ADS-B reed-solomon ?

Oliver Jowett oliver.jowett at gmail.com
Sat Jul 20 10:08:06 UTC 2019


On Fri, 19 Jul 2019 at 15:58, Brad Walker <bwalker at musings.com> wrote:

> I've been studying the rtl_adsb.c code and it's very interesting how it
> works..
>
> But, I have question.
>
> I noticed that if I request verbose output using the "-V" option, then the
> CRC is printed out. But, it doesn't look like the code actually does any
> Reed-Soloman error correction to the data  the ADS-B specification
> documents.
>

1090MHz (Mode S extended squitter) ADS-B does not use R-S error correction,
it's just a 24-bit CRC (or an xor of that with the aircraft address for
some message types). Maybe you are thinking of 978Mhz (UAT) ADS-B, which is
not handled by rtl_adsb at all?

There is some error correction that's possible even with just the CRC but
it's not particularly reliable.

Oliver
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