Laurent Cuvelier

Fractionally spaced linear and decision-feedback detectors for transmultiplexers

We investigate improved detectors for transmultiplexer-based high bit rate transmission over dispersive channels like telephone wires. The transmitter is based on a synthesis stage. For the receiver, we design fractionally spaced single-input/multiple-output linear detectors, possibly upgraded with a multiple-input/multiple-output decision-feedback section, for an MMSE criterion. The performance of the system is investigated for filter banks, classical DMT, and different channels. The potential of these detectors is demonstrated,.

An early-late timing recovery scheme for filter-bank-based multicarrier transmission

This paper is devoted to the design and the steady-state performance analysis of a data-aided or decision-directed timing recovery scheme for filter bank-based multicarrier transmission with equalization. The symbol synchronizer is obtained from a Mueller and Muller approach extended to multiband transmission. A simple synchronizer is first proposed which can be derived from an approximate likelihood function. Then, possible improvements are discussed. Timing jitter variances are computed and discussed for high bit-rate transmission over copper wires.

Bit-rate sensitivity of filter-bank-based VDSL transmission to timing errors

The performance degradation of filter-bank-based multicarrier transmission due to timing errors is investigated. The receiver is made of a fractionally spaced linear or decision-feedback equalizer designed for some sampling phase. The actual sampling phase is different and the impact of the difference on the performance is investigated. Sampling phase offset and jitter are considered. Besides, assuming the sampling phase error can be estimated the efficiency of various types of interpolation is investigated.

Coding of deinterlaced image sequences

This paper investigates a coding method for interlaced image sequences which uses deinterlaced images as an intermediate format. The purpose of this method is threefold: firstly, to achieve a higher coding gain, as the processing of progressive pictures raises much less difficulty than the processing of interlaced ones; secondly, to provide an intermediate step toward the development of a fully progressive production and transmission chain; and finally to open the way to efficient solutions for important image processing issues such as frame rate conversion and compatibility. In previous work by the authors (1994), an interlace-to-progressive converter was proposed. It was based on theoretically correct generalized interpolation formulas, working under the assumption of a uniform translational motion. The scheme proposed here makes use of this converter to produce the progressive images from the interlaced source, which are coded and then re-interlaced. Another solution is considered, with the purpose of improving the coding efficiency alone. It is based on an intermediate progressive format at half the original temporal sampling rate. However, in that case, some additional information needs to be transmitted in order to accurately recover the full rate interlaced signal. The two methods mentioned above are described in some detail and tested on actual sequences. The picture quality is assessed, both objectively and subjectively, and conclusions are drawn.<<ETX>>

Statistical properties of coded interlaced and progressive image sequences

In this paper, we investigate the statistical properties of interlaced and progressive image sequences in order to determine what is the most efficient format from a coding point of view. Intra- and inter-coding modes are both considered. The main result is that, for both intra- and inter-images, the coding of progressive images outperforms the coding of interlaced ones for low bit rates and large motion vectors. Particular attention is paid to inter-coding with subpel accuracy, where the effects of nonideal interpolation filters and finite precision of the motion vector are taken into account.

MMSE design of interpolation and downsampling FIR filters in the context of periodic nonuniform sampling

The generalized sampling theorem states that any analog signal whose spectrum is limited to 1/T can be exactly recovered from N sequences of samples taken at a rate 2/NT and all having a different sampling phase. When N=2, the exact interpolation formula can be derived quite easily. The ideal interpolation filters have infinite impulse responses (IIRs). This paper addresses first the question of recovering from the two initial sequences any other sequence taken at the same rate 1/T and with a different sampling phase. The design problem is dealt with for finite length filters, and the criterion is the minimization of the mean squared interpolation error. Next, the problem of computing from the two initial sequences a third one at a lower rate is addressed. FIR decimation filters are also designed for an MMSE criterion. These problems are illustrated for two typical covariance functions.

Asymptotic performance of MMSE MIMO decision-feedback equalization for uncoded single carrier and multicarrier modulations

We investigate the asymptotic performance of a multiple input/multiple output (MIMO) decision-feedback equalizer (DFE) used to detect a multicarrier signal transmitted without guard time over a linear dispersive channel. We design the MIMO DFE for a minimum mean square error criterion (MMSE) and compare its performance to that of a single carrier system also using an infinite length MMSE DFE equalizer. We demonstrate that both uncoded systems achieve the same capacity.

Human visual weighted quantization for transform/subband image coding revisited for interlaced pictures

This correspondence addresses the problem of human visual weighted quantization for transform/subband coding of interlaced pictures. Merged field coding is assumed. The criterion proposed for the optimization of the quantizer is the distortion measured on the deinterlaced and decoded image. This criterion and the associated weighting factors are shown to be dependent on the motion between two successive fields.

RLS design of polyphase components for the interpolation of periodically nonuniformly sampled signals

The generalized sampling theorem states that any analogue signal whose spectrum is limited to 1/T can be exactly recovered from N sequences of samples taken at a rate 2/NT and all having a different sampling phase. When N=2, the exact interpolation formula can be derived quite easily. The ideal interpolation filters have infinite impulse responses. This paper addresses the theoretical question of recovering from the 2 initial sequences, any other sequence taken at the some rate 1/T and with a different sampling phase. FIR filters are derived for a least square interpolation error. Moreover, an adaptive implementation is proposed and formulated as a Kalman algorithm. Simulation results obtained for AR processes show the effectiveness of the solution compared to static solutions.

An early-late timing recovery scheme for filter-bank based multicarrier transmission

This paper is devoted to a decision-directed timing recovery scheme for filter bank based multicarrier transmission. The symbol synchronizer is obtained from a maximum-likelihood approach and uses the equalizer outputs. The algorithm is first derived and computational results for the resulting timing error are provided for high bit rate transmission over copper wires. Finally, different improvements are discussed.