Encontrados 19 documentos, a visualizar página 1 de 2
Integração de sistemas de comunicação : caracterização funcional de novos servi...
Neves, Joaquim E.Com a progressiva integração de serviços de voz, vídeo e dados, em novos sistemas de comunicação, resultantes da convergência tecnológica das tradicionais redes locais de computador e das redes públicas de telecomunicações, tem sido possível satisfazer os requisitos específicos das aplicações telemáticas, recorrendo a capacidades e protocolos de transmissão e de comutação adequados aos diferentes níveis de ...
Scheduling algorithms to support QoS and service integration in sensor and actu...
Cabral, José; Rocha, J. G.; Neves, Joaquim E.; Ruela, JoséIn this paper we analyse and evaluate several Scheduling Algorithms that are candidates to support Quality of Service and Service Integration in Sensor and Actuator Networks. They should satisfy two main goals: to guarantee committed delays for time sensitive services, and to improve the network transmission efficiency. The algorithms are described and some results, obtained by simulation, are presented. The pr...
A system architecture for low bit rate traffic aggregation in control applications
Cabral, José; Rocha, J. G.; Neves, Joaquim E.; Ruela, JoséThis paper describes the results of research work aimed at providing an efficient solution to the aggregation of low bit rate traffic in control applications. It includes the proposal and analysis of an architecture that integrates Terminal Adapters and a Concentrator connected to a remote Control Application through a communication network. The ATM technology was selected to implement the proposed system due t...
Ensino das Tecnologias de Comunicação : a oportunidade de Bolonha?
Neves, Joaquim E.O processo de Bolonha, só por si, constitui motivação suficiente para abordar alguns aspectos mais ou menos problemáticos no ensino de tecnologias da informação e comunicação. Este artigo reflecte a articulação dos diferentes graus académicos com as condições de acesso, as durações da respectivos ciclos de escolaridade, e com a integração dos resultados da aprendizagem no sistema europeu de créditos curricula...
Fast retransmission of real-time traffic in HIPERLAN/2 systems
Afonso, José A.; Neves, Joaquim E.Automatic repeat request (ARQ) schemes are effective to recover non-real-time data corrupted by channel errors, but their use with real-time traffic is seldom considered because packet retransmissions tend to increase the delay beyond the deadline. However, the high-speed of modern wireless local area networks, together with their inherent low propagation times, favors the use of ARQ schemes with real-time traf...
Adaptador de terminal e concentrador ATM, baseado num PC com sistema operativo ...
Cabral, José; Rocha, J. G.; Neves, Joaquim E.; Ruela, JoséEspecificação de uma Arquitectura para Adaptação de Tráfego de Baixo Débito em redes de comunicação. O sistema é constituído por um Adaptador de terminal e por um Concentrador ligados, através de uma rede de comunicação a uma Aplicação de controlo. A especificação é feita em linguagem C usando o sistema operativo Linux. São apresentados resultados de testes efectuados ao Adaptador de terminal e ao Concentrador....
Scheduling of real-time traffic in IEEE 802.11 networks
Afonso, José A.; Neves, Joaquim E.Real-time applications require the provision of time-bounded services from the network, however, the scheduling algorithms used in wired networks are not suitable for wireless networks because they assume that the channel is error free. Besides, the scheduler has only a limited knowledge of the arrival processes of the uplink traffic. In this paper, we propose scheduling algorithms for the transport of real-tim...
New packet fragmentation for S-link to giiga bit ethernet adapter
Neves, Joaquim E.; Neufeld, Niko; Jacobsson, Richard; Jost, BeatHigh Speed Interconnect (HSI) systems are essential in order to transport the large amount of data generated by the detectors, to storage devices in high energy physics experiments. The integration of a new packet fragmentation mechanism on the S-Link to Gigabit Ethernet Adapter will permit not only the physical interconnection between involved interfaces, but also the conversion of data formats and transmissio...
S-link to giga bit ethernet adapter- new frame segmentation for LHCb data acqui...
Neves, Joaquim E.; Jacobsson, Richard; Neufeld, Niko; Jost, BeatData Acquisition and Control Systems used in high energy physics experiments, such as those which will take place in the Large Hadron Collider (LHC) at CERN, require the specification of data formats and transmission protocols as well as the use of high speed links and interfaces. In this context, a new Frame Segmentation process will be presented and discussed, based on data formats adopted by the LHCb experie...
Performance simulation of HIPERLAN/2 with low debit traffic for real time data ...
Afonso, José A.; Neves, Joaquim E.Wireless local area networks can be suitable for remote interconnection of different data acquisition and control systems over a standardized telecommunications network, using several communication technologies, such as ISDN, ATM or IP. This paper presents an overview of the HIPERLAN/2 specifications as well as simulation results of this system, with channel errors and mixed traffic generated by control applic...
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