Achieving Secrecy Without Knowing the Number of Eavesdropper Antennas

Abstract

Abstract-The existing research on physical layer security commonly assumes the number of eavesdropper antennas to be known. Although this assumption allows one to easily compute the achievable secrecy rate, it can hardly be realized in practice. In this paper, we provide an innovative approach to study secure communication systems without knowing the number of eavesdropper antennas by introducing the concept of spatial constraint into physical layer security. Specifically, the eavesdropper is assumed to have a limited spatial region to place (possibly an infinite number of) antennas. From a practical point of view, knowing the spatial constraint of the eavesdropper is much easier than knowing the number of eavesdropper antennas. We derive the achievable secrecy rates of the spatially-constrained system with and without friendly jamming. We show that a non-zero secrecy rate is achievable with the help of a friendly jammer, even if the eavesdropper places an infinite number of antennas in its spatial region. Furthermore, we find that the achievable secrecy rate does not monotonically increase with the jamming power, and hence, we obtain the closed-form solution of the optimal jamming power that maximizes the secrecy rate.

On the Design of Secure Non-Orthogonal Multiple Access Systems

“…Note that this assumption has been adopted in the previous work on the secrecy of NOMA systems [25]. In addition, we highlight that worst-case assumptions have been widely adopted in analyzing and designing transmission schemes with secrecy considerations; see, e.g., [23], [33], [34].…”

Correlation-Based Power Allocation for Secure Transmission with Artificial Noise

“…). Finally, substituting Ω * = WΦ * = (N t − 1)w I into (16) we achieve the result given in (17). As per Theorem 1, the instantaneous SINR at Eve of the CPA for a given α is given by…”

“…To the best knowledge of the authors, in the context of physical layer security the study on antenna correlation is still in its infancy. The impact of receiver-side correlation at Bob and Eve on the system performance was examined in [16] and [17], while the impact of the transmitter-side correlation has never been examined in the literature. This leaves an important gap in our understanding on the performance of the secure transmission with AN, and closing this gap forms the core of this work.…”

Artificial Noise Injection for Securing Single-Antenna Systems

“…For any given R b and R s , the optimal α is still given by (16). We find that the closed-form solutions of the optimal R b and R s are mathematically intractable due to the complicated expression for the PDF of the received SNR at Bob, i.e., (7). The optimal R b and R s for the design problem can be obtained only by numerically solving max…”