A New Multicarrier CDMA System Exploiting Frequency-Time Diversities

In this paper, a new variant of multicarrier code division multiple access (MC-CDMA) system is proposed and analyzed for time varying multipath fading channels. At the transmitter, data bits at different frequency bands are spread in the time domain and these spread chips are circularly shifted onto different frequency bands while the time lapses. As a result, the spread data chips are assigned to different frequency bands at different times. Significant performance improvement can be achieved compared to the conventional MC-CDMA system. The underlying reason is that in the proposed system, more diversities are introduced by spreading data chips both in the frequency and time domains. In the paper, the performance of the system using different combining techniques is analyzed and compared. Simulation results under different conditions arc also presented