SR-VCC Handover for Alerting State Voice Calls
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Solution Overview
Problem
Current networking technologies, such as LTE, may not provide universal coverage, leading to dropped calls during intersystem handovers from packet switched (PS) to circuit switched (CS) networks when a voice call is in an alerting state, as no procedures have been defined for Single Radio Voice Call Continuity (SR-VCC) in these scenarios.
Innovation Solution
The system detects when a user equipment device is in an alerting state during a handover from a PS network to a CS network and provides session state information to the CS network, enabling the creation of an appropriate circuit switched call state to maintain voice call continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SR-VCC procedures are implemented for active calls during intersystem handover from PS to CS network, then voice call continuity is maintained, but no procedures exist for alerting state calls resulting in call drops
Solution Approach 1:
The patent extends the SR-VCC procedure to handle multiple call states (alerting state and active state) using a unified approach. The network entity detects the call state and applies the same handover mechanism, making the procedure universally applicable to different call phases rather than requiring separate procedures for each state.
Solution Approach 2:
The patent implements preliminary detection of the alerting state before handover occurs. The network entity determines whether the UE is in an alerting state during the handover decision process, and if so, initiates the SR-VCC procedure in advance to prevent call drops before they can occur.
2Productivity
If handover from PS network to CS network occurs during alerting state, then network resource utilization is optimized, but voice calls are dropped due to lack of SR-VCC support
Solution Approach 1:
The network entity performs preliminary detection of the alerting state during the handover decision process. When the alerting state is detected, the SR-VCC procedure is initiated in advance to establish the necessary call control state before the handover completes, preventing call drops while enabling efficient resource utilization.
Solution Approach 2:
The patent implements feedback mechanisms where the network entity determines the call state based on signaling information exchanged during handover. The system uses this feedback to decide whether to apply SR-VCC procedures, ensuring reliable call continuity only when necessary while maintaining efficient resource management.
3Reliability
If SR-VCC procedure is applied to alerting state calls, then call continuity is maintained, but additional detection and notification procedures are required
Solution Approach 1:
The network entity performs the state detection and notification actions as a preliminary step during the handover decision process. By determining the alerting state and notifying the CS network entity before the actual handover execution, the procedure avoids the need for complex post-handover correction mechanisms.
Solution Approach 2:
The patent merges the state detection function with the existing handover decision logic. The determination of alerting state and the notification to the CS network entity are integrated into the standard handover procedure flow, avoiding the need for separate independent processes and reducing overall system complexity.
Data Source
AI summary
Systems, methods, apparatuses, and computer program products are provided for facilitating voice call continuity in intersystem handover. A method may include determining that a user equipment device being handed over from a packet switched network to a circuit switched network is a party to a voice call in an alerting state. The method may further include providing session state information indicating that the user equipment device is a party to a voice call in an alerting state to a network entity on the circuit switched network in response to the determination. Corresponding systems, computer program products and apparatuses are also provided.