以UWB網狀網路提升Wi-Fi室內定位精準度

Accuracy Improvement of Wi-Fi Indoor Positioning by UWB-Based Mesh Network

李兆祥(Chao-Hsiang Li)

指導教授 ： 吳瑞北

共同指導教授 ： 賴怡吉(Alexander I-Chi Lai)

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100994

摘要

本研究之主旨，即在於一無線網狀網路 (Wireless Mesh Network) 組態環境中，組成該網狀網路之各節點 (Node) 位置可各別大略測得但無基準真相 (Ground Truth)、且各節點成對兩兩之間的距離可以更佳精準測得之條件下，如何運用該額外之測距資訊，改善目標節點之定位準確度。為此，本研究提出一優化的方法與目標函數，透過目標節點與鄰近節點間所測得之距離，將各節點組成一相對之邏輯幾何結構；再將該結構中各節點之位置與距離資訊代入目標函數，使得該結構內各節點、含目標節點在內之定位誤差達到最小化。
為驗證本方法之有效性，除理論推導與模擬外，本研究並選擇Wi-Fi以免基站（Infrastructure-less）之K-近鄰（K-Nearest-Neighbor, KNN）指紋定位法作為定位演算法之基準，同時運用超寬頻 (Ultra-wideband, UWB）將空間中散佈的裝置節點組成網狀網路，並作為測量節點間測距之手段，據以實驗驗證本研究所提目標優化函數。以模擬至100個裝置節點並透過量測實際場域中的Wi-Fi KNN定位與UWB節點間距離結果與模擬交叉比對，結果顯示本研究所提方法與目標優化函數對原定位準度之改善幅度，可將原有誤差縮減至與所選擇之鄰近優化用節點個數成平方根反比。

關鍵字

室內定位 ； Wi-Fi指紋定位 ； UWB定位 ； 網狀網路

並列摘要

The objective of this study is to devise an optimization mechanism regarding how to improve the positioning accuracy of nodes without knowing the ground truth of locations a priori in a wireless mesh network (WMN) environment, given the availability of a much accurate distance meashurement between each pair of nodes. To achieve that, this study proposes an optimization methodology as well as the associated objective function. The proposed methodology formulates a logical geometric sturcuture of the target node as wll as its neighboring nodes through measuring the distances between each pair of nodes, and minimizes the total positioning error of all nodes formulating that structure, including the target node, by feeding the measured positions and mutual distances of the structure’s nodes into the objective function.
In addition to theoretical inferences and computer simulations, in this study a series of real-world experiments based on the infrastructure-less Wi-Fi K-Nearest-Neighbor (KNN) fingerprinting positioning algorithm, and Ultra-wideband (UWB) mesh and distance measurement mechanism, are conducted to validate the effectiveness of the proposed mechanism and the objective function. The results of simulations up to 100 nodes as well as the contrasts between simulations and the empirical results of the Wi-Fi/UWB ensemble show that, the improvement of the proposed approach is proportional to the square root of the number of the nearby optimization nodes selected.

並列關鍵字

Indoor positioning ； Wi-Fi fingerprinting localization ； UWB positioning ； Mesh network

參考文獻

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