VII International Telecommunications Symposium

In the context of object-based image compression, shape encoders that describe the contour of the objects, called chain codes, tend to be more efficient than that the one based on bitmap, which is the MPEG-4 Part 2 framework. Among the chain codes, those based on grid cells are expected to outperform the ones that employ a symbol to code...

Dirac, a relevant new open wavelet-based video codec, has been released recently. The main contribution of this paper is an adequate performance evaluation of this codec compared to the well-known H.264/AVC. This work differs significantly from previous ones which present unfair and inconclusive comparisons. Eight videos comprising three different...

This paper presents an improved stochastic model for the generalized subband decomposition least-mean-square (GSD-LMS) algorithm. This algorithm is used as an alternative to the standard LMS aiming to improve the convergence speed under correlated input data. An analytical model for the first moment of the adaptive filter weights is derived...

In this paper modifications are investigated to a previously introduced Key Regeneration system used to obtain cryptographic keys from biometric data, specifically from the iris. These modifications improve the performance of the previous system making possible the regeneration of longer and higher entropy cryptographic keys. The modified system was...

This work presents a dynamic bandwidth allocation scheme for DVB-RCS satellite standard aiming to avoid the conflict that arise when VoIP transmission with Voice Activity Detection (VAD) is used. A proposal is presented to improve the quality perceived by the user through bandwidth preallocation and validated by computer simulations using the Network...

In this work a fast Bragg grating-based tuning device, working according to the mechanical compression of the fiber, is demonstrated. The device achieves a tuning range of 10 nm and presents tuning speeds up to 15 nm/ms. The component can function as the basic element in wavelength routers and add-drop multiplexers.

Nowadays a number of Internet access possibilities can be simultaneously available to fixed or mobile users. Adequate selection of the most appropriate communication path can improve transmission quality for Voice over IP (VoIP) applications by providing smaller delay and smaller packet loss. Stream Control Transmission Protocol (SCTP) is currently...

New results and the analysis of the resonance frequency and pattern fields of microstrip antennas array, with superconductor patch for different very high critical temperatures, are presented. The linear superconducting rectangular microstrip antennas array uses the new materials Sn5InBa4Ca2Cu10Oy at temperature of 212 K, conductivity of 1.88x105...

In this paper we propose sub-optimum, reduced complexity decoding algorithms for convolutional codes. The algorithms are based on the minimal trellis representation for the convolutional code, and on the M algorithm. We analyze both the computational complexity, in terms of arithmetic operations, and the bit error rate performance of the...

In this work, a modified patch antenna with broad bandwidth and small size is proposed and investigated. Instead of rectangular patch of a known antenna we use a rounded patch. This modification increases significantly the upper frequency edge of the operating band. This allows one to obtain a -10 dB return loss bandwidth of 72 % and to flatten the...