SSC Modes – Session and Service Continuity in 5G

SSC, or Session and Service Continuity, in 5G refers to the ability of a mobile network to maintain an ongoing session or service for a user as they move between different access networks or across different generations of mobile technology. SSC is crucial for providing a seamless experience for users, allowing them to switch between various access technologies, such as 5G, LTE, and Wi-Fi, without interrupting their ongoing sessions or services.

SSC involves different modes to address various scenarios and ensure continuity. Here are the key SSC modes in 5G:

1. Redirection Mode:
   • Scenario: When a user moves from one access network to another (e.g., from 5G to LTE or vice versa), and the target network supports SSC.
   • Description:
     • The source network informs the target network about the ongoing session/service of the user.
     • The target network takes over the control of the session or service, allowing continuity without interruption.
     • This mode is suitable when the target network supports the same or higher capabilities compared to the source network.
2. Handover Mode:
   • Scenario: When a user moves from one access network to another, and the target network does not support SSC.
   • Description:
     • The source network transfers the ongoing session or service to the target network.
     • The target network may not be aware of the ongoing session or service initially, but it accepts and continues the session.
     • This mode is suitable when the target network does not support SSC or has lower capabilities.
3. Session Continuity Mode:
   • Scenario: When a user moves between different access networks within the same system (e.g., between 5G cells).
   • Description:
     • The user's session or service is maintained seamlessly as they move within the same system.
     • There is no need for explicit handover or redirection procedures between different access networks within the same system.
4. Local IP Access Mode:
   • Scenario: When a user moves to a new location, and the network supports local IP access.
   • Description:
     • The user's IP address is retained, even if they move to a new location served by a different access network.
     • Local IP access enables the continuity of the IP address and associated services, even when the user changes locations.
5. Inter-RAT (Radio Access Technology) Handover Mode:
   • Scenario: When a user moves between different generations of mobile technology (e.g., 5G to LTE).
   • Description:
     • The handover process involves transitioning the user's ongoing session or service from one radio access technology to another.
     • This ensures seamless connectivity for the user, even when moving across different generations of mobile networks.

These SSC modes collectively enable the continuity of user sessions and services in diverse scenarios, contributing to a more reliable and seamless user experience as they move across different access networks and technologies within the 5G ecosystem. The choice of the specific mode depends on the capabilities of the source and target networks and the specific scenario in which the user is transitioning.