Automatic retransmission in communications systems. In one embodiment, a portion of data is identified to be retransmitted based on feedback information indicating a negative acknowledgement (NACK) during a cyclic redundancy check (CRC) on a previous transmission of the portion of data. A retransmission mode is selected for the portion of data, from at least 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, based on first desired transmission characteristics; and a second mode that retransmits the portion of data simultaneously on at least the first and second transmitter antennas, based on second desired transmission characteristics.