Time-of-flight measurement correction for AGC delay
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Solution Overview
Problem
Time-of-flight-based location determination systems face inaccuracies due to automatic gain control (AGC) processing in wireless access points, which can alter time-of-arrival measurements, making it difficult to distinguish between accurate and inaccurate data for location estimation.
Innovation Solution
A method to correct time-of-flight measurements by classifying signals as strong, weak, or preferred, identifying distinct distributions, determining mean values, and discarding measurements affected by AGC processing to improve location determination accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If automatic gain control processing is applied to normalize received signals, then signal decoding capability is improved, but time-of-arrival measurement accuracy deteriorates due to processing delay
Solution Approach 1:
The patent applies preliminary action by performing automatic gain control processing before time-of-arrival measurement, and then compensating for the introduced delay. The system determines whether AGC processing was applied and calculates the corresponding delay, then subtracts this delay from the measured time-of-arrival to obtain a corrected accurate value.
Solution Approach 2:
The patent implements feedback by using the information about AGC processing status and delay characteristics to correct the time-of-arrival measurements. The system feeds back the delay compensation based on the detected AGC processing, thereby improving measurement accuracy while maintaining the benefits of AGC processing.
2Area of stationary object
If time-of-flight measurements are collected from multiple access points, then location determination coverage is improved, but measurement reliability deteriorates due to inclusion of AGC-processed inaccurate measurements
Solution Approach 1:
The patent applies local quality by treating different time-of-flight measurements differently based on their AGC processing status. Measurements identified as being affected by AGC processing are corrected or excluded, while measurements without AGC processing are used as-is. This selective quality adjustment improves overall measurement reliability while maintaining broad coverage.
3Productivity
If all received time-of-flight measurements are used for location determination, then data utilization is improved, but location accuracy deteriorates due to contamination from AGC-processed measurements
Solution Approach 1:
The patent applies discarding and recovering by identifying and discarding the inaccurate component (AGC-processing delay) from the measurements, while retaining and using the valid portion. The system determines which measurements were affected by AGC processing and either corrects them or excludes them from the final location calculation, thereby improving accuracy without unnecessarily discarding valid measurement data.
Data Source
AI summary
In an example, a method for correcting time-of-flight measurements includes receiving a plurality of time-of-flight measurements and determining whether the time-of-flight measurements relate to a strong signal client, a weak signal client, or a preferred signal client. If the time-of-flight measurements relate to a strong signal client or a weak signal client, the method determines whether the time-of-flight measurements constitute two distinct distributions. If the time-of-flight measurements constitute two distinct distributions, a mean value for each distribution is determined. If the mean values differ by a predetermined time delay attributable to automatic gain control processing, the time-of-flight measurements corresponding to the distribution having the lower mean value are used. If the mean values differ by less than the predetermined time delay attributable to automatic gain control processing, the time-of-flight measurements corresponding to both distributions are used.