OsmoPCU » History » Revision 16

Revision 15 (Anonymous, 02/19/2016 10:48 PM) → Revision 16/32 (Anonymous, 02/19/2016 10:48 PM)


 h1. [[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 [[OsmoBTS]] [wiki:OsmoBTS] (specifically its 
 "sysmoBTS": [ sysmoBTS] back-end), and also with 
 [[OsmoTRX]]. [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 [[osmo-sgsn]] [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. 


 == Source Code 


 The source code is available from git:// 

 You can browse it online via 


 == Mailing List 


 There is a mailing list for (development) discussion regarding the PCU: 
 You can subscribe to it (or manage your subscription) at 


 == Status 

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

 h3. [wiki:GPRS-testing] 

 === 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 


 === 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 


 == Authors / Credits 


 osmo-pcu was originally developed by Ivan Kluchnikov and Andreas Everberg. 

 Today it is maintaned by Jacob Erlbeck at sysmocom.
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