Research On Energy Efficiency Analysis Of Visible Light Communication System Based On Nonlinear LED

With the advent of the 5G era,the demand for mobile data services is increasing dramatically,and the available frequency band resources of radio frequency communication are increasingly scarce.Therefore,the visible light band with huge bandwidth has rapidly attracted widespread attention of research groups all over the world,and plenty of research work on visible light communication(VLC)has been carried out.VLC has abundant spectrum resources,meanwhile,it has the advantages of high data rate,high confidentiality,and no radiation.However,nowadays VLC widely adopts the light-emitting diode(LED)as emitting devices,and its nonlinear characteristic becomes the core factor in determining the performance of the VLC system.Consequently,it is undoubtedly of great importance to study the effect of nonlinear LED on the performance of the VLC system.Energy efficiency(EE)and spectral efficiency(SE)are two important metrics in the optical communication system.However,their maxima can hardly be achieved simultaneously.Hence,the tradeoff between EE and SE has become a critical problem in the optical communication system.This paper focuses on the EE-SE tradeoff in nonlinear VLC system,the effects of VLC system parameters on EE,and the nonlinear distortion compensation technology of the LED.The main contributions are summarized as follows.First,the Rapps model is employed to describe the nonlinear characteristic of the LED,and the distortion effect caused by the nonlinear LED is verified.On the basis of which,by taking the direct current-biased optical orthogonal frequency division multiplexing(DCO-OFDM)system as an example,the EE-SE tradeoff relationship of the nonlinear VLC system is theoretically analyzed.The closed-form expression of the EE-SE tradeoff is derived,and by introducing Lambertian function,the change trend of EE is obtained when the SE increases.Furthermore,closed-form expressions of the EE-SE tradeoff under the horizontal and vertical LED distributions are derived,respectively.Effects of various system parameters,such as horizontal distance and vertical distance between LED and photodetector(PD),the half power angle of the LED and the effective area of the PD,on EE are analyzed.Simulation results are provided to verify the theoretical analysis.Second,beginning with artificial neural network,a nonlinear distortion compensation technology of the LED based on multilayer perceptron(MLP)network is proposed.Starting from using the MLP network to build an LED nonlinear compensation model,a robust MLP network through multiple training and adjustment of model parameters is obtained.Then,for the VLC system of LED nonlinear compensation based on MLP network,the theoretical analysis of EE is carried out.Closed-form expressions of the EE-SE tradeoff under the horizontal and vertical LED distributions are derived respectively,and effects of various system parameters on EE are analyzed.Simulation results show that the EE and SE of the VLC system are deteriorated by the nonlinear characteristic of the LED,and the EE of the VLC system can be effectively improved by nonlinear distortion compensation technology based on MLP network.