Positioning Reference Signal Orthogonality via Permutation Matrices
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Solution Overview
Problem
In wireless communication networks, particularly in E-UTRA systems, the existing method for conveying positioning reference signals in downlink subframes can lead to loss of orthogonality due to channel delay spread exceeding the cyclic prefix length, affecting the accuracy of time of arrival (TOA) and time difference of arrival (TDOA) measurements.
Innovation Solution
The proposed solution involves an apparatus and method for communicating positioning reference signals based on an identifier associated with a base station, where the positioning reference signal is encoded and multiplexed into specific resource elements of OFDM symbols, ensuring orthogonality by using a pseudo-randomly selected permutation matrix or cyclic shifts of diagonal/anti-diagonal matrices to allocate resource elements, thereby minimizing overlap and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If positioning reference signals are transmitted in downlink subframes using conventional methods, then the system can provide basic positioning functionality, but orthogonality is lost when channel delay spread exceeds cyclic prefix length, degrading measurement accuracy
Solution Approach 1:
The patent changes the parameter of resource element allocation by using pseudo-randomly selected permutation matrices or cyclic shifts of diagonal/anti-diagonal matrices instead of conventional fixed patterns. This allows the system to maintain orthogonality between positioning reference signals from different base stations even when channel delay spread exceeds cyclic prefix length, thereby resolving the contradiction between measurement accuracy and reliability under varying channel conditions
Solution Approach 2:
The patent introduces dynamic resource element allocation where the permutation matrix or cyclic shift pattern is selected based on base station identifiers and can be changed across different subframes. This dynamic approach ensures that orthogonality is maintained adaptively under different channel delay spread conditions, improving both the reliability of orthogonality maintenance and the precision of TOA/TDOA measurements
2Measurement precision
If resource elements are allocated using fixed patterns, then the system structure is simple, but interference and overlap occur between signals from different base stations, reducing positioning accuracy
Solution Approach 1:
The patent employs parameter changes by using base station identifiers to select from multiple predefined permutation matrices or cyclic shift patterns. This provides a systematic and manageable approach to resource element allocation that reduces interference between base stations while maintaining reasonable system complexity through standardized matrix structures and selection rules
Solution Approach 2:
The patent segments the resource element allocation space by dividing it into distinct patterns represented by different permutation matrices or cyclic shifts. Each base station is assigned a specific segment (pattern) based on its identifier, which reduces inter-base-station interference and improves positioning accuracy while keeping the allocation mechanism structured and manageable
Data Source
AI summary
A base station communicates a positioning reference signal (PRS) to wireless communication devices over a downlink in a wireless communication system by encoding a PRS into a first set of transmission resources, encoding other information into a second set of transmission resources, multiplexing the two sets of resources into a subframe such that the first set of resources is multiplexed into at least a portion of a first set of orthogonal frequency division multiplexed (OFDM) symbols based on an identifier associated with the base station and the second set of resources is multiplexed into a second set of OFDM symbols. Upon receiving the subframe, a wireless communication device determines which set of transmission resources contains the PRS based on the identifier associated with the base station that transmitted the subframe and processes the set of resources containing the PRS to estimate timing (e.g., time of arrival) information.