Modulation Technology And Positioning Algorithm Based On Visible Light Communication

Visible light communication technology,which uses LED to illuminate and communicate,has great application prospects in the future communication field,such as 6G,so it has attracted continuous attention of researchers.The main reasons for the development of this technology include the increasing popularity of solid illumination,the higher brightness and longer lifetime of LED in proportion to other artificial light sources such as incandescent lamps,and the advantages of visible light communication(VLC)such as high speed,large bandwidth,good data security,no electromagnetic interference and low power consumption.These advantages will help to solve the problems faced by traditional communication systems and lighting technology.Modulation technology has always been an indispensable part of communication system.Due to the incoherence of light,modulation technology applied to visible light communication has some limitations compared with traditional radio frequency communication.At present,the research of visible light modulation technology is mostly the combination of various modulation technologies or the combination of modulation technology and coding.There is no comprehensive comparative analysis of visible light modulation technology,nor the research of background light noise in modulation system.Positioning is a typical application of indoor visible light communication.Previous positioning algorithms are always used for two-dimensional positioning,and the research on three-dimensional positioning has only begun to increase in recent years,but usually only focus on positioning accuracy as an indicator.In view of the above situation,the modulation technology and positioning algorithm of indoor visible light communication are studied in this paper.The main work is divided into three parts.Firstly,the characteristics of LED light source are studied and the channel model of indoor visible light is established.The basic channel models include line-of-sight link model and non-line-of-sight link model.This paper analyzes the channel gain and impulse response of these two basic models.The impulse response of two basic link models is simulated and analyzed.Taking the line-of-sight link as an example,the influence of half power angle on power distribution is discussed.Secondly,the modulation technologies applied to indoor visible light communication are studied.Under the limitation of IM/DD,modulation technologies for visible light communication can be divided into two categories:baseband modulation and subcarrier intensity modulation.In this paper,the simulation of OOK,PPM,DPIM and DH-PIM in baseband modulation and BPSK in subcarrier modulation are studied,and several baseband modulation technologies are compared and analyzed.Then,taking DPIM with moderate performance in all aspects as an example,the modulation system with background light noise is simulated and analyzed,and the method of removing background light interference is proposed.Finally,a novel three-dimensional positioning algorithm is proposed in this paper,which is based on received signal strength indication(RSSI).In view of the fact that the traditional RSSI is aimed at two-dimensional positioning,the minimum triangle method,which is applicable to more scenarios,is proposed to solve the altitude coordinates.In order to reduce the interference caused by occlusion,the centroid weighting method is introduced.The simulations show that this novel three-dimensional positioning algorithm can achieve an average error of 4.35 cm.Then,an optimization scheme is proposed for multi-LED scenarios.The first step is the optimization of LED selection.The simulation results show that the location accuracy can be improved by choosing an acute triangle topology.The second step is the optimization of the algorithm in three-dimensional positioning.After selecting the LED,the test points outside the LED connection area are not considered.Therefore,the minimum triangle method can be greatly optimized.The simulation results show that the positioning accuracy of the optimization algorithm is equivalent to that of the minimum triangle method,and the calculation time of the minimum triangle method is about 61 times of that of the optimization algorithm.