Impact of hardware impairments on secrecy performances of wireless relay systems

Abstract

Security is one of the most important issues in wireless communication. Because using wireless channels entails broadcasting data transmissions, malicious nodes can eavesdrop on wireless transmission, which leads to insecure data transmission. Traditional security methods are based on cryptography. Recently, physical-layer security (PLS) has gained much attention as an efficient method of obtaining secure information without using cryptography. PLS protocols employ the physical characteristics of wireless channels such as channel state information (CSI) and the distances between connection links in order to enhance secrecy performances in wireless systems. To enhance secrecy performances, the dual-hop/multi-hop relay protocols can be used efficiently. However, according to my best knowledge, there are few published works considering the impact of hardware impairments on secrecy performances for the wireless relaying networks. Hence, this dissertation examines the diversity-based relay protocols for wireless communication networks in order to improve secrecy performances in presence of hardware imperfections. First, new dual-hop and multi-hop cooperative relaying schemes with various relay selection methods are proposed in order to obtain improved secrecy performance compared with the existing schemes. Second, new joint relay and jammer selection protocols are also considered in order to improve the channel capacity for data links while reducing the channel capacity of eavesdropping links. Finally, this dissertation proposes harvest-to-transmit and harvest-to-jam protocols, where the relay and jammer nodes harvest energy from the radio frequency signal for use in the data transmission and the jamming process, respectively. To evaluate the performance of the proposed protocols over fading channels, this dissertation focuses on deriving the closed-form expressions for secrecy performances. Then, the derived expressions are verified by Monte Carlo simulations, which also present the advantages of the proposed protocols.