Channel Identification Using Chaos for an Uplink/Downlink Multicarrier Code Division Multiple Access System, Journal of Telecommunications and Information Technology, 2010, nr 1

A scheme of chaotic spreading sequence for multicarrier code division multiple access system (MC-CDMA) is proposed to estimate the transmission channel. This system spreads 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

Modélisation et observation des colonnes à distiller

LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Proportional integral observer design for time delay nonlinear triangular systems

International audienceIn this work an proportional integral observer for a class of delayed nonlinear triangular systems with multiple and simple time-delay is proposed. First, the proportional integral observer synthesis is presented for nonlinear systems with variable time-delay and is extended for nonlinear systems with multiple time-delay. The observer performance is evaluated through numerical simulations

Observer design for the state estimation of a class of communication

International audienceIn this work an observer is proposed for the state estimation of each node in a communication network composed of cascade active queue. The queue length of each node in the network must be estimated by the use of our proposed observer. This observer is based in the fluid flow dynamical model for an active link of communication between two hosts trough the network. We show that this model is include in a special triangular class of nonlinear system with an unknown disturbance and an observer for this class is proposed. The syntheses of such observer don't need any change of coordinate and the system is treated in his naturel structure. The performances of the proposed observer are illustrated through simulation results dealing with queue length estimation of each node in a cascade computer network

BER analysis of parallel and successive interference cancellation employing MMSE equalizer for MC-CDMA systems

International audienceThis paper introduces a parallel/sucessive interference cancellation scheme for multi-carriers code-division multiple access (MC-CDMA) in the case of a downlink transmission, that reduces the degrading effect on the desired user of interference from the other users who share the same channel. The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses an hybrid interference cancellation combining the advantages of these two schemes: parallel interference cancellation (PIC) and successive interference cancellation (SIC). The hybrid scheme (S-PIC) is faster, reliable and it reduces the computational load. Simulation results are given for different scenarios

Bearing detection of noised wideband sources for geolocation

International audienceIn this paper, we propose a method for the localisation of wideband sources in order to locate mobile station. Indeed, directions-of-arrival of wideband sources are estimated by coherent subspace methods, which use the focusing operators, in the presence of a correlated noise and, then, the angulation is used to determine the mobile's position. Practical methods of the estimation of the coherent signal subspace are given and are compared for mobile system location

Blind identification of indoor broadband radio access network using cumulants

International audienceThis paper describes a blind algorithm for estimating a time varying and frequency selective fading channel, representing the indoor broadband radio access network. In order to identify blindly the impulse response of this channel, we have used Higher Order Statistics (HOS). or cumulants, to build our algorithm, whitch is compared with the Zhang's one. The simulation results, in presence of colored noise and for different data input channel. demonstrate that the proposed algorithm give good estimation of the phase and magnitude. comparing to the Zhaug's, one 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