[[PageOutline]] = osmo-pcu = A PCU (Packet Control Unit) is one of the two GPRS elements in the BSS. It implements the RLC and MAC layers of the GPRS Um (radio) interface on the MS-facing side, as well as the Gb Interface (NS,BSSGP) on the SGSN-facing side. osmo-pcu is the Osmocom implementation of this PCU functionality. It implements a custom L1 interface that can be used with [wiki:OsmoBTS] (specifically its [http://www.sysmocom.de/products/sysmobts sysmoBTS] back-end), and also with [wiki:OsmoTRX]. Towards the SGSN, the BSSGP and NS protocols are implemented over UDP/IP, sometimes called "NS over IP". It has been tested with [wiki:osmo-sgsn] as well as an Ericsson SGSN so far. osmo-pcu is now considered considerd stable and already performing useful service for a number of users, but as one of the more recent additions to the Osmocom family, there still is plenty of area for improvement. == Source Code == The source code is available from git://git.osmocom.org/osmo-pcu.git You can browse it online via http://cgit.osmocom.org/cgit/osmo-pcu/ == Mailing List == There is a mailing list for (development) discussion regarding the PCU: email@example.com You can subscribe to it (or manage your subscription) at http://lists.osmocom.org/cgi-bin/mailman/listinfo/osmocom-net-gprs == Status == Information about testing is available here: [wiki:GPRS-testing] === Supported === * GPRS CS1 to CS4 with dynamic dynamik link/rate adaption * Single-slot single-slot and multi-slot operation on downlink * Single-slot single-slot operation on uplink * Independent TFI/USF per PDCH in single-slot allocation mode * Automatic or fixed PDCH allocation algorithm selection * Delayed release of downlink TBF * Active queue management for downlink TBF (!CoDel) * Initial setting of timing advance based on RACH * BSSGP BVC flow control support === Shortcomings / Limitations / Restrictions === * Pure GPRS PCU, no EGPRS (EDGE) functionality (yet) * Timeslots have to be assigned dedicated as a PDCH, no dynamic PDCH/TCH switching * No support for hand-over of any sort yet * No support of processing measurement reports * No timing advance loop, i.e. radial movement is limited maximum cell radius 2-3 km * No support for power control * No Packet Access Reject message on congestion, access is just ignored * No PCCCH support * Only "Dynamic allocation RLC data block transfer" is supported * No network controlled measurement/cell reselection order supported * No PTCCH support * No support for Packet Flow Contexts (PFC) * No support for MS or PFC flow control * No support for RLC unacknowledged mode operation * No support for MBMS == Authors / Credits == osmo-pcu was originally developed by Ivan Kluchnikov and Andreas Everberg. Today it is maintaned by Holger Freyther and Jacob Erlbeck at sysmocom.