Secure Beamforming For MIMO Broadcasting With Wireless Information And Power Transfer

TL;DR

This paper develops secure beamforming strategies for MIMO broadcast systems that simultaneously transmit information and energy, ensuring physical layer security and efficient energy harvesting through optimal and iterative algorithms.

Contribution

It introduces global optimal solutions for specific cases and an iterative algorithm for general cases to maximize secrecy rate in secure MIMO information-energy systems.

Findings

Proposed algorithms achieve higher secrecy rates than baseline methods.

The iterative IBCD algorithm converges monotonically to a KKT point.

Simulations validate the effectiveness of the beamforming designs.

Abstract

This paper considers a basic MIMO information-energy (I-E) broadcast system, where a multi-antenna transmitter transmits information and energy simultaneously to a multi-antenna information receiver and a dual-functional multi-antenna energy receiver which is also capable of decoding information. Due to the open nature of wireless medium and the dual purpose of information and energy transmission, secure information transmission while ensuring efficient energy harvesting is a critical issue for such a broadcast system. Assuming that physical layer security techniques are applied to the system to ensure secure transmission from the transmitter to the information receiver, we study beamforming design to maximize the achievable secrecy rate subject to a total power constraint and an energy harvesting constraint. First, based on semidefinite relaxation, we propose global optimal solutions to the secrecy rate maximization (SRM) problem in the single-stream case and a specific full-stream case where the difference of Gram matrices of the channel matrices is positive semidefinite. Then, we propose a simple iterative algorithm named inexact block coordinate descent (IBCD) algorithm to tackle the SRM problem of general case with arbitrary number of streams. We proves that the IBCD algorithm can monotonically converge to a Karush-Kuhn-Tucker (KKT) solution to the SRM problem. Furthermore, we extend the IBCD algorithm to the joint beamforming and artificial noise design problem. Finally, simulations are performed to validate the performance of the proposed beamforming algorithms.