In 5G networks, there isn’t a direct interface between the Mobility Management Entity (MME) and the Mobile Switching Center (MSC) as found in earlier generation networks like 2G and 3G. The architecture of 5G has evolved, and the roles traditionally performed by separate entities, such as the MME and MSC, are distributed across various elements within the 5G core network. Instead of a direct interface, the interaction between these functions is handled through the Service Management (SM) interface, the Session Management (SESM) function, and other elements within the 5G core. Here’s a detailed explanation:
- Mobility Management Entity (MME) Overview:
- The MME is a key element in the 5G core network responsible for mobility management, session management, and control plane functionalities. It handles tasks such as authentication, tracking area management, and connection establishment for User Equipment (UE).
- Mobile Switching Center (MSC) Overview:
- In traditional mobile networks like GSM and UMTS, the MSC is a central component responsible for call control, switching, and connection to the Public Switched Telephone Network (PSTN). However, in 5G, voice services are primarily handled over the IP-based IMS (IP Multimedia Subsystem) and not directly through the MSC.
- Evolution to 5G Core Network:
- In 5G, the core network architecture has evolved, and functions traditionally associated with separate entities have been distributed across various elements. Voice services in 5G are typically handled through the IMS, and the role of the MSC has transformed.
- Service Management (SM) Interface:
- The interaction between the MME and elements handling voice services, which may include IMS, is facilitated through the Service Management (SM) interface. The SM interface supports the exchange of information related to service management and session handling.
- Session Management (SESM) Function:
- The Session Management (SESM) function within the 5G core network plays a crucial role in managing sessions, including voice sessions. It interacts with the MME and other relevant functions to ensure seamless session establishment and management.
- IMS for Voice Services:
- Voice services in 5G are primarily handled through the IMS. The IMS supports IP-based voice services, allowing for the delivery of voice over the same infrastructure used for data services. This aligns with the trend toward an all-IP network architecture.
- Call Control in IMS:
- Call control functions, traditionally associated with the MSC in older networks, are now handled within the IMS in 5G. The IMS manages the setup, modification, and release of voice sessions, as well as supplementary services like call waiting and call forwarding.
- Interworking with Legacy Networks:
- While 5G networks transition to IMS-based voice services, there is still a need for interworking with legacy networks, especially during the early phases of 5G deployment. This interworking is managed through interfaces and gateways that facilitate communication between 5G and legacy network elements.
- Evolved Packet System (EPS) Bearer Handling:
- The MME is responsible for handling the establishment and management of Evolved Packet System (EPS) bearers, which carry user data. The interaction between the MME and IMS (or relevant functions) ensures the establishment of bearers for voice and other services.
- Security Considerations:
- Security mechanisms are implemented within the 5G core network, including the SM interface and IMS, to ensure the confidentiality, integrity, and authenticity of communication between network elements.
In summary, the interaction between the MME and the elements handling voice services, including IMS, is facilitated through the Service Management (SM) interface and other relevant components within the 5G core network. The traditional role of the MSC has evolved, and voice services are primarily managed through the IMS in alignment with the IP-based architecture of 5G.