The Low Cost GSM Network is Here

This post takes a look at custom hardware that can be used with open source GSM network software to enable the creation of extremely low cost mobile network infrastructure.

In October it will be two years since I wrote about the opening up of GSM via open source implementations of key technology, development of which has continued since then with many new features being added to software and a growing number of real world installations. In addition to which there are now three custom hardware platforms that support the software.

Open source

In that post from 2010 I mention in brief two open source infrastructure projects,OpenBTS and OpenBSC. The former implements a GSM base station or “BTS” transceiver as a software-defined radio (SDR), along with all the other functionality required that when combined with the Asterisk IP telephony switch enables GSM handsets to be turned into SIP (Voice-over-IP) endpoints.

The OpenBSC project is equally as impressive and provides software that can be used as a traditional GSM switching centre (BSC) and integrated into an existing mobile network, or alternatively can be combined with BTS hardware and configured as a “GSM network in a box”.

The above is something of a simplification and does not do justice to the projects, and for further details see their websites or an introductory article that I wrote for The H.

Early hardware support

Initial hardware support for OpenBTS was provided via the Universal Software Radio Peripheral (USRP), a modular and highly flexible companion to the open source SDR platform, GNU Radio.

OpenBSC started life as a GSM infrastructure research project and has since developed into something that is finding use in commercial networks. Most development work to date has made use of surplus BTS hardware, and this was really the only option available to greenfield network deployments which, not surprisingly, has proved problematic.

Custom hardware

The first purpose built hardware for OpenBTS came from the project sponsors,Range Networks, who provide turnkey development hardware which at the time of writing is priced at $4,995. With more substantial hardware options that are aimed at commercial deployments and that are P.O.A.

Prototype UmTRX hardware (UmTRX Project, CC BY-SA 3.0)

A Russian company called Fairwaves have been working on an open source hardware platform for OpenBTS that is called UmTRX. With the schematics and BoM published under a Creative Commons licence and FPGA firmware and driver code published under the GPL. Pricing for the UmTRX has not been announced as yet, but given that it's described as being “budget-friendly” and USRP and Range Networks options for OpenBTS already exist, it's likely that this is going to be competitive.

The sysmoBTS (© systems for mobile communication Gmbh) 

In realising that the ongoing success of OpenBSC in commercial deployments depended upon securing the availability of affordable BTS hardware, German company sysmocom developed the sysmoBTS product. While this is not open source hardware, the BTS firmware is at the very least in part open source, and it's also possible to run OpenBSC on the same hardware in order to create a single box turnkey solution. Pricing for the sysmoBTS is available on application, but some have suggested the single unit price to be circa 2,000-2,500 Euro.

Conclusion

It's still reasonably early days but OpenBTS and OpenBSC seem to be following the typical open source technology adoption curve, where initial use is primarily in research, by enthusiasts and communities with limited budgets, and by a small but growing number of forward thinking companies that are keen to shrink their operating cost base.

The emergence of custom hardware will lend support to the development of OpenBTS and OpenBSC whilst also enabling more widespread adoption, and is almost certainly a sign of things to come. For most of its life GSM technology has been off-limits to open innovation, but this is rapidly changing and it may just be that the projects covered here have sown the seeds for the disruption of the mobile network equipment provider industry.