Adaptive transmission scheme for multicarrier CDMA system in the reverse link

Abstract

In this thesis, we propose a simple adaptive transmission scheme for multicarrier CDMA system in the reverse link. The proposed system switches transmission mode by comparing the maximum of the subchannel power gains to a given adaptation threshold. If the maximum of subchannel power gains is greater than the adaptation threshold, then the transmitter modulates the data stream into multiple narrow-band DS subcarriers, and the receiver combines received signals coming through different subchannels as MC DS CDMA system with maximal ratio combining (MRC). Otherwise, the transmitter modulates the data stream into a single DS subcarrier providing the maximum subchannel power gain, and the receiver demodulates the received signal coming through the best subchannel as hybrid FH/DS CDMA system with adaptive hopping (AH). Based on such a simple adaptation scheme, we evaluate the system performance and derive the average bit error probability of the proposed system. The proposed system is bound to outperform MC DS CDMA system with MRC and hybrid FH/DS CDMA system with AH. We show that the proposed system provides significant performance improvement in bit error probability, system throughput, and power consumption over conventional systems. Such an improvement can be directly translated an increase in CDMA system capacity.