Secure Wireless Communications via Cooperation

TL;DR

This paper explores cooperative relay strategies to enhance physical-layer security in wireless communications, addressing challenges posed by eavesdroppers and imperfect channel information, and proposing optimal and suboptimal system designs.

Contribution

It introduces a decode-and-forward cooperative protocol with optimal and suboptimal designs for secrecy capacity maximization and power minimization, considering perfect and imperfect CSI.

Findings

Optimal power minimization scheme for single eavesdropper.

Closed-form solutions for nulling signals at multiple eavesdroppers.

Impact of imperfect CSI on ergodic secrecy capacity.

Abstract

The feasibility of physical-layer-based security approaches for wireless communications in the presence of one or more eavesdroppers is hampered by channel conditions. In this paper, cooperation is investigated as an approach to overcome this problem and improve the performance of secure communications. In particular, a decode-and-forward (DF) based cooperative protocol is considered, and the objective is to design the system for secrecy capacity maximization or transmit power minimization. System design for the DF-based cooperative protocol is first studied by assuming the availability of global channel state information (CSI). For the case of one eavesdropper, an iterative scheme is proposed to obtain the optimal solution for the problem of transmit power minimization. For the case of multiple eavesdroppers, the problem of secrecy capacity maximization or transmit power minimization is in general intractable. Suboptimal system design is proposed by adding an additional constraint, i.e., the complete nulling of signals at all eavesdroppers, which yields simple closed-form solutions for the aforementioned two problems. Then, the impact of imperfect CSI of eavesdroppers on system design is studied, in which the ergodic secrecy capacity is of interest.