Energy-Efficient Power Allocation for Secure SWIPT in IoT-DAS Using Fractional Optimization

Abstract

AbstractIn this paper, we study secrecy and energy-efficiency optimization in a distributed antenna system (DAS)-based IoT network with energy harvesting nodes. Considering simultaneous wireless information and power transfer (SWIPT), we define secure energy efficiency (SEE) as ratio of the achievable secrecy rate to the total consumed power. Our goal is to maximize SEE subject to maximum transmit power constraint of distributed antenna (DA) ports and minimum energy-harvesting requirement of the IoT devices. For a single IoT device and single eavesdropper, maximizing SEE is formulated as a constrained fractional optimization problem, and the optimal solution is derived by solving Karush–Kuhn–Tucker (KKT) conditions. We also consider the case of an energy-harvesting eavesdropper and attempt to restrain it from harvesting the energy from the radio signal. This is achieved by introducing one more constraint into the optimization problem corresponding to the energy harvesting requirement of the eavesdropper. Further, we also consider a general case of multiple IoT devices and multiple eavesdroppers in an N-port DAS.KeywordsWireless power transferDistributed antenna systemPhysical layer securityWireless energy harvesting