NSS Network Switching Subsystem

The Network Switching Subsystem (NSS) is a critical component of a cellular network. It is responsible for handling all the communication between mobile devices and the core network. The NSS is made up of several components, including the Mobile Switching Center (MSC), the Home Location Register (HLR), and the Visitor Location Register (VLR). These components work together to provide seamless communication services to mobile subscribers.

In this article, we will discuss the various components of the NSS, their functions, and how they work together to provide mobile communication services.

Mobile Switching Center (MSC)

The Mobile Switching Center (MSC) is the central component of the NSS. It is responsible for routing calls and data between mobile devices and the core network. The MSC is essentially a switch that connects mobile devices to the rest of the network.

The MSC has several functions, including call setup, call routing, call handover, and call termination. When a mobile device initiates a call, the MSC receives the call request and determines the best route for the call to take. The MSC also manages call handover, which is the process of transferring an ongoing call from one cell to another without interrupting the call.

The MSC is also responsible for call termination, which occurs when a call is ended by the caller or the receiver. When a call is terminated, the MSC releases the resources allocated for the call, including the voice channels and signaling channels.

Home Location Register (HLR)

The Home Location Register (HLR) is a database that contains information about all the mobile subscribers in a network. The HLR stores information about the subscriber's location, subscription data, and service data.

When a mobile device initiates a call or data session, the MSC queries the HLR to determine the location of the subscriber. The HLR responds with the subscriber's location, which allows the MSC to route the call or data to the correct destination.

The HLR is also responsible for managing subscriber data, including subscriber authentication and authorization. The HLR ensures that only authorized subscribers can access the network and that they are billed correctly for the services they use.

Visitor Location Register (VLR)

The Visitor Location Register (VLR) is a database that contains information about mobile subscribers who are currently roaming in a network. The VLR stores information about the subscriber's current location and temporary subscriber data.

When a mobile subscriber roams into a new network, the MSC queries the VLR to retrieve the subscriber's temporary data. The VLR responds with the subscriber's location and other information, which allows the MSC to route calls and data to the subscriber.

The VLR is also responsible for managing subscriber data while the subscriber is roaming in a network. The VLR ensures that the subscriber is authorized to use the network and that they are billed correctly for the services they use.

Authentication Center (AuC)

The Authentication Center (AuC) is a component of the NSS that is responsible for authenticating subscribers and ensuring the security of the network. The AuC stores subscriber authentication data, including the subscriber's authentication key and other security-related information.

When a subscriber initiates a call or data session, the MSC requests authentication data from the AuC. The AuC responds with the subscriber's authentication data, which allows the MSC to authenticate the subscriber and ensure that they are authorized to use the network.

Equipment Identity Register (EIR)

The Equipment Identity Register (EIR) is a database that stores information about mobile devices, including their International Mobile Equipment Identity (IMEI) numbers. The EIR is used to identify stolen or lost devices and to prevent them from being used on the network.

When a mobile device is reported as stolen or lost, the device's IMEI number is added to the EIR blacklist. When the device attempts to access the network, the MSC queries the EIR to check if the device is blacklisted. If the device is blacklisted, the MSC denies access to the network.

Base Station System (BSS)

The Base Station System (BSS) is the component of the NSS that interfaces with the radio access network (RAN). It consists of Base Transceiver Stations (BTS) and Base Station Controllers (BSC).

The BTS is responsible for transmitting and receiving voice and data signals between mobile devices and the network. It converts the analog voice signals from mobile devices into digital signals that can be transmitted over the network.

The BSC is responsible for managing and controlling multiple BTSs. It coordinates the handover process between cells and allocates radio resources to mobile devices.

Conclusion

The Network Switching Subsystem (NSS) is a crucial component of a cellular network. It consists of several components, including the Mobile Switching Center (MSC), the Home Location Register (HLR), the Visitor Location Register (VLR), the Authentication Center (AuC), the Equipment Identity Register (EIR), and the Base Station System (BSS).

These components work together to provide seamless mobile communication services to subscribers. The MSC handles call routing, handover, and termination. The HLR and VLR store subscriber data and manage subscriber authentication and authorization. The AuC ensures the security of the network by authenticating subscribers. The EIR prevents stolen or lost devices from accessing the network. The BSS interfaces with the radio access network and manages the transmission of voice and data signals.

By understanding the functions and interactions of these components, network operators can ensure the reliable and secure operation of their cellular networks, providing subscribers with high-quality mobile communication services.