Interworking Control for IMS-CS Media Composition Changes
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Solution Overview
Problem
Current communication systems face challenges in seamlessly changing the media composition of multimedia calls, particularly when one party's network is incapable of handling such changes, leading to user discomfort and potential disruptions during multimedia or video calls between IMS and CS networks.
Innovation Solution
An interworking control mechanism is implemented using a Media Gateway Control Function (MGCF) to determine the capabilities of each network leg, generate information elements to inform parties about unsupported media composition changes, and prevent such changes from occurring, while maintaining communication quality and user awareness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If media composition change is allowed during ongoing session, then communication flexibility is improved, but system reliability deteriorates when one party's network cannot support the change
Solution Approach 1:
The system performs preliminary capability assessment during session establishment by exchanging capability indication information between networks. This allows the system to determine in advance whether media composition changes are supported, preventing unreliable changes before they occur and maintaining session stability while preserving flexibility where supported.
Solution Approach 2:
The system implements feedback mechanisms where capability indication information is exchanged between IMS and CS networks during session establishment. This feedback loop allows each network to inform the other of its media composition change capabilities, enabling informed decisions about whether to allow such changes during the session, thus resolving the contradiction between flexibility and reliability.
2Reliability
If media composition change is prevented when unsupported, then session stability is improved, but communication flexibility deteriorates
Solution Approach 1:
The system applies local quality by treating different network segments differently based on their capabilities. The IMS network, which supports media composition changes, is granted this flexibility, while the CS network, which does not support such changes, maintains session stability. This localized approach allows flexibility where available while preserving reliability where needed.
Solution Approach 2:
The system changes the parameter of media composition flexibility based on network capability. When the CS network is involved, media composition changes are prevented (parameter set to fixed). When only IMS networks are involved, media composition changes are allowed (parameter set to flexible). This dynamic parameter adjustment resolves the contradiction by adapting the system behavior to local capabilities.
3Reliability
If capability indication information is exchanged during session establishment, then interworking control is improved, but signaling complexity increases
Solution Approach 1:
The system uses universal SIP signaling mechanisms that already exist in the IMS architecture to convey capability indication information. By leveraging existing multi-functional SIP protocols for both call setup and capability exchange, the system improves interworking control without significantly increasing signaling complexity, as the same signaling framework serves multiple purposes.
Data Source
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AI summary
An interworking control mechanism for a communication connection between at least two parties located in different networks provides the following functions: a parameter may be added in a signalling towards one party, which interprets the parameter and shows/indicates a message to the user that a media composition change is not possible and thus prevented even if it would be instructed; otherwise, an announcement is sent from the network to the other party being incapable to execute the media composition change to inform the user about the dropping of a media stream; and a negotiation between the network and the terminal device of the party being incapable to execute the media composition change is initiated in order to modify the remaining session streams, such as to rearrange the available bandwidth and possibly to change a codec to a better one.