.04, "stop": 2840.96, "id": 868}, {"text": " That's right.", "start": 2841.24, "stop": 2841.9, "id": 869}, {"text": " That's right.", "start": 2842.86, "stop": 2843.5, "id": 870}, {"text": " But maybe 50%.", "start": 2845.22, "stop": 2846.42, "id": 871}, {"text": " That's only 3 dB difference in the whole noise level.", "start": 2846.99, "stop": 2849.62, "id": 872}, {"text": " I don't think I said anything contrary to that.", "start": 2850.74, "stop": 2852.34, "id": 873}, {"text": " Are you assuming that the noise calculation, which hypothesis you gave", "start": 2853.15, "stop": 2858.86, "id": 874}, {"text": " against all other stations, all the stations within radius r?", "start": 2860.04, "stop": 2864.46, "id": 875}, {"text": " Well, to be truly orthogonal, it all have to be", "start": 2868.76, "stop": 2872.48, "id": 876}, {"text": " synchronized from the point of view of the receiver.", "start": 2872.48, "stop": 2874.42, "id": 877}, {"text": " I mean...", "start": 2875.38, "stop": 2875.74, "id": 878}, {"text": " Within 3 [...]", "start": 2875.74, "stop": 2877.46, "id": 879}, {"text": " Well, perhaps there are...", "start": 2877.46, "stop": 2879.8, "id": 880}, {"text": " I mean, do you consider random codes to be orthogonal?", "start": 2879.8, "stop": 2882.08, "id": 881}, {"text": " What kind of performance do you get if everybody uses codes that...", "start": 2885.62, "stop": 2890.54, "id": 882}, {"text": " The code...", "start": 2890.54, "stop": 2891.02, "id": 883}, {"text": " There's a lot of detail that we could go into here.", "start": 2891.98, "stop": 2894.98, "id": 884}, {"text": " What do you mean by orthogonal?", "start": 2897.5, "stop": 2901.32, "id": 885}, {"text": " Meaning that the correlation...", "start": 2902.08, "stop": 2905.66, "id": 886}, {"text": " [...] correlation... ...the system in there... [...] amount", "start": 2905.66, "stop": 2912.5, "id": 887}, {"text": " located in the correlation range... ...and the station [...]", "start": 2912.5, "stop": 2916.2, "id": 888}, {"text": " [...]", "start": 2916.88, "stop": 2917.32, "id": 889}, {"text": " In which case, the number of orthogonal codes you need... ...is equal to the", "start": 2917.6, "stop": 2923.1, "id": 890}, {"text": " number of stations...", "start": 2923.1, "stop": 2924.72, "id": 891}, {"text": " Yeah.", "start": 2926.52, "stop": 2927.12, "id": 892}, {"text": " There's a sort of a...", "start": 2927.8, "stop": 2928.98, "id": 893}, {"text": " There's a standard way that spread spectrum systems", "start": 2928.98, "stop": 2931.02, "id": 894}, {"text": " are built where everybody uses...", "start": 2931.02, "stop": 2932.66, "id": 895}, {"text": " They repeat the same chip pattern for every bit.", "start": 2936.96, "stop": 2939.72, "id": 896}, {"text": " Basically, the spreading code repetition rate is the same as the bit time.", "start": 2940.16, "stop": 2943.68, "id": 897}, {"text": " And you don't need to do that.", "start": 2944.38, "stop": 2945.4, "id": 898}, {"text": " So you can...", "start": 2945.62, "stop": 2946.28, "id": 899}, {"text": " You can have spreading codes that repeat over longer cycles.", "start": 2946.74, "stop": 2949.78, "id": 900}, {"text": " And when you go to that, then you actually have a larger number of codes.", "start": 2950.8599999999997, "stop": 2954.36, "id": 901}, {"text": " And now you have the problem of like, well, did I get this bit right?", "start": 2955.42, "stop": 2958.04, "id": 902}, {"text": " And it's like, well, there...", "start": 2958.48, "stop": 2959.9, "id": 903}, {"text": " That's the probabilistic thing.", "start": 2959.9, "stop": 2961.02, "id": 904}, {"text": " And you're probably going to have to wrap error correcting codes around that.", "start": 2961.58, "stop": 2963.82, "id": 905}, {"text": " And I appeal to the, you know, if you treat people with noise in the band...", "start": 2963.82, "stop": 2968.82, "id": 906}, {"text": " ...and, you know, Shannon... ...Saul Shannon's", "start": 2969.38, "stop": 2971.1, "id": 907}, {"text": " equation, then there ought to be some way to do it.", "start": 2971.1, "stop": 2972.78, "id": 908}, {"text": " I haven't...", "start": 2973.46, "stop": 2974.3, "id": 909}, {"text": " The literature talks about receiver-directed codes, transmitter-directed codes.", "start": 2974.3, "stop": 2977.52, "id": 910}, {"text": " I wave my hands and I say, everybody's using random codes.", "start": 2978.72, "stop": 2981.5, "id": 911}, {"text": " And when you're talking 20 dB of processing gain, you've got on the order of...", "start": 2982.28, "stop": 2986.82, "id": 912}, {"text": " You know, if you did it that way, you'd have on the order of 100 chips per bit.", "start": 2987.66, "stop": 2992.9, "id": 913}, {"text": " And even if you want to constrain so that the offset in any bit is at most", "start": 2993.82, "stop": 2998.14, "id": 914}, {"text": " 40, 60, the number of...", "start": 2998.14, "stop": 2999.82, "id": 915}, {"text": " There's a lot of space there.", "start": 3000.54, "stop": 3001.64, "id": 916}, {"text": " So I haven't really worried much about the number of codes.", "start": 3002.4, "stop": 3005.34, "id": 917}, {"text": " I want to solve it all, but I had to turn in the thesis at some point.", "start": 3008.72, "stop": 3015.04, "id": 918}, {"text": " So multiple of these spreading channels to solve a problem of", "start": 3019.04, "stop": 3021.8, "id": 919}, {"text": " people sending in multiple packets within time.", "start": 3021.8, "stop": 3023.4, "id": 920}, {"text": " And then the remaining collisions are", "start": 3023.4, "stop": 3025.32, "id": 921}, {"text": " those which are caused by your own transmitter.", "start": 3025.32, "stop": 3027.0, "id": 922}, {"text": " And I'm going to show you a scheduling method right now after the slide.", "start": 3027.5, "stop": 3032.04, "id": 923}, {"text": " How do I do that?", "start": 3032.68, "stop": 3033.34, "id": 924}, {"text": " Maybe six, maybe eight.", "start": 3033.98, "stop": 3038.84, "id": 925}, {"text": " And GPS...", "start": 3040.02, "stop": 3040.54, "id": 926}, {"text": " I mean, once you actually go to VLSI and you're not actually trying to do it all", "start": 3040.54, "stop": 3045.3, "id": 927}, {"text": " digitally... ...but you actually got analog circuits with buckets of integrate", "start": 3045.3, "stop": 3048.42, "id": 928}, {"text": " and dump and everything... ...it's not", "start": 3048.42, "stop": 3050.24, "id": 929}, {"text": " hard to replicate these spreading channels.", "start": 3050.24, "stop": 3051.84, "id": 930}, {"text": " You can share all the receiver front end.", "start": 3053.82, "stop": 3055.82, "id": 931}, {"text": " Now, power control...", "start": 3059.3, "stop": 3060.76, "id": 932}, {"text": " The method I wound up using, sort of...", "start": 3062.5, "stop": 3065.08, "id": 933}, {"text": " It was an ad hoc choice, but it turned out to work really well.", "start": 3065.08, "stop": 3067.34, "id": 934}, {"text": " And the simulation I sort of believe in is to choose a power level to deliver to", "start": 3067.76, "stop": 3071.84, "id": 935}, {"text": " the receiver... ...and then adjust the transmitter level to do that.", "start": 3071.84, "stop": 3074.32, "id": 936}, {"text": " And the stations will somehow rendezvous and learn where each other are.", "start": 3074.76, "stop": 3077.68, "id": 937}, {"text": " They can measure the propagation characteristics between", "start": 3077.68, "stop": 3080.96, "id": 938}, {"text": " them and then adjust appropriately.", "start": 3080.96, "stop": 3082.5, "id": 939}, {"text": " And so actually, in my simulations, I controlled power to deliver minus 120", "start": 3082.92, "stop": 3088.42, "id": 940}, {"text": " dBw... ...and to the receiver at the far end.", "start": 3088.42, "stop": 3092.36, "id": 941}, {"text": " Assuming isotropic...", "start": 3093.14, "stop": 3093.92, "id": 942}, {"text": " I mean, I also used isotropic antennas to handle anything.", "start": 3093.92, "stop": 3096.24, "id": 943}, {"text": " You know, it really doesn't matter because...", "start": 3096.68, "stop": 3100.18, "id": 944}, {"text": " Well, I'll show you something in a moment.", "start": 3100.18, "stop": 3101.34, "id": 945}, {"text": " And then how to do routing...", "start": 3101.84, "stop": 3103.68, "id": 946}, {"text": " Actually, Phil Carnes' paper in 1991 mentions minimum energy routing... ...and", "start": 3104.7599999999998, "stop": 3109.14, "id": 947}, {"text": " credits it to Dave Mills, who's on the faculty at Maryland.", "start": 3109.14, "stop": 3111.48, "id": 948}, {"text": " And Dave Mills got this intuition from thinking about a whole bunch of", "start": 3112.82, "stop": 3115.9, "id": 949}, {"text": " satellites... ...that are trying to form a network and communicate.", "start": 3115.9, "stop": 3118.54, "id": 950}, {"text": " And that minimum energy routing is the right thing to do.", "start": 3119.96, "stop": 3121.76, "id": 951}, {"text": " And so that's what I started with.", "start": 3122.66, "stop": 3125.4, "id": 952}, {"text": " When I started sort of trying to design this system through... ...I", "start": 3126.32, "stop": 3130.24, "id": 953}, {"text": " thought, well, this is what I'm going to use for", "start": 3130.24, "stop": 3131.76, "id": 954}, {"text": " now... ...but there's probably something more optimum.", "start": 3131.76, "stop": 3133.56, "id": 955}, {"text": " And when I get to the end, I'll try to find... ...figure out what's better.", "start": 3134.26, "stop": 3136.7, "id": 956}, {"text": " And I'll get to that towards the end of the talk.", "start": 3137.3, "stop": 3139.2, "id": 957}, {"text": " But this is sort of a whole picture of what I'm expecting to do.", "start": 3139.64, "stop": 3143.96, "id": 958}, {"text": " Now, I'm going to talk about... ...avoid remaining collisions by scheduling", "start": 3144.04, "stop": 3147.98, "id": 959}, {"text": " and how that works.", "start": 3147.98, "stop": 3149.7, "id": 960}, {"text": " And this is how I do it.", "start": 3150.46, "stop": 3151.72, "id": 961}, {"text": " Before I tell you how I do it, though... ...you can open, like, the Burt Segges", "start": 3154.16, "stop": 3158.38, "id": 962}, {"text": " and Gallagher textbook... ...and turn to the chapter or section on packet radio", "start": 3158.38, "stop": 3162.02, "id": 963}, {"text": " networks... ...and it explains what a packet radio network is.", "start": 3162.02, "stop": 3164.1, "id": 964}, {"text": " I think it only goes through about three or four pages on packet radio networks.", "start": 3164.2, "stop": 3167.48, "id": 965}, {"text": " But it talks about the problem of collisions.", "start": 3167.56, "stop": 3169.1, "id": 966}, {"text": " And that the way you solve this is you figure out which nodes can hear each", "start": 3169.66, "stop": 3173.04, "id": 967}, {"text": " other... ...and guarantee that, you know, at any receiver only one transmitter", "start": 3173.04, "stop": 3177.6, "id": 968}, {"text": " is transmitting.", "start": 3177.6, "stop": 3180.04, "id": 969}, {"text": " You know, at the intended receiver, that receiver can only hear... ...the", "start": 3180.72, "stop": 3183.5, "id": 970}, {"text": " one transmitter that's sending to it.", "start": 3183.5, "stop": 3185.04, "id": 971}, {"text": " And all of...you know, you don't have any other adjacent nodes in the network.", "start": 3185.04, "stop": 3188.6, "id": 972}, {"text": " And that the way you solve that problem", "start": 3189.08, "stop": 3190.54, "id": 973}, {"text": " is you have synchronized clocks everywhere.", "start": 3190.54, "stop": 3192.38, "id": 974}, {"text": " You figure out what the topology is... ...and you come up with a master schedule", "start": 3192.5, "stop": 3195.26, "id": 975}, {"text": " that just repeats every once in a while... ...that everybody sticks to", "start": 3195.26, "stop": 3197.8, "id": 976}, {"text": " that says who can send to who when.", "start": 3197.8, "stop": 3199.46, "id": 977}, {"text": " And...I mean, I have a few problems with that.", "start": 3203.46, "stop": 3205.6, "id": 978}, {"text": " One is the idea that propagation is... ...you can view the whole thing as a", "start": 3205.68, "stop": 3209.04, "id": 979}, {"text": " node and edges sort of situation.", "start": 3209.04, "stop": 3210.54, "id": 980}, {"text": " I mean, it's more complicated than that.", "start": 3210.86, "stop": 3212.42, "id": 981}, {"text": " But the real problem is, is there are a million stations out", "start": 3213.9399999999996, "stop": 3216.72, "id": 982}, {"text": " there... ...do you ever think we can get them all synchronized?", "start": 3216.72, "stop": 3218.3, "id": 983}, {"text": " And even if we could get them all synchronized... ...do you think we could do the", "start": 3218.98, "stop": 3221.64, "id": 984}, {"text": " computation to figure out what the master schedule", "start": 3221.64, "stop": 3224.12, "id": 985}, {"text": " is... ...and get it out to everybody?", "start": 3224.12, "stop": 3225.88, "id": 986}, {"text": " What I want is I want... ...I'd rather not have the system", "start": 3226.5, "stop": 3230.74, "id": 987}, {"text": " depend on GPS continuing to work.", "start": 3230.74, "stop": 3232.56, "id": 988}, {"text": " So...that's the GPS problem.", "start": 3234.3, "stop": 3235.78, "id": 989}, {"text": " So even if we could get them synchronized... ...I still don't have much", "start": 3236.04, "stop": 3239.1, "id": 990}, {"text": " confidence in being able to get a master schedule out to everybody.", "start": 3239.1, "stop": 3241.3, "id": 991}, {"text": " And these master schedules have the property that... ...the fact that", "start": 3241.3, "stop": 3245.98, "id": 992}, {"text": " connectivity has changed 30 hops away from you... ...affects everybody and then", "start": 3245.98, "stop": 3250.94, "id": 993}, {"text": " all the constraints keep propagating... ...and you wind up having to change the", "start": 3250.94, "stop": 3253.74, "id": 994}, {"text": " schedule globally for every little change.", "start": 3253.74, "stop": 3255.32, "id": 995}, {"text": " And people have tried to tackle that, but I wanted something simpler.", "start": 3255.9, "stop": 3259.08, "id": 996}, {"text": " How do people do that type of schedule?", "start": 3259.94, "stop": 3261.5, "id": 997}, {"text": " I'm busy now, I'll come back in an hour.", "start": 3262.62, "stop": 3264.26, "id": 998}, {"text": " That's kind of what I was thinking about.", "start": 3264.54, "stop": 3265.76, "id": 999}, {"text": " Yeah.", "start": 3266.72, "stop": 3267.16, "id": 1000}, {"text": " Well, I'll tell you what I came up with.", "start": 3268.6, "stop": 3271.16, "id": 1001}, {"text": " It wasn't the slide I expected.", "start": 3273.3799999999997, "stop": 3275.08, "id": 1002}, {"text": " I thought I had another slide here.", "start": 3277.56, "stop": 3279.4, "id": 1003}, {"text": " Maybe...no, this is the one.", "start": 3281.9, "stop": 3282.82, "id": 1004}, {"text": " Every station generates a pseudo-random schedule of... ...when it will transmit", "start": 3286.46, "stop": 3292.98, "id": 1005}, {"text": " and when it will receive... ...off into the future.", "start": 3292.98, "stop": 3297.42, "id": 1006}, {"text": " No, no. I now...I lay down.", "start": 3301.84, "stop": 3303.9, "id": 1007}, {"text": " At this time I will be transmitting, at this time I will be listening, at this", "start": 3304.92, "stop": 3308.56, "id": 1008}, {"text": " time I will be transmitting, at this time I will be listening.", "start": 3308.56, "stop": 3310.22, "id": 1009}, {"text": " But you make it pseudo-random.", "start": 3311.0, "stop": 3312.12, "id": 1010}, {"text": " The reason you make it pseudo-random is if I just said, okay, during odd seconds", "start": 3312.58, "stop": 3316.48, "id": 1011}, {"text": " I will transmit... ...and during even seconds I will receive... ...then you have", "start": 3316.48, "stop": 3320.94, "id": 1012}, {"text": " the problem that somebody next to me can do that... ...then you have the problem", "start": 3320.94, "stop": 3324.62, "id": 1013}, {"text": " that you have eight type A stations and type", "start": 3324.62, "stop": 3326.48, "id": 1014}, {"text": " B stations and not everybody can talk to everybody.", "start": 3326.48, "stop": 3328.04, "id": 1015}, {"text": " If they're making them pseudo-random, then everybody...then there will", "start": 3328.48, "stop": 3332.14, "id": 1016}, {"text": " be a chance in the future.", "start": 3332.14, "stop": 3333.74, "id": 1017}, {"text": " You know, for any pair of stations there will be", "start": 3334.2, "stop": 3335.86, "id": 1018}, {"text": " times when they can each talk to each other.", "start": 3335.86, "stop": 3337.38, "id": 1019}, {"text": " Well, there will be times.", "start": 3345.22, "stop": 3346.68, "id": 1020}, {"text": " So, you do a pseudo-random schedule off into the future.", "start": 3347.18, "stop": 3352.46, "id": 1021}, {"text": " I do a pseudo-random schedule off into the future.", "start": 3352.96, "stop": 3355.18, "id": 1022}, {"text": " There will be times when your schedule and my", "start": 3355.54, "stop": 3357.36, "id": 1023}, {"text": " schedule says you transmit, I transmit.", "start": 3357.36, "stop": 3358.92, "id": 1024}, {"text": " And there will be times in the future where it says you receive, I receive.", "start": 3359.18, "stop": 3361.7, "id": 1025}, {"text": " But there will be other times when it says you transmit, I receive.", "start": 3361.8, "stop": 3363.82, "id": 1026}, {"text": " And there will be other times when it says vice versa.", "start": 3363.92, "stop": 3365.48, "id": 1027}, {"text": " You accept that there are going to be conflicts in those pseudo-rands.", "start": 3366.4, "stop": 3369.66, "id": 1028}, {"text": " Right. There will be times when I cannot transmit to you.", "start": 3369.76, "stop": 3372.26, "id": 1029}, {"text": " There will be times when neither of us can talk to each other.", "start": 3372.72, "stop": 3375.18, "id": 1030}, {"text": " All these cases know that neither is scheduled.", "start": 3375.28, "stop": 3377.26, "id": 1031}, {"text": " Right. And so what you do...", "start": 3378.44, "stop": 3379.46, "id": 1032}, {"text": " And all you need to do is get this schedule to the neighbor", "start": 3379.46, "stop": 3383.58, "id": 1033}, {"text": " that you want to communicate with directly.", "start": 3383.58, "stop": 3385.26, "id": 1034}, {"text": " And by doing it this way, that has no impact on, you know, if I hand you a", "start": 3386.22, "stop": 3390.48, "id": 1035}, {"text": " schedule and you hand me my schedule.", "start": 3390.48, "stop": 3392.24, "id": 1036}, {"text": " So now we've had an interaction and now we can talk to each other.", "start": 3392.86, "stop": 3395.7, "id": 1037}, {"text": " And what we've done to arrange to talk to each other has no impact on your", "start": 3396.26, "stop": 3401.04, "id": 1038}, {"text": " negotiations with somebody else.", "start": 3401.04, "stop": 3403.18, "id": 1039}, {"text": " In fact, there's no negotiations. You just", "start": 3403.3, "stop": 3404.86, "id": 1040}, {"text": " tell your neighbor what your schedule is.", "start": 3404.86, "stop": 3406.38, "id": 1041}, {"text": " Oh, you have to transmit.", "start": 3406.38, "stop": 3407.82, "id": 1042}, {"text": " [...]", "start": 3409.44, "stop": 3409.88, "id": 1043}, {"text": " You only have to transmit three.", "start": 3410.28, "stop": 3411.6, "id": 1044}, {"text": " Well, yes. I'll get to that. Two more slides.", "start": 3411.76, "stop": 3415.24, "id": 1045}, {"text": " So I have a picture. Now, I don't...", "start": 3415.8, "stop": 3418.54, "id": 1046}, {"text": " I'm not even assuming that we have slot times synchronized.", "start": 3418.54, "stop": 3422.7, "id": 1047}, {"text": " You may think your watch may have the seconds starting... 300 milliseconds after", "start": 3423.64, "stop": 3428.5, "id": 1048}, {"text": " my watch. That's okay.", "start": 3428.5, "stop": 3430.42, "id": 1049}, {"text": " As long as when I communicate the schedule to you, you understand on", "start": 3431.46, "stop": 3434.5, "id": 1050}, {"text": " what time base I'm getting that on.", "start": 3434.5, "stop": 3436.06, "id": 1051}, {"text": " And then you can reckon it by your time base and figure", "start": 3436.06, "stop": 3438.82, "id": 1052}, {"text": " out where the opportunities are.", "start": 3438.82, "stop": 3440.32, "id": 1053}, {"text": " So here's a bunch of schedules and actually it's a little small,", "start": 3440.76, "stop": 3444.5, "id": 1054}, {"text": " but they're not synchronized.", "start": 3444.78, "stop": 3447.14, "id": 1055}, {"text": " But if you want to send a packet, you can find a spot.", "start": 3448.66, "stop": 3451.88, "id": 1056}, {"text": " You might have to wait a while, you know, but you'll be able to find a spot.", "start": 3453.2, "stop": 3459.1, "id": 1057}, {"text": " What are the ramifications on real time?", "start": 3459.92, "stop": 3462.94, "id": 1058}, {"text": " Delay. At the very end, I'll plug in some numbers.", "start": 3462.94, "stop": 3466.28, "id": 1059}, {"text": " The thesis has some formulas you can like plug in your own parameters for a", "start": 3467.64, "stop": 3471.12, "id": 1060}, {"text": " system and figure out what the delays are.", "start": 3471.12, "stop": 3472.62, "id": 1061}, {"text": " I'll plug in... I'll show you some results of plugged in numbers at the end.", "start": 3473.2, "stop": 3475.94, "id": 1062}, {"text": " So that's the pseudo random scheduling method.", "start": 3477.52, "stop": 3479.44, "id": 1063}, {"text": " Everybody generates a random schedule and just hands that.", "start": 3479.86, "stop": 3483.66, "id": 1064}, {"text": " Now, the implementation trick for that is all stations use the same schedule.", "start": 3483.8, "stop": 3488.48, "id": 1065}, {"text": " But everybody sets their clock to a random value when they turn on.", "start": 3490.02, "stop": 3493.52, "id": 1066}, {"text": " Now, you may be concerned about...", "start": 3494.16, "stop": 3495.48, "id": 1067}, {"text": " And then all you have to do is hand what your clock is to your neighbor.", "start": 3496.34, "stop": 3500.1, "id": 1068}, {"text": " And now you know what the offset is to what time your neighbor thinks it is.", "start": 3500.3, "stop": 3503.94, "id": 1069}, {"text": " And you remember that and then you can tell what the schedule is.", "start": 3505.8399999999997, "stop": 3508.62, "id": 1070}, {"text": " And maybe your clocks run at slightly different rates.", "start": 3508.7, "stop": 3511.28, "id": 1071}, {"text": " Well, that's something you can model as well.", "start": 3511.38, "stop": 3513.06, "id": 1072}, {"text": " If my clock's running faster and I've swapped time with you a few times,", "start": 3513.7, "stop": 3516.74, "id": 1073}, {"text": " then you can actually set a line to that.", "start": 3516.74, "stop": 3518.3, "id": 1074}, {"text": " And maybe your crystal's aging at a different rate than mine.", "start": 3518.78, "stop": 3520.96, "id": 1075}, {"text": " Well, you subtract those and you get a quadratic.", "start": 3521.2, "stop": 3523.14, "id": 1076}, {"text": " And you put a quadratic to that and then you can get amazing", "start": 3523.18, "stop": 3526.2, "id": 1077}, {"text": " stability that lasts over days maybe.", "start": 3526.2, "stop": 3528.06, "id": 1078}, {"text": " But you don't even need to do that.", "start": 3528.68, "stop": 3529.6, "id": 1079}, {"text": " I mean, or you could just track me.", "start": 3529.68, "stop": 3531.98, "id": 1080}, {"text": " You know, when we re-run these over as we", "start": 3532.1, "stop": 3534.3, "id": 1081}, {"text": " communicate, you can sort of figure out where I'm going.", "start": 3534.3, "stop": 3536.28, "id": 1082}, {"text": " Now, you may be concerned that, well, what if we set our clock to the same value?", "start": 3538.78, "stop": 3544.48, "id": 1083}, {"text": " Well, you can just make enough high order bits in the clock to push the", "start": 3545.2, "stop": 3549.42, "id": 1084}, {"text": " probability of that happening arbitrarily low.", "start": 3549.42, "stop": 3551.92, "id": 1085}, {"text": " If we exchange 64-bit clocks, the chances that we actually, you know, got close", "start": 3552.58, "stop": 3558.48, "id": 1086}, {"text": " enough to worry about overlapping exactly, you know, synchronizing our", "start": 3558.48, "stop": 3563.12, "id": 1087}, {"text": " schedules anytime soon is very low.", "start": 3563.12, "stop": 3564.84, "id": 1088}, {"text": " And all you really care, you don't care about if somebody across town", "start": 3565.18, "stop": 3568.56, "id": 1089}, {"text": " is exactly on your same schedule.", "start": 3568.56, "stop": 3570.28, "id": 1090}, {"text": " That doesn't matter.", "start": 3570.36, "stop": 3570.94, "id": 1091}, {"text": " All that matters is that about the six or so people that you're in direct", "start": 3570.94, "stop": 3573.78, "id": 1092}, {"text": " communication with didn't happen to land on the same schedule.", "start": 3573.78, "stop": 3577.26, "id": 1093}, {"text": " Well, here's the notion.", "start": 3577.72, "stop": 3578.52, "id": 1094}, {"text": " When you initially plug in, maybe you could select clock values of all neighbors", "start": 3579.62, "stop": 3584.8, "id": 1095}, {"text": " you hear and then figure out an appropriate clock", "start": 3584.8, "stop": 3587.74, "id": 1096}, {"text": " value for yourself based on that.", "start": 3587.74, "stop": 3589.38, "id": 1097}, {"text": " Yeah, but then you have the problem somebody else shows up.", "start": 3589.54, "stop": 3591.4, "id": 1098}, {"text": " It's easy just to add bits to the left of the clock.", "start": 3591.6, "stop": 3593.84, "id": 1099}, {"text": " Every new bit you get is only one more bit to hand to your neighbor, but it", "start": 3594.62, "stop": 3598.0, "id": 1100}, {"text": " produces the probability by two.", "start": 3598.0, "stop": 3599.74, "id": 1101}, {"text": " If you [...] in for them, there are a backhand direction on that one.", "start": 3600.16, "stop": 3604.14, "id": 1102}, {"text": " So the reality is everybody wouldn't have a comparison.", "start": 3605.4799999999996, "stop": 3608.2, "id": 1103}, {"text": " You can, it's a birthday paradox sort of thing.", "start": 3609.38, "stop": 3611.7, "id": 1104}, {"text": " You can actually put enough bits at the left so that no two in the world never", "start": 3612.18, "stop": 3615.32, "id": 1105}, {"text": " get close enough to each other, and you could actually make a bet on that.", "start": 3615.32, "stop": 3617.86, "id": 1106}, {"text": " I mean, you can't guarantee, because mathematically it's still possible, that", "start": 3619.22, "stop": 3622.48, "id": 1107}, {"text": " you can actually make the bet.", "start": 3622.48, "stop": 3624.06, "id": 1108}, {"text": " It's like the probabilistic test to test", "start": 3624.14, "stop": 3626.34, "id": 1109}, {"text": " whether a number is prime when they do cryptography.", "start": 3626.34, "stop": 3628.0, "id": 1110}, {"text": " They don't really ever quite prove that you're using a prime number to build your", "start": 3628.0, "stop": 3633.76, "id": 1111}, {"text": " key for RSA encryption.", "start": 3633.76, "stop": 3635.6, "id": 1112}, {"text": " But you can be so sure that, you know, you can be as sure as you like.", "start": 3636.14, "stop": 3641.14, "id": 1113}, {"text": " Just by every time you run the test again, the test runs quickly.", "start": 3641.32, "stop": 3644.84, "id": 1114}, {"text": " So that's the implementation trick.", "start": 3645.12, "stop": 3647.58, "id": 1115}, {"text": " Now, there's a question that is, well, okay, when you generate these pseudo", "start": 3647.94, "stop": 3650.42, "id": 1116}, {"text": "-random schedules, actually I've said everybody's going to use the same schedule.", "start": 3650.42, "stop": 3653.12, "id": 1117}, {"text": " So when we figure out what that one schedule is, what fraction of the slot should", "start": 3653.12, "stop": 3657.7, "id": 1118}, {"text": " be received, and what fraction of the slot should be transmitted?", "start": 3657.7, "stop": 3661.94, "id": 1119}, {"text": " And, well, I think of this as the received duty cycle.", "start": 3664.44, "stop": 3668.6, "id": 1120}, {"text": " What fraction of the slots are received slots?", "start": 3668.7, "stop": 3670.36, "id": 1121}, {"text": " I call that P.", "start": 3670.72, "stop": 3671.9, "id": 1122}, {"text": " And the fraction of time that I can send to a particular neighbor, if it's a good", "start": 3673.02, "stop": 3678.2, "id": 1123}, {"text": " hash function that generates the pseudo-random schedule, then you can think of", "start": 3678.2, "stop": 3681.4, "id": 1124}, {"text": " them as independent events.", "start": 3681.4, "stop": 3682.92, "id": 1125}, {"text": " And so you can do this sort of simple probabilistic analysis.", "start": 3683.26, "stop": 3685.66, "id": 1126}, {"text": " So the fraction of time you can send to a particular neighbor is the probability", "start": 3686.18, "stop": 3691.72, "id": 1127}, {"text": " that your neighbor is listening, which is P, the chance that it's a received", "start": 3691.72, "stop": 3696.16, "id": 1128}, {"text": " duty cycle, at any given moment.", "start": 3696.16, "stop": 3697.76, "id": 1129}, {"text": " And the probability that you're in a transmit slot, which is 1 minus P.", "start": 3699.6, "stop": 3705.6, "id": 1130}, {"text": " You multiply those two together.", "start": 3707.14, "stop": 3708.44, "id": 1131}, {"text": " And then there's actually a formula, skipping over some algebra.", "start": 3709.2599999999998, "stop": 3714.52, "id": 1132}, {"text": " So you can say, well, what fraction of the time is it", "start": 3715.04, "stop": 3718.94, "id": 1133}, {"text": " possible to send to a neighbor?", "start": 3718.94, "stop": 3720.54, "id": 1134}, {"text": " Assume you have traffic for all your neighbors, and you want to know, well, how", "start": 3720.94, "stop": 3725.06, "id": 1135}, {"text": " much can I keep my transmitter going?", "start": 3725.06, "stop": 3728.94, "id": 1136}, {"text": " And that's the formula here.", "start": 3730.3, "stop": 3731.84, "id": 1137}, {"text": " And it's basically, the fraction of time you can spend transmitting to your", "start": 3731.98, "stop": 3734.98, "id": 1138}, {"text": " neighbors is the fraction of time that your schedule says you can transmit, minus", "start": 3734.98, "stop": 3740.68, "id": 1139}, {"text": " the probability that you're a transmitter, that your schedule says transmit,", "start": 3740.68, "stop": 3747.2, "id": 1140}, {"text": " and everybody else's schedule says transmit.", "start": 3747.5, "stop": 3749.76, "id": 1141}, {"text": " And that's why it's K plus 1 for K neighbors.", "start": 3750.02, "stop": 3752.2, "id": 1142}, {"text": " And so what I've got on the next chart is a plot of this for various values of K.", "start": 3754.28, "stop": 3760.9, "id": 1143}, {"text": " This is the fraction of time you can spend sending to a neighbor for received", "start": 3763.48, "stop": 3769.72, "id": 1144}, {"text": " duty cycles from 0 all the way to 1.", "start": 3769.72, "stop": 3772.28, "id": 1145}, {"text": " And if you only have one neighbor, then the best value to pick is", "start": 3774.7999999999997, "stop": 3778.92, "id": 1146}, {"text": " 50% received duty cycle.", "start": 3778.92, "stop": 3780.54, "id": 1147}, {"text": " And that means the fraction of time you can send to him is 1 fourth, and the", "start": 3781.04, "stop": 3784.74, "id": 1148}, {"text": " fraction of time that he can send to you is also 1 fourth.", "start": 3784.74, "stop": 3787.18, "id": 1149}, {"text": " If you have two neighbors, you get a curve that looks like this.", "start": 3788.5799999999995, "stop": 3791.7, "id": 1150}, {"text": " This is the fraction of time that you can send to, it's the or of the two.", "start": 3792.14, "stop": 3795.82, "id": 1151}, {"text": " When can I send to this neighbor, and when can I send to that neighbor?", "start": 3795.94, "stop": 3798.14, "id": 1152}, {"text": " When can I send to either of them?", "start": 3798.26, "stop": 3799.76, "id": 1153}, {"text": " You know, is at least one or both listening.", "start": 3800.64, "stop": 3802.98, "id": 1154}, {"text": " And that's this curve.", "start": 3803.52, "stop": 3804.44, "id": 1155}, {"text": " When you go to three, you get this curve.", "start": 3804.82, "stop": 3806.24, "id": 1156}, {"text": " When you go to four, you get this curve.", "start": 3806.36, "stop": 3808.16, "id": 1157}, {"text": " And the top curve there is 20, but it kind of turns into a", "start": 3808.9, "stop": 3811.72, "id": 1158}, {"text": " triangle as you go off to many neighbors.", "start": 3811.72, "stop": 3813.34, "id": 1159}, {"text": " And I'm thinking that, you know, it's probably around six neighbors or something.", "start": 3813.34, "stop": 3818.92, "id": 1160}, {"text": " So somewhere in here.", "start": 3819.02, "stop": 3820.22, "id": 1161}, {"text": " Now the observation to make is, well, all we really wanted to do was pick a", "start": 3820.64, "stop": 3824.94, "id": 1162}, {"text": " received duty cycle here, because we're going to have", "start": 3824.94, "stop": 3826.54, "id": 1163}, {"text": " one master schedule for the whole system.", "start": 3826.54, "stop": 3828.2, "id": 1164}, {"text": " And notice that if we pick a value of 0.3, or maybe 0.33 or something, somewhere", "start": 3829.0, "stop": 3834.78, "id": 1165}, {"text": " around right in here, I think what I used in the rest of the", "start": 3834.78, "stop": 3838.22, "id": 1166}, {"text": " simulations is actually 0.3.", "start": 3838.22, "stop": 3839.86, "id": 1167}, {"text": " If you pick 0.3, you can ask, well, how far down are we from", "start": 3839.86, "stop": 3843.88, "id": 1168}, {"text": " the optimum in this case?", "start": 3843.88, "stop": 3845.46, "id": 1169}, {"text": " And we're already up to 20% here, so we're only at about 0.3.", "start": 3845.64, "stop": 3850.34, "id": 1170}, {"text": " So we're only, we're more or less about as good as we could have gotten, even", "start": 3850.9, "stop": 3855.28, "id": 1171}, {"text": " though we're only at 0.3 instead of 0.5.", "start": 3855.28, "stop": 3857.76, "id": 1172}, {"text": " And in the two case, well, we're right here.", "start": 3858.06, "stop": 3860.1, "id": 1173}, {"text": " Well, that's pretty close to the top two.", "start": 3860.22, "stop": 3861.52, "id": 1174}, {"text": " And in the three case, you're pretty close.", "start": 3861.84, "stop": 3863.2, "id": 1175}, {"text": " That's about right here.", "start": 3863.26, "stop": 3863.98, "id": 1176}, {"text": " And the four case, you're pretty right here.", "start": 3864.08, "stop": 3865.22, "id": 1177}, {"text": " And if you have to get around six, you're about the right place.", "start": 3865.56, "stop": 3867.58, "id": 1178}, {"text": " So it doesn't really matter much what you pick down here.", "start": 3868.1, "stop": 3871.18, "id": 1179}, {"text": " Something around 0.3 gets you pretty close to optimal in all the cases.", "start": 3871.3, "stop": 3875.6, "id": 1180}, {"text": " And that's the received duty cycle, and", "start": 3877.1, "stop": 3878.54, "id": 1181}, {"text": " the transmit duty cycle is whatever's left.", "start": 3878.54, "stop": 3880.06, "id": 1182}, {"text": " So you listen about 30% of the time, and you", "start": 3880.8, "stop": 3883.36, "id": 1183}, {"text": " schedule your hand to your neighbors.", "start": 3883.36, "stop": 3885.08, "id": 1184}, {"text": " The schedule of your hand to your neighbors is really a promise of when you're", "start": 3886.2, "stop": 3888.94, "id": 1185}, {"text": " going to be listening, because that's all they really care about.", "start": 3888.94, "stop": 3890.72, "id": 1186}, {"text": " So you have about a third of, or 0.30% of the time slots", "start": 3890.72, "stop": 3896.24, "id": 1187}, {"text": " in the future scheduled as received slots.", "start": 3896.24, "stop": 3897.88, "id": 1188}, {"text": " Now, of course, there's also a notion here of clusters", "start": 3898.52, "stop": 3902.88, "id": 1189}, {"text": " of overlap neighbors, right?", "start": 3902.88, "stop": 3904.42, "id": 1190}, {"text": " You might have six neighbors here, and the next six neighbors", "start": 3905.46, "stop": 3907.9, "id": 1191}, {"text": " here partially overlap, right?", "start": 3907.9, "stop": 3909.66, "id": 1192}, {"text": " Each station has their own view of the net.", "start": 3910.7, "stop": 3912.5, "id": 1193}, {"text": " Right.", "start": 3912.9, "stop": 3913.06, "id": 1194}, {"text": " So...", "start": 3916.9, "stop": 3917.38, "id": 1195}, {"text": " ...perhaps, yes.", "start": 3923.88, "stop": 3924.76, "id": 1196}, {"text": " You may not actually turn your transmitter on unless you actually have something", "start": 3925.66, "stop": 3928.7, "id": 1197}, {"text": " to send, and that depends on the traffic load, and that's sort of a...", "start": 3928.7, "stop": 3931.38, "id": 1198}, {"text": " ...what?", "start": 3935.14, "stop": 3935.38, "id": 1199}, {"text": " Vertical axis is...", "start": 3937.1, "stop": 3938.16, "id": 1200}, {"text": " Is the fraction of time that you can spend transmitting. 100%,", "start": 3938.16, "stop": 3941.66, "id": 1201}, {"text": " 80%, 60%, 40%, 20%.", "start": 3941.66, "stop": 3943.5, "id": 1202}, {"text": " The fraction of time you can spend transmitting and do something useful.", "start": 3944.3199999999997, "stop": 3947.84, "id": 1203}, {"text": " I mean, the fraction of time you can spend transmitting is just a line that runs", "start": 3948.26, "stop": 3950.96, "id": 1204}, {"text": " from this one up to this one.", "start": 3950.96, "stop": 3952.58, "id": 1205}, {"text": " One, you know, one minus P.", "start": 3952.7, "stop": 3955.48, "id": 1206}, {"text": " And that's why there's this limit here.", "start": 3956.48, "stop": 3957.86, "id": 1207}, {"text": " But it's not useful unless you've got at least one neighbor listening, and that's", "start": 3957.92, "stop": 3961.36, "id": 1208}, {"text": " the difference between this line and any particular curve we're on.", "start": 3961.36, "stop": 3963.86, "id": 1209}, {"text": " So, it's actually kind of weird.", "start": 3969.02, "stop": 3970.56, "id": 1210}, {"text": " I'm suggesting that you can spend more than half of the time transmitting", "start": 3970.56, "stop": 3973.5, "id": 1211}, {"text": " and less than half the time listening.", "start": 3973.92, "stop": 3975.44, "id": 1212}, {"text": " More than half of the time...", "start": 3977.14, "stop": 3978.54, "id": 1213}, {"text": " The closer you can get.", "start": 3979.3799999999997, "stop": 3980.52, "id": 1214}, {"text": " Yeah, you can actually...", "start": 3980.78, "stop": 3982.24, "id": 1215}, {"text": " If you have six neighbors, two, three, four, five, six, and at around 3% duty", "start": 3982.24, "stop": 3986.82, "id": 1216}, {"text": " cycle, you can actually have throughputs that are 60% duty cycles.", "start": 3986.82, "stop": 3990.42, "id": 1217}, {"text": " And that's kind of weird.", "start": 3991.0, "stop": 3991.68, "id": 1218}, {"text": " You're spending 60% of the time transmitting and only 40% of the time listening.", "start": 3991.8, "stop": 3995.1, "id": 1219}, {"text": " How can that possibly be?", "start": 3995.3, "stop": 3996.5, "id": 1220}, {"text": " Remember I said multiple of these spreading channels.", "start": 3997.02, "stop": 3998.88, "id": 1221}, {"text": " When you're sending, you're only sending one packet.", "start": 3999.52, "stop": 4001.8, "id": 1222}, {"text": " But when you're listening, you might be capturing multiple at a time.", "start": 4004.12, "stop": 4007.46, "id": 1223}, {"text": " That's similar to one of the things that a few years ago", "start": 4007.66, "stop": 4010.34, "id": 1224}, {"text": " was someone was proposing having that.", "start": 4010.34, "stop": 4012.1, "id": 1225}, {"text": " In case of your router.", "start": 4012.46, "stop": 4013.14, "id": 1226}, {"text": " And having one transmitter and multiple receivers.", "start": 4014.22, "stop": 4017.56, "id": 1227}, {"text": " That was it.", "start": 4018.8399999999997, "stop": 4019.92, "id": 1228}, {"text": " That was it.", "start": 4020.8, "stop": 4020.88, "id": 1229}, {"text": " I don't know what they called it.", "start": 4020.88, "stop": 4021.56, "id": 1230}, {"text": " I'll put the transport on.", "start": 4022.0, "stop": 4022.9, "id": 1231}, {"text": " [...]", "start": 4023.48, "stop": 4023.7, "id": 1232}, {"text": " We'll have to roll area.", "start": 4023.8, "stop": 4024.5, "id": 1233}, {"text": " Yeah.", "start": 4025.26, "stop": 4025.7, "id": 1234}, {"text": " Yeah, that's it.", "start": 4026.02, "stop": 4026.78, "id": 1235}, {"text": " What year was that?", "start": 4026.78, "stop": 4027.54, "id": 1236}, {"text": " I haven't seen that.", "start": 4027.54, "stop": 4028.48, "id": 1237}, {"text": " [...]", "start": 4028.64, "stop": 4028.82, "id": 1238}, {"text": " I just, at Dayton, I bought the whole proceedings for everything", "start": 4031.66, "stop": 4036.04, "id": 1239}, {"text": " from back to the first ECC.", "start": 4036.04, "stop": 4037.62, "id": 1240}, {"text": " And I didn't get up to that far.", "start": 4038.14, "stop": 4040.16, "id": 1241}, {"text": " I've only looked at the first five years.", "start": 4040.3, "stop": 4042.02, "id": 1242}, {"text": " We actually built a radio.", "start": 4043.16, "stop": 4044.64, "id": 1243}, {"text": " In fact, the Naval Research Lab actually built a network similar to that, using", "start": 4046.0, "stop": 4051.18, "id": 1244}, {"text": " 21 a bit per second.", "start": 4051.18, "stop": 4053.08, "id": 1245}, {"text": " [...] I think the channel went UHF tax that and on HF.", "start": 4053.08, "stop": 4057.46, "id": 1246}, {"text": " And they actually were doing that low rate of voice at like", "start": 4058.8, "stop": 4063.5, "id": 1247}, {"text": " 400 or 600 bits per second.", "start": 4063.5, "stop": 4065.46, "id": 1248}, {"text": " Was it a single channel?", "start": 4065.46, "stop": 4066.38, "id": 1249}, {"text": " [...]", "start": 4066.6, "stop": 4067.0, "id": 1250}, {"text": " It was a...", "start": 4067.42, "stop": 4067.96, "id": 1251}, {"text": " Single channel system?", "start": 4067.96, "stop": 4068.76, "id": 1252}, {"text": " Multiple, yeah.", "start": 4070.06, "stop": 4070.4, "id": 1253}, {"text": " Multiple, it was, each station had one transmitter.", "start": 4070.62, "stop": 4073.68, "id": 1254}, {"text": " It was on the air continuously.", "start": 4074.22, "stop": 4075.32, "id": 1255}, {"text": " It had like a router and you had multiple receivers feeding it in.", "start": 4076.24, "stop": 4079.68, "id": 1256}, {"text": " Must have been a multiple channel system.", "start": 4079.74, "stop": 4081.2, "id": 1257}, {"text": " [...] throughput system.", "start": 4081.2, "stop": 4082.5, "id": 1258}, {"text": " Yeah, that's a different, that's a whole different design place.", "start": 4083.46, "stop": 4086.54, "id": 1259}, {"text": " But it's not still because of what we're using", "start": 4086.86, "stop": 4088.74, "id": 1260}, {"text": " in current division instead of frequency.", "start": 4088.74, "stop": 4090.26, "id": 1261}, {"text": " [...]", "start": 4090.78, "stop": 4091.1, "id": 1262}, {"text": " I'll have to think about that.", "start": 4092.8, "stop": 4094.1, "id": 1263}, {"text": " It's actually, I think it's equivalent.", "start": 4095.22, "stop": 4097.24, "id": 1264}, {"text": " So...", "start": 4101.46, "stop": 4101.94, "id": 1265}, {"text": " So...", "start": 4103.580000000001, "stop": 4104.06, "id": 1266}, {"text": " Let's return to this side briefly.", "start": 4104.860000000001, "stop": 4106.46, "id": 1267}, {"text": " I sort of told you, I hope a little bit more of this is...", "start": 4106.72, "stop": 4110.0, "id": 1268}, {"text": " Avoid remaining collisions by scheduling.", "start": 4111.4800000000005, "stop": 4114.38, "id": 1269}, {"text": " I just told you about the collision, the scheduling method.", "start": 4114.5, "stop": 4116.48, "id": 1270}, {"text": " And I'm going to hand wave the rest of these issues", "start": 4117.52, "stop": 4119.74, "id": 1271}, {"text": " and start showing you simulation results.", "start": 4119.74, "stop": 4121.38, "id": 1272}, {"text": " I sort of wrote an ad hoc special purpose simulator to simulate the noise levels", "start": 4122.18, "stop": 4128.06, "id": 1273}, {"text": " or power levels in this kind of system.", "start": 4128.06, "stop": 4130.08, "id": 1274}, {"text": " And...", "start": 4132.280000000001, "stop": 4132.76, "id": 1275}, {"text": " I wanted to see if, you know, doing the scheduling method and with a whole bunch", "start": 4133.34, "stop": 4138.92, "id": 1276}, {"text": " of stations and actually compute routes and actually send packets around whether", "start": 4138.92, "stop": 4142.76, "id": 1277}, {"text": " my signal to noise ratio analysis actually works when you", "start": 4142.76, "stop": 4146.12, "id": 1278}, {"text": " actually have real stations out there.", "start": 4146.12, "stop": 4147.62, "id": 1279}, {"text": " So it's sort of a power level simulator.", "start": 4147.94, "stop": 4149.46, "id": 1280}, {"text": " It simulates the transfer of packets and transmitter power levels and actually", "start": 4149.64, "stop": 4154.14, "id": 1281}, {"text": " records at the receiver, you know, the power contribution by that transmitter.", "start": 4154.14, "stop": 4158.48, "id": 1282}, {"text": " And then when the transmitter shuts off, it goes to the receiver and subtracts", "start": 4158.6, "stop": 4160.94, "id": 1283}, {"text": " out its contribution to the noise without receiver.", "start": 4160.94, "stop": 4163.02, "id": 1284}, {"text": " So at every receiver as a function of time, I've got what is the received total", "start": 4163.02, "stop": 4169.52, "id": 1285}, {"text": " power level in the channel.", "start": 4169.52, "stop": 4171.62, "id": 1286}, {"text": " Sort of before, you know, somebody asked Matt yesterday in his talk, do you mean", "start": 4171.9, "stop": 4175.26, "id": 1287}, {"text": " like a received signal strength indicator?", "start": 4175.26, "stop": 4177.34, "id": 1288}, {"text": " Well, it'd be like sort of the before de-spreading received signal strength", "start": 4177.52, "stop": 4180.56, "id": 1289}, {"text": " indicator is what I computed.", "start": 4180.56, "stop": 4182.24, "id": 1290}, {"text": " And then if you want to signal the noise ratio for a given transfer, this", "start": 4182.4, "stop": 4185.98, "id": 1291}, {"text": " barrier, you know, this summation, this sort of add in and then subtract out that", "start": 4185.98, "stop": 4190.14, "id": 1292}, {"text": " it is the station is sort of the total power.", "start": 4190.14, "stop": 4192.4, "id": 1293}, {"text": " And if you want to signal to noise ratio, you have to again subtract out your own", "start": 4192.4, "stop": 4195.18, "id": 1294}, {"text": " signal level because what, if you just take the signal level to that, you", "start": 4195.18, "stop": 4198.12, "id": 1295}, {"text": " get the signal to signal plus noise ratio.", "start": 4198.12, "stop": 4199.68, "id": 1296}, {"text": " So I place stations randomly in a square by just picking two", "start": 4202.160000000001, "stop": 4205.84, "id": 1297}, {"text": " random numbers from the random number generator.", "start": 4205.84, "stop": 4207.46, "id": 1298}, {"text": " I computed minimum energy routes.", "start": 4207.64, "stop": 4210.3, "id": 1299}, {"text": " And what I've drawn on this picture are all the single hops", "start": 4211.68, "stop": 4214.82, "id": 1300}, {"text": " that any of the minimum energy routes use.", "start": 4214.82, "stop": 4216.4, "id": 1301}, {"text": " Now minimum energy routes have the property that if you have a route from B to C,", "start": 4217.0, "stop": 4221.38, "id": 1302}, {"text": " and the route from A to C goes through B, then the end of that route, once you", "start": 4223.18, "stop": 4228.44, "id": 1303}, {"text": " get to B, is the same as the route from B to C.", "start": 4228.44, "stop": 4230.52, "id": 1304}, {"text": " It's got to be that way.", "start": 4231.820000000001, "stop": 4233.26, "id": 1305}, {"text": " So you can sort of think about, you know, so all you need to remember, minimum", "start": 4234.360000000001, "stop": 4239.44, "id": 1306}, {"text": " energy routes, all you need to remember at any station is how to get there.", "start": 4239.44, "stop": 4242.02, "id": 1307}, {"text": " And then when the packet shows up, that's the way you send it.", "start": 4242.12, "stop": 4244.6, "id": 1308}, {"text": " You don't have to send it a different route depending on where it came", "start": 4244.6, "stop": 4247.24, "id": 1309}, {"text": " from, minimum energy route.", "start": 4247.24, "stop": 4249.14, "id": 1310}, {"text": " So I compute the routes, put a routing table at each station,", "start": 4249.28, "stop": 4252.78, "id": 1311}, {"text": " and then started playing with the simulator.", "start": 4253.34, "stop": 4255.18, "id": 1312}, {"text": " As I said, the length, the edges on this diagram between the random of the", "start": 4257.1, "stop": 4261.56, "id": 1313}, {"text": " playstations show where the", "start": 4261.56, "stop": 4263.06, "id": 1314}, {"text": " single hops are that are used by any route.", "start": 4263.06, "stop": 4268.94, "id": 1315}, {"text": " So I stared at some of these pictures, didn't really learn anything.", "start": 4270.48, "stop": 4274.26, "id": 1316}, {"text": " Are you thinking of it in context of like a metropolitan area network?", "start": 4275.58, "stop": 4279.4, "id": 1317}, {"text": " Absolutely, it was like about a million stations.", "start": 4279.52, "stop": 4281.16, "id": 1318}, {"text": " There's a hundred in this picture.", "start": 4282.04, "stop": 4283.14, "id": 1319}, {"text": " I'll get to a thousand in a minute.", "start": 4285.04, "stop": 4286.48, "id": 1320}, {"text": " I would imagine these are traditional methods for bridging that metropolitan", "start": 4287.88, "stop": 4293.2, "id": 1321}, {"text": " area network into a light area network.", "start": 4293.2, "stop": 4294.98, "id": 1322}, {"text": " Well, you'll have to have some probably...", "start": 4295.660000000001, "stop": 4297.48, "id": 1323}, {"text": " That's going to be a collapse back on there.", "start": 4297.48, "stop": 4299.12, "id": 1324}, {"text": " Yeah, absolutely. Fiber, you know, some long-distance provider that you'll pay", "start": 4299.76, "stop": 4303.04, "id": 1325}, {"text": " for service from to get somewhere.", "start": 4303.04, "stop": 4304.6, "id": 1326}, {"text": " Could you go back one price?", "start": 4304.74, "stop": 4305.58, "id": 1327}, {"text": " That was the diagram of the...", "start": 4307.000000000001, "stop": 4309.98, "id": 1328}, {"text": " Like, for example, what I'm looking at is the node right here, the center, the", "start": 4310.88, "stop": 4314.72, "id": 1329}, {"text": " 55, the [...] that guy.", "start": 4314.72, "stop": 4317.02, "id": 1330}, {"text": " Now, if everybody wants to talk to everybody equally, don't you have an infinite", "start": 4317.54, "stop": 4320.74, "id": 1331}, {"text": " amount of traffic going through every node?", "start": 4320.74, "stop": 4322.58, "id": 1332}, {"text": " Infinite going through?", "start": 4324.18, "stop": 4325.18, "id": 1333}, {"text": " I'll get to that.", "start": 4326.300000000001, "stop": 4327.44, "id": 1334}, {"text": " Actually, I'll get to that in a thousand stations.", "start": 4328.4800000000005, "stop": 4330.16, "id": 1335}, {"text": " There's actually more discussion about that", "start": 4331.22, "stop": 4332.7, "id": 1336}, {"text": " in the thesis I'm probably not going to get into.", "start": 4332.7, "stop": 4334.2, "id": 1337}, {"text": " You're worrying about exactly the right thing and...", "start": 4338.56, "stop": 4342.36, "id": 1338}, {"text": " I'm very excited.", "start": 4342.36, "stop": 4343.26, "id": 1339}, {"text": " And when I started looking at the simulation results, exactly what you're worried", "start": 4343.48, "stop": 4346.84, "id": 1340}, {"text": " about was in fact a problem, and", "start": 4346.84, "stop": 4349.08, "id": 1341}, {"text": " I haven't completely figured out how to solve it yet.", "start": 4349.08, "stop": 4350.68, "id": 1342}, {"text": " So you're on the right track.", "start": 4351.08, "stop": 4352.0, "id": 1343}, {"text": " The ball I'm posting is my neighbor's. You got a fantastic system.", "start": 4352.0, "stop": 4355.02, "id": 1344}, {"text": " Well, I'll wave my hands at the end of the talk.", "start": 4355.9, "stop": 4357.86, "id": 1345}, {"text": " I was going to...maybe it may relate to the same question.", "start": 4358.14, "stop": 4360.12, "id": 1346}, {"text": " I was going to want to...did you look at, say, varying the mix of", "start": 4360.36, "stop": 4364.1, "id": 1347}, {"text": " unicast versus multicast traffic?", "start": 4364.1, "stop": 4366.18, "id": 1348}, {"text": " I have...I have...", "start": 4366.44, "stop": 4368.0, "id": 1349}, {"text": " I forget what...", "start": 4368.0, "stop": 4370.0, "id": 1350}, {"text": " I'm going to read you the last sentence in the last", "start": 4373.14, "stop": 4375.24, "id": 1351}, {"text": " chapter of my thesis, or the last two.", "start": 4375.24, "stop": 4376.92, "id": 1352}, {"text": " Just a...", "start": 4379.88, "stop": 4380.72, "id": 1353}, {"text": " That's the question I was wondering whether multicast and...the", "start": 4380.72, "stop": 4383.68, "id": 1354}, {"text": " minimum range of routing still...", "start": 4383.68, "stop": 4385.56, "id": 1355}, {"text": " The last sentence was... ...still the optimal range of routing.", "start": 4385.56, "stop": 4388.38, "id": 1356}, {"text": " You know, where I ended my thesis was I said, after talking about a whole bunch", "start": 4388.38, "stop": 4391.64, "id": 1357}, {"text": " of issues, I said, these questions, these questions again depend on routing and", "start": 4391.64, "stop": 4396.02, "id": 1358}, {"text": " demand for service, questions that are difficult to determine before real users", "start": 4396.02, "stop": 4399.38, "id": 1359}, {"text": " are involved in the generation of traffic.", "start": 4399.38, "stop": 4401.08, "id": 1360}, {"text": " I don't know.", "start": 4402.12, "stop": 4402.72, "id": 1361}, {"text": " But I'll wave my hands at another picture that might actually", "start": 4405.6, "stop": 4408.52, "id": 1362}, {"text": " be able to get you excited.", "start": 4408.52, "stop": 4410.14, "id": 1363}, {"text": " That's why I wanted to show one of the notion on the", "start": 4410.14, "stop": 4412.2, "id": 1364}, {"text": " table here, and that's a deployment issue.", "start": 4412.2, "stop": 4413.92, "id": 1365}, {"text": " Obviously, there's got to be a consideration for the distance between", "start": 4416.64, "stop": 4420.4, "id": 1366}, {"text": " your initial stations.", "start": 4420.4, "stop": 4422.32, "id": 1367}, {"text": " What's the...you copy a man...", "start": 4422.52, "stop": 4424.14, "id": 1368}, {"text": " Yeah, what is...", "start": 4424.84, "stop": 4425.32, "id": 1369}, {"text": " There's two different... ...fringence of that man.", "start": 4425.32, "stop": 4427.14, "id": 1370}, {"text": " If you only have two stations, how far apart can they can be when you", "start": 4427.18, "stop": 4430.46, "id": 1371}, {"text": " initially put them up, and then you'll fill in.", "start": 4430.46, "stop": 4432.2, "id": 1372}, {"text": " Absolutely.", "start": 4433.34, "stop": 4433.56, "id": 1373}, {"text": " So, I think I said what was on this slide before I put up the last slide.", "start": 4435.68, "stop": 4440.16, "id": 1374}, {"text": " But I explicitly reported the contribution to the noise level at each", "start": 4441.08, "stop": 4443.8, "id": 1375}, {"text": " receiver for each transmission.", "start": 4443.8, "stop": 4445.48, "id": 1376}, {"text": " And I...by record, I mean I added into the total there, and when the", "start": 4448.32, "stop": 4451.52, "id": 1377}, {"text": " transmitter ends, I subtract it out again.", "start": 4451.52, "stop": 4453.28, "id": 1378}, {"text": " So there's a...I've got a variable for each", "start": 4453.78, "stop": 4455.9, "id": 1379}, {"text": " station, which is the current received.", "start": 4455.9, "stop": 4457.48, "id": 1380}, {"text": " There's a vent queue driven for the traffic, so you can simulate, you know...", "start": 4458.14, "stop": 4462.4, "id": 1381}, {"text": " I'm starting to send a packet, and I know the packet", "start": 4463.160000000001, "stop": 4465.46, "id": 1382}, {"text": " is this long, so it's going to...", "start": 4465.46, "stop": 4467.1, "id": 1383}, {"text": " The transmission is going to end at this time in the future.", "start": 4467.1, "stop": 4469.94, "id": 1384}, {"text": " It schedules an event in the event queue, which is a heat priority queue, so it", "start": 4470.16, "stop": 4473.9, "id": 1385}, {"text": " only takes long time to extract an event out of it.", "start": 4473.9, "stop": 4476.52, "id": 1386}, {"text": " It's only logged in the size of the queue, so it's a standard sort of", "start": 4477.08, "stop": 4480.62, "id": 1387}, {"text": " event driven network simulator.", "start": 4480.62, "stop": 4482.14, "id": 1388}, {"text": " And for each...when a station is actually receiving a packet, it's also", "start": 4483.540000000001, "stop": 4489.9, "id": 1389}, {"text": " got something which is taking sort of the max of the noise level, so that you can", "start": 4489.9, "stop": 4495.88, "id": 1390}, {"text": " find the NIV of the signal to noise ratio at the end of the reception of the", "start": 4495.88, "stop": 4499.46, "id": 1391}, {"text": " packet, and record what that was, and decide whether or not", "start": 4499.46, "stop": 4503.06, "id": 1392}, {"text": " that packet reception was successful.", "start": 4503.06, "stop": 4504.64, "id": 1393}, {"text": " Now, in the simulations I'm going to talk about today, I...", "start": 4506.4, "stop": 4510.76, "id": 1394}, {"text": " Do you need to piece that one more time?", "start": 4512.66, "stop": 4514.12, "id": 1395}, {"text": " The simulator has, at every station, a variable which is the current noise total", "start": 4517.9, "stop": 4523.98, "id": 1396}, {"text": " power level coming from all the other stations.", "start": 4523.98, "stop": 4525.76, "id": 1397}, {"text": " Actually, I initialized that variable with the thermal noise level, but I could", "start": 4526.84, "stop": 4529.6, "id": 1398}, {"text": " have initialized it with zero, and I would have gotten the same result", "start": 4529.6, "stop": 4531.84, "id": 1399}, {"text": " in the simulations, because that's far enough away.", "start": 4531.84, "stop": 4534.28, "id": 1400}, {"text": " So, that variable, I'm also...during the reset, while a station is", "start": 4534.28, "stop": 4541.22, "id": 1401}, {"text": " receiving a packet, I record for that packet what the max of this variable", "start": 4541.22, "stop": 4546.12, "id": 1402}, {"text": " was, which is the total power level.", "start": 4546.12, "stop": 4548.36, "id": 1403}, {"text": " So that when the event happens, it marks the end of the reception of a", "start": 4548.58, "stop": 4552.18, "id": 1404}, {"text": " packet in the simulator.", "start": 4552.18, "stop": 4553.7, "id": 1405}, {"text": " I can then go look at what the max noise level was during the reception of this", "start": 4554.28, "stop": 4558.02, "id": 1406}, {"text": " packet, compute the signal level for that packet, and", "start": 4558.02, "stop": 4559.98, "id": 1407}, {"text": " that's the signal to noise ratio for that packet.", "start": 4559.98, "stop": 4561.68, "id": 1408}, {"text": " That's the worst signal to noise ratio experience during", "start": 4563.32, "stop": 4566.24, "id": 1409}, {"text": " the reception time of this packet.", "start": 4566.24, "stop": 4568.66, "id": 1410}, {"text": " Are you going to take that one step further and actually make that variable", "start": 4569.0, "stop": 4573.26, "id": 1411}, {"text": " available in the real production unit, or...", "start": 4573.26, "stop": 4575.68, "id": 1412}, {"text": " Does that sound like a useful thing to do?", "start": 4576.68, "stop": 4578.16, "id": 1413}, {"text": " I don't know. I haven't fully thought", "start": 4578.8, "stop": 4580.86, "id": 1414}, {"text": " about exactly what a real production unit was.", "start": 4580.86, "stop": 4582.4, "id": 1415}, {"text": " This is for the purpose of understanding whether my signal to noise ratio", "start": 4582.42, "stop": 4585.34, "id": 1416}, {"text": " calculations were correct earlier.", "start": 4585.34, "stop": 4587.58, "id": 1417}, {"text": " I have no particular designs, plans to build any particular piece of hardware", "start": 4588.18, "stop": 4592.0, "id": 1418}, {"text": " at this moment, so I would love to build some hardware.", "start": 4592.0, "stop": 4593.6, "id": 1419}, {"text": " Yeah. So, now I call it...there's all sorts of constants.", "start": 4594.8, "stop": 4600.4, "id": 1420}, {"text": " I actually went through the simulator and tried", "start": 4600.56, "stop": 4602.58, "id": 1421}, {"text": " to actually get all the constants right.", "start": 4602.58, "stop": 4604.08, "id": 1422}, {"text": " I assumed isotropic antennas and actually figured out what the propagation", "start": 4604.24, "stop": 4609.18, "id": 1423}, {"text": " is based on isotropic antennas.", "start": 4609.18, "stop": 4610.88, "id": 1424}, {"text": " And so if you put it, you know, have antennas of some, you know, on the antennas", "start": 4611.1, "stop": 4614.42, "id": 1425}, {"text": " with like three or five dB of gain, that would be different. I plugged in all the", "start": 4614.42, "stop": 4619.18, "id": 1426}, {"text": " numbers for the 902 to 928 MHz band.", "start": 4619.18, "stop": 4621.68, "id": 1427}, {"text": " It assumed it's 26 MHz wide and we're using all of that.", "start": 4621.84, "stop": 4624.44, "id": 1428}, {"text": " So the sort of noise bandwidth before the spreading is 26 MHz wide,", "start": 4624.68, "stop": 4629.4, "id": 1429}, {"text": " which is the signal to noise ratio computation that I make.", "start": 4629.78, "stop": 4635.86, "id": 1430}, {"text": " And I assumed...now the scheduling method, I assumed 64 slots per second.", "start": 4637.0, "stop": 4641.86, "id": 1431}, {"text": " And actually I skipped over how you actually find the place a packet can sit in.", "start": 4641.86, "stop": 4646.2, "id": 1432}, {"text": " And I assumed fault small or fixed by packets of some size", "start": 4646.32, "stop": 4651.06, "id": 1433}, {"text": " without actually specifying a data rate.", "start": 4651.06, "stop": 4653.42, "id": 1434}, {"text": " So I'm actually just saying a time and the data rate we can get depends on the", "start": 4653.5, "stop": 4656.42, "id": 1435}, {"text": " processing gain that we need, which...and that'll determine", "start": 4656.42, "stop": 4659.3, "id": 1436}, {"text": " how many bits you can send in a packet.", "start": 4659.3, "stop": 4661.38, "id": 1437}, {"text": " But there are these things called sub slots.", "start": 4662.54, "stop": 4664.28, "id": 1438}, {"text": " So this is 1024 sub slots per slot, which means the packet is at most about", "start": 4664.28, "stop": 4670.42, "id": 1439}, {"text": " a millisecond long.", "start": 4670.42, "stop": 4673.22, "id": 1440}, {"text": " And a target power control of minus 120 dBw when I have power control turned on.", "start": 4673.92, "stop": 4677.98, "id": 1441}, {"text": " And I play with a bunch of stuff. The only simulations I wrote up in the thesis,", "start": 4680.9800000000005, "stop": 4684.98, "id": 1442}, {"text": " because they were the only ones that really informed anything, was this worst,", "start": 4685.78, "stop": 4689.54, "id": 1443}, {"text": " near worst case traffic load that I came up with.", "start": 4689.78, "stop": 4691.88, "id": 1444}, {"text": " I computed the routes to handle general traffic. I really have no idea", "start": 4691.88, "stop": 4695.76, "id": 1445}, {"text": " what traffic's going to be put on this.", "start": 4695.76, "stop": 4697.34, "id": 1446}, {"text": " But what I'm concerned about is, well, if it got really", "start": 4697.64, "stop": 4699.76, "id": 1447}, {"text": " bad, how bad would all the interference be?", "start": 4699.76, "stop": 4701.92, "id": 1448}, {"text": " And what I wanted to get is I wanted to get every station sort of sending", "start": 4702.26, "stop": 4704.56, "id": 1449}, {"text": " to all its neighbors as much as possible.", "start": 4704.56, "stop": 4706.16, "id": 1450}, {"text": " So coming back to this diagram of the network and the edges connecting them, if", "start": 4707.160000000001, "stop": 4712.3, "id": 1451}, {"text": " you imagine any station here, and each station here has like four or five", "start": 4712.3, "stop": 4716.36, "id": 1452}, {"text": " edges off to some nearby neighbor,", "start": 4716.36, "stop": 4718.08, "id": 1453}, {"text": " then for each station in the net, pick one station, I schedule the packet to", "start": 4721.840000000001, "stop": 4728.56, "id": 1454}, {"text": " each of its neighbors when the simulator initializes.", "start": 4728.56, "stop": 4732.86, "id": 1455}, {"text": " So every station starts out with one packet for each of its neighbors.", "start": 4733.02, "stop": 4735.4, "id": 1456}, {"text": " At the start time for transmission of each packet, I scheduled", "start": 4735.82, "stop": 4739.94, "id": 1457}, {"text": " another packet for that same neighbor.", "start": 4739.94, "stop": 4741.74, "id": 1458}, {"text": " And then it goes and finds a place in the", "start": 4741.98, "stop": 4743.98, "id": 1459}, {"text": " pseudo-random schedules where it can go.", "start": 4743.98, "stop": 4745.48, "id": 1460}, {"text": " So every station is always transmitting at any time it has a neighbor listening.", "start": 4745.48, "stop": 4750.44, "id": 1461}, {"text": " It's completely loaded. No opportunity. Now, the power level, if you turn on", "start": 4751.56, "stop": 4756.86, "id": 1462}, {"text": " power control, you're not always transmitting to your furthest neighbor.", "start": 4756.86, "stop": 4759.22, "id": 1463}, {"text": " So it's not entirely worst case. If you've got a, you know, it's sort of, you're", "start": 4759.72, "stop": 4764.24, "id": 1464}, {"text": " always transmitting to some neighbor, but if some of your neighbors are closer", "start": 4764.24, "stop": 4766.6, "id": 1465}, {"text": " than others, then your transmitter is not at the highest", "start": 4766.6, "stop": 4768.68, "id": 1466}, {"text": " level you ever run it at all the time.", "start": 4768.68, "stop": 4770.22, "id": 1467}, {"text": " Maybe I should do that simulation as well.", "start": 4771.72, "stop": 4773.64, "id": 1468}, {"text": " Does that mean like, you know, somebody's transmitting to your [...] for it?", "start": 4773.64, "stop": 4779.44, "id": 1469}, {"text": " No, the schedules are completely fixed. You have to fit the", "start": 4780.0, "stop": 4782.34, "id": 1470}, {"text": " packets in the schedules that are there.", "start": 4782.34, "stop": 4783.88, "id": 1471}, {"text": " So you have to, oh, okay. You can't, you can't send, you got 120 8-byte", "start": 4784.32, "stop": 4791.22, "id": 1472}, {"text": " packets, but then, and there's a few spots, 80 bytes long, you got an 80 byte", "start": 4791.22, "stop": 4795.58, "id": 1473}, {"text": " period, and wait for the next time.", "start": 4795.58, "stop": 4797.12, "id": 1474}, {"text": " Well, yeah, the way I probably, I don't know. Maybe the way I build the system", "start": 4797.24, "stop": 4801.18, "id": 1475}, {"text": " is I'd have a small, fixed-size cell.", "start": 4801.18, "stop": 4802.8, "id": 1476}, {"text": " Which is maybe one-fourth of a slot time. I think that's probably about right.", "start": 4803.780000000001, "stop": 4808.64, "id": 1477}, {"text": " And towards the end of the panel for the chapter in the thesis are some formulas.", "start": 4810.040000000001, "stop": 4814.24, "id": 1478}, {"text": " You can start plugging in what sizes of different things you want and see what", "start": 4814.42, "stop": 4818.78, "id": 1479}, {"text": " efficiencies you get in various pieces of the system.", "start": 4818.78, "stop": 4820.74, "id": 1480}, {"text": " Now here, what I have on this plot is, let me", "start": 4821.56, "stop": 4827.0, "id": 1481}, {"text": " think, which one, yeah, this one, okay.", "start": 4827.0, "stop": 4829.28, "id": 1482}, {"text": " This is, I just picked one of the stations in the net, actually, station 29,", "start": 4829.28, "stop": 4836.08, "id": 1483}, {"text": " which is this station that has three neighbors down here.", "start": 4836.98, "stop": 4840.6, "id": 1484}, {"text": " One of which is kind of nearby and two which are further away.", "start": 4840.88, "stop": 4843.42, "id": 1485}, {"text": " And I, what I have is here is a plot of received power level.", "start": 4845.8, "stop": 4849.78, "id": 1486}, {"text": " The thermal noise for 26 megahertz wide is around minus 150 dBw.", "start": 4850.92, "stop": 4855.3, "id": 1487}, {"text": " That's Boltzmann's constant times the temperature, 290 times 26 megahertz.", "start": 4857.62, "stop": 4863.46, "id": 1488}, {"text": " And so, you know, the, the, we're about 50 dB away from that, just", "start": 4864.08, "stop": 4868.72, "id": 1489}, {"text": " from the self-interference in the system.", "start": 4868.72, "stop": 4870.34, "id": 1490}, {"text": " What I've got on this axis is time, horizontal axis is time, and the vertical", "start": 4871.02, "stop": 4874.32, "id": 1491}, {"text": " axis here is received power level.", "start": 4874.32, "stop": 4876.98, "id": 1492}, {"text": " This is minus 60 dBw or a micro-lot, nano-lot, pico-lot.", "start": 4877.16, "stop": 4882.76, "id": 1493}, {"text": " And there's another little bit of hand waving here.", "start": 4886.28, "stop": 4888.6, "id": 1494}, {"text": " These, these tall spikes, when you see received power levels up around the micro", "start": 4891.18, "stop": 4894.92, "id": 1495}, {"text": "-lot, that's the station's own transmitter.", "start": 4894.92, "stop": 4897.98, "id": 1496}, {"text": " I forget the actual power level I had the transmitter running at, but it was on", "start": 4899.38, "stop": 4902.8, "id": 1497}, {"text": " the order of somewhere between 10 and 100 milliwatts, I think.", "start": 4902.8, "stop": 4906.32, "id": 1498}, {"text": " Actually, it's exactly 40 dB up from this because even though I think you can", "start": 4907.320000000001, "stop": 4911.3, "id": 1499}, {"text": " only build isolators or duplexors with about 20 dB of isolation.", "start": 4911.3, "stop": 4915.42, "id": 1500}, {"text": " Circulators, sometimes people call them.", "start": 4916.56, "stop": 4918.16, "id": 1501}, {"text": " They're duplexors to telephony people.", "start": 4918.36, "stop": 4919.9, "id": 1502}, {"text": " That's right.", "start": 4921.36, "stop": 4921.66, "id": 1503}, {"text": " I first plugged in 20 dBw and all my simulations diverged.", "start": 4925.040000000001, "stop": 4929.46, "id": 1504}, {"text": " And the problem is, is I initialize this variable.", "start": 4930.06, "stop": 4932.52, "id": 1505}, {"text": " I mean, this, but what happened is, is you, because a", "start": 4932.52, "stop": 4939.34, "id": 1506}, {"text": " round off error in IEEE floating point standard doubles, which only have", "start": 4939.34, "stop": 4945.56, "id": 1507}, {"text": " some, there's a footnote in the thesis about this.", "start": 4945.56, "stop": 4950.2, "id": 1508}, {"text": " There's only so many bits of mantissa.", "start": 4950.76, "stop": 4953.3, "id": 1509}, {"text": " And if you take a big thing, if you have a small thing and you add in a big", "start": 4953.96, "stop": 4957.6, "id": 1510}, {"text": " thing, and this just tracks the big thing out again, you might", "start": 4957.6, "stop": 4961.44, "id": 1511}, {"text": " not get exactly what you started with.", "start": 4961.44, "stop": 4963.06, "id": 1512}, {"text": " And if that starts creeping, then it runs away.", "start": 4963.52, "stop": 4966.26, "id": 1513}, {"text": " And I had to, there's only about 150 dB of dynamic range in the mantissa", "start": 4967.16, "stop": 4972.48, "id": 1514}, {"text": " of an IEEE floating point double.", "start": 4972.48, "stop": 4974.14, "id": 1515}, {"text": " Or 64 bits, yeah.", "start": 4975.28, "stop": 4976.3, "id": 1516}, {"text": " So if you want to add signals that are power levels that are more than 150 dB, or", "start": 4976.94, "stop": 4981.02, "id": 1517}, {"text": " that are close that approach 150 dB difference, then you need,", "start": 4981.02, "stop": 4985.74, "id": 1518}, {"text": " you need something bigger than IEEE double.", "start": 4986.32, "stop": 4989.5, "id": 1519}, {"text": " And the way I solve this problem, so I can run all my simulations, is I wave my", "start": 4989.5, "stop": 4992.88, "id": 1520}, {"text": " hands and let's say, okay, let's say the circulator gives us 40 dB of isolation.", "start": 4992.88, "stop": 4996.94, "id": 1521}, {"text": " So these tall spikes here are us hearing our own transmitter through a 40 dB", "start": 4997.38, "stop": 5002.86, "id": 1522}, {"text": " circulator, a circulator giving us 40 dB of isolation.", "start": 5002.86, "stop": 5005.6, "id": 1523}, {"text": " Really, these would be taller.", "start": 5006.46, "stop": 5007.7, "id": 1524}, {"text": " What? How do you do that?", "start": 5009.580000000001, "stop": 5010.8, "id": 1525}, {"text": " Yeah.", "start": 5014.84, "stop": 5015.24, "id": 1526}, {"text": " Yeah, yeah.", "start": 5016.240000000001, "stop": 5016.88, "id": 1527}, {"text": " So, so that's what these tall spikes are.", "start": 5017.860000000001, "stop": 5019.98, "id": 1528}, {"text": " So the transmitter actually radiated, you know, the power we're sending up the", "start": 5020.16, "stop": 5023.34, "id": 1529}, {"text": " antenna is 40 dB above this, because we're listening to it through,", "start": 5023.34, "stop": 5026.72, "id": 1530}, {"text": " effectively, a 40 dB of attenuation.", "start": 5027.0, "stop": 5028.62, "id": 1531}, {"text": " And, and notice that's about 40 dB above the received power levels, the total", "start": 5029.24, "stop": 5035.24, "id": 1532}, {"text": " received power level as well, and about 50 dB above the actual", "start": 5035.24, "stop": 5037.92, "id": 1533}, {"text": " receptions of the signal levels of the packets.", "start": 5037.92, "stop": 5039.8, "id": 1534}, {"text": " What I've drawn in here is the, the, the signal level of individual packets.", "start": 5039.8, "stop": 5046.58, "id": 1535}, {"text": " So this is the noise, and the noise goes, I mean, the noise includes all the", "start": 5046.68, "stop": 5050.62, "id": 1536}, {"text": " interference, and it's tall when it's up, minus 60", "start": 5050.62, "stop": 5054.46, "id": 1537}, {"text": " dBw when our own transmitter's on.", "start": 5054.46, "stop": 5056.04, "id": 1538}, {"text": " That's around minus 100 dBw when our own transmitter's off.", "start": 5056.28, "stop": 5058.82, "id": 1539}, {"text": " And the receptions are here. So the distance from these receptions up to the", "start": 5060.360000000001, "stop": 5064.0, "id": 1540}, {"text": " noise level is kind of the signal to noise plus signal ratio.", "start": 5064.0, "stop": 5069.7, "id": 1541}, {"text": " And you can't really learn much from this plot, except I can wave at my hands", "start": 5073.500000000001, "stop": 5077.6, "id": 1542}, {"text": " at it while I talk about how the simulator works.", "start": 5077.6, "stop": 5079.2, "id": 1543}, {"text": " And, show up for you here.", "start": 5080.28, "stop": 5081.24, "id": 1544}, {"text": " There's no, yeah, more or less, except this is signal to signal", "start": 5081.88, "stop": 5087.06, "id": 1545}, {"text": " plus noise ratio, not signal to noise ratio.", "start": 5087.06, "stop": 5088.72, "id": 1546}, {"text": " Which, if, if this were further apart, they're kind of the", "start": 5089.620000000001, "stop": 5092.48, "id": 1547}, {"text": " same thing. They approach the same thing.", "start": 5092.48, "stop": 5094.02, "id": 1548}, {"text": " Now, notice the receptions come at a different power level. That's because in", "start": 5094.44, "stop": 5097.92, "id": 1549}, {"text": " this simulation I was running a fixed", "start": 5097.92, "stop": 5100.04, "id": 1550}, {"text": " transmitter power level throughout the system.", "start": 5100.04, "stop": 5101.74, "id": 1551}, {"text": " All, no power control.", "start": 5101.96, "stop": 5103.32, "id": 1552}, {"text": " And I have, this is when you're on transmitter on.", "start": 5105.700000000001, "stop": 5110.48, "id": 1553}, {"text": " What this tall is, when the noise interference level pops up about 10 dB,", "start": 5110.48, "stop": 5115.96, "id": 1554}, {"text": " that's due to that really nearby neighbor who's got his transmitter on.", "start": 5116.84, "stop": 5121.52, "id": 1555}, {"text": " And he kind of pops up out of the noise. And if you had a reception down", "start": 5122.16, "stop": 5125.72, "id": 1556}, {"text": " here, you suddenly, you have a problem.", "start": 5125.72, "stop": 5127.64, "id": 1557}, {"text": " And I'll come back to that later. So that's, that should more or less explain,", "start": 5128.38, "stop": 5133.58, "id": 1558}, {"text": " you know. Exactly.", "start": 5133.64, "stop": 5135.32, "id": 1559}, {"text": " Some people call that a near-power problem.", "start": 5135.96, "stop": 5137.34, "id": 1560}, {"text": " [...]", "start": 5144.26, "stop": 5144.74, "id": 1561}, {"text": " Yeah, but I, yeah, that, I believe you. Absolutely. I think that would do it.", "start": 5154.64, "stop": 5160.12, "id": 1562}, {"text": " And you'd be doing a random, instead of always being biased", "start": 5160.12, "stop": 5163.44, "id": 1563}, {"text": " wrong, you'd be doing a random walk.", "start": 5163.44, "stop": 5166.46, "id": 1564}, {"text": " Which hopefully wouldn't walk too far. But this is an IEEE floating point unit in", "start": 5166.9, "stop": 5170.18, "id": 1565}, {"text": " my microprocessor. I don't know if I, I don't know if I can tweak that.", "start": 5170.18, "stop": 5172.98, "id": 1566}, {"text": " I'm just writing code in C and running it on a, I was actually running on a,", "start": 5173.24, "stop": 5177.52, "id": 1567}, {"text": " on a MIPSAR 3000 at the time.", "start": 5177.52, "stop": 5179.18, "id": 1568}, {"text": " And I, I think it had mode bits, but I don't think you could get at them from", "start": 5181.84, "stop": 5184.68, "id": 1569}, {"text": " user mode. So I'd have to hack the kernel.", "start": 5184.68, "stop": 5186.84, "id": 1570}, {"text": " Yeah, well I found another way around this.", "start": 5193.200000000001, "stop": 5197.52, "id": 1571}, {"text": " You should have talked to me four years ago.", "start": 5199.7, "stop": 5201.22, "id": 1572}, {"text": " I'm still not sure if I would have been able to do it in the computer I had.", "start": 5202.58, "stop": 5205.28, "id": 1573}, {"text": " So, interesting idea.", "start": 5205.6, "stop": 5208.22, "id": 1574}, {"text": " So this was, like, this is the flight I had up just a moment ago. This is the", "start": 5208.9, "stop": 5212.06, "id": 1575}, {"text": " without power control.", "start": 5212.06, "stop": 5213.9, "id": 1576}, {"text": " Here I turned on power control, and this", "start": 5213.9, "stop": 5216.5, "id": 1577}, {"text": " station was sending to three other stations.", "start": 5216.5, "stop": 5218.3, "id": 1578}, {"text": " And you can see that our transmitter power level", "start": 5218.46, "stop": 5220.26, "id": 1579}, {"text": " goes between three different values.", "start": 5220.26, "stop": 5222.12, "id": 1580}, {"text": " This is when we're sending to that guy who's really nearby. This is sending", "start": 5222.58, "stop": 5226.16, "id": 1581}, {"text": " to one of the other two visits further away.", "start": 5226.16, "stop": 5227.92, "id": 1582}, {"text": " And you can see this is quite different than power control. And the power control", "start": 5228.0, "stop": 5231.16, "id": 1583}, {"text": " throughout the whole network in this simulation, conspired to always deliver", "start": 5231.16, "stop": 5235.22, "id": 1584}, {"text": " minus 120 dBw to the receiver. So all the receptions are exactly this level.", "start": 5235.22, "stop": 5239.6, "id": 1585}, {"text": " Just to illustrate what I mean by power control, you can sort of see it here.", "start": 5241.580000000001, "stop": 5244.88, "id": 1586}, {"text": " Now you can't really learn anything. You know, these", "start": 5245.3, "stop": 5247.72, "id": 1587}, {"text": " two plots look a little different.", "start": 5247.72, "stop": 5249.76, "id": 1588}, {"text": " You know, with power control it was a little lower, but I could have conspired to", "start": 5250.48, "stop": 5254.78, "id": 1589}, {"text": " fix the transmitter power level so that they kind of look the same.", "start": 5254.78, "stop": 5257.3, "id": 1590}, {"text": " You know, there's really not much to learn by comparing those two.", "start": 5258.12, "stop": 5261.2, "id": 1591}, {"text": " What I've done here, now this is with, again with power control, this is from the", "start": 5262.62, "stop": 5266.04, "id": 1592}, {"text": " simulation without power control.", "start": 5266.04, "stop": 5267.88, "id": 1593}, {"text": " And what I've done on this, now remember this,", "start": 5268.92, "stop": 5272.48, "id": 1594}, {"text": " I told you what the traffic load was.", "start": 5273.02, "stop": 5274.62, "id": 1595}, {"text": " I was just loading up to send to nearby neighbors. So all, every station is", "start": 5274.62, "stop": 5279.16, "id": 1596}, {"text": " constantly, they'll be sending to a nearby neighbor throughout the entire NAT.", "start": 5279.16, "stop": 5282.34, "id": 1597}, {"text": " And so what I did for all my simulations, I, what I have on this axis, on the", "start": 5283.06, "stop": 5289.1, "id": 1598}, {"text": " horizontal axis, is signal to noise ratio in dustables.", "start": 5289.1, "stop": 5292.16, "id": 1599}, {"text": " There's 20 dB, 10 dB, 0 dB, minus 10 dB, minus 20 dB. So this is the", "start": 5292.16, "stop": 5298.9, "id": 1600}, {"text": " one, one in 100, one part in 100 signal to noise ratio.", "start": 5298.9, "stop": 5303.02, "id": 1601}, {"text": " I refuse to say negative signal to noise ratio. It's always a positive signal to", "start": 5304.72, "stop": 5308.64, "id": 1602}, {"text": " noise ratio. It's just the log of the signal to noise ratio that", "start": 5308.64, "stop": 5310.9, "id": 1603}, {"text": " is negative when you're in dB.", "start": 5310.9, "stop": 5312.4, "id": 1604}, {"text": " So this is what sort of distribution you get of signal, worst case signal to", "start": 5313.880000000001, "stop": 5318.42, "id": 1605}, {"text": " noise ratios during receptions of packets without power control turned on.", "start": 5318.42, "stop": 5321.28, "id": 1606}, {"text": " And you see this kind of blob. And if you picked, the way to think about this is", "start": 5321.28, "stop": 5326.38, "id": 1607}, {"text": " that if you picked a processing gain of say 23 dB, and you needed 5 dB of", "start": 5326.38, "stop": 5332.46, "id": 1608}, {"text": " headroom, then all of the packets to the right of here", "start": 5332.46, "stop": 5335.48, "id": 1609}, {"text": " in this distribution would have been received.", "start": 5335.48, "stop": 5337.92, "id": 1610}, {"text": " And only these few down here might not have been received. So this kind of sort", "start": 5338.02, "stop": 5344.4, "id": 1611}, {"text": " of, even this without power control sort of confirms,", "start": 5344.4, "stop": 5347.98, "id": 1612}, {"text": " you know, more or less what I was thinking about.", "start": 5348.08, "stop": 5349.82, "id": 1613}, {"text": " You know, this thing ought to work from my analysis earlier. And I'll", "start": 5349.82, "stop": 5354.34, "id": 1614}, {"text": " come back and actually do a comparison later.", "start": 5354.34, "stop": 5355.96, "id": 1615}, {"text": " What I want to do right now is actually turn on power control and it tightens up", "start": 5356.42, "stop": 5361.2, "id": 1616}, {"text": " the distribution. This plot is at the same scale as the previous.", "start": 5361.2, "stop": 5366.06, "id": 1617}, {"text": " What it's done is it's", "start": 5366.6, "stop": 5369.56, "id": 1618}, {"text": " taken what was in this distribution, I can put them over", "start": 5369.56, "stop": 5376.42, "id": 1619}, {"text": " each other, and scrunched them together.", "start": 5376.42, "stop": 5378.14, "id": 1620}, {"text": " And it sort of makes sense because what it's doing is it's fixing the signal", "start": 5378.14, "stop": 5381.76, "id": 1621}, {"text": " level everywhere. And we already think that because there's so many stations, the", "start": 5381.76, "stop": 5385.04, "id": 1622}, {"text": " noise level is sort of what it is in a large network.", "start": 5385.04, "stop": 5387.36, "id": 1623}, {"text": " There's only 100 stations in the simulation, but the power control, that's what", "start": 5387.44, "stop": 5392.44, "id": 1624}, {"text": " power control does for you. It sort of eliminates the very high signal to noise", "start": 5392.44, "stop": 5397.92, "id": 1625}, {"text": " ratios because when that would have happened, you turn your power down.", "start": 5397.92, "stop": 5401.22, "id": 1626}, {"text": " And because people turn their power down, it reduces the number of", "start": 5401.22, "stop": 5407.6, "id": 1627}, {"text": " very low signal to noise ratio", "start": 5407.6, "stop": 5409.42, "id": 1628}, {"text": " receptions and sort of brings them closer to the middle.", "start": 5409.42, "stop": 5411.28, "id": 1629}, {"text": " Now what I want to do is actually I'm going to zoom in on this picture. This is", "start": 5411.9, "stop": 5416.56, "id": 1630}, {"text": " with power control turned on. And I'm going to look at this tail here.", "start": 5416.56, "stop": 5421.24, "id": 1631}, {"text": " So I'm going to zoom in on this tail. I'm going to sort of blow the scale up of", "start": 5421.24, "stop": 5424.9, "id": 1632}, {"text": " this plot with my next plot. And I actually moved zero up, the zero level up a", "start": 5424.9, "stop": 5431.14, "id": 1633}, {"text": " little bit off the y-axis so we could see this more clearly.", "start": 5431.14, "stop": 5434.34, "id": 1634}, {"text": " And this tail goes out for a ways and there's some very low, there's some packets", "start": 5434.76, "stop": 5440.5, "id": 1635}, {"text": " that came in with fairly low signal to noise ratio. And what", "start": 5440.5, "stop": 5444.04, "id": 1636}, {"text": " happened? It's the near far problem.", "start": 5444.04, "stop": 5447.74, "id": 1637}, {"text": " And when I explained today my scheduling method, I just talked about well we'll", "start": 5450.04, "stop": 5455.14, "id": 1638}, {"text": " schedule to avoid, you know, my neighbors will know when they can send to me", "start": 5455.14, "stop": 5462.12, "id": 1639}, {"text": " because they'll know when I'm not transmitting.", "start": 5462.12, "stop": 5464.56, "id": 1640}, {"text": " So we don't have, you know, extreme, so there were no extremely low signal to", "start": 5464.56, "stop": 5469.02, "id": 1641}, {"text": " noise ratios. That never happened because the scheduling method was working. We", "start": 5469.02, "stop": 5473.32, "id": 1642}, {"text": " didn't see any minus 100 or minus 80 dB signal to noise ratios.", "start": 5473.32, "stop": 5477.68, "id": 1643}, {"text": " Or it would be closer to minus 40.", "start": 5477.94, "stop": 5479.54, "id": 1644}, {"text": " But, time's running along.", "start": 5479.54, "stop": 5484.74, "id": 1645}, {"text": " But there was this near far problem. Now, the scheduling method is fairly easy to", "start": 5488.0, "stop": 5492.04, "id": 1646}, {"text": " extend since I know what your schedule is and I know that I'm close to you.", "start": 5492.04, "stop": 5496.62, "id": 1647}, {"text": " And I know what my schedule is.", "start": 5497.16, "stop": 5498.68, "id": 1648}, {"text": " It's fairly easy for me, and I know what the path gain is. I'm assuming we've", "start": 5499.320000000001, "stop": 5503.02, "id": 1649}, {"text": " done enough for that for power control. So if I'm going to send over there and", "start": 5503.02, "stop": 5508.28, "id": 1650}, {"text": " I'm nearby some other receiver and I know what his schedule is, when I'm finding", "start": 5508.28, "stop": 5512.72, "id": 1651}, {"text": " the place that I'm going to send this packet to him, I can look at", "start": 5512.72, "stop": 5516.3, "id": 1652}, {"text": " his received schedule as well.", "start": 5516.3, "stop": 5517.88, "id": 1653}, {"text": " And choose to send when I, if I'm going to send a packet far away, I'm going,", "start": 5518.700000000001, "stop": 5524.66, "id": 1654}, {"text": " what I can do is I can look at, I need to find a time when that's a received", "start": 5524.88, "stop": 5528.04, "id": 1655}, {"text": " slot, I've got a transmit slot, and he's in a transmit slot.", "start": 5528.04, "stop": 5532.56, "id": 1656}, {"text": " Exactly. Now, does this really constrain things much? Well, it's only about", "start": 5534.22, "stop": 5539.9, "id": 1657}, {"text": " 20% of the time that I can send to him. What fraction of, and", "start": 5539.9, "stop": 5546.78, "id": 1658}, {"text": " so there's a given schedule that I can send across the room. You know, I can send", "start": 5546.78, "stop": 5551.04, "id": 1659}, {"text": " if somebody is fairly distant. What fraction of his, so, and all the schedules,", "start": 5551.04, "stop": 5556.2, "id": 1660}, {"text": " what fraction of his slots are transmit slots? 70%, a majority. So it actually", "start": 5556.4, "stop": 5562.18, "id": 1661}, {"text": " doesn't constrain you that much. And it's only when you're sitting right on top", "start": 5562.18, "stop": 5565.42, "id": 1662}, {"text": " of somebody. In fact, it never comes into play unless there's a factor of about", "start": 5565.42, "stop": 5570.9, "id": 1663}, {"text": " four or five difference in the distances. As long as there's sort of, you know,", "start": 5570.9, "stop": 5575.66, "id": 1664}, {"text": " What was the ratio? Yeah, so what I did in the thesis, I picked, picked the power", "start": 5575.66, "stop": 5582.66, "id": 1665}, {"text": " control. So it actually, if somebody's five times closer than somebody you're", "start": 5582.66, "stop": 5587.52, "id": 1666}, {"text": " transmitting to, then the scheduling constraint kicks in. And it was very rare.", "start": 5587.52, "stop": 5592.38, "id": 1667}, {"text": " As you can see, there are only a few packets that we need to do about. As I turn", "start": 5592.68, "stop": 5596.22, "id": 1668}, {"text": " that on, here's the whole distribution with what I call the respect neighbor", "start": 5596.22, "stop": 5600.92, "id": 1669}, {"text": " constraint to the scheduling.", "start": 5600.92, "stop": 5602.92, "id": 1670}, {"text": " And it was a tunable number, but I found the number that just works. It doesn't,", "start": 5605.66, "stop": 5612.2, "id": 1671}, {"text": " it hardly changes anything. The distribution doesn't really move anywhere. I", "start": 5612.6, "stop": 5617.46, "id": 1672}, {"text": " mean, at this scale, it looks the same. You can't tell the difference. But then", "start": 5617.46, "stop": 5620.72, "id": 1673}, {"text": " when you zoom in on the tail and you look at the worst case signal to noise", "start": 5620.72, "stop": 5624.14, "id": 1674}, {"text": " ratios, the worst one was around. It cut off, which means all the packets were", "start": 5624.14, "stop": 5629.24, "id": 1675}, {"text": " delivered here, which means that if you had, by my model for what a successful", "start": 5629.24, "stop": 5633.4, "id": 1676}, {"text": " reception is, if you had processing gain here for that sort of factor of three", "start": 5633.4, "stop": 5637.86, "id": 1677}, {"text": " fudge factor, maybe five dB, by my model, I can wave my hands and say, by my", "start": 5637.86, "stop": 5642.38, "id": 1678}, {"text": " model, no packets are dropped due to collisions. Or due to interference, or", "start": 5642.38, "stop": 5648.58, "id": 1679}, {"text": " whatever. And that's what I mean by collision free. So, I", "start": 5648.58, "stop": 5655.32, "id": 1680}, {"text": " also did simulations with a thousand stations.", "start": 5655.32, "stop": 5659.08, "id": 1681}, {"text": " Same idea. You've seen all these plots before with a hundred, but here's the, I", "start": 5662.16, "stop": 5669.04, "id": 1682}, {"text": " have power control turned on already. And you get a distribution that looks like", "start": 5669.04, "stop": 5674.64, "id": 1683}, {"text": " that. The tail of this distribution goes a little further. And that's because", "start": 5674.64, "stop": 5678.68, "id": 1684}, {"text": " with a thousand stations, the closest, the random guy who, you know, we wound up", "start": 5678.68, "stop": 5684.42, "id": 1685}, {"text": " with two guys sitting proportionally closer to each other than", "start": 5684.42, "stop": 5687.06, "id": 1686}, {"text": " we did in the thing. And that'll, that'll work.", "start": 5687.06, "stop": 5689.06, "id": 1687}, {"text": " And that'll happen as you have more chances for that to happen. So, so I'm going", "start": 5689.08, "stop": 5694.18, "id": 1688}, {"text": " to, again, zoom in on the lower left tail of that. And you can see that there's", "start": 5694.18, "stop": 5698.42, "id": 1689}, {"text": " some fairly low signal to noise ratios. And here's the minus 20 dB. And so", "start": 5698.42, "stop": 5703.74, "id": 1690}, {"text": " there's actually, we cut off at about minus 17 before. And there's, we've", "start": 5703.74, "stop": 5708.24, "id": 1691}, {"text": " actually got quite a, quite a lot out there. And I turn on the respect neighbor", "start": 5708.24, "stop": 5711.46, "id": 1692}, {"text": " constraint, which again, rarely comes into play. There's a lot of mass in this", "start": 5711.46, "stop": 5714.96, "id": 1693}, {"text": " distribution to the right of here. Even though we see a lot of stuff here.", "start": 5714.96, "stop": 5718.12, "id": 1694}, {"text": " And turn on the respect neighbor. What?", "start": 5719.1, "stop": 5722.9, "id": 1695}, {"text": " Yeah, that's right. And you turn on the respect neighbor constraint here in the", "start": 5726.26, "stop": 5729.66, "id": 1696}, {"text": " thousand station case. And again, it cuts off at about minus 17 dB. Now,", "start": 5729.66, "stop": 5736.22, "id": 1697}, {"text": " gosh, it's been a while. There was a time when I convinced myself that as you", "start": 5737.98, "stop": 5742.32, "id": 1698}, {"text": " turn up the number of stations in the network, and you have larger and larger", "start": 5742.32, "stop": 5745.58, "id": 1699}, {"text": " contributions from distance stations to those sort of total noise, that this, as", "start": 5745.58, "stop": 5752.04, "id": 1700}, {"text": " this walks left, as the sort of whole distribution walks left, you can, you can", "start": 5752.04, "stop": 5757.56, "id": 1701}, {"text": " cut it off tighter. So this actually doesn't move much. This minus 17 dB. It", "start": 5757.56, "stop": 5763.74, "id": 1702}, {"text": " moves over more slowly than the whole distribution moves over. So the respect", "start": 5763.74, "stop": 5767.44, "id": 1703}, {"text": " neighbor constraint is a fairly powerful thing. And that's why I claim that all", "start": 5767.44, "stop": 5771.98, "id": 1704}, {"text": " packets are received successfully by this", "start": 5771.98, "stop": 5774.16, "id": 1705}, {"text": " model. What's the difference between these two?", "start": 5774.16, "stop": 5776.88, "id": 1706}, {"text": " I have a surprise slide in here that I don't know what to steer for. I think I", "start": 5779.06, "stop": 5784.98, "id": 1707}, {"text": " have two duplicate slides. No, no, they're the same. They're the same because", "start": 5784.98, "stop": 5789.56, "id": 1708}, {"text": " once the zoom in. That's the one that's cut off. So,", "start": 5789.56, "stop": 5796.3, "id": 1709}, {"text": " where did Bob go? Back in the room now. Your question earlier was, what about the", "start": 5797.12, "stop": 5803.24, "id": 1710}, {"text": " hotspot? The middle or not?", "start": 5803.24, "stop": 5805.32, "id": 1711}, {"text": " Let me find my thousand station picture. I", "start": 5805.32, "stop": 5811.82, "id": 1712}, {"text": " had a better picture earlier. Thousand", "start": 5811.82, "stop": 5818.78, "id": 1713}, {"text": " stations, just to think about for a second. There are a thousand points in this", "start": 5818.78, "stop": 5824.1, "id": 1714}, {"text": " network. There are a million stations to station paths. Because", "start": 5824.1, "stop": 5830.76, "id": 1715}, {"text": " there's a, or there's 450,000 or something.", "start": 5830.76, "stop": 5834.3, "id": 1716}, {"text": " It's one, it's roughly, oh, one way path. There's a, if you include the path to", "start": 5834.3, "stop": 5839.78, "id": 1717}, {"text": " yourself, there's a million. Because there's a thousand sources and a thousand", "start": 5839.78, "stop": 5843.04, "id": 1718}, {"text": " destinations. Subtract out the thousand trivial ones. We're left with almost a", "start": 5843.04, "stop": 5849.06, "id": 1719}, {"text": " million. There's about a million paths in this. And so what I did is I went", "start": 5849.06, "stop": 5855.24, "id": 1720}, {"text": " through, so there's a million start, source the destination paths.", "start": 5855.24, "stop": 5859.88, "id": 1721}, {"text": " I went through and I traced every one of them. And every time I came across the", "start": 5860.72, "stop": 5865.98, "id": 1722}, {"text": " station, I incremented a counter. So now, for all thousand stations,", "start": 5865.98, "stop": 5871.18, "id": 1723}, {"text": " what I have is how many paths go through me. So, and that's always an even", "start": 5872.62, "stop": 5878.6, "id": 1724}, {"text": " number. Because it's symmetric. That's", "start": 5878.6, "stop": 5883.76, "id": 1725}, {"text": " what I did.", "start": 5883.76, "stop": 5885.68, "id": 1726}, {"text": " And I've lost the, here it is.", "start": 5885.68, "stop": 5891.14, "id": 1727}, {"text": " Now, for my thousand stations, what does the distribution look", "start": 5892.5, "stop": 5897.78, "id": 1728}, {"text": " like for the results of those numbers?", "start": 5897.78, "stop": 5899.38, "id": 1729}, {"text": " So, let's see. On this axis, I have number of paths, which goes out to about 200", "start": 5905.9, "stop": 5911.4, "id": 1730}, {"text": ",000, or about 20%. And there were a few cases over here.", "start": 5911.4, "stop": 5917.32, "id": 1731}, {"text": " Where there were, there were three stations in this, in the middle of this. That", "start": 5918.34, "stop": 5922.48, "id": 1732}, {"text": " had over 20% of the million paths going through them.", "start": 5922.48, "stop": 5926.0, "id": 1733}, {"text": " This is a hotspot in the routing. And there were, you know, quite a few that", "start": 5929.400000000001, "stop": 5936.28, "id": 1734}, {"text": " were over 100,000. Had more than 10% of the paths through them. I actually went", "start": 5936.28, "stop": 5940.6, "id": 1735}, {"text": " through, and the thesis is a plot. I don't have the foil for it, but there's a", "start": 5940.6, "stop": 5944.24, "id": 1736}, {"text": " plot that shows actually which stations had, I think, more than 10%. So all the", "start": 5944.24, "stop": 5949.3, "id": 1737}, {"text": " stations that contributed to here, I drew the plot. I drew this plot. But I left,", "start": 5949.3, "stop": 5954.68, "id": 1738}, {"text": " I didn't draw the square for the station unless it was one of", "start": 5954.94, "stop": 5957.34, "id": 1739}, {"text": " those. So you can actually see where they are.", "start": 5957.34, "stop": 5959.3, "id": 1740}, {"text": " This is frustrating because this seems to be like the bottleneck limiting sort", "start": 5961.160000000001, "stop": 5964.78, "id": 1741}, {"text": " of, if you're doing end-to-end traffic in the net. I think something can be done", "start": 5964.78, "stop": 5969.92, "id": 1742}, {"text": " to solve this. But I tried something while I was doing the thesis. And", "start": 5969.92, "stop": 5976.62, "id": 1743}, {"text": " what I came up with was, well, maybe I need to compute something other than", "start": 5976.62, "stop": 5980.74, "id": 1744}, {"text": " minimum energy routes. In fact, maybe what we want to do is, is go twice as far.", "start": 5980.74, "stop": 5985.2, "id": 1745}, {"text": " Well, you could put a wormhole there, right?", "start": 5986.5, "stop": 5988.02, "id": 1746}, {"text": " Well, you could lay fiber across town, absolutely. Or hop up to another frequency", "start": 5988.52, "stop": 5993.5, "id": 1747}, {"text": " and put a point to one at Microlink across town. So what I did is I, the", "start": 5993.5, "stop": 6000.4, "id": 1748}, {"text": " one thing, the one experiment I had time to do and write up and put in the thesis", "start": 6000.4, "stop": 6003.46, "id": 1749}, {"text": " was, I added a knob to the routing. So that instead of minimum energy routing,", "start": 6003.46, "stop": 6007.72, "id": 1750}, {"text": " I'm doing minimize energy plus number, some constant times number of hops.", "start": 6007.92, "stop": 6012.96, "id": 1751}, {"text": " And that constant is a knob I was able to turn. And I turned that knob until the", "start": 6013.68, "stop": 6018.04, "id": 1752}, {"text": " average path links had dropped in half. Meaning we're", "start": 6018.04, "stop": 6020.62, "id": 1753}, {"text": " going about twice as far in every hop.", "start": 6020.62, "stop": 6022.24, "id": 1754}, {"text": " This still has the property that a suffix of a route is the route of that suffix.", "start": 6025.22, "stop": 6030.62, "id": 1755}, {"text": " So you can still have just a routing table and", "start": 6031.28, "stop": 6033.48, "id": 1756}, {"text": " everything. That took me well to think about.", "start": 6033.48, "stop": 6035.04, "id": 1757}, {"text": " And so I did this simulation. Now this is the same simulation as before with the", "start": 6036.260000000001, "stop": 6040.92, "id": 1758}, {"text": " Thousand Stations, but it's plotted at the same scale as my next", "start": 6040.92, "stop": 6043.46, "id": 1759}, {"text": " slide so we can compare them.", "start": 6043.46, "stop": 6045.2, "id": 1760}, {"text": " This is the Thousand Station simulation with power control and respect neighbor", "start": 6045.78, "stop": 6048.66, "id": 1761}, {"text": " turned on. This is the Thousand Station simulation with power control, respect", "start": 6048.66, "stop": 6053.92, "id": 1762}, {"text": " neighbor, and my modified routing that only goes,", "start": 6053.92, "stop": 6058.74, "id": 1763}, {"text": " that goes twice as far and a half.", "start": 6059.34, "stop": 6060.84, "id": 1764}, {"text": " I didn't print out the plot, but it also, it reduced the sharing by about a", "start": 6062.6, "stop": 6066.44, "id": 1765}, {"text": " factor of two. And instead of having the worst stations be 20% of the paths", "start": 6066.44, "stop": 6070.28, "id": 1766}, {"text": " through them, the worst stations are only 10% of the paths through them.", "start": 6070.28, "stop": 6073.0, "id": 1767}, {"text": " So the difference is, is that this whole distribution moved over about 5 dB.", "start": 6073.98, "stop": 6078.86, "id": 1768}, {"text": " So, or you'd have to reduce the, increase the processing gain so you're lowering", "start": 6081.96, "stop": 6086.52, "id": 1769}, {"text": " the data rate that you could actually send that and give them a fixed size.", "start": 6086.52, "stop": 6090.12, "id": 1770}, {"text": " So, so we have about a 5 dB difference in signal noise ratio. Remember I said the", "start": 6091.700000000001, "stop": 6095.18, "id": 1771}, {"text": " bit rate that you can send has a proportional signal noise ratio. So you can, so", "start": 6095.18, "stop": 6101.1, "id": 1772}, {"text": " about a, so the way to actually think about it is if you're going about twice as", "start": 6101.1, "stop": 6103.96, "id": 1773}, {"text": " far per hop, that means you've turned your transmitter", "start": 6103.96, "stop": 6106.88, "id": 1774}, {"text": " up about a factor of four in power.", "start": 6106.88, "stop": 6108.54, "id": 1775}, {"text": " That'd be 6 dB. So actually we should expect about a 6 dB", "start": 6109.34, "stop": 6113.86, "id": 1776}, {"text": " worsening in the signal to noise ratio. And what we've done in the middle of the", "start": 6113.86, "stop": 6119.98, "id": 1777}, {"text": " network, so that means we can only send that one fourth of the data", "start": 6119.98, "stop": 6123.06, "id": 1778}, {"text": " rate we would have been able to in the other network.", "start": 6123.06, "stop": 6124.62, "id": 1779}, {"text": " So we've had a factor of four penalty in signal to noise ratio. However, we", "start": 6124.7, "stop": 6127.98, "id": 1780}, {"text": " picked up a factor of two in sort of the, the congestion", "start": 6127.98, "stop": 6132.16, "id": 1781}, {"text": " performance in the middle of the network.", "start": 6132.16, "stop": 6133.74, "id": 1782}, {"text": " Unfortunately it's in that loss of a factor of two in total system performance,", "start": 6134.26, "stop": 6138.52, "id": 1783}, {"text": " assuming that what you're concerned about is throughput.", "start": 6139.48, "stop": 6141.24, "id": 1784}, {"text": " So, shocks. It seems to me that it's important", "start": 6145.1, "stop": 6148.84, "id": 1785}, {"text": " to actually take the minimum energy route.", "start": 6148.84, "stop": 6150.46, "id": 1786}, {"text": " I tried to figure out, and never got anywhere, and there's nothing in the thesis", "start": 6152.96, "stop": 6157.22, "id": 1787}, {"text": " about this, but I tried to figure out what, how would you compute the optimum", "start": 6157.22, "stop": 6160.78, "id": 1788}, {"text": " routes given configuration.", "start": 6160.78, "stop": 6162.94, "id": 1789}, {"text": " I can't even figure out how to write down the problem right so that people who", "start": 6163.74, "stop": 6167.04, "id": 1790}, {"text": " are really good at algorithms could help me.", "start": 6167.04, "stop": 6168.87, "id": 1791}, {"text": " It strikes me that what you need to do is to apply this method to a certain", "start": 6171.1, "stop": 6177.76, "id": 1792}, {"text": " size network, certain number of units, and then start", "start": 6177.76, "stop": 6183.62, "id": 1793}, {"text": " using a collapse factor on the unit.", "start": 6183.62, "stop": 6186.52, "id": 1794}, {"text": " Yes, absolutely. Have ways of getting past the middle of the net. I'll still wave", "start": 6187.26, "stop": 6192.3, "id": 1795}, {"text": " my hands at the end though about something I think would be interesting.", "start": 6192.3, "stop": 6194.76, "id": 1796}, {"text": " This led me to believe that minimum energy routing is important, and maybe some", "start": 6195.18, "stop": 6200.04, "id": 1797}, {"text": " more work to do here. But for now I believe in it.", "start": 6200.04, "stop": 6202.94, "id": 1798}, {"text": " Anyway, that's sort of the, this is not the", "start": 6203.84, "stop": 6205.58, "id": 1799}, {"text": " end of my talk, this is sort of the end of my thesis.", "start": 6205.58, "stop": 6207.08, "id": 1800}, {"text": " Sort of the conclusion of my thesis is that spread spectrum plus the multi-hop", "start": 6207.08, "stop": 6211.12, "id": 1801}, {"text": " routing and the scheduling method and the minimum energy routing led to a", "start": 6211.12, "stop": 6214.8, "id": 1802}, {"text": " functional, scalable packet radio network.", "start": 6214.8, "stop": 6216.54, "id": 1803}, {"text": " And scale by scalable, I mean millions of stations.", "start": 6217.46, "stop": 6219.56, "id": 1804}, {"text": " I still have, okay.", "start": 6222.94, "stop": 6225.32, "id": 1805}, {"text": " For a metro area, yeah.", "start": 6229.8, "stop": 6233.56, "id": 1806}, {"text": " Packets.", "start": 6241.32, "stop": 6241.82, "id": 1807}, {"text": " Can you give us a sense of the people on the edges of the metropolitan area and", "start": 6245.56, "stop": 6251.78, "id": 1808}, {"text": " people towards the middle of the metropolitan area, how much proportion they are", "start": 6251.78, "stop": 6257.24, "id": 1809}, {"text": " relaying other people and how much they have originated?", "start": 6257.24, "stop": 6260.32, "id": 1810}, {"text": " Well, what you really care about is how much performance do you get in the system", "start": 6260.6, "stop": 6263.76, "id": 1811}, {"text": " scales. And I'm going to do that.", "start": 6263.76, "stop": 6265.76, "id": 1812}, {"text": " Okay, so now I started thinking about what we could build.", "start": 6267.400000000001, "stop": 6269.94, "id": 1813}, {"text": " And I want to get my back to my thousand station", "start": 6270.66, "stop": 6272.44, "id": 1814}, {"text": " picture because I'm going to wave my hands.", "start": 6272.44, "stop": 6276.22, "id": 1815}, {"text": " No, what you're asking is exactly the right question. I have a way of addressing", "start": 6278.3, "stop": 6281.42, "id": 1816}, {"text": " that, which is still coming later in my talk. Not there yet.", "start": 6281.42, "stop": 6284.52, "id": 1817}, {"text": " Good question.", "start": 6286.14, "stop": 6286.76, "id": 1818}, {"text": " Actually, the ratio, I'm not so much concerned about how much traffic is my own", "start": 6288.26, "stop": 6292.76, "id": 1819}, {"text": " that I'm sending and how much am I relaying.", "start": 6292.76, "stop": 6294.9, "id": 1820}, {"text": " What I care about is how much do I get.", "start": 6295.1, "stop": 6296.76, "id": 1821}, {"text": " But if you're not happy when I get done with the talk, ask your question again.", "start": 6301.460000000001, "stop": 6305.44, "id": 1822}, {"text": " So I started thinking about what can we build. It was originally this 47 CFR 15", "start": 6308.1, "stop": 6313.12, "id": 1823}, {"text": ".247 authorization that sort of inspired me to go off and figure all this out.", "start": 6313.12, "stop": 6317.66, "id": 1824}, {"text": " Now I go try to fit this system in that allocation.", "start": 6317.76, "stop": 6320.4, "id": 1825}, {"text": " And it's sort of frustrating. The widest of those authorizations is", "start": 6321.820000000001, "stop": 6325.18, "id": 1826}, {"text": " only 125 MHz wide.", "start": 6325.18, "stop": 6326.72, "id": 1827}, {"text": " And with 23DV processing gain, the raw transmitter data rate is going to be", "start": 6327.2, "stop": 6330.18, "id": 1828}, {"text": " around 625 kilos per second.", "start": 6330.18, "stop": 6331.82, "id": 1829}, {"text": " A little bit of hand waving here, but I'm not off by more than a factor of two.", "start": 6331.82, "stop": 6335.6, "id": 1830}, {"text": " So the maximum throughput to a single neighbor is about 94 kilos per second.", "start": 6336.34, "stop": 6340.26, "id": 1831}, {"text": " And actually, there's a factor that you didn't see, but this is basically what", "start": 6340.7, "stop": 6344.18, "id": 1832}, {"text": " fraction in that plot where I had all the received duty cycles.", "start": 6344.18, "stop": 6348.48, "id": 1833}, {"text": " With another factor thrown in for the actual fitting of the packet bin because", "start": 6349.08, "stop": 6352.24, "id": 1834}, {"text": " you can't always put full-size packets in.", "start": 6352.24, "stop": 6354.62, "id": 1835}, {"text": " Anyway, so you can only go to a single neighbor at about 94 kilos per second.", "start": 6355.06, "stop": 6360.06, "id": 1836}, {"text": " So the way to think of that is what you've got is", "start": 6360.06, "stop": 6362.6, "id": 1837}, {"text": " you've got a net that kind of looks like that.", "start": 6362.6, "stop": 6364.22, "id": 1838}, {"text": " And every one of those little edges is about a", "start": 6364.98, "stop": 6366.8, "id": 1839}, {"text": " 94 kilos per second bi-directional pipe.", "start": 6366.8, "stop": 6368.62, "id": 1840}, {"text": " And now you can start thinking about traffic in terms of nodes and edges.", "start": 6369.42, "stop": 6372.56, "id": 1841}, {"text": " That's kind of frustrating because that's got to be shared by", "start": 6373.94, "stop": 6377.2, "id": 1842}, {"text": " 200,000 paths through it.", "start": 6377.2, "stop": 6379.34, "id": 1843}, {"text": " And I don't know how many of those actually have traffic on them.", "start": 6379.44, "stop": 6381.56, "id": 1844}, {"text": " So think, well, what could I do? Well, maybe, you know, there's all sorts", "start": 6384.460000000001, "stop": 6387.32, "id": 1845}, {"text": " of millimeter wave spectrum up there.", "start": 6387.32, "stop": 6388.84, "id": 1846}, {"text": " And if we wait a while, maybe we'll be able to build stuff there sometime.", "start": 6388.84, "stop": 6393.84, "id": 1847}, {"text": " And so a two gigahertz wide system with 23U processing gain, you can have a raw", "start": 6395.16, "stop": 6400.16, "id": 1848}, {"text": " transmitter data of about 10 megabits per second.", "start": 6400.16, "stop": 6402.16, "id": 1849}, {"text": " Maximum throughput to a single neighbor would be about 1.5 megabits per second.", "start": 6404.02, "stop": 6406.82, "id": 1850}, {"text": " So that's similar to a T1 leased line.", "start": 6406.96, "stop": 6409.36, "id": 1851}, {"text": " But still, you've got to share that.", "start": 6409.44, "stop": 6410.62, "id": 1852}, {"text": " And it's not clear to me that this is interesting.", "start": 6410.76, "stop": 6412.56, "id": 1853}, {"text": " It doesn't seem like in a million-station", "start": 6413.12, "stop": 6415.22, "id": 1854}, {"text": " network, you're getting enough performance.", "start": 6415.22, "stop": 6417.0, "id": 1855}, {"text": " So you might have a rush in the body.", "start": 6417.0, "stop": 6419.22, "id": 1856}, {"text": " I thought I might be able to do that. You don't do it on my direction.", "start": 6420.14, "stop": 6423.76, "id": 1857}, {"text": " Yeah, well, so what I didn't have time, another thing I didn't have time to", "start": 6424.24, "stop": 6429.52, "id": 1858}, {"text": " explore in the thesis is what is the effect of directional antennas?", "start": 6429.52, "stop": 6432.08, "id": 1859}, {"text": " And the way to think about this is, it's just 12 dB of directional gain.", "start": 6435.26, "stop": 6440.06, "id": 1860}, {"text": " And that means 6 dB at each end.", "start": 6440.36, "stop": 6442.22, "id": 1861}, {"text": " This is directional gain over Omni.", "start": 6442.52, "stop": 6444.12, "id": 1862}, {"text": " And this is very interesting because...", "start": 6444.6, "stop": 6446.16, "id": 1863}, {"text": " So it's Don, right? Don's talk two days ago, I was sitting here listening to it,", "start": 6450.160000000001, "stop": 6455.88, "id": 1864}, {"text": " and I'm like, oh, he started with directionality and then kind of mixed by, you", "start": 6455.88, "stop": 6460.18, "id": 1865}, {"text": " know, by the end you realize maybe he wanted to add spread spectrum.", "start": 6460.18, "stop": 6462.54, "id": 1866}, {"text": " I started with spread spectrum and Omni, and I got to the end and", "start": 6462.86, "stop": 6465.92, "id": 1867}, {"text": " think, well, maybe I really want directional.", "start": 6465.92, "stop": 6467.46, "id": 1868}, {"text": " And it's kind of like, I think we wind up at the same place once we've really", "start": 6467.46, "stop": 6473.22, "id": 1869}, {"text": " thought everything through and thought through the stuff we'd understand.", "start": 6473.22, "stop": 6475.46, "id": 1870}, {"text": " But really, I think all we need for directional gain is about 12 dB.", "start": 6476.280000000001, "stop": 6480.26, "id": 1871}, {"text": " And that's, I mean, 6 dB at the transmitter and 6 dB at the receiver.", "start": 6481.86, "stop": 6484.88, "id": 1872}, {"text": " And this is 6 dB over Omni, meaning that I've got a sort of a 6 dB main lobe", "start": 6485.06, "stop": 6489.56, "id": 1873}, {"text": " that, such that everything that's not in that main lobe is down 6", "start": 6489.56, "stop": 6492.82, "id": 1874}, {"text": " dB from what I've got in that main lobe.", "start": 6492.82, "stop": 6494.4, "id": 1875}, {"text": " And you do that at the transmitter and receiver, and you can add those together.", "start": 6494.4, "stop": 6497.56, "id": 1876}, {"text": " Exactly. So if you could do hard sector, hard quadrants as sectors, you'd only", "start": 6500.34, "stop": 6505.52, "id": 1877}, {"text": " have to have, like, you know, look in four different directions.", "start": 6505.52, "stop": 6508.08, "id": 1878}, {"text": " Exactly what I'm thinking.", "start": 6513.76, "stop": 6514.76, "id": 1879}, {"text": " Now, in fact, you probably wouldn't be able to produce", "start": 6515.28, "stop": 6518.28, "id": 1880}, {"text": " hard sectors, but you probably built six.", "start": 6518.28, "stop": 6520.02, "id": 1881}, {"text": " And each of them would have sort of a 6 dB main lobe.", "start": 6520.26, "stop": 6522.06, "id": 1882}, {"text": " And maybe you could actually get maybe another dB out of it with", "start": 6522.06, "stop": 6525.9, "id": 1883}, {"text": " 6, or maybe a half a dB or something.", "start": 6525.9, "stop": 6528.08, "id": 1884}, {"text": " But anyway, now, maybe we could get through with maybe 10 or maybe 12 dB of", "start": 6528.56, "stop": 6533.72, "id": 1885}, {"text": " spread spectrum processing gain with the directional gain.", "start": 6533.72, "stop": 6535.68, "id": 1886}, {"text": " You'd absolutely have to wrap this up with good error correcting codes", "start": 6535.8, "stop": 6538.44, "id": 1887}, {"text": " with this little processing gain.", "start": 6538.44, "stop": 6540.3, "id": 1888}, {"text": " But I think it's doable.", "start": 6540.44, "stop": 6541.34, "id": 1889}, {"text": " And then a 2 GHz wide system could have a raw throughput when your transmitter is", "start": 6542.02, "stop": 6546.1, "id": 1890}, {"text": " turned on of about 200 megabits per second.", "start": 6546.1, "stop": 6548.22, "id": 1891}, {"text": " And so the maximum throughput to a single main lobe would be, actually, more", "start": 6548.22, "stop": 6552.22, "id": 1892}, {"text": " recently, I've been saying about 25 megabits per second.", "start": 6552.22, "stop": 6554.22, "id": 1893}, {"text": " These are kind of hand waving numbers because they, you know, it all depends on", "start": 6554.36, "stop": 6557.46, "id": 1894}, {"text": " what the traffic is and a lot of things like that.", "start": 6557.46, "stop": 6559.04, "id": 1895}, {"text": " I like to think of, when I made the slide, this slide", "start": 6559.38, "stop": 6562.32, "id": 1896}, {"text": " is more than three years old.", "start": 6562.32, "stop": 6563.92, "id": 1897}, {"text": " These days I'm thinking 25 megabits per second.", "start": 6565.08, "stop": 6566.9, "id": 1898}, {"text": " So now, let's think about what the capacity of a system would be.", "start": 6567.3, "stop": 6573.06, "id": 1899}, {"text": " Now, what I've got on this slide is only a thousand stations.", "start": 6573.46, "stop": 6575.78, "id": 1900}, {"text": " But imagine this is a million stations.", "start": 6575.78, "stop": 6578.02, "id": 1901}, {"text": " I'm not actually going to point at any one station.", "start": 6578.22, "stop": 6579.62, "id": 1902}, {"text": " I'm just going to wave at the whole network here.", "start": 6579.72, "stop": 6581.1, "id": 1903}, {"text": " If this is a million stations and it's like a metropolitan area, the number,", "start": 6581.6, "stop": 6587.66, "id": 1904}, {"text": " the bottleneck is kind of getting across the middle.", "start": 6588.72, "stop": 6591.06, "id": 1905}, {"text": " Now, I haven't figured out how to do the routing to spread all the traffic out.", "start": 6591.16, "stop": 6594.88, "id": 1906}, {"text": " But imagine, but what is the total capacity from the left side to the right side?", "start": 6594.96, "stop": 6599.02, "id": 1907}, {"text": " Well, cut it down the middle and ask how many of these 25 megabits per", "start": 6599.88, "stop": 6604.58, "id": 1908}, {"text": " second bidirectional links you have cut.", "start": 6604.58, "stop": 6606.12, "id": 1909}, {"text": " I've thought about it and my intuition is it ought to be about the square root of", "start": 6606.78, "stop": 6609.6, "id": 1910}, {"text": " the number of stations or proportional to that.", "start": 6609.6, "stop": 6611.84, "id": 1911}, {"text": " But it really ought to be, wave my hands a little bit.", "start": 6611.98, "stop": 6614.28, "id": 1912}, {"text": " I actually took a bunch of these plots, drew a line across them and counted, and", "start": 6614.74, "stop": 6618.9, "id": 1913}, {"text": " always came out to be right around the square root of the number of stations.", "start": 6618.9, "stop": 6621.5, "id": 1914}, {"text": " So I believe that number now.", "start": 6622.08, "stop": 6623.64, "id": 1915}, {"text": " It matches intuition.", "start": 6624.06, "stop": 6625.08, "id": 1916}, {"text": " So if you've got a million stations and you cut it down the", "start": 6626.26, "stop": 6628.68, "id": 1917}, {"text": " middle, you cut about a thousand links.", "start": 6628.68, "stop": 6630.28, "id": 1918}, {"text": " If each of those thousand links is a 25 megabits per second bidirectional pipe,", "start": 6632.56, "stop": 6636.42, "id": 1919}, {"text": " what you have cut is 25 gigabits per second of capacity", "start": 6636.78, "stop": 6640.48, "id": 1920}, {"text": " from the left half to the right half of the system.", "start": 6640.48, "stop": 6642.22, "id": 1921}, {"text": " So that's the bottleneck.", "start": 6644.06, "stop": 6645.1, "id": 1922}, {"text": " We've only got 25 gigabits per second capacity in the middle of the net.", "start": 6645.36, "stop": 6648.4, "id": 1923}, {"text": " We've got half a million users on each side.", "start": 6648.48, "stop": 6650.18, "id": 1924}, {"text": " How should we think about that?", "start": 6653.420000000001, "stop": 6654.78, "id": 1925}, {"text": " Well, the way to think about that is take the 25 gigabits per second and go ahead", "start": 6654.78, "stop": 6660.46, "id": 1926}, {"text": " and do the division divided by the 500,000.", "start": 6660.46, "stop": 6662.76, "id": 1927}, {"text": " You come out with a number which is in units of bits per second.", "start": 6662.84, "stop": 6665.06, "id": 1928}, {"text": " Actually, I've got this on the next slide.", "start": 6665.68, "stop": 6667.08, "id": 1929}, {"text": " All these numbers I was just saying in the past couple minutes. 200 megabits per", "start": 6668.96, "stop": 6671.78, "id": 1930}, {"text": " second, 25 megabits per second bidirectional links, shared 25 gigabits per second", "start": 6671.78, "stop": 6675.92, "id": 1931}, {"text": " capacity across the middle from the left half", "start": 6675.92, "stop": 6678.0, "id": 1932}, {"text": " to the right half, or top to bottom.", "start": 6678.0, "stop": 6679.56, "id": 1933}, {"text": " It doesn't matter where you slice it.", "start": 6679.68, "stop": 6680.76, "id": 1934}, {"text": " You've got a bottleneck from there to there.", "start": 6680.78, "stop": 6682.24, "id": 1935}, {"text": " So the per user, if you divide, do the division, 25 gigabits per second divided", "start": 6682.740000000001, "stop": 6687.88, "id": 1936}, {"text": " by half a million, you get 50 kilobits per second.", "start": 6687.88, "stop": 6690.42, "id": 1937}, {"text": " Sort of per user data rate.", "start": 6693.280000000001, "stop": 6694.74, "id": 1938}, {"text": " Now, how to understand that is to think about, well, what's the best connected", "start": 6694.9, "stop": 6699.14, "id": 1939}, {"text": " unit, you know, if you wanted to really be on the internet.", "start": 6699.14, "stop": 6701.44, "id": 1940}, {"text": " Where do you go?", "start": 6702.08, "stop": 6702.62, "id": 1941}, {"text": " Well, you go to some major university that's got like a big pipe.", "start": 6702.7, "stop": 6705.72, "id": 1942}, {"text": " And actually, this number is changing.", "start": 6707.120000000001, "stop": 6709.6, "id": 1943}, {"text": " But if you take those big pipes, when I first did this calculation three years", "start": 6709.6, "stop": 6713.56, "id": 1944}, {"text": " ago, the big universities were typically collected over maybe a DS3, which is", "start": 6713.56, "stop": 6719.86, "id": 1945}, {"text": " about 50 megabits per second, 45 megabits per second.", "start": 6719.86, "stop": 6722.36, "id": 1946}, {"text": " You do the division on a university campus and you start coming out with", "start": 6722.64, "stop": 6724.9, "id": 1947}, {"text": " numbers that are about 5 kilobits per second.", "start": 6724.9, "stop": 6726.52, "id": 1948}, {"text": " You take that pipe size, divide it by the number of people on", "start": 6727.12, "stop": 6729.44, "id": 1949}, {"text": " campus, about 5 kilobits per second.", "start": 6729.44, "stop": 6731.76, "id": 1950}, {"text": " So this system seems to have 10 times the capacity of a major university", "start": 6731.76, "stop": 6738.08, "id": 1951}, {"text": " in the mid 1990s, had to the internet.", "start": 6738.08, "stop": 6740.92, "id": 1952}, {"text": " And that's exciting because that means this sort of can provide capacity", "start": 6742.38, "stop": 6745.96, "id": 1953}, {"text": " in a metropolitan area.", "start": 6745.96, "stop": 6747.64, "id": 1954}, {"text": " If you could build the 2 gigahertz wide system, and I don't think we have the", "start": 6747.72, "stop": 6750.14, "id": 1955}, {"text": " semiconductor to do that yet, but...", "start": 6750.14, "stop": 6751.76, "id": 1956}, {"text": " Just like all students are and always on the computer.", "start": 6752.46, "stop": 6754.86, "id": 1957}, {"text": " Yeah, yeah. So then, so I mean, yeah, you're sharing this.", "start": 6755.12, "stop": 6757.84, "id": 1958}, {"text": " And so it's just like the telephone system. I think they typically engineer for", "start": 6757.84, "stop": 6760.96, "id": 1959}, {"text": " only 10 people to pick up their phone and make a call at any given time.", "start": 6760.96, "stop": 6763.5, "id": 1960}, {"text": " Question here.", "start": 6764.32, "stop": 6764.66, "id": 1961}, {"text": " In the starting supposition that everybody has equal traffic on the network...", "start": 6764.68, "stop": 6771.0, "id": 1962}, {"text": " I did not... ...with a number of messages.", "start": 6771.46, "stop": 6774.88, "id": 1963}, {"text": " What happens if in reality, like there is on the internet,", "start": 6777.48, "stop": 6780.14, "id": 1964}, {"text": " where you have some major site?", "start": 6780.42, "stop": 6782.1, "id": 1965}, {"text": " I don't know. I remember, you know, the last things in my thesis is", "start": 6783.26, "stop": 6787.6, "id": 1966}, {"text": " like, until we have real user generating", "start": 6787.6, "stop": 6789.26, "id": 1967}, {"text": " traffic, we have no idea what the traffic is going to be.", "start": 6789.26, "stop": 6790.8, "id": 1968}, {"text": " But yeah, there'll probably be some concentration.", "start": 6791.32, "stop": 6792.94, "id": 1969}, {"text": " But this is an interesting system. It's really all the only argument I'm trying", "start": 6793.92, "stop": 6798.18, "id": 1970}, {"text": " to make here. It's an interesting amount of capacity.", "start": 6798.18, "stop": 6800.34, "id": 1971}, {"text": " The other issue for this, again, thinking about this, million stations.", "start": 6800.88, "stop": 6804.78, "id": 1972}, {"text": " If this is a million stations and you want to get from one side to the other,", "start": 6805.52, "stop": 6808.72, "id": 1973}, {"text": " well, you got it. The number of hops you got to go is about the, again,", "start": 6808.8, "stop": 6811.86, "id": 1974}, {"text": " the square root of the number of stations.", "start": 6811.96, "stop": 6813.46, "id": 1975}, {"text": " So to get across the metropolitan area of the million stations, you might have to", "start": 6814.08, "stop": 6816.96, "id": 1976}, {"text": " go a thousand hops to get from one side to the other, all the way across.", "start": 6816.96, "stop": 6820.12, "id": 1977}, {"text": " And in a 2 GHz wide system with 200 mbps raw transmitter data rate, 500 bits per", "start": 6822.120000000001, "stop": 6828.32, "id": 1978}, {"text": " packet, the packet transmission time is only 2.5 microseconds.", "start": 6828.32, "stop": 6832.48, "id": 1979}, {"text": " Now, but you've got to wait in pseudo-random schedules until you can send", "start": 6834.860000000001, "stop": 6839.52, "id": 1980}, {"text": " it. You've actually got to wait some number of slot times.", "start": 6839.52, "stop": 6841.18, "id": 1981}, {"text": " I'm thinking 10 microsecond slots here. And you've got to wait about, on", "start": 6841.26, "stop": 6844.38, "id": 1982}, {"text": " average, four, maybe five slots.", "start": 6844.38, "stop": 6846.06, "id": 1983}, {"text": " So it takes about a scheduling delay of about 50 microseconds per hop.", "start": 6846.58, "stop": 6849.86, "id": 1984}, {"text": " And if you're going to go a thousand hops, that's 50 milliseconds. One", "start": 6851.14, "stop": 6854.46, "id": 1985}, {"text": " way delay across the metropolitan area.", "start": 6854.46, "stop": 6856.04, "id": 1986}, {"text": " So you could get everybody talking to everybody.", "start": 6856.68, "stop": 6858.74, "id": 1987}, {"text": " So this, the conclusion between this capacity, which is 50 kbps, that's more", "start": 6858.74, "stop": 6865.52, "id": 1988}, {"text": " trunk, 10 times more capacity than typical", "start": 6865.52, "stop": 6867.94, "id": 1989}, {"text": " well-conversed universities on the Internet.", "start": 6867.94, "stop": 6869.48, "id": 1990}, {"text": " It's also way more capacity than a telephone company in a large metropolitan area", "start": 6869.58, "stop": 6874.32, "id": 1991}, {"text": " would have to have in terms of trunking to support", "start": 6874.32, "stop": 6876.84, "id": 1992}, {"text": " all the voice calls in the metropolitan area.", "start": 6876.84, "stop": 6878.44, "id": 1993}, {"text": " So this is a system, the delay, you can do voice", "start": 6878.98, "stop": 6882.98, "id": 1994}, {"text": " with 100 millisecond round trip time.", "start": 6882.98, "stop": 6884.66, "id": 1995}, {"text": " So this system has more capacity in the metropolitan area telephone", "start": 6885.38, "stop": 6888.24, "id": 1996}, {"text": " system. Voice.", "start": 6888.24, "stop": 6890.04, "id": 1997}, {"text": " And that's really neat. We could cancel our phone service", "start": 6891.62, "stop": 6894.34, "id": 1998}, {"text": " and just talk over this.", "start": 6894.34, "stop": 6895.9, "id": 1999}, {"text": " And long distance telephone companies could provide, you know, packet voice long", "start": 6896.4, "stop": 6901.22, "id": 2000}, {"text": " distance, like Internet long distance or something, I don't", "start": 6901.22, "stop": 6904.1, "id": 2001}, {"text": " know, across this thing.", "start": 6904.1, "stop": 6905.86, "id": 2002}, {"text": " They could come into an area and just put up a few points of presence.", "start": 6907.04, "stop": 6909.34, "id": 2003}, {"text": " Or maybe if they wanted to provide better service with less", "start": 6909.5, "stop": 6911.54, "id": 2004}, {"text": " delay, they'd have to get closer to you.", "start": 6911.54, "stop": 6913.08, "id": 2005}, {"text": " And now you'd have a choice as to whether you wanted to go all the way across", "start": 6913.08, "stop": 6915.94, "id": 2006}, {"text": " town with a cheap guy who's only got one point of presence or the quality long", "start": 6915.94, "stop": 6920.64, "id": 2007}, {"text": " distance provider that's actually gone in and put 100 things so they can", "start": 6920.64, "stop": 6923.42, "id": 2008}, {"text": " get, maybe even give you a higher capacity.", "start": 6923.42, "stop": 6925.1, "id": 2009}, {"text": " Now, how soon? I don't know.", "start": 6925.42, "stop": 6927.9, "id": 2010}, {"text": " When I finished the thesis, I said that this will be feasible in 7 to 10 years.", "start": 6929.68, "stop": 6933.0, "id": 2011}, {"text": " You could actually, by feasible I mean you could actually do this in", "start": 6933.2, "stop": 6936.74, "id": 2012}, {"text": " affordable consumer electronics.", "start": 6936.74, "stop": 6938.46, "id": 2013}, {"text": " And that's, you know, how soon can we do a 2 GHz chipping rate in a receiver", "start": 6940.960000000001, "stop": 6945.56, "id": 2014}, {"text": " that's doing error correcting codes and everything in", "start": 6945.56, "stop": 6948.78, "id": 2015}, {"text": " BLSI. It'd be full cost in BLSI, of course.", "start": 6948.78, "stop": 6950.74, "id": 2016}, {"text": " So here we are three years later and I think my prediction's about right, which", "start": 6951.82, "stop": 6954.76, "id": 2017}, {"text": " means subtract 3 from 7 and you get 4, subtract 3 from 10. So it's 4 to 7 years.", "start": 6954.76, "stop": 6959.0, "id": 2018}, {"text": " I think this could be affordable.", "start": 6959.7, "stop": 6961.56, "id": 2019}, {"text": " And actually this is more my research talk. This is like things I want to", "start": 6963.800000000001, "stop": 6968.08, "id": 2020}, {"text": " understand. What does real propagation look like?", "start": 6968.08, "stop": 6970.96, "id": 2021}, {"text": " I want to go out and measure impulse responses for 2 GHz wide signals.", "start": 6971.02, "stop": 6974.46, "id": 2022}, {"text": " [...] guess of one the other.", "start": 6977.08, "stop": 6978.44, "id": 2023}, {"text": " Yeah. Does directionality really work the way I think it does?", "start": 6978.62, "stop": 6982.22, "id": 2024}, {"text": " I've made this hand waving argument about this directional gain, but I haven't", "start": 6982.32, "stop": 6985.84, "id": 2025}, {"text": " done any simulations there. I've just tried to wrap my brain around it.", "start": 6985.84, "stop": 6988.74, "id": 2026}, {"text": " I really need to go off and actually come up with the more robust argument that", "start": 6988.74, "stop": 6992.02, "id": 2027}, {"text": " could actually be written down about using directionality as a trade", "start": 6992.02, "stop": 6995.9, "id": 2028}, {"text": " off for spread spectrum processing gain.", "start": 6995.9, "stop": 6997.4, "id": 2029}, {"text": " And maybe it's not 1 to 1. Maybe 12 dB of directional gain total only gives you", "start": 6997.56, "stop": 7003.76, "id": 2030}, {"text": " about the ability to throw away, to reduce your spread spectrum", "start": 7003.76, "stop": 7007.52, "id": 2031}, {"text": " processing gain by maybe 10 or 8 dB.", "start": 7007.52, "stop": 7009.32, "id": 2032}, {"text": " But it's certainly still worth it.", "start": 7010.02, "stop": 7011.8, "id": 2033}, {"text": " There's all these sorts of real networking issues. And actually I was in graduate", "start": 7012.34, "stop": 7015.48, "id": 2034}, {"text": " school in a networking research group, not a radio research group.", "start": 7015.48, "stop": 7018.72, "id": 2035}, {"text": " And so actually I went off and tackled the", "start": 7019.08, "stop": 7020.92, "id": 2036}, {"text": " problems that I thought were hard first.", "start": 7020.92, "stop": 7022.42, "id": 2037}, {"text": " And I was on the radio stuff and the scalable radio system.", "start": 7022.92, "stop": 7025.78, "id": 2038}, {"text": " But there's all sorts of hard networking problems about a completely ad hoc", "start": 7026.34, "stop": 7030.4, "id": 2039}, {"text": " network about how to actually, how does the station get a name like by name I", "start": 7030.4, "stop": 7035.78, "id": 2040}, {"text": " need a unique ID, a pile of bets.", "start": 7035.78, "stop": 7037.32, "id": 2041}, {"text": " And then how do you do routing across this system?", "start": 7038.44, "stop": 7041.44, "id": 2042}, {"text": " How do you actually compute the routes? I mean you want something that produces", "start": 7041.44, "stop": 7044.44, "id": 2043}, {"text": " something close to minimum energy routing.", "start": 7044.44, "stop": 7046.06, "id": 2044}, {"text": " But how do you actually compute the routes and how do you find the", "start": 7046.6, "stop": 7048.8, "id": 2045}, {"text": " path, how do you find which way to swing.", "start": 7048.8, "stop": 7050.36, "id": 2046}, {"text": " And then if somebody, if people in the metropolitan area are offering services", "start": 7051.36, "stop": 7054.28, "id": 2047}, {"text": " available, how do they advertise those?", "start": 7054.28, "stop": 7056.98, "id": 2048}, {"text": " How do they even publicize or spread the information that, hey, I'm not only just", "start": 7057.06, "stop": 7061.58, "id": 2049}, {"text": " going to address here, but if you actually contact me I can provide some service.", "start": 7061.58, "stop": 7065.12, "id": 2050}, {"text": " And maybe the service you want to get is an access to the Internet.", "start": 7066.540000000001, "stop": 7069.46, "id": 2051}, {"text": " Maybe across this system somebody's offering a service which is global worldwide", "start": 7069.6, "stop": 7073.76, "id": 2052}, {"text": " Internet connectivity where they'll hand you an address which is globally", "start": 7073.76, "stop": 7077.2, "id": 2053}, {"text": " routable, maybe through some protocol and now you can route.", "start": 7077.2, "stop": 7079.98, "id": 2054}, {"text": " Now IPv6 by the way is going to be all automatic address configuration,", "start": 7080.7, "stop": 7083.78, "id": 2055}, {"text": " even all the way down through the tree and the routers.", "start": 7083.8, "stop": 7085.52, "id": 2056}, {"text": " And so I imagine there'll be a global Internet with IPv6 and that sort of thing.", "start": 7086.14, "stop": 7090.1, "id": 2057}, {"text": " How to fund further research and development? I don't know.", "start": 7091.26, "stop": 7094.4, "id": 2058}, {"text": " I'm burning my savings account at the moment.", "start": 7095.06, "stop": 7096.72, "id": 2059}, {"text": " And then how can this be brought to the market? One of these things, this thing", "start": 7097.84, "stop": 7100.42, "id": 2060}, {"text": " would be really cool if everybody had one, but how do you sell the first", "start": 7100.42, "stop": 7102.8, "id": 2061}, {"text": " hundred in the metropolitan area?", "start": 7102.8, "stop": 7104.46, "id": 2062}, {"text": " Maybe you have to give them away. Is that enough?", "start": 7104.56, "stop": 7106.96, "id": 2063}, {"text": " Is it interesting enough? I don't know.", "start": 7107.4, "stop": 7108.96, "id": 2064}, {"text": " Now the political talk, actually this is a historical talk. What I think is going", "start": 7110.300000000001, "stop": 7115.86, "id": 2065}, {"text": " on here, imagine in 1975, think about the computer industry, the computer", "start": 7115.86, "stop": 7120.78, "id": 2066}, {"text": " industry, I think from about early 1960s, certainly at IBM when they started", "start": 7120.78, "stop": 7125.06, "id": 2067}, {"text": " doing the plans for the IBM 360, they understood that, hey, we're creating", "start": 7125.06, "stop": 7129.72, "id": 2068}, {"text": " a computer revolution, isn't this great?", "start": 7129.72, "stop": 7131.32, "id": 2069}, {"text": " And the world of the future is the world after we're going to have a", "start": 7132.12, "stop": 7136.3, "id": 2070}, {"text": " computer and information processing revolution.", "start": 7136.3, "stop": 7138.4, "id": 2071}, {"text": " And everybody's going to be using computers. But if you look at all the research", "start": 7138.86, "stop": 7141.72, "id": 2072}, {"text": " work and all the development work in the late 60s, the vision was that everybody", "start": 7141.72, "stop": 7146.2, "id": 2073}, {"text": " in the future is going to be using computers. And computers are big things that", "start": 7146.2, "stop": 7148.54, "id": 2074}, {"text": " fill machine rooms that need air conditioning and use lots of power and need", "start": 7148.54, "stop": 7151.08, "id": 2075}, {"text": " tending and people got to mount tapes and everything.", "start": 7151.08, "stop": 7152.84, "id": 2076}, {"text": " And so computers are going to be centralized things. And then what they were", "start": 7153.42, "stop": 7156.28, "id": 2077}, {"text": " going to do is they were going to figure out how to make computers reliable", "start": 7156.28, "stop": 7158.34, "id": 2078}, {"text": " enough and run time sharing on them and offer computers as a utility", "start": 7158.34, "stop": 7162.48, "id": 2079}, {"text": " and you'd have your computer jack in the wall.", "start": 7162.48, "stop": 7164.28, "id": 2080}, {"text": " And the computer industry was a blooming industry. There were companies that were", "start": 7166.62, "stop": 7170.28, "id": 2081}, {"text": " manufacturing computers and selling computers, sort of as equipment providers,", "start": 7170.28, "stop": 7174.54, "id": 2082}, {"text": " and there were the companies that bought computers and sold time on them for", "start": 7174.94, "stop": 7180.06, "id": 2083}, {"text": " people to come and run their payroll, for people to come and do their scientific", "start": 7180.06, "stop": 7182.92, "id": 2084}, {"text": " calculations. And the big companies, well, they could", "start": 7182.92, "stop": 7185.12, "id": 2085}, {"text": " afford to finance it internally themselves.", "start": 7185.12, "stop": 7186.72, "id": 2086}, {"text": " But for the vision of the future, at least, is how everybody's going to be able", "start": 7186.96, "stop": 7190.66, "id": 2087}, {"text": " to get affordable computing is that it was going to be offered", "start": 7190.66, "stop": 7194.3, "id": 2088}, {"text": " as a service that you paid for.", "start": 7194.3, "stop": 7195.9, "id": 2089}, {"text": " You had a monthly bill. It was going to be your computer", "start": 7196.4800000000005, "stop": 7199.28, "id": 2090}, {"text": " bill. It was going to be utility on the wall.", "start": 7199.28, "stop": 7200.96, "id": 2091}, {"text": " It's really neat to read all the visionary papers from the 60s because the future", "start": 7202.2, "stop": 7205.72, "id": 2092}, {"text": " is a world where everybody has access to a computer, but it's off somewhere else.", "start": 7205.72, "stop": 7209.56, "id": 2093}, {"text": " And what happened is, in 1975, people started proposing that maybe, actually,", "start": 7210.74, "stop": 7217.24, "id": 2094}, {"text": " you build your computer or you go to the store and you buy your computer, you", "start": 7218.34, "stop": 7221.94, "id": 2095}, {"text": " write a check for it, or actually these days it's plastic money, but you take", "start": 7221.94, "stop": 7226.8, "id": 2096}, {"text": " the computer home. You can afford it.", "start": 7226.8, "stop": 7228.38, "id": 2097}, {"text": " And you carry it home and use it. And, of course, in 1975, that's a ridiculous", "start": 7229.2, "stop": 7234.74, "id": 2098}, {"text": " idea. You can't afford a real computer.", "start": 7234.74, "stop": 7237.86, "id": 2099}, {"text": " A computer is just a toy. You can't do anything useful on it. In", "start": 7238.02, "stop": 7241.34, "id": 2100}, {"text": " fact, they were just toys at the beginning.", "start": 7241.34, "stop": 7242.92, "id": 2101}, {"text": " But, actually, there's a wonderful book by Clayton Christensen called The", "start": 7242.92, "stop": 7247.84, "id": 2102}, {"text": " Innovator's Dilemma, and he talks about how disruptive technology", "start": 7247.84, "stop": 7254.54, "id": 2103}, {"text": " displaces established industries, like sort", "start": 7254.54, "stop": 7260.28, "id": 2104}, {"text": " of stealth coming from below.", "start": 7260.28, "stop": 7262.0, "id": 2105}, {"text": " And the PC was like this.", "start": 7262.24, "stop": 7263.54, "id": 2106}, {"text": " And, anyway, so here's my sort of grand statement. It's like", "start": 7266.06, "stop": 7269.92, "id": 2107}, {"text": " you could own your own telecommunications network.", "start": 7269.92, "stop": 7271.5599999999995, "id": 2108}, {"text": " My vision is that the box that goes on the house is something that you", "start": 7272.18, "stop": 7276.48, "id": 2109}, {"text": " go to the store and you buy one.", "start": 7276.48, "stop": 7278.82, "id": 2110}, {"text": " You take it home when you put it in your house, and there's no monthly bill.", "start": 7278.92, "stop": 7280.8, "id": 2111}, {"text": " Well, there's no monthly bill for long distance.", "start": 7281.32, "stop": 7282.74, "id": 2112}, {"text": " There's no monthly bill for the metropolitan area.", "start": 7283.02, "stop": 7284.56, "id": 2113}, {"text": " And the way to think about that is that", "start": 7285.1, "stop": 7287.76, "id": 2114}, {"text": " what is, you know, your bill for the long distance.", "start": 7287.76, "stop": 7291.02, "id": 2115}, {"text": " Most of what, even what you pay for a long distance call today goes to the phone", "start": 7291.02, "stop": 7295.08, "id": 2116}, {"text": " company on your end and the phone company at the far end.", "start": 7295.08, "stop": 7297.82, "id": 2117}, {"text": " And if you're paying nine cents a minute, it's like four cents a minute to the", "start": 7298.28, "stop": 7300.96, "id": 2118}, {"text": " far end, four cents a minute to your end.", "start": 7300.96, "stop": 7302.46, "id": 2119}, {"text": " And the long distance company gets to keep about a penny per minute to pay for", "start": 7302.68, "stop": 7306.16, "id": 2120}, {"text": " its infrastructure investment and all of its operating costs and profits.", "start": 7306.16, "stop": 7310.54, "id": 2121}, {"text": " Long distance is actually very cheap, except that they have to find a way to get", "start": 7311.74, "stop": 7315.62, "id": 2122}, {"text": " to you, the access.", "start": 7315.62, "stop": 7317.66, "id": 2123}, {"text": " Some people say the last model problem. It's", "start": 7317.66, "stop": 7319.66, "id": 2124}, {"text": " really the metropolitan area problem.", "start": 7319.66, "stop": 7321.34, "id": 2125}, {"text": " And I think that the right way to do this is to, you know, own most of all your", "start": 7322.1, "stop": 7326.88, "id": 2126}, {"text": " telecommunications and perhaps global worldwide internet connectivity for sort of", "start": 7326.88, "stop": 7331.3, "id": 2127}, {"text": " big packet data sort of stuff.", "start": 7331.3, "stop": 7332.8, "id": 2128}, {"text": " Maybe you can pay 60 bucks per year flat rate for sort of unlimited service that", "start": 7332.92, "stop": 7337.38, "id": 2129}, {"text": " you can get across one of these things.", "start": 7337.38, "stop": 7339.12, "id": 2130}, {"text": " And maybe long distance calls, because you actually care about the delay, maybe", "start": 7339.58, "stop": 7343.5, "id": 2131}, {"text": " that's something that would require that you actually pay on a per call basis,", "start": 7343.5, "stop": 7346.52, "id": 2132}, {"text": " that we could get the, you know, we could get the, maybe we could get the long", "start": 7346.52, "stop": 7349.78, "id": 2133}, {"text": " distance rates down to maybe one or two cents a minute.", "start": 7349.78, "stop": 7352.06, "id": 2134}, {"text": " If the access on both ends was across a network like this.", "start": 7352.32, "stop": 7355.78, "id": 2135}, {"text": " [...]", "start": 7356.22, "stop": 7357.48, "id": 2136}, {"text": " What? ...how they care about the long distance companies plugging into...", "start": 7358.52, "stop": 7362.44, "id": 2137}, {"text": " This system?", "start": 7362.44, "stop": 7363.22, "id": 2138}, {"text": " Oh, there's a huge political problem there, but fortunately, it's only a small", "start": 7363.54, "stop": 7367.24, "id": 2139}, {"text": " fraction of the world's population that lives under", "start": 7367.24, "stop": 7369.88, "id": 2140}, {"text": " phone companies that are regulated by the FCC.", "start": 7369.88, "stop": 7372.08, "id": 2141}, {"text": " It's only, it's the five billion population in the world, and there's only about", "start": 7374.599999999999, "stop": 7377.96, "id": 2142}, {"text": " a little over a quarter billion in the US.", "start": 7377.96, "stop": 7380.32, "id": 2143}, {"text": " So there's a factor of 20.", "start": 7380.52, "stop": 7381.52, "id": 2144}, {"text": " So about, what's the five percent of the world's population is in the US.", "start": 7381.74, "stop": 7384.86, "id": 2145}, {"text": " So...", "start": 7386.14, "stop": 7386.52, "id": 2146}, {"text": " So even just in the US, this sort of idea of monthly bills versus no monthly", "start": 7387.66, "stop": 7391.34, "id": 2147}, {"text": " bills, one of the things that a lot of people are talking about today, there's a", "start": 7391.34, "stop": 7394.7, "id": 2148}, {"text": " great feeling by a lot of people that we are", "start": 7394.7, "stop": 7396.48, "id": 2149}, {"text": " upon a telecommunications revolution.", "start": 7396.48, "stop": 7398.22, "id": 2150}, {"text": " The internet has just happened in a big way,", "start": 7398.22, "stop": 7400.28, "id": 2151}, {"text": " and there's all this, you know, mobile stuff.", "start": 7400.6, "stop": 7402.1, "id": 2152}, {"text": " What I've talked about is a fixed network.", "start": 7402.48, "stop": 7403.98, "id": 2153}, {"text": " I don't fully understand mobility yet and what should be done about that.", "start": 7404.38, "stop": 7407.92, "id": 2154}, {"text": " Deploy this...", "start": 7408.16, "stop": 7409.7, "id": 2155}, {"text": " Just changing the subject for a moment.", "start": 7409.7, "stop": 7410.74, "id": 2156}, {"text": " A fixed network like this sure would be a neat base from which maybe all these", "start": 7410.86, "stop": 7415.86, "id": 2157}, {"text": " boxes also have a little micro cell thing from which you can then get in on some", "start": 7415.86, "stop": 7419.88, "id": 2158}, {"text": " other partition device up to one of these to go across town.", "start": 7419.88, "stop": 7422.7, "id": 2159}, {"text": " But anyway...", "start": 7424.1, "stop": 7424.9, "id": 2160}, {"text": " I've run around and said, no monthly bills, no monthly bills.", "start": 7425.76, "stop": 7428.34, "id": 2161}, {"text": " Actually, David Hughes is running around and saying, free communication.", "start": 7428.54, "stop": 7431.8, "id": 2162}, {"text": " You know, this part 15 devices have it.", "start": 7432.62, "stop": 7434.46, "id": 2163}, {"text": " Actually, free is not the right word.", "start": 7434.52, "stop": 7435.64, "id": 2164}, {"text": " It's user financed.", "start": 7435.74, "stop": 7436.58, "id": 2165}, {"text": " The user paid for it all up front, just like the PC is not free computing.", "start": 7437.32, "stop": 7442.4, "id": 2166}, {"text": " It is free computing compared to maybe the point of view of a computer utility.", "start": 7442.84, "stop": 7447.1, "id": 2167}, {"text": " But you paid for it all up front.", "start": 7447.4, "stop": 7449.14, "id": 2168}, {"text": " It's user...", "start": 7449.4, "stop": 7450.06, "id": 2169}, {"text": " Yeah, it's user financed.", "start": 7450.9800000000005, "stop": 7452.24, "id": 2170}, {"text": " I guess you do have to pay the power bill.", "start": 7452.52, "stop": 7453.74, "id": 2171}, {"text": " Maybe you can pedal your bicycle or solar panels, as we heard about last night.", "start": 7453.74, "stop": 7458.08, "id": 2172}, {"text": " But I actually think this version of, you know, for", "start": 7458.74, "stop": 7461.5, "id": 2173}, {"text": " all of us, you know, for society...", "start": 7461.5, "stop": 7464.14, "id": 2174}, {"text": " I don't know, I'm rambling on here.", "start": 7464.14, "stop": 7466.44, "id": 2175}, {"text": " But I think the idea of no monthly bills is a very important one because", "start": 7466.54, "stop": 7470.46, "id": 2176}, {"text": " telephone penetration in the United States is somewhere", "start": 7470.46, "stop": 7472.92, "id": 2177}, {"text": " between 90 and 95 percent.", "start": 7472.92, "stop": 7474.44, "id": 2178}, {"text": " And the people who study this thing get into big arguments about whether", "start": 7474.54, "stop": 7476.92, "id": 2179}, {"text": " it's 90 or 95 percent.", "start": 7476.92, "stop": 7478.46, "id": 2180}, {"text": " It's stunningly low.", "start": 7479.6, "stop": 7480.44, "id": 2181}, {"text": " I thought I'd already had a phone.", "start": 7480.44, "stop": 7481.4, "id": 2182}, {"text": " But actually, quite a few, you know, maybe one in 20 or one in 10 households", "start": 7481.6, "stop": 7484.74, "id": 2183}, {"text": " in the U.S. do not have a working telephone.", "start": 7484.74, "stop": 7486.42, "id": 2184}, {"text": " And what's the problem?", "start": 7488.22, "stop": 7489.36, "id": 2185}, {"text": " Well, the standard mantra among those who worry about this problem is", "start": 7489.8, "stop": 7494.04, "id": 2186}, {"text": " that it's the problem of affordability.", "start": 7494.04, "stop": 7495.68, "id": 2187}, {"text": " But it's not.", "start": 7496.84, "stop": 7497.52, "id": 2188}, {"text": " It's not the affordability.", "start": 7497.68, "stop": 7499.22, "id": 2189}, {"text": " It's that in order to have a telephone, you have to have good credit.", "start": 7499.6, "stop": 7502.32, "id": 2190}, {"text": " Because a phone, you can run up a bill.", "start": 7503.08, "stop": 7504.44, "id": 2191}, {"text": " Or if you fail to pay, you know, before they go in trouble putting in", "start": 7504.46, "stop": 7506.94, "id": 2192}, {"text": " service, then they'll actually want to know they're going to get their money.", "start": 7506.94, "stop": 7508.64, "id": 2193}, {"text": " So it's actually easier to afford for end users, for those who aren't terribly", "start": 7508.64, "stop": 7514.1, "id": 2194}, {"text": " wealthy or not the most wealthy in society, it's easier for them to figure out", "start": 7514.1, "stop": 7519.0, "id": 2195}, {"text": " how to save up their money and pay to buy the PC or buy the television than it is", "start": 7519.0, "stop": 7523.8, "id": 2196}, {"text": " to figure out how for them to reliably enough pay a monthly bill for a service.", "start": 7523.8, "stop": 7528.28, "id": 2197}, {"text": " And so this sort of system, instead of the cross subsidy thing, which is what", "start": 7528.8, "stop": 7533.46, "id": 2198}, {"text": " we've got now with the whole telephone, you can still get a phone light, you", "start": 7533.46, "stop": 7538.32, "id": 2199}, {"text": " know, in some states you can still, you know, if you", "start": 7538.32, "stop": 7540.96, "id": 2200}, {"text": " qualify for certain federal assistance.", "start": 7540.96, "stop": 7542.72, "id": 2201}, {"text": " I think this is actually a better way to provide communication to everybody.", "start": 7543.34, "stop": 7548.04, "id": 2202}, {"text": " In fact, you know, I think back in the 70s there were probably people who", "start": 7548.7, "stop": 7551.56, "id": 2203}, {"text": " had CB radios who didn't have telephones.", "start": 7551.56, "stop": 7553.14, "id": 2204}, {"text": " And we have a question here.", "start": 7554.36, "stop": 7555.88, "id": 2205}, {"text": " That's television penetration.", "start": 7555.96, "stop": 7557.04, "id": 2206}, {"text": " Yeah, more people have, that was the second point on my slide.", "start": 7558.6, "stop": 7562.26, "id": 2207}, {"text": " Apparently, television penetration in the United States is like 99.5 or 99.8", "start": 7562.26, "stop": 7567.08, "id": 2208}, {"text": " percent of households have a television, working television.", "start": 7567.08, "stop": 7569.76, "id": 2209}, {"text": " So, and there's no monthly bill associated with a television.", "start": 7570.8, "stop": 7573.48, "id": 2210}, {"text": " You just go to the store and you", "start": 7574.04, "stop": 7575.16, "id": 2211}, {"text": " buy it. Well, you know, they're paying for it with that.", "start": 7575.16, "stop": 7576.8, "id": 2212}, {"text": " They're paying for the, yeah, that's true. Now England is different.", "start": 7577.5, "stop": 7580.78, "id": 2213}, {"text": " So, what about spectrum? Actually, I believe 59 to 64 gigahertz is", "start": 7581.28, "stop": 7586.62, "id": 2214}, {"text": " already sort of open.", "start": 7586.62, "stop": 7588.54, "id": 2215}, {"text": " And maybe this whole system could be built there. The problem there is you get a", "start": 7588.54, "stop": 7591.7, "id": 2216}, {"text": " 15 dB per kilometer attenuation of a free space loss because of an oxygen.", "start": 7591.7, "stop": 7595.62, "id": 2217}, {"text": " There's a quantum resonance. That would be an advantage except it reduces the", "start": 7595.96, "stop": 7601.48, "id": 2218}, {"text": " maximum range of when you start with two stations.", "start": 7601.48, "stop": 7603.62, "id": 2219}, {"text": " And so, actually, I don't think it, it might not be the right place to start.", "start": 7603.92, "stop": 7606.88, "id": 2220}, {"text": " And I'm still thinking about all this.", "start": 7607.26, "stop": 7609.14, "id": 2221}, {"text": " But what, this, the idea that the maximum utility is extracted from spectrum", "start": 7609.14, "stop": 7615.9, "id": 2222}, {"text": " when everybody is sort of experiencing maximum interference", "start": 7615.9, "stop": 7618.9, "id": 2223}, {"text": " kind of taught me something.", "start": 7618.9, "stop": 7622.26, "id": 2224}, {"text": " And I think the FCC, you know, the micromanagement of the spectrum, which is more", "start": 7623.06, "stop": 7627.8, "id": 2225}, {"text": " or less what the FCC has been doing for most of the century, they think they", "start": 7627.8, "stop": 7632.26, "id": 2226}, {"text": " started in the 1920s, was the right public policy given that the radio technology", "start": 7632.26, "stop": 7636.3, "id": 2227}, {"text": " we had at the time was stuff that was linear modulation", "start": 7636.3, "stop": 7641.0, "id": 2228}, {"text": " and linear detection basically.", "start": 7641.0, "stop": 7642.52, "id": 2229}, {"text": " It's AM, linear modulation, even single side band.", "start": 7642.7, "stop": 7645.0, "id": 2230}, {"text": " But now that we have computers, and, you know, there's, there's more law, more is", "start": 7646.86, "stop": 7650.52, "id": 2231}, {"text": " law thing, where every 18 months for the same money you", "start": 7650.52, "stop": 7652.66, "id": 2232}, {"text": " can buy something that's twice as fast.", "start": 7652.66, "stop": 7654.2, "id": 2233}, {"text": " You know, we wait maybe 15 more years and the computer's gonna be a thousand", "start": 7654.2, "stop": 7658.46, "id": 2234}, {"text": " times faster. And that's just a computer.", "start": 7658.46, "stop": 7661.04, "id": 2235}, {"text": " Well, even with custom VLSI, the amount of processing is gonna be able to do to", "start": 7661.22, "stop": 7664.98, "id": 2236}, {"text": " go from wide, to take wide band signals and like figure out, you", "start": 7664.98, "stop": 7668.82, "id": 2237}, {"text": " know, who's trying to send you what in them.", "start": 7668.82, "stop": 7670.4, "id": 2238}, {"text": " Makes me think that for the future, where we should be headed for public policy", "start": 7671.78, "stop": 7677.3, "id": 2239}, {"text": " for spectrum allocation is deregulation.", "start": 7677.3, "stop": 7679.52, "id": 2240}, {"text": " And what I mean by that is, basically remove rules so that you can transmit", "start": 7679.9800000000005, "stop": 7686.32, "id": 2241}, {"text": " whatever you want, whenever you want, more or less without any", "start": 7686.32, "stop": 7689.02, "id": 2242}, {"text": " rules. And maybe we need some power caps.", "start": 7689.02, "stop": 7690.78, "id": 2243}, {"text": " That goes against your power control because...", "start": 7691.98, "stop": 7694.52, "id": 2244}, {"text": " Actually, I mean, I think you build power control in the", "start": 7695.56, "stop": 7698.72, "id": 2245}, {"text": " system. Yeah, there's a problem there.", "start": 7698.72, "stop": 7700.6, "id": 2246}, {"text": " And I was like, they still would have to cooperate.", "start": 7700.8, "stop": 7702.38, "id": 2247}, {"text": " No, you could just go to another band. There's a lot of 2 GHz wide", "start": 7703.64, "stop": 7707.18, "id": 2248}, {"text": " bands between 0 and 100 GHz.", "start": 7707.18, "stop": 7708.68, "id": 2249}, {"text": " So I actually think...", "start": 7709.52, "stop": 7710.7, "id": 2250}, {"text": " It's regulated so your neighbor could be occupying 17 of them.", "start": 7711.06, "stop": 7714.46, "id": 2251}, {"text": " But then there's 93, you know, 83 other GHz wide spectrum. And I think perhaps", "start": 7715.2, "stop": 7721.7, "id": 2252}, {"text": " maybe it only makes sense to deregulate the spectrum above maybe a GHz. Maybe.", "start": 7721.7, "stop": 7726.98, "id": 2253}, {"text": " But actually, I don't know. I have a suggested target rate for... Why say", "start": 7728.580000000001, "stop": 7733.02, "id": 2254}, {"text": " deregulate? I mean, basically get rid of any federal licensing or", "start": 7733.02, "stop": 7737.98, "id": 2255}, {"text": " type acceptance rules for regulation.", "start": 7737.98, "stop": 7739.98, "id": 2256}, {"text": " And, you know, every time you double the frequency, you get sort of different", "start": 7740.88, "stop": 7743.52, "id": 2257}, {"text": " propagation characteristics. So different pieces of the spectrum are useful for", "start": 7743.52, "stop": 7746.64, "id": 2258}, {"text": " different things. Even above a GHz, you get different properties.", "start": 7746.64, "stop": 7750.12, "id": 2259}, {"text": " And so you might want to build a system here or you might want to build a system", "start": 7750.56, "stop": 7753.3, "id": 2260}, {"text": " there. But I think the sort of...", "start": 7753.3, "stop": 7755.280000000001, "id": 2261}, {"text": " You know, where the technology sort of could take over and we wouldn't need rules", "start": 7756.38, "stop": 7759.76, "id": 2262}, {"text": " anymore for the spectrum is that we could do 2% in each octave each year", "start": 7759.76, "stop": 7764.2, "id": 2263}, {"text": " beginning in the year 2000, which would nearly", "start": 7764.2, "stop": 7766.4, "id": 2264}, {"text": " complete deregulation by the year 2050.", "start": 7766.4, "stop": 7768.22, "id": 2265}, {"text": " That's, I think, my intuition sort of says would be sort of the right rate at", "start": 7768.96, "stop": 7773.4, "id": 2266}, {"text": " which to deregulate for public policy reasons.", "start": 7773.4, "stop": 7775.18, "id": 2267}, {"text": " Now, what about amateur radio? I still want to be able to do sideband and", "start": 7775.18, "stop": 7779.42, "id": 2268}, {"text": " see if I can, you know, hear that guy in New", "start": 7779.42, "stop": 7780.98, "id": 2269}, {"text": " Zealand who's only transmitting with 5 watts.", "start": 7780.98, "stop": 7783.04, "id": 2270}, {"text": " Well, that's shortwave. I've already said that. But actually, I think it might", "start": 7783.76, "stop": 7788.32, "id": 2271}, {"text": " make sense to keep some handband kind of things around and call them the public", "start": 7788.32, "stop": 7795.22, "id": 2272}, {"text": " parts of the spectrum.", "start": 7795.22, "stop": 7797.48, "id": 2273}, {"text": " The place where you can actually go play with what we think of as weak signal or", "start": 7797.48, "stop": 7801.82, "id": 2274}, {"text": " linear modulation techniques. Because there's an important educational aspect to", "start": 7801.82, "stop": 7806.6, "id": 2275}, {"text": " actually, you know, transmitting and playing with the receiver and being able to", "start": 7806.6, "stop": 7809.6, "id": 2276}, {"text": " run around with it and doing things like I was doing, which was Fox-Honing.", "start": 7809.6, "stop": 7812.4, "id": 2277}, {"text": " You could Fox-Honed in a spread spectrum world as well. But I don't think I ever", "start": 7813.1, "stop": 7818.26, "id": 2278}, {"text": " would have done this thesis if I wasn't actually running around playing with", "start": 7818.26, "stop": 7820.9, "id": 2279}, {"text": " radios for fun because I learned a lot there.", "start": 7820.9, "stop": 7824.4, "id": 2280}, {"text": " And I think it'd be nice to have some spectrum to play with for learning", "start": 7824.4, "stop": 7828.4, "id": 2281}, {"text": " purposes. You can learn with wideband systems as", "start": 7828.4, "stop": 7831.0, "id": 2282}, {"text": " well, even with everybody else out there.", "start": 7831.0, "stop": 7832.54, "id": 2283}, {"text": " But there's something nice about actually being able to turn a receiver on and", "start": 7832.56, "stop": 7835.82, "id": 2284}, {"text": " hear the thermal noise floor. And it'd be nice", "start": 7835.82, "stop": 7838.12, "id": 2285}, {"text": " if there were some places in the spectrum.", "start": 7838.12, "stop": 7839.98, "id": 2286}, {"text": " Now, the other places in the spectrum which we can never deregulate are the radio", "start": 7840.14, "stop": 7843.6, "id": 2287}, {"text": " astronomy people. If they want to continue to do earth-based radio astronomy or", "start": 7843.6, "stop": 7847.76, "id": 2288}, {"text": " they could go build a base on the far side of the moon.", "start": 7847.76, "stop": 7849.78, "id": 2289}, {"text": " But now I'm getting really wacko and that's really all I had to say today. And I", "start": 7850.700000000001, "stop": 7855.0, "id": 2290}, {"text": " can't...", "start": 7855.0, "stop": 7857.04, "id": 2291}, {"text": " Thank you.", "start": 7857.04, "stop": 7857.6, "id": 2292}, {"text": " And while I talked longer than I thought I was going to.", "start": 7861.4400000000005, "stop": 7863.52, "id": 2293}, {"text": " Build a base on the far side of the moon? Yeah.", "start": 7871.580000000001, "stop": 7873.88, "id": 2294}, {"text": " So thank you, Greg, for inviting me to do this.", "start": 7875.96, "stop": 7877.88, "id": 2295}, {"text": " Thank you.", "start": 7878.18, "stop": 7878.74, "id": 2296}]}