In mid-2007, Kestrel Signal Processing, Inc., a small software radio consulting shop in northern California, started writing an implementation of a GSM basestation. The initial developers were Kestrel co-founder Harvind Samra and myself. Our goal was to create a new kind of light-weight cellular network that could be built out inexpensively in remote and sparsely populated areas. Our software-radio GSM system, now called OpenBTS, was released publicly under the GPLv3 license in September 2008 and will be used in pilot deployments with small operators by the time this article goes to publication.
This will probably be the first use of a free software basestation in a public cellular network, where both network operators and subscribers can download and read the full source code of the GSM protocol stack that connects their handsets to the rest of the world and where the operators will be free to modify the system to meet their specific needs. This article introduces the goals and evolution of the OpenBTS project.