Research On Indoor Localization Algorithm Using Wi-Fi Channel State Information

With the advent of the Internet of Things era,location information will become an important part of mobile devices and mobile applications.At present,Wi-Fi,as one of the most common wireless communication technologies,has been deployed in most public infrastructures.Therefore,it is very valuable and meaningful to study how to achieve indoor localization using the ubiquitous Wi-Fi.Considering the instability of received signal strength(RSS)in indoor environment,this thesis will study the indoor localization algorithm based on Wi-Fi channel state information(CSI).The main research contents and contributions of this thesis are as follows:Firstly,due to the number of array antennas in the commercial Wi-Fi chip is insufficient,the multiple signal classification(MUSIC)algorithm cannot resolve the angle of arrival(AoA)for each signal.To solve the problem,this thesis makes full use of the frequency domain information of the subcarriers in Wi-Fi CSI to expand the number of sensors.Therefore,the basic idea of the traditional MUSIC algorithm can be applied to the measured CSI matrix,so as to construct a CSI-based AoA-ToF joint estimation algorithm,and estimate the AoA and time of flight(ToF)for each path finally.The simulation experiment proves the feasibility of the algorithm.Secondly,in order to solve the problem that the CSI-based spatial smoothing algorithm has low resolution of coherent signals in the case of low SNRs,this thesis proposes a CSI-based forward and backward spatial smoothing algorithm to decoherence signals.The simulation and experimental results show that the proposed algorithm effectively improves the resolution of coherent signals at low SNRs and complex indoor environments,thus ensuring the accuracy of CSI-based AoA-ToF joint estimation algorithm.Thirdly,this thesis studies how to identify the direct path from the multi-path propagation and obtain the corresponding AoA estimation.The existing direct path identification methods have a large amount of computation and requires user participation.To solve these problems,a direct path identification method based on multi-transmit antenna measurements is proposed.Experiments show that our method is accurate and time-sensitive for direct path identification,and does not require user participation,which effectively solves the problem of direct path identification in indoor multipath environment.Finally,the thesis estimates the localization by combining the angle and distance informations between the target device and each anchor node,and then implements an indoor localization system based on the process of the designed positioning algorithm.According to the experimental results,the localization system designed in this thesis achieves a median localization error of about 0.7m in a typical indoor environment,which is better than SpotFi,one of the most representative AoA localization systems on the current Wi-Fi platform...