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arXiv 1706.07549cs.ITmath.IT
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利用大规模MIMO的反向多用户无线功率传输

Retrodirective Multi-User Wireless Power Transfer with Massive MIMO

Seunghyun Lee, Yong Zeng, Rui Zhang

摘要:

这封信研究了射频(RF)多用户无线功率传输(WPT)系统,其中具有大量天线的能量发射器(ET)将能量无线传输到多个分布式能量接收器(ER)。我们研究了一种低复杂度的WPT方案的基础上的反向波束形成技术,其中所有ER发送一个共同的信标信号同时在上行链路中的ET和ET简单地共轭和放大其接收的和信号,并发送到所有ER在下行链路中的WPT。我们表明,这样一个低复杂度的计划实现了大规模的多输入多输出(MIMO)能量波束成形增益。然而,由于往返(上行链路信标和下行链路WPT)信号传播损耗而存在“双近-远”问题,其中如果使用相同的上行链路信标功率,则从ET收集的远ER的功率可能显著低于近ER的功率。为了解决这个问题,我们提出了一个分布式的上行链路信标功率更新算法,其中每个ER独立地调整信标功率的基础上,其当前收获的功率在一个迭代的方式。结果表明,该算法快速收敛到一个唯一的固定点的解决方案,这有助于实现所需的用户公平性与最大努力。

英文摘要:

This letter studies a radio-frequency (RF) multi-user wireless power transfer (WPT) system, where an energy transmitter (ET) with a large number of antennas delivers energy wirelessly to multiple distributed energy receivers (ERs). We investigate a low-complexity WPT scheme based on the retrodirective beamforming technique, where all ERs send a common beacon signal simultaneously to the ET in the uplink and the ET simply conjugates and amplifies its received sum-signal and transmits to all ERs in the downlink for WPT. We show that such a low-complexity scheme achieves the massive multiple-input multiple-output (MIMO) energy beamforming gain. However, a "doubly near-far" issue exists due to the round-trip (uplink beacon and downlink WPT) signal propagation loss where the harvested power of a far ER from the ET can be significantly lower than that of a near ER if the same uplink beacon power is used. To tackle this problem, we propose a distributed uplink beacon power update algorithm, where each ER independently adjusts the beacon power based on its current harvested power in an iterative manner. It is shown that the proposed algorithm converges quickly to a unique fixed-point solution, which helps achieve the desired user fairness with best efforts.

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