| The wireless communication technology has brought huge convenience to the society,and has now become an indispensable component of people's daily life.Nevertheless,the advance of wire-less communication technology also brings in new challenges.On the one hand,with the emerging wireless services such as online banking and mobile payment,the security issue has become in-creasingly critical,and how to provide secure and reliable wireless connections is one of the most important challenges for future wireless systems.On the other hand,the wireless communication technology could also be misused by criminals or terrorists to commit crime and violence.Hence,how to enforce powerful surveillance measures on suspicious individuals or communications is of paramount importance.Motivated by the above observations,this dissertation provides a detailed study on wireless powered secure communication systems and wireless legitimate surveillance systems.First,in order to address the energy bottleneck issue in wireless secure communication sys-tems,a new idea of deploying fixed energy station in the network was proposed,and a detailed analysis on the secrecy performance of wireless powered communication systems was conducted.Specifically,for the two popular multi-antenna information transmission schemes,namely,maxi-mum ratio transmission and transmit antenna selection,closed-form expressions are derived for the achievable secrecy outage probability and average secrecy rate,which reveal the impact of the key parameters on the secrecy performance.The results demonstrate that the introduction of the energy station does not affect the secrecy diversity gain and the high signal-to-noise ratio slope of the com-munication systems.However,increasing the transmit power of the energy station enhances the secrecy performance by achieving a higher secrecy diversity gain and a lower high signal-to-noise ratio power offset.Next,in order to fully exploit the potential of the energy station,the novel idea of transmitting artificial jamming signals to combat against eavesdropping was proposed.Specifically,depend-ing on the availability of channel state information,five different jamming strategies were devised for secrecy performance enhancement.Closed-form expressions are derived for the achievable secrecy outage probability of the proposed schemes,and the performance of different strategies is compared.The outcomes suggest that when the noise is ignored at the eavesdropper,the jam-ming signals induced by the energy station affects the secrecy diversity gain of the communication systems.Also,the number of multiple antennas at the energy station has different effects on the secrecy performance of the system with different strategies.For wireless legitimate surveillance systems,the multi-antenna full-duplex technology was proposed.Specifically,depending on the number of antennas at the legitimate monitor,four dif-ferent configurations were investigated.By the joint design of the jamming power,receive and transmit beamformers at the legitimate monitor,the eavesdropping non-outage probability is max-imized.Moreover,three low-complexity suboptimal beamforming schemes are proposed and the closed-form expressions are derived for the eavesdropping non-outage probability,which reveal the influence of the key parameters on the monitoring performance.The analytical findings demon-strate that by exploiting multiple antennas at the legitimate monitor,the eavesdropping non-outage probability can be significantly improved.Also,the optimal scheme always yields the best perfor-mance.Finally,considering the dual-hop suspicious communication scenario,novel legitimate surveil-lance schemes are proposed.Specifically,depending on the role of the legitimate monitor,two s-trategies are proposed,where the corresponding optimal jamming beamformer and jamming power are devised to maximize the effective eavesdropping rate.The results demonstrate that the proposed strategies attain better performance compared with intuitive benchmark schemes. |
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