Automatic retransmission in communications systems. An embodiment includes retransmitting data. A cyclic redundancy check (CRC) is executed on a portion of data received as part of a data stream at a receiver antenna. Feedback information of acknowledgment (ACK) or negative acknowledgement (NACK) for the portion of data is determined based on a result of the CRC. It is identified that the portion of data is to be retransmitted based on the feedback information indicating a NACK with respect to the portion of data. A retransmission mode is selected for the portion of data based on desired characteristics of the data stream, including a first mode that retransmits the portion of data on at least a first transmitter antenna while transmitting new data on at least a second transmitter antenna; and a second mode that retransmits the portion of data simultaneously on at least the first and second transmitter antennas.