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Bug #4823

closed

osmo-bts-trx sends dummy bursts (instead of BFI) in the absence of RTP frames

Added by fixeria over 3 years ago. Updated 7 months ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
osmo-bts-trx
Target version:
-
Start date:
10/21/2020
Due date:
% Done:

100%

Spec Reference:

Description

While working on TC_meas_res_speech_{tchf,tchh,tchh_toa256} as a part of #4799, I noticed that osmo-bts-trx logs the following:

DL1P INFO sched_lchan_tchf.c:539 001477/01/21/49/41 (bts=0,trx=0,ts=1) TCH/F: No TCH or FACCH prim for transmit.
DL1P INFO sched_lchan_tchf.c:539 001482/01/00/03/46 (bts=0,trx=0,ts=1) TCH/F: No TCH or FACCH prim for transmit.
DL1P INFO sched_lchan_tchf.c:539 001486/01/04/07/50 (bts=0,trx=0,ts=1) TCH/F: No TCH or FACCH prim for transmit.
DL1P INFO sched_lchan_tchf.c:539 001490/01/08/11/02 (bts=0,trx=0,ts=1) TCH/F: No TCH or FACCH prim for transmit.

and transmits dummy bursts on active TCH channels. This of course causes decoding errors on the MS side (trxcon):

20201019024408686 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1788 for TCH/F
20201019024408704 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1792 for TCH/F
20201019024408727 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1797 for TCH/F
20201019024408746 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1801 for TCH/F
20201019024408764 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1805 for TCH/F
20201019024408787 DSCHD ERROR sched_lchan_tchf.c:127 Received bad TCH frame ending at fn=1810 for TCH/F

I would expect the BTS to send Bad Frame Indications instead. Imagine a situation when for some reason one or more MT RTP frames get lost during a voice call. On the MS side this would look like an RF failure.


Related issues

Related to OsmoBTS - Bug #6049: TRX version transmits dummy FACCH instead of proper downlink BFIsResolvedjolly05/31/2023

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