In almost a year since its release, Raspberry Pi has been used for a variety of exotic projects. We have seen supercomputers housed in racks made of Lego, microservers for accounting software, conversions of old hardware into laptops. The clever device was shown to be running not just specific Linux distributions, but HTML5-based Firefox OS and Google’s Android too.
Now, it turns out the tiny computer can also successfully route voice and SMS traffic through a GSM network. PA hooked up the Raspberry Pi to a radio interface and,
using two pieces of open source software (OpenBTS and FreeSWITCH), made it perform the same functions as a 30-foot cellphone tower.
The wireless experts had to tweak the software by hand, as well as code-optimise the signal processing. Once this was done, the new network was capable of connecting mobile phones at labs. The consultancy tested the device in a special facility.
setting up our Raspberry Pi in a screened-room facility to ensure we didn’t break any laws on frequency spectrum
hooking up the Raspberry Pi to a radio interface
hand-optimising some of the software
code-optimising the signal processing – we are experts in this and needed to use all our skills to get parts of the code running fast enough.
The Raspberry Pi was used to set up three pieces of software:
OpenBTS – this implements the GSM mobile phone standard
FreeSWITCH – this routes calls in a similar way to Skype
Ruby OR Python features – a programming script that assigns telephone numbers to colleagues.