My question is: Is FACCH channel used at any point during call setup? I understand that the BTS sends the ASSIGNMENT COMMAND (for tch assignment) on the SDCCH, but I read somewhere that the returning ASSIGNMENT COMPLETE message sent by the MS is on FACCH? Can anybody confirm?
Dear All, Assignment Command (containing the information about the new TCH channel already opened) is sent on SDCCH. then MS sends SABM on the FACCH associated to the new channel and BTS answers with UA on FACCH. At receiption of UA, MS sends the Assignment Complete on FACCH.
The FACCH is the one associated to the new channel on which the MS in going to camp on. It has been already opened by BSS.
FACCH is the Fast Associated Control CHannel, the fast signaling channel, and is always related to a TCH.
DangerousMinds : FACCH is physically located on the same timeslot as the TCH (same TRX, same frequency, same timeslot…). The only difference is that the burst is actually carrying “signalling” rather than “speech”.