Multicarrier Signal Receiver Location Estimation via Phase Compensation
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Solution Overview
Problem
Existing navigation systems face challenges in accurately determining the location of a receiver due to multipath distortion, which is caused by ground clutter and obstructions, leading to inaccuracies in time of arrival measurements.
Innovation Solution
A method and system using OFDM-like multitone signals with subcarriers modulated by pseudo-random noise codes, where a first estimator provides a course estimate of time of arrival and a second estimator aligns subcarrier phases to compensate for multipath distortion, allowing for precise location determination by adjusting the time of arrival and phase error compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If terrestrial navigation signals are used for location determination, then location information can be obtained, but accuracy is degraded due to multipath distortion from ground clutter and buildings
Solution Approach 1:
The patent segments the navigation signal into multiple orthogonal subcarriers (OFDM modulation), where each subcarrier can be independently processed. This segmentation allows the receiver to analyze phase relationships across different frequency components, enabling more robust time of arrival estimation that is less susceptible to multipath distortion effects on individual subcarriers.
Solution Approach 2:
The patent transforms the time-domain signal into the frequency domain by analyzing phase slopes across multiple subcarriers. By changing the domain of analysis from time to frequency and utilizing the phase relationship parameter across subcarriers, the system achieves more accurate time of arrival measurement that compensates for multipath effects.
2Measurement precision
If conventional single-carrier signals are used for navigation, then system complexity is low, but location determination accuracy is limited by multipath effects
Solution Approach 1:
The OFDM signal structure serves multiple functions simultaneously: it provides the navigation timing information needed for location determination, carries data information, and enables multipath resistance through the phase slope analysis across subcarriers. This multi-functionality achieves improved accuracy without proportionally increasing system complexity.
Solution Approach 2:
The patent replaces conventional time-domain correlation methods with frequency-domain phase analysis. By substituting the mechanical/time-domain approach with a frequency-domain mathematical approach, the system achieves better multipath resistance while maintaining computational efficiency through FFT-based processing.
Data Source
AI summary
A data processor estimates the location of the receiver or estimated range from multicarrier signal. The data processor determines phase compensation data for each ranging subcarrier in the multipath signal. The phase compensation data comprises an adjustment to the estimated range based on a difference between an observed phase of the observed signal vector and a direct path phase of a direct path vector, where the direct path phase is estimated based on one or more prior measurements of a certain observed signal vector when an average amplitude of all (or a majority of) ranging subcarriers converge to substantially the same value.