Channel identification using chaos for an uplink/downlink multicarrier code division multiple access system
Résumé
A scheme of chaotic spreading sequence for multi- carrier 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 pa- rameters according to dynamics of the chaotic sequence. En- coding 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 pa- rameters 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 re- veal that the proposed system (chaos plus orthogonal codes) significantly outperforms the Walsh-Hadamard code spread- ing 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 signifi- cant improvement in the channel identification, comparing to using others training sequence or the least square method.
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