Physical layer security in wireless networks : design and enhancement

Security and privacy have become increasingly significant concerns in wireless communication networks, due to the open nature of the wireless medium which makes the wireless transmission vulnerable to eavesdropping and inimical attacking. The emergence and development of decentralized and ad-hoc wireless networks pose great challenges to the implementation of higher-layer key distribution and management in practice. Against this background, physical layer security has emerged as an attractive approach for performing secure transmission in a low complexity manner. This thesis concentrates on physical layer security design and enhancement in wireless networks. First, this thesis presents a new unifying framework to analyze the average secrecy capacity and secrecy outage probability. Besides the exact average secrecy capacity and secrecy outage probability, a new approach for analyzing the asymptotic behavior is proposed to compute key performance parameters such as high signal-to-noise ratio slope, power offset, secrecy diversity order, and secrecy array gain. Typical fading environments such as two-wave with diffuse power and Nakagami-m are taken into account. Second, an analytical framework of using antenna selection schemes to achieve secrecy is provided. In particular, transmit antenna selection and generalized selection combining are considered including its special cases of selection combining and maximal-ratio combining. Third, the fundamental questions surrounding the joint impact of power constraints on the cognitive wiretap channel are addressed. Important design insights are revealed regarding the interplay between two power constraints, namely the maximum transmit at the secondary network and the peak interference power at the primary network. Fourth, secure single carrier transmission is considered in the two-hop decode-and-