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MMDVM operation mode

Digital voice modes base station

QRadioLink can act as a SDR base station transceiver for DMR, System Fusion, D-Star or M17 by connecting to MMDVM-SDR, a fork of MMDVM which runs on Linux operating systems. MMDVM-SDR is slightly different from the original MMDVM software and is tested and developed at https://github.com/qradiolink/MMDVM-SDR on the mmdvm_sdr branch. A fork of MMDVMHost is also necessary, which is maintained at https://github.com/qradiolink/MMDVMHost-SDR on the mmdmv_sdr branch.

This operation mode requires a hardware device with support for FPGA timestamps. Currently the LimeSDR family and the Ettus USRP are supported for the MMDVM base station mode.

DMR tier III trunked radio base station mode

QRadioLink can also act as a DMR tier III trunked radio base station using MMDVM-SDR, MMDVMHost-SDR, DMRGateway and dmrtc (https://codeberg.org/qradiolink/dmrtc). This mode requires using the trunking branch from MMDVM-SDR, MMDVMHost-SDR and DMRGateway, and the master branch of dmrtc.

Single and multi-carrier operation

QRadioLink can work either as a normal single carrier transceiver or as a multi-channel / multi-carrier transceiver. So far only DMR, System Fusion and M17 have been tested and confirmed to work, but D-Star and other digital modes supported by MMDVM should work as well.

Multi-carrier transmission

Multi-carrier and single carrier MMDVM modes are only supported with LimeSDR and Ettus USRP devices so far due to the need for device timestamps used in TDMA mode. The LimeNet-Micro, the LimeSDR-mini and the USRP B20X were tested and confirmed to function in this mode. Other UHD based devices (AntSDR?) may also work but were not tested.

Note that you can mix any types of MMDVM digital transmissions on top of the QRadioLink multi-carrier system. Even DMR tier III trunked radio can be mixed with other channels like M17 or YSF. The only limitation is that carrier number 0 in QRadioLink (the baseband carrier) needs to be allocated to a DMR channel.

Support for other devices like BladeRF may be added in the future. If you have such hardware and are interested in getting it working, please create a pull request based on the next branch.

Due to performance issues, MMDVM multi-carrier operation mode is limited on ARM Linux platforms like Raspberry Pi. The maximum number of RF carriers on a Raspberry Pi 4 platform should be equal or less than four. At the moment it is recommended to run MMDVM modes on x86_64 platforms with at least 4 cores if more than four carriers are needed.