Domain Selection in IMS Terminated Calls
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Solution Overview
Problem
The existing method for domain selection during a terminated call in IMS networks generates significant signaling loads between SGSN/MME and HSS, particularly when IMS VOIP capability changes, leading to network instability and service disruptions, especially in high-user-density areas like traffic vehicles.
Innovation Solution
A method where the AS sends a query request to the HSS to obtain information about the called terminal and network from the PS domain mobility management network element, allowing the HSS to feed back IMS VOIP capability, registration time, and other relevant details, enabling the AS to select the appropriate domain for the call without continuous updates from SGSN/MME on VOIP capability changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SGSN/MME continuously updates the HSS on IMS VOIP capability changes, then the domain selection accuracy is improved, but the signaling load increases significantly
Solution Approach 1:
The patent extracts the VOIP capability indication from continuous update mechanisms and embeds it only in the location update message when the UE actually changes its location. This eliminates unnecessary continuous signaling while preserving the essential capability information needed for domain selection.
Solution Approach 2:
Instead of continuous updates, the system adopts periodic action where the VOIP capability is reported only at specific intervals - namely when the UE performs a location update. This reduces signaling frequency while maintaining necessary information availability for domain selection.
2Adaptability or versatility
If the HSS stores detailed network access information, then the domain selection capability is improved, but the system complexity increases
Solution Approach 1:
The patent extracts only the essential VOIP capability indication from the complex location update information and stores only this extracted feature in the HSS. This reduces the amount of data stored and processed while maintaining the capability to make domain selection decisions.
Solution Approach 2:
The patent applies local quality by storing different types of information in different network elements - the HSS stores only the VOIP capability indication while the MME/SGSN retains the full location update information. This distributes the information storage responsibility according to the specific needs of each network element.
3Measurement precision
If the AS queries the HSS for each terminated call, then the call routing accuracy is improved, but the call setup time increases
Solution Approach 1:
The patent applies preliminary action by pre-obtaining and storing the VOIP capability information in the HSS during location updates, before the terminated call occurs. This prepares the information in advance so that when a call comes in, the AS can quickly retrieve pre-prepared routing information without extensive real-time querying.
Solution Approach 2:
The system establishes a feedback mechanism where the AS queries the HSS for the stored VOIP capability information, and the HSS provides the pre-stored routing information. This feedback loop is optimized because the HSS already has the information ready, reducing the time needed for the query-response cycle during call setup.
Data Source
AI summary
The present application discloses a method and a system for implementing domain selection during a terminated call, in which an application server (AS) sends, according to a received call request message, a query request message to a home subscriber server (HSS); the HSS queries, according to the query request message, a packet switching (PS) domain mobility management network element to obtain information of a called terminal and/or a network accessed by the called terminal in the call request message; the HSS feeds back the obtained information of the called terminal and/or the network accessed by the called terminal to the AS; and the AS selects a domain to which a call message is to be routed according to the information of the called terminal and/or the network accessed by the called terminal.