MIMO Wireless Networks: A Promising Rate Splitting Transceiver Architecture

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.

Besides the academic beneficiaries, the project will benefit a much wider audience and have potential economic and societal impacts:
1) 5G and beyond communication systems are expected to have applications in developed and emerging markets and a large number of sectors, e.g. building automation, healthcare (health monitoring), telecommunications, smart grid, structural monitoring, consumer electronics, military, etc. All those new applications will in the long term enhance the economic competitiveness of the UK and the quality of life of its residents.
2) Given the enormous interest for high speed communications (as evidenced by 3GPP and IEEE standards), the project has a bright future to benefit the industry sector active in the area of communication equipment manufacturing and standards. By benefiting from our industry partners Toshiba and InterDigital's involvements in 3GPP standards and by Dr. Clerckx's experience in standardization, the project is expected to lead to several 3GPP/IEEE standard contributions on RS-based MIMO wireless networks.
3) The project will also benefit the standard bodies and regulators in the telecom sector and give them the opportunity to understand the benefits and feasibility of a radically new physical layer.
4) ICT is known to be a significant factor contributing to global warming and mobile wireless traffic sees 2-3 fold annual growth. It is an absolute requirement to fully understand how to reduce the ambient RF pollution and make our network greener and more energy efficient. The RS-based MIMO wireless networks, by making a better use of the imperfect CSIT, can achieve higher spectral efficiency with a lower transmit power consumption than conventional approaches. The project will therefore also benefit researchers, policy makers, government agencies active in understanding how technologies could be designed to make our environment greener and reduce the impact of ICT on climate change.