A method of transmitting data from a transmitter to a receiver includes transmitting a first data unit to the receiver via a plurality of antennas, the first data unit including a payload that has a plurality of symbols; determining whether the receiver has successfully received the first data unit; and, in response to determining that the receiver has not successfully received the first data unit, transmitting a second data unit to the receiver, the second data unit including the payload, such that transmitting the second data unit includes transmitting the plurality of symbols via at least one of different antennas and different subcarriers with respect to the first data unit.