Sidelink Positioning with Multiple Reference WTRUs
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Solution Overview
Problem
In scenarios where a WTRU is within 5G coverage but lacks sufficient gNBs for Uu-based positioning, sidelink (SL) positioning is employed, requiring connection with multiple reference WTRUs, necessitating network coordination for resource allocation and measurement information sharing.
Innovation Solution
The WTRU reports a list of available reference WTRUs to the LMF, negotiates positioning methods, and initiates location requests when coverage is available, updating methods as needed based on available reference WTRUs, with network assistance for SL positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SL positioning is used when gNBs are insufficient for Uu-based positioning, then positioning capability is maintained, but the complexity of coordinating multiple reference WTRUs increases
Solution Approach 1:
The LMF acts as an intermediary that centralizes the coordination of multiple reference WTRUs. The target WTRU reports available reference WTRUs to the LMF, which then selects appropriate reference WTRUs and coordinates the positioning procedure, reducing the coordination burden on individual WTRUs and simplifying the overall system complexity while maintaining positioning reliability
Solution Approach 2:
The positioning system is segmented into distinct functional components: the target WTRU that reports available reference WTRUs, the LMF that performs selection and coordination, and the reference WTRUs that provide positioning measurements. This segmentation allows each component to perform its specific function independently, reducing overall system complexity
2Measurement precision
If multiple reference WTRUs are connected for SL positioning, then positioning accuracy is improved, but the time required for discovery and setup increases
Solution Approach 1:
The target WTRU performs preliminary discovery and reporting of available reference WTRUs before the actual positioning procedure. By pre-identifying and reporting available reference WTRUs to the LMF, the system reduces the time required during the actual positioning execution, as the LMF can immediately select from the pre-reported list without performing discovery during the positioning event
3Adaptability or versatility
If the WTRU reports all available reference WTRUs to the LMF, then the LMF has more options for selection, but the signaling overhead increases
Solution Approach 1:
The system extracts only the essential information needed for positioning from the full list of available reference WTRUs. The target WTRU reports available reference WTRUs to the LMF, which then selects only the necessary subset for the positioning procedure. This extraction approach provides the LMF with sufficient options while minimizing signaling overhead by not requiring transmission of all possible reference WTRU information
Data Source
AI summary
A procedure is provided on how a target WTRU and LMF negotiate for supported WTRU initiated positioning method, and how the target WTRU discovers reference WTRUs for SL positioning and perform proper SL positioning with multiple reference WTRUs. A procedure is provided on how to perform SL positioning between target WTRU and reference WTRUs in coordination with LMF. The proper SL positioning method may be updated when the available number of reference WTRUs change. Each WTRU positioning method needs a different number of reference WTRUs for SL positioning. As the WTRU moves around, there may not be enough reference WTRUs available for SL positioning. A negotiation may be considered between the WTRU and network for a positioning method to be employed. When certain WTRU positioning methods are not possible, the requested positioning method may be updated to one or more other available positioning methods.