Mobile Switching Center

What is it? 

A mobile switching center (MSC) is the central component of a network switching subsystem (NSS), which switches calls between the mobile and other fixed or mobile network users. 

The functionalities of an MSC include call set-up, release, and routing as well as routing SMS messages, conference calls, fax, and service billing and interfacing with other networks. 

How does it work? 

Base stations link to a mobile switching center, while it links to the PSTN, i.e., a global combination of interconnected voice-oriented public telephone networks. Since mobile phones link to the base stations, all kinds of communication between two mobile phones or between a mobile phone and a landline telephone go through the MSC.  

Small network operators can use a single MSC while large ones may leverage many of them. Mobile switching centers are crucial to handovers, especially those involving multiple base station controllers (inter-BSC or intra-MSC handovers) and those involving multiple MSCs (inter-MSC handovers). 

In an inter-BSC handover and after identifying that a mobile device is nearing the edge of its cell, a BSC makes a handover assistance request to an MSC. Afterward, the MSC checks out a list of adjacent cells and their BSCs. Finally, it facilitates handover to the fitting BSC. 

An MSC is also responsible for recognizing mobile phones’ locations as they move, so it deals with a home location register (HLR), a relevant database. However, employing the HLR is a resource-intensive process. As a result, the majority of operators choose to utilize visitor location registers (VLRs), which are smaller and integrated with the MSC.

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