Mobile Country Code(MCC) : MCC consists of 3 decimal numbers. It indicates the home country of the mobile subscriber. MCC is composed of 3 decimal numbers. The coding range is decimal 000-999.

MCC is used in international mobile subscriber identity (IMSI) and location area identity (LAI).

1. LAI.  It is periodically transmitted in system information of each cell. MCC indicates the home country of GSM PLMN. MS uses the received information as the important basis for network selection.

2. IMSI of MS.  MS’s IMSI also contains MCC. It shows the resident country of the mobile subscriber. When MS logs on the network or applies for a certain service, it must report its IMSI to the network (When TMSI is unavailable.). The network uses the MCC in IMSI to judge whether this subscriber is an international roaming subscriber.

As the unique country identity standard, MCCs are allocated and managed by the International Telecommunication Union (ITU). ITU Recommendation E.212 (blue book) stipulated the MCC number for every country. Due to the special meaning of MCC, modification of it is prohibited once it has been set in the network.

Mobile Network Code(MNC) : MNC is used to uniquely identify a specific GSM PLMN network in a certain country (decided by MCC).MNC is composed of two decimal numbers. The coding range is decimal 00-99.

MNC is used in international mobile subscriber identity (IMSI) and location area identity (LAI).

LAI. It is periodically transmitted in system information of each cell. Here, MNC indicates the network number of GSM PLMN. MS uses the received information as an important basis for network selection.

IMSI also contains MNC. It shows the home GSM PLMN network of the subscriber. When MS logs on the network or applies for a certain service, it must report IMSI to the network (When TMSI is unavailable.). The network judges whether this subscriber is a roaming subscriber according to the MNC in IMSI,  and uses it as one of the important parameters for addressing to subscriber HLR.

If a country has more than one GSM PLMN, different networks must have different MNC. MNC is allocated by relevant telecommunication management department of the country.

One operator can have one or more MNC (which regards to the scale provided by the service, usually one operator has one MNC.). Different operators can share the same MNC. Due to the special meaning of MNC, modification is prohibited once it has been set in the network.