A method includes determining, by a Media Access Control (MAC) layer of a first wireless station, a total length of user data in a first Physical Layer (PHY) Protocol Data Unit (PPDU); determining, by the MAC layer, a Hybrid Automatic Repeat Request (HARQ) block size; adding a first indication to a transmission vector, wherein the first indication indicates the total length of user data in the first PPDU; adding a second indication to the transmission vector, wherein the second indication indicates the HARQ block size; passing the transmission vector to a PHY layer of the first wireless station; generating, by the PHY layer, the first PPDU based on the first indication and the second indication, wherein the first PPDU includes a first set of HARQ blocks that each have a size equal to the HARQ block size; and transmitting the first PPDU to a second wireless station.