Fading Channel
Mostrando 1-12 de 28 artigos, teses e dissertações.
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1. Multi-Step-Ahead Spectrum Prediction for Cognitive Radio in Fading Scenarios
Abstract This paper analyzes multi-step-ahead spectrum prediction for Cognitive Radio (CR) systems using several future states. A slot-based scenario is used, and prediction is based on the Support Vector Machine (SVM) algorithm. The aim is to determine whether multi-step-ahead spectrum prediction has gains in terms of reduced channel-switching and increased
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2020-12
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2. A Construction of Rotated Lattices via Totally Real Subfields of the Cyclotomic Field ℚ(ζp)
RESUMO A teoria de reticulados têm mostrado útil na teoria da informação e reticulados ideais com alta diversidade de modulação têm sido extensamente estudados como uma alternativa de transmissão via o canal de Rayleigh, onde o desempenho destes esquemas de modulação depende essencialmente da diversidade de modulação e da distância produto míni
TEMA (São Carlos). Publicado em: 13/12/2019
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3. Evaluation of OFDM Channel Sounding Techniques with Three Modulation Sequences
Abstract This paper presents an evaluation of multicarrier channel sounding techniques using different random and pseudo-random sequences to modulate the OFDM sounding signal. The Random (Rand), Pseudo-Noise (PN) and Zadoff-Chu (ZC) were tested, both in laboratory simulations and in field measurements. For the laboratory simulations Matlab routines were used
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 11/11/2019
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4. Channel characterization in the 5.8GHz band in a suburban area
Based on signal measurements carried out in the 5.8 GHz band, which is reserved for unlicensed WiMAX in Brazil, this paper evaluates narrowband and wideband characteristics on the suburban area of Tanguá city in Rio de Janeiro State. Fading statistics, coverage and adjusted prediction model such as Hata-COST 231, SUI and UFPA were used in order to find the
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2014-06
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5. Um estudo sobre a robustez de técnicas de processamento de sinais em sistemas MIMO / A study regarding robustness of signal processing techniques in MIMO systems
Multiple antenna wireless communication systems achieve high data transmission rates and good robustness to channel fading when signals traveling through the system are jointly processed in their transmitters and/ or receivers. In general, signal detection techniques assume perfect knowledge of the channel state information, in both transmitter and receiver,
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 17/06/2011
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6. 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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7. Caracterização da distribuição de Weibull em ambientes indoor / Characterization of the Weibull distribution in Indoor environments
The literature describes the fast flat fading propagation model in mobile environment as a Rayleigh distribution with different standard deviations which considers only one parameter to describe the channel fading. In the Weibull distribution there are two parameters to be modeled: shape factor and scale factor. The Rayleigh distribution is a particular case
Publicado em: 2008
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8. Evaluation of the spread sequences selection algorithm over frequency selective fading channels with error correcting codes / Avaliação do algoritmo de busca de sequencias de espalhamento em canais com desvanecimento seletivo em frequencia com codigos corretores de erros
The performance of wireless communication systems that use the multiple access code division technique, CDMA, is interference-limited. A sequence selection algorithm allows a reduction in the mean interference of the system. In the standards like CDMA2000 and WCDMA no algorithm is defined for choosing the sequences. For this reason, in this dissertation we e
Publicado em: 2008
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9. Modelo de canal de estados finitos para canais com desvanecimento correlacionado no tempo e desisÃo suave / Finite-state channel model for time-correlated fading channels with soft-decision
Modelos de canais de estados finitos Markovianos (FSMC, do inglÃs Finite State Markov Channel) sÃo comumente usados para caracterizar a memÃria de canais discretos binÃrios (entrada binÃria, saÃda binÃria). Este trabalho propÃe um novo modelo pertencente à classe FSMC, denominado de modelo com apagamento (MA), que foi idealizado para modelar canais
Publicado em: 2008
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10. Contribuições teoricas para ambientes generalizados do canal sem fio / Theoretical contributions for generalized scenarios of wireless channels
Recentemente, três novos modelos probabilísticos de canal, modelos α-u, η-u e κ-u, foram propostos com o intuito de prover uma análise mais realística do sinal propagante. Por apresentarem um grau de liberdade a mais que os demais já existentes na literatura, um melhor ajuste a medidas de campo verificou-se com a utilização dos mesmos.
Publicado em: 2008
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11. Power allocation in wireless communication systems : stochastic via CVaR and robust approaches / Alocação de potencia em sistemas de comunicações sem fio : abordagens estocastica via o CVaR e robusta
This thesis deals with the power allocation problem under the stochastic and robust approaches, where the channel gains describe the wireless communication system state and are partially known by the controller. The stochastic approach considers the channel gains as random variables which represent the fast fading of the radio signal. Under these settings, t
Publicado em: 2007
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12. m estudo sobre o uso da codificação de canal para otimização do consumo de energia em redes de sensores
Wireless Sensor Networks (WSN) are a set of tiny electronic devices, which monitor physical phenomena over a specific region and send this data to a sink node. The sensor nodes connect to the other ones in the range of the transmitted signal, establishing a collaborative network operation. The collected data are forwarded to other nodes until the sink is rea
Publicado em: 2007