The Physical Layer Security Of Wireless Communication System In Multi-scenario

The increasing demands of information acquisition and exchange promote the rapid development of wireless communication technology, so that communication security issues become particularly important in the transmission and interaction of information. Heterogeneous networks(HetNets) and massive multiple-input multiple-output (MIMO) are hotspots in academia and industry, which have the advantage of increasing network coverage, improving network throughput, improving spectrum efficiency and reliability and reducing interference. Meanwhile, in order to improve the coverage and data rates, cooperative relaying communications technology start to be used. Due the switch of different scenarios and the employment of different wireless communication systems, security issues should be considered. Based on this situation, the dissertation studies the physical layer security of wireless communication system in multi-scenario.The main innovations and contributions of the dissertation are as follows.First, this dissertation summarizes the advantages of HetNets and massive MIMO in physical layer security, and analyses the physical layer security in massive MIMO aided two-tier HetNets. We focus on the downlink secure transmission in the presence of multiple eavesdroppers.We first address the impact of massive MIMO on the maximum receive power based user association. Then we derive the tractable upper bound expressions for the secrecy outage probability of a HetNets user. The simulation results show that the application of large-scale antenna can greatly improve the secrecy outage probability of macro-cell users. The combination of heterogeneous and large-scale antenna has a great influence on improving the security of the system. Our work demonstrated the importance of base station (BS) deployment density and massive MIMO design on safeguarding the secure downlink transmission in HetNets.Second, this dissertation studies the physical layer security in heterogeneous relay scenarios. We focus on the following two scenarios,Device-to-device (D2D) cooperation based heterogeneous single-relay scenario and heterogeneous multi-relay scenario.1.This dissertation studies the physical layer security in D2D cooperation based on heterogeneous single-relay scenario. In the presence of passive eavesdroppers, we propose a two times cooperative jamming scheme based on secrecy strategy to enhance the security, where the BS is considered as a jammer and transmits artificial noise (AN) during two phases to jam the eavesdropper. Simulation results show the proposed scheme improves the security effectively.2.This dissertation develops a joint cooperative beamforming and AN scheme to enhance the security of a cooperative multi-relay system. In our scheme, a part of relays adopt distributed beamforming and others jam the eavesdropper by transmitting AN, simultaneously. 'Simulation results show the joint scheme greatly improves the security.