Sidelink Positioning Reference Signal Transmission in Unlicensed Spectrum
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Solution Overview
Problem
Sidelink positioning in unlicensed spectrum faces challenges due to Listen Before Talk (LBT) uncertainty, leading to inefficiencies and latency in determining user equipment position, as existing slot structures and transmission schemes are not optimized for unlicensed frequency bands.
Innovation Solution
The solution involves configuring user equipment to perform sidelink positioning using a dedicated resource pool, where the sidelink positioning reference signal (SL-PRS) is transmitted in a SL-PRS occasion only after a successful Listen Before Talk procedure, and the slot is divided into mini-slots to allow for efficient multiplexing and resource sharing, reducing the need for additional LBT procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Listen Before Talk procedure is performed before each transmission in unlicensed spectrum, then channel access reliability is improved, but transmission latency increases
Solution Approach 1:
The transmitting UE performs LBT procedure in advance to acquire channel access before transmitting positioning reference signals. By performing the channel access procedure preliminarily and caching the acquired channel rights, the system ensures reliable transmission while reducing latency for subsequent transmissions within the same channel occupancy time.
Solution Approach 2:
Once a UE successfully acquires channel access through LBT, it maintains continuous transmission of positioning reference signals and control information without performing additional LBT procedures. This continuity principle allows multiple transmissions to occur back-to-back within the acquired channel occupancy time, eliminating repeated LBT delays and reducing overall positioning latency.
2Reliability
If additional LBT procedures are performed for each transmission opportunity, then channel access reliability is improved, but positioning efficiency deteriorates
Solution Approach 1:
The patent combines multiple transmission functions (positioning reference signals, control information, and data) into a single channel occupancy time acquired through one LBT procedure. By merging these transmissions and eliminating redundant LBT procedures, the system maintains reliable channel access while significantly improving positioning efficiency through continuous transmission.
Solution Approach 2:
The transmitting UE performs the LBT procedure preliminarily to acquire channel access rights before initiating the positioning transmission sequence. This preliminary channel acquisition enables subsequent transmissions to proceed without additional LBT delays, thereby improving positioning efficiency while maintaining the reliability guaranteed by the initial LBT procedure.
3Productivity
If slot structure is optimized for licensed spectrum, then transmission efficiency is improved, but adaptability to unlicensed spectrum deteriorates
Solution Approach 1:
The patent introduces dynamic channel access mechanisms by integrating LBT procedures and channel occupancy time concepts into the slot structure. This dynamic adaptation allows the system to maintain efficient transmission patterns while becoming versatile across both licensed and unlicensed spectrums by adjusting channel access behavior according to spectrum type.
Solution Approach 2:
The system changes key parameters including channel access procedures (adding LBT), transmission timing (using channel occupancy time), and resource allocation patterns to adapt from licensed to unlicensed spectrum. These parameter changes enable the slot structure to maintain transmission efficiency while achieving spectrum adaptability.
Data Source
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AI summary
There is provided a transmitting user equipment (1) configured to perform sidelink positioning by transmitting a sidelink positioning reference signal SL-PRS and associated sidelink control information SCI to at least one receiving user equipment (5) in a slot, using a dedicated resource pool. The SCI indicates the sidelink resources for the transmission of the SL-PRS. The transmitter user equipment (1) performs a Listen Before Talk LBT procedure to initiate a Channel Occupancy Time procedure COT. The transmitting user equipment is configured to transmit the SL-PRS in a SL-PRS occasion to the at least one receiving user equipment (5), if the LBT succeeds, and determine his position using responding sidelink positioning reference signals received from the receiving user equipment(s). A slot is divided into a plurality of mini-slots and the transmitting user equipment is configured to transmit the SCI and then the associated SL-PRS in the beginning of a mini-slot.