Research On Precoding Technology Of New Generation Visible Light Communication

With the exponential growth of the number of wireless access devices and related applications of the Internet of Things,spectrum resources are in a state of shortage.The visible light communication technology with abundant spectrum resources has sparked the widespread interest of the research community and the industrial.Visible light communication modulates information to the visible light emitted by LEDs and other lighting equipments for data transmission.It has high transmission rate,green,safe and energy-saving characteristics,and has become one of the most promising technologies in the sixth generation mobile communication system.In order to achieve high data rate,the visible light communication system has introduced MIMO technology.In order to suppress the interference caused by MIMO technology and further improve the system performance,this paper focuses on the precoding technology in the new generation of visible light communication.The main contents are as follows:1.The precoding design problem of multi-source visible light system based on fairness optimization is studied.Aiming at the scenario where the transmitter cannot obtain completely accurate channel state information,a robust precoding scheme is designed.This scheme considers satisfying the constraints of visible light signal transmission characteristics,takes max-min fairness as the optimization goal,maximizes the user’s minimum signal-to-interference plus noise ratio,and compares it with the non-robust scheme.Simulation results show that the designed robust precoding can better adapt to scenarios with imperfect CSI.2.The joint optimization of precoding and receiver equalization in the multi-color MIMO-VLC system is studied.Aiming at the problem of signal crosstalk caused by non-ideal filters used in multi-color MIMO-VLC systems,a joint design scheme of precoding and receiving end equalization is constructed.This scheme combines the amplitude constraints of visible light signals,Mac Adam ellipse chromaticity constraints and luminous flux constraints to establish an optimization model with the goal of minimizing the mean square error of the received signal,and optimize the precoding matrix,equalization matrix and luminous flux.The research results show that with a small increase in complexity,the constructed scheme has better performance than the fixed equalization matrix that only optimizes the transmitter precoding and the pseudo-inverse-based zero-forcing precoding.3.The energy efficiency optimization problem in the multi-color visible light multi-user MIMO system is studied.Aiming at the problem of maximizing energy efficiency in multi-color visible light multi-user MIMO systems with signal crosstalk,this paper proposes a two-layer iterative optimization algorithm based on Dinkelbach’s method.The algorithm considers the visible light signal amplitude constraint,Mac Adam ellipse chromaticity constraint and luminous flux constraint,and solves the optimization problem of maximizing the energy efficiency of the system.In order to turn the fractional non-convex problem into a solvable convex problem,the outer layer uses the Dinkelbach method to update the auxiliary variables,and the inner layer uses the relationship between the system rate and the mean square error to further transform the problem,and then optimize the variables Alternate iterative solution.The research results show that the proposed energy efficiency maximization algorithm can quickly converge to the optimal solution and obtain higher system energy efficiency.