Robust 3D Beamforming using Electronically Steerable Metamaterial Antennas for Millmeter wave Communications

使用电子可操纵的超材料天线进行毫米波通信的鲁棒3D波束形成3D波束形成是一种很有前途的毫米波（mmWave）通信技术，因为需要更高的容量，并且需要克服高毫米波频率下的强大气吸收。通过在方位角和仰角方向形成窄波束，3D波束形成允许有效的空间划分，从而实现更高的用户容量，更好的覆盖范围，更少的干扰和更好的能源效率。然而，由于硬件和算法方面的巨大挑战，这项技术的真正前景尚未实现。现有的波束形成方法依赖于相控阵天线，其体积庞大，耗电的移相器和相关放大器不适合实际的手机。真正的毫米波波束形成需要薄而轻的天线，能够产生在三维大角度范围内电子操纵的尖锐波束。为了实现有效的波束形成，由于毫米波传播的强方向性、高路径损耗以及容易受到阴影和阻塞的影响，在接收端和发送端都难以准确估计信道。这样的信道条件需要强大的3D波束形成算法，这些算法与新颖的天线设计紧密耦合，以便将它们集成到高效的通信系统中。本提案提出了跨越信号处理、天线设计和集成系统层面的几个关键创新。(1)信号处理方面的创新在于针对平面天线阵列的鲁棒三维波束形成算法，该算法考虑了信道估计误差，特别是毫米波传播特有的出发角和到达角误差，以及由于所提出的超材料天线固有的非理想性和工艺不匹配导致的天线波束形成变化。这两种误差来源以前都没有被考虑过。(2)硬件方面的创新在于使用超薄的基于超材料的谐振腔发射/接收天线来实现电子束导向，这种天线通过在超材料中嵌入变容管等有源元件来实现，这些有源元件在软件中进行智能偏置。所提出的天线是对现有相控阵天线的根本性转变，现有相控阵天线采用笨重的机械运动部件或移相器和相关放大器，从而节省了大量功率，同时提供了宽转向角的灵活窄波束宽度。(3)然后将这两个创新方面整合到一个多层次的评估计划中，包括在组件（天线）、系统（收发器对）和网络（蜂窝）级别进行详细的测试和评估。将天线波束轮廓特征集成到网络仿真中，通过详细的毫米波信道模型实现了所提出的鲁棒三维波束形成。预计项目结果将对毫米波通信产生直接影响，以满足蜂窝、车辆和物联网系统对高数据速率连接的需求。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Robust 3D Beamforming using Electronically Steerable Metamaterial Antennas for Millmeter wave Communications3D beamforming is a promising technology for millimeter wave (mmWave) communications, due to the demand for higher capacity and the need to overcome strong atmospheric absorption at high mmWave frequencies. By forming narrow beams in both the azimuth and elevation directions, 3D beamforming allows efficient spatial division and leads to higher user capacity, better coverage, less interference, and better energy efficiency. The true promise of this technology, however, has not yet been realized due to immense challenges in both hardware and algorithms. Existing beamforming approaches rely on phased array antennas with bulky, power-hungry phase shifters and related amplifiers and size not suitable for practical handsets. True mmWave beamforming requires thin, lightweight antennas with the ability to produce sharp beams that are electronically steerable over a wide range of angles in three dimensions. For effective beamforming, there is an added difficulty in estimating the channel accurately at both the receiver and transmitter because of strong directionality of mmWave propagation, its high path loss and vulnerability to shadowing and blockage. Such channel conditions call for robust 3D beamforming algorithms that are tightly coupled to novel antenna designs in order to integrate them into efficient communication systems.This proposal puts forth several key innovations spanning across signal processing, antenna design and integrated system levels. (1) The signal processing innovation lies in robust 3D beamforming algorithms for a planar antenna array, taking into account errors in channel estimation, particularly in angles of departure and arrival specific to mmWave propagation, and also variation in antenna beam formation caused by inherent non-idealities in hardware and process mismatch specific for the proposed metamaterial antenna. Both of these sources of error have not previously been considered. (2) The hardware innovation lies in the use of metamaterial-based resonant cavity transmit/receive antennas that are ultra-thin for electronic beam steering, achieved by embedding active components such as varactors in the metamaterial that are biased intelligently in software. The proposed antenna is a fundamental shift from the existing phase-array antennas with bulky mechanical moving parts or phase shifters and related amplifiers, thereby also saving significant power, while providing flexible narrow beam-width of wide steering angles. (3) These two innovative aspects are then integrated in a multi-level evaluation plan, including detailed testing and evaluation at component (antenna), system (transceiver pair), and network (cellular) levels. Characterized antenna beam profile is integrated in a network simulation that implements the proposed robust 3D beamforming with detailed mmWave channel model. Project results are expected to have direct impact on mmWave communications in meeting the demand for high data rate connectivity in cellular, vehicular, and IoT systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.