Performance Evaluation of Wavelet Packet Based MC-CDMA and HHT Based MC-CDMA System

Abstract

ABSTRACT:The main aim of this paper is to investigate the performance of multi-carrier code division multiple access (MC-CDMA) technique, which has gain much attention due to its high frequency spectrum efficiency and high data rate transmission and makes the wireless communication more reliable and efficient. MC-CDMA technique is the combination of both orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA), which found to be very effective to mitigate the effect of fading channels and to improve the system performance.In this paper, we investigate the performance of conventional MC-CDMA system, orthogonal wavelet packet based MC-CDMA system (WP-MC-CDMA), and Huang Hilbert Transformation (HHT) based MC-CDMA system. However, the conventional MC-CDMA has already been discussed in the literature, and used as a benchmark for other two schemes. In addition, the orthogonal wavelet packet based MC-CDMA technique is designed with a set of wavelet packets and used as the modulation waveforms in a multicarrier CDMA system. The WP-MC-CDMA shows their superiority over conventional MC-CDMA in terms of bit error rate (BER), and helps to mitigate the effects of interference and channel fading. Moreover, we also investigate the performance of Huang Hilbert Transformation based MC-CDMA. This scheme outperforms than that of other two techniques. This is due to Huang Hilbert Transformation based MC-CDMA is based on the knowledge of the instantaneous channel state information and instantaneous imperfect channel estimates. Therefore, by the knowledge of their instantaneous channel gains, it shows their superiority over of conventional MC-CDMA and WP-MC-CDMA in terms of spectral efficiency and data rate transmission. Furthermore, we also present the comparison all three techniques in terms of BER. Finally, our numerical and simulation results validate our proposed theoretical findings. KEYWORDS:Hilbert Huang Transform Based MC-CDMA, Bit Error Rate (BER), OFDM, MC-CDMA, WP MC-CDMA. I.INTRODUCTIONMulti-carrier code division multiple access (MC-CDMA) is a digital modulation technique in which a single data symbol is transmitted at multiple narrowband subcarrier encoded with a phase offset of 0 and π instead of spreading code as in conventional MC-CDMA. The narrowband subcarrier are generated using binary phase shift keying (BPSK) modulated signals, each at different baseband frequencies. Consequently, the subcarriers are orthogonal to each other at baseband frequency, and the component at each subcarrier may be filtered out by modulating the received signal with the frequency corresponding to the particular subcarrier of interest and integrating over a symbol duration [1]. The orthogonality between the subcarriers is maintained if the subcarrier frequencies are spread apart by the multiple of F, where F is an integer (e.g F=1, 2…) and the phase of each subcarrier corresponds to one element of the spreading code. For a spreading code of length N, there are N subcarriers. In other words, MC-CDMA transm...