In GSM (Global System for Mobile Communications), CCCH stands for “Common Control Channel.” CCCH is a type of logical channel that plays a crucial role in facilitating control signaling between the mobile device (MS – Mobile Station) and the network infrastructure, including the Base Transceiver Station (BTS) and the Mobile Switching Center (MSC).
Types of CCCH Channels in GSM:
- Random Access Channel (RACH):
- The Random Access Channel (RACH) is a downlink CCCH that allows mobile devices to initiate communication with the network when there is no dedicated channel available. It is used for call setup, location updating, and other initial access procedures.
- Paging Channel (PCH):
- The Paging Channel (PCH) is an uplink CCCH used by the network to send paging messages to mobile devices. When the network needs to establish communication with a specific mobile device, it uses the PCH to alert the device and request it to respond.
- Access Grant Channel (AGCH):
- The Access Grant Channel (AGCH) is a downlink CCCH that is used by the network to grant access to a mobile device that has initiated communication through the RACH. Once access is granted, the mobile device is assigned a dedicated channel for further communication.
- Cell Broadcast Channel (CBCH):
- The Cell Broadcast Channel (CBCH) is a downlink CCCH used for broadcasting cell-specific information, such as cell identity and information related to Cell Broadcast Service messages.
Functions of CCCH Channels:
- Call Setup and Paging:
- CCCH channels are essential for call setup procedures and for alerting mobile devices through paging messages. When a call is initiated or when the network needs to communicate with a specific mobile device, CCCH channels are involved in the process.
- Random Access and Location Updating:
- The RACH, which is a type of CCCH, allows mobile devices to initiate communication when there is no dedicated channel available. It is used for tasks like location updating, where the mobile device informs the network about its current location.
- Access Grant:
- The AGCH, another type of CCCH, is used to grant access to a mobile device that has initiated communication through the RACH. Once access is granted, the mobile device is assigned a dedicated channel for the ongoing communication.
- Broadcasting Cell-Specific Information:
- CCCH channels, such as the CBCH, are used for broadcasting cell-specific information to mobile devices. This information helps mobile devices in cell selection and reselection procedures.
In summary, Common Control Channel (CCCH) in GSM comprises various channels, including RACH, PCH, AGCH, and CBCH. These channels are crucial for signaling and control functions, including call setup, paging, random access, access grant, and broadcasting cell-specific information within the GSM network.