Based on a characteristic-function approach, an exact expression is derived for the bit error probabilities (BEP) of direct-sequence code-division multiple-access (DS CDMA) communication systems over Nakagami flat fading channels. The chip sequences are assumed to be random. The received signal amplitudes of the desired user and interfering users are modeled as Nakagami-m and Nakagami-n (Rician) distributed, respectively. The different forms of the amplitude distributions make it possible to derive an exact BEP expression, based on a previous result for Rayleigh-distributed signal amplitudes. Though in different forms, the Nakagami-n and Nakagami-m distributions can closely approximate each other. The BEP expression can thus be used for cases where the desired and interfering users are in nearly the same or different fading conditions.
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