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

据估计，今天使用的无线设备比地球上的人还多。这种爆炸式的增长给移动的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。无线通信现在是一种商品，就像道路，水和电一样，国家的经济发展和政府服务都依赖于它。紧急服务、医疗信息系统、环境监测、智能电网配电、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，频谱接入和容量将很快需要大幅改善，以适应随时随地需要宽带服务的众多用户。本提案旨在通过确定如何利用三项新技术的潜在收益来满足这一关键需求：（1）使用非常高的频带，比当今无线网络中使用的频带高10-20倍，（2）减小无线“小区”的大小以允许以更密集的方式重复使用频率，以及（3）采用数百个天线的大规模阵列，以便处理干扰的不可避免的增加和对用户选择性的需要。 这些新技术之间似乎存在相当大的共生关系，可以利用这些技术来实现网络速度和连接性的变革性收益-将其增加1000倍-尽管首先必须克服许多挑战。 鉴于工业、政府、医疗和家庭普遍需要改善宽带接入，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影响。频谱短缺的一个潜在补救措施是使用毫米波频段，它提供的带宽比今天的系统要大得多。用于增加无线容量的其他方法也重新点燃了对用于蜂窝通信的毫米波频率的潜在使用的兴趣，例如使用具有10-200米量级的范围的皮科和毫微微小区以增加频率重用，以及配备有可以同时容纳许多同信道用户的非常大量的天线的基站的想法，一种被称为大规模多输入多输出无线的想法。 这些想法相互结合起来效果很好：较小的小区对于在射频路径损耗显著较高的毫米波频率下操作是有吸引力的，与较高频率相关联的较短波长对于大规模多输入多输出无线设计是有吸引力的，因为天线阵列和相关联的电子器件的物理尺寸减小了，利用非常大的天线阵列可实现的大波束成形增益可以扩展覆盖范围以帮助克服高毫米波路径损耗，并且毫米波频率处的信道相干时间的减少被较低的移动性以及因此较高的信道相干带宽所抵消，在小细胞中运行。如果这些方法所提供的能力的单独增益可以相互结合来实现，那么人们可以设想实现预计在未来几年所需的吞吐量的数量级增加。本提案的目标是研究实现超过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的性能相关的问题。最终，这项研究工作将展示毫米波小蜂窝大规模多输入多输出无线系统在多大程度上可以实现其极大增强无线电频谱接入的潜力。以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，涵盖天线阵列几何形状，解调，基带处理，采样和多通道数据聚合等关键方面的影响。之前的努力仅限于具有少量天线、较低频率或混合架构的场景，其中无法获得完整的波束成形灵活性。在分析联合利用毫米波频率、大规模多输入多输出无线和小小区的系统以及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增益可能对无线应用产生革命性的影响。这种影响不仅包括消费类应用，还包括涉及紧急服务、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高速宽带无线服务的接入。

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.