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Reply To: SDCCH & TCH


Oh, here are some (good) answers :
GSM 04.11

I was wrong before, the SMS should be interrupted in order to setup the TCH call.

Extract :

The short message service will be supported by an SDCCH or SACCH, depending on the use of a TCH;
– When a TCH is not allocated, the short message service will use an SDCCH;
– If a TCH is allocated during a short message transaction on an SDCCH, the short message
transaction will stop and continue on the SACCH associated with the TCH;
– If a TCH is allocated for the short message service, the short message service will use the
associated SACCH;
– When an entity using a TCH finishes its transaction, the RR-sublayer may choose to continue an
ongoing short message transfer on the SACCH, or optionally transfer it to an SDCCH.

I knew the answer about what happens to the Measurement Reports when the SMS being sent during a TCH call (on the SACCH).

It’s true that SACCH is already used to transmit MR. So how the hell does the SMS go through… I knew the answer, but i can’t recall… sorry.