This book presents physical-layer security as a promising paradigm for achieving the information-theoretic secrecy required for wireless networks. It explains how wireless networks are extremely vulnerable to eavesdropping attacks and discusses a range of security techniques including information-theoretic security, artificial noise aided security, security-oriented beamforming, and diversity assisted security approaches. It also provides an overview of the cooperative relaying methods for wireless networks such as orthogonal relaying, non-orthogonal relaying, and relay selection.Chapters...