Open Source DMR Modem Implementation in SDR with GNU Radio and Codec2

by threeme3on 4/19/2025, 12:23:50 PM with 4 comments
  • by fsiefkenon 4/19/2025, 3:11:50 PM

    I wonder if Codec2 could be replaced by one of the low bitrate neural audio codecs, HILcodec and SementiCodec sound better at 2-3 kbps.

    https://arxiv.org/pdf/2405.04752

    https://arxiv.org/pdf/2409.14085

  • by glzone1on 4/19/2025, 5:42:26 PM

    I really wish we could find some "HD" voice codec / mode - all the SIP protocols have gone pretty HD / zoom etc are HD at this point, a lot of cell has gone HD.

    Are the bands really so crowded (think on 70cm?) that we can't afford the bandwidth for something a bit more HD?

  • by teleforceon 4/20/2025, 3:42:03 AM

    There's an excellent guide to DMR technology by Andrew Barron (ZL3DW) and brief overview by Motorola Solutions, one of the major suppliers of commercial DMR [1],[2].

    [1] Work the world with DMR: Digital Mobile Radio (2022):

    https://www.hamradio.com/detail.cfm?pid=H0-019172

    [2] WHAT IS DMR?

    https://www.motorolasolutions.com/en_xp/solutions/what-is-dm...

  • by lpribison 4/19/2025, 1:50:25 PM

    I see this is only tier 2 for now (conventional channels) and not tier 3/trunked yet.

    Are trunked networks ever used in amateur radio or outside of big commercial/government systems? Is there a standardized way to feed back channel info to the SDR frontend for trunked operation in GNU Radio? Eg. The control channel will tell the terminal to tune to traffic channel at X Mhz to receive or send a call, which requires reconfiguring the frontend.