Research On Physical Layer Security Performance Of VLC/RF Hybrid Communication System

In 2019,the 6th Generation(6G)Wireless Summit was held in Finland,marking the beginning of 6G related research.In the 6G white paper issued by the conference,Visible Light Communication(VLC)has been considered as an extremely promising communication technology for 6G research and development due to its high-speed,high-frequency,green,and safe communication performance.However,the visible light signal is easily affected by distance and environment,resulting in serious signal attenuation,which has become one of the important reasons restricting the development of VLC.The relay technology commonly used in radio frequency(RF)communication can overcome the shortcomings of VLC transmission distance,thereby improving the transmission performance of the visible light communication system and broadening the communication margin.In addition,if VLC wants to be integrated into the traditional RF communication environment,it must be integrated with traditional RF communication before it can be applied to more practical scenarios.Based on the above background,researchers have proposed a VLC/RF hybrid communication system model based on relay cooperation,which can give full duplex mode to the superior performance of visible light.However,the introduction of relays not only improves the communication performance,but also brings the following two deficiencies to the communication system: One introduces more uncertain safety factors;the other requires more energy consumption for large-scale relay node deployment.In view of the above two shortcomings,considering the broadcast characteristics of wireless communication,this article focuses on the physical layer security performance and energy consumption of the VLC/RF hybrid cooperative communication system.The main work content is as follows:(1)Mathematical modeling and theoretical analysis of the physical layer security performance of the hybrid VLC/RF cooperative communication system based on relay energy collection.The relay is equipped with a light energy harvesting device to collect the DC bias in the light signal and use it for relay signal decoding and forwarding.The impact of energy harvesting technology on system performance is studied.In terms of reliable communication,the end-to-end communication rate is deduced,and the optimal DC bias is obtained;in terms of safety communication,the safety performance indicators such as the system’s safe interruption probability and the average safe channel capacity are mainly derived,and correspondingly,Close analysis.The simulation results show that a proper DC bias can effectively improve the safety performance of the system.(2)Further expand the research on the basis of the point-to-point communication architecture to discuss the physical layer security performance of the VLC/RF communication system in the multi-user scenario.The introduction of NOMA technology further improves the spectrum efficiency of the system and makes the system model more general.The closed-form expressions of the system secrecy outage probability and the non-zero secrecy capacity probability under the conditions of high signal-to-noise ratio and Chebyshev approximation are deduced respectively,and the optimal power allocation factor is discussed.The simulation results verify the correctness of the theoretical derivation.The existence of an optimal power distribution factor minimizes the secrecy outage probability of the entire system,and a suitable DC bias can improve the safety performance of the system.