Techniques for efficiently sending and receiving data in a wireless communication system are described herein. The techniques utilize a slot structure that is backward compatible with existing design. The techniques include sending and receiving forward link packets that occupy less than a full slot of the slot structure. An output waveform, which includes at least one slot, is generated at an access point. Each slot is segmented into two half-slots, wherein at least one half-slot includes a data unit of a packet. At a terminal, the output waveform is received and processed to extract the data unit and the data unit is processed to determine whether it is accurate. The terminal also generates ACK/NACK information in response to the results of processing the data unit and transmits channel information including the ACK/NACK information. The access point interprets the ACK/NACK information to determine if the data unit should be resent.