  Low-resolution analog-to-digital converters (ADCs) are promising for reducing
energy consumption and costs of multiuser multiple-input multiple-output (MIMO)
systems with many antennas. We propose low-resolution multiuser MIMO receivers
where the signals are simultaneously processed by 1-bit ADCs and a comparator
network, which can be interpreted as additional virtual channels with binary
outputs. We distinguish the proposed comparator networks in fully and partially
connected. For such receivers, we develop the low-resolution aware linear
minimum mean-squared error (LRA-LMMSE) channel estimator and detector according
to the Bussgang theorem. We also develop a robust detector which takes into
account the channel state information (CSI) mismatch statistics. By exploiting
knowledge of the channel coefficients we devise a mean-square error (MSE)
greedy search and a sequential signal-to-interference-plus-noise ratio (SINR)
search for optimization of partially connected networks. Numerical results show
that a system with extra virtual channels can outperform a system with
additional receive antennas, in terms of bit error rate (BER). Furthermore, by
employing the proposed channel estimation with its error statistics, we
construct a lower bound on the ergodic sum rate for a linear receiver.
Simulation results confirm that the proposed approach outperforms the
conventional 1-bit MIMO system in terms of BER, MSE and sum rate.
