Design Of WiFi Positioning System Based On Android Mobile Phone

With the development of mobile Internet,the demand for locat ion-based services is increased.Since the GPS can't be used in the indoor environment,WiFi positioning becomes a hot topic.While because of low accuracy on current WiFi positioning system,it can't meet the needs of indoor positioning.This paper focus on the mechanism of WiFi positioning,the main contents are as follows:Firstly,low probability error is reduced by filtering the received signal strength of indoor environment.By measuring the received signal strength from plurality directions within the plane of the terminal,the direction of the under test terminal is found affecting greatly on the received signal strength,the difference of data from various direction is up to 30% which is one of the important factors that affect the positioning accuracy.By measuring the received signal strength from plurality directions several times,and processing the measured data,modifying the logarithmic propagation model.By testing in indoor environment,it shows that error is reduced by using modified model.Secondly,based on the research of above algorithm,this study achieves a high-precision WiFi positioning system based on Android.This system is divided into Android client and server side,the Android client gets the received signal strength of the wireless AP and after the Kalman filter process,the data sent to the server,completing the phone's location in the server: the signal strength based on the signal propagation model is converted into the distance,and then using the maximum likelihood method to get the phone's coordinates.Server through the interface displays and manages wireless AP information,phone information and indoor maps.The test shows that,the error of modified propagation model could be 1.02 meters,the precision of positioning system could be 2.47 meters.