On the performance of M-QAM sigalling with multi-user detection and interference cancellation

Binary phase shift keying (BPSK) and quaternary phase shift keying (QPSK) were often used as the underlying modulation scheme for demonstrating the performances of the various multi-user detection and interference cancellation methods for direct sequence-code division multiple access (DS-CDMA) systems. On the other hand, M-level quadrature amplitude modulation (M-QAM) is fast becoming an attractive modulation technique for future wireless communications, due to its high spectral efficiency. Based on a fixed bit and chip rate, we study the performance of a decorrelator as well as a successive interference cancellation (SIC) scheme for an M-QAM-based DS-CDMA system.