Link adaptation method and apparatus in wireless LAN system
A link adaptation method performed by a station (STA) in a wireless local area network (LAN) system supporting multi-user multiple-input multiple-output (MU-MIMO) is provided. The method includes: receiving a modulation and coding scheme (MCS) request, a steered sounding physical layer convergence procedure (PLOP) protocol data unit (PPDU) which is beam-formed to the STA, and a MIMO indicator including MU-MIMO-related information from an access point (AP); and transmitting feedback information including an MCS acquired from the steered sounding PPDU and the MU-MIMO-related information to the AP in response to the MCS request.
1. A method for a wireless local area network (LAN) system supporting multi-user multiple-input multiple-output (MU-MIMO), the method comprising:
receiving, by a station (STA), a training request to request a channel feedback from an access point, the training request including a MIMO indicator for indicating paired STAs which are targets of a MU-MIMO scheme together with the STA and which are expected to prepare the requested channel feedback;
receiving, by the STA, a null data packet (NDP) from the access point after receiving the training request; and
transmitting, by the STA, feedback information to the access point, the feedback information including channel information and stream information, the channel information indicating an estimated channel obtained by assuming the MU-MIMO scheme, and the stream information indicating a number of spatial streams obtained from the NDP.
2. The method of claim 1 , wherein the MIMO indicator indicates a number of the paired STAs which are the targets of the MU-MIMO scheme together with the STA.
3. The method of claim 1 , wherein the NDP includes a long training field and does not include a data field.
4. The method of claim 1 , wherein the training request includes number information indicating a first number, and the estimated channel is measured based on the first number.
5. A station (STA) for a wireless local area network (LAN) system supporting multi-user multiple-input multiple-output (MU-MIMO), the STA comprising:
a radio frequency (RF) unit; and
a processor operatively coupled to the RF unit and configured to:
instruct the RF unit to receive a training request to request a channel feedback from an access point, the training request including a MIMO indicator for indicating paired STAs which are targets of a MU-MIMO scheme together with the STA and are expected to prepare the requested channel feedback;
instruct the RF unit to receive a null data packet (NDP) from the access point after receiving the training request; and
instruct the RF unit to transmit feedback information to the access point, the feedback information including channel information and stream information, the channel information indicating an estimated channel measured by assuming the MU-MIMO scheme, the stream information indicating a number of spatial streams obtained from the NDP.