| As the development of internet of things and next generation mobile communication technology,data transmission quantity will be more than ten billion.Visible light communication(VLC)technology based on white LED has become a key technology of the next generation mobile communication due to its functions of illumination,high transmission rate,anti-electromagnetic interference,energy conservation and environmental protection,etc.In recent years,it has developed rapidly and regained the interests from both academia and industry.In order to figure out the essential performance of VLC system,VLC channel should be studied carefully.However,an increase in the number of VLC equipments results in that shadow occlusion effect will become a serious problem in indoor VLC system.In order to describe the influence of shadow occlusion in detail,this paper studies the shadow effect in indoor VLC channel model,and investigates the multi-light sources shadow occlusion indoor VLC channel model.The main work of this paper is as follows:Firstly,this paper introduces the research background and significance of VLC system,as well as the research status of it.Then,the important components and basic principles of VLC system are studied and analyzed carefully,and the existing VLC channel modeling methods are introduced in detail.Aiming at the problem that the shadow occlusion has serious influence on the communication quality of VLC system,the quantitative research on the shadow occlusion effect of single light source is carried out.In order to make the calculation of shadow occlusion effect more consistent with the actual situation,this paper gives the mathematical derivation of the shadow position and shadow area,which are classified by whether the shadow overlaps with the boundary of the communication room of VLC system.Through the mathematical and geometry principle,this paper deduces shadow position and the formula of shadow area to realize accurate quantization.In the actual indoor VLC environment,due to the different number of light sources,there are different ways to quantify the shadow occlusion effect.The quantitative research on the shadow occlusion effect of multi-light sources is completed,and the indoor VLC channel model of multi-light sources shadow occlusion is further investigated.According to the different number of light sources,the formulas for calculating the shadow area under two light sources,three light sources and four light sources are derived,so as to achieve the purpose of quantifying the shadow occlusion effect of multi-light sources.Furthermore,by combining the quantization of multi-light sources shadow occlusion effect with the multi-light sources non-shadow occlusion indoor VLC channel model,the purpose of building multi-light sources shadow occlusion indoor VLC channel model is achieved.Finally,the communication quality of multi-light sources shadow occlusion indoor VLC channel model is simulated and analyzed.In order to show the distribution of signal-to-noise ratio more intuitively,the outage probability is proposed as the measurement standard,and the outage probability under different number of light sources and shadows is simulated and compared.The simulation results show that when the number of light sources and transmission power are fixed,with the increase of the number of obstacle shadows,the signal-to-noise ratio decreases,and the outage probability increases.When the number of obstacle shadows and the transmission power are constant,increasing the number of light sources,the signal-to-noise ratio increases,and the outage probability decreases.It is concluded that the shadow occlusion effect can be reduced by appropriately increasing the number of light sources.In a deeper level,based on the outage probability,a simulation optimization of the VLC system’s room size,the field of view angle and the LEDs’ half power angle is also presented.This paper figures out that the optimal value of the LEDs’ half power angle is 60°,and the optimal value of the field of view angle is 60°. |
