Afin de répondre au besoin de capacité dans les réseaux sans fil, les techniques de transmission, et les modèles pour les étudier, ont évolués rapidement. Des communications point à point avec une seule antenne nous sommes passé aux réseaux cellulaires de nos jours: de multiples cellules et de multiples antennes. Progressivement, plusieurs hypothèses ont été faites, soit afin d'avoir des modèles réalistes, mais aussi parfois pour permettre une analyse plus simple. Nous analysons l'impact de trois aspects des réseaux réels. Nous nous concentrons sur le délai dans l'acquisition des coefficients des canaux par l'émetteur puisque sa prise en compte détériore grandement le gain de multiplexage du canal si rien n'est fait pour utiliser efficacement le temps mort au cours duquel les émetteurs ne transmettent pas et n'ont pas encore la connaissance du canal. Nous proposons des schémas de transmission pour utiliser efficacement ce temps mort afin d'améliorer le gain de multiplexage. Dans les réseaux multi-cellulaires, un schéma de transmission optimal est proposé et permet de n'avoir aucune perte de gain de multiplexage même en cas de retard important dans la connaissance de canal. Concernant le nombre d'utilisateurs, nous proposons un nouveau critère pour la sélection des utilisateurs de les configurations à une seule cellule afin de bénéficier de la diversité multi-utilisateurs, et nous proposons deux schémas d'alignement d'interférence pour systèmes multicellulaires afin de bénéficier du fait qu'il y a généralement plusieurs utilisateurs dans chaque cellule. Des schémas bénéficiant de la connectivité partielle pour augmenter le gain de multiplexage sont également proposés. / In order to meet ever-growing needs for capacity in wireless networks, transmission techniques and the system models used to study their performances have rapidly evolved. From single-user single-antenna point-to-point communications to modern multi-cell multi-antenna networks there have been large advances in technology. Along the way, several assumptions are made in order to have either more realistic models, but also to allow simpler analysis. We analyze three aspects of actual networks and try to benefit from them when possible or conversely, to mitigate their negative impact. We focus on the delay in the CSI acquisition. Precisely, when taken into account, this delay greatly impairs the channel multiplexing gain if nothing is done to use the dead time during which the transmitters are not transmitting and do not yet have the CSI. We review and propose different schemes to efficiently use this dead time to improve the multiplexing gain in both the BC and the interference channel (IC). We evaluate the more relevant net multiplexing gain, taking intoaccount the training and feedback overhead. Results are surprising because potential schemes to fight delay reveal to be burdened byimpractical overheads in the BC. In the IC, an optimal scheme is proposed. It allows avoiding any loss of multiplexing gain even forsignificant delay in the CSI acquisition. Concerning the number of users, we propose a new criterion for the greedy user selection in a BC to benefit of the multi-user diversity, and two interference alignment schemes for the IC to benefit of having multiple users in each cell. Finally, partially connected cellular networks are considered and schemes to benefit from said partial connectivity to increase the multiplexing gain are proposed.

In this thesis I address the fundamental question that how the information gain is possible in the realm of quantum mechanics where a single measurement alters the state of the system. I study an ensemble of particles in some unknown (but product) state in detail and suggest an optimal way of gaining the maximum information and also quantify the corresponding information exactly. We find a rather novel result which is quite different from other well-known definitions of the information gain in quantum theory.

Sensorless control of the synchronous reluctance motor has been a topic of research for more than a decade, producing several successful methods to accomplish this goal. However, a technique that has been overlooked is the full-order nonlinear observer, which is essentially a software model of the motor driven by measurements from the actual motor. Presented in this thesis is the design, implementation, and experimental testing of a full-order observer-based sensorless control technique which requires only the phase current and voltage measurements that are typically available in standard three-phase inverters. A technique is also presented for calculating a table of observer feedback gains parameterized only by the steady-state motor speed. This allows a gain-scheduling observer to be implemented which, as shown using experiments, improves the transient response of the observer over a wide speed range. The sensorless controller consists of a full-order nonlinear observer coupled with an input-output linearization speed controller. The resulting controller was implemented in Simulink and executed on a dSPACE DS1103 real-time DSP board using the Real-Time Workshop extension to Simulink. A custom built three-phase IGBT inverter was used to interface the DSP to a 100 watt synchronous reluctance motor for laboratory testing. The resulting sensorless controller was able to successfully track a varying speed reference from 150 rpm to 1800 rpm with a tracking error under 5% for most of the speed range. At the lowest speeds, the tracking error begins to increase but the observer remains stable down to 150 rpm.

In this paper, we investigate the optimal design of optically gain-clamped (GC) erbium-doped fiber amplifier (EDFA). Three configurations under discussion, the first uses two optical circulators (OC), one optical band pass filter (OBPF), and one variable optical attenuator (VOA), to form ring cavity. Such ring cavity can regulate itself: when the channel numbers increase, the amounts of optical feedback decrease; contrarily, when the channel numbers decrease, the amounts of optical feedback increase. So it has the gain-clamped ability. The second employs one or double fiber Bragg grating (FBG) to reflect the residual Amplified Spontaneous Emission (ASE) for regulating the signal gain, such configurations have the same self-regulation as before. The choice of center wavelength and bandwidth of FBG can control the signal gain to reach the optimal gain and fairly low noise figure (NF). The third configuration is similar to the first; the difference is that the third with figure-8 cavity, which uses a common OBPF and VOA, can regulate the gain of C- and L-bands at the same time. The choice of OBPF is just located within the dead-zone between the C- and L-bands, where no WDM channels can be transmitted. If we choose suitable loop attenuation, we can get an equal signal gain of C- and L-bands¡¦ channels.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references (p.97-107).

In this thesis I address the fundamental question that how the information gain is possible in the realm of quantum mechanics where a single measurement alters the state of the system. I study an ensemble of particles in some unknown (but product) state in detail and suggest an optimal way of gaining the maximum information and also quantify the corresponding information exactly. We find a rather novel result which is quite different from other well-known definitions of the information gain in quantum theory.

One critical component of the communication receiver of front-end system is the low-noise amplifier (LNA). For good sensitivity and dynamic range, the LNA should provide a low noise figure and maximum attainable power gain. Another concern is the linearity of the LNA. Strong signals produce intermodulation products in a frequency band close to the operating frequency that might affect the performance of the receiver. In many cases, the intermodulation products can be reduced by increasing the current through the active device. Hence, a trade-off between power consumption and linearity must be considered when designing the LNA. The thesis includes the bias network design, stability analysis, matching network design and layout design of the LNA RF module with layout simulation. The simulation has been performed using Advanced Design System (ADS) simulation software. After implementation of LNA on a PCB, the LNA is measured with the help of the power supply unit and vector network analyzer. The proposed design aim is to provide a low noise figure (NF) and high gain while maintaining the low power consumption.

Thesis (M.S.)--Virginia Polytechnic Institute, 1957. / Vita. Abstract. Includes bibliographical references (leaves 114-117). Also available via the Internet.

Overweight and obesity have significant health and economic consequences for people living in the UK. The psychological factors involved in the development of overweight and obesity are very important and can make a significant contribution to the development of interventions that inform public health policy and services. The current thesis employed three studies to examine the psychological factors that may predict overweight and obesity and contribute to the development of interventions that help to promote long-term weight loss maintenance, which have implications for improving health outcomes and reducing the economic burden. Study One (N=60) employed a 5-day diary to examine overweight and obese individuals' perceived reasons for eating (particularly in relation to unhealthy snacking). Study Two (N=30) was a follow-up to Study One and examined the factors that may predict long-term weight change. Finally, Study Three (N=60) employed an exploratory randomised controlled trial to examine the efficacy of a combined mindfulness plus implementation intentions intervention for promoting physical activity. The results of Study One provided evidence for the existence of reasons for eating unhealthy snacks other than hunger and highlighted the importance of addressing these factors within weight management interventions. Study Two did not conclusively demonstrate that psychological reasons for eating were long-term predictors of weight change, suggesting future research is needed to obtain further information on this complicated issue. This will help to determine whether reasons for eating can indeed predict weight change. The combined intervention in Study Three failed to promote physical activity, but highlighted a number of interesting factors such as task difficulty, unsupportive environments and insufficient motivation that need to be addressed in future research. Ensuring the population maintain a healthy weight and improving long-term health outcomes is very important, and therefore needs to be addressed at multiple levels in order to inform effective public health policy and services.

In this thesis I address the fundamental question that how the information gain is possible in the realm of quantum mechanics where a single measurement alters the state of the system. I study an ensemble of particles in some unknown (but product) state in detail and suggest an optimal way of gaining the maximum information and also quantify the corresponding information exactly. We find a rather novel result which is quite different from other well-known definitions of the information gain in quantum theory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate