Systems, methods, and devices for reducing the overhead required to transmit acknowledgment messages (ACKs) are described herein. In some aspects, the ACKs are reduced in size. In some aspects the ACKs include several short training fields. In some aspects, a receiver of the ACKs can determine the transmitter of the ACK based on when the ACK is received. In some aspects, a receiver of the ACKs can determine the transmitter of the ACK based on information superimposed on the short training fields in the ACK.