Joint Beam-Forming Optimization for Active-RIS-Assisted Internet-of-Things Networks with SWIPT

Future Internet Pub Date : 2024-01-06 DOI:10.3390/fi16010020
Lidong Liu, Shidang Li, Mingsheng Wei, Jinsong Xu, Bencheng Yu
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Abstract

Network energy resources are limited in communication systems, which may cause energy shortages in mobile devices at the user end. Active Reconfigurable Intelligent Surfaces (A-RIS) not only have phase modulation properties but also enhance the signal strength; thus, they are expected to solve the energy shortage problem experience at the user end in 6G communications. In this paper, a resource allocation algorithm for maximizing the sum of harvested energy is proposed for an active RIS-assisted Simultaneous Wireless Information and Power Transfer (SWIPT) system to solve the problem of low performance of harvested energy for users due to multiplicative fading. First, in the active RIS-assisted SWIPT system using a power splitting architecture to achieve information and energy co-transmission, the joint resource allocation problem is constructed with the objective function of maximizing the sum of the collected energy of all users, under the constraints of signal-to-noise ratio, active RIS and base station transmit power, and power splitting factors. Second, the considered non-convex problem can be turned into a standard convex problem by using alternating optimization, semi-definite relaxation, successive convex approximation, penalty function, etc., and then an alternating iterative algorithm for harvesting energy is proposed. The proposed algorithm splits the problem into two sub-problems and then performs iterative optimization separately, and then the whole is alternately optimized to obtain the optimal solution. Simulation results show that the proposed algorithm improves the performance by 45.2% and 103.7% compared to the passive RIS algorithm and the traditional without-RIS algorithm, respectively, at the maximum permissible transmitting power of 45 dBm at the base station.
利用 SWIPT 实现主动 RIS 辅助物联网网络的联合波束成形优化
在通信系统中,网络能源资源是有限的,这可能会造成用户端移动设备的能源短缺。有源可重构智能表面(A-RIS)不仅具有相位调制特性,还能增强信号强度,因此有望解决 6G 通信中用户端遇到的能量短缺问题。本文为有源 RIS 辅助同步无线信息和功率传输(SWIPT)系统提出了一种最大化收获能量总和的资源分配算法,以解决乘法衰落导致的用户收获能量性能低下的问题。首先,在有源 RIS 辅助的 SWIPT 系统中,使用功率分配结构实现信息和能量的协同传输,在信噪比、有源 RIS 和基站发射功率以及功率分配系数的约束下,构建了联合资源分配问题,其目标函数为最大化所有用户的采集能量之和。其次,通过交替优化、半无限松弛、连续凸近似、惩罚函数等方法,将所考虑的非凸问题转化为标准凸问题,然后提出一种交替迭代的能量收集算法。所提算法将问题分成两个子问题,分别进行迭代优化,然后整体交替优化,得到最优解。仿真结果表明,在基站最大允许发射功率为 45 dBm 时,与无源 RIS 算法和传统的无 RIS 算法相比,所提算法的性能分别提高了 45.2% 和 103.7%。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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