  Multiuser multiple-input-multiple-output (MU-MIMO) systems are known to be
hindered by dimensionality loss due to channel state information (CSI)
acquisition overhead. In this paper, we investigate user-scheduling in MU-MIMO
systems on account of CSI acquisition overhead, where a base station
dynamically acquires user channels to avoid choking the system with CSI
overhead. The genie-aided optimization problem (GAP) is first formulated to
maximize the Lyapunov-drift every scheduling step, incorporating user queue
information and taking channel fluctuations into consideration. The scheduling
scheme based on GAP, namely the GAP-rule, is proved to be throughput-optimal
but practically infeasible, and thus serves as a performance bound. In view of
the implementation overhead and delay unfairness of the GAP-rule, the T-frame
dynamic channel acquisition scheme and the power-law DCA scheme are further
proposed to mitigate the implementation overhead and delay unfairness,
respectively. Both schemes are based on the GAP-rule and proved
throughput-optimal. To make the schemes practically feasible, we then propose
the heuristic schemes, queue-based quantized-block-length user scheduling
scheme (QQS), T-frame QQS, and power-law QQS, which are the practical versions
of the aforementioned GAP-based schemes, respectively. The QQS-based schemes
substantially decrease the complexity, and also perform fairly close to the
optimum. Numerical results evaluate the proposed schemes under various system
parameters.
