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
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
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
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.
Discussions related to osmo-pcu are happening on the firstname.lastname@example.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
- 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