  This paper considers an uplink multiuser multiple-input-multiple-output
(MU-MIMO) system with one-bit analog-to-digital converters (ADCs), in which $K$
users with a single transmit antenna communicate with one base station (BS)
with $N_{\rm r}$ receive antennas. In this system, a novel MU-MIMO detection
method, named weighted minimum distance (wMD) decoding, was recently proposed
by introducing an equivalent coding problem. Despite of its attractive
performance, the wMD decoding has the two limitations to be used in practice:
i) the hard-decision outputs can degrade the performance of a channel code; ii)
the computational complexity grows exponentially with the $K$. To address those
problems, we first present a soft-output wMD decoding that efficiently computes
soft metrics (i.e., log-likelihood ratios) from one-bit quantized observations.
We then construct a low-complexity (soft-output) wMD decoding by introducing
{\em hierarchical code partitioning}. This method can be regarded as a sphere
decoding in Hamming space, in that a search-spare is considerably reduced.
Finally, we demonstrate that the proposed method significantly performs the
state-of-the-art methods with a comparable complexity.
