Enhanced performance of DFTs-OFDM-CDMA system using interleave spreading code

Discrete Fourier transform spread orthogonal frequency division multiplexing (DFTs-OFDM) has recently attacked much interest in research and developments on wireless communication systems. The combination of direct sequence code division multiple access (DS-CDMA) and DFTs-OFDM potentially offers the degradation of bit error rate (BER) performance as indicated in literatures. This paper presents the causes of such degradation on BER performance through the analysis of cross-correlation between Walsh Hadamard (WH) spread and DFT-spread, which produces destructive interference to a subcarrier. The new proposed interleaving spreading code technique is simple and can address the problem. Simulation results reveal that the combined DFTs-OFDM and DS-CDMA can potentially enhance the BER performance as those existing DFTs-OFDM system.