This thesis presents and evaluates how to select the data to be logged in an embedded realtime system so as to be able to give confidence that it is possible to perform an accurate identification of the fault(s) that caused any runtime errors. Several log-selection strategies were evaluated by injecting random faults into a simulated real-time system. An instrument was created to perform accurate detection and identification of these faults by evaluating log data. The instrument’s output was compared to ground truth to determine the accuracy of the instrument. Three strategies for selecting the log entries to keep in limited permanent memory were created. The strategies were evaluated using log data from the simulated real-time system. One of the log-selection strategies performed much better than the other two: it minimized processing time and stored the maximum amount of useful log data in the available storage space. / Denna uppsats illustrerar hur det blev fastställt vad som ska loggas i ett inbäddat realtidssystem för att kunna ge förtroende för att det är möjligt att utföra en korrekt identifiering av fel(en) som orsakat körningsfel. Ett antal strategier utvärderades för loggval genom att injicera slumpmässiga fel i ett simulerat realtidssystem. Ett instrument konstruerades för att utföra en korrekt upptäckt och identifiering av dessa fel genom att utvärdera loggdata. Instrumentets utdata jämfördes med ett kontrollvärde för att bestämma riktigheten av instrumentet. Tre strategier skapades för att avgöra vilka loggposter som skulle behållas i det begränsade permanenta lagringsutrymmet. Strategierna utvärderades med hjälp av loggdata från det simulerade realtidssystemet. En av strategierna för val av loggdata presterade klart bättre än de andra två: den minimerade tiden för bearbetning och lagrade maximal mängd användbar loggdata i det permanenta lagringsutrymmet.

It is well known that multi-input multi-output (MIMO) wireless communication systemsthat employ precoding techniques are capable of meeting the high expectations of modernand future wireless communication standards. In order to fully utilize these techniques, thecommunication system typically requires information of the channel, commonly referred toas channel state information (CSI). In practice, the CSI at the transmitter (CSIT) is oftennot perfect which addresses the need for robust precoding designs, that can mitigate theeffects of precoding with imperfect CSIT. By modeling the imperfect CSIT as deterministic,it can be assumed that the estimated channel, as represented by the CSIT, belongs to aconvex uncertainty set. With this approach, the problem of finding a robust precoding designcan be formulated as a convex maximin problem, where the solution optimizes the systemperformance for the worst channel that belongs to the uncertainty set. How the uncertaintyset is modeled impacts the performance of the communication system, which calls for theevaluation of several robust precoding designs. While different characteristics of the convexuncertainty sets has been evaluated for MIMO flat-fading channels represented by i.i.d. zero-mean, unit variance Gaussian elements, it is of interest to apply the theory of worst-caserobust precoding designs on real-world measured MIMO channels.More concisely, this project investigates MIMO precoding designs with deterministic im-perfect CSIT for real-world measured channels that utilizes orthogonal frequency divisionmultiplexing (OFDM) schemes. The worst-case received signal-to-noise ratio (SNR) will bepresented as a result of using MIMO precoding designs on real-world channels, and the effectof the choice of model parameters and characteristics of the chosen uncertainty set will bevisualized and discussed. Furthermore, orthogonal space-time block code (OSTBC) transmis-sion designs will be employed to measure the worst case symbol error rate (SER) as a tool toevaluate the system performance in different scenarios. The results will be compared to thatwhen the channel is composed of i.i.d. zero-mean, unit variance Gaussian elements and forthe case when the channel is based on the Kronecker model.The results indicate that a further analysis of how the Kronecker model behaves in termsof capacity is required in order to draw accurate conclusions regarding the implementation ofrobust precoding strategies when each pair of antennas are correlated. Also, it is essential todevelop a framework that offers methods on how to accurately model the uncertainty set sothat it can represent errors that originates from both quantization errors, estimation errorsand outdated estimates. / Det är välkänt att trådlösa multi-input, multi-output (MIMO) system som använder förkodar-tekniker har kapabilitet att möta de höga förväntningar som är fastställt av moderna ochframtida kommunikationsstandarder. För att utnyttja dessa förkodartekniker till fullo be-hövs information om kanalen (CSI). I praktiska kommunikationssystem är kanalinformatio-nen hos sändaren (CSIT) ofta inte perfekt vilket adresserar betydelsen av att använda robustaförkodare som kan mildra den negativa effekten som uppstår av att förkoda med CSIT som in-nehåller fel. Genom att använda en deterministisk modell för CSIT med fel kan man anta attden skattade kanalen som är representerad av CSIT tillhör en konvex osäkerhetsregion. Meddetta tillvägagångssätt kan man formulera problemet att hitta en robust förkodardesign somett konvext maximin-problem, där lösningen optimerar systemets prestanda för den värstakanalskattningen i osäkerhetsregionen. Olika modeller av osäkerhetsregioner ger upphov tillolika systemprestanda vilket betyder att olika modeller med tillhörande robusta förkodare be-höver utvärderas. Medan tidigare forskningsrapporter behandlat MIMO flat fädnings-kanalerför i.i.d. Gaussisk fördelning av elementen finns det ett intresse att applicera teorin omvärsta-fallet robust förkodning på riktiga uppmätta MIMO-kanaler.Mer koncist undersöker detta projekt designs på förkodare för riktiga uppmätta MIMO-kanaler utifrån en deterministisk modell på felaktigt CSIT, där MIMO-kanalerna utnyttjarorthogonal frequency divsion multiplexing (OFDM) scheman. Värsta-fallet signal-to-noiseratio (SNR) kommer presenteras för olika förkodar-designs och MIMO-kanaler. Hur olika valav modellparametrar och karakteristik hos osäkerhetsregionerna påverkar systemprestandankommer att diskuteras. Vidare kommer även orthogonal space-time block codes (OSTBC)användas som transmissionsscheman för att mäta symbol error rate (SER). Resultaten kom-mer att jämföras med när MIMO-kanalen består av i.i.d. Gaussisk fördelning av elementenoch för fallet när kanalen är baserad på en Kronecker-modell.Resultaten indikerar att en fortsatt analys av hur Kronecker-modellen beter sig medavseende på kapacitet är nödvändig för att dra tillförlitliga slutsatser om systemprestan-dan för förkodar-designs när antennparen är korrelerade. Det är även väsentligt att utvecklaen teori som behandlar metoder för hur man kan på ett tillförlitligt sätt modellera osäker-hetsregionen så CSIT så att kvantiseringsfel, skattningsfel och utdaterade skattningar kanrepresenteras i den.

Increasing complexity of real-time systems and demands for enabling their configurability and tailorability are strong motivations for applying new software engineering principles such as aspect-oriented and component-based software development. The integration of these two techniques into real-time systems development would enable: (i) efficient system configuration from the components in the component library based on the system requirements, (ii) easy tailoring of components and/or a system for a specific application by changing the behavior (code) of the component by aspect weaving, and (iii) enhanced flexibility of the real-time and embedded software through the notion of system configurability and component tailorability. In this thesis we focus on applying aspect-oriented and component-based software development to real-time system development. We propose a novel concept of aspectual component-based real-time system development (ACCORD). ACCORD introduces the following into real-time system development: (i) a design method that assumes the decomposition of the real-time system into a set of components and a set of aspects, (ii) a real-time component model denoted RTCOM that supports aspect weaving while enforcing information hiding, (iii) a method and a tool for performing worst-case execution time analysis of different configurations of aspects and components, and (iv) a new approach to modelling of real-time policies as aspects. We present a case study of the development of a configurable real-time database system, called COMET, using ACCORD principles. In the COMET example we show that applying ACCORD does have an impact on the real-time system development in providing efficient configuration of the real-time system. Thus, it could be a way for improved reusability and flexibility of real-time software, and modularization of crosscutting concerns. In connection with development of ACCORD, we identify criteria that a design method for component-based real-time systems needs to address. The criteria include a well-defined component model for real-time systems, aspect separation, support for system configuration, and analysis of the composed real-time system. Using the identified set of criteria we provide an evaluation of ACCORD. In comparison with other approaches, ACCORD provides a distinct classification of crosscutting concerns in the real-time domain into different types of aspects, and provides a real-time component model that supports weaving of aspects into the code of a component, as well as a tool for temporal analysis of the weaved system. / <p>Report code: LiU-TEK-LIC-2003:23.</p>

Os circuladores tradicionais são amplamente utilizados em telecomunicações e defesa militar para o simultâneo envio e recepção de sinais por um único meio. Esses circuitos passivos, fabricados a partir de materiais ferromagnéticos, possuem a desvantagem do aumento de dimensões, peso e custos de fabricação com a diminuição da frequência de operação definida no projeto destes dispositivos, inviabilizando sua aplicação em frequências abaixo de 500 MHz. O circulador ativo surgiu como uma alternativa aos tradicionais, tendo aplicações em frequências desde o nível DC até a ordem de dezenas de gigahertz. As suas maiores aplicações ocorrem quando são necessários dispositivos compactos, de baixo custo e de baixa potência. Os primeiros circuitos propostos possuíam uma grande limitação em termos de frequência de operação e de potência entregue à carga. Entretanto, com os avanços tecnológicos na eletrônica, tais problemas podem ser amenizados atualmente. Neste trabalho é apresentado o desenvolvimento de um circuito circulador ativo para a utilização em instrumentação eletrônica, em particular para a operação em frequências na ordem das utilizadas em equipamentos de ultrassom Doppler de ondas contínuas, na faixa de 2 MHz a 10 MHz. As possíveis vantagens da implementação de circuladores em sistemas de ultrassom estão relacionadas ao incremento da relação sinal-ruído, aumento da área de recepção do transdutor, simplificação da construção do transdutor, simplificação do circuito de demodulação/ processamento, e maior isolação entre os circuitos de transmissão e recepção de sinais. Na fase inicial, o circulador ativo proposto é modelado por equacionamento, utilizando-se tanto o modelo ideal dos amplificadores operacionais como o seu modelo de resposta em frequência. Simulações computacionais foram executadas para confirmar a validade do equacionamento. Um circuito montado em placa de prototipagem rápida foi apresentado, e testes de prova de conceito em baixas frequências foram realizados, mostrando uma grande semelhança entre o teórico, o simulado e o experimental. A segunda parte contou com o projeto do circuito circulador para a operação em maiores frequências. O circuito proposto é composto por três amplificadores operacionais de realimentação por corrente e vários componentes passivos. Uma análise de sensibilidade utilizando os métodos de Monte-Carlo e análise do pior caso foi aplicada, resultando em um perfil de comportamento frente às variações dos componentes do circuito e às variações da impedância de carga. Uma placa de circuito impressa foi projetada, utilizando-se de boas práticas de leiaute para a operação em altas frequências. Neste circuito montado, foram realizados os seguintes testes e medições: comportamento no domínio do tempo, faixa dinâmica, nível de isolação em relação à amplitude do sinal, largura de banda, levantamento dos parâmetros de espalhamento, e envio e recepção de sinais por transdutor de ultrassom Doppler de ondas contínuas. Os resultados dos testes de desempenho foram satisfatórios, apresentando uma banda de transmissão de sinais para frequências de 100 MHz, isolação entre portas não consecutivas de 39 dB na frequência de interesse para ultrassom Doppler e isolação maior que 20 dB para frequências de até 35 MHz. A faixa dinâmica excedeu a tensão de 5 Vpp, e o circuito teve bom comportamento no envio e na recepção simultânea de sinais pelo transdutor de ultrassom. / Traditional circulators are widely used in both telecommunications and military defense for sending and receiving signals simultaneously through a single medium. These passive circuits which are manufactured from ferromagnetic materials, have the disadvantages of having suffered an increase in dimensions, weight, and manufacturing costs along with the decrease in the operation frequency established in the designs of such devices, thus preventing their useful employment in frequencies below 500 MHz. The active circulator emerged as an alternative to the traditional ones, and has applications on frequencies ranging from a DC level to levels involving dozens of gigahertz. It is applicable when compact devices are made necessary, at a low cost, and for low frequencies. The first circuits to be introduced had a major limitation in terms of operating frequency and power delivered to the load. However, due to technological advances in electronics, problems such as the aforementioned can now be minimized. This research work presents the development of an active circulator circuit to be used in electronic instrumentation, particularly for operation at frequencies such as those used in continuous wave Doppler ultrasound equipment, ranging from 2 MHz to 10 MHz. The advantages made possible by implementing ultrasound systems with circulators are related to an increase in the signal-to-noise ratio, an increase in the transducers reception area, a simplified construction of the transducer, simplification of the demodulation/processing circuit, and a greater isolation between the transmission circuits and signal reception. In the initial phase, the proposed active circulator was modeled by means of an equating method, using both the ideal model of operational amplifiers and the model of frequency response. Computer simulations were carried out in order to confirm the validity of the equating method. A circuit mounted upon a breadboard was introduced and proof of concept assessments were performed at low frequencies, showing a great similarity among the theoretical, simulated and experimented data. The second phase is when the circulator circuits design was developed in order make its operation at higher frequencies possible. The proposed circuit is comprised of three currentfeedback operational amplifiers and several passive components. A sensitivity analysis was carried out using Monte-Carlo methods and worst-case analyses, resulting in a certain behavioral profile influenced by variations in circuit components and variations in load impedance. A printed circuit board was designed, employing good practice layout standards so that operation at high frequencies would be achieved. The following evaluations and measurements were performed on the circuit that was assembled: time domain behavior, dynamic range, isolation level relative to signal amplitude, bandwidth, survey of the scattering parameters, and transmission and reception of signals by a continuous wave Doppler ultrasound transducer. The results of the performance tests were satisfactory, presenting a 100 MHz signal transmission band, isolation between non-consecutive ports of 39 dB at the frequency of interest to the Doppler ultrasound, and an isolation greater than 20 dB for frequencies of up to 35 MHz. The dynamic range exceeded the 5Vpp and the circuit performed satisfactorily in the simultaneous transmission and reception of signals through the ultrasound\'s transducer.

Afin de garantir qu'un programme respectera toutes ses contraintes temporelles, nous devons être capable de calculer une estimation fiable de son temps d'exécution au pire cas (WCET: worst case execution time). Cependant, identifier une borne précise du pire temps d'exécution devient une tâche très complexe du fait de la sophistication croissante des processeurs. Ainsi, l'objectif de nos travaux de recherche a été de définir une méthode formelle qui puisse s'adapter aux évolutions du matériel. Cette méthode consiste à développer un modèle du processeur cible, puis à l'exécuter symboliquement afin d'associer à chaque trace d'exécution un temps d'exécution au pire cas. Une méthode de fusionnement est également prévue afin d'éviter une possible explosion combinatoire. Cette méthode a pour principale contrainte de ne pas introduire trop d'imprécision sur les temps calculés. / To ensure that a program will respect all its timing constraints we must be able to compute a safe estimation of its worst case execution time (WCET). However with the increasing sophistication of the processors, computing a precise estimation of the WCET becomes very difficult. In this report, we propose a novel formal method to compute a precise estimation of the WCET that can be easily parameterized by the hardware architecture. Assuming that we developed an executable timed model of the hardware, we use symbolic execution to precisely infer the execution time for a given instruction flow. We also merge the states relying on the loss of precision we are ready to accept, in order to avoid a possible states explosion.

Les tâches critiques en systèmes temps-réel sont soumises à des contraintes temporelles et de correction. La validation d'un tel système repose sur l'estimation du comportement temporel au pire cas de ses tâches. Le partage de ressources, inhérent aux architectures multi-cœurs, entrave le calcul de ces estimations. Le comportement temporel d'une tâche dépend de ses rivales du fait de l'arbitrage de l'accès aux ressources ou de modifications concurrentes de leur état. Cette étude vise à l'estimation de la contribution temporelle de la hiérarchie mémoire au pire temps d'exécution de tâches critiques. Les méthodes existantes, pour caches d'instructions, sont étendues afin de supporter caches de données privés et partagés, et permettre l'analyse de hiérarchies mémoires riches. Le court-circuitage de cache est ensuite utilisé pour réduire la pression sur les caches partagés. Nous proposons à cette fin différentes heuristiques basées sur la capture de la réutilisation de blocs de cache entre différents accès mémoire. Notre seconde proposition est la politique de partitionnement Preti qui permet l'allocation d'un espace sans conflits à une tâche. Preti favorise aussi les performances de tâches non critiques concurrentes aux temps-réel dans les systèmes de criticité hybride. / Critical tasks in the context of real-time systems submit to both timing and correctness constraints. Whence, the validation of a real-time system rely on the estimation of its tasks’ Worst case execution times. Resource sharing, as it occurs on multicore architectures, hinders the computation of such estimates. The timing behaviour of a task is impacted by its concurrents, whether because of resource access arbitration or concurrent modifications of a resource state. This study focuses on estimating the contribution of the memory hierarchy to tasks’ worst case execution time. Existing analysis methods, defined for instruction caches, are extended to support private and shared data caches, hence allowing for the analysis of rich memory hierarchies. Cache bypass is then used to reduce the pressure laid by concurrent tasks on shared caches levels. We propose different bypass heuristics, based on the capture of cache blocks’ reuse between memory accesses. Our second proposal is the Preti partitioning scheme which allows for the allocation to tasks of a cache space, free from inter-task conflicts. Preti offers the added benefit of providing for average-case performance to non-critical tasks concurrent to real-time ones on hybrid criticality systems.

<p>Real-time systems do not only require that the logical operations are correct. Equally important is that the specified time constraints always are complied. This has successfully been studied before for mono-processor systems. However, as the hardware in the systems gets more complex, the previous approaches become invalidated. For example, multi-processor systems-on-chip (MPSoC) get more and more common every day, and together with a shared memory, the bus access time is unpredictable in nature. This has recently been resolved, but a safe and not too pessimistic cache analysis approach for MPSoC has not been investigated before. This thesis has resulted in designed and implemented algorithms for cache analysis on real-time MPSoC with a shared communication infrastructure. An additional advantage is that the algorithms include improvements compared to previous approaches for mono-processor systems. The verification of these algorithms has been performed with the help of data flow analysis theory. Furthermore, it is not known how different types of cache miss characteristic of a task influence the worst case execution time on MPSoC. Therefore, a program that generates randomized tasks, according to different parameters, has been constructed. The parameters can, for example, influence the complexity of the control flow graph and average distance between the cache misses.</p>

Cooperative relaying is a promising diversity achieving technique to provide reliable transmission, high throughput and extensive coverage for wireless networks in a variety of applications. Two-way relaying is a spectrally efficient protocol, providing one solution to overcome the half-duplex loss in one-way relay channels. Moreover, incorporating the multiple-input-multiple-output (MIMO) technology can further improve the spectral efficiency and diversity gain. A lot of related work has been performed on the two-way relay network (TWRN), but most of them assume perfect channel state information (CSI). In a realistic scenario, however, the channel is estimated and the estimation error exists. So in this thesis, we explicitly take into account the CSI error, and investigate its impact on the performance of amplify-and-forward (AF) TWRN where either multiple distributed single-antenna relays or a single multiple-antenna relay station is exploited. For the distributed relay network, we consider imperfect self-interference cancellation at both sources that exchange information with the help of multiple relays, and maximal ratio combining (MRC) is then applied to improve the decision statistics under imperfect signal detection. The system performance degradation in terms of outage probability and average bit-error rate (BER) are analyzed, as well as their asymptotic trend. To further improve the spectral efficiency while maintain the spatial diversity, we utilize the maximum minimum (Max-Min) relay selection (RS), and examine the impact of imperfect CSI on this single RS scheme. To mitigate the negative effect of imperfect CSI, we resort to adaptive power allocation (PA) by minimizing either the outage probability or the average BER, which can be cast as a Geometric Programming (GP) problem. Numerical results verify the correctness of our analysis and show that the adaptive PA scheme outperforms the equal PA scheme under the aggregated effect of imperfect CSI. When employing a single MIMO relay, the problem of robust MIMO relay design has been dealt with by considering the fact that only imperfect CSI is available. We design the MIMO relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. The optimization problem corresponding to the robust MIMO relay design is shown to be nonconvex. This motivates the pursuit of semidefinite relaxation (SDR) coupled with the randomization technique to obtain computationally efficient high-quality approximate solutions. Numerical simulations compare the proposed MIMO relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. / Graduate

Optimised allocation of system architectures is a well researched area as it can greatly reduce the developmental cost of systems and increase performance and reliability in their respective applications.In conjunction with the recent shift from federated to integrated architectures in automotive, and the increasing complexity of computer systems, both in terms of software and hardware, the applications of design space exploration and optimised allocation of system architectures are of great interest.This thesis proposes a method to derive architectures and their allocations for systems with real-time constraints.The method implements integer linear programming to solve for an optimised allocation of system architectures according to a set of linear constraints while taking resource requirements, communication dependencies, and manual design choices into account.Additionally, this thesis describes and evaluates an industrial use case using the method wherein the timing characteristics of a system were evaluated, and, the method applied to simultaneously derive a system architecture, and, an optimised allocation of the system architecture.This thesis presents evidence and validations that suggest the viability of the method and its use case in an industrial setting.The work in this thesis sets precedence for future research and development, as well as future applications of the method in both industry and academia.

Norovirus (NoV) is a significant cause of gastroenteritis globally, and the consumption of oysters is frequently linked to outbreaks. Depuration is the principle means employed to reduce levels of potentially harmful agents or toxins in shellfish. The aim of this thesis is to construct mathematical models which can describe the depuration dynamics of water-borne pathogens, and specifically examine the dynamics of NoV during depuration for a population shellfish. Legislation is currently under consideration within the EU by the Directorate-General for Health and Consumers (DG SANCO) to limit the maximum level of NoV that consumers are exposed to via this route. Therefore it is important to the utility of the thesis that any models constructed should incorporate control measures which could be used to implement minimum NoV levels. Doing so allowed calculation of minimum depuration times that would be required to adhere to the control measures incorporated into the models. In addition to modelling the impact on pathogens during the depuration, we wished to gain some insight into how the variability, and not just the mean levels, of water-borne pathogens can be as important with respect to the length of depuration required to minimise any food safety risks to the consumer. This proved difficult in the absence of any data sets that can be used to calculate variability measures, as little data is currently available to inform these values for NoV. However, our modelling techniques were able to calculate an upper limit on the variability of water-borne pathogens that can be well approximated by lognormal distributions. Finally we construct a model which provided linkage between the depuration process and the accretion of pathogens by shellfish while still within farming waters. This model proposed that the pulses of untreated waste waters released by sewage treatment works due to high levels of rainfall would be transmitted into shellfish whilst filter-feeding.