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OsmoPCU » History » Version 6

zecke2, 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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an unofficial version of OpenBTS that is being created by Fairwaves.
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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:OsmoSGSN] as well as an Ericsson SGSN so far.
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osmo-pcu is not fully stable yet, but already performing useful service for a number of users.
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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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The branch to be used with [wiki:OsmoBTS] and sysmoBTS is the 'jolly_merge' branch.
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== Mailing List ==
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There is a mailing list for (development) discussion regarding the PCU: osmocom-pcu@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-pcu
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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
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 * single-slot and multi-slot operation on downlink
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 * only single-slot operation on uplink
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=== Shortcomings / Limitations / Restrictions ===
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 * Pure GPRS PCU, no EGPRS (EDGE) functionality
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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. maximum cell radius 2-3 km
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 * No dynamic link adaption for different coding schemes
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 * No resource-dependent flow control
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 * Single slot allocator only allocates from the first available PDCH
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