Improving OsmoSGSN and the PCU

Throughout the last quarters we have greatly improved the OsmoSGSN (which is part of the OpenBSC project). The software is more reliable, handles re-starts and error conditions more gracefully, e.g a long standing reliability issue with an unreachable PCU and segmented SNDCP messages leading to a crash has been fixed, LLC and status mismatches are handled more quickly.

On top of the reliability improvements we created a protocol that allows another process to handle authentication and access-control of subscribers. We have implemented this protocol and combined it with our SS7 stack. The outcome is that OsmoSGSN can be used in real GSM/EDGE networks.

The last missing piece is our Packet Control Unit (PCU). The software has been reliable in lab environments and we have started the work to make it production ready. Our initial focus has been on reliability and throughput for GSM and we made great progress. The PCU has a lot of freedom in terms of scheduling and has to make trade-offs between the battery life of a phone and throughput. Our initial focus is on improving throughput.

We will continue to work on the PCU this quarter and intend to begin work on EDGE support.