Project

General

Profile

Actions

Feature #5927

open

use "Direct TLLI" method to confirm IMMEDIATE ASSIGNMENT messages towards PCU

Added by dexter 23 days ago. Updated 22 days ago.

Status:
New
Priority:
Normal
Assignee:
Category:
-
Target version:
-
Start date:
02/28/2023
Due date:
% Done:

0%

Spec Reference:

Description

To assign downlink TBFs, the PCU sends an IMMEDIATE ASSIGNMENT MAC block through the PCU SOCK interface to the BTS. The BTS confirms the sending of this IMMEDIATE ASSIGNMENT to the PCU by sending the MAC block back to the PCU. The MAC block essentially serves as a reference for the confirmation message. This method has some disadvantages so we decided to replace it.

The new method attaches a TLLI (and a paging group field) to the MAC block when it send to the BTS. The BTS then uses the TLLI instead of the MAC block as an identifier to confirm the sending of the IMMEDIATE ASSIGNMENT. The OsmoPCU already supports the method but OsmoBTS still have to be upgraded.

The related PCU/BTS TTCN3 tests also require an update.

Actions #1

Updated by fixeria 22 days ago

A patch for osmo-bts can be found here:

https://gerrit.osmocom.org/c/osmo-bts/+/31600 pcuif_proto: version 11: rework sending IMM ASS over PCH [WIP]

Some highlights (proposed changes):

  • Remove PCU_IF_MSG_DATA_CNF_DT, there is already PCU_IF_MSG_DATA_CNF which already contains the TLLI;
  • Remove PCU_IF_SAPI_AGCH_DT, DATA.req with PCU_IF_SAPI_PCH contains the TLLI now;
  • struct gsm_pcu_if_data_cnf: remove meaningless fields like lqual_cb and arfcn (why would they be present in CNF?!?);
  • struct gsm_pcu_if_data_cnf: add padding after sapi to facilitate aligned access;
  • struct gsm_pcu_if_pch_data: new structure, which is included in DATA.req with SAPI=PCU_IF_SAPI_PCH;
  • struct gsm_pcu_if_pch_data: this structure carries IMSI % 1000 (needed for paging group calculation);
Actions

Also available in: Atom PDF

Add picture from clipboard (Maximum size: 48.8 MB)