Study On Key Techniques In Smartphone-Based Visible Light Indoor Positioning System

Since the twenty-first Century,the demand for indoor location services has been growing dramatically.The rapid popularization of the Internet has led the development of indoor positioning technology into a fast lane.The traditional global positioning system(GPS)is difficult to be widely-used in the indoor environment because the signal can not penetrate the wall.Compared with other methods which based on radio frequency(RF),Bluetooth or WLAN,visible light positioning(VLP)has unique advantages of simple deployment,no electromagnetic interference and high accuracy.Due to these advantages,VLP is regard as a new indoor positioning technology that is widely researched by researchers at home and abroad.With the angle of arrival(AOA)algorithm,camera based VLP can achieve to sub-meter precision.As image sensors are integrated in smart phones,this scheme is more convenient than other visible optical positioning techniques.In the indoor environment,window glass,polishing furniture,etc.will introduce mirror interference in the captured image,which affects the recognition of the LED beacon.Therefore,it is of great significance to eliminate the specular interference in the camera based indoor positioning system.This paper describes a smartphone-based visible light indoor positioning system.At the transmitter end,the OOK signal is generated by voltage source driving FPGA,and the location ID is modulated to LED current in white light.At the receiving end,the smart phone captures the location ID of the beacon which contained in the LED beacon.Based on the system,we did some research aiming at the positioning ID's generation and recognition,the pixel of the smartphone,LED beacons' layout,spacing and the height of LED beacons above the floor.A preliminary exploration of specular reflection was conducted aiming at the common problem in the VLC-based indoor positioning system,which laid a theoretical foundation for the further study.Specific work are as follows:First,two methods of location beacon recognition are proposed,which are the Hough transform based edge detection and the fast Fourier transform based recognition algorithm.Second,based on the visible indoor positioning model,we built a visible indoor positioning system,researched and analyzed the factors that affect the positioning performance(camera pixel,positioning height and LED beacons spacing).Third,the algorithm of specular reflection cancellation based on LED beacons' layout is proposed for the first time,and an experimental system is set up to verify the algorithm.The experimental results show that under different LED beacons' layouts,the algorithm can identify and eliminate the specular reflection accurately and improve the robustness of the positioning system.