Sidelink Positioning TA Validation in RRC INACTIVE UEs
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Solution Overview
Problem
There is a need for improved methods and apparatuses to determine parameters for positioning in wireless communication systems, particularly in the context of next-generation wireless access technologies like New Radio (NR), which support enhanced mobile broadband communication, massive machine type communication, and ultra-reliable and low latency communication.
Innovation Solution
A method and apparatus for determining a parameter for positioning in a wireless communication system, involving configuring a timing advance (TA) and starting a time alignment timer (TAT) for a positioning sounding reference signal (SRS), with operations performed by a user equipment (UE) in an RRC INACTIVE state, including transmitting the positioning SRS based on valid TA, measuring reference signal received power (RSRP), and restarting TAT based on RSRP threshold differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UE in RRC INACTIVE state performs positioning SRS transmission with TA validation, then positioning accuracy is improved, but device complexity increases due to additional timer management and RSRP measurement operations
Solution Approach 1:
The network pre-configures the TAT duration and RSRP threshold values before the UE enters RRC INACTIVE state. This preliminary configuration enables the UE to autonomously manage TA validation and positioning SRS transmission without continuous network intervention, improving positioning accuracy while avoiding the complexity of real-time network coordination.
Solution Approach 2:
The UE autonomously performs RSRP measurements, compares them against pre-configured thresholds, and manages the TAT lifecycle itself. This self-service approach allows the UE to maintain TA validity and perform positioning operations independently in RRC INACTIVE state, enhancing positioning accuracy without requiring complex network-side control mechanisms.
2Productivity
If the UE autonomously manages TA validity with TAT in RRC INACTIVE state, then communication efficiency is improved, but reliability deteriorates due to potential TA expiration and positioning interruption
Solution Approach 1:
The UE continuously monitors RSRP values and provides feedback by comparing them against pre-configured thresholds. When RSRP indicates good channel conditions, the UE restarts TAT to maintain TA validity. This feedback mechanism ensures reliable positioning operations by proactively renewing TA before expiration, balancing autonomous operation with reliability maintenance.
Solution Approach 2:
The network provides a pre-configured TAT duration that acts as a cushion before TA expiration. The UE uses this time buffer to perform positioning SRS transmissions and RSRP measurements, ensuring that TA remains valid throughout the positioning process. This prior cushioning prevents TA expiration and positioning interruptions, maintaining reliability while enabling efficient autonomous operation.
3Reliability
If the UE restarts TAT based on RSRP threshold comparison, then timing alignment is maintained improving signal transmission quality, but energy consumption increases due to continuous RSRP measurements
Solution Approach 1:
The UE performs RSRP measurements periodically rather than continuously, triggered by specific events such as SRS transmission opportunities or timer expirations. This periodic measurement approach maintains timing alignment reliability by restarting TAT when needed, while significantly reducing energy consumption compared to continuous monitoring.
Solution Approach 2:
The UE performs RSRP measurements only to the extent necessary for TAT management - comparing measurements against pre-configured thresholds to decide whether to restart TAT. This partial action approach maintains sufficient timing alignment quality without the excessive energy consumption of continuous or overly frequent measurements, optimizing the balance between reliability and energy efficiency.
Data Source
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AI summary
The disclosure relates to a method of performing sidelink positioning by a user equipment (UE) in a radio resource control (RRC) INACTIVE state in a wireless communication system. Specifically, the method comprises configuring a timing advance (TA) for a positioning sounding reference signal (SRS) and starting a time alignment timer (TAT) for the positioning SRS, wherein the TA is considered valid while the TAT is running, transmitting the positioning SRS based on the TA being valid, measuring a reference signal received power (RSRP), and restarting the TAT, based on a difference between the measured RSRP and latest measured RSRP being less than a threshold.