Method for performing channel sounding in wireless LAN system and apparatus for supporting same

• US 9,525,474 B2
• Filed: 11/22/2012
• Issued: 12/20/2016
• Est. Priority Date: 11/24/2011
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Park, Jong Hyun, You, Hyang Sun, Seok, Yong Ho
• Primary Examiner(s): Sefcheck, Gregory
• Assistant Examiner(s): Van, Jenkey
• Application Number:
  US14/360,506
• Publication Number:
  US 20140348097A1
• Time in Patent Office: 1,489 Days
• Field of Search: None
• US Class Current: 1/1
• 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,

wherein the NDP includes a signal field, a first long training field (LTF) used in channel estimation for decoding the signal field and a second LTF used in channel estimation for a multiple input multiple output (MIMO) channel,

wherein the signal field includes a repetition indication subfield,

wherein the repetition indication subfield indicates whether orthogonal frequency division multiplexing (OFDM) symbol repetition is applied to the second LTF,

wherein the first LTF is transmitted as an OFDM symbol for the first LTF and as a repetition OFDM symbol in which the first LTF is repeated regardless of the repetition indication subfield, and

wherein when the repetition indication subfield indicates that the OFDM symbol repetition is not applied to the second LTF, the second LTF is transmitted as a first long training symbol (LTS) for each LTF.

2. The method of claim 1, wherein:

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.

3. The method of claim 1, wherein a long guard interval (LGI) is inserted in front of the first LTS.

4. The method of claim 1, wherein

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

the second LTF is transmitted as a second 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 in front of the second LTS and the repetition LTS.

6. The method of claim 4, wherein a double guard interval (DGI) is inserted in front of the second LTS and the repetition LTS.

7. The method of claim 4, wherein a first long guard interval (LGI) is inserted in front of the second LTS, and a second long guard interval (LGI) is inserted in front of the repetition 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;

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

transmits the NDP, and

receives a feedback frame from a station (STA),

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

wherein the NDP includes a signal field, a first long training field (LTF) for channel estimation for decoding the signal field and a second LTF for channel estimation of a multiple input multiple output (MIMO) channel,

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

wherein the signal field includes a repetition indication subfield,

wherein the repetition indication subfield indicates whether orthogonal frequency division multiplexing (OFDM) symbol repetition is applied to the second LTF,

wherein the first LTF is transmitted as an OFDM symbol for the first LTF and as a repetition OFDM symbol in which the first LTF is repeated regardless of the repetition indication subfield, and

wherein when the repetition indication subfield indicates that the 01-DM symbol repetition is not applied to the second LTF, the second LTF is transmitted as a first long training symbol (LTS) for each LTF.

10. The wireless apparatus of claim 9, wherein:

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.

11. The wireless apparatus of claim 9, wherein a long guard interval (LGI) is inserted in front of the first LTS.

12. The wireless apparatus of claim 9, wherein:

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

the second LTF is transmitted as a second 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 in front of the second LTS and the repetition LTS.

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

15. The wireless apparatus of claim 12, wherein a first long guard interval (LGI) is inserted in front of the second LTS, and a second long guard interval (LGI) is inserted in front of the repetition 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.