Samir Bendoukha

MVDR broadband beamforming using polynomial matrix techniques

This paper presents initial progress on formulating minimum variance distortionless response (MVDR) broadband beam-forming using a generalised sidelobe canceller (GSC) in the context of polynomial matrix techniques. The quiescent vector is defined as a broadband steering vector, and we propose a blocking matrix design obtained by paraunitary matrix completion. The polynomial approach decouples the spatial and temporal orders of the filters in the blocking matrix, and decouples the adaptive filter order from the construction of the blocking matrix. For off-broadside constraints the polynomial approach is simple, and more accurate and considerably less costly than a standard time domain broadband GSC.

Blind adaptive equalizer for broadband MIMO time reversal STBC based on PDF fitting

This work presents a new blind multiuser equalization strategy for Time Reversal Space Time Block Coding (TRSTBC) signals transmitted over a dispersive MIMO channel. The adaptation is based on forcing the probability density function (PDF) of the equalizer output to match the desired PDF of corresponding source symbols. In the proposed approach, the PDFs are estimated by means of the Parzen window method using Gaussian Kernels. The cost function combines this PDF fitting with an orthogonality criterion derived from the TR-STBC structure. The performance is demonstrated in a number of simulations and benchmarked against other blind schemes. The proposed algorithm has a moderate computational complexity and can perform with higher adaptation rate.

A Fast Converging Blind Receiver for Space-Time Block Codes over Frequency Selective Channels

Space-time block coding (STBC) and a number of derivative techniques have been developed to maximise the diversity gain of a multiple-input multiple-output (MIMO) channel. For frequency selective fading - i.e. dispersive - MIMO channels, solutions in the literature are fewer, and are in their majority block based, such as MIMO OFDM or time-reversal STBC. In order to ultimately achieve better tracking behaviour, in this paper we focus on the development of a non-block-based method which utilises the constant modulus algorithm (CMA). Due to the slow convergence of the CMA, we propose the use of Newtons method to find the optimum solution for the equalizer. A comparison of two different techniques of estimating the inverse of the correlation matrix is presented.

On Chaos in the Fractional-Order Discrete-Time Unified System and Its Control Synchronization

In this paper, we propose a fractional map based on the integer-order unified map. The chaotic behavior of the proposed map is analyzed by means of bifurcations plots, and experimental bounds are placed on the parameters and fractional order. Different control laws are proposed to force the states to zero asymptotically and to achieve the complete synchronization of a pair of fractional unified maps with identical or nonidentical parameters. Numerical results are used throughout the paper to illustrate the findings.

A gradient descent implementation of the adaptive robust narrowband constrained LMS beamformer

Classical adaptive beamforming strategies have been shown to exhibit a substantial performance degradation if an error exists in the estimation of the angle of arrival (AOA). The optimization problem can be modified to incorporate an improved constraint allowing for robustness to AOA imperfections. In this paper, we propose a gradient descent implementation of the robust adaptive beamformer whereby a direct relation is established between the Lagrange multiplier and the adaptation step size. This allows for the heuristic approximation of one of the parameters while establishing a valid range for the other. Computer simulations have been used to confirm the findings of this study and illustrate the performance of the developed algorithm.

The Co-existence of Different Synchronization Types in Fractional-order Discrete-time Chaotic Systems with Non–identical Dimensions and Orders

This paper is concerned with the co-existence of different synchronization types for fractional-order discrete-time chaotic systems with different dimensions. In particular, we show that through appropriate nonlinear control, projective synchronization (PS), full state hybrid projective synchronization (FSHPS), and generalized synchronization (GS) can be achieved simultaneously. A second nonlinear control scheme is developed whereby inverse full state hybrid projective synchronization (IFSHPS) and inverse generalized synchronization (IGS) are shown to co-exist. Numerical examples are presented to confirm the findings.

Fractional Form of a Chaotic Map without Fixed Points: Chaos, Entropy and Control

In this paper, we investigate the dynamics of a fractional order chaotic map corresponding to a recently developed standard map that exhibits a chaotic behavior with no fixed point. This is the first study to explore a fractional chaotic map without a fixed point. In our investigation, we use phase plots and bifurcation diagrams to examine the dynamics of the fractional map and assess the effect of varying the fractional order. We also use the approximate entropy measure to quantify the level of chaos in the fractional map. In addition, we propose a one-dimensional stabilization controller and establish its asymptotic convergence by means of the linearization method.

On the – Chaos Synchronization of Fractional-Order Discrete-Time Systems: General Method and Examples

In this paper, we propose two control strategies for the – synchronization of fractional-order discrete-time chaotic systems. Assuming that the dimension of the response system is higher than that of the drive system , the first control scheme achieves -dimensional synchronization whereas the second deals with the -dimensional case. The stability of the proposed schemes is established by means of the linearization method. Numerical results are presented to confirm the findings of the study.

A Blind CM Receiver for STBC over Channels with Inter-Symbol Interference

Alamoutis Space-Time Block Coding (STBC) scheme has received considerable attention due to its ability to maximize the diversity gain of a Multi-Input-Multi-Output (MIMO) transmission link. For frequency selective fading, only a few receivers can be found in the literature. These are mainly trained and block based, such as Time Reversal STBC (TRSTBC), introduced by [3], [4]. In order to ultimately achieve better tracking behavior, this paper focuses on the development of a non-block-based method. The Constant Modulus (CM) criterion is utilized on the received signals with the orthogonality constraint of the transmitted STBC signals. A novel criterion is derived to enforce the STBC structure on the equalizer outputs and consequently minimize the cross-correlation. Simulation results are presented to demonstrate the performance of the proposed algorithm.