This paper deals with the spatio-temporal scheduling of a set of users for downlink transmission in a cell where the base station is provided with multiple antennas. Two main issues are addressed: how the users are distributed into space-time groups and how the available power is allocated among the users within a group. Since the former is an NP-complete combinatorial problem, we develop fast and low-complexity algorithms, which might be capable to fulfill the real-time requirements of a practical scheduling scheme. Regarding the power allocation, we consider different fairness criteria under the capacity point of view. To be precise, we compare the alternatives of equal rate and maximum sum rate with our proposed equal proportional rate solution.