Timing Advance Validation Using Delay Spread in NR Uplink
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Solution Overview
Problem
Existing methods for validating timing advance (TA) in RRC_INACTIVE state are inadequate, particularly in NR systems with beam-based operations, as RSRP-based validation does not accurately reflect UE mobility, leading to potential TA misalignment and increased block error rates and power consumption.
Innovation Solution
A UE-based TA validation method using an enhanced metric that incorporates a correction factor (Δdp) to account for the UE's current propagation conditions, ensuring that uplink transmissions remain within the cyclic prefix duration, thereby preventing inter-symbol interference and improving TA validation robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RSRP-based TA validation is used in beam-based NR systems, then the validation process is simple, but it does not accurately reflect UE mobility leading to TA misalignment
Solution Approach 1:
The patent changes the validation parameter from RSRP (reference signal received power) to a time-based metric comparing expected vs. actual reception times of downlink signals. This parameter change enables accurate TA validation in beam-based NR systems by directly measuring timing alignment rather than relying on power-based indicators that don't reflect mobility accurately.
2Reliability
If TA validation is performed frequently to maintain alignment accuracy, then TA alignment accuracy is improved, but power consumption increases
Solution Approach 1:
The patent enables the UE to autonomously validate its own TA status by comparing expected reception times (calculated from stored TA values and downlink timing) with actual reception times of downlink signals. This self-service validation mechanism allows frequent accuracy checks without requiring continuous network interaction, reducing overall power consumption while maintaining alignment accuracy.
3Reliability
If TA validation is performed to prevent misalignment, then communication reliability is improved, but false positives and negatives increase with simple validation methods
Solution Approach 1:
The patent implements a feedback-based validation mechanism where the UE continuously compares expected reception times (based on stored TA and downlink timing) with actual reception times. This feedback loop provides precise TA status determination, reducing false positives and negatives by using direct timing measurements rather than indirect power-based indicators.
Data Source
AI summary
An apparatus configured to: receive a downlink signal; determine whether a TA stored at the apparatus is valid based, at least partially, on a reception timing of the received downlink signal and a delay spread value; and initiate small data transmission with a pre-configured uplink resource based, at least partially, on the determination that the TA is valid. An apparatus configured to: transmit, to a UE, a configuration comprising information related to TA validation for the UE, wherein the information comprises at least one of: an indication of a value configured to indicate a fraction of a cyclic prefix length of a symbol for reception of an uplink transmission from the UE, or a delay spread value; transmit a downlink signal; and receive a SDT based, at least partially, on the fraction of the length of the cyclic prefix, the transmitted downlink signal, and the delay spread value.