Cooperative Diversity in Coded CDMA Systems over Frequency-Selective Fading Channels

We investigate the performance of cooperative diversity when employed in convolutionally coded direct-sequence code-division multiple-access (DS-CDMA) systems over frequency-selective fading channels. The performance of the coded system is evaluated through bit error rate upper bounds and compared with simulations. In our analysis, we obtain closed form expressions for the bit error rate upper bounds for multi-relay cooperative systems employing multiuser detection at both the relay and base station receivers. We show that the full benefits of cooperative diversity cannot be achieved if no interference suppression is employed at both the cooperative user and base station receiver. Both simulation and analytical results are presented to validate and demonstrate the performance gain with different system parameters.