Dual Channel vs Single Channel?

Hi there,
I’m just getting into LoRaWAN and there’s one thing I don’t get. I set up a Things Stack and was able to setup a gateway on my RPi + LoRa Hat, which is connected to my Things Stack. Furthermore I was able to build a LoRa Node with an Uno and a LoRa shield that is able to send messages to the gateway, which is passing it to the application I want.

However now I’m trying to publish a message on the downlink using mosquitto_pub and the node’s device id.

root@raspberrypi:/opt/thingsstack#  mosquitto_pub -h localhost -p 1883 -u my-test- application -t "my-test-application/devices/my-test-device/down" -m '{"port":1, "payload_raw":"AQIDBA=="}' -P NNSXS.**** -d

Client mosqpub|22639-raspberry sending CONNECT
Client mosqpub|22639-raspberry received CONNACK (0)
Client mosqpub|22639-raspberry sending PUBLISH (d0, q0, r0, m1, ‘my-test-application/devices/my-test-device/down’, … (36 bytes))
Client mosqpub|22639-raspberry sending DISCONNECT

Inside my Things Stack I get a:

my-test-applicationunsubscribe application
my-test-applicationsubscribe application

but no “receive/forward downlink message”.

Currently I’m using a “single_chan_pkt_fwd” I found on Github as my gateway program and saw that there are also “dual_chan_pkt_fwd” ones. However when running the “dual_chan_pkt_fwd” it does connect to my ThingsStack but does not receive any uplink messages from my Node, as well not publishing downlink messages to my Node.

Now two questions came to mind, when reading through the stuff:

  1. Do I actually need a dual chan program? I mean as far as I can tell it only allows me to send on two frequencies, however I could just broadcast the downlink message on 868.1 as well, couldn’t I?
  2. Would I need two LoRa modules, one for each channel respectively or is it enough to have one module (The one on my shield) to use in the dual chan program? When running the dual chan program it tells me:
    Trying to detect module CE0 with NSS=6 DIO0=7 Reset=0 Led1=unused
    Transceiver version 0x00
    Trying to detect module CE1 with NSS=6 DIO0=7 Reset=0 Led1=unused
    Transceiver version 0x00
    Gateway ID: <gateway_id>
    Listening at SF7 on 868.100000 Mhz.
    Listening at SF7 on 868.300000 Mhz.

So it does seem that it is actually listening to both channels. Why then can I receive neither uplink messages from my node nor downlink messages from my mosquitto instance?

Neither! - recommend scrap your Single/dual channel packet forwarder implementation and go buy a TTIG or another u-Gateway - they are not expensive and are fully compliant with LoRaWAN spec and support the full 8 channels and ability to psuedo randomly choose a channel to avoid congestion and spread RF across more channels making them more socially acceptable. Also if established under TTN the use of a S/DCPF can disrupt network behaviour for other community members and users causing confusion, grief, lost time and lost money. S/DCPF’s were economic and often only option when gateways cost >$1k now they are <$150 (e.g. RAK or Dragino full GW, etc.) or even <$100 (TTIG or if you want a dev kit vs end product e.g. ST NUCLEO LRWAN2 Starter/Dev kit etc.) there is no excuse for not deploying compliant kit! :wink:

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Well, unfortunately that is not an option and I need to work with the hardware provided. :frowning:

Update: I can receive uplink messages on the “dual_chan_pkt_fwd” and the gateway also issues a response message uplink messages.

The other problem still persists. The mosquitto_pub messages do not seem to get picked up by the application and then forwarded to the gateway.

Since “the hardware provided” is not suitable, that puts you in a bit of a difficult position. There isn’t really much interest in supporting such things here, even to the limited degree that they are workable.

A radio network designed to work within the limitations of node-class radios would work rather differently from LoRaWAN, and more like, say, BLE which uses a bunch of frequencies but only one at a time, unlike LoRaWAN which has the availability of always-on 8-channel multi-SF receivers as a basic design assumption.