Multi-Rate Performance in DS/CDMA Systems
Tony Ottosson Gadd, Arne Svensson · 1995
ABSTRACTDifferent modulation schemes supporting multiple data rates in a Direct Sequence Code DivisionMultiple Access (DS/CDMA) system are studied. Both AWGN and multipath Rayleigh fadingchannels are considered. It is shown that the multi processing-gain scheme and the multi-channelscheme have almost the same performance. However, the multi-channel scheme may have someadvantages due to near-far resistance, easier code design and multi-user receiver construction.The drawback though, is the need for linear amplifiers also in mobile terminals. A multi-modula-tion scheme is also possible, but the performance for the users with the high data rates are signifi-cantly worse than for the other schemes. Furthermore multi chip-rate, parallel combinatory spreadspectrum (PC/SS) and pulse position modulation (PPM) are discussed briefly.Keywords: DS/CDMA, Spread spectrum, multi-rate schemes, PCS, multi-channel, multi chip-rate, multi processing-gain and multi-modulation schemes, Parallel Combinatory Spread Spec-trum (PC/SS), parallel channels, Amplitude Modulation (AM), Quadrature Amplitude Modula-tion (QAM).