A novel hyperchaotic spreading code and its application to 2D-CDMA

According to the advantages of chaotic binary sequences, this paper presents a method of generating advanced hyperchaotic complex binary sequences called oversampled Ikeda map (IM) sequences (OIMS) by oversampling IM. To choose proper oversample rate, the relation between OIMS¿ performance and adopted rates is analyzed via merit factor function of auto-correlation, mean-square cross-correlation (MSCC) function and balance degree. Obtained statistic results verify that with higher security level, OIMS possess much better correlation property and balance property than former IM sequences. Furthermore, an optimal filter strategy in 2D-CDMA is proposed for best selection of complex spreading sequences including IM sequences and OIMS. Under a variety of channel conditions, simulation results show that the bit-error rate performance of OIMS is anyway more desirable than that of IM sequences in the 2D-CDMA system and that of gold sequences in conventional CDMA system.