SRVCC Call Transfer Handling for Multiple IMS Calls
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE networks, the existing Single Radio Voice Call Continuity (SRVCC) technology lacks clear guidelines for handling multiple IP Multimedia System (IMS) calls during handover procedures, leading to ambiguity in selecting calls for switching and determining transaction identifier (TI) values, which affects correct call retrieval after handover.
Innovation Solution
A method for handling call transferring in SRVCC procedures involves switching multiple IMS calls to corresponding circuit-switched (CS) calls and setting appropriate transaction identifier values based on received handover commands, ensuring clear identification and management of active and inactive calls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple IMS calls are switched to CS calls during SRVCC handover, then call continuity is maintained, but ambiguity arises in determining transaction identifier values for each CS call
Solution Approach 1:
The patent segments the handling of multiple IMS calls by assigning distinct transaction identifier values to each individual CS call. Instead of using a single TI value for all calls, the system divides the identification task into separate segments, with each CS call receiving its own unique TI value derived from the corresponding IMS call identity. This segmentation eliminates ambiguity in TI assignment while maintaining call continuity.
Solution Approach 2:
The patent applies preliminary action by determining and assigning transaction identifier values before the CS calls are fully established. The UE derives TI values from IMS call identity values in advance, and includes these predetermined TI values in the handover confirmation message sent to the network. This preliminary assignment ensures that TI values are already determined and unambiguous when the CS calls are established, preventing information loss.
2Loss of information
If transaction identifier values are not consistently determined, then call switching becomes ambiguous, but implementing consistent determination requires additional signaling overhead
Solution Approach 1:
The patent implements self-service by enabling the UE to autonomously derive transaction identifier values from its own stored IMS call identity values without requiring additional network signaling. The UE independently determines TI values based on the correspondence between IMS calls and CS calls, then includes these self-determined TI values in the handover confirmation message. This self-service approach eliminates information loss while avoiding the need for complex additional signaling procedures.
3Reliability
If held calls are not properly retrieved after handover, then call management fails, but proper retrieval requires clear TI value assignment
Solution Approach 1:
The patent applies local quality by assigning different transaction identifier values to different call states (active vs. held calls). Each CS call receives a TI value that is locally optimized for its specific state, allowing the network to properly distinguish and retrieve held calls after handover. The TI value assignment is tailored to the local characteristics of each call rather than using a uniform approach, ensuring reliable call retrieval while maintaining clear call state information.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method of handling call transferring for a communication device during a SRVCC handover procedure is disclosed. The method comprise switching a plurality of IP Multimedia System (IMS) calls to a plurality of corresponding circuit-switched (CS) calls according to reception of a handover command when a mobile device has the plurality of IMS calls; and setting a plurality of transaction identifier (TI) values for each of the plurality of corresponding CS calls according to the plurality of IMS calls. The plurality of IMS calls share a packet switched (PS) configuration. Alternatively, the mobile device and the network may set the TI values according to the commands which include TI values for each of the CS calls. Alternatively, the mobile device and the network may only switch the active IMS call to the CS call or not even initiate the SRVCC handover procedure when the mobile device has multiple IMS calls with the network.