MIMO Wireless Networks: A Promising Rate Splitting Transceiver Architecture

近年来，由于不断努力提高无线网络的频谱效率（SE）和能量效率（EE），无线通信已经实现了大量的新应用。多天线（MIMO）处理在利用这些增益方面起着核心作用。MIMO已经远远超出了最初的点对点信道，现在可以指各种集中和分布式部署（例如多小区MIMO，合作/协调MIMO，分布式MIMO，大规模MIMO，网络MIMO）。在多用户MIMO网络中实现巨大的频谱和能效优势的根本瓶颈在于对发射机（CSIT）精确信道状态信息的巨大需求。由于下一代无线网络中依赖于非常密集的异构网络和配备有非常多天线的发射机的天线和接入点数量的增加，这已经变得越来越难以满足。CSIT不准确会导致多用户干扰，从而显著降低网络性能。回顾过去，问题在于如何将为完美的CSIT设计的技术应用于不完美的CSIT场景。这个项目背后的动机是：考虑到不完美的CSIT，从零开始设计无线网络不是更明智吗？在本项目中，我们利用信息理论的最新进展和pi的初步结果，通过引入速率分裂（RS）网络架构来解决上述基本CSIT问题（及其产生的多用户干扰）。与当前以广播方式操作传输的方法相反，每个用户都有一个私有消息，所考虑的方法包括将一个接收者的消息分成公共部分和私有部分，并将该公共消息叠加在所有用户的私有消息之上。通用消息由所有用户解码，但只针对其中一个用户。从信息论的角度来看，这种方法最近被发现在具有不完善CSIT的多用户部署中是最佳的，并且在频谱效率和功率利用率方面，pi已经证明了比传统方法有显着增强。这个有远见的项目由伦敦帝国理工学院和爱丁堡大学的无线通信理论领先专家进行，旨在利用这些最新发现来设计和演示基于rs的MIMO无线网络架构在多种场景中的适用性。为了将这种新颖的无线网络解决方案以可靠的方式组合在一起，本项目重点设计1)单个传输点的RS， 2)微波和毫米波频段的大量共定位天线（也称为大规模MIMO）的RS， 3)代表密集异构网络的大量分布式天线的RS， 4)多天线中继信道的RS，最后5)评估基于RS的网络的系统级性能。该项目将与设备制造和标准化领域的领导者（东芝和InterDigital）以及国防和应急服务领域的领导者（Qinetiq）合作执行。该项目要求在无线通信，MIMO信号处理，优化，信息论方面有良好的记录，并且它将在一个独特的研究小组中进行，具有理论和实践技能的正确组合。综上所述，考虑到该主题的新颖性和原创性，研究成果将对改变无线技术的未来具有相当大的价值，并为业界提供对强大的MIMO无线网络发展的新鲜及时的见解，推动英国在世界无线通信领域的研究。它的成功将从根本上改变无线通信系统物理层的设计，并对标准化产生巨大影响。

Wireless communications have enabled a plethora of novel applications in recent years thanks to the continuous research efforts to increase the spectral efficiency (SE) and energy efficiency (EE) of wireless networks. Multi-antenna (MIMO) processing plays a central part towards harnessing those gains. MIMO has grown much beyond the original point-to-point channel and can nowadays refer to a diverse range of centralized and distributed deployments (e.g. multi-cell MIMO, cooperative/coordinated MIMO, distributed MIMO, massive MIMO, network MIMO).The fundamental bottleneck towards enormous spectral and energy efficiency benefits in multiuser MIMO networks lies in a huge demand for accurate channel state information at the transmitter (CSIT). This has become increasingly difficult to satisfy due to the increasing number of antennas and access points in next generation wireless networks relying on very dense heterogeneous networks and transmitters equipped with a very large number of antennas. CSIT inaccuracy results in a multi-user interference that significantly degrades the network performance.Looking backward, the problem has been to strive to apply techniques designed for perfect CSIT to scenarios with imperfect CSIT. The motivation behind this project is the following: wouldn't it be wiser to design wireless networks from scratch accounting for imperfect CSIT? In this project, we leverage recent progress in information theory and initial results by the PIs to address the above fundamental CSIT problem (and its resulting multi-user interference) by introducing a rate-splitting (RS) network architecture. Contrary to current approaches where transmission is operated in a broadcast manner with one private message per user, the approach considered consists in splitting one receiver's message into a common and a private part and superposing this common message on top of all users' private messages. The common message is decoded by all users but intended to only one of the users. Such approach has recently been found to be optimal from an information theoretic perspective in a multiuser deployment with imperfect CSIT and significant enhancements over conventional approaches in terms of spectral efficiency and power utilization have been demonstrated by the PIs. This visionary project conducted at Imperial College London and University of Edinburgh by leading experts in wireless communication theory aims at leveraging those recent findings to design and demonstrate the suitability of an RS-based MIMO wireless network architecture in a multitude of scenarios.To put together this novel wireless network solution in a credible fashion, this project focuses on designing 1) RS for a single transmission point, 2) RS for a large number of co-localized antennas (also called Massive MIMO) in microwave and millimeter-wave bands, 3) RS for a large number of distributed antennas representative of dense heterogeneous networks, 4) RS for multi-antenna relay channel and finally 5) evaluating the system level performance of RS-based networks.The project will be performed in partnership with leaders in equipment manufacturing and standardization (Toshiba and InterDigital) and in defence and emergency services (Qinetiq). The project demands a strong track record in wireless communication, MIMO signal processing, optimization, information theory and it is to be conducted in a unique research group with a right mix of theoretical and practical skills. With the above and given the novelty and originality of the topic, the research outcomes will be of considerable value to transform the future of wireless and give the industry a fresh and timely insight into the development of robust MIMO wireless networks, advancing UK's research profile of both wireless communication in the world. Its success would radically change the design of the physical layer of wireless communication systems and have a tremendous impact on standardization.