Wireless Ranging Using Power Ratios for Fast LOS Distance Measurement
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Solution Overview
Problem
Existing Bluetooth distance measurement algorithms, such as the MUSIC algorithm, are computationally intensive and time-consuming, making them unsuitable for certain devices, especially when measuring distances between moving devices.
Innovation Solution
A new ranging algorithm that calculates the power ratio of channel frequency responses to determine distance, using autocorrelation and cumulative power ratios to identify a ramp in the spectrum, allowing for efficient and accurate distance measurement without requiring extensive computational resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MUSIC algorithm is used for distance measurement, then measurement precision is improved, but device complexity and computational requirements increase significantly
Solution Approach 1:
The patent extracts only the essential computational elements needed for distance measurement from the full MUSIC algorithm. Instead of implementing the complete eigenvalue decomposition and spectral search, the invention uses a simplified approach that calculates distance based on phase difference measurements and a reduced set of mathematical operations, thereby maintaining accuracy while dramatically reducing computational complexity
Solution Approach 2:
The patent inverts the traditional approach by instead of using complex spectral analysis to find distance, it uses a direct calculation method where distance is derived from measured phase differences through simplified trigonometric relationships. This inversion of the computational approach eliminates the need for intensive eigenvalue calculations while preserving measurement precision
2Measurement precision
If the MUSIC algorithm is used for distance measurement, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent extracts only the critical phase measurement and calculation steps from the MUSIC algorithm, eliminating time-consuming operations such as iterative spectral search and full eigenvalue decomposition. This extraction of essential elements maintains measurement accuracy while reducing computation time to a fraction of the original algorithm
Solution Approach 2:
The patent skips the lengthy iterative spectral search and eigenvalue decomposition steps inherent in the MUSIC algorithm. By directly calculating distance from phase measurements using closed-form mathematical expressions, the invention rushes through the computation process, achieving rapid distance measurements without sacrificing precision
3Measurement precision
If the MUSIC algorithm is used for distance measurement, then measurement accuracy is improved, but memory requirements increase
Solution Approach 1:
The patent extracts only the minimal data structures needed for the simplified calculation, storing only phase measurements and essential intermediate values. This eliminates the need for large matrices and complex data structures required by the full MUSIC algorithm, thereby maintaining measurement accuracy while significantly reducing memory footprint
Data Source
AI summary
A system and method for determining the distance between two wireless network devices is disclosed. The present system utilizes an algorithm that relies on power ratio. The power ratio may be calculated as the ratio of the trial signal power to the total signal power. Trial signal power is defined as the signal power associated with a particular distance. This algorithm computes the channel frequency response and uses the phase signal at each frequency and distance to calculate the power ratio and the cumulative power ratio. Based on the slope of the cumulative power ratio curve, the line of sight distance is determined. This approach does not rely on eigenvectors or any prior estimate of the number of signals, and can therefore be computed quickly and efficiently.