Visibility-Map Localization for Mobile Nodes Under NLOS Bias
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Solution Overview
Problem
Existing localization methods face challenges in accurately determining the position of a mobile node due to synchronization errors and environmental factors like multipath propagation and non-line of sight conditions, which are computationally expensive and energy-intensive.
Innovation Solution
A method involving the creation of visibility maps that indicate line of sight or non-line of sight conditions between a mobile node and reference nodes, combined with confidence and consistency scoring to filter out biased measurements, allowing for accurate localization without excessive computational or energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precise clock synchronization is implemented between reference nodes and mobile node, then measurement accuracy is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent extracts the synchronization defect Δi as a separate unknown parameter from the measurement equations, rather than attempting to eliminate it through complex synchronization protocols. By treating the synchronization error as an additional unknown to be solved alongside position coordinates, the system avoids the complexity of precise clock synchronization while maintaining measurement capability
Solution Approach 2:
The patent segments the measurement model into distinct components: the true distance di, the synchronization defect Δi, and measurement noise εi. This segmentation allows each component to be handled separately in the solution process, with the synchronization defect being resolved through the overdetermined system of equations rather than requiring complex synchronization infrastructure
2Reliability
If redundancy of measurements with many reference nodes is used to resolve synchronization defects, then measurement reliability is improved, but computational complexity increases
Solution Approach 1:
The patent uses an overdetermined system where the number of reference nodes Na exceeds the minimum required (n+1). This excessive action provides redundancy that allows the system to resolve synchronization defects and measurement inconsistencies through least-squares optimization, improving reliability while keeping computational complexity manageable through efficient algorithms
3Reliability
If sequential algorithms exploiting previous solutions are used, then measurement reliability in dynamic environments is improved, but energy consumption increases due to higher measurement refresh rates
Solution Approach 1:
The patent pre-calculates visibility indicators for all cells in the service area before localization occurs. This preliminary action creates a lookup table of LOS/NLOS conditions that can be quickly referenced during actual localization without requiring real-time recalculation, enabling sequential algorithms to operate efficiently with lower measurement refresh rates and reduced energy consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides high-accuracy localization with reduced energy consumption by leveraging pre-calculated visibility maps and confidence scoring to filter out biased measurements, enhancing the reliability and efficiency of the positioning process.
Implementation Method 1
measuring the time of flight of the signal between reference nodes (A1, A2, A3), whose position is generally known, and a mobile node TM
Implementation Method 2
Knowing the speed of wave propagation, which is equal to that of light, it is possible to determine the distance traveled by the wave
Implementation Method 3
establish, for each reference node, a visibility map comprising, for a plurality of cells in the visibility map, a visibility indicator corresponding to line-of-sight radio propagation between the cell and the reference node
Data Source
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AI summary
The invention relates to a method for locating a mobile node (NM) in a given area, using reference nodes whose positions are known in said area, comprising the steps of: a) establishing a visibility map (Cj) comprising, for a plurality of cells (Pi) a visibility indicator (lij) corresponding to line-of-sight radio propagation between the cell (Pi) and the reference node (Nj); b) providing a set of ranging measurements (mj) from signals emitted or received by a plurality of reference nodes (Nj); c) calculating a coherence score (si) between the position of the cell (Pi) and the set of ranging measurements (mj), the coherence score (si) being calculated from the visibility indicator (lij) between the cell (Pi) and the reference node (Nj); d) determining the position of the mobile node (NM) as a function of the coherence score (si) of each cell (Pi).