Based on interpolation methods, a low complexity channel estimation method for MC-CDMA system based chaos under fast fading multipath channel is proposed.Different interpolation methods are used; Linear interpolation (LI), cubic spline interpolation (CSI), and piecewise cubic Hermite interpolation (PCHI). The multi-carrier scheme is established by using a chaotic generator with different initial conditions, while the pilots are established using another chaotic generator with another different initial conditions. The proposed channel estimator without and with interpolation methods for single user and multiusers is tested under fast frequency selective Rayleigh fading channel. Simulation results demonstrate that the channel estimation of MC-CDMA system based chaos using interpolation methods and when the pilots are chaos signal too, achieves better performance improvement in fast multipath environment compared to the conventional MC-CDMA system when the pilots are considered as Walsh-Hadamard codes. The proposed system is also built and tested using Simulink program.

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A B S T R A C T:Because single carrier modulation has low peak average power ratio (PAPR), it is used instead of multicarrier modulation in uplink transmission in Long Term Evolution (LTE). Channel state information (CSI) is very important issue in SC-FDMA system when applying equalization technique especially in high frequency selective fading channels where a linear equalizer is inefficient to remove the fading channel effects. To solve the inefficient performance of the multiple output multiple input (MIMO) SC-FDMA system in high frequency selective fading channels, an iterative (adaptive) frequency domain equalizer is presented using least mean square algorithm (IFDE-LMS or AFDE-LMS). The proposed IFDE-LMS shows better system performance compared to conventional zero forcing (ZF) equalizer. Simulation results show the effect of IFDE-LMS on the performance of MIMO SC-FDMA system using both localized SC-FDMA (LSC-FDMA) and interleaved SC-FDMA (ISC-FDMA) transmission types, where LSC-FDMA outperforms ISC-FDMA.