  In this paper, a low-complexity multiple feedback successive interference
cancellation (MF-SIC) strategy is proposed for the uplink of multiuser
multiple-input multiple-output (MU-MIMO) systems. In the proposed MF-SIC
{algorithm with shadow area constraints (SAC)}, an enhanced interference
cancellation is achieved by introducing {constellation points as the
candidates} to combat the error propagation in decision feedback loops. We also
combine the MF-SIC with multi-branch (MB) processing, which achieves a higher
detection diversity order. For coded systems, a low-complexity soft-input
soft-output (SISO) iterative (turbo) detector is proposed based on the MF and
the MB-MF interference suppression techniques. The computational complexity of
the MF-SIC is {comparable to} the conventional SIC algorithm {since very little
additional complexity is required}. {Simulation} results show that the
algorithms significantly outperform the conventional SIC scheme and {approach}
the optimal detector.
