Open Source DMR Modem Implementation with GNU Radio and Codec2

This article details an open-source Digital Mobile Radio (DMR) modem implementation using Software Defined Radio (SDR), GNU Radio, and Codec2. This proof-of-concept modem, capable of voice calls, uses GNU Radio for the physical layer, MMDVMHost for the data link and partial call control layers, and Codec2 as the vocoder. Future development aims to incorporate more DMR standard features, including data messaging, Tier III functionality, and IPv4 transport. Tested with a LimeSDR-mini, the project faces challenges such as latency and precise TDMA timing.