An MSc student at EPFL Lausanne has developed a method of enabling Single Frequency Network (SFN) transmission using the free/open mmbTools DAB+ software-defined radio transmission set from the Communications Research Center Canada (CRC). Matthias Brändli, studying at EPFL's School of Computer and Communication Sciences, completed his thesis thanks to a collaboration between the EPFL Processor Architecture Laboratory (EPFL LAP), the EBU and CRC.


Professor Paolo Ienne and his research associate René Beuchat hosted and validated the project, supervising Matthias during his four months of work. François Lefebvre and Pascal Charest from CRC provided advice, testing and early access to the source code of an advanced version of the CRC-DABMOD modulator. This enabled him to include synchronization routines for SFN transmission in DAB mode I. The EBU provided support and expertise on digital radio and also provided some of the equipment for the project, such as the Ettus USRP software-defined radio peripherals.


Following this work, CRC has decided to release their most recent version of CRC-DABMOD as GPL source code to fully support all DAB modes. Matthias' work is currently offered as a patch for CRC mmbTools under the same licence. More tests are needed before his work can be fully integrated into the CRC tools. Specifically, a real field trial must be performed using GPS disciplined clocks instead of the simulated lab environment.


The shaded boxes show time information added to CRC- DABMUX and the UHD driver included in CRC-DABMOD. (source)


By making it possible to create SFNs using CRC mmbTools, this project has opened the way to a further democratization of digital radio transmission. It also enables new developments like small DAB microtransmitters to complete coverage holes in terrestrial digital radio networks. As the code is GPL licensed, it is open, usable and modifiable by anyone, under the condition that the source code stays open.

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