Some good progress on support for VHF/UHF data using Codec 2 modems: http://www.rowetel.com/?p=7207
- David On 22/6/20 7:24 am, David Rowe wrote: > Hi Glen, > > Sounds like you are quite experienced and have had some fun times with > LDPC work in the past. Thanks for your offer but I think we are good > with LDPC in Codec 2. > > We currently have support for LDPC at the Octave simulation and C level > using the CML library with great support on from Bill, VK5DSP. It's all > running on the stm32 thanks to Don's fine work with the 700D port last year. > > Cheers, > David > > On 21/6/20 9:19 pm, glen english wrote: >> David, I have quite a bit of code in this area from modem stuff from >> years ago. >> >> Mostly based on David Mackay's work from memory. I can dig it all out. >> >> I generated : >> >> LDPC matrix generator, parametizable. >> >> C++ encoder, C encoder, encoders with precalculated LUTs that I used on >> STM32L0 at 16 MHz .. >> >> My decoder (soft) was all C/C++ for a processor with a bit of memory and >> speed, mildly optimized. >> >> But, depending on the code size, and rate rate, might work in a STM32. >> >> It was all teamed up with a chirp + D^2-BPSK hybrid modem with an >> optimized decoder ( and highly NEON optimized to run on an cortex A5 >> and keep up. >> >> all is in a linux environment. I can dig out the LDPC stuff if ya like. >> >> -glen >> >> >> >> On 13/06/2020 3:31 pm, Bill Cowley wrote: >>> Hi Jeroen, >>> >>> Further to David's reply, you might like to look at the AFF3CT >>> sitehttps://aff3ct.github.io/ which provides comprehensive info on >>> channel coding. David's codes have been Repeat Accumulate (RA) LDPC >>> codes - we used them initially as encoding is very easy (eg well >>> suited to a microController). Of course you probably don't need this >>> - so you might get slightly better performance with other options. I >>> haven't played with the AFF3CT software much, but it does cover RA. >>> >>> Cheers, Bill >>> >>> Cc: >>> Bcc: >>> Date: Thu, 11 Jun 2020 23:30:58 +0200 >>> Subject: [Freetel-codec2] Generating LDPC code for 6000 mode >>> Hi, >>> >>> The experiments with mode 6000 are going pretty well. >>> Another local HAM (PE1ITR) even managed to work our repeater with >>> just a >>> HackRF. >>> Compared to analog FM it seems to perform pretty well. >>> >>> But I would like to take it a bit further and try to introduce >>> some FEC. >>> Since the currently used codec2 mode only needs 3200bps there is >>> still >>> plenty of room. >>> I was thinking about a rate 2/3 code (687 code bits for 458 data >>> bits), >>> but I am a bit puzzled with the ldpc octave code. >>> How exactly do I generate the needed matrix (and ofcourse the C and >>> header files)? >>> >>> Regards, >>> Jeroen >>> >>> >>> >>> >>> >>> >>> ---------- Forwarded message ---------- >>> From: David Rowe <[email protected] <mailto:[email protected]>> >>> To: [email protected] >>> <mailto:[email protected]> >>> Cc: >>> Bcc: >>> Date: Fri, 12 Jun 2020 07:29:34 +0930 >>> Subject: Re: [Freetel-codec2] Generating LDPC code for 6000 mode >>> Hi Jeroen, >>> >>> Hey that's great work with working the new mode on a HackRF, is that >>> about 50mW max? >>> >>> Yes, FEC is a fine idea. >>> >>> A friend has been kind enough to generate the codes for me, >>> however it's >>> not a process that is automated or straight forward. Couple of >>> options: >>> >>> 1/ Use an existing code. >>> 2/ Use a code with more data bits than you require, and fill them >>> with >>> known bits at the encoder and decoder that you don't transmit. This >>> effectively lowers the code rate a little. I do that for FreeDV >>> 2020. >>> 3/ Peruse the CML library codes and see if they have one that fits >>> your >>> use case, e.g. ldpcut.m >>> >>> There is an Octave utility to generate .[ch] files and run the >>> codes in C. >>> >>> Cheers, >>> David >>> >>> On 12/6/20 7:00 am, Jeroen Vreeken wrote: >>> > Hi, >>> > >>> > The experiments with mode 6000 are going pretty well. >>> > Another local HAM (PE1ITR) even managed to work our repeater >>> with just a >>> > HackRF. >>> > Compared to analog FM it seems to perform pretty well. >>> > >>> > But I would like to take it a bit further and try to introduce >>> some FEC. >>> > Since the currently used codec2 mode only needs 3200bps there is >>> still >>> > plenty of room. >>> > I was thinking about a rate 2/3 code (687 code bits for 458 data >>> bits), >>> > but I am a bit puzzled with the ldpc octave code. >>> > How exactly do I generate the needed matrix (and ofcourse the C and >>> > header files)? >>> > >>> > Regards, >>> > Jeroen >>> > >>> > >>> > >>> > _______________________________________________ >>> > Freetel-codec2 mailing list >>> > [email protected] >>> <mailto:[email protected]> >>> > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >>> > >>> >>> >>> _______________________________________________ >>> Freetel-codec2 mailing list >>> [email protected] >>> <mailto:[email protected]> >>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >>> >>> >>> >>> _______________________________________________ >>> Freetel-codec2 mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> > > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
