IMS Domain Selection for Voice and AV Calls
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Solution Overview
Problem
The existing mobile communication systems face challenges in selecting the appropriate domain for transferring terminating signals for both voice and audio/video (AV) communications, particularly when AV communication via IMS is not supported in E-UTRAN cells, leading to the need for CSFB (Circuit Switch Fallback) and inability to select a suitable domain for AV communication.
Innovation Solution
A mobile communication method and application server apparatus that include a call session control server and an application server, which receive terminating signals with call-type information, send inquiry signals to a subscriber management server, and determine the appropriate domain for signal transfer based on this information, ensuring proper routing for both voice and AV communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the mobile communication system uses the existing T-ADS mechanism for domain selection, then voice communication can be provided to UE in both UTRAN/GERAN and E-UTRAN, but the IMS cannot select a domain for AV communication when it is not supported in E-UTRAN cells
Solution Approach 1:
The patent segments the domain selection process by introducing separate handling mechanisms for voice communication and AV communication. The SCC-AS performs different domain selection operations depending on the communication type, allowing voice to use existing T-ADS while AV communication gets specialized CSFB-based domain selection when E-UTRAN AV support is unavailable
Solution Approach 2:
The patent applies preliminary action by having the SCC-AS determine AV communication capability in E-UTRAN cells before attempting domain selection. This advance determination allows the system to proactively select CSFB domain for AV communication when needed, preventing service failure
2Ease of operation
If AV communication via IMS is not supported in E-UTRAN cells, then CSFB must be used for AV communication, but the IMS cannot automatically select the appropriate domain for AV terminating signals
Solution Approach 1:
The patent implements feedback by having the SCC-AS send inquiry signals to the HSS to obtain AV communication capability information for E-UTRAN cells. This feedback mechanism enables the SCC-AS to make informed domain selection decisions based on actual network capabilities rather than making selections blind to service availability
Solution Approach 2:
The patent introduces the SCC-AS as an intermediary between the IMS and the domain selection process. The SCC-AS receives terminating signals from the S-CSCF, determines the appropriate domain based on call-type information and HSS feedback, and then routes signals to the correct domain, thereby enabling automatic domain selection for AV communication
3Reliability
If the terminating signal does not include call-type information, then the IMS cannot differentiate between voice and AV communication, but adding call-type information increases signaling complexity
Solution Approach 1:
The patent applies universality by using a multi-functional existing signaling structure. The terminating signal leverages existing information elements that can serve multiple purposes - the same signal structure handles both voice and AV communication by interpreting existing fields differently based on the communication type, rather than creating entirely separate signaling paths
Data Source
AI summary
A mobile communication method according to the present invention includes the steps of: when an S-CSCF in an IMS receives a terminating signal directed to a UE, sending the terminating signal from the S-CSCF to an SCC-AS in the IMS, the terminating signal including call-type information indicating whether the terminating signal is for voice communication or AV communication; sending an inquiry signal including the call-type information from the SCC-AS to an HSS; and determining, by the SCC-AS, a domain to which the terminating signal is to be transferred, based on the call-type information and a response signal received from the HSS as a response to the inquiry signal.