FEC in LoRa/LoRaWAN

End Devices (Nodes)
1

Hello,

I am curious to know what type of FEC is used in the LoRa phy or LoRaWAN MAC layer. Is it plain hamming codes?

Is there a way I can read about this instance when instantiating a LoRa class.?

2
3

Hello Thanks for sharing this. I had gone through this already. I was just wondering if it is possible to implement any other type of error control coding over lora.?

is this possible?

4

my guess is NO, that’s not possible.

5

if you could share with me your thoughts it will be helpful. I am just starting to explore lora.

6

I just did :sunglasses:

1 Like
7

FEC is part of LoRa at the hardware level.

I guess you could take a payload and add your own bespoke FEC coding, the FIFO will have the packet even if it has bit errors and fails CRC.

Going from 4:5 to 4:8 already increases time on air by 25%.

What the application ?

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8

Currently just testing the transmission of data packets from one lopy node to the other. Otherwise, in future we may implement it or our IOT systems.

9

But then one would also need to configure the gateways to forward such messages, despite the bad CRC. So I’d guess that adding an application-level error correction is not possible on the community network?

(Except for redundancy distributed over multiple uplinks, to mitigate uplinks that go missing altogether.)

10

Indeed, and that sounds impractical for TTN application, I would have thought. You would need to apply the ‘custom FEC’ tothe packet before the gateway could forward the packet.

11

I have done some link tests at the various FEC levels, and the signal gains are small compared to the increase in packet length, which is not a good idea.

If your intention is to implement an additional FEC layer for TTN, which is what this forum is about, its difficult to see that such a change would be agreed, there seems to be no benefit.

12

Hello,

Thanks for your thoughts. I was just keen in exploring other error control codes , say instead of FEC, if I would use Incremental Forward error correction how would that affect the data rates.

Just to clarify are you saying that any community level thoughts / modifications cannot be implemented with TTN? I am relatively new to TTN as well, and not sure how it works.

13

hello,

I tried to implement Reed solomon code on lora and it does not work that effectively compared to FEC using hamming code. Any suggestions as to what you had used?

14

I had checked the reception difference between the different FEC levels built into the LoRa device firmware, 4:5 to 4:8.

How are you intending to implement this changed FEC within TTN ?

15

I am afraid there is a provision to do so. Right now it is just over the physical layer of lora.

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