MSC Server Handover Failure Recovery via Session Transfer Feedback
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Solution Overview
Problem
During single radio voice call continuity procedures, the failure of voice media switching from packet switched to circuit switched in the mobile switching center server leads to unsuccessful handovers, as the session transfer number update fails, causing users to be handed back to LTE without a functional circuit switched connection.
Innovation Solution
A method where the mobile switching center server and mobility management entity handle handover requests by receiving notifications of failure from the IP multimedia subsystem, sending negative responses to initiate error handling, and preventing further handover attempts by updating session transfer numbers and releasing reserved resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mobile switching center server sends a positive handover response based on successful circuit switched bearer reservation, then handover is triggered, but the session transfer fails due to incorrect session transfer number
Solution Approach 1:
The mobile switching center server implements feedback by monitoring the result of session transfer operations. When session transfer fails, the server detects this failure state and sends a negative handover response to the mobility management entity, preventing repeated failed handovers and allowing the system to recover by updating the session transfer number.
Solution Approach 2:
The system performs preliminary verification by checking session transfer status before finalizing the handover response. The mobile switching center server determines the handover response based on both bearer reservation success and session transfer status, ensuring that handover only proceeds when both conditions are favorable.
2Productivity
If the mobile switching center server continuously attempts handover without detecting session transfer failure, then handover retries occur, but resources are wasted and service continuity is compromised
Solution Approach 1:
The mobile switching center server uses feedback from session transfer results to control handover retry behavior. When session transfer failure is detected, the server sends a negative response and prevents further handover attempts until the session transfer number is updated, thereby avoiding continuous resource consumption from futile retries.
Solution Approach 2:
The system implements self-service by automatically detecting session transfer failures and triggering appropriate error handling procedures. The mobile switching center server autonomously determines when to send negative responses and when to allow handover retries, eliminating the need for external intervention to prevent resource waste.
Data Source
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AI summary
A scenario may arise in which a circuit switched (CS) bearer reservation is successful but a voice media switching from packet switched (PS) to CS performed by a mobile switching center (MSC) server fails. Certain embodiments provides systems, apparatuses, and methods for recovery from such a scenario. A method, for example, can include determining whether session transfer of a user equipment is possible in response to a request from a network element to initiate session transfer of the user equipment and reporting to the requesting network element either a generic or specific indication that the transfer is not possible, when it is determined that the session transfer is not possible.