Please read the abstract in the section 00front of this document / Dissertation (M Eng (Electronic Engineering))--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / unrestricted

The Internet of Things (IoT) industry has been thriving for the past few years, especially in the household field. The proposal of smart homes has enabled a increasing number of IoT products to enter people’s daily lives. However, the access control in smart homes has gradually grown up to be a prominent problem. Traditional access control mechanisms consider one unique trusted user that controls all access to the devices. However, multiuser and multi-device smart home scenarios pose fundamentally different challenges to the traditional single-user systems. Multiple trusted users are expected to manage the whole smart home system. Furthermore, the access control system of smart homes needs to consider the complexity of user relationships, the convenience of user experience, and the flexibility of access control. So the basic question this project is intended to answer can be concluded as: how to design an access control system based on the user-desired access control mechanism in the context of multiple users and multiple devices? This project first investigates both technical background and user study researches, summarizing current issues. Then, to study user perceptions of current access control systems, this project carries out semi-structured interviews, identifying user needs in access control systems. Finally, a fine-grained prototype satisfying user needs is offered. It consists of three modules, namely the user interaction module, the backend module and the manager module. Permissions are assigned through the user interaction module, translated into access control policies at the backend module and enforced by the manager module. The proposed prototype is then implemented in a simulated smart home environment and evaluated on its feasibility to identified requirements. / Internet of Things (IoT) industrin har blomstrat de senaste åren, särskilt inom hushållsområdet. Förslaget om smarta hem har gjort det möjligt för ett ökande antal IoT produkter att komma in i människors vardag. Tillgångskontrollen i smarta hem har dock gradvis vuxit till att bli ett framstående problem. Traditionella åtkomstkontrollmekanismer överväger en unik betrodd användare som styr all åtkomst till enheterna. Men smarta hemscenarier för flera användare och flera enheter utgör emellertid fundamentalt olika utmaningar för de traditionella enanvändarsystemen. Flera betrodda användare förväntas hantera hela systemet för smarta hem. Dessutom måste system för åtkomstkontroll i smarta hänsyn beakta komplexiteten i användarrelationer, användarupplevelsens bekvämlighet och flexibiliteten i åtkomstkontroll. Så den grundläggande frågan som detta projekt är tänkt att besvara kan slutas som: hur man utformar ett åtkomstkontrollsystem baserat på den användarönskade åtkomstkontrollmekanismen i flera användare och flera enheter? Detta projekt undersöker först både teknisk bakgrund och användarstudier, som sammanfattar aktuella frågor. För att studera användaruppfattningar om nuvarande åtkomstkontrollsystem genomför detta projekt halvstrukturerade intervjuer som identifierar användarens behov i åtkomstkontrollsystem. Slutligen erbjuds en finkornig prototyp som uppfyller användarens behov. Den består av tre moduler, nämligen användarinteraktionsmodulen, backendmodulen och chefsmodulen. Behörigheter tilldelas via användarinteraktionsmodulen, översätts till åtkomstkontrollpolicyer på backend-modulen och tillämpas av chefsmodulen. Den föreslagna prototypen implementeras sedan i en simulerad smart hemmiljö och utvärderas om det är genomförbart för identifierade krav.

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This thesis describes the use of a multi-amplitude minimum shift keying (MAMSK) signal in various types of wireless communication system. A MAMSK signal is a bandwidth efficient modulation scheme obtained by superimposing ℳ minimum shift keying (MSK) signals with unequal amplitudes. The overall phase of a MAMSK signal is controlled by the phase of the largest component MSK signal which allows the use of a low-complexity differential detector. A closed form expression for the average bit error rate (BER) for coherent detection of an MAMSK in AWGN is derived and is shown to achieve the same BER as that of square constellation quadrature amplitude modulation (QAM) with the same average transmit power. We describe the design and implementation of a STBC-based MIMO radio system in conjunction with MAMSK modulation. The proposed system provides high capacity data transmission by carrying information not only in the phases but also in the amplitude. Despite using a simple MAMSK differential receiver the system achieves performance within 1 dB of coherent detection. The existing MSK modems in conjunction with STBC could easily be modified to construct the proposed system. The MAMSK modulation scheme is extended to a multiuser relaying network where two nodes cooperate in a half-duplex environment to achieve diversity gain. The cooperative scheme is based on superposition modulation using a decode-and-forward (DF) strategy. In the proposed scheme, each node simultaneously transmits its own and the relayed signals by superimposing one on the other. A MAMSK signal is an excellent choice for this type of cooperative communication due its being obtained by a superposition technique. The proposed system exploits the overall phase of a MAMSK signal which allows differential detection and as a result it provides the lowest decoding complexity and memory requirements among the existing superposition based cooperation schemes. The performance of the system is evaluated by simulation, where it is shown that the MAMSK cooperative system outperforms a conventional DF scheme in terms of both power and bandwidth efficiency.

The main topic of this thesis is integer quadratic programming with applications to problems arising in the areas of automatic control and communication. One of the most widespread modern control methods is Model Predictive Control (MPC). In each sampling time, MPC requires the solution of a Quadratic Programming (QP) problem. To be able to use MPC for large systems, and at high sampling rates, optimization routines tailored for MPC are used. In recent years, the range of application of MPC has been extended to so-called hybrid systems. Hybrid systems are systems where continuous dynamics interact with logic. When this extension is made, binary variables are introduced in the problem. As a consequence, the QP problem has to be replaced by a far more challenging Mixed Integer Quadratic Programming (MIQP) problem, which is known to have a computational complexity which grows exponentially in the number of binary optimization variables. In modern communication systems, multiple users share a so-called multi-access channel. To estimate the information originally sent, a maximum likelihood problem involving binary variables can be solved. The process of simultaneously estimating the information sent by multiple users is called Multiuser Detection (MUD). In this thesis, the problem to efficiently solve MIQP problems originating from MPC and MUD is addressed. Four different algorithms are presented. First, a polynomial complexity preprocessing algorithm for binary quadratic programming problems is presented. By using the algorithm, some, or all, binary variables can be computed efficiently already in the preprocessing phase. In numerical experiments, the algorithm is applied to unconstrained MPC problems with a mixture of real valued and binary valued control signals, and the result shows that the performance gain can be significant compared to solving the problem using branch and bound. The preprocessing algorithm has also been applied to the MUD problem, where simulations have shown that the bit error rate can be significantly reduced compared to using common suboptimal algorithms. Second, an MIQP algorithm tailored for MPC is presented. The algorithm uses a branch and bound method where the relaxed node problems are solved by a dual active set QP algorithm. In this QP algorithm, the KKT systems are solved using Riccati recursions in order to decrease the computational complexity. Simulation results show that both the proposed QP solver and MIQP solver have lower computational complexity compared to corresponding generic solvers. Third, the dual active set QP algorithm is enhanced using ideas from gradient projection methods. The performance of this enhanced algorithm is shown to be comparable with the existing commercial state-of-the-art QP solver \cplex for some random linear MPC problems. Fourth, an algorithm for efficient computation of the search directions in an SDP solver for a proposed alternative SDP relaxation applicable to MPC problems with binary control signals is presented. The SDP relaxation considered has the potential to give a tighter lower bound on the optimal objective function value compared to the QP relaxation that is traditionally used in branch and bound for these problems, and its computational performance is better than the ordinary SDP relaxation for the problem. Furthermore, the tightness of the different relaxations is investigated both theoretically and in numerical experiments. / This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the Linköping University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this material, you agree to all provisions of the copyright laws protecting it.

[pt] Esta tese apresenta novas estruturas e algoritmos adaptativos para detecção às cegas de sinais DS-CDMA. São investigados receptores cegos com restrições lineares baseados nas funções custo de mínima variância (CMV) e módulo constante (CCM). Algoritmos adaptativos do tipo Affine-Projection para estimação dos parâmetros do receptor são desenvolvidos e seu desempenho em estado estacionário é analisado. Também são apresentados algoritmos adaptativos para estimação às cegas do canal de comunicações. Em seguida, novas estruturas de canceladores de interferência são propostas. Primeiramente um cancelador de interferência paralelo (PIC) linear baseado na função custo CCM é proposto. Em seguida é desenvolvido um novo esquema não-supervisionado de cancelamento sucessivo de interferência (SIC), baseado no conceito de arbitragem paralela. Por fim, é apresentado um esquema híbrido (HIC) que combina a estrutura SIC com uma estrutura multi- estágio, resultando em melhores estimativas para detecção e desempenho uniforme para os usuários do sistema. / [en] This thesis presents new structures and adaptive algorithms for blind detection of DS-CDMA signals. Linearly constrained minimum variance (CMV) and constant modulus (CCM) receivers are investigated. Blind adaptive Affine- Projection like algorithms for receiver parameter estimation are derived and its steady-state performance is analyzed. Blind adaptive channel estimation algorithms are also presented. This work also proposes new interference cancellation structures. Firstly, a blind linear parallel interference canceller (PIC) based on the CCM cost function is proposed. Secondly, a new non-supervised serial interference canceller (SIC) based on the parallel arbitration concept is developed. Finally, an hybrid interference cancellation scheme (HIC) which combines SIC and multiple PIC stages is presented.

Os problemas de separação cega de fontes e desconvolução cega multiusuário vêm sendo intensamente estudados nas últimas décadas, principalmente devido às inúmeras possibilidades de aplicações práticas. A desconvolução multiusuário pode ser compreendida como um problema particular de separação de fontes em que o sistema misturador é convolutivo, e as estatísticas das fontes, que possuem alfabeto finito, são bem conhecidas. Dentre os desafios atuais nessa área, cabe destacar que a obtenção de soluções adaptativas para o problema de separação cega de fontes com misturas convolutivas não é trivial, pois envolve ferramentas matemáticas avançadas e uma compreensão aprofundada das técnicas estatísticas a serem utilizadas. No caso em que não se conhece o tipo de mistura ou as estatísticas das fontes, o problema é ainda mais desafiador. Na área de Processamento Estatístico de Sinais, soluções vêm sendo propostas para resolver casos específicos. A obtenção de algoritmos adaptativos eficientes e numericamente robustos para realizar separação cega de fontes, tanto envolvendo misturas instantâneas quanto convolutivas, ainda é um desafio. Por sua vez, a desconvolução cega de canais de comunicação vem sendo estudada desde os anos 1960 e 1970. A partir de então, várias soluções adaptativas eficientes foram propostas nessa área. O bom entendimento dessas soluções pode sugerir um caminho para a compreensão aprofundada das soluções existentes para o problema mais amplo de separação cega de fontes e para a obtenção de algoritmos eficientes nesse contexto. Sendo assim, neste trabalho (i) revisitam-se a formulação dos problemas de separação cega de fontes e desconvolução cega multiusuário, bem como as relações existentes entre esses problemas, (ii) abordam-se as soluções existentes para a desconvolução cega multiusuário, verificando-se suas limitações e propondo-se modificações, resultando na obtenção de algoritmos com boa capacidade de separação e robustez numérica, e (iii) relacionam-se os critérios de desconvolução cega multiusuário baseados em curtose com os critérios de separação cega de fontes. / Blind source separation and blind deconvolution of multiuser systems have been intensively studied over the last decades, mainly due to the countless possibilities of practical applications. Blind deconvolution in the multiuser case can be understood as a particular case of blind source separation in which the mixing system is convolutive, and the sources, which exhibit a finite alphabet, have well known statistics. Among the current challenges in this area, it is worth noting that obtaining adaptive solutions for the blind source separation problem with convolutive mixtures is not trivial, as it requires advanced mathematical tools and a thorough comprehension of the statistical techniques to be used. When the kind of mixture or source statistics are unknown, the problem is even more challenging. In the field of statistical signal processing, solutions aimed at specific cases have been proposed. The development of efficient and numerically robust adaptive algorithms in blind source separation, for either instantaneous or convolutive mixtures, remains an open challenge. On the other hand, blind deconvolution of communication channels has been studied since the 1960s and 1970s. Since then, various types of efficient adaptive solutions have been proposed in this field. The proper understanding of these solutions can suggest a path to further understand the existing solutions for the broader problem of blind source separation and to obtain efficient algorithms in this context. Consequently, in this work we (i) revisit the problem formulation of blind source separation and blind deconvolution of multiuser systems, and the existing relations between these problems, (ii) address the existing solutions for blind deconvolution in the multiuser case, verifying their limitations and proposing modifications, resulting in the development of algorithms with proper separation performance and numeric robustness, and (iii) relate the kurtosis based criteria of blind multiuser deconvolution and blind source separation.

Os problemas de separação cega de fontes e desconvolução cega multiusuário vêm sendo intensamente estudados nas últimas décadas, principalmente devido às inúmeras possibilidades de aplicações práticas. A desconvolução multiusuário pode ser compreendida como um problema particular de separação de fontes em que o sistema misturador é convolutivo, e as estatísticas das fontes, que possuem alfabeto finito, são bem conhecidas. Dentre os desafios atuais nessa área, cabe destacar que a obtenção de soluções adaptativas para o problema de separação cega de fontes com misturas convolutivas não é trivial, pois envolve ferramentas matemáticas avançadas e uma compreensão aprofundada das técnicas estatísticas a serem utilizadas. No caso em que não se conhece o tipo de mistura ou as estatísticas das fontes, o problema é ainda mais desafiador. Na área de Processamento Estatístico de Sinais, soluções vêm sendo propostas para resolver casos específicos. A obtenção de algoritmos adaptativos eficientes e numericamente robustos para realizar separação cega de fontes, tanto envolvendo misturas instantâneas quanto convolutivas, ainda é um desafio. Por sua vez, a desconvolução cega de canais de comunicação vem sendo estudada desde os anos 1960 e 1970. A partir de então, várias soluções adaptativas eficientes foram propostas nessa área. O bom entendimento dessas soluções pode sugerir um caminho para a compreensão aprofundada das soluções existentes para o problema mais amplo de separação cega de fontes e para a obtenção de algoritmos eficientes nesse contexto. Sendo assim, neste trabalho (i) revisitam-se a formulação dos problemas de separação cega de fontes e desconvolução cega multiusuário, bem como as relações existentes entre esses problemas, (ii) abordam-se as soluções existentes para a desconvolução cega multiusuário, verificando-se suas limitações e propondo-se modificações, resultando na obtenção de algoritmos com boa capacidade de separação e robustez numérica, e (iii) relacionam-se os critérios de desconvolução cega multiusuário baseados em curtose com os critérios de separação cega de fontes. / Blind source separation and blind deconvolution of multiuser systems have been intensively studied over the last decades, mainly due to the countless possibilities of practical applications. Blind deconvolution in the multiuser case can be understood as a particular case of blind source separation in which the mixing system is convolutive, and the sources, which exhibit a finite alphabet, have well known statistics. Among the current challenges in this area, it is worth noting that obtaining adaptive solutions for the blind source separation problem with convolutive mixtures is not trivial, as it requires advanced mathematical tools and a thorough comprehension of the statistical techniques to be used. When the kind of mixture or source statistics are unknown, the problem is even more challenging. In the field of statistical signal processing, solutions aimed at specific cases have been proposed. The development of efficient and numerically robust adaptive algorithms in blind source separation, for either instantaneous or convolutive mixtures, remains an open challenge. On the other hand, blind deconvolution of communication channels has been studied since the 1960s and 1970s. Since then, various types of efficient adaptive solutions have been proposed in this field. The proper understanding of these solutions can suggest a path to further understand the existing solutions for the broader problem of blind source separation and to obtain efficient algorithms in this context. Consequently, in this work we (i) revisit the problem formulation of blind source separation and blind deconvolution of multiuser systems, and the existing relations between these problems, (ii) address the existing solutions for blind deconvolution in the multiuser case, verifying their limitations and proposing modifications, resulting in the development of algorithms with proper separation performance and numeric robustness, and (iii) relate the kurtosis based criteria of blind multiuser deconvolution and blind source separation.

Facility pode ser compreendida como um conjunto de serviços e valores que auxilia e torna mais fácil alguma ação. Para que o serviço entregue pela facility cumpra os seus objetivos de qualidade, otimização de tempo e de espaço, assim como redução de custo, é necessário que ela seja bem gerida. O crescimento dessas facilities no meio acadêmico tem aumentado vertiginosamente, permitindo que o acesso a determinados equipamentos e informações seja ampliado. É o caso do Centro Avançado em Diagnóstico por Imagem (CADI), uma plataforma da Faculdade de Medicina Veterinária e Zootecnia (FMVZ) da USP que conta com diversos equipamentos de imagem sofisticados e que estão agrupados em diferentes locais da FMVZ. Dentre esses equipamentos, podem ser citados os microscópios, que estão presentes no prédio da Anatomia (chamado de Facility FMVZ/USP). Nesse contexto, o trabalho objetivou-se a fazer uma análise de funcionamento do CADI com o intuito de avaliar a gestão de atendimento . Para cumprir esse objetivo, foi aplicada uma pesquisa de opinião para os usuários da Facility, contendo14 perguntas que englobavam o perfil do usuário, os equipamentos mais utilizados e frequência de uso, a funcionalidade do agendamento e a importância da Central na pesquisa. Ao todo, 42 usuários responderam a pesquisa, mostrando que a maioria dos usuários era da pós-graduação da própria FMVZ; que já tinha utilizado o laboratório dez ou mais vezes; que o agendamento para utilização da Central se da de forma rápida e clara; e que a existência do laboratório é essencial para suas pesquisas. Além dos usuários saberem a importância da Facility nas suas pesquisas, muitos resultados positivos foram gerados na Central, tais como artigos científicos, projetos acadêmicos e atendimento a grupos de pesquisa, contribuindo para o maior desenvolvimento da Universidade. / Facility can be understood as a set of services and values that assists and makes some action easier. In order for the service delivered by the facility to meet its objectives of quality, time and space optimization, as well as cost reduction, it must be well managed. The growth of these facilities in academia has skyrocketed, allowing access to certain equipment and information to be expanded. This is the case of the Advanced Center for Diagnostic Imaging (CADI), a platform of the Faculty of Veterinary Medicine and Animal Science (FMVZ) of USP that has several sophisticated imaging equipment and are grouped in different FMVZ locations. Among these equipment, microscopes can be mentioned, which are present in the building of Anatomy (called Facility FMVZ / USP). In this context, the objective was to perform an analysis of the functioning of CADI in order to evaluate the management of care. To fulfill this objective, an opinion survey was applied to Facility users, containing 14 questions that included the user profile, the most frequently used equipment and frequency of use, the scheduling functionality and the importance of the Central in the research. Altogether, 42 users answered the survey, showing that the majority of users were FMVZ\'s graduate students; who had already used the laboratory ten or more times; that the scheduling for use of the Central is given quickly and clearly; and that the existence of the laboratory is essential for their research. In addition to the users knowing the importance of the Facility in their research, many positive results were generated in the Central, such as scientific articles, academic projects and attendance to research groups, contributing to the greater development of the University.