XXX Simpósio Brasileiro de Telecomunicações

Este artigo propõe uma nova abordagem para o projeto de detectores para sensoriamento espectral no contexto de sistemas de rádios cognitivos. Detectores ótimos minimax são projetados através de otimização convexa e aplicados ao teste de razão de verossimilhança generalizado baseado em autovalores. Para este teste é apresentada uma comparação entre os...

Um aspecto importante nas redes sem fio multimídia é o escalonamento da transmissão dos pacotes gerados pelos terminais da rede. O DQCA (Distributed Queuing Collision Avoidance) é um protocolo de acesso ao meio de alto desempenho e estável, que mantém uma vazão alta com qualquer carga de tráfego. Entretanto, ele pode permitir índices altos de atraso e...

The channel capacity independent from any internal structure of the channel input alphabet X. Also, the noisy channel coding theorem do not depend from any internal structure of X. However, all the major linear encoding schemes require that X must have some kind of algebraic structure that can be a field or else a ring. This algebraic structure of X is...

A hybrid decoding system for LDPC codes em- ploying min-sum belief propagation (BP) decoding to correct errors, combined with erasure iterative decoding, is investigated by means of computer simulation. The proposed hybrid decoding system by employing a reduced number of iterations becomes more efficient, especially in the error-floor region, achieving a...

Network integration of aeronautical and space systems should have a low failure rate when used in electromagnetic environments critics, whose spurious signal interference is inevitable. This paper analyzes the capability of operating a network of terminals MIL-STD-1553B in the presence of white noise induced intensity and bandwidth manageable. A sequence...

This work presents a study about the impact of Erbium-doped Fiber Amplifier (EDFA) gain variation problem may have on the performance of Dynamic Optical Networks. An analytical model to estimate the EDFA gain variation considering amplifier input power is proposed. Two Impairment Aware RWA algorithms are also proposed. Numerical simulations suggest that...

Neste trabalho será mostrado como subespaços livres de descoerência em canais quânticos com descoerência coletiva podem ser usados para transmitir informação clássica com sigilo absoluto. Além disso, também será mostrado que, se determinadas condições de simetrias forem garantidas, então a taxa máxima em que estas comunicações sigilosas acontecem...

The frequency bands used in mobile communications are allocated according to the type of application. With the need for more channels, the frequency spectrum has become a scarce natural resource. This study shows the results of a proposed modulation using the variation of the autocorrelation of pseudo-random codes to carry information. The work...

The objective video quality assessment is a quick and low cost alternative compared with the subjective evaluation. However, the objective evaluation is not as reliable, because their results are not always according to the perceived quality of the human visual system. This paper presents a new metric for objective video quality assessment, called...

The performance of communications systems and networks over time-varying fading channels is significantly affected not only by the average bit error rate (BER), but also by the occurrence of burst errors that may seriously degrade the operation of upper-layer communication protocols. Several recent works have shown that the adaptive modulation...