LR-FHSS in Network server

Could anyone explain how LR-FHSS works in a Chirpstack server. What is the difference when it is enabled?
Is there anywhere to read more or does anyone have experience having tried it?

LR-FHSS is an alternative modulation to LoRa. Please note, both the device and gateway must be LR-FHSS capable. You need a v2 reference design gateway with FPGA and it must be configured (and updated) to support LR-FHSS.

Once ChirpStack receives a LR-FHSS modulated uplink, it will handle it for you. If you know that your devices and gateways support LR-FHSS you can decide to use a LR-FHSS ADR algorithm, either to select the best data-rate (which could be LoRa or LR-FHSS), or to force the device to always use LR-FHSS.

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Hi Orne,
Apologize for bringing back to life an old post.

Have you ever seen a Gateway that supports LR-FHSS?

Thank you for your support.

With best regards


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It seems LR-FHSS requires MCU from TI.
So far, I have not seen any commercial LR-FHSS gateways and nodes.

I am keen to know about them too.

For example, the Kerlink iBTS (which is a commercially available gateway) hardware supports LR-FHSS, but it requires additional software / firmware. But you are right that there aren’t many (if they exist at all) off-the-shelve end-devices that support LR-FHSS.

I did test LR-FHSS, but the software that I have been using is not publicly available. If you want to test LR-FHSS for your use-cases, the best would be to get in touch with Semtech.

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Hi @brocaar, I have the gateway and the firmware/software. But the LR-FHSS packets did not show up in Chirpstack Gateway live frames (Only legit LoRaWAN packets listed). Is it any addition setting I have to set/enable in the configuration? I am using lastest Chirpstack docker and leave everything to default (I am quite a newbie to Chirpstack). Could you help me on this? Thanks a lot!

Here are some additional information. I hope they could help for understanding the situation:

  • I am using EU868 frequency band
  • My end-device settings: freq=868000000, cr=2/3, bw=137kHz, grid=3.9kHz
  • Device profile is using MAC version 1.1.0, Regional parameters revision: RP002-1.0.3, ADR algorithm: LoRa & LR-FHSS ADR algorithm
  • The packet did show in the Gateway’s Packet Forwarder log
  • The Chirpstack log said: chirpstack::uplink: Deduplication error error=No channel found for frequency: 868000000, dr: 9.
  • I also tested with TTN community server. The packet did show up in the gateway live data but not in the application live data.
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This looks like a frequency issue, as in the default config that frequency is not used. Shouldn’t this be 868100000?

What the error means is that ChirpStack failed to map the frequency to a channel index (868.1 MHz -> 0, 868.3 -> 1, 868.5 -> 2, 867.1 -> 3, 867.3 -> 4, ....)

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Hi @brocaar, thank you so much for your responce! The Gateway supports LoRaWAN & LR-FHSS simultaneously. The uplink frequency you saw from my last post is default in Semtech configuration. I didn’t change anything.
FYI, I solved this by adding additional channels to my Chirpstack server. Just wonder why there is a difference between CR2/4 & CR2/6 of Chirpstack and CR1/2 & CR1/3 of others? They supposed to be the same, right?

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Yes, these are the same.

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Hi @brocaar, @cgt, We are currently setting up Chirpstack 4.7 to receive LoRaWAN messages via 4 Kerlink iBTS v2 for this balloon flight balloons/2024-04 · master · ThingSat / public · GitLab . We have the same problem. Could you provide us with the detailed configuration that you have implemented to solve this problem? Thank you

Hi @cgt and @brocaar we solved our issue thanks to the github of @cgt : Chirpstack-v4-LRFHSS-HTTPs/ at master · nguyenmanhthao996tn/Chirpstack-v4-LRFHSS-HTTPs · GitHub

Thank you !