Wireless local area network communications with varying subcarrier spacings

1. A transmission method performed in a station, the transmission method comprising:

generating a legacy preamble;

generating a high efficiency (HE) preamble including at least one HE-signal (HE-SIG) field, a HE-short training field (HE-STF), and at least one HE-long training field (HE-LTF);

generating a HE physical layer convergence procedure protocol data unit (HE PPDU) including the legacy preamble and the HE preamble; and

transmitting, over a wireless medium, the HE PPDU,

wherein the legacy preamble, the at least one HE-SIG field, and the HE-STF each have a subcarrier spacing of 312.5 kHz, and

wherein the at least one HE-LTF has a subcarrier spacing of 156.25 kHz and a Discrete Fourier Transform (DFT) period having a length of 6.4 μsec when the HE PPDU is transmitted in a first communication environment, and has a subcarrier spacing of 78.125 kHz and a DFT period having a length of 12.8 μsec when the HE PPDU is transmitted in a second communication environment.

2. The transmission method of claim 1 , wherein the at least one HE-SIG field includes a HE-signal1 (HE-SIG1) field, a HE-signal2 (HE-SIG2) field, and a HE-signal3 (HE-SIG3) field.

3. The transmission method of claim 2 , wherein the HE-SIG1 field and the HE-SIG2 field are modulated in binary phase shift keying (BPSK) manner, and the HE-SIG3 field is modulated in quadrature BPSK (QBPSK) manner.

4. The transmission method of claim 1 , wherein the HE-SIG field includes a discrete Fourier transform (DFT) period having a length of 3.2 μsec.

5. The transmission method of claim 1 , wherein the HE-SIG field is duplicated in unit of 20 MHz bandwidth.

6. The transmission method of claim 1 , wherein a number of the at least one HE-LTF included in the HE preamble is configured based on a number of spatial streams onto which the HE PPDU is mapped.

7. The transmission method of claim 1 , wherein the HE-STF includes a DFT period having a length of 3.2 μsec.

8. The transmission method of claim 1 , wherein the HE-LTF includes a guard interval (GI) having a length of 0.8 μsec, 1.6 μsec, or 3.2 μsec.

9. The transmission method of claim 1 , wherein the HE-SIG field is an HE Signal A (HE-SIG-A) field or an HE Signal B (HE-SIG-B) field.

10. The transmission method of claim 1 , wherein the first communication environment is an indoor environment and the second communication environment is an outdoor environment.

11. A reception method performed in a station, the reception method comprising:

receiving, over a wireless medium, a high efficiency physical layer convergence procedure protocol data unit (HE PPDU), the HE PPDU including a legacy preamble and an HE preamble including at least one high efficiency signal (HE-SIG) field, a HE-short training field (HE-STF), and at least one HE Long Training Field (HE-LTF); and

performing channel estimation using the HE-LTF,

wherein the legacy preamble, the at least one HE-SIG field, and the HE-STF each have a subcarrier spacing of 312.5 kHz, and

wherein the at least one HE-LTF has a subcarrier spacing of 156.25 kHz and a DFT period having a length of 6.4 μsec when the HE PPDU is received in a first communication environment, and has a subcarrier spacing of 78.125 kHz and a DFT period having a length of 12.8 μsec when the HE PPDU is received in a second communication environment.

12. The reception method of claim 11 , wherein the at least one HE-SIG field includes a HE-signal1 (HE-SIG1) field, a HE-signal2 (HE-SIG2) field, and a HE-signal3 (HE-SIG3) field.

13. The reception method of claim 12 , wherein the HE-SIG1 field and the HE-SIG2 field are modulated in binary phase shift keying (BPSK) manner, and the HE-SIG3 field is modulated in quadrature BPSK (QBPSK) manner.

14. The reception method of claim 11 , wherein the HE-SIG field includes a discrete Fourier transform (DFT) period having a length of 3.2 μsec.

15. The reception method of claim 11 , wherein the HE-SIG field is duplicated in unit of 20 MHz bandwidth.

16. The reception method of claim 11 , wherein the HE-STF includes a DFT period having a length of 3.2 μsec.

17. The reception method of claim 11 , wherein the HE-LTF includes a guard interval (GI) having a length of 0.8 μsec, 1.6 μsec, or 3.2 μsec.

18. The reception method of claim 11 , wherein the HE-SIG field is an HE Signal A (HE-SIG-A) field or an HE Signal B (HE-SIG-B) field.

19. The reception method of claim 11 , wherein the first communication environment is an indoor environment and the second communication environment is an outdoor environment.