Inter-RAT RLF Report Correlation for Mobility Optimization
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Solution Overview
Problem
In 3GPP networks, there is no effective way to correlate radio link failure (RLF) reports with the UE context of the previous serving cell, leading to double bookkeeping and unreliable mobility optimization, especially when UE transitions between different Radio Access Technologies (RATs), causing incorrect self-optimization actions and delayed reporting due to limited base station memory.
Innovation Solution
A method is proposed to correlate failure event reports by using correlation information, such as the previous Cell Radio Network Temporary ID (C-RNTI) or RACH preamble and timing information, to identify the UE and avoid double bookkeeping, even when UE transitions between cells or RATs, ensuring accurate mobility optimization and efficient reporting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network uses X2 RLF indication procedure to notify the eNB of the previous UE serving cell after successful re-establishment, then the network can perform accounting based on this indication for mobility optimization, but there is no way to correlate the subsequent RLF report with the UE context in the previous serving cell, leading to double bookkeeping
Solution Approach 1:
The patent introduces correlation information as an intermediary element that bridges the RLF report and the UE context in the previous serving cell. This correlation information is included in the RLF report message, enabling the network to match the report with the correct UE context without double bookkeeping, thus resolving the information loss problem while maintaining reliability
Solution Approach 2:
The patent applies preliminary action by including correlation information in advance within the RLF report message structure. This allows the network to immediately correlate the report with the UE context upon receipt, preventing the double bookkeeping issue before it occurs and ensuring reliable mobility optimization from the start
2Quantity of substance
If statistics are updated based on both RRC re-establishment attempts and UE RLF report, then comprehensive mobility optimization data is collected, but double bookkeeping occurs making failure statistics unreliable and causing incorrect MRO actions
Solution Approach 1:
The patent implements feedback by using the correlation information in the RLF report to provide the network with feedback about which UE context the report refers to. This enables the network to update statistics only once for each actual failure event, preventing double bookkeeping while maintaining comprehensive data collection for reliable MRO decisions
3Adaptability or versatility
If the UE transmits a failure event report after transitioning to another RAT, then inter-RAT failure information is captured, but the base station may not have the UE context in memory due to limited memory and time elapsed, preventing correlation
Solution Approach 1:
The patent uses correlation information as an intermediary that enables the UE to identify itself in the failure report even when the base station no longer has the UE context in memory. This correlation information acts as a key that allows the network to retrieve or associate the correct UE context from storage, maintaining inter-RAT failure reporting capability while overcoming memory limitations
Solution Approach 2:
The patent applies preliminary action by pre-configuring the UE with correlation information that identifies the previous serving cell and UE context. This preparation ensures that when the UE transitions to another RAT and returns with a failure report, the correlation information is already available to enable proper matching with the stored UE context, preventing information loss due to memory constraints
Data Source
AI summary
A method of inter-RAT failure event report is proposed. A UE detects a failure event in a first cell served by a first base station, and the first cell belongs to a first RAT. The failure event may include a radio link failure or a handover failure. The UE then performs an RRC establishment procedure with a second cell served by a second base station, and the second cell belongs to a second RAT. After the RRC establishment, the UE transmits a failure event report to the wireless network. The failure event can be a radio link failure, or be associated with a mobility command such as a handover command. By providing more reliable information in the failure event report than a network solution could provide, inter-RAT mobility performance can be improved.