Indoor AOA Localization Algorithm Based On Channel State Information Of WLAN

With the development of the social economy,the indoor location information is getting more and more attention.Usually,Positioning in outdoors mainly rely on the Global Position System(GPS).In indoor environment,the GPS can not be used since the satellitate signal is seriously attenuated.Therefore,researching the indoor localization is significant.At the same time,with the development of wireless communication there has been large number of indoor localization technologies,different scheme utilizes diffent network and hardware platform,has not yet formed a unified standard.The localization technology based on Wireless Local Area(WLAN)is developing rapidly,the main reason is that the wide deployment and low cost of WLAN.Based on this,this paper conducts the research on indoor AOA localization algorithm based on Channel State Information(CSI)of WLAN.The research contents of this paper are as follows:First of all,based on detailed analyzing of the equivalent model of frequency domain in Orthogonal Frequency Division Multiplexing(OFDM)transmission system,the CSI of subcarrier is used to establish one-dimension Multiple Signal Classfication(MUSIC)in frequency domain.Aiming at the hardware limitation of three antennas,the CSI between subcarriers is correlated with the Time of Flight(TOF),and the super-resolution AOA and TOF joint estimation MUSIC algorithm which expands the number of antennas effectively is established by using two-dimension spatial smoothing technique.The simulation results of two-dimension spatial smoothing MUSIC algorithm prove its effectiveness.At the same time,the CSI data are collected in the real indoor environment to verify the two-dimension MUSIC algorithm,and the results show that the three-antenna AP can be used to realize the super-resolution AOA esimtaion of the multipath singal in indoor environment.Then,the influence of existing 802.11 n communication protocol on signal TOF estimation is analyzed in detail,and the phase offset cancellation algorithm is given.Aiming at the problem of localization using multiple APs,the differences between the spatial features of Line-of-Sight(LOS)and Non Line-of-Sight(NLOS)path are analyzed.Then,the affinity propagation clustering is used to cluster the paths,and a LOS path recognition based on weight allocation is adopted.At last,the least square algorithm is used to locate the target combining multiple LOS paths accurately.The experiment results show that the AOA-based indoor localization system designed in this paper can obtain the AOA estimation accuracy of 67% error 8.5 degrees and localization accuracy of 67% error 1.3 meters in a typical room.Thus,the proposed indoor localization algorithm can utilize the existing three-antennas AP to achieve sub-meter localziaiton accuaracy.