Research On Scheduling Algorithm And Protocol Implementaion Of Visible Light Communication Network

In recent years,as the mobile communication technology develops rapidly,better quality and higher speed are required.However,traditional wireless communication using radio frequency(RF)as the medium gradually fails to meet people's need due to the scarcity of spectrum resources.In addition,with the concept of green technology and environmental protection propagates,the cost and energy efficiency of communication technology are under consideration.Situations mentioned above urge new communication methods as replacement.Visible light communication(VLC)attracts a great attention for the advantages in rich spectrum resources,green and safe use,high energy conversion rate.This paper focuses on the analysis of obstacle environment of the VLC system and design of effective algorithm which can relieve obstacle's effect,the design and implementation of MAC layer protocol are also included.Firstly,the paper gives an overview of the components of VLC system and its basic principles.The paper introduces a typical model of VLC system,based on which the detailed components,channel model and noise model are analyzed,and obstacle environment is also introduced.The paper also introduces the VLC MAC layer protocol,listing two popular MAC protocols,among which IEEE 802.15.7 standard is stressed.Additionally,the paper analyzes indoor VLC environment with obstacles.The paper divide the blocking situations into two categories,vertical obstacle and horizontal obstacle,according to the number of links being blocked.Simulations are made to show the effect of different obstacles on the receiving signal to noise ratio(SNR)and overall throughput.Then,based on the obstacle categorization mentioned above,obstacle decision algorithm is proposed and different patterns of light layout are applied to this algorithm so that the most suitable layout is selected.Furthermore,the paper studied the scheduling algorithm under obstacle effect.The paper proposed an improved method based on the incremental light scheduling algorithm suitable for the indoor VLC system.The proposed algorithm deploy different strategies to the blocked user based on the obstacle types.For vertical obstacles,time slots of non-blocked lights nearby are dedicated to the blocked user as compensation.For horizontal obstacles,time slots of adjacent non-blocked lights are shifted to the blocked user.Simulation results show the proposed algorithm can effectively relieve the attenuation caused by obstacles.Finally,the paper introduces the design and implementation of functionality modules in VLC MAC layer protocol.The paper introduces the overall framework and module division of an improved VLC MAC protocol based on the IEEE 802.15.7 standard.Then the frame structure and primitive design of disassociation module and handoff module are proposed.Strategies including hysteresis and dwell timer are introduced to the handoff process to eliminate the Ping Pong effect,and the handoff process is simplified to shorten the delay.In the simulation,we run the program representing coordinator on PC and run the program representing the device on the Raspberry,and the effectiveness of each function module was verified.