Enabling multi-service radio access networks with Massive MIMO

Mobile communication networks have evolved over past decade from systems providing voice and basic messaging service to an integral part of society, enabling a rich set of services from voice and video communications, internet access, banking, logistics, navigation and emergency services. A growing customer base with highly capable data centric devices has fuelled a demand for capacity in radio access networks (RAN). To meet this demand, research and development has delivered generations of radio access technologies, rolled out globally, with 4G enabling true mobile broadband experience in the UK from October 2012. The latest manifestation, 5G, being deployed globally following the completion of standardisation in 2018-2019.

One of the key technological differences in 5G RAN compared to 4G RAN is native use of active antenna systems to deliver an unprecedented step change in the efficiency of use by base stations of limited spectrum resources. Active antenna systems (AAS, also known as Massive MIMO) benefit from progress in circuit and electronics technology and low cost computing power in baseband processors to provide independent control over the multiple antenna elements comprising a cellular antenna. Such finer level of control enables basestations to fine-tune transmissions to individual user conditions and to enhance the reception of transmissions by users. The net effect on user experience can be described as a perception of infinite capacity, with a user receiving the resources that their service requires and consequent enhanced responsiveness of services and applications.

The challenge beyond the impressive first steps in AAS research and implementation is to be able to address emerging applications and services carrying different connectivity requirements in terms of latency, reliability, coverage and speed. Many of such new use cases including various machine-to-network communications, industrial automation and transportation, emergency and critical services will have to be provided using the same network infrastructure, including the base stations and antenna systems. No technology exploiting capabilities of AAS for such multi-service use cases exists to date since the primary driver in research and academia has been capacity and energy efficiency. A concept of 'network slicing' does not address this research challenge either since it does not consider digital signal processing and architectures of AAS.

This research programme will explore and deliver a multi-service processing capability in AAS, capable of balancing reliability, coverage and overall network capacity. Specifically, we will investigate the feasibility and performance bounds of such multiservice RAN in delivering mixed types of services sustainably through a single physical infrastructure. We will identify fundamental trade-off factors between reliability and capacity achievable on physical layer of RAN with AAS, and design processing methods to effectively support user differentiation while maintaining network capacity. We will work with industry and academic stakeholders within standardisation bodies and industry to drive the identified solutions to practical realisation and shape further evolution of technology.

Who will benefit from the research and how:
This research will directly contribute to the Future of Mobility Grand Challenge set in the Industrial Strategy by the UK Government. Specifically, AAS capable of balancing network capacity and link reliability will be able to provide a higher reliability in communication with autonomous vehicles. Additionally, such connectivity service enhancement will be available with a larger geographical footprint through realisation in a common radio access network infrastructure.

More generally, following beneficiaries are identified:
Industry stakeholders: RAN manufacturers, providers and users of solutions and services with specific connectivity requirements will benefit in the long term through end products utilising scientific results and techniques developed in this proposal, or derivatives of these. Since we do not know the full spectrum of possible users, this project will involve requirement gathering and continuous engagement with wider industry players within WP4 to understand and meet needs of such users in the project timeframe, i.e. with technology readiness in 2024.

Communication services providers (such as BT) will benefit through being able to address a wider set of use cases through single network infrastructure, which will have lower CAPEX and OPEX components. Such improved investment profile is expected to benefit the pace and reach of deployment of new technologies to a larger proportion of UK population.

UK economy as a whole will benefit from development of ecosystem of users, providers and developers of new services utilising new capabilities not previously offered by mobile networks, this may include infrastructure projects, start-up companies, creation of jobs and increased economic activity in general. In the short to medium term, benefits will come through development and practical application of skills in communications networks, antenna technology and digital signal processing. Open approach to research will help enhance research reputation of BT and the UK setting foundation for future collaborations on impactful research topics.

Timescales
Delivery of practical solutions based on this project depend on three factors: lifespan of basestation hardware, pace of standardisation and emergence of requirements. Experience with 3G and 4G mobile systems suggests that it takes about a decade to swap hardware components in basestations in support of new technologies, although incremental evolution of capabilities can take place within this period.
This project will be starting in Sept 2020 when 3GPP Release 17 will be nearing completion in 2020-21, and workstack for Release 18 (2021-22) will have been already agreed. Hence Release 19 (2022-23) is the earliest release for input of project outcomes. With 4-3 years required for introduction in user devices, national rollout would be viable from approx. 2026, although specific services in can emerge quicker where are existing requirements, as early as 2022-23.

Approach to openness
This project will have an open nature through publication of results and engagement in collaborative research with project stakeholders on terms that are as open as possible whilst preserving sensitive commercial confidentiality. We will make available outcomes of the project, interim results through participation in conferences and industry workshops, publications and social media. Confidential BT information such as deployment statistics and properties will not be open, but will be used to guide technical decisions in appropriate manners, e.g. in a similar way to collaboration in 3GPP working groups.