On Low-Complexity Full-diversity Detection In Multi-User MIMO   Multiple-Access Channels
  Multiple-input multiple-output (MIMO) techniques are becoming commonplace in recent wireless communication standards. This added dimension (i.e., space) can be efficiently used to mitigate the interference in the multi-user MIMO context. In this paper, we focus on the uplink of a MIMO multiple access channel (MAC) where perfect channel state information (CSI) is only available at the destination. We provide a new set of sufficient conditions for a wide range of space-time block codes (STBC)s to achieve full-diversity under \emph{partial interference cancellation group decoding} (PICGD) with or without successive interference cancellation (SIC) for completely blind users. Explicit interference cancellation (IC) schemes for two and three users are then provided and shown to satisfy the derived full-diversity criteria. Besides the complexity reduction due to the fact that the proposed IC schemes enable separate decoding of distinct users without sacrificing the diversity gain, further reduction of the decoding complexity may be obtained. In fact, thanks to the structure of the proposed schemes, the real and imaginary parts of each user's symbols may be decoupled without any loss of performance. Finally, our theoretical claims are corroborated by simulation results and the new IC scheme for two-user MIMO MAC is shown to outperform the recently proposed two-user IC scheme especially for high spectral efficiency while requiring significantly less decoding complexity. 
Amr Ismail and Mohamed-Slim Alouini
cs.IT math.IT