Research On Indoor Localization Based On Weak Multipath Effect Recognition

Wireless LANs,especially Wi-Fi,have been pervasively deployed and have fostered myriad wireless communication services and ubiquitous computing applications.Indoor localization is an essential modules of these applications.A primary concern in designing scenario-tailored application is to obtain precise estimated distance combatting with harsh indoor wireless signal propagation issues,particularly multipath effect.The traditional propagation model based on received signal strength indicator(RSSI)is easily affected by temporal and spatial fluctuation due to the multipath effect,which leads to most of the distance estimation errors in current indoor localization systems.Intuitively,these points in weak multipath effect(WME)conditions,which are slightly affected by multipath effect,perform better under pass loss propagation model.Therefore,the ability to distinguish weak multipath effect,which is slightly affected by multipath effect is a key enabler for accurate distance estimation.Enabling such capabilities on commercial Wi-Fi infrastructure,however,is difficult due to the coarse multipath resolution with the MAC layer RSSI.There is an alternative between positioning performance and positioning generality in traditional indoor localization scheme.If we want to improve the positioning performance,the positioning generality will drop.The positioning generality of most of precise indoor localization scheme is low.Because they aimed at specific environment.When they are applied to other environment,the positioning performance drop sharply.Therefore,a universal precise scheme is needed for indoor localization.In this thesis,we propose a universal precise indoor localization scheme based on weak multipath effect identification,leveraging the channel state information(CSI)from the PHY layer.We extracted three features from the time domain and frequency domain of the CSI.Then we distinguish the weak multipath condition and the strong multipath condition,using the threshold value of these three features.Based on the weak multipath identification,we proposed a universal precise indoor localization scheme,combining RSSI and CSI.Then we designed an indoor localization system,using the universal precise indoor localization scheme.In our indoor localization system,we first select points which are identified as weak multipath effect conditions through features extracted from CSI.Then we build a pass loss propagation model with RSSI to estimate distance between the transmitter and the receiver,choosing these selected points.At last,we calculate the position of the receiver by using location algorithm.Experimental results demonstrate that weak multipath effect conditions improve the accuracy of distance estimation,outperforming strong multipath effect conditions in typical indoor environments.Therefore,the positioning performance,which include positioning accuracy and positioning accuracy,is well performed.Thus,we obtain a universal precise indoor localization system.