Explain IMSI&& TMSI?

 IMSI:

- 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.

b) TMSI:

- Temporary Mobile Subscriber Identity for most commonly sent between the mobile and the network.
- TMSI is assigned randomly by VLR to each mobile in the area.
- The TMSI number is local for a specific local area, and need to be updated every time when the mobile moves to a new geographical area.
- Paging a mobile is the key use of the TMSI.
- The communication between the mobile and the base station is known as paging.
- The emphasis of broadcast information is top set up channels for paging.
- Broadcast mechanism is available in every cellular system for distributing broadcast information to a plurality of mobiles