System Level Performance Evaluation of Distributed Embedded Systems

In order to evaluate the feasibility of the distributed embedded systems in different application domains at an early phase, the System Level Performance Evaluation (SLPE) must provide reliable estimates of the nonfunctional properties of the system such as end-to-end delays and packet losses rate. The values of these non-functional properties depend not only on the application layer of the OSI model but also on the technologies residing at the MAC, transport and Physical layers. Therefore, the system level performance evaluation methodology must provide functionally accurate models of the protocols and technologies operating at these layers. After conducting a state of the art survey, it was found that the existing approaches for SLPE are either specialized for a particular domain of systems or apply a particular model of computation (MOC) for modeling the communication and synchronization between the different components of a distributed application. Therefore, these approaches abstract the functionalities of the data-link, Transport and MAC layers by the highly abstract message passing methods employed by the different models of computation. On the other hand, network simulators such as OMNeT++, ns-2 and Opnet do not provide the models for platform components of devices such as processors and memories and totally abstract the application processing by delays obtained via traffic generators. Therefore the system designer is not able to determine the potential impact of an application in terms of utilization of the platform used by the device. Hence, for a system level performance evaluation approach to estimate both the platform utilization and the non-functional properties which are a consequence of the lower layers of OSI models (such as end-to-end delays), it must provide the tools for automatic workload extraction of application workload models at various levels of refinement and functionally correct models of lower layers of OSI model (Transport MAC and Physical layers). Since ABSOLUT is not restricted to a particular domain and also does not depend on any MOC, therefore it was selected for the extension to a system level performance evaluation approach for distributed embedded systems. The models of data-link and Transport layer protocols and automatic workload generation of system calls was not available in ABSOLUT performance evaluation methodology. The, thesis describes the design and modelling of these OSI model layers and automatic workload generation tool for system calls. The tools and models integrated to ABSOLUT methodology were used in a number of case studies. The accuracy of the protocols was compared to network simulators and real systems. The results were 88% accurate for user space code of the application layer and provide an improvement of over 50% as compared to manual models for external libraries and system calls. The ABSOLUT physical layer models were found to be 99.8% accurate when compared to analytical models. The MAC and transport layer models were found to be 70-80% accurate when compared with the same scenarios simulated by ns-2 and OMNeT++ simulators. The bit error rates, frame error probability and packet loss rates show close correlation with the analytical methods .i.e., over 99%, 92% and 80% respectively. Therefore the results of ABSOLUT framework for application layer outperform the results of performance evaluation approaches which employ virtual systems and at the same time provide as accurate estimates of the end-to-end delays and packet loss rate as network simulators. The results of the network simulators also vary in absolute values but they follow the same trend. Therefore, the extensions made to ABSOLUT allow the system designer to identify the potential bottlenecks in the system at different OSI model layers and evaluate the non-functional properties with a high level of accuracy. Also, if the system designer wants to focus entirely on the application layer, different models of computations can be easily instantiated on top of extended ABSOLUT framework to achieve higher simulation speeds as described in the thesis

Early validation of satellite COTS-on-board computing systems

International audienceThe competitive market of nano and micro satellites opens perspectives for use of COTS (Com-mercial Off-The-Shelf) electronic components. Current modular electronics design for embedded On-Board Computing systems (OBC) is being challenged by the integration of flexible Systems on Chip (SoC). The deployment of generic avionics and user/payload functionalities on these components is becoming increasingly complex, while Quality of Service must remain compliant with demanding requirements. It is therefore most important to estimate/evaluate those properties as early as possible, regarding a given ap-plication's deployment on a given COTS-based architecture. Model Based System Engineering (MBSE), while a leading practice in architecture description, may still require further study on its use for early evaluation , especially regarding analysis of emerging behaviors and qualitative model-based mapping of ap-plicative functions onto architectural platform. In this paper, we present methods to enhance MBSE design, helping the designer in evaluating candidate mappings and design choices by providing concrete quality measures. We focus on two aspects that were identified as critical in the ATIPPIC IRT project: first, the cost and conflicts in data communications in on-board and peripheral interconnects, which has a bottleneck impact on mapping choices; second, the availability of functions in case of resource failures (from solar radiations), to validate fault-mitigation techniques and estimate the (un)availability of the OBC system. We illustrate the approach on a simplified satellite model, abstracted from a design conceived in the ATIPPIC IRT project

The appendicular skeleton variability of the Sauropoda Titanosauria from the Upper Cretaceous of Lo Hueco (Cuenca, Spain)

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 24-01-2020Esta tesis tiene embargado el acceso al texto completo hasta el 24-07-2021En este volumen se presentan nuevos datos acerca del esqueleto apendicular de los titanosaurios del yacimiento Campano-Maastrichtiense de Lo Hueco (Cuenca, España). En este yacimiento se ha recuperado una muestra abundante de restos referidos a saurópodos titanosaurios, con varios ejemplares en conexión y decenas de ejemplares aislados. En esta muestra se identifica una elevada variabilidad morfológica en cada tipo de elemento apendicular y la presencia de ejemplares de pequeño tamaño. Hasta ahora solo se ha descrito en el yacimiento una forma exclusiva de titanosaurio, Lohuecotitan pandafilandi. No obstante, los estudios de los abundantes restos encontrados en el yacimiento habían permitido identificar dos morfotipos principales de dientes, dos tipos de basicraneos de titanosaurio, tres posibles morfotipos identificados en el esqueleto axial correspondiente a las vértebras dorsales, y cuatro morfotipos en el estudio de las vértebras caudales. En el presente estudio se explora la elevada variabilidad encontrada en la muestra de restos apendiculares. Para ello se utilizan una serie de técnicas analíticas relacionadas con el machine learning y la morfometría geométrica en 3D con el objetivo de identificar posibles morfotipos que ayuden a explicar esta variabilidad. Se desarrolla un flujo de trabajo de digitalización del ejemplar en 3D, proceso de restauración virtual en caso de ser ejemplares fragmentarios, y su posterior análisis estadístico. Mediante estas técnicas se determina la presencia de dos morfotipos principales. A partir de esta identificación, se procede a la cuantificación de la variabilidad intraespecífica en cada uno de ellos, así como la determinación de posibles secuencias ontogenéticas y la variabilidad debida a cambios durante el crecimiento del esqueleto apendicular de los titanosaurios. Algunos indicios apuntan a la que los dos morfotipos identificados en el yacimiento pertenecerían a dos gremios distintos que tendrían dos estrategias tróficas distintas. En el presente trabajo se discuten las posibles implicaciones en las diferencias morfológicas observadas entre ambos morfotipos principales. Se realiza un modelo aproximado con el que relacionar la morfología general de las extremidades en neosaurópodos con estos dos tipos de gremios y se relacionan los dos morfotipos principales con dos estrategias tróficas congruentes con los datos del estudio de material craneal. La variabilidad intraespecífica observada en cada morfotipo permite determinar sus implicaciones en la codificación de caracteres morfológicos apendiculares. En este trabajo se han identificado varias secuencias ontogenéticas relativas a cada tipo de elemento analizado. Se describe en detalle por primera vez las secuencias de transformaciones ontogenéticas en estos titanosaurios, así como el estadio y tiempo relativo en que se producen dichos cambios y sus implicaciones en las codificaciones de caracteres morfológicosIn the current dissertation a revision of new data of the appendicular skeleton of the Campanian-Maastrichtian fossil site of Lo Hueco (Cuenca, Spain) is presented. This fossil site have yielded an abundant sample of specimens referable to titanosaur sauropods, with several individuals partially articulated and tens of isolated specimens. There has been identified a high morphological variability in each appendicular element and the presence of several small-sized specimens in this sample. Until now, a single titanosaur exclusive form have been described, Lohuecotitan pandafilandi. However, the study of abundant isolated specimens from the fossil site have allowed to identify two main teeth morphotypes, two types of braincase, three morphotypes identified in the axial skeleton of the dorsal region, and four morphotypes among the caudal vertebrae. The current study explores the high variability found in the sample of appendicular elements. For this matter, a series of analytical techniques related with modern machine learning and 3D geometric morphometrics are used with the objective of identifying the probable morphotypes that help explain the morphological variance. A 3D digitizing workflow of the specimens of study is herein proposed, with a new proposal for virtual restoration of fragmentary elements and its incorporation to statistical analyses. Using these techniques it has been identified two main appendicular morphotypes. Based on this morphotypes, the intraspecific variability has been quantified in each of them, the ontogenetic sequences have been identified and the variability related to transformations during titanosaur ontogenetic development. Previous studies indicates that two titanosaur morphotype from Lo Hueco could have been pertain to two different guilds with two different types of feeding niche exploitation. In the current study, the implications of several morphological differences between both main morphotypes are discussed under the hypothesis of differences in the ecomorphological specialization. A statistical proxy model was created to test the relationships between main appendicular morphology with ecomorphological specialization related with the height of the feeding envelope among neosauropods. The results allow relating the two main morphotypes with two different feeding niche exploitation strategies congruent with previous analyses in the cranial material. The observed intraspecific variability in each morphotype allows determining its impact on morphological character scoring. In the current dissertation it has been identified the presence of several ontogenetic sequences in each morphotype. The ontogenetic sequences have been comprehensively described for first time in this group, as well as the ontogenetic stage and relative time estimation of the morphological character changes with implications for character scoringsEsta tesis fue realizada gracias a la Ayuda para Contratos Predoctorales para la Formación de Doctores BES-2013-065509 - Ministerio de Economía y Competitividad. Esta beca doctoral está asociada al Proyecto de Investigación CGL2012-35199 - Ministerio de Economía y Competitivida

A Model-Based Development and Verification Framework for Distributed System-on-Chip Architecture

The capabilities and thus, design complexity of VLSI-based embedded systems have increased tremendously in recent years, riding the wave of Moore’s law. The time-to-market requirements are also shrinking, imposing challenges to the designers, which in turn, seek to adopt new design methods to increase their productivity. As an answer to these new pressures, modern day systems have moved towards on-chip multiprocessing technologies. New architectures have emerged in on-chip multiprocessing in order to utilize the tremendous advances of fabrication technology. Platform-based design is a possible solution in addressing these challenges. The principle behind the approach is to separate the functionality of an application from the organization and communication architecture of hardware platform at several levels of abstraction. The existing design methodologies pertaining to platform-based design approach don’t provide full automation at every level of the design processes, and sometimes, the co-design of platform-based systems lead to sub-optimal systems. In addition, the design productivity gap in multiprocessor systems remain a key challenge due to existing design methodologies. This thesis addresses the aforementioned challenges and discusses the creation of a development framework for a platform-based system design, in the context of the SegBus platform - a distributed communication architecture. This research aims to provide automated procedures for platform design and application mapping. Structural verification support is also featured thus ensuring correct-by-design platforms. The solution is based on a model-based process. Both the platform and the application are modeled using the Unified Modeling Language. This thesis develops a Domain Specific Language to support platform modeling based on a corresponding UML profile. Object Constraint Language constraints are used to support structurally correct platform construction. An emulator is thus introduced to allow as much as possible accurate performance estimation of the solution, at high abstraction levels. VHDL code is automatically generated, in the form of “snippets” to be employed in the arbiter modules of the platform, as required by the application. The resulting framework is applied in building an actual design solution for an MP3 stereo audio decoder application.Siirretty Doriast