When we want to explain how a protocol works, we usually use layers to represent it. 1
The bottom layer called LoRa modulation is also often called PHY layers for physical layer. 2
It represents the modulation used to transfer data from one point to another. 3
We saw earlier that this modulation is called Chirp Spread Spectrum, but in short, we call it LoRa 4
modulation. 5
With this kind of modulation, you can send and receive data from a device to another device, or in 6
most cases, from a device to a gateway. That has nothing to do with LoRaWAN. 7
And if you want, you can only use the LoRa modulation for your application. 8
But as security is a major concern in Iot, we need to add new services to this LoRa modulation. 9
Any secure device need to take care about confidentiality, authenticity and integrity. 10
And there are other concerns because we also need a way to identify the device to acknowledge data, 11
specify the application port and so on. 12
You can obviously build your own protocol that support all the requirements we've listed. 13
But actually this is exactly what LoRaWAN does. 14
So yes, we can design our own protocol, but we'll probably end up with something similar to LoRaWAN 15
and certainly not as good. 16
We said that the LoRaWAN protocol stands on top of the LoRa modulation. 17
This is called the Mac layer or LoRa Mac. 18
So when you see LoRa Mac in the specification, it's just a way to speak about the LoRaWAN protocol 19
part. 20
LoRa Mac implement services up to the application layer. 21
Then as an output, it provides an encrypted payload to the user, and that's up to the last layer to 22
decrypt it. 23
This top layer is called the application layer. 24
This representation works in both ways. 25
It means that if you want to send data, then the application layer will encrypt it. 26
It will be carried out by the LoRa mac. 27
And finally, the LoRa modulation, which transmit the radiofrequency message. In this layer representation, 28
it's also interesting to notice that these layers also help to understand each part of the LoRa frame over 29
the air. 30
Indeed, the LoRa frame begin with information on the LoRa protocol. 31
There is a preamble, a LoRa header, and at the end there is a CRC. 32
Then there are many fields concerning the Mac layer. 33
So the LoRaWAN protocol. 34
We already talked about these fields, about the identification, authentication, acknowledgement and 35
so on. 36
And finally, there is the application field of the LoRaWAN protocol, which is basically the user data. 37
Okay. 38
So now in the next video, I will dive on each part of the frame to see the relevance of each field 39
of this frame. 40
Let's begin with the LoRa modulation layer.