| With the rapid development of internet,the demand of wireless service is growing.However,wireless electromagnetic spectrum that used by radio frequency(RF)communication was reduced.In this background,visible light communication(VLC)using LED is the hot spots in optical wireless communication,which has the characteristics of higher speed modulation and green lighting.Compared with RF communication,VLC with high security,without radiation and no spectrum license.Indoor VLC is an effective complement to indoor wireless communication system,and provides a new wireless access.At present,researching on indoor VLC mainly focus on promoting communication rate by optimizing channel and modulation,and increasing the received signal by designing condenser.The research on the effect of LED array layout for VLC system can be ignored.Therefore,the distribution of LED array has been studied in this dissertation to lay a foundation for practical application.Firstly,in the case of energy loss optimal,for reducing indoor communication blind zone according to the room size is 5m ×5m ×3m,with average outage area rate as the optimization goal,the standard particle swarm optimization(PSO)algorithm has been used for studying of indoor LED array layout.The algorithm’s parameters such as inertia weight,learning factor,population size,maximum velocity and termination conditions have been designed.Meanwhile,system performances of LED rectangular array layout and circular array layout,such as received power distribution,signal to noise ratio distribution,average outage area rate and energy loss,have been analyzed.It is clear from the results that received power enhanced regardless of increasing the number of LED or improving the single LED transmission power.LED array layout used PSO algorithm has reduced the power outage rate of system and blind zone.When received power distribution satisfies the requirement of communication,compared with rectangular array layout,the number of LED in circular array layout is only half.Secondly,rectangular and circular array layouts suitable for any room size are established based on optimal mean square error of illumination.The expression of illumination and power is deduced by integral,the optimization model function F(l,x,y)of rectangular layout and F(r,x,y)of circular layout has been builded on the basis of the mean square error of illumination.In order to verify the feasibility of model function,simulation experiment was crried out in the size of 5m ×5m×3m.Results show that,the best location for rectangular array layout is l =1.46 m,illumination uniformity increased from 80.5% to 84.3%,the best location and illumination uniformity has no change along with the increase of the number LED.The optimal radius for circular array layout is r =2m,illumination uniformity increased to 89.2% when the number of LED is 16,form 85.2% at the number of LED is 4,which showed illumination uniformity can be enhanced by increasing the number of LED.In addition,field of view(FOV)for two kinds of layout is FOV =80deg.Thirdly,in order to do not limit the layout,providing mean square error of received power which can reflect the received power consistency,and LED array layout has optimized by using an improved artificial fish swarm algorithm(IAFSA).The order method based on exchanging list during the action of preying increases the population diversity,and adopts an adaptive moving during the action of random move enhance the ability of global search and search efficiency,which ensures the convergence of IAFSA.The algorithm’s parameters such as the vision of artificial fish,step length,the degree of congestion,the number of artificial fish,and the maximum number of trying have been designed.Simulation results show that,the received power consistency of the optimized array layout increased by 33.5%,the illumination distribution more uniform and signal to noise ratio has also been enhanced,when the number of LED is 4.When the number of LED is 16,compared with rectangular and circular array layout,the the received power consistency of the optimized array layout increased by 45.1% and 35.3% respectively.At the same time,the illumination distribution becomed more reasonable,the indoor luminance conformed international standards.Compared with evolutionary algorithm and gene density genetic algorithm found that the global searching ability and the searching efficiency of the IAFSA is higher,and efficiency of layout is better by optimizing.Finally,in order to verify the schemes of layout based on the optimal energy loss,the optimal mean square error of illumination and the IAFSA in an indoor VLC system,an experimental system is established.Diagram of experimental system is introduced,the key circuit of transmitter and receiver are designed.The experimental results show that the feasibility of three kinds of layouts in an indoor VLC system,the theoretical and experimental support for the practical application of indoor VLC system. |
PDF Full Text Request