I’m new on this forum and I’m trying to set up LoRaWAN network. There are few topics which I don’t understand as it isn’t explained anywhere or it’s very badly explained.
I’m using EU863-870 standard and I see there are 8 channels in frequencies array:
[
868100000,
868300000,
868500000,
867100000,
867300000,
867500000,
867700000,
867900000,
]
There are also two other channels:
LoRa STD channel at frequency=868300000.
And
FSK channel. at frequency=868800000.
Can someone please explain questions below:
what is purpose of these two additional channels (STD and FSK)? What exactly do they do?
Are these 8 channels in array above fixed in EU region and can’t be changed?
which channels does remote node use? Is it randomly selected or is there any algorithm behind? How can remote node change channel or is it fixed after communication between node and gateway is established?
why is there bandwidth 250kHz in ChirpStack GW Bridge configuration if EU region is mostly using only 125kHz for most of the channels? Does it mean that 250kHz will be used for all channels? Is that allowed?
Is Adaptive Data Rate algorithm changing only spreading factor to improve signal?
Hello, Im very new to all this, and I cannot answer all your questions, they seem to be more related whit LoRaWAN protocol rather than chirpstack itself
ADR change DR, and changing DR change other values, like spread factor, potency requiered to send a signal, length of the message, this things has to do more whit the end device itself
This explains the “knobs” you’re asking about.
I found this helpful too; you’ll want to scroll down to “Frequencies” section.
Maybe this posting helps?
I’m in the US so haven’t had to understand it deeper
I’ve looked at links that you’ve posted but this is still unclear.
Firstly, If we discuss ADR: Understanding ADR | DEVELOPER PORTAL
According to this official documentation, ADR is changing only spreading factor. As I understand this, consequence of changing spreading factor is different data rate and transmission power of course.
If I’m honest I still don’t understand these questions on my first post:
what is purpose of these two additional channels (STD and FSK)? What exactly do they do?
Are these 8 channels in array above fixed in EU region and can’t be changed?
which channels does remote node use? Is it randomly selected or is there any algorithm behind? How can remote node change channel or is it fixed after communication between node and gateway is established?
why is there bandwidth 250kHz in ChirpStack GW Bridge configuration if EU region is mostly using only 125kHz for most of the channels? Does it mean that 250kHz will be used for all channels? Is that allowed?
The EU868 band defines 3 channels that a device must implement (which for OTAA devices are initially the only channels it knows about). In most cases you want to extend this to 8 channels by adding 5 additional frequencies (commonly 867.1, 867.3, .5, .7 and .9). These frequencies are signaled to the device as part of the join-accept message (in the CFList field).
You can not assign EVERY frequency you like because:
There are regulations with regards to the frequencies that you can freely use
These channels must be within the bandwidth supported by the gateway
The SX1301/1302/1303 chips support:
8 multi SF channels (LoRa)
1 single SF channel (LoRa)
1 FSK channel
Please also have a look at the LoRaWAN Regional Parameter specs. There you will find the data-rates that are available for the EU868 band.
So, the remote node/device then chooses one of these 8 frequencies or channels and is using it all the time? Or does device jump between frequencies on that CFList? I understand that gateway listens on all channels, but what about remote device when it transmitts? It probably uses only one channel at the time and it’s probably never changed during the session? Is there any algorithm behind? What about scenario, when all devices would choose same frequency or channel?
1. These channels must be within the bandwidth supported by the gateway → Is this related to bandwidth specified in ChirpStack GW Bridge configuration? On the configuration specified on this page, this is 250kHz: Configuration - ChirpStack open-source LoRaWAN<sup>®</sup> Network Server
Are all channels (signaled to the device as part of CFList) using 250kHz bandwidth?
The SX1301/1302/1303 chips support:
8 multi SF channels (LoRa) 1 single SF channel (LoRa) → is this LoRa STD channel? Is it ever used? Is it using SF7? 1 FSK channel → Is that channel using FSK modulation instead of LoRa modulation? What is the purpose of it and why is it used?
For uplink the device uses channel-hopping where possible. The downlink frequency is a function of the uplink frequency (please see the Regional Parameter specs for more details).
These channels must be within the bandwidth supported by the gateway → Is this related to bandwidth specified in ChirpStack GW Bridge configuration?
Usually a gateway has two radios + one SX1301/2/3 concentrator chip. Each radio will be set to a center frequency and the channels that are configured need to fit within the bandwidth that is provided by these radios.
