Research On Distributed Safety Beamforming Algorithm Based On Feedback Control

Recent years,research work on the technology of physical layer security(PLS)has attracted much attention,which is one of key technologies in the future communication system.The basic idea of PLS is to achieve secure communication by making some performance metric(e.g.,signal to noise ratio(SNR))of the legitimate receiver better by compared with the eavesdropper.Moreover,the traditional technology of distributed transmitting beamforming(DTB)became popular with many years of development,but there are some challenges for the PLS in DTB.The motivation of this thesis is to make a research on the PLS in DTB.The recent progress of PLS focuses on the fading wiretap channel,and most of them require the legitimate receiver to feedback the channel state information(CSI)to the transmitter.However,to acquire the precise CSI is not feasible under some situations,which limits the application of some exiting approaches of PLS in practice.There are three sources to cause the uncertainty of CSI,which are estimation errors,delay and the capacity limitation of feedback link.This thesis proposes a new system of secure DTB based on one-bit feedback information.Note that the proposed system requires only one-bit feedback information transmitted from the legitimate receiver instead of any CSI,which takes little network resources to improve the secrecy capacity.Based on the proposed system,this thesis further design an implementation algorithm,referred to as secure distributed transmitting beamforming with phase mismatch(SDTB-PM).The superiority of SDTB-PM includes: firstly,only one-bit feedback information from the legitimate receiver is required to control the phase offset of an artificial noise(AN)in each distributed transmitter.Furthermore,SDTB-PM utilizes the cumulative positive feedback information and the successive negative feedback information to improve the convergence speed;Secondly,the legitimate transmitters and receiver of SDTB-PM introduce AN to lower the estimation precise of the channel direction information(CDI)obtained by the eavesdropper,even it utilizes the technique of multiple antennas;Thirdly,due to the mechanism of the cumulative positive feedback information,SDTB-PM can track the phase drift and then work well in a complex communication environment.At last,SDTB-PM has a good robustness on parameters selection.Through simulation results,the proposed SDTB-PM has been analyzed carefully to validate its superiority.