Distance Estimation Using Phase Rotation and Linear Regression
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Solution Overview
Problem
Distance estimation techniques using radio signals face accuracy decreases due to multipath fading, which causes fluctuations in reception levels and noise interference, making it difficult to perform steady distance measurements, especially in environments where signals from multiple access points are not consistently received.
Innovation Solution
A distance estimation device that receives radio signals with multiple subcarriers, calculates phase differences, performs phase addition processing, and uses linear regression analysis to determine a characteristic coefficient for accurate distance estimation, even in situations with multipath fading, by analyzing the relationship between phase rotation amounts and frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radio signals are used for distance measurement, then distance estimation can be performed, but multipath fading causes reception level fluctuations and interference, decreasing measurement accuracy
Solution Approach 1:
The patent changes the measurement parameter from reception level (amplitude) to phase difference between subcarriers. By using phase information instead of amplitude information, the system becomes immune to multipath fading effects that cause amplitude fluctuations, thereby improving both measurement precision and reliability
Solution Approach 2:
The patent introduces phase difference as an intermediary parameter to indirectly measure distance. Instead of directly using reception level which is affected by multipath fading, the phase difference between subcarriers serves as a stable intermediary that correlates with distance but is not affected by amplitude fluctuations
2Measurement precision
If multiple access points are used for distance measurement, then more measurement data can be obtained, but communication with all access points cannot be ensured in reality
Solution Approach 1:
The patent segments the measurement process into subcarrier-level phase difference calculations. By dividing the OFDM signal into multiple subcarriers and calculating phase differences between them, the system can achieve accurate distance measurement using signals from a single access point, eliminating the requirement for simultaneous communication with multiple access points
3Measurement precision
If phase addition processing is performed to handle phase discontinuity, then distance estimation accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent implements dynamic phase unwrapping that adaptively detects phase discontinuities and applies phase addition only when necessary. The system monitors phase differences between consecutive subcarriers and dynamically adjusts by adding 360 degrees when phase wraparound is detected, rather than applying fixed processing to all data points
Data Source
AI summary
A phase rotation amount of each of subcarriers is calculated by calculating a difference between the first phase difference and the second phase difference between consecutive subcarriers included in radio signals, and performing phase addition processing based on the difference. A characteristic coefficient regarding a change rate of the phase rotation amount of each of the subcarriers with respect to a frequency is calculated by performing a linear regression analysis of the relationship between a frequency and the phase rotation amount, and a distance is estimated based on the characteristic coefficient.