Mobile Communications Systems
Mostrando 1-12 de 25 artigos, teses e dissertações.
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1. Segurança em sistemas de comunicação pessoal : um modelo de arquitetura de protocolos para a interconexão de sistemas heterogêneos / Security in personal communications systems. one model of protocol architecture for the interworking of heterogeneous systems
A evolução dos sistemas de comunicação sem fio ou wireless apresentam até agora três gerações em menos de duas décadas. Fazendo parte desta evolução estão os sistemas de telefonia celular e os emergentes Sistemas de Comunicação Pessoal ou PCS (Personal Communications Systems). Este trabalho visa apresentar duas questões importantes na evoluç�
Publicado em: 2010
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2. Códigos LDPC quaternários aplicados à técnica de transmissão OFDM / Quaternary LDPC codes applied to OFDM transmission technique
This dissertation addresses the study of error correcting codes based on sparse non-binary matrices. The LDPC (Low Density Parity Check) codes constitute a efficient family of codes generated by sparse parity check matrices and it is considered as one of the classes of codes that presents the best performance in digital communications systems. LDPC codes ove
Publicado em: 2010
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3. Impacto da utilização de tecnicas de lifting explorando diferença entre ferramentas interpretada e compilada na velocidade computacional da codificação wavelet de imagens estaticas / Impact of using lifting techniques to explore the differences between interpreted and compiled tools in the computational speed of wavelet static image coding
The field of analysis and compression of images has been received special attention of the scientific community because of including in the main systems of digital TV, satellite communications and mobile communications. In this context, the Discrete Transform Wavelet (TWD) arise how a powerful tool and its many advantages allowed your insertion in important
Publicado em: 2009
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4. Aplicação comercial do sistema omnisat da autotrac e qualcomm com o uso de terminais móveis e análise de técnicas de múltiplo acesso em sistemas via satélites
The purpose of this work is to show the OmniSAT system of data mobile communication and tracking vehicles of Autotrac, applied to vehicles fleet market. The OmniTRACS system was developed in the United States by Qualcomm Incorporated and implements, besides security and logistic, also bi-directional mobile communications applied to government and utilities m
Publicado em: 2008
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5. FROM THE TECHNOLOGICAL SUBLIME TO THE FLOW CARTOGRAPHIES / DO SUBLIME TECNOLÓGICO ÀS CARTOGRAFIAS DOS FLUXOS
Recently, a growing number of artists and designers are producing interactive artworks equipped with mobile and wireless communications devices, including mobile phones, PDAs and laptops, connected to computer networks and location-based systems. These artworks are mapping new forms of flow that accumulate invisibly in space in layers of our technological li
Publicado em: 2008
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6. Aplicações de antenas adaptativas em sistemas de comunicações móveis / Applications of adaptive antennas in wireless communications systems
The increasing demand for wireless communications services has demanded the development of technologies that allow serving a bigger amount of users without increasing the bandwidth used today. It also has an increasing demand for services that need high transmission rates on mobile terminal, as Internet and video transfer. On the other hand, the user desires
Publicado em: 2007
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7. Methodology for calculation of spectrum requirements estimation for the future development of cell mobile system / Metodologia de cálculo de espectro para suportar a evolução do sistema móvel celular
This work presents a methodology for calculation of spectrum requirement estimation for future development of 3G and beyond-3G systems based on ITU-R recommendations. It presents a systematic approach that incorporates service category definitions, service environments, radio environments, market data analysis and traffic estimation for these categories and
Publicado em: 2007
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8. Sobre equalizadores autodidatas de decisão realimentada aplicados a sistemas multiusuário
Due to the growing demand for mobile communications, adaptive equalizers play an important role for enhancing the efficiency of data transmission. In this scenario, the Decision Feedback Equalizer (DFE) stands out. It presents a favorable tradeoff between computational cost and efficient behavior, mainly when compared to Linear Transversal Equalizer. In this
Publicado em: 2007
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9. Simulador para servidor habilitador de localizaÃÃo em plataforma LBS
Since XIX centuryâs end, the telephony suffered to constant technological evolution. In the 70âs, a new need was looked for: mobility. So, it began the age of the mobile communications. The increasing integration between cellular systems and computer science made possible the development of new technologies and services to the mobile networks. Currently, t
Publicado em: 2006
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10. Analysis of optical CDMA systems / Análise de sistemas CDMA ópticos
The evolution of optical networks verified in the last few years has been characterized by the search for better bandwidth utilization efficiency. The successful implementation of practical code division for multiple access techniques (CDMA) in mobile communications systems has stimulated new investigations on this topic, particularly in the optical domain (
Publicado em: 2006
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11. Proposta de um esquema de codificaÃÃo de vÃdeo a baixas taxas de transmissÃo para comunicaÃÃes mÃveis celulares / Proposal for low bit rate video coding for cellular phones communications
Very low bit rate coding below 64 kbit/s will be an important issue in forthcoming visual services such as videophone and multimedia systems. The trend of increasing interest in, and demand for, mobile phone, interactive TV and multimedia services, has led to significant acceleration of video coding research worldwide. This paper introduces and presents simu
Publicado em: 2006
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12. New methods for transmit space-time processing combining diversity and beamforming / Novas tecnicas de processamento espaço-temporal em transmissão conciliando diversidade e beamforming
O presente trabalho trata da utilização, em transmissão, de um arranjo de antenas na estação rádio-base de um sistema de comunicação celular. Na recepção, as soluções para explorar o arranjo são atualmente bem estabelecidas na literatura. Por outro lado, na transmissão, o problema se mantém aberto. Duas abordagens são possíveis: explorar o a
Publicado em: 2006