In this thesis we study wireless networks modeled by the additive white Gaussian noise (AWGN) model. The AWGN capacity region of most network topologies is unknown, which means that the optimal transmission scheme is unknown as well. This motivates the search for capacity approximations and for approximately optimal schemes. Deterministic channel models have been proposed as means to approximat...

The recent development of vehicular networking technologies brings the promise of improved driving safety and traffic efficiency. Cooperative communication is recognized as a low-complexity solution for enhancing both the reliability and the throughput of vehicular networks. However, due to the openness of wireless medium, the vehicular wireless communications (VWC) is also vulnerable to potent...

Recently, the finite state Markov channel (FSMC) with an additional eavesdropper and delayed feedback from the legitimate receiver to the transmitter has been shown to be a useful model for the physical layer security of the practical mobile wireless communication systems. In this paper, we extend this model to a multiple-access situation (up-link of the wireless communication systems), which w...

We study the secrecy capacity of a helper-assisted Gaussian wiretap channel with a source, a legitimate receiver, an eavesdropper and an external helper, where each terminal is equipped with multiple antennas. Determining the secrecy capacity in this scenario generally requires solving a nonconvex secrecy rate maximization (SRM) problem. To deal with this issue, we first reformulate the origina...

We propose and study the secrecy cooperative MIMO architecture to enable and to improve the secrecy transmissions between clusters of mobile devices in presence of an eavesdropper with certain location constraint. The cooperative MIMO is formed by temporarily activating clusters of nearby trusted devices, with each cluster being centrally coordinated by its corresponding cluster head. We assume...

We consider the Shannon cipher system with a variable key rate, and study the necessary and sufficient conditions for perfect secrecy in the sense that the exponential rate of the probability of breaking into the system would not be improved by observing the cryptogram. For a memoryless plaintext source, we derive achievable lower bounds on the number of key bits needed for almost every plainte...

This paper establishes the utility of user cooperation in facilitating secure wireless communications. In particular, the four-terminal relay-eavesdropper channel is introduced and an outer-bound on the optimal rate-equivocation region is derived. Several cooperation strategies are then devised and the corresponding achievable rate-equivocation region are characterized. Of particular interest i...

We analyze physical-layer security based on the premise that the coding mechanism for secrecy over noisy channels is tied to the notion of resolvability. Instead of considering capacity-based constructions, which associate to each message a sub-code that operates just below the capacity of the eavesdropper’s channel, we consider resolvability-based constructions, which associate to each message...

This paper investigates the physical layer security (PLS) problem of visible light communication (VLC) systems relying on generalized space-shift keying (GSSK) termed as GSSK-VLC. The GSSK-VLC system considered is assumed to be comprised of three nodes: a transmitter equipped with multiple light-emitting diodes (LEDs), a legitimate receiver as well as a passive eavesdropper. Each of them is equ...