GSM FACCH(Fast Associated Control Channel)
This page describes GSM FACCH(Fast Associated Control Channel).
In GSM, FACCH is used to exchange information between GSM Mobile Station(MS) and Base Transceiver Station(BTS) more quickly than possible with SACCH.
FACCH information message can easily be transmitted in 20 ms duration, as used by traffic channel(TCH).
SACCH usually is trasmitted once every 26 frame and hence if fast information to be conveyed than FACCH is employed. One signalling block of FACCH replace one TCH speech block. In case higher data rate is required, TCH time slot is usually stolen to be used by FACCH.
FACCH is used both in uplink as well as downlink.
FACCH processing
The figure depicts FACCH channel information through the physical layer.
GSM Channels
GSM SDCCH
GSM SACCH
GSM RACH
GSM PCH
GSM FACCH
GSM BCCH
GSM AGCH
GSM SCH
GSM FCCH
GSM TCH
GSM CCCH