Bug #2790

dynamic timeslots: failure when all TS are used as PDCH and the phone requests a TCH

Added by neels about 2 years ago. Updated over 1 year ago.

Target version:
Start date:
Due date:
% Done:


Spec Reference:


If a phone requests a TCH channel from OsmoBTS, but all dyn timeslots are used as PDCH, the MS gets rejected completely. OsmoBTS should probably assign an SDCCH if no TCH are available, so that the MSC can then request a TCH from the BSC and trigger a change from PDCH to TCH.

There is a "paging any use tch (0|1)", so there could be a similar policy decision to assign an SDCCH instead of a TCH ... ?

As long as this is not fixed, it may be impossible for MS to dial numbers.

Related issues

Related to OsmoBSC - Feature #1606: hand-over for load distribution among BTSsResolved02/23/2016


#1 Updated by laforge about 2 years ago

  • Assignee set to dexter

#2 Updated by laforge about 2 years ago

#3 Updated by neels about 2 years ago

Note that the handover code from jolly that I'm working on has changes in this direction, so it would make sense to talk about this before implementing, or also re-assign to me ... #1606

#4 Updated by neels about 2 years ago

  • Related to Feature #1606: hand-over for load distribution among BTSs added

#5 Updated by laforge almost 2 years ago

I'm not sure if this is an issue anymore, it needs to be investigated (and possibly get a test case?). With the current code base we should always do late assignment, even if the MS requests a TCH in RACH...

#6 Updated by dexter over 1 year ago

  • Status changed from New to Feedback
  • Assignee changed from dexter to neels

@Neels, can you give me some feedback on this. Is this still relevant?

#7 Updated by laforge over 1 year ago

  • Priority changed from Normal to High

neels ping? Would be godo to give dexter his requested feedback

#8 Updated by neels over 1 year ago

  • Status changed from Feedback to Rejected

ah yes, sorry for the delay.

Ok, so, quick recap to think about it:

- when MS requests a channel, even if it is TCH, OsmoBSC always assigns an SDCCH first as long as it is available.
- when no SDCCH are left, the upcoming refactored OsmoBSC will pick a TCH instead. The new timeslot and lchan FSMs will make sure that the dyn TS is switched from PDCH first, if required.

So, yeah, this should actually not be a problem anymore.

Also available in: Atom PDF

Add picture from clipboard (Maximum size: 48.8 MB)