面對通訊與資訊科技的大幅進步、網際網路的蓬勃發展、以及電信自由化帶來的激烈競爭，通訊網路正在進行一個巨大的變革，企圖將原有Circuit Switching 與 Packet Switching 網路整合成一個單一整合型網路－All-IP網路以支援所有的應用服務。All-IP網路受限於封包交換網路原有的特性，有服務品質問題（QoS）有待克服，因此有必要在All-IP網路上提供服務品質管理機制以實現整合型網路的目標。而要提供適當的QoS 管理，其成功之關鍵主要在於是否能提供一個簡單易行之架構。本論文先提出BBQ(Budget-Based QoS)採用以預算為基礎之服務品質管理，以簡化管理、追求效率，不增加管理複雜度為原則。BBQ提供一個高適用性的管理架構和相關的管理工具，可適用於不同的下層網路架構和不同營運目標的網管政策。 本論文為提出在BBQ管理系統中之端對端服務品質解決方案。透過承載服務的概念，端對端之服務由接取網路和骨幹網路之承載服務提供支援。本論文依據分層負責的精神提出一系列的資源規劃及路徑建構方式，提高網路資源運用效率，並可快速的以即時方式建構具服務品質保證的端對端路徑給使用者。骨幹網路由許多核心網路相連而成，各個核心網路各自獨立規劃內部路徑而端對端的路徑規劃只需選擇所欲通過的核心網路即可，計算量可大幅降低，因此可適用即時的路徑建構。路徑規劃之研究重心為如何挑選最佳核心網路路徑，以規劃具服務品質之端對端路徑並可達到資源之最有效利用。 / The advance in communication and information technology and impact of telecommunication liberalization cause a revolution in telecommunication world. It attempt to merge circuit-switching and packet-switching network into one standalone perform. All-IP is one of those candidates. But All-IP also inherit the characteristics of packet-switching network, the problem of transmission quality. So, we need some management system of quality on All-IP network to achieve the ambition of converged network. In this thesis, we propose BBQ management system. BBQ offers a highly adaptive management architecture and some management tools for operators. Those tools can be used in different underlying network layer and can tune network by different network policy. We propose an End-to-End QoS solution in BBQ management system. By the concept of bearer services, we separate the End-to-End service into Backbone and Stub Network bearer services. According to the hierarchical management, we propose an approach for resource and path planning in order to enhance network efficiency and provide End-to-End path with QoS in real time. Because Backbone Network is connected by Core Networks and each Core Network plans its internal path independently, End-to-End path planning is to choose Core Networks to pass through. This scheme could reduce the enormous computation and fit for real time path setup. The key point of path planning is how to choose the better Core Network path to compose End-to-End path with QoS and reach efficient resource utilization.

[pt] Esta Tese visa explorar as oportunidades de melhoria do desempenho dos Sistemas Automáticos de Reconhecimento de voz com amplo vocabulário para o Português Brasileiro quando aplicados em um cenário distribuído (Reconhecimento de Voz Distribuído). Com esta finalidade, foi construída uma base de vozes para reconhecimento de voz contínua para o Português Brasileiro com 100 locutores, cada um falando 1000 frases foneticamente balanceadas. A gravação foi realizada em estúdio, ambiente sem ruído, com uma especificação de gravação que pudesse abranger a entrada dos diversos codificadores de voz utilizados em Telefonia Móvel Celular e IP, em particular os codecs ITU-T G.723.1, AMR-NB e AMR-WB. Para um bom funcionamento dos Sistemas Automáticos de Reconhecimento de voz é necessário que os atributos de reconhecimento sejam obtidos a uma taxa elevada, porém os codificadores de Voz para Telefonia IP e Móvel Celular normalmente geram seus parâmetros a taxas mais baixas, o que degrada o desempenho do reconhecedor. Usualmente é utilizada a interpolação linear no domínio das LSFs (Line Spectral Frequencies) para resolver este problema. Nesta Tese foi proposta a realização da interpolação com a utilização de um Filtro Digital Interpolador que demonstrou ter um desempenho de reconhecimento muito superior ao da interpolação linear. Foi avaliado também o uso das ISFs (Immittance Spectral Frequencies) interpoladas como atributo de reconhecimento, as quais se mostraram inadequadas para esta finalidade, assim como as LSFs. Outro aspecto de fundamental importância para os reconhecedores de voz distribuídos é a recuperação de perda de pacotes, que tem impacto direto no desempenho de reconhecimento. Normalmente os codificadores inserem zeros nos pacotes perdidos ou interpolam linearmente os pacotes recebidos visando restaurar estes pacotes. Foi proposta nesta tese uma nova técnica baseada em Redes Neurais que se mostrou mais eficiente na restauração destes pacotes com a finalidade da realização do reconhecimento. / [en] This Thesis aims at exploring several approaches for performance improvement of the Automatic Speech Recognition System with large vocabulary for the Brazilian Portuguese when applied in a distributed scenario (Distributed Speech Recognition). With this purpose, a speech database for continuous speech recognition for the Brazilian Portuguese with 100 speakers was constructed, each one uttering 1000 phonetic balanced sentences. The recording was carried out in a studio (environment without noise) with a specification of recording that would be able to allow the input of several speech codecs in Cellular Mobile Telephony and IP Networks, in particular the ITU-T G.723.1, AMR-NB and AMR-WB. In order to work properly, Automatic Speech Recognition Systems require that the recognition features be extracted at a high rate. However, the Speech codecs for Cellular Mobile Telephony and IP Networks normally generate its parameters at lower rates, which degrades the performance of the recognition system. Usually the linear interpolation in the LSF (Line Spectral Frequencies) domain is used to solve this problem. In this Thesis the accomplishment of the interpolation with the use of a Digital Filter Interpolator was proposed and demonstrated to have a higher performance than the linear interpolation in recognition systems. The use of the interpolated ISFs (Immittance Spectral Frequencies) was also evaluated as recognition feature, which had shown to be inadequate for this purpose, as well as the LSFs. Another very important aspect for the distributed speech recognizers is the recovery of lost packets, that has direct impact in the recognition performance. Normally the coders insert zeros in the lost packets or interpolate linearly the received packets aiming to restore them. A new technique based on Neural Networks was proposed in this thesis that showed to be more efficient in the restoration of these lost packets with the purpose of speech recognition.

Αντικείμενο της παρούσας Διατριβής είναι η μελέτη της απόδοσης και η εισαγωγή νέων χαρακτηριστικών σε μοντέλα για την παροχή υπηρεσιών με εγγυήσεις ποιότητας στα σύγχρονα IP δίκτυα καθώς και η εισαγωγή των απαραίτητων επιχειρησιακών λειτουργιών για την εφαρμογή των μοντέλων αυτών, με στόχο τη βελτίωση της απόδοσης. Ακολουθώντας μια καταγραφή και αξιολόγηση των μηχανισμών και αρχιτεκτονικών που εισάγουν τη διαφοροποίηση εξυπηρέτησης στα IP δίκτυα, η μελέτη που παρουσιάζεται εδώ ακολουθεί σε όλα της τα στάδια τις αρχές της αρχιτεκτονικής DiffServ, η οποία επιτρέπει την παροχή ενός συγκεκριμένου εύρους υπηρεσιών με εγγυήσεις ποιότητας σε συναθροίσεις ροών και περιορίζει την πολυπλοκότητα στα όρια του δικτύου. Η απόδοση και η αποτελεσματικότητα των μηχανισμών και λειτουργιών διαφοροποίησης εξυπηρέτησης με βάση την αρχιτεκτονική DiffServ αξιολογούνται με βάση την εξασφάλιση εγγυημένης χωρητικότητας, φραγμένης από-άκρο-σε-άκρο καθυστέρησης, ελαχιστοποιημένων απωλειών πακέτων και φραγμένου jitter. Ωστόσο, σε κάθε μοντέλο υπηρεσίας για την παροχή QoS, τονίζεται η σημασία της εξασφάλισης των καλύτερων δυνατών εγγυήσεων ποιότητας με την ελάχιστη δυνατή πολυπλοκότητα. Τα διαφορετικά μοντέλα υπηρεσιών θέτουν συγκεκριμένους στόχους λαμβάνοντας υπόψη τις ανάγκες των εφαρμογών στις οποίες απευθύνονται. Οι δύο επικρατέστερες κατηγορίες υπηρεσιών στα πλαίσια της αρχιτεκτονικής DiffServ είναι η κατηγορία των υπηρεσιών μέγιστης προτεραιότητας και η κατηγορία των υπηρεσιών εγγυημένης χωρητικότητας σε συνθήκες συμφόρησης. Στην πρώτη κατηγορία, προτείνεται το μοντέλο υπηρεσίας Gold, το οποίο ακολουθεί τις αρχές τις αρχιτεκτονικής DiffServ για να παρέχει βέλτιστη ποιότητα εξυπηρέτησης σε συναθροίσεις IP ροών, ενώ ταυτόχρονα μπορεί να εφαρμοστεί πρακτικά σε δίκτυα παραγωγής. Στη δεύτερη κατηγορία, προτείνεται το μοντέλο υπηρεσίας Relative για την παροχή υπηρεσιών εγγυημένης χωρητικότητας σε συνθήκες συμφόρησης, με βασικά χαρακτηριστικά την μείωση της υπολογιστικής πολυπλοκότητας και την βελτίωση της δικαιοσύνης μεταξύ των εξυπηρετούμενων TCP ροών. Η υπηρεσία Gold διατηρεί την αρχή της επεκτασιμότητας και παρέχει αυστηρές εγγυήσεις ποιότητας αλλά ταυτόχρονα επιτρέπει την εφαρμογή μηχανισμού ελέγχου αποδοχής νέων αιτημάτων χωρίς διακοπή της λειτουργίας του δικτύου. Eισάγει επίσης ένα νέο χαρακτηριστικό σε σχέση με τα υπάρχοντα σχήματα: την διαφοροποίηση ως προς την εγγυημένη μέγιστη καθυστέρηση που παρέχεται στις ροές. Υλοποιείται με τη χρονοδρομολόγηση LA-EDF, που εισάγει την έννοια της διαφοροποιημένης εξυπηρέτησης εντός της ίδιας κλάσης υπηρεσίας και λειτουργεί ως υποστηρικτικός μηχανισμός του ελέγχου αποδοχής κλήσεων, τον αλγόριθμο DBAC για την αποδοχή κλήσεων χωρίς επέμβαση στη λειτουργία του δικτύου και την δρομολόγηση εξισορρόπησης φόρτου για την καλύτερη αξιοποίηση των διαθέσιμων πόρων χωρίς να παραβιάζονται οι εγγυήσεις ποιότητας. Η υπηρεσία Relative επιτυγχάνει προσαρμοστικότητα σε συνθήκες μεταβαλλόμενου φόρτου, δίκαιη διαφοροποίηση, υψηλή απόδοση, αύξηση της χρησιμοποίησης των διαθέσιμων πόρων ενώ αντιμετωπίζει πολλές από τις αδυναμίες που παρουσιάζουν αντίστοιχα μοντέλα. Υλοποιείται με τον μηχανισμό μαρκαρίσματος TWAM ο οποίος εφαρμόζεται στο σημείο εισόδου των ροών στο δίκτυο και αντιμετωπίζει τα θέματα της μη δίκαιης μεταχείρισης TCP ροών με τη μικρότερη δυνατή υπολογιστική επιβάρυνση σε σχέση με υπάρχοντες μηχανισμούς μαρκαρίσματος και τον μηχανισμό DWRED για την ενεργητική διαχείριση του αποθηκευτικού χώρου των ουρών, ο οποίος λειτουργεί με βάση το μαρκάρισμα της κίνησης που επιφέρει ο TWAM και προσαρμόζεται στις μεταβαλλόμενες συνθήκες λειτουργίας. Μεταξύ των καθοριστικών παραγόντων για την ευρεία υιοθέτηση υπηρεσιών βασισμένων στην αρχιτεκτονική DiffServ στα σύγχρονα δίκτυα παραγωγής, αναδεικνύονται η εισαγωγή ευέλικτων επιχειρηματικών μοντέλων για την υλοποίηση των υπηρεσιών αυτών στο εσωτερικό ενός δικτύου καθώς και χρέωσης των παρεχόμενων υπηρεσιών. Ο ορισμός Συμβολαίων Εξασφάλισης Επιπέδου Υπηρεσιών (ΣΕΕΥ) για δίκτυα που υποστηρίζουν την παροχή QoS υπηρεσιών με βάση την αρχιτεκτονική DiffServ έχει ως στόχο την εξασφάλιση της συμβατότητας των παρεχόμενων από διαφορετικά διασυνδεδεμένα δίκτυα υπηρεσιών προκειμένου για την από-άκρο-σε-άκρο εξασφάλιση εγγυήσεων ποιότητας. Προτείνεται ένα πρότυπο για την υλοποίηση διμερών ΣΕΕΥ σε IP δίκτυα που παρέχουν υπηρεσίες μέγιστης προτεραιότητας καθώς και μια μεθοδολογία για την υλοποίηση από-άκρο-σε-άκρο Συμβολαίων πάνω από διασυνδεδεμένα δίκτυα. Σε ένα IP δίκτυο, η εισαγωγή ενός αριθμού κλάσεων υπηρεσιών που διαφοροποιούνται στις παρεχόμενες ποιοτικές εγγυήσεις απαιτεί την εισαγωγή διαφοροποιημένων μοντέλων χρέωσης που επιπρόσθετα οδηγούν τους χρήστες στην επιλογή της κατάλληλης κλάσης υπηρεσίας η οποία μεγιστοποιεί την αντιληπτή χρησιμότητα. Προκειμένου για τη χρέωση υπηρεσιών με βάση την αρχιτεκτονική DiffServ, τα προφίλ κίνησης των χρηστών και οι διαφορές στην αντιληπτή ποιότητα αντιπροσωπεύουν τη χρησιμότητα που αντιλαμβάνεται ο χρήστης. Προτείνεται ένα μοντέλο χρέωσης όπου το προφίλ της κίνησης αποτελεί το αντικείμενο διαπραγμάτευσης του χρήστη με τον πάροχο, αφού ο χρήστης συνυπολογίσει τις εγγυήσεις ποιότητας εξυπηρέτησης που ανακοινώνονται από τον τελευταίο προκαταβολικά. Η καινοτομία του προτεινόμενου μοντέλου συνίσταται στις εξωτερικές συνθήκες (externalities) που υπεισέρχονται στα υφιστάμενα κόστη και προκαλούνται από τη φύση των υπηρεσιών που υλοποιούνται με βάση το μοντέλο DiffServ, καθώς επίσης και στον καθορισμό των πραγματικών τιμών με βάση τις οποίες χρεώνονται οι χρήστες. / The goal of this Dissertation is to study the performance of existing tools and the introduction of new features to quality of service provisioning models in IP networks as well as the introduction of the business models required for applying these models in an operational environment in ways that the performance is improved. Following the evaluation of mechanisms and architectures for differentiation of service in IP networks, the principles of the DiffServ framework have been adopted. The DiffServ framework specifies the provision of a set of services with qualitative guarantees to traffic aggregates, while keeping complexity at the network edges. The performance and effectiveness of service differentiation mechanisms according to the principles of the DiffServ framework are evaluated according to the following metrics: guaranteed capacity, bounded end-to-end delay, minimization of packet losses and jitter. However, in any QoS model, it is important to ensure the best quality possible by keeping complexity low. Each QoS model is designed to meet the needs of a different traffic type. The two prevailing service models within the DiffServ framework are the maximum priority, maximum quality model and the guaranteed capacity under congestion model. The proposed Gold service falls within the first category above, offering advanced quality to IP traffic aggregates with a set of principles that can easily be applied to operational networks. The proposed Relative service model provides guaranteed capacity under congestion by reducing the complexity and improving fairness among TCP flows. The Gold service preserves scalability and provides strict quality guarantees, incorporating a call admission control mechanism that operates without interfering with the network operations. It introduces a novel feature: differentiation of the guarantees on end-to-end delay provided to traffic flow. It is implemented using LA-EDF scheduling that introduces service differentiation within the same class and supports the call admission control functions, the DBAC algorithm for admission control and flow routing with load balancing for optimizing the use of available resources without compromising in terms of the guaranteed quality. The Relative service achieves high adaptability in transient load conditions, fair differentiation, high quality, increase in the utilization of available resources without demonstrating the same weaknesses as equivalent service models. It is implemented using the TWAM marking mechanism, which is applied at the network ingress and ensures fairness with less overhead than similar mechanisms, and DWRED, the active queue management mechanism that depends upon the TWAM marking and adapts to the varying load levels. The introduction of effective business and pricing models is crucial for the adoption of qualitative service models based on the DiffServ framework in a production network. The definition of Service Level Agreements (SLAs) for networks that provide QoS according to the principles of the DiffServ framework aims at introducing compatibility among the services provided for the provisioning of end-to-end quality guarantees. A template for the implementation for bilateral SLAs between networks that support the maximum priority, maximum quality service model is proposed, together with a methodology for implementing, based on the bilateral SLA, an end-to-end SLA over multiple domains. In an IP network, the introduction of a set of services classes with differing quality guarantees necessitates the application of differentiated pricing models that lead the users to the selection of the appropriate service class in order to maximize their perceived utility. Based on the principles of the DiffServ framework, the utility for each user is determined by the profile of his traffic and the quality of service he perceives. The proposed pricing model appoints the traffic profile as the parameter for negotiation between the user and the provider, after the user assesses the quality guarantees announced by the provider prior to the service provisioning. The innovation here lies in the introduction of externalities to the costs induced as well as the announcement of the actual prices upon which the user will eventually be charged. The externalities are imposed by the nature of the service models implemented according to the DiffServ framework.

The aim of the diploma thesis is to choose network simulator suitable for network technologies laboratory tasks for educational use. Theoretical part of thesis describes basics of network communication, addressing, reference models. Thesis also describes standards Wi Fi, Ethernet and routing protocol OSPF - technologies which are discussed in laboratory tasks. The practical part of diploma thesis describes a few available network simulators suitable for creating two laboratory tasks. Finally, the NS-3 simulator was chosen. Both laboratory tasks include theoretical introduction, detailed description of source code, individual tasks, expected outputs and control questions which senses understanding of discussed technologies.

Thesis deals with data technology, which can be used for communication between mobile and IP networks. The aim of the project is to design data communication and the subsequent implementation of the mobile and IP networks. First of all, it made an introduction to telecommunications systems with focus on GSM. Subsequently, the work examines data provided by GSM technology standard with a focus on GPRS, which is in the other chapters discusses in more detail. The resulting communication application protocol is designed in two versions, which is achieved by the creation of an autonomous system. Communication is implemented using JAVA programming language, which created an application client, server and implemented application protocol. Client application is tested on a mobile phone with Internet connection with support for GPRS technology. Server application is installed on a PC workstation, which is assigned a public IP address, it is easily addressable from the Internet.

下一代網路（Next Generation Network，NGN）是因應未來語音、數據、影像等Triple Play之資訊服務對頻寬與網路能力要求日益增加下所提出的一種新網路形態概念。同時，NGN以IP 多媒體子系統（IP Multimedia Subsystem，IMS）為其核心可以降低系統供應商的營運佈建成本。NGN強調的固網行動融合（Fixed Mobile Convergence，FMC）與全IP網路（All IP Network）化以及強化服務品質（Quality of Service，QoS）精神，都使資訊服務與系統供應業者需要思考出一套新的經營模式（Business Model），使其能在NGN上獲利。本研究之主要目的為以NGN的架構與特性為出發，剖析此一網路的數位匯流趨勢與其成功經營模式研究。 本研究採個案研究法（Case Study Method），透過次級資料的蒐集以及與本研究有關之文獻探討的方式，找出未來NGN的經營模式形貌，並透過訪談相關業者來佐證本研究所提出經營模式之合理性。 由於資訊服務產業範圍廣泛，故本研究選定VoIP及IPTV為主要研究對象，期盼能找出一套適合在NGN上獲利的模式。另外針對企業用戶，NGN也能協助企業增加競爭力，在商業情報的取得、溝通成本的降低、資訊管理系統等都能有所貢獻。 / Next Generation Network，NGN, is a new form of internet concept of Triple play informational service integrated voice mail, data and video as the requirements of more wider bandwidth and high internet power increase. Meanwhile, The core of IP Multimedia Subsystem，IMS, NGN targets can lower operational cost to system suppliers. NGN emphasizes the spirit to combine Fixed Mobile Convergence，FMC, all IP network and Enhanced Quality of Service. The spirit makes the suppliers of informational service and system to think a new business model to make profits in NGN. The research of this thesis bases on NGN’s structure and features to analyze the trend of digital convergence in internet and succeeded business model. This essay adopts Case Study Research. By collecting sub data and relative document research figures out future image of NGN business model. Besides, it is interviewed with pertaining businesses to testify the reality of business model offered in this thesis. Owning to the scope of informational service business is unlimited, the thesis is chosen VoIP and IPTV as main targets to find out an appropriate and a profitable business model in this informational field. Furthermore, to business user, NGN can support industries to increase competitive ability and gain useful business information, decrease communicative cost and upgrade the performance of MIS

[pt] Com o crescimento gigantesco da Internet e dos sistemas de comunicações móveis celulares, as aplicações de processamento de voz nessas redes têm despertado grande interesse . Um problema particularmente importante nessa área consiste no reconhecimento de voz em um sistema servidor, baseado nos parâmetros acústicos calculados e quantizados no terminal do usuário (Reconhecimento de Voz Distribuído). Como em geral estes parâmetros não são os mais indicados como atributos de voz para o sistema de reconhecimento remoto, é importante que sejam examinadas diferentes transformações dos parâmetros, que permitam um melhor desempenho do reconhecedor. Esta dissertação trata da extração de atributos de reconhecimento eficientes a partir dos parâmetros dos codificadores utilizados em redes móveis celulares e em redes IP. Além disso, como a taxa dos parâmetros fornecidos ao reconhecedor de voz é normalmente superior àquela com a qual os codificadores geram os parâmetros, é importante analisar o efeito da interpolação dos parâmetros sobre o desempenho do sistema de reconhecimento, bem como o melhor domínio sobre o qual esta interpolação deve ser realizada. Estes são outros tópicos apresentados nesta dissertação. / [en] The huge growth of the Internet and cellular mobile communication systems has stimulated a great interest in the applications of speech processing in these networks. An important problem in this field consists in speech recognition in a server system, based on the acoustic parameters calculated and quantized in the user terminal (Distributed Speech Recognition). Since these parameters are not the most indicated ones for the remote recognition system, it is important to examine different transformations of these parameters, in order to allow a better performance of the recogniser. This dissertation is concerned with the extraction of efficient recognition features from the coder parameters used in cellular mobile networks and IP networks. In addition, as the rate that parameters supplied for the speech recogniser must be usually higher than that generated by the codec, it is important to analyze the effect of the interpolation of the parameters over the performance of the recognition system. Moreover, it is paramount to establish the best domain over which this interpolation must be carried out. These are other topics presented in this dissertation.

Scalable and accurate analysis of networks is essential to a wide variety of existing and emerging network systems. Specifically, network measurement and analysis helps to understand networks, improve existing services, and enable new data-mining applications. To support various services and applications in large-scale networks, network analytics must address the following challenges: (i) how to conduct scalable analysis in networks with a large number of nodes and links, (ii) how to flexibly accommodate various objectives from different administrative tasks, (iii) and how to cope with the dynamic changes in the networks. This dissertation presents novel path analysis schemes that effectively address the above challenges in analyzing pair-wise relationships among networked entities. In doing so, we make the following three major contributions to large-scale IP networks, social networks, and application service networks. For IP networks, we propose an accurate and flexible framework for path property monitoring. Analyzing the performance side of paths between pairs of nodes, our framework incorporates approaches that perform exact reconstruction of path properties as well as approximate reconstruction. Our framework is highly scalable to design measurement experiments that span thousands of routers and end hosts. It is also flexible to accommodate a variety of design requirements. For social networks, we present scalable and accurate graph embedding schemes. Aimed at analyzing the pair-wise relationships of social network users, we present three dimensionality reduction schemes leveraging matrix factorization, count-min sketch, and graph clustering paired with spectral graph embedding. As concrete applications showing the practical value of our schemes, we apply them to the important social analysis tasks of proximity estimation, missing link inference, and link prediction. The results clearly demonstrate the accuracy, scalability, and flexibility of our schemes for analyzing social networks with millions of nodes and tens of millions of links. For application service networks, we provide a proactive service quality assessment scheme. Analyzing the relationship between the satisfaction level of subscribers of an IPTV service and network performance indicators, our proposed scheme proactively (i.e., detect issues before IPTV subscribers complain) assesses user-perceived service quality using performance metrics collected from the network. From our evaluation using network data collected from a commercial IPTV service provider, we show that our scheme is able to predict 60% of the service problems that are complained by customers with only 0.1% of false positives. / text

[pt] Este trabalho examina o impacto da quantização vetorial das LSFs sobre a qualidade de voz em codecs a baixas taxas operando em redes IP e em diversos ambientes ruidosos. São considerados diferentes esquemas de quantização vetorial (QV) multiestágio com busca em árvore envolvendo QV sem memória e QV preditiva chaveada com 2 e 4 classes. A distribuição de perda de quadros em redes IP foi modelada de acordo com o Modelo de Gilbert e a avaliação de desempenho foi realizada tanto em termos das distorções espectrais como da qualidade de voz resultante de codecs a baixas taxas. Ainda neste trabalho, foi avaliada a qualidade da voz codificada após a utilização de uma técnica de supressão de ruído baseada em transformadas wavelets (Wavelet Denoising). / [en] This work investigates the impact of LSF vector quantisation over the voice quality in low rate codecs operating in IP networks. Tree-structured multistage vector quantisation (VQ) schemes involving memoryless VQ and switched-predictive VQ with 2 and 4 classes are considered. The packet loss frame distribution in IP networks was modelled according to the Gilbert Model and the performance was carried out both in terms of spectral distortions and the speech quality at the out put of low rate codecs. In this work, we also evaluated the quality of the coded speech after employing Wavelet Denoising.

[pt] Este trabalho faz um estudo da arquitetura Diffserv para oferecimento de QoS na internet.São revistos conceitos básicos e descritos os principais mecanismos de controle de tráfego.Utilizando o software NS2, avalia-se o desempenho desses algoritmos de controles de tráfego.Para um cenário específico foram estudados: disciplinas de serviço, mecanismos de gerenciamento de buffers, para diferentes fontes de tráfego, procurando-se obter medidas de desempenho que possam ser úteis em projetos de rede com qualidade de serviço. / [en] This work presents a Diffserv architecture study to provide QoS in the Internet. A review of some basic concepts of the main traffic control algorithm and a performance evaluation, through the NS simulation program, is done. In order to get important performance measurement of the QoS network, it was done, for a specific scenario, a study of the queue discipline, queue activity management, with different traffic source.