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- Benoît Champagne, Stéphane Bédard, Alex Stephenne
- IEEE Trans. Speech and Audio Processing
- 1996

In this correspondence, synthetic microphone signals generated with the image model technique are used to study the eeects of room reverberation on the performance of the maximum likelihood (ML) estimator of the time delay, in which the estimate is obtained by maximizing the cross-correlation between ltered versions of the microphone signals. The results… (More)

- Amine Laourine, Alex Stephenne, Sofiène Affes
- IEEE Communications Letters
- 2007

In this paper, we first provide a very accurate estimation of the capacity of a single-input single-output system operating in a log-normal environment. Then, hinging on the fact that the sum of log-normal Random Variables (RV) is well approximated by another log-normal RV, we apply the obtained results to find the capacity of Maximum Ratio Combining and… (More)

- Alex Stephenne, Benoît Champagne
- Signal Processing
- 1997

A microphone array can be used for hands-free acquisition of speech under reverberant conditions. This requires knowledge about the desired talker location, which can be obtained by estimating the time delays between the signals received by one or more pairs of spatially separated microphones. However, in a typical audio-conference room, strong… (More)

- Faouzi Bellili, Alex Stephenne, Sofiène Affes
- IEEE Trans. Communications
- 2010

In this paper, we derive for the first time analytical expressions for the exact Cramér-Rao lower bounds on the variance of unbiased non-data-aided (NDA) signal-to-noise ratio (SNR) estimators of square QAM-modulated signals. The channel is assumed to be constant over the observation interval and the received signal is supposed to be corrupted by additive… (More)

Composite multipath fading/shadowing environments are frequently encountered in different realistic scenarios. These channels are generally modeled as a mixture of Nakagamim multipath fading and log-normal shadowing. The resulting composite probability density function (pdf) is not available in closed form, thereby making the performance evaluation of… (More)

- Amine Laourine, Alex Stephenne, Sofiène Affes
- IEEE Trans. Communications
- 2009

In this letter we provide an analytical expression for the moments of the capacity for the log-normal fading channel. Since the developed expression involves infinite series, we show that the error that results from the truncation of these series is insignificant. We also analyze in more details the ergodic capacity by giving a simpler expression for the… (More)

- Alex Stephenne, Faouzi Bellili, Sofiène Affes
- IEEE Trans. Wireless Communications
- 2010

In this paper, we develop a new method for signalto-noise ratio (SNR) estimation when multiple antenna elements receive linearly-modulated signals in complex additive white Gaussian noise (AWGN) spatially uncorrelated between the antenna elements. We also derive extensions of other existing moment-based SNR estimators to the single-input multipleoutput… (More)

- Mohamed Ali Boujelben, Faouzi Bellili, Sofiène Affes, Alex Stephenne
- IEEE Transactions on Signal Processing
- 2010

In this paper, we address the problem of data-aided (DA) and nondata-aided (NDA) per-antenna signal-to-noise ratio (SNR) estimation over wireless single-input multiple-output (SIMO) channels from linearly modulated signals. Under constant channels and additive white Gaussian noise (AWGN), we first derive the DA maximum-likelihood (ML) SNR estimator in… (More)

- Amine Laourine, Mohamed-Slim Alouini, Sofiène Affes, Alex Stephenne
- IEEE Trans. Wireless Communications
- 2007

This paper investigates the capacity of generalizedK fading channels. This very general model describes accurately composite multipath/shaodwing fading channels which are widely encountered in real-world environments. We derive closed-form expressions for three adaptive transmission techniques, namely, i) optimal rate adaptation with constant power, ii)… (More)

- Alex Stephenne, Benoît Champagne
- IEEE Trans. Vehicular Technology
- 2000

In this paper, we present a new, computationally efficient simulator for time-varying multi-path (fast fading) vector channels that can be used to evaluate the performance of antenna array wireless receivers at the base station. The development of the simulator is based on the emulation of the spatio-temporal correlation properties of the vector channel.… (More)