Beamforming Algorithm For Satellite Communication Based On Statistical Channel Sate Information

With the development of modern aerospace and communication technology,satellite communication has been widely used in broadcasting communications,navigation and positioning,as well as the construction of global three-dimensional coverage network.However,with the increasing demand of high rate data transmission and diversified services such as broadband information broadcast service,how to provide users with more reliable and efficient communication service under the condition of limited on-board resources is one of the key issues in the field of satellite communication.With the development of satellite-borne antenna technology,beamforming(BF)can enhance the received signal power of legitimate users and greatly reduce the probability of eavesdropping by illegal users,which has become one of the important means to achieve reliable information transmission.However,in the satellite communication system,perfect channel state information(CSI)is usually difficult to obtain,so this paper focuses on the statistical CSI satellite communication system beamforming algorithm.The main work of this paper is as follows:1.For the multibeam satellite communication system,assuming that the statistical channel state informations of multiple eavesdroppers are available,an optimization problem is formulated to minimize the satellite total transmit power while satisfying the achievable secrecy rate(ASR)requirement.Then,we propose two robust BF methods to solve the complex optimization problem for both coordinated and uncoordinated Eves.For the case of coordinated Eves,the analytical expression of optimal BF weight vector is obtained by adopting the Lagrange multiplier method.For uncoordinated Eves,the semi-definite relaxation method is used to covert the non-convex problem into a convex one,and the analytical expression of optimal BF weight vector is obtained by using standard Matlab package.Simulation results show that the proposed BF algorithms can effectively improve the safety performance of the system.2.Aiming at the security transmission problem of the physical layer of multibeam satellite communication in the scenario of multiple eavesdroppers,under the condition of available statistical channel state information,two optimization problems are established to maximize secrecy rate with the constraint of total transmit power and per-antenna power budget,respectively.For the total transmit power constraint,the analytic expression of optimal BF weight vector is obtained by using generalized Rayleigh quotient method.For the per-antenna power constraint,the non-convex problem is converted into a convex one by introducing auxiliary variable,and further an iterative golden section-based algorithm is proposed.Finally,simulation results confirmed that the effectiveness and validity of the proposed BF schemes,and the effect of the system parameters on the security performance is also analyzed.3.By considering the co-channel interferences at the amplify and forward unmanned aerial vehicle(UAV)relays,assuming that the statistical CSI of multiple eavesdroppers are available,different beamforming schemes are proposed to improve the communication performance.The closed expressions of signal to interference and noise ratio(SINR)and achievable rate(AR)at the ground receiver are first presented.Then,two optimization problems are formulated,namely total relay transmit power minimization and achievable rate maximization,and the corresponding BF schemes is designed to obtain the optimal BF analytical expressions.Finally,the effectiveness and validity of the proposed BF schemes are verified by simulations.