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Recently, it has been studied how to reduce the probability of interception and to increase the efficient security in the wireless digital communication systems. Among the possible approaches for the information security, the chaotic signal can be used to encode information very efficiently in many ways due to the inherent characteristic of irregularity. In this paper, in noise and interference environment,...
In downlink orthogonal frequency division multiple access (OFDMA) systems, available subcarriers are divided into groups and assigned to multiple uses for simultaneous transmissions. The ideal universal receiver sampling the incoming signals just after a RF stage is very seducing but not realistic at this time due to limitations in sampling capabilities for high frequency systems. Software-defined...
Orthogonal frequency division multiplexing (OFDM) is effective method for transmitting high speed data at frequency selective channel. But OFDM is sensitive to the carrier frequency offset (CFO) and sample timing offset (STO). As these effects, inter-carrier interference (ICI), inter-symbol interference (ISI) and common phase noise error (CPE) occur. And these effects cause degradation of performance...
OFDM can use frequency band efficiently and has strong characteristic for fading channel. But orthogonality collapse when carrier frequency offset and sample timing offset occur. Sample timing offset is represented as phase rotation and ISI. And Carrier frequency offset is represented as phase rotation and ICI. To compensate those effects, many studies were processed based on frequency domain. In...
In this paper, we propose a cross-layer design (CLD) scheme combining rate adaptation and four types of hybrid automatic repeat request (HARQ) for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) systems following the ECMA-368 standard. The time varying property is incorporated into standard UWB channel models for the purpose of investigating rate adaptation. To...
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