Location Area Update for Wireless Reachability
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Solution Overview
Problem
In wireless communication systems, particularly in 3GPP LTE networks, there is a technical challenge where a UE becomes unreachable when CS paging is initiated due to the PS MM backoff timer running, preventing the UE from performing a successful RAU procedure, leading to issues with CS fallback and location area updates across different radio access networks.
Innovation Solution
The solution involves performing a Location Area Update (LAU) operation even when the old and new Location Area Identities (LAI) are identical, and the PS MM backoff timer is running, ensuring that UE information is updated in the VLR via the LAU procedure, and disabling LTE capability in specific scenarios to handle CS emergency calls effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PS MM backoff timer is running to prevent excessive PS domain signaling, then signaling reduction is achieved, but the UE becomes unreachable for CS paging and cannot perform RAU procedure
Solution Approach 1:
The patent segments the location update procedure into two independent parts: LAU (Location Area Update) for CS domain and RAU (Routing Area Update) for PS domain. By allowing LAU to proceed independently even when PS MM backoff timer is running, the system enables CS domain reachability without triggering PS domain signaling, thus resolving the contradiction between signaling reduction and UE reachability.
Solution Approach 2:
The patent introduces a new indicator parameter (laUpdateIndicator) that acts as an intermediary to coordinate between CS and PS domains. This indicator allows the network to track whether LAU has been performed, enabling proper handling of CS paging scenarios without interfering with the PS MM backoff timer mechanism.
2Loss of time
If the UE performs normal RAU procedure only when old and new LAI differ, then unnecessary updates are avoided, but UE information is not updated in VLR when LAI remains identical
Solution Approach 1:
The patent performs LAU as a preliminary action before CS paging can occur, ensuring that the VLR has up-to-date UE location information. By checking the laUpdateIndicator and performing LAU when needed (even with identical LAI), the system proactively ensures information freshness in the VLR, preventing information loss while avoiding unnecessary updates through the indicator mechanism.
3Speed
If LTE capability is always enabled for seamless mobility, then mobility performance is improved, but CS emergency call handling becomes complex in specific scenarios
Solution Approach 1:
The patent dynamically adjusts LTE capability based on operational context. By disabling LTE capability in specific scenarios (identified through the laUpdateIndicator and CS paging conditions), the system simplifies CS emergency call handling while maintaining high mobility performance in normal conditions. This dynamic adjustment resolves the contradiction by adapting the system behavior to specific operational needs.
Data Source
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AI summary
The technical features of this document provide a method and wireless apparatus for performing UE's location area update in a communication system comprising two different radio access network (e.g., E-UTRAN and GERAN/UTRAN). In the communication system, various entities such as MME, VLR, RNC and VLR are included. This document provides a condition when a location area update (LAU) procedure is initiated. In particular, the LAU is performed when the UE which has first performed a combined TAU to the MME and VLR moves from an E-UTRAN cell to a GERAN/UTRAN cell both belonging to a same location area (LA).