Patent ID: 8588122

Claim:
A method of transmitting data to multiple destinations in a wireless local area network (WLAN) system, the method comprising: generating, by a transmitting device, a media access control protocol data unit (MPDU) for each of a plurality of destination devices; generating, by the transmitting device, an aggregated-MPDU (A-MPDU) by sequentially adding the MPDU for each of the destination devices; adding a physical header to the A-MPDU, and transmitting the A-MPDU with the physical header added, to the plurality of destination devices, by the transmitting device; transmitting, by the respective destination devices, ACK frames, which notify a successful reception, to the transmitting device after receiving a self-destined MPDU from the A-MPDU and verifying the received MPDU; and adding a physical header to an MPDU for a specific destination device, when the transmitting device fails to receive ACK frames from the specific destination device, and transmitting the MPDU with the physical header added, to the specific destination device, after the lapse of a short interframe space (SIFS) from a timing when a sequential transmission of the ACK frames is terminated, wherein the transmitting of the ACK frames to the transmitting device comprises: detecting, by the respective destination devices, a position and an order of a self-destined MPDU from the A-MPDU; and transmitting, by the respective destination devices, the ACK frames to the transmitting device according to the detected order, and the transmitting of the ACK frames to the transmitting device according to the detected order comprises transmitting the ACK frame to the transmitting device at a timing when a time T determined by the following Equation elapses after the transmission of the A-MPDU is terminated, T =SIFS+( ACK — Tx _Time+RIFS)×(Order−1) (1) where ACK_Tx_time is a length of the ACK frame, and Order is the detected order.