Time-of-Arrival Estimation Using Polynomial Timing Offset Correction
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Solution Overview
Problem
Existing methods for localizing a receiver, such as Bluetooth devices, face challenges in accurately determining the time of arrival of signals due to insufficient synchronization precision, which affects distance measurement accuracy to within 1 meter.
Innovation Solution
A method involving a bit-pattern detector and correlator that uses a polynomial function to estimate timing offset, separating rough match detection from precise correlation calculation, allowing for reduced processing overhead with low-precision initial detection and high-precision refinement, enabling accurate timestamping and distance estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision arithmetic (e.g., 10 bit) is used for correlation calculation to achieve accurate timestamping, then measurement precision improves, but processing overhead and computational complexity increase significantly
Solution Approach 1:
The patent divides the correlation calculation into two stages: a first correlation calculation using low precision arithmetic (e.g., 6-bit) to identify a candidate time of arrival, followed by a second correlation calculation using high precision arithmetic (e.g., 10-bit) only on samples around the candidate time. This segmentation reduces the number of high precision operations while maintaining timestamp accuracy.
Solution Approach 2:
Instead of performing high precision correlation calculations on all samples, the patent applies high precision arithmetic only partially - specifically, only to a limited set of samples surrounding the candidate time of arrival identified by the low precision first correlation calculation. This partial action achieves the necessary precision with reduced computational overhead.
2Device complexity
If low precision arithmetic (e.g., 6 bit) is used in correlator to reduce processing overhead, then device complexity reduces, but measurement precision of timestamp deteriorates
Solution Approach 1:
The patent segments the correlation process into two distinct phases with different precision requirements. The first phase uses low precision arithmetic to efficiently identify a candidate time of arrival, while the second phase uses high precision arithmetic to accurately determine the final timestamp. This segmentation allows each phase to use appropriate precision levels.
Solution Approach 2:
The low precision first correlation calculation serves as a preliminary action that identifies a candidate time of arrival before the high precision second correlation calculation is performed. This preliminary filtering reduces the search space for the subsequent high precision calculation, ensuring both efficiency and accuracy.
3Ease of operation
If synchronous time-grid is used across multiple Bluetooth devices for localization, then ease of operation improves, but measurement precision of time of arrival deteriorates due to insufficient synchronization
Solution Approach 1:
The patent replaces reliance on external synchronization mechanisms (such as GPS or precise network time synchronization) with an autonomous correlation-based time of arrival detection method. Each device independently determines ToA by correlating received signals with known bit patterns, eliminating the need for complex external synchronization infrastructure while achieving high precision.
Data Source
AI summary
A method for estimating a time-of-arrival of a packet received by a receiver includes storing a reference bit-pattern and receiving a plurality of samples in a samples-buffer. In a bit-pattern detector, a matching group of samples having a bit-pattern which matches the reference bit-pattern is identified. In a correlator, a group of three correlation values is determined from the matching group of samples, including a local maximum correlation value, P0, an immediately preceding correlation value, Pm, and an immediately succeeding correlation value Pp. In an estimation unit, a polynomial function f(δ) of the difference, δ, between Pm and Pp is used to estimate a timing offset Tfrac, between the local maximum correlation value and a correlation peak. The time-of-arrival is estimated from a time of the local maximum correlation value P0, and Tfrac.