Trilateration LOS Path Filtering for Range Error Reduction
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Solution Overview
Problem
Existing navigation systems face errors due to mistaking non-Line of Sight (NLOS) signals as Line of Sight (LOS) signals, leading to biased range estimates and increased probability of errors, as they lack effective pre-measurement filtering to distinguish between signal paths.
Innovation Solution
A method and device for trilateration that predicts the performance of each LOS path and filters out signals with performance below a predetermined threshold, selecting the best-performing radio links for range measurements to accurately determine a device's location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If post-measurement filtering is used to remove NLOS signals, then some NLOS errors can be corrected, but the probability of error increases because NLOS ranging errors have already been introduced and information about path performance is lost
Solution Approach 1:
The patent applies preliminary action by performing LOS path identification and filtering BEFORE range measurements are taken. The system predicts LOS probability for each signal path using transmitter-receiver geometry and environmental data, then filters out NLOS paths before they can contaminate the range measurements. This prevents NLOS ranging errors from being introduced in the first place, rather than attempting to correct them after measurement.
Solution Approach 2:
The patent introduces an intermediary filtering mechanism that acts as a gatekeeper between signal reception and range measurement. This intermediary layer predicts LOS probability and selectively passes only high-confidence LOS paths to the measurement process, while blocking NLOS paths. This intermediary filtering step prevents erroneous measurements while preserving valid LOS data.
2Productivity
If all received signals are used for trilateration, then more measurement data is available, but the position estimate becomes biased due to inclusion of NLOS signals with positive ranging errors
Solution Approach 1:
The patent applies the taking out principle by extracting and removing NLOS signals from the set of received signals before trilateration. The system identifies NLOS paths through LOS probability prediction based on geometric and environmental analysis, then extracts only the high-confidence LOS signals for position estimation. This extraction process eliminates the positive bias introduced by NLOS ranging errors while maintaining sufficient measurement data from valid LOS paths.
Solution Approach 2:
The patent applies local quality by treating different signal paths differently based on their individual LOS probability characteristics. Rather than uniformly processing all signals, the system evaluates each path's local quality (LOS probability) using transmitter-receiver geometry and environmental factors, then selectively includes or excludes each path based on its predicted quality. This ensures high-precision position estimates by including only locally-validated LOS paths.
3Reliability
If pre-measurement LOS path filtering is applied, then NLOS errors are prevented, but additional computational processing is required to predict and evaluate path performance
Solution Approach 1:
The patent performs preliminary LOS probability prediction using transmitter-receiver geometry and environmental data before the actual trilateration measurement. By pre-evaluating each signal path's LOS probability and filtering NLOS paths in advance, the system prevents NLOS errors from contaminating the position estimate, thereby improving trilateration reliability without requiring complex real-time filtering during measurement.
Data Source
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AI summary
A method for trilateration may include receiving signals via each of a plurality of LOS paths and predicting performance of each LOS path. The method may also include filtering out signals received via LOS paths with performance below a predetermined threshold value. The method may further include performing trilateration using the unfiltered signals to substantially determine a location of a device.