MSC/VLR Mobile services switching centre/visitor location register

Introduction:

In a mobile communication network, the Mobile Services Switching Centre (MSC) and Visitor Location Register (VLR) are two important components that are responsible for ensuring seamless communication between mobile subscribers. The MSC/VLR is a critical element in the mobile network as it plays a crucial role in routing and managing calls, as well as tracking the location of mobile subscribers. This article will provide an in-depth explanation of MSC/VLR, its architecture, functionalities, and how it operates.

Mobile Services Switching Centre (MSC):

The Mobile Services Switching Centre (MSC) is a central component of the mobile network that acts as a gateway between the mobile network and the public switched telephone network (PSTN). The MSC is responsible for handling call setup and call routing for mobile subscribers, as well as providing other value-added services such as call forwarding, call waiting, and three-way calling. The MSC is also responsible for managing the mobility of subscribers by tracking their location and updating the location in the VLR.

The MSC is composed of several functional units, including the Call Control Function (CCF), Mobility Management Function (MMF), and Operation and Maintenance Centre (OMC). The CCF is responsible for call setup and call routing, while the MMF is responsible for managing the mobility of subscribers. The OMC is responsible for managing and monitoring the performance of the MSC.

Visitor Location Register (VLR):

The Visitor Location Register (VLR) is a database that stores information about mobile subscribers who are currently within the coverage area of a particular MSC. The VLR is responsible for maintaining up-to-date information on the subscriber's location, services, and other related information. The VLR is also responsible for managing subscriber mobility by tracking their location and updating the location in the MSC.

The VLR contains two types of subscriber data: permanent subscriber data and temporary subscriber data. Permanent subscriber data includes the subscriber's name, address, phone number, and other personal information, while temporary subscriber data includes information about the subscriber's location and the services they are currently using.

Architecture of MSC/VLR:

The architecture of MSC/VLR is designed to support the seamless mobility of subscribers within the mobile network. The MSC/VLR is typically connected to several base station subsystems (BSS), which are responsible for communicating with mobile devices within a particular coverage area. The BSS consists of several functional units, including the Base Transceiver Station (BTS), Base Station Controller (BSC), and the Packet Control Unit (PCU).

The BTS is responsible for transmitting and receiving radio signals to and from mobile devices, while the BSC is responsible for managing the BTS and controlling the handover of calls between cells. The PCU is responsible for managing data traffic within the BSS.

The MSC/VLR is also connected to the Home Location Register (HLR), which is a centralized database that stores information about all subscribers in the network. The HLR is responsible for managing permanent subscriber data, including the subscriber's profile and the services they are subscribed to.

Functionality of MSC/VLR:

The MSC/VLR provides several key functionalities that are essential to the operation of the mobile network. These functionalities include call setup and routing, mobility management, and service provisioning.

Call Setup and Routing:

The MSC/VLR is responsible for establishing a connection between two or more mobile subscribers by routing calls through the network. When a call is initiated, the MSC/VLR performs a series of operations to establish a connection between the calling and called parties. These operations include authentication and authorization, location tracking, call setup and routing, and call handover.

Authentication and Authorization:

Before a call can be established, the MSC/VLR verifies the identity of the calling party to ensure that the subscriber is authorized to make the call. This is done by comparing the subscriber 's phone number and other identification data with the information stored in the HLR. If the subscriber is authorized, the MSC/VLR proceeds with call setup and routing.

Location Tracking:

The MSC/VLR is responsible for tracking the location of mobile subscribers within the network. This is done by constantly monitoring the signals transmitted by the subscriber's mobile device. If the subscriber moves to a new location, the MSC/VLR updates the subscriber's location information in the VLR and notifies the HLR of the new location.

Call Handover:

When a subscriber moves from one cell to another while on a call, the MSC/VLR performs a handover operation to ensure that the call is not interrupted. The handover operation involves transferring the call from the current cell to the new cell without interrupting the call. The MSC/VLR ensures that the handover operation is smooth and seamless, without any loss of quality.

Mobility Management:

The MSC/VLR is responsible for managing the mobility of subscribers within the network. This involves tracking the location of subscribers, updating their location information in the VLR, and facilitating handover operations when subscribers move from one cell to another. The MSC/VLR also manages subscriber authentication and authorization, ensuring that only authorized subscribers can access the network.

Service Provisioning:

The MSC/VLR is responsible for provisioning services to subscribers within the network. This involves managing subscriber profiles and service subscriptions, activating and deactivating services, and ensuring that the subscriber is billed correctly for the services they use.

Conclusion:

The Mobile Services Switching Centre (MSC) and Visitor Location Register (VLR) are critical components of the mobile network architecture. The MSC/VLR is responsible for routing calls, managing subscriber mobility, and providing value-added services to subscribers. The architecture of MSC/VLR is designed to support seamless mobility within the network, with the MSC/VLR connected to several base station subsystems and the Home Location Register (HLR). The MSC/VLR provides several key functionalities, including call setup and routing, mobility management, and service provisioning, making it a critical component of the mobile network.