Session Adding for CSI to IMS Interworking
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Solution Overview
Problem
CSI terminals lack the capability to initiate multimedia sessions with IMS terminals during interworking due to limitations in bearing real-time media in IMS sessions, preventing simultaneous handling of real-time and non-real-time media in a single IMS session.
Innovation Solution
An interworking control function entity correlates and matches existing sessions, allowing a CSI terminal to initiate a second session by adding media components to existing IMS sessions, using GRUU information to route requests and merge sessions, enabling multimedia session initiation across CSI and IMS terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CSI terminal uses CS domain to establish real-time voice session, then QoS requirements are met, but the terminal cannot initiate multimedia sessions with IMS terminals
Solution Approach 1:
The session request is segmented into separate real-time media components and non-real-time media components. The interworking control function entity processes each component independently, allowing real-time voice to use CS domain while other media use IMS domain, thus resolving the contradiction between QoS requirements and multimedia session capability
Solution Approach 2:
The interworking control function entity acts as an intermediary between the CSI terminal and IMS network. It receives session requests, determines the terminal type, and coordinates the establishment of both CS and IMS sessions, enabling multimedia session initiation while maintaining QoS for real-time voice through the mediator's control
2Ease of operation
If an IMS session is established directly between IMS UE and CSI UE, then session establishment is simple, but the CSI UE cannot handle real-time media in IMS session due to bearing capability limitations
Solution Approach 1:
The session is segmented into real-time media components handled by CS domain and non-real-time media components handled by IMS domain. The interworking control function entity splits the session request and establishes appropriate bearers for each component, maintaining simplicity while enabling real-time media handling
Solution Approach 2:
The solution moves from a single-domain (IMS) approach to a multi-dimensional approach by introducing CS domain for real-time media while keeping IMS for non-real-time media. This dimensional expansion allows the system to handle both real-time and non-real-time media simultaneously
3Adaptability or versatility
If the CSI terminal initiates a second session to the same terminal, then multimedia session capability is achieved, but session management complexity increases
Solution Approach 1:
Multiple sessions (first IMS session and second session for additional media) are merged into a unified session managed by the interworking control function entity. The entity correlates and matches sessions, combining them into a single coordinated session that provides multimedia capability while managing complexity centrally
Data Source
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AI summary
A method for session adding during interworking between a CSI terminal and an IMS terminal in a packet network is disclosed, which includes the following steps: a calling terminal initiating a session request to a called terminal, and a home domain S-CSCF of the called terminal forwarding the session request to a interworking control function entity in the local domain which controls the interworking; the interworking control function entity correlating and matching the existing sessions after receiving the session request; and performing session adding operation according to a result of the correlating and matching. Further disclosed are an apparatus for session adding, and a packet network system for the session adding. In the embodiments of the invention, a second session initiated by the calling terminal may be terminated on the same terminal as the first session; or, the first session initiated by the calling terminal and the existing original first session may be merged into an IMS session on the Called Network side, and the IMS session may be terminated to a called terminal. By using the invention, a CSI terminal may initiate a multimedia session to an opposite IMS terminal.