Analysis Of Security And Practical Feasibility Of Indoor Visible Light Communication System

With the continuous development of science and technology,the lifestyles continue to diversify,and the demand for high-speed communications continues to increase.However,in the traditional wireless communication system,spectrum resources are becoming increasingly tight and can no longer meet the needs of high-speed and high-quality communications.Expansion to the visible light band with rich spectrum resources is an effective method to meet the demand.Therefore,research on visible light communication technology has important practical significance.This paper makes the following researches on the security and practical feasibility of indoor visible light communication:This paper first studies the secrecy performance of an indoor visible light communication(VLC)system based on spatial modulation(SM).The system mainly includes multiple transmitters,a legitimate receiver,and an eavesdropper.At the transmitting end,the SM scheme and the uniform selection scheme that the probability of selecting each transmitter is equal are adopted.Under the constraints of non-negative and average light intensity,the lower and upper bounds of the secrecy rate are obtained,respectively.On this basis,the additional peak light intensity constraint is further considered,and the new upper and lower bounds of the secrecy rate can be further obtained.At high signal-to-noise ratios(SNR),we analyze the asymptotic properties of the upper and lower bounds of the secrecy rate and the asymptotic performance gap.Simulation results show that the upper and lower bounds of the secrecy rate are tight.At high SNR,the asymptotic performance gap between the upper and lower bounds of the secrecy rate is small.In order to further improve the security performance,an adaptive selection scheme and a greedy selection scheme are proposed when selecting a transmitter.In addition,the greedy selection scheme has the best performance,followed by the channel adaptive selection scheme and the uniform selection scheme.When there are multiple eavesdroppers indoors,we consider a system that includes a transmitter,a legitimate receiver,and multiple eavesdroppers.In this system,considering the randomness of the receiver position,we studied the safety transmission performance in the indoor VLC system.We consider three constraints on the input light signal: non-negative,peak,and average light intensity constraints.According to the principle of information theory,the upper and lower bounds of the secrecy outage probability(SOP)in the indoor VLC system are derived.The numerical results show that the derived upper and lower bounds of the SOP can be used to evaluate the system performance.In addition,the number of eavesdroppers,the light intensity,and the size of the area radius have a great impact on the SOP.Finally,the feasibility of the indoor visible light communication system in the real scene is discussed.To ensure that the number of bits mapped by the transmitter index on each time slot is an integer,the number of transmitters in a VLC system based on SM is usually set to a power of two.In order to break the limitation on the number of required transmitters and provide more design flexibility,this paper will use a channel adaptive bit mapping(CABM)scheme to study a communication system with any number of transmitters.This article will analyze the theoretical expression of mutual information and derive the lower bound of mutual information.Both theoretical analysis and numerical results show that the gap between mutual information and its lower bound is small.Finally,in order to further improve system performance,a precoding scheme is proposed to maximize the minimum distance between any two constellation points in the received signal space.As shown by the numerical results,the performance of mutual information can be improved by using the precoding scheme,and the system performance is significantly improved.