Multiuser transreceiving method in wireless communication system and device for same
A method for transmitting data from a station (STA) device in a wireless LAN (WLAN) system, according to one embodiment of the present invention, comprises the steps of: generating a physical protocol data unit (PPDU) including a physical preamble, which includes a legacy preamble and a high efficiency-long training field (HE-LTF), and a data field; and transmitting the PPDU, wherein the data field is transmitted at four times (4×) the inverse discrete Fourier transform (IDFT)/discrete Fourier transform (DFT) cycle of the legacy preamble, the HE-LTF is a 4×HE-LTF or a 2×HE-LTF which is respectively transmitted at the four times or two times (2×) the IDFT/DFT cycle of the legacy preamble, and wherein pilot tones of the HE-LTF may be inserted only into subcarriers having an even number of indexes from among subcarriers to which the 4×HE-LTF is mapped.
1. A data transmission method of a station (STA) in a wireless LAN (WLAN) system, comprising:
generating a physical protocol data unit (PPDU) including a data field, and a physical preamble which includes a legacy preamble and a high efficiency-long training field (HE-LTF); and
transmitting the PPDU,
wherein the data field is transmitted in a period quadruple (4×) an inverse discrete Fourier transform/discrete Fourier transform (IDFT/DFT) period of the legacy preamble,
wherein the HE-LTF is a 4×HE-LTF transmitted in a period quadruple (4×) the IDFT/DFT period of the legacy preamble or a 2×HE-LTF transmitted in a period double the IDFT/DFT period of the legacy preamble,
wherein pilot tones of the HE-LTF are inserted into only subcarriers having even indices from among subcarriers to which the 4×HE-LTF is mapped,
wherein values of the pilot tones are determined as a pilot sequence predetermined per stream based on a total number of streams carrying the PPDU or determined as a pilot sequence fixed for all streams irrespective of the total number of streams,
wherein pilot values included in the pilot sequence satisfy a following equation 1,
Ψ j =Ψ (n-j+1) , and [Equation 1]
wherein n is a total number of pilot tones inserted into the subcarriers, j is a natural number less than or equal to n, Ψ j is a pilot value at a j-th position in the pilot sequence, and Ψ (n-j+1) is a pilot value at an (n−j+1)-th position in the pilot sequence.
2. The data transmission method according to claim 1 , wherein the subcarriers having even indices from among the subcarriers carry data and subcarriers having odd indices from among the subcarriers do not carry data.
3. The data transmission method according to claim 1 , wherein orthogonality is satisfied between pilot sequences determined for each stream.
4. The data transmission method according to claim 3 , wherein each of the pilot sequences is determined as each column of a matrix generated by combining a plurality of Hadamard matrices.
5. The data transmission method according to claim 1 , wherein each pilot sequence is determined by pairing predetermined sequences.
6. The data transmission method according to claim 1 , wherein the frequency resources correspond to a bandwidth of 20 MHz, 40 MHz, 80 MHz or 160 MHz.
7. The data transmission method according to claim 6 ,
wherein the pilot tones are inserted into 8 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 20 MHz,
wherein the pilot tones are inserted into 16 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 40 MHz,
wherein the pilot tones are inserted into 16 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 80 MHz, and
wherein the pilot tones are inserted into 32 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 160 MHz.
8. The data transmission method according to claim 7 , wherein a pilot sequence with respect to 8 pilot tones inserted into the frequency resources of the bandwidth of 40 MHz or 80 MHz is determined by duplicating a pilot sequence with respect to 4 pilot tones inserted into the frequency resources of the bandwidth of 20 MHz two times, and
wherein a pilot sequence with respect to 32 pilot tones inserted into the frequency resources of the bandwidth of 160 MHz is determined by duplicating a pilot sequence with respect to 16 pilot tones inserted into the frequency resources of the bandwidth of 40 MHz or 80 MHz two times.
9. An STA in a WLAN system, comprising:
an RF unit including a transceiver configured to transmit and receive RF signals; and
a processor configured to control the RF unit,
wherein the processor is further configured to generate a PPDU including a data field and a physical preamble which includes a legacy preamble and an HE-LTF, and to transmit the PPDU,
wherein the data field is transmitted in a period quadruple (4×) an IDFT/DFT period of the legacy preamble,
wherein the HE-LTF is a 4×HE-LTF transmitted in a period quadruple (4×) the IDFT/DFT period of the legacy preamble or a 2×HE-LTF transmitted in a period double the IDFT/DFT period of the legacy preamble, and
wherein pilot tones of the HE-LTF are inserted into only subcarriers having even indices from among subcarriers to which the 4×HE-LTF is mapped,
wherein values of the pilot tones are determined as a pilot sequence predetermined per stream based on a total number of streams carrying the PPDU or determined as a pilot sequence fixed for all streams irrespective of the total number of streams,
wherein pilot values included in the pilot sequence satisfy a following equation 1,
Ψ j =Ψ (n-j+1) , and [Equation 1]
wherein n is a total number of pilot tones inserted into the subcarriers, j is a natural number less than or equal to n, Ψ j is a pilot value at a j-th position in the pilot sequence, and Ψ (n-j+1) is a pilot value at an (n−j+1)-th position in the pilot sequence.
10. The STA according to claim 9 , wherein the subcarriers having even indices from among the subcarriers carry data and subcarriers having odd indices from among the subcarriers do not carry data.
11. The STA according to claim 9 , wherein orthogonality is satisfied between pilot sequences determined for each stream.
12. The STA according to claim 11 , wherein each of the pilot sequences is determined as each column of a matrix generated by combining a plurality of Hadamard matrices.
13. The STA according to claim 9 , wherein each pilot sequence is determined by pairing predetermined sequences.
14. The STA according to claim 9 , wherein the frequency resources correspond to a bandwidth of 20 MHz, 40 MHz, 80 MHz or 160 MHz.
15. The STA according to claim 14 ,
wherein the pilot tones are inserted into 8 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 20 MHz,
wherein the pilot tones are inserted into 16 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 40 MHz,
wherein the pilot tones are inserted into 16 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 80 MHz, and
wherein the pilot tones are inserted into 32 subcarriers from among subcarriers included in the frequency resources when the frequency resources correspond to the bandwidth of 160 MHz.
16. The STA according to claim 15 , wherein a pilot sequence with respect to 8 pilot tones inserted into the frequency resources of the bandwidth of 40 MHz or 80 MHz is determined by duplicating a pilot sequence with respect to 4 pilot tones inserted into the frequency resources of the bandwidth of 20 MHz two times, and
wherein a pilot sequence with respect to 32 pilot tones inserted into the frequency resources of the bandwidth of 160 MHz is determined by duplicating a pilot sequence with respect to 16 pilot tones inserted into the frequency resources of the bandwidth of 40 MHz or 80 MHz two times.