No description available.

Priority schemes employing the inherent properties of carrier-sense multiple-access (CSMA) schemes are investigated and then applied to the integrated transmission of voice and data. A priority scheme composed of 1-persistent and non-persistent CSMA protocols is proposed. The throughput and delay characteristics of this protocol are evaluated by mathematical analysis and simulation, respectively. The approach of throughput analysis is further extended to another more general case, p-persistent CSMA with two persistency factors, the throughput performance of which had not been analyzed before. Simulations are carried out to study the delay characteristics of this protocol. After careful consideration of the features of the priority schemes studied, two protocols are proposed for integrated voice and data transmission. While their ultimate purpose is for integrated services, they have different application. One of them is applied to local area network; the other is suitable for packet radio network. The distinctive features of the former are simplicity and flexibility. The latter is different from other studies in that collision detection is not required, and that it has small mean and variance of voice packet delay. Performance characteristics of both of these protocols are examined by simulations under various system parameter values. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Master 's thesis deals about computer networks, which constitutes a global communication structure and play a very important role in today's society. The rapid development of Internet, the emergence of new multimedia applications and their increasing use of calls to the efficient functioning of the creation of such governance mechanisms of transmission, which are able to secure the required parameters. The thesis deals about the issue of quality of service (QoS) in IP networks. It presents the basic characteristics and requirements of these networks for the transmission of sensitive data by the quality of services, deals with the QoS definition, and describes the essential parameters to be followed to achieve the required quality of service in practical deployment. In addition, lists the various principles and options to ensure QoS in computer networks. Generally, it represents the Cisco 1841 router features and options to ensure quality of service in the network based on these routers. Practical thesis part provides two types of model IP networks, which were designed in order to verify the impact of service quality in real practice. Of the known methods to ensure QoS, which include a mechanism of Integrated services, Differentiated services, it focus its content about the Differentiated Services and the implementation of these in proposed network model. The last part of the work presents the results obtained by the impact of quality of service for the applications and their assessment.

Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

Our research addresses two important problems that arise in modern large-scale distributed systems: 1. The necessity to virtualize their data flows by applying actions such as filtering, format translation, coalescing or splitting, etc. 2. The desire to separate such actions from application level logic, to make it easier for future service-oriented codes to inter-operate in diverse and dynamic environments. This research considers the runtimes of the `information appliances used for these purposes, particularly with respect to their ability to provide diverse levels of Quality of Service (QoS) in lieu of dynamic application behaviors and the consequent changes in the resource needs of their data flows. Our specific contribution is the enrichment of these runtimes with methods for QoS-awareness, thereby giving them the ability to deliver desired levels of QoS even under sudden requirement changes IQ-appliances. For experimental evaluation, we enrich a prototype implementation of an IQ-appliance, based on the Intel IXP network processor, with the additional functionality needed to guarantee QoS constraints for diverse data streams. Measurements demonstrate the feasibility and utility of the approach. Further, we enhance the Self-Virtualized Network Interface developed in previous work from our group with QoS awareness and demonstrate the importance of such functionality in end-to-end virtualized infrastructures.

No description available.

Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 107-112.

Thesis (M. Eng.)--Carleton University, 1999. / Also available in electronic format on the Internet.

Made available in DSpace on 2015-04-22T22:00:47Z (GMT). No. of bitstreams: 1 jose.pdf: 2255469 bytes, checksum: cebe37770c4719e5ebf2b60e4ae0d2a6 (MD5) Previous issue date: 2013-06-07 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Currently, the majority of multicarrier transmission systems are based on the Fourier transform, which is used as frequency multiplexing technique. The main advantages of this approach include multipath immunity and low computational complexity, due to the use of a family of fast algorithms, known as Fast Fourier Transform (FFT). However, when used to provide a robust transmission, this technique presents some disadvantages, like the need for a cyclic prefix, which demands part of the useful datarate. In this work, a study for verifying the possibility of replacing the FFT, by the wavelet transform, was carried out, which has the potential to raise some advantages, such as the removal of the cyclic prefix and a simpler synchronization procedure. A computational model for the transmission layer of the Integrated Services Digital Broadcasting Terrestrial, Brazilian version (ISDB-Tb) was created, aiming to provide a direct comparison between two versions: the traditional one, which is based on FFT, and a new proposal, which is based on wavelets. Such an evaluation was performed through the relation between error bit rate and signal-to-noise ratio, in additive white gaussian noise, Rayleigh and Rician fading and also in frequency-selective Rayleigh fading channels. Similar comparisons were also performed for the ETSI TS 101 475 (HIPERLAN-2) and Digital Video Broadcasting Terrestrial (DVB-T) systems. The simulation results show that the wavelet-based systems present a similar performance, when compared with the FFT-based ones, for the chosen channel models, and without employing a cyclic prefix, which allows a more efficiente spectrum use. / Atualmente, uma grande parte dos sistemas de transmissão multiportadoras é baseada na transformada de Fourier, como técnica de multiplexação em frequência. Dentre as suas principais vantagens, encontram-se a imunidade a multipercursos e a baixa complexidade computacional, através de algoritmos rápidos conhecidos como Fast Fourier Transform (FFT). Esta técnica, entretanto, para proporcionar uma transmissão robusta, apresenta a desvantagem de exigir prefixo cíclico, o que resulta no consumo de uma fatia do espectro útil. Neste trabalho, um estudo para se verificar a viabilidade de substituição da FFT pela transformada wavelet foi realizado, o que promete trazer algumas vantagens, tais como a não exigência de prefixo cíclico e uma sincronização mais simples. Um modelo computacional para a camada de transmissão do Integrated Services Digital Broadcasting - Terrestrial, Brazilian version (ISDB-Tb) foi criado, com o objetivo de proporcionar uma comparação entre duas versões: a atual, baseada em FFT, e uma nova proposta, baseada em wavelets. Tal avaliação foi realizada em termos das curvas de taxa de erro de bit versus relação sinal ruído, em canais com adição de ruído gaussiano branco, com desvanecimento plano de Rayleigh e Rice e também com desvanecimento seletivo em frequência de Rayleigh. Comparações similares também foram realizadas para os sistemas ETSI TS 101 475 (HIPERLAN-2) e Digital Video Broadcasting Terrestrial (DVB-T). Os resultados obtidos mostram que os sistemas baseados em wavelets apresentam desempenhos similares aos dos baseados em FFT, para os modelos de canal simulados, com a vantagem adicional de não utilizarem prefixo cíclico, o que promove um uso mais eficiente do espectro.