0 00:00:00,000 --> 00:00:30,000 Dear viewer, these subtitles were generated by a machine via the service Trint and therefore are (very) buggy. If you are capable, please help us to create good quality subtitles: https://c3subtitles.de/talk/51 Thanks! 1 00:00:13,030 --> 00:00:15,039 OK, for decision, I think we will do 2 00:00:15,040 --> 00:00:17,139 something more interactive, 3 00:00:17,140 --> 00:00:19,359 so according to Data Cobb, if it's 4 00:00:19,360 --> 00:00:21,519 OK for you, we can if 5 00:00:21,520 --> 00:00:23,679 anybody has any question at any time, 6 00:00:23,680 --> 00:00:25,779 just put up your hand and 7 00:00:25,780 --> 00:00:27,849 I will try to to come there 8 00:00:27,850 --> 00:00:30,069 and try 9 00:00:30,070 --> 00:00:31,249 to answer your questions. 10 00:00:31,250 --> 00:00:33,309 Yeah. Um, so you 11 00:00:33,310 --> 00:00:34,959 will introduce yourself. 12 00:00:34,960 --> 00:00:36,429 So good luck. 13 00:00:36,430 --> 00:00:37,329 Thank you. 14 00:00:37,330 --> 00:00:39,909 Thanks. Um, I hope I can 15 00:00:39,910 --> 00:00:41,229 just set up this. 16 00:00:53,980 --> 00:00:55,840 OK, I'm sorry I 17 00:00:57,760 --> 00:00:59,049 was late, it's only. 18 00:01:02,330 --> 00:01:03,330 OK, 19 00:01:04,550 --> 00:01:06,290 that's the wrong window, the wrong. 20 00:01:33,400 --> 00:01:34,689 Are there any questions so far? 21 00:01:51,710 --> 00:01:54,099 OK, I don't know why 22 00:01:54,100 --> 00:01:56,450 is insisting to use my second screen. 23 00:02:02,630 --> 00:02:05,209 OK, I'll just 24 00:02:05,210 --> 00:02:07,129 yeah, OK, I'll just use it this way, 25 00:02:08,360 --> 00:02:10,579 and I haven't got it on my screen, so 26 00:02:10,580 --> 00:02:12,589 I have to look at the presentation at the 27 00:02:12,590 --> 00:02:13,610 PMI. I'm sorry. 28 00:02:15,200 --> 00:02:16,520 And I'm sorry for interrupt. 29 00:02:17,930 --> 00:02:19,490 OK, there's also a screen. 30 00:02:20,770 --> 00:02:22,039 Thanks. 31 00:02:22,040 --> 00:02:23,040 Um, 32 00:02:24,500 --> 00:02:26,879 so my name is Kim 33 00:02:26,880 --> 00:02:29,239 Topfer. I am from Vienna. 34 00:02:29,240 --> 00:02:32,179 Um, I made my amateur radio 35 00:02:32,180 --> 00:02:34,489 license in 2010 36 00:02:34,490 --> 00:02:36,919 and in 2006 37 00:02:36,920 --> 00:02:39,199 I started at the Frankfurt, 38 00:02:39,200 --> 00:02:41,359 uh, Community Wireless Network. 39 00:02:41,360 --> 00:02:43,429 And since then I've been 40 00:02:43,430 --> 00:02:45,769 interested in wireless communications, 41 00:02:45,770 --> 00:02:48,079 high frequency engineering and of 42 00:02:48,080 --> 00:02:50,119 course, digital modulations and 43 00:02:50,120 --> 00:02:51,120 communications. 44 00:02:51,920 --> 00:02:53,439 And, um, 45 00:02:54,710 --> 00:02:58,219 I'm studying at, uh, Venice 46 00:02:58,220 --> 00:03:00,319 Technical University, uh, 47 00:03:00,320 --> 00:03:01,939 electrical engineering. 48 00:03:01,940 --> 00:03:03,889 And so I thought, um, 49 00:03:05,030 --> 00:03:07,129 because there's not that 50 00:03:07,130 --> 00:03:09,349 much wireless hacking 51 00:03:09,350 --> 00:03:11,389 or stuff at the physical layers. 52 00:03:11,390 --> 00:03:13,519 Uh, the Congress, I thought maybe an 53 00:03:13,520 --> 00:03:16,519 introduction in, um, 54 00:03:16,520 --> 00:03:19,039 basic wireless stuff, digital stuff 55 00:03:19,040 --> 00:03:20,040 would be interesting. 56 00:03:21,290 --> 00:03:23,599 And, um, let's 57 00:03:23,600 --> 00:03:25,999 start with the 58 00:03:26,000 --> 00:03:28,199 era of quantum content. 59 00:03:28,200 --> 00:03:30,889 Um, I've basically 60 00:03:33,560 --> 00:03:35,089 divided this in a few parts 61 00:03:36,410 --> 00:03:38,779 in wireless basics, 62 00:03:38,780 --> 00:03:40,729 um, modulations. 63 00:03:40,730 --> 00:03:43,579 We actually to, um, 64 00:03:43,580 --> 00:03:44,580 analog, 65 00:03:45,770 --> 00:03:47,899 although we are doing digital, 66 00:03:47,900 --> 00:03:50,059 um, radio communications, we still have 67 00:03:50,060 --> 00:03:52,249 to do analog stuff, um, 68 00:03:52,250 --> 00:03:53,719 channel coding, the first error 69 00:03:53,720 --> 00:03:55,819 correction and so on and a bit 70 00:03:55,820 --> 00:03:56,820 of channel access. 71 00:03:58,850 --> 00:04:00,949 And the first, 72 00:04:00,950 --> 00:04:03,119 uh, start with is 73 00:04:03,120 --> 00:04:05,359 the uh channel 74 00:04:05,360 --> 00:04:08,089 communications uh model 75 00:04:08,090 --> 00:04:10,969 which is basically 76 00:04:10,970 --> 00:04:14,059 consisting of a source, uh, transmitter 77 00:04:14,060 --> 00:04:16,789 or, uh, encoder and 78 00:04:16,790 --> 00:04:18,919 uh, channel and receiver and uh, 79 00:04:18,920 --> 00:04:20,809 I think where you actually want to 80 00:04:20,810 --> 00:04:23,389 transmit your information. 81 00:04:23,390 --> 00:04:25,819 So, um, 82 00:04:25,820 --> 00:04:27,889 that's what you at least need 83 00:04:27,890 --> 00:04:30,379 to have to have wireless communications 84 00:04:30,380 --> 00:04:32,689 or any kind of communications and 85 00:04:32,690 --> 00:04:34,669 channel is something very abstract. 86 00:04:34,670 --> 00:04:36,889 So you can have, uh, wireless 87 00:04:36,890 --> 00:04:39,169 channel, you can transmit over 88 00:04:39,170 --> 00:04:41,119 basically any medium. 89 00:04:41,120 --> 00:04:43,459 And, uh, you will always, almost 90 00:04:43,460 --> 00:04:45,859 always have noise, different 91 00:04:45,860 --> 00:04:48,229 kind of noise and interference, 92 00:04:48,230 --> 00:04:51,259 interference coming from other, um, 93 00:04:51,260 --> 00:04:54,109 other people, other devices, 94 00:04:54,110 --> 00:04:56,659 even from yourself. 95 00:04:56,660 --> 00:04:57,900 And, um, 96 00:04:59,690 --> 00:05:01,729 you have to make sure that your encoder 97 00:05:01,730 --> 00:05:03,829 and your decoder can actually 98 00:05:03,830 --> 00:05:06,290 make the most of your channel 99 00:05:07,460 --> 00:05:08,929 so you can transmit your data. 100 00:05:12,250 --> 00:05:14,439 A bit about wireless channels, so 101 00:05:14,440 --> 00:05:16,779 wireless channels are very 102 00:05:16,780 --> 00:05:18,249 unreliable. 103 00:05:18,250 --> 00:05:19,250 You can 104 00:05:21,280 --> 00:05:23,529 in very small ways 105 00:05:23,530 --> 00:05:26,169 like predict it, but it's 106 00:05:26,170 --> 00:05:28,119 still very noisy. 107 00:05:28,120 --> 00:05:30,189 You can have in 108 00:05:30,190 --> 00:05:32,589 you can have interruptions 109 00:05:32,590 --> 00:05:34,479 like interference. 110 00:05:34,480 --> 00:05:35,480 And 111 00:05:37,420 --> 00:05:39,609 for mobile wireless channels, 112 00:05:39,610 --> 00:05:42,009 it's even worse because you can 113 00:05:42,010 --> 00:05:44,109 because of the movement 114 00:05:44,110 --> 00:05:46,809 of the different stations, you have 115 00:05:46,810 --> 00:05:50,199 interference between your own station, 116 00:05:50,200 --> 00:05:51,669 parts of, uh, 117 00:05:52,750 --> 00:05:55,120 like buildings around you, which are 118 00:05:56,710 --> 00:05:58,929 basically reflecting a signal 119 00:05:58,930 --> 00:06:01,269 and interfering with the signal 120 00:06:01,270 --> 00:06:03,069 you actually want to receive. 121 00:06:03,070 --> 00:06:05,439 And, um, because 122 00:06:05,440 --> 00:06:07,449 of different, uh, time 123 00:06:09,340 --> 00:06:11,889 like time directions between the 124 00:06:11,890 --> 00:06:13,120 sending and receiving, 125 00:06:14,140 --> 00:06:15,140 uh. 126 00:06:17,220 --> 00:06:19,549 Time, so, yeah, OK, 127 00:06:19,550 --> 00:06:20,550 sorry. 128 00:06:25,460 --> 00:06:27,829 We have a digital communications model 129 00:06:27,830 --> 00:06:28,939 which is 130 00:06:29,960 --> 00:06:32,599 used when we do digital stuff, 131 00:06:32,600 --> 00:06:34,729 so we have a source like 132 00:06:34,730 --> 00:06:36,979 before with Oscoda, 133 00:06:36,980 --> 00:06:39,169 which is, for example, an 134 00:06:39,170 --> 00:06:41,419 impact coder or any kind 135 00:06:41,420 --> 00:06:44,749 of audio codec, GSM codec, 136 00:06:44,750 --> 00:06:47,809 um, which does 137 00:06:47,810 --> 00:06:50,989 code, which does data compression 138 00:06:50,990 --> 00:06:53,809 and tries to minimize 139 00:06:53,810 --> 00:06:54,810 your data. 140 00:06:55,580 --> 00:06:57,949 And then we have a channel code which 141 00:06:57,950 --> 00:07:00,379 tries to add redundancy 142 00:07:00,380 --> 00:07:01,069 again. 143 00:07:01,070 --> 00:07:03,739 So your receiver, um, 144 00:07:03,740 --> 00:07:06,439 has, uh, 145 00:07:06,440 --> 00:07:08,869 or it's easier for receiver to receive 146 00:07:08,870 --> 00:07:11,179 a signal and to make most of your 147 00:07:11,180 --> 00:07:12,180 channel 148 00:07:13,670 --> 00:07:15,929 than we have got modulator 149 00:07:15,930 --> 00:07:18,079 encoder where you're actually where we 150 00:07:18,080 --> 00:07:20,539 are actually transmitting the signal 151 00:07:20,540 --> 00:07:22,609 and sending it to 152 00:07:22,610 --> 00:07:24,259 a radio channel. 153 00:07:24,260 --> 00:07:27,409 And on the receiving part, it's 154 00:07:27,410 --> 00:07:29,839 the same thing just the other way around. 155 00:07:31,730 --> 00:07:34,519 And what I'm going to talk about is 156 00:07:34,520 --> 00:07:36,739 the channel coder and modulations 157 00:07:36,740 --> 00:07:38,839 and a bit of, uh, wireless 158 00:07:38,840 --> 00:07:40,389 channels or wireless stuff. 159 00:07:44,420 --> 00:07:46,399 First of all, when we speak about 160 00:07:46,400 --> 00:07:49,459 wireless spectrum, what do we actually 161 00:07:49,460 --> 00:07:50,599 mean? 162 00:07:50,600 --> 00:07:52,889 And I found this great 163 00:07:52,890 --> 00:07:55,549 Cassidy slide, 164 00:07:55,550 --> 00:07:57,219 which shows this pretty good. 165 00:07:57,220 --> 00:07:59,479 Um, we are, 166 00:07:59,480 --> 00:08:01,639 um, using 167 00:08:01,640 --> 00:08:03,739 this part of 168 00:08:03,740 --> 00:08:05,569 the electromagnetic magnetic spectrum. 169 00:08:05,570 --> 00:08:07,789 So from three megahertz to three hundred 170 00:08:07,790 --> 00:08:09,949 gigahertz, of course, 171 00:08:09,950 --> 00:08:12,199 most of the communication 172 00:08:12,200 --> 00:08:13,279 isn't done in this 173 00:08:14,810 --> 00:08:17,179 spectrum because three megahertz is 174 00:08:17,180 --> 00:08:18,949 shortwave radio where you're only 175 00:08:18,950 --> 00:08:21,319 transmitting a very 176 00:08:21,320 --> 00:08:24,439 narrow band signals and use 177 00:08:24,440 --> 00:08:26,599 usually huge antennas, 178 00:08:26,600 --> 00:08:28,909 um, to get like 179 00:08:28,910 --> 00:08:30,619 a few hundred kilometers or a thousand 180 00:08:30,620 --> 00:08:31,939 kilometers. 181 00:08:31,940 --> 00:08:34,219 And at the upper end we've 182 00:08:34,220 --> 00:08:36,649 got really high frequencies where 183 00:08:36,650 --> 00:08:39,319 it's actually it's actually extremely 184 00:08:39,320 --> 00:08:41,779 hard to build devices for this. 185 00:08:41,780 --> 00:08:42,860 So, for example, 186 00:08:44,480 --> 00:08:45,480 um, 187 00:08:47,770 --> 00:08:50,569 radar devices are 188 00:08:50,570 --> 00:08:52,639 in this area or even 189 00:08:52,640 --> 00:08:53,929 or a bit lower, 190 00:08:55,040 --> 00:08:57,469 but most of it is done between, 191 00:08:57,470 --> 00:08:59,629 um, like one hundred 192 00:08:59,630 --> 00:09:01,999 megahertz and 30 193 00:09:02,000 --> 00:09:03,049 to 60 gigahertz. 194 00:09:04,760 --> 00:09:06,919 A few examples we all know 195 00:09:06,920 --> 00:09:09,169 wi fi, which is 196 00:09:09,170 --> 00:09:11,449 at two point four and five 197 00:09:11,450 --> 00:09:12,450 gigahertz bands, 198 00:09:13,580 --> 00:09:15,739 uh, which are some bands. 199 00:09:16,790 --> 00:09:17,900 Uh, and. 200 00:09:22,760 --> 00:09:24,919 This spectrum bands that are actually 201 00:09:24,920 --> 00:09:27,019 free for use, so you 202 00:09:27,020 --> 00:09:28,909 still have to have a license for your 203 00:09:28,910 --> 00:09:31,219 device, but the license 204 00:09:31,220 --> 00:09:33,139 is on the device itself, but you can 205 00:09:33,140 --> 00:09:35,719 freely use it for any 206 00:09:36,890 --> 00:09:39,859 Wi-Fi access point you want to 207 00:09:39,860 --> 00:09:42,499 do. And it's for 208 00:09:42,500 --> 00:09:44,479 industrial, scientific and medical stuff. 209 00:09:44,480 --> 00:09:46,429 That's what the abbreviation stands for. 210 00:09:47,510 --> 00:09:49,649 Um, we are also using HITECH, 211 00:09:49,650 --> 00:09:51,769 which is in the upper, uh, side 212 00:09:51,770 --> 00:09:54,739 of the GSM, uh, 213 00:09:54,740 --> 00:09:56,839 band, and it's 214 00:09:56,840 --> 00:09:59,389 using one point eight 215 00:09:59,390 --> 00:10:01,849 to ten point nine gigahertz 216 00:10:01,850 --> 00:10:03,049 approximately. 217 00:10:03,050 --> 00:10:05,269 UMTS supply is at 218 00:10:05,270 --> 00:10:07,459 two point one gigahertz. 219 00:10:07,460 --> 00:10:09,799 Uh, and LTE is in 220 00:10:09,800 --> 00:10:12,079 Europe, uh, using these 221 00:10:12,080 --> 00:10:14,359 for, um, frequency bands. 222 00:10:14,360 --> 00:10:16,669 But, uh, these three are actually GSM 223 00:10:16,670 --> 00:10:19,319 bands and um, 224 00:10:19,320 --> 00:10:21,379 uh, converted to 225 00:10:21,380 --> 00:10:23,629 LTE and two point 226 00:10:23,630 --> 00:10:26,089 six gigahertz is, um, 227 00:10:26,090 --> 00:10:28,339 the frequency 228 00:10:28,340 --> 00:10:31,039 band, which is actually at the moment 229 00:10:31,040 --> 00:10:33,169 mostly used for LTE 230 00:10:33,170 --> 00:10:35,509 and um 231 00:10:35,510 --> 00:10:37,909 three hundred, four hundred thirty 232 00:10:37,910 --> 00:10:40,999 three and four and eight hundred 233 00:10:41,000 --> 00:10:44,119 sixty eight megahertz are um 234 00:10:44,120 --> 00:10:46,399 small free bands which are also HSM 235 00:10:46,400 --> 00:10:48,629 and still Asadi for 236 00:10:48,630 --> 00:10:49,789 short range devices, 237 00:10:51,020 --> 00:10:53,269 um which are also 238 00:10:53,270 --> 00:10:56,089 free to use for uh like weather stations, 239 00:10:56,090 --> 00:10:57,769 uh telemetry data or 240 00:10:58,820 --> 00:11:01,130 part of smart meters actually using this. 241 00:11:03,160 --> 00:11:05,239 And what you 242 00:11:05,240 --> 00:11:07,399 usually buy when you get an RF module 243 00:11:07,400 --> 00:11:09,619 for your Arduino is in this frequency 244 00:11:09,620 --> 00:11:11,869 bands as long as it's not two point four 245 00:11:11,870 --> 00:11:12,870 gigahertz. 246 00:11:17,230 --> 00:11:19,059 When we come to wireless bandwidth, 247 00:11:19,060 --> 00:11:21,309 there's one 248 00:11:21,310 --> 00:11:24,069 main rule in telecommunications, 249 00:11:24,070 --> 00:11:26,139 um, transmitted information 250 00:11:26,140 --> 00:11:27,309 always has a bandwidth. 251 00:11:27,310 --> 00:11:29,259 If you haven't got if you have a signal 252 00:11:29,260 --> 00:11:31,299 that has no bandwidth, you have you can't 253 00:11:31,300 --> 00:11:33,369 transmit information. 254 00:11:33,370 --> 00:11:35,439 So this also means 255 00:11:35,440 --> 00:11:37,509 the faster you transmit information, the 256 00:11:37,510 --> 00:11:39,529 higher your bandwidth will be. 257 00:11:39,530 --> 00:11:42,249 And if you look at the Wi-Fi, 258 00:11:42,250 --> 00:11:45,099 the new Wi-Fi specifications, 259 00:11:45,100 --> 00:11:47,739 you will always see that the new 260 00:11:47,740 --> 00:11:49,989 specifications have bigger channel 261 00:11:49,990 --> 00:11:52,149 bandwidth and 262 00:11:52,150 --> 00:11:53,950 so they can transmit faster. 263 00:11:56,450 --> 00:11:57,750 And, um, 264 00:11:58,920 --> 00:12:01,099 a short thing about wireless 265 00:12:01,100 --> 00:12:03,769 channels, actually, two definitions 266 00:12:03,770 --> 00:12:05,539 of channels, uh, telecommunications, the 267 00:12:05,540 --> 00:12:07,159 first one is that the transmission 268 00:12:07,160 --> 00:12:09,739 channel way where we actually have 269 00:12:09,740 --> 00:12:11,809 a physical, um, 270 00:12:11,810 --> 00:12:14,809 like channel where the 271 00:12:14,810 --> 00:12:17,099 information gets transmitted and 272 00:12:17,100 --> 00:12:19,279 the logical channel, which is 273 00:12:19,280 --> 00:12:22,039 much is more or less 274 00:12:22,040 --> 00:12:25,009 standardized frequency 275 00:12:25,010 --> 00:12:27,469 for, um, 276 00:12:27,470 --> 00:12:29,209 your transmission system. 277 00:12:29,210 --> 00:12:31,759 So your wi fi has got specified 278 00:12:31,760 --> 00:12:34,249 channels and you don't need to enter 279 00:12:34,250 --> 00:12:36,409 your, um, exact 280 00:12:36,410 --> 00:12:37,410 frequency. 281 00:12:38,960 --> 00:12:41,899 And these are specified to have 282 00:12:41,900 --> 00:12:43,220 optimal spectrum usage. 283 00:12:48,220 --> 00:12:51,369 One of the most important 284 00:12:51,370 --> 00:12:54,219 theorems in telecommunications 285 00:12:54,220 --> 00:12:56,529 is the Shannon Hartley theory, 286 00:12:56,530 --> 00:12:59,139 which tells the upper limit 287 00:12:59,140 --> 00:13:00,969 of information rate you can actually 288 00:13:00,970 --> 00:13:03,039 transmit over a channel if you 289 00:13:03,040 --> 00:13:05,319 have only one transmitter 290 00:13:05,320 --> 00:13:07,179 and one receiver. 291 00:13:07,180 --> 00:13:09,279 So, um, this 292 00:13:09,280 --> 00:13:11,559 is, uh, even if you have 293 00:13:11,560 --> 00:13:13,629 perfect error correction, 294 00:13:13,630 --> 00:13:15,729 you can't get over this limit. 295 00:13:15,730 --> 00:13:17,919 Although, um, in wireless 296 00:13:17,920 --> 00:13:20,019 communications, we can have multiple, uh, 297 00:13:20,020 --> 00:13:22,389 transmitters and multiple receivers, 298 00:13:22,390 --> 00:13:24,759 which we actually use when we do more 299 00:13:24,760 --> 00:13:27,009 stuff like the, uh, like LTE 300 00:13:27,010 --> 00:13:30,429 or, uh, the wi fi end standard. 301 00:13:30,430 --> 00:13:33,159 This is sort of an 302 00:13:33,160 --> 00:13:34,690 exploit. This, uh, 303 00:13:36,490 --> 00:13:38,889 the theory is basically thought 304 00:13:38,890 --> 00:13:41,169 for, um, 305 00:13:41,170 --> 00:13:43,389 cables and it's not 306 00:13:43,390 --> 00:13:45,450 designed for, um, 307 00:13:46,480 --> 00:13:48,609 channels where you can wire channel 308 00:13:48,610 --> 00:13:51,039 changes and where 309 00:13:51,040 --> 00:13:53,409 a few centimeters of spacing of 310 00:13:53,410 --> 00:13:55,899 antennas, um, is completely 311 00:13:55,900 --> 00:13:57,909 different in the sense of a channel. 312 00:13:59,230 --> 00:14:00,230 Um. 313 00:14:04,220 --> 00:14:05,899 And this is this a 314 00:14:07,030 --> 00:14:09,049 formula where we have got to see the 315 00:14:09,050 --> 00:14:11,749 channel bandwidth in bits per second 316 00:14:11,750 --> 00:14:14,269 because our signal bandwidth in 317 00:14:14,270 --> 00:14:16,759 Hertz and beyond 318 00:14:16,760 --> 00:14:18,919 the binary logarithm of one 319 00:14:18,920 --> 00:14:21,559 plus s and our Westernize 320 00:14:21,560 --> 00:14:23,809 the signal to noise ratio 321 00:14:23,810 --> 00:14:25,669 in telecommunications, we always speak 322 00:14:25,670 --> 00:14:27,139 about signal to noise ratio. 323 00:14:27,140 --> 00:14:28,900 So, um, 324 00:14:30,080 --> 00:14:32,239 independent of how high your 325 00:14:32,240 --> 00:14:34,909 noise actually is, um, you know, 326 00:14:34,910 --> 00:14:36,979 you always know how 327 00:14:36,980 --> 00:14:39,049 good your quality of the your 328 00:14:39,050 --> 00:14:41,089 receiving signal is if you have got to 329 00:14:41,090 --> 00:14:42,260 signal to noise ratio. 330 00:14:44,520 --> 00:14:46,589 And this is specified for noisy 331 00:14:46,590 --> 00:14:49,019 channels, for additive 332 00:14:49,020 --> 00:14:51,089 white noise, which 333 00:14:51,090 --> 00:14:53,399 is the 334 00:14:53,400 --> 00:14:55,379 more or less the worst case of noise you 335 00:14:55,380 --> 00:14:56,759 can have because it's completely 336 00:14:56,760 --> 00:14:57,760 unpredictable. 337 00:15:00,700 --> 00:15:01,700 Um, 338 00:15:02,830 --> 00:15:04,250 digital, um, 339 00:15:05,710 --> 00:15:07,839 digital signal 340 00:15:07,840 --> 00:15:10,209 processing is done in baseband 341 00:15:10,210 --> 00:15:12,339 signals usually, so 342 00:15:12,340 --> 00:15:13,929 if you've got an analog signal, you 343 00:15:13,930 --> 00:15:16,779 usually have intermediate frequency, 344 00:15:16,780 --> 00:15:19,059 which is about depends on the signal. 345 00:15:19,060 --> 00:15:21,309 Depends on the, uh, depends on your 346 00:15:21,310 --> 00:15:22,989 receiver transmitter is about a few 347 00:15:22,990 --> 00:15:24,579 hundred kilometers kilohertz or 348 00:15:24,580 --> 00:15:25,989 megahertz. 349 00:15:25,990 --> 00:15:28,119 And, um, in 350 00:15:28,120 --> 00:15:31,499 digital systems we use, 351 00:15:31,500 --> 00:15:33,729 uh, zero hertz 352 00:15:33,730 --> 00:15:34,929 intermediate frequency, 353 00:15:35,950 --> 00:15:38,409 um, which is complex because 354 00:15:38,410 --> 00:15:40,509 computers can easily, 355 00:15:40,510 --> 00:15:41,510 um. 356 00:15:42,900 --> 00:15:45,119 Can easily calculate 357 00:15:45,120 --> 00:15:46,120 with complex. 358 00:15:48,950 --> 00:15:50,240 Signals and, 359 00:15:51,260 --> 00:15:52,260 um, 360 00:15:53,570 --> 00:15:55,939 when we get to modulations, 361 00:15:55,940 --> 00:15:57,250 it will be a bit clearer. 362 00:16:00,610 --> 00:16:02,769 When we sent this 363 00:16:02,770 --> 00:16:05,109 hurts, we, of course, have the left part, 364 00:16:05,110 --> 00:16:07,479 which are actually negative 365 00:16:07,480 --> 00:16:09,189 frequencies, which is a bit odd. 366 00:16:09,190 --> 00:16:11,589 But if you think about 367 00:16:11,590 --> 00:16:13,749 a channel where we have got a frequency 368 00:16:13,750 --> 00:16:15,729 here and the starting and end frequency 369 00:16:15,730 --> 00:16:18,039 here, um, you 370 00:16:18,040 --> 00:16:20,439 still have the left part of the channel. 371 00:16:20,440 --> 00:16:23,499 So if we, um, 372 00:16:23,500 --> 00:16:25,989 generate we generate a complex 373 00:16:27,280 --> 00:16:28,899 representation of the signal. 374 00:16:28,900 --> 00:16:31,329 We still have the, uh, negative 375 00:16:31,330 --> 00:16:32,980 and positive parts of the frequency 376 00:16:34,570 --> 00:16:36,699 of the frequency of frequency of 377 00:16:36,700 --> 00:16:37,700 the whole channel. 378 00:16:39,880 --> 00:16:40,880 Um, 379 00:16:42,490 --> 00:16:44,919 this is, uh, typical receiver 380 00:16:44,920 --> 00:16:47,459 of, uh, software defined radio, 381 00:16:47,460 --> 00:16:49,539 a system which is just 382 00:16:49,540 --> 00:16:52,149 a band pass filter at the front 383 00:16:52,150 --> 00:16:53,829 or after the antenna. 384 00:16:53,830 --> 00:16:55,869 Then you've got the low noise amplifier, 385 00:16:55,870 --> 00:16:58,209 which is a really good amplifier, 386 00:16:58,210 --> 00:17:00,369 which amplifies your received 387 00:17:00,370 --> 00:17:02,439 signal and adds a 388 00:17:02,440 --> 00:17:04,868 very or every 389 00:17:04,869 --> 00:17:07,358 amplifier adds noise and his amplifier 390 00:17:07,359 --> 00:17:08,470 has very low noise. 391 00:17:09,550 --> 00:17:12,068 And then you've got two mixers 392 00:17:12,069 --> 00:17:14,049 which are locked over the same local 393 00:17:14,050 --> 00:17:16,118 oscillator, but with 394 00:17:16,119 --> 00:17:18,699 a different face of that and 395 00:17:18,700 --> 00:17:21,309 uh, with zero, 396 00:17:21,310 --> 00:17:23,469 um, degrees face offset and 397 00:17:23,470 --> 00:17:25,328 ninety degrees face offset. 398 00:17:25,329 --> 00:17:27,848 So we generate our, 399 00:17:27,849 --> 00:17:30,039 um, real part of 400 00:17:30,040 --> 00:17:32,529 the complex representation 401 00:17:32,530 --> 00:17:34,359 and our imaginary part of the complex 402 00:17:34,360 --> 00:17:35,859 representation. 403 00:17:35,860 --> 00:17:38,049 And after this we 404 00:17:38,050 --> 00:17:39,999 already have the analog digital 405 00:17:40,000 --> 00:17:42,879 converters which um. 406 00:17:42,880 --> 00:17:43,880 Yeah. 407 00:17:45,850 --> 00:17:47,979 Just convert your analog signal into 408 00:17:47,980 --> 00:17:50,169 digital and then the 409 00:17:50,170 --> 00:17:52,569 digital signal processing, and because 410 00:17:52,570 --> 00:17:55,119 we do all the signal processing and 411 00:17:55,120 --> 00:17:57,309 most of the filtering software, 412 00:17:57,310 --> 00:17:59,409 it's very easy to 413 00:17:59,410 --> 00:18:01,539 adapt, um, 414 00:18:01,540 --> 00:18:02,540 digital wireless 415 00:18:04,000 --> 00:18:05,119 communication systems. 416 00:18:05,120 --> 00:18:07,959 So, for example, your Wi-Fi 417 00:18:07,960 --> 00:18:10,039 with your phone, the 418 00:18:10,040 --> 00:18:13,419 base of your phone usually can 419 00:18:13,420 --> 00:18:15,819 transmit or receive different 420 00:18:15,820 --> 00:18:18,009 modulations or a lot of 421 00:18:18,010 --> 00:18:20,229 different types of 422 00:18:20,230 --> 00:18:22,329 telecommunication standard like GSM 423 00:18:22,330 --> 00:18:23,500 a lot, and also 424 00:18:24,520 --> 00:18:26,919 to UMTS and LTE, 425 00:18:26,920 --> 00:18:29,299 LTE in the same baseband chip. 426 00:18:30,850 --> 00:18:33,039 And this is because the signal 427 00:18:33,040 --> 00:18:34,569 processing is all done in software. 428 00:18:34,570 --> 00:18:37,869 And, uh, if you have a new 429 00:18:37,870 --> 00:18:40,209 signal send out, you trust you 430 00:18:40,210 --> 00:18:42,279 basically just to 431 00:18:42,280 --> 00:18:43,280 firmware update. 432 00:18:47,750 --> 00:18:50,149 And the other way around, 433 00:18:50,150 --> 00:18:52,219 if you want to send signals, if 434 00:18:52,220 --> 00:18:54,589 you want to modulate signals, 435 00:18:54,590 --> 00:18:56,749 it's just you 436 00:18:56,750 --> 00:18:58,819 have a signal processor, your digital 437 00:18:58,820 --> 00:19:01,069 analog converter, and 438 00:19:01,070 --> 00:19:03,439 again, makes us switch to converting 439 00:19:03,440 --> 00:19:05,659 to your designated frequency 440 00:19:05,660 --> 00:19:07,249 and then your power amplifier. 441 00:19:07,250 --> 00:19:09,349 So it's the same set up 442 00:19:09,350 --> 00:19:10,549 just the other way around. 443 00:19:16,150 --> 00:19:18,519 Then about baseband modulation, 444 00:19:18,520 --> 00:19:20,589 the first question is, why do we actually 445 00:19:20,590 --> 00:19:22,809 modulate data we could just 446 00:19:22,810 --> 00:19:25,209 send like rectangular 447 00:19:25,210 --> 00:19:27,489 impulses over our wi fi channel 448 00:19:27,490 --> 00:19:28,749 or wireless channel, 449 00:19:29,800 --> 00:19:31,899 but, um, rectangular 450 00:19:31,900 --> 00:19:34,059 puzzles have very high 451 00:19:34,060 --> 00:19:37,179 bandwidth and are very inefficient. 452 00:19:37,180 --> 00:19:39,819 So they would just use 453 00:19:39,820 --> 00:19:42,849 most of the spectrum and 454 00:19:42,850 --> 00:19:45,399 you would need a lot of power or you can 455 00:19:45,400 --> 00:19:47,739 actually not that easily 456 00:19:47,740 --> 00:19:49,329 transmits rectangular pulses. 457 00:19:49,330 --> 00:19:51,459 You also you always have to modulate 458 00:19:51,460 --> 00:19:52,460 them. 459 00:19:53,530 --> 00:19:55,809 Um, and what we also 460 00:19:55,810 --> 00:19:57,789 want to do is to match the channel 461 00:19:57,790 --> 00:19:58,699 characteristics. 462 00:19:58,700 --> 00:20:00,789 So if we have got in a noisy 463 00:20:00,790 --> 00:20:03,219 channel and a small, uh, 464 00:20:03,220 --> 00:20:05,439 signal to noise ratio, we want to use 465 00:20:05,440 --> 00:20:07,809 a modulation that 466 00:20:07,810 --> 00:20:10,779 is more robust, um, for this 467 00:20:10,780 --> 00:20:12,939 noise. And if we have a very good 468 00:20:12,940 --> 00:20:15,189 channel, for example, if your Wi-Fi 469 00:20:15,190 --> 00:20:17,049 access point is just a few meters apart 470 00:20:17,050 --> 00:20:20,319 from your laptop, you can use 471 00:20:20,320 --> 00:20:22,569 modulations which are high in bandwidth 472 00:20:22,570 --> 00:20:24,339 and, uh, which just 473 00:20:25,390 --> 00:20:27,339 as a lot of throughput. 474 00:20:30,380 --> 00:20:32,749 There are a few modulations I picked, 475 00:20:32,750 --> 00:20:35,029 which mostly used, um, 476 00:20:35,030 --> 00:20:37,279 the first one is české 477 00:20:37,280 --> 00:20:39,509 amplitude shifting. 478 00:20:39,510 --> 00:20:41,899 Um, I want 479 00:20:41,900 --> 00:20:43,759 I haven't got a slide for this because 480 00:20:43,760 --> 00:20:45,209 it's actually quite easy. 481 00:20:45,210 --> 00:20:47,959 You just take one or two, 482 00:20:47,960 --> 00:20:50,029 um, amplitude 483 00:20:50,030 --> 00:20:52,249 levels and just 484 00:20:52,250 --> 00:20:53,779 modulated with your amplitude. 485 00:20:53,780 --> 00:20:55,819 So if you have only got one, you're 486 00:20:55,820 --> 00:20:57,679 basically doing one of king. 487 00:20:57,680 --> 00:20:59,719 So if you've got a signal, you, for 488 00:20:59,720 --> 00:21:02,479 example, receive 489 00:21:02,480 --> 00:21:04,819 a one. And if you have got no signal, 490 00:21:04,820 --> 00:21:06,950 you're, for example, receive zero 491 00:21:08,750 --> 00:21:11,089 frequency shift. King is, uh, 492 00:21:11,090 --> 00:21:13,279 doing something similar 493 00:21:13,280 --> 00:21:16,129 just with two frequencies and is 494 00:21:16,130 --> 00:21:18,709 a bit similar, similar to 495 00:21:18,710 --> 00:21:20,779 a form modulation, 496 00:21:20,780 --> 00:21:22,160 analog modulation. 497 00:21:23,240 --> 00:21:25,519 We have two, um, 498 00:21:25,520 --> 00:21:27,919 frequencies and 499 00:21:27,920 --> 00:21:30,709 two modulating one depends 500 00:21:30,710 --> 00:21:32,479 depending on what we actually want to 501 00:21:32,480 --> 00:21:34,639 send with two 502 00:21:34,640 --> 00:21:35,640 frequencies. 503 00:21:37,950 --> 00:21:41,159 Then we've got Festschrift King 504 00:21:41,160 --> 00:21:43,439 with us, which is a face modulation 505 00:21:43,440 --> 00:21:45,989 and is commonly commonly 506 00:21:45,990 --> 00:21:48,299 used, um, 507 00:21:48,300 --> 00:21:50,379 this is PPK Binary Face 508 00:21:50,380 --> 00:21:53,129 with King, which is the easiest 509 00:21:53,130 --> 00:21:56,429 form. We have the 510 00:21:56,430 --> 00:21:58,179 caution complex. 511 00:21:58,180 --> 00:21:59,180 Um. 512 00:22:00,750 --> 00:22:01,750 At the complex, 513 00:22:02,870 --> 00:22:03,870 um. 514 00:22:06,450 --> 00:22:08,549 I only know the drama, what it's the 515 00:22:08,550 --> 00:22:11,649 German, it's even 516 00:22:11,650 --> 00:22:13,859 the complex 517 00:22:13,860 --> 00:22:15,049 plane. 518 00:22:15,050 --> 00:22:16,050 Thanks. 519 00:22:16,410 --> 00:22:18,719 We've got a complex 520 00:22:18,720 --> 00:22:19,720 plane 521 00:22:20,790 --> 00:22:21,960 and we've got two 522 00:22:23,100 --> 00:22:24,579 symbols here. 523 00:22:24,580 --> 00:22:26,639 Um, and 524 00:22:26,640 --> 00:22:28,709 these are spaced 180 525 00:22:28,710 --> 00:22:30,899 degrees apart. So we got we 526 00:22:30,900 --> 00:22:33,359 have got a positive symbol 527 00:22:33,360 --> 00:22:34,360 and a negative symbol, 528 00:22:36,180 --> 00:22:38,459 um, and which is 529 00:22:38,460 --> 00:22:41,279 with this modulation, we have got 530 00:22:41,280 --> 00:22:43,649 a wireless bandwidth of about, 531 00:22:43,650 --> 00:22:44,819 uh, the symbol. Right. 532 00:22:44,820 --> 00:22:47,339 We actually use and we can transmit 533 00:22:47,340 --> 00:22:48,479 one bit possible 534 00:22:50,340 --> 00:22:51,929 if we enhance this. 535 00:22:51,930 --> 00:22:54,629 Um, we have, 536 00:22:54,630 --> 00:22:56,879 uh, Kupinski where we have 537 00:22:56,880 --> 00:23:00,269 got, um, four symbols, 538 00:23:00,270 --> 00:23:02,759 which is actually not much different 539 00:23:02,760 --> 00:23:04,109 than this, which just, 540 00:23:05,250 --> 00:23:07,469 um. Beeps Okay. 541 00:23:07,470 --> 00:23:09,689 Uh, and Autobytel or 542 00:23:09,690 --> 00:23:11,979 um, spaced 90 degrees 543 00:23:11,980 --> 00:23:14,159 apart and which 544 00:23:14,160 --> 00:23:16,889 it with each symbol we can transmit 545 00:23:16,890 --> 00:23:18,179 to bits. 546 00:23:18,180 --> 00:23:20,489 And the nice thing about this is, 547 00:23:20,490 --> 00:23:22,859 um, it has got the same 548 00:23:22,860 --> 00:23:25,409 bandwidth as BAPS Care 549 00:23:25,410 --> 00:23:27,839 and um 550 00:23:27,840 --> 00:23:30,209 the same uh 551 00:23:30,210 --> 00:23:31,299 error probabilities. 552 00:23:31,300 --> 00:23:33,719 So uh, it's 553 00:23:33,720 --> 00:23:37,109 usually more efficient to use Kupinski 554 00:23:37,110 --> 00:23:38,969 because you don't need more power and you 555 00:23:38,970 --> 00:23:40,379 have got the same signal. 556 00:23:40,380 --> 00:23:42,779 Uh, you only need the same signal levels 557 00:23:42,780 --> 00:23:43,780 at the receiving part. 558 00:23:45,270 --> 00:23:47,999 And this is because, um, these 559 00:23:48,000 --> 00:23:50,759 are two pairs of symbols 560 00:23:50,760 --> 00:23:52,079 which are orthogonal. 561 00:23:54,950 --> 00:23:57,559 Um, then we have got MPC, 562 00:23:57,560 --> 00:24:00,409 we can just add more symbols, 563 00:24:00,410 --> 00:24:02,329 which means that the spacing between the 564 00:24:02,330 --> 00:24:05,269 symbols, um, gets lower. 565 00:24:05,270 --> 00:24:07,639 So we need more actually 566 00:24:07,640 --> 00:24:09,739 more, um, power of the 567 00:24:09,740 --> 00:24:11,899 signal at the receiving end to transmit 568 00:24:11,900 --> 00:24:13,969 this or to have lower 569 00:24:13,970 --> 00:24:16,219 or lower errors, 570 00:24:16,220 --> 00:24:17,220 a low error rate. 571 00:24:20,460 --> 00:24:21,460 Um. 572 00:24:26,330 --> 00:24:27,919 The next thing is 573 00:24:29,540 --> 00:24:31,880 credit amplitude modulation, 574 00:24:33,260 --> 00:24:35,359 which is a combination 575 00:24:35,360 --> 00:24:37,999 of amplitude 576 00:24:38,000 --> 00:24:40,099 and phase modulation, 577 00:24:40,100 --> 00:24:42,889 and it's just, um, 578 00:24:42,890 --> 00:24:45,019 uh, the symbols 579 00:24:45,020 --> 00:24:47,299 in grid arrangement 580 00:24:47,300 --> 00:24:49,429 and you can have any signs of 581 00:24:49,430 --> 00:24:51,739 grid, for example, you can have, uh, 582 00:24:51,740 --> 00:24:54,559 two hundred sixty five 583 00:24:54,560 --> 00:24:56,959 of fifty six, um, 584 00:24:56,960 --> 00:24:59,119 any number of symbols you want 585 00:24:59,120 --> 00:25:01,189 to have and which each 586 00:25:01,190 --> 00:25:04,279 with each symbol you transmit. 587 00:25:04,280 --> 00:25:05,280 In this case 588 00:25:06,440 --> 00:25:07,939 it's for four bits. 589 00:25:07,940 --> 00:25:10,210 So it's 16 590 00:25:11,240 --> 00:25:12,240 curium. 591 00:25:15,810 --> 00:25:18,010 Um, then we come to channel coding, 592 00:25:19,750 --> 00:25:21,939 what we usually wants to 593 00:25:21,940 --> 00:25:25,059 do is, uh, if we've got our, 594 00:25:25,060 --> 00:25:27,219 um, binary stream, which we want 595 00:25:27,220 --> 00:25:29,379 to transmit, uh, 596 00:25:29,380 --> 00:25:32,289 the stream is, um, 597 00:25:32,290 --> 00:25:34,359 can have like a 598 00:25:34,360 --> 00:25:36,799 lot of zeros, uh, 599 00:25:36,800 --> 00:25:39,069 large number of ones after 600 00:25:39,070 --> 00:25:41,529 another. And we want 601 00:25:41,530 --> 00:25:43,869 to have, uh, basically 602 00:25:43,870 --> 00:25:46,119 a random data stream we don't 603 00:25:46,120 --> 00:25:48,429 want to have and modulated signals. 604 00:25:49,600 --> 00:25:51,789 And for this we are using 605 00:25:51,790 --> 00:25:54,219 um usually um, um, 606 00:25:54,220 --> 00:25:56,409 sort of random sequence. 607 00:25:56,410 --> 00:25:58,839 And this is, for example, the generator 608 00:25:58,840 --> 00:26:00,939 for DBS, which 609 00:26:00,940 --> 00:26:03,549 is, uh, fifteen bits of 610 00:26:03,550 --> 00:26:05,889 feedback, shifting register 611 00:26:05,890 --> 00:26:08,259 and the output is here and just 612 00:26:08,260 --> 00:26:10,569 gets excited with 613 00:26:10,570 --> 00:26:12,219 your input stream. 614 00:26:12,220 --> 00:26:14,889 And the receiver also 615 00:26:14,890 --> 00:26:17,049 needs to notice so 616 00:26:17,050 --> 00:26:19,739 he can actually add and uh 617 00:26:19,740 --> 00:26:20,770 and unscramble 618 00:26:21,850 --> 00:26:24,460 the received, um, bitstream. 619 00:26:29,950 --> 00:26:30,950 Um. 620 00:26:32,650 --> 00:26:34,539 Due to feeding and interference, we 621 00:26:34,540 --> 00:26:36,759 usually want to have forward error 622 00:26:36,760 --> 00:26:39,040 correction, and you will 623 00:26:40,090 --> 00:26:42,759 very unlikely find 624 00:26:42,760 --> 00:26:44,379 a wireless system which hasn't got 625 00:26:44,380 --> 00:26:45,789 forward error correction. 626 00:26:45,790 --> 00:26:48,009 And there are two types of 627 00:26:49,070 --> 00:26:51,159 codes which are used 628 00:26:51,160 --> 00:26:52,539 or which are also used, 629 00:26:54,520 --> 00:26:56,739 for example, DVD or any, 630 00:26:56,740 --> 00:26:59,199 um, when you want to transmit 631 00:26:59,200 --> 00:27:00,200 or store data. 632 00:27:01,450 --> 00:27:03,669 And these are black codes 633 00:27:03,670 --> 00:27:04,959 and codes. 634 00:27:04,960 --> 00:27:07,539 And when you do wireless stuff, 635 00:27:07,540 --> 00:27:09,819 they or digital wireless transmissions, 636 00:27:09,820 --> 00:27:12,549 they usually get combined, 637 00:27:12,550 --> 00:27:14,709 um, in an 638 00:27:14,710 --> 00:27:16,569 inner and outer kode. 639 00:27:16,570 --> 00:27:18,639 Um, the inner code 640 00:27:18,640 --> 00:27:21,009 is usually the code that's 641 00:27:21,010 --> 00:27:23,499 at the end of your 642 00:27:23,500 --> 00:27:24,789 sending. 643 00:27:24,790 --> 00:27:27,339 Um so 644 00:27:27,340 --> 00:27:28,340 which is 645 00:27:29,440 --> 00:27:31,779 at the basically 646 00:27:31,780 --> 00:27:33,699 just before transmitting or before 647 00:27:33,700 --> 00:27:35,019 modulating the data. 648 00:27:35,020 --> 00:27:37,449 And the other code is 649 00:27:37,450 --> 00:27:40,059 um your 650 00:27:40,060 --> 00:27:42,189 um code which is 651 00:27:42,190 --> 00:27:44,359 used after your, you 652 00:27:44,360 --> 00:27:46,390 usually randomize your bitstream 653 00:27:48,090 --> 00:27:49,719 um decoder. 654 00:27:49,720 --> 00:27:51,819 It is K divided by NDS, 655 00:27:51,820 --> 00:27:54,189 which is the 656 00:27:54,190 --> 00:27:56,439 number of inputs, item input 657 00:27:56,440 --> 00:27:58,659 bits and, and a number 658 00:27:58,660 --> 00:28:01,619 of. OK, I've got a typo here. 659 00:28:01,620 --> 00:28:02,620 Um 660 00:28:04,980 --> 00:28:07,029 is the number of input bits and and it's 661 00:28:07,030 --> 00:28:08,289 the number of output bits. 662 00:28:08,290 --> 00:28:10,419 So for example, 663 00:28:10,420 --> 00:28:12,519 uh code rate of 664 00:28:12,520 --> 00:28:14,979 one half means that 665 00:28:14,980 --> 00:28:17,529 you're actually doubling your bitrate. 666 00:28:20,510 --> 00:28:22,879 The simplest codes, parity, 667 00:28:22,880 --> 00:28:25,419 parity, check codes, um, 668 00:28:25,420 --> 00:28:27,619 and usually do this 669 00:28:27,620 --> 00:28:30,919 with, um, generate a matrixes 670 00:28:30,920 --> 00:28:31,920 and 671 00:28:33,080 --> 00:28:35,389 for example, if you use 672 00:28:35,390 --> 00:28:37,609 if you, um, at 673 00:28:37,610 --> 00:28:39,919 a parity beat to every fight, 674 00:28:39,920 --> 00:28:40,920 um. 675 00:28:42,240 --> 00:28:44,839 Uh, then you have, 676 00:28:44,840 --> 00:28:46,440 uh, Kudret of 677 00:28:48,270 --> 00:28:51,089 eight, divided by nine, for example, and 678 00:28:51,090 --> 00:28:53,039 the distance between the different code 679 00:28:53,040 --> 00:28:55,409 words used, uh, uh, determines 680 00:28:55,410 --> 00:28:58,199 what your distance, 681 00:28:58,200 --> 00:29:00,059 uh, an error correction is. 682 00:29:01,770 --> 00:29:04,319 So, um, if you use, 683 00:29:04,320 --> 00:29:06,599 um, a few code 684 00:29:06,600 --> 00:29:08,759 words, but, uh, huge code 685 00:29:08,760 --> 00:29:11,220 words, then you can usually, um. 686 00:29:13,000 --> 00:29:14,529 Have high error correction 687 00:29:15,610 --> 00:29:17,769 and an example for this is 688 00:29:17,770 --> 00:29:18,770 having code. 689 00:29:22,280 --> 00:29:25,759 I read someone read Solomon, quote, is 690 00:29:25,760 --> 00:29:28,089 very often used is, 691 00:29:28,090 --> 00:29:30,619 for example, firstly use that 692 00:29:30,620 --> 00:29:31,929 as a transmissions, 693 00:29:33,020 --> 00:29:35,179 um, where it is 694 00:29:35,180 --> 00:29:37,879 also used with the convolutional kode 695 00:29:37,880 --> 00:29:40,369 and is a non 696 00:29:40,370 --> 00:29:43,099 binary code where we actually, 697 00:29:43,100 --> 00:29:45,769 um, use the code word as, 698 00:29:45,770 --> 00:29:48,019 um, coefficients to, 699 00:29:48,020 --> 00:29:49,819 uh, finish field. 700 00:29:49,820 --> 00:29:51,979 And it's also used 701 00:29:51,980 --> 00:29:54,799 by devious activity, 702 00:29:54,800 --> 00:29:56,899 um, the digital audio 703 00:29:56,900 --> 00:29:59,149 broadcasting and ATC, 704 00:29:59,150 --> 00:30:01,389 the American Digital Television 705 00:30:01,390 --> 00:30:02,449 Television Standard. 706 00:30:05,670 --> 00:30:07,799 Um, then we have 707 00:30:07,800 --> 00:30:10,139 got low density Perry to check 708 00:30:10,140 --> 00:30:12,719 codes, which are actually 709 00:30:12,720 --> 00:30:14,879 not new, but, uh, were 710 00:30:14,880 --> 00:30:17,489 forgotten for a long time and 711 00:30:17,490 --> 00:30:20,609 used, for example, that Alti 712 00:30:20,610 --> 00:30:22,919 and DVC, as far 713 00:30:22,920 --> 00:30:25,229 as I remember, 714 00:30:25,230 --> 00:30:27,389 if I remember correctly, 715 00:30:27,390 --> 00:30:28,390 um. 716 00:30:29,970 --> 00:30:32,279 And are 717 00:30:32,280 --> 00:30:35,459 basically parity checks over huge 718 00:30:35,460 --> 00:30:37,109 block sizes. 719 00:30:37,110 --> 00:30:38,599 Um, so you. 720 00:30:39,730 --> 00:30:40,730 Of. 721 00:30:42,530 --> 00:30:45,829 Um, a very large, um, 722 00:30:45,830 --> 00:30:48,469 matrix, and you 723 00:30:48,470 --> 00:30:51,559 usually can only solve this matrix by, 724 00:30:51,560 --> 00:30:54,379 um, iterating over the 725 00:30:54,380 --> 00:30:56,629 elements and this 726 00:30:56,630 --> 00:30:58,230 is the. 727 00:30:59,610 --> 00:31:02,369 Uh, blockquote 728 00:31:02,370 --> 00:31:04,799 error correcting code, which is 729 00:31:06,360 --> 00:31:08,879 very close to the final limit, or is 730 00:31:08,880 --> 00:31:09,880 the 731 00:31:10,950 --> 00:31:12,679 error correcting code, which is most 732 00:31:12,680 --> 00:31:13,680 always 733 00:31:14,940 --> 00:31:17,379 which comes to the sun limits 734 00:31:17,380 --> 00:31:19,589 like, uh, very 735 00:31:19,590 --> 00:31:20,590 close. 736 00:31:25,520 --> 00:31:28,309 OK, um, two computer codes, 737 00:31:28,310 --> 00:31:31,099 these are not blackouts, but are, 738 00:31:31,100 --> 00:31:33,259 um, codes where we 739 00:31:33,260 --> 00:31:35,539 take our bitstream or input bitstream 740 00:31:35,540 --> 00:31:38,449 and convolve it mathematically. 741 00:31:38,450 --> 00:31:40,849 So, um, for example, 742 00:31:40,850 --> 00:31:42,949 this is a, uh, simple coda 743 00:31:42,950 --> 00:31:45,529 with, uh, lengths of three or 744 00:31:45,530 --> 00:31:47,779 we have two, uh, elements where we 745 00:31:47,780 --> 00:31:50,059 save the last bit and 746 00:31:50,060 --> 00:31:52,879 for every bit that, um. 747 00:31:52,880 --> 00:31:55,189 Comes at the input we shift 748 00:31:55,190 --> 00:31:57,469 this one and two 749 00:31:57,470 --> 00:31:58,579 exclusive or 750 00:31:59,930 --> 00:32:01,939 operations on the output and we have got 751 00:32:01,940 --> 00:32:04,099 two outputs, so that means 752 00:32:04,100 --> 00:32:06,169 that we have got a half hour 753 00:32:06,170 --> 00:32:07,170 rate codec. 754 00:32:08,400 --> 00:32:11,249 And you can do this for any 755 00:32:11,250 --> 00:32:13,349 number of raids, for 756 00:32:13,350 --> 00:32:15,659 example, for you can also 757 00:32:15,660 --> 00:32:17,880 have for pots if you really want high. 758 00:32:19,850 --> 00:32:22,429 Error correcting possibilities, 759 00:32:22,430 --> 00:32:23,430 but. 760 00:32:24,520 --> 00:32:27,609 Means that you also 761 00:32:27,610 --> 00:32:30,489 have a lot of redundancy and, 762 00:32:30,490 --> 00:32:31,490 um. 763 00:32:32,890 --> 00:32:34,989 Usually this gets used as 764 00:32:34,990 --> 00:32:37,239 a base code or mother code, 765 00:32:37,240 --> 00:32:39,399 and then we have got punctuation, which 766 00:32:39,400 --> 00:32:42,039 means we actually 767 00:32:42,040 --> 00:32:44,169 leave bits out, 768 00:32:44,170 --> 00:32:46,489 which we don't transmit and receive 769 00:32:46,490 --> 00:32:48,639 Edzard again. So we are 770 00:32:48,640 --> 00:32:51,009 doing or we are making actively 771 00:32:51,010 --> 00:32:52,339 errors. 772 00:32:52,340 --> 00:32:54,399 Um, but we don't have to 773 00:32:54,400 --> 00:32:56,979 transmit the whole, um, 774 00:32:56,980 --> 00:32:58,450 bitstream we generate. 775 00:33:06,580 --> 00:33:08,859 This is usually decoded 776 00:33:08,860 --> 00:33:10,260 with the Iturbi algorithm, 777 00:33:11,350 --> 00:33:13,420 and the reason why it is 778 00:33:14,620 --> 00:33:17,079 these codes were actually forgotten 779 00:33:17,080 --> 00:33:19,329 is because the Viterbi algorithm 780 00:33:19,330 --> 00:33:21,909 is quite complex 781 00:33:21,910 --> 00:33:24,039 to solve for hire a 782 00:33:24,040 --> 00:33:25,040 length of code. 783 00:33:26,020 --> 00:33:28,569 For example, WPT uses 784 00:33:28,570 --> 00:33:30,219 code length of seven. 785 00:33:30,220 --> 00:33:32,589 And you can, 786 00:33:32,590 --> 00:33:35,199 uh, if you take this, 787 00:33:35,200 --> 00:33:37,059 uh, you can actually do a state machine 788 00:33:37,060 --> 00:33:38,409 out of it. 789 00:33:38,410 --> 00:33:40,689 And you have got 790 00:33:40,690 --> 00:33:43,619 the state so far to, 791 00:33:43,620 --> 00:33:44,620 um. 792 00:33:46,480 --> 00:33:48,729 For two 793 00:33:48,730 --> 00:33:51,279 elements here, you have got 794 00:33:51,280 --> 00:33:53,859 two bids for the state 795 00:33:53,860 --> 00:33:55,929 and what we are 796 00:33:55,930 --> 00:33:58,209 doing at the Riverside side is 797 00:33:58,210 --> 00:34:00,880 we try to. 798 00:34:03,500 --> 00:34:05,879 We try to think what, 799 00:34:05,880 --> 00:34:08,238 uh, uh, what's the, uh, 800 00:34:08,239 --> 00:34:10,069 state machine at the US at the moment 801 00:34:10,070 --> 00:34:11,119 doing? 802 00:34:11,120 --> 00:34:13,488 And, uh, at this 803 00:34:13,489 --> 00:34:14,780 diagram, uh. 804 00:34:16,570 --> 00:34:18,638 Uh, this is, 805 00:34:18,639 --> 00:34:20,888 uh, for example, zero, and 806 00:34:20,889 --> 00:34:23,479 if we go down, we actually transmitted 807 00:34:23,480 --> 00:34:24,760 the one, so. 808 00:34:27,929 --> 00:34:29,460 If we at first. 809 00:34:31,150 --> 00:34:33,039 Um, received these symbols, 810 00:34:34,090 --> 00:34:36,669 um, and understand this one, 811 00:34:36,670 --> 00:34:39,229 we can actually recalculates 812 00:34:39,230 --> 00:34:41,319 the path finished state 813 00:34:41,320 --> 00:34:42,879 machine that the sender was actually 814 00:34:42,880 --> 00:34:45,099 using and 815 00:34:45,100 --> 00:34:47,198 the receiver tries to find the path 816 00:34:47,199 --> 00:34:49,388 with lowest distance or with lowest 817 00:34:49,389 --> 00:34:50,389 error. 818 00:34:58,460 --> 00:34:59,460 The second 819 00:35:01,310 --> 00:35:03,439 type of quotes which are coming close 820 00:35:03,440 --> 00:35:06,079 to the limit to barcodes, 821 00:35:06,080 --> 00:35:08,209 which are actually, um, 822 00:35:08,210 --> 00:35:11,329 parallel, um, concatenated, 823 00:35:11,330 --> 00:35:13,519 uh, criminal records, uh, this is 824 00:35:13,520 --> 00:35:15,709 a bit of, uh, mixture of 825 00:35:15,710 --> 00:35:17,839 blockquote and convoluted codes 826 00:35:17,840 --> 00:35:19,189 we use here. 827 00:35:19,190 --> 00:35:21,530 Um, this is actually fundi from the 828 00:35:22,610 --> 00:35:24,319 original paper about this. 829 00:35:25,640 --> 00:35:27,979 Uh, we use, uh, to convolutional 830 00:35:27,980 --> 00:35:28,980 codes. 831 00:35:30,000 --> 00:35:32,339 And used them as 832 00:35:32,340 --> 00:35:34,010 parity with us, 833 00:35:35,160 --> 00:35:37,379 we use them to add information, but 834 00:35:37,380 --> 00:35:39,659 we are still using the bitstream, which 835 00:35:39,660 --> 00:35:42,030 is on the input side. 836 00:35:45,090 --> 00:35:46,090 And 837 00:35:47,250 --> 00:35:49,019 low density parity check records are 838 00:35:49,020 --> 00:35:50,999 better than this, but this comes also 839 00:35:51,000 --> 00:35:52,000 very close. 840 00:35:54,790 --> 00:35:56,380 And after. 841 00:35:57,500 --> 00:36:00,079 Um, after 842 00:36:00,080 --> 00:36:02,659 our forward error correction, you 843 00:36:02,660 --> 00:36:04,879 you usually do data 844 00:36:04,880 --> 00:36:07,219 interleaving because wireless 845 00:36:07,220 --> 00:36:09,779 channels have 846 00:36:09,780 --> 00:36:11,649 usually got past errors. 847 00:36:11,650 --> 00:36:13,969 So you've got a small time 848 00:36:13,970 --> 00:36:16,309 amount where you can away, uh, signal 849 00:36:16,310 --> 00:36:18,439 to noise ratio is really bad and you have 850 00:36:18,440 --> 00:36:19,549 got a lot of errors. 851 00:36:19,550 --> 00:36:22,009 And then you can all again have, 852 00:36:22,010 --> 00:36:24,589 um, a time span where 853 00:36:24,590 --> 00:36:26,659 you receive signals 854 00:36:26,660 --> 00:36:29,239 without any errors and. 855 00:36:30,980 --> 00:36:33,439 Um, convolutional codes 856 00:36:33,440 --> 00:36:36,249 are bad at, um, 857 00:36:36,250 --> 00:36:38,419 uh, when it comes to, 858 00:36:38,420 --> 00:36:40,840 uh, a lot of errors after another. 859 00:36:41,960 --> 00:36:43,999 So what we are doing is we are 860 00:36:44,000 --> 00:36:45,739 interleaving. The signal and this is the 861 00:36:45,740 --> 00:36:47,869 interleave of tubes. 862 00:36:47,870 --> 00:36:50,179 There are different approaches 863 00:36:50,180 --> 00:36:52,339 to interleave us, for example, that you 864 00:36:52,340 --> 00:36:54,829 can have a permutation matrix 865 00:36:54,830 --> 00:36:57,379 like Altius or Convolutional 866 00:36:57,380 --> 00:36:59,539 interleave, where you've got 867 00:36:59,540 --> 00:37:02,739 these storage elements and you, 868 00:37:02,740 --> 00:37:05,149 um, which each with each, but 869 00:37:05,150 --> 00:37:08,419 you switch one of the positions. 870 00:37:08,420 --> 00:37:10,669 So you're actually doing, 871 00:37:10,670 --> 00:37:11,670 um. 872 00:37:12,500 --> 00:37:15,589 Like, randomizing 873 00:37:15,590 --> 00:37:17,959 your packets over a specific 874 00:37:19,580 --> 00:37:20,539 span. 875 00:37:20,540 --> 00:37:22,999 So if we if you've got, 876 00:37:23,000 --> 00:37:25,129 um, for example, 877 00:37:25,130 --> 00:37:27,259 10 bites in a 878 00:37:27,260 --> 00:37:28,260 single row, which 879 00:37:29,510 --> 00:37:31,879 which could not be decoded after 880 00:37:31,880 --> 00:37:32,900 to the 881 00:37:34,120 --> 00:37:35,120 Adira 882 00:37:36,440 --> 00:37:38,569 interleaving at the receiver side, 883 00:37:38,570 --> 00:37:41,029 did these 10 bytes 884 00:37:41,030 --> 00:37:43,189 spread around across 885 00:37:43,190 --> 00:37:45,349 the whole input stream 886 00:37:46,460 --> 00:37:48,439 and then your blockhouse and your 887 00:37:48,440 --> 00:37:51,079 computer codes have it easier to 888 00:37:51,080 --> 00:37:52,189 decode them again? 889 00:37:55,010 --> 00:37:57,949 Um, then we come to channel access 890 00:37:57,950 --> 00:38:00,529 to a channel access we have got is, 891 00:38:00,530 --> 00:38:03,889 uh, Simplex are broadcasting, 892 00:38:03,890 --> 00:38:06,439 um, which is like 893 00:38:06,440 --> 00:38:08,389 every radio station does. 894 00:38:08,390 --> 00:38:11,209 You've got one sender and, 895 00:38:11,210 --> 00:38:12,210 uh. 896 00:38:13,200 --> 00:38:14,219 You can have many, 897 00:38:15,510 --> 00:38:16,510 many receivers 898 00:38:17,820 --> 00:38:19,679 you don't need synchronization to and 899 00:38:20,700 --> 00:38:23,549 you can't have any synchronization, 900 00:38:23,550 --> 00:38:26,279 and because you have you don't have a 901 00:38:26,280 --> 00:38:27,780 back channel to your 902 00:38:29,440 --> 00:38:30,449 to your transmitter. 903 00:38:32,550 --> 00:38:33,550 Um. 904 00:38:34,840 --> 00:38:37,719 Often this is also used if you've got, 905 00:38:37,720 --> 00:38:39,789 for example, a few wireless nodes 906 00:38:39,790 --> 00:38:42,639 which are only transmitting 907 00:38:42,640 --> 00:38:44,739 at a very low 908 00:38:44,740 --> 00:38:45,849 rate of very 909 00:38:47,150 --> 00:38:49,239 low time of year, 910 00:38:49,240 --> 00:38:51,249 actually time slots. 911 00:38:51,250 --> 00:38:53,499 So there is no 912 00:38:53,500 --> 00:38:56,019 interaction between the transmitters 913 00:38:56,020 --> 00:38:57,020 and the receivers. 914 00:39:00,610 --> 00:39:01,610 Um. 915 00:39:02,410 --> 00:39:04,869 Then we can have TDMA, 916 00:39:04,870 --> 00:39:06,159 which is a time division, multiple 917 00:39:06,160 --> 00:39:08,379 access, where we use one 918 00:39:08,380 --> 00:39:10,719 channel and divide it into 919 00:39:10,720 --> 00:39:12,819 different time spans for 920 00:39:12,820 --> 00:39:15,069 different, um, uh, 921 00:39:15,070 --> 00:39:18,459 centers or for different transmitters. 922 00:39:18,460 --> 00:39:20,829 For example, um, this 923 00:39:20,830 --> 00:39:23,139 is each one of these boxes 924 00:39:23,140 --> 00:39:24,399 is a time slot. 925 00:39:24,400 --> 00:39:26,619 And, uh, in each of these time 926 00:39:26,620 --> 00:39:29,049 spans, a different transmitter 927 00:39:29,050 --> 00:39:31,179 sends, uh, this 928 00:39:31,180 --> 00:39:33,879 is usually used almost 929 00:39:33,880 --> 00:39:36,670 always used at mobile communications 930 00:39:37,840 --> 00:39:39,909 and for example, tacts, 931 00:39:39,910 --> 00:39:42,099 LTE, GSM, 932 00:39:42,100 --> 00:39:44,609 UMTS, um, 933 00:39:44,610 --> 00:39:45,610 all using this. 934 00:39:46,600 --> 00:39:49,569 And because we 935 00:39:49,570 --> 00:39:52,209 have um, 936 00:39:52,210 --> 00:39:54,579 this time splits were the second 937 00:39:54,580 --> 00:39:57,039 or the next transmitter, 938 00:39:57,040 --> 00:39:59,139 um has to 939 00:39:59,140 --> 00:40:01,389 send as fast as possible 940 00:40:01,390 --> 00:40:03,489 after the uh the last one 941 00:40:03,490 --> 00:40:04,839 has entered. 942 00:40:04,840 --> 00:40:06,909 Um you have uh 943 00:40:06,910 --> 00:40:09,009 you need to have exact timings 944 00:40:09,010 --> 00:40:11,909 and add wireless 945 00:40:11,910 --> 00:40:12,910 or at uh. 946 00:40:14,040 --> 00:40:16,679 Um, mobile communications, where 947 00:40:16,680 --> 00:40:19,049 where you have got base stations, usually 948 00:40:19,050 --> 00:40:21,209 base base stations, tell the 949 00:40:21,210 --> 00:40:23,370 clients when they should send. 950 00:40:27,210 --> 00:40:28,210 Um, 951 00:40:29,340 --> 00:40:31,889 we can also have, um, multiple 952 00:40:31,890 --> 00:40:34,049 channels where we send 953 00:40:34,050 --> 00:40:36,599 simultaneously, which is frequency 954 00:40:36,600 --> 00:40:38,699 division, multiple access, 955 00:40:38,700 --> 00:40:40,829 uh, where we have an uplink and 956 00:40:40,830 --> 00:40:43,109 downlink channel, uh, 957 00:40:43,110 --> 00:40:45,569 which is based by duplex offset. 958 00:40:45,570 --> 00:40:47,939 And both channels can 959 00:40:47,940 --> 00:40:49,439 be active at the same time. 960 00:40:49,440 --> 00:40:51,299 And if you have got a good analog 961 00:40:51,300 --> 00:40:53,369 filtering, you can receive 962 00:40:53,370 --> 00:40:54,929 at the same time that you transmit. 963 00:40:54,930 --> 00:40:57,509 So to us actually full duplex, 964 00:40:57,510 --> 00:41:00,030 um, possible over wireless. 965 00:41:01,200 --> 00:41:03,449 And um, 966 00:41:03,450 --> 00:41:05,969 most of the mobile networks 967 00:41:05,970 --> 00:41:06,970 use this. 968 00:41:09,230 --> 00:41:11,509 Um, for example, 969 00:41:11,510 --> 00:41:14,569 if you combine this with TDMA, then 970 00:41:14,570 --> 00:41:15,739 the uplinked channels 971 00:41:17,000 --> 00:41:19,819 get each client gets a single, 972 00:41:19,820 --> 00:41:20,820 um. 973 00:41:21,880 --> 00:41:24,339 At times in a single time slot 974 00:41:24,340 --> 00:41:25,340 and. 975 00:41:27,920 --> 00:41:30,379 The base station basically 976 00:41:30,380 --> 00:41:32,030 owns the downlinked channel. 977 00:41:35,170 --> 00:41:36,909 And there's also called division multiple 978 00:41:36,910 --> 00:41:39,189 access, if we want to 979 00:41:39,190 --> 00:41:41,769 transmit simultaneously, we on 980 00:41:41,770 --> 00:41:44,109 we usually need to have something 981 00:41:44,110 --> 00:41:47,199 that is orthogonal. 982 00:41:47,200 --> 00:41:48,850 Um, for example, um. 983 00:41:50,510 --> 00:41:53,059 Frequency division, multiple access is 984 00:41:53,060 --> 00:41:55,489 using different frequencies so 985 00:41:55,490 --> 00:41:57,589 we can distinguish them at code 986 00:41:57,590 --> 00:41:59,299 division, multiple access for use the 987 00:41:59,300 --> 00:42:01,219 same frequency and we transmit at the 988 00:42:01,220 --> 00:42:02,359 same time. 989 00:42:02,360 --> 00:42:04,999 And it's only because of 990 00:42:05,000 --> 00:42:08,089 digital coding, um, 991 00:42:08,090 --> 00:42:10,909 that we can distinguish 992 00:42:10,910 --> 00:42:12,260 two signals from each other. 993 00:42:13,940 --> 00:42:16,039 And this is, for example, used at 994 00:42:17,040 --> 00:42:19,819 such Gallileo and 995 00:42:19,820 --> 00:42:22,279 CDMA and, uh, 996 00:42:22,280 --> 00:42:23,280 UMTS. 997 00:42:27,270 --> 00:42:29,459 OK, and thanks 998 00:42:29,460 --> 00:42:31,530 for your attentions at any. 999 00:42:33,340 --> 00:42:34,340 And the questions. 1000 00:42:51,170 --> 00:42:53,039 Everything's OK. 1001 00:42:53,040 --> 00:42:55,489 OK, so thanks. 1002 00:42:55,490 --> 00:42:56,439 Who was the next? 1003 00:42:56,440 --> 00:42:58,959 OK, so OK. 1004 00:43:01,430 --> 00:43:03,949 Yeah, um, so, um, 1005 00:43:03,950 --> 00:43:05,689 probably most of the people in this room 1006 00:43:05,690 --> 00:43:07,609 understand a lot of the of the digital 1007 00:43:07,610 --> 00:43:09,799 and what you explained and the coding and 1008 00:43:09,800 --> 00:43:11,899 the error correction in your 1009 00:43:11,900 --> 00:43:14,409 eyes. If you rate well, 1010 00:43:14,410 --> 00:43:15,919 do not even know if this question 1011 00:43:15,920 --> 00:43:17,959 actually if you have to compare the 1012 00:43:17,960 --> 00:43:20,119 analog or the real transmission stuff to 1013 00:43:20,120 --> 00:43:22,759 get it to the antenna and to get it 1014 00:43:22,760 --> 00:43:24,649 like into the air compared with the 1015 00:43:24,650 --> 00:43:26,809 digital stuff, how would you rate it? 1016 00:43:26,810 --> 00:43:28,939 Like the ratio is 1017 00:43:28,940 --> 00:43:31,039 is most of the work on the on 1018 00:43:31,040 --> 00:43:33,199 the transmission, on the antenna, on the 1019 00:43:33,200 --> 00:43:35,269 amplifying, on the on the 1020 00:43:35,270 --> 00:43:37,309 signal processing or is it on the digital 1021 00:43:37,310 --> 00:43:38,329 end. 1022 00:43:38,330 --> 00:43:40,579 Um, well this depends, just depends 1023 00:43:40,580 --> 00:43:42,979 a lot on your signal or on your 1024 00:43:42,980 --> 00:43:45,049 um what you actually 1025 00:43:45,050 --> 00:43:46,609 want to do. If you want to have a 1026 00:43:46,610 --> 00:43:49,699 wireless signal, a wireless transmission, 1027 00:43:49,700 --> 00:43:53,179 um which is um 1028 00:43:53,180 --> 00:43:55,909 possible to adapt to a lot of uh 1029 00:43:55,910 --> 00:43:58,999 or if you want to have a system, 1030 00:43:59,000 --> 00:44:01,219 um, which can 1031 00:44:01,220 --> 00:44:03,799 do a lot of stuff, for example, 1032 00:44:03,800 --> 00:44:05,929 for um, if you have a software 1033 00:44:05,930 --> 00:44:08,029 defined radio, you usually want 1034 00:44:08,030 --> 00:44:10,039 to have, uh, large bandwidth where you 1035 00:44:10,040 --> 00:44:12,109 can choose which signal you actually 1036 00:44:12,110 --> 00:44:14,749 want to use, then, um, 1037 00:44:14,750 --> 00:44:17,329 analog stuff gets much complicated, 1038 00:44:17,330 --> 00:44:19,069 much more complicated. 1039 00:44:19,070 --> 00:44:21,469 Um, also 1040 00:44:21,470 --> 00:44:23,689 if you have got um, 1041 00:44:23,690 --> 00:44:25,849 for example, uh, 1042 00:44:25,850 --> 00:44:28,489 very different 1043 00:44:28,490 --> 00:44:30,109 thing, uh, very difficult. 1044 00:44:30,110 --> 00:44:31,110 Uh. 1045 00:44:34,530 --> 00:44:36,869 For example, mobile communications 1046 00:44:36,870 --> 00:44:38,489 for mobile communications, you need 1047 00:44:38,490 --> 00:44:39,949 really good amplifiers, 1048 00:44:40,950 --> 00:44:43,419 you need to do a lot of 1049 00:44:43,420 --> 00:44:46,259 frequency engineering 1050 00:44:46,260 --> 00:44:48,839 so you can go to your cell 1051 00:44:48,840 --> 00:44:50,489 sites in the right direction, in the 1052 00:44:50,490 --> 00:44:50,889 right. 1053 00:44:50,890 --> 00:44:52,830 Uh, um. 1054 00:44:54,470 --> 00:44:56,329 Sizes in the red. 1055 00:44:56,330 --> 00:44:57,330 Yeah, OK, 1056 00:44:59,240 --> 00:45:00,240 I hope you 1057 00:45:01,910 --> 00:45:02,910 yes, OK. 1058 00:45:04,050 --> 00:45:05,639 I thanks for the talk. 1059 00:45:05,640 --> 00:45:07,649 I'm a radiometer myself, and I want to 1060 00:45:07,650 --> 00:45:09,209 get into this stuff. 1061 00:45:09,210 --> 00:45:10,679 What's your recommendation on free 1062 00:45:10,680 --> 00:45:12,929 software? Do you recommend starting this 1063 00:45:12,930 --> 00:45:15,329 new radio? Is that too complex 1064 00:45:15,330 --> 00:45:16,979 or what's your recommendation? 1065 00:45:16,980 --> 00:45:19,529 Which which software should I look into? 1066 00:45:19,530 --> 00:45:21,629 Um, I started with 1067 00:45:21,630 --> 00:45:24,689 Radio Free a few years ago, and 1068 00:45:24,690 --> 00:45:27,389 I've done a few 1069 00:45:27,390 --> 00:45:29,769 a bit of radio projects. 1070 00:45:29,770 --> 00:45:30,770 Um. 1071 00:45:32,360 --> 00:45:34,909 The problem was the four 1072 00:45:34,910 --> 00:45:37,099 people which are good at 1073 00:45:37,100 --> 00:45:39,259 coding or at 1074 00:45:39,260 --> 00:45:41,419 writing software is that 1075 00:45:41,420 --> 00:45:43,789 radio is mostly 1076 00:45:43,790 --> 00:45:46,009 C++. If you want if you really 1077 00:45:46,010 --> 00:45:48,979 want to go into the details, 1078 00:45:48,980 --> 00:45:51,109 um, if you just 1079 00:45:51,110 --> 00:45:53,929 want to experiment with different kinds, 1080 00:45:53,930 --> 00:45:56,329 it can get 1081 00:45:56,330 --> 00:45:58,309 very difficult. 1082 00:45:58,310 --> 00:46:00,559 That's the first thing you 1083 00:46:00,560 --> 00:46:01,609 need to get into it. 1084 00:46:01,610 --> 00:46:03,919 So it's a very steep learning 1085 00:46:03,920 --> 00:46:06,689 curve, but it's very nice. 1086 00:46:06,690 --> 00:46:08,329 Um, yeah. 1087 00:46:08,330 --> 00:46:10,039 It's a very nice software development 1088 00:46:10,040 --> 00:46:11,040 kit. 1089 00:46:14,650 --> 00:46:15,650 And also, 1090 00:46:18,070 --> 00:46:20,259 yeah, OK, we 1091 00:46:20,260 --> 00:46:21,260 have questions, 1092 00:46:22,540 --> 00:46:24,690 no, any other question, 1093 00:46:26,520 --> 00:46:28,509 you know. OK, thank you. 1094 00:46:28,510 --> 00:46:29,510 OK, thanks.