Abstract

This paper investigates a secure energy efficiency (SEE) optimization problem in a multiple-input single-output (MISO) underlay cognitive radio (CR) network. In particular, a multi-antenna secondary transmitter (SU-Tx) simultaneously sends secured information and energy to a secondary receiver (SU-Rx) and an energy receiver (ER), respectively, in the presence of a primary receiver (PU-Rx). It is assumed that the SU-Rx, ER and PU-Rx are each equipped with a single antenna. In addition, the SU-Tx should satisfy constraints on maximum interference leakage to the PU-Rx and minimum harvested energy at the ER. In this CR network, we consider the transmit covariance matrix design with the assumption of perfect channel state information (CSI) at the SU-Tx. In addition, it is assumed that the ER is a potential passive eavesdropper due to broadcast nature of wireless transmission. On the other hand, we consider the worst-case scenario that ER's energy harvesting requirement is only satisfied when it performs only energy harvesting without intercepting or eavesdropping information intended for the SU-Rx. We formulate this transmit covariance matrix design as a SEE maximization problem which is a non-convex problem due the non-linear fractional objective function. To realize the solution for this non-convex problem, we utilize the non-linear fractional programming and difference of concave (DC) functions approaches to reformulate into a tractable form. Based on these techniques and the Dinkelbach's method, we propose iterative algorithms to determine the solution for the original SEE maximization problem. Numerical simulation results are provided to demonstrate the performance of the proposed transmit covariance matrix design and convergence of the proposed algorithms.

Highlights

  • Without doubt, information security is one of the most critical issues of wireless communications due to the open nature of transmission over the wireless medium

  • Motivated by the aforementioned aspects, we investigate the secure energy efficiency (SEE) maximization problem for an underlay multiple-input single-output (MISO) cognitive radio (CR) network with energy harvesting (EH) requirement

  • We have considered the SEE maximization problem for an underlay MISO CR network

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Summary

INTRODUCTION

Information security is one of the most critical issues of wireless communications due to the open nature of transmission over the wireless medium. Information theoretic studies have proven that if the signal to noise ratio (SNR) of the legitimate channel is larger than that of the eavesdropper’s channel, secure communication can be guaranteed [5], which is known as physical layer security in the literature This approach was first theoretically proposed by Shannon [5] and the secrecy capacity of wiretap and related channels were developed by Wyner [6] and Csiszar [7]. Energy efficiency and information security are the essential requirements of future wireless communications, including fifth generation (5G) wireless networks. With the exponential growth of the number of wireless devices with high data rate and security requirements, energy consumption has become one of the critical issues in terms of both environmental and economic aspects [12].

Notations
SYSTEM MODEL
PROBLEM FOMULATION
Non-linear fractional programming
DC programming
SIMULATION RESULTS
CONCLUSION
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