OsmoPCU » History » Revision 7
Revision 6 (Anonymous, 02/19/2016 10:48 PM) → Revision 7/33 (jolly, 02/19/2016 10:48 PM)
[[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 an unofficial version of OpenBTS that is being created by Fairwaves. Towards the SGSN, the BSSGP and NS protocols are implemented over UDP/IP, sometimes called "NS over IP". It has been tested with [wiki:OsmoSGSN] as well as an Ericsson SGSN so far. osmo-pcu is not fully stable yet, but already performing useful service for a number of users. == 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/ The branch to be used with [wiki:OsmoBTS] and sysmoBTS is the 'jolly_merge' branch. == Mailing List == There is a mailing list for (development) discussion regarding the PCU: osmocom-pcu@lists.osmocom.org. You can subscribe to it (or manage your subscription) at http://lists.osmocom.org/cgi-bin/mailman/listinfo/osmocom-pcu == Status == Information about testing is available here: [wiki:GPRS-testing] === Supported === * GPRS CS1 to CS4 * single-slot and multi-slot operation on downlink * only single-slot operation on uplink === Shortcomings / Limitations / Restrictions === * Pure GPRS PCU, no EGPRS (EDGE) functionality * 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. maximum cell radius 2-3 km * No dynamic link adaption for different coding schemes * No resource-dependent flow control * Single slot allocation algorithm allocator only allocates from the first available PDCH * Multi slot allocation algorithm - only allocates single uplink PDCH - limits allocation of type 1 mobile classes to 5 downlink PDCH - does not choose other uplink PDCH, if no USF is avaiable * No Packet Access Reject message on congestion, access is just ignored