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Bug #1950

LC15: BTS does not send L2 fill frame

Added by mqng2 over 4 years ago. Updated 7 months ago.

Status:
Resolved
Priority:
High
Assignee:
Category:
osmo-bts-litecell15
Target version:
-
Start date:
02/13/2017
Due date:
% Done:

0%

Spec Reference:

Description

We have noticed that the LC15 BTS does not send L2 fill frame in case there is nothing to transmit.
This leads to bad RXQUAL repored by MS during signaling in TCH channel. Please refer to GSM 05.08, section 8.3

"On any TCH this subset of TDMA frames is always used for transmission during DTX. For speech, when
no signalling or speech is to be transmitted these TDMA frames are occupied by the SID (Silence
Descriptor) speech frame, see TS GSM 06.12 and TSM GSM 06.31 for detailed specification of the SID
frame and its transmission requirements. In other cases when no information is required to be transmitted,
e.g. on data channels, the L2 fill frame (see GSM 04.06 section 5.4.2.3) shall be transmitted as a FACCH
in the TDMA frame subset always to be transmitted.

On the SDCCH and on the half rate speech traffic channel in signalling only mode DTX is not allowed. In
these cases and during signalling on the TCH when DTX is not used, the same L2 fill frame shall be
transmitted in case there is nothing else to transmit."


Related issues

Related to OsmoBTS - Bug #4801: BTS_Tests.TC_tch_sign_l2_fill_frame_dtxd failsStalled10/11/2020

Associated revisions

Revision 0ab50934 (diff)
Added by Stefan Sperling over 2 years ago

fix conditions for sending fill frames during RTS IND

Rewrite an if-statement to better match the description given
in GSM 05.08, and quote the relevant paragraph in a comment.
Since this entire block of code only runs for SDCCH and TCH,
this new condition should provide the same result expect that
in accordance with the standard we now stop sending fill-frames
on a signalling TCH if DTX is in use.

Also note that this code should already cover parts of the
patch proposed at https://gerrit.osmocom.org/c/osmo-bts/+/5753
The changes to osmo-bts-litecell15/l1_if.c proposed there
should be equivalent to the fill-frame logic in this
existing common BTS code which is handling RTS IND.

Change-Id: Ibaf3ecbd0bde4f37e799d5e2f5d00dc695e0139a
Related: OS#1950

Revision 9bffa87c (diff)
Added by Stefan Sperling over 2 years ago

send TCH/F fill frames in DTX mode (WIP)

Send DTX TCH fill frames according to GSM 05.08, section 8.3.

Change-Id: I7bff00b8cf41dc1b0e6e668173bebce23be0d253
Related: OS#1950

History

#1 Updated by laforge over 3 years ago

Hi Minh, what is the status of this bug report from almost one year ago? Can you please update us? Thanks!

#2 Updated by mqng2 over 3 years ago

laforge wrote:

Hi Minh, what is the status of this bug report from almost one year ago? Can you please update us? Thanks!

Hi Harald,

This bug was fixed in our public repository in the following commit

https://gitlab.com/nrw_noa/osmo-bts/commit/b32834b0e89ee987ff00e38041bd5683eea3cefd

I forgot to submit it to gerrit at that time. Do you want to submit it to gerrit?

#3 Updated by laforge over 3 years ago

Hi Minh,

On Mon, Jan 08, 2018 at 02:38:21PM +0000, mqng2 [REDMINE] wrote:

This bug was fixed in our public repository in the following commit

https://gitlab.com/nrw_noa/osmo-bts/commit/b32834b0e89ee987ff00e38041bd5683eea3cefd

I forgot to submit it to gerrit at that time. Do you want to submit it to gerrit?

It would be great if we could all work together, including Nutaq / Nuran making sure
that bug fixes are submitted to upstream osmocom. It is a collaborative software
development project, which only works if people actually collaborate :)

Thanks a lot, it is appreciated.

#4 Updated by mqng2 over 3 years ago

Hi Harald,

The patch has been submitted to gerrit https://gerrit.osmocom.org/#/c/5753

#5 Updated by laforge over 3 years ago

On Thu, Jan 11, 2018 at 02:51:44PM +0000, mqng2 [REDMINE] wrote:

The patch has been submitted to gerrit https://gerrit.osmocom.org/#/c/5753

Thanks!

#6 Updated by laforge over 3 years ago

  • Assignee set to stsp

#7 Updated by stsp about 3 years ago

  • Status changed from New to In Progress

Setting status to in-progress since this is being worked on.

It looks like this issue is currently waiting for an updated patch from Minh-Quang Nguyen at https://gerrit.osmocom.org/#/c/5753

#8 Updated by stsp about 3 years ago

Vadim Yanitskiy has updated Minh-Quang Nguyen's patch. The patch is now waiting for another round of review and testing.

#9 Updated by fixeria about 3 years ago

Vadim Yanitskiy has updated Minh-Quang Nguyen's patch.

Just had some spare time, and decided to move this work forward.
I am not familiar with this part of specifications, so only
cosmetic / code style changes were made.

#10 Updated by laforge about 3 years ago

stsp wrote:

It looks like this issue is currently waiting for an updated patch from Minh-Quang Nguyen at https://gerrit.osmocom.org/#/c/5753

the point of assigning the ticket to you was that no such update appears to be coming, and that you should take things into your hands, sorry for not being explicit about it.

Also, it feels wrong that this is done in the bts-model specific part. The knowledge whether or not any real information or a L2 fill frame is to be sent in a given timeslot/frame number is something that's the same for all BTSs.

It's probably best to first establish some kind of decision tree (on paper, ...) looking at all the different cases and how we should behave in those cases, followed by some tests using the trxcon-fake_trx-osmo-bts-trx chain.

#11 Updated by stsp about 3 years ago

In that case it's probably best if we sit down together and discuss this face to face.
I need to properly understand the goals you have in mind, and I need to learn which parts of the spec to study and learn whatever else I need to know to start working on this in earnest.

#12 Updated by stsp almost 3 years ago

I have started working on this after doing some related reading.

The following patch is related:
https://gerrit.osmocom.org/c/osmo-bts/+/10280

I will also be working on a bunch of new related tests for our BTS TTCN3 test suite.

#13 Updated by stsp almost 3 years ago

First two tests have been implemented: https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/10372

#14 Updated by stsp over 2 years ago

There are some related work-in-progress patches for this issue:

https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/10414
https://gerrit.osmocom.org/c/osmo-bts/+/10415

These changes are currently stalled because the foundations for testing DTX mode are missing from trxcon.
My DTX TTCN3 tests are currently unable to deal with frame numbers in a reliable way.
A hardware setup might serve as a workaround but AFAIK won't result in automated tests which can be run in our current jenkins setup.

#15 Updated by laforge almost 2 years ago

  • Status changed from In Progress to Stalled
  • Assignee changed from stsp to pespin

#16 Updated by mqng2 almost 2 years ago

I am currenlty out of office today. I will be back on Jul 22 2019.

#17 Updated by laforge 7 months ago

  • Status changed from Stalled to Resolved

#18 Updated by laforge 7 months ago

  • Related to Bug #4801: BTS_Tests.TC_tch_sign_l2_fill_frame_dtxd fails added

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