PATH DIVERSITY FOR DS-SSMA COMMUNICATIONS IN NAKAGAMI FADING CHANNELS

Average error probability and outage probability for an asynchronous d irect sequence spread spectrum multiple access communications through slow nonselective Nakagami fading channels are evaluated for nondivers ity and diversity receptions. Using the Gauss quadrature rule, the mom ents of the self-interference and the multiple access interferences ar e used to evaluate average error probability and outage probability. C ombining the diversity technique and error correcting codes, compariso ns between the uncoded nondiversity DS-SSMA system and that of the cod ed diversity system are shown for the Gold Code of codelength 127. Usi ng fourth-order diversity and the Reed-Solomon code, the maximum achie vable number of users is 12 percent of the codelength for Rayleigh fad ing, when the average probability is 10(-3). The corresponding outage probability is less than 5 percent. Performance comparisons between Ri cian and Nakagami fading channels are made. Since the system is interf erence limited, the performance seems to show no significant differenc e for the two fading channel models when the number of users is large.