IMS CSCF Bearer Re-establishment for VoIP Call Continuity
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Solution Overview
Problem
Existing solutions fail to establish VoIP calls between a calling UE and a called UE when dedicated data bearer setup fails due to temporary failures, especially in areas without circuit-switched access, leading to call failures.
Innovation Solution
The method involves enabling the re-establishment of a bearer between the calling UE and the gateway node over a packet-switched radio access network (PS-RAN) by the IMS Call Session Control Function (CSCF) upon notification of a temporary failure, using a list of failure cause codes to determine and retry the bearer setup, and requesting the gateway node or UE to re-establish the VoIP call.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If retry is performed via circuit-switched access after packet-switched bearer establishment failure, then call setup can be attempted through alternative access, but call continuity cannot be ensured in areas without circuit-switched coverage
Solution Approach 1:
Instead of falling back to circuit-switched access when packet-switched bearer establishment fails, the patent inverts the approach by enabling multiple retry attempts over the packet-switched access network itself. The CSCF node configures the gateway node to retry bearer establishment when temporary failures occur, eliminating the need for circuit-switched fallback and ensuring call continuity in packet-switched only areas.
2Device complexity
If immediate call failure is returned upon bearer establishment failure, then signaling overhead is reduced, but call setup success rate decreases due to temporary failures
Solution Approach 1:
The patent applies preliminary action by pre-configuring retry parameters and failure cause code lists at the CSCF node before bearer establishment attempts. When temporary failures occur, the gateway node automatically retries based on these pre-configured parameters, avoiding the need for complex real-time signaling decisions and reducing overall signaling overhead while improving call setup success rates.
3Reliability
If multiple retry attempts are enabled for bearer establishment, then call setup success rate improves for temporary failures, but signaling overhead and network load increase
Solution Approach 1:
The patent implements partial action by enabling retry attempts only for specific temporary failure scenarios identified through failure cause code lists. The CSCF node configures which failure codes should trigger retries, allowing selective retry behavior that balances call setup success rate improvement with controlled signaling overhead, avoiding excessive retries for all failure types.
Data Source
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AI summary
A method of establishing a Voice over Internet Protocol, VoI P, call between a calling User Equipment, UE, and a called UE, wherein said calling UE is served by a core network via a packet-switched radio access network, PS-RAN, and wherein a bearer is to be established between said calling U E and a gateway node in said core network, over said PS-RAN, for obtaining access to an Internet Protocol, IP, multimedia subsystem, I MS, network, wherein said method comprises the steps receiving, by a an IMS Call Session Control Function, CSCF, node a notification message thereby notifying said I MS node that said VoIP call establishment is in progress and initiating, by said I MS CSCF, re-establishment of said bearer between said calling UE and said gateway node, over said PS-RAN, in case said establishment of said bearer has failed due to a temporary failure.