<p>Communicating over a wireless channel poses many unique challenges not found in wired communication because of the special characteristics of the wireless channel. The capacity in a wireless network is typically scarce as a result of the limited bandwidth and many distinct phenomenons, like attenuation and interference, that work destructively on the received signals.</p><p>The Medium Access Control (MAC) layer is responsible for sharing this limited resource among the users. This allocation problem should be handled by considering the Quality of Service (QoS) requirements of each user as to maximize the utility. Efficient MAC algorithms are crucial in minimizing collisions between transmissions and thus achieving high utilization of the channel.</p><p>This thesis focuses on conflict resolution and service differentiation algorithms for wireless local area networks, where there is no central control of the channel and each sender independently contends for access.</p><p>In part I, we study three approaches to improve the IEEE 802.11(e) standards with focus on QoS. In the first approach, utility functions are considered, that model application preferences, to achieve service differentiation and maximize the aggregated utility. We provide algorithms for two subsidiary problems that arise from the maximization problem, and show that a near--optimal solution is found. In the second approach a collision detection algorithm for multicast transmissions is proposed, that increases the reliability for multicast compared to the protected unicast traffic. The third approach is an improved MAC algorithm for the QoS standard IEEE 802.11e. The improved algorithm outperforms the standard and achieves close to optimal performance for large number of scenarios, which significantly reduces the need of adjusting the contention parameters.</p><p>In part II, we focus on channel bursting protocols that use noise bursts to resolve channel conflicts. These protocols is capable of achieving very low collision probability. We propose two new bursting protocols, that achieve very high channel utilization, and show that the bursting technique has good fairness properties and provides efficient support for service differentiation. We also show that it is possible to reduce the number of bursts without loosing performance.</p><p>In part III, the optimal backoff distribution that minimizes the collision probability is derived. We then propose a heuristic backoff distribution with similar properties that yields high channel utilization. An extension for service differentiation is provided where the sizes of the backoff windows are adjusted.</p>

Communicating over a wireless channel poses many unique challenges not found in wired communication because of the special characteristics of the wireless channel. The capacity in a wireless network is typically scarce as a result of the limited bandwidth and many distinct phenomenons, like attenuation and interference, that work destructively on the received signals. The Medium Access Control (MAC) layer is responsible for sharing this limited resource among the users. This allocation problem should be handled by considering the Quality of Service (QoS) requirements of each user as to maximize the utility. Efficient MAC algorithms are crucial in minimizing collisions between transmissions and thus achieving high utilization of the channel. This thesis focuses on conflict resolution and service differentiation algorithms for wireless local area networks, where there is no central control of the channel and each sender independently contends for access. In part I, we study three approaches to improve the IEEE 802.11(e) standards with focus on QoS. In the first approach, utility functions are considered, that model application preferences, to achieve service differentiation and maximize the aggregated utility. We provide algorithms for two subsidiary problems that arise from the maximization problem, and show that a near--optimal solution is found. In the second approach a collision detection algorithm for multicast transmissions is proposed, that increases the reliability for multicast compared to the protected unicast traffic. The third approach is an improved MAC algorithm for the QoS standard IEEE 802.11e. The improved algorithm outperforms the standard and achieves close to optimal performance for large number of scenarios, which significantly reduces the need of adjusting the contention parameters. In part II, we focus on channel bursting protocols that use noise bursts to resolve channel conflicts. These protocols is capable of achieving very low collision probability. We propose two new bursting protocols, that achieve very high channel utilization, and show that the bursting technique has good fairness properties and provides efficient support for service differentiation. We also show that it is possible to reduce the number of bursts without loosing performance. In part III, the optimal backoff distribution that minimizes the collision probability is derived. We then propose a heuristic backoff distribution with similar properties that yields high channel utilization. An extension for service differentiation is provided where the sizes of the backoff windows are adjusted.

Cette thèse vise à améliorer la pile de protocoles pour réseaux de capteurs sans fil à récupération d'énergie afin de les rendre autonomes dans un contexte multi-saut. Elle s'inscrit dans le projet GreenNet de STMicroelectronics qui a pour objectif de concevoir et développer une nouvelle génération d'objets intelligent basés sur la récupération d'énergie ambiente en vue de l'intégration dans l'Internet des Objets. L'originalité de la plateforme GreenNet repose sur sa petite taille qui implique une faible capacité de stockage d'énergie ainsi qu'une faible capacité de récupération d'énergie. Avec un si faible budget d'énergie, les protocoles standards ou les solutions proposées par les communautés académique/industrielle ne permettant pas d'assurer un fonctionnement autonome de ces réseaux. Dans cette thèse, nous analysons les protocoles standards et les solutions existantes pour identifier leurs limites avec la plateforme GreenNet. Ensuite, nous proposons 3 contributions afin de permettre cette autonomie. La première contribution est MCBT, un protocole permettant d'accélérer la découverte et le rattachement de nouveaux noeuds à un réseau multi saut et multi-canaux en formation ou existent. Ce protocole réduit efficacement l'énergie dépensée dans cette phase fortement consommatrice. La deuxième contribution est STADA, un algorithme adaptant l'activité des capteurs en fonction des conditions locales de trafic et d'énergie disponible. STADA est basé sur une fonction de pondération qui tient compte de l'énergie présente dans la batterie, du taux de récupération d'énergie et du trafic local. Enfin, notre troisième contribution propose une nouvelle métrique de routage basée sur Expected Delay synthétisant en une seule variable monotone des facteurs tels que l'éloignement au puits, les chemins bénéficiant d'un ordonnancement de relayage de paquet privilégié et de périodes cumulées d'activité des radios sur le chemin favorable. Toutes les solutions proposées sont conçues pour fonctionner avec la norme IEEE 802.15.4 slotté et sont facilement transposables à son évolution définie par la norme IEEE 802.15.4e. Nous avons validé les protocoles proposés grâce à un simulateur émulant des noeuds réels (Cooja) et au simulateur WSNet. Les résultats ont montré de meilleures performances en termes de consommation d'énergie et de qualité de service par rapport à l'existant. / This thesis concerns energy efficient protocols for harvested wireless sensor networks. It is a part of an industrial Internet of Things project. STMicroelectronics started the GreenNet project with the objective to develop and design a new generation of harvesting smart objects to be integrated in the Internet of Things. The GreenNet platform is novel with respect to the existing solutions due to its small size that implies a small energy buffer and small harvesting capabilities. This aspect makes the standard protocols and precedent solutions not directly applicable on this extremely low power platform. In this dissertation, we analyse standard protocols and existing solutions to identify their issues in the gn platform. Then, we provide protocol and algorithm adaptations to make feasible the concept of auto configurable and sustainable networks of GreenNet nodes. We proposed MCBT, an energy efficient protocol for the bootstrap procedure. It enables low power nodes to be enrolled in mh mc wireless sensor networks thanks to the network support for enrolling new nodes. It represents an energy efficient solution that extends the standard protocol. We proposed STADA, a sustainable algorithm to adapt the node activity according to the available energy and traffic conditions. STADA is based on a weighted function that takes into account the energy present in the battery, the energy harvesting rate, and network traffic. In this way, the algorithm takes into account all main parameters to adapt the energy consumption and improve the node performance. To make the harvested network more efficient according to light variations, we proposed a novel metric that makes the path choice a simple process. With the Expected Delay, we synthesize all network parameters in a single monotonic variable that facilitates the path choice in mh harvesting wireless sensor networks. All proposed solutions are designed to work with standard beacon-enabled IEEE 802.15.4 protocols and are easily portable on the future version of IEEE 802.15.4e. We validated the proposed protocols with emulations and simulations. The evaluation results shown better performance in terms of energy consumption and quality of service.

Το ζήτημα της κατανάλωσης ενέργειας σε ασύρματα ad hoc δίκτυα αποτελεί ένα ερευνητικό πεδίο το οποίο έχει λάβει ιδιαίτερη προσοχή τα τελευταία χρόνια. Οι σταθμοί σε ένα ασύρματο ad hoc δίκτυο λειτουργούν επί το πλείστον με μπαταρίες με αποτέλεσμα η εξοικονόμηση ενέργειας στο δίκτυο να αποτελεί πρώτιστο στόχο για την βιωσιμότητα των σταθμών του δικτύου και την αξιόπιστη παραλαβή των πακέτων δεδομένων από τους παραλήπτες τους. Μέχρι σήμερα, έχουν αναπτυχθεί διάφορα ενεργό-αποδοτικά πρωτόκολλα τα οποία μπορούν να υιοθετηθούν σε ένα ασύρματο ad hoc δίκτυo. Τα πρωτόκολλα αυτά λειτουργούν σε διαφορετικό επίπεδο το καθένα (ελέγχου πρόσβασης στο μέσο, δικτύου, υψηλότερα). Η παρούσα εργασία συντάχθηκε με σκοπό την μελέτη αυτών των ενεργό-αποδοτικών πρωτοκόλλων που μπορούν να υιοθετηθούν σε ασύρματα ad hoc δίκτυα, την καταγραφή των ιδιαίτερων χαρακτηριστικών κάθε πρωτοκόλλου καθώς και την ανάπτυξη ενός νέου πρωτοκόλλου ελέγχου της ισχύος μετάδοσης σε ασύρματα ad hoc δίκτυα με κύριο στόχο την περαιτέρω μείωση της κατανάλωσης ενέργειας στο δίκτυο με παράλληλη αύξηση του throughput του δικτύου. Συγκεκριμένα, στην παρούσα μελέτη, αναλύονται και παρουσιάζονται τα ακόλουθα ζητήματα. Στο Κεφάλαιο 1 παρουσιάζονται οι στόχοι της παρούσας εργασίας καθώς και η συνεισφορά της στο ζήτημα της κατανάλωσης ενέργειας στα ασύρματα ad hoc δίκτυα. Στο Κεφάλαιο 2 αρχικά πραγματοποιείται μία εισαγωγή στην αρχιτεκτονική των ασυρμάτων ad hoc δικτύων και ακολούθως παρουσιάζονται οι διάφορες κατηγορίες των ασυρμάτων ad hoc δικτύων, δίνοντας ιδιαίτερη έμφαση στην 802.11 τεχνολογία και πρωτόκολλα. Στο Κεφάλαιο 3 παρουσιάζονται υπάρχοντα ενεργό-αποδοτικά πρωτόκολλα τα οποία μπορούν να χρησιμοποιηθούν σε ασύρματα ad hoc δίκτυα. Τα πρωτόκολλα αυτά παρουσιάζονται ταξινομημένα ανάλογα με το επίπεδο στο οποίο το καθένα λειτουργεί (επίπεδο ελέγχου πρόσβασης στο μέσο, επίπεδο δικτύου, υψηλότερα επίπεδα). Στο Κεφάλαιο 4 περιγράφεται το προτεινόμενο MAC πρωτόκολλο ελέγχου της ισχύος μετάδοσης το οποίο μπορεί να χρησιμοποιηθεί σε ασύρματα ad hoc δίκτυα. Παρουσιάζεται η λειτουργία του πρωτοκόλλου, περιγράφοντας το χαρακτηριστικό της αργής εκκίνησης που το προτεινόμενο πρωτόκολλο υιοθετεί για την μετάδοση των RTS πλαισίων, καθώς και τον CTS μηχανισμό που χρησιμοποιείται. Στο τέλος του κεφαλαίου, πραγματοποιείται μια σύγκριση της λειτουργίας του προτεινόμενου ενεργό-αποδοτικού πρωτοκόλλου με υπάρχοντα πρωτόκολλα MAC επιπέδου που παρουσιάστηκαν στο Κεφάλαιο 3. Στο Κεφάλαιο 5 πραγματοποιείται αξιολόγηση της απόδοσης του προτεινόμενου πρωτοκόλλου. Η αξιολόγηση της απόδοσης του προτεινόμενου πρωτοκόλλου πραγματοποιείται μέσω της εκτέλεσης πειραμάτων με την βοήθεια του εξομοιωτή δικτύων network simulator 2. Η αξιολόγηση του προτεινόμενου πρωτοκόλλου πραγματοποιείται ως προς διάφορες παραμέτρους – κατανάλωση ενέργειας στο δίκτυο, διασπορά της καταναλόμενης ενέργειας, μέση καθυστέρηση παραλαβής των πακέτων, throughput του δικτύου, πλήθος συγκρούσεων RTS πλαισίων, λόγος ληφθέντων προς απεσταλμένα πακέτα – έχοντας ως βάση το πρόβλημα της εκκένωσης των πακέτων στο δίκτυο και για την περίπτωση δύο διαφορετικών προσεγγίσεων. Μία στην οποία κάθε σταθμός χρησιμοποιεί στατική ισχύ για τις μεταδόσεις του και μία στην οποία κάθε σταθμός ρυθμίζει την ισχύ μετάδοσής του στην ελάχιστη απαιτούμενη τιμή για την ορθή παραλαβή των πακέτων από τους παραλήπτες τους. Τέλος στο Κεφάλαιο 6 παρουσιάζονται τα συμπεράσματα που προκύπτουν από την παρούσα εργασία καθώς και διάφορα ανοιχτά ζητήματα προς περαιτέρω έρευνα. / Power consumption at wireless ad hoc networks has received last years much attention. Mobile stations in a wireless ad hoc network operate in the most cases with batteries, so power conservation at the network is a major objective for the viability of the mobile stations of the network and the reliable delivery of packets to their destinations. Till today, various power-aware protocols have been developed for wireless ad hoc networks. Each one of these protocols operates at different layer (medium access control, network, higher layers). The main objectives of this study are the review of the power-aware protocols that can be used at wireless ad hoc networks, the detection of the special characteristics of each protocol, and the development of a new power control MAC-layer protocol for wireless ad hoc networks. The main objective of this new protocol is the farther reduction of the power consumption in the network, with parallel increment at network throughput. More specifically speaking, in this study, the following points are represented and analyzed: in Chapter 1 the various objectives of this study are represented as the contribution of the study in point of power consumption at wireless ad hoc networks. In Chapter 2, initially an introduction at the architecture of wireless ad hoc networks is performed, while afterwards the various categories of wireless ad hoc networks are represented, by emphasizing the 802.11 technology and protocols. In Chapter 3 various energy-aware protocols for wireless ad hoc networks are represented. These protocols are represented categorized by the layer at which every one operates (medium access control layer, network layer and higher layers). In Chapter 4 the proposed power control MAC protocol for mobile ad hoc networks is represented. The operation of the protocol is represented, by describing the slow start mechanism used for RTS frames transmissions, and the CTS mechanism used. At the end of Chapter 4, a comparison between the operation of the proposed power-aware protocol and previous MAC-layer power aware protocols is performed. In Chapter 5, the performance evaluation of the proposed protocol is performed. The performance evaluation of the proposed protocol was done via execution of experiments with network simulator 2. The performance parameters that were measured are: the power consumption in the network, the variance of the consumed energy, the average delay for packets delivery, the network throughput, the number of RTS frames collisions and the received-to-sent packets ratio. The performance of the proposed protocol was evaluated in the setting of the evacuation problem and for two different approaches. One in which every node uses static power for its transmissions and one in which every node adjusts its transmission power at the minimum required value for coherent reception of the packets from the recipients. Finally in Chapter 6 are represented the results that are derived from this study and various open issues for further investigation.

Cette thèse vise à améliorer la pile de protocoles pour réseaux de capteurs sans fil à récupération d'énergie afin de les rendre autonomes dans un contexte multi-saut. Elle s'inscrit dans le projet GreenNet de STMicroelectronics qui a pour objectif de concevoir et développer une nouvelle génération d'objets intelligent basés sur la récupération d'énergie ambiente en vue de l'intégration dans l'Internet des Objets. L'originalité de la plateforme GreenNet repose sur sa petite taille qui implique une faible capacité de stockage d'énergie ainsi qu'une faible capacité de récupération d'énergie. Avec un si faible budget d'énergie, les protocoles standards ou les solutions proposées par les communautés académique/industrielle ne permettant pas d'assurer un fonctionnement autonome de ces réseaux. Dans cette thèse, nous analysons les protocoles standards et les solutions existantes pour identifier leurs limites avec la plateforme GreenNet. Ensuite, nous proposons 3 contributions afin de permettre cette autonomie. La première contribution est MCBT, un protocole permettant d'accélérer la découverte et le rattachement de nouveaux noeuds à un réseau multi saut et multi-canaux en formation ou existent. Ce protocole réduit efficacement l'énergie dépensée dans cette phase fortement consommatrice. La deuxième contribution est STADA, un algorithme adaptant l'activité des capteurs en fonction des conditions locales de trafic et d'énergie disponible. STADA est basé sur une fonction de pondération qui tient compte de l'énergie présente dans la batterie, du taux de récupération d'énergie et du trafic local. Enfin, notre troisième contribution propose une nouvelle métrique de routage basée sur Expected Delay synthétisant en une seule variable monotone des facteurs tels que l'éloignement au puits, les chemins bénéficiant d'un ordonnancement de relayage de paquet privilégié et de périodes cumulées d'activité des radios sur le chemin favorable. Toutes les solutions proposées sont conçues pour fonctionner avec la norme IEEE 802.15.4 slotté et sont facilement transposables à son évolution définie par la norme IEEE 802.15.4e. Nous avons validé les protocoles proposés grâce à un simulateur émulant des noeuds réels (Cooja) et au simulateur WSNet. Les résultats ont montré de meilleures performances en termes de consommation d'énergie et de qualité de service par rapport à l'existant. / This thesis concerns energy efficient protocols for harvested wireless sensor networks. It is a part of an industrial Internet of Things project. STMicroelectronics started the GreenNet project with the objective to develop and design a new generation of harvesting smart objects to be integrated in the Internet of Things. The GreenNet platform is novel with respect to the existing solutions due to its small size that implies a small energy buffer and small harvesting capabilities. This aspect makes the standard protocols and precedent solutions not directly applicable on this extremely low power platform. In this dissertation, we analyse standard protocols and existing solutions to identify their issues in the gn platform. Then, we provide protocol and algorithm adaptations to make feasible the concept of auto configurable and sustainable networks of GreenNet nodes. We proposed MCBT, an energy efficient protocol for the bootstrap procedure. It enables low power nodes to be enrolled in mh mc wireless sensor networks thanks to the network support for enrolling new nodes. It represents an energy efficient solution that extends the standard protocol. We proposed STADA, a sustainable algorithm to adapt the node activity according to the available energy and traffic conditions. STADA is based on a weighted function that takes into account the energy present in the battery, the energy harvesting rate, and network traffic. In this way, the algorithm takes into account all main parameters to adapt the energy consumption and improve the node performance. To make the harvested network more efficient according to light variations, we proposed a novel metric that makes the path choice a simple process. With the Expected Delay, we synthesize all network parameters in a single monotonic variable that facilitates the path choice in mh harvesting wireless sensor networks. All proposed solutions are designed to work with standard beacon-enabled IEEE 802.15.4 protocols and are easily portable on the future version of IEEE 802.15.4e. We validated the proposed protocols with emulations and simulations. The evaluation results shown better performance in terms of energy consumption and quality of service.

Este trabalho apresenta um modelo analítico para a análise de vazão (throughput) da camada MAC do IEEE 802.11. A proposta se diferencia da maioria dos desenvolvimentos realizados na área por apresentar uma modelagem de ambientes com estações não-saturadas, levando em consideração o perfil do tráfego gerado pelas camadas superiores ao nível de enlace. Dessa maneira, o modelo permite uma análise do desempenho de aplicações reais sobre redes sem fio, a partir de resultados provenientes de um modelo matemático, enquanto diversos outros trabalhos avaliam somente situações de saturação das estações. Simulações utilizando Network Simulator 2 e comparações com resultados obtidos em trabalhos análogos desenvolvidos por outros pesquisadores validam o modelo proposto. Cenários com variações na quantidade de estações e carga oferecida à rede são avaliados utilizando o modelo teórico e comparados aos resultados simulados, provendo uma análise do comportamento dos limites de vazão do sistema. As estruturas do IEEE 802.11 MAC foram estudadas a fim de embasar o desenvolvimento do modelo proposto. Também foi realizada uma pesquisa a respeito de Cadeias de Markov, que serve como estrutura básica para a descrição do IEEE 802.11 DCF. / This work provides an analytical model to compute the IEEE 802.11 DCF throughput. The proposed analysis differs from most of the related work by presenting scenario modeling with unsaturated stations, accounting for the traffic characteristics generated by the upper layers to the data link layer. As a consequence, the proposed model allows for an accurate analysis of real applications over wireless networks, based on mathematical model results, while several other researches evaluate only saturate stations situations. Simulations ran using Network Simulator 2 and comparisons with results obtained on similar works developed by other researchers are used to validate the proposed model. Scenarios with different number of stations and offered loads are evaluated using the theoretical model and compared to the simulated results, providing an analysis on the behavior of the maximum throughput provided by the network. A study was made on the structures and mechanisms of IEEE 802.11 MAC in order to support the development of the proposed model. A research on Markov Chains was also done, since it is the basic structure used to describe the IEEE 802.11 DCF.

NOGUEIRA, Antonia Diana Braga. Uma proposta de integração das redes UMTS e IEEE 802.11 com suporte a mobilidade. 2007. 112 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2007. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-08T18:49:42Z No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-18T13:41:19Z (GMT) No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) / Made available in DSpace on 2016-07-18T13:41:19Z (GMT). No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) Previous issue date: 2007 / Wireless Local Area Networks (WLANs) IEEE 802.11 reach relatively high data transmission rates when compared to other wireless networks, such as Bluetooth. These high data transmission rates have gained attention from the cellular networks operators, which have been considering IEEE 802.11 networks as a complement to their access networks. This interoperability between cellular systems and WLANs has been frequently discussed in the literature. For example, 3GPP (Third Generation Partnership Project) has defined six levels for the complete integration of the third generation cellular networks and WLANs. However, the mobility support has not been specified yet, which is necessary to make feasible voice and data transmission transparence for the final users. Thus, this work presents two approaches for the mobility management of the integration between UMTS and IEEE 802.11 networks: the first one is based on SIP (Session Initiation Protocol), and the other one is based on MIPv6 (Mobile IP version 6). This proposal extends the Loose Interworking architecture and uses the fourth level of the 3GPP specification. First, these approaches are modeled using sequence diagrams and, then, they are mapped to the SDL (Specification and Description Language) formal description technique. SDL, which is largely used to formally specify telecommunications systems, presents simulation and validation procedures that are applied to evaluate the specification and, consequently, the proposed approaches. / As redes locais sem fio (Wireless Local Area Networks - WLANs) IEEE 802.11 atingem taxas de transmissão de dados relativamente altas quando comparadas `a outras redes sem fio, por exemplo, Bluetooth. Essas altas taxas de transmissãao têm interessado as operadoras de redes celulares, as quais começam a ver as redes IEEE 802.11 como um complemento as suas redes de acesso. Esta interoperabilidade entre sistemas celulares e WLANs tem sido um tema bastante discutido na literatura. Por exemplo, o 3GPP (Third Generation Partnership Project) define seis n´ıveis para a total integração das redes celulares de terceira geração com as redes locais sem fio. No entanto, a integração com suporte a mobilidade ainda não foi especificada, o que é necessário para viabilizar a transparência de transmissão de voz e dados para os usuários finais. Esta dissertação apresenta então duas abordagens para o gerenciamento de mobilidade na integração do sistema 3G UMTS com as redes IEEE 802.11: uma baseada no SIP (Session Initiation Protocol ) e a outra no MIP versão 6 (Mobile IP version 6 - MIPv6). A proposta estende a arquitetura Loose Interworking e utiliza os requisitos do nível 4 do 3GPP. Para especificar a proposta, as abordagens de integração das redes UMTS e IEEE 802.11 foram modeladas em diagramas de seqüência e, em seguida, mapeadas para a técnica de descrição formal SDL (Specification and Description Language). SDL, que é bastante utilizada para especificar formalmente sistemas de telecomunicações, apresenta procedimentos de simulação e validação que são aplicados para avaliar a especificação e, em conseqüência, as abordagens propostas.

NOGUEIRA, Antonia Diana Braga. Uma proposta de integração das redes UMTS e IEEE 802.11 com suporte a mobilidade. 2007. 91 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Departamento de Computação, Fortaleza-CE, 2007. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-05-30T19:51:57Z No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-05-30T19:52:27Z (GMT) No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) / Made available in DSpace on 2016-05-30T19:52:27Z (GMT). No. of bitstreams: 1 2007_dis_adbnogueira.pdf: 13756193 bytes, checksum: bb4a338bd2622ad6f90479ce37824ccd (MD5) Previous issue date: 2007 / Wireless Local Area Networks (WLANs) IEEE 802.11 reach relatively high data transmission rates when compared to other wireless networks, such as Bluetooth. These high data transmission rates have gained attention from the cellular networks operators, which have been considering IEEE 802.11 networks as a complement to their access networks. This interoperability between cellular systems and WLANs has been frequently discussed in the literature. For example, 3GPP (Third Generation Partnership Project) has defined six levels for the complete integration of the third generation cellular networks and WLANs. However, the mobility support has not been specified yet, which is necessary to make feasible voice and data transmission transparence for the final users. Thus, this work presents two approaches for the mobility management of the integration between UMTS and IEEE 802.11 networks: the first one is based on SIP (Session Initiation Protocol), and the other one is based on MIPv6 (Mobile IP version 6). This proposal extends the Loose Interworking architecture and uses the fourth level of the 3GPP specification. First, these approaches are modeled using sequence diagrams and, then, they are mapped to the SDL (Specification and Description Language) formal description technique. SDL, which is largely used to formally specify telecommunications systems, presents simulation and validation procedures that are applied to evaluate the specification and, consequently, the proposed approaches. / As redes locais sem fio (Wireless Local Area Networks - WLANs) IEEE 802.11 atingem taxas de transmissão de dados relativamente altas quando comparadas `a outras redes sem fio, por exemplo, Bluetooth. Essas altas taxas de transmissãao têm interessado as operadoras de redes celulares, as quais começam a ver as redes IEEE 802.11 como um complemento as suas redes de acesso. Esta interoperabilidade entre sistemas celulares e WLANs tem sido um tema bastante discutido na literatura. Por exemplo, o 3GPP (Third Generation Partnership Project) define seis n´ıveis para a total integração das redes celulares de terceira geração com as redes locais sem fio. No entanto, a integração com suporte a mobilidade ainda não foi especificada, o que é necessário para viabilizar a transparência de transmissão de voz e dados para os usuários finais. Esta dissertação apresenta então duas abordagens para o gerenciamento de mobilidade na integração do sistema 3G UMTS com as redes IEEE 802.11: uma baseada no SIP (Session Initiation Protocol ) e a outra no MIP versão 6 (Mobile IP version 6 - MIPv6). A proposta estende a arquitetura Loose Interworking e utiliza os requisitos do nível 4 do 3GPP. Para especificar a proposta, as abordagens de integração das redes UMTS e IEEE 802.11 foram modeladas em diagramas de seqüência e, em seguida, mapeadas para a técnica de descrição formal SDL (Specification and Description Language). SDL, que é bastante utilizada para especificar formalmente sistemas de telecomunicações, apresenta procedimentos de simulação e validação que são aplicados para avaliar a especificação e, em conseqüência, as abordagens propostas.

Este trabalho apresenta um modelo analítico para a análise de vazão (throughput) da camada MAC do IEEE 802.11. A proposta se diferencia da maioria dos desenvolvimentos realizados na área por apresentar uma modelagem de ambientes com estações não-saturadas, levando em consideração o perfil do tráfego gerado pelas camadas superiores ao nível de enlace. Dessa maneira, o modelo permite uma análise do desempenho de aplicações reais sobre redes sem fio, a partir de resultados provenientes de um modelo matemático, enquanto diversos outros trabalhos avaliam somente situações de saturação das estações. Simulações utilizando Network Simulator 2 e comparações com resultados obtidos em trabalhos análogos desenvolvidos por outros pesquisadores validam o modelo proposto. Cenários com variações na quantidade de estações e carga oferecida à rede são avaliados utilizando o modelo teórico e comparados aos resultados simulados, provendo uma análise do comportamento dos limites de vazão do sistema. As estruturas do IEEE 802.11 MAC foram estudadas a fim de embasar o desenvolvimento do modelo proposto. Também foi realizada uma pesquisa a respeito de Cadeias de Markov, que serve como estrutura básica para a descrição do IEEE 802.11 DCF. / This work provides an analytical model to compute the IEEE 802.11 DCF throughput. The proposed analysis differs from most of the related work by presenting scenario modeling with unsaturated stations, accounting for the traffic characteristics generated by the upper layers to the data link layer. As a consequence, the proposed model allows for an accurate analysis of real applications over wireless networks, based on mathematical model results, while several other researches evaluate only saturate stations situations. Simulations ran using Network Simulator 2 and comparisons with results obtained on similar works developed by other researchers are used to validate the proposed model. Scenarios with different number of stations and offered loads are evaluated using the theoretical model and compared to the simulated results, providing an analysis on the behavior of the maximum throughput provided by the network. A study was made on the structures and mechanisms of IEEE 802.11 MAC in order to support the development of the proposed model. A research on Markov Chains was also done, since it is the basic structure used to describe the IEEE 802.11 DCF.

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-16Bitstream added on 2014-06-13T20:07:42Z : No. of bitstreams: 1 jesus_rm_me_ilha.pdf: 1779220 bytes, checksum: d4da2fb210cd7f8994e968a719e1fcc7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta dissertação é apresentada uma aplicação web, dinâmica e interativa, para o controle e monitoramento de transdutores inteligentes conectados em rede de acordo com o padrão IEEE 1451. O ambiente está hospedado em um computador pessoal que desempenha as funções de um servidor web e da parte lógica de um processador com capacidade de operar em rede. O acesso aos transdutores da rede é realizado através de um módulo de interface para transdutores inteligentes, implementado em um dispositivo lógico programável. No desenvolvimento do MATIW 1451 utilizou-se somente plataforma operacional e linguagens de programação de domínio público, abertas e padronizadas como estabelece o comitê gestor do padrão IEEE 1451. O sistema foi testado em uma rede de transdutores contendo um sensor de temperatura e uma ventoinha e em uma rede de distribuição de água, contendo sensores de pressão, vazão e um redutor de pressão. / This paper presents an interactive and dynamic web application to control and monitor smart transducers connected in network according to the IEEE 1451 standart, named MATIW 1451. A personal computer acts as a web server and as the logical part of a NCAP (Network Capable Application Process). The transducers are accessed via a STIM (Smart Transducer Interface Module) implemented by a PLD (Programmable Logic Device). The tools used in the implementation of MATIW 1451 are all in public domain, open as defined by the 1451 committee, including the operating system, languages, libraries and API s. The system was tested in a network of transducers comprised by a temperature sensor and cooler, and also tested in a water distribution kit with pressure and flow sensors, and a pressure reducer.