The forecast by International Telecommunication Union (ITU) predicts that by 2030, the overall mobile data traffic will reach 5 zettabytes (ZB) per month. Multiple-input multiple-output (MIMO) is the most celebrated mobile technology that provides the needed upgrade from 2G to 3G, from 3G to 4G and most recently from 4G to 5G in the form of massive MIMO. In 5G, the number of antennas at the base station (BS) has been increased to 64 to cope with the rising demands. However, the number of antennas at a mobile handset (referred to as user equipment (UE) in the standards) remains small (<=4). This is due to the limited space at the UE, as the common practice is to deploy multiple antennas only if they are sufficiently apart (>=half of the wavelength) to have sufficient diversity of signals at different antennas for ensuring performance gains. It makes us wonder if it is possible to utilise the spatial diversity in a small space of UE more effectively. What if an antenna can be formless, shapeless like water? This is what this project is all about - to design novel antenna systems, coined fluid antennas, that can provide the ultimate reconfigurability and agility for signal and information processing. It is worth pointing out that seawater, albeit much less conductive than metal, has already been demonstrated a radiation efficiency of 70% by Mitsubishi Electric, and fluid antennas using conductive fluids or liquid metals for different reconfigurabilities have been actively researched in recent years. Despite the interest for fluid antennas in the antenna community, it was not until the original work by the investigators when the characteristics of fluid antenna was exploited for the optimisation of wireless communications systems. In the pioneering work, it was revealed that an agile fluid antenna system could, for the first time, realise: (*) Fading-free communications: one fluid antenna could achieve the same diversity as a massive number of fixed antennas. (*) Interference-free communications: spatial multiplexing for multiuser communications can be obtained by skimming through the fading envelopes observed in the space of the fluid antenna, by tuning to the most favourable position (or port) where the interference is in a deep fade, without the need for complex coordination and signal processing. Motivated by the great potential, this project identifies several fundamental challenges of fluid antenna systems, including, design and implementation, signal processing and optimisation, and fundamental network performance analysis, and aims to overcome these challenges in the realisation of the fluid antenna empowered mobile communications technologies by researching on four fronts: (1) Design and implementation of a pump-less, droplet fluid antenna - this addresses the implementation challenges of the fluid antenna system. (2) Information-theoretic network performance analysis in general channel models, representing the 5G/6G bands - this addresses the performance analysis of the communication networks using fluid antennas in the 5G and potential 6G bands. (3) Port selection and opportunistic fluid antenna multiple access (FAMA) - this tackles the network management and resource allocation of mobile communication networks using fluid antennas. (4) Fluid MIMO - this investigates the design and optimisation of MIMO using fluid antennas and multi-droplet fluid MIMO systems. The research directions have never been explored and will play a key role in revolutionising mobile communications. This project has received strong support from BT, Toshiba TRL and VIAVI Solutions who will advise on testbed implementations and ensure industrial relevance of the project.

Future wireless communication networks are expected to address unprecedented challenges to cope with a high degree of heterogeneity in terms of devices, deployment types, environments, carrier frequency, etc. Moreover, they are expected to provide orders of magnitude improvement to such heterogeneous networks in key technical requirements including throughput, number of connected devices, latency and reliability. With such diverse services and diverging requirements, it is cumbersome to design a unified all-in-one radio system to meet the technical needs for all types of services. In addition, designing separate systems that run on separate infrastructures make the operation and management of the system highly complex, expensive and spirally inefficient. The scope of the project is to establish a radio ecosystem on a common infrastructure that efficiently accommodates communication services for all vertical sections from manufacturing, entertainment, public safety, public transport, healthcare, financial services, automotive and energy utilities. This can be enabled by an algorithmic framework orchestrating all radio slices that are individually customised and optimally designed. Network slicing is an overarching feature towards 5G-and-beyond to support all scenarios efficiently. Core network slicing has attracted much attention through network functions virtualisation. However, from the radio level, an algorithmic framework for spectrum- and cost-efficient air-interface to achieve the true potential of end-to-end network slicing for the future diverse radio systems is still an open problem yet to be solved. To guarantee the required performance for each individual user case efficiently, the physical layer (PHY) configurations should be delicately optimised and medium access control layer (MAC) radio resource should be allocated on-demand. For instance, subcarrier spacing is one of the paramount importance parameters for modern multicarrier communication systems (e.g., LTE, WiFi, etc.), the service for future massive machine type communications (mMTC) might require smaller subcarrier spacing (thus larger symbol duration) to support massive delay-tolerant devices. While vehicle to vehicle (V2V) communications, on the other hand, have more stringent latency requirements, thus, symbol duration should be significantly reduced compared to mMTC. However, cohabitation of the individually optimised services in one system may bring several technical challenges from both PHY and MAC. It will destroy the system orthogonality and PHY algorithm framework that the state-of-the-art telecommunication systems built on. From the resource allocation perspective, one of the challenges is that not only the multi-slice system forests a complex multiple layers resource structure, but also technical requirement of each slice can be significantly different. Thus, a cross-layer and cross-slice optimisation is envisioned to maximise the overall air-inference performance. The aim of REORDER is to address the abovementioned challenges, by establishing the framework of air-interface heterogeneous signal orchestration and efficient resource allocation. The proposed work fills in the last piece of the puzzle for realistic and efficient end-to-end network slicing. From this sense, REORDER will "reorder" the radio resource allocation caused by slice configuration disorders. The project will be undertaken in the Communication, Sensing and Imaging research group (CSI) in the University of Glasgow, by the PI, a PDRA and a PhD student based at the University of Glasgow. Our industrial partners include NEC Telecom MODUS (UK), Mathworks Research Centre Glasgow, and VIAVI Solutions (UK). The radical approaches proposed in this project will be verified though both state-of-the-art standard compatible system-level simulation and software defined radio (SDR) based over-the-air experimentations.

The term microwave is used in reference to electromagnetic radiation with wavelengths ranging from about one meter to one millimetre. In the electromagnetic spectrum microwave wavelengths are shorter than those of radio waves but longer than those of infrared waves. Microwaves are used extensively in modern communication systems, including: mobile networks, WiFi, GPS, satellite TV, etc.. Other applications, include: heating, radar, imaging, etc.. The number of applications for microwaves is increasing due to the increasing use of electronic devices and the convenience of communication without wires. In the future microwaves will be used in 5G mobile networks, which will see the introduction of a multitude of new devices, all relying on communication via wireless signals. Those new devices and applications include: driverless cars, remote surgery, virtual reality, internet of things, etc.. Today most of the components within a system, operating at microwave frequencies, are designed specifically for that particular application. This increases the cost, and time required to bring a new product to market. In turn, this impacts the price which consumers pay for goods and services e.g. mobile handsets. In this research we ask the question; what if a communication system could be assembled from a collection of standardised bricks in just the same way that anything can be constructed from standard Lego(TM) bricks? Then the design task would reduce to that of devising and designing a suitable set of bricks with which to create a range of different systems. To some extent this already happens; for example, companies produce a range of frequency selective filters having different specifications, and one can select a filter for a particular application. However, the enormous variety of different systems means that a large number of different variations are required. So a huge amount of design effort is still required. In this research we consider what would happen if, we could devise a generic Lego(TM) brick that would assume different sizes and forms. This would enable us to construct any system from a collection of this single almost magical Lego(TM) brick. If this could be achieved the task of designing a complex microwave system, such as the radio within a mobile handset, would merely involve deciding how to assemble a collection of these "magic" Lego(TM) bricks to create the required system. The idea, although attractive, sounds like a fantasy because from our everyday experience we "know" that no object cannot mutate to assume any form and then hold that form, at will. Surely, such a concept is pure science fiction and the stuff of movies like the terminator... Well, no in fact it is not, since 2014 researcher have been working intensively on a new and exciting material which behaves in a way very much like the metal seen in the terminator movies. This material is a metal and yet it is also a liquid at room temperature. Excitingly it can be caused to move under direct electrical control and to hold its shape, at will. In this research we plan to use that material to a create this "magic" Lego(TM) brick which behaves as a universal microwave component. Being made from liquid the component can be flowed into different sizes and forms and thus we obtain 'liquid wires'. To create larger systems, we will simply need to decide how to join the bricks together so that they can operate in unison to perform more complex functions. Our research is highly interdisciplinary in nature and will benefit the U.K. economy across a wide range of different areas, including: chemistry, materials science, and engineering. The technology could revolutionise the way that communications systems are designed and built, resulting in entire new industries.

Current highly sensitive gravimeters, such as superconducting spheres, atom interferometers, and torsion pendulums, suffer from high manufacture and maintenance cost (up to £400k), bulky size (as large as 2.5m^3) and slow measurement speed (typically 1 hour). Here we propose an exciting innovation in quantifying gravity, based on the frequency measurement of the gravity-induced precession in an optically levitated fast-spinning particle. This novel levitated optomechanical systems (LOMS) gravimeter can be fabricated on a silicon wafer with wafer-level vacuum encapsulation, making its footprint as small as one mm^2. The small size device is mass-producible with a fabrication cost potentially less than £4k. The proposed research uses the analogy of the precession of the Earth, a slow and continuous change in the orientation of the Earth's rotational axis induced by the gravity of the sun, to develop the novel gravimeter. In December 2018, our research for the first time revealed that the precessional motion also appears in sophisticatedly designed LOMS and that optical scattering techniques can precisely measure the frequency of precession [U9]. Our calculation predicts that levitated rotating particles of 10um diameter can achieve the sensitivity of 10^-9 g/sqrt(Hz) and a very fast-spinning particle (GHz reported in 2018 [x19]) can achieve 10^-11 g/sqrt(Hz) sensitivity, respectively. The novel gravimeter can also measure the acceleration due to the Einstein equivalence principle. Thanks to the ultra-high Quality-factor (7.7x10^11 demonstrated in 2017 [x3]) of the rotating particles, the novel sensor will have the potential to cover 11 orders of magnitude of acceleration measurement. Moreover, using the advanced silicon fabrication technique, we will be able to differentiate the centre-of-mass and the centre-of-optical-force of the levitated particle, in order to optimise the range of the gravity (or acceleration) induced torque, and correspondingly design the sensing range and sensitivity of the acceleration, e.g. 10^-6 m/s^2 to 10^5 m/s^2 to cover the seismic and mining health monitoring applications or 1 m/s^2 to 10^11 m/s^2 for fundamental physics research. The sensor only requires short integration times (1ns to 100s, depend on the precession frequency). Thus, it can complete the measurement very rapidly. This novel precession sensing principle can also be utilised to measure force, strain, charge and mass, with similar ultra-wide dynamic range and ultra-high sensitivity potentially. The innovative gravimeter (accelerometer) can be a powerful tool for investigating fundamental physics questions in gravitation, which are pressing and very hard to access experimentally due to the weakness of the gravitational interaction if compared to other interactions. The proposed research can also provide a platform for quantum manipulation of mesoscopic mechanical devices in the nano-scale regime and can serve as a testbed for theoretical predictions. Furthermore, our novel sensor can equipt the oil and gas industry with its applications in CO2-EOR and exploration. It can track temporal and spatial variations of the gravitational field and provide highly accurate information of mass redistribution below the surface. The prototype on-chip LOMS gravimeter has a small footprint so that it can be installed close to the drilling bit. Based on Newton's law of universal gravitation, the gravimeter has the potential to detect 1.5x10^7 kg mass redistribution above the ground, and 1.5x10^5 kg mass redistribution inside the wellbore. The sensitivity of the novel gravimeters installed inside wellbores can be four orders of magnitude better than that of the existing highly sensitive gravimeters. Our research also contributes to CSS, mineral exploration, structural safety monitoring for mining, earthquake warning, inertial navigation and geoscience, and can lead to significant cost savings in multiple industries.