Energy And Spectral Efficiency Optimization For Multi-carrier Visible Light Communication Systems

With the rapid development of mobile communication technology,people's demand for data services has promoted the development of communication technology.The direct current biased optical orthogonal frequency division multiplexing(Direct Current biased Optical Orthogonal Frequency Division Multiplexing,DCO-OFDM)schemes have been widely used in visible light communication(VLC)systems due to their simple implementation and higher spectral efficiency(SE).However,the sharp increase in the amount of data has also led to tremendous energy consumption in wireless communication systems.higher requirements are proposed on spectral efficiency and energy efficiency(EE).This research(1)is based on the optimization of energy efficiency and spectral efficiency of single user DCO-OFDM visible light communication system.(2)Optimization of energy efficiency and spectral efficiency for direct current biased optical orthogonal frequency division multiplexing access(Direct Current biased Optical Orthogonal Frequency Division Multiplexing Access,DCO-OFDM)multi-user visible light communication system.This dissertation studies the joint optimization of energy efficiency and spectral efficiency in DCO-OFDM systems and seeks a tradeoff between EE and SE.Specifically,the data rate achievable by the DCO-OFDM system with power and bit load is derived by introducing the Lagrangian multiplier method,and the closed expression of energy efficiency and spectral efficiency is obtained.Based on this,the influence of transmitted power on energy efficiency and spectral efficiency is theoretically derived.This topic studies the influence of different parameters on the maximum point,such as the horizontal distance,vertical distance at the receiving end,and the receiving area of the photodiode.In addition,in order to obtain the best transmitted power,a multi-objective optimization based on Pareto optimal set is established.The Cobb-Douglas production function is introduced as a utility function,it is successfully converted into the EE-SE trade-off metric.Single-objective optimization,deriving the relationship between optimal transmit power and weight under different weights,simulation results show that when the weight is large,the optimal transmission power is equal to the maximum transmission power.Considering the power limitation and the minimum data rate requirement limitation for each user,this paper studies the energy efficiency and spectral efficiency optimization of a multi-user DCO-OFDMA visible light communication system.It introduces iterative optimization algorithm and resource sharing algorithm to obtain visible light Communication system data rate.The advantages and disadvantages of the two algorithms are compared.The simulation results show that the resource allocation method can flexibly optimize the spectrum efficiency and energy efficiency.The iterative optimization algorithm is better than the resource sharing algorithm,and the complexity of the resource sharing algorithm is relatively low.