All you need to know about switch centers

Mobile switch centers, also known as Mobile Switching Centers (MSCs), are essential to the mobile network architecture for functionality and security. The MSC is the hub through which all mobile communications are routed and is “situated” between the mobile network’s base station and the public telephone network. We use the term situated lightly because the physical hardware aspect of MSCs has become less prominent as the intelligence has shifted to the software layer. So, MSCs are not strictly physical centers, but rather a combination of physical and logical/software components.

An MSC acts as the center for the Global System for Mobile Communication (GSM) or the Code Division Multiple Access (CDMA) cellular network and is involved in the process of call routing, subscriber management, and communication with other components of the telecom network. An MSC also executes real-time monitoring, pre-paid billing, and detects any potential network security threats.

MSCs have 4 primary functions: network integration, mobility management, billing, and security and monitoring. Let’s review each of these.

• Network integration: The MSC is the gateway between the mobile network and networks such as the Public Switched Telephone Network (PSTN). The MSC ensures that mobile subscribers and fixed-line users can communicate. The MSC also routes and switches voice calls and Short Message Service (SMS), and sends faxes between mobile subscribers and other networks (such as the PSTN).
• Mobility management: The MSC coordinates with the Home Location Register (HLR) to track where users are and ensure a smooth handover between cell towers as users move. This ensures that users do not drop a call as they drive along a highway and the cell phone taps the nearest tower and then the next nearest one.
• Billing: The MSC captures details about phone usage for real-time billing and account management.
• Security and monitoring: As previously mentioned, the MSC is crucial to enable real-time monitoring, facilitate pre-paid billing, and ensure threat detection to keep the network secure.

There are five main types of MSCs, each with slightly different functions.

• A Visited MSC (V-MSC) is the MSC in which the subscriber is currently located and determines which visitor location register (VLR) will store that subscriber’s data.
• The Gateway MSC (G-MSC) obtains information about which V-MSC the subscriber is digitally located, in addition to handling all mobile-to-mobile and PSTN-to-mobile calls.
• The Anchor MSC initiates handovers, which are received by the Target MSC.
• Finally, the Mobile Switching Center Server (MSS or MSC-Server) offers circuit-switched calling, further mobility management, and GSM services. The MSS also splits functions for signaling and subscriber use.

The MSC is the central hub that connects the GSM network’s base stations to the wider telephone network, enabling seamless mobility, call management, and value-added services for mobile subscribers.

The MSC plays a crucial role in connecting and managing calls within a GSM network. It acts as the control center that handles the following key functions:

• Call routing and switching: The MSC establishes connections between mobile subscribers by routing and switching the digital voice packets between network channels. It handles call setup, supervision, and release for calls to/from mobile subscribers, as well as calls forwarded to other networks like the PSTN.
• Interfacing with other network elements: The MSC communicates with the HLR to obtain subscriber information needed for call routing and service provisioning. It also interfaces with other MSCs to enable handovers between cells belonging to different MSCs during an active call.
• Service provisioning: The MSC manages a variety of mobile services beyond just voice calls, such as SMS, fax, and conference calls. It also handles real-time pre-paid billing and account management for subscribers.
• Network security: The MSC enables real-time monitoring of network activities and call transactions to detect and mitigate security threats. It also facilitates regulatory compliance features such as emergency 911, lawful intercept, and number portability.

In other words, the MSC is the central hub that connects the GSM network’s base stations to the wider telephone network, enabling seamless mobility, call management, and value-added services for mobile subscribers.

The continually increasing number of mobile users and amount of data traffic lead to several key challenges for mobile switching centers.

The larger geographic spread of subscribers means that MSCs have to effectively facilitate a seamless handover between networks as subscribers move around, which is a complex process requiring constant coordination with external databases, such as the HLR and VLR.

MSC systems are also required to be highly reliable to ensure subscribers have uninterrupted service availability. MSC systems must also have robust security measures to address vulnerabilities, such as call interception and unauthorized network access. Moreover, MSCs are still adapting to the transition to 5G cellular networks that use new architecture.  These challenges force telecommunications operators to be creative as they build and scale MSCs.

In addition to the technological evolution of MSCs, other key challenges revolve around the operational complexities of the supporting data center infrastructure and the broader industry-wide issues around sustainability, networking, and talent acquisition and retention.

Both MSCs and data centers are vital to their respective ecosystems, but they play different roles. MSCs focus on mobile network operations, while data centers are general-purpose facilities that store and manage computing resources.

Other differences include the type of network connectivity they engage in and offer. MSCs connect and integrate with a mobile network, while data centers connect to and manage internal network infrastructure and physical architecture. MSCs are specifically designed network elements of both hardware and software, whereas data centers use general supplies like cooling systems and power.

Mobile switching centers are vital for GSM or CDMA cellular network functionality and security because of the role MSCs play in voice call routing and switching, billing, threat monitoring, and other important operations. There are several specialized types of MSCs, each with distinct roles in the architecture of a mobile network. As mobile traffic grows, MSCs face challenges related to scalability, reliability, security, and integration with newer technologies such as 5G.