Abstract
In this paper, we study a simultaneous wireless information and power transfer (SWIPT) system aided by the intelligent reflecting surface (IRS) technology, where an AP transmits confidential information to the legitimate information receiver (IR) in the presence of an energy harvesting (EH) receiver that could be a potential eavesdropper. We aim to maximize the secrecy rate at the legitimate IR by jointly optimizing the information beamforming vector and the energy transfer beamforming vector at the access point (AP), and the phase shift matrix at the IRS, subject to the minimum harvested power required by the EH receiver. The semi-definite relaxation (SDR) approach and the alternating optimization (AO) method are proposed to convert the original non-convex optimization problem to a series of semi-definite programs (SDPs), which are solved iteratively. Numerical results show that the achievable secrecy rate of the proposed IRS-assisted SWIPT system is higher than that of the SWIPT system without the assistance of the IRS.
Highlights
The increasing demand of high data rates on future communication systems leads to more complex signal processing hardware and more energy consumption
(3) We show that when information should be kept secret to the energy harvesting receiver, a dedicated energy beam should be designed, which is different to that in the intelligent reflecting surfaces (IRS)-assisted simultaneous wireless information and power transfer (SWIPT) system without eavesdroppers
We introduce an semi-definite relaxation (SDR)-based algorithm to convert the original optimization problem (P1) to semi-definite programs (SDPs) and apply an alternating optimization approach to solve the SDPs by optimizing the phase shift matrix Θ and the beamforming vectors (w and v) iteratively with the other fixed
Summary
The increasing demand of high data rates on future communication systems leads to more complex signal processing hardware and more energy consumption. In simultaneous wireless information and power transfer (SWIPT) systems, the radio frequency signal plays a role in both information transmission and energy transfer [1,2,3,4,5]. Intelligent reflecting surfaces (IRS), a planar array composed of a great number of reconfigurable elements, is regarded as a potential solution for achieving higher efficiency of both the energy and spectrum for the future communication systems, and has been proposed and studied in [6,7]. The IRS passively reflects the RF signals with programmable phase shifts of the reflecting elements. The beamforming vector at the source can be jointly optimized with the passive reflection coefficients of the IRS to improve, e.g., the signal to noise ratio (SNR) at the receiver for the multiple-input single-output (MISO) channel [7]
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