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OsmoPCU » History » Version 15

Anonymous, 02/19/2016 10:48 PM

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[[PageOutline]]
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= 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
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Um (radio) interface on the MS-facing side, as well as the Gb Interface (NS,BSSGP) on the SGSN-facing side.
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osmo-pcu is the Osmocom implementation of this PCU functionality.
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It implements a custom L1 interface that can be used with [wiki:OsmoBTS] (specifically its
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[http://www.sysmocom.de/products/sysmobts sysmoBTS] back-end), and also with
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[wiki:OsmoTRX].
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Towards the SGSN, the BSSGP and NS protocols are implemented over UDP/IP, sometimes called "NS over IP". 
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It has been tested with [wiki:osmo-sgsn] as well as an Ericsson SGSN so far.
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osmo-pcu is now considered stable and already performing useful service for a number of users, but as one
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of the more recent additions to the Osmocom family, there still is plenty of area for improvement.
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== Source Code ==
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The source code is available from git://git.osmocom.org/osmo-pcu.git
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You can browse it online via http://cgit.osmocom.org/cgit/osmo-pcu/
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== Mailing List ==
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There is a mailing list for (development) discussion regarding the PCU: osmocom-net-gprs@lists.osmocom.org
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You can subscribe to it (or manage your subscription) at http://lists.osmocom.org/cgi-bin/mailman/listinfo/osmocom-net-gprs
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== Status ==
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Information about testing is available here: [wiki:GPRS-testing]
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=== Supported ===
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 * GPRS CS1 to CS4 with dynamic link/rate adaption
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* EDGE MCS1-MCS9 with dynamic link/rate adaption
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 * Single-slot and multi-slot operation on downlink
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 * Single-slot operation on uplink
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 * Independent TFI/USF per PDCH in single-slot allocation mode
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 * Automatic or fixed PDCH allocation algorithm selection
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 * Delayed release of downlink TBF
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 * Active queue management for downlink TBF (!CoDel)
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 * Initial setting of timing advance based on RACH
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 * BSSGP BVC flow control support
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=== Shortcomings / Limitations / Restrictions ===
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 * No GPRS/EGPRS mixed mode (yet)
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 * Timeslots have to be assigned dedicated as a PDCH, no dynamic PDCH/TCH switching
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 * No support for hand-over of any sort yet
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 * No support of processing measurement reports
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 * No timing advance loop, i.e. radial movement is limited
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 * No support for power control
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 * No Packet Access Reject message on congestion, access is just ignored
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 * No PCCCH support
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 * Only "Dynamic allocation RLC data block transfer" is supported
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 * No network controlled measurement/cell reselection order supported
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 * No PTCCH support
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 * No support for Packet Flow Contexts (PFC)
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 * No support for MS or PFC flow control
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 * No support for RLC unacknowledged mode operation
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 * No support for MBMS
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== Authors / Credits ==
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osmo-pcu was originally developed by Ivan Kluchnikov and Andreas Everberg.
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Today it is maintaned by Jacob Erlbeck at sysmocom.
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