ER PERFORMANCE OF 2D-SPREADING CODES IN MC-DS-CDMA WITH NAKAGAMI-m FADING

Abstract

Orthogonal frequency division multiplexing (OFDM) combined with code division multiple access (CDMA) makes the multicarrier (MC-) CDMA systems one of the promising candidates for the next generation mobile communication systems. MC-CDMA systems have advantage of both OFDM and CDMA i.e. high spectral efficiency and robustness to fading. MC-DS-CDMA systems also offer both temporal and frequency diversities, support narrowband interference suppression and require a lower chip rate than that of single carrier systems utilizing the same bandwidth. Although MC-DS-CDMA systems are promising candidates for high data rate services, the multiple access interference (MAI) problems inherent to the single-carrier (Sc-) DS-CDMA system also exists and is the limitation to its achievable capacity. To reduce the level of MAI, spreading codes with good correlation properties are required. In this dissertation, one of the three basic MC CDMA schemes, namely MC-DS-CDMA, is combined with 2-dimensional spreading code. Two families of 2-dimensional codes have been considered, a family of Orthogonal Variable Spreading Factor (OVSF) codes and other one Complete Complementary Codes (CCC). These codes can be recursively generated using Kronecker Product. A multi-rate system is considered having users with two data rates. Simulations have been carried out for BER analysis of these codes for MC-DS-CDMA in Nakagami-m fading channel. Finally, BER performance of 2D-Orthogonal Variable Spreading Factor codes and 2D-Complete Complementary Codes are compared