Channel Estimation
Mostrando 13-24 de 66 artigos, teses e dissertações.
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13. Uma Contribuicão a Estimação de Canais PLC Variantes no Tempo utilizando Sinais Pilotos
In this dissertation is discussed and analyzed the performance of pilot-assisted channel estimation techniques for OFDM (Orthogonal Frequency Division Multiplexing) modulation that is applied to data transmission through PLC (power line communications) channels. The PLC channels are modeled as linear and time-invariant (LIT), linear and time variant (LTV), a
Publicado em: 2009
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14. Estimação de canais MIMO variantes no tempo usando filtros de Kalman / Time-varying MIMO channel estimation using Kalman filters
In this work we use Kalman filters to estimate time-varying wireless channels in multiple-input, multiple-output (MIMO) systems. First, we propose an optimal estimator (in the minimum mean squared error sense) to track flat channels in orthogonal space-time block coded systems. Due to the orthogonality inherent to these codes, the Kalman filter equations can
Publicado em: 2009
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15. DYNAMIC PILOT-SYMBOL ALLOCATION FOR CLOSED-LOOP OFDM SYSTEMS / ALOCACÃO DINÂMICA DE SÍMBOLOS-PILOTO PARA SISTEMAS OFDM DE ENLACE FECHADO
OFDM systems have gathered quite some attention from international standardization bodies for the past decade. Various works in literature aim at optimizing transmission for these systems in the open-loop scenario, i.e. when there is no feedback communication between transmitter and receiver. This work focuses on the utilization of a closed-loop for OFDM sys
Publicado em: 2009
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16. ESTIMAÇÃO DE CANAL E DETECÇÃO CEGA DE SINAIS EM SISTEMAS DE TRANSMISSÃO OFDM / BLIND CHANNEL ESTIMATION AND SIGNAL DETECTION IN OFDM TRANSMISSION SYSTEMS
O esquema OFDM (Orthogonal Frequency Division Multiplexing) é um esquema de transmissão de sinais por multiplexação em freqüência e sua adoção vem mostrando-se bastante promissora no que diz respeito à transmissão de sinais em canais seletivos em freqüência. Sua relativa robustez frente a canais com múltiplos percursos é conseguida efetuando-se
Publicado em: 2009
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17. Uso de imagens ALOS/PALSAR multipolarizadas para detecção de incremento de desflorestamento na Amazônia / Use of multipolarized ALOS/PALSAR image for detection of increment of deforestation in the Amazon
The Amazon forest is a region of rainforest, which has about 5,4 million square kilometers, and with great biodiversity of species on the planet. However, its traditional model of occupation has lead to significant levels of increase of deforestation in the brazilian Legal Amazon. Through remote sensing, these areas can be constantly monitored, offering rate
Publicado em: 2009
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18. Managing trust relationships: calculative, affective, belief and performance
There is an ongoing concern among managers and scholars: how can firms develop trust and achieve performance? Our paper aims to review the emerging perspective of trust and propose mechanisms to build trust in channel relationships. In the literature, we identified six mechanisms: calculative, affective, belief, embeddedness, continuity and capability. A cen
BAR - Brazilian Administration Review. Publicado em: 2008-12
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19. MÃtodos estatÃsticos multi-percursos para a identificaÃÃo cega de canais da fonte de aplicaÃÃes Ãs comunicaÃÃes sem fio / High-order statistical methods for blind channel identification and source detection with applications to wireless communications
Les systÃmes de tÃlÃcommunications modernes exigent des dÃbits de transmission trÃs ÃlevÃs. Dans ce cadre, le problÃme dâidentification de canaux est un enjeu majeur. Lâutilisation de techniques aveugles est dâun grand intÃrÃt pour avoir le meilleur compromis entre un taux binaire adÃquat et la qualità de lâinformation rÃcupÃrÃe. En utilis
Publicado em: 2008
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20. CHANNEL ESTIMATION AND SIGNAL DETECTION IN CDMA SYSTEMS WITH MULTI CARRIER / ESTIMAÇÃO DE CANAL E DETECÇÃO DE SINAIS EM SISTEMAS CDMA COM MÚLTIPLAS PORTADORAS
Este trabalho investiga o impacto da utilização de técnicas para melhorar a qualidade da estimação de canal em sistemas MC CDMA (Multi Carrier Code Division Multiple Access) e MC DS CDMA (Multi Carrier Direct Sequence Code Division Multiple Access) em canais seletivos em frequência. Dois tipos de intevalos de guarda são considerados: Prefixo Cíclico
Publicado em: 2008
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21. Frequency domain concurrent channel equalization for multicarrier systems
Receivers for wireless Orthogonal Frequency Division Multiplexing (OFDM) systems usually perform the channel estimation based on pilot carriers in known positions of the channel spectrum. Interpolation between pilot carriers is applied to determine the channel transfer function in all carrier frequencies. Channel variations along time are compensated by mean
Journal of the Brazilian Computer Society. Publicado em: 2007-03
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22. ESTIMAÇÃO DE CANAL EM SISTEMAS DE COMUNICAÇÃO SOBRE LINHAS DE POTÊNCIA / CHANNEL ESTIMATION OVER POWER LINE COMMUNICATIONS SYSTEMS
The powerline communications systems have been receiving increasing attention in last few years. Power line communications presents a no new wires solution with the additional advantages of ubiquitous node availability, easy installation, and cost effectiveness. This thesis investigation the powerline estimation channel. It was presented parametric channel e
Publicado em: 2007
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23. New proposals for optmization of digital TV receivers based on OFDM in regional single frequency network environments / Novas propostas para otimização de receptores de TV digital baseados em OFDM em ambientes de redes de frequencia unica regionais
This thesis deals with the optimization of Digital TV receivers based on OFDM, with performance evaluation in regional single frequency networks (SFN). Such environment facilitates the channel distribution, however its characteristics degrade the receiver operation. Initially, projects of loop canceller filters in relay stations are treated, and they are nec
Publicado em: 2007
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24. Modelagem tensorial e processamento de sinais por sistemas de comunicaÃÃes de redes / Tensor modeling and signal processing for wireless communication systems
In several signal processing applications for wireless communications, the received signal is multidimensional in nature and may exhibit a multilinear algebraic structure. In this context, the PARAFAC tensor decomposition has been the subject of several works in the past six years. However, generalized tensor decompositions are necessary for covering a wider
Publicado em: 2007