Energy-efficient secure communications in MISO-SE systems

The problem of resource allocation for energy-efficient secure communications in multiple-input single-output (MISO) systems is investigated, wherein a malicious user tries to eavesdrop the communication between two legitimate users. The legitimate transmitter has multiple antennas, whereas the eavesdropper and the receiver have a single antenna. Unlike most papers dealing with physical layer security, in this paper the goal of the resource allocation process is not to maximize the secrecy capacity, but rather to maximize the secrecy energy efficiency (SEE), defined as the ratio between the secrecy capacity and the total consumed power. This performance metric is measured in bit/Hz/Joule, and represents the amount of information bits that can be reliably and securely transmitted per unit of bandwidth and per Joule of consumed energy. The energy-efficient resource allocation is carried out considering three different channel state information (CSI) scenarios as to the channel from the legitimate transmitter to the eavesdropper, namely perfect CSI, partial CSI, and statistical CSI.