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
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 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.
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: firstname.lastname@example.org
You can subscribe to it (or manage your subscription) at http://lists.osmocom.org/cgi-bin/mailman/listinfo/osmocom-net-gprs
Information about testing is available here: [wiki:GPRS-testing]
=== Supported === * GPRS CS1 to CS4 with dynamic link/rate adaption * Single-slot and multi-slot operation on downlink * 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 * 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
osmo-pcu was originally developed by Ivan Kluchnikov and Andreas Everberg.
Today it is maintaned by Holger Freyther and Jacob Erlbeck at sysmocom.