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Estudo de um Sistema de Telefonia sem Infraestrutura através de Modelagem e Simulação baseada em Agentes; Study of an Infrastructureless Communication System through Agent-based Modeling and Simulation.

Oliveira, André Luiz Machado de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/09/2012 Português
Relevância na Pesquisa
56.01%
A evolução tecnológica das redes de telecomunicações sem fio permite que organizações de redes mais inteligentes sejam vislumbradas. É possível imaginar um sistema de telefonia formado por dispositivos móveis autônomos que não necessite de nenhuma infraestrutura pré-estabelecida para trocar informações com seus vizinhos, de acordo com o alcance do raio de transmissão. Assim, as informações poderiam ser repassadas de nó em nó, formando uma rede de múltiplos saltos. A ausência de uma entidade central também poderia melhorar a tolerância a falhas do sistema, principalmente por gerar uma redundância de caminhos possíveis entre os nós. Analisamos o desempenho desse sistema em diferentes cenários e a sensibilidade à variação de parâmetros como o raio de transmissão, interferências, a quantidade de nós e número de saltos máximo permitido (TTL), e testamos estratégias de comunicação com raio fixo, raio variável, número de vizinhos mínimo e etc., através de modelagem e simulação baseada em agentes. De maneira geral, a estratégia de transmissão com raio variável apresentou a melhor taxa de mensagens recebidas e a menor média de saltos até o destino, porém com maior nível de energia do sistema. A estratégia de raio fixo apresentou a menor energia total gasta pelo sistema para enviar as mensagens...

Monitoramento de dados via internet baseado em telefonia celular

Tateoki, Getúlio Teruo
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 123 f. : il. fotos (algumas color.)
Português
Relevância na Pesquisa
46.01%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia Elétrica - FEIS; A aquisição de dados tem evoluído de forma significativa nos últimos anos e passa a ser indispensável em várias aplicações nas áreas de engenharia, agricultura, medicina, aeronáutica, etc. O estado da arte nessa área envolve o uso de sistemas de comunicação sem fio e da internet. Neste trabalho é apresentado um sistema moderno de aquisição de dados, que é baseado em uma comunicação sem fio via rede GSM (Global Mobile for System), com conexão via Internet através de um sistema de telefonia celular GPRS (General Packet Radio Service), monitoramento de dados via página Web (World Web Browser) e interface de aplicação com base em um microcontrolador. O sistema é bastante flexível e foi testado em operações reais no monitoramento de temperatura ambiente. Os resultados obtidos são altamente satisfatórios e mostra que o sistema pode servir de base para aplicações em diferentes áreas onde a telemetria seja indispensável.; Data acquisition has significantly been developed in the last years and became indispensable in many application area of engineering such as agriculture, medicine, aeronautic...

Analise de desempenho dos sistemas moveis celulares 2G, 2,5G e 3G; Performance analysis of 2G, 2.5G and 3G cellular mobile systems

Carlos Henrique Rodrigues de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/08/2005 Português
Relevância na Pesquisa
56.03%
Este trabalho de tese estuda e analisa o desempenho dos sistemas móveis celulares GSM de segunda geração (2G), GPRS de segunda geração intermediária (2,5G) e CDMA2000 de terceira geração (3G). Na primeira parte deste trabalho de tese são avaliadas estratégias de compartilhamento dos canais de comunicação utilizados pelos sistemas GSM e GPRS, em busca daquela que resulte no menor impacto na qualidade dos serviços prestados por ambas as redes. Para esta avaliação, e como contribuição deste trabalho de tese, são desenvolvidos algoritmos aplicados em um simulador de eventos discretos desenvolvido em linguagem de programação C/C++. Os resultados das simulações mostram que a reserva de canais exclusivos ao sistema GPRS apresenta degradação na qualidade de serviço prestado pelo sistema GSM e que a melhor estratégia de compartilhamento é utilizar os canais de comunicação para o sistema GPRS nos momentos em que estes canais não são usados pelo sistema GSM. Na segunda parte deste trabalho de tese são feitas análises de desempenho dos sistemas móveis celulares de terceira geração, CDMA2000 lxRTT e CDMA2000 lxEVDO, baseadas na qualidade do serviço prestado por estas redes operando com várias aplicações simultâneas fim-a-fim entre cliente e servidor. Técnicas de detecção multiusuário e de antenas adaptativas são utilizadas na recepção destas aplicações e é avaliada a nova qualidade de serviço. Para estas análises de desempenho e como contribuição deste trabalho de tese...

Performance evaluation of fixed and mobile relay in WiMAX system

Mumtaz, S.; Tu, L.T.; Sadeghi, R.; Gameiro, A.
Fonte: Digital Information Research Foundation Publicador: Digital Information Research Foundation
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.05%
Future wireless communication systems are expected to provide more stable and higher data rate transmissions in the whole network. WiMAX is one of the technologies to cover diverse geographic regions. WiMAX covers the high dense urban areas and provide access over large geographic regions in remote rural area. However, in both scenarios it is challenging to cover the entire service area. In both cases relays are foreseen to extend the range of the BS and to increase the system throughput allowing for a cost-efficient deployment and service. As multi-hop/relay has complex interactions between the routing and medium access control decisions, the extent to which analytical expressions can be used to explore its benefits are limited. Consequently simulations tend to be the preferred way of assessing the performance of relays. In this paper, we explain, how to deploy fixed-relay and mobile relay by using computer simulation in WiMAX system and we consistently observed that the throughput is increased and the outage is decreased in the relay-augmented WiMAX network, which is converted to range extension without any capacity penalty, for the realistic range of values of the propagation and other system parameters investigated.

CONNECTOR: a geolocated mobile social service

Almeida, Pedro; Silva, Lídia; Abreu, Jorge; Saraiva, Melissa; Almeida, Margarida; Teixeira, Jorge; Antunes, Maria; Ramos, Fernando
Fonte: Information Science Reference (IGI) Publicador: Information Science Reference (IGI)
Tipo: Parte de Livro
Português
Relevância na Pesquisa
56.01%
The widespread and availability of increasingly powerful mobile devices is contributing for the incorporation of new services and features on our daily communications and social relationships. In this context, geolocation of users and points of interest in mobile devices may contribute, in a natural way, to support either the mediation of remote conversations as the promotion of face-to-face meetings between users, leveraging social networks. The CONNECTOR system is based on geolocation data (people, contente and activities), enabling users to create and develop their personal relations with other members of the CONNECTOR social network. Users, maps, sharing features and multimedia content are actors in this social network allowing CONNECTOR to address the promotion of geolocated social networks driven by physical proximity and common interests among users. This chapter discusses the work undertaken for the conceptualization and development of the CONNECTOR system. Preliminary evaluation results along with usage contexts are also presented. The chapter concludes with a discussion about future developments in geolocation and personalization in mobile communication services.

Low data rate visible light communication system; Sistema de comunicação por luz visível de baixo débito

Farias, Gonçalo Nuno Brás
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
46.03%
Recent advances in light emission diodes (LED) technology led them to an important place on lighting systems. This conquer allied to its switching speed permitted the development of new visible light communication systems (VLC), these are included in unguided optical communications. In the past, unguided optical communications were restricted to infrared spectrum due to LEDs ine ciency, but nowadays this is changing. Visible light communication systems can o er viable or complementary alternatives to the existing communication systems, due to its easy integration in certain environments. One possible integration environment are the mobile communications, and that fact is in the origin of this work. Old mobile phones had interfaces that allowed optical communication, for example IrDA but with the advances of technology these become obsolete and were eliminated. Due to that, modern smartphones do not o er any kind of interface for optical communications. However most of them have one camera that uses a ash device based on high intensity LEDs. Controlling with some precision one smartphone ash allows the implementation of one low data rate VLC systems which can be used for smart tagging, remote control of electronic devices or to control access to buildings. The main goal of this project is study the viability of the use of one smartphone as emitter in a VLC system.; Os recentes avanços na tecnologia dos diodos emissores de luz (LED) levaram a que estes conquistassem um lugar muito importante nos sistemas de iluminação. Esta conquista aliada à sua velocidade de comuta ção levou ao desenvolvimento de sistemas de comunicação por luz visível (VLC)...

FEW phone file system

Soares, João Paulo da Conceição
Fonte: FCT - UNL Publicador: FCT - UNL
Tipo: Dissertação de Mestrado
Publicado em //2009 Português
Relevância na Pesquisa
46.16%
Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia Informática; The evolution of mobile phones has made these devices more than just simple mobile communication devices. Current mobile phones include such features as built-in digital cameras, the ability to play and record multimedia contents and also the possibility of playing games. Most of these devices have support for Java developed applications, as well as multiple wireless technologies (e.g. GSM/GPRS, UMTS, Bluetooth, and Wi-Fi). All these features have been made possible due to technological evolution that led to the improvement of computational power, storage capacity, and communication capabilities of these devices. This thesis presents a distributed data management system, based on optimistic replication,named FEW Phone File System. This system takes advantage of the storage capacity and wireless communication capabilities of current mobile phones, by allowing users to carry their personal data “in” their mobile phones, and to access it in any workstation, as if they were files in the local file system. The FEW Phone File System is based on a hybrid architecture that merges the client/server model with peer-to-peer replication...

Mobile Money Services Development : The Cases of the Republic of Korea and Uganda

Gutierrez, Eva; Choi, Tony
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
46.15%
This study intends to increase understanding of how different types of mobile money services have developed in different environments. For this purpose, two countries were selected, the Republic of Korea and Uganda. From these study cases, some conclusions emerge. The development of mobile banking services can appear at different stages of financial sector development, but it requires a vibrant and competitive telecommunications sector. The regulatory environment does not need to be very sophisticated for the mobile industry to emerge. However, some elements appear to be important. The legal framework should allow (or at least not explicitly forbid) nonbank financial institutions to issue money and use banking agents or correspondents. To ensure wider use of the service by the population, it is important to educate the population on the benefits of mobile money services.

Implementation of a portable-IP system for mobile TCP/IP

Qu, Xun; Xu Yu, Jeffrey; Brent, Richard P
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Working/Technical Paper Formato: 251340 bytes; 356 bytes; application/pdf; application/octet-stream
Português
Relevância na Pesquisa
56.06%
In the current TCP/IP-based systems, the hardness of mobile communication stems from the IP routing and addressing schemes. In this paper, we refine our mobile solution using two mappings: namely; a prtable-IP mapping and a mobile mapping. We also explicity distinguish our two mapping approach from the existing mobile-IP solutions which are of a single mapping scheme. The portable-IP mapping is supported using DHCP and DNS functions and requiring no modifications to the TCP/IP protocols. The mobile mapping is implemented in the socket layer. Our mobile solution achieves high compatibility with the current TCP/IP systems mainly because that no special functionality is required to support mobility in the network and the transport layers. In terms of performance, our mobile solution can reduce both the cost for distributing the location information of mobile hosts and the cost of forwarding IP datagrams across the Intenet. In this paper,we also focus on the implementation details of the portable-IP system for supporting the portable-IP mapping. Two registration procedures and DNS updating approaches are given. We show that using the new BIND version 8.1.1. can avoid to reload the whole DNS database frequently.; no

Smart antenna application in DS-CDMA mobile communication system

Ng, Kok Keng.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
55.96%
This thesis examine the use of an equally- spaced linear adaptive antenna array at the mobile station for a typical Direct Sequence Code Division Multiple Access (DS-CDMA) cellular mobile communications system with forward error correction, with soft decision decoding is studied. We analyze the performance of a randomly positioned mobile terminal with a randomly orientated adaptive antenna array in the forward channel (base-station to mobile) of a multi-cell DS-CDMA system and established four performance boundaries. Using the more conservative optimized array antenna performance boundary for the 2-, 3- and 4-element linear array, we compare the capacity and the performance of different cellular systems under a range of shadowing conditions, with and without antenna sectoring at the base-station, and for various user capacities, using Monte Carlo simulation. We further apply tapped-delay line (transversal filter) to each antenna element channel, to allow frequency dependent amplitude and phase adjustment for broadband signals. The performance of a DS-CDMA cellular system with a mobile terminal equipped with a linear array and a tapped-delay line is analyzed. It has been demonstrated that the optimization process has been extremely computationally expensive and hence minimum taps should be used for practical consideration. The results illustrated that...

Nationwide mobile communication systems

Schworer, William Joseph
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 3 v. (various pagings) bill., maps
Português
Relevância na Pesquisa
56.04%
Approved for public release; distribution unlimited.; This thesis provides a basic understanding of nationwide terrestrial and satellite mobile communications and tracking technologies. Covered are systems currently available and in development. An analysis of user costs is performed for comparison. A more detailed mobile satellite cost/benefit analysis for use by the trucking industry is also presented. Follow-on chapters contain discussions of the basic economic issues faced by satellite system operators and the regulatory history of mobile satellite services. Contained in the appendices are a more detailed discussion of mobile satellite systems and a layman's explanation of communication and navigation technologies. The conclusion presents comments on the possible future direction of these new mobile communication services and makes recommendations for trucking industry use.; Lieutenant Commander, Supply Corps, United States Navy

Mobile Usage at the Base of the Pyramid : Research Findings from Kenya and South Africa

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
Português
Relevância na Pesquisa
46.07%
While the growth of mobile communications in developing countries has been phenomenal, using mobile phones and applications to meet human and economic development goals is not widespread, for they have not proven acceptable or desirable to the locality into which they are introduced. Therefore, it is deduced that technical know-how and entrepreneurial acumen must be complemented by sociocultural understanding. InfoDev's Mobile Use at the Base of the Pyramid program seeks to contribute to this agenda through on-the-ground studies in developing markets. The first phase of this program supported both qualitative and quantitative research on mobile usage by low-income populations in Kenya and South Africa. This report documents the findings of this program.

Content-independent ubiquitous system for mobile learning

Sousa, Diogo Videira
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2010 Português
Relevância na Pesquisa
46.06%
Mobile learning introduces the idea of learning from virtually anywhere, regardless of the in-motion learner. Mobile learning can provide access to different kinds of learning materials, promote communication between learners and foster collaborative learning. Although it is still a very young concept, many people will use it in the following years and learning using a mobile device will increasingly blend into our everyday lives. In this thesis is described the design and construction of a mobile learning system capable of delivering multimedia contents to the learner. This system is called CiVUS (Content-independent Versatile Ubiquitous System). This solution promotes communication between learners and their teachers by encouraging learners to share self-made multimedia contents. A background study was made to evaluate the impact that mobile technologies can have now and in the future, in a learning perspective. Advantages and drawbacks will be addressed and examples of similar applications will be mentioned. The research made provides a good know-how starting point for investigators interested in this subject. The reader of this dissertation will obtain a good notion of what mobile learning is and what it represents for the future of learning. Also...

Modeling, Performance Analysis and Comparison of Two Level Single Chain Pointer Forwarding Strategy For Location Management in Wireless Mobile Communication

Kant, Chhaya Ravi; Arun, P.; Prakash, Nupur
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/09/2006 Português
Relevância na Pesquisa
46.07%
Global wireless networks enable mobile users to communicate regardless of their locations. Location management is an important part of the emerging wireless and mobile technology. A Personal Communication System (PCS) network must have an efficient way to keep track of the mobile users to deliver services effectively. Global System for Mobile Communication (GSM) is a commonly accepted standard for mobility management of mobile users. Location management involves location tracking, and location information storage. Location management requires mobile users to register at various registration areas whenever they are on the move. The registration process may cause excessive signaling traffic and long service delays. To improve the efficiency of location tracking and avoid call set up delays, several strategies such as local anchor scheme, per-user caching scheme and several pointer forwarding schemes have been proposed in the past. In this paper, we propose a new "Two Level Single Chain Pointer Forwarding (TLSCP) Strategy" in which a two level hierarchy of level-1 and level-2 forwarding pointers reduced to single chain length are used. Organizing the pointers in a two level hierarchy and further restricting the pointer chain lengths at both the levels to single chain localizes the network signaling traffic and reduces the call set up delays. To justify the effectiveness of our proposed strategy...

Comparison of Performance Metrics for QPSK and OQPSK Transmission Using Root Raised Cosine and Raised Cosine Pulse shaping Filters for Applications in Mobile Communication

Chattopadhyay, Sudipta; Sanyal, Salil Kumar
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/12/2009 Português
Relevância na Pesquisa
56.07%
Quadrature Phase Shift Keying (QPSK) and Offset Quadrature Phase Shift Keying (OQPSK) are two well accepted modulation techniques used in Code Division Multiple Access (CDMA) system. The Pulse Shaping Filters play an important role in digital transmission. The type of Pulse Shaping Filter used, and its behavior would influence the performance of the communication system. This in turn, would have an effect on the performance of the Mobile Communication system, in which the digital communication technique has been employed. In this paper we have presented comparative study of some performance parameters or performance metrics of a digital communication system like, Error Vector Magnitude (EVM), Magnitude Error, Phase Error and Bandwidth Efficiency for a QPSK transmission system. Root Raised Cosine (RRC) and Raised Cosine (RC) Pulse shaping filters have been used for comparison. The measurement results serve as a guideline to the system designer to select the proper pulse shaping filter with the appropriate value of filter roll off factor (a) in a QPSK modulated mobile communication system for optimal values of its different performance metrics.; Comment: 7 pages IEEE format, International Journal of Computer Science and Information Security...

A Comprehensive Study and Performance Comparison of M-ary Modulation Schemes for an Efficient Wireless Mobile Communication System

Haque, Md. Emdadul; Rashed, Md. Golam; Kabir, M. Hasnat
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/03/2012 Português
Relevância na Pesquisa
55.75%
Wireless communications has become one of the fastest growing areas in our modern life and creates enormous impact on nearly every feature of our daily life. In this paper, the performance of M-ary modulations schemes (MPSK, MQAM, MFSK) based wireless communication system on audio signal transmission over Additive Gaussian Noise (AWGN) channel are analyzed in terms of bit error probability as a function of SNR. Based on the results obtained in the present study, MPSK and MQAM are showing better performance for lower modulation order whereas these are inferior with higher M. The BER value is smaller in MFSK for higher M, but it is worse due to the distortion in the reproduce signal at the receiver end. The lossless reproduction of recorded voice signal can be achieved at the receiver end with a lower modulation order.; Comment: International Journal of Computer Science, Engineering and Applications (IJCSEA) Vol.1, No.3, June 2011

Mobile web resource tracking during a disaster or crisis situation

Douangboupha, Phavanhna
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
46.08%
This paper proposes a prototype solution for a mobile web resource tracking system using mobile devices during an emergency situation. The system provides real time data to a decision maker so that he/she can effectively and efficiently monitor resources and assess the situation accordingly. Mobile devices (i.e., smart phones) support the ease of use for any location and at anytime. The Internet technology is selected to enable multiple or cross platform technology solutions for different mobile devices. Resources in the scope of this project are human resources (e.g., a doctor, a police officer) and a chemical list in a room. With the use of a GPS-enabled device or a wireless-enabled device, the system is used to provide the current location of the human resources. Transferring data between system databases and mobile devices is one of the important areas to address in this project. Since location data of a user is sensitive data, data should be protected via an encrypted protected network. In addition, because of the urgency of any crisis situation, it is critical that data from the system be able to be retrieved in a reasonable time frame. The investigation includes the exploration of database and data transfer solutions to meet the data availability during emergency conditions on mobile devices. This document includes a description of the system design...

Communication framework for distributed computer vision on stationary and mobile platforms

Armenio, Christopher
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
46.12%
Recent advances in the complexity and manufacturability of digital video cameras coupled with the ubiquity of high speed computers and communication networks have led to burgeoning research in the fields of computer vision and image understanding. As the generated vision algorithms become increasingly complex, a need arises for robust communication between remote cameras on mobile units and their associated distributed vision algorithms. A communication framework would provide a basis for modularization and abstraction of a collection of computer vision algorithms; the resulting system would allow for straightforward image capture, simplified communication between algorithms, and easy replacement or upgrade of existing component algorithms. The objective of this thesis is to create such a communication framework and demonstrate its viability and applicability by implementing a relatively complex system of distributed computer vision algorithms. These multi-camera algorithms include body tracking, pose estimation and face recognition. Although a plethora of research exists documenting individual algorithms which may utilize multiple networked cameras, this thesis aims to develop a novel way of sharing information between cameras and algorithms in a distributed computation system. In addition...

Mobile telephone system and non-wire line network

Cheung, Daniel Chi Man
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
56.03%
The need to communicate with non-fixed points without the use of wires led to the development of mobile telephone systems in the early 1920's. Since then, the expanding need for mobile phone service and resulting growth have led to the development of the Advanced Mobile Phone Service (AMPS) by the Bell System. This thesis describes the AMPS system and explains how service is provided to mobile units roaming in a typical area of up to 25 square miles. A network is proposed to interconnect service areas to expand the coverage to a much larger geographic area. Efficient use is made of the limited bandwidth available for network communication. The network is able to manage mobile units that move from one service area to another during a call, and can efficiently locate mobile units throughout the network area.

Information Capacity of the Space Division Multiple Access Mobile Communication System

Rapajic, P
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
65.99%
An expression for the Shannon capacity lower bound of the space division multiple access (SDMA) mobile communication channel with interference is shown. The bound is tightly approaching the Shannon capacity of the orthogonal SDMA system over Gaussian channel with no interference. The information capacity of the SDMA system with adaptive MMSE receivers is presented as well. The SDMA system with MMSE receivers achieves at least 50% of the orthogonal SDMA system capacity for the input signal to noise ratio of practical interest in cellular mobile communications (10-30 dB).