CCCH-CONF

Value range: 1 non-combined CCCH,  1 combined CCCH,  2 non-combined CCCH,  3 non-combined CCCH,  4 non-combined CCCH.

Content: It is “Common Control Channel Configuration”.The number of CCCH message blocks in one corresponding BCCH multi-frame are 9,  3,  18,  27,  and 36 respectively. CCCH configuration determines the capacity of PCH,  AGCH and RACH.

Unit: None

Recommendation: When there is one TRX in the cell,  one combined CCCH is recommended (in a system with few paging messages in location area). For others,  it is configured according to the number of TRX in the cell.

 

In GSM system, the common control channel mainly include Access Granted Channel (AGCH) and Paging Channel (PCH). It serves to send the access granted (immediate assignment) and paging message. CCCH is shared. According to the configuration of traffic channel and traffic model, CCCH can be carried by either one or multiple physical channels. Moreover, CCCH and SDCCH can share one physical channel. Which combination mode to be adopted in the cell depends on CCCH_CONF.

When CCCH is a physical channel which combined with SDCCH, the capacity of CCCH is the lowest. When CCCH is a physical channel which does not combined with SDCCH, the capacity is higher. For other cases, the more the physical channels used as CCCH, the higher the capacity.

Configuration of CCCH_CONF is specified according to the traffic model. This model is closely related to the cell location and environment. According to experiences, when TRX quantity in the cell is 1 or 2, it is recommended to use a combined CCCH as the common control channel. When TRX quantity in the cell is 3 or 4, it is recommended to use a non-combined CCCH as the common control channel.

Currently CCCH can be configured according to actual traffic load. If the paging load is very heavy, the paging traffic of cell can be distributed via multiple CCCH physical channels or other ways. Special attention should be paid to PCH in CCCH. Generally PCH capacities of various cells under one LAC must be the same.