Decorrelator detection for quasi-synchronous multicarrier CDMA

A new multicarrier CDMA receiver is proposed for the reverse channel (mobiles to base) of a quasi-synchronous CDMA (QS-CDMA) system, which uses a decorrelator to demodulate the signal in each carrier. The advantage of the multi-carrier CDMA system for quasi-synchronous operation is that the timing uncertainty interval can be progressively decreased by increasing the number of carriers and bits in the serial-to-parallel buffer. It has previously been shown that a modified decorrelator based on chip matched filter samples completely rejects undesired users with delays falling in the quasi-synchronous uncertainty interval. Here, it is also shown that the decorrelator rejects adjacent carrier undesired users, in contrast to the case of a system employing conventional matched filtering. Analytic BER results are presented for the decorrelator-based multicarrier CDMA system, tinder the conditions of Rayleigh frequency non-selective fading in each sub-band.