Design of massive distributed antenna systems in 5G networks

移动网络目前正处于一个流量增长史无前例、消费者兴趣空前的时代。在全球范围内，移动数据流量在2015年增长了74%，达到每月3.7艾字节，并预计在2020年将以每月9至30.6艾字节的速度增长。然而，无线网络提供商可用的带宽增长非常缓慢。为了解决供需不匹配的问题，即将到来的第五代(5G)网络必须更加强大和可靠。此外，设备制造商，如我们的合作伙伴爱立信加拿大公司，都很清楚需要缓解无线网络能耗的快速增长。应对这些挑战将需要越来越多样化的技术，包括异质网络、致密化、大规模多输入多输出(MIMO)技术，可能还有毫米波系统。在这方面，预计将于2017年年中发布第一个5G标准，将标志着正在进行的研究工作进入新阶段。该方案着眼于5G网络，重点关注大规模分布式天线系统(DAS)或分布式大规模MIMO(DM-MIMO)系统。术语“分布式天线系统”指的是一组地理上分布的远程射电头(RRH)，每个RRH有一个天线或只有几个天线，协调对用户组的传输。DAS的主要优点是覆盖范围相对均匀(因为天线分布在覆盖区域内)，并增强了对衰落的稳健性，包括重要的阴影(因为用户能够同时连接到多个空间分布的RRH)。然而，大幅增加RRH的数量在理论分析和实际设计方面都提出了巨大的挑战。我们希望解决的正是这一挑战。

Mobile networks are currently in an era of unprecedented traffic growth and consumer interest. Globally, mobile data traffic grew 74% in 2015 to 3.7 exabytes per month - and is further expected to grow by a factor of nine to 30.6 exabytes per month in 2020. However, the bandwidth available to wireless network providers is growing extremely slowly. To account for the mismatch between supply and demand, the upcoming fifth generation (5G) of networks must be orders of magnitude more capable and reliable. Furthermore, equipment manufacturers, such as our partner, Ericsson Canada, are well aware of the need to mitigate the rapid increase in the energy consumed by wireless networks. Addressing these challenges will require increasingly diversified technologies, including heterogeneous networks, densification, massive multiple-input, multiple output (MIMO) technology, and possibly millimeter-wave systems. In this regard, the release of the first 5G standard, expected in mid-2017, will mark the beginning of a new phase in on-going research efforts. Focusing on 5G networks, this proposal focuses on massive distributed antenna systems (DAS) or distributed massive MIMO (DM-MIMO) systems. The term "distributed antennas systems" refers to a group of geographically distributed remote radio heads (RRHs), each with a single antenna or just a few antennas, coordinating transmissions to groups of users. The key benefit of DAS is the relative uniformity in coverage (as antennas are distributed across the coverage area) and increased robustness against fading including, importantly, shadowing (since users are able to connect to multiple, spatially distributed, RRHs simultaneously). However, greatly expanding the number of RRHs raises enormous challenges in both theoretical analyses and practical designs. It is this challenge that we hope to address.