Design of Sustainable Cloud Radio Access Networks

The exponential growth in terms of wireless data traffic along with the number of mobile devices is expected to continue. For example, according to Cisco, it is predicted that the number of mobile devices will reach 1.5 per capita in 2021; there will be 11.6 billion mobile-connected devices including machine-to-machine modules. Global mobile data traffic will increase sevenfold between 2016 and 2021. On the other hand, the energy consumption of cellular networks world-wide per year is around 60 billion kWh and is expected to double within the next few years. Specifically, the large portion (80%) of electricity used in cellular networks is consumed by base stations, emitting over a hundred million tons of carbon dioxide annually. Combining the need for high wireless data rates, the increase in power prices and the raising environmental concerns, cellular network providers are facing unique challenges leading to huge increases in capital and operating expenditures. As a result, the need for wireless networks meeting the ever increasing demand in wireless data in a sustainable way is more pressing than ever.

To achieve sustainable energy and spectrally efficient wireless networks, several promising technologies, such as massive multiple-input multiple-output (MIMO), millimetre wave communication, network densification and energy harvesting, are under investigation. Cloud radio access network (CRAN) is considered as a potential solution to achieve network densification, and hence will meet the exponential growth in wireless network traffic, in a cost and energy efficient manner. CRANs facilitate increase in network capacity and energy efficiency while reducing both network capital expenditure and operating expense. However, we strongly believe that the potential of CRANs is still not fully exploited and their performance can significantly be improved via incorporating new technologies such as massive MIMO and energy harvesting. The aim of this project is to design sustainable high energy and spectral efficiency CRANs. The novelty of this project is that we propose and optimise a new CRAN architecture incorporating a massive MIMO central unit and remote radio heads (RRHs) equipped with hybrid energy sources (i.e., with energy harvesting capability and connection to the power grid) to further improve the energy and spectral efficiencies of wireless networks while being sustainable.

To achieve the goal of this project, we will consider both long-term and short-term performance optimisation of the proposed CRAN architecture. In terms of long-term performance, given the flexibility in placing the RRHs offered by using wireless fronthaul, we propose to optimise the placement of the RRHs. In terms of short-term performance, we propose to design a low complexity channel estimation method and to jointly design the fronthaul and access links. The optimised design of the new CRAN architecture will lead to sustainable and improved energy and spectral efficiency wireless networks.

The research outlined in this proposal will likely generate wide impact on economy, society, knowledge and people.

1. Economy.
The proposed research will lead to sustainable high energy and spectral efficiency wireless networks. The outcomes will support UK competitiveness in the ICT industry through proposing low carbon emission technologies and at the same time reduced operating expense (OPEX) and capital expenditure (CAPEX), while providing high quality services. The environmentally friendly aspect of the proposed research will be an asset to UK telecommunications companies and will enforce their international leadership position.

2. Society.
The proposed research will enable a connected society with an environmentally friendly technology. A low carbon footprint of communications networks will have direct positive impact on the environment and hence on the life and health of people. Also, the general public will benefit from our research via our outreach activities (see Pathways to Impact). This will increase the general public awareness about the efforts to develop environmentally friendly wireless networks.

3. Knowledge.
The proposed and optimised CRAN architecture is novel and will advance the state-of-the-art of sustainable wireless networks. In particular, this proposal will open the possibility of using a massive MIMO central unit in CRANs which can be exploited by the research community in investigating other related research problems such as scheduling, remote radio head selection and coverage expansion.

4. People.
The applicant, PDRA and PhD student would gain more skills to enhance their research profile and careers. Also, the PDRA and PhD student will be offered training on highly transferable skills such as project and time management, presentation and written and oral communication skills.