What is BCCH and TCH in GSM?

Common Control Channel. Common Control Channels support common procedures required to establish a dedicated link with the network . Typical channels include the RACH (Random Access Channel), PCH (Paging Channel) and AGCH (Access Grant Channel) within GSM.

Dedicated control channel (DCCH): A point-to-point bidirectional channel that transmits dedicated control information between a UE and the network . It is used by UEs that have RRC connection. The traffic channels are exclusively used for the transfer of user-plane information.

Broadcast control channels are transmitted in downlink direction only i.e. only transmitted by BTS . . The broadcast channels are used to broadcast synchronization and general network information to all the MSs within a cell. .

GSM uses a variety of ‘channels’ in which the data is carried. In GSM, these channels are separated into physical channels and logical channels . The Physical channels are determined by the timeslot, whereas the logical channels are determined by the information carried within the physical channel.

The traffic channels are the resources available to the user for either speech or data . A logical traffic channel in GSM is abbreviated by TCH. It can be used for either data or speech. The radio interface must support bi-directional transmission in order to support speech and data communication.