GSM NETWORK SYSTEM

 Q: What is the Visitor Location Register (VLR)?

A: The Visitor Location Register (VLR) is a database that supports an MSC in storing and retrieving data of subscribers present in its area. When a mobile station appears in a location area, it starts a registration procedure and the MSC transfers its identity to the VLR, which is responsible for managing the mobile station in that area. The VLR contains data necessary to manage the mobile station such as IMSI, MSISDN, MSRN, and TMSI.

Q: What is the role of the Home Location Register (HLR)?

A: The Home Location Register (HLR) is a database that permanently stores data related to subscribers. It provides data needed to route calls to all MS-SIMs home based in its MSC area, even when they are roaming. The HLR also provides the current location data for incoming calls, stores SIM authentication and encryption parameters, and maintains a record of subscribed supplementary services. The HLR also identifies SMS gateways that have messages for the subscriber.

Q: What is the function of the Authentication Center (AUC)?

A: The Authentication Center (AUC) stores information necessary to protect communication through the air interface against intrusions. The AUC performs the authentication of the subscriber each time he makes or receives a call and protects user information against unwanted disclosure and access. The AUC stores authentication information and ciphering keys in its database, and uses a random number and response mechanism to establish the legitimacy of the subscriber.

Q: What is the Equipment Identity Register (EIR)?

A: The Equipment Identity Register (EIR) is a database that stores IMEI numbers for all registered mobile equipment units. It keeps track of all mobile equipment units in the PLMN and maintains various lists of ME units such as white list, black list, and grey list. The EIR has nothing to do with the subscriber who is receiving or originating a call.

Q: What is the function of the Interworking Function (IWF)?

A: The Interworking Function (IWF) provides interfacing capability for the GSM system with various public and private data networks. The IWF is responsible for allowing data services to be offered to subscribers by the GSM system and interfacing with other data networks.

What is the International Mobile Subscriber Identity (IMSI)?

The International Mobile Subscriber Identity (IMSI) is assigned to each authorized GSM user and consists of a mobile country code (MCC), mobile network code (MNC), and a PLMN unique mobile subscriber identification number (MSIN). It is maintained on a SC by an authorized subscriber and is the only absolute identity that a subscriber has within the GSM system.

What is the Temporary Mobile Subscriber Identity (TMSI)?

The Temporary Mobile Subscriber Identity (TMSI) is a MSC-VLR specific alias designed to maintain user confidentiality. It is assigned only after successful subscriber authentication and the correlation of a TMSI to an IMSI only occurs during a mobile subscriber's initial transaction with an MSC.

What is the Mobile Station ISDN Number (MSISDN)?

The Mobile Station ISDN Number (MSISDN) is the international number that must be dialed after the international prefix to obtain a mobile subscriber in another country. It is composed of the country code (CC) followed by the National Significant Number (NSN).

What is the Mobile Station Roaming Number (MSRN)?

The Mobile Station Roaming Number (MSRN) is a temporary number allocated when the MS roams into another numbering area. It is used by the HLR for rerouting calls to the MS and is assigned upon demand by the HLR on a per-call basis.

What is the International Mobile Equipment Identity (IMEI)?

The International Mobile Equipment Identity (IMEI) is the unique identity of the equipment used by a subscriber by each PLMN. It is used to determine authorized, unauthorized, and malfunctioning GSM hardware and in conjunction with the IMSI, it is used to ensure that only authorized users are granted access to the system.

What is the conclusion made about mobile communication in the text?

The conclusion made about mobile communication in the text is that it will always be useful due to its mobility and that the newer antenna system MIMO will play a very important role in modern day communication.