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Title: Adaptation techniques in optical wireless communications
Author: Alresheedi, Mohammed Thamer
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2013
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The need for high-speed local area networks to meet the recent developments in multimedia and video transmission applications has recently focused interest on optical wireless communication. Optical wireless systems boast some advantages over radio frequency (RF) systems, including a large unregulated spectrum, freedom from fading, confidentiality and immunity against interference from electrical devices. They can satisfy the dual need for mobility and broadband networking. However, optical wireless links are not without flaws. They are affected by background noise (artificial and natural light sources) and suffer from multipath dispersion. The former can degrade the signal-to-noise ratio, while the latter restricts the maximum transmission rate available. The aim of this thesis is to investigate a number of techniques to overcome these drawbacks and design a robust high-speed indoor optical wireless system with full mobility. Beam delay and power adaptation in a multi-spot diffusing system is proposed in order to increase the received optical signal, reduce the delay spread and enable the system to operate at higher data rates. The thesis proposes employing angle diversity receivers and imaging diversity receivers as in order to reduce background noise components. Moreover, the work introduces and designs a high-speed fully adaptive optical wireless system that employs beam delay, angle and power adaptation in a multi-spot diffusing configuration and investigates the robustness of the link design in a realistic indoor office. Furthermore, a new adaptive optical wireless system based on a finite vocabulary of stored holograms is introduced. This method can effectively optimise the spots’ locations and reduce the design complexity of an adaptive optical wireless system. A fast adaptation approach based on a divide-andconquer methodology is proposed and integrated with the system to reduce the time required to identify the optimum hologram. The trade-off between complexity and performance enhancement of the adaptive finite holograms methods compared with the original beam power and angle adaptation is investigated.
Supervisor: Elmirghani, Jaafar Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available