Frequency-domain approach to DS-CDMA multiuser detection over frequency-selective slowly fading channels

By extending our frequency-domain approach (see Cha´o-Ming Chang and Kwang-Cheng Chen, IEEE Communications Letters, vol.4, no.11, p.331-3, 2000) to practical scenarios such as frequency selective slowly fading channels, we justify the value of our proposed frequency-domain approach to multiuser detection in DS-CDMA communications systems. With this frequency-domain approach, which maintains frequency-domain orthogonality between different users, DS-CDMA communication is MAI-free even in frequency-selective slowly fading asynchronous channels. This frequency-domain approach not only saves the cost of maintaining synchronous channels as in practical communications systems employing time-domain orthogonal codes (e.g. IS-95 and cdma2000), but also enjoys low complexity properties as in conventional point-to-point communications; it therefore holds many desirable properties attractive to practical communications systems.