Space-time coded turbo equalization and multiuser detection-asymptotic performance analysis in the presence of unknown interference

Turbo MIMO equalization in multiuser space-time-trellis-coded (STTrC) system is considered in this paper. The low complexity MMSE receiver with soft cancellation (SC) is proposed for joint inter-symbol-interference (ISI), known co-channel interference (CCI) and unknown co-channel interference (UCCI) suppression. It is shown that in the multiuser scenario without UCCI the proposed iterative receiver achieves maximum-likelihood (ML) bound on performance of the single user. The number of receive antennas is thereby equal to the number of users and not to the number of transmit antennas. Furthermore, the upper bound on pairwise error probability (PEP) is derived in the presence of UCCI in the asymptotic case of ideal SC. The result shows that the effect of the interference on the diversity and coding gain is very similar to that of the channel correlation at the receiver side. Namely the diversity and coding gain depend on the rank of the inverse of the matrix R of the UCCI.