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1

Higher Order Cumulants for Identification and Equalization of Multicarrier Spreading Spectrum Systems

Safi S., Frikel M., Zeroual A., M'Saad M.

Journal of Telecommunications and Information Technology

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2011

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nr 2

74-84

EN

This paper describes two blind algorithms for multicarrier code division multiple access (MC-CDMA) system equalization. In order to identify, blindly, the impulse response of two practical selective frequency fading channels called broadband radio access network (BRAN A and BRAN E) normalized for MC-CDMA systems, we have used higher order cumulants (HOC) to build our algorithms. For that, we have focussed on the experimental channels to develop our blind algorithms able to simulate the measured data with high accuracy. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the proposed algorithms are able to estimate the impulse response of these channels blindly (i.e., without any information about the input), except that the input excitation is i.i.d. (identically and independent distributed) and non-Gaussian. In the part of MC-CDMA, we use the zero forcing and the minimum mean square error equalizers to perform our algorithms. The simulation results demonstrate the effectiveness of the proposed algorithms.

2

Channel Identification Using Chaos for an Uplink/Downlink Multicarrier Code Division Multiple Access System

Frikel M., Safi S., Targui B., M'Saad M.

Journal of Telecommunications and Information Technology

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2010

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nr 1

48-54

EN

A scheme of chaotic spreading sequence for multicarrier code division multiple access system (MC-CDMA) iproposed to estimate the transmission channel. This systespreads spectrum and identifies the channel, simultaneously. The proposed scheme uses a chaotic sequence generated by a logistic map as a training signal and estimate channel parameters according to dynamics of the chaotic sequence. Encoding data by chaotic sequences is first built and then the orthogonal codes are used to spread the encrypted data for multiusers scheme. At the reception, first the channel parameters are identified using a training chaotic sequence in order to equalize the received data, and then the encrypted information is decoded for the desired user. The studies reveal that the proposed system (chaos plus orthogonal codes) significantly outperforms the Walsh-Hadamard code spreading in MC-CDMA system. The performance of the system is considered in the multiuser case by means of simulation. The simulation result shows that the proposed chaotic code spreading approach for channel identification achieves significant improvement in the channel identification, comparing to using others training sequence or the least square method.

3

General adaptive observer-based fuzzy control of uncertain nonaffine systems

Boulkroune A., Tadjine M., M'Saad M., Farza M.

Archives of Control Sciences

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2006

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Vol. 16, no. 4

383-410

EN

This paper focuses on the construction of an adaptive fuzzy output feedback control based on any adaptive fuzzy observer for a class of single-input-single-output SISO uncertain or ill-defined nonaffine nonlinear system. Indeed, the corrective term of the proposed observer involves a well defined design function which is shown to be satisfied by the commonly used high-gain based observers, namely for the usual high-gain observers and the sliding modes observers together with their implementable versions. The design of the underlying update law as well as the robust control term is based on an appropriate filtering of the output tracking error. This particularly allows to overcome yhe output observation error flitering or the necessity of the famous strictly positive real (SPR) condition.