This paper investigates the optimal transmit beamforming design of simultaneous wireless information and power transfer (SWIPT) in the multiuser multiple-input-single-output (MISO) downlink with specific absorption rate (SAR) constraints. We consider the power splitting technique for SWIPT, where each receiver divides the received signal into two parts: one for information decoding and the other for energy harvesting with a practical non-linear rectification model. The problem of interest is to maximize as much as possible the received signal-to-interference-plus-noise ratio (SINR) and the energy harvested for all receivers, while satisfying the transmit power and the SAR constraints by optimizing the transmit beamforming at the transmitter and the power splitting ratios at different receivers. The optimal beamforming and power splitting solutions are obtained with the aid of semidefinite programming and bisection search. Low-complexity fixed beamforming and hybrid beamforming techniques are also studied. Furthermore, we study the effect of imperfect channel information and radiation matrices, and design robust beamforming to guarantee the worst-case performance. Simulation results demonstrate that our proposed algorithms can effectively deal with the radio exposure constraints and significantly outperform the conventional transmission scheme with power backoff.

中文翻译：

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MISO 下行链路 SWIPT 系统中的特定吸收率感知波束成形

本文研究了具有特定吸收率 (SAR) 约束的多用户多输入单输出 (MISO) 下行链路中同时无线信息和功率传输 (SWIPT) 的最佳发射波束成形设计。我们考虑 SWIPT 的功率分配技术，其中每个接收器将接收到的信号分为两部分：一部分用于信息解码，另一部分用于使用实用的非线性整流模型进行能量收集。感兴趣的问题是尽可能最大化接收到的信号与干扰加噪声比 (SINR) 和为所有接收器收集的能量，同时通过优化发射波束形成在满足发射功率和 SAR 约束的同时发射器和不同接收器的功率分配比。借助半定规划和二分搜索获得最佳波束成形和功率分配解决方案。还研究了低复杂度固定波束成形和混合波束成形技术。此外，我们研究了不完善的信道信息和辐射矩阵的影响，并设计了稳健的波束成形以保证最坏情况下的性能。仿真结果表明，我们提出的算法可以有效地处理无线电暴露约束，并显着优于具有功率回退的传统传输方案。并设计稳健的波束成形以保证最坏情况下的性能。仿真结果表明，我们提出的算法可以有效地处理无线电暴露约束，并显着优于具有功率回退的传统传输方案。并设计稳健的波束成形以保证最坏情况下的性能。仿真结果表明，我们提出的算法可以有效地处理无线电暴露约束，并显着优于具有功率回退的传统传输方案。