Network identity parameters mainly include cell global identity (CGI) and base station identity code (BSIC).
CGI=MCC+MNC+LAC+CI
Once MS receives SYS INFO, it decodes the CGI information, and decides whether it can stay in the cell according to the MCC and MNC indicated by CGI. At the same time, it judges whether the current location area is changed, so as to decide whether to execute location update. During the location update process, MS will report the new LAI to the network, so that the network can know the LA in which MS is currently located.

As a global cellular mobile communication system, GSM conducts strict coding for each GSM network in every country, and even every location area, BTS, and cell, so as to ensure that each cell corresponds to a unique number all over the world.

The adoption of this coding scheme can achieve the following objectives:

1. Ensure that MS can correctly identify the current network, so that MS can accurately select the network expected by subscribers and operators.

2. Ensure that the network can know the real-time position of MS, so that the network can connect various service requests to the MS.

3. Ensure that the MS can report correct neighbor cells’ information to the network during conversation, so that network can perform handover when necessary to keep continuous conversation for the mobile subscribers.