M17 Project Forum

Please take a look at my new ECC proposal

https://m17project.org/files/download.ph...XkBVBQmP6u

(12-03-2019, 11:18 AM)KE0WVA link Wrote:I would suggest either some sort of trellis code on the FSK signal, or a rate 1/2 LDPC over the entire frame.

A trellis code would give continuous correction over a bit stream.  I am not sure that an LDPC code is going to be a good choice for digital voice -- LDPC codes work best on large blocks (like thousands of bits), which would introduce a lot of latency. And of course a decode failure would then create a large drop-out.  LDPC might be good for a data channel that also incorporates some kind of ARQ, though. 

Another poster mentioned Golay codes -- I need to refresh myself on what those are -- memory fade :/

I have encoded the Link Information Channel (LICH) with 24,12 Golay (since its partitioned into 48-bit chunks). The rest is going to be convolutionally coded with constraint K=5 and punctured (exactly like in NXDN, but with a different puncturing matrix).

Check this thread for details (post #1):
https://m17project.org/forum/index.php?t....msg6#msg6