DE ALMEIDA , André

In several signal processing applications for wireless communications, the received signal is multidimensional in nature and may exhibit a multilinear algebraic structure. In this context, the PARAFAC tensor decomposition has been the subject of several works in the past six years. However, generalized tensor decompositions are necessary for...

In this paper, we first introduce two new classes of constrained tensor models that we call generalized PARATUCK- (N1, N) and Tucker- (N1, N) models. A new tensor space-time-frequency (TSTF) coding structure is then proposed for MIMO OFDM-CDMA wireless communication systems. Two semi-blind receivers relying on the new generalized PARATUCK model...

This paper presents a unified tensor model for space-frequency spreading-multiplexing (SFSM) multiple-input multiple-output (MIMO) wireless communication systems that combine space- and frequency-domain spreadings, followed by a space-frequency multiplexing. Spreading across space (transmit antennas) and frequency (subcarriers) adds resilience...

We first introduce a new class of tensor models for fourth-order tensors, referred to as "nested PARAFAC models." Then, we present a space-time-frequency (STF) coding scheme for multiple antenna orthogonal frequency division multiplexing systems. This scheme, called double Khatri-Rao STF (D-KRSTF) coding, combines time-domain spreading with...

Some tensor prerequisites with a particular emphasis on mode combination using Kronecker products of canonical vectors that makes easier matricization operations, are first reviewed. Then, after a brief reminder of PARAFAC and Tucker models, two families of constrained tensor models, the co-called PARALIND/CONFAC and PARATUCK models, are...

International audience

A new multi-antenna coding framework is proposed for space-time-frequency (STF) transmissions over broadband multiple input multiple output (MIMO) systems based on orthogonal frequency division multiplexing (OFDM). A tensor decomposition known as PARAFAC is used as the core of a multi- stream space-time-frequency coder that jointly multiplex...

National audience

Blind identification of underdetermined mixtures can be addressed efficiently by using the second ChAracteristic Function (CAF) of the observations. Our contribution is two-fold. First, we propose the use of a Levenberg-Marquardt algorithm, herein called LEMACAF, as an alternative to an Alternating Least Squares algorithm known as ALESCAF,...

This paper considers the downlink of a multiple-input multiple-output (MIMO) code-division multiple-access (CDMA) system based on space-time spreading (STS) using multiuser/multicode transmission. A constrained tensor model is proposed for the STS transmitted signal. The new STS model generalizes existing ones by allowing multiuser spatial...

No description

In this work we consider the problem of blind identification of underdetermined mixtures using the generating function of the observations. This approach had been successfully applied on real sources but had not been extended to the more attractive case of complex mixtures of complex sources. This is the main goal of the present study. By...

In this letter, we present a sequential closed-form semi-blind receiver for a one-way multi-hop amplify-and-forward (AF) relaying system. Assuming Khatri-Rao space-time (KRST) coding at each relay, it is shown that the system with K relays can be modeled by means of a generalized nested PARAFAC model. Decomposing this model into K +1...

International audience

No description

National audience

No description

In some antenna array-based wireless communication systems the received signal is multidimensional and can be treated as a tensor (3D array) instead of a matrix (2D array). In this paper, we make use of a generalized tensor decomposition known as constrained Block-PARAFAC and propose a tensor (3D) model for the signal received by three types of...

In this work, we consider the problem of blind identification of underdetermined mixtures in a cyclostationary context relying on sixth-order statistics. We propose to exploit the cyclostationarity at higher orders by taking into account the knowledge of source cyclic frequencies in the sample estimator of the observation hexacovariance. Two...

This work was originally motivated by a classification of tensors proposed by Richard Harshman. In particular, we focus on simple and multiple ''bottlenecks'', and on ''swamps''. Existing theoretical results are surveyed, some numerical algorithms are described in details, and their numerical complexity is calculated. In particular, the...

International audience

In this paper, we present new space-time multiplexing codes (STMC) for multiple-antenna transmissions, which rely on a three-dimensional tensor modeling of the transmitted/received signals. The proposed codes combine spatial multiplexing and space-time coding by spreading a linear combination of different sub-streams of data over the space and...

In this paper, we present a new space-time spreading-multiplexing model for multiple-input multiple-output (MIMO) wireless communication systems relying on a tensor modeling of the transmitted and received signals. At the transmitter, we exploit the core of a PARATUCK-2 tensor model composed of a precoding matrix and two allocation matrices...