PRS Time-Frequency Mapping for Location Accuracy
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Solution Overview
Problem
Conventional wireless communication systems face challenges in accurately determining the location of user equipment (UE) due to secondary correlation peaks in the detection of positioning reference signal (PRS) sequences, which affect trilateration and triangulation processes.
Innovation Solution
A time-frequency domain structure for PRS is introduced, where a base station assigns modulation symbols to each frequency tone in a block of time-frequency resources, and the UE receives and utilizes this PRS sequence to produce a location estimate, mitigating secondary correlation peaks through specific time-frequency patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PRS sequences are used for location estimation, then the positioning function can be implemented, but secondary correlation peaks occur which reduce measurement precision
Solution Approach 1:
The PRS sequence is divided into multiple segments with different patterns. Each segment contains reference symbols that are mapped to specific resource elements according to defined patterns. This segmentation allows the system to distinguish between primary and secondary correlation peaks by analyzing different segment characteristics, thereby improving location estimation accuracy while maintaining reliable measurement.
Solution Approach 2:
Different patterns are applied to different resource elements within the PRS sequence. Specifically, reference symbols are mapped to resource elements based on local pattern characteristics, where certain resource elements use one pattern while others use different patterns. This local differentiation enables the receiver to identify the primary correlation peak more reliably and reduce the impact of secondary peaks.
2Ease of manufacture
If PRS sequences are transmitted without specific time-frequency patterns, then transmission simplicity is maintained, but secondary correlation peaks affect trilateration and triangulation processes
Solution Approach 1:
The system pre-defines multiple patterns for mapping reference symbols to resource elements before transmission. These patterns are established in advance based on the base station's cell ID and other parameters. By preparing these patterns beforehand, the system maintains transmission simplicity while ensuring that the received signal contains sufficient structure for accurate time-of-flight measurement and peak identification.
Solution Approach 2:
The mapping pattern parameters are changed based on the base station's cell ID and other configuration parameters. Different cell IDs result in different pattern configurations, which spreads the correlation peaks across different time-frequency locations. This parameter variation maintains ease of transmission while improving measurement precision by reducing the likelihood of secondary peaks interfering with the primary peak detection.
3Device complexity
If standard PRS mapping is used, then device complexity is low, but the precision of UE positioning is reduced due to secondary correlation peaks
Solution Approach 1:
The system uses the base station's cell ID and other known parameters as feedback to determine the appropriate mapping pattern. The receiver uses the same feedback information to reconstruct the expected pattern and identify the primary correlation peak. This feedback mechanism enables accurate positioning without requiring complex processing, as both transmitter and receiver use the same simple rule-based approach.
Solution Approach 2:
The receiver creates a local copy of the expected PRS sequence using the same mapping patterns defined by the base station's cell ID. By comparing the received signal with this locally generated copy, the receiver can accurately identify correlation peaks without requiring complex processing algorithms. This copying approach maintains low device complexity while improving positioning precision.
Data Source
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AI summary
Systems and methods are described to supply positioning reference signal (PRS) in a telecommunication system. A base station supplies a PRS sequence according at least to a time-frequency pattern of modulation symbols, wherein the time-frequency pattern assigns a modulation symbol to each frequency tone in a block of time-frequency resources allocated to transmit PRS. The base station associates a modulation symbol in the time-frequency pattern with a reference symbol in the PRS sequence through a mapping that represents the time-frequency pattern. The PRS sequence is conveyed to user equipment through delivery of a set of modulation symbols established through the mapping. Different time-frequency patterns can be exploited based on time-structure of a radio sub-frame. The user equipment receives the PRS sequence according to at least the time-frequency pattern of modulation symbols and utilizes at least the PRS sequence as part of a process to produce a location estimate.