<p>Development of distributed real-time applications, in contrast to best effort applications, traditionally have been a slow process due to the lack of available standards, and the fact that no commercial off the shelf (COTS) distributed object computing (DOC) middleware supporting real-time requirements have been available to use, in order to speed up the development process without sacrificing any quality.</p><p>Standards and DOC middlewares are now emerging that are addressing key requirements of real-time systems, predictability and efficiency, and therefore, new possibilities such as component decomposition of real-time systems arises.</p><p>A number of component decomposed architectures of the distributed active real-time database system DeeDS is described and discussed, along with a discussion on the most suitable DOC middleware. DeeDS is suitable for this project since it supports hard real-time requirements and is distributed. The DOC middlewares that are addressed in this project are OMG's Real-Time CORBA, Sun's Enterprise JavaBeans, and Microsoft's COM/DCOM. The discussion to determine the most suitable DOC middleware focuses on real-time requirements, platform support, and whether implementations of these middlewares are available.</p>

<p>Admission controllers in dynamic real-time systems perform traditional schedulability tests in order to determine whether incoming tasks will meet their deadlines. These tests are computationally expensive and typically run in n * log n time where n is the number of tasks in the system. An incoming task might therefore miss its deadline while the schedulability test is being performed, when there is a heavy load on the system. In our work we evaluate a new approach for admission control in firm real-time systems. Our work shows that ANNs can be used to perform a schedulability test in order to work as an admission controller in firm real-time systems. By integrating the ANN admission controller to a real-time simulator we show that our approach provides feasible performance compared to a traditional approach. The ANNs are able to make up to 86% correct admission decisions in our simulations and the computational cost of our ANN schedulability test has a constant value independent of the load of the system. Our results also show that the computational cost of a traditional approach increases as a function of n log n where n is the number of tasks in the system.</p>

<p>This work aims to investigate the state of the art in test case generation for real-time systems, to analyze existing methods, and to propose future research directions in this area. We believe that a combination of design for testability, automation, and sensible test case selection is the key for verifying modern real-time systems. Existing methods for system-level test case generation for real-time systems are presented, classified, and evaluated against a real-time system model. Significant for real-time systems is that timeliness is crucial for their correctness. Our system model of the testing target adopts the event-triggered design paradigm for maximum flexibility. This paradigm results in target systems that are harder to test than its time-triggered counterpart, but the model improves testability by adopting previously proposed constraints on application behavior. This work investigates how time constraints can be tested using current methods and reveals problems relating to test-case generation for verifying such constraints. Further, approaches for automating the test-case generation process are investigated, paying special attention to methods aimed for real-time systems. We also note a need for special test-coverage criteria for concurrent and real-time systems to select test cases that increase confidence in such systems. We analyze some existing criteria from the perspective of our target model. The results of this dissertation are a classification of methods for generating test cases for real-time systems, an identification of contradictory terminology, and an increased body of knowledge about problems and open issues in this area. We conclude that the test-case generation process often neglects the internal behavior of the tested system and the properties of its execution environment as well as the effects of these on timeliness. Further, we note that most of the surveyed articles on testing methods incorporate automatic test-case generation in some form, but few consider the issues of automated execution of test cases. Four high-level future research directions are proposed that aim to remedy one or more of the identified problems.</p>

<p>In this dissertation, we consider the problem of recovering a crashed node in a distributed database. We especially focus on real-time recovery in eventually consistent databases, where the consistency of replicated data is traded off for increased predictability, availability and performance. To achieve this focus, we consider consistency preservation techniques as well as recovery mechanisms.</p><p>Our approach is to perform a thorough literature survey of these two fields. The literature survey considers not only recovery in real-time, distributed, eventually consistent databases, but also related techniques, such as recovery in main-memory resident or immediately consistent databases. We also examine different techniques for consistency preservation.</p><p>Based on this literature survey, we present a taxonomy and state-of-the-art report on recovery mechanisms and consistency preservation techniques. We contrast different recovery mechanisms, and highlight properties and aspects of these that make them more or less suitable for use in an eventually consistent database. We also identify unexplored areas and uninvestigated problems within the fields of database recovery and consistency preservation. We find that research on real-time recovery in distributed databases is lacking, and we also propose further investigation of how the choice of consistency preservation technique affects (or should affect) the design of a recovery mechanism for the system.</p>

<p>Simulation is a good way to gain insight into a system, for example during development, without having to run or build the actual system. This is especially true for real-time systems, which often operate in hazardous environments or control critical entities in the 'real' world, making testing of these systems in their real environment unsafe during development.</p><p>When building simulations, one simulator is not likely to fit every type of simulation project. Therefore, different simulators, which focus on different aspects of simulation, are built. The High Level Architecture (HLA) from the Defense Modeling and Simulation Office (DMSO) is an architecture for distributed simulations providing a means to communicate between different simulations.</p><p>However, the HLA standard has limitations if viewed from a real-time perspective. For example, there is no built-in support for fault tolerance. In this thesis some of the limitations in HLA are identified and an extended architecture that uses a distributed active real-time database as a way to overcome these limitations is presented. One of the major advantages with this new extended HLA architecture is that it is still compliant with HLA, i.e., no modifications have been made to the HLA interfaces.</p>

<p>Real-time systems are required to answer to external stimuli within a specified time-period. For this to be possible, the systems behaviour must be predictable. The use of active databases in real-time systems introduces unpredictability in the system, e.g. due to their use of active rules. The behaviour in active databases is usually specified in ECA-rules. Sets of ECA-rules are hard to analyse, which implies that the behaviour of the ECA-rule set is hard to predict.</p><p>The purpose of this project is to evaluate the ability to support the development of a predictable ECA-rule set. Using a formal method for the specification task is desirable, since a formal specification is analysable and can be proven correct. In this project, timed-automata are used for specifying the systems behaviour. A method for deriving predictable ECA-rules from a timed-automaton specification is developed, and successfully applied on a case-study specification. For this case-study specification, a set of ECA-rules preserving the analysed behaviour of the timed-automata specification is derived.</p>

<p>In a distributed real-time environment where it is imperative to make correct decisions it is important to have all facts available to make the most accurate decision in a certain situation. An example of such an environment is an Unmanned Aerial Vehicle (UAV) system where several UAVs cooperate to carry out a certain task and the data recorded is analyzed after the completion of the mission. This project aims to define and implement a time series architecture for use together with a distributed real-time database for the ability to store temporal data. The result from this project is a time series (TS) architecture that uses DeeDS, a distributed real-time database, for storage. The TS architecture is used by an application modelled from a UAV scenario for storing temporal data. The temporal data is produced by a simulator. The TS architecture solves the problem of storing temporal data for applications using DeeDS. The TS architecture is also useful as a foundation for integrating time series in DeeDS since it is designed for space efficiency and real-time requirements.</p>

<p>Visualization of large scale time-varying volumetric datasets is an active topic of research. Technical limitations in terms of bandwidth and memory usage become a problem when visualizing these datasets on commodity computers at interactive frame rates. The overall objective is to overcome these limitations by adapting the methods of an existing Direct Volume Rendering pipeline. The objective is considered to be a proof of concept to assess the feasibility of visualizing large scale time-varying datasets using this pipeline. The pipeline consists of components from previous research, which make extensive use of graphics hardware to visualize large scale static data on commodity computers.</p><p>This report presents a diploma work, which adapts the pipeline to visualize flow features concealed inside the large scale Computational Fluid Dynamics dataset. The work provides a foundation to address the technical limitations of the commodity computer to visualize time-varying datasets. The report describes the components making up the Direct Volume Rendering pipeline together with the adaptations. It also briefly describes the Computational Fluid Dynamics simulation, the flow features and an earlier visualization approach to show the system’s limitations when exploring the dataset.</p>

Title from PDF of title page. / Document formatted into pages; contains 93 pages. / Thesis (M.S.Cp.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The increasing application of cryptographic algorithms to ensure secure communications across virtual networks has led to an ever-growing demand for high performance hardware implementations of the encryption/decryption methods. The inevitable inclusion of the cryptographic algorithms in network communications has led to the development of several encryption standards, one of the prominent ones among which, is the Rijndael, the Advanced Encryption Standard. Rijndael was chosen as the Advanced Encryption Standard (AES) by the National Institute of Standard and Technology (NIST), in October 2000, as a replacement for the Data Encryption Standard (DES). This thesis presents the architecture for the VLSI implementation of the Rijndael, the Advanced Encryption Standard algorithm. Rijndael is an iterated, symmetric block cipher with a variable key length and block length. The block length is fixed at 128 bits by the AES standard [4]. / ABSTRACT: The key length can be designed for 128,192 or 256 bits. The VLSI implementation, presented in this thesis, is based on a feed-back logic and allows a key length specification of 128-bits. The present architecture is implemented in the Electronic Code Book(ECB) mode of operation. The proposed architecture is further optimized for area through resource-sharing between the encryption and decryption modules. The architecture includes a Key-Scheduler module for the forward-key and reverse-key scheduling during encryption and decryption respectively. The subkeys, required for each round of the Rijndael algorithm, are generated in real-time by the Key-Scheduler module by expanding the initial secret key. The proposed architecture is designed using the Custom-Design Layout methodology with the Cadence Virtuoso tools and tested using the Avanti Hspice and the Nanosim CAD tools. / ABSTRACT: Successful implementation of the algorithm using iterativearchitecture resulted in a throughput of 232 Mbits/sec on a 0.35[mu] CMOS technology. Using 0.35[mu] CMOS technology, implementation of the algorithm using pipelining architecture resulted in a throughput of 1.83 Gbits/sec. The performance of this implementation is compared with similar architectures reported in the literature. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Mehr und mehr werden neue und dabei zunehmend multimediale Anwendungen fuer das Internet entwickelt und eingesetzt. In gleichem Masze wachsen auch die Qualitaetsanforderungen an diese Dienste. So gibt sich heute niemand mehr mit reiner ASCII--Text--Uebertragung von Informationen zufrieden. E-Mails werden mit MIME--Attachments versendet, Web--Seiten mit unzaehligen Grafiken ansehnlicher gemacht, und Konferenzen in Datennetzen erheben den Anspruch auf Audio-- und Video--Uebertragung in Echtzeit. Fuer Provider stellt sich hier nun das Problem der Finanzierung. Gegenstand dieser Arbeit ist es, anhand des Szenarios des Internet--Service--Providers ¨Freie Presse Online¨ ein Tarifmodell zu entwickeln, welches mittels Ressourcensteuerung arbeitet. Es soll ein Anreizsystem etabliert werden, um eine effizientere Ausnutzung der Ressourcen zu erzielen. Die finanzielle Grundlage bildet Prepayment. Die Einflusznahme geschieht nicht mittels veraenderlicher Entgelte, sondern direkt auf die dem Nutzer zur Verfuegung gestellten Ressourcen (Bandbreite, Verzoegerungszeit). Fuer den Entwurf des Modells werden Anleihen bei artverwandten Modellen genommen, so zum Beispiel bei der Tarifierung von elektrischer Energie, da die beiden Ressourcen Bandbreite (in Datennetzen) und Energie (in Stromnetzen) markante Aehnlichkeiten aufweisen. Weiterhin wird eine Analyse des Verhaltens der Nutzer im Bezug auf die Dauer und Tageszeit der Nutzung, Datenvolumen und Lastkurven durchgefuehrt. Die Analyse und das Accounting werden mittels der von der Real Time Flow Measurement Group vorgeschlagenen Architektur realisiert. Konkret kommt die Referenz-- Implementation NeTraMet zum Einsatz.