Design Of Tunnel Vehicle Positioning System Based On Visible Light Communication

With the acceleration of the pace of highway construction in our country,especially in the mountainous areas,the number of highway tunnels has increased dramatically.Due to the tunnel has a small internal space,complicated structure,closeness and other characteristics,the GPS positioning system has lost its positioning function in the tunnel,which brings some obstacles to the safety driving and smooth traffic.Therefore,we need a new technology that does not rely on the GPS signal to achieve the positioning.At the background of the existing short-range wireless location system which represented by Wi-Fi,Bluetooth,ZigBee,that have the low positioning accuracy,the wireless spectrum resource consumption is serious,the project implementation cost is high and the system layout is complex.As the main application of visible light communication,VLC positioning technology which makes full use of the existing lighting facilities,we can get the higher positioning accuracy at the same time.Based on the laboratory project,this paper mainly sthdies the tunnel vehicle positioning systen based on the visible light communication from the three aspects of the channel characteristics of tunnel visible light communication,communicationnode design and the localization algorithm.First of all,starting from the characteristics of LED,the principle of LED light-emitting,the electrical and the optical properties and the radiation modle are described in detail.Combined with the environmrnt of the tunnel,the VLC link is analyzed.Thenwe utilize the Matlab to design the layout of the light source,to guarantee the average brightness of the illumination area achieves the system requirement of the lighting and the communication.Then,according to the demand of the system,the circuit of the anchor node and the mobile node are designed.The anchor node can transform the data information in the form of the light without affecting the normal lighting.The mobile node can get the optical signal and transform the signal to the RSS signal and the data information.At the same time,the software of the communication unit and the control unit are designed based on the FPGA module.Finally,the design of the visible lightlocalizationalgorithm based on the trilateral positioning is proposed.The "RSS-diatance" empirical formula is obtained by fitting the received RSS signal in the offline modeling stage.In the online positioning stage,three groups of RSS data are seclected from all the data at first,then the final positioning result can be estimated by combined with the "RSS-diatance" empirical formula and the trilateral positioning algorithm which based on the maximum likehood estimate.