This OpenBTS socket interface was originally added to enable GPRS capabilitie with a forked version of OpenBTS, at a time when the public OpenBTS release didn't yet have any GPRS support. Meanwhile, the later OpenBTS releases included their own version of GPRS, without any external PCU/SGSN/GGSN, so this interface is no longer needed. This also means that the OsmoBTS socket interface is now the default at compilation time. There is no other interface.
This is an implementation of Packet Control Unit (PCU) according to TS 04.60 The PCU is part of BSS, so it connects directly to SGSN. == Current limitations == * No PFC support * No fixed allocation support * No extended dynamic allocation support * No unacknowledged mode operation * No PCCCH/PBCCH support * Only single slot assignment on uplink direction * No half-duplex class support (only semi-duplex) * No handover support * No measurement support * No TA loop * No power loop * No CS loop * No EGPRS