Wi-Fi Time-of-Flight Waveform Design for Accuracy
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Solution Overview
Problem
Current Wi-Fi-based positioning systems face challenges in accurately estimating the time-of-flight for distance determination, especially in environments with multipath issues or signal blockage, such as indoors, where GPS and GLONASS technologies perform poorly.
Innovation Solution
The implementation of a waveform design for time-of-flight estimation in IEEE 802.11 wireless communication systems, which includes a waveform with a greater number of signal tones than the receiving device can decode, using a cyclic prefix and postfix, and employing quaternary phase shift keying (QPSK) encoding to enhance accuracy and security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a waveform with more signal tones than the receiving device can decode is used, then timing resolution and measurement precision are improved, but device complexity and difficulty of detecting and measuring increase
Solution Approach 1:
The waveform is segmented into more signal tones than the receiving device can fully decode, allowing the device to process only a subset (M tones) while the transmitting device processes all N tones. This segmentation enables high-resolution time-of-flight estimation at the transmitter while keeping receiver complexity manageable.
Solution Approach 2:
The system changes the parameter of signal tone count from the standard M tones to N tones (where N > M) in the transmitted waveform. This parameter change improves timing resolution without requiring the receiving device to increase its decoding capability, as the extra tones are processed only by the transmitting device.
2Reliability
If QPSK encoding is used instead of standard BPSK encoding, then security and data rate are improved, but device complexity increases
Solution Approach 1:
The encoding scheme is changed from BPSK (binary phase shift keying) to QPSK (quaternary phase shift keying). This parameter change doubles the data rate and improves security through more complex modulation, while the receiving device complexity remains manageable because it only needs to decode M tones out of N total tones.
Data Source
AI summary
Some embodiments relate to a waveform design for time-of-flight estimation in a wireless communication system. The waveform may include a number N of signal tones, wherein the number N of signal tones is greater than a number M of signal tones that the receiving wireless device is configured to decode. Upon receipt of the waveform, the receiving wireless device may store a timestamp which indicates a time of receipt of the waveform. The receiving wireless device may decode M of the N signal tones. For example, the receiving wireless device may decode the middle M signal tones of the N signal tones. One or more of the transmitting or receiving wireless devices may then estimate a distance between them based at least in part on the timestamp.