Abstract
The smartphone-based Wi-Fi fine time measurement (FTM) technique has provided a new approach for Wi-Fi-based indoor location on mobile phones since the 2018 release of the Google Android Pie system, which supports the IEEE 802.11-2016 protocol and can directly measure the distance between the initiator and the responder. This paper studies in detail the properties of mobile phone Wi-Fi ranging and positioning performance. Considering non-line-of-sight (NLOS) error identification, a real-time ranging error compensation model based on the least-squares (LS) method and an adaptive Wi-Fi FTM positioning algorithm (AWFP) utilizing the weighted least-squares (WLS) method are devised. To improve accuracy, a new tightly coupled fusion positioning algorithm integrating Wi-Fi FTM and built-in mobile phone sensors based on the extended Kalman filter (EKF) is constructed. The experimental results show that the ranging precision and Wi-Fi positioning accuracy are improved. Based on the high-precision Wi-Fi ranging and positioning results, the final location accuracy of the proposed fusion method is 0.98 m, and the root-mean-square error (RMSE) is 1.10 m, which are better than those of the PDR, Wi-Fi FTM and loosely coupled PDR/Wi-Fi FTM integration based on the EKF.
Highlights
Indoor positioning is attracting increasing attention because of the rapid development of society and the increased demand for location-based services (LBSs) in people’s lives [1], [2]
Less than one-meter ranging accuracy could be obtained; 2) We devised an adaptive Wi-Fi positioning algorithm based on the weighted least-squares (WLS) method. This algorithm could dynamically adjust the ranging data to meet the positioning conditions and the final location accuracy was better than that of the traditional Wi-Fi trilateral positioning method; 3) We proposed the Wi-Fi fine time measurement (FTM) and Pedestrian dead reckoning (PDR) tightly coupled fusion positioning model based on the extended Kalman filter (EKF) algorithm and validated positioning performance in a typical office environment
RELATED WORKS Time-based Wi-Fi positioning techniques using TDOA protocol [20], [22] and time of arrival (TOA) protocol [19], [31] have been studied by many researchers and these related works show that this technology is very attractive, even if it is difficult to implement on mobile phones and requires special hardware support
Summary
Indoor positioning is attracting increasing attention because of the rapid development of society and the increased demand for location-based services (LBSs) in people’s lives [1], [2]. Apart from the above approaches, another time-based Wi-Fi positioning method using the improved time of flight [23] (TOF) protocol is receiving increasing attention due to its high positioning accuracy This TOF protocol can provide precise time measurements and is the basis of the fine time measurement (FTM) technique, which has been introduced and standardized by the IEEE 802.11 working group [24]. RELATED WORKS Time-based Wi-Fi positioning techniques using TDOA protocol [20], [22] and TOA protocol [19], [31] have been studied by many researchers and these related works show that this technology is very attractive, even if it is difficult to implement on mobile phones and requires special hardware support. Compared with other indoor positioning techniques, Wi-Fi FTM ranging positioning has a promising future and high application value due to its convenience and high positioning accuracy
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