Control channel

It is most often used in the context of a trunked radio system, where the control channel sends various data which coordinates users in talkgroups.

The mobile station (MS) monitors the information carried on the BCCH periodically (at least every 30 secs), when it is switched on and not in a call.

Broadcast Control Channel (BCCH): Carries the following information: The BCCH is transmitted at constant power at all times, and all MS that may seek to use it to measure its signal strength.

“Dummy” bursts are transmitted to ensure continuity when there is no BCCH carrier traffic.

The MS will move to the dedicated channel in order to proceed with either a call setup, response to a paging message, Location Area Update or Short Message Service.

The DCCH is a single timeslot on an RF carrier that is used to convey eight Stand-alone Dedicated Control Channels (SDCCH).

Slow Associated Control Channel (SACCH) Conveys power control and timing information in the downlink direction (towards the MS) and Receive Signal Strength Indicator (RSSI), and link quality reports in the uplink direction.

This allows efficient passing of control information without wasting capacity that could be used for call traffic.

To do this we must organize the times lots between those, which will be used for traffic, and those, which will carry control signaling.