Low-complexity processing for mm-Wave massive MIMO

There are more than five billion wirelessly connected mobile devices in service today, most of which are handheld terminals or mobile-broadband devices such as computers and tablets. By 2020, mobile communications data traffic is expected to increase 1,000-fold, by which time there will be an estimated 50 billion Internet-capable devices. This transition will present a formidable challenge. Improving the energy efficiency (EE) of existing telecommunication networks is not just a necessary contribution towards the fight against global warming, but with the inevitable increases in the price of energy, it is becoming also a financial imperative. Future technologies (e.g. 5G) on which these devices will operate will require dramatically higher data rates and will consume far more power, and as a consequence increase their environmental footprint. To mitigate this, significant network densification, that is increasing the number of antennas per unit area, seems inevitable. To this end, a novel technological paradigm, known as massive MIMO, considers the deployment of hundreds of low-power antennas on the base station (BS) site to provide enhanced performance, reduced energy consumption, and better reliability.

At the same time, the spectrum scarcity in the RF bands has stimulated a lot of research effort into mm-wave frequencies (30 to 300GHz). These frequencies offer numerous advantages: massive bandwidth/data rates, reduced RF interference, narrow beamwidths. The combination of the above technologies gives rise to mm-Wave massive MIMO, which is considered by many experts as the 'next big thing in wireless'. This paradigm shift avails of the vast available bandwidth at mm-frequencies, smaller form factors than designs implemented at current frequencies, reduced RF interference, channel orthogonality, and large beamforming/multiplexing gains. Yet, the practical design of mm-Wave massive MIMO faces many fundamental challenges, in respect of total energy consumption, circuitry cost, digital signal processing among others. In the context of the project, we envision a mm-wave massive MIMO topology performing a fraction of processing in the baseband (digital) and the remaining fraction in the RF band (analogue), with a reduced number of RF chains, to effectively address most of these challenges. In addition, by deploying low-resolution (coarse) analog-to-digital converters (ADCs), we can substantially reduce the power dissipation of mm-Wave massive MIMO transceivers.

This visionary project will investigate the realisable potential of hybrid processing and 1-bit ADC quantisation. The specific project goals will be to: (a) find the optimal balance between analogue and digital processing for future MIMO configurations in order to maximise the end-to-end EE and experimentally validate the proposed solution, and; (b) investigate the realisable potential of 1-bit ADC quantisation and the channel estimation/resource allocation challenges it induces.

By bringing together a world leading research team with expertise in communications engineering, signal processing, microwave engineering and antenna theory, and with the technical support of the biggest telecom equipment manufacturer in the world, Huawei Technologies Ltd, we will devise scalable low-complexity, low-power solutions suitable for the new generation of BS. We will investigate the algorithms and hardware that will optimise the performance of future BS to precisely meet performance and QoS targets, allied to minimum energy consumption. The application of the project results will contribute to the reduction of the ICT sector's contribution to global warming, through reduced power consumption and improved EE of future BSs. It will also influence many dynamic economical sectors within the UK: telecom equipment manufacturing, telecom operators, positioning systems, surveillance sector, smart cities, e-health, military equipment and automotive companies.

Wireless communications, together with its underlying applications, is amongst today's most active areas of technology development, with the demand for data-rates expected to continue to grow substantially for the foreseeable future. Mobile communications data traffic is expected to increase 1,000 fold by 2020, by which time there will be an estimated 50 billion Internet-capable devices. These forecasts have dictated the development of 5G enabling technologies. Although the UK played an active role in the creation of 2G (GSM) cellular standards, it has increasingly fallen behind in succeeding generations 3G and 4G standards. For the UK to maintain its leading position in this area of research and development, new energy-efficient technologies need to be developed which should deliver remarkably higher data rates compared to today's systems. This projects aims to investigate a novel technological paradigm, namely mm-Wave massive MIMO, which represents a fundamentally different way we see things in terms of electronics, communication theory, microwave engineering. The project will influence broad communities and facilitate the development of vibrant businesses around the proposed technology. The following list summarises potential beneficiaries:

1) The results of the project, through its successful implementation, will make an important contribution to the UK's economical status: telecom companies (vendors and operators), vehicular, Smart grid, security, positioning and surveillance. In the long run, the implementation of the research will lead to the creation of new jobs in existing and start-up companies able to exploit the benefits provided by the proven mm-Wave massive MIMO concept, thereby creating wealth and jobs, and subsequently better and more reliable services for the UK population, once fully commercially exploited.

2) The new knowledge will also be timely for standards bodies (IEEE, ITU-IMT 2020), government agencies (Ofcom), hardware manufacturers (BAE, Thales,) network operators (Vodafone-UK, O2-UK) and network optimisers (Keima), which are currently investing an extensive amount of resources into 5G-oriented research, in order to deliver unprecedented and ubiquitous data rates to billions of users. It is expected that the outcomes of the project will help these authorities to reap the theoretical benefits of deploying a massive number of antennas at future base-stations to serve the UK citizens.

3) Given the scarcity of bandwidth, moving to higher frequencies is a very promising choice. Such a transition will enable the development of new applications, such as wireless cloud computing, HDTV, video streaming, wireless docking stations, and 3D gaming. Referring to the former application, the biggest bottleneck at the moment is that 90% of the WCC's power consumption (approximately 38TWh in 2015) is attributable to wireless access network technologies (4G LTE and WiFi), whilst datacentres account for only 9% (circa 4TWh). Hence, we envision that the proposed technological paradigm will contribute significantly towards the reduction of the energy consumption of wireless networks while maintaining their implementation cost to affordable levels.

4) Last but not least, one of the project's main objectives is to minimise the power consumption of wireless networks and improve their energy efficiency. We recall that the ICT sector is said to account for 2-2.5% of the world total of CO2 emissions, while the environmental footprint of newly industrialised nations, such as China and India, is becoming alarmingly large. As the ICT industry is growing faster than the rest of the economy, this share may well increase over time. Thus, it is of paramount importance to suggest novel solutions for improving the energy efficiency of wireless networks. This project aligns squarely with this vision, since mm-Wave massive MIMO is a key enabler of future 'green' networks while delivering unprecedented data rates.