Concatenated trellis coding and CPM for DS/SSMA communication in Rayleigh fading channel

In this paper, direct sequence spread spectrum multiple access (DS/SSMA) system employing serially concatenated trellis-coded modulation (TCM) and continuous phase modulation (CPM) techniques, referred to as TCM/CPM-SSMA, over a flat Rayleigh fading channel is presented. In this concatenated coded modulation system, TCM and CPM can be equivalently regarded as outer and inner codes, respectively. The inner code gives desirable spectral efficiency and coding gain by using maximum likelihood sequence estimator. The outer code contributes significant coding gain to the DS/SSMA system. The performance of this concatenated TCM/CPM DS/SSMA system is evaluated by theoretical analysis and numerical simulations. The results demonstrate that this DS/SSMA system can achieve significant improvements in bit error rate over the conventional DS/SSMA with single TCM or CPM under the same conditions.