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Bug #3645

internal handover: when handover changes the speech codec, it should notify the MSC with BSSMAP Handover Performed

Added by neels 2 months ago. Updated about 14 hours ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
Handover
Target version:
-
Start date:
10/11/2018
Due date:
% Done:

100%

Spec Reference:

Description

See 3GPP TS 44.018 3.2.1.25 HANDOVER PERFORMED

and see handover_decision_2.c, which does want to change TCH/* kind on occasions.


Related issues

Related to OsmoBSC - Feature #1608: various handover improvements, meta-issueRejected2016-02-23

Related to OsmoBSC - Bug #3503: osmo-bsc: codec-list VTY cfg implementation not filtering correctlyIn Progress2018-08-27

Related to Cellular Network Infrastructure - Feature #3714: implement Internal Handover With MSC SupportNew2018-11-27

History

#1 Updated by neels 2 months ago

  • Related to Feature #1608: various handover improvements, meta-issue added

#2 Updated by neels 2 months ago

  • Related to Bug #3503: osmo-bsc: codec-list VTY cfg implementation not filtering correctly added

#3 Updated by neels about 2 months ago

  • Category set to Handover

#4 Updated by laforge about 2 months ago

  • Assignee set to dexter

#5 Updated by dexter about 1 month ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 20

I have done some changes to libosmocore and osmo-bsc now. In libosmocore basically only the generator function for the HANDOVER PERFORMED message is missing. In osmo-bsc tere is now a check which checks if we are doing an INTRA BSC HANDOVER, if yes, it will send the HANDOVER PERFORMED message.

Now I am working on the optional elements. I think the most desireable ones are CHOSEN CHANNEL, CHOSEN ENCRYPTION, SPEECH VERSION and SPEECH CODEC CHOSEN. These IEs appear also in the ASSIGNMENT COMPLETE message, so I can borrow from there. However the ASSIGNMENT COMPLETE message lacks the SPEECH VERSION and the CHOSEN ENCRYPTION field. I think we should add those two there as well just to be complete. The missing SPEECH VERSION in ASSIGNMENT COMPLETE also indeed a spec violation as we do choose the SPEECH VERSION when we chose a codec.

Also I noticed that the TTCN3 tests will need to be aware of the HANDOVER PERFORMED message, at least BSC_Tests.TC_ho_int now fails.

#6 Updated by neels about 1 month ago

dexter, open a separate issue for the Assignment Complete problems?

#7 Updated by dexter about 1 month ago

  • % Done changed from 20 to 40

I fixed the TTCN3 tests so that they check for the presence of the HANDOVER PERFORMED message. The template was missing, so I added one.

See also: https://gerrit.osmocom.org/11607

I did not push the full patch yet since it would break the internal handover test.

#8 Updated by dexter 28 days ago

  • % Done changed from 40 to 90

The BSC now sends HANDOVER PERFORMED message that contains all important information. While integrating this I saw that someone was kind enough to add the missing fields to the ASSIGNMENT COMPLETE message I mentioned above.

To generate the HANDOVER PERFORMED message I added a message generator function to libosmocore:
https://gerrit.osmocom.org/#/c/libosmocore/+/11728/

In osmo-bsc I now check if the handover is internal and if it is internal a HANDOVER PERFORMED message will be generated:
https://gerrit.osmocom.org/#/c/osmo-bsc/+/11734/

Since the TTCN3 tests do not expect a HANDOVER PERFORMED message the test TC_ho_int will fail, I have added a receive() at the end of the test now that checks if the HANDOVER PERFORMED message is present:
https://gerrit.osmocom.org/#/c/osmo-ttcn3-hacks/+/11732/
https://gerrit.osmocom.org/#/c/osmo-ttcn3-hacks/+/11732/
https://gerrit.osmocom.org/#/c/osmo-ttcn3-hacks/+/11733/

#9 Updated by dexter 21 days ago

The tests on the TTCN3 side are basically through the review. The last patch with the actual test is not merged yet since it depends on the changes in osmo-bsc.

The patches for osmo-bsc are not building in jenkins yet because the related libosmocore patch is not through the review yet.
See also: https://gerrit.osmocom.org/#/c/libosmocore/+/11728/

#10 Updated by dexter 14 days ago

I have fixed the review issues and I hope the API of the related libosmocore changes is now fine.

#11 Updated by neels 13 days ago

I have now encountered 3GPP TS 23.009 6.3.1 "General Description of Internal Handover with MSC Support",
which implies that if we want to change the codec, we should actually not only tell the MSC about it in the end, but involve it from the start.
See #3714

#12 Updated by neels 13 days ago

  • Related to Feature #3714: implement Internal Handover With MSC Support added

#13 Updated by laforge 13 days ago

On Tue, Nov 27, 2018 at 11:18:26PM +0000, neels [REDMINE] wrote:

I have now encountered 3GPP TS 23.009 6.3.1 "General Description of Internal Handover with MSC Support",
which implies that if we want to change the codec, we should actually not only tell the MSC about it in the end, but involve it from the start.
See #3714

Why are we even bothering with that? I would take the simple approach and just not do any hand-over
if the codec on the A interface would need to change. Let's not make our life more complicated
than needed without a strong requirement for a given feature.

#14 Updated by neels 12 days ago

the main reason why I'm thinking codec changes might be useful is that
handover_decision_2.c includes some logic that wants to move between TCH/F and TCH/H. (which we might want to disable)
So far only trying to write down how it would be done properly.

#15 Updated by dexter 10 days ago

I have worked through the review issues now. To me it looks good now. Regarding the codec changes, I would say we may consider to create another ticket for that as it is slightly out of scope of this one.

#16 Updated by dexter 7 days ago

The libosmocore patch is now in current master and the handover performed patch now builds. The osmo-bsc patch and the patch for TTCN3 is still in review:

https://gerrit.osmocom.org/#/c/osmo-bsc/+/11734/
https://gerrit.osmocom.org/#/c/osmo-ttcn3-hacks/+/11733/

#17 Updated by dexter about 14 hours ago

  • Status changed from In Progress to Resolved
  • % Done changed from 90 to 100

Now all patches made it into master. The TTCN3 test is also merged. I have jecked jenkins.osmocom.org, the tests look ok, so no problems here. I think the we can close this now.

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