LTE Tracking Area Update Reject Delay Reduction
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Solution Overview
Problem
In LTE network transitions, when multi-radio user equipment (UE) moves and lacks a Packet Data Protocol (PDP) context, the tracking area update (TAU) is rejected, leading to a delay in service due to the RRC connection release and subsequent failed attach procedure, causing a greater than 10-second delay in obtaining network service.
Innovation Solution
The UE notifies the Non-Access Stratum (NAS) of the ongoing RRC release, places it in a hold status, and only initiates an attach request after the RRC release is complete, avoiding the activation of the NAS attach retry timer and reducing the delay by ensuring the RRC connection is fully released before attempting re-establishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE immediately initiates an attach procedure after receiving RRC release message, then the attach attempt can be made quickly, but the NAS attach retry timer is activated causing a 10 second delay
Solution Approach 1:
The patent applies preliminary action by having the UE wait for the RRC release to complete before initiating the attach procedure. The RRC layer notifies the NAS layer about the ongoing release, and the NAS layer delays attach until notified that release is complete. This preliminary sequencing prevents the premature attach attempt that would trigger the 10-second retry timer, thereby resolving the contradiction between quick initiation and actual service acquisition time.
2Reliability
If the RRC connection is released with a 60 ms delay for RLC ACK, then the network can properly release UE contexts, but the overall service restoration time increases
Solution Approach 1:
The patent implements feedback by establishing a notification mechanism where the RRC layer informs the NAS layer about the status of RRC release. The NAS layer receives feedback about when the release is complete and adjusts its attach procedure timing accordingly. This feedback loop ensures that the 60 ms delay for reliable context release is properly coordinated with the attach procedure, preventing unnecessary delays while maintaining reliability.
Data Source
AI summary
A method, apparatus and computer program product are described for reducing delay when making a network connection between user equipment (UE) and a network node when a tracking area update (TAU) request has been denied during LTE reselection. Following a revised signaling protocol, a UE can avoid activation of a NAS Attach Retry timer and move directly to establishing a connection to the network, reducing the UE communications delay from about eleven seconds to less than one second.