MIMO Wireless Networks: A Promising Rate Splitting Transceiver Architecture

近年来，由于不断的研究努力以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颖应用。多天线（MIMO）处理在利用这些增益方面发挥着核心作用。MIMO的发展已经远远超出了最初的点对点信道，现在可以指各种集中式和分布式部署（例如，多小区MIMO、协作/协调MIMO、分布式MIMO、大规模MIMO、网络MIMO）。多用户MIMO网络中巨大的频谱和能量效率优势的根本瓶颈在于对发射机处的准确信道状态信息（CSIT）的巨大需求。由于依赖于非常密集的异构网络和配备有非常大量天线的发射机的下一代无线网络中的天线和接入点的数量不断增加，这已经变得越来越难以满足。CSIT不准确导致多用户干扰，这显著降低了网络性能。回顾过去，问题一直是努力将为完美CSIT设计的技术应用于具有不完美CSIT的场景。这个项目背后的动机如下：从头开始设计无线网络考虑不完美的CSIT不是更明智吗？在这个项目中，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）。与其中以广播方式操作传输且每个用户具有一个私有消息的当前方法相反，所考虑的方法包括将一个接收器的消息分成公共和私有部分，并且将该公共消息叠加在所有用户的私有消息之上。公共消息由所有用户解码，但仅针对其中一个用户。这种方法最近已被发现是最佳的，从信息理论的角度来看，在多用户部署与不完善的CSIT和显着增强传统的方法在频谱效率和功率利用率方面已被证明的PI。由伦敦帝国理工学院和爱丁堡大学的无线通信理论领域的顶尖专家共同完成的这一富有远见的项目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。为了以可靠的方式将这一新颖的无线网络解决方案组合在一起，该项目侧重于设计1）用于单个传输点的RS，2）用于大量共定位天线的RS（也称为大规模MIMO），3）用于代表密集异构网络的大量分布式天线的RS，4）用于多天线中继信道的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合作执行（东芝和InterDigital）以及国防和应急服务（Qinetiq）。该项目要求在无线通信，MIMO信号处理，优化，信息理论方面有很好的记录，并且将在一个独特的研究小组中进行，该研究小组具有理论和实践技能的正确组合。鉴于上述情况以及该主题的新奇和独创性，研究成果将具有相当大的价值，以改变无线的未来，并为业界提供一个新的和及时的见解，以发展强大的MIMO无线网络，推进英国在世界无线通信领域的研究概况。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.