MSC/VLR Supervision for CSFB Call Completion
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Solution Overview
Problem
Current mobile terminating call handling during circuit switched fallback (CSFB) in 4G to 2G/3G networks results in network resource wastage and low successful connection probabilities due to inefficient resource management and failure handling.
Innovation Solution
Implementing supervision of the CSFB internetwork change at the Mobile Switching Centre / Visitor Location Register (MSC/VLR) to monitor and manage the completion of the change, including monitoring connection requests and initiating paging to ensure timely resource release and re-attempts, thereby improving call completion rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the awaiting address complete timer T7 is set to a long duration (20-30 seconds) to allow completion of CSFB steps, then the probability of successful call connection is improved, but network resources are blocked for unnecessarily long time
Solution Approach 1:
The MSC/VLR initiates paging procedures and monitors for connection requests before the T7 timer expires. By performing preliminary actions to establish the connection or detect failure early, the system can release resources promptly while still giving the mobile terminal sufficient opportunity to complete the CSFB procedure, thus resolving the contradiction between maintaining high connection success probability and reducing resource blocking time
Solution Approach 2:
The MSC/VLR actively monitors the radio access network for connection requests from the mobile terminal and uses this feedback to determine whether to continue waiting or release resources early. This feedback mechanism allows the system to adapt the resource holding time based on actual connection progress rather than relying solely on a fixed long timer, thereby improving both connection success and resource efficiency
2Productivity
If the MSC/VLR monitors receipt of connection request for a short period, then network resource usage is optimized, but the likelihood of detecting failed CSFB and initiating re-attempts is reduced
Solution Approach 1:
The MSC/VLR performs preliminary paging actions and begins monitoring for connection requests immediately after initiating CSFB, rather than waiting for the full T7 timer duration. This preliminary action allows early detection of connection failures and prompt initiation of re-attempts or alternative procedures, maintaining high call completion rates while enabling faster resource release when connections fail
Solution Approach 2:
The monitoring duration is made dynamic rather than fixed - the MSC/VLR continues monitoring for connection requests only as long as necessary to detect failure, then transitions to resource release or re-attempt procedures. This dynamic approach allows the system to adapt the monitoring period to actual connection outcomes, optimizing both resource turnover and call completion rates
Data Source
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AI summary
The present invention relates to a method of improving mobile terminating call handling in a change of a receiving mobile terminal (UE) from a first network to a second network, wherein the change is carried out as circuit switched fallback (CSFB) from the first network not providing circuit switched (CS) domain services to the second network providing circuit switched (CS) domain services. The method is characterized in that the Mobile Switching Centre / Visitor Location Register (MSC / VLR) of the second network supervises completion of the circuit switched fallback (CSFB) internetwork change to the second network.