Cell Identity (CI) is one part of Cell Global Identity (CGI), transmitted in system information of each cell.
There is generally no restriction for the allocation of CI. Value from 0 to 65535 (decimal) can be obtained. But it should be ensured that one location area cannot have two cells with the same CI.
CI is usually determined in the network design. Except for some special cases, CI value should not be changed during the operation of the system.
Please note that one location area is not permitted to have two or more cells using the same CI. CI on MSC should be the same as that on BSC. Otherwise, MS cannot make calls in this cell.