Class A RX1 transmit frequency is wrong

My nodes is Class A using ICUBE-LRWAN 1.2.1 on US915 on Loraserver 3.0.1

I’ve noticed that Loraserver 3.0.1 instructs the gateway to transmit on 923300000 Hz practically all of the time. Downlinks never arrive at the end node. My test node is sending every 5 seconds and downlinks are being sent every 10 seconds. I have my minimum DR set to 0 and my max DR set to 3.

The node is looking for downlinks on RX1 at the appropriate frequency but Loraserver is telling the gateway to transmit at DR8 which is SF12 500 KHz at 923300000.

At first it seems that Loraserver is stuck at the frequency corresponding to RX2 yet the uplinks are coming in at the appropriate frequency which should trigger the correct RX1 window frequency. After over 40 downlinks at 923300000 the gateway starts to transmitting on different frequencies but many times there is a mismatch between what the node expects and what the gateway is sending.

Some times the downlinks come in on SF7 500 KHz and the downlinks work appropriately but a lot of time those don’t work either due to the incorrect frequency or something else.

I verified it by doing the calculation:
RX1 Channel Number = Transmit Channel Number *modulo 8*

My node is opening the window at the correct frequency but loraserver is looking elsewhere

Any comments on this? I’d like to file a bug if this is correct. From what I see it is.

Subscribe an MQTT client to the gateway/#/rx and gateway/#/tx and post a series of uplinks which are followed by what you believe to be erroneous downlinks, then human eyes can evaluate the mapping of uplink to downlink settings and see if its the server or node firmware which is out of spec.

Hey @cstratton,

I’ve monitored this for quite some time by doing just that and actually working out the calculation. I’m sending downlinks every 5 seconds on a Class A node. There is an led that lights when the downlink is received and it rarely ever turns on.

Below rx is the frequency from txInfo that the gateway received from gateway/+/event/up. tx is the transmit channel from txInfo at the topic gateway/+/command/down

rx: 904500000 tx: 923300000
rx: 904900000 tx: 923300000
rx: 904700000 tx: 923300000
rx: 903900000 tx: 923300000
rx: 903500000 tx: 923300000
rx: 902300000 tx: 923300000
rx: 904100000 tx: 923300000

My node always opens RX1 modulo 8 of the transmit channel number. So it’s listening for packets on the correct frequency but they’re not sent there or they are rarely sent on the correct frequency.

I’ve tested this with 4 different gateways, naturally the network server commands this behavior so it’s replicated on each of the gateways.

Your downlink transmit frequencies are indeed wrong, at least for RX1. They should increase 600 KHz for each 200 KHz increase in the uplink, same as you see the node attempting for reception.

Do you have the server configured for the correct bandplan? Are you sure these are RX1 downlinks? you should see that the timestamp value for the downlink is exactly 1000000 more than that for the uplink which triggered it for normal traffic, a few times that (check the spec) for join accepts.