User-Centric Visible Light Communications aided Networks

Visible Light Communications (VLC) is an emerging field of optical communications that focuses on the specific part of the electromagnetic spectrum that humans can see. The use of the visible light spectrum has gained substantial interest, because it is licence-free and can be readily modulated by flickering the intensity of light using Light Emitting Diodes (LEDs). Furthermore, it can be detected using inexpensive photo-detectors. VLC exhibits several appealing characteristics, including the anticipated presence of a ubiquitous and efficient LED lighting infrastructure both indoors and outdoors, which is inherently secure, has a vast bandwidth and does not interfere with the Radio Frequency (RF) band. The potential for VLC is recognised by the burgeoning mobile industry using the traditional RF band and it is supported by the rapid evolution of LED based lighting. Since more than 70% of tele-traffic occurs indoors, there is a huge opportunity for indoor tele-traffic offloading, where VLC creates a unique opportunity to meet the above requirements.

Hence, tremendous efforts have been invested in improving the performance of point-to-point single-user VLC transceivers by conveying data from a single LED array to a single receiver, where ambitious GBits/s targets have been achieved. By contrast, this project stimulates research interests dedicated to VLC aided networks comprised of multiple LED arrays and multiple users. Specifically, in VLC aided networks, each Access Point (AP), i.e. an LED array, exhibits a coverage confined to a few meters due to the nature of light propagation. As a result, the number of APs may be much higher than the number of users, which is completely different from the current RF aided networks supporting much higher number of users than that of the APs. This creates hitherto-unexplored ultra-dense small-cell networks, which require a new system architecture. Hence, we conceived the User-Centric VLC (UC-VLC) aided networks concept of this project.

In its simplest guise, user-centric design refers to forming networks based on the users' geo-locations, mobility trajectories and service requirements. To achieve this ambitious goal, a disruptive design relying on the association between APs and users is required, where the association determines which specific set of APs serves which particular group of users. The novel idea proposed in this research is to group the users together based on their geo-locations and then associate specific APs with them. In this way, the resultant cells are of amorphous shape, since the users' locations are random. Moreover, these amorphous cells are capable of evolving upon the users' movements and service requirements, where new APs may join in the association in order to replace old APs that are leaving the association. Hence, the resultant networks always follow the users' activities, as recorded in the animation at http://www.ecs.soton.ac.uk/research/projects/924.

To elaborate, the proposed research is dedicated to the design and optimisation of hitherto-unexplored UC-VLC aided networks relying on amorphous cells, with the aid of the following three Work Packages (WPs):

WP A - Optimising Network Efficiency: We design amorphous cells by optimising the spectral and energy efficiency, when considering a range of physical layer techniques, optical constraints and practical imperfections.
WP B - Enhancing Service Quality: As an evolution from WP A, we design amorphous cells for satisfying diverse user-specific service requirements and as an application of WP A, we also consider scalable video streaming over UC-VLC aided networks by exploiting content-awareness.
WP C - Improving System Robustness: In addition to WP A and B focusing on a stationary case, we design time-variant amorphous cells that are capable of adapting to the users' mobility and to their blocking patterns for improving the attainable handover experience and system robustness.

The proposed research on User Centric Visible Light Communications (UC-VLC) aided networks strongly aligns with the EPSRC portfolio and strategy as detailed in the `National Importance' section of the Case for Support (CfS) document. It has an impact in four important aspects:

Economic - When compared to conventional designs, the proposed research would be capable of exhibiting over an order of magnitude throughput enhancement. Hence, all the designs generated from the proposed research would result in direct benefit for a range of important indoor use-cases, as exemplified by home, offices, hospitals, museums, libraries, factories etc, where potentially hundreds of people and thousands of appliances would be connected. As detailed in the `Letter for Support' (LfS) documents, our supporting company Bell Labs has been innovating in all areas related to the future evolution, deployment and operation of small-cell networks in order to address the exponential growth in mobile data traffic. Hence, the proposed research would provide direct benefits to them in the context of next generation user-centric small-cell networks. Similarly, the proposed research would be capable of creating indoor 5G hotspots supporting in excess of a GBits/s throughput, which would facilitate new mobile applications for entertainment, collaborative design, education, social networking, etc. This perfectly aligns with the 5G research vision of our supporting company BT, as detailed in the LfS documents.

Societal - Reducing energy consumption has been one of the salient topics in the 21th century. In addition to designing energy-efficient Light Emitting Diodes (LEDs), optimising the system-wide energy efficiency of VLC aided networks would directly contribute towards the all-important `green' agenda. As further advances, the proposed research is strategically focused on the networking aspect of VLC to create a stepping stone for the Light-As-A-Service (LAAS) mode of operation. In particular, the extremely flexible construction of user-centric amorphous cells of the proposed research would find important applications in hospitals, including also the internet of medical `things', where RF aided networks are normally prohibited. This would improve the individuals' quality of life with the aid of an enhanced mobile healthcare experience associated with the inherent secrecy and privacy of VLC.

Knowledge - The research would make a substantial impact on the wider research community, as detailed in the `Academic Beneficiaries' document. To emphasize, the proposed research is strategically focused on the networking aspects of VLC, which perfectly complements the UK's most recent investments in VLC system research (EP/K00042X/1) and in advanced LED development (EP/K00042X/1). Together, our proposed research would contribute towards covering the full spectrum of VLC-related research and development, strengthening the leading position of the UK in this field.

Personal - The proposed research would help in developing the expertise and project leadership skills of the Principle Investigator (PI), who undertakes this role for the first time in an EPSRC project. Furthermore, valuable networking opportunities would be provided for the PI, where his academic-industrial links would be vastly expanded. Hence, the experience obtained under this EPSRC project would enable him to undertake more ambitious projects in the future, for making an even wider impact. Finally, the experience that the named RA will gain from his involvement in the proposed research would significantly further develop his expertise, which is highly desirable to both British industry and academia.

Hence, the success of the proposed research is vital and lies within the primary focus of the UK's mission in a world of ever-increasing communications demands, as drivers of economic competitiveness as well as environmental sustainability.