Secure Beamforming Optimization in IRS-assisted CR-SWIPT MIMO System

• Shuo Yang,
• Xiaorong Xu,
• Zhaoting Liu,
• Jun Wu,
• Jianrong Bao,

Vol. 19, No. 2, February 28, 2025
10.3837/tiis.2025.02.017, Download Paper (Free):

• Intelligent reflecting surface (IRS)
• CR-SWIPT MIMO system
• Secure beamforming
• secrecy rate
• Inexact block coordinate descent (IBCD)

Abstract

This paper investigates the joint design and optimization of secure beamforming in Intelligent Reflecting Surface (IRS) assisted multiuser Cognitive Radio (CR) Simultaneous Wireless Information and Power Transfer (SWIPT) system. We consider the scenario where cognitive energy harvesting nodes are potential eavesdroppers (Eve). Optimization objective is to maximize secrecy rate at cognitive information decoding node with multiple constraints, including transmit power control, energy harvesting, IRS phase shifts and the maximum tolerable interference power. We utilize an inexact block coordinate descent (IBCD) method to solve the nonconvex optimization problem and introduce successive convex approximation (SCA) based suboptimal alternating algorithm to reduce computational complexity. The beamforming matrix, phase shift matrix as well as the auxiliary variables are jointly optimized through alternating iterations to obtain the optimal beamforming scheme. Simulation results show that the increasing of IRS elements, setting the cognitive base station transmit power properly and optimizing the energy harvesting strategy all contribute to the enhancement of secrecy rate performance. Compared with the random phase scheme, the secrecy rate obtains nearly 44%-47% enhancement with the maximum transmit power. The effectiveness of the improvement of security performance can be verified via the proposed scheme in IRS-assisted multiuser CR-SWIPT MIMO system.

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