IMS Access Domain Selection via Stored Indicators
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Solution Overview
Problem
Current Access Domain Selection (ADS) mechanisms in IMS networks face challenges when handling Circuit Switched (CS) access networks, leading to incorrect routing of SIP INVITE requests, especially when both CS and Packet Switched (PS) access networks are registered, resulting in failed calls due to inability to exclusively route to the correct access domain.
Innovation Solution
The introduction of an access domain indicator, such as a Feature Tag or Globally Routable User Agent URL (GRUU), is used by the Call Session Control Function (CSCF) to instruct the ADS function to select the appropriate access domain for routing SIP messages, preventing incorrect routing by modifying headers or URIs in INVITE messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both CS and PS access networks are registered in the IMS network, then the user can access services through multiple access domains, but incorrect routing of SIP INVITE requests occurs leading to failed calls
Solution Approach 1:
The patent applies preliminary action by storing access domain indicators (such as Feature Tags or GRUU) in the user profile during the registration phase. When a user registers with the IMS network, the CSCF retrieves and stores the access domain indicator associated with the user's contact address. This pre-stored information is then used by the ADS function to make accurate routing decisions later, preventing the routing ambiguity that would otherwise occur when both CS and PS access networks are registered.
2Productivity
If the ADS function selects the wrong access domain, then routing efficiency is reduced, but call delivery fails completely
Solution Approach 1:
The patent introduces an intermediary mechanism by using access domain indicators (Feature Tags or GRUU) as mediators between the user's multiple contact addresses and the correct access domain. The ADS function uses these indicators to identify which contact address corresponds to the currently active access domain. This intermediary information allows the system to efficiently and accurately route SIP INVITE requests to the correct access domain without trial-and-error attempts, ensuring both routing efficiency and call delivery success.
3Device complexity
If access domain selection is made without specific indicators, then the system remains simple, but routing accuracy deteriorates when multiple access domains are registered
Solution Approach 1:
The patent applies parameter changes by introducing access domain indicators (Feature Tags or GRUU) as additional parameters in the user profile and SIP signaling. These parameters encode information about the user's preferred or currently active access domain. The ADS function queries these parameters to make routing decisions. This approach maintains relative system simplicity while dramatically improving access domain identification accuracy, as the indicators provide explicit guidance without requiring complex analysis of multiple contact addresses.
Data Source
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AI summary
A method and apparatus for managing access domain selection for a user device accessing an IP Multimedia Subsystem (IMS) network. A Call Session Control Function (CSCF) in the IMS network stores an access domain indicator associated with a user s contact address. The access domain indicator is associated with the user s contact address when the user registers with the IMS network. The CSCF sends the access domain indicator to an Access Domain Selection (ADS) function in the IMS network, the access domain indicator to be used by the ADS function in selecting an access domain. This allows the ADS function to select the correct access domain to use when sending messages to the user device.