Method and apparatus for multiple frame transmission for supporting MU-MIMO
A method of transmitting multiple frames in a wireless local area network (WLAN) system supporting multi user-multiple input multiple output (MU-MIMO) is provided. The method comprises transmitting a first frame and a second frame consecutively to a first station (STA) and transmitting a third frame and a fourth frame consecutively to a second STA, wherein a transmission start time of the first frame and a transmission start time of the third frame are aligned to each other, and wherein a transmission start time of the second frame and a transmission start time of the fourth frame are aligned to each other.
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.
2. The method of claim 1 , wherein the MPDU delimiter field is 4 byte information and is directly followed by the MPDU, which is directly followed by a padding field.
3. The method of claim 1 , wherein the MPDU delimiter field further includes a Cyclic Redundancy Check (CRC) field, which is directly followed by a delimiter signature field.
4. The method of claim 1 , wherein each bit of the null data is set to ‘1’.
5. A transmitting device for multi user multiple input multiple output (MIMO) communication in a wireless local area network (WLAN) system, the transmitting device comprising:
a processor configured to generate 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; and
a radio unit configured to:
transmit a control frame to initiate channel sounding,
receive a sounding frame including channel estimation information,
select 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 radio unit 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
transmit 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.
6. The transmitting device of claim 5 , wherein the MPDU delimiter field is 4 byte information and is directly followed by the MPDU, which is directly followed by a padding field.
7. The transmitting device of claim 5 , wherein the MPDU delimiter field further includes a Cyclic Redundancy Check (CRC) field, which is directly followed by a delimiter signature field.
8. The transmitting device of claim 5 , wherein each bit of the null data is set to ‘1’.