Research On Security Transmission Schemes Based On Energy Harvesting And Artificial Noise In Cooperation Wireless Networks

The secure transmission of information has always been an important problem in the field of communication research.Because of the openness of transmission medium,the security of the information transmitted in wireless communication systems are faced with severe threat.With the development of multi-antenna technology,cooperative communication technology and coding technology,the physical layer security technology is developing rapidly.The randomness of wireless channels is exploited to achieve the security transmission of information in physical layer security.The wireless energy harvesting technique provides a new way to solve the energy supply problem in communication systems to solve the limited energy supply problem.As a special kind of wireless communication system,it still has the problem of safe transmission.This thesis studies security transmission schemes based on energy harvesting and artificial noise in cooperative wireless networks.The main works are as follows:1.physical layer security transmission protocol in a two-hop relay system,which is composed by a source node,a relay node,a destination node and a eavesdropper is studied.All nodes are equipped with an antenna and have the ability of energy harvesting.There are direct links between the source node and the eavesdropper as well as the relay node and the eavesdropper.Each transmission time slot is divided into two stages,which are respectively used for energy harvesting and data transmitting.The energy harvested is used to send data.The amplify-and-forward protocol is adopted,and the destination node sends artificial noise to protect the information transmitted in the first and second hop.To maximize the secrecy rate,the time for energy harvesting and the power of artificial noise are optimized.Considering that eavesdropper can intercept the information transmitted in the two hops,our scheme is more practical and the optimization problem is more complicate.Iterative algorithm is used to solve the optimization problem of two variables.The simulation results show that the optimization algorithm is accurate and the cooperative jamming can effectively improve the secrecy rate.2.A physical layer security transmission scheme is studied in a two-hop relay system,which is composed of a source node,a relay node,a destination node and some eavesdroppers.The relay node is equipped with multiple antennas and the others just one.The eavesdroppers’ position and their channel state information are unknown,so the destination node sends artificial noise to protect the information transmitted in the first and second hop.The relay node works in simultaneous wireless information and power transfer(SWIPT)mode,and harvests energy from the received signal and artificial noise in the first hop.The harvested energy is used to forward the signals in the second hop.In the first hop,the antennas of relay are divided into two groups,one receiving and combining signals,and the other converting the received signal into energy.In the second hop,the relay node uses all antennas to forward signals.Because the eavesdroppers’ channel state information cannot be obtained,the strategy of antenna grouping and signal beamforming vector are optimized through the maximization of the rate of the destination node.A low complexity antenna grouping strategy is given.The simulation results show that an appreciable secrecy rate can be achieved,and it is higher than when the power splitting strategy is used.