FCCH in GSM

FCCH stands for the Frequency correction channel in GSM.

It is a base to mobile channel that provides information for carrier synchronization. It is a special data burst that occupies the TS0 slot for the first GSM frame. It is repeated every ten frames within a control channel multi-frame.

The FCCH allows the mobile subscriber to synchronize its internal frequency standard with the frequency of the base station.

In the first burst of FCCH, all zero bits are sent to indicates the unmodulated carrier.

FCCH burst structure