Interference resistance of Adaptive Multiuser Detection in asynchronous Detect and Forward relaying CDMA networks

The uplink of an asynchronous Detect and Forward CDMA wireless network interference tolerance is investigated in this paper where relays and base station use Adaptive Multiuser Detection to detect incoming signals. Relays exchange data and channel information with the base station to achieve diversity gains. Due to non orthogonality of random spreading waveforms, Multiple Access Interference occurs, at both the relays and base station. In order to mitigate Multiple Access Interference, Adaptive Multiuser detection is been used by fractionally spaced linear transversal bank of filters. It is shown that Adaptive Multiuser Detection enables asynchronous cooperative communications while it is extremely effective with mitigating channel interference. It is also shown that the BER and Capacity performance of the scheme proposed in this paper is arbitrarily close to non linear MLSE theoretical upper bound results in a channel interference free operation. However, in the presence of channel interference our scheme outperforms the theoretical upper bound approach by nearly 9 dB at a BER of 10 -3 and by 17 bits/s/Hz in Capacity at a SNR of 30dB.