Signal processing techniques for cell-free massive MIMO

While the deployment of 5G cellular systems will continue well into the next decade, much interest is already being generated towards technologies that will underlie its successor, 6G. 6G is anticipated to support the Internet-of-Everything (IoE), where upwards of a million devices per km^3 (both terrestrial and aerial) will require ubiquitous, reliable, low-latency connectivity. To realise this ambitious vision of 6G, disruptive technological paradigms have to be developed.

To this end, this project will be looking into a very promising wireless technology, coined as cell-free massive MIMO. The main idea here is to deploy an unconventionally large number of access points, that are geographically distributed, to coherently serve many users in the same time-frequency resources. Cell-free massive MIMO can theoretically offer uniform quality of services across users (a feature known as user fairness in the related literature), lower latency and ubiquitous connectivity. Yet, transforming this disruptive academic concept into a commercial reality is a very challenging exercise and is precisely the core of this PhD project.

In particular, the student will be developing new signal processing solutions suitable for cell-free massive MIMO network. Of particular interest are the following technical objectives: (a) propose new practical user-centric approaches, wherein each user is served by its selected subset
of access points; (b) develop scalable power control schemes to combat the inherent interference problem by using deep learning or machine learning; (c) introduce new advanced signal processing techniques that can be implemented in a distributed manner and offer satisfactory performance.

Vision and timeliness: The scientific community needed nearly 5 years to appreciate the importance of massive MIMO (2010-2014) and 5 more years were required (2015-2020) in order to make this technology mature and ready for commercial use. Looking ahead, cell-free massive MIMO emerges as the natural evolution of concurrent wireless technologies.

This project will maximise national impact by exploring the following EPSRC's research areas and cross-ICT priorities (2017-2020):
Future Intelligent Technologies - Cell-free massive MIMO will open new horizons for low-power, ubiquitous communication between different objects, machines and humans, fully aligned with the EPSRC vision to "promote research which aims to develop intelligent, adaptive or autonomous systems that can learn, adapt and make decisions without the need for human control''.

ICT networks and distributed systems - The novel techniques proposed in this project will enable ultra-high speed cellular communications in the 5G+ era (2025 onwards). Moreover, the project will create socio-economic impact by reducing the power consumption of wireless networks, therefore contributing to the systematic efforts of the UK government to reduce the country's CO2 emissions. Future commercial exploitation of the work will eventually lead to the creation of new jobs, start-up companies developing new technologies using wireless technologies, thereby producing wealth and better services for the UK population and contribute to future UK economic success in order to maintain its leading position in this area of endeavour.

Since the area of cell-free massive MIMO is still in its infancy, the project will also have substantial academic impact on diverse fields: signal processing, information theory, data sciences, optimisation, electronics, antenna theory to name but a few. Accordingly, the project's publications could become reference literature and eventually lead to the inclusion of the created knowledge in the educational curricula will further establish the UK as a world leader in state-of-the-art knowledge transfer. All research findings will be prepared for timely dissemination in a number of relevant high impact factor journals and at top international conference