Jean-Marc Brossier

Water filling capacity of Rayleigh MIMO channels

MIMO channels can attain high capacities provided that the propagation medium contains enough scatterers. The capacity of MIMO channels can further be increased by performing optimal power distribution over transmit antennas. This, in turn, necessitates knowledge of the channel at the transmitter. It is shown in this paper that for low signal-to-noise ratios (SNR) and small number of antennas, this increase in capacity can be of interest. Rayleigh fading conditions are considered.

Phase tracking: what do we gain from optimality? particle filtering versus phase-locked loops

This paper studies the problem of tracking a Brownian phase with linear drift observed to within one digital modulation and one additive white Gaussian noise. This problem is of great importance as it models the problem of carrier synchronization in digital communications. The ultimate performances achievable for this problem are evaluated and are compared to the performances of three solutions of the problem. The optimal filter cannot be explicitly calculated and one goal of the paper is to implement it using recent sequential Monte-Carlo techniques known as particle filtering. This approach is compared to more traditional loops such as the Costas loop and the decision feedback loop. Moreover, since the phase has a linear drift, the loops considered are second-order loops. To make fair comparisons, we exploit all the known information to put the loops in their best configurations (optimal step sizes of the loops). We show that asymptotically, the loops and the particle filter are equivalent in terms of mean square error. However, using Monte-Carlo simulations we show that the particle filter outperforms the loops when considering the mean acquisition time (convergence rate), and we argue that the particle filter is also better than the loops when dealing with the important problem of mean time between cycle slips.

On the Hybrid Cramér Rao Bound and Its Application to Dynamical Phase Estimation

This letter deals with the Cramer-Rao bound for the estimation of a hybrid vector with both random and deterministic parameters. We point out the specificity of the case when the deterministic and the random vectors of parameters are statistically dependent. The relevance of this expression is illustrated by studying a practical phase estimation problem in a non-data-aided communication context.

Equalizer for video rate transmission in multipath underwater communications

This paper concerns the equalization problem of an underwater high rate transmission system. Because the channel delay spread of an horizontal link is large compared with the data duration, we have developed an adaptive equalizer in order to minimize the calculus burden of the moving receiver. The performance of this equalizer on synthetic and real channels is discussed.

Adaptive estimation of the fourth-order cumulant of a white stochastic process

Abstract This communication is devoted to the introduction and study of a new adaptive estimator of the fourth-order cumulant of a white, zero-mean stochastic process. We show that this estimator is asymptotically unbiased and normal. Moreover, we give an explicit form for the asymptotic variance. This allows us to show that the algorithm is robust with respect to the estimation of the second-order moment. This fact leads to the introduction of a simpler estimator of the cumulant which uses a single recursive equation.

On capacity of Rician MIMO channels

Use of antenna arrays at both sides of the communication link can result in high channel capacities provided that the propagation medium is rich scattering. Previous studies on MIMO wireless structures have mostly considered Rayleigh fading conditions. Here a study is made on the capacity of Rician channels; it is shown that depending on the number of antennas, the MIMO capacity achieved under the condition of Rician fading may be greater or smaller than the capacity in the case of Rayleigh fading. In particular, for a large number of antennas, Rician channels exhibit smaller capacity than Rayleigh channels. On the other hand, for Rician channels, if the line-of-sight component is not very significant, the increase in capacity by an increase in the number of antennas can still be considerable.

A low complexity block turbo decoder architecture - [transactions letters]

In this letter we present a low-complexity architecture designed for the decoding of block turbo codes. In particular we simplify the implementation of Pyndiahs algorithm by not storing any of the concurrent codewords generated by the list decoder.

Smoothing PLLs for QAM Dynamical Phase Estimation

This paper presents a near-optimum, low-complexity, fixed-interval smoothing algorithm that approaches the performance of an optimal smoother for the price of two low-complexity sequential estimators (two PLLs). The proposed Smoothing PLL (S-PLL) algorithm is easy to implement and fits the Cramer-Rao bounds over a wide range of signal-to-noise ratios. Moreover we show that, compared to the conventional forward loop, the proposed scheme allows to have a large gain of several dBs and is able to track frequency offsets.

Block turbo codes for multicarrier local loop transmission

We investigate the performance of different block turbo codes in the context of Enhanced VDSL. We first describe the VDSL system used in our simulation link. We then propose an iterative decoding algorithm based on Pyndiahs (1998) SISO decoder for product turbo block codes that can be implemented with reasonable complexity. We also illustrate several results for various QAM modulation schemes. The coding gains obtained for the different codes and modulations then allow us to predict the attainable bit rates as a function of the line length. We show that such a turbo block decoding outperforms the classical Reed Solomon hard decoding used in the ADSL system.

Asymptotic analysis of the multiuser MMSE receiver for the downlink of a MC-CDMA system

This paper considers multi-carrier CDMA (MC-CDMA) communication systems. Recently, the asymptotic performance of a multiuser MMSE receiver for a MC-CDMA system has been established, assuming orthogonal spreading codes and equal powers. A similar study has also been conducted for a DS-CDMA system, considering in this case unequal powers. The introduction of orthogonal codes can be considered as a breakthrough for the asymptotic analysis of such systems, and requires an intensive use of the free probability theory. Based on these results, we investigate in this paper the asymptotic performance of the multiuser MMSE receiver for a MC-CDMA downlink transmission, with orthogonal codes. The asymptotic value of the signal to interference plus noise ratio (SINR) is derived, as a function of the channel loading, the noise power and the power distribution /spl mu//sub power/(p). Simulations show that the asymptotic SINR is applicable to realistic systems.