Research On WLAN Indoor Positioning Based On Location Fingerprint

With the explosive development of mobile Internet and the popularity of intelligent terminals,the demand of location-based services is getting higher and higher.In the complex indoor environment,the positioning accuracy of the global positioning system is not ideal because the signal of satellite is very weak.There have been many studies on the indoor positioning,and the indoor positioning technology based on WLAN has come to the foreground by virtue of the advantages of the wide range of WiFi networks.And WLAN indoor positioning based on location fingerprint has become the most popular research topic because of its high precision.WLAN indoor positioning based on location fingerprint is still facing some problems to be solved.In the offline phase,the traditional collecting method needs to traverse all the reference points and collect its fingerprint.And the positioning error increases when people flow,which is not conducive to the popularization of WLAN indoor positioning based on location fingerprint especially in large scenes.In addition,the number and location of the access point have influence on the positioning accuracy.And when any access point is in a fault,the positioning accuracy will decline.So,the dynamic change of access points should be taken into consideration when deploying access points.In order to solve those problems,this thesis proposes and implements the improved scheme of access point layout and fingerprint database construction.The main work of this thesis is as follows:1)This thesis analyzes the shortcomings of the existing access point layout methods and proposes an access point layout optimization scheme based on the reliability of positioning.The optimal scheme increases the reliability of the system up to 0.99 by adding the minimal number of redundant access points,and satisfies full coverage and sufficient positioning accuracy when any access point fails in the redundant system.Then the simulation and analysis of the optimal scheme are carried out.2)This thesis analyzes the shortcomings of the existing fingerprint database construction methods and proposes a fingerprint database construction method based on the time-varying characteristics of received signal strength.And the ordinary Kriging interpolation method is extended from the spatial dimension to the space-time dimension.Then the fingerprint database is constructed by collecting the fingerprint of spatial reference points.3)The experiments are carried out in a building near to Wuhan University of Technology.In the offline phase,the fingerprint database is constructed by Kriging interpolation based on the time-varying characteristics of received signal strength.The experimental results show that the proposed method reduces the average interpolation error by 28% compared with the ordinary Kriging interpolation method and reduces the average positioning error by 37% compared with the traditional collecting method when the interpolation rate is 50%,thus verifying the effectiveness and practicability of the proposed method.In this thesis,we focus on the optimization of the layout of access point and the construction of fingerprint database,and realize the improved schemes in the corresponding scene,which has certain practical value and reference significance for the research of WLAN indoor positioning.