Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (p. 159-167). Also available in electronic format on the Internet.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 106-113). Also available in electronic version.

abstract: It is commonly known that High Performance Computing (HPC) systems are most frequently used by multiple users for batch job, parallel computations. Less well known, however, are the numerous HPC systems servicing data so sensitive that administrators enforce either a) sequential job processing - only one job at a time on the entire system, or b) physical separation - devoting an entire HPC system to a single project until recommissioned. The driving forces behind this type of security are numerous but share the common origin of data so sensitive that measures above and beyond industry standard are used to ensure information security. This paper presents a network security solution that provides information security above and beyond industry standard, yet still enabling multi-user computations on the system. This paper's main contribution is a mechanism designed to enforce high level time division multiplexing of network access (Time Division Multiple Access, or TDMA) according to security groups. By dividing network access into time windows, interactions between applications over the network can be prevented in an easily verifiable way. / Dissertation/Thesis / M.S. Computer Science 2013

Solar energy is widely used for electricity generation, heating systems, and indoor environment daytime illumination. Indeed, large amounts of Sunlight energy remain insufficiently used. In this work, we aim at employing sunlight for data transmission as another option for wireless communications. Being emitted by an uncontrollable source, taming the Sunlight is a challenging task that requires appropriate technolo- gies to manipulate incident light. Throughout this thesis, we first review switchable glass technologies and investigate their potential use for light modulation. Liquid Crystal Devices (LCD) have adequate response time and contrast characteristics for such an application. In this regard, we design a novel Dual-cell Liquid Crystal Shutter (DLS) by stacking two Liquid Crystal cells that operate in opposite manners, and we build our Sunlight modulator with an array of DLSs. Then, we adopt Time Division Multiplexing and polarization-based modulation to boost the data rate and eliminate the flickering effect. In addition, we provide mathematical modeling of the system and study its performance in terms of communication and energy consumption. Finally, we introduce some numerical results to examine the impact of multiple parameters on the system’s performance and compare it with state-of-the-art, which showed that our system features higher data rates and extended link ranges.

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Made available in DSpace on 2016-03-15T19:38:10Z (GMT). No. of bitstreams: 1 Mauricio Moderno de Carvalho.pdf: 2212181 bytes, checksum: 274e2da279304668d738afe9e3483c45 (MD5) Previous issue date: 2008-08-06 / Fundo Mackenzie de Pesquisa / By adopting a ring topology and optical switches we propose a novel protection mechanism for time division multiplexed passive optical network (TDM-PON) that provides resilience against multiple network fails. Some protection schemes have been proposed in order to give resilience for passive optical network (PON) as defined at ITU-T Recommendation G983.1. However that recommendation defines the optical distribution network (ODN) and equipment duplication to protect it against multiple points of fail. We propose a ring topology with dual fibers paths capable to protect the network by switching these lines individually according to the local alarms detected by each optical network unit (ONU). According to our proposal neither equipment nor network should be duplicated to provide survivability to the system. / Adotando uma topologia em anel e chaves ópticas, estamos propondo um novo mecanismo de proteção para redes ópticas passivas TDM (Time Division Multiplexed) que possibilita a proteção da rede contra múltiplos pontos de falha. Muitos esquemas de proteção foram propostos para dar confiabilidade para as redes ópticas passivas como definido pela recomendação ITUT G.983.1. Para permitir proteção contra múltiplos pontos de falhas a recomendação ITU-T define a duplicação da rede óptica (ODN) e equipamento. Apresentamos, então, uma topologia em anel com dois caminhos ópticos distintos protegendo a rede pela comutação individual destas linhas de acordo com a detecção de alarmes locais por cada Optical Network Unit (ONU). Conforme nossa proposta, nem o equipamento ou a rede precisam ser duplicadas para prover proteção do sistema.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Current ground-based tracking systems at the DoD test and training ranges require transmission of a variety of signals from rotating platform to fixed control and process center. Implementation of commercial off the shelf (COTS) solution for transmitting high-speed, multiple-channel data signals over a rotational platform prompt the development of an advanced electro-optic hybrid rotating-to-fixed information transmission technology. Based on current demand, an Air Force-sponsored Small Business Innovative Research (SBIR) contract has been awarded to Physical Optics Corporation (POC) to modify existing tracking mounts with a unique electro-optic hybrid rotary joint (EOHRJ). The EOHRJ under current development is expected to provide the following features: 1) include a specially designed electrical slip-ring, which is able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed data signals; 2) include an optical fiber slip-ring which, by incorporating with electrical time division mulitplexing (TDM) and optical wavelength division multiplexing (WDM) technologies, is able to provide multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; and 3) is designed to be reliable for harsh environmental operation, adaptive to stringent size requirement, and accommodating to existing electrical and mechanical interfaces. Besides the military use, other possible commercial applications include on board monitoring of satellite spinners, surveillance systems, instrumentation and multi spectral vision systems, emergency/medical instruments, remote sensing, and robotics.

Ho Chi-Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 63-[64]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The 2.5G Systems --- p.3 / Chapter 1.2.1 --- HSCSD --- p.3 / Chapter 1.2.2 --- GPRS --- p.3 / Chapter 1.2.3 --- EDGE --- p.4 / Chapter 1.2.4 --- IS-136 --- p.4 / Chapter 1.3 --- The Evolution from 2G/2.5G to 3G --- p.4 / Chapter 1.3.1 --- GSM Data Evolution --- p.4 / Chapter 1.3.2 --- TDMA Data Evolution --- p.5 / Chapter 1.3.3 --- CDMA Data Evolution --- p.6 / Chapter 1.4 --- UTRA --- p.7 / Chapter 1.4.1 --- UTRA FDD --- p.8 / Chapter 1.4.2 --- UTRA TDD --- p.18 / Chapter 1.4.3 --- Transport Channels --- p.25 / Chapter 2 --- Spreading Factor Optimization for FDD Downlink --- p.27 / Chapter 2.1 --- The Optimal Channel Splitting Problem --- p.28 / Chapter 2.2 --- Spreading Factor Optimization for FDD Downlink Dedicated Chan- nel --- p.30 / Chapter 3 --- Random Access Channel Stability Control --- p.33 / Chapter 3.1 --- Random Access Slotted Aloha --- p.33 / Chapter 3.1.1 --- System model --- p.33 / Chapter 3.1.2 --- Probability of Code-Collision --- p.34 / Chapter 3.1.3 --- Throughput Analysis of Random Access in TD/CDMA System --- p.37 / Chapter 3.1.4 --- Retransmission --- p.42 / Chapter 3.1.5 --- System Delay --- p.42 / Chapter 3.2 --- Random Access Channel Stability Control --- p.43 / Chapter 3.2.1 --- System Model --- p.43 / Chapter 3.2.2 --- Random Access Procedure --- p.44 / Chapter 3.3 --- Random Access Channel Stability Control Alogrithm --- p.47 / Chapter 3.3.1 --- Simulation --- p.49 / Chapter 3.4 --- Multi-class Model --- p.55 / Chapter 4 --- Conclusions and Topics for Future Study --- p.60 / Chapter 4.1 --- Thesis Conclusions --- p.60 / Chapter 4.2 --- Future Work --- p.61 / Chapter 4.2.1 --- Downlink and Uplink resource allocation in TDD --- p.61 / Chapter 4.2.2 --- Resource Unit Packing in TDD --- p.62 / Chapter 4.2.3 --- Other Topics --- p.62 / Bibliography --- p.63

This dissertation studies fundamental limits of modern digital communication systems in presence/absence of delay and secrecy constraints. In the first part of this dissertation, we consider a typical time-division wireless communication system wherein the channel strengths of the wireless users vary with time with a power constraint at the base station and which is not subject to any delay constraint. The objective is to allocate resources to the wireless users in an equitable manner so as to achieve a specific throughput. This problem has been looked at in different ways by previous researchers. We address this problem by developing a systematic way of designing scheduling schemes that can achieve any point on the boundary of the rate region. This allows us to map a desired throughput to a specific scheduling scheme which can then be used to service the wireless users. We then propose a simple scheme by which users can cooperate and then show that a cooperative scheduling scheme enlarges the achievable rate region. A simple iterative algorithm is proposed to find the resource allocation parameters and the scheduling scheme for the cooperative system. In the second part of the dissertation, a downlink time-division wireless sys- tem that is subject to a delay constraint is studied, and the rate region and optimal scheduling schemes are derived. The result of this study concludes that the achievable throughput of users decrease as the delay constraint is increased. Next, we consider a problem motivated by cognitive radio applications which has been proposed as a means to implement efficient reuse of the licensed spectrum. Previous research on this topic has focussed largely on obtaining fundamental limits on achievable throughput from a physical layer perspective. In this dissertation, we study the impact of im- posing Quality of Service constraints (QoS) on the achievable throughput of users. The result of this study gives insights on how the cognitive radio system needs to be operated in the low and high QoS constraint regime. Finally, the third part of this dissertation is motivated by the need for commu- nicating information not only reliably, but also in a secure manner. To this end, we study a source coding problem, wherein multiple sources needs to be communicated to a receiver with the stipulation that there is no direct channel from the transmitter to the receiver. However, there are many \agents" that can help carry the information from the transmitter to the receiver. Depending on the reliability that the transmit- ter has on each of the agents, information is securely encoded by the transmitter and given to the agents, which will be subsequently given to the receiver. We study the overhead that the transmitter has to incur for transmitting the information to the receiver with the desired level of secrecy. The rate region for this problem is found and simple achievable schemes are proposed. The main result is that, separate secure coding of sources is optimal for achieving the sum-rate point for the general case of the problem and the rate region for simple case of this problem.