Successive Interference Cancellation Schemes In Multi-Rate DS/CDMA Systems

In this paper we propose successive interference cancellers (IC) for a variable data rate environment. Firstly, a successive interference cancellation (IC) scheme for Mlevel rectangular QAM in DS/CDMA systems is analysed. Secondly, the performance under Rayleigh fading is analysed for single modulation systems and different systems for handling multiple data rates. One alternative for handling multi-rate systems is to use mixed modulation, which imply that each user chooses modulation format according to need. Another alternative is to use parallel channels, where each user transmits over one or several synchronous channels. We show that the successive IC, for mixed modulation or parallel channel systems, has a performance close to the single BPSK user bound and, consequently, it gives a considerable increase in performance and flexibility compared to both single modulation systems and mixed modulation or parallel channel systems employing a conventional detector. 1 INTRODUCTION In th..