Error rate analysis of asynchronous multicode DS-CDMA systems

A precise bit-error probability analysis method is derived for a multicode DS-CDMA system in an additive white Gaussian noise channel. The method is applicable to a multicode DS-CDMA system with an arbitrary number of multiple code sequences and any selection of multiple code sequences. The precise method gives results that discriminate the effect of the selection of multiple code sequences on the bit-error probability, whereas Gaussian approximations do not. Thus, the new method can be used to select the best multicode set for a given system, a task that cannot be achieved using Gaussian approximations. A two-step analytical procedure enables deriving an explicit, compact form for the characteristic function of the receiver decision statistic in a DS-CDMA system with an arbitrary number of multiple code sequences, and for any selection of multiple code sequences.