Class C - downlink

1

Dear,

I have node (Murata module) configured in C Class device. The uplnik works fine, but behavior of downlink is like for device in Class A. When I want to send a downlink message from TTN to end device, so no data are transmitted from GW to the node immediately. The transmitting is just scheduled and it waits for my node will send the uplink. Once is uplnik recieved the scheduled downlink is send to my node.

My expectation is that in the Class C the downlink could be sent any time, because the node is always listening.

What I did a wrong?

Thank you for support.

Jan.

2

in the upcoming stack V3 class C will be implemented

3

Thank you, I had no idea that class C is not implemented yet :slight_smile:

1 Like
4

here is the announcement

@arjanvanb made a rather interesting point regarding possible downlink limitations (RN2483 now supporting Class C: what does that mean for TTN?)

5

Dear,

I have node in Class C and Gateway
I disabled the ADR on my node.
When I set datarate DR5 - so uplnik work fine, but the downlink is not succesful.(even in one window).
When I set the DR3 - so uplink and downlink is succesful, but the downlink works only in RXwindow2. As you can see in the image - the GW does not transmitt at all in RXwindow1 - only in RXwindow2.
Sharp_traffic
Could you help me please where the problem is?

Thank you very much.

6

…Suppose that the the downlink data should be transmitted first in Rxwindow1 (independently on selected Class). Is not it?

7

I don’t know if they are downloadable online yet but you can ask for the specs here :

Email admin@mail.lora-alliance.org to request the latest LoRaWAN 1.1, LoRaWAN 1.1 Regional Parameters rev A, and LoRaWAN Backend Interfaces 1.0 Specifications.

8

From the specs:

The Class C end-device will listen with RX2 windows parameters as often as possible. The
end-device listens on RX2 when it is not either (a) sending or (b) receiving on RX1,
according to Class A definition. To do so, it will open a short window on RX2 parameters
between the end of the uplink transmission and the beginning of the RX1 reception window
and it will switch to RX2 reception parameters as soon as the RX1 reception window is
closed; the RX2 reception window will remain open until the end-device has to send another
message.

So my assumption is correct, is not it?

9

As I know in classC after transmitting and closing RX1 window, node will leave RX2 open on default RX2 frequency.
So when you send to Class C you always send at defined RX2 freq…