Downlink Spreading Factor Gateway Config

1

HI

I have a fully working setup with both uplink and downlink working fine. However I have a question I cant find the answer to.

What determines the Downlink (gateway to node) spreading factor/power and frequency?

I ask because both gateways I use allow me to set this (Dragino and Microchip Development Kit) as well as frequency. But I see in gateway profiles on the application server that I can set desired channel and SF so I wonder how this comes in to play as it appears to have no effect. Messages are all sent depending on how I configure the physical gateway as opposed to whatever config I have in chirpstack.

Thanks

2

Gateway-Profiles only really take into effect if you are using concentratord (tested) and i dont remember if basic station also takes this into account.
The config get’s pushed to the gateway and applied. Even if you do not use concentratord, I would recommend that your gw-profile matches what you defined at the gateway. It can affect the “advertised” frequencies and proper scheduling of downlinks.

3

Hi
Yeah thats what I was thinking.

One thing that is confusing me is I have changed the spreading factor to 9 on the gateway but it is still showing SF12 in the downlink gateway message in the application manager

chirp
chirp1911Ă—973 93.3 KB

4

Hi,
you really don’t need to use gateway-profiles unless you have concentratord on the gateway or if you want to adjust gateway stats interval so that you can see active/inactive gateway conut on dashboard properly.
And in latter case you do not even need to fill correct channel seting anyways (tested).

Settings you looking for are part of network-server config: https://www.chirpstack.io/network-server/install/config/ and depends on your regional parameters too.

Most inportant part of config regarding downlink settings would be[network_server.network_settings]

1 Like
5

The downlink spreading-factor and frequency is based on the uplink sent by the device. For EU868 uplink freq. = downlink freq. By default the DR is equal, unless you have configured the rx1_offset config option. For US915 the downlink channels = uplink channel (not freq.) % 8. All this information, including how the uplink DR maps to the downlink DR can be found in the LoRaWAN Regional Parameter specs.

6

Hi, I’m on v3 in EU868 and started to see an issue when node changes temporarily SF7->S12 due to App Clock Sync that disables ADR. Network Server however still schedules Downlink with SF7, and as an effect, it is not recognized by the node in its RX windows. Both node and application profiles are RP002-1.0.3. Running basicstation on GW and GW-bridge. no rx_offset is configured in the network server toml.

Would I be missing something obvious here?

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image1438Ă—1278 108 KB