Hybrid Beamforming With Discrete Phase Shifts for RIS-Assisted Multiuser SWIPT System
Hybrid Beamforming With Discrete Phase Shifts for RIS-Assisted Multiuser SWIPT System
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DOI：
10.1109/lwc.2022.3218332
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发表时间：
2023-01
影响因子：
6.3
通讯作者：
Zhen Chen;Jie Tang;Nan Zhao;Mingqian Liu;D. So
中科院分区：
文献类型：
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作者：
Zhen Chen;Jie Tang;Nan Zhao;Mingqian Liu;D. So
可重构智能表面 (RIS) 通过利用大量低成本可重构反射阵列元件，提供了一种新兴的经济型解决方案。在这封信中，通过利用低成本无源反射元件，在RIS辅助的多用户同时无线信息和电力传输（SWIPT）系统中研究了具有离散相移设计的联合混合波束形成。然而，公式化的和速率最大化问题是非凸的，并且解决起来非常具有挑战性。为了克服这个困难，我们将原始的最大化问题分解为数字、相移和模拟子问题。具体来说，针对数字子问题的非凸性，我们对目标函数进行一阶泰勒级数展开，然后制定迭代策略来解决离散优化变量施加的最大发射功率约束的困难。随后，采用有效的凸优化技术来优化RIS的反射元件。最后，提出基于最小均方误差(MMSE)方案的贪婪选择方法来求解模拟子问题。进行数值模拟以证明所提出方案的性能优势。
Reconfigurable Intelligent Surfaces (RIS) provides an emerging affordable solution by leveraging massive low-cost reconfigurable reflective array elements. In this letter, by utilizing low-cost passive reflecting elements, a joint hybrid beamforming with discrete phase shifts design is studied in RIS-assisted multiuser simultaneous wireless information and power transfer (SWIPT) systems. However, the formulated sum rate maximization problem is nonconvex and very challenging to solve. To overcome this difficulty, we decouple the original maximization problem into the digital-, phase shifts and analog subproblem. Specifically, for the nonconvexity of the digital subproblem, we perform the first order Taylor series expansion on the objective function, and then an iterative strategy is developed to tackle the difficulty of the maximum transmit power constraint imposed by discrete optimization variables. Subsequently, an effective convex optimization technique was employed to optimize reflecting elements of RIS. Finally, the greedy selection method based on minimum mean squared error (MMSE) scheme is proposed to solve the analog subproblem. Numerical simulations are conducted to demonstrate the performance advantages of the proposed scheme.