0 1 00:00:01,200 --> 00:00:06,810 We now look at several LoRa's transceiver documentation, and we will start by looking at the 1 2 00:00:06,810 --> 00:00:07,950 SX1272. 2 3 00:00:08,640 --> 00:00:11,130 It's not a recent transceiver, but never mind. 3 4 00:00:11,670 --> 00:00:13,370 We'll see a new one after this. 4 5 00:00:13,380 --> 00:00:14,460 You'll see the differences. 5 6 00:00:15,390 --> 00:00:24,840 So, we'll do a quick Google search for the SX1272 and the first result heads us to Semtech website. 6 7 00:00:25,860 --> 00:00:28,650 And we can have a lot of information about this company. 7 8 00:00:30,300 --> 00:00:33,840 So we'll immediately download the documentation in PDF format. 8 9 00:00:35,070 --> 00:00:40,650 In this documentation, very quickly in the first page, we have the key product features. 9 10 00:00:41,520 --> 00:00:48,240 In this key product features, we learn that it is a LoRa modem and that's exactly what we wanted. 10 11 00:00:49,320 --> 00:00:57,810 We also learn that the maximum link budget is 157 dB, means that this transceiver will have a maximum transmitted 11 12 00:00:57,810 --> 00:01:06,060 power of 20 dBm, and that if we want to respect the standard, we'll use the maximum power of 14 dBm 12 13 00:01:07,080 --> 00:01:15,390 and finally we'll also learn that the sensitivity is -137 dBm. And what can we notice ? 13 14 00:01:15,840 --> 00:01:22,140 We can notice that the link budget that has been calculated here has simply been found by subtracting 14 15 00:01:22,140 --> 00:01:33,960 the maximum transmitted power with the sensitivity that is 20 dBm minus -137 dBm, which is 157 dB. 15 16 00:01:35,520 --> 00:01:41,790 Let's now see a component of the same range, but a little more recent, the SX1276. 16 17 00:01:42,690 --> 00:01:50,490 So we do another quick search on Google SX1276. Of course again, we fall on Semtech's website. And 17 18 00:01:50,490 --> 00:01:55,820 this time we'll not download the documentation but we'll simply note that we're still dealing with a LoRa 18 19 00:01:55,830 --> 00:01:56,220 modem, 19 20 00:01:57,120 --> 00:01:59,280 but the link budget is better. 20 21 00:02:00,150 --> 00:02:05,370 We went from 157 dB to 168 dB. 21 22 00:02:06,480 --> 00:02:13,530 Indeed, the transmitted power is still 20 dBm and if we want to respect the standard, it's still 14 dBm. 22 23 00:02:13,530 --> 00:02:18,300 But this time the sensitivity is -148 dBm. 23 24 00:02:19,050 --> 00:02:24,870 And of course if we make the same calculation, substracting the transmitted power with the sensitivity, 24 25 00:02:25,230 --> 00:02:33,690 we find 20 dBm minus -148, which is in that case 168 dB of link budget. 25 26 00:02:33,700 --> 00:02:42,750 Now we'll see what is said about the Signal Over Noise Ratio. So we can go on any transceivers documentation 26 27 00:02:43,200 --> 00:02:45,750 and we'll see a table with the following information. 27 28 00:02:46,380 --> 00:02:51,000 This table present the Signal Over Noise Ratio according to the Spreading Factor. 28 29 00:02:51,990 --> 00:02:57,750 We've already talked about this Spreading Factor and we've said that we could take any value between 5 29 30 00:02:57,750 --> 00:03:01,080 and 12. In this specific transceiver, 30 31 00:03:01,440 --> 00:03:03,360 the lowest Spreading Factor is 6. 31 32 00:03:03,360 --> 00:03:09,330 But anyway, when we'll speak about LoRaWAN, the Spreading Factor will have to be between 7 to 12. 32 33 00:03:09,330 --> 00:03:12,360 And obviously all LoRa transceiver will be fine. 33 34 00:03:12,390 --> 00:03:13,380 So no worries. 34 35 00:03:14,370 --> 00:03:15,990 So let's take a first example. 35 36 00:03:15,990 --> 00:03:22,590 If I take a Spreagin Factor of 8, the LoRa demodualtor will be able to work at -10 36 37 00:03:22,590 --> 00:03:23,040 dB. 37 38 00:03:23,760 --> 00:03:25,050 So what's -10dB ? 38 39 00:03:25,050 --> 00:03:29,790 -10dB is ten times more noise than signal. 39 40 00:03:29,790 --> 00:03:36,210 It means that the LoRa demodulator is able to find a transmitted signal in spite of the fact that 40 41 00:03:36,210 --> 00:03:40,710 there is ten times more noise than signal, which is quite considerable. 41 42 00:03:41,610 --> 00:03:48,450 Just imagine you're talking to someone and there is noise around and the noise is ten times louder 42 43 00:03:48,450 --> 00:03:50,040 than the person talking to you. 43 44 00:03:50,040 --> 00:03:52,650 And yet, you can understand what's being said. 44 45 00:03:53,340 --> 00:03:59,610 If you now take the spreading factor 12 you can demodulate a signal with SNR ratio of -20 dB. 45 46 00:04:00,300 --> 00:04:06,240 This means that you able to find a signal that is drawn in a noise that is 100 times stronger. 46 47 00:04:07,050 --> 00:04:09,960 You're talking to someone, you have noise around. 47 48 00:04:10,440 --> 00:04:12,870 This noise is 100 times louder. 48 49 00:04:12,870 --> 00:04:15,000 And yet, you can consider that 49 50 00:04:15,000 --> 00:04:16,590 you can understand what's being said. 50 51 00:04:17,220 --> 00:04:18,540 That is really amazing. 51 52 00:04:19,710 --> 00:04:22,050 Of course, there is some counterpart to that. 52 53 00:04:22,530 --> 00:04:27,900 Actually, in the second column there is another information and we'll get back to it later. 53 54 00:04:28,290 --> 00:04:34,710 But what it does basically say is that every time we use the highest Spreading Factor, we send more information 54 55 00:04:34,710 --> 00:04:35,400 in the frame. 55 56 00:04:35,970 --> 00:04:39,000 So in other words, that we'll have an influence on the bitrate. 56 57 00:04:39,000 --> 00:04:41,520 But once again, we'll see that in the next chapter.