thanks 😉 I’m glad I can help. On the other hand, “westbay engineers” is paying me 100$ per post.
To come back to your initial question… I don’t mind spending time on it, so let’s go as deep as you need !
The BSC allocated the voice call on a specific TS, so there is no need to identify anything else after the call setup. The call will always be on that RTS.
Therefore there is no need to identify each burst sent on this RTS. The BSC knows that they all belong to one subscriber.
At call setup, of course, the MS is identified and authenticated thanks to its IMSI/TMSI, and those checks are done by the core network. But that is of no interest to the BSC.
The BSC only maps a specific call (identified by its SS7 id) to a RTS. After a HO, the BSC will map the SS7-id to another RTS.
SS7-ID is the identifier of the call from a CN point of view.
It does not identify one particular subscriber.
Indeed, the BSC does not know anything about the subscriber ! It only sees the subscriber as a “call”, nothing else.