Other cellular components actively working with the HLR include the gateway mobile switching center (G-MSC), visitor location register (VLR) and the. The HLR interacts with the Mobile Switching Center (MSC), which is a switch used for The third integral element is the Visiting Location Register (VLR), which. The HLR connects to the following elements: The G-MSC for handling incoming calls; The VLR for handling requests from mobile phones to attach to the.

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Network switching subsystem NSS or GSM core network is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobile phone operators and allows mobile devices to communicate with each other and telephones in the wider public switched telephone network PSTN.

The architecture contains specific features and functions which are needed because the phones are not fixed in one location. It was extended with an overlay architecture to provide packet-switched data services known as the GPRS core network. The MSC sets up and releases the end-to-end connectionhandles mobility and hand-over requirements during the call and takes care of charging and real time prepaid account monitoring.

In the GSM mobile phone system, in contrast with earlier analogue services, fax and data information is sent digitally encoded directly to the MSC. There are various different names for MSCs in different contexts which reflects their complex role in the network, all of these terms though could refer to the same MSC, but doing different things at different times.

It also interfaces with the PSTN. The term is only valid in the context of one call, since any MSC may provide both the gateway function and the visited MSC function. However, some manufacturers design dedicated high capacity MSCs which do not have any base station subsystems BSS connected to them.

The mobile switching center server is a soft-switch variant therefore it may be referred as mobile soft switch, MSS of the mobile switching center, which provides circuit-switched calling mobility management, and GSM services to the mobile phones roaming within the area that it serves.


The term Circuit switching CS used here originates from traditional telecommunications systems. MSS software may run on generic computers or virtual machines in cloud environment. The home location register HLR is a central database that contains details of each mohile phone subscriber that is authorized to use the GSM core network.

The HLR data is stored for as long as a nlr remains with the mobile phone operator. The HLR is a system which directly receives and processes MAP transactions and messages from elements in the GSM network, for example, the location update messages received as mobile phones roam around.

The following procedures are implemented to deal with this:. The authentication center AuC is a function to authenticate moblie SIM card that attempts to connect to the gsm core network typically when the phone is powered on.

An encryption key is also generated that is subsequently used to encrypt all wireless communications voice, SMS, etc. If the authentication fails, then no services are possible from that particular combination of SIM card and mobile phone operator attempted.

There is an additional form of identification check performed on hle serial number of the mobile phone described in the EIR section below, but this is not relevant to the AuC processing.

What is a Visitor Location Register (VLR)? – Definition from Techopedia

Proper implementation of security in and around the AuC is a key part of an operator’s strategy to avoid SIM cloning. The AuC does not engage directly in the authentication process, but instead generates data known as triplets for the MSC to use during the procedure. After successful authentication, the MSC sends the encryption key K c to the base station controller BSC so that all communications can be encrypted and decrypted.

Of course, the mobile phone can generate the K c itself by feeding the same RAND supplied during authentication and the K i into the A8 algorithm. Whilst the procedure is secure for most everyday use, it is by no means hack proof.

Therefore, a new set of security methods was designed for 3G phones. It is used to authenticate the customer and generate a key for encrypting voice and data traffic, as defined in 3GPP TS Development of A3 and Andd algorithms is considered a matter for individual GSM network operators, although example implementations are available.

If VLR data is corrupted it can lead to serious issues with text messaging and call services. The equipment identity register is often integrated to the HLR. This is designed to allow tracking of stolen mobile phones. It is clear, however, that there are some countries where this is not in operation. The EIR data does mboile have to change in real time, which means that this function can be less distributed than the function of the HLR.


The EIR is a database that contains information about the identity of the lvr equipment that prevents calls from stolen, unauthorized or defective mobile stations.

Some EIR also have the capability to log Handset attempts and store it in a log file. The billing center is responsible for processing the toll tickets generated by the VLRs and HLRs and generating a bill for each subscriber. It is also responsible for generating billing data of roaming subscriber.

GSM – The Network Switching Subsystem (NSS)

The multimedia messaging service center supports the sending of multimedia messages e. The voicemail system records and stores voicemail. There must be some level of support for this built into any of the different elements. The concept of lawful interception is also known, following the relevant U.

Generally, lawful Interception implementation is similar to the implementation of conference call. While A and B are talking with each other, C can join the call and listen silently. From Wikipedia, the free encyclopedia. This article needs additional citations for verification.

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What is HLR and VLR and its function in GSM?

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List of mobile phone generations. Retrieved from ” https: GSM standard Telecommunications infrastructure. Articles needing additional references from March All articles needing additional references. Views Read Edit View history.

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