LimeSDR enables multi-carrier, multi-standard amateur radio base stations based on MMDVM and GNU Radio

[Adrian Musceac]

Using LimeSDR equipment (LimeNET-Micro / LimeSDR-mini) and MMDVM + GNU radio 
as core components, the implementation of a full duplex SDR base station was 
created in order to support the DMR, System Fusion, D-Star and M17 amateur 
digital voice standards in a multi-carrier configuration, with up to 7 
transmitted carriers within 200 kHz bandwidth, in any combination of operating 
modes and with a configurable channel separation. The channel / mode matrix is 
entirely user configurable by using multiple MMDVM instances, each of them 
dedicated to one operating channel.

The long term goal is to continue software development and combine LimeSDR 
equipment with the LimeRFE front-end and capable computing hardware to supply 
a self-contained, easily deployable base station in NITB style. The end-user 
should only need to supply their own antennas, power amplification and 
duplexing hardware for a complete SDR base station solution.

The current testing status has confirmed operation of the DMR and System Fusion 
standards, while D-Star and M17 modes are still theoretical and need to be 
tested. There is interest in further extended support for the new M17 open 
digital voice standard and investigating how a multi-carrier approach can 
provide amateur radio operators new avenues of experimentation with topics 
like trunking, multiple access, IP network facilities and other such topics. 
Work is in progress to improve code, refine user documentation and create 
deployable packages.

A video demonstrating the operation of a four-channel mixed DMR and System 
Fusion duplex repeater system can be seen here:
https://www.youtube.com/watch?v=kbQeckQ6M1g

All credit for the work supporting this project goes to Jonathan Naylor, Peter 
Rakesh and all the people who created or contributed to MMDVM and GNU Radio 
along the years.

Best regards,
Adrian YO8RZZ