Sidelink PRS Timing Under LBT for Low-Latency Positioning

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Solution Overview

Problem

Existing sidelink positioning techniques in unlicensed radio frequency spectrum bands face inefficiencies due to processing delays and interference from other devices, leading to increased latency and reduced reliability in sidelink reference signal transmissions.

Innovation Solution

The first UE transmits the first PRS for a duration based on the processing delay of the second UE, ensuring reduced latency and improved efficiency by minimizing interference from other devices accessing the channel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the first UE transmits the first PRS for a duration based on the processing delay of the second UE, then latency is reduced and efficiency is improved, but interference from other devices accessing the channel increases

Engineering Contradiction:

ImprovelatencyVSAvoidinterference from other devices

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The first UE performs a Listen Before Talk (LBT) procedure before transmitting the first PRS to check if the channel is idle. This preliminary action ensures that the transmission only occurs when no other devices are actively using the channel, thereby reducing interference while maintaining low latency through prompt transmission upon channel availability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The first UE transmits the first PRS continuously for a duration that covers the processing delay of the second UE. This continuous transmission ensures that the second UE can always detect the PRS and respond timely, reducing latency while the LBT mechanism prevents interference from other devices

Inventive Principle:

Principle #20Continuity of useful action

2Object-affected harmful factors

If the first UE performs LBT before transmitting the first PRS, then interference from other devices is reduced, but channel access time and latency increase

Engineering Contradiction:

Improveinterference from other devicesVSAvoidchannel access time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The duration of the first PRS transmission is dynamically adjusted based on the processing delay capability of the second UE. By changing this parameter, the system ensures that the PRS remains detectable throughout the second UE's processing time, reducing latency without requiring extended LBT procedures, thus balancing channel access time with interference avoidance

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4352903B1Techniques for sidelink reference signal transmission

Publication Date: 2025.12.31 QUALCOMM INC

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AI summary

Methods, systems, and devices for wireless communications are described. A first user equipment (UE) may communicate with a second UE using a shared radio frequency spectrum band. The first UE may perform a listen before talk (LBT) and may transmit a first positioning reference signal (PRS) based on a result of the LBT. The first UE may transmit the first PRS using a first time resource that is based on a duration of the first PRS. In response to detecting the first PRS, the second UE may transmit a second PRS using a second time resource that is based on the duration of the first PRS. The second UE may transmit the second PRS based on performing an LBT without a random back-off, which may enable the second UE to transmit the second PRS with reduced latency and improved reliability.