Ignace Bruyland

Throughput Optimization for a Generalized Stop-and-Wait ARQ Scheme

This paper deals with a generalized stop-and-wait ARQ scheme, whereby data blocks are sent to the receiver in sets containing an arbitrary number of identical copies. The main idea behind this scheme is a reduction of the idle time of the transmitter.

Performance study of statistical multiplexing in case of slow message generation

The queuing behavior is investigated for a slotted statistical multiplexer to which variable-length messages arrive via low-speed access lines at a rate of one packet per slot. Some explicit results are derived by using a two-dimensional state description of the system. A message of length n contributes to the packet-arrival stream into the multiplexers buffer during n consecutive slots. This introduces a degree of correlation into the packet-arrival process. The state description used accounts for this inherent correlation in the packet-arrival stream process.<<ETX>>

Comment on "Algorithm for Construction of Variable Length Code with Limited Maximum Word Length"

In the above correspondence, two algorithms for the construction of a minimum redundancy code have been described. In this correspondence, it is pointed out that the strategy in the correspondence does not always lead to an optimal code. A correction of both algorithms is presented.

The Influence of Finite Bandwidth on the Capture Effect in FM Demodulators

In this paper a formula is derived for the capture ratio of an FM demodulator of which the finite bandwidth has been taken into account. The results obtained in a numerical example are in complete agreement with the measurements made on a physical detector.

Analysis/synthesis filter banks designed for subband video compression

Abstract In this paper, some numerical analysis and synthesis filter banks for subband image coding are summarized and designed. They can be used in subband compression of digital video telephone, video conference, television (TV) and high-definition television (HDTV) signals. A small part of the numerical results presented in this paper can also be found in literature. However, our results cover all the possible typical filter banks whose length range from 2 to 10. Furthermore, new approximate reconstruction filter banks are derived over which the constraint is the loosest when compared with QMF and perfect reconstruction banks already existing.

Parallel computation of image curve velocity fields

Abstract The computation of the velocity field along image curves belongs to the class of ill-posed problems (in the sense of Hadamard). Local measurements of image pattern changes are usually insufficient to solve the velocity field uniquely. Therefore regularization techniques are applied, yielding solutions that are robust against noise and that are correct for a limited class of curve velocity fields. It is shown in the paper that regularization problems, such as the smoothest velocity field computation and the computation of the minimum dilatation velocity field, can be solved with a parallel algorithm or a fast sequential algorithm. This follows from the block-tridiagonal structure to which these variational techniques give rise.

Edge grouping by using orientation information

The edge is an important feature required by many computer vision tasks. One crucial step of edge or line detection is grouping. Local orientation in a gray scale image provides an important clue for grouping. An algorithm, used for edge or grouping based on the local orientation information, is proposed. The results are shown, and compared with a well-known transform.

Comments on "A subjective evaluation of noise-shaping quantization for adaptive intra-/interframe DPCM coding of color television signals" (by B. Girod et al.)

In the above named work by B. Girod et al. (see ibid., vol.36, no.3, p.332-46, 1988), a stability condition for a DPCM (differential pulse code modulation) system with additional quantization error noise shaping has been proposed. In the present work, a correction of this stability condition is derived. >

Single stage 280 Mbit/s coding of HDTV using HDPCM with a vector quantizer based on masking functions

Abstract Hybrid Differential Pulse Code Modulation (HDPCM) of coloured pictures can be combined with vector quantization of the coloured prediction errors to an efficient coding scheme for pictures, of which the chrominance is subsampled by a factor 2. First, this contribution describes the reasons for the combination of DPCM and vector quantization, i.e., the joint probability density of the prediction errors and the intercomponent masking. Then, the text treats how a combination of HDPCM and vector quantization can be more resistant to transmission errors than DPCM, and how it can be implemented with one ROM and one adder in the critical path by pipelining the recursive loop of the HDPCM-coder. Simulation results illustrate the performance of the coding scheme with a vector quantizer with 32 output vectors for the compression of the bit rate of HDTV-signals to 280 Mbit/s. kwBit rate reduction, picture coding, Differential Pulse Code Modulation, vector quantization

Corrections to "Comment on &#769;Algorithm for Construction of Variable Length Code with Limited Maximum Word Length&#769;"

In this correspondence we determine an upper bound on the error recovery time of a decision feedback equalizer (DFE) operating on a high signal to noise ratio channel of exponential impulse response to be used for binary transmission. This bound is related to the channel time constant and we show that exponential impulse response channels form a favourable class of channels with regard to DFE error recovery ‘properties. Paper approved by the Editor for Digital Communications of the IEEE Communications Society. Manuscript received November 25, 1986; revised March 6, 1987. This work was supported by the Australian Telecommunications and Electronics Research Board. The authors are with the Department of Systems Engineering, Research School of Physical Sciences, Australian National University, Canberra, A.C.T. 2601, Australia. IEEE Log Number 8715681. ~~