Let's do exactly the same demonstration, but this time for a class C end-device. 2 2
Whatever the device and network Server, if 3 3
you want to set up a class C LoRaWAN transmission, we have to : First register 4 4
a class C end-device on the Network Server. 5 5
In my case, I'm still with my class A end 6 6
device, so I just need to switch from class A to class C. 7 7
Secondly, we have to configure the end device as a class C, on the device itself. 8 8
Okay, so let's do this. 9 9
I set up exactly the same environment with 10 10
once again my device log on the left and on the right two tabs. 11 11
The first tab is the gateway log and the second tab is my application. 12 12
As I said, I'm still with my class A end device called device1-OTAA. 13 13
So I need to change its class. On the 14 14
network server used for this demonstration. 15 15
I can do that in general settings. 16 16
Go down to network layer section and we can find the LoRaWAN class capabilities. 17 17
Keep in mind that even if the procedure is different on the network server you use, 18 18
if your LoRaWAN server supports class C, then you just have to find where in the 19 19
user interface you can change this parameter. 20 20
On the device side, it was a class A end device for the last demonstration. 21 21
So I just have to change class A to class C in the config file. 22 22
Then I compile and program my end device. 23 23
And now we're ready. 24 24
I can now power up my end device and the Join procedure starts. 25 25
Once again, 26 26
when the join procedure is completed, the device application waits for the user to 27 27
press the push button to send a temperature through the lower network. 28 28
However, at this point there is one last 29 29
requirement before using class C capabilities. 30 30
Because, we could think that if I send a 31 31
downlink from the network right now, it would arrive to the end device. 32 32
Actually, this is not true, at least not yet. 33 33
Because the specification says that the 34 34
device must validate its activation to the network server. 35 35
What does it mean? 36 36
It means that the network server wants to 37 37
be sure that the device has finished its activation and is running a valid session. 38 38
Doing that is very easy. 39 39
It only has to send one uplink and that's okay. 40 40
This activation validation is just a way to prevent the network server to send down 41 41
link data to a device for which the join procedure has failed. 42 42
Because in that case, all downlink would be useless. 43 43
The downlink transmission on a gateway is shared between all LoRaWAN device, so it's 44 44
very limited and there is no need to waste it with useless transmission. 45 45
So I launched an uplink with the push 46 46
button and I can check that everything has been transmitted to my application. 47 47
So now the network server knows that my device has a valid session. 48 48
Great. 49 49
Now I go back to the downlink messaging tool, messaging tab and downlink. 50 50
Let's choose again 51 51
Fport equal 20 and AA for the payload. 52 52
Then I hit the schedule downlink button. 53 53
As soon as I hit the button, then the 54 54
message goes all the way to my gateway and IoT is received on my end device. 55 55
And I didn't have to send any uplink frame for that. 56 56
I can also see that this packet has been received in the Class C time slot. 57 57
This time slot is actually the time between two uplinks where the radio has 58 58
been kept power up to receive data, so I can send as many downlinks as I want. 59 59
The only restriction you have is the 60 60
regional reglementation, for example the 1% duty-cycle on the 868 MHz band. 61 61
And there can also be some restriction 62 62
depending on the subscription you have with your network server operator. 63 63
For example, they can limit the number of 64 64
downlink, or they can charge you an extra fee for this.