IMSI

admin — Tue, 13 Mar 2007 11:18:58 +0000

IMSI (international mobile subscriber identifier)

A unique 15-digit number which designates the subscriber. This number is used for provisioning in network elements. (Cingular)

IMSI[im-zee] is an acronym for International Mobile Subscriber Identity. This is a unique number that is associated with all GSM and UMTS network mobile phone users. The number is stored in the SIM. It is sent by the mobile to the network and is used to look up the other details of the mobile in the HLR or as locally copied in the VLR. In order to avoid the subscriber being identified and tracked by eavesdroppers on the radio interface, the IMSI is sent as rarely as possible and a randomly generated TMSI is sent instead.

An IMSI is usually fifteen digits long. However, they can be shorter (eg. MTN SouthAfrica's are 14 digits). The first three digits are the country code (MCC), and the next digits are the network code (MNC). The MNC can be either two digits long (normal e.g. in Europe) or three digits long (normal in North America), the remaining digits, up to the maximum length are the unique subscriber number (MSIN) within the network's customer base. » read more »