US 20170170937A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2017/0170937 A1 CHUN et al. (43) Pub. Date: Jun. 15, 2017
(54) METHOD FOR MULTI-USER UPLINK DATA Related U.S. Application Data TRANSMISSION IN WIRELESS (60) Provisional application No. 62/017.821, filed on Jun. COMMUNICATION SYSTEMAND DEVICE 26, 2014. THEREFOR s Publication Classification (71) Applicant: E. ELECTRONICS INC., Seoul (51) Int. Cl. (KR) H04L 5/00 (2006.01) (72) Inventors: Jinyoung CHUN, Seoul (KR); Kiseon ( 52) U.S. Cl. RYU, Seoul (KR); Wookbong LEE, CPC ...... H04L 5/0048 (2013.01); inities Seoul (KR); Hangyu CHO, Seoul (KR); Suhwook KIM, Seoul (KR) (57) ABSTRACT Disclosed are a method for transmitting multi-user uplink data in a wireless communication system and a device (73) Assignee: LG ELECTRONICS INC., Seoul therefor. In detail, a method for transmitting multi-user (KR) uplink data in a wireless communication system, includes: receiving, by a station (STA), a Sounding request frame from (21) Appl. No.: 15/322,062 an access point (AP); and transmitting, by the STA, a (22) PCT Filed: Jan. 29, 2015 Sounding frame to the AP in response to the Sounding request frame, wherein the sounding request frame may include information indicating the number of streams in (86). PCT No.: PCT/KR2O15/OOO996 which the STA needs to transmit the sounding frame, and the S 371 (c)(1), Sounding frame may include a long training field (LTF) (2) Date: Dec. 23, 2016 symbols as many as the number of streams.
MAC SAP H H MAC Sublayer Management Data Link MAC Sublayer Entity (230) Layer (210) -Ho- MLME-SAP MLME PHY SAP PLME SAP -
PHY Subayer Station Physical PHY Sublayer Management PLME-SAP Management Layer (220) Entity (240) Entity (250) HD Patent Application Publication Jun. 15, 2017 Sheet 1 of 32 US 2017/0170937 A1
FIG. 1
802.11 Components
Patent Application Publication Jun. 15, 2017. Sheet 2 of 32 US 2017/0170937 A1
FIG 2 MAC SAP H H MAC Sublayer Management Data Link MAC Sublayer Entity (230) Layer (210) -HD MLME-SAP MLME PHY SAP PLME SAP H H
PHY Subayer Station Physical PHY Sublayer Management Management Layer (220) E PLME-SAP Entity (250) -HD Patent Application Publication Jun. 15, 2017 Sheet 3 of 32 US 2017/0170937 A1
FIG 3
Format of Data fied SERVICE Scrambled 6.NES Pad (non LDPC case only) 16 bits PSDU Tabits bits Non-HT PPDU y
8 LS 8 uS 4 LS
(a) L-STF L-LTF SIG
HT-mixed format PPDU Extension Data HT-LTFS HT-LTFs 8 LIS 8 uS 4 LIS 8 LIS 4 LS 4 us per LTF 4 LIS per LTF L- HT- HT- HT- HT- HT (b) L-STF L-LTF SIG HT-SIG STF LTF LTF Er LTF Data
HT-greenfield format PPDU Extension Data HT-LTFS HT-LTFS 8 uS 8 uS 8 uS 4 us per LTF 4 us per LTF HT- HT- HT- HT (c) HT-GF-STF HT-LTF1 HT-SIG LTF LTF LTF LTF Data Patent Application Publication Jun. 15, 2017 Sheet 4 of 32 US 2017/0170937 A1
FIG. 4 4 LIS per 8 US 8 uS 4 LIS 8 US 4 uS WHT-LTF symbol 4 LS L- VHT- whT L-STF L-LTF SIG WHT-SIG-A STF WHT-LTF SIG-B Data Patent Application Publication Jun. 15, 2017 Sheet 5 of 32 US 2017/0170937 A1
FIG. 5
(a) non-HT PPDU
Q Q +1 +1 (b) HT-mixed PPDU I I -1 -1 (OFDM symbol #1) (OFDM symbol i2)
Q +1 (c) WHT PPDU
(OFDM symbol #1) (OFDM symbol i2) Patent Application Publication Jun. 15, 2017 Sheet 6 of 32 US 2017/0170937 A1
FIG. 6
Octets. 2 2 6 6 6 2 6 2 4. variable 4 Frame Duration Address Address Address Sequence Address QoS HT Frame FCS Contro /ID 1 2 3 Control 4. Control Control Body
-e e MAC Header Patent Application Publication Jun. 15, 2017 Sheet 7 of 32 US 2017/0170937 A1
FIG 7 BO B1 B2 B3 B4 B7 B8 B9 B10 B11 B12 B13 B14 B15 More ProtoCO To From Power More Protected Version Type Subtype DS DS Art. Retry Management Data Frame Order
Bits. 2 2 4 1 1 1 1 1 1 1 1 Patent Application Publication Jun. 15, 2017. Sheet 8 of 32 US 2017/0170937 A1
FIG. 8
station
Station 2
station 3
station 4
station 5
busy medium not idle (frame, ack etc.) gelapsed back off time
packet arrival at MAC residual back Off time Patent Application Publication Jun. 15, 2017 Sheet 9 of 32 US 2017/0170937 A1
FIG. 9 - ArtAFSi III | | | Immediate access when | AIFS Medium is idle >= DIFS or AIFSi DIFS C ontention Window PIFS —D I toBusy Mediuma SIFS III// / /Bickoff?cher slotSlots II Nextat freFrame -> --Slot time !------Defer Access Select Slot and Decrement Backoff as long as Medium is idle Patent Application Publication Jun. 15, 2017. Sheet 10 of 32 US 2017/0170937 A1
FIG 10
BO B1 B29 B30 B31 AC RDG/More WHT HT COntrol el. PPDU Bits: 1- 29 1 - - -
- B1 B2 B3 B5, B6 B8 B9 B23 B24 B26 B27 B28 B29s. MSIA MFSIA Coding FB, TX UnSOC ited Reserved MRQ STBC GID-L MFB GID–H Type Type MFB BitS. 1 1 3 3- 15 is 3 1 1 1
- E9 B11 B12 B15 B16 B17 B18 B23. NUMSTS WHT-MCS BW SNR BitS. 3 4 2 6 Patent Application Publication Jun. 15, 2017. Sheet 11 of 32 US 2017/0170937 A1
FIG 11
WHT NDP Beam former Announce ment WHT Compressed ae ae aa. Beamformee 1 Beamforming WHT Compressed Beamformee 2 Beamforming WHT Compressed Beam formee 3 Beamformin
Patent Application Publication Jun. 15, 2017. Sheet 12 of 32 US 2017/0170937 A1
FIG. 12
Frame Sounding Duration RA Dialog Control Token Octets: 2 2
B0- B11 B12 B13 B15, f AID12 Feedback Type NC Index Bits: 12 1 3 Patent Application Publication Jun. 15, 2017. Sheet 13 of 32 US 2017/0170937 A1
FIG. 13
4 LIS per 8 US 8 US 4 US 8 US 4 US WHT-LTF Symbol 4 US L- WHT- WHT L-STF L-LTF SIG WHT-SIG-A STF WHT-LTF SIG-B Patent Application Publication Jun. 15, 2017. Sheet 14 of 32 US 2017/0170937 A1
FIG 14 Free boy
VHT MIMO compressedWHT 'E' Category WHT Act. On Control Beamforming Beamforming Report Report Octets: 1 1- 3 variable variable
BOB2B3 B5 B6 B7, B8 B9 B10 B1 B12 B14 B15 B16 B17 B8-B23
Sounding Codebook Feedback Dialog Grouping Information Token Number Bits: 3 3 2 2 3 2 6 Patent Application Publication Jun. 15, 2017. Sheet 15 of 32 US 2017/0170937 A1
FIG. 15
Frame Feedback Segment Control Duration RA RA Retransmission Bitmap FCS Octets: 2 2 6 6 1 4 Patent Application Publication Jun. 15, 2017. Sheet 16 of 32 US 2017/0170937 A1
FIG 16
Membership User Position Status Array Array Octets: 1 1 8 16 Patent Application Publication Jun. 15, 2017. Sheet 17 of 32 US 2017/0170937 A1
FIG. 17 PPDU Duration (it of symbols) p Last Symbol b WHT-Service WHT A - MPDU PHY Pad Tai L-TFs ||SIG SGY. A | VisigTFs service VHT A - MPDU PHY Pad3C Tai2 B Service WHT A - MPDU PHY Pad Tai - - - S------Less --- / than --- 0-3 MPDU MPDU O-3 / 8-bit - Octets Length=0 Length=0 Octets - Last byte A-MPDU | A-MPDU || A-MPDU Dword Null NU Final boundary Subframe 1 subframe2 SubframenAC Pad subframe Subframe MAC Pad Patent Application Publication Jun. 15, 2017. Sheet 18 of 32 US 2017/0170937 A1
FIG. 18 TXOP
RASTA-1, RASTA-1, RA=STA-1, pad
AC WI (1) AC WI (2) AC WI (3) RA=STA-2, RA=STA-2, RA=STA-2, AP AC WO (2) pad cWE35 pad AC BE (1) RA=STA-3, i RA=STA-3, RA=STA-3, AC WI (4) AC WO(1) AC BE (2)
Time Patent Application Publication Jun. 15, 2017. Sheet 19 of 32 US 2017/0170937 A1
FIG. 19
L-part HE-part - HE-data (a) is re L-STF L-LTF L-SIG HE-STF HE-SIG | HE-LTF
12.8LIS 4-times FFT ------as (b) L-STF LLTF LSIG SAHE- SIFHE- HELTF SBHE Data
4-times FF- --
(c) L-STF | L-LTF L-SIG STFE. SIGE. | HE-LTF Data
4-times FFT ------HE- HE (d) L-STF L-LTF L-SIG STF SIG Data Patent Application Publication Jun. 15, 2017. Sheet 20 of 32 US 2017/0170937 A1
FIG. 20
L-STF L-LTF L-SIG HE-SIG A
L-STF L-LTF L-SIG | HE-SIG A HE-STF HE-LTF HE-SIG B Data L-STF L-LTF L-SIG | HE-SIG A
L-STF L-LTF L-SIG | HE-SIG A Patent Application Publication Jun. 15, 2017. Sheet 21 of 32 US 2017/0170937 A1
FIG 21
L-STF L-LTF L-SIG HE-SIG A
HE-SIG A
HE-SIG B
HE-SIG A
HE-SIG A
Patent Application Publication Jun. 15, 2017. Sheet 22 of 32 US 2017/0170937 A1
FIG. 22
Data for L-STF L-LTF STA1 Data for L-STF L-LTF STA2 HE-SIG B Data for L-STF L-LTF L-SIG | HE-SIG A HE-STF HE-LTF STA3 Data for L-STF L-LTF L-SIG | HE-SIG A HE-STF HE-LTF STA4 Patent Application Publication Jun. 15, 2017. Sheet 23 of 32 US 2017/0170937 A1
FIG. 23
L-STF L-LTF L-SIG | HE-SIG A HE-SIG B | HE-STF | HE-LTF Dator
L-STF L-LTF L-SIG | HE-SIG A HE-SIG B | HE-STF | HE-LTF Dair
L-STF L-LTF L-SIG | HE-SIG A HE-SIG B | HE-STF | HE-LTF Dator
Data for L-STF L-LTF L-SIG | HE-SIG A HE-SIG B | HE-STF | HE-LTF STA4 Patent Application Publication Jun. 15, 2017. Sheet 24 of 32 US 2017/0170937 A1
FIG. 24
HE PPDU
Q Q Q
I I -1 +1 -1 +1 -1 (OFDM symbol #1) (OFDM symbol i2) (OFDM symbol i3) Patent Application Publication Jun. 15, 2017. Sheet 25 of 32 US 2017/0170937 A1
FIG. 25
2510 25.30
AP UL MU scheduling frame ACK s STA1 UL MU Data frame
2522
STA2 UL MU Data frame
2523
STA3 UL MU Data frame Patent Application Publication Jun. 15, 2017. Sheet 26 of 32 US 2017/0170937 A1
FIG. 26
2610 / 2630 2650 UL MU / AP scheduling Adjustment frame frame ACK
262 264 /
STA1 SignalSync UL MU Data frame
2622 2642 / / STA2 SignalSync U MU Data frame
2623 2643
/ t / STA3 SignalSync U MU Data frame Patent Application Publication Jun. 15, 2017. Sheet 27 of 32 US 2017/0170937 A1
FIG. 27 HE-part & HE-data (to STA1, 2, 3, 4) 20MHz (a) HE-part & HE-data 20MHZ 2 HE-part & HE-data 2OMHz HE-part & HE-data 20MHZ
HE-part & HE-data (to STA1) 2OMHZ HE-part & HE-data (to STA2) 2OMHz (b) HE-part & HE-data (to STA3) 2OMHZ HE-part & HE-data (to STA4) 2OMHz
L-part 20MHZ
2OMHz (c) HE-part & HE-data (to STA1, 2, 3, 4) 20MHZ L-part 2OMHz Patent Application Publication Jun. 15, 2017. Sheet 28 of 32 US 2017/0170937 A1
FIG. 28
2810 2830 2850 NDP / announ Cement for UL Polling Polling 2820
STA NDP
2840
STA2 NDP
2860
STA3 NDP Patent Application Publication Jun. 15, 2017. Sheet 29 of 32 US 2017/0170937 A1
FIG. 29
2910 / 2930 2950 Buffer status/ / AP Sounding request Polling Polling
2920
STA Buffer status/ Sounding p STA2 Buffer status/ Sounding 2960 / STA3 Buffer status/ Sounding Patent Application Publication Jun. 15, 2017. Sheet 30 of 32 US 2017/0170937 A1
FIG. 30
Sounding Dialog
Octets:
B0. B1 B2 B7 - B0, B11 B12 B13 Bis Sounding Dialog k Reserved Token Number AID12 Feedback Type NC Index Bits: 2 6 BitS. 12 1 3 Patent Application Publication Jun. 15, 2017. Sheet 31 of 32 US 2017/0170937 A1
FIG 31
AP STA 1 . . . STA in
SOUNDING AND/OR BUFFER STATUS REQUEST FRAME 310
3102 SOUNDING AND/OR BUFFER STATUS FRAME
303 SOUNDING AND/OR BUFFER STATUS FRAME Patent Application Publication Jun. 15, 2017. Sheet 32 of 32 US 2017/0170937 A1
FIG. 32 3210
MEMORY
3213
PROCESSOR RF UNIT US 2017/017.0937 A1 Jun. 15, 2017
METHOD FOR MIUILT-USER UPLINK DATA system performance in a dense environment in which many TRANSMISSION IN WIRELESS APs and many STAs are present is discussed based on the COMMUNICATION SYSTEMAND DEVICE corresponding scenarios. THEREFOR (0010. In the future, it is expected in IEEE 802.11ax that the improvement of system performance in an overlapping TECHNICAL FIELD basic service set (OBSS) environment, the improvement of an outdoor environment, cellular offloading, and so on rather 0001. The present invention relates to a wireless com than single link performance improvement in a single basic munication system, and more particularly, to a method for service set (BSS) will be actively discussed. The directivity Supporting uplink data transmission of multi-users and a of such IEEE 802.11ax means that the next-generation device for Supporting the same. WLAN will have a technical scope gradually similar to that of mobile communication. Recently, when considering a BACKGROUND ART situation in which mobile communication and a WLAN technology are discussed together in Small cells and direct 0002 Wi-Fi is a wireless local area network (WLAN) to-direct (D2D) communication coverage, it is expected that technology which enables a device to access the Internet in the technological and business convergence of the next a frequency band of 2.4 GHz, 5 GHz or 6 GHz. generation WLAN based on IEEE 802.11ax and mobile 0003 A WLAN is based on the institute of electrical and communication will be further activated. electronic engineers (IEEE) 802.11 standard. The wireless next generation standing committee (WNG SC) of IEEE DETAILED DESCRIPTION OF INVENTION 802.11 is an ad-hoc committee which is worried about the next-generation wireless local area network (WLAN) in the Technical Problem medium to longer term. 0004 IEEE 802.11n has an object of increasing the speed 0011. An object of the present invention is to propose an and reliability of a network and extending the coverage of a uplink multi-user transmission method in a wireless com wireless network. More specifically, IEEE 802.11n supports munication system. a high throughput (HT) providing a maximum data rate of 0012. Further, an object of the present invention is to 600Mbps. Furthermore, in order to minimize a transfer error propose a pre-procedure for acquiring channel state infor and to optimize a data rate, IEEE 802.11n is based on a mation and/or buffer state information for uplink multi-user multiple inputs and multiple outputs (MIMO) technology in transmission in the wireless communication system. which multiple antennas are used at both ends of a trans 0013. In addition, an object of the present invention is to mission unit and a reception unit. propose a frame structure for the uplink multi-user trans 0005. As the spread of a WLAN is activated and appli mission in the wireless communication system. cations using the WLAN are diversified, in the next-genera 0014. The objects of the present invention are not limited tion WLAN system Supporting a very high throughput to the technical objects described above, and other technical (VHT), IEEE 802.11ac has been newly enacted as the next objects not mentioned herein may be understood to those version of an IEEE 802.11n WLAN system. IEEE 802.11ac skilled in the art from the description below. supports a data rate of 1 Gbps or more through 80 MHz bandwidth transmission and/or higher bandwidth transmis Technical Solution sion (e.g., 160 MHz), and chiefly operates in a 5 GHz band. 0015. According to one aspect of the present invention, a 0006 Recently, a need for a new WLAN system for method for transmitting multi-user uplink data in a wireless Supporting a higher throughput than a data rate Supported by communication system, includes: receiving, by a station IEEE 802.11ac comes to the fore. (STA), a sounding request frame from an access point (AP); 0007. The scope of IEEE 802.11ax chiefly discussed in and transmitting, by the STA, a Sounding frame to the AP in the next-generation WLAN study group called a so-called response to the Sounding request frame, wherein the sound IEEE 802.11ax or high efficiency (HEW) WLAN includes 1) ing request frame may include information indicating the the improvement of an 802.11 physical (PHY) layer and number of streams in which the STA needs to transmit the medium access control (MAC) layer in bands of 2.4 GHz, 5 Sounding frame, and the Sounding frame may include a long GHz, etc., 2) the improvement of spectrum efficiency and training field (LTF) symbols as many as the number of area throughput, 3) the improvement of performance in StreamS. actual indoor and outdoor environments, such as an envi 0016. According to another aspect of the present inven ronment in which an interference source is present, a dense tion, a station (STA) device for transmitting multi-user heterogeneous network environment, and an environment in uplink data in a wireless communication system, includes: a which a high user load is present and so on. radio frequency (RF) unit for transmitting/receiving a wire 0008 Ascenario chiefly taken into consideration in IEEE less signal; and a processor, wherein the processor may be 802.11ax is a dense environment in which many access configured to receive a Sounding request frame from an points (APs) and many stations (STAs) are present. In IEEE access point (AP), and transmit a sounding frame to the AP 802.11ax, the improvement of spectrum efficiency and area in response to the Sounding request frame, the Sounding throughput is discussed in Such a situation. More specifi request frame may include information indicating the num cally, there is an interest in the improvement of Substantial ber of streams in which the STA needs to transmit the performance in outdoor environments not greatly taken into Sounding frame, and the Sounding frame may include a long consideration in existing WLANs in addition to indoor training field (LTF) symbols as many as the number of environments. StreamS. 0009. In IEEE 802.11ax, there is a great interest in 0017 Preferably, the sounding request frame may include scenarios, such as wireless offices, Smart homes, stadiums, information for the Sounding request frame to indicate a hotspots, and buildings/apartments. The improvement of Sounding request for transmitting uplink data. US 2017/017.0937 A1 Jun. 15, 2017
0018 Preferably, the sounding request frame may include Advantageous Effects information for indicating the sounding request for the uplink data transmission in a Modulation and Coding 0029. According to embodiments of the present inven Scheme (MCS) feedback request (MRQ) subfield of a VHT tion, uplink multi-user transmission can be performed control field. through respective different spatial streams or frequency 0019 Preferably, the sounding request frame may include resources in a wireless communication system. information for indicating the sounding request for the 0030. Further, according to the embodiments of the pres uplink data transmission in a Sounding Dialog Token field. ent invention, the uplink multi-user transmission can be 0020 Preferably, the sounding frame may be constituted Smoothly performed based on channel state information only by a High Efficiency STF (HE-STF), a High Efficiency and/or buffer state information for the uplink multi-user LTF (HE-LTF), and a High Efficiency SIGNAL (HE-SIG) transmission in the wireless communication system. except for a Legacy-Short Training Field (L-STF), a 0031. In addition, according to the embodiments of the Legacy-Long Training Field (L-LTF), and a Legacy SIG present invention, the uplink multi-user transmission can be NAL (L-SIG) field. smoothly performed based on a frame structure for the 0021 Preferably, the sounding request frame may include uplink multi-user transmission in the wireless communica information for requesting buffer status information of the tion system. STA, and the sounding frame may include the buffer status 0032. The technical effects of the present invention are information of the STA. not limited to the technical effects described above, and 0022 Preferably, the buffer status information may other technical effects not mentioned herein may be under include at least one information of access category (AC) of stood to those skilled in the art from the description below. uplink data to be transmitted by the STA, the size of the uplink data, the size of a queue in which the uplink data are DESCRIPTION OF DRAWINGS accumulated, a backoff count for the uplink data transmis 0033. The accompanying drawings, which are included Sion, and a contention window for the uplink data transmis herein as a part of the description for help understanding the S1O. present invention, provide embodiments of the present 0023 Preferably, the sounding request frame may be a invention, and describe the technical features of the present Null Data Packet Announcement (NDPA) frame. invention with the description below. 0024 Preferably, the sounding frame may be a Null Data 0034 FIG. 1 is a diagram illustrating an example of IEEE Packet (NDP). 802.11 system to which the present invention may be 0025. According to yet another aspect of the present applied. invention, a method for transmitting multi-user uplink data 0035 FIG. 2 is a diagram exemplifying a structure of in a wireless communication system, includes: transmitting, layer architecture in IEEE 802.11 system to which the by an access point (AP), a Sounding request frame to a present invention may be applied. station (STA) which participates in transmitting the multi 0036 FIG. 3 exemplifies a non-HT format PPDU and an user uplink data; and receiving, by the AP, a Sounding frame HT format PPDU of a wireless communication system to from the STA in response to the Sounding request frame, which the present invention may be applied. wherein the Sounding request frame may include informa 0037 FIG. 4 exemplifies a VHT format PPDU of a tion indicating the number of streams in which the STA wireless communication system to which the present inven needs to transmit the Sounding frame, and the sounding tion may be applied. frame may include long training fields (LTFs) as many as the 0038 FIG. 5 is a diagram exemplifying a constellation number of streams. for distinguishing a format of PPDU in a wireless commu 0026. According to still yet another aspect of the present nication system to which the present invention may be invention, an access point (AP) device for transmitting applied. multi-user uplink data in a wireless communication system, includes: a radio frequency (RF) unit for transmitting/ 0039 FIG. 6 exemplifies a MAC frame format in IEEE receiving a wireless signal; and a processor, wherein the 802.11 system to which the present invention may be processor may be configured to transmit a Sounding request applied. frame to a plurality of stations (STAs) which participate in 0040 FIG. 7 is a diagram illustrating a frame control field transmitting the multi-user uplink data, and receive a Sound in an MAC frame in the wireless communication system to ing frame from the STA in response to the Sounding request which the present invention may be applied. frame, the sounding request frame may include information 0041 FIG. 8 is a diagram for exemplifying a predeter indicating the number of streams in which the STA needs to mined back-off period and a frame transmission procedure transmit the Sounding frame, and the Sounding frame may in the wireless communication system to which the present include long training fields (LTFs) as many as the number of invention can be applied. StreamS. 0042 FIG. 9 is a diagram illustrating an IFS relationship 0027 Preferably, the method for transmitting multi-user in the wireless communication system to which the present uplink data may further include: transmitting, by the AP, a invention may be applied. polling frame to a second STA which participates in trans 0043 FIG. 10 illustrates a VHT format of an HT control mitting the multi-user uplink data in order to request trans field in the wireless communication system to which the mitting the Sounding frame; and receiving, by the AP, the present invention may be applied. Sounding frame from the second STA in response to the 0044 FIG. 11 is a diagram for conceptually describing a polling frame. channel sounding method in the wireless communication 0028 Preferably, the method for transmitting multi-user system to which the present invention can be applied. uplink data may further include allocating, by the AP an 004.5 FIG. 12 is a diagram illustrating a VHT NDPA uplink radio resource to the STA based on uplink channel frame in the wireless communication system to which the information measured through the Sounding frame. present invention may be applied. US 2017/017.0937 A1 Jun. 15, 2017
0046 FIG. 13 is a diagram illustrating an NDP PPDU in 0064 Specific terminologies used in the description the wireless communication system to which the present below may be provided to help the understanding of the invention may be applied. present invention. And, the specific terminology may be 0047 FIG. 14 is a diagram illustrating a VHT com modified into other forms within the scope of the technical pressed beam forming frame format in the wireless commu concept of the present invention. nication system to which the present invention may be 0065. The following technologies may be used in a applied. variety of wireless communication systems, such as code 0048 FIG. 15 is a diagram illustrating a beam forming division multiple access (CDMA), frequency division mul report poll frame format in the wireless communication tiple access (FDMA), time division multiple access system to which the present invention may be applied. (TDMA), orthogonal frequency division multiple access 0049 FIG. 16 is a diagram illustrating a Group ID (OFDMA), single carrier frequency division multiple access management frame in the wireless communication system to (SC-FDMA), and non-orthogonal multiple access (NOMA). which the present invention may be applied. CDMA may be implemented using a radio technology, Such 0050 FIG. 17 is a diagram illustrating a downlink multi as universal terrestrial radio access (UTRA) or CDMA2000. user PPDU format in the wireless communication system to TDMA may be implemented using a radio technology, Such which the present invention may be applied. as global system for Mobile communications (GSM)/gen 0051 FIG. 18 is a diagram illustrating a downlink MU eral packet radio service (GPRS)/enhanced data rates for MIMO transmission process in the wireless communication GSM evolution (EDGE). OFDMA may be implemented system to which the present invention may be applied. using a radio technology, Such as institute of electrical and 0052 FIGS. 19 to 23 are diagrams illustrating a high electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 efficiency (HE) format PPDU according to an embodiment (WiMAX), IEEE 802.20, or evolved UTRA (E-UTRA). of the present invention. UTRA is part of a universal mobile telecommunications 0053 FIG. 24 illustrates phase rotation for HE format system (UMTS). 3rd generation partnership project (3GPP) PPDU detection according to an embodiment of the present long term evolution (LTE) is part of an evolved UMTS invention. (E-UMTS) using evolved UMTS terrestrial radio access 0054 FIG. 25 is a diagram illustrating an uplink multi (E-UTRA), and it adopts OFDMA in downlink and adopts user transmission procedure according to an embodiment of SC-FDMA in uplink. LTE-advanced (LTE-A) is the evolu the present invention. tion of 3GPP LTE. 0055 FIG. 26 is a diagram illustrating the uplink multi 0.066 Embodiments of the present invention may be user transmission procedure according to an embodiment of Supported by the standard documents disclosed in at least the present invention. one of IEEE 802, 3GPP, and 3GPP2, that is, radio access 0056 FIG. 27 is a diagram illustrating a downlink PPDU systems. That is, steps or portions that belong to the embodi structure associated with uplink multi-user transmission ments of the present invention and that are not described in according to an embodiment of the present invention. order to clearly expose the technical spirit of the present 0057 FIG. 28 is a diagram illustrating a pre-procedure invention may be supported by the documents. Furthermore, for the uplink multi-user transmission according to an all terms disclosed in this document may be described by the embodiment of the present invention. standard documents. 0058 FIG. 29 is a diagram illustrating a pre-procedure 0067. In order to more clarify a description, IEEE 802.11 for the uplink multi-user transmission according to an is chiefly described, but the technical characteristics of the embodiment of the present invention. present invention are not limited thereto. 0059 FIG. 30 is a diagram illustrating a null data packet 0068 General System announcement (NDPA) frame according to an embodiment 0069 FIG. 1 is a diagram showing an example of an of the present invention. IEEE 802.11 system to which an embodiment of the present 0060 FIG. 31 is a diagram illustrating a pre-procedure invention may be applied. for the uplink multi-user transmission according to an (0070. The IEEE 802.11 configuration may include a embodiment of the present invention. plurality of elements. There may be provided a wireless 0061 FIG. 32 is a block diagram illustrating a wireless communication system Supporting transparent station (STA) apparatus according to an embodiment of the present inven mobility for a higher layer through an interaction between tion. the elements. A basic service set (BSS) may correspond to a basic configuration block in an IEEE 802.11 system. MODE FOR INVENTION (0071 FIG. 1 illustrates that three BSSs BSS 1 to BSS 3 0062 Hereinafter, a preferred embodiment of the present are present and two STAs (e.g., an STA 1 and an STA2 are invention will be described by reference to the accompany included in the BSS 1, an STA3 and an STA 4 are included ing drawings. The description that will be described below in the BSS 2, and an STA 5 and an STA 6 are included in the with the accompanying drawings is to describe exemplary BSS 3) are included as the members of each BSS. embodiments of the present invention, and is not intended to (0072. In FIG. 1, an ellipse indicative of a BSS may be describe the only embodiment in which the present inven interpreted as being indicative of a coverage area in which tion may be implemented. The description below includes STAs included in the corresponding BSS maintain commu particular details in order to provide perfect understanding nication. Such an area may be called a basic service area of the present invention. However, it is understood that the (BSA). When an STA moves outside the BSA, it is unable present invention may be embodied without the particular to directly communicate with other STAs within the corre details to those skilled in the art. sponding BSA. 0063. In some cases, in order to prevent the technical (0073. In the IEEE 802.11 system, the most basic type of concept of the present invention from being unclear, struc a BSS is an independent a BSS (IBSS). For example, an tures or devices which are publicly known may be omitted, IBSS may have a minimum form including only two STAs. or may be depicted as a block diagram centering on the core Furthermore, the BSS3 of FIG. 1 which is the simplest form functions of the structures or the devices. and from which other elements have been omitted may US 2017/017.0937 A1 Jun. 15, 2017
correspond to a representative example of the IBSS. Such a system, a network of Such a method is called an extended configuration may be possible if STAS can directly commu service set (ESS) network. The ESS may correspond to a set nicate with each other. Furthermore, a LAN of such a form of BSSs connected to a single DS. However, the ESS does is not previously planned and configured, but may be not include a DS. The ESS network is characterized in that configured when it is necessary. This may also be called an it looks like an IBSS network in a logical link control (LLC) ad-hoc network. layer. STAs included in the ESS may communicate with 0074. When an STA is powered off or on oran STA enters each other. Mobile STAs may move from one BSS to the into or exits from a BSS area, the membership of the STA other BSS (within the same ESS) in a manner transparent to in the BSS may be dynamically changed. In order to become the LLC layer. a member of a BSS, an STA may join the BSS using a I0082 In an IEEE 802.11 system, the relative physical synchronization process. In order to access all of services in positions of BSSs in FIG. 1 are not assumed, and the a BSS-based configuration, an STA needs to be associated following forms are all possible. with the BSS. Such association may be dynamically con I0083. More specifically, BSSs may partially overlap, figured, and may include the use of a distribution system which is a form commonly used to provide consecutive service (DSS). coverage. Furthermore, BSSs may not be physically con 0075. In an 802.11 system, the distance of a direct nected, and logically there is no limit to the distance between STA-to-STA may be constrained by physical layer (PHY) BSSs. Furthermore, BSSs may be placed in the same posi performance. In any case, the limit of Such a distance may tion physically and may be used to provide redundancy. be sufficient, but communication between STAs in a longer Furthermore, one (or one or more) IBSS or ESS networks distance may be required, if necessary. In order to Support may be physically present in the same space as one or more extended coverage, a distribution system (DS) may be ESS networks. This may correspond to an ESS network configured. form if an ad-hoc network operates at the position in which 0076. The DS means a configuration in which BSSs are an ESS network is present, if IEEE 802.11 networks that interconnected. More specifically, a BSS may be present as physically overlap are configured by different organizations, an element of an extended form of a network including a or if two or more different access and security policies are plurality of BSSs instead of an independent BSS as in FIG. required at the same position. 1 I0084. In a WLAN system, an STA is an apparatus oper 0077. The DS is a logical concept and may be specified ating in accordance with the medium access control (MAC)/ by the characteristics of a distribution system medium PHY regulations of IEEE 802.11. An STA may include an (DSM). In the IEEE 802.11 standard, a wireless medium AP STA and a non-AP STA unless the functionality of the (WM) and a distribution system medium (DSM) are logi STA is not individually different from that of an AP. In this cally divided. Each logical medium is used for a different case, assuming that communication is performed between an purpose and used by a different element. In the definition of STA and an AP, the STA may be interpreted as being a the IEEE 802.11 standard, such media are not limited to the non-APSTA. In the example of FIG. 1, the STA 1, the STA same one and are also not limited to different ones. The 4, the STA5, and the STA 6 correspond to non-APSTAS, and flexibility of the configuration (i.e., a DS configuration or the STA 2 and the STA3 correspond to AP STAs. another network configuration) of an IEEE 802.11 system I0085. A non-APSTA corresponds to an apparatus directly may be described in that a plurality of media is logically handled by a user, Such as a laptop computer or a mobile different as described above. That is, an IEEE 802.11 system phone. In the following description, a non-APSTA may also configuration may be implemented in various ways, and a be called a wireless device, a terminal, user equipment (UE), corresponding system configuration may be independently a mobile station (MS), a mobile terminal, a wireless termi specified by the physical characteristics of each implemen nal, a wireless transmit/receive unit (WTRU), a network tation example. interface device, a machine-type communication (MTC) 0078. The DS can support a mobile device by providing device, a machine-to-machine (M2M) device or the like. the seamless integration of a plurality of BSSs and providing I0086. Furthermore, an AP is a concept corresponding to logical services required to handle an address to a destina a base station (BS), a node-B, an evolved Node-B (eNB), a tion. base transceiver system (BTS), a femto BS or the like in 0079 An AP means an entity which enables access to a other wireless communication fields. DS through a WM with respect to associated STAs and has I0087 Hereinafter, in this specification, downlink (DL) the STA functionality. The movement of data between a BSS means communication from an AP to a non-APSTA. Uplink and the DS can be performed through an AP For example, (UL) means communication from a non-AP STA to an AP. each of the STA 2 and the STA 3 of FIG. 1 has the In DL, a transmitter may be part of an AP, and a receiver may functionality of an STA and provides a function which be part of a non-APSTA. In UL, a transmitter may be part enables associated STAs (e.g., the STA 1 and the STA4) to of a non-APSTA, and a receiver may be part of an AP. access the DS. Furthermore, all of APs basically correspond I0088 FIG. 2 is a diagram exemplifying a structure of to an STA, and thus all of the APs are entities capable of layer architecture in IEEE 802.11 system to which the being addressed. An address used by an AP for communi present invention may be applied. cation on a WM and an address used by an AP for commu I0089 Referring to FIG. 2, the layer architecture in the nication on a DSM may not need to be necessarily the same. IEEE 802.11 system may include Medium Access Control 0080 Data transmitted from one of STAs, associated (MAC) sublayer/layer and PHY sublayer/layer. with an AP, to the STA address of the AP may be always (0090. The PHY sublayer (220) may be divided into a received by an uncontrolled port and processed by an IEEE Physical Layer Convergence Procedure (PLCP) entity and a 802.1X port access entity. Furthermore, when a controlled Physical Medium Dependent (PMD) entity. In this case, the port is authenticated, transmission data (or frame) may be PLCP entity performs a role of connecting the MAC sub delivered to a DS. layer and a data frame, and the PMD entity performs a role 0081. A wireless network having an arbitrary size and of wirelessly transmitting and receiving data with two or complexity may include a DS and BSSs. In an IEEE 802.11 more STAs. US 2017/017.0937 A1 Jun. 15, 2017
0091. Both of the MAC sublayer (210) and the PHY the A-MPDU. PHY sublayer (220) receives the A-MPDU Sublayer (220) may include management entities, and each from MAC sublayer (210) as a single PSDU. That is, the of them may be referred to MAC Sublayer Management PSDU includes a plurality of MPDUs. Accordingly, the Entity (MLME, 230) and Physical Sublayer Management A-MPDU is transmitted through a wireless medium within Entity (PLME, 240), respectively. These management enti a single PPDU. ties (230, 240) provide a layer management service interface 0100 Physical Protocol Data Unit (PPDU) Format through an operation of layer management function. The 0101 A Physical Protocol Data Unit (PPDU) signifies a MLME (230) may be connected to the PLME (240), and data block which is generated in physical layer. Hereinafter, perform a management operation of MAC Sublayer (21), the PPDU format will be described based on IEEE 802.11 and similarly, the PLME (240) may be connected to the WLAN system to which the present invention may be MLME (230), and perform a management operation of PHY applied. sublayer (220). 0102 FIG. 3 exemplifies a non-HT format PPDU and an 0092. In order to provide an accurate MAC operation, a HT format PPDU of a wireless communication system to Station Management Entity (SME, 250) may be existed in which the present invention may be applied. each STA. The SME (250) is a management entity indepen 0103 FIG. 3(a) exemplifies the non-HT format for Sup dent from each layer, and collects layer based state infor porting IEEE 802.11a/g system. The non-HT PPDU may mation from the MLME (230) and the PLME (240) or also be called a legacy PPDU. configures a specific parameter value of each layer. The 0104 Referring to FIG. 3(a), the non-HT format PPDU SME (250) may perform such a function by substituting includes a legacy format preamble that includes a Legacy (or general system management entities, and may implement a Non-HT) Short Training field (L-STF), a Legacy (or Non standard management protocol. HT) Long Training field (L-LTF) and a Legacy (or Non-HT) 0093. The MLME (230), the PLME (240) and the SME SIGNAL (L-SIG) field, and a data field. (250) may interact in various methods based on a primitive. 0105. The L-STF may include a short training orthogonal Particularly, XX-GET request primitive is used for request frequency division multiplexing (OFDM). The L-STF may ing a Management Information Base (MIB) attribute value. be used for frame timing acquisition, Automatic Gain Con XX-GET.confirm primitive returns the corresponding MIB trol (AGC), diversity detection and coarse frequency/time attribute value when the state of it is in SUCCESS, synchronization. otherwise, returns a state field with an error mark. XX-SET. request primitive is used for requesting to configure a 0106 The L-LTF may include a long training orthogonal designated MIB attribute to a given value. When the MIB frequency division multiplexing (OFDM) symbol. The attribute signifies a specific operation, the request requests L-LTF may be used for fine frequency/time synchronization an execution of the specific operation. And, when a state of and channel estimation. XX-SET request primitive is in SUCCESS, this means that 0107 The L-SIG field may be used for transmitting the designated MIB attribute is configured as the requested control information for demodulating and decoding a data value. When the MIB attribute signifies a specific operation, field. The L-SIG field may include information on a data rate the primitive is able to verify that the corresponding opera and a data length. tion is performed. (0.108 FIG. 3(b) exemplifies an HT-mixed format PPDU 0094. The operation in each sublayer will be briefly for supporting both IEEE 802.11n system and IEEE 802. described as follows. 11a/g system. 0095 MAC sublayer (210) generates one or more MAC 0109 Referring to FIG.3(b), the HT-mixed format PPDU Protocol Data Unit (MPDU) by attaching a MAC header and includes an HT format preamble that includes a legacy Frame Check Sequence (FCS) to a MAC Service Data Unit format preamble including the L-STF, the L-LTF and the (MSDU) delivered from a higher layer (e.g., LLC layer) or L-SIG field, an HT-Signal (HT-SIG) field, an HT Short a fragment of the MSDU. The generated MPDU is delivered Training field (HT-STF) and an HT Long Training field to PHY sublayer (220). (HT-LTF), and a data field. 0096. When an aggregated MSDU (A-MSDU) scheme is 0110 Since the L-STF, the L-LTF and the L-SIG field used, a plurality of MSDUs may be merged into one signify legacy fields for backward compatibility, the fields A-MSDU. The MSDU merging operation may be performed from the L-STF to the L-SIG field are identical to those of in a MAC higher layer. The A-MSDU is delivered to PHY the non-HT format. The L-STA may interpret a data field sublayer (220) as a single MPDU (i.e., not being frag through the L-STF, the L-LTF and the L-SIG field even mented). though the L-STA receives a HT-mixed PPDU. However, the 0097 PHY sublayer (220) generates a Physical Protocol L-LTF may further include information for channel estima Data Unit (PPDU) by attaching an additional field that tion Such that an HT-STA receives the HT-mixed PPDU and includes required information to a Physical Service Data demodulates the L-SIG field and the HT-SIG field. Unit (PSDU) received from MAC sublayer (210) by a 0111. The HT-STA may notice that the field behind the physical layer transceiver. The PPDU is transmitted through legacy field is the HT-mixed format PPDU using the HT-SIG a wireless medium. field, and based on this, the HT-STA may decode the data 0098. Since the PSDU is a unit that PHY sublayer (220) field. receives from MAC sublayer (210) and MPDU is a unit that 0112 The HT-LTF field may be used for channel estima MAC sublayer (210) transmits to PHY sublayer (220), the tion for demodulating the data field. Since IEEE 802.11n PSDU is the same as the MPDU, substantially. standard supports Single-User Multi-Input and Multi-Output 0099. When an aggregated MPDU (A-MPDU) scheme is (SU-MIMO), a plurality of the HT-LTF fields may be used, a plurality of MPDUs (in this case, each MPDU may included for the channel estimation with respect to each data carry the A-MPDU) may be merged into a single A-MPDU. field transmitted via a plurality of spatial streams. The MPDU merging operation may be performed in a MAC 0113. The HT-LTF field may include a data HT-LTF used lower layer. Various types of MPDU (e.g., QoS data, for channel estimation with respect to spatial stream and an Acknowledge (ACK), block ACK, etc.) may be merged into extension HT-LTF additionally used for full channel sound US 2017/017.0937 A1 Jun. 15, 2017
ing. Accordingly, the number of a plurality of HT-LTF may simultaneously, the size of transmitted control information be equal to or more than the number of transmitted spatial may increase as the number of STAs that receive the control Stream. information. 0114. In the HT-mixed format PPDU, the L-STF, the L-LTF and the L-SIG field are firstly transmitted such that I0129. As such, in order to effectively transmit the increas an L-STA also receives and acquires data. Later, the HT-SIG ing size of the control information, a plurality of control field is transmitted for demodulating and decoding the data information required for the MU-MIMO transmission may transmitted for the HT-STA. be transmitted by being classified into common control 0115 Up to the HT-SIG field, fields are transmitted information commonly required for all STAs and dedicated without performing beam forming such that the L-STA and control information individually required for a specific STA. the HT-STA receive the corresponding PPDU and acquire I0130 FIG. 4 exemplifies a VHT format PPDU of a data, and wireless signal transmission is performed through wireless communication system to which the present inven precoding for the HT-STF, the HT-LTF and the data field, tion may be applied. which are transmitted later. Herein, the plurality of HT-LTF and the data field are transmitted after transmitting the I0131 Referring to FIG. 4, the VHT format PPDU HT-STF such that the STA that receives data through pre includes a legacy format preamble that includes the L-STF, coding may consider the part in which power is varied by the L-LTF and the L-SIG field and a VHT format preamble precoding. that includes a VHT-Signal-A (VHT-SIG-A) field, a VHT 0116 FIG. 3(c) exemplifies an HT-greenfield (HT-GF) Short Training field (VHT-STF), a VHT Long Training field format PPDU for supporting IEEE 802.11n system only. (VHT-LTF) and a VHT-Signal-B (VHT-SIG-B) field and a 0117 Referring to FIG. 3(c), the HT-GF format PPDU data field. includes an HT-GF-STF, an HT-LTF1, an HT-SIG field, a plurality of HT-LTF2 and a data field. (0132 Since the L-STF, the L-LTF and the L-SIG field 0118. The HT-GF-STF is used for frame time acquisition signify legacy fields for backward compatibility, the fields and AG.C. from the L-STF to the L-SIG field are identical to those of 0119 The HT-LTF1 is used for channel estimation. the non-HT format. However, the L-LTF may further include 0120. The HT-SIG field is used for demodulating and information for channel estimation to be performed to decoding the data field. demodulate the L-SIG field and the VHT-SIG-A field. 0121. The HT-LTF2 is used for channel estimation for 0133. The L-STF, the L-LTF, the L-SIG field and the demodulating the data field. Similarly, since the HT-STA VHT-SIG-A field may be repeatedly transmitted in a unit of requires channel estimation for each data field transmitted 20 MHZ channel. For example, when a PPDU is transmitted via a plurality of spatial streams due to the use of SU through four 20 MHZ channels (i.e., 80 MHz bandwidth), MIMO, a plurality of HT-LTF2 may be included. the L-STF, the L-LTF, the L-SIG field and the VHT-SIG-A 0122) The plurality of HT-LTF2 may include a plurality field may be repeatedly transmitted in every 20 MHZ chan of DATA HT-LTF and a plurality of extension HT-LTF, nel. similar to the HT-LTF field of the HT-mixed PPDU. 0123. In FIGS. 3(a) to 3(c), the data field is a payload, I0134) The VHT-STA may be aware whether the PPDU is and the data field may include a SERVICE field, a scrambled the VHT format PPDU using the VHT-SIG-A field which PSDU field, Tail bits, and padding bits. follows the legacy field, and based on this, the VHT-STA 0.124. In order to effectively utilize radio channels, IEEE may decode the data field. 802.11ac WLAN system supports a transmission of down 0135) In the VHT format PPDU, the L-STF, the L-LTF link Multi User Multiple Input Multiple Output (MU and the L-SIG field are firstly transmitted such that an MIMO) scheme in which a plurality of STAs access channel simultaneously. According to the MU-MIMO transmission L-STA also receives and acquires data. Later, the VHT scheme, an AP may transmit packets to one or more STAS SIG-A field is transmitted for demodulating and decoding that are paired by MIMO simultaneously. the data transmitted for the VHT-STA. 0.125. A downlink multi-user (DL MU) transmission I0136. The VHT-SIG-A field is a field for transmitting means a technique that an AP transmits a PPDU to a plurality common control information between VHT STAs paired of non-AP STAs through the same time resource through with an AP in MIMO scheme, and includes the control One Or more antenna S. information for interpreting the received VHT format 0.126 Hereinafter, the MU PPDU means a PPDU that PPDU. transmits one or more PSDUs for one or more STAs using the MU-MIMO technique or the OFDMA technique. And I0137 The VHT-SIG-A field may include a VHT-SIG-A1 the SU PPDU means a PPDU which is available to deliver field and a VHT-SIG-A2 field. only one PSDU or a PPDU that has a format in which the (0.138. The VHT-SIG-A1 field may include channel band PSDU is not existed. width (BW) information to use, information on whether to 0127. For the MU-MIMO transmission, the size of the apply Space Time Block Coding (STBC), Group Identifier control information transmitted to an STA may be relatively (Group ID) information for indicating a group of STAs that greater than that of the control information based on 802. are grouped in MU-MIMO scheme, information of the 11n. Examples of the control information additionally Number of space-time stream (NSTS) to use/Partial asso required for supporting the MU-MIMO may include infor ciation Identifier (AID) and Transmit power save forbidden mation indicating the number of spatial stream received by information. Herein, the Group ID may signify an identifier each STA, the information related to modulating and coding allocated to an STA group which is to be transmitted for the data transmitted to each STA, and the like. supporting MU-MIMO transmission, and may represent 0128. Accordingly, when the MU-MIMO transmission is whether the currently used MIMO transmission scheme is performed for providing data service to a plurality of STAs MU-MIMO or SU-MIMO. US 2017/017.0937 A1 Jun. 15, 2017
0139 Table 1 below exemplifies the VHT-SIG-A1 field. TABLE 1. Field Bit Description BW 2 he case of 20 MHz, set to O, he case of 40 MHz, set to 1, he case of 80 MHz, set to 2, he case of 160 MHz or 80 + 80 MHz, set to 3. Reserved 1 STBC 1 he case of VHTSU PPDU: he case that STBC is used, set to 1, herwise, set to 'O he case of VHT MUPPDU: to O Group ID 6 icate Group ID *O or 63 indicates VHT SU PPDU, otherwise indicates VHT MU PPDU NSTS Partial AID 12 In the case of VHT MU PPDU, divided by 4 user position p each having 3 bits he case that space time stream is 0, set to 0, he case that space time stream is 1, set to 1, he case that space time stream is 2, set to 2, he case that space time stream is 3, set to 3, he case that space time stream is 4, set to 4. he case of VHT SU PPDU, 3 bits are set as follows. he case that space time stream is 1, set to 0, he case that space time stream is 2, set to 1, he case that space time stream is 3, set to 2, he case that space time stream is 4, set to 3, he case that space time stream is 5, set to 4, he case that space time stream is 6, set to 5, he case that space time stream is 7, set to 6, he case that space time stream is 8, set to 7, Bottom 9 bits indicate Partial AID. TXOP PS NOT ALLOWED 1 When a VHT AP allows non-AP VHT STA shifted top a power save mode for transmission opportunity (TXOP), set to 0. Otherwise, set to 1. in the case of a VHT PPDU transmitted by non-AP VHT STA, Set to 1. Reserved 1
0140. The VHT-SIG-A2 field may include information ing related information, redundancy bits for Cyclic Redun on whether to use a short Guard Interval (GI). Forward Error dancy Checking (CRC), a tail bit of convolutional decoder, Correction (FEC) information, information on Modulation and the like and Coding Scheme (MCS) for a single user, information on types of channel coding for a plurality of users, beam form- 0141 Table 2 below exemplifies the VHT-SIG-A2 field. TABLE 2 Field Bit Description Short GI 1 In the case that short GI is not used in a data field, set to o, in the case that short GI is used in a data field, set to 1. Short GI 1 In the case that short GI is used and an additional symbol disambiguation is required for a payload of PPDU, set to 1, in the case that an additional symbol is not required, set to “O. SU/MU Coding 1 In the case of VHT SUPPDU: in the case of BCC(binary convolutional code), set to 0, he case of LDPC (low-density parity check), set to 1. he case of VHT MUPPDU: he case that NSTS field of which user position is '0' is not O, indicates coding to use. in the case of BCC, set to O, in the case of LDPC, set to 1. in the case that NSTS field of which user position is 0 is O, set to 1 as a reserved field. LDPC Extra OFDM 1 In the case that an additional extra OFDM symbol is Symbol required owing to LDPC PPDU encoding procedure (in the case of SU PPDU) or PPDU encoding procedure of at least one LDPC user (in the case of VHT MU PPDU), set to 1. Otherwise, set to O. US 2017/017.0937 A1 Jun. 15, 2017
TABLE 2-continued Field Bit Description SU VEHT MCSMU 4 In the case of VHT SUPPDU: Coding Represents VHT-MCS index. in the case of VHT MUPPDU: indicates coding for user positions 1 to 3 in an order of ascending order from top bit. in the case that NSTS field of each user is not “1, indicates coding to use. in the case of BCC, set to O, in the case of LDPC, set to 1. in the case that NSTS field of each user is 0, set to 1 as a reserved field. Beamformed 1 In the case of VHT SUPPDU: in the case that Beamforming steering matrix is applied to SU transmission, set to 1. Otherwise, set to 'O' in the case of VHT MUPPDU: Set to 1 as a reserved field. Reserved 1 CRC 8 Include CRC for detecting error of PPDU in receiver Tail 6 Used for trellis end of convolutional decoder Set to O.
0142. The VHT-STF is used for improving the perfor 0.148. The data field in FIG. 4 is a payload, and may mance of AGC estimation in MIMO transmission. include a SERVICE field, a scrambled PSDU, tail bits and 0143. The VHT-LTF is used for a VHT-STA to estimate padding bits. a MIMO channel. Since a VHT WLAN system support the 0149. As such, since several formats of PPDU are used in MU-MIMO, the VHT-LTF may be setup as much as the a mixed manner, an STA should be able to distinguish a number of spatial streams through which a PPDU is trans format of received PPDU. mitted. Additionally, in the case that full channel sounding (O150 Herein, the meaning of distinguishing PPDU (or is supported, the number of VHT-LTFs may increase. classifying the format of PPDU) may have various mean 0144. The VHT-SIG-B field includes dedicated control ings. For example, the meaning of distinguishing PPDU may information required to acquire data for a plurality of have a meaning of determining whether the received PPDU VHT-STAs paired in MU-MIMO scheme by receiving a is a PPDU that is available to be decoded (or interpreted) by PPDU. Accordingly, only in the case that the common an STA. In addition, the meaning of distinguishing PPDU control information included in the VHT-SIG-A field indi may have a meaning of determining whether the received cates a MU-MIMO transmission by a PPDU which is PPDU is a PPDU that is available to be supported by an currently received, a VHT-STA may be designed to decode STA. Further, the meaning of distinguishing PPDU may be the VHT-SIG-B field. On the contrary, in the case that the interpreted as a meaning of classifying what the information common control information indicates that a PPDU cur is that is transmitted through the received PPDU. rently received is for a single VHT-STA (including SU 0151. This will be described in more detail by reference MIMO), an STA may be designed not to decode the VHT to the drawing below. SIG-B field. 0152 FIG. 5 is a diagram exemplifying a constellation for distinguishing a format of PPDU in a wireless commu (0145 The VHT-SIG-B field includes information on nication system to which the present invention may be modulation, encoding and rate-matching of each of the applied. VHT-STAs. A size of the VHT-SIG-B field may be different (O153 FIG. 5(a) exemplifies a constellation of an L-SIG depending on types of MIMO transmission (MU-MIMO or field included in a non-HT format PPDU and FIG. 5(b) SU-MIMO) and channel bandwidths which are used for exemplifies a phase rotation for detecting an HT-mixed PPDU transmissions. format PPDU. And FIG. 5(c) exemplifies a phase rotation 0146 In order to transmit PPDUs of the same size to for detecting a VHT format PPDU. STAs paired with an AP in a system that supports the 0154) In order for an STA to distinguish the non-HT MU-MIMO, information indicating a bit size of a data field format PPDU, the HT-GF format PPDU, the HT-mixed that configures the PPDU and/or information indicating a bit format PPDU and the VHT format PPDU, a phase of stream size that configures a specific field may be included constellation of the L-SIG field and the OFDM symbol in the VHT-SIG-A field. transmitted after the L-SIG field are used. That is, the STA 0147. However, in order to efficiently use the PPDU may classify a PPDU format based on the phase of constel format, the L-SIG field may be used. In order for the PPDUs lation of the L-SIG field and the OFDM symbol transmitted of the same size to be transmitted to all STAs, a length field after the L-SIG field. and a rate field transmitted with being included in the L-SIG (O155 Referring to FIG. 5(a), the OFDM symbol that field may be used for providing required information. In this configures the L-SIG field utilizes Binary Phase Shift Key case, since a MAC Protocol Data Unit (MPDU) and/or an ing (BPSK). Aggregate MAC Protocol Data Unit (A-MPDU) are config 0156 First, in order to distinguish the HT-GF format ured based on bytes (or octet (oct)) of the MAC layer, an PPDU, when an initial SIG field is detected in a received additional padding may be required in the physical layer. PPDU, an STA determines whether the SIG field is the US 2017/017.0937 A1 Jun. 15, 2017
L-SIG field. That is, the STA tries to decode based on the (0169. The MAC Header is defined by regions that include constellation example shown in FIG. 5(a). When the STA Frame Control field, Duration/ID field, Address 1 field, fail to decode, it may be determined that the corresponding Address 2 field, Address 3 field, Sequence Control field, PPDU is the HT-GF format PPDU. Address 4 field, QoS Control field and HT Control field. (O157 Next, in order to classify the non-HT format (0170 The Frame Control field includes information on PPDU, the HT-mixed format PPDU and the VHT format characteristics of the corresponding MAC frame. Detailed PPDU, the phase of constellation of the OFDM symbol description for the Frame Control field will be described transmitted after the L-SIG field may be used. That is, the below. modulation method of the OFDM symbol transmitted after 0171 The Duration/ID field may be implemented to have the L-SIG field may be different, and the STA may classify different values according to a type and a Subtype of the the PPDU formats based on the modulation method for the corresponding MAC frame. field after the L-SIG field of the received PPDU. 0172. In the case that a type and a subtype of the 0158 Referring to FIG. 5(b), in order to distinguish the corresponding MAC frame is a PS-Poll frame for the power HT-mixed format PPDU, the phase of two OFDM symbols save (PS) operation, the Duration/ID field may be config transmitted after the L-SIG field in the HT-mixed format ured to include an association identifier of the STA that PPDU may be used. transmits the frame. In other case, the Duration/ID field may 0159 More particularly, the phases of both OFDM sym be configured to have a specific duration value depending on bol #1 and OFDM symbol #2 that correspond to the HT-SIG the corresponding type and subtype of the MAC frame. In field transmitted after the L-SIG field in the HT-mixed addition, in the case that the frame is an MPDU included in format PPDU rotate as much as 90 degrees in counter-clock the aggregate-MPDU (A-MPDU) format, all of the Dura wise direction. That is, the modulation method for OFDM tion/ID fields included in the MAC header may be config symbol #1 and OFDM symbol #2 uses Quadrature Binary ured to have the same value. Phase Shift Keying (QBPSK). The QBPSK constellation may be a constellation of which phase rotates as much as 90 (0173 Address 1 field to Address 4 field are used to degrees in counter-clock wise direction with respect to the indicate BSSID, source address (SA), destination address BPSK constellation. (DA), transmitting address (TA) representing an address of (0160. An STA tries to decode OFDM symbol #1 and a transmission STA and a receiving address (RA) represent OFDM symbol #2 that correspond to the HT-SIG field ing an address of a reception STA. transmitted after the L-SIG field of the received PPDU based (0174 Meanwhile, the address field implemented as the on the constellation example shown in FIG. 5(b). When the TA field may be set to a bandwidth signaling TA value. In STA is successful in decoding, the STA determines the this case, the TA field may indicate that the corresponding corresponding PPDU to be the HT format PPDU. MAC frame has additional information to the scrambling 0161 Next, in order to distinguish the non-HT format sequence. Although the bandwidth signaling TA may be PPDU and the VHT format PPDU, the phase of constellation represented as a MAC address of the STA that transmits the of the OFDM symbol transmitted after the L-SIG field may corresponding MAC frame, Individual/Group bit included in be used. the MAC address may be set to a specific value (e.g., 1). 0162 Referring to FIG. 5(c), in order to distinguish the 0.175. The Sequence Control field is configured to include VHT format PPDU, the phases of two OFDM symbols a sequence number and a fragment number. The sequence transmitted after the L-SIG field in the VHT format PPDU number may indicate the number of sequence allocated to may be used. the corresponding MAC frame. The fragment number may (0163 More particularly, the phase of OFDM symbol #1 indicate the number of each fragment of the corresponding that corresponds to the VHT-SIG-A field after the L-SIG MAC frame. field in the VHT format PPDU does not rotate, but the phase 0176 The QoS Control field includes information related of OFDM symbol #2 rotates as much as 90 degrees in to QoS. The QoS control field may be included in the case counter-clock wise direction. That is, the modulation that a QoS data frame is indicated in a Subtype subfield. method for OFDM symbol #1 uses the BPSK and the 0177. The HT Control filed includes control information modulation method for OFDM symbol #2 uses the QBPSK. related to HT and/or VHT transmission and reception tech (0164. An STA tries to decode OFDM symbol #1 and niques. The HT Control field is included in Control Wrapper OFDM symbol #2 that correspond to the VHT-SIG field frame. Further, the HT Control field is existed in the QoS transmitted after the L-SIG field of the received PPDU based data frame of which Order subfield value is 1, and existed in on the constellation example shown in FIG. 5(c). When the Management frame. STA is successful in decoding, the STA may determine the 0.178 The Frame Body is defined as a MAC payload, and corresponding PPDU to be the VHT format PPDU. data to be transmitted in a higher layer is located therein. 0.165. On the other hand, when the STA fails to decode, And the Frame body has a variable size. For example, a the STA may determine the corresponding PPDU to be the maximum size of MPDU may be 11454 octets, and a non-HT format PPDU. maximum size of PPDU may be 5.484 ms. (0166 MAC Frame Format 0179 The FCS is defined as a MAC footer, and used for (0167 FIG. 6 exemplifies a MAC frame format in IEEE searching an error of the MAC frame. 802.11 system to which the present invention may be 0180 First three fields (the Frame Control field, the applied. Duration/ID field and the Address 1 field) and the last field (0168 Referring to FIG. 6, a MAC frame (i.e., MPDU) (FCS field) configure a minimum frame format, and are includes a MAC Header, a Frame Body and a frame check existed in all frames. Other fields may be existed in a specific sequence (FCS). frame type. US 2017/017.0937 A1 Jun. 15, 2017
0181 FIG. 7 is a diagram illustrating a frame control field MAC frame to be additionally transmitted exists, the More in an MAC frame in the wireless communication system to Data subfield may be set to 1 and if not, the More Data which the present invention may be applied. subfield may be set to 0. 0182 Referring to FIG. 7, the frame control field is (0194 The Protected Frame subfield may indicate comprised of a Protocol Version subfield, a Type sub field, whether a frame body field is encrypted. When the frame a Subtype subfield, a To DS subfield, a From DS subfield, a body field includes information processed by a crypto More Fragments subfield, a Retry subfield, a Power Man graphic encapsulation algorithm, the Protected Frame Sub agement subfield, a More Data subfield, a Protected Frame field may be set to 1 and if not, the Protected Frame subfield, and an Order subfield. subfield may be set to 0. 0183 The Protocol Version subfield may indicate a ver 0.195. The information included in the aforementioned sion of a WLAN protocol applied to the corresponding MAC respective fields may follow a definition of the IEEE 802.11 frame. system. Further, the respective fields correspond to 0184 The Type subfield and the Subtype subfield may be examples of the fields which may be included in the MAC set to indicate information identify a function of the corre frame and are not limited thereto. That is, each field may be sponding MAC frame. substituted with another field or further include an additional 0185. A type of the MAC frame may include three frame field and all fields may not be requisitely included. types of a management frame, a control frame, and a data Medium Access Mechanism frame. (0196) 0186. In addition, each of the frame types may be divided (0197). In IEEE 802.11, communication is basically dif into Subtypes again. ferent from that of a wired channel environment because it 0187. For example, the control frames may include a is performed in a shared wireless medium. request to send (RTS) frame, a clear-to-send (CTS) frame, an 0.198. In a wired channel environment, communication is acknowledgment (ACK) frame, a PS-Poll frame, a conten possible based on carrier sense multiple access/collision tion free (CF)-End frame, a CF-End--CF-ACK frame, a detection (CSMA/CD). For example, when a signal is once block ACK request (BAR) frame, a block acknowledgement transmitted by a transmission stage, it is transmitted up to a (BA) frame, a control wrapper (Control+HTcontrol) frame, reception stage without experiencing great signal attenua null data packet announcement (NDPA), and a beam forming tion because there is no great change in a channel environ report poll frame. ment. In this case, when a collision between two or more 0188 The management frames may include a beacon signals is detected, detection is possible. The reason for this frame, an announcement traffic indication message (ATIM) is that power detected by the reception stage becomes frame, a dissociation frame, an association request/response instantly higher than power transmitted by the transmission frame, a reassociation request/response frame, a probe stage. In a radio channel environment, however, since vari request/response frame, an authentication frame, a deau ous factors (e.g., signal attenuation is great depending on the thentication frame, an action frame, an action No ACK distance or instant deep fading may be generated) affect a frame, and a timing advertisement frame. channel, a transmission stage is unable to accurately perform (0189 The To DS subfield and the From DS subfield may carrier sensing regarding whether a signal has been correctly include information required for interpreting an Address 1 transmitted by a reception stage or a collision has been field to an Address 4 field included in the corresponding generated. MAC frame header. In the case of the Control frame, both 0199 Accordingly, in a WLAN system according to the To DS Subfield and the From DS Subfield are set to 0. IEEE 802.11, a carrier sense multiple access with collision In the case of the Management frame, both the To DS avoidance (CSMA/CA) mechanism has been introduced as subfield and the From DS subfield may be sequentially set the basic access mechanism of MAC. The CAMA/CA to 1 and 0 when the corresponding frame is a QoS mechanism is also called a distributed coordination function management frame (QMF) and both the To DS subfield and (DCF) of IEEE 802.11 MAC, and basically adopts a “listen the From DS subfield may be sequentially set to 0 and 0 before talk access mechanism. In accordance with Such a when the corresponding frame is not the QMF. type of access mechanism, an AP and/or an STA perform 0190. The More Fragments subfield may indicate clear channel assessment (CCA) for sensing a radio channel whether a fragment to be transmitted subsequently to the or a medium for a specific time interval (e.g., a DCF corresponding MAC frame exists. When another fragment inter-frame space (DIFS)) prior to transmission. If, as a of the MSDU or MMPDU exists, the More Fragments result of the sensing, the medium is determined to be an idle subfield may be set to 1 and if not, the More Fragments state, the AP and/or the STA starts to transmit a frame subfield may be set to 0. through the corresponding medium. In contrast, if as a result 0191 The Retry subfield may indicate whether the cor of the sensing, the medium is determined to be a busy state responding MAC frame depends on retransmission of the (or an occupied status), the AP and/or the STA do not start previous MAC frame. In the case of retransmission of the their transmission, may wait for a delay time (e.g., a random previous MAC frame, the Retry subfield may be set to 1 backoff period) for medium access in addition to the DIFS and if not, the Retry subfield may be set to 0. assuming that several STAs already wait for in order to use 0.192 The Power Management subfield may indicate a the corresponding medium, and may then attempt frame power management mode of the STA. When a Power transmission. Management subfield value is 1, the corresponding Power 0200 Assuming that several STAs trying to transmit Management subfield value may indicate that the STA may frames are present, they will wait for different times because be switched to a power save mode. the STAs stochastically have different backoff period values (0193 The More Data subfield may indicate whether the and will attempt frame transmission. In this case, a collision MAC frame to be additionally transmitted exists. When the can be minimized by applying the random backoff period. US 2017/017.0937 A1 Jun. 15, 2017
0201 Furthermore, the IEEE 802.11 MAC protocol pro (0208. The STA 1 and the STA5 stop countdown and wait vides a hybrid coordination function (HCF). The HCF is while the STA2 occupies the medium. When the occupation based on a DCF and a point coordination function (PCF). of the medium by the STA is finished and the medium The PCF is a polling-based synchronous access method, and becomes an idle state again, each of the STA 1 and the STA refers to a method for periodically performing polling so that 5 waits for a DIFS and resumes the stopped backoff count. all of receiving APs and/or STAs can receive a data frame. That is, each of the STA 1 and the STA 5 may start frame Furthermore, the HCF has enhanced distributed channel transmission after counting down the remaining backoff slot access (EDCA) and HCF controlled channel access corresponding to the remaining backoff time. The STA 5 (HCCA). In EDCA, a provider performs an access method starts frame transmission because the STA 5 has a shorter for providing a data frame to multiple users on a contention remaining backoff time than the STA 1. basis. In HCCA, a non-contention-based channel access (0209 While the STA 2 occupies the medium, data to be method using a polling mechanism is used. Furthermore, the transmitted by an STA4 may be generated. In this case, from HCF includes a medium access mechanism for improving a standpoint of the STA4, when the medium becomes an idle the quality of service (QoS) of a WLAN, and may transmit state, the STA4 waits for a DIFS and counts down a backoff QoS data in both a contention period (CP) and a contention slot corresponding to its selected random backoff count free period (CFP). value. 0202 FIG. 8 is a diagram illustrating a random backoff 0210 FIG. 8 shows an example in which the remaining period and a frame transmission procedure in a wireless backoff time of the STA5 coincides with the random backoff communication system to which an embodiment of the count value of the STA 4. In this case, a collision may be present invention may be applied. generated between the STA 4 and the STA 5. When a 0203 When a specific medium switches from an occu collision is generated, both the STA4 and the STA 5 do not pied (or busy) state to an idle state, several STAs may receive ACK, so data transmission fails. In this case, each of attempt to transmit data (or frames). In this case, as a scheme the STA 4 and the STA 5 doubles its CW value, select a for minimizing a collision, each of the STAS may select a random backoff count value, and counts down a backoff slot. random backoff count, may wait for a slot time correspond 0211. The STA 1 waits while the medium is the busy state ing to the selected random backoff count, and may attempt due to the transmission of the STA4 and the STA 5. When transmission. The random backoff count has a pseudo the medium becomes an idle state, the STA 1 may wait for random integer value and may be determined as one of a DIFS and start frame transmission after the remaining uniformly distributed values in 0 to a contention window backoff time elapses. (CW) range. In this case, the CW is a CW parameter value. 0212. The CSMA/CA mechanism includes virtual carrier In the CW parameter, CW min is given as an initial value. sensing in addition to physical carrier sensing in which an If transmission fails (e.g., if ACK for a transmitted frame is AP and/or an STA directly sense a medium. not received), the CW min may have a twice value. If the 0213 Virtual carrier sensing is for supplementing a prob CW parameter becomes CW max, it may maintain the lem which may be generated in terms of medium access, CW max value until data transmission is successful, and the such as a hidden node problem. For the virtual carrier data transmission may be attempted. If the data transmission sensing, the MAC of a WLAN system uses a network is successful, the CW parameter is reset to a CW min value. allocation vector (NAV). The NAV is a value indicated by an The CW. CW min, and CW max values may be set to AP and/oran STA which now uses a medium or has the right 2n-1 (n=0, 1, 2, . . . ). to use the medium in order to notify another AP and/or STA 0204 When a random backoff process starts, an STA of the remaining time until the medium becomes an avail counts down a backoff slot based on a determined backoff able state. Accordingly, a value set as the NAV corresponds count value and continues to monitor a medium during the to the period in which a medium is reserved to be used by countdown. When the medium is monitored as a busy state, an AP and/or an STA that transmit corresponding frames. the STA stops the countdown and waits. When the medium 0214. An AP and/or an STA may perform a procedure for becomes an idle state, the STA resumes the countdown. exchanging a request to send (RTS) frame and a clear to send 0205. In the example of FIG. 8, when a packet to be (CTS) frame in order to provide notification that they will transmitted in the MAC of an STA3 is reached, the STA3 access a medium. The RTS frame and the CTS frame include may check that a medium is an idle state by a DIFS and may information indicating a temporal section in which a wire immediately transmit a frame. less medium required to transmit/receive an ACK frame has 0206. The remaining STAs monitor that the medium is been reserved to be accessed if substantial data frame the busy state and wait. In the meantime, data to be trans transmission and an acknowledgement response (ACK) are mitted by each of an STA 1, an STA 2, and an STA 5 may supported. Another STA which has received an RTS frame be generated. When the medium is monitored as an idle from an AP and/or an STA attempting to send a frame or state, each of the STAs waits for a DIFS and counts down a which has received a CTS frame transmitted by an STA to backoff slot based on each selected random backoff count which a frame will be transmitted may be configured to not value. access a medium during a temporal section indicated by 0207. The example of FIG. 8 shows that the STA2 has information included in the RTS/CTS frame. This may be selected the smallest backoff count value and the STA 1 has implemented by setting the NAV during a time interval. selected the greatest backoff count value. That is, FIG. 10 0215 Interframe Space (IFS) illustrates that the remaining backoff time of the STA 5 is 0216 A time interval between frames is defined as an shorter than the remaining backoff time of the STA 1 at a interframe space (IFS). An STA may determine whether a point of time at which the STA2 finishes a backoff count and channel is used during an IFS time interval through carrier starts frame transmission. sensing. In an 802.11 WLAN system, a plurality of IFSs is US 2017/017.0937 A1 Jun. 15, 2017
defined in order to provide a priority level by which a 0239 ATXOP holder for continuous transmission after a wireless medium is occupied. transmission failure 0217 FIG. 9 is a diagram illustrating an IFS relation in a 0240 A reverse direction (RD) initiator for continuous wireless communication system to which an embodiment of transmission using error recovery the present invention may be applied. 0241. An HT AP during a PSMP sequence in which a 0218 All of pieces of timing may be determined with power save multi-poll (PSMP) recovery frame is transmitted reference to physical layer interface primitives, that is, a 0242 An HT AT performing CCA within a secondary PHY-TXEND.confirm primitive, a PHYTXSTART.confirm channel before sending a 40 MHz mask PPDU using EDCA primitive, a PHY-RXSTART.indication primitive, and a channel access PHY-RXEND.indication primitive. 0243 In the illustrated examples, an STA using the PIFS 0219. An interframe space (IFS) depending on an IFS starts transmission after a carrier sense (CS) mechanism for type is as follows. determining that a medium is an idle state in a Tx PIFS slot 0220. A reduced interframe space (IFS) (RIFS) boundary other than the case where CCA is performed in a 0221) A short interframe space (IFS) (SIFS) secondary channel 0222 A PCF interframe space (IFS) (PIFS) 0244. The DIFS may be used by an STA which operates 0223) A DCF interframe space (IFS) (DIFS) to send a data frame (MPDU) and a MAC management 0224. An arbitration interframe space (IFS) (AIFS) protocol data unit management (MMPDU) frame under the 0225. An extended interframe space (IFS) (EIFS) DCF. An STA using the DCF may transmit data in a TxDIFS 0226 Different IFSs are determined based on attributes slot boundary if a medium is determined to be an idle state specified by a physical layer regardless of the bit rate of an through a carrier sense (CS) mechanism after an accurately STA. IFS timing is defined as a time gap on a medium. IFS received frame and a backoff time expire. In this case, the timing other than an AIFS is fixed for each physical layer. accurately received frame means a frame indicating that the 0227. The SIFS is used to transmits a PPDU including an PHY-RXEND.indication primitive does not indicate an error ACK frame, a CTS frame, a block ACK request (Block and an FCS indicates that the frame is not an error (i.e., error AckReq) frame, or a block ACK (Block Ack) frame, that is, free). an instant response to an A-MPDU, the second or consecu 0245 An SIFS time (“aSIFSTime') and a slot time tive MPDU of a fragment burst, and a response from an STA (“aSlot Time') may be determined for each physical layer. with respect to polling according to a PCE. The SIFS has the The SIFS time has a fixed value, but the slot time may be highest priority. Furthermore, the SIFS may be used for the dynamically changed depending on a change in the wireless point coordinator of frames regardless of the type of frame delay time “a AirPropagationTime.” during a non-contention period (CFP) time. The SIFS indi 0246 The “aSIFSTime' is defined as in Equations 1 and cates the time prior to the start of the first symbol of the 2 below. preamble of a next frame which is subsequent to the end of aSIFSTime(16 Is)=aRxRFDelay(0.5)+aRxPLCPDe the last symbol of a previous frame or from signal extension lay (12.5)+aMACProcessingDelay (1 or <2)+aRx (if present). TxTurnaroundTime(<2) Equation 1 0228 SIFS timing is achieved when the transmission of aRxTxTurnaroundTime=aTxPLCPDelay(1)+aRxTx consecutive frames is started in a TX SIFS slot boundary. SwitchTime(0.25)+a TxRampOnTime(0.25)+ 0229. The SIFS is the shortest in IFS between transmis a TxRFDelay(0.5) Equation 2 sions from different STAs. The SIFS may be used if an STA 0247 The “aSlot Time' is defined as in Equation 3 below. occupying a medium needs to maintain the occupation of the aSlot Time=aCCATime(<4)+aRxTxTurnaroundTime medium during the period in which the frame exchange (<2)+a AirPropagationTime(<1)+aMACPro sequence is performed. cessing Delay (<2) Equation 3 0230. Other STAs required to wait so that a medium becomes an idle state for a longer gap can be prevented from 0248. In Equation 3, a default physical layer parameter is attempting to use the medium because the Smallest gap based on “aMACProcessing Delay' having a value which is between transmissions within a frame exchange sequence is equal to or smaller than 1 us. A radio wave is spread 300 used. Accordingly, priority may be assigned in completing a m/us in the free space. For example, 3 LS may be the upper frame exchange sequence that is in progress. limit of a BSS maximum one-way distance ~450 m (a round trip is ~900 m). 0231. The PIFS is used to obtain priority in accessing a 0249. The PIFS and the SIFS are defined as in Equations medium. 4 and 5, respectively. 0232. The PIFS may be used in the following cases. 0233. An STA operating under a PCF PIFS(16 Is)=aSIFSTime+aSlot Time Equation 4 0234. An STA sending a channel switch announcement frame DIFS(34 Is)=aSIFSTime+2*aSlot Time Equation 4 0235 An STA sending a traffic indication map (TIM) 0250 In Equations 1 to 5, the numerical value within the frame parenthesis illustrates a common value, but the value may be 0236. A hybrid coordinator (HC) starting a CFP or trans different for each STA or for the position of each STA. mission opportunity (TXOP) 0251. The aforementioned SIFS, PIFS, and DIFS are 0237. An HC or non-APQoS STA, that is, a TXOP holder measured based on an MAC slot boundary (e.g., a TX SIFS, polled for recovering from the absence of expected reception a Tx PIFS, and a TxDIFS) different from a medium. within a controlled access phase (CAP) 0252. The MAC slot boundaries of the SIFS, the PIFS, 0238 An HT STA using dual CTS protection before and the DIFS are defined as in Equations 6 to 8, respectively. sending CTS2 TSIFS=SIFS-aRxTxTurnaroundTime Equation 6 US 2017/017.0937 A1 Jun. 15, 2017 13
TPIFS=TSIFS+aSlotTime Equation 7 0261 FIG. 10 illustrates a VHT format of an HT control field in the wireless communication system to which the TxDIFS=TSIFS-2SOtTIme Equation 8 present invention may be applied. 0253 Channel State Information Feedback Method 0262 Referring to FIG. 10, the HT Control field may be 0254 An SU-MIMO technology in which a beam former comprised of a VHT subfield, an HT Control Middle sub communicates by allocating all antennas to a beam formee field, an AC constraint subfield, and a Reverse Direction increases a channel capacity through diversity gain and Grant (RDG)/More PPDU subfield. stream multiple transmission using a time and a space. The 0263. The VHT subfield indicates whether the HT Con SU-MIMO technology may contribute to performance trol field has a format of the HT Control field for the VHT enhancement of a physical layer by extending a spatial or whether the HT Control field has the format of the HT degree of freedom by increases the number of antennas as Control field for the HT. In FIG. 10, the HT Control field for compared with a case where an MIMO technology is not the VHT is assumed and described. The HT Control field for applied. the VHT may be referred to as a VHT Control field. 0255. Further, an MU-MIMO technology in which the 0264. The HT Control Middle subfield may be imple beam former allocates the antennas to a plurality of beam mented to have another format according to the indication of formees may enhance the performance of an MIMO antenna the VHT subfield. More detailed description of the HT by increasing transmission rate per beam formee or reliabil Control Middle Subfield will be made below. ity of the channel through a link layer protocol for multiple 0265. The AC Constraint subfield indicates whether a access of the plurality of beam formees accessing the beam mapped access category (AC) of a reverse direction (RD) former. data frame is limited to a single AC. 0256 In an MIMO environment, since how accurately 0266 The RDG/More PPDU subfield may be differently the beam former knows the channel information may exert a interpreted according to whether the corresponding field is large influence on the performance, a feedback procedure for transmitted by an RD initiator or RD responder. acquiring the channel is required. 0267 In the case where the corresponding field is trans 0257. As the feedback procedure for acquiring the chan mitted by the RD initiator, when the RDG exists, the nel information, two modes may be largely Supported. One RDG/More PPDU field is set to 1 and when the RDG does is a mode using the control frame and the other one is mode not exist, the RDG/More PPDU field is set to 0. In the case using a channel Sounding procedure not including the data where the corresponding field is transmitted by the RD field. Sounding means using a corresponding training field responder, when the PPDU including the corresponding in order to measure the channel for a purpose other than data subfield is a last frame transmitted by the RD responder, the demodulation of the PPDU including the training field. RDG/More PPDU field is set to 1 and when another PPDU 0258. Hereinafter, a channel information feedback is transmitted, the RDG/More PPDU field is set to 0. method using the control frame and a channel information 0268. The HT Control Middle subfield may be comprised feedback method using a null data packet (NDP) will be of a reserved bit, a Modulation and Coding Scheme (MCS) described in more detail. feedback request (MRQ) subfield, an MRQ sequence iden 0259 1) Feedback Method Using Control Frame tifier (MSI)/space-time block coding (STBC) subfield, a 0260. In the MIMO Environment, the Beamformer May MCS feedback sequence identifier (MFSI)/Least Significant Indicate Feedback of the channel state information through Bit (LSB) of Group ID (GID-L) subfield, an MCS feedback the HT control field included in the MAC header or report (MFB) subfield, a Most Significant Bit (MSB) of Group ID the channel state information through the HT control field (GID-H) subfield, a coding type subfield, a feedback trans included in the MAC frame header. The HT control field mission type (FBTX type) subfield, and an unsolicited MFB may be included in a control wrapper frame, a QoS Data subfield. frame in which the Order subfield of the MAC header is set 0269 Table 3 shows description of each subfield included to 1, or a management frame. in the HT Control Middle Subfield of the VHT format. TABLE 3
Subfield Meaning Definition MCS request MRQ is set to 1 when MCS feedback (unsolicited MFB) is requested If not, MRQ is set to 0 MSI MRQ sequence When the unsolicited MFB subfield is 0 and the identifier MRQ subfield is set to 1, the MSI subfield includes a sequence number in the range of 0 to 6 to identify a specific request When the unsolicited MFB subfield is 1, the MSI subfield includes a compressed MSI subfield (2 bits) and an STBC indication subfield (1 bit) MFSIGID-L MFB sequence When the unsolicited MFB subfield is set to 0, the identifier:LSB of MFSIGID-L subfield includes a reception value of Group ID the MSI included in the frame associated with the MFB information When the unsolicited MFB subfield is set to 1 and the MFB is estimated from the MU PPDU, the MFSIGID-L subfield includes LSB 3 bits of the group ID of the estimated PPDU US 2017/017.0937 A1 Jun. 15, 2017
TABLE 3-continued Subfield Meaning Definition MFB VHT N STS, The MFB subfield includes the recommended MFB. MCS, BW, SNR VHT-MCS = 15 and NUM STS = 7 indicates there is no feedback eedback GID-H MSB of Group ID When the unsolicited MFB subfield is set to 1 and he MFB is estimated from the VHT MU PPDU, the GID-H subfield includes MSB 3 bits of the group ID of the estimated PPDU of the Solicited MFB The MFB is estimated from the SUPPDU and all of he GID-H subfields are set to 1 Coding Type Coding type of When the unsolicited MFB subfield is set to 1, the MFB response coding type subfield includes a coding type (binary convolutional code (BCC)) is 0 and a low-density parity check (LDPC) is 1) of a frame in which the solicited MFB is estimated FBTX Type Transmission type When the unsolicited MFB subfield is set to 1 and of MFB response he MFB is estimated from an unbeamformed VHT PPDU, the FB Tx Type subfield is set to 0 When the unsolicited MFB subfield is set to 1 and he MFB is estimated from the unbeamformed VHT PPDU, the FB Tx Type subfield is set to 1 Unsolicited Unsolicited MCS When the MFB is a response to the MRQ, the MFB feedback unsolicited MFB is set to 1 indicator When the MFB is not the response to the MRQ, the unsolicited MFB is set to 0
(0270. In addition, the MFB subfield may include a Num NDP, and as a result, the beam formee may prepare for ber of space time streams (NUM STS) subfield, a VHT feeding back the channel state information before receiving MCS subfield, a bandwidth (BW) subfield, and a signal to the NDP frame. noise ratio (SNR) subfield. (0279. The VHT NDPA frame may include association 0271 The NUM STS subfield indicates the number of identifier (AID) information, feedback type information, and recommended spatial streams. The VHT-MCS subfield indi the like of the beam formee that will transmit the NDP. More cates a recommended MCS. The BW subfield indicates detailed description of the VHT NDPA frame will be made bandwidth information associated with the recommended below. MCS. The SNR subfield indicates an average SNR value on 0280. In the case where data is transmitted by using the a data Subcarrier and the spatial stream. MU-MIMO and in the case where the data is transmitted by 0272. The information included in the aforementioned using the SU-MIMO, the VHT NDPA frame may be trans respective fields may follow the definition of the IEEE mitted by different transmission methods. For example, 802.11 system. Further, the respective fields correspond to when the channel sounding for the MU-MIMO is per examples of the fields which may be included in the MAC formed, the VHT NDPA frame is transmitted by a broadcast frame and are not limited thereto. That is, each field may be method, but when the channel sounding for the SU-MIMO substituted with another field or further include an additional is performed, the VHT NDPA frame may be transmitted to field and all fields may not be requisitely included. one target STA by a unicast method. 0273 2) Feedback Method Using Channel Sounding (0281 (2) The beam former transmits the VHT NDPA 0274 FIG. 11 is a diagram for conceptually describing a frame and thereafter, transmits the NDP after an SIFS time. channel sounding method in the wireless communication The NDP has a VHT PPDU structure except for the data system to which the present invention can be applied. field. 0282. The beam formees that receive the VHT NDPA 0275. In FIG. 11, a method that feeds back the channel frame may verify an AID12 subfield value included in the state information between the beam former (for example, STA information field and verify the beam formees as sound AP) and the beam formee (for example, non-APSTA) based ing target STAs. on a Sounding protocol is illustrated. The Sounding protocol may mean a procedure that feeds back information on the 0283. Further, the beam formees may know a feedback channel State information. order through the order of the STA Info field included in the NDPA. In FIG. 11, a case where the feedback order is the 0276 A channel state information sounding method order of beam formee 1, beam formee 2, and beam formee 3 between the beam former and the beam formee based on the is illustrated. Sounding protocol may be performed by steps given below. 0284 (3) Beamformee 1 acquires the downlink channel (0277. The beamformer transmits a VHT Null Data Packet state information based on the training field included in the Announcement (VHT NDPA) frame announcing sounding NDP to generate feedback information to be transmitted to transmission for feedback of the beam formee. the beam former. 0278. The VHT NDPA frame means the control frame 0285 Beamformee 1 receives the NDP frame and there used to announce that the channel sounding is initiated and after, transmits a VHT compressed beam forming frame the null data packet (NDP) is transmitted. In other words, the including the feedback information to the beam former after VHT NDPA frame is transmitted before transmitting the the SIFS. US 2017/017.0937 A1 Jun. 15, 2017
0286 The VHT compressed beam forming frame may 0301 The VHT NDPA frame includes at least one STA include an SNR value for the space-time stream, information Info field. That is, the VHT NDPA frame includes an STA on a compressed beam forming feedback matrix for a Sub Info field including information on a Sounding target STA. carrier, and the like. More detailed description of the Com One STA Info field may be included in each sounding target pressed Beamforming frame will be made below. STA (0287 (4) The beam former receives the VHT Compressed (0302) Each STA Info field may be constituted by an Beamforming frame beam formee 1 and thereafter, transmits AID12 subfield, a Feedback Type subfield, and an Nc Index the beam forming report poll frame to beam formee 2 in order subfield. to the channel information from beam formee 2 after the 0303 Table 4 shows the subfield of the STA Info field SIFS. included in the VHT NDPA frame. 0288 The beam forming report poll frame is a frame that performs the same role as the NDP frame and beam formee TABLE 4 2 may measure the channel state based on the transmitted beam forming report poll frame. Subfield Description 0289 More detailed description of the beam forming AID12 includes the AID of the STA which becomes the sounding report poll frame will be made below. eedback target When the target STA is the AP, a mesh STA, or the STA 0290 (5) Beamformee 2 that receives the beam forming which is an IBSS member, the AID12 subfield value report poll frame transmits the VHT compressed beam form is set to 0 ing frame including the feedback information to the beam Feedback Indicates the feedback request type for the sounding former after the SIFS. arget STA Type in the case of the SU-MIMO, 'O' 0291 (6) The beam former receives the VHT Compressed in the case of the MU-MIMO, 1 Beamforming frame beam formee 2 and thereafter, transmits Nc Index When the Feedback Type subfield indicates the MU-MIMO, the beam forming report poll frame to beam formee 3 in order Nc Index indicates a value acquired by Subtracting 1 from to the channel information from beam formee 3 after the he number (Nc) of columns of the compressed beamforming feedback matrix SIFS. in the case of Nc = 1, 0, 0292 (7) Beamformee 3 that receives the beam forming in the case of Nc = 2, 1, report poll frame transmits the VHT compressed beam form in the case of Nc = 8, 7 ing frame including the feedback information to the beam in the case of the SU-MIMO, the Nc Index is set as a former after the SIFS. reserved subfield 0293. Hereinafter, the frame used in the aforementioned channel Sounding procedure will be described. 0294 FIG. 12 is a diagram illustrating a VHT NDPA 0304. The information included in the aforementioned frame in the wireless communication system to which the respective fields may follow the definition of the IEEE present invention may be applied. 802.11 system. Further, the respective fields correspond to 0295 Referring to FIG. 12, the VHTNDPA frame may be examples of the fields which may be included in the MAC comprised of a frame control field, a duration field, a frame and substituted with another field or an additional receiving address (RA) field, a transmitting address (TA) field may be further included. field, a sounding dialog token field, an STA information 1 (0305 FIG. 13 is a diagram illustrating an NDP PPDU in (STA Info 1) field to an STA information n (STA Info n) the wireless communication system to which the present field, and an FCS. invention may be applied. 0296. The RA field value represents a receiver address or (0306 Referring to FIG. 13, the NDP may have a format STA address that receives the VHT NDPA frame. in which the data field is omitted from the VHT PPDU 0297. When the VHT NDPA frame includes one STA Info format. The NDP is precoded based on a specific precoding field, the RA field value has an address of the STA identified matrix to be transmitted to the Sounding target STA. by the AID in the STA Info field. For example, when the (0307. In the L-SIG field of the NDP, a length field VHT NDPA frame is transmitted to one target STA for indicating the length of the PSDU included in the data field SU-MIMO channel sounding, the AP transmits the VHT is set to 0. NDPA frame to the STA by unicast. 0308 A Group ID field indicating whether a transmission 0298. On the contrary, when the VHT NDPA frame technique used for transmitting the NDP in the VHT-SIG-A includes one or more STA Info fields, the RA field value has field of the NDP is the MU-MIMO or the SU-MIMO is set a broadcast address. For example, when the VHT NDPA to a value indicating the SU-MIMO transmission. frame is transmitted to one or more target STAs for MU 0309 Adata bit of the VHT-SIG-B field of the NDP is set MIMO channel sounding, the AP broadcasts the VHT NDPA to a bit pattern fixed for each bandwidth. frame. 0310. When the sounding target STA receives the NDP. 0299. The TA field value represents a bandwidth for the Sounding target STA estimates the channel and acquires signaling a transmitter address to transmit the NDPA frame the channel state information based on the VHT-LTF field of or an address of the STA which transmits the VHT NDPA the NDP. frame, or the TA. 0311 FIG. 14 is a diagram illustrating a VHT compressed 0300. The Sounding Dialog Token field may be referred beam forming frame format in the wireless communication to as a Sounding sequence field. A Sounding Dialog Token system to which the present invention may be applied. Number subfield in the Sounding Dialog Token field 0312 Referring to FIG. 14, the VHT compressed beam includes a value selected by the beam former in order to forming frame as a VHT action frame for Supporting the identify the VHT NDPA frame. VHT function includes the Action field in the frame body. US 2017/017.0937 A1 Jun. 15, 2017 16
The Action field provides a mechanism for specifying man 0318 Whether the VHT Compressed Beamforming agement operations included in and extended to the frame Report field and the MU Exclusive Beamforming Report body of the MAC frame. field exist and contents of the VHT Compressed Beamform 0313 The Action field is comprised of a Category field, ing Report field and the MU Exclusive Beamforming Report a VHT Action field, a VHT MIMO Control field, a VHT field may be determined according to values of a Feedback Compressed Beamforming Report field, and an MU Exclu Type subfield, a Remaining Feedback Segments subfield, sive Beamforming Report field. and a First Feedback Segment subfield of the VHT MIMO 0314. The Category field is set to a value indicating a Control field. VHT category (that is, VHT Action frame) and the VHT 0319. Hereinafter, the VHT MIMO Control field, the Action field is set to a value indicating the VHT Compressed VHT Compressed Beamforming Report field, and the MU Beamforming frame. Exclusive Beamforming Report field will be described in 0315. The VHT MIMO Control field is used for feeding more detail. back control information associated with beam forming feed back. The VHT MIMO Control field may always exist in the 0320 1) The VHT MIMO Control field is comprised of VHT Compressed Beamforming frame. an Nc Index subfield, an Nr Index subfield, a Channel Width 0316. The VHT Compressed Beamforming Report field subfield, a Grouping subfield, a Codebook Information is used for feeding back information on the beam forming subfield, a Feedback Type subfield, a Remaining Feedback matrix including the SNR information for the space-time Segments subfield, a First Feedback Segment subfield, a stream used for transmitting the data. reserved subfield, and a Sounding Dialog Token Number 0317. The MU Exclusive Beamforming Report field is subfield. used for feeding back the SNR information for a spatial 0321 Table 5 shows the subfield of the VHT MIMO stream when the MU-MIMO transmission is performed. Control field. TABLE 5
The number Subfield of bits Description Nc Index 3 Nc Index indicates a value acquired by Subtracting 1 from the number (Nc) of columns of the compressed beamforming feedback matrix in the case of Nc = 1, 0, in the case of Nc = 2, 1, in the case of Nc = 8, 7 Nr Index 3 Nr Index indicates a value acquired by Subtracting 1 from he number (Nr) of rows of the compressed beam forming eedback matrix l he case of Nr = 1, 0, l he case of Nr = 2, 1, he case of Nr = 8, 7 Channel Width cates the bandwidth of the channel measured in order enerate the compressed beamforming feedback matrix he case of 20 MHz, O, he case of 40 MHz, 1, he case of 80 MHz, 2, he case of 160 MHz or 80 + 80 MHz, 3 Grouping icates Subcarrier grouping (Ng) used in the compressed beamforming feedback matrix in the case of Ng = 1 (no grouping), O, in the case of Ng = 2, 1, in the case of Ng = 4, 2, A value of 3 is set to a preliminary value Codebook 1 indicates the sizes of codebook entries Information When the feedback type is the SU-MIMO, in the case of bp = 2 and boD = 4, '0, in the case of bp = 4 and boD = 6, 1 When the feedback type is the MU-MIMO, in the case of bp = 5 and boD = 7, '0, in the case of bp = 7 and boD = 9, 1 Herein, by and bop mean the number of quantized bits Feedback Type 1 indicates the feedback type in the case of the SU-MIMO, O, in the case of the MU-MIMO, 1 Remaining indicates the number of remaining feedback segments for Feedback he associated VHT Compressed Beamforming frame Segments in the case of a last feedback segment of the segmented report or a segment of an unsegmented report, the Remaining Feedback Segments are set to 0 US 2017/017.0937 A1 Jun. 15, 2017 17
TABLE 5-continued
The number Subfield of bits Description When the Remaining Feedback Segments are not first and ast feedback segments of the segmented report, the Remaining Feedback Segments are set to a value between 1 and 6 When the Remaining Feedback Segments are feedback segments other than the last segment, the Remaining Feedback Segments are set to the value between 1 and 6 in the case of a retransmitted feedback segment, the field is set to the same value as the segment associated with original transmission First Feedback in the case of a first feedback segment of the segmented Segment report or a segment of an unsegmented report, the First Feedback Segment is set to 1 When the corresponding feedback segment is not the first eedback segment or the VHT Compressed Beamforming Report field or the MU Exclusive Beamforming Report field does not exist in the frame, the First Feedback Segment is set to 0 in the case of a retransmitted feedback segment, the field is set to the same value as the segment associated with the original transmission Sounding The Sounding Dialog Token Number is set to a sounding Dialog Token dialog token value of the NDPA frame Number
0322. When the VHT Compressed Beamforming frame 0325 Table 6 shows the subfield of the VHT compressed does not transfer the entirety or a part of the VHT Com beam forming report field.
TABLE 6
The number Subfield of bits Description Average SNR of Space-Time Stream 1 8 Average SNR on all subcarriers for space-time stream 1 in beamformee Average SNR of Space-Time Stream Nc 8 Average SNR on all subcarriers for the space-time stream Nc in beamformee Compressed Beamforming Feedback Na * (b. + Order of the angle of Compressed Matrix V for Subcarrier k = scidx(0) bd)/2 Beamforming Feedback Matrix for the corresponding Subcarrier Compressed Beamforming Feedback Na * (b. + The order of the angle of Compressed Matrix V for Subcarrier k = scidx.(1) bd)/2 Beamforming Feedback Matrix for the corresponding Subcarrier Compressed Beamforming Feedback Na * (b. + The order of the angle of Compressed Matrix V for Subcarrier k = scidx(Ns - 1) Beamforming Feedback Matrix for the corresponding Subcarrier pressed Beamforming Report field, the Nc Index subfield, 0326 Referring to Table 6, the VHT compressed beam the Channel Width subfield, the Grouping subfield, the forming report field may include the average SNR for each Codebook Information subfield, the FeedbackType subfield, time-space stream and the Compressed Beamforming Feed and the Sounding Dialog Token Number subfield are set as back Matrix V for the respective subcarriers. The Com a preliminary field, the First Feedback Segment subfield is pressed Beamforming Feedback Matrix as a matrix includ set to 0, and the Remaining Feedback Segments subfield is ing information on a channel state is used to for calculating Set to 7. a channel matrix (that is, a steering matrix Q) in the 0323. The Sounding Dialog Token field may be referred transmission method using the MIMO. to as a Sounding Sequence Number subfield. 0327 scidx() means the subcarrier in which the Com 0324 2) The VHT compressed beam forming report field pressed Beamforming Feedback Matrix subfield is transmit is used for transferring explicit feedback information repre ted. Na is fixed by a value of NrxNc (for example, in the case senting the compressed beam forming feedback matrix V of NrxNc=2x1, d11, p21, . . . ). which a transmission beam former uses a steering matrix Q 0328 Ns means the number of subcarriers in which the for determining in the form of an angle. compressed beam forming feedback matrix is transmitted to US 2017/017.0937 A1 Jun. 15, 2017
the beam former. The beam formee may reduce the Ns in Beamforming Report field may be used for the MU beam which the compressed beam forming feedback matrix is former to determine the steering matrix Q. transmitted by using the grouping method. For example, a 0332 Table 8 shows the subfield of the MU Exclusive plurality of Subcarriers is bundled as one group and the Beamforming Report field included in the VHT compressed compressed beam forming feedback matrix is transmitted for beam forming report frame. TABLE 8
The number Subfield of bits Description Delta SNR for space-time stream 1 for 4 Difference between the SNR for the Subcarrier k = s.scidx(0) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream Delta SNR for space-time stream Nc for 4 Difference between the SNR for the Subcarrier k = s.scidx(0) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream Delta SNR for space-time stream 1 for 4 Difference between the SNR for the Subcarrier k = SScidX(1) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream Delta SNR for space-time stream Nc for 4 Difference between the SNR for the Subcarrier k = SScidX(1) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream Delta SNR for space-time stream 1 for 4 Difference between the SNR for the Subcarrier k = s.scidx(Ns' - 1) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream Delta SNR for space-time stream Nc for 4 Difference between the SNR for the Subcarrier k = s.scidx(Ns' - 1) corresponding Subcarrier and the average SNR for all subcarriers o he corresponding time-space stream each corresponding group to reduce the number of com 0333 Referring to Table 8, the SNR per time-space pressed beam forming feedback matrices which are fed back. stream may be included for each subcarrier in the MU The Ns may be calculated from the Channel Width subfield Exclusive Beamforming Report field. and the Grouping subfield included in the VHT MIMO 0334 Each Delta SNR subfield has a value which Control field. increases by 1 dB between -8 dB and 7 dB. 0329 Table 7 exemplifies an average SNR of space-time 0335 scidx() represents the subcarrier(s) in which the stream subfield. Delta SNR subfield is transmitted and Ns means the number of Subcarriers in which the Delta SNR subfield is transmit ted. TABLE 7 0336 FIG. 15 is a diagram illustrating a beam forming Average SNR of Space-Time i subfield AvgSNR, report poll frame format in the wireless communication system to which the present invention may be applied. -128 s-10 dB -127 -9.75 dB 0337 Referring to FIG. 15, the Beamforming Report Poll -126 -9.5 dB frame is configured to include the Frame Control field, the Duration field, the Receiving Address (RA) field, the Trans +126 53.5 dB mitting Address (TA) field, the Feedback Segment Retrans --127 e53.75 dB mission Bitmap field, and the FCS. 0338. The RA field value represents the address of an intended recipient. 0330 Referring to Table 7, the average SNR for each 0339. The TA field value represents a bandwidth for time-space stream is calculated by calculating the average signaling the address of the STA which transmits the Beam SNR value for all subcarriers included in the channel and forming Report Poll or the TA. mapping the calculated average SNR value to the range of 0340. The Feedback Segment Retransmission Bitmap -128 to +128. field indicates the feedback segment requested by the VHT 0331 3) The MU Exclusive Beamforming Report field is Compressed Beamforming report. used to transfer the explicit feedback information shown in 0341. In the Feedback Segment Retransmission Bitmap the form of delta (A) SNR. Information in the VHT Com field value, when the bit of position n is 1 (in the case of pressed Beamforming Report field and the MU Exclusive the LSB, n=0 and in the case of the MSB, n=7), the feedback US 2017/017.0937 A1 Jun. 15, 2017 segment corresponding to n in the Remaining Feedback that the STA is the member of the corresponding group. One Segments subfield in the VHT MIMO Control field of the or more Membership Status subfields in the Membership VHT compressed beam forming frame is requested. On the Status Array field are set to 1 to allocate one or more contrary, when the bit of position n is 0, the feedback groups to the STA. segment corresponding to n in the Remaining Feedback 0353. The STA may have one user position in each group Segments subfield in the VHT MIMO Control field is not which belongs thereto. Herein, the user position indicates requested. which position the spatial stream set of the corresponding (0342 Group ID STA corresponds to in the entire spatial stream depending on (0343 Since the VHT WLAN system supports the MU the MU-MIMO transmission when the STA belongs to the MIMO transmission method for higher throughput, the AP corresponding group ID. may simultaneously transmit the data frame to one or more 0354. The User Position Array field is comprised of a STAS which are MIMO-paired. The AP may simultaneously User Position subfield of 2 bit for each group. The user transmit data to the STA group including one or more STAS position of the STA in the group which belongs to the STA among the plurality of STAs which are associated therewith. is indicated by the User Position subfield in the User For example, the maximum number of paired STA may be Position Array field. The AP may allocate the same user 4 and when the maximum of time-space streams is 8, a position to different STAs in each group. maximum of 4 time-space streams may be allocated to each 0355 The AP may transmit the Group ID Management STA frame only when a dot11VHTOption Implemented param 0344) Further, in the WLAN system that supports Tun eter is true. The Group ID Management frame is transmit neled Direct Link Setup (TDLS), Direct Link Setup (DLS), ted only to a VHT STA in which an MU Beamformee or a mesh network, the STA that intends to transmit data may Capable field in a VHT Capabilities element field is set to transmit the PPDU to the plurality of STAs by using the 1. The Group ID Management frame is transmitted to a MU-MIMO transmission technique. frame addressed to each STA. 0345 Hereinafter, the case in which the AP transmits the 0356. The STA receives the Group ID Management PPDU to the plurality of STAs according to the MU-MIMO frame having the RA field which matches the MAC address transmission technique will be described as an example. thereof. The STA updates GROUP ID MANAGEMENT (0346. The AP simultaneously transmits the PPDU to the which is a PHYCONFIG VECTOR parameter based on STAS which belongs to the transmission target STA group, contents of the Group ID Management frame which are which are paired through different spatial streams. As received. described above, the VHT-SIG A field of the VHT PPDU 0357 Transmission of the Group ID Management to the format includes the group ID information and the time-space STA and transmission of the ACK from the STAtherefor are stream information, and as a result, each STA may verify completed before transmitting the MU PPDU to the STA. whether the corresponding PPDU is a PPDU transmitted 0358. The MUPPDU is transmitted to the STA based on thereto. In this case, since the spatial stream is not allocated the contents of the Group ID Management frame most to a specific STA of the transmission target STA group, data recently transmitted to the STA and the ACK is received. may not be transmitted. 0359 DL MU-MIMO Frame 0347 A Group ID Management frame is used in order to 0360 FIG. 17 is a diagram illustrating a DL multi-user assign or change user positions corresponding to one or (MU) PPDU format in a wireless communication system to more Group IDs. That is, the AP may announce STAs which an embodiment of the present invention may be connected with a specific group ID through the Group ID applied. Management frame before performing MU-MIMO trans 0361. In FIG. 17, the number of STAs receiving a cor mission. responding PPDU is assumed to be 3 and the number of 0348 FIG. 16 is a diagram illustrating a Group ID spatial streams allocated to each STA is assumed to be 1, but management frame in the wireless communication system to the number of STAs paired with an AP and the number of which the present invention may be applied. spatial streams allocated to each STA are not limited thereto. 0349 Referring to FIG. 16, the Group ID Management as 0362 Referring to FIG. 17, the MUPPDU is configured the VHT action frame for supporting the VHT function to include L-TFs (i.e., an L-STF and an L-LTF), an L-SIG includes the Action field in the frame body. The Action field field, a VHT-SIG-A field, a VHTTFs (i.e., a VHT-STF and provides a mechanism for specifying management opera a VHT-LTF), a VHT-SIG-B field, a service field, one or more tions included in and extended to the frame body of the PSDUs, a padding field, and a tail bit. The L-TFs, the L-SIG MAC frame. field, the VHT-SIG-A field, the VHTTFs, and the VHT 0350. The Action field is constituted by the Category SIG-B field are the same as those of FIG. 4, and a detailed field, the VHT Action field, a Membership Status Array description thereof is omitted. field, and a User Position Array field. 0363 Information for indicating PPDU duration may be 0351. The Category field is set to the value indicating a included in the L-SIG field. In the PPDU, PPDU duration VHT category (that is, VHT Action frame) and the VHT indicated by the L-SIG field includes a symbol to which the Action field is set to a value indicating the Group ID VHT-SIG-A field has been allocated, a symbol to which the Management frame. VHTTFs have been allocated, a field to which the VHT 0352. The Membership Status Array field is comprised of SIG-B field has been allocated, bits forming the service a Membership Status subfield of 1 bit for each group. When field, bits forming a PSDU, bits forming the padding field, the Membership Status subfield is set to 0, the Membership and bits forming the tail field. An STA receiving the PPDU Status subfield indicates that the STA is not a member of the may obtain information about the duration of the PPDU corresponding group and when the Membership Status Sub through information indicating the duration of the PPDU field is set to 1, the Membership Status subfield indicates included in the L-SIG field. US 2017/017.0937 A1 Jun. 15, 2017 20
0364. As described above, group ID information and time 0375. In 802.11ac, the MU-MIMO is defined in downlink and spatial stream number information for each user are toward the client (that is, non-APSTA) from the AP. In this transmitted through the VHT-SIG-A, and a coding method case, a multi-user frame is simultaneously transmitted to and MCS information are transmitted through the VHT-SIG multiple receipients, but reception acknowledgement needs B. Accordingly, beam formees may check the VHT-SIG-A to be individually transmitted in uplink. and the VHT-SIG-B and may be aware whether a frame is 0376 Since all MPDUs transmitted in the VHT MU an MU MIMO frame to which the beam formee belongs. PPDU based on 802.11ac are included in the A-MPDU, not Accordingly, an STA which is not a member STA of a an immediate response to the VHT MU PPDU but a corresponding group ID or which is a member of a corre response to the A-MPDU in the VHT MU PPDU is trans sponding group ID, but in which the number of streams mitted in response to a block Ack request (BAR) frame by allocated to the STA is 0 is configured to stop the reception the AP. of the physical layer to the end of the PPDU from the 0377 First, the AP transmits the VHTMU PPDU (that is, VHT-SIG-A field, thereby being capable of reducing power a preamble and data) to all receipients (that is, STA 1, STA consumption. 2, and STA 3). The VHT MU PPDU includes the VHT 0365. In the group ID, an STA can be aware that a A-MPDU transmitted to each STA. beam formee belongs to which MU group and it is a user who 0378 STA 1 that receives the VHT MUPPDU from the belongs to the users of a group to which the STA belongs and AP transmits a block acknowledgement (ACK) frame to the who is placed at what place, that is, that a PPDU is received AP after the SIFS. More detailed description of the BA through which stream by previously receiving a group ID frame will be made below. management frame transmitted by a beam former. 0379 The AP that receives the BA from STA 1 transmits 0366 All MPDUs transmitted in the VHT MU PPDU block acknowledgement request (BAR) to next STA 2 after based on 802.11ac are included in the A-MPDU. In the data the SIFS and STA 2 transmits the BA frame to the AP after field of FIG. 17, an upper box exemplifies the VHT the SIFS. The AP that receives the BA frame from STA 2 A-MPDU transmitted to STA 1, a middle box exemplifies transmits the BAR frame to STA 3 after the SIFS and STA the VHT A-MPDU transmitted to STA 2, and a lower box 3 transmits the BA frame to the AP after the SIFS. exemplifies the VHT A-MPDU transmitted to STA3. 0380 When such a process is performed with respect to 0367 The A-MPDU is configured to include one or more all STAS, the AP transmits the next MUPPDU to all STAs. consecutive A-MPDU subframes and an end-of-frame pad 0381 Multi-User Uplink Data Transmitting Method having a length of 0 to 3 octets. 0382 IEEE 802.11ax as a next-generation WLAN system 0368 Each A-MPDU subframe may be configured to for Supporting higher data rate and processing a higher user include one MPDU delimiter field and thereafter, selectively load is one of WLAN systems that have been newly pro include the MPDU. Each A-MPDU subframe which is not posed in recent years is called high efficiency WLAN positioned last in the A-MPDU has a pad field so that the (HEW). length of the subframe becomes the multiple of 4 octets. (0383. The IEEE 802.11ax WLAN system may operate in 0369. In FIG. 17, the A-MPDUs may have different bit a 2.4 GHz frequency band and a 5 GHz frequency band sizes because the size of data transmitted to each STA may similarly to the existing WLA system. Further, the IEEE be different. 802.11ax WLAN system may operate even in 6 GHz or a 60 0370. In this case, null padding may be performed so that GHz frequency band higher therethan. the time when the transmission of a plurality of data frames 0384 FIGS. 19 to 23 are diagrams illustrating a high transmitted by a beam former is ended is the same as the time efficiency (HE) format PPDU according to an embodiment when the transmission of a maximum interval transmission of the present invention. data frame is ended. The maximum interval transmission (0385 FIG. 19(a) illustrates a schematic structure of the data frame may be a frame in which valid downlink data is HE format PPDU and FIGS. 19(b) to 19(d) illustrates a more transmitted by a beam former for the longest time. The valid detailed Structure of the HE format PPDU. downlink data may be downlink data that has not been null (0386 Referring to FIG. 19(a), the HE format PPDU for padded. For example, the valid downlink data may be the HEW may be generally comprised of a legacy part included in the A-MPDU and transmitted. Null padding may L-part, an HE part HE-part, and a data field HE-data. be performed on the remaining data frames other than the (0387. The L-part is constituted by an L-STF field, an maximum interval transmission data frame of the plurality L-LTF field, and an L-SIG field similarly to a form main of data frames. tained in the existing WLAN system. 0371 For the null padding, a beam former may fill one or 0388. The HE-part as a part which is newly defined for more A-MPDU subframes, temporally placed in the latter the 802.11ax standard may include an HE-STF field, an part of a plurality of A-MPDU subframes within an HE-SIG field, and an HE-LTF field. In FIG. 19(a), the order A-MPDU frame, with only an MPDU delimiter field of the HE-STF field, the HE-SIG field, and the HE-LTF field through encoding. is illustrated, but the HE-STF field, the HE-SIG field, and 0372. When the EOF field is detected in the MAC layer the HE-ITF field may be configured in a different order ofan STA on the receiving side, the reception of the physical therefrom. Further, the HE-LTF may be omitted. layer is stopped, thereby being capable of reducing power (0389. The HE-SIG may include information (for consumption. example, OFDMA, ULMU MIMO, enhanced MCS, and the 0373 Block Ack Procedure like) for decoding the HE-data field. 0374 FIG. 18 is a diagram illustrating a downlink MU 0390 The L-part and the HE-part may have different fast MIMO transmission process in the wireless communication Fourier transform (FFT) sizes (that is, subcarrier spacing) system to which the present invention may be applied. and use different cyclic prefixes (CPs). US 2017/017.0937 A1 Jun. 15, 2017
0391 Referring to FIG. 19(b), the HE-SIG field may be 0400 Similarly thereto, the FFT having a size which is divided into an HE-SIG A field and an HE-SIG B field. four times larger than the existing PPDU may be applied to 0392 For example, the HE-part of the HE format PPDU the HE-part. That is, the FFT having sizes of 256,512, 1024, may include an HE-SIG A field having a length of 12.8 us, and 2048 may be applied from the HE-STF fields of the HE an HE-STF field of 1 OFDM symbol, one or more HE-LTF format PPDUs of 20 MHz, 40 MHz, 80 MHz, and 160 MH, fields, and an HE-SIG B field of 1 OFDM symbol. respectively. 0393. Further, in the HE-part, FFT having a size which is 04.01. The HE format PPDU for the WLAN system four times larger than the existing PPDU may be applied according to the present invention may be transmitted from the HE-STF field except for the HE-SIGA field. That through at least one 20-MHZ channel. For example, the HE is, FFT having sizes of 256, 512, 1024, and 2048 may be format PPDU may be transmitted in the 40 MHz, 80 MHz, applied from the HE-STF fields of the HE format PPDUs of or 160 MHz frequency band through a total of four 20-MHz 20 MHz, 40 MHz, 80 MHz, and 160 MH, respectively. channel. This will be described in more detail with reference 0394 However, as illustrated in FIG. 19(b), when the to a drawing given below. HE-SIG is transmitted while being divided into the HE-SIG 0402. Hereinafter, the described PPDU format is A field and the HE-SIG B field, the positions of the HE-SIG described based on FIG. 19(b) for easy description, but the A field and the HE-SIG B field may be different from those present invention is not limited thereto. of FIG. 18(b). For example, the HE-SIG B field may be transmitted after the HE-SIGA field, and the HE-STF field 0403 FIG. 20 is a diagram illustrating an HE format and the HE-LTF field may be transmitted after the HE-SIG PPDU according to an embodiment of the present invention. B field. Similarly even in this case, FFT having a size which 04.04. In FIG. 20, the PPDU format when 80 MHZ is is four times larger than the existing PPDU may be applied allocated to one STA or when different streams of 80 MHz from the HE-STF field. are allocated to the plurality of STAs, respectively is illus 0395. Referring to FIG. 19(c), the HE-SIG field may not trated. be divided into the HE-SIGA field and the HE-SIG B field. 04.05 Referring to FIG. 20, the L-STF, the L-LTF, and the 0396 For example, the HE-part of the HE format PPDU L-SIG may be transmitted to the OFDM symbol generated may include the HE-STF field of 1 OFDM symbol, the based on 64 FFT points (alternatively, 64 subcarriers) in HE-SIG field of 1 OFDM symbol and one or more HE-LTF each 20-MHz channel fields. 0406. The HE-SIG A field may include common control 0397) Similarly thereto, the FFT having a size which is information commonly transmitted to the STAS receiving four times larger than the existing PPDU may be applied the PPDU. The HE-SIGA field may be transmitted in one to from the HE-part. That is, the FET having sizes of 256, 512, three OFDM symbols. The HE-SIGA field is duplicated by 1024, and 2048 may be applied from the HE-STF fields of the unit of 20 MHz and includes the same information. the HE format PPDUs of 20 MHz, 40 MHz, 80 MHz, and Further, the HE-SIG-A field announces total bandwidth 160 MH, respectively. information of the system. 0398 Referring to FIG. 19(d), the HE-SIG field may not 04.07 Table 9 is a diagram illustrating information be divided into the HE-SIGA field and the HE-SIG B field included in the HE-SIGA and the HE-LTF field may be omitted. 0399. For example, the HE-part of the HE format PPDU FIELD may include the HE-STF field of 1 OFDM symbol and the HE-SIG field of 1 OFDM symbol. 04.08 TABLE 9
The number of Field bits Description
Bandwidth 2 indicates the bandwidth in which the PDDU is transmitted For example, 20 MHz, 40 MHz, 80 MHz, or 160 MHz Group ID 6 indicates the STA or the group of the STAs which will receive the PPDU Stream information 12 indicates the position or the number of the spatial stream for each STA, or indicates the position or the number of the spatial stream for the group of the STAs UL indication 1 indicates whether the PPDU is transmitted toward the AP (uplink) or the STA (downlink) MU indication 1 indicates whether the PPDU is the SU-MIMO PPDU or the MU-MIMO PPDU GI indication 1 indicates whether a short GI or a long GI is used Allocation 12 indicates a band or channel (subchannel index or Subband information index) allocated to each STA in a band in which the PPDU is transmitted Transmission power 12 indicates transmission power for each channel or each STA US 2017/017.0937 A1 Jun. 15, 2017 22
04.09. The information included in the respective fields 0419. In FIG. 22, a case in which 20-MHz channels are may follow the definition of the IEEE 802.11 system. allocated to different STAs (for example, STA1, STA2, STA Further, the respective fields correspond to examples of the 3, and STA4), respectively is assumed. fields which may be included in the PPDU and are not 0420 Referring to FIG. 22, the HE-SIG B field is posi limited thereto. That is, each field may be substituted with tioned after the HE-SIGA field. In this case, the FFT size per another field or further include an additional field and all frequency may further increase from the HE-STF (alterna fields may not be requisitely included. tively, HE-SIGB). For example, 256 FFT may be used in the 0410 The HE-STF is used to enhance performance of 20-MHz channel from the HE-STF (alternatively, HE-SIG AGC estimation in MIMO transmission. B), 512 FFT may be used in the 40-MHz channel, and 1024 0411. The HE-SIG B field may include user-specific FFT may be used in the 80-MHz channel. information required for each STA to receive data (for 0421 Since the information transmitted in each field example, PSDU) thereof. The HE-SIG B field may be included in the PPDU is the same as the example of FIG. 20. transmitted in one or two OFDM symbols. For example, the description of the information will be hereinafter omitted. HE-SIG B field may include a modulation and coding 0422 The HE-SIG B field may include information spe scheme (MCS) of the corresponding PSDU and information cific to each STA, but be encoded throughout all bands (that on the length of the PSDU. is, indicated in the HE-SIG A field). That is, the HE-SIG B field includes information on all STAs and all STAs receive 0412. The L-STF, L-LTF, L-SIG, and HE-SIG A fields the HE-SIG B may be repeatedly transmitted by the unit of the 20-MHz channel. For example, when the PPDU is transmitted FIELD through four 20-MHz channels (that is, 80-MHz band), the L-STF, L-LTF, L-SIG, and HE-SIGA fields may be repeat 0423. The HE-SIG B field may announce frequency edly transmitted by the unit of the 20-MHZ channel. bandwidth information allocated for each STA and/or stream 0413. When the size of the FFT increases, the legacy STA information in the corresponding frequency band. For Supporting the existing IEEE 802.11a/g/n/ac may not decode example, in FIG. 22, in the HE-SIG B, 20 MHz may be the corresponding HE PPDU. The L-STF, L-LTF and L-SIG allocated to STA 1, the next 20 MHz may be allocated to fields are transmitted through 64 FFT in the 20-MHZ channel STA2, the next 20 MHz may be allocated to STA3, and the so as to be received by the legacy STA so that the legacy next 20 MHz may be allocated to STA 4. Further, 4.0 MHz STA and the HE STA coexist. For example, the L-SIG field may be allocated to STA 1 and STA2 and the next 40 MHz may occupy one OFDM symbol, one OFDM symbol time may be allocated to STA3 and STA 4. In this case, different may be 4 us, and the GI may be 0.8 us. streams may be allocated to STA 1 and STA 2 and different 0414. The FFT size for each frequency unit may further streams may be allocated to STA 3 and STA 4. increase from the HE-STF (alternatively, HE-SIGA). For 0424. Further, the HE-SIG C field is defined to add the example, 256 FFT may be used in the 20-MHZ channel, 512 HE-SIG C field to the example of FIG. 22. In this case, in FFT may be used in the 40-MHz channel, and 1024 FET the HE-SIG B field, information on all STAs may be may be used in the 80-MHz channel. When the FET size transmitted throughout all bands and control information increases, an interval between OFDM subcarriers decreases, specific to each STA may be transmitted by the unit of 20 and as a result, the number of OFDM subcarriers per MHz through the HE-SIG C field. frequency increases, but the OFDM symbol time is length 0425 Further, in the examples of FIGS. 20 to 22, the ened. For improvement the efficiency of the system, the HE-SIG B field may not be transmitted through all bands but transmitted by the unit of 20 MHz similarly to the HE-SIG length of the GI after the HE-STF may be set to be the same A field. This will be described in detail with reference to the as the length of the GI of the HE-SIG A. following drawings. 0415. The HE-SIG A field may include information 0426 FIG. 23 is a diagram illustrating an HE format required for the HE STA to decode the HE PPDU. However, PPDU according to an embodiment of the present invention. the HE-SIG A field may be transmitted in the 20-MHz channel through 64 FFT so as to be received by both the 0427. In FIG. 23, the case in which 20-MHZ channels are legacy STA and the HE STA. The reason is that the HE STA allocated to different STAs (for example, STA1, STA2, STA may receive the existing HT/VHT format PPDU as well as 3, and STA4), respectively is assumed. the HE format PPDU, and the legacy STA and the HE STA 0428 Referring to FIG. 23, the HE-SIG B field is posi need to distinguish the HT/VHT format PPDU and the HE tioned after the HE-SIG A field, similarly to FIG. 22. format PPDU. However, the HE-SIG B field is not transmitted throughout all bands, but transmitted by the unit of 20 MHZ similarly to 0416 FIG. 21 is a diagram illustrating an HE format the HE-SIG A field. PPDU according to an embodiment of the present invention. 0429. In this case, the FET size per frequency may further 0417 Referring to FIG. 21, the example is the same as the increase from the HE-STF (alternatively, HE-SIG B). For example of FIG. 20 except the HE-SIG B field is positioned example, 256 FFT may be used in the 20-MHz channel from after the HE-SIG A field. In this case, the FFT size per the HE-STF (alternatively, HE-SIG B), 512 FFT may be frequency may further increase from the HE-STF (alterna used in the 40-MHz channel, and 1024 FFT may be used in tively, HE-SIGB). For example, 256 FFT may be used in the the 80-MHZ channel 20-MHz channel from the HE-STF (alternatively, HE-SIG 0430 Since the information transmitted in each field B), 512 FET may be used in the 40-MHz channel, and 1024 included in the PPDU is the same as the example of FIG. 20. FFT may be used in the 80-MHz channel. description of the information will be hereinafter omitted. 0418 FIG. 22 is a diagram illustrating an HE format 0431. The HE-SIG A field is transmitted while being PPDU according to an embodiment of the present invention. duplicated by the unit of 20 MHz. US 2017/017.0937 A1 Jun. 15, 2017
0432. The HE-SIG B field may announce the frequency 0445. Uplink transmission by the plurality of respective bandwidth information allocated for each STA and/or the STAS may be multiplexed in a frequency domain or a spatial stream information in the corresponding frequency band. domain. 0433. The HE-SIG B field is transmitted by the unit of 20 0446. When the uplink transmission by the plurality of MHz similarly to the HE-SIG A field. In this case, since the respective STAS is multiplexed in the frequency domain, HE-SIG B field includes the information on each STA, the different frequency resources may be allocated to the plu information on each STA may be included for each HE-SIG rality of respective STAS as uplink transmission resources B field of the unit of 20 MHz. In this case, in the example based on orthogonal frequency division multiplexing of FIG. 28, the case in which 20 MHz is allocated for each (OFDMA). The transmission method through the different STA is exemplified, but for example, when 40 MHz is frequency resources may be referred to as ULMU OFDMA allocated to the STA, the HE-SIG B field may be duplicated transmission. and transmitted by the unit of 20 MHz. 0447. When the uplink transmission by the plurality of 0434 Further, the information (that is, all information respective STAs is multiplexed on the spatial domain, dif specific to the respective STAs is combined) on all STAs is ferent spatial streams may be allocated to the plurality of included in the HE-SIG B field to be duplicated and trans respective STAs and the plurality of respective STAs may mitted by the unit of 20 MHz similarly to the HE-SIG A transmit the uplink data through the different spatial streams. field. The transmission method through the different spatial 0435 Like the examples of FIGS. 21 to 23, when the streams may be referred to as ULMU MIMO transmission. HE-SIG B field is positioned before the HE STF field and 0448. At present, ULMU transmission may not be sup the HE LTF field, the length of the symbol may be config ported due to the following constraints in the WLAN sys ured to be short by using 64 FFT at 20 MHz, and like the tem. example of FIG. 20, when the HE-SIG B field is positioned 0449 At present, in the WLAN system, synchronization after the HE STF field and the HE LTF field, the length of with a transmission timing of the uplink data transmitted the symbol may be configured to be long by using 256 FFT from the plurality of STAs is not supported. For example, at 20 MHZ. when the case where the plurality of STAs transmits the 0436 When a partial bandwidth having a low interfer uplink data through the same time resource in the existing ence level from an neighboring BSS is allocated to the STA WLAN system is assumed, the plurality of respective STAs in an environment in which different bandwidths are Sup may not know the transmission timing of the uplink data of ported for each BSS, it may be more preferable not to another STA in the WLAN system at present. Accordingly, transmit the HE-SIG B field throughout all bands as it is difficult for the AP to receive the uplink data on the same described above. time resource from the plurality of respective STAs. 0437. In FIGS. 20 to 23, the data field as a payload may 0450. Further, frequency resources used for transmitting include a Service field, a scrambled PSDU, tail bits, and the uplink data may overlap with each other by the plurality padding bits. of STAs in the WLAN system at present. For example, when 0438 FIG. 24 illustrates phase rotation for HE format oscillators of the plurality of respective STAs are different PPDU detection according to an embodiment of the present from each other, frequency offsets may be expressed to be invention. different from each other. When the plurality of respective 0439. In order to classify the HE format PPDU, phases of STAs in which the frequency offsets are different simulta 3 OFDM symbols transmitted after the L-SIG field may be neously performs the uplink transmission through different used in the HE format PPDU. frequency resources, some of frequency areas used by the 0440 Referring to FIG. 24, the phases of OFDM symbol plurality of respective STAs may overlap with each other. #1 and OFDM symbol #2 transmitted after the L-SIG field 0451. Further, in the existing WLAN system, power do not rotate in the HE format PPDU, but the phase of control for the plurality of respective STAs is not performed OFDM symbol #3 may rotate at 90° counterclockwise. That in the existing WLAN system. The AP may receive signals is, as a demodulation method of OFDM symbol #1 and having different powers from the plurality of respective OFDM symbol #2, BPSK may be used as the demodulation STAS dependently to distance and channel environments method of OFDM symbol #3, QBPSK may be used. between each of the plurality of STAs and the AP. In this 0441. The STA attempts decoding the first to third OFDM case, it may relatively more difficult for the AP to detect a symbols transmitted after the L-SIG field of the received signal which reaches with weak power than a signal which PPDU based on a constellation illustrated in the example of reaches with strong power. FIG. 24. When the STA succeeds in decoding, the STA may 0452. As a result, the present invention proposes the UL determine that the corresponding PPDU is the HE format MU transmission method in the WLAN system. PPDU. 0453 FIG. 25 is a diagram illustrating an uplink multi 0442. Herein, when the HE-SIGA field is transmitted in user transmission procedure according to an embodiment of 3 OFDM symbols after the L-SIG field, this means that all the present invention. of OFDM symbol #1 to OFDM symbol #3 are used for 0454 Referring to FIG. 25, the AP indicates preparing for transmitting the HE-SIG A field. the ULMU transmission to the STAs which participate in 0443 Hereinafter, the multi-user uplink data transmitting the ULMU transmission, receives a ULMU data frame from method in the WLAN system will be described. the corresponding STAs, and transmits the ACK frame in 0444. A scheme in which Further, the plurality of STAs response to the ULMU data frame. which operates in the wireless LAN system transmits data to 0455 First, the AP transmits a ULMU scheduling frame the AP on the same time resource may be referred to as 2510 to indicate preparing for the ULMU transmission to uplink multi-user (UL MU) transmission. the STAs that will transmit the ULMU data. Herein, the UL US 2017/017.0937 A1 Jun. 15, 2017 24
MU scheduling frame may also be called a term such as UL of 1, the first field may indicate the UL MU MIMO MU trigger frame or trigger frame. transmission. The size of the first field may be configured by 0456. Herein, the UL MU scheduling frame 2510 may 1 bit. include control information including STA identifier (ID)/ 0467 A second field (for example, STAIDfaddress field) address information, resource allocation information, dura announces STAIDs or STA addresses that will participate in tion information, and the like. the ULMU transmission. The size of the second field may 0457. The STAIDfaddress information means informa be configured by the number of bits for announcing the STA tion on an identifier or address for specifying each STA that ID X the number of STAs which will participate in ULMU. transmits the uplink data. For example, when the second field is configured by 12 bits, the second field may indicate the ID/address of each STA for 0458. The resource allocation information means infor each 4 bit. mation on an uplink transmission resource (for example, 0468. A third field (for example, resource allocation field) frequency/subcarrier information allocated to each STA in indicates a resource area allocated to each STA for the UL the case of the ULMU OFDMA transmission and a stream MU transmission. In this case, the resource area allocated to index allocated to each STA in the case of the UL MU each STA may be sequentially indicated to each STA accord MIMO transmission) allocated for each STA. ing to the order of the second field. 0459. The duration information means information for 0469 When the first field value is 0, the third field value determining a time resource for transmitting the uplink data represents frequency information (for example, a frequency frame transmitted by the plurality of respective STAs. Here index, a subcarrier index, and the like) for the UL MU inafter, the duration information is referred to as MAC transmission in the order of the STAIDfaddress included in duration. the second field and when the first field value is 1, the third 0460 For example, the MAC duration may include inter field value represents MIMO information (for example, a val information of a transmit opportunity (TXOP) allocated stream index, and the like) for the ULMU transmission in for uplink transmission of each STA, or information (for the order of the STAIDfaddress included in the second field. example, a bit or symbol) on the length of the uplink frame. 0470. In this case, since multiple indexes (that is, the 0461) Further, the UL MU scheduling frame 2510 may frequency/subcarrier index or stream index) may be known further include control information, including MCS infor to one STA, the size of the third field may be configured by mation, coding information, and the like to be used at the a plurality of bits (alternatively, may be configured in a time of transmitting the ULMU data frame for each STA. bitmap format) x the number of STAs which will participate 0462. The control information may be transmitted in the in the ULMU transmission. HE-part (for example, the HE-SIG A field or HE-SIG B 0471. For example, it is assumed that the second field is field) of the PPDU transferring the scheduling frame 2510 or Set in the order of STA 1 and STA 2 and the third field is a control field (for example, the frame control field of the set in the order of 2 and 2. MAC frame, and the like) of the ULMU scheduling frame 0472. In this case, when the first field is 1, the frequency 251O. resource may be allocated to STA 1 from a higher (alterna tively, lower) frequency domain the next frequency resource 0463. The PPDU transferring the UL MU scheduling may be sequentially allocated to STA 2. As one example, frame 2510 has a structure which starts with the L-part (for when 20 MHz-unit OFDMA is supported in the 80 MHz example, the L-STF field, the L-LTF field, the L-SIG field, band, STA may use a higher (alternatively, lower) 40 MHz and the like). As a result, the legacy STAS may perform band and STA 2 may use the next 40 MHz band. network allocation vector (NAV) setting from the L-SIG 0473. On the contrary, when the first field is 1, a higher field. For example, the legacy STAS may calculate a duration (alternatively, lower) may be allocated to STA 1 and the next (hereinafter, L-SIG protection duration) for the NAV set stream may be sequentially allocated to STA 2. In this case, ting based on data length and data rate information in the a beam forming scheme depending on each stream may be L-SIG In addition, the legacy STAs may determine that there predesignated or more detailed information on the beam is no data transmitted thereto during the calculated L-SIG forming scheme depending on the stream may be included protection duration. in the third field or a fourth field. 0464 For example, the L-SIG protection duration may be 0474 Each STA transmits UL MU data frames 2521, determined as the sum of an MAC duration value of the UL 2522, and 2523 to the AP based on the ULMU scheduling MU scheduling frame 2510 and a residual duration after the frame 2510 transmitted by the AP. Herein, each STA may L-SIG field in the PPDU transferring the ULMU scheduling receive the ULMU scheduling frame 2510 and thereafter, frame 2510. As a result, the L-SIG protection duration may transmit the ULMU data frames 2521, 2522, and 2523 to the be set to a value up to a duration in which an ACK frame AP after the SIFS. 2530 transmitted to each STA is transmitted according to the 0475 Each STA may determine a specific frequency MAC duration value of the ULMU scheduling frame 2510. resource for the UL MU OFDMA transmission and the 0465 Hereinafter, the resource allocation method for UL spatial stream for the ULMU MIMO transmission based on MU transmission to each STA will be described in more the resource allocation information of the ULMU schedul detail. For easy description, the field including the control ing frame 2510. information is distinguished and described, but the present 0476. In detail, in the case of the UL MU OFDMA invention is not limited thereto. transmission, the respective STAS may transmit the uplink 0466. A first field may distinguish and indicate the UL data frame on the same time resource through different MU OFDMA transmission and the UL MU MIMO trans frequency resources. mission. For example, in the case of 0, the first field may 0477. Herein, respective STA 1 to STA3 may be allocated indicate the ULMU OFDMA transmission and in the case with different frequency resources for transmitting the US 2017/017.0937 A1 Jun. 15, 2017
uplink data frame based on the STAID/address information perform the NAV setting up to the ACK frame 2530 through and the resource allocation information included in the UL the L-SIG field of the ULMU scheduling frame 2510. MU scheduling frame 2510. For example, the STA ID/ad 0484. When the uplink data frame may be sufficiently dress information may sequentially indicate STA 1 to STA3 configured with the information of the ULMU scheduling and the resource allocation information may sequentially frame 2510, the SIG field (that is, an area in which control indicate frequency resource 1, frequency resource 2, and information for a configuration scheme of the data frame) in frequency resource 3. In this case, STA 1 to STA 3 sequen the PPDU transferring the ULMU scheduling frame 2510 tially indicated based on the STA ID/address information may not also be required. For example, the HE-SIG A field may be allocated with frequency resource 1, frequency and/or the HE-SIG B field may not be transmitted. Further, resource 2, and frequency resource 3 sequentially indicated the HE-SIG A field and the HE-SIG C field may be trans based on the resource allocation information, respectively. mitted and the HE-SIG B field may not be transmitted. That is, STA 1, STA 2, and STA 3 may transmit the uplink 0485 The AP may transmit the ACK frame 2530 in data frames 2521, 2522, and 2523 to the AP through response to the uplink data frames 2521, 2522, and 2523 frequency 1, frequency 2, and frequency 3, respectively. received from each STA. Herein, the AP may receive the 0478. Further, in the case of the UL MU MIMO trans uplink data frames 2521, 2522, and 2523 from each STA and mission, the respective STAS may transmit the uplink data transmit the ACK frame 2530 to each STA after the SIFS. frame on the same time resource through one or more 0486. When the existing structure of the ACK frame is different streams among the plurality of spatial streams. similarly used, AIDs (alternatively, partial AID) of the STAs 0479. Herein, respective STA 1 to STA3 may be allocated which participate in the UL MU transmission may be with the spatial streams for transmitting the uplink data configured to be included in the RA field having a size of 6 frame based on the STA IDfaddress information and the OctetS. resource allocation information included in the UL MU 0487. Alternatively, when the ACK frame having a new scheduling frame 2510. For example, the STA ID/address structure is configured, the ACK frame may be configured in information may sequentially indicate STA 1 to STA 3 and a form for the DLSU transmission or DL MU transmission. the resource allocation information may sequentially indi That is, in the case of the DL SU transmission, the ACK cate spatial stream 1, spatial stream 2, and spatial stream 3. frame 2530 may be sequentially transmitted to the respective In this case, STA 1 to STA3 sequentially indicated based on STAS which participate in the ULMU transmission, and in the STA ID/address information may be allocated with the case of the DL MU transmission, the ACK frame 2530 spatial stream 1, spatial stream 2, and spatial stream 3 may be simultaneously transmitted to the respective STAs sequentially indicated based on the resource allocation infor which participate in the ULMU transmission through the mation, respectively. That is, STA 1, STA2, and STA3 may resources (that is, the frequencies or streams) allocated to the transmit the uplink data frames 2521, 2522, and 2523 to the respective STAs. AP through spatial stream 1, spatial stream 2, and spatial 0488. The AP may transmit only the ACK frame 2530 for stream 3, respectively. the ULMU data frame which is successfully received to the 0480. As described above, a transmission duration (alter corresponding STA. Further, the AP may announce whether natively, a transmission end time) of the uplink data frames the ULMU data frame is successfully received as ACK or 2521, 2522, and 2523 transmitted by each STA may be NACK through the ACK frame 2530. When the ACK frame determined by the MAC duration information included in 2530 includes NACK information, the ACK frame 2530 the ULMU scheduling frame 2510. Accordingly, each STA may include even a reason for the NACK or information (for may synchronize the transmission end time of the uplink example, the ULMU scheduling information, and the like) data frames 2521, 2522, and 2523 (alternatively, the uplink for a Subsequent procedure. PPDU transferring the uplink data frames) through bit 0489. Alternatively, the PPDU transferring the ACK padding or fragmentation based on the MAC duration value frame 2530 may be configured in a new structure without the included in the ULMU scheduling frame 2510. L-part. 0481. The PPDU transferring the uplink data frames 0490 The ACK frame 2530 may include the STA ID or 2521, 2522, and 2523 may be configured even in a new address information, but when the order of the STAs indi structure without the L-part. cated by the UL MU scheduling frame 2510 is similarly 0482. Further, in the case of the UL MU MIMO trans applied, the STAID or address information may be omitted. mission or ULMU OFDMA transmission of a subband type 0491. Further, a frame for next ULMU scheduling or a less than 20 MHz, the L-part of the PPDU transferring the control frame including correction information for the next uplink data frames 2521, 2522, and 2523 may be transmitted ULMU transmission, and the like may be included in the in an SFN scheme (that is, all STAs simultaneously transmit TXOP by extending the TXOP (that is, the L-SIG protection the same L-part configuration and content). On the contrary, duration) of the ACK frame 2530. in the case of the UL MU OFDMA transmission of a 0492 Meanwhile, an adjustment process such as syn subband type equal to or more than 20 MHz, the L-part of chronizing the STAs, or the like may be added for the UL the PPDU transferring the uplink data frames 2521, 2522, MU transmission. and 2523 may be transmitted by the unit of 20 MHz in the 0493 FIG. 26 is a diagram illustrating the uplink multi band to which each STA is allocated. user transmission procedure according to an embodiment of 0483. As described above, the MAC duration value in the the present invention. ULMU scheduling frame 2510 may be set to a value up to 0494. Hereinafter, for easy description, the same descrip a duration in which the ACK frame 2530 is transmitted and tion as the example of FIG. 25 will be omitted. the L-SIG protection section may be determined based on 0495 Referring to FIG. 26, the AP may indicate the STAs the MAC duration value. Accordingly, the legacy STA may which will be used for the ULMU to prepare for the ULMU, US 2017/017.0937 A1 Jun. 15, 2017 26 and receive the ULMU data frame and transmit the ACK ously transmitted to the respective STAs which participate in after the adjustment process Such as synchronizing the STAS the ULMU transmission through the resources (that is, the for the UL MU, or the like. frequencies or streams) allocated to the respective STAs. 0496 First, the AP transmits a ULMU scheduling frame (0506. The adjustment frame 2630 may include the STA 2610 to indicate preparing for the ULMU transmission to ID or address information, but when the order of the STAs the STAs that will transmit the ULMU data. indicated by the ULMU scheduling frame 2610 is similarly 0497. Each STA that receives the UL MU scheduling applied, the STAID or address information may be omitted. frame 2610 from the AP transmits sync signals 2621, 2622, 0507 Further, the adjustment frame 2630 may include an and 2623 to the AP. Herein, each STA may receive the UL adjustment field. MU scheduling frame 2610 and transmit the sync signals 0508. The adjustment field may include information for 2621, 2622, and 2623 to the AP after the SIFS. adjusting the errors including the time? frequency/power, and 0498. In addition, the AP that receives the sync signals the like. Herein, the errors including the time/frequency/ 2621, 2622, and 2623 from each STA transmits an adjust power, and the like may occur in the signals of the STAS, ment frame 2630 to each STA. Herein, the AP may receive which are received by the AP and the adjustment informa the sync signals 2621, 2622, and 2623 and transmit the tion means information for announcing an error gap to be adjustment frame 2630 after the SIFS. adjusted. Besides, even any information to more accurately 0499. A procedure of transceiving the synchronization adjust the errors including the time? frequency/power, and signals 2621, 2622, and 2623 and the adjustment frame 2630 the like of each STA based on the sync signals 2621, 2622, is a procedure for adjusting the time/frequency/power, and and 2623 received by the AP may be included in the the like among the respective STAs for transmitting the UL adjustment frame 2630. MU data frame. That is, the procedure is a procedure in (0509. The PPDU transferring the adjustment frame 2630 which the STAs transmit the sync signals 2621, 2622, and may be configured in a new structure without the L-part. 2623 thereof and the AP announces adjustment information to adjust errors including the time/frequency/power, and the 0510 Meanwhile, a procedure of transceiving the sync like based on the values to each STA through the adjustment signals 2621, 2622, and 2623 and the adjustment frame 2630 frame 2630 to adjust and transmit the values in the ULMU may be performed before transmitting the UL MU sched data frame to be transmitted next. Further, the procedure is uling frame 2610 of each STA. performed after the ULMU scheduling frame 2610, and as 0511 Further, transmission of the sync signals 2621, a result, the STA may have a time to prepare for configuring 2622, and 2623 may be omitted and the AP may transmit the the data frame according to scheduling. UL MU scheduling frame 2610 including the adjustment 0500. In more detail, the STAs indicated in the ULMU information through implicit measurement. For example, in scheduling frame 2610 transmit the sync signals 2621, 2622, a pre-procedure to be described below, the AP may generate and 2623 to resource areas indicated or designated thereby, the adjustment information to adjust the errors including the respectively. Herein, the sync signals 2621, 2622, and 2623 time? frequency/power, and the like among the respective transmitted from each STA may be multiplexed by time STAs through the NDP or buffer status/sounding frame division multiplexing (TDM), code division multiplexing transmitted from each STA and transmit the adjustment (CDM), and/or spatial division multiplexing (SDM) information to each STA through the UL MU scheduling schemes. frame 2610. 0501) For example, when the order of the STAs indicated 0512 Further, a procedure in which STAs (for example, by the ULMU scheduling frame 2610 is STA 1, STA2, and a case in which an adjustment procedure among the respec STA 3 and the sync signals 2621, 2622, and 2623 of each tive STAs that will perform the UL MU transmission is STA are multiplexed by the CDM, Sequence 1, Sequence 2. previously completed, and the like) of which adjustment is and Sequence 3 which are allocated may be transmitted to not required transceive the sync signals 2621, 2622, 2623 the AP in the order of the designated STAs, respectively. and the adjustment frame 2630 may be omitted. 0502. Herein, the resources (for example, the time/se 0513. Further, when only a partial adjustment procedure quence/stream, and the like) to be used by each STA may be is required, only the procedure may be adjusted. For indicated or defined to each STA in advance so as to example, when the cyclic prefix (CP) length of the ULMU multiplex and transmit the sync signals 2621, 2622, and data frame is as long as asychronization among the STAS 2623 of each STA by the TDM, the CDM, and/or the SDM. does not become an issue, a procedure for adjusting a time 0503. Further, the PPDU transferring the sync signals difference may be omitted. Alternatively, when the ULMU 2621, 2622, and 2623 may be included the L-part, or be OFDMA transmission is performed, if a guard band between transmitted by only a physical layer signal without config the STAS is Sufficient, a procedure for adjusting a frequency uring the MAC frame. difference may be omitted. 0504 The AP that receives the sync signals 2621, 2622, 0514. Each STA transmits UL MU data frames 2641, and 2623 from each STA transmits the adjustment frame 2642, and 2643 to the AP based on the ULMU scheduling 2630 to each STA. frame 2610 and the adjustment frame 2630 transmitted by 0505. In this case, the AP may transmit the adjustment the AP. Herein, each STA may receive the adjustment frame frame 2630 to each STA by the DLSU transmission scheme 2630 from the AP and thereafter, transmit the ULMU data or transmit the adjustment frame 2630 to each STA by the frames 2641, 2642, and 2643 to the AP after the SIFS. DLMU transmission scheme. That is, in the case of the DL 0515. The AP may transmit an ACK frame 2650 as a SU transmission, the adjustment frame 2630 may be sequen response to the uplink data frames 2641, 2642, and 2643 tially transmitted to the respective STAs which participate in received from each STA. Herein, the AP may receive the the UL MU transmission and in the case of the DL MU uplink data frames 2641, 2642, and 2643 from each STA and transmission, the adjustment frame 2630 may be simultane transmit the ACK frame 2650 to each STA after the SIFS. US 2017/017.0937 A1 Jun. 15, 2017 27
0516. In FIGS. 25 and 26, a structure of ULMU trans the L-part. That is, a part of the HE-part may be continuously mission associated downlink PPDU including the ULMU configured by the unit of 20 MHz. scheduling frame, the adjustment frame, the ACK frame, 0531. Further, the UL MU associated DL PPDU may and the like may be configured based on 20 MHz. This will have different structures for each frame. For example, the be described in more detail with reference to a drawing ULMU scheduling frame may follow a structure in which given below. the ULMU scheduling frame is copied to all bands by the 0517 FIG. 27 is a diagram illustrating a downlink PPDU unit of 20 MHz, and as a result, the same information is structure associated with uplink multi-user transmission transmitted to all bands as illustrated in FIG. 27(a) and the according to an embodiment of the present invention. downlink ACK frame may be transmitted only through one 0518. In FIG. 27, it is assumed that the full band is 80 20 MHz-unit PPDU in FIG. 27(a). MHz and the bandwidth is allocated by the unit of 20 MHz 0532. Meanwhile, the DL PPDU structure associated for each STA for the UL OFDMA transmission. with the UL MU transmission according to FIG. 27 is 0519 Referring to FIG. 27(a), all information of STAs of described by assuming the case in which the channel is the ULMU is included in the 20 MHZ PPDU and the same allocated by the unit of 20 MHz for each STA in the ULMU information may be copied and transmitted to other 20 MHz OFDMA transmission for easy description, but the above channels. method may be similarly applied even to the case of the UL 0520. When a primary channel is configured in the cor MU MIMO transmission. responding BSS, the STA first verifies information in the 0533. For example, when 20 MHz-unit stream 1 to primary channel configured in the corresponding BSS, and stream 4 are sequentially allocated to STA 1 to STA4 at 20 as a result, the information of the STAs of the UL MU MHz and the ULMU MIMO transmission is performed, the transmission may be transmitted only in the primary 20 information on all STAs may be included and transmitted in MHZ channel. However, in this case, when interference each stream as illustrated in FIG. 27(a). occurs in the corresponding primary channel due to an 0534) Further, as illustrated in FIG. 27(b), for each 20 neighboring BSS, the information may be lost. MHz-unit stream, only information on an STA to which the 0521. Each STA may read all available channels accord corresponding stream is allocated may be included and ing to a capability thereof. For example, when STA 1 is an transmitted. STA that supports the 40 MHz band, STA 1 may read first 0535. In addition, when 80 MHz-unit UL MU MIMO and second channels from the top. Further, when STA4 is an transmission is supported for each STA at full-band 80 MHz, STA that supports the 80 MHz band, STA4 may read all four the information on all STAs may be included and transmitted channels. for each 80 MHz-unit stream as illustrated in FIG. 27(c). 0522. Accordingly, it may be preferable to transmit infor 0536. However, the PPDU structure illustrated in FIG. mation on all STAs in all channels for each 20 MHz as 27(a) may be preferable in order to support both the ULMU illustrated in FIG. 27(a) in order to prevent such a problem. OFDMA transmission and the ULMU MIMO transmission. That is, even though the information is lost in a specific For example, in order to support the 20 MHz-unit ULMU channel due to the interference, the information may be OFDMA transmission for each STA at the full-band 80 Successfully transmitted through other channels. MHz, the PPDU may be configured like the example of FIG. 27(a) and in order to support the 5 MHZ-unit or 20 MHz-unit 0523 Referring to FIG. 27(b), information regarding the UL MU MIMO transmission for each STA at the full-band ULMU transmission of the respective STAs to be allocated 20 MHz, only one 20 MHz PPDU structure in the example for each 20 MHz may be transmitted. of FIG. 27(a) may be transmitted. In this case, DL frame 0524. Further, when the 40 MHZ channel is allocated to structures associated with the ULMU OFDMA transmission STA 1 unlike FIG. 27(b), the information may be transmitted and the UL MU MIMO transmission may be configured through the 40 MHZ channel in a PPDU structure in which through the same PPDU structure. the information is copied to STA 1 by the unit of 20 MHz. 0537. A pre-procedure for the ULMU transmission is Further, the information may be transmitted in the 40 MHz required for the ULMU transmission. PPDU Structure. 0538. The pre-procedure means a step of preparing for 0525. As described above, each STA may verify the reporting channel states of the STAs and/or the buffer status information transmitted thereto by reading all available of the STAs required for the ULMU transmission, and the channels according to the capability thereof. like. 0526. The case of FIG. 27(b) may be preferable when the 0539 Herein, buffer status information may include primary channel is not configured in the corresponding BSS. information on which format data which the STA will 0527. Referring to FIG. 27(c), the HE-part other than the transmit uplink has (for example, access category (AC) L-part and the data may be transmitted in a full-band PPDU information (for example, Voice, video, data, and the like), Structure. how many the data are accumulated in a queue (for example, 0528. This case may be preferable when the AP knows the size of the uplink data, the size of the queue in which the that all terminals associated with the UL MU support 80 uplink data are accumulated, and the like), how urgent the MHz in advance. uplink data is transmitted (for example, backoff count, a 0529. The bandwidths including 80 MHz, 20 MHz, and contention window value, and the like), and the like. the like illustrated in FIG. 27 are just exemplary values for (0540 1) Method Using NDP Procedure easy description and the present invention is not limited 0541. The pre-procedure the ULMU transmission may thereto. be performed by using the NDP similarly to the example of 0530. Further, a part (for example, at least any one of the FIG. 11. That is, the NDP is received from each STA which HE-SIGA field, the HE-STF field, the HE-LTF field, and the participates in the ULMU transmission, and as a result, the HE-SIG B field) of the HE-part may follow the structure of AP may acquire the uplink channel state information and/or US 2017/017.0937 A1 Jun. 15, 2017 28 buffer status information for each STA. This will be channel state in the case of the ULMU MIMO transmission) described with reference to drawings. indicated by the NDPA frame 2810. 0542 FIG. 28 is a diagram illustrating a pre-procedure 0554. First, STA 1 that receives the NDPA frame 2810 for the uplink multi-user transmission according to an transmits the NDP 2820 to the AP embodiment of the present invention. 0555 STA 1 may receive the NDPA frame 2810 and (0543. In FIG. 28, a case in which three STAs (STA 1, transmit the NDP 2820 to the AP after the SIFS. STA 2, and STA 3) participate in the ULMU transmission 0556. Herein, the NDPs 2820, 2840, and 2860 transmit is assumed. ted by each STA are configured by similarly using the NDP 0544 Referring to FIG. 28, the AP transmits a null data format transmitted by the AP. However, the VHT-LTF field packet announcement (NDPA) frame 2810 to each STA (alternatively, the HE-LTF field) of the NDPs 2820, 2840, which participates in the ULMU transmission for a buffer and 2860 transmitted by each STA may be included as large status/sounding request. as the resource area (as large as the number of frequencies/ (0545. Herein, the NDPA frame 2810 may be configured streams) indicated by the NDPA frame 2810. in the same format as the example of FIG. 12. 0557. The AP acquires the uplink channel state informa (0546) However, in order to distinguish the NDPA frame tion based on the training field (for example, the VHT-LTF 2810 from the NDPA frame used for the existing downlink field or the HE-LTF field) of the NDP 2820 received from sounding procedure, the NDPA frame 2810 may notify STA 1. announcement for the ULMU transmission by using the 0558 Next, the AP transmits a beam forming report poll reserved bit (for example, reserved 2 bits of the sounding frame 2830 to STA 2 in order to acquire the uplink channel dialog token field). information from STA 2. (0547. The NDPA frame 2810 includes an STA Info field 0559 The AP may receive the NDP from STA 1 and including information on a target STA which participates in transmit the beam forming report poll frame 2830 to STA2 the ULMU. One STA Info field may be included for each after the SIFS. sounding target STA and the AID for identifying the target 0560 Herein, the beam forming report poll frames 2830 STA which participates in the UL MU transmission is and 2850 may be configured in the same format as the included in the AID12 subfield. example of FIG. 15. (0548. Further, the NDPA frame 2810 may further include 0561 STA 2 that receives the Beamforming Report Poll the resource allocation field for the ULMU transmission. frame 2830 transmits the NDP 2840 to the AP Alternatively, the resource allocation information for the UL 0562 Herein, STA 2 may receive the Beamforming MU transmission allocated to each STA may be transmitted Report Poll frame 2830 and transmit the NDP 2840 to the AP by using the Nc Index subfield of the STA Info field. after the SIFS. Hereinafter, the field including the resource allocation infor 0563) Next, similarly to the process for STA 2, the AP mation is collectively called the resource allocation field. transmits the beam forming report poll frame 2850 to STA3 0549. The resource allocation field indicates a resource in order to acquire the uplink channel information from STA area (for example, frequency/subcarrier information for each 3 and STA3 that receives the beam forming report poll frame STA to report the channel state in the case of the ULMU 2850 transmits the NDP 2860 to the AP OFDMA transmission and a stream index for each STA to 0564. The AP may acquire the channel state information report the channel state in the case of the UL MU MIMO and/or buffer status information through the NDP received transmission) for reporting a frequency/stream channel State from each STA. In addition, the AP may allocate the ULMU of each STA for the ULMU transmission. In this case, the resources (for example, the stream for each STA in the case resource area allocated to each STA may be sequentially of the ULMU MIMO and the frequency/subcarrier for each indicated to each STA according to the order of the AID12 STA in the case of the ULMU OFDMA) to each STA based subfield. on the acquired information. 0550. In the case of the ULMU MIMO transmission, the 0565. 2) Method for Configuring New Frame spatial stream allocated to each STA may be indicated based 0566. The pre-procedure for the UL MU transmission on in AID12 subfields and resource allocation fields. Further, may be performed by using a newly configured frame unlike in the case of the UL MU OFDMA transmission, the the example of FIG. 28. That is, the new frame for acquiring frequency resources allocated to the plurality of respective the uplink channel state information and buffer status infor STAS may be indicated based on n AID12 subfields and mation may be defined without using the existing defined resource allocation fields. NDPA frame or NDP. This will be described with reference 0551 STAs that receive the NDPA frame 2810 may to the following drawings. verify the AID12 subfield value included in the STA Info 0567 FIG. 29 is a diagram illustrating a pre-procedure field and verify whether the STAs are the target STA for the for the uplink multi-user transmission according to an ULMU transmission. embodiment of the present invention. 0552. Further, the STAs may know the order of the NDP 0568. In FIG. 29, the case in which three STAs (STA 1, transmission through the order of the STA Info field included STA 2, and STA 3) participate in the ULMU transmission in the NDPA. In FIG. 28, a case in which NDPs 2820, 2840, is assumed. and 2860 are transmitted to the AP in the order of STA 1, 0569. Referring to FIG. 29, the AP transmits a buffer STA 2, and STA 3 is illustrated. status request (BSR)/sounding request (SR) frame 2910 to 0553 Each of the STAs may transmit the NDPs 2820, each STA for the buffer status/sounding request to each STA 2840, and 2860 to the AP through the resource area (for which participates in the ULMU transmission. example, frequency/subcarrier information for each STA to 0570 Herein, the BSR/SR frame 2910 includes an ID report the channel state in the case of the ULMU OFDMA (for example, AID) and/or address of the target STA which transmission and a stream index for each STA to report the participates in the ULMU. US 2017/017.0937 A1 Jun. 15, 2017 29
0571. Further, the BSR/SR frame 2910 may include 0581. Next, the AP transmits a polling frame 2930 to STA information for the target STA which participates in the UL 2 in order to acquire the uplink channel information from MU to report the buffer status and transmit the sounding STA 2. frame to the AP. In addition, the information may be 0582. The AP may receive the BS/sounding frame 2920 included in the order of the STAs that transmit the buffer from STA 1 and transmit the polling frame 2930 to STA 2 status (BS)/Sounding frame. after the SIFS. 0572 Moreover, the BSR/SR frame 2910 may further 0583. The polling frame means a frame that helps the include the resource allocation field for the ULMU trans next STA to transmit the BS/sounding frame. When the mission. BS/sounding frame is not received within a predetermined 0573. The resource allocation field indicates a resource time (for example, SIFS), the AP may transmit the polling area (for example, the frequency/subcarrier information for frame so that the next STA transmits the BS/sounding frame. each STA to report the channel state in the case of the UL 0584 STA 2 that receives the polling frame 2930 trans MU OFDMA transmission and the stream index for each mits the BS/sounding frame 2940 to the AP STA to report the channel state in the case of the ULMU 0585. Herein, STA2 may receive the polling frame 2930 MIMO transmission) for reporting the frequency/stream and transmit the BS/sounding 2940 to the AP after the SIFS. channel state of each STA for the ULMU transmission. In 0586) Next, similarly to the process for STA 2, the AP this case, the resource area allocated to each STA may be transmits the polling frame 2950 to STA3 in order to acquire sequentially indicated to each STA according to the order of the uplink channel information from STA3 and STA 3 that the STAIDfaddress. receives the polling frame 2930 transmits the BS/sounding 0574. In the case of the ULMU MIMO transmission, the frame 2960 to the AP spatial stream allocated to each STA may be indicated based on n STAIDfaddress and resource allocation fields. Further, 0587. The AP may acquire the channel state information in the case of the UL MU OFDMA transmission, the and/or buffer status information through the BS/sounding frequency resources allocated to the plurality of respective frame received from each STA. In addition, the AP may STAS may be indicated based on n STA ID/address and allocate the ULMU resources (for example, the stream for resource allocation fields. each STA in the case of the UL MU MIMO and the (0575. Each of the STAs transmits buffer status (BS)/ frequency/subcarrier for each STA in the case of the ULMU sounding frames 2920, 2940, and 2960 to the AP. Herein, the OFDMA) to each STA based on the acquired information. STAS may know the transmission order of the BS/sounding 0588 Meanwhile, in the example of FIG. 29, the PPDU frames 2920, 2940, and 2960 through the order of the STA transferring the respective frames (the BSR/SR frame, the IDfaddress information included in the BSR/SR frame 2910. BS/sounding frame, and the polling frame) may include or In FIG. 29, a case in which the BS/sounding frames 2920, not include the L-part. When the PPDU does not include the 2940, and 2960 are transmitted to the AP in the order of STA L-part, the PPDU may be constituted only by the HE-SIG 1, STA 2, and STA 3 is illustrated. field (alternatively, the HE-SIGA and the HE-SIG B), the 0576. Each of the STAs may transmit the BS/sounding HE-STF, and the HE-LTF and when the PSDU additionally frames 2920, 2940, and 2960 to the AP through a resource exists, the PPDU may include the data field. area (for example, frequency/subcarrier information for each 0589 For example, only the PPDU transferring the BSR/ STA to report the channel state in the case of the ULMU SR frame which is a first transmitted frame includes the OFDMA transmission and a stream index for each STA to L-part to allow the legacy STA to perform the NAV setting report the channel state in the case of the UL MU MIMO based on the L-SIG field and the PPDU transferring other transmission) indicated by the BSR/SR frame 2910. frames may be configured without the L-part. In this case, 0577 First, STA 1 that receives the BSR/SR frame 2910 the L-SIG field value may be set as a value up to a duration transmits the BS/sounding frame 2920 to the AP. in which the BS/sounding frame is received from the last 0578. STA 1 may receive the BSR/SR frame 2910 and STA transmit the BS/sounding 2920 to the AP after the SIFS. 0590 3) Scheme of Updating Control Field Included in 0579. Herein, the BS/sounding frames 2920, 2940, and Existing Frame without Configuring New Frame 2960 transmitted by each STA may include the training field 0591. The pre-procedure for the UL MU transmission (for example, the VHT-LTF field or HE-LTF field) for buffer may be performed by updating the frame control field status information and sounding. For example, the buffer included in the MAC frame used in the related art without status information may be included in the Frame Control configuring the new frame. field and the LTF field (for example, the VHT-LTF field or 0592 For example, when the frame including the VHT HE-LTF field) may be included as large as the resource area control field (see FIG. 10) is used, the reserved bit in the (that is, as large as the number of frequencies/streams) VHT control field is configured for the UL MU (for indicated by the BSR/SR frame 2910. example, set to 1), and as a result, other buffer status 0580 Further, each STA may transmit the BS/sounding information to transmit and receive the control information frames 2920, 2940, and 2960 (for example, the Frame of the VHT control field may also be included. That is, when Control field) including information required for configuring the reserved bit in the VHT control field is not configured for the ULMU transmission instead of transmitting the training the ULMU, the reserved bit may be used similarly to the field for the sounding. For example, each STA may transmit existing frame configuration and when the reserved bit is the BS/sounding frames 2920, 2940, and 2960 (for example, configured for the ULMU, the reserved bit may be used for the Frame Control field) including information such as the the pre-procedure for the ULMU transmission. number of streams preferred by each STA, the beam forming 0593. In this case, the AP may configure the reserved bit matrix, an MCS configuration, the position of the subcarrier, in the VHT control field for the UL MU and the MRQ and the like. subfield is set to 1 to request the buffer status/sounding. US 2017/017.0937 A1 Jun. 15, 2017 30
0594. The STA changes fields not required for the UL 0603 The TA field value represents a transmitter address MU transmission to fields for the UL MU transmission for transmitting the NDPA frame or an address of the STA together the existing other information by receiving a which transmits the NDPA frame, or a bandwidth signaling request from the AP through the VHT control field (that is, TA an involuntary transmission case) or Voluntary determina 0604. The Sounding Dialog Token field (alternatively, tion (that is, a Voluntary transmission case) to perform buffer Sounding Sequence field) may be constituted by a Reserved status/sounding reporting. For example, 6 bits indicating the subfield and a Sequence Number subfield. buffer status information including access category (access 0605. The Sounding Dialog Token field may include category) information (2 bits) and data size (4 bits) may be information indicating whether the pre-procedure is the included instead of GID 6 bits (an MFSI/GID-L subfield and pre-procedure (that is, Sounding reporting and/or buffer a GID-H subfield in FIG. 10). status information reporting) for the ULMU transmission or 0595. Further, a buffer status for each STA may be the pre-procedure (that is, Sounding reporting) for the DL checked by using a signal (alternatively, frame) which is MU transmission. periodically transmitted, such as a beacon frame, or the like. 0606 Table 10 is a table showing the Sounding Dialog 0596 For example, the AP may make the channel state Token field according to an embodiment of the present and/or buffer status request information to be included in the invention. beacon frame and thereafter, receives a report of the buffer status from each STA by using a contention free-poll (CF TABLE 10 poll) frame, and the like, or indicate the uplink frame including the channel state and/or buffer status to be trans The number mitted by using the CF-poll frame, and the like. In this case, of the AP may make the channel state and/or buffer status Subfield bits Description request information to be always included in the beacon Reserved 2 In the case of the legacy STA, this field frame or included only when needed. is disregarded. I the case of 80.11ax STA 0597 For example, when the pre-procedure for the UL (that is, HE STA), this field is interpreted MU transmission is performed by using the null data packet as follows. announcement (NDPA) frame, the NDPA fame may be 0: DL beamforming (alternatively, DL MU) configured as follows. * 1: UL beamforming (alternatively, ULMU) Sounding 6 Value selected by beamformer in order to 0598 FIG. 30 is a diagram illustrating a null data packet Dialog Token identify the NDPA frame announcement (NDPA) frame according to an embodiment Number of the present invention. 0599 Referring to FIG. 30, the NDPA frame may be comprised of the frame control field, the duration field, the 0607 Referring to Table 10, the legacy STA disregards receiving address (RA) field, the transmitting address (TA) the Reserved subfield. field, the sounding dialog token field, the STA information 0608. When the Reserved subfield value is 0, the HE 1 (STA Info 1) field to the STA information n (STA Info n) STA interprets the case as DL beam forming (that is, DL MU field, and the FCS. transmission). In addition, as described above, the downlink 0600 The RA field value represents a receiver address or channel is estimated through the NDP (alternatively, beam STA address that receives the NDPA frame. forming report poll frame) to feedback channel information 0601 When the NDPA frame includes one STA Info field, to the AP through the VHT Compressed Beamforming the RA field value may have an address of the STA identified frame. by the AID in the STA Info field. For example, when the 0609. On the contrary, when the Reserved subfield value NDPA frame is transmitted to one target STA for DL is 1, the HE STA interprets the case as UL beam forming SU-MIMO or UL SU-MIMO channel sounding, the AP (that is, UL MU transmission). In addition, each STA transmits the NDPA frame to the target STA by unicast. transmits the uplink packet or frame to the AP so that the AP 0602. On the contrary, when the NDPA frame includes estimates the uplink channel one or more STA Info fields, the RA field value may have a 0610 Each STA Info field may be comprised of an AID12 broadcast address. For example, when the NDPA frame is subfield, a Feedback Type subfield, and an Nc Index sub transmitted to one or more target STAs for DL MU MIMO/ field. OFDMA or UL MU MIMO/OFDMA channel sounding, the 0611 Table 11 is a table showing the STA Info field AP broadcasts the NDPA frame. according to an embodiment of the present invention. TABLE 11
The number of Subfield bits Description AID12 12 Includes the AID of the STA which becomes the sounding feedback target When the target STA is the AP, a mesh STA, or the STA which is an IBSS member, the AID12 subfield value is set to 'O Feedback Type 1 Indicates the feedback request type for the sounding target STA In the case of SU, 'O' In the case of MU, 1 US 2017/017.0937 A1 Jun. 15, 2017 31
TABLE 11-continued
The number Subfield bits Description Nc Index 3 When interpreted as the DL beamforming (that is, DL MU) through the Reserved subfield of the Sounding Dialog Token field in the legacy STA and the 802.11ax STA (that is, HE STA), Nc Index is interpreted as follows. When the Feedback Type subfield indicates the MU-MIMO, Nc Index indicates a value acquired by Subtracting 1 from the number (Nc) of columns of the compressed beamforming feedback matrix In the case of Nc = 1, O' In the case of Nc = 2, 1, In the case of Nc = 8, 7 In the case of the SU-MIMO, the Nc Index is set as the Reserved subfield When interpreted as the UL beamforming through the Reserved subfield of the Sounding Dialog Token field in the 802.11ax STA (that is, HE STA), Nc Index is interpreted as follows. The number of sounding streams which each STA needs to transmit
0612 Referring to Table 11, the Nc Index subfield may 0620 Referring to FIG. 31, the AP transmits a sounding include different information according to the DL MU and/or buffer status request frame to STA 1 to STA n (n is 2 transmission or the ULMU transmission. or more) which participate in the UL MU transmission 0613 First, when the Reserved subfield value of the (S3101). Sounding Dialog Token field is 0 (that is, in the case of the 0621. As the sounding and/or buffer status request frame, DL MU transmission), the Nc Index subfield includes the the VHT Null Data Packet Announcement (NDPA) frame, number Nc of columns of a compressed beam forming the beacon frame, and the like may be used. Further, as feedback matrix (in the case of the MU-MIMO) or is described above, the new frame is not defined and the frame configured as the Reserved subfield (in the case of the control field of the existing MAC frame may be updated and SU-MIMO). used. Further, a newly defined buffer status request/sounding 0614. Accordingly, the legacy STA or the 802.11ax STA request frame may be used. (that is, HE STA) feeds back to the AP the downlink channel 0622. The sounding and/or buffer status request frame information estimated through the NDP (alternatively, may include information indicating the number of streams to beam forming report poll frame) received from the AP which each STA needs to transmit the sounding and/or buffer according to the Nc Index subfield value. status frame. 0615. On the contrary, when the Reserved subfield value 0623 Further, the sounding and/or buffer status request of the Sounding Dialog Token field is 1 (that is, in the case frame may include order information in which each STA will of the ULMU transmission), the Nc Index subfield includes transmit the sounding and/or buffer status frame. For the number of sounding streams which each STA needs to example, the Sounding and/or buffer status request frame transmit. may include the sounding stream number information 0616. Herein, the number of sounding streams is inter according to the order information of the respective STAs. preted as a meaning that the NDP including the LTF fields 0624. When the existing VHT Null Data Packet (for example, HE-LTF or HE-midamble) as large as the Announcement (NDPA) frame is used as the sounding number of corresponding sounding streams is transmitted. and/or buffer status request frame, the Sounding and/or 0617. Accordingly, the 802.11ax STA (that is, HE STA) buffer status request frame may include information for transmits the NDP including the LTF fields as large as the distinguishing whether the Sounding and/or buffer status number of streams indicated by the Nc Index subfield to the request frame is the frame for the DLMU transmission or AP so that the AP estimates the uplink channel. In this case, the frame for the ULMU transmission. even though the STA capability Supports a maximum of 4 0625 STA 1 to STA in that receive the sounding and/ streams, when the AP commands the STA to transmit the buffer status request frame transmits the Sounding and/or NDP including the LTF fields for two streams through the buffer status frame to the AP (S3102). Nc Index subfield, the corresponding STA transmits the 0626 STA 1 to STA in may transmit the sounding and/or NDP including the LTF fields for two streams indicated by buffer status frame to the AP in order according to the order the Nc Index subfield. information indicated by the sounding and/or buffer status 0618. The third scheme described up to now may be request frame. configured together with the first scheme or the second 0627. Further, STA 1 to STA in may transmit to the AP the scheme. For example, the channel information may be Sounding and/or buffer status frame including the number of transceived by the first scheme and the buffer status infor LTE symbols (for example, HE-ITF or HE-midamble) as mation may be transceived by the third scheme. large as the number of streams indicated by the Sounding 0619 FIG. 31 is a diagram illustrating a pre-procedure and/or buffer status request frame. for the uplink multi-user transmission according to an 0628. Meanwhile, the PPDU transferring the sounding embodiment of the present invention. and/or buffer status request frame may include the L-part So US 2017/017.0937 A1 Jun. 15, 2017 32 that the legacy STA may perform the NAV setting based on 0639. The embodiments described so far are those of the the L-SIG field value, but the PPDU transferring the sound elements and technical features being coupled in a prede ing and/or buffer status frame may include or not include the termined form. So far as there is not any apparent mention, L-part. When the PPDU does not include the L-part, the each of the elements and technical features should be PPDU may be comprised only of the HE-SIG field (alter considered to be selective. Each of the elements and tech natively, the HE-SIGA and the HE-SIG B), the HE-STF, and nical features may be embodied without being coupled with the HE-LTF and when the PSDU additionally exists, the other elements or technical features. In addition, it is also PPDU may include the data field. possible to construct the embodiments of the present inven 0629 Further, although not illustrated in S3101, the STA tion by coupling a part of the elements and/or technical after the second order may receives the polling frame from features. The order of operations described in the embodi the AP and thereafter, transmit the sounding and/or buffer ments of the present invention may be changed. A part of Status frame to the AP as illustrated in FIG. 28 or 29. For elements or technical features in an embodiment may be example, when the STA of the first order transmits the included in another embodiment, or may be replaced by the sounding and/or buffer status frame to the AP, the AP may elements and technical features that correspond to other transmit the polling frame to the STA of the second order and embodiment. It is apparent to construct embodiment by when the STA of the second order may receive the polling combining claims that do not have explicit reference relation frame and thereafter, transmit the sounding and/or buffer in the following claims, or to include the claims in a new status frame to the AP. The STAs after the third order may claim set by an amendment after application. also perform the operation by the same scheme. 0640 The embodiments of the present invention may be 0630. Thereafter, the AP may acquire the channel state implemented by various means, for example, hardware, information and/or buffer status information through the firmware, software and the combination thereof. In the case sounding and/or buffer status frame received from each of the hardware, an embodiment of the present invention STA. In addition, the AP may allocate the ULMU resources may be implemented by one or more application specific (for example, the stream for each STA in the case of the UL integrated circuits (ASICs), digital signal processors MU MIMO and the frequency/subcarrier for each STA in the (DSPs), digital signal processing devices (DSPDs), pro case of the UL MU OFDMA) to each STA based on the grammable logic devices (PLDS), field programmable gate acquired information. arrays (FPGAs), a processor, a controller, a micro controller, 0631 General Apparatus to which the Present Invention a micro processor, and the like. May be Applied (0641. In the case of the implementation by the firmware 0632 FIG. 32 is a block diagram exemplifying a wireless or the Software, an embodiment of the present invention may apparatus according to an embodiment of the present inven be implemented in a form such as a module, a procedure, a tion. function, and so on that performs the functions or operations described so far. Software codes may be stored in the 0633 Referring to FIG. 32, an apparatus 3210 according memory, and driven by the processor. The memory may be to the present invention may include a processor 3211, a located interior or exterior to the processor, and may memory 3212, and a radio frequency (RF) unit 3213. The exchange data with the processor with various known apparatus 3210 may be an AP or a non-AP STA for imple CaS. menting the embodiments of the present invention. 0642. It will be understood to those skilled in the art that 0634. The RF unit 3213 is connected to the processor various modifications and variations can be made without 3211 to transmit and/receive a wireless signal. For example, departing from the essential features of the inventions. the RF unit 3213 may implement the physical layer accord Therefore, the detailed description is not limited to the ing to the IEEE 802.11 system. embodiments described above, but should be considered as 0635. The processor 3211 is connected to the RF unit examples. The scope of the present invention should be 3213 to implement the physical layer and/or MAC layer determined by reasonable interpretation of the attached according to the IEEE 802.11 system. The processor 3211 claims, and all modification within the scope of equivalence may be configured to perform the operations according to should be included in the scope of the present invention. the various embodiments of the present invention according to FIGS. 1 to 31 above. In addition, a module that imple INDUSTRIAL APPLICABILITY ments the operations of the AP and/or the STA according to the various embodiments of the present invention according 0643. In the wireless communication system, the to FIGS. 1 to 16 above may be stored in the memory 3212 example in which the uplink multi-user transmission method and executed by the processor 3211. is applied to the IEEE 802.11 system is primarily described, 0636. The memory 3212 is connected to the processor but the uplink multi-user transmission method can be 3211 and stores various pieces of information for driving the applied to various wireless communication systems in addi processor 3211. The memory 3212 may be included in the tion to the IEEE 802.11 system. processor 3211, or installed exterior to the processor 3211 1. A method for transmitting multi-user uplink data in a and connected to the processor 3211 with a known means. wireless communication system, the method comprising: 0637. Further, the apparatus 3210 may have a single receiving, by a station (STA), a Sounding request frame antenna or multiple antennas. from an access point (AP); and 0638. Such a detailed configuration of the apparatus 3210 transmitting, by the STA, a sounding frame to the AP in may be implemented such that the features described in response to the Sounding request frame, various embodiments of the present invention described wherein the Sounding request frame includes information above are independently applied or two or more embodi indicating the number of streams in which the STA ments are simultaneously applied. needs to transmit the Sounding frame, and US 2017/017.0937 A1 Jun. 15, 2017
the sounding frame includes a long training field (LTF) backoff count for the uplink data transmission, and a con symbols as many as the number of streams. tention window for the uplink data transmission. 2. The method for transmitting multi-user uplink data of 8. The method for transmitting multi-user uplink data of claim 1, wherein the sounding request frame includes infor claim 1, wherein the Sounding request frame is a Null Data mation for the Sounding request frame to indicate a sounding Packet Announcement (NDPA) frame. request for transmitting uplink data. 9. The method for transmitting multi-user uplink data of claim 1, wherein the sounding frame is a Null Data Packet 3. The method for transmitting multi-user uplink data of (NDP). claim 2, wherein the sounding request frame includes infor 10. A method for transmitting multi-user uplink data in a mation for indicating the Sounding request for the uplink wireless communication system, the method comprising: data transmission in a Modulation and Coding Scheme transmitting, by an access point (AP), a Sounding request (MCS) feedback request (MRQ) subfield of a VHT control frame to a station (STA) which participates in trans field. mitting the multi-user uplink data; and 4. The method for transmitting multi-user uplink data of receiving, by the AP, a sounding frame from the STA in claim 2, wherein the sounding request frame includes infor response to the Sounding request frame, mation for indicating the Sounding request for the uplink wherein the Sounding request frame includes information data transmission in a Sounding Dialog Token field. indicating the number of streams in which the STA 5. The method for transmitting multi-user uplink data of needs to transmit the Sounding frame, and claim 1, wherein the sounding frame is constituted only by the Sounding frame includes long training fields (LTFs) as a High Efficiency STF (HE-STF), a High Efficiency LTF many as the number of streams. (HE-LTF), and a High Efficiency SIGNAL (HE-SIG) except 11. The method for transmitting multi-user uplink data of for a Legacy-Short Training Field (L-STF), a Legacy-Long claim 10, further comprising: Training Field (L-LTF), and a Legacy SIGNAL (L-SIG) transmitting, by the AP, a polling frame to a second STA field. which participates in transmitting the multi-user uplink 6. The method for transmitting multi-user uplink data of data in order to request transmitting the Sounding claim 1, wherein the sounding request frame includes infor frame; and mation for requesting buffer status information of the STA, receiving, by the AP, the sounding frame from the second and STA in response to the polling frame. the sounding frame includes the buffer status information 12. The method for transmitting multi-user uplink data of of the STA. claim 10, further comprising: 7. The method for transmitting multi-user uplink data of allocating, by the AP, an uplink radio resource to the STA claim 6, wherein the buffer status information include at based on uplink channel information measured through least one information of access category (AC) of uplink data the Sounding frame. to be transmitted by the STA, the size of the uplink data, the 13-14. (canceled) size of a queue in which the uplink data are accumulated, a