Cell Identity and Location Area Identity

   Cell Global Identity (CGI) consists of Location Area Identity (LAI) and Cell Identity (CI). And LAI includes Mobile Country Code (MCC), Mobile Network Code (MNC), and Location Area Code (LAC). SYS INFO 3, 6, and 4 contain all or part of the information of CGI. According to the received SYS INFO, MS decodes the CGI, and decide whether it can register in the network based on the MCC and MNC indicated by CGI. At the same time, it can judge whether the current location area is changed, so as to decide whether it is necessary to start the location updating process.

MCC is allocated globally. It consists of three decimal numbers. For example, China is 460. MNC is allocated by the country. It consists of two decimal numbers. 00 is for China Mobile, 01 is for China Unicom. LAC and CI are planned by each GSM network operator. They consist of two bytes. Please note that the value range of CI is 0X0001- 0XFFFE. 0X0000 and 0XFFFF are reserved for other use.