Cellular Network Infrastructure » Radio Access Network » OsmoBSC

On Fri, Oct 01, 2021 at 03:31:55AM +0000, redmine@lists.osmocom.org wrote:

The comment is
/* Use the TSC provided in the modification request, if any. Otherwise use the timeslot's configured

• TSC. */

but for know I don't figure out where the modification request is coming from. maybe it makes some sense to neels

The comment should have said "Use the TSC provided in the activation request",
it's a copy paste error from the TSC code for Channel Mode Modify. (Patch to fix is out)

- lchan->activate.tsc = (lchan->activate.info.tsc >= 0) ? lchan->activate.info.tsc : gsm_ts_tsc(lchan->ts);
+ lchan->activate.tsc = (lchan->activate.info.tsc >= 1) ? lchan->activate.info.tsc : gsm_ts_tsc(lchan->ts);

It should actually be >= 0, gsm_data.h:627:

/* TSC to use, or -1 for automatically determining the TSC to use. Valid range is 0 to 7, as described in 3GPP * TS 45.002. */
int tsc;

But I see that the channel activation during handover fails to set tsc to -1.
Goodness, thanks for spotting this, I pretty much broke handover with the TSC refactoring!

I tweaked ttcn3 tests to detect the ill TSC in handover, and submitted a patch
to fix the TSC and help prevent future errors like this:

https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/25662
https://gerrit.osmocom.org/c/osmo-bsc/+/25659

neels wrote in #note-4:

I tweaked ttcn3 tests to detect the ill TSC in handover, and submitted a patch
to fix the TSC and help prevent future errors like this:

https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/25662
https://gerrit.osmocom.org/c/osmo-bsc/+/25659

those two patches are merged - does this mean this issue can be closed?