Time-frequency coded modulation scheme for multicarrier DS-CDMA systems

A novel time-frequency coded modulation scheme for multicarrier DS-CDMA systems is studied. Based on the concept of transmission diversity in the time-frequency domain, we propose a code design criterion that includes diversity gain and coding gain. In terms of the proposed criterion, we can search for trellis codes that have larger coding gain while keeping the maximum diversity. Results show that the bit error rate performance of the system with the novel time-frequency coded modulation is much better than that of traditional system while not occupying additional spectral bandwidth.