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<a href="https://outernet.is">Outernet</a> is a company whose goal is to ease worldwide access to internet contents by broadcasting files through geostationary satellites. Currently, they broadcast an L-band signal from 3 Inmarsat satellites, giving them almost worldwide coverage. The bitrate of the signal is 2kbps (or 20MB of content per day), and they use the signal to broadcast Wikipedia pages, weather information and other information of public interest.
Most of the software used for Outernet is open source, but the key parts of their receiver are closed source and the protocols and specifications of the signal used are secret. I think this is contrary to the goal of providing free worldwide access to internet contents. Therefore, I have worked to reverse engineer the protocols and build an open source receiver. I have been able to <a href="http://destevez.net/tag/outernet/">reverse engineer</a> most of the protocols, and a functional <a href="https://github.com/daniestevez/free-outernet">open source</a> receiver is now available.
In this talk, I'll explain which modulation, coding and framing is used for the Outernet L-band signal, what are the ad-hoc network and transport layer used, how the file broadcasting system works, and some of the tools and techniques I have used to do reverse engineering.