Physical Layer Security for Energy-Efficient IoT with Information and Power Transfer

Abstract

Because of the recent advancements in 5G technology, Internet of Things (IoT) is not only a technology shifting from aspirational visions to real-world applications, but is also evolving as a challenging problem in the context of security and energy efficiency. This chapter covers an approach to optimize both of these aspects simultaneously at the physical layer in a Distributed Antenna System (DAS) by using Wyner's wire-tap channel code at all transmitters which achieve secrecy rate. This framework is well known as physical layer security because security is provided by exploiting the channel noise, rather than sharing a secret key prior to data transmission. For a given user, we define Secure Energy Efficiency (SEE) as a ratio of the secrecy rate to the total power consumed at transmitters. Achieving higher secrecy rates at the minimum possible energy consumption thus requires maximizing SEE by varying the transmit power at each Distributed Antenna (DA) port. We formulate SEE as a non-linear constrained optimization problem and use the Karush–Kuhn–Tucker (KKT) conditions to arrive at the optimal solution. Further, we extend the approach to the case of Simultaneous Wireless Information and Power Transfer (SWIPT), wherein, power splitting is applied at the receiver nodes of IoT devices to coordinate the Energy Harvesting (EH) and Information Decoding (ID) processes. SEE is optimized for different eavesdropper scenarios by the corresponding reformulation of the optimization problem. Finally, SEE optimization in a generalized and practical IoT scenario is considered.