EARS: Millimeter Wave Massive MIMO: A New Frontier for Enhanced Radio Access

据估计，现在使用的无线设备比地球上的人口还多。这种爆炸性的增长给移动运营商带来了容量危机，其影响远远超出了普通用户所经历的不便。无线通信现在已经成为一种商品，就像道路、水和电一样，是国家经济发展和政府服务所依赖的。应急服务、医疗信息系统、环境监测、智能电网能源分配、智能交通系统——所有这些技术都依赖于高速宽带无线的可靠接入。很明显，很快就需要大幅度改进频谱接入和容量，以满足随时随地需要宽带服务的众多用户。该提案旨在通过确定如何利用三种新技术的潜在收益来解决这一关键需求：(1)使用非常高的频带，比今天的无线网络使用的频带高10-20倍；(2)减小无线“单元”的大小，以允许频率以更密集的方式重复使用；(3)采用数百个天线的大规模阵列，以应对不可避免的干扰增加和用户选择性需求。这些新技术之间似乎存在相当大的共生关系，可以潜在地利用它们来实现网络速度和连接性的变革性收益-将它们增加1000倍-尽管必须首先克服许多挑战。鉴于工业、政府、医疗和家庭对改进宽带接入的普遍需求，这项研究在克服这些挑战方面取得的进展将对各行各业产生广泛的影响。解决频谱短缺的一个潜在方法是使用毫米波频段，它提供的带宽比现在的系统大得多。其他增加无线容量的方法也重新点燃了对毫米波频率用于蜂窝通信的潜在使用的兴趣，例如使用范围在10-200米的微型和飞基站来增加频率重用，以及配备大量天线的基站的想法，这些天线可以同时容纳许多同信道用户，这种想法被称为大规模多输入多输出无线。这些想法可以很好地相互结合：较小的单元对于毫米波频率的操作具有吸引力，其中射频路径损耗显着较高，由于天线阵列和相关电子设备的物理尺寸减小，与较高频率相关的较短波长对大规模多输入多输出无线设计具有吸引力，通过非常大的天线阵列可以实现的大波束形成增益可以扩展覆盖范围，以帮助克服高毫米波路径损耗。在毫米波频率下，信道相干时间的减少被低迁移率所抵消，因此，由于在小蜂窝中操作，信道相干带宽更高。如果这些方法提供的单个容量增益可以相互结合实现，那么可以设想实现未来几年预计需要的吞吐量的数量级增长。本提案的目标是研究实现包含超过100个天线的毫米波大规模多输入多输出系统的可行性，解决与毫米波信号传播、通信系统设计、通信和信号处理要求对硬件设计的影响以及实际硬件限制如何影响可实现性能相关的问题。最终，这项研究工作将证明毫米波小蜂窝大规模多输入多输出无线系统可以实现其潜力的程度，以显着增强无线电频谱的访问。之前的工作没有完全解决与实现完整的毫米波大规模多输入多输出无线收发器相关的跨学科问题，包括天线阵列几何形状的影响、解调、基带处理、采样和多通道数据聚合等关键方面。先前的努力仅限于天线数量少、频率低或混合架构的情况，在这些情况下，波束形成的灵活性是不可用的。在分析一个联合利用毫米波频率、大规模多输入多输出无线和小型蜂窝的系统并量化其提供增强频谱接入的潜力之前，必须解决许多跨学科的挑战。毫米波大规模多输入多输出无线系统在容量和频谱效率方面的巨大收益可能会对无线应用产生革命性的影响。这种影响不仅包括消费者应用，还包括那些涉及紧急服务、医疗信息系统、环境监测、智能电网能源分配、智能交通系统的应用——所有这些技术都依赖于接入高速宽带无线服务。

It is estimated that there are more wireless devices in use today than people on the planet. This explosive growth has created a capacity crisis for mobile operators whose impact goes well beyond the inconveniences experienced by casual users. Wireless communication is now a commodity, like roads, water, and electricity, on which the nation's economic development and government services rely. Emergency services, medical information systems, environmental monitoring, smart-grid energy distribution, smart transportation systems - all of these technologies depend on reliable access to high speed broadband wireless. It is clear that dramatic improvements in spectral access and capacity will be needed soon to accommodate the multitude of users who need broadband services anytime, anywhere. This proposal aims to address this critical need by determining how to harness potential gains from three new technologies: (1) the use of very high frequency bands, 10-20 times higher than those used in today's wireless networks, (2) decreasing the size of wireless "cells" to allow frequencies to be reused in a more dense fashion, and (3) the adoption of massive arrays of hundreds of antennas in order to handle the inevitable increase in interference and need for user selectivity. There appears to be considerable symbiosis among these new technologies that could potentially be exploited to achieve transformative gains in network speed and connectivity - increasing them by a factor of 1000 - although numerous challenges would have to first be vercome. Given the ubiquitous need for improved broadband access in industry, government, medicine and the home, the progress made by this research in overcoming these challenges will have a broad impact on all walks of life. A potential remedy for the shortage of spectrum is the use of millimeter wave frequency bands, which offer significantly more bandwidth than today's systems. Other approaches for increasing wireless capacity are also rekindling interest in the potential use of millimeter wave frequencies for cellular communications, such as using pico- and femto-cells with ranges on the order of 10-200 meters to increase frequency reuse, and the idea of basestations equipped with a very large number of antennas that can simultaneously accommodate many co-channel users, an idea referred to as massive multi-input multi-output wireless. These ideas work well in combination with each other: smaller cells are attractive for operation at millimeter wave frequencies where radio frequency path loss is significantly higher, the shorter wavelength associated with higher frequencies is appealing for massive multi-input multi-output wireless designs since the physical dimensions of the antenna array and associated electronics are reduced, the large beamforming gains achievable with very large antenna arrays can extend coverage to help overcome the high millimeter wave path loss, and the reduction in channel coherence time at millimeter wave frequencies is offset by the lower mobility and hence the higher channel coherence bandwidth due to operation in small cells. If the individual gains in capacity offered by these approaches could be achieved in combination with one another, then one could envision realizing the orders-of-magnitude increases in throughput that are predicted to be required in coming years. The goal of this proposal is to investigate the feasibility implementing a millimeter wave massive multi-input multi output system incorporating in excess of 100 antennas, addressing issues associated with millimeter wave signal propagation, communication system design, the impact of communication and signal processing requirements on the hardware design, and how practical hardware limitations affect achievable performance. Ultimately, this research effort will demonstrate the degree to which millimeter wave small-cell massive multi-input multi-output wireless systems can achieve their potential for dramatically enhanced access to the radio spectrum. No prior work has fully addressed the interdisciplinary issues associated with implementing a complete millimeter wave massive multi-input multi-output wireless transceiver, covering crucial aspects such as the impact of antenna array geometries, demodulation, baseband processing, sampling and multichannel data aggregation. Prior efforts have been restricted to scenarios with a small number of antennas, lower frequencies, or hybrid architectures in which full beamforming flexibility is not available. There are many interdisciplinary challenges that must be addressed before a system that jointly exploits millimeter wave frequencies, massive multi-input multi-output wireless and small cells could be analyzed and its potential for providing enhanced spectrum access quantified. The enormous gains in capacity and spectral efficiency that could be provided by a millimeter wave massive multi-input multi-output wireless system could have a revolutionary effect on wireless applications. This impact includes not only consumer applications, but those involving emergency services, medical information systems, environmental monitoring, smart-grid energy distribution, smart transportation systems - all technologies that rely on access to high-speed broadband wireless services.