Effects of Codes and Subcarrier Interleaving on Multi-code Multicarrier CDMA System

Abstract

Future wireless communication systems are required to transport data at much higher bit rates and this motivates a researcher to work on the new technologies for the next generation of wireless mobile communication systems. Multi-code Multi-carrier CDMA (MC-MC-CDMA) has emerged as a powerful candidate due to its capabilities of minimizing frequency selective fading and Multiple Access Interference (MAI).This transmission method combining the multiple access technologies (CDMA), to those multiple codes and multiple carriers. This research thesis focuses on the effect of interleaving in time and frequency diversity in MC-MC-CDMA system. This thesis first analyses the MC-MC-CDMA system and investigates the Bit Error Ratio (BER) performance on the basis of several factors such as: users number, M-ary symbol number, code sequence and combiner type. Next, this thesis presents a new time-frequency interleaving in a MC-MC-CDMA system, which allows two-dimensional spreading in both time and frequency domains. Our contribution consists in implementing a two-dimensional interleaving inside the time and frequency diversity. We demonstrate via simulation results that the proposed method yields better performances in BER. Also, we observe that BER of both the 2D-prime interleaving and the 2D-random interleaving are similar. Furthermore, the interleaving gain is larger in a frequency-diversity than time-diversity. Finally, we reach better Peak Signal to Noise Ratio (PSNR) when we transmit images (color, black and white) through the proposed technique.