New MIMO Techniques for Future Generation of Wireless Communications

无线通信对更大容量和更好质量的需求不断增加。通过对当前增长趋势的外推预测，到2020年，我们的数据速率需求将增长1000倍。为了满足如此显著的需求增长，MIMO(多输入多输出)技术被广泛认为是关键要素。它们能够在不增加带宽或传输功率成本的情况下显著提高数据速率、效率和可靠性。MIMO技术已经在当前的无线系统中得到了很好的开发和应用，例如第四代(4G)无线系统。然而，今天的MIMO技术不能满足下一代显著增长的需求。我建议为下一代无线通信开发新的MIMO技术和概念。更具体地说，我建议从以下三个方面进行研究。 1.多用户大规模MIMO设计。大规模MIMO指的是其天线阵列尺寸比目前的多天线系统多一个数量级的系统，例如具有数百个天线的站。它是一项新兴的技术，初步研究表明，它在数据速率、能量效率、减少延迟、健壮性和多用户通信方面具有巨大的潜力。为了充分理解和利用大规模MIMO的好处，需要定制设计和新的性能分析框架。在这个研究项目中，我计划致力于有效的收发机设计，硬件经济的天线选择方法，以及精确分析多用户大规模MIMO系统的基本性能。 2.能源效率设计。随着无线用户的普及和无线业务量的迅速增加，无线基础设施的能耗急剧增加。因此，近年来，绿色通信引起了人们的极大关注，并将在未来十年继续变得更加重要。在这个研究项目中，我将寻求新的多用户MIMO通信的能效措施，推导出能够同时保持服务质量的能效MIMO设计，并分析所提出的设计的性能。 3.多输入多输出系统的信道信息获取。研究表明，MIMO通信的质量在很大程度上取决于信道信息的可用性和准确性。新的MIMO技术给信道信息的获取带来了新的问题和挑战。目前的MIMO信道估计方案主要基于线性模型和高斯估计。我将开发新的非线性估计模型和规则，它们可能在估计降阶和相关MIMO信道方面取得更好的性能。本文还将研究传统MIMO系统和大规模MIMO系统中多用户干扰MIMO信道的信道估计问题。 在这项研究计划中，我的目标是提出新的MIMO概念和技术，以满足下一代无线通信的需求，高数据速率和高能量效率是两个主要目标。同时，我将重点放在低复杂度的设计上，这些设计是可扩展的，可以应用于用户量大、维度高的系统。研究结果将有助于揭示下一代无线通信的特点。所提出的技术可以为下一代无线系统的设计、分析和实现提供指导。我也期待通过研究计划开辟新的研究方向和想法。

The demands in wireless communications for higher capacity and better quality are constantly increasing. It is predicted by extrapolations of current growth trends that we will experience a 1000-fold increase in data-rate requirement by 2020. In meeting such significant demand increase, MIMO (multi-input-multi-output) techniques are widely believed to be key elements. They have the capability of offering significant boost in data-rate, efficiency, and reliability without additional cost in bandwidth or transmit power. MIMO techniques have been well-developed and employed in current wireless systems, such as the 4th Generation (4G) wireless systems. However, today’s MIMO techniques fall short of the dramatic demand increase for the next generation. I propose to develop new MIMO techniques and concepts for wireless communications of future generation. More specifically, I propose to research on the following three aspects. 1. Multi-User Massive MIMO Designs. Massive MIMO refers to systems whose antenna array size is an order of magnitude more than current multiple-antenna systems, such as a station with hundreds of antennas. It is an emerging technology and preliminary research shows that it has great potential in data-rate, energy-efficiency, reduction of latency, robustness, and multi-user communications. To fully understand and utilize the benefits of massive MIMO, customized designs and new frameworks for performance analysis are needed. In this research program, I plan to work on effective transceiver designs, hardware-economical antenna selection methods, and precise analysis of the fundamental performance of multi-user massive MIMO systems. 2. Energy Efficiency Designs. As the popularity of wireless users and the volume of wireless traffic rapidly multiply, the energy consumption in wireless infrastructure drastically increases. As a result, green communications have attracted significant attention in recent years and will continuously become more important for the next decade. In this research program, I will seek novel energy efficiency measures for multi-user MIMO communications, derive energy efficient MIMO designs that can at the same time maintain the quality-of-service, and analyze the performance of the proposed designs. 3. Channel Information Acquisition for MIMO Systems. Research show that the quality of MIMO communications depends heavily on the availability and accuracy of the channel information. New MIMO techniques bring fresh questions and challenges in the acquirement of channel information. Current MIMO channel estimation schemes are based on linear model and Gaussian estimation. I will develop new non-linear estimation models and rules which potentially achieve better performance in estimating MIMO channels with reduced-rank and with correlation. I will also study the channel estimation for multi-user interference MIMO channel for both traditional MIMO systems and massive MIMO systems. In this research program, I target at proposing novel MIMO concepts and technologies that can fulfill the demands of next generation wireless communications, with high date-rate and high energy-efficiency being the two major objectives. At the same time, I focus on low complexity designs that are scalable and can be applied to systems with a large volume of users and high dimension. The outcomes will help uncover the features of next generation wireless communications. The proposed techniques can provide guidance in the design, analysis, and implementation of next generation wireless systems. I also expect new research directions and ideas to be opened up through the research program.