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Feature #3906

Automatically adjust LAPDm timer values with 'fn-advance' parameter

Added by fixeria 7 months ago. Updated 4 months ago.

Status:
Resolved
Priority:
High
Assignee:
Category:
osmo-bts-trx
Target version:
-
Start date:
04/06/2019
Due date:
% Done:

100%

Spec Reference:

Description

Currently we use fn-advance=20 by default, so the burst scheduler is working 20 TDMA frames in advance. This advance gives the transceiver some time to receive a burst, process it (i.e. modulate), and send to the Tx buffer of SDR. As a side effect, this increases the delay between UL and DL: 20 TDMA frames => 92.3ms of delay.

Higher fn-advance values cause a longer delay, resulting in LAPDm frame retransmissions.
OsmoBTS should automatically adjust LAPDm timer values with the configured 'fn-advance' value.


Related issues

Related to OsmoBTS - Bug #3506: FACCH LAPDm sequence error (state LAPD_STATE_MF_EST)Feedback08/28/2018

Related to OsmoBTS - Bug #2294: T200 values set by OML (TS 12.21) are ignoredResolved05/27/2017

Related to OsmoBTS - Bug #4037: LAPDm N200 values are incorrectResolved06/02/2019

History

#1 Updated by fixeria 7 months ago

  • Related to Bug #3506: FACCH LAPDm sequence error (state LAPD_STATE_MF_EST) added

#2 Updated by laforge 5 months ago

  • Related to Bug #2294: T200 values set by OML (TS 12.21) are ignored added

#3 Updated by laforge 5 months ago

  • Assignee set to laforge
  • Priority changed from Normal to High

#4 Updated by laforge 5 months ago

  • Related to Bug #4037: LAPDm N200 values are incorrect added

#5 Updated by laforge 5 months ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 80

See https://gerrit.osmocom.org/c/osmo-bts/+/14337 for a proposed implementation.

#6 Updated by laforge 4 months ago

  • Status changed from In Progress to Resolved
  • % Done changed from 80 to 100

patch merged__

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