Simple GSM base station based on universal software radio peripheral

GNU Radio is a free and open-source software development toolkit that provides signal processing blocks to implement software radios. Through its operation and signal processing module, an ordinary PC can implement modern communication process, codec, time and frequency synchronization process in a flexible manner. Because of the high cost of traditional base station, people in low-populated and low-income rural areas cannot have access to the service of mobile communication system. Fortunately, SDR enables the quick and low-cost deployment of a simple GSM basestaion (BS) that provides short messages and voice communications. In this paper, we choose USRP1 as the hardware platform and realize the Um interface between mobile station and base-station of a GSM system by using OpenBTS, GNU Radio and Asterisk. More specifically, we build up a simple GSM base station that can provide automatic user-registration, short message and voice communication service for mobile users. We will introduce the system architecture of our USRP-based GSM base station, present the details of the implementation procedure for the construction. Furthermore, we perform extensive tests on the performance of the built GSM BS in the practical network environment, including the mean time between failure under empty-load and loaded scenario, the mean last time of a voice call, and so on. Test results show that the mean time between failure of our GSM station is 62.5 minutes and 42.5 minutes under empty-load and loaded scenario, respectively.