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
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