Research On Key Technologies Of Integrated Optical/Radio Frequency Wireless Communication Link

Both the military and civilian sectors are putting forward increased expectations for enormous and high-speed data transmission as information and communication technology develops at a rapid pace.High-speed transmission rate,huge channel capacity,high anti-interference ability,high confidentiality,and unregulated spectrum are all advantages of optical wireless communication technology.It is one of the most important means to meet the needs of military and civil applications.However,optical wireless communication is susceptible to weather conditions such as cloud and fog,which leads to reduced reliability.Radio frequency(RF)communication are more reliable and insensitivity to the cloud and fog weather conditions.However,RF communications are not able to meet the increasing demand for high performance communications.Therefore,the concept of combining wireless lasers and radio frequencies is one of the effective solutions for building future high performance wireless communication networks.However,due to multiple application scenarios,the feasibility of the implementation of the integrated optical/RF communication link is limited.The main restrictions include no channel state information feedback,non--line-of--sight communication,long distance,strong fading and turbulence,and energy limitations of relay nodes.This dissertation mainly models and analyzes the integrated optical/RF communication link under the above constraints,and derives the analytical expressions of important performance indicators such as the overall link outage probability,average bit error rate(BER),channel capacity,and secrecy outage probability.This provides a theoretical basis for future engineering practice.Firstly,this dissertation addresses the problem for timely and accurate channel state information feedback for traditional hard-switched hybrid optical/RF wireless communi-cation links and the problem of pointing error that seriously affects the performance of communication links in practical scenarios.A model based on the selection combining scheme of parallel hybrid optical/RF wireless communication link considering the effect on fading,turbulence and alignment errors is established.Closed-form analytical expres-sions for the link outage and BER performance are derived with the help of mathematical tools such as special functions.The results facilitate direct use in practical calculations,thus avoiding the problem of consuming a large amount of computational time for simu-lations and providing a theoretical reference for further revealing the potential of hybrid links.Secondly,this dissertation addresses the problem of hybrid optical/RF communica-tion links subject to radio eavesdropping and interference,and uses a modeling analysis approach to model a hybrid optical/RF communication link in a non-cooperative target scenario based on a generic Malaga distribution.The effect on multiple model parameters including the number of RF antennas,turbulence intensity,pointing error,and interference signal-to-noise ratio(SNR)on the probability of outage,the effect on the eavesdropping SNR on the security performance and BER of the hybrid link are analyzed.The closed-form analytical expressions of the lower bound of the end-to-end outage probability,the average BER,and the secrecy outage probability of the hybrid link are derived.Further-more,the asymptotic performance of the hybrid link at high SNR region is further ana-lyzed,and the determinants of the link diversity gain are obtained.The above inferences and simulation analysis results can provide a theoretical reference for solving the factors limiting the performance of the hybrid link in this scenario.Thirdly,this dissertation addresses the problem that traditional hybrid communica-tion links using near-infrared wavelengths cannot cross obstacles for non-line-of-sight communication.A solution using a parallel hybrid ultraviolet(UV)/RF communication link is proposed.Using the method of mathematical modeling,a hybrid UV/RF commu-nication link model under the single edge peak occlusion model considering the link loss and turbulence is established.On the one hand,the relationship between the path loss and the baseline distance,the height of obstacles,and the position of the path loss is ana-lyzed to provide a theoretical reference for the optimal deployment method in the actual engineering of the system.On the other hand,the closed-form analytical expressions for the outage probability and BER of the hybrid UV/RF communication link under weak,medium and strong turbulence conditions are derived under the input restrictive condi-tions of the dissertation,which will provide some theoretical basis for future engineering practice.Fourthly,the energy-constrained relay nodes often become the performance limiting factor of the long-distance wireless communication link.This dissertation adopts the idea of reducing the hardware and software complexity of relay node and spreading the com-plexity to the source node as well as the destination node.The dissertation establishes a model of a cascaded RF/optical wireless communication link under the energy constraint of relay node by using single antenna amplified forwarding for relay node and multiple antennas for source and destination nodes in order to improve the overall link transmission performance of the link.This dissertation analyzes and discusses the performance indica-tors of the hybrid link under the above model.The closed-form analytical expressions of the link end-to-end outage probability,BER,and channel capacity under the above model are derived.The model proposed in this dissertation has larger channel capacity,stronger robustness and can enhance the link performance due to turbulence without increasing the complexity of the relay node.Finally,knowing that the SISO systems can not combat the fading efficiently.This dissertation uses a multi-antenna technique to model the unified cascaded mixed MIMO RF/optical relay wireless communication link in good working conditions for acquisition tracking and pointing system.With the help of mathematical methods such as special functions,the closed-form analytical expressions of mixed link outage probability,aver-age BER and channel capacity are derived.The influence trend of various model param-eters on link performance is analyzed.Based on this,the dissertation further derives an expression for the asymptotic performance of the hybrid link at high SNR region and dis-cusses the diversity-multiplexing trade-off of the link.The variables that determine the diversity/multiplexing gain of the entire link under different antenna configurations and channel conditions are given.The above mentioned research provides a certain theoretical basis for actual engineering practice in the future.In summary,the research conducts mathematical modeling and theoretical deriva-tion and analysis of the main performance of the integrated optical/RF communication link under the constraints of a variety of practical scenarios.Closed-form analytical ex-pressions for main performance metrics such as outage probability,average BER,and channel capacity are derived.The simulation results verify the correctness of the model establishment and theoretical analysis.It provides a theoretical reference for future high performance wireless communication design and a certain theoretical basis for the design of high speed backbone networks.