Osmocom Packet control Unit (PCU): Network-side GPRS (RLC/MAC); BTS- or BSC-colocated https://osmocom.org/projects/osmopcu
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Philipp Maier 469584f136 gprs_rlcmac_sched: fix condition for generating dummy blocks on idle
When a PDCH is idle, then the gaps are filled with dummy blocks. OsmoPCU
supports generating the dummy blocks locally, so that a continous stream of
PDCH blocks is sent to L1. However, some BTS models (the OsmoTRX based models
in particular) are able to generate the idle blocks locally. In this case the
PCU should leave the genration of the dummy blocks to the BTS in order to
save processing time and load on the PCUIF interface.

In gprs_rlcmac_sched we already have a flag to skip idle frames in case we do
not use the so called "direct phy access". A similar mechanism also exists in
pcu_l1_if.cpp in function pcu_rx_rts_req_ptcch().

Unfortunately this check is not implemented correctly. The flag gets set when
the ENABLE_DIRECT_PHY define constant is set. However, this does not say
anything about whether the BTS model supports the generation of idle blocks or
not. The define constant is intended to be used to disable direct phy related
code in on platforms where no direct phy code is used or cannot be used. We
must instead check the BTS model (bts->bts_model) in order to decide whether
this particular BTS type requires the generation of dummy blocks or not.

Related: OS#6191
Change-Id: I7a08d8cc670fa14f7206ffffdbc22351f3668a17
2023-11-24 14:18:51 +01:00
contrib Increase RR scheduler priority to 20, to avoid dropped bursts 2023-10-09 13:11:36 +02:00
debian Bump version: → 1.3.1 2023-09-15 11:33:49 +02:00
doc doc: Add details regarding BSC co-location 2023-03-24 20:01:53 +01:00
include pcu_l1_if: signal BTS model via PCUIF 2023-11-21 09:17:14 +00:00
src gprs_rlcmac_sched: fix condition for generating dummy blocks on idle 2023-11-24 14:18:51 +01:00
tests pcuif_proto: drop support for PCUIF v10 2023-10-23 11:46:13 +02:00
.gitignore Makefile.am: generate missing .version file 2022-08-07 19:31:47 +07:00
.gitreview add .gitreview 2016-05-19 06:39:45 +00:00
COPYING import GPLv2 license text to this project 2012-07-22 22:05:44 +02:00
Makefile.am Makefile.am: add 'git-version-gen' to EXTRA_DIST 2022-08-07 19:39:03 +07:00
README.md update git URLs (git -> https; gitea) 2022-06-18 12:31:20 +02:00
TODO TODO: remove those that have obviously been implemented 5+ years ago 2020-04-17 16:02:26 +00:00
TODO-RELEASE pdch_ul_controller: migrate from fn_cmp() to gsm0502_fncmp() 2023-09-26 20:33:37 +07:00
configure.ac Bump version: → 1.3.0 2023-09-12 16:00:30 +02:00
git-version-gen Add auto-foo (partial cleanup, master makefile/configure.ac 2012-06-14 21:05:44 +08:00
osmoappdesc.py Remove dash from name used in VTY cmd prompt 2019-12-02 11:14:26 +00:00


osmo-pcu - Osmocom Packet Control Unit

This repository contains a C/C++-language implementation of a GPRS Packet Control Unit, as specified by ETSI/3GPP. It is part of the Osmocom Open Source Mobile Communications project.

The Packet Control Unit is terminating the Layer 2 (RLC/MAC) of the GPRS radio interface and adapting it to the Gb Interface (BSSGP+NS Protocol) towards the SGSN.

The PCU interfaces with the physical layer of the radio interface. OsmoPCU is typically used co-located with the BTS, specifically OsmoBTS. For legacy BTSs that run proprietary sotware without an interface to OsmoPCU, you may also co-locate it with the BSC, specifically OsmoBSC


The official homepage of the project is https://osmocom.org/projects/osmopcu/wiki/OsmoPCU

GIT Repository

You can clone from the official osmo-pcu.git repository using

git clone https://gitea.osmocom.org/cellular-infrastructure/osmo-pcu

There is a web interface at https://gitea.osmocom.org/cellular-infrastructure/osmo-pcu


We provide a user manual as well as a vty reference manual

Please note that a lot of the PCU configuration actually happens inside the BSC, which passes this configuration via A-bis OML to the BTS, which then in turn passes it via the PCU socket into OsmoPCU.

Mailing List

Discussions related to osmo-pcu are happening on the osmocom-net-gprs@lists.osmocom.org mailing list, please see https://lists.osmocom.org/mailman/listinfo/osmocom-net-gprs for subscription options and the list archive.

Please observe the Osmocom Mailing List Rules when posting.


Our coding standards are described at https://osmocom.org/projects/cellular-infrastructure/wiki/Coding_standards

We us a gerrit based patch submission/review process for managing contributions. Please see https://osmocom.org/projects/cellular-infrastructure/wiki/Gerrit for more details

The current patch queue for osmo-pcu can be seen at https://gerrit.osmocom.org/#/q/project:osmo-pcu+status:open

Current limitations

  • No PFC support
  • No fixed allocation support (was removed from 3GPP Rel >= 5 anyway)
  • No extended dynamic allocation support
  • No unacknowledged mode operation
  • Only single slot assignment on uplink direction
  • No half-duplex class support (only semi-duplex)
  • No TA loop
  • No power loop
  • Multi-BTS support not tested