AP Pair LoS Classification Using Multi-Frequency FTM Metrics
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Solution Overview
Problem
Existing wireless networking technologies face challenges in accurately determining the distance between access points (APs) due to non-line-of-sight conditions, leading to erroneous distance estimations and inaccurate positioning in indoor environments, especially when APs are mounted on ceilings and obstructed by physical barriers.
Innovation Solution
A method and system for classifying AP pairs as line-of-sight (LoS) or non-line-of-sight (NLoS) using channel diversity and dynamically tuning timestamping parameters, such as search window and threshold values, to improve the accuracy of timestamping direct wireless path signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional timestamping methods are used for distance estimation between APs, then the process is simple, but the accuracy deteriorates under non-line-of-sight conditions due to multipath propagation
Solution Approach 1:
The system performs preliminary classification of AP pairs into LoS and NLoS categories before timestamping. This preliminary action allows the system to apply different timestamping strategies appropriate to each category, improving overall accuracy without requiring complex real-time decision-making during the actual timestamping process
Solution Approach 2:
The system dynamically adjusts timestamping parameters such as search window size and threshold values based on the LoS/NLoS classification. By changing these parameters according to the propagation conditions, the system achieves higher measurement precision while keeping the base timestamping mechanism relatively simple
2Adaptability or versatility
If APs are mounted on ceilings for optimal coverage, then wireless connectivity is improved, but line-of-sight between APs deteriorates due to physical obstructions
Solution Approach 1:
The system dynamically adapts its operation based on the LoS/NLoS classification of AP pairs. By identifying the propagation conditions and adjusting the timestamping parameters accordingly, the system maintains positioning accuracy even when APs are mounted on ceilings where direct line-of-sight is blocked by physical obstructions
Solution Approach 2:
Different timestamping parameters are applied based on whether the AP pair is classified as LoS or NLoS. This parameter adaptation allows the system to compensate for the ceiling mounting configuration and maintain measurement precision despite the reduced line-of-sight probability
3Measurement precision
If channel diversity is used to classify AP pairs into LoS and NLoS, then positioning accuracy is improved, but the complexity of the system increases
Solution Approach 1:
The system segments the AP pair population into distinct LoS and NLoS categories based on channel diversity analysis. This segmentation allows the application of simplified, category-specific timestamping rules rather than requiring a single complex algorithm to handle all cases, thereby improving accuracy while managing system complexity
Solution Approach 2:
The LoS/NLoS classification acts as an intermediary step that bridges the gap between simple timestamping and accurate positioning. This intermediate classification layer enables the system to achieve high positioning accuracy through relatively simple, classification-based decision rules rather than requiring complex real-time signal processing
Data Source
AI summary
An example method and a network device are presented. The example network device configures a first access point (AP) and a second AP to communicate over a first frequency and to receive a first set of Fine Timing Measurement (FTM) metrics between the first AP and the second AP over the first frequency from one or both of the first AP or the second AP. Further, the network device reconfigures the first AP and the second AP to communicate over a second frequency and receives a second set of FTM metrics between the first AP and the second AP over the second frequency from one or both of the first AP or the second AP. Furthermore, the network device determines whether the first AP and the second AP are in Line-of-Sight (LoS) based on the first set of FTM metrics and the second set of FTM metrics.