Multi-Channel Passive Ranging for Wireless Locationing
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Solution Overview
Problem
Current ranging operations in wireless networks, particularly in Wi-Fi enabled devices, face inaccuracies due to uncertainties in SIFS values, leading to errors in distance determination, and there is a need to maximize frequency bandwidth for FTM frames without degrading signal-to-noise ratio (SNR) or range.
Innovation Solution
The solution involves performing multi-channel passive ranging operations by receiving signal exchanges on multiple wireless channels, using channel concatenation techniques to combine these channels, allowing for wider frequency bandwidth usage without sacrificing SNR or range, and determining differential distances based on the exchanges of signals across these channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-channel passive ranging operations are performed, then device complexity is reduced, but measurement precision deteriorates due to limited frequency bandwidth and SIFS uncertainties
Solution Approach 1:
The patent segments the ranging operation into multiple independent channel measurements. Instead of performing a single ranging operation on one channel, the system performs separate ranging operations on multiple channels (e.g., 2.4 GHz and 5 GHz bands), then combines the results. This segmentation allows each channel to contribute independently to the final distance estimate, improving overall measurement precision while managing complexity through modular processing
Solution Approach 2:
The patent adds the frequency domain dimension to the ranging operation by utilizing multiple wireless channels across different frequency bands. This dimensional expansion transforms a single-channel measurement into a multi-dimensional measurement space, where distances are determined by combining information from multiple frequency dimensions, thereby improving measurement precision through increased observational diversity
2Measurement precision
If frequency bandwidth is increased for FTM frames, then timing accuracy is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent merges measurements from multiple frequency channels to achieve the timing accuracy benefits of wide bandwidth while mitigating the SNR penalty. By combining the timing information from multiple narrower channels, the system achieves an effective wide-bandwidth measurement without suffering from the SNR degradation that would occur if all the power were concentrated in a single wide channel
Solution Approach 2:
The patent skips the intermediate step of transmitting wide-bandwidth signals at low power by instead transmitting multiple narrow-bandwidth signals at higher power levels. This approach rushes through the measurement process by taking multiple rapid, high-SNR measurements on narrow channels and combining them to achieve the timing precision of a wide-channel measurement without the SNR penalty
Data Source
AI summary
Apparatuses and methods for performing multi-channel passive ranging operations are disclosed. In one example, a passive listening device may receive, on a first wireless channel, a first exchange of signals between a first wireless device and a second wireless device, and then receive on a second wireless channel, a second exchange of signals between the first wireless device and the second wireless device, the first wireless channel different than the second wireless channel. The passive listening device may determine a differential distance between the passive listening device and the first and second wireless devices based, at least in part, on the first and second exchanges of signals on the first and second wireless channels, respectively.