No description available.

No description available.

The objective of this research is to develop a Markovian model in the form of a discrete-time queueing network to assess the performance of random access code division multiple access networks (CDMA). An approximation method called equilibrium point analysis (EPA) has been used to solve the model. The CDMA protocol IS an important application of spread spectrum communications that allows simultaneous transmission of multiple users to occupy a wideband channel with small interference. This is done by assigning each user a unique pseudo noise code sequence. These codes have low cross-correlation between each pair of sequences. Both slotted direct sequence CDMA (DS) and frequency hopping CDMA (FH) are considered with an emphasis on DS-CDMA systems. The EPA method has previously been used to evaluate the performance of other random access systems such as the ALOHA protocol, but has not previously been used in the context of a CDMA protocol. Throughput and mean packet delay of random access CDMA networks are evaluated, since these two measures are usually used in the study of the performance assessment of mUltiple access protocols. The analytical results of the random access model are validated against a discrete-event simulation which is run for large number of slots. The study then proceeds by using the model to examine the effect on performance of introducing error correcting codes to the DS-CDMA systems. Optimum error correcting codes that give the best performances in terms of the throughput and the delay are determined. The perfonnance of random access CDMA systems applied to radio channels, as in packet radio networks, is then studied, and the effect of multipath fading on the perfonnance is evaluated. Finally, the perfonnance of DS-CDMA with different user classes (non-identical users case) is investigated. An extended equilibrium point analysis (EEPA) method has been used to solve the Markovian model in this situation. This extended model is used to assess the effects on perfonnance of the unequal powers due to varying distances of the users to an intended receiver or to a base station (near-far problem).

No description available.

Several new multiuser detectors are developed for different direct-sequence codedivision multiple-access (DS-CDMA) application environments. The first detector is based on a semidefinite-programming (SDP) relaxation technique. In this detector, maximum likelihood (ML) detection is achieved by 'relaxing' the associated combinatorial problem into an SDP problem, which leads to a detector of polynomial complexity. It is shown that the SDP-relaxation (SDPR) based detector can be obtained by solving a dual SDP problem which leads to improved efficiency. Computer simulations demonstrate that the SDPR detector offers near-optimal performance with much reduced computational complexity compared with that of the ML detector proposed by Verdu for both synchronous and asynchronous DS-CDMA systems. The second detector is based on a recursive convex programming (RCP) approach. In this detector, ML detection is carried out in two steps: first, the combinatorial problem associated with ML detection is relaxed to a convex programming problem, and then a recursive approach is used to obtain an approximate solution for ML detection. Efficient unconstrained relaxation approach is proposed for the proposed detector to reduce the involved computational complexity. Computer simulations demonstrate that the proposed detectors offer near-optimal detection performance which is superior to that offered by many other suboptimal detectors including the SDPR detector. However, the computational complexity involved in the proposed detectors is much lower relative to that involved in Verdu's ML detector as well as our SDPR detector. The third detector entails a subspace estimation-based constrained optimization approach for channel estimation in DS-CDMA systems with multipath propagation channels. The proposed approach offers an improved approximation for the noise iii subspace compared with that offered by several existing algorithms. Computer simulations show that the performance of the proposed detector offers nearly the same performance as that of existing subspace detectors but leads to a significant reduction in the amount of computation. Relative to some existing constrained optimization methods, the proposed detector offers a significantly improved performance while requiring a comparable amount of computation. The fourth detector is proposed based on a vector constant-modulus (VCM) approach. This detector is designed for DS-CDMA systems with multipath propagation channels where the effective signatures observed at receiver are distorted by multipath propagation and aliasing concurrently. In this detector, detection is carried out by solving a linear constrained optimization problem whose objective function is formulated based on the VCM criterion. Two adaptation algorithms, namely, the constrained stochastic gradient algorithm and the recursive vector constant-modulus algorithm, are developed. Analysis are presented to investigate the performance of the proposed detector. Computer simulations show that the proposed detectors are able to suppress multiuser interference and inter-symbol interference effectively. More importantly, they offer robust detection performance against the effective signature distortion caused by aliasing at the receiver.

In this dissertation, direct-sequence code-division multiple access (DS-CDMA) systems with multiuser detectors used at receiver are investigated and two kinds of multiuser detectors are developed for DS-CDMA systems. In the investigation of DS-CDMA systems using multiuser detectors at receiver, a study on the performance of the system is presented, where heterogeneous traffic with different transmission rates and quality of service (QoS) requirements is supported. The effects of some realistic factors, such as imperfect power control and the existence of multiple cells, on the system performance are studied. In addition, algorithms are proposed to deal with the forward link power allocation problem based on the measurements of random characteristics of the received signals. This power allocation problem is formulated as a constrained optimization problem. To make the problem easy to solve, an additional appropriate constraint is proposed. Two methods are developed to identify the feasible region of this constrained optimization problem. The first proposed multiuser detector is an adaptive minimum mean-squared-error (MMSE) detector. Particularly, it is desirable for the cases where communication channels have severe near-far problem, and thus the convergence rates of adaptive MMSE detectors for users with different power are quite different. To improve the convergence rates of adaptive MMSE detectors for weak power users, the interference effects of the strong power user signals are subtracted from the received signal successively. The method to estimate the parameters required in the proposed detector is also developed. It is shown that the proposed detector achieves fast convergence rates in various near-far scenarios. Other studies conducted include the transient mean-squared-error (MSE) analysis to explain the different convergence rates of adaptive MMSE detectors for users with different power, and the bit-error-rate (BER) performance analysis for the proposed detector. The second proposed multiuser detector is a set of semi-blind linear parallel interference cancellation (PIC) detectors for the reverse link of multiple-cell systems, where only information about intra-cell users is available. To decrease the interference from inter-cell users whose information is unavailable to the receiver, the inter-cell user signal subspace is identified first by making use of the available information about intra-cell users. The eigenvectors and eigenvalues of this signal subspace are then used in the traditional linear PIC structure, in place of the unknown inter-cell users’ signature codes and signal amplitudes. Based on this idea, three detection schemes are proposed. In addition, an efficient adaptation implementation method is developed, and the performance of the proposed detectors is studied. The proposed detectors are shown to be suitable for practical implementations and have satisfactory performance. / Graduate

Au Québec, la Loi sur les services de santé et les services sociaux, Chapitre S-4.2, à son article 233, demande à ce que chacun des établissements de santé, dispose d’un code d’éthique qui essentiellement demande de préciser les droits des usagers et de fixer les conduites attendues du personnel. Le législateur souhaitait améliorer les conduites du personnel dès le début des années 1990 et envisageait désigner un organisme de surveillance pour s’en assurer. Cette contrainte ne fut pas retenue et 20 ans plus tard, la volonté d’assurer des conduites attendues n’est toujours pas assujettie de contraintes ou de contrôles même si elle est toujours souhaitée. En 2003 toutefois, le Ministre a mis en place un processus de visites ministérielles dans les milieux d’hébergement et à ce jour quelques 150 établissements ont été visités. Ces équipes se sont préoccupées entre autre de la fonction du code d’éthique pour soutenir les directions de ces établissements. Elles ne réussissent pas à pouvoir s’appuyer sur le code d’éthique pour qu’il soit l’assise pour baser les décisions cliniques, organisationnelles et de gestion de chacune des organisations du réseau de la santé et des services sociaux du Québec. Il faut à ce moment-ci faire le constat que le code d’éthique, obligatoire, figure au nombre des nombreuses contraintes rencontrées par les organisations. Les établissements doivent passer un processus d’agrément aux trois ans et le code d’éthique n’est pas davantage un élément dynamique retenu à ce processus de validation de normes de qualité. De plus, une revue québécoise spécialisée en gestion de la santé a consacré un numéro complet de 15 articles sur « éthique et comportements » et le code d’éthique y est absent sauf pour deux articles qui s’y attardent spécifiquement. Est-ce une question d’éthique dont il est question par ce code, ou si ce n’est pas davantage de la déontologie, d’autant que le législateur veut avant tout s’assurer de comportements adéquats de la part des employés et des autres personnes qui exercent leur profession. Est-ce qu’un code de conduite ne serait pas plus approprié pour atteindre les fins visées? Cette question est répondue dans ce mémoire qui regarde les concepts d’éthique, de déontologie, de codes, de régulation des comportements. De plus, des analyses détaillées de 35 codes d’éthique actuels de divers établissements et de diverses régions du Québec iv sont présentées. La littérature nous donne les conditions de réussite pour un code et outre l’importance à accorder aux valeurs énoncées dans l’organisation, il est également question des sanctions à prévoir au non-respect de ces valeurs. Elles se doivent d’être claires et appliquées. Enfin, beaucoup d’organisations parlent maintenant de code de conduite et ce terme serait tout à fait approprié pour rejoindre le souhait du législateur qui veut assurer des conduites irréprochables des employés et autres personnes qui y travaillent. C’est la conclusion de ce travail, énoncée sous forme de recommandation. / Quebec’s Health and Social Services Law, ch. S-4.2, art. 233, requires that every health institution have a code of ethics that, in essence, sets out the rights of patients and the manner in which staff are expected to conduct themselves. The legislator had hoped that improvements in the conduct of personnel would begin to be seen at the start of the 1990s, and wanted to set up a watchdog body to ensure that progress was made. In the end, no such body was created, and 20 years later, even though they are still very much wished for, constraints and controls over staff conduct remain sorely lacking. In 2003 the Minister of Health and Social Services began a series of official visits to hospitals which to date have covered 150 institutions, and in each of these visits the minister’s teams have, with the backing of the hospitals’ administrators, made a point of looking at how each institution’s code of ethics is working. The general consensus of administrators, however, is that no health institution in Quebec has been able to use the ethics code as a basis for making clinical, organizational or managerial decisions. On the contrary, having a mandatory ethics code is seen by many as a hindrance, one among many that the institutions have to deal with. Every three years each institution goes through a process of re-accreditation to ensure it complies with government standards of quality, but its ethics code is not considered an important and dynamic element in this re-evaluation. One example of this blind spot: When a Quebec periodical specializing in health-care management published a special issue on “ethics and behaviour,” only two of its 15 articles specifically mentioned the notion of a code of ethics. This raises the question: Is “ethics” too general a term? Given that the legislator’s goal is to ensure proper behaviour on the part of staff and others who exercise their profession in the institutions – in other words, a preoccupation with professional ethics – would it not be more appropriate to instead refer to a “code of conduct”? This question is addressed in this thesis, through an examination of the concepts of ethics, professional ethics, codes and regulation of behaviour. As well, a detailed analyses of 35 ethics codes in diverse institutions throughout Quebec is presented. The vi academic literature provides ways of measuring the success of a code of ethics, and besides the importance given to institutional values, there is also the question of sanctions to impose when those values are not respected. Values must be clear to be properly applied. Finally, many organizations now refer to “codes of conduct” – a highly appropriate term, given that the legislator’s goal is to ensure that the conduct of employees and other personnel in health establishments is beyond reproach. This, in fact, is my conclusion, spelled out in the form of a recommendation.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Les phénomènes physiques complexes peuvent être simulés numériquement par des techniques mathématiques. Ces simulations peuvent mener ainsi à la résolution de très grands systèmes. La parallélisation des codes de simulation numérique est alors une nécessité pour parvenir à faire ces simulations en des temps non-exorbitants. Le parallélisme s’est imposé au niveau des architectures de processeurs et les cartes graphiques sont maintenant utilisées pour des fins de calcul généraliste, aussi appelé "General-Purpose GPU", avec comme avantage évident l’excellent rapport performance/prix. Cette thèse se place dans le domaine de la conception de ces applications hautes-performances pour la simulation des machines électriques. Nous fournissons une méthodologie basée sur l’Ingénierie Dirigées par les Modèles (IDM) qui permet de modéliser une application et l’architecture sur laquelle l’exécuter, afin de générer un code OpenCL. Notre objectif est d’aider les spécialistes en algorithmes de simulations numériques à créer un code efficace qui tourne sur les architectures GPGPU. Pour cela, une chaine de compilation de modèles qui prend en compte plusieurs aspects du modèle de programmation OpenCL est fournie. De plus, nous fournissons des transformations de modèles qui regardent des niveaux d’optimisations basées sur les caractéristiques de l’architecture.Comme validation expérimentale, la méthodologie est appliquée à la création d’une application qui résout un système linéaire issu de la Méthode des Éléments Finis. Dans ce cas nous montrons, entre autres, la capacité de la méthodologie de passer à l’échelle par une simple modification de la multiplicité des unités GPU disponibles. / Complex physical phenomena can be numerically simulated by mathematical techniques. Usually, these techniques are based on discretization of partial differential equations that govern these phenomena. Hence, these simulations enable the solution of large-scale systems. The parallelization of algorithms of numerical simulation, i.e., their adaptation to parallel processing architectures, is an aim to reach in order to hinder exorbitant execution times. The parallelism has been imposed at the level of processor architectures and graphics cards are now used for purposes of general calculation, also known as "General- Purpose GPU". The clear benefit is the excellent performance/price ratio. This thesis addresses the design of high-performance applications for simulation of electrical machines. We provide a methodology based on Model Driven Engineering (MDE) to model an application and its execution architecture in order to generate OpenCL code. Our goal is to assist specialists in algorithms of numerical simulations to create a code that runs efficiently on GPGPU architectures. To ensure this, we offer a compilation model chain that takes into account several aspects of the OpenCL programming model. In addition, we provide model transformations that analyze some levels of optimizations based on the characteristics of the architecture. As an experimental validation, the methodology is applied to the creation of an application that solves a linear system resulting from the Finite Element Method (FEM). In this case, we show, among other things, the ability of the methodology of scaling by a simple modification of the number of available GPU devices.

This dissertation is focused on multi-service and direct sequence code division multiple access (DS/CDMA) wireless cellular systems. The reverse link performance of a slotted DS/CDMA cellular system with multi-service traffic is analyzed. Services with/without packet retransmission to meet their Quality of Service, share the entire bandwidth. Packet failure probabilities and packet delay are obtained based on analyzing the mutual interaction among services. The impacts of power level allocation and power control error of services on capacity, throughput and delay are analyzed under given Quality of Service. The system capacity is maximized by appropriate power allocation. The impact of power control error on capacity is dependent on whether packet retransmission is allowed or not. Admission control policies for multi-service systems are proposed and analyzed. Both nonprioritized and prioritized admission control are studied. Services difference in terms of resource requirement and degree of importance are considered. Analytical models are developed. Blocking probability of each type of calls are found under given amount of traffic. Fair access by soft capacity is addressed. The cost of protecting certain type(s) of calls on the rest of calls is investigated. The impact of traffic distribution on the performance of the policies is also examined. In a hierarchical cellular system, user mobility estimation helps channel assignment so as to reduce the handoff rate and avoid high mobility users travel among small cells. Two different strategies are compared. It is found that when high mobility users are served by overlay macrocells, call drop rate is reduced. Speed estimation error only has limited impact on the system performance. User membership in a cellular CDMA network is simulated based on the estimation of the local mean value of the pilot signal from surrounding base stations. The base station providing strongest pilot local mean controls the mobile station. Simulation is conducted under different fading environments. Two performance measurements are simulated: the number of membership switchings per second and the probability of wrong base station selection. An optimum window length for filtering out Rayleigh fading is found. Simulation results are in good fit with those of analysis. / Graduate