GSM Question:

★ International Mobile Subscriber Identity - a unique identification that is associated with all GSM and UMTS network mobile phones.
★ The SIM inside the phone contains it as a 64 bit field.
★ Used for acquiring certain details in Home Location Register or Visitor Location Register.
★ IMSI is rarely sent for preventing eavesdroppers to identify and track the subscriber on the radio interface.
★ It is presented as 15 digit long number, where first 3 digits represent the Mobile Country Code and followed by the Mobile Network Code.
★ Remaining digits are mobile station identification number within the customer base network.