Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 74-78). Also available on the World Wide Web.

Thesis (Ph. D.)--Massachusetts Institute of Technology, 1966. / Bibliography: leaves 86-88.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 75-82). Also available on the World Wide Web.

Thesis (M.P.A.)--University of Alabama at Birmingham, 2007. / Description based on contents viewed June 26, 2007; title from title screen. Includes bibliographical references (p. 177-191).

No description available.

There is a trend to move the frequency band for wireless transmission to ever higher frequencies in the radio frequency (RF) spectrum to fulfil the exponentially increasing demand in wireless communication capacity. Research work has gone into improving the spectral efficiency of wireless communication system to use the scarce and expensive resources in the most efficient way. However, to make wireless communication future-proof, it is essential to explore ways to transmit wirelessly outside the traditional RF spectrum. The visible light (VL) spectrum bandwidth is 1000 times wider than the entire 300 GHz RF spectrum and is, therefore, a viable alternative. Visible light communication (VLC) enables existing lighting infrastructures to provide not only illumination but also wireless communication. In conjunction with the concept of cell densification, a networked VLC system, light fidelity attocell (LAC) network, has been proposed to offer wide coverage and high speed wireless data transmission. In this study, many issues related to the downlink system in LAC networks have been investigated. When analysing the downlink performance of LAC networks, a large number of random channel samples are required for the empirical calculation of some system metrics, such as the signal-to-interference-plus-noise ratio (SINR). However, using state-of-the-art approaches to calculate the non-line-of-sight (NLoS) channel component leads to significant computational complexity and prolonged computation time. An analytical method has been presented in this thesis to efficiently calculate the NLoS channel impulse response (CIR) in VLC systems. The results show that the proposed method offers significant reduction in computation time compared to the state-of-the-art approaches. A comprehensive performance evaluation of the downlink system of LAC networks is carried out in this thesis. Based on the research results in the literature in the field of optical wireless communication (OWC), a system level framework for the downlink system in LAC networks is developed. By using this framework, the downlink performance subject to a large number of parameters is evaluated. Additionally, the effect of varying network size, cell deployment and key system parameters are investigated. The calculation of downlink SINR statistics, cell data rate and outage probability are considered and analysed. The results show that the downlink performance of LAC networks is promising in terms of achievable data rate per unit area compared to other state-of-the-art RF small-cell networks. It is found that co-channel interference (CCI) is a major source of signal impairment in the downlink of LAC network. In order to mitigate the influence of CCI on signal distortion in LAC networks, widely used interference mitigation techniques for RF cellular systems are borrowed and extensively investigated. In this study, fractional frequency reuse (FFR) is adapted to the downlink of LAC networks. The SINR statistics and the spectral efficiency in LAC downlink system with FFR schemes are evaluated. Results show that the FFR technique can greatly improve the performance of cell edge users and as well the overall spectral efficiency. Further performance improvements can be achieved by incorporating angular diversity transmitters (ADTs) with FFR and coordinated multi-point joint transmission (JT) techniques.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 339-359). Also available via the Internet

I investigate light as a variable that defines and re-defines space. I develop a technique to implement this theory in physical space. The space becomes a tool to further explore how light affects space, and how I can create a space that interoperates the change in light. I work physically, investigating, in model and full scale. I develop the principal as well as details of the space. Both are of great importance to the impression of the space.  My investigation into light begun as a norm-questioning way of measuring space. How can we study space without numbers and hard values? And what spaces can we create if we break free from the flat norm? I study how light can change our perception of a surface. I started investigate in model how I could manipulate the perception of surfaces through changing the light inlet and how I could sculpt surfaces to make them appear different in different light conditions. The relation between inlet and surface became the principal that I started developing space with. I found that the directions of a surface structure is where I can control the appearance of a surface. By casting plaster I develop surfaces with directions and study light on them. I started developing elements with directions that I assemble into one structure.  I use plaster to create the elements. Plaster is interesting in the process of casting, the material goes from being able to take any shape, to become static and unchangeable, unless you break it. The plaster has the properties that it copies features from other materials, such as the shiny surface of the rubber. The plaster gets a beautiful surface that in combination with its color reveals light well. The space I’ve created is based on directions and how light changes its appearance. In one light, a veil like structure in gray and in another a contrasting with a shadows casted and fragmented on the surface.

Population pulsations are fluctuations in the population difference (of a two level system) due to the presence of two or more coherent waves interfering in the medium. In this work, we show that population pulsations generated by three waves, a central wave and two mode-locked sidebands, are responsible for both the multiwavelength and the single-wavelength instabilities of single-mode lasers containing homogeneously-broadened media. The role of the population pulsations in establishing these instabilities, however, diminish as the central mode is detuned away from the atomic resonance frequency. For homogeneously-broadened lasers, we find two regions of single-wavelength instability. The first is at line center, for which population pulsations are solely responsible, and the second is off line center where the unsaturated medium provides the required gain and anomalous dispersion. For the case of inhomogeneously-broadened lasers, we show that population pulsations significantly increase the instability range over that predicted by Casperson for single-mode bad-cavity lasers. Both the unidirectional ring and the standing-wave cavities are treated. The Fourier expansion technique, used in this work, for treating three-frequency operation in saturation spectroscopy is shown to be equivalent (in appropriate limits) to the linear stability analysis in laser theory and optical bistability. We also show, in single-sideband saturation spectroscopy, that for long interaction lengths propagation effects can significantly influence the absorption and dispersion coefficients of the medium. Finally, we show that under certain conditions the pronounced splittind effects of the population pulsations develop into regions of intense absorption.

No description available.