Sidelink PRS Scheduling for Unlicensed-Spectrum LBT Uncertainty
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Solution Overview
Problem
In scenarios where a terminal device is located outside the coverage of a cellular network, the uncertainty in completing Listen Before Talk (LBT) for accessing an unlicensed spectrum channel leads to missed transmission opportunities for sidelink positioning reference signals (SL PRS), necessitating improved SL PRS transmission and scheduling methods.
Innovation Solution
The method involves configuring SL PRS resources and physical channel resources within a slot with multiple starting orthogonal frequency-division multiplexing (OFDM) symbol positions, allowing flexible scheduling and transmission of SL PRS and physical channels, with network devices managing these resources to ensure accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the terminal device uses a fixed SL PRS resource configuration, then the scheduling is simple, but the transmission reliability deteriorates due to uncertain LBT completion time
Solution Approach 1:
The SL PRS resource is divided into multiple candidate resources within a slot, each with different starting OFDM symbol positions. The terminal device selects one candidate resource based on LBT completion timing, transforming a single rigid resource into multiple flexible options that adapt to channel access uncertainty.
Solution Approach 2:
The starting OFDM symbol position of the SL PRS resource is made dynamic rather than fixed. Multiple candidate resources with different starting positions allow the terminal device to adapt the transmission timing according to when LBT is successfully completed, enhancing transmission reliability under uncertain channel conditions.
2Reliability
If the terminal device waits for LBT completion before transmitting SL PRS, then channel access is ensured, but transmission delay increases
Solution Approach 1:
Multiple candidate SL PRS resources are pre-configured within the slot before the terminal device performs LBT. Once LBT succeeds, the terminal device can immediately select and transmit on an appropriate candidate resource without waiting for a fixed transmission time, reducing the delay between channel access and actual transmission.
Solution Approach 2:
The transmission timing is made dynamic by allowing the terminal device to select from multiple candidate resources with different starting positions. This enables the device to transmit as soon as LBT completes, rather than waiting for a predetermined time, thus minimizing transmission delay while ensuring reliable channel access.
3Adaptability or versatility
If multiple candidate SL PRS resources are configured, then transmission flexibility improves, but resource configuration complexity increases
Solution Approach 1:
The SL PRS resource is segmented into multiple candidate resources, each with distinct starting OFDM symbol positions within the slot. This segmentation provides transmission flexibility by offering multiple timing options, while the network device manages the configuration to keep complexity可控.
Solution Approach 2:
The multiple candidate SL PRS resources serve a universal function of providing flexible transmission opportunities. Rather than creating separate specialized resources for different scenarios, the candidate resources collectively provide adaptability for various LBT completion times and channel conditions.
Data Source
AI summary
A wireless communication method includes: transmitting, by a terminal device, an SL PRS and/or a physical channel according to one or more resources configured within a slot, the physical channel being used for indicating transmission of the SL PRS, where each resource corresponds to one starting OFDM symbol position available for transmitting the SL PRS and/or the physical channel, or the resource corresponds to multiple starting OFDM symbol positions available for transmitting the SL PRS and/or the physical channel. The physical channel includes a PSCCH and/or a PSSCH.