what an impressive name !
when the MS performs a Location Update, it first makes a “call setup”, in order to get a SDCCH. I wouldn’t actually call it a call setup, but in SwissQual I assume they are making this assumption ?
Anyway, the MS required a SDCCH channel, in order to perform the location update.
The failure means that either:
SDCCH has failed (radio fail ?)
SDCCH was congested (MS couldn’t get a SDCCH because BSC detects a SDCCH congestion)
Location Update was failed (hte MS gets the SDCCH, but the Loc Upd was rejected by the NSS.
I would say that the last option is probably the one which is indicated by SwissQual.
Could you look at layer 3 traces ? Check the Location Update Request (in the Connection Request, isn’t it ?)
And check the content of the Location Reject message.