Embedded computing systems in portable devices need to be energy efficient, yet they have to deliver adequate performance to the often computationally expensive applications. Dynamic voltage scaling is a technique that offers a speed versus power trade-off, allowing the application to achieve considerable energy savings and, at the same time, to meet the imposed time constraints. In this thesis, we explore the possibility of using optimal voltage scaling algorithms based on nonlinear programming at the system level, for a complex multiprocessor scheduling problem. We present an optimization approach to the modeled nonlinear programming formulation of the continuous voltage selection problem excluding the consideration of transition overheads. Our approach achieves the same optimal results as the previous work using the same model, but due to its speed, can be efficiently used for design space exploration. We validate our results using numerous automatically generated benchmarks.

Referências de tensão integradas sempre foram um bloco fundamental de qualquer sistema eletrônico e um importante tópico de pesquisa que tem sido estudado extensivamente nos últimos 50 anos. Uma tensão de referência é um circuito que provê uma tensão estável com baixa sensibilidade a variações em temperatura, alimentação, carga, características do processo de fabricação e tensões mecânicas de encapsulamento. Elas são normalmente implementadas através da soma ponderada de dois fenômenos físicos diferentes, com comportamentos em temperatura opostos. Normalmente, a tensão térmica, relacionada à constante de Boltzmann e à carga do elétron, fornece uma dependência positiva com temperatura, enquanto que a tensão base-emissor VBE de um transistor bipolar ou a tensão de limiar de um MOSFET fornece o termo complementar. Um bloco auxiliar é às vezes utilizado para fornecer as correntes de polarização do circuito, e outros blocos adicionais implementam a soma ponderada. A evolução da tecnologia de processos é o principal fator para aplicações em baixa tensão, enquanto que a emergência de dispositivos portáteis operados a bateria, circuitos biomédicos implantáveis e dispostivos de captura de energia do ambiente restringem cada circuito a consumir o mínimo possivel. Portanto, alimentações abaixo de 1 V e consumos na ordem de nanoWatts se tornaram características fundamentais de tais circuitos. Contudo, existem diversos desafios ao projetar referências de tensão de alta exatidão em processos CMOS modernos sob essas condições. As topologias tradicionais não são adequadas pois elas provêm uma referência de tensão acima de 1 V, e requerem resistências da ordem de G para atingir tão baixo consumo de potência, ocupando assim uma grande área de silício. Avanços recentes atingiram tais níveis de consumo de potência, porém com limitada exatidão, custosos procedimentos de calibração e grande área ocupada em silício. Nesta dissertação apresentam-se duas novas topologias de circuitos: uma tensão de junção bipolar com compensação de curvatura que não utiliza resistores e é auto-polarizada; e um circuito de referência bandgap sem resistores que opera abaixo de 1 V (também chamado de sub-bandgap). Ambos circuitos operam com consumo na ordem de nanoWatts e ocupam pequenas áreas de silício. Resultados de simulação para dois processos diferentes, 180 nm e 130 nm, e resultados experimentais de uma rodada de fabricação em 130 nm apresentam melhorias sobre tais limitações, mantendo as características desejadas de não conter resistores, ultra baixo consumo, baixa tensão de alimentação e áreas muito pequenas. / Integrated voltage references have always been a fundamental block of any electronic system, and an important research topic that has been extensively studied in the past 50 years. A voltage reference is a circuit that provides a stable voltage with low sensitivity to variations in temperature, supply, load, process characteristics and packaging stresses. They are usually implemented through the weighted sum of two independent physical phenomena with opposite temperature dependencies. Usually the thermal voltage, related to the Boltzmann’s constant and the electron charge, provides a positive temperature dependence, while the silicon bandgap voltage or a MOSFET’s threshold voltage provide the complementary term. An auxiliary biasing block is sometimes necessary to provide the necessary currents for the circuit to work, and additional blocks implement the weighted sum. The scaling of process technologies is the main driving factor for low voltage operation, while the emergence of portable battery-operated, implantable biomedical and energy harvesting devices mandate that every circuit consume as little power as possible. Therefore, sub-1 V supplies and nanoWatt power have become key characteristics for these kind of circuits, but there are several challenges when designing high accuracy voltage references in modern CMOS technologies under these conditions. The traditional topologies are not suitable because they provide a reference voltage above 1 V, and to achieve such power consumption levels would require G resistances, that occupy a huge silicon area. Recent advances have achieved these levels of power consumption but with limited accuracy, expensive calibration procedures and large silicon area.

Orientador: Fabiano Fruett / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-06T06:47:54Z (GMT). No. of bitstreams: 1 Garcia_Vitor_M.pdf: 2431852 bytes, checksum: 99df32075176f9b0322278b0ce286ba5 (MD5) Previous issue date: 2006 / Resumo: Apresentamos neste trabalho um sensor de pressão de baixo consumo de potência. totalmente compatível com o processo de fabricação CMOS. constituído por um amplificador operacional sensível ao estresse mecânico fabricado sobre uma membrana. O desenho do layout do amplificador é feito de forma a maximizar o efeito do estresse sobre os transistores do par de entrada e minimizar sobre o restante do circuito. O projeto da membrana. bem como a localização dos elementos sensores sobre a mesma. Foram determinados através de simulação por elementos finitos. O sensor foi fabricado utilizando o processo CMOS 0.35 IJ.m AMS disponibilizado pelo Projeto Multi-Usuário (PMU) Fapesp. A membrana do sensor foi obtida através de um processo de desbaste mecânico da pastilha de silício onde o circuito foi fabricado. Analisamos também a dependência da tensão de limiar e da mobilidade de um transistor PMOS com relação ao estresse mecânico. O sensor fabricado apresentou um consumo de potência da ordem de 3 IJ. W e uma sensibilidade de 8.9 mV/psi / Abstract: A nove I Iow power totally CMOS compatible mechanical-stress sensitive differential amplifier. which can be used as a pressure sensor. is presented. This amplifier is based on a special designed layout where the stress sensitivity of the input differential pair. is maximized and the stress effects on the second stage are minimized. Finite element simulation was used to design the membrane and to locate the element sensor on it. The sensor was fabricated in a CMOS 0.35 IJ.m AMS process supported by the Fapesp Multi -User Project. In order to make a pressure sensor without a backside bulk micro-machining process. the thickness of the die was reduced by a mechanical polishing process. This work also analised the limiar-voltage and the mobility dependence with regard to mechanical stress. The sensor power consumption amounts to 3 IJ. W and the sensitivity amounts to 8.9 m V/psi / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Made available in DSpace on 2015-09-25T12:18:22Z (GMT). No. of bitstreams: 1 THIAGO MACIEL CAVALCANTI.pdf: 1062270 bytes, checksum: 27c54a41e663f3e10d627bb93d161d7f (MD5) Previous issue date: 2011-07-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The increased resistance of bacteria to antibiotic drugs creats the need to develop new bacteriostatics ways and bactericidals to cooperate with the treatment of infected individuals. Among those tools are the complementary and alternative therapies involving laser therapy and photodynamic therapy. Lasers are being used isolated or associated with photosensitizing substances to work as helpers in the inactivation of bacterias, fungis and viruses. Photodynamic therapy (PDT) based on the activation of photosensitizers for visible light in low doses, with appropriate wavelength, has become an alternative to conventional treatments in the fight against oral micro-organisms, leading to death the organism by disorders in cell wall and DNA. IN VITRO study two therapies were used, Photodynamic therapy (PDT) and Low-Level Laser (LBP). For PDT we used the dye (methylene blue) to the bacteria in various concentrations, using the disk diffusion technique stimulated by laser light, wavelength 660nm, red light, InGaAlP active medium (Aluminum Indium Gallium Phosphorus). For use in the LBP isolated in micro-organisms several dosages were used with two parameters: medium active InGaAlP (Aluminum Indium Gallium Phosphorus), wavelength 660 nm, red laser and continuous emission and the active medium AsGaAl (Gallium Arsenide and Aluminum), 808 nm infrared laser and continuous emission. The bacteria used in this experiment were the standard strains American Type Culture Coletion - ATCC: Staphylococcus aureus ATCC 25922, Escherichia coli ATCC 25923 and Pseudomonas aeruginosa ATCC 27853 covering the spectrum Gram-negative bacteria, Gram-positive, aerobic and facultative anaerobic. The antibacterial effect IN VITRO of PDT in different bacteria was quantified in millimeters by observing the diameter of inhibition halos measured with the aid of a halometer. Were considered present antibacterial activities of therapy with diameter of inhibition halos greater than or equal to 8mm. Observed antibacterial effects of PDT for Staphylococcus aureus and Escherichia coli with the presence of inhibition halos with an average of 12mm, as well as for the individual use of methylene blue dye. For Pseudomonas aeruginosa was not observed anyantibacterial effect as well as for the individual use of low power laser. / O aumento da resistência das bactérias às drogas antibióticas gera a necessidade de desenvolver novos meios bacteriostáticos e bactericidas que colaborem com a terapêutica de indivíduos infectados. Dentre esses meios estão as terapias complementares, envolvendo a laserterapia e a terapia fotodinâmica. Os laseres estão sendo utilizados isolados ou associados a substâncias fotossensibilizadoras para serem auxiliares na inativação de bactérias, fungos e vírus. A terapia fotodinâmica (TFD) baseada na ativação de fotossensibilizadores por luz visível em baixas doses, com comprimento de onda apropriado, tem se tornado uma alternativa aos tratamentos convencionais no combate aos micro-organimos bucais, levando à morte do micro-organismo através de desordens na sua parede celular e no seu DNA. Nesse estudo, IN VITRO, duas terapias foram empregadas, a terapia fotodinâmica (TFD) e o Laser de Baixa Potência (LBP). Para TFD empregou-se o corante azul de metileno frente às bactérias em várias concentrações, utilizando-se da técnica disco-difusão estimulado através da luz Laser, comprimento de onda 660nm, luz vermelha, 320J/cm 2 , meio ativo InGaAlP (Índio Gálio Alumínio Fósforo). Para o uso do LBP,isoladamente, sobre o crescimento bacteriano utilizou-se várias dosimetrias com dois parâmetros: meio ativo InGaAlP (Índio Gálio Alumínio Fósforo), comprimento de onda 660 nm, laser vermelho e emissão contínua e o meio ativo AsGaAl (Arseneto de Gálio e Alúminio) 808 nm, laser infravermelho e emissão contínua. As bactérias utilizadas nesse experimento foram as cepas padrão American Type Culture Coletion ATCC: Staphylococcus aureus ATCC 25922, Escherichia coli ATCC 25923 e Pseudomonas aeruginosa ATCC 27853 abrangendo o espectro bacteriano Gram-negativo, Gram-positivo, aeróbias e anaeróbias facultativas. O efeito antibacteriano, IN VITRO, da TFD em diferentes bactérias foi quantificado em milímetros através da observação do diâmetro dos halos de inibição de crescimento medidos com o auxílio de um halômetro. Foram consideradas como presentes as atividades antibacterianas das terapias com resultados de diâmetro de halos de inibição de crescimento maiores ou iguais a 8mm. Observou-se efeitos antibacterianos da TFD para Staphylococcus aureus e Escherichia coli com a presença de halos de inibição com média de 12mm, assim como para o uso isolado do corante azul de metileno. Para Pseudomonas aeruginosa não foi observado qualquer efeito antibacteriano assim como para o uso isolado do laser de baixa potência.

O câncer é um problema de saúde pública mundial. O Instituto Nacional do Câncer (INCA) estimou que no Brasil, no ano de 2015, 576 mil novos casos surgiram, representando a segunda maior causa de mortes por esta doença. Entre os tratamentos oferecidos para o câncer, podemos destacar a radioterapia, que utiliza fontes ionizantes para erradicar ou impedir a proliferação das células tumorais. Entretanto, o uso da radiação ionizante (R.I), pode acarretar danos às células não tumorais circunvizinhas ao tumor. Assim, tratamentos coadjuvantes que possam diminuir os efeitos deletérios da radiação são extremamente importantes. Neste contexto, o laser de baixa potência (LBP) surge como alternativa para modular a resposta das células frente à radiação ionizante. Sendo esse nosso objetivo, células de fibroblastos de gengiva humana (FMM1) e câncer de mama (MDA-MB-231) foram expostas as doses de 2,5 e 10 Gy e após 24 h receberam LBP (λ= 660 nm, 40 mW e 0,04 cm²) com as densidades de energia de 30, 60, 90, 120 e 150 J/cm². A viabilidade celular foi quantificada através do teste de exclusão com azul de tripan durante quatro dias. A influência do LBP nas fases do ciclo celular e a expressão do Antígeno Nuclear de Proliferação celular (PCNA) foram realizadas por citometria de fluxo. A expressão de β-Galactosidase foi considerada para quantificar a senescência celular. Considerando os parâmetros utilizados, observou-se aumento na viabilidade celular, da expressão de PCNA, maior população nas fases S e G2/m do ciclo celular, e a diminuição de células senescentes para as células não tumorais, enquanto que para as tumorais, nenhuma resposta foi observada na viabilidade celular, maior população nas fases S e G2/m do ciclo celular e na quantidade de células senescentes enquanto que a expressão de PCNA diminuiu. Diante disso, concluímos que o LBP exerceu efeitos em ambas as linhagens celulares. / Cancer is considered a public health problem worldwide. According to the Brazils National Cancer Institute (INCA), 576,000 new cases of cancer were estimated for 2015 in Brazil, representing the second leading cause of death. Radiotherapy may be a treatment to several of types of cancer, frequently using ionizing radiation to eradicate or prevent the proliferation of tumor cells. This treatment, however, can lead to death of non-tumor cells around in irradiated tissue. Given this, adjuvant therapies that can minimize the side effects of ionizing radiation are of extremely importance. In this context, low power laser (LPL) may be an alternative to modulate the response of healthy cells to ionizing radiation. In this study, cells of human gingival fibroblasts (FMM1) and breast cancer (MDAMB- 231) were exposed to gamma radiation at doses of 2.5 and 10 Gy. After twenty-four hours, cell were irradiated with LPL (λ= 660 nm, 40 mW and total area of 0.04 cm²) with energy densities of 30, 60, 90, 120 and 150 J/cm². The cell viability was measured during four days, using the trypan blue technique. The influence of LPL on the cell cycle and on expression of the nuclear antigen of cellular proliferation (PCNA) was evaluated by flow cytometry. The expression of β-Galactosidase was the chosen method to assess cell senescence. Considering our adopted parameters, and focusing on the non-tumor cells, we have observed an increase in: 1) cell viability; 2) cell population in phases S and G2/M cell cycle; 3) PCNA expression with decrease in senescence. No alterations were observed in the cell viability, with greater population in phases S and G2/M cell cycle, while the number of senescent cells and the expression of PCNA were decreased. Therefore, we have concluded that the LPL promoted effects on both cell lineages, with increased cell viability on FMM1 cells, whether cancer cells maintained a decreased proliferation.

Made available in DSpace on 2014-08-20T14:30:05Z (GMT). No. of bitstreams: 1 dissertacao_Rodrigo_Varella_de_Carvalho.pdf: 598355 bytes, checksum: 322409e41faaa4fcdb65cd8f7b7e200d (MD5) Previous issue date: 2006-05-29 / The aim of the present study was to evaluate the gelatinase activity (MMP-2 and 9), and proliferation of human pulp fibroblasts in vitro, after irradiation with a low level diode laser (780nm). The activity was evaluated with zymography and the proliferation rate was obtained through growth curves made in SigmaPlot (8.0), after the counting in Neubauer chamber.in light microscope. Cells used to zimography were cultived in DMEM, 10% fetal bovine serum and incubated at 37ºC in atmosphere of 5% CO2 and 95% air, in 100% humidity. Cells used to proliferation rate were cultivated in nutritional deficit (5% SFB). Groups to zymography and cell proliferation were determined: zymography - Z1 = not irradiated, Z2 = 3J/cm2 e Z3 = 6J/cm2, cell proliferation: L1 = not irradiated, L2 = 3J/cm2 e L3 = 6J/cm2. The counting was made after 2, 4 and 6 days. Assays were performed in triplicate. The zymography showed that the MMP-2 activity was major with MMP-9, and, Z2 e Z3 produced a higher activity than MMP-2, when compared to Z1. Results of the zymography and proliferation test were compared by either ANOVA complemented by Tukey´s test. The level of significance was 5% (p<0,05). Statistical analysis demonstrate difference between the groups in different days. The L3 obtained higher proliferation in the finish of the six days. L2 demonstrated higher growth than L1. Irradiated fibroblasts with the low power laser expressed a higher amount of MMP-2 activity and 6J/cm2 produced a higher proliferation rate in the initial days / O objetivo do presente estudo foi avaliar a atividade das gelatinases (MMP-2 e MMP-9), e a proliferação de fibroblastos pulpares humanos in vitro, após a irradiação com um diodo laser de baixa de baixa potência (780nm). A atividade foi avaliada com zimografia e as taxas de proliferação e contagem celular foram obtidas através de curvas de crescimento feitas com o software SigmaPlot (8.0), após a contagem em câmara de Neubauer ao microscópio óptico. As células usadas para a zimografia foram cultivvadas em DMEM, com SFB a 10% e incubadas a 37ºC em atmosfera de 5% CO2 e 95% de ar, em 100% de umidade. Já, as células usadas para a taxa de proliferação e contagem celular foram cultivadas em déficit nutricional (5% SFB). Os grupos para zimmografia e para a contagem e taxa de proliferação foram determinados: a) zimografia - Z1 = sem irradiação, Z2 = 3J/cm2 e Z3 = 6J/cm2 e b) proliferação e contagem celular - L1 = sem irradiação, L2 = 3J/cm2 e L3 = 6J/cm2. A contagem celular foi realizada em após 2, 4 e 6 dias. Os ensaios foram realizados em triplicata. A zimografia mostrou que a ativiidade da MMP-2 foi maior que a MMP-9, e Z2 e Z3 produziram uma grande atividade, quando comparados ao rupo Z1. Os resultados da zimografia e dos testes de contagem e proliferação celular foram comparados por análise de variância (ANOVA) e complementado pelo teste Tukey. O nível de significância utilizado foi de % (p<0,05). A análise estatística demonstrou diferença entre os grupos nos diferentes dias para a proliferação e contagem celular. O grupo L3 obteve a maior contagem celular ao final dos seis dias avaliados. O grupo L2 demonstrou maior proliferação que o grupo L1. Os fibroblastos irradiados com o laser de baixa potência expressaram uma alta atividade de MMP-2 e a dose 6J/cm2 produziu uma alta taxa de proliferação nos primeiros dias

Abstract This thesis describes the development of low-voltage, low-power circuit blocks and structures for portable, battery-operated applications such as heart rate detectors, pacemakers and hearing-aid devices. In this work, the definition for low supply voltage operation is a voltage equal to or less than the minimum supply voltage needed to operate an analogue switch, i.e. VDD(min) ≤ 2VT + Vov, which enables the use of a single cell battery whose polar voltage is 1 – 1.5 V. The targeted power consumption is in a range of microwatts. The design restrictions for analogue circuit design caused by the low supply voltage requirement of the latest and future CMOS process technologies were considered and a few circuit blocks, namely two operational amplifiers, a Gm–C filter and a bandgap voltage reference circuit, were first designed to investigate their feasibility for the above-mentioned low-voltage and low-power environment. Two operational amplifiers with the same target specifications were designed with two different types of input stages, i.e. a floating-gate and a bulk-driven input stage, in order to compare their properties. Based on the experiences collected from the designed circuit blocks, an analogue CMOS preprocessing stage for a heart rate detector and a self-calibrating RC oscillator for clock and resistive/capacitive sensor applications were designed, manufactured and tested. The analogue preprocessing stage for a heart rate detector includes a continuous-time offset-compensated preamplifier with a gain of 40 dB, an 8th-order switched-opamp switched-capacitor bandpass filter, a 32-kHz crystal oscillator and a bias circuit, and it achieves the required performance with a supply voltage range of 1.0 – 1.8 V and a current consumption of 3 μA. The self-calibrating RC oscillator operates with supply voltages of 1.2 – 3.0 V and achieves a tunable frequency range of 0.2 – 150 MHz with a total accuracy of ±1% within a supply voltage range of 1.2 – 1.5 V, a temperature range from -20 to 60 °C and a current consumption of less than 70 μA @ 5 MHz with external high precision resistor and capacitor. The measurement results prove that the developed low-voltage low-power analogue circuit structures can achieve the required performance and therefore be successfully implemented with modern CMOS process technologies with limited supply voltages. / Tiivistelmä Tämä väitöskirja käsittelee matalan käyttöjännitteen pienitehoisten piirirakenteiden kehittämistä kannettaviin, paristokäyttöisiin sovelluksiin kuten esimerkiksi sykemittareihin, sydämen tahdistimiin ja kuulolaitteisiin. Matalalla käyttöjännitteellä tarkoitetaan jännitettä, joka on pienempi tai yhtäsuuri kuin analogisen kytkimen tarvitsema pienin mahdollinen käyttöjännite, VDD(min) ≤ 2VT + Vov, joka mahdollistaa piirin toiminnan yhdellä paristolla, jonka napajännite on 1 – 1,5 V. Tavoiteltu tehonkulutus on mikrowattiluokkaa. Piirirakenteiden suunnittelussa otettiin huomioon viimeisimpien ja lähitulevaisuuden CMOS-valmistusteknologioiden aiheuttamat matalan käyttöjännitteen erityisvaatimukset ja niiden pohjalta kehitettiin aluksi kaksi erilaista operaatiovahvistinta, GmC-suodatin, ja bandgap-jännitereferenssi. Operaatiovahvistimet toteutettiin samoin tavoitevaatimuksin kahdella eri tekniikalla käyttäen toisen vahvistimen tuloasteessa ns. kelluvahilaisia tulotransistoreita ja toisen tuloasteessa ns. allasohjattuja tulotransistoreita. Kehitetyistä rakenteista saatujen kokemusten pohjalta suunniteltiin, valmistettiin ja testattiin kaksi erilaista CMOS-teknologialla toteutettua mikropiiriä, jotka olivat analoginen esikäsittelypiiri sydämen sykkeen mittaukseen ja itsekalibroiva RC-oskillaattori resistiivisiin/kapasitiivisiin sensorisovelluksiin. Sydämen sykkeen esikäsittelypiiri sisältää jatkuva-aikaisen, offset-kompensoidun esivahvistimen, jonka vahvistus on 40 dB, kytketyistä kapasitansseista ja kytketyistä operaatiovahvistimista koostuvan kahdeksannen asteen kaistanpäästösuodattimen, 32 kHz kideoskillaattorin ja bias-piirin. Esikäsittelypiiri saavuttaa vaadittavan suorituskyvyn 1,0 – 1,8 V käyttöjännitteellä ja 3 μA virrankulutuksella. Itsekalibroivan RC-oskillaattorin käyttöjännitealue puolestaan on 1,2 – 3,0 V ja käyttökelpoinen taajuusalue 0,2 – 150 MHz. Ulkoista tarkkuusvastusta ja kondensaattoria käytettäessä oskillaattori saavuttaa ±1 % tarkkuuden 1,2 – 1,5 V käyttöjännitteillä ja -20 – 60 °C lämpötila-alueella virrankulutuksen jäädessä alle 70 μA @ 5 MHz. Mittaustulokset osoittavat, että kehitetyt matalan käyttöjännitteen pienitehoiset analogiset rakenteet saavuttavat vaadittavan suorituskyvyn ja voidaan näin ollen menestyksekkäästi valmistaa moderneilla matalan käyttöjännitteen CMOS-teknologioilla.

A Wireless Sensor Network is formed of several small devices encompassing the capability of sensing a physical characteristic and sending it hop by hop to a central node via low power and short range transceivers. The Sensor network lifetime strongly depends on the routing protocol in use. Routing protocol is responsible for forwarding the traffic and making routing decisions. If the routing decisions made are not intelligent, more re-transmissions will occur across the network which consumes limited resources of the wireless sensor network like energy, bandwidth and processing. Therefore a careful and extensive performance analysis is needed for the routing protocols in use by any wireless sensor network. In this study we investigate Objective Functions and the most influential parameters on Routing Protocol for Low power and Lossy Network (RPL) performance in Contiki (WSN OS) and then evaluate RPL performance in terms of Energy, Latency, Packet Delivery Ratio, Control overhead, and Convergence Time for the network. We have carried out extensive simulations yielding a detailed analysis of different RPL parameters with respect to the five performance metrics. The study provides an insight into the different RPL settings suitable for different application areas. Experimental results show ETX is a better objective, and that ContikiRPL provides very efficient network Convergence (14s), Control traffic overhead (1300 packets), Energy consumption (1.5% radio on time), Latency (0.5s), and Packet Delivery Ratio (98%) in our sample RPL simulation of one hour with 80 nodes, after careful configuration of DIO interval minimum/doublings, Radio duty cycling, and Frequency of application messages. / En Wireless Sensor Network består av flera små enheter som omfattar de förmåga avkänning en fysisk egenskap och skicka den hoppa med hopp till en centrala noden via låg effekt och kort sändtagare räckvidd. Det sensornätverk livslängd är starkt beroende av routingprotokoll som används. Routingprotokoll är ansvarar för att vidarebefordra trafik och göra routing beslut. Om dirigeringen beslut som fattas inte är intelligenta, kommer fler återsändningar förekomma på nätverk som förbrukar begränsade resurser trådlösa sensornätverk som energi, bandbredd och bearbetning. Därför är en noggrann och omfattande prestanda analys behövs för routingprotokoll används av alla trådlösa sensornätverk. I denna studie undersöker vi mål Funktioner och den mest inflytelserika parametrar Routing Protokoll för låg effekt och Förstörande nätverk (RPL) prestanda i Contiki (WSN OS) och sedan utvärdera RPL prestanda vad gäller av energi, fördröjning, Packet Delivery Ratio, kontroll overhead och konvergens Dags för nätverket. Vi har genomfört omfattande simuleringar som ger en detaljerad analys av olika RPL parametrar med avseende på de fem resultatstatistik. Studien ger en inblick i de olika RPL inställningar som är lämpliga för olika användningsområden. Experimentella resultat visar ETX är en bättre målsättning och att ContikiRPL ger mycket effektivt nätverk Konvergens (14s), Control trafik overhead (1300 paket), Energiförbrukning (1,5% radio i tid), Latens (0,5 s), och paket Leverans Ratio (98%) i vårt urval RPL simulering av en timme med 80 noder, efter noggrann konfiguration av DIO intervall minimum / dubbleringar, Radio plikt cykling, och frekvensen av ansökan meddelanden. / tocomputerscientist@gmail.com Mob: 0046760721720

The growing demand for wireless communication systems is driving the integration of radio frequency (RF) front-ends on the same chip with multi-band functionality and higher spectral efficiency. Microelectromechanical systems (MEMS) have an overarching applicability to RF communications and are critical components in facilitating this integration process. Among a variety of RF MEMS devices, piezoelectric MEMS resonators have sparked significant research and commercial interest for use in oscillators, filters, and duplexers. Compared to their bulky quartz crystal and surface acoustic wave (SAW) counterparts, MEMS resonators exhibit impressive advantages of compact size, lower production cost, lower power consumption, and higher level of integration with CMOS fabrication processes. One of the promising piezoelectric MEMS resonator technologies is the aluminum nitride (AlN) contour mode resonator (CMR). On one hand, AlN is chemically stable and offers superior acoustic properties such as large stiffness and low loss. Furthermore, CMRs offer low motional resistance over a broad range of frequencies (few MHZ to GHz), which are lithographically-definable on the same silicon substrates. To date, RF MEMS resonators (include CMRs) have been extensively studied; however, one aspect that was not thoroughly investigated is how to modulate/tune their equivalent parameters to enhance their performance in oscillators and duplexers. The goal of this thesis is to investigate various modulation methods to improve the thermal stability of the resonator, its “effective” quality factor when used in an oscillator, and build completely novel non-reciprocal components. Broadly defined, modulation refers to the exertion of a modifying or controlling influence on something, herein specifically, the resonator admittance. In this thesis, three categories of modulation methods are investigated: thermal modulation, force modulation, and external electronic modulation. Firstly, the AlN CMR’s center frequency can be tunned by the applied thermal power to the resonator body. The resonator temperature is kept constant (for example, 90 °C) via a temperature sensor and feedback control such that the center frequency is stable over the whole operation temperature range of interest (e.g. –35 to 85 °C). The maximum power consumption to sustain the maximum temperature difference (120 ºC in this thesis) between resonator and ambient is reduced to a value as low as 353 μW – the lowest ever reported for any MEMS device. These results were attained while simultaneously maintaining a high quality factor (up to 4450 at 220 MHz device). The feedback control was implemented by either analog circuits or via a microprocessor. The analog feedback control, which innovatively utilized a dummy resistor to compensate for temperature gradients, resulted in a total power consumption of 3.8 mW and a frequency stability of 100 ppm over 120 ºC. As for the digital compensation, artificial neural network algorithm was employed to facilitate faster calibration of look-up tables for multiple frequencies. This method attained a frequency stability of 14 ppm over 120 ºC. The second modulation method explored in this thesis is based on the use of an effective external force to enhance the 3-dB quality factor of AlN CMRs and improve the phase noise performance of resonator-based oscillators. The force modulation method was embodied in a two-port device, where one of the two ports is used as a one-port resonator and the other is driven by an external signal to effectively apply an external force to the first port. Through this technique, the quality factor of the resonator was boosted by 140 times (up to 150,000) and the phase noise of the corresponding oscillator realized using the resonator was reduced by 10 dBc/Hz. Lastly, a novel magnetic-free electrical circulator topology that facilitates the development of in-band full duplexers (IBFD) for simultaneous transmit and receive (STAR) is proposed and modeled. Fundamentally, a linear time-invariant (LTI) filter network parametrically modulated via a switching matrix is used to break the reciprocity of the filter. The developed model accurately predicts the circulator behavior and shows very good agreement with the experimental results for a 21.4 MHz circulators built with MiniCircuit filter and switch components. Furthermore, a high frequency (1.1 GHz) circulator was synthesized based on AlN MEMS bandpass filters and CMOS RF switches, hence showing a compact approach that can be used in handheld devices. The modulation frequency and duty cycle are optimized so that the circulator can provide up to 15 dB of isolation over the filter bandwidth while good power transfer between the other two ports is maintained. The demonstrated device is expected to intrinsically offer low noise and high linearity. The combination of the first two modulation methods facilitates the implementation of monolithic, temperature-stable, ultra-low noise, multi-frequency oscillator banks. The third modulation technique that was investigated sets the path for the development of CMOS-compatible in-band full duplexers for simultaneous transmit and receive and thus facilitates the efficient utilization of the electromagnetic spectrum. With the aid of all these three modulation approaches, the author believes that a fully integrated, multi-frequency, spectrum-efficient transceiver is enabled for next-generation wireless communications.

The concept of wireless sensor network (WSN) is where tiny devices (sensor nodes), positioned fairly close to each other, are used for sensing and gathering data from its environment and exchange information through wireless connections between these nodes (e.g. sensor nodes distributed through out a bridge for monitoring the mechanical stress level of the bridge continuously). In order to easily deploy a relatively large quantity of sensor nodes, the sensor nodes are typically designed for low price and small size, thereby causing them to have very limited resources available (e.g. energy, processing power). Over the years, different security (cryptographic) primitives have been proposed and refined aiming at utilizing modern processor’s power e.g. 32-bit or 64-bit operation, architecture such as MMX (Multi Media Extension) and etc. In other words, security primitives have targeted at high-end systems (e.g. desktop or server) in software implementations. Some hardware-oriented security primitives have also been proposed. However, most of them have been designed aiming only at large message and high speed hashing, with no power consumption or other resources (such as memory space) taken into considerations. As a result, security mechanisms for ultra-low power (<500µW) devices such as the wireless sensor nodes must be carefully selected or designed with their limited resources in mind. The objective of this project is to provide implementations of security primitives (i.e. encryption and authentication) suitable to the WSN environment, where resources are extremely limited. The goal of the project is to provide an efficient building block on which the design of WSN secure routing protocols can be based on, so it can relieve the protocol designers from having to design everything from scratch. This project has provided three main contributions to the WSN field.  Provides analysis of different tradeoffs between cryptographic security strength and performances, which then provide security primitives suitable for the needs in a WSN environment. Security primitives form the link layer security and act as building blocks for higher layer protocols i.e. secure routing protocol.  Implements and optimizes several security primitives in a low-power microcontroller (TI MSP430F1232) with very limited resources (256 bytes RAM, 8KB flash program memory). The different security primitives are compared according to the number of CPU cycles required per byte processed, specific architectures required (e.g. multiplier, large bit shift) and resources (RAM, ROM/flash) required. These comparisons assist in the evaluation of its corresponding energy consumption, and thus the applicability to wireless sensor nodes.  Apart from investigating security primitives, research on various security protocols designed for WSN have also been conducted in order to optimize the security primitives for the security protocols design trend. Further, a new link layer security protocol using optimized security primitives is also proposed. This new protocol shows an improvement over the existing link layer security protocols. Security primitives with confidentiality and authenticity functions are implemented in the TinyMote sensor nodes from the Technical University of Vienna in a wireless sensor network. This is to demonstrate the practicality of the designs of this thesis in a real-world WSN environment. This research has achieved ultra-low power security primitives in wireless sensor network with average power consumption less than 3.5 µW (at 2 second packet transmission interval) and 700 nW (at 5 second packet transmission interval). The proposed link layer security protocol has also shown improvements over existing protocols in both security and power consumption. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted