Methods, devices, and systems for retransmitting Media Access Control (MAC) protocol data units (MPDUs) in a multi-user multiple-input and multiple-output (MU-MIMO) communication system are disclosed. Concurrent data streams within a first transmission window are transmitted. Each concurrent data stream is associated with a different recipient and includes an equal number of MPDUs. An indication of a retransmission subset of the MPDUs to be retransmitted for each concurrent data stream may be obtained if errors are present. The retransmission subset for each concurrent data stream is retransmitted within a second transmission window. A length of the second transmission window is as long as the longest of the retransmission subsets of the concurrent data streams. One or more new MPDUs may be added to the concurrent data streams in the second transmission window so that each concurrent data stream in the second transmission window carries a same number of MPDUs.