Method and apparatus for transmitting feedback frame in wireless local area network system

Patent metadata

Field	Value
Publication number	US-10153877-B2
Application number	US-201615296997-A
Country	US
Kind code	B2
Filing date	Oct 18, 2016
Priority date	Oct 19, 2015
Publication date	Dec 11, 2018
Grant date	Dec 11, 2018

Abstract

Provides are a method and an apparatus for transmitting a feedback frame in a wireless local area network (WLAN) system. Specifically, a station (STA) receives, from an access point (AP), a null data packet announcement (NDPA) frame indicating transmission of a null data packet (NDP). The STA receives the NDP from the AP. The STA transmits, to the AP, a feedback frame including channel state information determined based on the NDP. The channel state information indicates a feedback subcarrier in each subcarrier group. The subcarrier group is generated based on grouping information using subcarriers in a frequency band excluding a guard subcarrier and a DC subcarrier. The feedback subcarrier is included in a subcarrier with an odd-numbered subcarrier index. The feedback subcarrier corresponds to a subcarrier with an even-numbered subcarrier index that is adjacent to the subcarrier with the odd-numbered subcarrier when the subcarrier with the odd-numbered subcarrier is a null subcarrier.

First claim

What is claimed is:

1. A method of transmitting a feedback frame based on a sounding procedure in a wireless local area network (WLAN) system, the method performed by a station (STA) and comprising:
receiving, from an access point (AP), a null data packet announcement (NDPA) frame indicating transmission of a null data packet (NDP);
receiving the NDP from the AP in response to NDPA; and
transmitting, to the AP, a feedback frame comprising channel state information (CSI) determined based on the received NDP,
wherein the CSI indicates a first feedback subcarrier in a first subcarrier group and a second feedback subcarrier in a second subcarrier group,
wherein the first subcarrier group and the second subcarrier group are generated based on grouping information using subcarriers in a frequency band excluding a guard subcarrier and a DC subcarrier,
wherein the first feedback subcarrier is included in subcarriers in the first subcarrier group having an odd-numbered subcarrier index, and
wherein the second feedback subcarrier is included in subcarriers in the second subcarrier group having an even-numbered subcarrier index that are adjacent to subcarriers having an odd-numbered subcarrier index when the subcarriers having the odd-numbered subcarrier index include a null subcarrier.

2. The method of claim 1 , wherein:
a fourth subcarrier group is generated by grouping the second subcarrier group and a third subcarrier group that is adjacent to the second subcarrier group if there is no feedback subcarrier in the third subcarrier group; and
the second feedback subcarrier is included in the fourth subcarrier group.

3. The method of claim 1 , wherein a pilot subcarrier is included in subcarriers in the first subcarrier group having an even-numbered subcarrier index.

4. The method of claim 3 , wherein the CSI comprises either average channel information estimated in subcarriers in the first or second subcarrier group excluding the null subcarrier and a pilot subcarrier or channel information estimated in the feedback subcarrier.

5. The method of claim 4 , wherein the CSI is transmitted through the first or second feedback subcarrier.

6. The method of claim 1 , wherein the grouping information is received through the NDPA frame.

7. The method of claim 1 , wherein:
the NDP comprises a first field area and a second field area;
the first field area comprises a Legacy-Long Training Field (L-LTF);
the second field area comprises a High Efficiency-LTF (HE-LTF); and
an inverse fast Fourier transform (IFFT) applied to the second field area has a size twice or four times a size of an IFFT applied to the first field area.

8. A wireless device transmitting a feedback frame in a wireless local area network system (WLAN) system, the wireless device comprising:
a radio frequency (RF) unit configured to transmit and receive a radio signal; and
a processor operatively coupled with the RF unit, the processor is configured to:
control the RF unit to receive, from an access point (AP), a null data packet announcement (NDPA) frame indicating transmission of a null data packet (NDP);
control the RF unit to receive the NDP from the AP in response to the NDPA, and
control the RF unit to transmit, to the AP, a feedback frame comprising channel state information (CS) determined based on the received NDP,
wherein the CSI indicates a first feedback subcarrier in a first subcarrier group and a second feedback subcarrier in a second subcarrier group,
wherein the first subcarrier group and the second subcarrier group are generated based on grouping information using subcarriers in a frequency band excluding a guard subcarrier and a DC subcarrier,
wherein the first feedback subcarrier is included in subcarriers in the first subcarrier group having an odd-numbered subcarrier index, and
wherein the second feedback subcarrier is included in subcarriers in the second subcarrier group having an even-numbered subcarrier index that are adjacent to subcarriers having an odd-numbered subcarrier index when the subcarriers having the odd-numbered subcarrier index include a null subcarrier.

9. The wireless device of claim 8 , wherein:
a fourth subcarrier group is generated by grouping the second subcarrier group and a third subcarrier group that is adjacent to the second subcarrier group if there is no feedback subcarrier in the third subcarrier group; and
the second feedback subcarrier is included in the fourth subcarrier group.

10. The wireless device of claim 8 , wherein a pilot subcarrier is included in subcarriers in the first subcarrier group having an even-numbered subcarrier index.

11. The wireless device of claim 10 , wherein the CSI comprises either average channel information estimated in subcarriers in the first subcarrier group excluding the null subcarrier and a pilot subcarrier or channel information estimated in the feedback subcarrier.

12. The wireless device of claim 11 , wherein the CSI is transmitted through the first or second feedback subcarrier.

13. The wireless device of claim 8 , wherein the grouping information is received through the NDPA frame.

14. The wireless device of claim 8 , wherein:
the NDP comprises a first field area and a second field area;
the first field area comprises a Legacy-Long Training Field (L-LTF);
the second field area comprises a High Efficiency-LTF (HE-LTF); and
an inverse fast Fourier transform (IFFT) applied to the second field area has a size twice or four times a size of an IFFT applied to the first field area.

Assignees

• Lg Electronics Inc

Inventors

• Park Eunsung
• Choi Jinsoo
• Lim Dongguk
• Cho Hangyu

Classifications

• H04L5/0048 Primary

  Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091) · CPC title

• H04W84/12

  WLAN [Wireless Local Area Networks] · CPC title

• H04L1/0026

  Transmission of channel quality indication · CPC title

• H04L1/0075

  Transmission of coding parameters to receiver (H04L1/0023 takes precedence) · CPC title