Diversity combining for DS CDMA systems with synchronization errors

An efficient series that is used to calculate the probability of error for a BPSK modulated DS CDMA system with chip timing and carrier phase errors in a slowly fading multipath channel is derived. The receiver is assumed to be a coherent RAKE receiver. Three types of diversity schemes are considered: selection diversity, equal gain diversity combining and maximal ratio diversity combining. The error probability derivation does not resort to the widely used Gaussian approximation for the intersymbol interference and multiple access interference and is very accurate. Systems of 1.25 MHz and 5 MHz are considered for different numbers of diversity branches.