Wireless Technology Terms, Glossary and Dictionary
IMSI: International Mobile Subscriber Identity
International Mobile Subscriber Identity (IMSI) is a unique number that is associated with all GSM and Universal Mobile Telecommunications System (UMTS) network mobile phone users. The number is stored in the Subscriber Identity Module (SIM). It is sent by the mobile phone to the network and is also used to acquire other details of the mobile in the Home Location Register (HLR) or as locally copied in the Visitor Location Register. 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.