laforge, 03/06/2016 05:22 AM
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 [[OsmoBTS]] (specifically its
"sysmoBTS":http://www.sysmocom.de/products/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 [[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.
* User Manual: http://ftp.osmocom.org/docs/latest/osmopcu-usermanual.pdf
* VTY Reference: http://ftp.osmocom.org/docs/latest/osmopcu-vty-reference.pdf
h2. 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/
h2. 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: [[GPRS-testing]]
* GPRS CS1 to CS4 with dynamic link/rate adaption
* EDGE MCS1-MCS9 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
h3. Shortcomings / Limitations / Restrictions
* No GPRS/EGPRS mixed mode (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
h2. Authors / Credits
osmo-pcu was originally developed by Ivan Kluchnikov and Andreas Everberg.
Today it is maintaned by Jacob Erlbeck at sysmocom.