WTRU Timer for Expedited Emergency CSFB in Congested Networks
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Solution Overview
Problem
The conventional Circuit Switched (CS) Fallback (CSFB) call establishment procedure in an evolved packet system (EPS) is inefficient, particularly when the CS domain is congested, leading to unnecessary waiting times for users and delayed emergency calls due to the lack of expedited handling mechanisms.
Innovation Solution
A method and apparatus that manage CS service request messages by activating a timer in the wireless transmit/receive unit (WTRU) based on service reject messages, allowing immediate retry for emergency calls and deactivating the timer upon receipt of a mobile terminated (MT) CS call page, thereby expediting CSFB procedures during network congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timer is activated in the WTRU based on service reject messages to control CS service requests during network congestion, then network congestion is managed and unnecessary service requests are reduced, but waiting time for users increases and emergency calls are delayed
Solution Approach 1:
The patent applies different quality of service treatments to different types of service requests. Normal CS service requests are blocked during congestion by the timer mechanism, while emergency service requests are allowed to proceed without restriction. This local differentiation resolves the contradiction by protecting network resources from non-critical traffic while ensuring critical emergency calls can still access the network immediately.
Solution Approach 2:
The system dynamically adjusts its behavior based on the type of service request. The timer mechanism is selectively applied - activated for normal services to manage congestion, but effectively deactivated or bypassed for emergency services. This dynamic adjustment allows the system to maintain congestion control while providing expedited handling for time-critical emergency calls.
2Loss of time
If the timer is deactivated upon receipt of an MT CS call page, then emergency call handling is expedited and waiting time is reduced, but the congestion control mechanism is weakened
Solution Approach 1:
The system performs preliminary identification of emergency service requests before applying congestion control. By detecting the nature of the service request (emergency vs. normal) at the point of receipt, the system can take preliminary action to exempt emergency calls from timer-based blocking while maintaining congestion control for other services. This preliminary differentiation resolves the contradiction between expedited emergency handling and overall congestion management.
Data Source
AI summary
Methods and apparatus for transmitting extended service request messages in a congested network are described. An apparatus includes a timer, a receiver and a processor. The receiver receives a message that includes a timer value. The processor sets the timer based on the timer value, activates the timer, and attempts mobile-originated circuit switched fallback for an emergency call during a period that corresponds to the timer value and during which mobile-originated circuit switched fallback is otherwise prohibited.