Which register stores information about each subscriber that belongs to it?
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The Network switching system (NSS), the main part of which is the Mobile Switching Center (MSC), performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as authentication. Show
The switching system includes the following functional elements: Home Location Register (HLR)The HLR is a database used for storage and management of subscriptions. The HLR is considered the most important database, as it stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. When an individual buys a subscription in the form of SIM, then all the information about this subscription is registered in the HLR of that operator. Mobile Services Switching Center (MSC)The central component of the Network Subsystem is the MSC. The MSC performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. It also performs such functions as toll ticketing, network interfacing, common channel signaling, and others. Every MSC is identified by a unique ID. Visitor Location Register (VLR)The VLR is a database that contains temporary information about subscribers that is needed by the MSC in order to service visiting subscribers. The VLR is always integrated with the MSC. When a mobile station roams into a new MSC area, the VLR connected to that MSC will request data about the mobile station from the HLR. Later, if the mobile station makes a call, the VLR will have the information needed for call setup without having to interrogate the HLR each time. Authentication Center (AUC)The Authentication Center is a protected database that stores a copy of the secret key stored in each subscriber's SIM card, which is used for authentication and ciphering of the radio channel. The AUC protects network operators from different types of fraud found in today's cellular world. Equipment Identity Register (EIR)The Equipment Identity Register (EIR) is a database that contains a list of all valid mobile equipment on the network, where its International Mobile Equipment Identity (IMEI) identifies each MS. An IMEI is marked as invalid if it has been reported stolen or is not type approved. Home Location Register (HLR) is a database that contains data regarding authorized subscribers using a global system for mobile communication (GSM) core network. The home location register stores information ranging from phone numbers to current location of the subscriber. Some data contained in the home location register include the mobile Station International Subscriber Directory Number (MSISDN) which is a list of the telephone numbers used by the subscriber and the International Mobile Subscriber Identity (IMSI) which is a unique identifier of each subscriber identity module (SIM) and is the primary key for each HLR record of each subscriber. Cell phones and their corresponding SIMs are mostly on the move. The HLR is used to identify their last known location. This information is updated each time the device is transferred in to another location. The HLR also facilitates Short message services (SMS) by scanning through the HLR to identify the mobile switching center (MSC) currently used by the receiving party. If the recipient is reported as not available by the receiving MSC, a message waiting flag is sent on the HLR. The message is then delivered once the recipient is located on any MSC. Other mobile components associated with the HLR include the gateway mobile switching center (G-MSC), the authentication center (AUC) and the visitor location register (VLR). Home location register (HLR) database: The HLR stores information, both permanent and temporary, about each of the subscribers that "belongs" to it (i.e., for which the subscriber has its telephone number associated with the switching center). Visitor location register (VLR) database: One important, temporary piece of information is the location of the subscriber. The location is determined by the VLR into which the subscriber is entered. The visitor location register maintains information about subscribers that are currently physically in the region cov- ered by the switching center. It records whether or not the subscriber is active and other parameters associated with the subscriber. For a call coming to the subscriber, the system uses the telephone number associated with the subscriber to identify the home switching center ofthe subscriber. This switching center can find in its HLR the switching center in which the subscriber is currently physi- cally located. For a call coming from the subscriber, the VLR is used to initiate the call. Even if the subscriber is in the area covered by its home switching cen- ter, it is also represented in the switching center's VLR, for consistency. Authentication center database (AuC): This database is used for authentication activities of the system; for example, it holds the authentication and encryption keys for all the subscribers in both the home and visitor location registers. The center controls access to user data as well as being used for authentication when a subscriber joins a network. GSM transmission is encrypted, so it is private. A stream cipher, A5, is used to encrypt the transmis- sion from subscriber to base transceiver. However, the conversation is in the clear in the landline network. Another cipher, A3, is used for authentication. Equipment identity register database (EIR): The EIR keeps track of the type of equipment that exists at the mobile station. It also plays a role in security (e.g., blocking calls from stolen mobile stations and preventing use of the network by stations that have not been approved). What is stored in HLR?The HLR stores IMSI, MS ISDN number, VLR address, and subscriber data (e.g., supplementary services, etc.). The VLR is linked to one or more MSCs. The VLR is a functional unit that stores subscriber information, such as location area, when the subscriber is located in the area covered by the VLR.
Which database contains all the administrative information about each subscriber?Home Location Register (HLR):
This database contains all the administrative information about each subscriber along with their last known location. In this way, the GSM network is able to route calls to the relevant base station for the MS.
What is the role of HLR and VLR?A VLR is a database, similar to a HLR, which is used by the mobile network to temporarily hold profiles of roaming users (users outside their home area). This VLR data is based on the user information retrieved from a HLR. MSCs use a VLR to handle roaming users.
Which is the master database that holds the information of the network subscribers?10.1 Home Subscriber Server (HSS) The HSS can be described as the master database for a given user. It is the entity containing the subscription-related information to support the network entities handling mobility and user IP sessions. HSS also supports the entities handling circuit-switched calls.
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