Made available in DSpace on 2016-04-04T18:31:32Z (GMT). No. of bitstreams: 1 Aturo Jose Fenile Peris.pdf: 4348655 bytes, checksum: 34479e7af136c0f06a1b46d21b30c1c4 (MD5) Previous issue date: 2012-06-22 / The design of the IEEE 802.11 standard allows, in certain situations, competition for access to the transmission medium results in an anomaly. As a result of this anomaly, mobile stations that should achieve high rates of transmission are impaired and don t get those rates. The consequence is the transmission capacity low utilization of the wireless system and the natural increasing of the time mobile stations stays on (and consuming energy); because of this, the increase in energy consumption is another effect of this anomaly. From this scenario, one way to deal with this anomaly is to have a better utilization of the wireless transmission medium. In this context, this work proposes a bench for studies of flow control in IEEE 802.11; this bench allows the management of bandwidth and the collection of traffic statistics from users sessions connected to the wireless network. As a resulting study from the bench using, there is a proposal to mitigate the anomaly through the user traffic management. The results indicate that the controlling the traffic from users who are in poor wireless transmission may produce a better utilization of transmission capacity of an IEEE 802.11 access point. / A concep??o do padr?o IEEE 802.11 permite que, em determinadas situa??es, a competi??o pelo acesso ao meio de transmiss?o resulte em uma anomalia. Como resultado dessa anomalia, esta??es m?veis que deveriam conseguir altas taxas de transmiss?o s?o prejudicadas e acabam por n?o conseguir essas taxas. A consequ?ncia ? o baixo aproveitamento da capacidade de transmiss?o do sistema sem fio e o natural aumento do tempo em que as esta??es m?veis permanecem ligadas e consumindo energia; por conta disso, o aumento no consumo de energia ? outro efeito dessa anomalia. A partir desse cen?rio, uma forma de combater essa anomalia ? a melhoria da utiliza??o do meio de transmiss?o sem fio. Nesse contexto, este trabalho apresenta uma proposta de bancada para estudos de controle de vaz?o em redes IEEE 802.11; essa bancada permite gerenciar a largura de banda e coletar dados estat?sticos relativos ao tr?fego das sess?es dos usu?rios conectados ? rede sem fio. Como estudo resultante da utiliza??o da bancada, h? uma proposta de mitiga??o da anomalia por meio da gest?o do tr?fego dos usu?rios. Os resultados indicam que o controle do tr?fego de usu?rios que est?o em m?s condi??es de transmiss?o sem fio pode melhorar o aproveitamento da capacidade de transmiss?o de um ponto de acesso IEEE 802.11.

Le Wi-Fi est omniprésent dans les villes, que ce soit par le nombre grandissant de point d'accès public, ou la déploiement massif de points d'accès privés, sous la forme de boxes d'opérateurs notamment. Si nous supposons que l'ensemble de ces points d'accès soient utilisables afin de permettre à n'importe quel appareil d'accéder à Internet, alors nous aurions potentiellement une couverture réseau sur l'ensemble de la ville. Ce postulat nous a conduit à nous demander si le Wi-Fi pouvait être utilisé comme réseau à l'échelle urbaine. Ce réseau pourrait plus particulièrement être utilisé dans un contexte de mobilité. Or, le Wi-Fi n'a pas été conçu dans le but de gérer des utilisateurs mobiles,et les appareils doivent régulièrement changer de points d'accès lorsqu'ils n'ont plus de connectivité. Ce mécanisme, appelé handover, peut être long car les appareils doivent d'abord constater leurs pertes de connectivité avant de commencer à chercher le prochain point d'accès auquel s'associer. Il peut être particulièrement long pour des appareils comme les smartphones car ces derniers sont contraint en énergie et n'appliquent donc pas une politique de handover aggressive. Dans ce contexte nous avons cherché à caractériser les applications possible sur le Wi-Fi lorsqu'un utilisateur est mobile, en fonction de la durée de handover de son équipement, de sa vitesse et de la densité des points d'accès présents dans la ville. Nous avons constaté que pour les utilisateurs se déplaçant à faible allure, l'impact de la durée de handover est faible au regard de la connectivité totale, ce qui leur permet d'utiliser des applications gourmandes en terme de bande passante tant que celles-ci possèdent un certain degré de tolérances aux déconnexions. Cependant lorsque la vitesse de déplacement augmente, la durée de handover dégrade progressivement la connectivité des utilisateurs, de telle sorte que ceux ayant une allure élevée ne peuvent plus espérer utiliser les différents points d'accès. En effet, les équipements passent alors plus de temps à effectuer des handovers qu'à échanger des données applicatives. Les retransmissions jouant un rôle important dans la durée de handover, nous avons étudié finement leurs fonctionnement en 802.11.Pour cela nous avons mis en place un banc d'essai nous permettant d'observer les séquences de messages retransmis par différentes implémentations de 802.11lorsque l'on fait subitement disparaitre le point d'accès. Nous avons comparé ces séquences avec celle décrite dans le standard, et nous avons constaté que le nombre de retransmissions maximal ainsi que l'augmentation de la fenêtre de contention n'étaient pas respectés. De plus, ces implémentations passent beaucoup de temps à tenter de retransmettre avant d'initier leurs procédures de handover. Les retransmissions sont aussi utilisées dans les algorithmes d'adaptation de débits afin de déterminer si le lien se dégrade. Or, lors de la contention, le nombres de pertes augmente avec la plus forte probabilité de collisions. Afin d'observer l'impact des retransmissions sur les algorithmes d'adaptation de débits lors de la contention, nous avons mis en place un banc d'essai composé d'une trentaine de stations identiques. Nous avons constaté que l'algorithme de contrôle de débit utilisé est sous optimal par rapport à l'utilisation d'une modulation unique. Enfin, nous nous sommes intéressés à l'utilisation d'un tel réseau à l'échelle de la ville afin d'acheminer des données ayant une forte validité spatiale. Nous avons alors proposé un schéma d'adressage géographique exploitant l'infrastructure d'Internet. Il permet à la fois d'obtenir un découpage hiérarchique du monde, et d'avoir un préfixe hiérarchique des adresses, similaire à celui de CIDR. Nous montrons que ce schéma d’adressage peut être utilisé dans des adresses multicast pour envoyer des messages à destination de zones géographiques précises (surface minimale d'un mètre carré). / Wi-Fi is everywhere in cities, whether through the growing number of publicaccess points, or the massive private access points deployment, in the formof set-top boxes for the major part.If we assume that all these access points are usable in order to allow anydevice to access the Internet, then we would potentially have network coveragethroughout the city.This assumption led us to wonder if Wi-Fi could be used as a city-wide network.This network could, more specifically, be used in a context of mobility.However, Wi-Fi was not designed to manage mobile users, and devices have tooften change their access points when they no longer have connectivity.This mechanism, called handover, can be long because devices must first detecttheir connectivity losses before they can start looking for the next accesspoint to associate with.It can be particularly long for devices such as smartphones because they areenergy constrained and therefore do not apply an aggressive handover policy.In this context we tried to characterize the possible Wi-FI applications for amoving user, considering the handover duration, the user speed and the accesspoints density in the city.We found that for slow-moving users, the impact of the handover is smallcompared to the their overall connectivity.This allows them to use bandwidth-intensive applications as long as they areto some extend delay-tolerant.However, when the user’s speed increases, the impact of handover’s durationgradually degrades the user’s connectivity, so that high speed users can nolonger expect to use different access points.Fast moving devices spend more time performing handovers with new access pointsthan transmitting application data.Retransmissions play an important role in the duration of handover.In order to study in detail the retransmissions in 802.11, we have set up atestbed allowing us to observe the sequences of retransmitted messages usingdifferent implementations of 802.11 when we suddenly make the access pointdisappear.We compared these sequences with the one described in the standard, and we wefound that the maximum number of retransmissions as well as the growth in thecontention window were not respected.In addition, these implementations spend a lot of time trying to retransmitbefore initiating their handover procedures.Retransmissions are also used in the rate control algorithms to determine ifthe link is deteriorating.However, during contention, the number of losses increases with the higherprobability of collisions.In order to observe the impact of retransmissions on the rate controlalgorithms during contention, we have set up a testbed composed of about thirtyidentical stations.We found that the rate control algorithm used underperforms compared to theuse of a single modulation.Finally, we proposed a geographical addressing scheme compliant with theInternet infrastructure.It allows to obtain both a hierarchical division of the world, and ahierarchical prefix for the addresses, similar to the one used in the CIDRformat.We show that this addressing scheme can be used in multicast addresses to sendmessages to specific geographical areas (minimum area of one square meter).

This thesis is concerned with the development of new mathematical models for the IEEE 802.11??s access mechanisms, with a particular focus on DCF and EDCA. Accurate mathematical models for the DCF and EDCA access mechanisms provide many benefits, such as improved performance analysis, easier network capacity planning, and robust network design. A feature that permeates the work presented in this thesis is the application of our new models to network environments where both saturated and non-saturated traffic sources are present. The scenario in which multiple traffic sources are present is more technically challenging, but provides for a more realistic setting. Our first contribution is the development of a new Markov model for non-saturated DCF in order to predict the network throughput. This model takes into account several details of the protocol that have been hitherto neglected. In addition, we apply a novel treatment of the packet service time within our model. We show how the inclusion of these effects provides more accurate predictions of network throughput than earlier works. Our second contribution is the development of a new analytical model for EDCA, again in order to predict network throughput. Our new EDCA model is based on a replacement of the normal AIFS parameter of EDCA with a new parameter more closely associated with DCF. This novel procedure allows EDCA to be viewed as a modified multi-mode version of DCF. Our third contribution is the simultaneous application of our new Markov models to both the non-saturated and the saturated regime. Hitherto, network throughput predictions for these regimes have required completely separate mathematical models. The convergence property of our model in the two regimes provides a new method to estimate the network capacity of the network. Our fourth contribution relates to predictions for the multimedia capacity of 802.11 networks. Our multimedia capacity analysis, which is based on modifications to our Markov model, is new in that it can be applied to a broad range of quality of service requirements. Finally, we highlight the use of our analysis in the context of emerging location-enabled networks.

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.

This thesis is concerned with the development of new mathematical models for the IEEE 802.11??s access mechanisms, with a particular focus on DCF and EDCA. Accurate mathematical models for the DCF and EDCA access mechanisms provide many benefits, such as improved performance analysis, easier network capacity planning, and robust network design. A feature that permeates the work presented in this thesis is the application of our new models to network environments where both saturated and non-saturated traffic sources are present. The scenario in which multiple traffic sources are present is more technically challenging, but provides for a more realistic setting. Our first contribution is the development of a new Markov model for non-saturated DCF in order to predict the network throughput. This model takes into account several details of the protocol that have been hitherto neglected. In addition, we apply a novel treatment of the packet service time within our model. We show how the inclusion of these effects provides more accurate predictions of network throughput than earlier works. Our second contribution is the development of a new analytical model for EDCA, again in order to predict network throughput. Our new EDCA model is based on a replacement of the normal AIFS parameter of EDCA with a new parameter more closely associated with DCF. This novel procedure allows EDCA to be viewed as a modified multi-mode version of DCF. Our third contribution is the simultaneous application of our new Markov models to both the non-saturated and the saturated regime. Hitherto, network throughput predictions for these regimes have required completely separate mathematical models. The convergence property of our model in the two regimes provides a new method to estimate the network capacity of the network. Our fourth contribution relates to predictions for the multimedia capacity of 802.11 networks. Our multimedia capacity analysis, which is based on modifications to our Markov model, is new in that it can be applied to a broad range of quality of service requirements. Finally, we highlight the use of our analysis in the context of emerging location-enabled networks.

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.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-10-25T12:55:35Z No. of bitstreams: 2 Dissertação - Henrique Valle de Lima - 2018.pdf: 6140413 bytes, checksum: 4bb41779722574af9e9b07103ad3ba20 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-10-25T13:11:28Z (GMT) No. of bitstreams: 2 Dissertação - Henrique Valle de Lima - 2018.pdf: 6140413 bytes, checksum: 4bb41779722574af9e9b07103ad3ba20 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-10-25T13:11:28Z (GMT). No. of bitstreams: 2 Dissertação - Henrique Valle de Lima - 2018.pdf: 6140413 bytes, checksum: 4bb41779722574af9e9b07103ad3ba20 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-09-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / LTE (Long Term Evolution) in unlicensed band (LTE-U) has emerged as a promising solution to the problem of the huge growth in mobile data traffic. It expands the benefits of LTE with bands of the unlicensed 5 GHz spectrum, mainly used in IEEE 802.11. But uncertainties as to the availability of these bands make the adoption of LTE-U a great challenge. In this dissertation, we propose a mixed linear programming approach for allocating resources in order to expand service by LTE-U. Subsequently, we propose a stochastic programming approach, taking into account the randomness of the unlicensed band, allocating resources under a certain control in the risk of conflict with IEEE-802.11. We used three models of the literature for the demand for IEEE 802.11 in our tests. The results highlight the importance of prior knowledge about the distribution of this demand. / A LTE (Long Term Evolution) em banda não-licenciada (LTE-U) surgiu como uma solução promissora para o problema do enorme crescimento no tráfego de dados móveis. Ela amplia os benefícios da LTE com bandas do espectro não-licenciado de 5 GHz, usado principalmente em IEEE 802.11. Mas incertezas quanto à disponibilidade dessas bandas tornam a adoção da LTE-U um grande desafio. Nesta dissertação, propomos uma abordagem de programação linear mista, para alocação de recursos a fim de expandir o atendimento por LTE-U. Posteriormente, propomos uma abordagem de programação estocástica, levando em consideração a aleatoriedade da banda não-licenciada, alocando recursos sob um certo controle no risco de conflito com o IEEE 802.11. Usamos três modelos da literatura para a demanda por IEEE 802.11 em nossos testes. Os resultados destacam a importância do conhecimento prévio sobre a distribuição dessa demanda.