| In recent years,with the rise of the Internet of Things,there are more and more indoor devices that need to access the network,which means that indoor communication has high requirements on the bandwidth and speed of the network.Visible light communication(VLC)technology has received wide attention due to its high speed and large bandwidth characteristics,while taking into account lighting and communication.VLC is one of the most promising technologies for indoor wireless communication.However,VLC has the disadvantage of small coverage and easy occlusion.For this reason,the combination of device-to-device(D2D)communication technology and VLC can complement the shortcomings in VLC and improve indoor communication quality.To meet the requirements of high speed,large bandwidth and low latency of indoor wireless communication,this paper designs the D2D-VLC omnidirectional communication platform,researches the device neighbor discovery and improves the omnidirectional communication terminal performance?The innovative work of this paper mainly includes the following three aspects:ˇDesigns and implements the D2D-VLC omnidirectional communication network demonstration platform.The platform combines VLC with D2D.The intelligent terminal bidirectionally communicate with the background network management system by the uplink and downlink white light communication module,and the visible light-based omnidirectional D2D communication can be realized between the terminals.The platform can implement functions such as cell positioning,file transfer between terminals,and video real-time communication.ˇProposes a neighbor discovery method based on color separation back-off mechanism in D2D-VLC omnidirectional communication network.Neighbor discovery is the premise of communication.The existing neighbor discovery methods are divided into two categories:direct and indirect neighbor discovery.Through analysis,Neighbor discovery of the D2D-VLC omnidirectional communication network has characteristics of limited communication range,short communication distance and easily blocking.Consequently,direct neighbor discovery is more suitable in the communication network,but the existing neighbor discovery mechanism cannot be directly applied into the platform.When the device receives the discovery information request which sent by multiple neighbors in a certain direction,the information may be seriously interfered by each other,which causes the discovery to fail.To this end,we propose the neighbor discovery method based on color separation back-off mechanism in D2D-VLC omnidirectional communication network.This method which can well solve the problems in neighbor discovery mainly includes four technologies:the color separation back-off mechanism,the collision detection mechanism,the neighbor list maintenance mechanism and the optimal back-off time slot TM selection.ˇImplements neighbor discovery in the D2D-VLC omnidirectional communication network platform and optimizes the terminal performance.The implementation of neighbor discovery mainly includes two aspects:software and hardware.The software can dynamically display the name,direction and signal strength information of the discovered neighbors,and can display the dynamic information of neighbor discovery.In order to meet the hardware requirements of the neighbor discovery,the hardware implements the core processing module,the receiving module and the sending module.In addition,the omnidirectional communication terminal is the core device of the D2D-VLC omnidirectional communication network platform,and the quality of communication largely depends on the performance of the communication terminal.The omnidirectional communication terminal is mainly optimized from two aspects:1)To reduce the channel interference and improve the discovery efficiency of D2D user,the position of the terminal PD and LED(such as angle,distance,etc.)are studied.2)To reduce the discovery delay and complete rapid discovery among D2D users,the circuit of receiving and transmitting module is improved. |
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