Wireless Node Synchronization for Precise Sidelink OTDOA Timing
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Solution Overview
Problem
Sidelink-based OTDOA positioning faces challenges in achieving high-accuracy synchronization between anchor UEs due to limited precision, typically at the order of one cyclic prefix, which is several orders of magnitude larger than the desired positioning accuracy of 0.5-2 meters.
Innovation Solution
Enhance synchronization by incorporating a signal from a target UE, transmitted at a specified time instant, with timestamps of signal receipt reported by both anchor and target UEs, allowing for precise timing corrections and synchronization between anchor UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sidelink-based OTDOA positioning is used for synchronization between anchor UEs, then the positioning can be implemented, but the synchronization accuracy is limited to the order of one cyclic prefix which is several orders of magnitude larger than the desired positioning accuracy
Solution Approach 1:
The patent introduces a target UE as an intermediary element in the synchronization process. The target UE transmits a signal that is received by multiple anchor UEs, and the network uses the receipt timestamps from the target UE to calculate timing offsets for the anchor UEs. This intermediary signal transmission enables precise synchronization measurements that overcome the limitations of direct anchor UE-to-anchor UE timing alignment.
Solution Approach 2:
The patent implements a feedback mechanism where the network calculates timing offsets based on the target UE's signal receipt timestamps and provides correction information to the anchor UEs. The anchor UEs use this feedback to adjust their timing, creating a closed-loop synchronization system that continuously improves accuracy through iterative correction.
2Productivity
If anchor UEs transmit reference signals at predetermined times for synchronization, then the positioning process can proceed, but the timing alignment between anchor UEs remains imprecise due to lack of real-time timing correction
Solution Approach 1:
The patent performs preliminary timing measurements using the target UE's signal before final positioning calculations. The network calculates timing offsets in advance based on the receipt timestamps, allowing anchor UEs to pre-adjust their timing before participating in the actual positioning process, thereby improving both efficiency and precision.
Solution Approach 2:
The patent replaces direct mechanical/time-based synchronization between anchor UEs with a signal-processing-based synchronization method. Instead of relying on predetermined timing signals and direct timing alignment, the system uses the target UE's transmitted signal and network-calculated timing offsets to achieve precise synchronization through computational correction.
3Measurement precision
If high-accuracy synchronization is achieved through additional signal transmissions and timestamp reporting, then positioning precision improves, but the system complexity and signaling overhead increase
Solution Approach 1:
The patent makes the target UE serve multiple functions: it acts as both a positioning target and a synchronization reference source. The same signal transmission from the target UE is used for both positioning measurements and timing offset calculations, eliminating the need for separate synchronization reference signals and reducing overall system complexity.
Solution Approach 2:
The target UE's transmitted signal serves the dual purpose of enabling positioning measurements and providing the reference for synchronization calculations. The system leverages the existing positioning signal infrastructure to simultaneously achieve both positioning and synchronization goals, reducing the need for additional dedicated synchronization mechanisms.
Data Source
AI summary
According to an example aspect of the present invention, there is provided an apparatus configured at least to function as a node in a wireless communication system, participate in a synchronization process with at least one target node of the wireless communication system, wherein the apparatus is configured to transmit, as part of the synchronization process, via node-to-node signalling, a reference signal at a time instant specified in assistance information received from the wireless communication system, and report, as part of the synchronization process, to the wireless communication system, a time of receipt of a signal from each one of the at least one target node.