Method and apparatus for transmitting PPDU on basis of S-TDMA in wireless LAN system
11641237 · 2023-05-02
Assignee
Inventors
- Insun JANG (Seoul, KR)
- Suhwook Kim (Seoul, KR)
- Jeongki Kim (Seoul, KR)
- Kiseon Ryu (Seoul, KR)
- Taewon Song (Seoul, KR)
- Jinsoo Choi (Seoul, KR)
Cpc classification
International classification
Abstract
A method and apparatus for transmitting a PPDU on the basis of S-TDMA in a wireless LAN system are presented. In particular, an AP generates a PPDU, and transmits the PPDU to a first STA and a second STA. When a PPDU further comprises a third signal field, the third signal field comprises information about S-TDMA. The information about S-TDMA comprises STDMA indication information indicating that S-TDMA can be carried out, first symbol offset information about a first data field, and second symbol offset information about a second data field. The S-TDMA indication information comprises information indicating that the first and second data fields are assigned to a first RU. The first data field is transmitted from the first RU during a first symbol determined on the basis of the first symbol offset information. The second data field is transmitted from the first RU during a second symbol determined on the basis of the second symbol offset information.
Claims
1. A method for transmitting a Physical layer Protocol Data Unit (PPDU) based on Scheduled-Time Division Multiple Access (S-TDMA) in a wireless LAN system, the method comprising: generating, by an access point (AP), the PPDU; and transmitting, by the AP, the PPDU to a first station (STA) and a second STA, wherein the PPDU includes a legacy header field, a first signal field, a second signal field, a first data field for the first STA, and a second data field for the second STA, wherein the second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU, wherein, in case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA, wherein the information on the S-TDMA includes S-TDMA indication information on that the S-TDMA can be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field, wherein the S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU, wherein the first data field is transmitted in the first RU based on the first symbol offset information, wherein the second data field is transmitted in the first RU based on the second symbol offset information, wherein, in case a third signal field is not included in the DL PPDU, the second signal field further includes information on the S-TDMA, wherein the information on Resource Unit (RU) layout and the information on a number of STAs using the first RU are included in a common field of the second signal field, and wherein the information on the S-TDMA is included in a user field of the second signal field.
2. The method of claim 1, wherein the first symbol offset information includes information on a transmission start point of the first data field, wherein the second symbol offset information includes information on a transmission start point of the second data field, wherein a first symbol being a time duration during which the first data field is transmitted is determined based on the first symbol offset information, wherein a second symbol being a time duration during which the second data field is transmitted is determined based on the second symbol offset information, and wherein the first symbol and the second symbol are positioned in the first RU based on TDMA.
3. The method of claim 1, wherein the first symbol offset information includes information on a transmission end point of the first data field, wherein the second symbol offset information includes information on a transmission end point of the second data field, wherein a first symbol being a time duration during which the first data field is transmitted is determined based on the first symbol offset information, wherein a second symbol being a time duration during which the second data field is transmitted is determined based on the second symbol offset information, wherein the first symbol and the second symbol are positioned in the first RU based on TDMA, and wherein the information on S-TDMA further includes End of S-TDMA information for a data field being last transmitted in the first RU.
4. The method of claim 1, wherein the PPDU further includes a Short Training Field (STF) and Long Training Field (LTF) for the first STA and an STF and LTF for the second STA, wherein the STF and LTF for the second STA are transmitted after the first data field and before the second data field, wherein a guard time is included between the first data field and the STF and LTF for the second STA, and wherein the first signal field includes signaling information notifying whether or not the third signal field and the STF and LTF for the second STA are included in the PPDU.
5. The method of claim 1, further comprising: transmitting, by the AP, the PPDU to a third STA, wherein the PPDU further includes a third data field for the third STA, wherein the third data field is transmitted in a second RU being determined based on the second signal field, and wherein the first RU and the second RU are different frequency bands.
6. The method of claim 1, wherein the PPDU is generated by using a High Efficiency Multi User PPDU (HE MU PPDU), wherein the legacy header field is related to Legacy-Short Training Field (L-STF), Legacy-Long Training Field (L-LTF), Legacy-Signal (L-SIG) field, or Repeated Legacy-Signal (RL-SIG) field all being included in the HE MU PPDU, wherein the first signal field is related to the HE-SIG-A field being included in the HE MU PPDU, and wherein the second signal field is related to the HE-SIG-B field being included in the HE MU PPDU.
7. The method of claim 1, wherein the number of STAs using the first RU is equal to 2 or more.
8. A wireless device being an access point (AP) for transmitting a Physical layer Protocol Data Unit (PPDU) based on Scheduled-Time Division Multiple Access (S-TDMA) in a wireless LAN system, the wireless device comprising: a memory; a transceiver; and a processor being operatively coupled with the memory and the transceiver, wherein the processor: generates the PPDU, and transmits the PPDU to a first station (STA) and a second STA, wherein the PPDU includes a legacy header field, a first signal field, a second signal field, a first data field for the first STA, and a second data field for the second STA, wherein the second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU, wherein, in case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA, wherein the information on the S-TDMA includes S-TDMA indication information on that the S-TDMA can be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field, wherein the S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU, wherein the first data field is transmitted in the first RU based on the first symbol offset information, wherein the second data field is transmitted in the first RU based on the second symbol offset information, wherein, in case a third signal field is not included in the DL PPDU, the second signal field further includes information on the S-TDMA, wherein the information on Resource Unit (RU) layout and the information on a number of STAs using the first RU are included in a common field of the second signal field, and wherein the information on the S-TDMA is included in a user field of the second signal field.
9. The wireless device of claim 8, wherein the first symbol offset information includes information on a transmission start point of the first data field, wherein the second symbol offset information includes information on a transmission start point of the second data field, wherein a first symbol being a time duration during which the first data field is transmitted is determined based on the first symbol offset information, wherein a second symbol being a time duration during which the second data field is transmitted is determined based on the second symbol offset information, and wherein the first symbol and the second symbol are positioned in the first RU based on TDMA.
10. The wireless device of claim 8, wherein the first symbol offset information includes information on a transmission end point of the first data field, wherein the second symbol offset information includes information on a transmission end point of the second data field, wherein a first symbol being a time duration during which the first data field is transmitted is determined based on the first symbol offset information, wherein a second symbol being a time duration during which the second data field is transmitted is determined based on the second symbol offset information, wherein the first symbol and the second symbol are positioned in the first RU based on TDMA, and wherein the information on S-TDMA further includes End of S-TDMA information for a data field being last transmitted in the first RU.
11. The wireless device of claim 8, wherein the PPDU further includes a Short Training Field (STF) and Long Training Field (LTF) for the first STA and an STF and LTF for the second STA, wherein the STF and LTF for the second STA are transmitted after the first data field and before the second data field, wherein a guard time is included between the first data field and the STF and LTF for the second STA, and wherein the first signal field includes signaling information notifying whether or not the third signal field and the STF and LTF for the second STA are included in the PPDU.
12. The wireless device of claim 8, wherein the processor transmits the PPDU to a third STA, wherein the PPDU further includes a third data field for the third STA, wherein the third data field is transmitted in a second RU being determined based on the second signal field, and wherein the first RU and the second RU are different frequency bands.
13. The wireless device of claim 8, wherein the PPDU is generated by using a High Efficiency Multi User PPDU (HE MU PPDU), wherein the legacy header field is related to Legacy-Short Training Field (L-STF), Legacy-Long Training Field (L-LTF), Legacy-Signal (L-SIG) field, or Repeated Legacy-Signal (RL-SIG) field all being included in the HE MU PPDU, wherein the first signal field is related to the HE-SIG-A field being included in the HE MU PPDU, and wherein the second signal field is related to the HE-SIG-B field being included in the HE MU PPDU.
14. The wireless device of claim 8, wherein the number of STAs using the first RU is equal to 2 or more.
15. A method for receiving a Physical layer Protocol Data Unit (PPDU) based on Scheduled-Time Division Multiple Access (S-TDMA) in a wireless LAN system, the method comprising: receiving, by a first station (STA), the PPDU from an access point (AP), wherein the PPDU includes a first data field for the first STA and a second data field for the second STA; and decoding, by the first STA, the first data field, wherein the PPDU includes a legacy header field, a first signal field, and a second signal field, wherein the second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU, wherein, in case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA, wherein the information on the S-TDMA includes S-TDMA indication information on that the S-TDMA can be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field, wherein the S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU, wherein the first data field is transmitted in the first RU based on the first symbol offset information, wherein the second data field is transmitted in the first RU based on the second symbol offset information, wherein, in case a third signal field is not included in the DL PPDU, the second signal field further includes information on the S-TDMA, wherein the information on Resource Unit (RU) layout and the information on a number of STAs using the first RU are included in a common field of the second signal field, and wherein the information on the S-TDMA is included in a user field of the second signal field.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DESCRIPTION OF EXEMPLARY EMBODIMENTS
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(25) An upper part of
(26) Referring the upper part of
(27) The BSS may include at least one STA, APs providing a distribution service, and a distribution system (DS) (110) connecting multiple APs.
(28) The distribution system (110) may implement an extended service set (ESS) (140) extended by connecting the multiple BSSs (100, 105). The ESS (140) may be used as a term indicating one network configured by connecting one or more APs (125, 130) through the distribution system (110). The AP included in one ESS (140) may have the same service set identification (SSID).
(29) A portal (120) may serve as a bridge which connects the wireless LAN network (IEEE 802.11) and another network (e.g., 802.X).
(30) In the BSS illustrated in the upper part of
(31) A lower part of
(32) Referring to the lower part of
(33) The STA as a predetermined functional medium that includes a medium access control (MAC) that follows a regulation of an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and a physical layer interface for a radio medium may be used as a meaning including all of the APs and the non-AP stations (STAs).
(34) The STA may be called various a name such as a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), user equipment (UE), a mobile station (MS), a mobile subscriber unit, or just a user.
(35) Meanwhile, the term user may be used in various meanings, for example, in wireless LAN communication, this term may be used to signify a STA participating in uplink MU MIMO and/or uplink OFDMA transmission. However, the meaning of this term will not be limited only to this.
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(37) As illustrated in
(38) In the embodiment, an improved technique is provided, which is associated with a signal (alternatively, a control information field) used for the data field of the PPDU. The signal provided in the embodiment may be applied onto high efficiency PPDU (HE PPDU) according to an IEEE 802.11ax standard. That is, the signal improved in the embodiment may be HE-SIG-A and/or HE-SIG-B included in the HE PPDU. The HE-SIG-A and the HE-SIG-B may be represented even as the SIG-A and SIG-B, respectively. However, the improved signal proposed in the embodiment is not particularly limited to an HE-SIG-A and/or HE-SIG-B standard and may be applied to control/data fields having various names, which include the control information in a wireless communication system transferring the user data.
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(40) The control information field provided in the embodiment may be the HE-SIG-B included in the HE PPDU. The HE PPDU according to
(41) As illustrated in
(42) More detailed description of the respective fields of
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(44) As illustrated in
(45) As illustrated in an uppermost part of
(46) Meanwhile, the RU layout of
(47) In one example of
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(49) Similarly to a case in which the RUs having various RUs are used in one example of
(50) In addition, as illustrated in
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(52) Similarly to a case in which the RUs having various RUs are used in one example of each of
(53) Moreover, as illustrated in
(54) Meanwhile, the detailed number of RUs may be modified similarly to one example of each of
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(56) A block illustrated in
(57) An illustrated L-STF (700) may include a short training orthogonal frequency division multiplexing (OFDM) symbol. The L-STF (700) may be used for frame detection, automatic gain control (AGC), diversity detection, and coarse frequency/time synchronization.
(58) An L-LTF (710) may include a long training orthogonal frequency division multiplexing (OFDM) symbol. The L-LTF (710) may be used for fine frequency/time synchronization and channel prediction.
(59) An L-SIG (720) may be used for transmitting control information. The L-SIG (720) may include information regarding a data rate and a data length. Further, the L-SIG (720) may be repeatedly transmitted. That is, a new format, in which the L-SIG (720) is repeated (for example, may be referred to as R-LSIG) may be configured.
(60) An HE-SIG-A (730) may include the control information common to the receiving station.
(61) In detail, the HE-SIG-A (730) may include information on 1) a DL/UL indicator, 2) a BSS color field indicating an identify of a BSS, 3) a field indicating a remaining time of a current TXOP period, 4) a bandwidth field indicating at least one of 20, 40, 80, 160 and 80+80 MHz, 5) a field indicating an MCS technique applied to the HE-SIG-B, 6) an indication field regarding whether the HE-SIG-B is modulated by a dual subcarrier modulation technique for MCS, 7) a field indicating the number of symbols used for the HE-SIG-B, 8) a field indicating whether the HE-SIG-B is configured for a full bandwidth MIMO transmission, 9) a field indicating the number of symbols of the HE-LTF, 10) a field indicating the length of the HE-LTF and a CP length, 11) a field indicating whether an OFDM symbol is present for LDPC coding, 12) a field indicating control information regarding packet extension (PE), and 13) a field indicating information on a CRC field of the HE-SIG-A, and the like. A detailed field of the HE-SIG-A may be added or partially omitted. Further, some fields of the HE-SIG-A may be partially added or omitted in other environments other than a multi-user (MU) environment.
(62) In addition, the HE-SIG-A (730) may be composed of two parts: HE-SIG-Al and HE-SIG-A2. HE-SIG-A1 and HE-SIG-A2 included in the HE-SIG-A may be defined by the following format structure (fields) according to the PPDU. First, the HE-SIG-A field of the HE SU PPDU may be defined as follows.
(63) TABLE-US-00001 TABLE 1 Two Parts of Number HE-SIG-A Bit Field of bits Description HE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU from an HE TB PPDU: Set to 1 for an HE SU PPDU and HE ER SU PPDU B1 Beam 1 Set to 1 to indicate that the pre-HE modulated fields of Change the PPDU are spatially mapped differently from the first symbol of the HE-LTF. Equation (28-6), Equation (28-9), Equation (28-12), Equation (28-14), Equation (28-16) and Equation (28-18) apply if the Beam Change field is set to 1. Set to 0 to indicate that the pre-HE modulated fields of the PPDU are spatially mapped the same way as the first symbol of the HE-LTF on each tone. Equation (28- 8), Equation (28-10), Equation (28-13), Equation (28- 15), Equation (28-17) and Equation (28-19) apply if the Beam Change field is set to 0. (#16803) B2 UL/DL 1 Indicates whether the PPDU is sent UL or DL. Set to the value indicated by the TXVECTOR parameter UPLINK_FLAG. B3-B6 MCS 4 For an HE SU PPDU: Set to n for MCSn, where n = 0, 1, 2, . . . , 11 Values 12-15 are reserved For HE ER SU PPDU with Bandwidth field set to 0 (242-toneRU): Set to n for MCSn, where n = 0, 1, 2 Values 3-15 are reserved For HE ER SU PPDU with Bandwidth field set to 1 (upper frequency 106-tone RU): Set to 0 for MCS 0 Values 1-15 are reserved B7 DCM 1 Indicates whether or not DCM is applied to the Data field for the MCS indicated. If the STBC field is 0, then set to 1 to indicate that DCM is applied to the Data field. Neither DCM nor STBC shall be applied if(#15489) both the DCM and STBC are set to 1. Set to 0 to indicate that DCM is not applied to the Data field. NOTE-DCM is applied only to HE-MCSs 0, 1, 3 and 4. DCM is applied only to 1 and 2 spatial streams. DCM is not applied in combination with STBC(#15490). B8-B13 BSS Color 6 The BSS Color field is an identifier of the BSS. Set to the value of the TXVECTOR parameter BSS_COLOR. B14 Reserved 1 Reserved and set to 1 B15-B18 Spatial Reuse 4 Indicates whether or not spatial reuse is allowed during the transmission of this PPDU(#16804). Set to a value from Table 28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ER SU PPDU, and HE MU PPDU), sec 27.11.6 (SPATIAL_REUSE). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B19-B20 Bandwidth 2 For an HE SU PPDU: Set to 0 for 20 MHz Set to 1 for 40 MHz Set to 2 for 80 MHz Set to 3 for 160 MHz and 80 + 80 MHz For an HE ER SU PPDU: Set to 0 for 242-tone RU Set to 1 for upper frequency 106-tone RU within the primary 20 MHz Values 2 and 3 are reserved B21-B22 GI + LTF Size 2 Indicates the GI duration and HE-LTF size. Set to 0 to indicate a 1x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2x HE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Set to 3 to indicate: a 4x HE-LTF and 0.8 μs GI if both the DCM and STBC fields are 1. Neither DCM nor STBC shall be applied if(#Ed) both the DCM and STBC fields arc set to 1. a 4x HE-LTF and 3.2 μs GI, otherwise B23-B25 NSTS And 3 If the Doppler field is 0, indicates the number of space- Midamble time streams. Periodicity Set to the number of space-time streams minus 1 For an HE ER SU PPDU, values 2 to 7 are reserved If the Doppler field is 1, then B23-B24 indicates the number of space time streams, up to 4, and B25 indicates the midamble periodicity. B23-B24 is set to the number of space time streams minus 1. For an HE ER SU PPDU, values 2 and 3 are reserved B25 is set to 0 if TXVECTOR parameter MIDAMBLE_PERIODICITY is 10 and set to 1 if TXVECTOR parameter MIDAMBLE_PERIODICITY is 20. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information (HE SU if(#15491) TXVECTOR parameter TXOP_DURATION PPDU) or is set to UNSPECIFIED. HE-SIG-A3 Set to a value less than 127 to indicate duration (HE ER SU information for NAV setting and protection of the PPDU) TXOP as follows: If TXVECTOR parameter TXOP_DURATION is less than 512, then B0 is set to 0 and B1-B6 is set to floor(TXOP_DURATION/8)(#16277). Otherwise, B0 is set to 1 and B1-B6 is set to floor ((TXOP_DURATION − 512)/128)(#16277). where(#16061) B0 indicates the TXOP length granularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6 indicates the scaled value of the TXOP_DURATION B7 Coding 1 Indicates whether BCC or LDPC is used: Set to 0 to indicate BCC Set to 1 to indicate LDPC B8 LDPC Extra 1 Indicates the presence of the extra OFDM symbol Symbol segment for LDPC: Segment Set to 1 if an extra OFDM symbol segment for LDPC is present Set to 0 if an extra OFDM symbol segment for LDPC is not present Reserved and set to 1 if the Coding field is set to 0(#15492). B9 STBC 1 If the DCM field is set to 0, then set to 1 if space time block coding is used. Neither DCM nor STBC shall be applied if(#15493) both the DCM field and STBC field are set to 1. Set to 0 otherwise. B10 Beam- 1 Set to 1 if a beamforming steering matrix is applied to formed(#16038) the waveform in an SU transmission. Set to 0 otherwise. B11-B12 Pre-FEC 2 Indicates the pre-FEC padding factor. Padding Set to 0 to indicate a pre-FEC padding factor of 4 Factor Set to 1 to indicate a pre-FEC padding factor of 1 Set to 2 to indicate a pre-FEC padding factor of 2 Set to 3 to indicate a pre-FEC padding factor of 3 B13 PE Disambiguity 1 Indicates PE disambiguity(#16274) as defined in 28.3.12 (Packet extension). B14 Reserved 1 Reserved and set to 1 B15 Doppler 1 Set to 1 if one of the following applies: The number of OFDM symbols in the Data field is larger than the signaled midamble periodicity plus 1 and the midamble is present The number of OFDM symbols in the Data field is less than or equal to the signaled midamble periodicity plus 1 (see 28.3.11.16 Midamble), the midamble is not present, but the channel is fast varying. It recommends that midamble may be used for the PPDUs of the reverse link. Set to 0 otherwise B16-B19 CRC 4 CRC for bits 0-41 of the HE-STG-A field (see 28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 of HE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of the convolutional decoder. Set to 0.
(64) In addition, the HE-SIG-A field of the HE MU PPDU may be defined as follows.
(65) TABLE-US-00002 TABLE 2 Two Parts of Number HE-SIG-A Bit Field of bits Description HE-SIG-A1 B0 UL/DL 1 Indicates whether the PPDU is sent UL or DL. Set to the value indicated by the TXVECTOR parameter UPLINK_FLAG. (#16805) NOTE-The TDLS peer can identify the TDLS frame by To DS and From DS fields in the MAC header of the MPDU. B1-B3 SIGB MCS 3 Indicates the MCS of the HE-SIG-B field: Set to 0 for MCS 0 Set to 1 for MCS 1 Set to 2 for MCS 2 Set to 3 for MCS 3 Set to 4 for MCS 4 Set to 5 for MCS 5 The values 6 and 7 are reserved B4 SIGB DCM 1 Set to 1 indicates that the HE-SIG-B is modulated with DCM for the MCS. Set to 0 indicates that the HE-SIG-B is not modulated with DCM for the MCS. NOTE-DCM is only applicable to MCS 0, MCS 1, MCS 3, and MCS 4. B5-B10 BSS Color 6 The BSS Color field is an identifier of the BSS. Set to the value of the TXVECTOR parameter BSS_COLOR. B11-B14 Spatial Reuse 4 Indicates whether or not spatial reuse is allowed during the transmission of this PPDU(#16806). Set to the value of the SPATIAL_REUSE parameter of the TXVECTOR, which contains a value from Table 28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ER SU PPDU, and HE MU PPDU) (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B15-B17 Bandwidth 3 Set to 0 for 20 MHz. Set to 1 for 40 MHz. Set to 2 for 80 MHz non-preamble puncturing mode. Set to 3 for 160 MHz and 80 + 80 MHz non-preamble puncturing mode. If the SIGB Compression field is 0: Set to 4 for preamble puncturing in 80 MHz, where in the preamble only the secondary 20 MHz is punctured. Set to 5 for preamble puncturing in 80 MHz, where in the preamble only one of the two 20 MHz sub- channels in secondary 40 MHz is punctured. Set to 6 for preamble puncturing in 160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble only the secondary 20 MHz is punctured. Set to 7 for preamble puncturing in 160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble the primary 40 MHz is present. If the SIGB Compression field is 1 then values 4-7 are reserved. B18-B21 Number Of 4 If the HE-SIG-B Compression field is set to 0, indicates HE-SIG-B the number of OFDM symbols in the HE-SIG-B Symbols Or field: (#15494) MU-MIMO Set to the number of OFDM symbols in the HE-SIG-B Users field minus 1 if the number of OFDM symbols in the HE-SIG-B field is less than 16; Set to 15 to indicate that the number of OFDM symbols in the HE-SIG-B field is equal to 16 if Longer Than 16 HE SIG-B OFDM Symbols Support subfield of the HE Capabilities element transmitted by at least one recipient STA is 0; Set to 15 to indicate that the number of OFDM symbols in the HE-SIG-B field is greater than or equal to 16 if the Longer Than 16 HE SIG-B OFDM Symbols Support subfield of the HE Capabilities element transmitted by all the recipient STAs are 1 and if the HE-SIG-B data rate is less than MCS 4 without DCM. The exact number of OFDM symbols in the HE-SIG-B field is calculated based on the number of User fields in the HE-SIG-B content channel which is indicated by HE-SIG-B common field in this case. If the HE-SIG-B Compression field is set to 1, indicates the number of MU-MIMO users and is set to the number of NU-MIMO users minus 1(# 15495). B22 STGB 1 Set to 0 if the Common field in HE-SIG-B is present. Compression Set to 1 if the Common field in HE-SIG-B is not present. (#16139) B23-B24 GI + LTF Size 2 Indicates the GI duration and HE-LTF size: Set to 0 to indicate a 4x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2x HE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Set to 3 to indicate a 4x HE-LTF and 3.2 μs GI B25 Doppler 1 Set to 1 if one of the following applies: The number of OFDM symbols in the Data field is larger than the signaled midamble periodicity plus 1 and the midamble is present The number of OFDM symbols in the Data field is less than or equal to the signaled midamble periodicity plus 1 (see 28.3.11.16 Midamble), the midamble is not present, but the channel is fast varying. It recommends that midamble may be used for the PPDUs of the reverse link. Set to 0 otherwise. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information if(#15496) TXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED. Set to a value less than 127 to indicate duration information for NAV setting and protection of the TXOP as follows: If TXVECTOR parameter TXOP_DURATION is less than 512, then B0 is set to 0 and B1-B6 is set to floor(TXOP_DURATION/8)(#16277). Otherwise, B0 is set to 1 and B1-B6 is set to floor ((TXOP_DURATION − 512)/128)(#16277). where(#16061) B0 indicates the TXOP length granularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6 indicates the scaled value of the TXOP_DURATION B7 Reserved 1 Reserved and set to 1 B8-B10 Number of 3 If the Doppler field is set to 0(#15497), indicates the HE-LTF number of HE-LTF symbols: SymbolsAnd Set to 0 for 1 HE-LTF symbol Midamble Set to 1 for 2 HE-LTF symbols Periodicity Set to 2 for 4 HE-LTF symbols Set to 3 for 6 HE-LTF symbols Set to 4 for 8 HE-LTF symbols Other values are reserved. If the Doppler field is set to 1(#15498), B8-B9 indicates the number of HE-LTF symbols(#16056) and B10 indicates midamble periodicity: B8-B9 is encoded as follows: 0 indicates 1 HE-LTF symbol 1 indicates 2 HE-LTF symbols 2 indicates 4 HE-LTF symbols 3 is reserved B10 is set to 0 if the TXVECTOR parameter MIDAMBLE_PERIODICITY is 10 and set to 1 if the TXVECTOR parameter PREAMBLE_PERIODICITY is 20. B11 LDPC Extra 1 Indication of the presence of the extra OFDM symbol Symbol segment for LDPC. Segment Set to 1 if an extra OFDM symbol segment for LDPC is present. Set to 0 otherwise. B12 STBC 1 In an HE MU PPDU where each RU includes no more than 1 user, set to 1 to indicate all RUs are STBC encoded in the payload, set to 0 to indicate all RUs are not STBC encoded in the payload. STBC does not apply to HE-SIG-B. STBC is not applied if one or more RUs are used for MU-MIMO allocation. (#15661) B13-B14 Pre-FEC 2 Indicates the pre-FEC padding factor. Padding Set to 0 to indicate a pre-FEC padding factor of 4 Factor Set to 1 to indicate a pre-FEC padding factor of 1 Set to 2 to indicate a pre-FEC padding factor of 2 Set to 3 to indicate a pre-FEC padding factor of 3 B15 PE 1 Indicates PE disambiguity(#16274) as defined in Disambiguity 28.3.12 (Packet extension). B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see 28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 of HE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of the convolutional decoder. Set to 0.
(66) In addition, the HE-SIG-A field of the HE TB PPDU may be defined as follows.
(67) TABLE-US-00003 TABLE 3 Two Parts of Number HE-SIG-A Bit Field of bits Description HE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU from an HE TB PPDU: Set to 0 for an HE TB PPDU B1-B6 BSS Color 6 The BSS Color field is an identifier of the BSS. Set to the value of the TXVECTOR parameter BSS_COLOR. B7-B10 Spatial Reuse 1 4 Indicates whether or not spatial reuse is allowed in a subband of the PPDU during the transmission of this PPDU, and if allowed, indicates a value that is used to determine a limit on the transmit power of a spatial reuse transmission. If the Bandwidth field indicates 20 MHz, 40 MHz, or 80 MHz then this Spatial Reuse field applies to the first 20 MHz subband. If the Bandwidth field indicates 160/80 + 80 MHz then this Spatial Reuse field applies to the first 40 MHz sub- band of the 160 MHz operating band. Set to the value of the SPATIAL_REUSE(1) parameter of the TXVECTOR, which contains a value from Table 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B11-B14 Spatial Reuse 2 4 Indicates whether or not spatial reuse is allowed in a subband of the PPDU during the transmission of this PPDU, and if allowed, indicates a value that is used to determine a limit on the transmit power of a spatial reuse transmission. If the Bandwidth field indicates 20 MHz, 40 MHz, or 80 MHz: This Spatial Reuse field applies to the second 20 MHz subband. If(#Ed) the STA operating channel width is 20 MHz, then this field is set to the same value as Spatial Reuse 1 field. If(#Ed) the STA operating channel width is 40 MHz in the 2.4 GHz band, this field is set to the same value as Spatial Reuse 1 field. If the Bandwidth field indicates 160/80 + 80 MHz the this Spatial Reuse field applies to the second 40 MHz subband of the 160 MHz operating band. Set to the value of the SPATIAL_REUSE(2) parameter of the TXVECTOR, which contains a value from Table 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B15-B18 Spatial Reuse 3 4 Indicates whether or not spatial reuse is allowed in a subband of the PPDU during the transmission of this PPDU, and if allowed, indicates a value that is used to determine a limit on the transmit power of a spatial reuse transmission. If the Bandwidth field indicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse field applies to the third 20 MHz subband. If(#Ed) the STA operating channel width is 20 MHz or 40 MHz, this field is set to the same value as Spatial Reuse 1 field. If the Bandwidth field indicates 160/80 + 80 MHz: This Spatial Reuse field applies to the third 40 MHz subband of the 160 MHz operating band. If(#Ed) the STA operating channel width is 80 + 80 MHz, this field is set to the same value as Spatial Reuse 1 field. Set to the value of the SPATIAL_REUSE(3) parameter of the TXVECTOR, which contains a value from Table 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B19-B22 Spatial 4 Indicates whether or not spatial reuse is allowed in a Reuse 4 subband of the PPDU during the transmission of this PPDU, and if allowed, indicates a value that is used to determine a limit on the transmit power of a spatial reuse transmission. If the Bandwidth field indicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse field applies to the fourth 20 MHz subband. If(#Ed) the STA operating channel width is 20 MHz, then this field is set to the same value as Spatial Reuse 1 field. If(#Ed) the STA operating channel width is 40 MHz, then this field is set to the same value as Spatial Reuse 2 field. If the Bandwidth field indicates 160/80 + 80 MHz: This Spatial Reuse field applies to the fourth 40 MHz subband of the 160 MHz operating band. If(#Ed) the STA operating channel width is 80 + 80 MHz, then this field is set to same value as Spatial Reuse 2 field. Set to the value of the SPATIAL_REUSE(4) parameter of the TXVECTOR, which contains a value from Table 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B23 Reserved 1 Reserved and set to 1. NOTE-Unlike other Reserved fields in HE-SIG-A of the HE TB PPDU, B23 does not have a corresponding bit in the Trigger frame. B24-B25 Bandwidth 2 (#16003)Set to 0 for 20 MHz Set to 1 for 40 MHz Set to 2 for 80 MHz Set to 3 for 160 MHz and 80 + 80 MHz HE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information if(#15499) TXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED. Set to a value less than 127 to indicate duration information for NAV setting and protection of the TXOP as follows: If TXVECTOR parameter TXOP_DURATION is less than 512, then B0 is set to 0 and B1-B6 is set to floor(TXOP_DURATION/8)(#16277). Otherwise, B0 is set to 1 and B1-B6 is set to floor ((TXOP_DURATTON − 512)/128)(#16277). where(#16061) B0 indicates the TXOP length granularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6 indicates the scaled value of the TXOP_DURATION B7-B15 Reserved 9 Reserved and set to value indicated in the UL HE-SIG-A2 Reserved sublield in the Trigger frame. B16-B19 CRC 4 CRC of bits 0-41 of the HE-SIG-A field. See 28.3.10.7.3 (CRC computation). Bits 0-41 of the HE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 of HE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of the convolutional decoder. Set to 0.
(68) An HE-SIG-B (740) may be included only in the case of the PPDU for the multiple users (MUs) as described above. Principally, an HE-SIG-A (750) or an HE-SIG-B (760) may include resource allocation information (alternatively, virtual resource allocation information) for at least one receiving STA.
(69)
(70) As illustrated in
(71) A previous field of the HE-SIG-B (740) may be transmitted in a duplicated form on a MU PPDU. In the case of the HE-SIG-B (740), the HE-SIG-B (740) transmitted in some frequency band (e.g., a fourth frequency band) may even include control information for a data field corresponding to a corresponding frequency band (that is, the fourth frequency band) and a data field of another frequency band (e.g., a second frequency band) other than the corresponding frequency band. Further, a format may be provided, in which the HE-SIG-B (740) in a specific frequency band (e.g., the second frequency band) is duplicated with the HE-SIG-B (740) of another frequency band (e.g., the fourth frequency band). Alternatively, the HE-SIG B (740) may be transmitted in an encoded form on all transmission resources. A field after the HE-SIG B (740) may include individual information for respective receiving STAs receiving the PPDU.
(72) The HE-STF (750) may be used for improving automatic gain control estimation in a multiple input multiple output (MIMO) environment or an OFDMA environment.
(73) The HE-LTF (760) may be used for estimating a channel in the MIMO environment or the OFDMA environment.
(74) The size of fast Fourier transform (FFT)/inverse fast Fourier transform (IFFT) applied to the HE-STF (750) and the field after the HE-STF (750), and the size of the FFT/IFFT applied to the field before the HE-STF (750) may be different from each other. For example, the size of the FFT/IFFT applied to the HE-STF (750) and the field after the HE-STF (750) may be four times larger than the size of the FFT/IFFT applied to the field before the HE-STF (750).
(75) For example, when at least one field of the L-STF (700), the L-LTF (710), the L-SIG (720), the HE-SIG-A (730), and the HE-SIG-B (740) on the PPDU of
(76) In other words, a subcarrier space/subcarrier spacing may have a size which is 1/N times (N is the natural number, e.g., N=4, the subcarrier spacing is set to 78.125 kHz) the subcarrier space used in the legacy wireless LAN system. That is, subcarrier spacing having a size of 312.5 kHz, which is legacy subcarrier spacing may be applied to the first field of the HE PPDU and a subcarrier space having a size of 78.125 kHz may be applied to the second field of the HE PPDU.
(77) Alternatively, an IDFT/DFT period applied to each symbol of the first field may be expressed to be N (=4) times shorter than the IDFT/DFT period applied to each data symbol of the second field. That is, the IDFT/DFT length applied to each symbol of the first field of the HE PPDU may be expressed as 3.2 μs and the IDFT/DFT length applied to each symbol of the second field of the HE PPDU may be expressed as 3.2 μs*4 (=12.8 μs). The length of the OFDM symbol may be a value acquired by adding the length of a guard interval (GI) to the IDFT/DFT length. The length of the GI may have various values such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs, and 3.2 μs.
(78) For simplicity in the description, in
(79) The user (e.g., a receiving station) may receive the HE-SIG-A (730) and may be instructed to receive the downlink PPDU based on the HE-SIG-A (730). In this case, the STA may perform decoding based on the FFT size changed from the HE-STF (750) and the field after the HE-STF (750). On the contrary, when the STA may not be instructed to receive the downlink PPDU based on the HE-SIG-A (730), the STA may stop the decoding and configure a network allocation vector (NAV). A cyclic prefix (CP) of the HE-STF (750) may have a larger size than the CP of another field and the during the CP period, the STA may perform the decoding for the downlink PPDU by changing the FFT size.
(80) Hereinafter, in the embodiment of the present disclosure, data (alternatively, or a frame) which the AP transmits to the STA may be expressed as a terms called downlink data (alternatively, a downlink frame) and data (alternatively, a frame) which the STA transmits to the AP may be expressed as a term called uplink data (alternatively, an uplink frame). Further, transmission from the AP to the STA may be expressed as downlink transmission and transmission from the STA to the AP may be expressed as a term called uplink transmission.
(81) In addition, a PHY protocol data unit (PPDU), a frame, and data transmitted through the downlink transmission may be expressed as terms such as a downlink PPDU, a downlink frame, and downlink data, respectively. The PPDU may be a data unit including a PPDU header and a physical layer service data unit (PSDU) (alternatively, a MAC protocol data unit (MPDU)). The PPDU header may include a PHY header and a PHY preamble and the PSDU (alternatively, MPDU) may include the frame or indicate the frame (alternatively, an information unit of the MAC layer) or be a data unit indicating the frame. The PHY header may be expressed as a physical layer convergence protocol (PLCP) header as another term and the PHY preamble may be expressed as a PLCP preamble as another term.
(82) Further, a PPDU, a frame, and data transmitted through the uplink transmission may be expressed as terms such as an uplink PPDU, an uplink frame, and uplink data, respectively.
(83) In the wireless LAN system to which the embodiment of the present description is applied, the total bandwidth may be used for downlink transmission to one STA and uplink transmission to one STA. Further, in the wireless LAN system to which the embodiment of the present description is applied, the AP may perform downlink (DL) multi-user (MU) transmission based on multiple input multiple output (MU MIMO) and the transmission may be expressed as a term called DL MU MIMO transmission.
(84) In addition, in the wireless LAN system according to the embodiment, an orthogonal frequency division multiple access (OFDMA) based transmission method is preferably supported for the uplink transmission and/or downlink transmission. That is, data units (e.g., RUs) corresponding to different frequency resources are allocated to the user to perform uplink/downlink communication. In detail, in the wireless LAN system according to the embodiment, the AP may perform the DL MU transmission based on the OFDMA and the transmission may be expressed as a term called DL MU OFDMA transmission. When the DL MU OFDMA transmission is performed, the AP may transmit the downlink data (alternatively, the downlink frame and the downlink PPDU) to the plurality of respective STAs through the plurality of respective frequency resources on an overlapped time resource. The plurality of frequency resources may be a plurality of subbands (alternatively, subchannels) or a plurality of resource units (RUs). The DL MU OFDMA transmission may be used together with the DL MU MIMO transmission. For example, the DL MU MIMO transmission based on a plurality of space-time streams (alternatively, spatial streams) may be performed on a specific subband (alternatively, subchannel) allocated for the DL MU OFDMA transmission.
(85) Further, in the wireless LAN system according to the embodiment, uplink multi-user (UL MU) transmission in which the plurality of STAs transmits data to the AP on the same time resource may be supported. Uplink transmission on the overlapped time resource by the plurality of respective STAs may be performed on a frequency domain or a spatial domain.
(86) When the uplink transmission by the plurality of respective STAs is performed on the frequency domain, different frequency resources may be allocated to the plurality of respective STAs as uplink transmission resources based on the OFDMA. The different frequency resources may be different subbands (alternatively, subchannels) or different resources units (RUs). The plurality of respective STAs may transmit uplink data to the AP through different frequency resources. The transmission method through the different frequency resources may be expressed as a term called a UL MU OFDMA transmission method.
(87) When the uplink transmission by the plurality of respective STAs is performed on the spatial domain, different time-space streams (alternatively, spatial streams) may be allocated to the plurality of respective STAs and the plurality of respective STAs may transmit the uplink data to the AP through the different time-space streams. The transmission method through the different spatial streams may be expressed as a term called a UL MU MIMO transmission method.
(88) The UL MU OFDMA transmission and the UL MU MIMO transmission may be used together with each other. For example, the UL MU MIMO transmission based on the plurality of space-time streams (alternatively, spatial streams) may be performed on a specific subband (alternatively, subchannel) allocated for the UL MU OFDMA transmission.
(89) In the legacy wireless LAN system which does not support the MU OFDMA transmission, a multi-channel allocation method is used for allocating a wider bandwidth (e.g., a 20 MHz excess bandwidth) to one terminal. When a channel unit is 20 MHz, multiple channels may include a plurality of 20 MHz-channels. In the multi-channel allocation method, a primary channel rule is used to allocate the wider bandwidth to the terminal. When the primary channel rule is used, there is a limit for allocating the wider bandwidth to the terminal. In detail, according to the primary channel rule, when a secondary channel adjacent to a primary channel is used in an overlapped BSS (OBSS) and is thus busy, the STA may use remaining channels other than the primary channel. Therefore, since the STA may transmit the frame only to the primary channel, the STA receives a limit for transmission of the frame through the multiple channels. That is, in the legacy wireless LAN system, the primary channel rule used for allocating the multiple channels may be a large limit in obtaining a high throughput by operating the wider bandwidth in a current wireless LAN environment in which the OBSS is not small.
(90) In order to solve the problem, in the embodiment, a wireless LAN system is disclosed, which supports the OFDMA technology. That is, the OFDMA technique may be applied to at least one of downlink and uplink. Further, the MU-MIMO technique may be additionally applied to at least one of downlink and uplink. When the OFDMA technique is used, the multiple channels may be simultaneously used by not one terminal but multiple terminals without the limit by the primary channel rule. Therefore, the wider bandwidth may be operated to improve efficiency of operating a wireless resource.
(91) As described above, in case the uplink transmission performed by each of the multiple STAs (e.g., non-AP STAs) is performed within the frequency domain, the AP may allocate different frequency resources respective to each of the multiple STAs as uplink transmission resources based on OFDMA. Additionally, as described above, the frequency resources each being different from one another may correspond to different subbands (or sub-channels) or different resource units (RUs).
(92) The different frequency resources respective to each of the multiple STAs are indicated through a trigger frame.
(93)
(94) Each of the fields shown in
(95) A Frame Control field (910) shown in
(96) Also, the RA field (930) includes address information of a receiving STA of the corresponding trigger frame and may be omitted if necessary. The TA field (940) includes address information of an STA triggering the corresponding trigger frame (for example, an AP), and the common information field (950) includes common control information applied to a receiving STA that receives the corresponding trigger frame. For example, a field indicating the length of the L-SIG field of the UL PPDU transmitted in response to the corresponding trigger frame or information controlling the content of the SIG-A field (namely, the HE-SIG-A field) of the UL PPDU transmitted in response to the corresponding trigger frame may be included. Also, as common control information, information on the length of the CP of the UP PPDU transmitted in response to the corresponding trigger frame or information on the length of the LTF field may be included.
(97) Also, it is preferable to include a per user information field (960#1 to 960#N) corresponding to the number of receiving STAs that receive the trigger frame of
(98) Also, the trigger frame of
(99) It is preferable that each of the per user information fields (960#1 to 960#N) shown in
(100)
(101) The trigger type field (1010) of
(102) TABLE-US-00004 TABLE 4 Trigger Type subfield value Trigger frame variant 0 Basic 1 Beamforming Report Poll (BFRP) 2 MU-BAR 3 MU-RTS 4 Buffer Status Report Poll (BSRP) 5 GCR MU-BAR 6 Bandwidth Query Report Poll (BQRP) 7 NDP Feedback Report Poll (NFRP) 8-15 Reserved
(103) The UL BW field (1020) of
(104) TABLE-US-00005 TABLE 5 UL BW subfield value Description 0 20 MHz 1 40 MHz 2 80 MHz 3 80 + 80 MHz or 160 MHz
(105) The Guard Interval (GI) and LTF type fields (1030) of
(106) TABLE-US-00006 TABLE 6 GI And LTF field value Description 0 1x HE-LTF + 1.6 μs GI 1 2x HE-LTF + 1.6 μs GI 2 4x HE- LTF + 3.2 μs GI(#15968) 3 Reserved
(107) Also, when the GI and LTF type fields (1030) have a value of 2 or 3, the MU-MIMO LTF mode field (1040) of
(108) If the trigger frame allocates an RU that occupies the whole HE TB PPDU bandwidth and the RU is allocated to one or more STAs, the MU-MIMO LTF mode field (1040) indicates one of an HE single stream pilot HE-LTF mode or an HE masked HE-LTF sequence mode.
(109) If the trigger frame does not allocate an RU that occupies the whole HE TB PPDU bandwidth and the RU is not allocated to one or more STAs, the MU-MIMO LTF mode field (1040) indicates the HE single stream pilot HE-LTF mode. The MU-MIMO LTF mode field (1040) may be defined as follows.
(110) TABLE-US-00007 TABLE 7 MU-MIMO LTF subfield value Description 0 HE single stream pilot HE-LTF mode 1 HE masked HE-LTF sequence mode
(111)
(112) The User Identifier field of
(113) Also, an RU Allocation field (1120) may be included. In other words, when a receiving STA identified by the User Identifier field (1110) transmits a UL PPDU in response to the trigger frame of
(114) The subfield of
(115) Additionally, the subfield of
(116) Also, the subfield of
(117) Hereinafter, the present disclosure proposes an example of improving a control field included in a PPDU. The control field improved according to the present disclosure includes a first control field including control information required to interpret the PPDU and a second control field including control information for demodulate the data field of the PPDU. The first and second control fields may be used for various fields. For example, the first control field may be the HE-SIG-A (730) of
(118) Hereinafter, a specific example of improving the first or the second control field will be described.
(119) In the following example, a control identifier inserted to the first control field or a second control field is proposed. The size of the control identifier may vary, which, for example, may be implemented with 1-bit information.
(120) The control identifier (for example, a 1-bit identifier) may indicate whether a 242-type RU is allocated when, for example, 20 MHz transmission is performed. As shown in
(121) The control identifier (for example, a 1-bit identifier) may indicate that a 242-type RU has been used. In other words, the control identifier may indicate that a 242-RU, a 484-RU, or a 996-RU is included. If the transmission frequency band in which a PPDU is transmitted has a bandwidth of 20 MHz, a 242-RU is a single RU corresponding to the full bandwidth of the transmission frequency band (namely, 20 MHz). Accordingly, the control identifier (for example, 1-bit identifier) may indicate whether a single RU corresponding to the full bandwidth of the transmission frequency band is allocated.
(122) For example, if the transmission frequency band has a bandwidth of 40 MHz, the control identifier (for example, a 1-bit identifier) may indicate whether a single RU corresponding to the full bandwidth (namely, bandwidth of 40 MHz) of the transmission frequency band has been allocated. In other words, the control identifier may indicate whether a 484-RU has been allocated for transmission in the frequency band with a bandwidth of 40 MHz.
(123) For example, if the transmission frequency band has a bandwidth of 80 MHz, the control identifier (for example, a 1-bit identifier) may indicate whether a single RU corresponding to the full bandwidth (namely, bandwidth of 80 MHz) of the transmission frequency band has been allocated. In other words, the control identifier may indicate whether a 996-RU has been allocated for transmission in the frequency band with a bandwidth of 80 MHz.
(124) Various technical effects may be achieved through the control identifier (for example, 1-bit identifier).
(125) First of all, when a single RU corresponding to the full bandwidth of the transmission frequency band is allocated through the control identifier (for example, a 1-bit identifier), allocation information of the RU may be omitted. In other words, since only one RU rather than a plurality of RUs is allocated over the whole transmission frequency band, allocation information of the RU may be omitted deliberately.
(126) Also, the control identifier may be used as signaling for full bandwidth MU-MIMO. For example, when a single RU is allocated over the full bandwidth of the transmission frequency band, multiple users may be allocated to the corresponding single RU. In other words, even though signals for each user are not distinctive in the temporal and spatial domains, other techniques (for example, spatial multiplexing) may be used to multiplex the signals for multiple users in the same, single RU. Accordingly, the control identifier (for example, a 1-bit identifier) may also be used to indicate whether to use the full bandwidth MU-MIMO described above.
(127) The common field included in the second control field (HE-SIG-B, 740) may include an RU allocation subfield. According to the PPDU bandwidth, the common field may include a plurality of RU allocation subfields (including N RU allocation subfields). The format of the common field may be defined as follows.
(128) TABLE-US-00008 TABLE 8 Number Subfield of bits Description RU Allocation N × 8 Indicates the RU assignment to be used in the data portion in the frequency domain. It also indicates the number of users in each RU. For RUs of size greater than or equal to 106-tones that support MU-MIMO, it indicates the number of users multiplexed using MU-MIMO. Consists of N RU Allocation subfields: N = 1 for a 20 MHz and a 40 MHz HE MU PPDU N = 2 for an 80 MHz HE MU PPDU N = 4 for a 160 MHz or 80 + 80 MHz HE MU PPDU Center 26-tone RU 1 This field is present only if(#15510) the value of the Bandwidth field of HE-SIG-A field in an HE MU PPDU is set to greater than 1. If the Bandwidth field of the HE-SIG-A field in an HE MU PPDU is set to 2, 4 or 5 for 80 MHz: Set to 1 to indicate that a user is allocated to the center 26- tone RU (see FIG. 28-7 (RU locations in an 80 MHz HE PPDU(#16528))); otherwise, set to 0. The same value is applied to both HE-SIG-B content channels. If the Bandwidth field of the HE-SIG-A field in an HE MU PPDU is set to 3, 6 or 7 for 160 MHz or 80 + 80 MHz: For HE-SIG-B content channel 1, set to 1 to indicate that a user is allocated to the center 26-tone RU of the lower frequency 80 MHz; otherwise, set to 0. For HE-SIG-B content channel 2, set to 1 to indicate that a user is allocated to the center 26-tone RU of the higher frequency 80 MHz; otherwise, set to 0. CRC 4 See 28.3.10.7.3 (CRC computation) Tail 6 Used to termmate the trellis of the convolutional decoder. Set to 0
(129) The RU allocation subfield included in the common field of the HE-SIG-B may be configured with 8 bits and may indicate as follows with respect to 20 MHz PPDU bandwidth. RUs to be used as a data portion in the frequency domain are allocated using an index for RU size and disposition in the frequency domain. The mapping between an 8-bit RU allocation subfield for RU allocation and the number of users per RU may be defined as follows.
(130) TABLE-US-00009 TABLE 9 8 bits indices (B7 B6 B5 B4 Number B3 B2 B1 B0) #1 #2 #3 #4 #5 #6 #7 #8 #9 of entries 00000000 26 26 26 26 26 26 26 26 26 1 00000001 26 26 26 26 26 26 26 52 1 00000010 26 26 26 26 26 52 26 26 1 00000011 26 26 26 26 26 52 52 1 00000100 26 26 52 26 26 26 26 26 1 00000101 26 26 52 26 26 26 52 1 00000110 26 26 52 26 52 26 26 1 00000111 26 26 52 26 52 52 1 00001000 52 26 26 26 26 26 26 26 1 00001001 52 26 26 26 26 26 52 1 00001010 52 26 26 26 52 26 26 1 00001011 52 26 26 26 52 52 1 00001100 52 52 26 26 26 26 26 1 00001101 52 52 26 26 26 52 1 00001110 52 52 26 52 26 26 1 00001111 52 52 26 52 52 1 00010y.sub.2y.sub.1y.sub.0 52 52 — 106 8 00011y.sub.2y.sub.1y.sub.0 106 — 52 52 8 00100y.sub.2y.sub.1y.sub.0 26 26 26 26 26 106 8 00101y.sub.2y.sub.1y.sub.0 26 26 52 26 106 8 00110y.sub.2y.sub.1y.sub.0 52 26 26 26 106 8 00111y.sub.2y.sub.1y.sub.0 52 52 26 106 8 01000y.sub.2y.sub.1y.sub.0 106 26 26 26 26 26 8 01001y.sub.2y.sub.1y.sub.0 106 26 26 26 52 8 01010y.sub.2y.sub.1y.sub.0 106 26 52 26 26 8 01011y.sub.2y.sub.1y.sub.0 106 26 52 52 8 0110y.sub.1y.sub.0z.sub.1z.sub.0 106 — 106 16 01110000 52 52 — 52 52 1 01110001 242-tone RU empty 1 01110010 484-tone RU with zero User fields indicated in this RU Allocation subfield of 1 the HE-SIG-B content channel 01110011 996-tone RU with zero User fields indicated in this RU Allocation subfield of 1 the HE-SIG-B content channel 011101x.sub.1x.sub.0 Reserved 4 01111y.sub.2y.sub.1y.sub.0 Reserved 8 10y.sub.2y.sub.1y.sub.0z.sub.2z.sub.1z.sub.0 106 26 106 64 11000y.sub.2y.sub.1y.sub.0 242 8 11001y.sub.2y.sub.1y.sub.0 484 8 11010y.sub.2y.sub.1y.sub.0 996 8 11011y.sub.2y.sub.1y.sub.0 Reserved 8 111x.sub.4x.sub.3x.sub.2x.sub.1x.sub.0 Reserved 32 If(#Ed) signaling RUs of size greater than 242 subcarriers, y.sub.2y.sub.1y.sub.0 = 000-111 indicates number of User fields in the HE-SIG-B content channel that contains the corresponding 8-bit RU Allocation subfield. Otherwise, y.sub.2y.sub.1y.sub.0 = 000-111 indicates number of STAs multiplexed in the 106-tone RU, 242-tone RU or the lower frequency 106-tone RU if there are two 106-tone RUs and one 26-tone RU is assigned between two 106-tone RUs. The binary vector y.sub.2y.sub.1y.sub.0 indicates 2.sup.2 × y.sub.2 + 2.sup.1 × y.sub.1 + y.sub.0 + 1 STAs multiplexed the RU. z.sub.2z.sub.1z.sub.0 = 000-111 indicates number of STAs multiplexed in the higher frequency 106-tone RU if there are two 106-tone RUs and one 26-tone RU is assigned between two 106-tone RUs. The binary vector z.sub.2z.sub.1z.sub.0 indicates 2.sup.2 × z.sub.2 + 2.sup.1 × z.sub.1 + z.sub.0 + 1 STAs multiplexed in the RU. Similarly, y.sub.1y.sub.0 = 00-11 indicates number of STAs multiplexed in the lower frequency 106-tone RU. The binary vector y.sub.1y.sub.0 indicates 2.sup.1 × y.sub.1 + y.sub.0 + 1 STAs multiplexed in the RU. Similarly, z.sub.1z.sub.0 = 00-11 indicates the number of STAs multiplexed in the higher frequency 106-tone RU. The binary vector z.sub.1z.sub.0 indicates 2.sup.1 × z.sub.1 + z.sub.0 + 1 STAs multiplexed in the RU. #1 to #9 (from left to the right) is ordered in increasing order of the absolute frequency. x.sub.1x.sub.0 = 00-11, x.sub.4x.sub.3x.sub.2x.sub.1x.sub.0 = 00000-11111. ‘—’ means no STA in that RU.
(131) The user-specific field included in the second control field (HE-SIG-B, 740) may include a user field, a CRC field, and a Tail field. The format of the user-specific field may be defined as follows.
(132) TABLE-US-00010 TABLE 10 Number Subfield of bits Description User field N × 21 The User field format for a non-MU-MIMO allocation is defined in Table 28-26 (User field format for a non-MU- MIMO allocation). The User field format for a MU-MIMO allocation is defined in Table 28-27 (User field for an MU- MIMO allocation). N = 1 if it is the last User Block field, and if there is only one user in the last User Block field. N = 2 otherwise. CRC 4 The CRC is calculated over bits 0 to 20 for a User Block field that contains one User field, and bits 0 to 41 for a User Block field that contains two User fields. See 28.3.10.7.3 (CRC computation). Tail 6 Used to terminate the trellis of the convolutional decoder. Set to 0.
(133) Also, the user-specific field of the HE-SIG-B is composed of a plurality of user fields. The plurality of user fields are located after the common field of the HE-SIG-B. The location of the RU allocation subfield of the common field and that of the user field of the user-specific field are used together to identify an RU used for transmitting data of an STA. A plurality of RUs designated as a single STA are now allowed in the user-specific field. Therefore, signaling that allows an STA to decode its own data is transmitted only in one user field.
(134) As an example, it may be assumed that the RU allocation subfield is configured with 8 bits of 01000010 to indicate that five 26-tone RUs are arranged next to one 106-tone RU and three user fields are included in the 106-tone RU. At this time, the 106-tone RU may support multiplexing of the three users. This example may indicate that eight user fields included in the user-specific field are mapped to six RUs, the first three user fields are allocated according to the MU-MIMO scheme in the first 106-tone RU, and the remaining five user fields are allocated to each of the five 26-tone RUs.
(135) User fields included in the user-specific field of the HE-SIG-B may be defined as described below. Firstly, user fields for non-MU-MIMO allocation are as described below.
(136) TABLE-US-00011 TABLE 2 Number Bit Subfield of bits Description B0-B10 STA-ID 11 Set to a value of the element indicated from TXVECTOR parameter STA_ID_LIST (see 27.11.1 (STA_ID_LIST)). B11-B13 NSTS 3 Number of space-time streams. Set to the number of space-time streams minus 1. B14 Beam- 1 Use of transmit beamforming. formed(#16038) Set to 1 if a beamforming steering matrix is applied to the waveform in an SU transmission. Set to 0 otherwise. B15-B18 MCS 4 Modulation and coding scheme Set to n for MCSn, where n = 0, 1, 2 . . . , 11 Values 12 to 15 are reserved B19 DCM 1 Indicates whether or not DCM is used. Set to 1 to indicate that the payload(#Ed) of the corresponding user of the HE MU PPDU is modulated with DCM for the MCS. Set to 0 to indicate that the payload of the corresponding user of the PPDU is not modulated with DCM for the MCS. NOTE-DCM is not applied in combination with STBC. (#15664) B20 Coding 1 Indicates whether BCC or LDPC is used. Set to 0 for BCC Set to 1 for LDPC NOTE If the STA-ID subfield is set to 2046, then the other subfields can be set to arbitrary values. (#15946)
(137) User fields for MU-MIMO allocation are as described below.
(138) TABLE-US-00012 TABLE 13 Number Bit Subfield of bits Description B0-B10 STA-ID 11 Set to a value of element indicated from TXVECTOR parameter STA_ID_LIST (see 27.11.1 (STA_ID_LIST)). B11-B14 Spatial 4 Indicates the number of spatial streams for a STA in an Configuration MU-MIMO allocation (see Table 28-28 (Spatial Configuration subfield encoding)). B15-B18 MCS 4 Modulation and coding scheme. Set to n for MCSn, where n = 0, 1, 2, . . . , 11 Values 12 to 15 are reserved B19 Reserved 1 Reserved and set to 0 B20 Coding 1 Indicates whether BCC or LDPC is used. Set to 0 for BCC Set to 1 for LDPC NOTE If the STA-ID subfield is set to 2046, then the other subfields can be set to arbitrary values. (#15946)
(139)
(140) As shown in the figure, the PPDU of
(141) Although a PHY transmit/receive procedure in Wi-Fi may have different detailed packet configuration methods, the PHY transmit/receive procedure will be described as follows. For simplicity, although examples will only be presented for 11n and flax, 11g/ac also follows a similar procedure.
(142) That is, in a PHY transmit procedure, when a MAC protocol data unit (MPDU) or Aggregate MPDU (A-MPDU) arrives at a MAC end, the MPDU or A-MPDU are converted to a Single PHY service data unit (PSDU), at a PHY end, and then transmitted after inserting a Preamble, Tail bits, and padding bits (if needed). This is referred to as a PPDU.
(143) Generally, a PHY receive procedure is as described below. When energy detection and preamble detection (L/HT/VHT/HE-preamble detection per Wi-Fi version) are performed, information on a PSDU configuration is obtained (or acquired) from a PHY header (L/HT/VHT/HE-SIG), and, then, a MAC header is read, and data is read.
(144) 1. Embodiments Applicable to the Present Disclosure
(145)
(146) When performing OFDMA DL transmission, in case a data size, MCS, and so on, of each STA is/are different, a MU packet matches its length to a packet length of STA 3, which has the longest length. And, accordingly, after filling each packet of the RU being allocated to STAs 1, 4, and 5, the remaining resource parts are filled with padding bits. Therefore, the present disclosure proposes a Scheduled-Time Division Multiple Access (S-TDMA) technique enabling DL transmission to be performed by additionally allocating data of one or more STAs to empty parts, i.e., padding parts of the RU, when performing DL MU packet transmission using 802.11 OFDMA. S-TDMA is a technique for allocating data to the RU via scheduling while additionally considering a time domain, in addition to the frequency domain, which is considered in the conventional OFDMA. That is, by time-dividing one RU and allocating the time-divided RU to multiple STAs, waste of resources may be reduced.
(147)
(148) As shown in
(149) 2. Proposed Embodiments
(150) 2.1. S-TDMA MU PPDU Structure
(151) The PPDU structure that is proposed in this specification is referred to as an S-TDMA MU PPDU. The S-TDMA PPDU structure, which will hereinafter be described, assumes a situation where data of STA 1 and data of STA 2 are consecutively allocated in RU 2 of
(152) 2.1.1. New S-TDMA MU PPDU Structure
(153)
(154) As shown in
(155) Information that may be included in each field of
(156) <S-TDMA SIG-A> Common information (information related to bandwidth, BSS color, LTF, and so on) being included in HE-SIG-A of 802.11ax and an S-TDMA PPDU format (indicating whether or not SIG-C, A-STF, A-LTF, and so on, is/are included), and so on, are included herein.
(157) <S-TDMA SIG-B & SIG-C> In case SIG-C does not exist, S-TDMA SIG-B includes information (RU allocation, MCS, coding, and so on) included HE-SIG-B of 802.11ax, which is information related to data transmission using OFDMA, and additional information (S-TDMA indication, Starting/Ending symbol offset, End of S-TDMA, and so on) caused by the application of S-TDMA. In case SIG-C exists, SIG-B includes only the information related to data transmission using OFDMA (RU allocation, MCS, coding, and so on), such as the HE-SIG-B of 802.11ax, and the additional information caused by the application of S-TDMA may be included the SIG-C information.
(158) In the S-TDMA MU PPDU structure, in case A-STF and A-LTF are included, in a situation where the channel status changes abruptly, the decoding likelihood of the STA 2 data may be increased. However, an overhead equivalent to the added STF and LTF exists, and, in case a larger number of STAs exists, the overhead increases accordingly.
(159) In the S-TDMA MU PPDU structure, in case SIG-C is included, the HE-SIG-A and HE-SIG-B of the conventional 802.11ax may be reused, and only the additional information caused by the application of S-TDMA may be included in the SIG-C. However, an overhead equivalent to the added SIG-C exists.
(160) 2.1.2. S-TDMA MU PPDU Structure Considering an HE MU PPDU Structure
(161)
(162) As shown in
(163) Firstly, in HE-SIG-A, a method for indicating the S-TDMA PPDU format (indicating whether or not SIG-C, A-STF, and A-LTF is/are included, and so on) is needed. And, the indication method is as follows.
(164) 1) Use B7 Bit, Which is a Reserved Bit of HE-SIG-A2 By using the existing bits, the whole format of SIG-A does not change. However, in case additional information is needed in the SIG-A due to the usage of remaining reserved bits, bits shall be added.
(165) 2) Add Bits to Format field in HE-SIG-A
(166) o By adding bit to a first field that differentiates formats in the conventional 11ax, although the application or non-application of S-TDMA may be immediately identified, due to the addition of bits, the length of the SIG-A may be extended (or increased).
(167) 3) Generate a New Field by Adding Bits
(168) S-TDMA SIG-C may include additional information caused by the application of S-TDMA. Although the SIG-C may exist separately, the SIG-C may be integrated with SIG-B. That is, if the SIG-C is integrated with SIG-B, the HE-SIG-B shall notify S-TDMA related information. In this case, although the HE-SIG-B indicates a RU that is to be allocated to each STA through a RU allocation field of a common field, with the exception for the case of MU-MIMO, when applying S-TDMA, whether or not the same RU has been allocated and time points where each STA receives data cannot be differentiated. And, the indication method is as follows.
(169) 1) The indication method of the RU allocation field of the common field may be modified so that allocation considering S-TDMA can be included, and a starting symbol offset or ending symbol offset may be included by adding a bit to a user field, and the additional bit may include B19, which is a reserved bit of the User field.
(170) 2) By adding a bit to the User field, S-TDMA indication and a starting symbol offset are included. The additional bit may include B19, which is a reserved bit of the User field. That is, the RU is allocated as it is (i.e., without modification) by the RU allocation field of the Common field. And, the STA decodes the S-TDMA indication so as to verify whether or not it is capable of receiving data based on S-TDMA in the corresponding RU. Additionally, the STA may decode the starting symbol offset so as to verify from which start point the STA can receive data.
(171) 3) By adding a bit to the User field, S-TDMA indication, End of S-TDMA, and an ending symbol offset are included. The additional bit may include B19, which is a reserved bit of the User field. As described above in method 2), the RU is allocated as it is (i.e., without modification) by the RU allocation field of the Common field. And, the STA decodes the S-TDMA indication so as to verify whether or not it is capable of receiving data based on S-TDMA in the corresponding RU. Herein, the STA may decode the ending symbol offset so as to verify an end point of the data. Instead, by using an additional bit, the STA may indicate whether the data of the STA is the last data of the corresponding RU.
(172) 4) The part performing S-TDMA indication in each user field, in methods 2) and 3), are relocated to the common field, so as to be indicated in a bitmap format according to a user order. Although an additional bit may be used in all of the four methods from method 1) to method 4) so as to support S-TDMA from the conventional 11ax format, an overhead equivalent to the added bit may be generated.
(173)
(174)
(175) In case it is given that the S-TDMA MU PPDU of
(176)
(177)
(178) Hereinafter, the above-described embodiment will be described according to a time flow with reference to
(179)
(180) S-TDMA is a scheme allocating a data field to a RU via scheduling while considering OFDMA in a frequency domain and additionally considering TDMA in a time domain.
(181) Referring to
(182) STA1 decodes a control field of the S-TDMA MU PPDU so as to verify that it is using a first RU and the S-TDMA is being applied. Thus, STA1 may receive a first data field, which is its own data, in the first RU during a first symbol.
(183) STA2 decodes a control field of the S-TDMA MU PPDU so as to verify that it is using a first RU and the S-TDMA is being applied. Similarly, STA2 may receive a second data field, which is its own data, in the first RU during a second symbol. That is, from the same first RU, the first data field is transmitted during the first symbol, and the second data field is transmitted during the second symbol.
(184) However, STA3 shows that only OFDMA is being applied. That is, STA3 decodes the control field of the S-TDMA MU PPDU so as to verify that S-TDMA is not applied even though it is using a second RU. That is, STA3 alone is allocated with the second RU. STA3 may receive a third data field, which is its own data, in the second RU. That is, the first data field and the second data field may be transmitted in the first RU, and the third data field may be transmitted in the second RU. According to
(185) Detailed description of the S-TDMA MU PPDU will be described later on with reference to
(186)
(187) An example of
(188) Firstly, the terms will be defined. HE MU PPDU, HE-SIG-A field, HE-SIG-B field, HE-STF field, and HE-LTF field may all be PPDU and fields that are defined in the 802.11ax system. S-TDMA MU PPDU, S-TDMA SIG-A field (first signal field), S-TDMA SIG-B field (second signal field), S-TDMA STF, and S-TDMA LTF may be PPDU and fields that are defined for performing S-TDMA in a next generation wireless LAN system. S-TDMA SIG-C field (third signal field) may be a signal field that is newly defined for performing S-TDMA in a next generation wireless LAN system. However, the PPDU and fields that are defined for performing S-TDMA may be generated by using each subfield of the HE PPDU without any modification in order to satisfy backward compatibility with the 802.11ax system.
(189) An example of
(190) In step S2010, an access point (AP) generates the PPDU.
(191) In step S2020, the AP transmits the PPDU to a first station (STA) and a second STA. The PPDU may be an S-TDMA MU PPDU, which may be newly defined in a next generation wireless LAN system. Additionally, the PPDU may be generated by using a High Efficiency Multi User PPDU (HE MU PPDU). That is, the PPDU may be an S-TDMA MU PPDU, which is generated by reusing the HE MU PPDU.
(192) The PPDU includes a legacy header field, a first signal field, a second signal field, a first data field for the first STA, and a second data field for the second STA.
(193) The legacy header field may be related to Legacy-Short Training Field (L-STF), Legacy-Long Training Field (L-LTF), Legacy-Signal (L-SIG) field, or Repeated Legacy-Signal (RL-SIG) field, which are included in the HE MU PPDU.
(194) The first signal field may be related to the HE-SIG-A field, which is included in the HE MU PPDU. Since the first signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-A field.
(195) The second signal field may be related to the HE-SIG-B field, which is included in the HE MU PPDU. Since the second signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-B field.
(196) The first data field and the second data field may be related to downlink (DL) data, which applies S-TDMA being scheduled to the same RU while considering the time domain.
(197) The second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU. The information on RU layout and the information on the number of STAs using the first RU may be an 8-bit RU allocation subfield for RU allocation, as shown in Table 9. The information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field.
(198) That is, the first STA or second STA may decode the second signal field so as to know the RU layout within the whole frequency band and the number of STAs using each RU being included in RU layout. At this point, the number of STAs using the first RU may be equal to 2 or more. This is because S-TDMA is a scheme in which two or more STAs transmit/receive data fields from one RU.
(199) In case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA. The information on the S-TDMA includes S-TDMA indication information on that the S-TDMA may be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field. According to the above-described embodiment, a third signal field is additionally inserted in the PPDU, thereby generating an S-TMDA MU PPDU. Since the third signal field is newly defined for performing S-TDMA operations, the third signal field may be referred to as an S-TDMA SIG-C field.
(200) The S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU. That is, the first STA or the second STA decodes the S-TDMA indication information so as to verify that the first STA or the second STA is using the first RU and that the first STA or the second STA is being allocated with its data field in the first RU via S-TDMA.
(201) The first data field is transmitted in the first RU during a first symbol, which is determined by the first symbol offset information. The second data field is transmitted in the first RU during a second symbol, which is determined by the second symbol offset information.
(202) For example, the first symbol offset information may include information on a transmission start point of the first data field. The second symbol offset information may include information on a transmission start point of the second data field (in case the symbol offset information is a Starting Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The second symbol may be positioned immediately after the first symbol. Additionally, the first symbol may be positioned immediately after the second symbol.
(203) As another example, the first symbol offset information may include information on a transmission end point of the first data field. The second symbol offset information may include information on a transmission end point of the second data field (in case the symbol offset information is an Ending Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The information on S-TDMA may further include End of S-TDMA information for a data field being last transmitted in the first RU. If the transmission end point of a data field is only known, since it is difficult to determine whether or not a data field is being last transmitted from the corresponding RU, information on that the corresponding data field is being last transmitted may be notified through the End of S-TDMA information by using an additional bit.
(204) In case a third signal field is not included in the PPDU, the second signal field may further include the information on S-TDMA. At this point, the information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field. The information on S-TDMA may be included in a user field of the second signal field.
(205) The PPDU may further include a Short Training Field (STF) and Long Training Field (LTF) for the first STA and an STF (S-TDMA A-STF) and LTF (S-TDMA A-LTF) for the second STA. That is, not only the STF and LTF for the first STA being allocated in the first RU but also the STF and LTF for the second STA being allocated in the first RU may be added. The STF and LTF for the second STA may be transmitted after the first data field and before the second data field. A guard time may be included between the first data field and the STF and LTF for the second STA.
(206) Additionally, the AP may transmit the PPDU to a third STA. The PPDU may further include a third data field for the third STA. The third data field may be transmitted in a second RU, which is determined based on the second signal field. The first RU and the second RU are different frequency bands. That is, the third data field indicates that it may be received based on OFDMA.
(207) Hereinafter, in case a third signal field is not included in the PPDU, the embodiment in which the second signal field includes the information on S-TDMA will be described in detail. Additionally, the embodiment in which the PPDU reuses a HE MU PPDU will be described in detail.
(208) For example, the first signal field may include an additional bit indicating whether or not an S-TDMA MU PPDU includes a third signal field, and STF and LTF for a second STA (additional STF and LTF). According to the above-described assumption, the additional bit may indicate that the PPDU does not include the third signal field but include the STF and LTF for the second STA. That is, the first signal field may include signaling information notifying whether or not the third signal field and the STF and LTF for the second STA are included in the PPDU. That is, the third signal field and the STF and LTF for the second STA may be determined to be included or not included in the PPDU by signaling information being included in the first signal field.
(209) The information on RU layout and the information on the number of STAs using the first RU may correspond to an RU allocation subfield being included in a common field of the second signal field. As an 8-bit field, the RU allocation subfield may be assumed to be ‘01000000’. According to the 8-bit RU allocation subfield shown in Table 9, the ‘01000000’ includes RU layout information on that 106 RU/26 RU/26 RU/26 RU/26 RU are being used in the whole frequency band (herein, the frequency band is assumed to be 20 MHz). That is, if the RU layout information is 01000000, the whole frequency band may be positioned with one 106 RU and four 26 RUs.
(210) A user field of the second signal field may include a first user field for a first STA and a second user field for a second STA. That is, each of the first user field and the second user field may include the information on S-TDMA.
(211) S-TDMA indication information being included in the first user field may indicate that the first STA is capable of performing S-TDMA. First symbol offset information, which is included in the first user field, may indicate from which point a first data field is being transmitted. That is, the first STA may decode the common field of the second signal field and the first user field so as to know that the first data field is being received in the first RU during the first symbol.
(212) S-TDMA indication information being included in the second user field may indicate that the second STA is capable of performing S-TDMA. Second symbol offset information, which is included in the second user field, may indicate from which point a second data field is being transmitted. That is, the second STA may decode the common field of the second signal field and the second user field so as to know that the second data field is being received in the first RU during the second symbol.
(213) In case of a third STA where the S-TDMA is not applied and only the OFDMA is being applied, the third STA is described as follows. A user field of the second signal field may include a third user field for the third STA. S-TDMA indication information being included in the third user field may indicate that the third STA cannot perform S-TDMA. That is, the third STA may decode the common field of the second signal field and the third user field so as to know that the third data field is received only in the second RU by using a simple OFDMA scheme.
(214) According to the above-described method, by time-dividing one RU and allocating the time-divided RU to multiple STAs, waste of resource may be reduced.
(215)
(216) An example of
(217) Firstly, the terms will be defined. HE MU PPDU, HE-SIG-A field, HE-SIG-B field, HE-STF field, and HE-LTF field may all be PPDU and fields that are defined in the 802.11ax system. S-TDMA MU PPDU, S-TDMA SIG-A field (first signal field), S-TDMA SIG-B field (second signal field), S-TDMA STF, and S-TDMA LTF may be PPDU and fields that are defined for performing S-TDMA in a next generation wireless LAN system. S-TDMA SIG-C field (third signal field) may be a signal field that is newly defined for performing S-TDMA in a next generation wireless LAN system. However, the PPDU and fields that are defined for performing S-TDMA may be generated by using each subfield of the HE PPDU without any modification in order to satisfy backward compatibility with the 802.11ax system.
(218) An example of
(219) In step S2110, a first station (STA) receives the PPDU from an access point (AP). The PPDU includes a first data field for the first STA and a second data field for the second STA. The PPDU may be an S-TDMA MU PPDU, which may be newly defined in a next generation wireless LAN system. Additionally, the PPDU may be generated by using a High Efficiency Multi User PPDU (HE MU PPDU). That is, the PPDU may be an S-TDMA MU PPDU, which is generated by reusing the HE MU PPDU.
(220) In step S2120, the first STA decodes the first data field.
(221) The PPDU further includes a legacy header field, a first signal field, and a second signal field.
(222) The legacy header field may be related to Legacy-Short Training Field (L-STF), Legacy-Long Training Field (L-LTF), Legacy-Signal (L-SIG) field, or Repeated Legacy-Signal (RL-SIG) field, which are included in the HE MU PPDU.
(223) The first signal field may be related to the HE-SIG-A field, which is included in the HE MU PPDU. Since the first signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-A field.
(224) The second signal field may be related to the HE-SIG-B field, which is included in the HE MU PPDU. Since the second signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-B field.
(225) The first data field and the second data field may be related to downlink (DL) data, which applies S-TDMA being scheduled to the same RU while considering the time domain.
(226) The second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU. The information on RU layout and the information on the number of STAs using the first RU may be an 8-bit RU allocation subfield for RU allocation, as shown in Table 9. The information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field.
(227) That is, the first STA or second STA may decode the second signal field so as to know the RU layout within the whole frequency band and the number of STAs using each RU being included in RU layout. At this point, the number of STAs using the first RU may be equal to 2 or more. This is because S-TDMA is a scheme in which two or more STAs transmit/receive data fields from one RU.
(228) In case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA. The information on the S-TDMA includes S-TDMA indication information on that the S-TDMA may be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field. According to the above-described embodiment, a third signal field is additionally inserted in the PPDU, thereby generating an S-TMDA MU PPDU. Since the third signal field is newly defined for performing S-TDMA operations, the third signal field may be referred to as an S-TDMA SIG-C field.
(229) The S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU. That is, the first STA or the second STA decodes the S-TDMA indication information so as to verify that the first STA or the second STA is using the first RU and that the first STA or the second STA is being allocated with its data field in the first RU via S-TDMA.
(230) The first data field is transmitted in the first RU during a first symbol, which is determined by the first symbol offset information. The second data field is transmitted in the first RU during a second symbol, which is determined by the second symbol offset information.
(231) For example, the first symbol offset information may include information on a transmission start point of the first data field. The second symbol offset information may include information on a transmission start point of the second data field (in case the symbol offset information is a Starting Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The second symbol may be positioned immediately after the first symbol. Additionally, the first symbol may be positioned immediately after the second symbol.
(232) As another example, the first symbol offset information may include information on a transmission end point of the first data field. The second symbol offset information may include information on a transmission end point of the second data field (in case the symbol offset information is an Ending Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The information on S-TDMA may further include End of S-TDMA information for a data field being last transmitted in the first RU. If the transmission end point of a data field is only known, since it is difficult to determine whether or not a data field is being last transmitted from the corresponding RU, information on that the corresponding data field is being last transmitted may be notified through the End of S-TDMA information by using an additional bit.
(233) In case a third signal field is not included in the PPDU, the second signal field may further include the information on S-TDMA. At this point, the information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field. The information on S-TDMA may be included in a user field of the second signal field.
(234) The PPDU may further include a Short Training Field (STF) and Long Training Field (LTF) for the first STA and an STF (S-TDMA A-STF) and LTF (S-TDMA A-LTF) for the second STA. That is, not only the STF and LTF for the first STA being allocated in the first RU but also the STF and LTF for the second STA being allocated in the first RU may be added. The STF and LTF for the second STA may be transmitted after the first data field and before the second data field. A guard time may be included between the first data field and the STF and LTF for the second STA. That is, the first signal field may include signaling information notifying whether or not the third signal field and the STF and LTF for the second STA are included in the PPDU. That is, the third signal field and the STF and LTF for the second STA may be determined to be included or not included in the PPDU by signaling information being included in the first signal field.
(235) Additionally, the AP may transmit the PPDU to a third STA. The PPDU may further include a third data field for the third STA. The third data field may be transmitted in a second RU, which is determined based on the second signal field. The first RU and the second RU are different frequency bands. That is, the third data field indicates that it may be received based on OFDMA.
(236) Hereinafter, in case a third signal field is not included in the PPDU, the embodiment in which the second signal field includes the information on S-TDMA will be described in detail. Additionally, the embodiment in which the PPDU reuses a HE MU PPDU will be described in detail.
(237) For example, the first signal field may include an additional bit indicating whether or not an S-TDMA MU PPDU includes a third signal field, and STF and LTF for a second STA (additional STF and LTF). According to the above-described assumption, the additional bit may indicate that the PPDU does not include the third signal field but include the STF and LTF for the second STA.
(238) The information on RU layout and the information on the number of STAs using the first RU may correspond to an RU allocation subfield being included in a common field of the second signal field. As an 8-bit field, the RU allocation subfield may be assumed to be ‘01000000’. According to the 8-bit RU allocation subfield shown in Table 9, the ‘01000000’ includes RU layout information on that 106 RU/26 RU/26 RU/26 RU/26 RU are being used in the whole frequency band (herein, the frequency band is assumed to be 20 MHz). That is, if the RU layout information is 01000000, the whole frequency band may be positioned with one 106 RU and four 26 RUs.
(239) A user field of the second signal field may include a first user field for a first STA and a second user field for a second STA. That is, each of the first user field and the second user field may include the information on S-TDMA.
(240) S-TDMA indication information being included in the first user field may indicate that the first STA is capable of performing S-TDMA. First symbol offset information, which is included in the first user field, may indicate from which point a first data field is being transmitted. That is, the first STA may decode the common field of the second signal field and the first user field so as to know that the first data field is being received in the first RU during the first symbol.
(241) S-TDMA indication information being included in the second user field may indicate that the second STA is capable of performing S-TDMA. Second symbol offset information, which is included in the second user field, may indicate from which point a second data field is being transmitted. That is, the second STA may decode the common field of the second signal field and the second user field so as to know that the second data field is being received in the first RU during the second symbol.
(242) In case of a third STA where the S-TDMA is not applied and only the OFDMA is being applied, the third STA is described as follows. A user field of the second signal field may include a third user field for the third STA. S-TDMA indication information being included in the third user field may indicate that the third STA cannot perform S-TDMA. That is, the third STA may decode the common field of the second signal field and the third user field so as to know that the third data field is received only in the second RU by using a simple OFDMA scheme.
(243) According to the above-described method, by time-dividing one RU and allocating the time-divided RU to multiple STAs, waste of resource may be reduced.
(244) 3. Device Configuration
(245)
(246) A wireless device (100) of
(247) The transmitting device (100) may include a processor (110), a memory (120), and a transceiver (130), and the receiving device (150) may include a processor (160), a memory (170), and a transceiver (180). The transceiver (130, 180) transmits/receives a radio signal and may be operated in a physical layer of IEEE 802.11/3GPP, and so on. The processor (110, 160) may be operated in the physical layer and/or MAC layer and may be operatively connected to the transmitting/receiving unit (130, 180).
(248) The processor (110, 160) and/or the transceiver (130, 180) may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processor. The memory (120, 170) may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage unit. When the embodiments are executed by software, the techniques (or methods) described herein can be executed with modules (e.g., processes, functions, and so on) that perform the functions described herein. The modules can be stored in the memory (120, 170) and executed by the processor (110, 160). The memory (120, 170) can be implemented (or positioned) within the processor (110, 160) or external to the processor (110, 160). Also, the memory (120, 170) may be operatively connected to the processor (110, 160) via various means known in the art.
(249) The processor (110, 160) may implement the functions, processes and/or methods proposed in the present disclosure. For example, the processor (110, 160) may perform the operation according to the present embodiment.
(250) Detailed operations of the processor (110) of the transmitting device are as follows. The processor (110) of the transmitting device generates a PPDU for S-TDMA and transmit the PPDU to a first station (STA) and a second STA.
(251) Detailed operations of the processor (160) of the receiving device are as follows. The processor (160) of the receiving device receives the PPDU for S-TDMA and decodes its data field to which the S-TDMA scheme is applied.
(252)
(253) A wireless device includes a processor (610), a power management module (611), a battery (612), a display (613), a keypad (614), a subscriber identification module (SIM) card (615), a memory (620), a transceiver (630), one or more antennas (631), a speaker (640), and a microphone (641).
(254) The processor (610) may be configured to implement proposed functions, procedures and/or methods of the present disclosure that are described below. Layers of the radio interface protocol may be implemented in the processor (610). The processor (610) may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The processor (610) may be an application processor (AP). The processor (610) may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor (610) may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor.
(255) The power management module (611) manages power for the processor (610) and/or the transceiver (630). The battery (612) supplies power to the power management module (611). The display (613) outputs results processed by the processor (610). The keypad (614) receives inputs to be used by the processor (610). The keypad (614) may be shown on the display (613). The SIM card (615) is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contact information on many SIM cards.
(256) The memory (620) is operatively coupled with the processor (610) and stores a variety of information to operate the processor (610). The memory (620) may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. When the embodiments are implemented in software, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules may be stored in the memory (620) and executed by the processor (610). The memory (620) may be implemented within the processor (610) or external to the processor (610) in which case those can be communicatively coupled to the processor (610) via various means as is known in the art.
(257) The transceiver (630) is operatively coupled with the processor (610) and transmits and/or receives a radio signal. The transceiver (630) includes a transmitter and a receiver. The transceiver (630) may include baseband circuitry to process radio frequency signals. The transceiver (630) controls the one or more antennas (631) to transmit and/or receive a radio signal.
(258) The speaker (640) outputs sound-related results processed by the processor (610). The microphone (641) receives sound-related inputs to be used by the processor (610).
(259) In case of the transmitting device, the processor (610) generates a PPDU for S-TDMA and transmits the PPDU to a first station (STA) and a second STA.
(260) In case of the receiving device, the processor (610) receives the PPDU for S-TDMA and decodes its data field, which applied the S-TDMA scheme.
(261) The PPDU includes a legacy header field, a first signal field, a second signal field, a first data field for the first STA, and a second data field for the second STA.
(262) The legacy header field may be related to Legacy-Short Training Field (L-STF), Legacy-Long Training Field (L-LTF), Legacy-Signal (L-SIG) field, or Repeated Legacy-Signal (RL-SIG) field, which are included in the HE MU PPDU.
(263) The first signal field may be related to the HE-SIG-A field, which is included in the HE MU PPDU. Since the first signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-A field.
(264) The second signal field may be related to the HE-SIG-B field, which is included in the HE MU PPDU. Since the second signal field is defined for performing S-TDMA operations, this field may be referred to as an S-TDMA SIG-B field.
(265) The first data field and the second data field may be related to downlink (DL) data, which applies S-TDMA being scheduled to the same RU while considering the time domain.
(266) The second signal field includes information on Resource Unit (RU) layout and information on a number of STAs using the first RU. The information on RU layout and the information on the number of STAs using the first RU may be an 8-bit RU allocation subfield for RU allocation, as shown in Table 9. The information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field.
(267) That is, the first STA or second STA may decode the second signal field so as to know the RU layout within the whole frequency band and the number of STAs using each RU being included in RU layout. At this point, the number of STAs using the first RU may be equal to 2 or more. This is because S-TDMA is a scheme in which two or more STAs transmit/receive data fields from one RU.
(268) In case a third signal field is further included in the PPDU, the third signal field includes information on the S-TDMA. The information on the S-TDMA includes S-TDMA indication information on that the S-TDMA may be performed, first symbol offset information for the first data field, and second symbol offset information for the second data field. According to the above-described embodiment, a third signal field is additionally inserted in the PPDU, thereby generating an S-TMDA MU PPDU. Since the third signal field is newly defined for performing S-TDMA operations, the third signal field may be referred to as an S-TDMA SIG-C field.
(269) The S-TDMA indication information includes information on that the first and second data fields are being allocated to the first RU. That is, the first STA or the second STA decodes the S-TDMA indication information so as to verify that the first STA or the second STA is using the first RU and that the first STA or the second STA is being allocated with its data field in the first RU via S-TDMA.
(270) The first data field is transmitted in the first RU during a first symbol, which is determined by the first symbol offset information. The second data field is transmitted in the first RU during a second symbol, which is determined by the second symbol offset information.
(271) For example, the first symbol offset information may include information on a transmission start point of the first data field. The second symbol offset information may include information on a transmission start point of the second data field (in case the symbol offset information is a Starting Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The second symbol may be positioned immediately after the first symbol. Additionally, the first symbol may be positioned immediately after the second symbol.
(272) As another example, the first symbol offset information may include information on a transmission end point of the first data field. The second symbol offset information may include information on a transmission end point of the second data field (in case the symbol offset information is an Ending Symbol offset). The first symbol and the second symbol may be positioned by TDMA in the first RU. The information on S-TDMA may further include End of S-TDMA information for a data field being last transmitted in the first RU. If the transmission end point of a data field is only known, since it is difficult to determine whether or not a data field is being last transmitted from the corresponding RU, information on that the corresponding data field is being last transmitted may be notified through the End of S-TDMA information by using an additional bit.
(273) In case a third signal field is not included in the PPDU, the second signal field may further include the information on S-TDMA. At this point, the information on RU layout and the information on the number of STAs using the first RU may be included in a common field of the second signal field. The information on S-TDMA may be included in a user field of the second signal field.
(274) The PPDU may further include a Short Training Field (STF) and Long Training Field (LTF) for the first STA and an STF (S-TDMA A-STF) and LTF (S-TDMA A-LTF) for the second STA. That is, not only the STF and LTF for the first STA being allocated in the first RU but also the STF and LTF for the second STA being allocated in the first RU may be added. The STF and LTF for the second STA may be transmitted after the first data field and before the second data field. A guard time may be included between the first data field and the STF and LTF for the second STA.
(275) Additionally, the AP may transmit the PPDU to a third STA. The PPDU may further include a third data field for the third STA. The third data field may be transmitted in a second RU, which is determined based on the second signal field. The first RU and the second RU are different frequency bands. That is, the third data field indicates that it may be received based on OFDMA.
(276) Hereinafter, in case a third signal field is not included in the PPDU, the embodiment in which the second signal field includes the information on S-TDMA will be described in detail. Additionally, the embodiment in which the PPDU reuses a HE MU PPDU will be described in detail.
(277) For example, the first signal field may include an additional bit indicating whether or not an S-TDMA MU PPDU includes a third signal field, and STF and LTF for a second STA (additional STF and LTF). According to the above-described assumption, the additional bit may indicate that the PPDU does not include the third signal field but include the STF and LTF for the second STA.
(278) The information on RU layout and the information on the number of STAs using the first RU may correspond to an RU allocation subfield being included in a common field of the second signal field. As an 8-bit field, the RU allocation subfield may be assumed to be ‘01000000’. According to the 8-bit RU allocation subfield shown in Table 9, the ‘01000000’ includes RU layout information on that 106 RU/26 RU/26 RU/26 RU/26 RU are being used in the whole frequency band (herein, the frequency band is assumed to be 20 MHz). That is, if the RU layout information is 01000000, the whole frequency band may be positioned with one 106 RU and four 26 RUs.
(279) A user field of the second signal field may include a first user field for a first STA and a second user field for a second STA. That is, each of the first user field and the second user field may include the information on S-TDMA.
(280) S-TDMA indication information being included in the first user field may indicate that the first STA is capable of performing S-TDMA. First symbol offset information, which is included in the first user field, may indicate from which point a first data field is being transmitted. That is, the first STA may decode the common field of the second signal field and the first user field so as to know that the first data field is being received in the first RU during the first symbol.
(281) S-TDMA indication information being included in the second user field may indicate that the second STA is capable of performing S-TDMA. Second symbol offset information, which is included in the second user field, may indicate from which point a second data field is being transmitted. That is, the second STA may decode the common field of the second signal field and the second user field so as to know that the second data field is being received in the first RU during the second symbol.
(282) In case of a third STA where the S-TDMA is not applied and only the OFDMA is being applied, the third STA is described as follows. A user field of the second signal field may include a third user field for the third STA. S-TDMA indication information being included in the third user field may indicate that the third STA cannot perform S-TDMA. That is, the third STA may decode the common field of the second signal field and the third user field so as to know that the third data field is received only in the second RU by using a simple OFDMA scheme.
(283) According to the above-described method, by time-dividing one RU and allocating the time-divided RU to multiple STAs, waste of resource may be reduced.