GMSC (Gateway mobile services switching center)

Introduction:

Gateway Mobile Services Switching Center (GMSC) is a critical element in the circuit-switched network of a telecommunication service provider. It is a switch that performs call routing and handling for mobile-originated and mobile-terminated calls. The GMSC is responsible for interworking between different networks and service providers, and it is also responsible for managing the signaling and communication protocols involved in mobile call processing. In this article, we will explore the various aspects of GMSC in detail.

GMSC Functions:

The primary function of GMSC is to provide call routing and handling for mobile-originated and mobile-terminated calls. It receives the call from the originating MSC and routes it to the destination MSC or PSTN (Public Switched Telephone Network). It also performs number translation, charging, and billing functions for the calls. Let's look at each of these functions in more detail.

Call Routing:

The GMSC performs call routing based on the dialed number, which could be a mobile number, a landline number, or an international number. The GMSC queries the Home Location Register (HLR) to determine the current location of the called party. Based on the location information, the GMSC routes the call to the appropriate MSC or PSTN.

Number Translation:

The GMSC is responsible for performing number translation, which involves converting the dialed number into a format that is recognizable by the destination network. For example, if a call is made from a GSM network to a CDMA network, the GMSC will convert the GSM number into a CDMA number format so that it can be routed to the destination network.

Charging and Billing:

The GMSC is responsible for charging and billing for the calls. It collects call detail records (CDRs) for each call and sends them to the billing system. The billing system calculates the charges based on the duration of the call, the distance, and other factors. The charges are then sent back to the GMSC, which deducts them from the subscriber's account balance.

GMSC Architecture:

The GMSC is part of the Mobile Switching Center (MSC) family and is typically implemented as a separate entity within the MSC. The GMSC communicates with other entities in the network using various protocols, including Signaling System 7 (SS7), Mobile Application Part (MAP), and Base Station System Application Part (BSSAP).

The GMSC is connected to other MSCs and PSTNs via Trunk interfaces. The Trunk interfaces are high-speed communication links that carry voice and signaling traffic between the GMSC and other network elements.

GMSC Deployment:

The GMSC can be deployed in various configurations depending on the size and complexity of the network. In smaller networks, the GMSC can be integrated with the MSC, while in larger networks, it is usually implemented as a separate entity. In some cases, multiple GMSCs may be deployed to provide redundancy and load balancing.

The GMSC can also be deployed in different geographical locations to provide better coverage and support roaming subscribers. In this case, the GMSCs are interconnected using SS7 links to ensure seamless call routing and handling.

GMSC Interworking:

The GMSC is responsible for interworking between different networks and service providers. It provides call routing and handling for calls originating from or terminating to other networks. For example, if a subscriber from a GSM network wants to call a subscriber on a CDMA network, the GMSC will perform number translation and route the call to the appropriate network.

The GMSC also supports roaming subscribers by providing call routing and handling when they move from one network to another. When a subscriber roams to a different network, the GMSC of the visited network communicates with the GMSC of the home network to ensure seamless call routing and handling.

Conclusion:

GMSC is a critical component in the circuit-switched network of a telecommunication service provider. It is responsible for call routing and handling, number translation, charging, and billing functions for mobile-originated and mobile-terminated calls. The GMSC is usually deployed as a separate entity within the Mobile Switching Center (MSC) and communicates with other entities in the network using various protocols, including SS7, MAP, and BSSAP.

In addition to providing call routing and handling within the same network, the GMSC also supports interworking between different networks and service providers. This allows subscribers to communicate with each other regardless of the network they are using. The GMSC also supports roaming subscribers by providing call routing and handling when they move from one network to another.

Overall, GMSC plays a critical role in ensuring seamless call routing and handling for mobile subscribers, and its proper functioning is essential for delivering high-quality mobile services to customers.