International Mobile Subscriber Identity or IMSI

International Mobile Subscriber Identity (IMSI)

The IMSI is the information which uniquely identifies a subscriber in a GSM/PLMN.

For a correct identification over the radio path and through the GSM PLMN network, a specific identity is allocated to each subscriber. This identity is called the International Mobile Subscriber Identity (IMSI) and is used for all signalling in the PLMN. It will be stored in the Subscriber Identity Module (SIM), as well as in the Home Location Register (HLR) and in the serving Visitor Location Register (VLR).

The IMSI consists of three different parts:
IMSI = MCC + MNC + MSIN
MCC = Mobile Country Code (3 digits)
MNC = Mobile Network Code (2 digits)
MSIN = Mobile Subscriber Identification Number (max 10 digits)

According to the GSM recommendations, the IMSI will have a length of maximum 15 digits.

All network–related subscriber information is connected to the IMSI.