73 research outputs found

    A comparison of some performance evaluation techniques

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    In this thesis we look at three approaches to modelling interactive computer systems: Simulation, Operational analysis and Performance-Oriented design. The simulation approach, presented first, is applied to a general purpose, multiprogrammed, machine independent, virtual memory computer system. The model is used to study the effects of different performance parameters upon important performance indices. It is also used to compare or validate the results produced by the other two methods. The major drawback of the simulation model (i.e. its relatively high cost) has been overcome by combining regression techniques with simulation, using simple experimental case studies. Next, operational analysis was reviewed in a hierarchical way (starting by analysing a single-resource queue and ending up by analysing a multi-class customer general interactive system), to study the performance model of general interactive systems. The results of the model were compared with the performance indices produced using the simulation results. The performance-oriented design technique was the third method used for building system performance models. Here, several optimization design problems have been reviewed to minimize the response time or maximize the system throughput subject to a cost constraint. Again, the model results were compared with the simulation results using different cost constraints. We suggest finally, that the above methods should be used together to assist the designer in building computer performance models

    Beyond Transmitting Bits: Context, Semantics, and Task-Oriented Communications

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    Communication systems to date primarily aim at reliably communicating bit sequences. Such an approach provides efficient engineering designs that are agnostic to the meanings of the messages or to the goal that the message exchange aims to achieve. Next generation systems, however, can be potentially enriched by folding message semantics and goals of communication into their design. Further, these systems can be made cognizant of the context in which communication exchange takes place, thereby providing avenues for novel design insights. This tutorial summarizes the efforts to date, starting from its early adaptations, semantic-aware and task-oriented communications, covering the foundations, algorithms and potential implementations. The focus is on approaches that utilize information theory to provide the foundations, as well as the significant role of learning in semantics and task-aware communications

    An Experiment in the complexity of load balancing algorithms

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    Beyond Transmitting Bits: Context, Semantics, and Task-Oriented Communications

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    Communication systems to date primarily aim at reliably communicating bit sequences. Such an approach provides efficient engineering designs that are agnostic to the meanings of the messages or to the goal that the message exchange aims to achieve. Next generation systems, however, can be potentially enriched by folding message semantics and goals of communication into their design. Further, these systems can be made cognizant of the context in which communication exchange takes place, providing avenues for novel design insights. This tutorial summarizes the efforts to date, starting from its early adaptations, semantic-aware and task-oriented communications, covering the foundations, algorithms and potential implementations. The focus is on approaches that utilize information theory to provide the foundations, as well as the significant role of learning in semantics and task-aware communications.Comment: 28 pages, 14 figure

    Обзор подходов к организации физического уровня в СУБД

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    In this paper we survey various DBMS physical design options. We will consider both vertical and horizontal partitioning, and briefly cover replication. This survey is not limited only to local systems, but also includes distributed ones. The latter adds a new interesting question — how to actually distribute data among several processing nodes. Aside from theoretical approaches we consider the practical ones, implemented in any contemporary DBMS. We cover these aspects not only from user, but also architect and programmer perspectives.В данной работе мы рассмотрели различные методы организации физического уровня СУБД: вертикальное и горизонтальное фрагментирование, а также вкратце нами затронут вопрос репликации. Указанные методы были рассмотрены не только для локальных, но и для распределенных СУБД. Последним было уделено повышенное внимание: были рассмотрены методы размещения данных на узлах распределенной системы. Кроме теоретических работ, приведены работы практического характера, в которых освещены вопросы применения вышеуказанных методов в современных коммерческих СУБД. Они были рассмотрены как с позиции пользователя, так и с позиций архитектора и программиста СУБ

    Event processing in web of things

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    The incoming digital revolution has the potential to drastically improve our productivity, reduce operational costs and improve the quality of the products. However, the realization of these promises requires the convergence of technologies — from edge computing to cloud, artificial intelligence, and the Internet of Things — blurring the lines between the physical and digital worlds. Although these technologies evolved independently over time, they are increasingly becoming intertwined. Their convergence will create an unprecedented level of automation, achieved via massive machine-to-machine interactions whose cornerstone are event processing tasks. This thesis explores the intersection of these technologies by making an in-depth analysis of their role in the life-cycle of event processing tasks, including their creation, placement and execution. First, it surveys currently existing Web standards, Internet drafts, and design patterns that are used in the creation of cloud-based event processing. Then, it investigates the reasons for event processing to start shifting towards the edge, alongside with the standards that are necessary for a smooth transition to occur. Finally, this work proposes the use of deep reinforcement learning methods for the placement and distribution of event processing tasks at the edge. Obtained results show that the proposed neural-based event placement method is capable of obtaining (near) optimal solutions in several scenarios and provide hints about future research directions.A nova revolução digital promete melhorar drasticamente a nossa produtividade, reduzir os custos operacionais e melhorar a qualidade dos produtos. A concretizac¸ ˜ao dessas promessas requer a convergˆencia de tecnologias – desde edge computing à cloud, inteligência artificial e Internet das coisas (IoT) – atenuando a linha que separa o mundo físico do digital. Embora as quatro tecnologias mencionadas tenham evoluído de forma independente ao longo do tempo, atualmente elas estão cada vez mais interligadas. A convergência destas tecnologias irá criar um nível de automatização sem precedentes.The research published in this work was supported by the Portuguese Foundation for Science and Technology (FCT) through CEOT (Center for Electronic, Optoelectronic and Telecommunications) funding (UID/MULTI/00631/2020) and by FCT Ph.D grant to Andriy Mazayev (SFRH/BD/138836/2018)

    Second year technical report on-board processing for future satellite communications systems

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    Advanced baseband and microwave switching techniques for large domestic communications satellites operating in the 30/20 GHz frequency bands are discussed. The nominal baseband processor throughput is one million packets per second (1.6 Gb/s) from one thousand T1 carrier rate customer premises terminals. A frequency reuse factor of sixteen is assumed by using 16 spot antenna beams with the same 100 MHz bandwidth per beam and a modulation with a one b/s per Hz bandwidth efficiency. Eight of the beams are fixed on major metropolitan areas and eight are scanning beams which periodically cover the remainder of the U.S. under dynamic control. User signals are regenerated (demodulated/remodulated) and message packages are reformatted on board. Frequency division multiple access and time division multiplex are employed on the uplinks and downlinks, respectively, for terminals within the coverage area and dwell interval of a scanning beam. Link establishment and packet routing protocols are defined. Also described is a detailed design of a separate 100 x 100 microwave switch capable of handling nonregenerated signals occupying the remaining 2.4 GHz bandwidth with 60 dB of isolation, at an estimated weight and power consumption of approximately 400 kg and 100 W, respectively
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