Configurable Timer Handling for MT CSFB Call Setup
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Solution Overview
Problem
The existing handling of timer expiry during extended service request procedures for mobile terminating (MT) CSFB calls in wireless communication systems leads to unnecessary call drops and reduced success rates due to mismatched timer values between the UE and the MSC/VLR, causing premature abortion of CS fallback procedures.
Innovation Solution
Implementing a configurable timer Ts14 at the MSC/VLR and allowing the UE to use a shorter value for T3417ext, with coordinated configuration via Non-Access Stratum (NAS) signaling, ensuring the UE attempts GERAN or UTRAN selection upon T3417ext expiry, and setting T3417ext to Ts14 minus an offset to account for signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE uses a longer timer T3417ext to wait for network redirection or handover, then the call setup time increases, but the call success rate improves because the network has more time to buffer the MT call
Solution Approach 1:
The patent changes the timer parameter T3417ext from a fixed value to a configurable value that can be adjusted based on network conditions. The network can signal different timer values to the UE through NAS signaling, allowing optimization between call setup time and call success rate depending on the specific scenario
Solution Approach 2:
The patent introduces dynamic timer adjustment where the UE adapts its timer value based on network signaling. Instead of using a static timer, the system dynamically selects appropriate timer values to match network buffering capabilities and call priorities
2Reliability
If the network buffers the MT call for a longer time, then the call success rate improves, but the network resources are occupied for longer periods
Solution Approach 1:
The patent enables dynamic adjustment of the buffering duration parameter at the network side. By signaling different timer values to the UE, the network effectively controls how long it needs to buffer calls, optimizing resource usage while maintaining call success rates
3Loss of time
If the UE autonomously selects GERAN or UTRAN immediately upon timer expiry, then the call setup time decreases, but the call success rate deteriorates because the network may have already released the buffered call
Solution Approach 1:
The patent applies preliminary action by having the UE prepare for autonomous selection in advance. The network signals the appropriate timer value beforehand, so when the timer expires, the UE is already prepared to immediately select GERAN or UTRAN without delay, while the network knows the call is still buffered for that duration
Data Source
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AI summary
Apparatuses and computer-readable storage media for handling timers for mobile terminated circuit-switched fallback (MT CSFB) calls. An apparatus for a user equipment (UE) includes processing circuitry operably coupled to a data storage device. The data storage device is configured to store a value of an extended service request for mobile terminated services (EXT-MT) timer. The value of the EXT-MT timer is less than a value of a guard timer of a Visitor Location Register (VLR). The processing circuitry is configured to start the EXT-MT timer and generate an extended service request message to be transmitted to a Mobility Management Entity (MME) responsive to a paging for an MT CSFB call, and attempt to select a radio access technology of a different type of network if the EXT-MT timer expires before the UE successfully performs inter system change and a circuit switched fallback cancellation request was not received from a subscriber.