Reconfigurable intelligent surface (RIS)-based communication networks promise to improve channel capacity and energy efficiency. However, the promised capacity gains could be negligible for passive RISs because of the double pathloss effect. Active RISs can overcome this issue because they have reflector elements with a low-cost amplifier. This letter studies the active RIS-aided simultaneous wireless information and power transfer (SWIPT) in a multiuser system. The users exploit power splitting (PS) to decode information and harvest energy simultaneously based on a realistic piecewise nonlinear energy harvesting model. The goal is to minimize the base station (BS) transmit power by optimizing its beamformers, PS ratios, and RIS phase shifts/amplification factors. The simulation results show significant improvements (e.g., 19% and 28%) with the maximum reflect power of 10 mW and 15 mW, respectively, compared to the passive RIS without higher computational complexity cost. We also show the robustness of the proposed algorithm against imperfect channel state information.

中文翻译：

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多用户 MISO PS-SWIPT 系统：主动或被动 RIS？


基于可重构智能表面（RIS）的通信网络有望提高信道容量和能源效率。然而，由于双路径损耗效应，无源 RIS 所承诺的容量增益可能可以忽略不计。有源 RIS 可以克服这个问题，因为它们具有带有低成本放大器的反射器元件。这封信研究了多用户系统中主动 RIS 辅助的同步无线信息和电力传输 (SWIPT)。用户基于现实的分段非线性能量收集模型，利用功率分裂（PS）来解码信息并同时收集能量。目标是通过优化波束形成器、PS 比和 RIS 相移/放大系数来最小化基站 (BS) 发射功率。仿真结果显示，与无源RIS相比，最大反射功率分别为10 mW和15 mW，显着提高（例如，19%和28%），且计算复杂度成本不更高。我们还展示了所提出的算法针对不完美信道状态信息的鲁棒性。