Patent ID: 9344312
Filing Date: 2016-05-17
CPC Classification: H04B,H04L,H04W

Claim Text:
1. A method of multi user multiple input multiple output (MIMO) communication in a wireless local area network (WLAN) system, the method being performed by a transmitting device and comprising: transmitting, by the transmitting device, a control frame to initiate channel sounding; receiving, by the transmitting device, a sounding frame including channel estimation information; generating, by the transmitting device, an Aggregate-Medium Access Control Protocol Data Unit (A-MPDU) including an A-MPDU subframe, the A-MPDU subframe including a Medium Access Control Protocol Data Unit (MPDU) delimiter field; selecting, by the transmitting device, a type of a guard interval to be applied to the A-MPDU among a short guard interval and a long guard interval by checking a capability of a receiving device, wherein, when the A-MPDU is generated for a plurality of receiving devices, the transmitting device checks whether all of the plurality of receiving devices support the short guard interval and selects the short guard interval only if all of the plurality of receiving devices support the short guard interval; and transmitting, by the transmitting device, the A-MPDU by using the selected guard interval, wherein the MPDU delimiter field includes a null field and an MPDU length field, the null field indicates a corresponding A-MPDU subframe is used to pad the A-MPDU, and the MPDU length field indicates a length of an MPDU of the corresponding A-MPDU subframe, and wherein the null field is a 1-bit information field and a value of the null field is set to ‘1’ when the corresponding A-MPDU subframe is used to pad the A-MPDU.