Design and optimisation of user-centric visible-light networks

In order to counteract the explosive escalation of wireless tele-traffic, the communication spectrum has been gradually expanded from the conventional radio frequency (RF) band to the optical domain. By integrating the RF band relying on diverse radio techniques and optical bands, the next-generation heterogeneous networks (HetNets) are expected to be a potential solution for supporting the ever-increasing wireless tele-traffic. Owing to its abundant unlicensed spectral resources, visible light communications (VLC) combined with advanced illumination constitute a competent candidate for complementing the existing RF networks. Although the advantages of VLC are multi-fold, some challenges arise when incorporating VLC into the classic RF HetNet environments, which may require new system architectures. This motivates our research on the system design of user-centric (UC) VLC.Our investigations are focused on system-level design of VLC and it is constituted by three major aspects, namely 1) by the cooperative load balancing (LB) in hybrid VLC and wireless local area network (WLAN) as discussed in Chapter 2; 2) by the UC cluster formation and multiuser scheduling (MUS) of Chapter 3; 3) as well as by the energy-efficient scalable video streaming design example of Chapter 4. Explicitly, we first study VLC as a complementary extension of the existing WLAN. In Chapter 2 we study various conventional cell formations invoked for networks in order to tackle the significant inter-cell interference (ICI) problem, including the traditional unity/nonunity frequency reuse (FR) techniques as well as the advanced combined transmission (CT) and vectored transmission (VT) schemes. Then a distributed LB algorithm is proposed for a hybrid VLC and WLAN network, which is then evaluated from various perspectives.In order to further mitigate the ICI in VLC networks, we focus our attention on novel UC-VLC cluster formation techniques in Chapter 3 and Chapter 4. The concept of UC cluster formation is a counterpart of the conventional network-centric (NC) cell formation, which is dynamically constructed according to the users’ location. Relying on graph theory, the joint cluster formation and MUS problem is solved in Chapter 3. Furthermore, another important optimisation aspect in most wireless networks is the achievable energy efficiency (EE). Hence, we design an energy-efficient scalable video streaming scheme for our UC-VLC network, which achieves superior performance compared to the NC cells in terms of its throughput attained, EE as well as the quality of service (QoS)