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.
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