Maximum Likelihood Position Estimation for Multipath TOA Signals
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Solution Overview
Problem
Existing network-based positioning methods struggle with accuracy in environments with multipath and non-line-of-sight conditions, particularly when propagation delay values for line-of-sight components are uncertain.
Innovation Solution
A method for maximum likelihood position estimation that generates probability maps based on channel impulse responses and propagation delay values, combining conditional probability masses to determine the most likely position of a target device, incorporating pre-computed probability distributions to enhance accuracy and reduce computational costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional positioning methods are used, then device complexity is low, but positioning accuracy deteriorates in multipath and non-line-of-sight conditions
Solution Approach 1:
The patent pre-computes probability distributions for different propagation delay values and stores them in lookup tables before actual positioning operations. During positioning, the system retrieves pre-computed probability maps instead of performing complex real-time calculations, significantly reducing computational complexity while maintaining high positioning accuracy in multipath and non-line-of-sight conditions
Solution Approach 2:
The patent transforms the positioning problem from direct distance calculation to probability-based estimation by changing the parameter representation. Instead of computing exact positions from propagation delays, the system computes probability distributions over possible positions and selects the most likely position, which is more robust to multipath effects and computational constraints
2Measurement precision
If real-time probability map generation is performed, then positioning accuracy is improved, but response time increases
Solution Approach 1:
The system pre-computes and stores probability distributions for various propagation delay values in lookup tables during system initialization or offline processing. During real-time positioning, it retrieves these pre-computed probability maps and combines them using simple operations, achieving both high positioning accuracy and fast response time by avoiding complex real-time calculations
Data Source
AI summary
A method includes: calculating a first probability distribution representing a first set of probability masses for the device occupying positions of a reference coordinate system based on a first set of time-of-arrival estimates, for a signal transmitted from a device and received at a first node, and a first position occupied by the first node; calculating a second probability distribution representing a second set of probability masses for the device occupying the positions based on a second set of time-of-arrival estimates, for the signal received at a second node, and a second position occupied by the second node; calculating a joint probability distribution for the positions based on a product of the first set of probability masses and the second set of probability masses; and calculating an estimated position occupied by the device, the estimated position characterized by the greatest probability mass in the joint probability distribution.