34th Chaos Communication Congress

»Running GSM mobile phone on SDR«
2017-12-29, 20:00–20:30, Saal Clarke

Since SDR (Software Defined Radio) becomes more popular and more available for everyone, there is a lot of projects based on this technology. Looking from the mobile telecommunications side, at the moment it's possible to run your own GSM or UMTS network using a transmit capable SDR device and free software like OsmoBTS or OpenBTS. There is also the srsLTE project, which provides open source implementation of LTE base station (eNodeB) and moreover the client side stack (srsUE) for SDR. Our talk is about the R&D process of porting the existing GSM mobile side stack (OsmocomBB) to the SDR based hardware, and about the results we have achieved.

There is a great open source mobile side GSM protocol stack implementation - OsmocomBB project. One could be used for different purposes, including education and research. The problem is that the SDR platforms were out of the hardware the project could work on. The primary supported hardware for now are old Calypso based phones (mostly Motorola C1XX).

Despite they are designed to act as mobile phone, there are still some limitations, such as the usage of proprietary firmware for DSP (Digital Signal Processor), which is being managed by the OsmocomBB software, and lack of GPRS support. Moreover, these phones are not manufactured anymore, so it's not so easy to find them nowadays.

Taking the known problems and limitations into account, and having a strong desire to give everyone the new possibilities for research and education in the telecommunications scope, we decided to write a 'bridge' between OsmocomBB and SDR. Using GNU Radio, a well known environment for signal processing, we have managed to get some interesting results, which we would like to share with community on the upcoming CCC.