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

Abstract

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.