Multipath
Mostrando 1-12 de 35 artigos, teses e dissertações.
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1. 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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2. Improved PLL-based MUSIC Algorithm for Single Receiver DF Systems
Abstract In this paper we propose an improved version of a single receiver DF system that combines a PLL scheme with the MUSIC algorithm to obtain both azimuthal and zenithal angles. The new approach uses a more efficient algorithm to remove the typical ambiguities of PLL-based schemes. We carry out several experiments to assess the algorithm performance. Am
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2017-12
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3. Simulating a Multi-Vehicle Traffic Sensing System Based on Radio Tomographic Imaging
Abstract One of the most recently developed wireless technologies is Radio Tomographic Imaging (RTI). RTI employs a wireless sensor network that produces images of the change in the electromagnetic field of a monitored area using Received Signal Strength (RSS) measurements. This allows the tracking of device-free objects such as humans and cars. This paper i
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2016-12
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4. The Smart Grid Concept in Oil & Gas Industries by a Field Trial of Data Communication in MV Power Lines
Abstract Nowadays, communication and networking technologies are essential for Oil & Gas industries in order to guarantee reliability, safety and low costs in the producing process. Information access and commands and set-points transmission from/to automation systems are challenging tasks mainly due to distributed production areas and hostile environments.
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2016-06
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5. Harmonic Analysis of Multipath Index Time Series in GPS Stations
A identificação de variações cíclicas e sazonais é muito importante em séries temporais. Neste artigo, objetiva-se identificar a presença de variações cíclicas e sazonais nos índices do efeito do multicaminho em estações GPS (Global Positioning System) de monitoramento contínuo. Devido ao modelo usado na obtenção de tais series, não deveria
TEMA (São Carlos). Publicado em: 2015-04
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6. SFN channel measurements in Brazil
In this paper, field measurements carried out in a suburban SFN network with two synchronized transmitters are reported. It is found that the radio signal coverage of the distributed transmission scheme is distinctly improved when compared to a single transmitter system. The path loss gain and improvement associated to the SFN scheme are obtained as well as
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2013-06
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7. Modulação quantizada para sistemas com codificação wavelet sujeitos ao desvanecimento rayleigh
Wavelet coding is an efficient technique to overcome the multipath fading effects, which are characterized by fluctuations in the intensity of the transmitted signals over wireless channels. Since the wavelet symbols are non-equiprobable, modulation schemes play a significant role in the overall performance of wavelet systems. Thus the development of an effi
Publicado em: 2009
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8. Contribuições teoricas para o estudo de funções de distribuição correlacionadas em um canal sem fio / Theoretical contributions to the study of correlated distributions funcions of wireless channels
In wireless communications, the multipath fading is modeled by several distributions including Hoyt, Rayleigh, Weibull, Nakagami-m, and Rice. In this thesis, new, exact expressions for the bivariate Hoyt (Nakagami-q) processes with arbitrary correlation in a nonstationary environment are derived. More specifically, the following are obtained: joint probabili
Publicado em: 2009
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9. IDEA: um protocolo para o isolamento e desvio de anomalias em redes de sensores
The number of applications that relies on wireless sensor networks has grown fast. However those networks are vulnerable to fails and attacks that may disturb or even stop completely important information diffusion through it. In most scenarios, removing or disabling the bad nodes causing those anomalies is simply not possible. The alternative we found to so
Publicado em: 2009
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10. 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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11. 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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12. EQUALIZAÇÃO DE CANAL EM SISTEMAS COM TRANSMISSÃO EM BLOCOS / CHANNEL EQUALIZATION IN BLOCK TRANSMISSION SYSTEMS
The demand for high rate transmission systems, for example in HDTV, third and fourth generation cellular telephony, DSL and so on, causes the rise of a problem: The multipath communications channel (specially in wireless communications), which leads to intersymbol interference phenomenon (ISI). The present work investigates the performance of single-carrier
Publicado em: 2007