Cellular Network Infrastructure » Radio Access Network » OsmoPCU

h1. osmo-pcu

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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

[[OsmoTRX]].

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.

h2. Manuals

* 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: osmocom-net-gprs@lists.osmocom.org

You can subscribe to it (or manage your subscription) at http://lists.osmocom.org/cgi-bin/mailman/listinfo/osmocom-net-gprs

h2. Status

Information about testing is available here: [[GPRS-testing]]

h3. Supported

* 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.