Mobile Communications

Concepts and Terms

IMSI International Mobile Subscriber Identity is an unique number, usually fifteen digits, associated with Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UTMS) network mobile phone users, identifying a GSM subscriber. The number has two parts: first six digits (North American standard) identify the network operator in a specific country with whom the subscriber holds an account. The second part is allocated by the network operator to uniquely identify a subscriber.