Integrated Communications And Positioning Technology In Wireless Local Area Networks

In recent years,with the development of mobile communication technology and Internet of Things technology,precise positioning of users plays an increasingly important role in some location-based services.Satellite positioning technology takes a huge leap in the last century.In 2007,the United Nations identified the US Global Positioning System(GPS),Beidou,GLONASS,and Galileo as the world’s four major navigation systems.However,compared with outdoor environments,indoor environments are more complex.Leading to more severe challenges to achieve positioning.Therefore,it is meaningful to conduct the research on indoor positioning technology.In this work,according to the principle of OFDM transmission system,the method of collecting Channel State Information(CSI)based on IEEE 802.11 ac protocol is introduced.Then,multiple signal classification algorithm(MUSIC)is utilized to esitmate the angle of arrival and time of flight of the direct ray combining with the preestimated CSI.In particular,an 8-element non-uniform planar array with the element spacing greater than one wavelength is designed,which will be of benefit to the improment of the array angular resolution,as well as the suppression of the spurious peaks in the MUSIC angular spectrum.Secondly,Matlab and Wireless In Site are used to design an indoor positioning system simulation link based on the above basic principles.In this simulation link,the IEEE 802.11 ac transmit waveform is generated in Matlab,the indoor multipath channel information is generated in Wireless In Site,and this channel information is considered as the input of Matlab to generate the receive waveform.Then,channel estimation is performed to obtain the CSI of the wireless channel.Combined with the MUSIC algorithm,the angle of arrival and time of flight can be estimated.Finally,based on the angle information of two APs(Access Point)or the angle and delay information of a single AP,the location of target in three-dimensional space is estimated.Finally,an indoor positioning experimental platform is setup based on the Universal Software Radio Peripheral(USRP),combined with Matlab.Experiments are carried out in three scenarios: a conference room,a cubicle office and a hall.To compare the positioning performance,the non-uniform array is replaced by a uniform array with inter-element spacing of half-wavelength.And the positioning performance under different bandwidths is also compared.The experimental results show that the median error of positioning is all within one meter,which achieves high-precision indoor positioning.