We're going to focus here on the LoRa transmission from one end device to a gateway. 1
For the moment, you can consider the gateway as a simple LoRa receiver, and I picked up randomly one 2
of the receiver frame on the gateway logs. 3
What kind of information do we have here? 4
First of all, we can check that we use the 868 megahertz band on a specific channel, which is in this 5
case, 867.9. 6
There is also the spreading factor. 7
The one used for this packet is SF12. 8
And finally there is the data size of 52 bytes. 9
This is simply the payload carried by the lower frame. 10
If I click on this packet, I have some additional details. 11
First, I see that this device is operated by Bouygues Telecom. 12
It doesn't belong to me. 13
And yet I received the packet on my gateway. 14
Yes, my gateway is the LoRa receiver 15
And it receives every LoRaWAN frames in its range. 16
It will be up to the server to verify if it will accept it or not, but we will see that later. 17
I have also the detail of the payload. 18
However, it's obviously encrypted and I can't understand it because of course I don't have the corresponding 19
encryption keys. 20
If I go into the details of the transmission, I have information that is related to the radio frequency 21
transmission. 22
I find that the received power of my gateway is -121 dBm. 23
This is the RSSI. 24
I also have the information that the signal over noise ratio on my gateway is minus 2 dB and again, 25
my gateway reminds me the channel used: 867.9 megahertz. 26
There are also other information that we will have to explain: "air time", "bandwidth", "frame counter", "device adress" 27
and "CR" for Coding Rate. 28
Some information are part of the LoRa modulation and some others are part of the LoRaWAN protocol. 29
But again, no worries. 30
We'll take it step by step.