# Quantum PSO-Based Optimization of Secured IRS-Assisted Wireless-Powered IoT Networks
###### Abstract  
In this paper, we explore intelligent reflecting surface (IRS)-assisted physical layer security (PLS) in a wireless-powered Internet of Things (IoT) network (WPIN) by combining an IRS, a friendly jammer, and energy harvesting (EH) to maximize sum secrecy throughput in the WPIN. Specifically, we propose a non-line-of-sight system where a hybrid access point (H-AP) has no direct link with the users, and a secure uplink transmission scheme utilizes the jammer to combat malicious eavesdroppers. The proposed scheme consists of two stages: wireless energy transfer (WET) on the downlink (DL) and wireless information transmission (WIT) on the uplink (UL). In the first phase, the H-AP sends energy to users and the jammer, and they then harvest energy with the help of the IRS. Consequently, during WIT, the user transmits information to the H-AP while the jammer emits signals to confuse the eavesdropper without interfering with the legitimate transmission. The phase-shift matrix of the IRS and the time allocation for DL and UL are jointly optimized to maximize the sum secrecy throughput of the network. To tackle the non-convex problem, an alternating optimization method is employed, and the problem is reformulated into two sub-problems. First, the IRS phase shift is solved using quantum particle swarm optimization (QPSO). Then, the time allocation for DL and UL are optimized using the bisection method. Simulation results demonstrate that the proposed method achieves significant performance improvements as compared to other baseline schemes. Specifically, for IRS elements \(N=35\), the proposed scheme achieves a throughput of \(19.4\,\mathrm{bps/Hz}\), which is \(85\%\) higher than the standard PSO approach and \(143\%\) higher than the fixed time, random phase (\(8\,\mathrm{bps/Hz}\)) approach. These results validate the proposed approach's effectiveness in improving network security and overall performance. Sixth-generation technology is anticipated to bring revolutionary improvements in speed, capacity, and new communication paradigms. However, these advancements also raise concerns about increased energy consumption, which could lead to significant environmental and economic challenges. The short battery life of many IoT devices poses serious problems, particularly in applications where continuous operation is essential [4]. IoT devices are critical to real-time data transmission and communication, and maintaining smooth, intelligent connections among them requires efficient energy usage and battery management. The main goal of energy-efficient communications is to develop and implement technologies and strategies that maximize energy utilization while concurrently minimizing environmental impacts. A promising method for extending network lifespan is energy harvesting (EH), which captures energy from the surrounding environment and offers a potentially limitless power source for wireless networks. As a result, wireless-powered IoT networks (WPINs) have attracted significant attention as a cost-effective and energy-efficient solution, facilitating flexible energy transfer and enhancing communication efficiency [5; 6]. Physical layer security (PLS) has recently emerged as a promising approach to prevent information eavesdropping. It has gained significant attention in wireless communication systems, with numerous technologies proposed to enhance security performance. These include directional antenna designs and multiple-input multiple-output techniques. PLS plays a crucial role in safeguarding information from interception. Key performance metrics, such as security outage probability and average security capacity, are the primary focus of researchers analyzing PLS performance. Specifically, designing a beamforming vector at the transmitter equipped with multiple antennas has been shown to effectively enhance PLS [7].