Time- and frequency-domain spreading assisted MC DS-CDMA using interference rejection spreading codes for quasi-synchronous communications

In this contribution, we considered a time-frequency (TF)-domain spreading aided MC DS-CDMA system, which employed so-called generalized orthogonal spreading codes exhibiting an interference free window (IFW). Provided that the propagation delay differences of the different users are within this IFW, no multiuser interference is inflicted, and hence a near-single-user performance may be attained without invoking a multiuser detector. As an additional benefit, the proposed MC DS-CDMA system is capable of extending the width of the IFW in comparison to a conventional DS-CDMA system. Furthermore, it is capable of achieving a significantly higher frequency diversity gain in comparison to a single-carrier DS-CDMA system while reducing the MUD complexity.