This research considers physical layer security in wireless networks. It serves as a counterpoint to traditional methods of security, such as computationally secure crypto-systems, by considering security in the wireless medium itself. An important motivator for this research is the rapid proliferation of wireless communication devices, technologies, and applications, in general. The very nature of wireless networks exposes not only the risks and vulnerabilities that a malicious user can exploit and severely compromise the network but also information confidentiality concerns with respect to the in-network terminals. Although wireless technologies are becoming more and more secure, attackers are becoming smarter, and sole reliance on cryptographic keys in large distributed networks, for example, where terminals can be compromised is unsustainable from the security perspective. A direct consequence of this process is the need to, additionally, tackle security at the very basic physical layer level where the (unconditional) secrecy may be embodied within the information itself, and, also, adapted to the communication medium and network conditions. Furthermore, there is a need for a secure key distribution, a process which can be performed in perfect secrecy only using physical layer techniques, even when, henceforth, relying on conventional cryptographic techniques. This research studies how, in secure wireless networks, the application delay requirement relative to the communication channel coherence time aspects the selection of signaling strategies and the achievable communication rates at a prescribed security level. In addition, perhaps surprisingly, successful design of practical secure nested forward error correction codes and secure adaptive incremental error correction strategies applicable to wireless channels is virtually non-existent. Hence, this research focuses on practical coding-scheme designs as essential enabling tools.
