Authors : Nader Abdullah Khadam, Arash Ahmadi, Seyed Vahab Makki and Golamreza Karimi
Abstract: This study evaluates the OFDM performance over a flat fading Ryleigh channel. The simulated system incorporates the benefits of the orthogonal space-time block code with the Multi-Carrier Code Division Multiple Access (MC-CDMA) to enhance the performance of the OFDM over the multi-path channels.The environment is assumed to be a moving transmitter with speeds 2, 45 and 100 km/h with outdoor Rayleigh flat fading channel. The system employs 4 antennas at the receiver end to mitigate the effect of multipath signal. The system&$146;s orthogonal frequencies are generated using Haar, Daubechies 4 (dB4) 4, Symlets 4 (Sym4), Cohen-Daubechies-Feauveau (CDF) 1.1 and 9.7 and B-spline 3 (Bs3). The number of used carriers is 128, 256, 512, 1024 and 2048 with subcarriers 64, 180, 360 and 720. The modulation is QPSK with cyclic prefix 1/16 and bandwidth of 20 MHz. The system’s BER is compared with the traditional FFT system to highlight the enhancements of using Discrete Wavelet Packet Transform (DWPT) instead the FFT method. The PN-s sequence is generated using gold code. The proposed system shows significant improvement in BER over the system that uses FFT to generate the orthogonal carriers and presents itself as a powerful candidate to replace these traditional FFT systems. The STBC is used as an enhancement to improve the system capability to correct the potentially erroneous bits within the frame due to the AWGN and channel Inter-Symbol Interference (ISI) in the channel. The results shows a significant improvement in the BER using this proposed arrangement.
Nader Abdullah Khadam, Arash Ahmadi, Seyed Vahab Makki and Golamreza Karimi, 2018. Performance Evaluation of OSTBC-MC-CDMA with 4-Antennas MIMO Over Rayleigh Flat Fading Channel. Journal of Engineering and Applied Sciences, 13: 11091-11107.