Research On Physical Layer Security Based On Large-Scale MIMO Relay

Wireless network security is an important indicator for measuring the performance of mobile communication systems.Physical layer security is a technology that uses the random and time-varying characteristics of wireless channels to implement secure transmission of wireless information at the physical layer.Large scale multiple input multiple output have the advantages of greatly improving system energy efficiency and spectrum efficiency.Simultaneous communication among multiple users in the same spectrum resource can be achieved by using relay nodes equipped with large-scale antennas for relay transmission.At the same time,high security information transmission can also be achieved by using its huge array gain.The thesis study the physical layer security scheme in a massive MIMO relay system under conditions where eavesdropper's channel state information is unknown.The main contents are as follows:1.The multi-user security transmission scheme on physical layer in a massive multiple-input multiple-output one-way relay based network is studied when the user is equipped with single antenna.In the system model,there is no direct link between users,so relay is needed to achieve the information transmission.The eavesdropper node has a direct link with the source node and the relay node.The eavesdropper node can receive signal send by the source node and the relay.The relay employs low-complexity maximum ratio combining in the first stage and maximum ratio transmission in the second stage by using this scheme and assisted by the null-space artificial noise sent by the relay and the collaboration interference sent by the destination node,security transmission of information between the multi user-pairs is realized.Theoretical analysis is performed on the secrecy rate and its asymptotic value when the number of antennas of the relay grows indefinitely.The simulation results show that the secrecy sum rate of the system increases with the number of relay antenna,and eventually reaches the asymptotic value.Furthermore,a considerable secrecy rate can be achieved even if the eavesdropper has the capability to cancel the multi-user interference and to intercept the signals sent by the source nodes and the relay.2.The multi-user security transmission scheme on physical layer in a massive MIMO two-way relay based network is studied when the user is equipped with multiple antennas.The eavesdropper node can receive signal sent by the users in the first stage and the relay in the second stage.The relay node adopts amplify and forward protocol,and the signal precoding and the interference cancellation for receiving signal are completed by the users.The transmission precoding matrix and the interference cancellation matrix for receiving signal are constructed by singular value decomposition on the legitimate channel matrix.Eavesdropper are disturbed by null-space artificial noise sent by the relay.Simulation results show that even if the eavesdropper node has ideal capability to eliminate interference,the scheme can still achieve security transmission of information.