0 1 00:00:00,600 --> 00:00:05,850 When we want to explain how a protocol works, we usually use layers to represent it. 1 2 00:00:06,390 --> 00:00:12,990 The bottom layer called LoRa modulation is also often called PHY layers for physical layer. 2 3 00:00:13,680 --> 00:00:18,120 It represents the modulation used to transfer data from one point to another. 3 4 00:00:18,720 --> 00:00:25,130 We saw earlier that this modulation is called Chirp Spread Spectrum, but in short, we call it LoRa 4 5 00:00:25,140 --> 00:00:25,920 modulation. 5 6 00:00:26,610 --> 00:00:32,940 With this kind of modulation, you can send and receive data from a device to another device, or in 6 7 00:00:32,940 --> 00:00:38,040 most cases, from a device to a gateway. That has nothing to do with LoRaWAN. 7 8 00:00:38,220 --> 00:00:42,510 And if you want, you can only use the LoRa modulation for your application. 8 9 00:00:43,170 --> 00:00:49,410 But as security is a major concern in Iot, we need to add new services to this LoRa modulation. 9 10 00:00:50,040 --> 00:00:55,710 Any secure device need to take care about confidentiality, authenticity and integrity. 10 11 00:00:55,710 --> 00:01:01,900 And there are other concerns because we also need a way to identify the device to acknowledge data, 11 12 00:01:01,920 --> 00:01:04,590 specify the application port and so on. 12 13 00:01:05,190 --> 00:01:09,540 You can obviously build your own protocol that support all the requirements we've listed. 13 14 00:01:09,810 --> 00:01:14,380 But actually this is exactly what LoRaWAN does. 14 15 00:01:14,400 --> 00:01:21,630 So yes, we can design our own protocol, but we'll probably end up with something similar to LoRaWAN 15 16 00:01:21,630 --> 00:01:23,460 and certainly not as good. 16 17 00:01:23,490 --> 00:01:27,360 We said that the LoRaWAN protocol stands on top of the LoRa modulation. 17 18 00:01:27,390 --> 00:01:30,600 This is called the Mac layer or LoRa Mac. 18 19 00:01:30,750 --> 00:01:36,780 So when you see LoRa Mac in the specification, it's just a way to speak about the LoRaWAN protocol 19 20 00:01:36,780 --> 00:01:37,410 part. 20 21 00:01:37,980 --> 00:01:41,490 LoRa Mac implement services up to the application layer. 21 22 00:01:41,820 --> 00:01:48,360 Then as an output, it provides an encrypted payload to the user, and that's up to the last layer to 22 23 00:01:48,360 --> 00:01:49,230 decrypt it. 23 24 00:01:49,260 --> 00:01:52,500 This top layer is called the application layer. 24 25 00:01:53,010 --> 00:01:55,620 This representation works in both ways. 25 26 00:01:55,680 --> 00:02:01,170 It means that if you want to send data, then the application layer will encrypt it. 26 27 00:02:01,530 --> 00:02:03,760 It will be carried out by the LoRa mac. 27 28 00:02:03,780 --> 00:02:10,720 And finally, the LoRa modulation, which transmit the radiofrequency message. In this layer representation, 28 29 00:02:10,740 --> 00:02:17,340 it's also interesting to notice that these layers also help to understand each part of the LoRa frame over 29 30 00:02:17,340 --> 00:02:17,880 the air. 30 31 00:02:17,910 --> 00:02:21,900 Indeed, the LoRa frame begin with information on the LoRa protocol. 31 32 00:02:21,930 --> 00:02:27,090 There is a preamble, a LoRa header, and at the end there is a CRC. 32 33 00:02:27,480 --> 00:02:30,660 Then there are many fields concerning the Mac layer. 33 34 00:02:30,660 --> 00:02:32,130 So the LoRaWAN protocol. 34 35 00:02:32,220 --> 00:02:37,410 We already talked about these fields, about the identification, authentication, acknowledgement and 35 36 00:02:37,410 --> 00:02:37,980 so on. 36 37 00:02:38,400 --> 00:02:44,730 And finally, there is the application field of the LoRaWAN protocol, which is basically the user data. 37 38 00:02:45,500 --> 00:02:45,780 Okay. 38 39 00:02:45,780 --> 00:02:52,200 So now in the next video, I will dive on each part of the frame to see the relevance of each field 39 40 00:02:52,200 --> 00:02:53,100 of this frame. 40 41 00:02:53,250 --> 00:02:55,530 Let's begin with the LoRa modulation layer.