Yes / A new generation of satellite systems that support regenerative on-board processors (OBPs) and multiple spot beam technology have opened new and efficient possibilities of implementing IP multicast communication over satellites. These new features have widened the scope of satellite-based applications and also enable satellite operators to efficiently utilize their allocated bandwidth resources. This makes it possible to provide cost effective satellite network services. IP multicast is a network layer protocol designed for group communication to save bandwidth resources and reduce processing overhead on the source side. The inherent broadcast nature of satellites, their global coverage (air, land, and sea), and direct access to a large number of subscribers imply satellites have unrivalled advantages in supporting IP multicast applications. IP mobility support in general and IP mobile multicast support in particular on mobile satellite terminals like the ones mounted on long haul flights, maritime vessels, continental trains, etc., still remain big challenges that have received very little attention from the research community. This paper proposes how Proxy Mobile IPv6 (PMIPv6)-based IP multicast mobility support defined for terrestrial networks can be adopted and used to support IP mobile multicast in future satellite networks, taking cognizance of the trend in the evolution of satellite communications.

[pt] O conhecimento profundo de como o meio-ambiente influencia na radiopropagação, objetivando o aumento da capacidade e da cobertura de Sistemas de Comunicações Móveis Celulares, tem motivado inúmeros estudos relativos ao tema. Conforme pode ser observado na literatura técnica, estes estudos tem se concentrado na caracterização da influência das edificações na propagação do sinal. Poucos estudos relacionados à influência da vegetação têm sido relatados. Considerando-a como parte integrante dos ambientes urbanos. T. Tamir, na década de 60, utilizando a teoria rigorosa da propagação em camadas múltiplas desenvolvida por L.M. Brekhovskikh, propôs aproximações de ordem prática que permitiram a utilização de seus modelos na implementação de radioenlaces operando em ambientes de florestas. Seus modelos foram desenvolvidos para a faixa de freqüências de 2 a 200 MHz, para radioenlaces fixos e conseqüentemente, não consideram os desvanecimentos lento e rápido que normalmente estão presentes nos sistemas celulares e provocam a deterioração da qualidade do sinal recebido. Apesar disso, alguns autores, sem qualquer comprovação experimental, têm se válido de extensões dos modelos de Tamir para prever a cobertura dos sistemas celulares. Este trabalho enfocou a caracterização da influência da vegetação típica dos ambientes urbanos nos Sistemas de Comunicações Móveis Celulares, concentrando esforços na caracterização e análise dos desvanecimentos rápidos (estatística de pequena escala) provocados pela propagação por multipercurso, à luz de resultados de testes de propagação realizados no Campo de Santana. Os modelos propostos por Tamir foram testados para se verificar o seu grau de aderência às medições realizadas. A dependência do sinal recebido em ambiente de parque com a altura de transmissão, freqüências e polarização foi determinada. Foram feitas, também, algumas considerações sobre os modelos propostos por R. Lang, que se aplicam à propagação de sinais incoerentes em regiões de florestas. / [en] The knowledgment of how the environment affects radio propagation in order to increase the Cellular Móbile Communication Systems capacity and coverage hás lead to a grreat number of related studies. As can be seen in the technical literature, these studies have been concentrated on the characterization of the influence of buildings on signal propagation. For this characterization, the vegetation, as a part of the urban environment, was not considered. T. Tamir has proposed, based on the rigorous propagation theory of multiple layers due to L. M. Brekhovskikh, some practical approximations which has allowed him to develop models for radio links operating on forest environments. His models were developed for the 2 a 200 MHz range fixed links and hence the fast and slow fading conditions, generally present on mobile systems, weren´t considered. Even so, some authors use Tamir´s model extensions to account for the coverage of cellular mobile systems without any experimental proof. This work has addressed the characterization of how the typical vegetation of urban environments affects Cellular Mobile Communication Systems. Great efforts have been made on the fast fading studies through statistical small-scale variations due to the multipath propagation condition. The Tamir models were tested against the experimental data collected in Campo de Santana. The received signal dependence on transmitter height, frequency and polarization were determined. Also the models proposed by R. Lang for incoherent reception inside forests, were investigated.

The resources (memory, power and bandwidth) are limited in wireless and mobile networks. Previous research has shown that the quality of service (QoS) of the mobile client can be improved through efficient resources management. This thesis contains two areas of research that are strongly interrelated. In the first area of research, we extended the MoSync Algorithm, a network application layer media synchronization algorithm, to allow play-out of multimedia packets by the base station upon the mobile client in a First-In-First-Out (FIFO), Highest-Priority-First (PQ), Weighted Fair-Queuing (WFQ) and Round-Robin (RR) order. In the second area of research, we make modifications to the DSR and TORA routing algorithms to make them energy aware routing protocols. Our research shows that the QoS of the mobile client can be drastically improved through effective resource allocation.

Wireless sensor networks are an indispensable tool in this highly connected world. WSNs have been the focus of research efforts in areas of communication, electronics and control for many years. Advancements in the fields of MEMS, RF and digital circuit technology has led to the development of low cost and extremely power efficient smart sensors. This has led to the need of a fast, reliable and inexpensive method of consensus building for these sensor networks. Basic concepts of graph theory and consensus building are explained in this thesis. This thesis reviews the models and strategies for consensus building present in the literature. The shortcomings of these models are explained through examples and a leader-follower model based consensus building strategy is presented. Algorithm to convert any graph into a bipartite graph by edge removal and a strategy to select effective leaders based on a weighted combination of node centrality, ratio of leaders to the total number of nodes and presence of leaf nodes in the group is presented in this thesis. Proposed leader-follower model is compared against classic models for consensus building are compared and proven to be better. Mobility is studied using deterministic and random mobility models to show the improvement in convergence rate of the network. It is shown that mobility can turn any disconnected network into a connected network, which is able to reach consensus.

Wireless networks provide communications to fixed, portable and mobile users and offer substantial flexibility to both end-users and service providers. Current cellular/PCS networks do not offer cost effective high data rate services for applications, such as, telematics, traffic surveillance and rescue operations. This research studies the feasibility and behavior of outdoor implementation of low-cost wireless LANs used for high mobility telematics and traffic surveillance. A multi-hop experimental wireless data network is designed and tested for this purpose. Outdoor field measurements show the wireless coverage and throughput patterns for static and mobile users. The results suggest that multi-hop wireless LANs can be used for high mobility applications if some protocols are improved. / Master of Science

付記する学位プログラム名: 社会を駆動するプラットフォーム学卓越大学院プログラム / 京都大学 / 新制・課程博士 / 博士(情報学) / 甲第25441号 / 情博第879号 / 新制||情||147(附属図書館) / 京都大学大学院情報学研究科情報学専攻 / (主査)教授 原田 博司, 教授 佐藤 高史, 教授 林 和則 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DGAM

The purpose of this research was to examine ESL (English as a second language) students' current use of their mobile phones for English skill building activities outside of class in a U.S. school setting. In addition, this research reported on students' perceptions of the potential benefits of using smartphones in class for English learning. Also learners' current English related activities using mobile devices and time duration of using different phone features were studied. The literature review included smartphones, computer education, mobile learning, mobile assisted language learning (MALL), computer assisted language learning (CALL), theories of second language learning, second language learner attributes and the use of smartphones outside the classroom. An electronic survey was used to collect the quantitative data which were analyzed by descriptive and inferential statistics. The results concluded that students used mobile applications on a daily basis to read and write email, read books and news, check a dictionary, talk, text and video chat. Students used mobile phones outside of class to improve the English skills listed in the survey and the same participants perceived the potential benefits of using smartphones in class for the same English skills. Among the English skills, vocabulary exercises, finding example sentences of English words and English grammar exercises had a significant difference between out of class and in class variable. The results indicated a direction for future research on using mobile phones for ESL learning. This study also revealed a focus of practice for utilizing mobile technologies in the teaching and learning of ESL.

It is desirable to develop a universal digital receiver which is capable of operating with many different wireless communication systems. Time Dependent Adaptive Filter (TDAF) Processing represents an effective approach for CDMA interference rejection. This technique is especially appropriate at the mobile receiver where there is little prior knowledge of the spreading codes of the other users. This thesis presents enhanced forms of the Time Dependent Adaptive Filter (TDAF), which is an optimal periodically time-varying adaptive filter. It is able to fully exploit the cyclostationarity and spectral correlation in certain DS-SS signals. It is shown how multiple AVM service providers can exist in adjacent channels within the ISM band. It is demonstrated that using the realistic channel models the TDAF can provide substantial improvement in interference rejection over the conventional correlation receiver. Computationally efficient TDAF structures have been also proposed to handle the case of different code repeat intervals for different systems. Results of CDMA overlay system simulation have shown that TDAF processing can achieve tremendous gain in narrowband interference rejection compared to notch/matched filter processing. An input signal which has 45 dB narrowband interference-to-signal power ratio (J/S), the SIR of the TDAF processed output signal can be 20 dB, a 65 dB improvement. The use of TDAF processing and a spectral shaping filter can minimize the impact of adjacent channel interference. Even in an environment which has a 30 dB adjacent channel J/S, the SIR at output is demonstrate to be a 50 dB improvement. System performance shows little degradation by adjacent channel and narrowband interference. / Master of Science

This thesis presents a study of several algorithms for enhancing speech degraded by additive noise in mobile cellular communications. The primary goal of this multi-stage study was to examine adaptive noise cancellation techniques in which one microphone is used to measure the speech plus noise signal and another microphone is used to form an estimate of the interfering background noise. The first stage of this research project involved the design and operation of a measurement system to gather dual channel audio samples in mobile radio environments for use in testing adaptive noise cancellation algorithms developed at Northeastern University. In the second phase of this research, several adaptive algorithms were used to implement noise cancellation systems which were applied to the measured speech signals. In the third phase of this research, several of the adaptive noise cancellation algorithms are compared and additional speech enhancement techniques are investigated. / Master of Science

Adaptive antenna arrays have tremendous potential for increasing the capacity of mobile communications, by reducing co-channel interference, multipath, and noise. Blind adaptive algorithms, that is, algorithms which do not require a training sequence, are investigated and compared in this study. These algorithms are tested for common cellular signals. The performances of three blind adaptive algorithms: the Constant Modulus Algorithm (CMA), the Spectral self-COherence Restoral Algorithm (SCORE), and the spectral correlation predictor using a Time-Dependent Adaptive Array (TDAA), are studied. The TDAA is introduced as a new blind algorithm that exploits the cyclostationary property of the signal. Results show that the TDAA is able to out-perform the other blind algorithms for most of the test conditions and provides the optimal MSE solution. / Master of Science