Multiuser Detection
Wireless Communications
The performance of space-time coded cooperative diversity in an asynchronous cellular uplink
MILCOM'06 Proceedings of the 2006 IEEE conference on Military communications
Multiuser detection for cooperative networks and performance analysis
IEEE Transactions on Signal Processing
Cooperative diversity in wireless networks: Efficient protocols and outage behavior
IEEE Transactions on Information Theory
Cooperative communication in wireless networks
IEEE Communications Magazine
Relay-Assisted Decorrelating Multiuser Detector (RAD-MUD) for Cooperative CDMA Networks
IEEE Journal on Selected Areas in Communications
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In this paper, we investigate cooperative diversity in the uplink of a code division multiple access (CDMA) system, in which users cooperate by relaying each other's messages to the Base Station (BS). We assume that the spreading waveforms are not orthogonal and hence multiple access interference (MAI) might exist at both the relay nodes as well as the BS. This MAI causes cooperative diversity gain to decrease. To alleviate this problem, the maximum likelihood multiuser detector (MUD) is introduced. We assume that direct and inter-user Channel State Information (CSI) is present at the BS, and it can use this information to optimally combine received signals from both direct and relay paths. Simulation results show that the proposed Maximum Likelihood (ML) detector can exploit maximum diversity and also cancel MAI at the BS. However, the complexity of this detector increases exponentially with the number of users. To address this issue, a Genetic Algorithm (GA) is employed and it will be shown that the proposed detector can achieve a near-optimum bit-error-rate performance with a reasonable complexity.