Multi-rate schemes in DS/CDMA systems

Abstract

Different modulation schemes supporting multiple data rates in a direct sequence code division multiple access (DS/CDMA) system are studied, focusing on how to support personal communication services. Both AWGN and multipath Rayleigh fading channels are considered. It is shown that the multi processing-gain scheme and the multi-channel scheme have almost the same performance. However, the multi-channel scheme has some advantages due to near-far resistance, easier code design and easier multi-user receiver construction. The drawback though, is the need for linear amplifiers. A multi-modulation scheme is also possible, but the performance for the users with the high data rates is significantly worse than for the other schemes.