Joint Optimization Design Of Communication And Lighting For Multi-color Visible Light Communications

Visible Light Communication(VLC)utilizes ubiquitous Light Emitting Diodes(LEDs)as the illumination source and signal transmitter to achieve high-speed communications as well as LED green lighting at the same time,which has great potential for development and wide application prospect.However,the limited modulation bandwidth of LED limits the increase of its communication speed.Multiple wicks in a multicolor LED provide a natural multi-input structure.Using multiple wicks of a multi-color LED light source to achieve color multiplexing is a viable way of increasing the transmission rate,so multi-color transmissions has important significance for the future high-speed signal transmission and is of great research value.Jointly considering the communication performance and actual lighting requirements adds a certain degree of difficulty to theoretical research on multi-color transmission technology.For the multi-color parallel transmission of visible light,this article is aimed at the essential requirement of deep integration of communication and lighting in visible light communication.Based on the analysis of the relationship between lighting parameters and communication parameters,this paper proposes an integrated design method for communication and lighting.The specific research contents are as follows:1.The causes of crosstalk in multi-color visible light transmission are analyzed,and the system model of multi-color visible light communication is established.To minimize the minimum signal to interference and noise ratio of data streams,a convex relaxation method for non-convex optimization of communication and lighting parameters is proposed.The LED spectrum is modeled and the cause of crosstalk in the multi-color transmission channel is analyzed.In consideration of multi-color crosstalk,a multi-color MIMO-VLC model different from traditional wavelength division multiplexing is proposed.Based on the multi-color MIMO model,considering the communication constraints and the actual lighting requirements,a joint optimization problem of communication and lighting parameters is proposed.Since the original optimization problem is non-convex,slack variables and variable substitution are introduced.The method transforms non-convex objective functions and proposes a convex relaxation method.Finally,the convex optimization related theory and tools are used to solve the problem and carry out simulation analysis.The simulation results show that compared with the exhaustive search,the proposed method has a certain performance loss,but the loss is very small but it significantly reduces the difficulty of the problem.At the same time,the system performance corresponding to the luminous flux distribution obtained by the proposed method is superior to the equal distribution.When other conditions are equal,the higher correlated color temperature means the better system performance.2.Focusing on the essential requirement of deep integration of lighting and communication in visible light communication,with the objective of minimizing the total mean square error of all data streams,an adaptive transceiver design problem based on multi-color MIMO-VLC system is proposed.The QLED-based transceiver design system model used is introduced to illustrate the processing of the transmit and receive signals.The description and analysis of the optimization objective function,brightness limit,chromaticity limit,and signal amplitude limit are described and analyzed.The mathematical model of the optimization problem is constructed by minimizing the total mean square error of all data streams,and the iterative idea and convex optimization are used.We solve the optimization problem,propose an adaptive illumination transceiver design algorithm,analyze the convergence and complexity of the proposed algorithm,and finally use the simulation to verify and contrast the proposed algorithm.Simulation results show that compared with the traditional zero-forcing precoding design and fixed receiver precoding design,the proposed transceiver design method achieves better system performance.In addition,the proposed method is superior to the conventional wavelength division multiplexing receiver because multi-color crosstalk is considered.Also,a high color temperature corresponds to better system performance.3.In view of the fact that the non-defective characteristics of the signal design of the transceiver in visible light communication,considering the communication and illumination constraints jointly to maximize the minimum Euclidean distance of the receiver constellation,we design a channel adaptive multicolor constellation and the system performance is improved.The issue of multi-color constellation design is analyzed and summarized.The system channel model is introduced.The constellation optimization problem is described,including the objective function and some communication illumination constraints.An optimization model based on channel adaptive multi-color constellation design is established.Due to the non-convexity of the optimization problem,a first-order Taylor series linear approximation method was used to solve the problem.An effective method to solve the optimization problem was proposed and an optimized constellation design was obtained.Finally,the simulation analysis is performed,and the commonly used transmit-side constellation optimization scheme and the channel-adaptive multi-color constellation design scheme proposed in this paper are compared and analyzed.The results show that the proposed design scheme is better than the constellation design method optimized at the transmitter.The proposed constellation design can be adjusted adaptively as the channel conditions change.