On the frequency domain approach for spread spectrum receivers: towards a convergence of DS-CDMA, MC-CDMA and OFDM

The RAKE receiver is suboptimal when noise is non white, as in wideband CDMA systems. Frequency domain processing provides an efficient way to eliminate narrowband interference or exploit colored noise and it can significantly outperform the RAKE receiver. Additionally, other functions can be carried out directly in frequency domain, such as despreading, synchronization that is crucial for performance and equalization, which can mitigate multiuser interference. We discuss the frequency domain processing for DS-CDMA and potential gains are assessed by simulation results. An additional and important feature is that the frequency domain receiver for DS-CDMA also provides a common platform for MC-CDMA and OFDM, paving the way for an universal receiver.