METHOD FOR PERFORMING CHANNEL SOUNDING IN WIRELESS LAN SYSTEM AND APPARATUS FOR SUPPORTING SAME

• US 20140348097A1
• Filed: 11/22/2012
• Published: 11/27/2014
• Est. Priority Date: 11/24/2011
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Park, Jong Hyun, Seok, Yong Ho, You, Hyang Sun
• Granted Patent: US 9,525,474 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26132 using repetition
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The present invention relates to a method of performing channel sounding in a wireless LAN system. The method includes transmitting a Null Data Packet Announcement (NDPA) frame for providing notice of an NDP to be transmitted, and transmitting the NDP and receiving a feedback frame from a station (STA). The feedback frame includes channel state information created on the basis of the NDP. The NDP includes a signal field and at least one long training field (LTF) for a multiple input multiple output channel. The signal field includes a repetitive instruction subfield. The repetitive instruction subfield provides instruction on whether orthogonal frequency division multiplexing (OFDM) symbol repetition is applied to the at least one LTF.

Claims

1. A method for performing channel sounding in a wireless LAN system, the method comprising the steps of:

transmitting a null data packet announcement (NDPA) frame to announce a transmission of a null data packet (NDP);

transmitting the NDP; and

receiving a feedback frame from a station (STA),

wherein the feedback frame includes channel state information generated based on the NDP,

the NDP includes at least one long training field (LTF) for a signal field and a multiple input multiple output (MIMO) channel,

the signal field includes a repetition indication subfield, and

the repetition indication subfield indicates whether orthogonal frequency division multiplexing (OFDM) symbol repetition is applied to the at least one LTF.

2. The method of claim 1, wherein:

when the repetition indication subfield indicates that the OFDM symbol repetition is not applied,

the signal field is transmitted as an OFDM symbol for the signal field and a repetition OFDM symbol in which the signal field is repeated, and

the at least one LTF is transmitted as a long training symbol (LTS) for each LTF.

3. The method of claim 2, wherein a double guard interval (DGI) is inserted into the LTS.

4. The method of claim 2, wherein

when the repetition indication subfield indicates that the OFDM symbol repetition is applied,

the at least one LTF is transmitted as a long training symbol (LTS) for each LTF and as a repetition LTS for a repetition LTF in which the each LTF is repeated.

5. The method of claim 4, wherein a long guard interval (LGI) is inserted into the LTS and the repetition LTS.

6. The method of claim 4, wherein the double guard interval (DGI) is inserted into the LTS.

7. The method of claim 4, wherein the long guard interval (LGI) is inserted into the LTS.

8. The method of claim 1, wherein the NDPA frame, the NDP, and the feedback frame are transmitted through a 1 MHz channel in a frequency band of 1 GHz or less.

9. A wireless apparatus that operates in a wireless LAN system, the apparatus comprising:

a transceiver configured to transmit and receive a radio signal; and

a processor configured to operate in functional association with the transceiver,

wherein the processor is configured to

transmit a null data packet announcement (NDPA) frame to announce to a transmission of a null data packet (NDP),

transmit the NDP, and

receive a feedback frame from a station (STA),

the feedback frame includes channel state information generated based on the NDP,

the NDP includes at least one long training field (LTF) for a signal field and a multiple input multiple output (MIMO) channel,

the signal field includes a repetition indication subfield, and

the repetition indication subfield indicates whether orthogonal frequency division multiplexing (OFDM) symbol repetition is applied to the at least one LTF.

10. The wireless apparatus of claim 9, wherein:

when the repetition indication subfield indicates that the OFDM symbol repetition is not applied,

the signal field is transmitted as an OFDM symbol for the signal field and a repetition OFDM symbol in which the signal field is repeated, and

the at least one LTF is transmitted as a long training symbol (LTS) for each LTF.

11. The wireless apparatus of claim 10, wherein a double guard interval (DGI) is inserted into the LTS.

12. The wireless apparatus of claim 10, wherein:

when the repetition indication subfield indicates that the OFDM symbol repetition is applied,

the at least one LTF is transmitted as a long training symbol (LTS) for each LTF and as a repetition LTS for a repetition LTF in which the each LTF is repeated.

13. The wireless apparatus of claim 12, wherein a long guard interval (LGI) is inserted into the LTS and the repetition LTS.

14. The wireless apparatus of claim 12, wherein the double guard interval (DGI) is inserted into the LTS.

15. The wireless apparatus of claim 12, wherein the long guard interval (LGI) is inserted into the LTS.

16. The wireless apparatus of claim 9, wherein the NDPA frame, the NDP, and the feedback frame are transmitted through a 1 MHz channel in a frequency band of 1 GHz or less.