Wireless connectivity is currently considered a de-facto capability, enabling people and machines to communicate. Range of applications supported by such Radio Access Networks (RAN) ranges from voice and video calling, content streaming services, banking, cloud data storage, navigation and many more. The volume of data carried by cellular networks delivering the connectivity for such applications grows approximately by 40% every year, which means the data traffic approximately doubles every two years, according to Ofcom. Research and development effort within industry and academia has been focussed on technologies capable of meeting this growing demand for capacity, delivering innovations in digital signal processing, computer science, optical transmission, circuitry, and antenna technology. Spectral efficiency, which is the amount of information that can be carried in a radio channel, has been the key focus for such inter-disciplinary effort since radio spectrum is a scarce resource and has to be used efficiently. Active Antenna Systems (AAS, also referred to as Massive MIMO) is the latest generation of base station technology for mobile networks delivering increased spectral efficiency by combining innovations and experience from multiple disciplines. AAS are already being rolled out as part of 5G network deployments globally and will continue to play a key role in future generations of mobile networks. However, in order for investment in mobile networks to be viable, more services need to be able to use mobile network efficiently, calling for support for multiple services to be concurrently delivered over the same cellular infrastructure. Practical potential of AAS to concurrently deliver multiple services is the focus of the original FLF. Sustainability has emerged as a key theme in recent years with a view to reduce carbon emissions by a substantial amount to help reverse the negative impact of industrialisation on the climate. In mobile networks this has resulted in energy efficiency (EE) becoming a key design objective. With 0.8% of the overall UK energy consumption falling on BT network alone, finding both short and long-term solutions to this challenge is of critical importance. The specific challenge for RAN is to minimise the consumption of electrical power while also meeting increasing demand for diverse connectivity services. This project will focus on ambitious enhancements to practical mobile network. The aim of the renewed fellowship is to increase the practical EE of diverse connectivity services provided by mobile networks - from traditional delivery of bits over the wireless interface, to provision of non-data bearing services such as positioning. To achieve this goal, the project will establish practical EE benchmarks for data and service provision in current mobile networks, and then assess and develop approaches to improve the EE, both in short and long term. Specifically, technologies such as muting of transmitters, sending base stations to varying states of sleep will be considered as reference capabilities available in short term, while the use of AI to tailor transmission technology and the use of energy-efficient waveforms with be considered as longer-term research objective aiming the development of 6G air interface. Applications and benefits from this project will include benchmarks for EE gains from key technology choices under practical operating conditions and constraints. This will enable a realistic assessment of potential contribution to sustainable RAN, and also help design EE-native communication and network deployment strategies for 5G and 6G RAN.

As the standardization of 5G wireless networks progresses, the research community has started focusing on what 6G will be. Motivated by the need of ensuring high data-rates, while at the same time saving spectrum, a major technology that has been proposed for 6G is the integration of communication and sensing services in the same infrastructure. This enables wireless networks to perceive the surrounding environments, triggering new services and leading to a more efficient use of resources. The INTEGRATE project focuses on the theoretical, algorithmic, and architectural foundations of integrated communication and sensing networks, developing the first open access network-level simulator for joint communication and sensing. To this end, a new implementation of wireless transceiver is proposed, which leverages the use of reconfigurable holographic surfaces and allows the integration of communication and sensing with remarkable performance while at the same time reducing the energy consumption. Specifically, INTEGRATE will: 1) Develop reconfigurable holographic surfaces capable of supporting joint communication and sensing tasks and that can be integrated in wireless transceivers with minimal cost and energy requirements. 2) Characterize the fundamental performance limits of integrated communication and sensing networks, developing an algorithmic framework and protocol suite to approach these limits. 3) Build the first open access software simulation platform for joint communication and sensing networks.

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.

Mark Weiser's vision of ubiquitous computing, in which computers become transparently and seamlessly woven into the many activities of our daily lives, is slowly becoming a reality. Researchers have created prototype ubiquitous computing environments such as 'smart homes' that can automatically sense the presence of a resident in a particular room and change some aspect of the environment of the room such as turning on the lights, or 'smart museums' that can play recorded information about the museum artefact a visitor is standing in front of. There seem to be limitless possibilities for the kinds of environments and applications that can be developed for ubiquitous computing, yet the very nature of ubiquitous computing creates new and significant challenges for engineers who would like to build these environments and applications. Anybody who has ever used a computer has experienced the extreme frustration of using a software package that doesn't work the way it's supposed to, or that unceremoniously crashes in the middle of its operation, or that runs extremely slowly, or that transmits sensitive information such as credit card numbers over untrusted networks. For ubiquitous computing to achieve true transparent and seamless integration with its surroundings, it is important to prevent such mishaps, crashes, inefficiencies and insecurities from happening to the greatest extent possible. This project will define and implement a suite of sound, systematic methods that engineers can use to create correctly functioning, efficient and secure ubiquitous computing environments and applications. The research will be conducted and evaluated using the smart urban spaces and applications being developed in another ubiquitous computing project called Cityware.

At a glance: Microstructured optical fibres are transforming science and technology in fields spanning telecommunications through to healthcare. Their unique offering of guiding properties continues to push the limits of established photonics and drive novel innovation and scientific discovery. However, a limit to this potential is approaching because many theoretically transformative fibres cannot be realised in practice due to manufacturing challenges. With this fellowship, I aim to unlock this unmet potential by developing a freeform optical fibre manufacturing process, which is unbound from conventional manufacturing constraints. The vast majority of optical fibre is produced for the telecommunications sector to satisfy exponentially rising data capacity needs. The type of fibre used in telecoms is typically conventional step-index fibre, comprised of a silica glass core surrounded by a lower-index doped-silica cladding. Solid fibre is inexpensive and guides with reasonably low-loss, but is fundamentally limited in performance by material absorption, scattering and high-dispersion amongst other factors. Over the past few decades, another type of optical fibre has emerged - microstructured optical fibre (MOF). MOF utilises a structured-material core-cladding in which light is guided through complex waveguiding mechanisms. Depending on the type, MOF can offer several advantages over conventional fibre including broad spectral transmission, low bend-loss, low latency and high-power delivery. Remarkably, certain MOFs guide light within a hollow region of the fibre. These so-called hollow-core fibres overcome problems faced by solid-core fibres such as material absorption, dispersion, optical damage and latency, as well as enabling an innovation-rich field of gas-filled sensors and light sources. MOF is manufactured by an approach known as stack-and-draw. Stack-and-draw is a two-step process: firstly, circular glass capillaries, rods and tubes are stacked laterally, often with added spacers, to form a scaled-up approximation of the fibre known as a preform. Secondly, the preform is drawn to fibre through a high-temperature furnace. The design of MOF developed so far has been heavily steered by the restrictive stacking process, e.g., hexagonally-packed Kagomé fibre and circle-tubular antiresonant fibre. Unfortunately, several types of MOF that have shown huge potential theoretically cannot be reasonably stacked, and so the vast applicability of MOF is beginning to plateau. To unlock this potential, we will develop a new preform manufacturing process capable of producing freeform fibre, i.e., fibre with arbitrarily structured cross-section, without compromising on fibre quality. In the proposed approach, short segments of the preform are precisely and arbitrarily machined using tailored laser-manufacturing methods. These segments are then bonded axially to form the preform which is drawn to fibre using traditional methods. Building upon a recent early feasibility demonstration, the fellowship will facilitate an overhaul of the laser-based approach to fabricating preforms and investigation of optimal glass bonding techniques. Amongst a trove of benefits, freeform fibre will bring drastically lower loss, increased stability, faster data transfer speeds and novel spectral guidance. The later stages of the fellowship will focus on developing fibre with unprecedented guiding performance and exploring applications of fibre with novel geometry. We aim to develop an industry-ready manufacturing method for freeform silica optical fibre, and further improve high-resolution glass macro-fabrication and advanced bonding and assembly capabilities. This work is expected to open up a new field of fibre optics research and nurture a team of dedicated researchers.