Performance of Hybrid FH/DS CDMA Systems with Transmitter Diversity

We investigate the performance of a hybrid direct-sequence/frequency-hopping (DS/FH) scheme for spread spectrum systems over Rayleigh fading channels. In this hybrid scheme, the users are divided into a number of groups, where each group of users use one of a cyclic FH sequences designed to eliminate signal collisions among different groups. To improve the user-capacity, we assign to each user within a group a different DS sequence. Given this arrangement, our results show significant performance improvements relative to conventional DS/FH systems that employ randomly generated hopping sequences. The proposed frequency-hopping scheme is then investigated in a space-time convolutionally-coded system with two transmit and one receive antennas