Physical Layer Security: Wireless Location Verification and Secure Communications

Abstract

This thesis focuses on the utilization of reliable location information in wireless physical layer security. Specifically, new optimal Location Verification Systems (LVSs) are first developed to authenticate claimed locations, and then robust transmission strategies that utilize the verified locations are exploited in order to enhance physical layer security.

In the first half of this thesis, new optimal LVSs are developed and analyzed, leading to the following three main contributions. First, an information-theoretic framework for optimizing an LVS is developed and analyzed, in which the mutual information between the input and output data of the LVS is utilized as the optimization metric. Our analysis reveals that relative to more general frameworks the information-theoretic framework has a weaker dependence on critical unknown parameters of the system. Second, new optimal LVSs for a range of optimization metrics are proposed and examined under spatially correlated shadowing, with the conclusion that correlation in shadowing can lead to dramatic LVSs performance improvements. Third, analysis on an LVS under Rician fading channels discloses that the performance of the LVS increases significantly as the proportion of the line-of-sight component in the legitimate channel increases, or the tracking information on claimed locations accumulates. Surprisingly, our analysis also demonstrates that the performance limit of the LVS does not depend on the inherent properties of the channel between an adversary and the LVS.

In the second half of this thesis, robust transmission strategies utilizing verified location information are developed, leading to the following additional contributions. Fourth, an optimal location-based beamforming scheme that solely requires the locations of the intended receiver and the potential eavesdropper is proposed and analyzed under a Rician wiretap channel. Specifically, we provide the optimal location-based beamformer that minimizes the secrecy outage probability. Fifth, new antenna selection schemes which rely on verified locations are proposed. Our analysis reveals that the new antenna selection schemes enhance wireless physical layer security at the cost of only a minor increase in the feedback overhead. Sixth and finally, the optimization of wiretap code rates is investigated for a range of passive eavesdropping scenarios. Specifically, the optimal wiretap code rates for given locations of the eavesdropper are determined.