Research On Light Source Optimization And Safety Performance Of Indoor Visible Light Communication System

Visible Light Communication(VLC)is a very promising wireless communication technology as a strong complement to traditional Radio Frequency(RF)communication.VLC technology is safe,energy efficient and economical,especially in indoor environments.The technology is one of the research hotspots because it can utilize existing white lightemitting diodes(LED)for data transmission,i.e.,it can be illuminated while enabling communication.In a practical VLC system,the position and parameters of the white LEDs will greatly affect the optical power,signal-to-noise ratio and illumination distribution in the reception plane of the communication system.Therefore,in order to improve the fairness of user communication,the optimization of light source layout must be studied.In addition,the explosive increase of Internet information and the emergence of massive users in recent years have led to the increasing interest in Non-Orthogonal Multiple Access(NOMA)technology.The effective combination of VLC and NOMA allows the communication system to take advantage of its potential advantages in spectrum and large-scale access with a manageable complexity.However,due to the characteristics of NOMA-VLC system such as open spectrum and multi-user signal overlay coding,it makes it easy for eavesdroppers to obtain information of multiple users at the same time,which leads to security problems.To solve the above problems,based on the established indoor visible light communication system model,the paper proposes an immune clone bat algorithm to optimize the indoor light source layout and improve the flatness of received optical power,signal-to-noise ratio and illumination distribution in the VLC system.In addition,the security performance of the NOMA-VLC system is studied and analyzed by introducing pseudo-users.The specific work is as follows:(1)In order to make the LEDs satisfy the illumination in the VLC system while better delivering information to the users,the paper proposes a hybrid immune clonal bat algorithm(ICBA)to optimize the layout of the indoor light sources.Specifically,the position of the LED lamp on the ceiling of the room and the half-power angle parameters are optimized by taking into account the effect of primary reflections from the room walls and using the variance of the received light power in the receiving plane as the fitness function.To demonstrate the effectiveness of the proposed algorithm,the received optical power,signalto-noise ratio(SNR),and illuminance distribution of the optimized ICBA are compared with the unoptimized and the optimized data using the Bat Algorithm(BA)and Immune Clonal Algorithm(ICA),respectively.ICA)respectively.The results show that the ICBA optimized for indoor VLC light sources has obvious advantages in terms of received optical power,signal-to-noise ratio(SNR)and illuminance,especially the variance of optical power in the receiving plane can be as low as 0.026 d B after the optimization of this algorithm.(2)To address the potential security issues of the NOMA-VLC system,the concept of "pseudo-user" is introduced to suppress the decoding capability of the eavesdropper assuming the existence of an eavesdropper in the system.Specifically,the eavesdropper is required to steal information only at the periphery of the LED light source coverage area,and its steady-state position distribution satisfies the Random Waypoint(RWP)movement model.The theoretical expression of Signal to Interference plus Noise Ratio(SINR)of the eavesdropper is first derived under this condition,and its statistical properties are analyzed to obtain the theoretical expressions of security interruption probability and throughput of the VLC system.Second,in order to interfere with the eavesdropper’s decoding of the legitimate user’s information,a pseudo-user is introduced and the theoretical expressions for the security interruption probability and throughput of the system are derived under this condition.Finally,the correctness of the theoretical model is verified by Monte Carlo(MC)simulations.Both theoretical calculations and simulations show that the security performance of the system is significantly improved after the introduction of pseudo-users,thus demonstrating the effectiveness of the proposed scheme.The paper work provides some reference for the study of indoor VLC technology.