Abstract

WiFi fingerprinting indoor positioning systems have extensive applied prospects. However, a vast amount of data in a particular environment has to be gathered to establish a fingerprinting database. Deficiencies of these systems are the lack of universality of multipath effects and a burden of heavy workload on fingerprint storage. Thus, this paper presents a novel Random Forest fingerprinting localization (RFFP) method using channel state information (CSI), which utilizes the Random Forest model trained in the offline stage as fingerprints in order to economize memory space and possess a good anti-multipath characteristic. Furthermore, a series of specific experiments are conducted in a microwave anechoic chamber and an office to detail the localization performance of RFFP with different wireless channel circumstances, system parameters, algorithms, and input datasets. In addition, compared with other algorithms including K-Nearest-Neighbor (KNN), Weighted K-Nearest-Neighbor (WKNN), REPTree, CART, and J48, the RFFP method provides far greater classification accuracy as well as lower mean location error. The proposed method offers outstanding comprehensive performance including accuracy, robustness, low workload, and better anti-multipath-fading.

Highlights

  • With the increasing proliferation rate of smart devices, Location Based Services (LBSs) have gained considerable attention

  • We tackled the problem of channel state information (CSI)-based localization system by the Random Forest fingerprinting localization (RFFP), which is a Random Forest-based indoor fingerprinting system that utilizes Feedback Decision Trees (FDT)

  • A series of specific experiments were conducted in a microwave anechoic chamber and an office to detail the localization performance of RFFP with different system parameters, algorithms, and input datasets

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Summary

Introduction

With the increasing proliferation rate of smart devices, Location Based Services (LBSs) have gained considerable attention. A subset is randomly extraced from all attributes of CSI values as the training data set to construct a fast decision tree; the size of the RF determines the number of DTs. Second, a root mean squared error (RMSE)-based pruning strategy is applied to reduce the computational complexity as well as overcome the overfitting problem and improve the precision rate of DTs. Third, the votes in the output of every decision tree are counted, and the most frequently occurring class number is the final classification result of the proposed method. The improved Random Forest-based fingerprinting localization method possesses the large number of virtues mentioned previously and discovers the feature of wireless channel data.

CSI Data Analysis
Location Correlation
Time-Varying
Incompleteness
RFFP System
Proposed Algorithm
Feedback Decision Tree
Random Forest
RFFP System Architecture
Experiments and Discussion
Experiment Setting
Localization Precision
Impact of Wireless Channel Circumstances
Impact of Channel Environment
Impact of Input Datasets
Effects of Different Hyperparameters
Impact of Maximum Depths of FDT
Impact of the Number of FDTs in RFFP
Findings
Impact of the Number of Features
Conclusions
Full Text
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