SSC (Session and Service Continuity)

SSC, which stands for Session and Service Continuity, is a concept that refers to the uninterrupted continuation of communication sessions and services during mobility or network changes in telecommunications systems. It ensures that users can maintain ongoing connections, services, and applications even when they move between different network domains or experience disruptions in the network.

In traditional telecommunication networks, such as circuit-switched networks, the continuity of communication sessions was challenging when a user moved from one network to another. For example, when a mobile phone user moved from one cell to another, there was a high probability of call drops or service interruptions. The same issue arose when switching between different types of networks, such as from a cellular network to a Wi-Fi network.

SSC addresses these challenges by providing mechanisms and protocols that enable seamless handovers, transitions, and transfers of communication sessions and services between different network domains. It ensures that ongoing sessions and services are maintained without interruption or noticeable impact on the user experience. SSC is especially critical in the context of mobile communications, where users frequently move between different coverage areas or network technologies.

There are several key components and techniques involved in SSC:

1. Handover/Handoff: Handover is the process of transferring an ongoing communication session from one network element to another without interrupting the session. It involves coordinating the transfer of session-related information, such as IP addresses, quality of service parameters, and authentication credentials. Handovers can occur between different cells within a cellular network or between different types of networks, such as from cellular to Wi-Fi.
2. Mobility Management: Mobility management encompasses the procedures and protocols that handle the tracking, authentication, and location updates of mobile devices as they move within a network. It ensures that the network is aware of the mobile device's location and can facilitate the appropriate handover procedures when necessary.
3. Session Initiation Protocol (SIP): SIP is a signaling protocol used for initiating, modifying, and terminating communication sessions in IP networks. It plays a crucial role in SSC by allowing the transfer of session-related information during handovers. SIP enables the establishment of a new session with the target network and facilitates the transfer of ongoing sessions from the source network.
4. Seamless Vertical Handover: A vertical handover refers to the handover between different types of networks, such as cellular to Wi-Fi or Wi-Fi to satellite. Seamless vertical handover mechanisms aim to provide uninterrupted service during the transition. These mechanisms involve techniques such as pre-authentication, network discovery, and fast authentication to ensure a smooth transfer between networks.
5. Quality of Service (QoS) Management: QoS management involves maintaining and ensuring the required level of service quality for ongoing sessions during handovers. It includes mechanisms to prioritize and allocate network resources based on session requirements, such as latency, bandwidth, and reliability. QoS management is critical to maintaining a seamless user experience during network transitions.
6. Session Border Controllers (SBCs): SBCs are network elements responsible for controlling and securing communication sessions at network borders. They play a vital role in SSC by facilitating the transfer of sessions between different network domains while ensuring security and maintaining session continuity.

Overall, SSC is a fundamental concept in modern telecommunications systems that enables uninterrupted communication sessions and services during mobility or network changes. It involves a combination of protocols, techniques, and network elements to ensure seamless handovers, maintain session-related information, and manage the quality of service. SSC enhances the user experience by minimizing disruptions and allowing users to maintain ongoing sessions without interruption, regardless of their location or network changes.