GNSS Snapshot Correlation for Multipath Delay Estimation
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Solution Overview
Problem
Accurate estimation of GNSS signal delays is challenging in multipath scenarios, especially when power saving requires non-continuous snapshots, as conventional tracking loops are ineffective.
Innovation Solution
Process individual snapshots of GNSS signals using correlators with different delays to compute complex and real values, selecting a reference complex value to suppress non-line-of-sight components and enhance delay estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional closed tracking loops are used for signal processing, then continuous signal tracking is achieved, but power consumption increases and the system cannot effectively estimate delays with non-continuous snapshots
Solution Approach 1:
The patent implements periodic snapshot acquisition instead of continuous signal processing. The receiver takes discrete snapshots at predetermined intervals, processes them through correlators to obtain delay estimates, and then enters a low-power state until the next snapshot is required. This periodic operation mode dramatically reduces power consumption while maintaining adequate positioning accuracy for the application.
Solution Approach 2:
The patent replaces the mechanical/continuous operation of closed tracking loops with a computational approach using correlators and digital signal processing on discrete snapshots. Instead of continuously adjusting local oscillator frequencies and phases through feedback loops, the system uses batch processing of snapshot data with correlators to estimate delays, eliminating the need for continuous active tracking hardware operation.
2Use of energy by moving object
If individual non-continuous snapshots are processed for power saving, then power consumption is reduced, but delay estimation accuracy deteriorates especially in multipath scenarios
Solution Approach 1:
The patent segments the signal processing task by dividing the snapshot data into multiple correlation operations with different local replica signals. Each correlator processes the same snapshot independently with a locally generated PRN code at a specific time offset, producing separate correlation outputs. This segmentation allows the system to extract delay information from individual snapshots without requiring continuous signal availability, maintaining accuracy while enabling power-saving modes.
Solution Approach 2:
The patent introduces local PRN code replicas as intermediary signals that are correlated with the received snapshot. These locally generated codes serve as references to extract the embedded navigation data and timing information from the weak satellite signal. By correlating the received signal with multiple locally generated replicas at different time offsets, the system can accurately determine the signal delay even from a single non-continuous snapshot.
3Measurement precision
If multiple correlators with different delays are used to improve delay estimation accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges multiple correlation operations into a unified processing framework where several correlators work in parallel on the same snapshot input. The correlation outputs from multiple correlators are then combined through selection or averaging to produce the final delay estimate. This merging approach allows the system to benefit from multiple processing paths improving accuracy while sharing common resources such as the snapshot acquisition circuitry and local PRN code generation, thereby limiting the increase in overall system complexity.
Data Source
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AI summary
A method for processing GNSS signals comprises obtaining respective output sequences from N correlators for a snapshot of a received GNSS signal, wherein each sequence has K values, and the N correlators correspond to N different delays of a PRN code sequence; computing one or more complex values using the output sequence; computing a reference complex value using the one or more complex values; for each output sequence, computing respective one or more real values using the reference complex value and the respective one or more complex values of the output sequence; and estimating a delay of the received GNSS signal using the one or more real values of the output sequences.