WO2017030342A1 - Procédé pour transmettre une trame de déclenchement dans un système de communication sans fil, et dispositif associé - Google Patents

Procédé pour transmettre une trame de déclenchement dans un système de communication sans fil, et dispositif associé Download PDF

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Publication number
WO2017030342A1
WO2017030342A1 PCT/KR2016/008975 KR2016008975W WO2017030342A1 WO 2017030342 A1 WO2017030342 A1 WO 2017030342A1 KR 2016008975 W KR2016008975 W KR 2016008975W WO 2017030342 A1 WO2017030342 A1 WO 2017030342A1
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field
sta
information
frame
ppdu
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PCT/KR2016/008975
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English (en)
Korean (ko)
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천진영
류기선
최진수
조한규
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엘지전자(주)
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access, e.g. scheduled or random access
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to a wireless communication system, and more particularly, to a method for transmitting a trigger frame and an apparatus for supporting the same.
  • Wi-Fi is a Wireless Local Area Network (WLAN) technology that allows devices to access the Internet in the 2.4 GHz, 5 GHz, or 60 GHz frequency bands.
  • WLAN Wireless Local Area Network
  • WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard.
  • IEEE 802.11 The Wireless Next Generation Standing Committee (WNG SC) of IEEE 802.11 is an ad hoc committee that considers the next generation wireless local area network (WLAN) in the medium to long term.
  • WNG SC Wireless Next Generation Standing Committee
  • IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT), which provides up to 600 Mbps data rate, and also supports both transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology using multiple antennas.
  • HT High Throughput
  • MIMO Multiple Inputs and Multiple Outputs
  • IEEE 802.11ac supports data processing speeds of 1 Gbps and higher via 80 MHz bandwidth transmission and / or higher bandwidth transmission (eg 160 MHz) and operates primarily in the 5 GHz band.
  • IEEE 802.11ax often discussed in the next-generation WLAN task group, also known as IEEE 802.11ax or High Efficiency (HEW) WLAN, includes: 1) 802.11 physical layer and MAC in the 2.4 GHz and 5 GHz bands; (medium access control) layer enhancement, 2) spectral efficiency and area throughput improvement, 3) environments with interference sources, dense heterogeneous network environments, and high user loads. Such as improving performance in real indoor environments and outdoor environments, such as the environment.
  • IEEE 802.11ax Scenarios considered mainly in IEEE 802.11ax are dense environments with many access points (APs) and stations (STAs), and IEEE 802.11ax discusses spectral efficiency and area throughput improvement in such a situation. . In particular, there is an interest in improving the performance of the indoor environment as well as the outdoor environment, which is not much considered in the existing WLAN.
  • IEEE 802.11ax we are interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment. There is a discussion about improving system performance in dense environments with many STAs.
  • IEEE 802.11ax improves system performance in outdoor basic service set (OBSS) environment, outdoor environment performance, and cellular offloading rather than single link performance in one basic service set (BSS). Discussion is expected to be active.
  • the directionality of IEEE 802.11ax means that next-generation WLANs will increasingly have a technology range similar to that of mobile communication. Considering the situation where mobile communication and WLAN technology are recently discussed in the small cell and direct-to-direct communication area, the technical and business of next-generation WLAN and mobile communication based on IEEE 802.11ax Convergence is expected to become more active.
  • An object of the present invention is to propose an efficient trigger frame format applicable to the next generation wireless communication system.
  • DL in an uplink (UL) multi-user (MU) transmission method of a STA (Station) in a WLAN (Wireless LAN) system in a WLAN (Wireless LAN) system DL Receiving an MU Physical Protocol Data Unit (PPDU);
  • the DL MU PPDU comprising: a trigger frame including trigger information for UL MU transmission, and transmitting a UL MU PPDU based on the trigger information;
  • the trigger frame corresponds to a unicast trigger frame for a single STA transmitted in an aggregated (A-MPDU) or a broadcast trigger frame transmitted through a subchannel of the DL OFMDA.
  • the unicast trigger frame or the broadcast trigger frame is configured in a unified frame format, and commonly includes a common information field and a user info field.
  • Resource unit allocation information indicating a resource unit allocated to the STA may be included.
  • the broadcast trigger frame may include resource unit allocation information for an STA that receives a frame transmitted through a subchannel different from the subchannel through which the broadcast trigger frame is transmitted among all transmission channels of the DL MU PPDU. You can't.
  • the common info field may include at least one of type information of the trigger frame, guard interval information, long training field (LTF) type information, transmission bandwidth information, packet extension information, and the number of LTFs for transmission of the UL MU PPDU. It may include.
  • LTF long training field
  • the type information of the trigger frame can indicate the RTS trigger type.
  • the common info field may further include a type-specific common info field
  • the user info field may further include a type-specific per user info field.
  • the User Info field may include an Association Identifier (AID) of the STA, coding type information of the UL MU PPDU and Modulation and Coding Scheme (MCS) information, and a resource unit to be used by the STA to transmit the UL MU PPDU. It may include at least one of the related resource unit allocation information.
  • AID Association Identifier
  • MCS Modulation and Coding Scheme
  • different indexes may be assigned to resource units assignable to the STA in an 80 MHz channel, and the resource allocation information may indicate an index assigned to the resource unit allocated to the STA.
  • bit size for indicating the index in the resource allocation information may be a total of 7 bits.
  • the trigger frame may correspond to a trigger frame for random access for indicating random access.
  • the trigger frame for random access when transmitted in a cascade format, the trigger frame may further include an indicator for indicating the cascade frame format.
  • the random access trigger frame indicates a predetermined AID and a resource unit corresponding to the predetermined AID
  • the transmitting of the UL MU PPDU may include performing random access to the resource unit and performing the random access. Transmitting the UL MU PPDU using the resource unit based on a performance result; Can be.
  • STA (Station) device in a wireless LAN (WLAN) system according to another embodiment of the present invention, RF unit for transmitting and receiving radio signals; And a processor for controlling the RF unit;
  • the STA may receive a downlink (DL) multi-user (MU) multiprotocol (PPDU) physical protocol data unit (PPDU), and the DL MU PPDU may provide trigger information for UL MU transmission.
  • a UL MU PPDU based on the trigger information, wherein the trigger frame is included in A (Aggregated) -MPDU and transmitted to a unicast trigger frame for a single STA.
  • the unicast trigger frame or the broadcast trigger frame is configured in a unified frame format, and includes a common information field and a common information field.
  • a user info field may be included in common, and the user info field may include resource unit allocation information indicating a resource unit allocated to the STA.
  • the broadcast trigger frame may include resource unit allocation information for an STA that receives a frame transmitted through a subchannel different from the subchannel through which the broadcast trigger frame is transmitted among all transmission channels of the DL MU PPDU. You can't.
  • the User Info field may include an Association Identifier (AID) of the STA, coding type information of the UL MU PPDU and Modulation and Coding Scheme (MCS) information, and a resource unit to be used by the STA to transmit the UL MU PPDU. It may include at least one of the related resource unit allocation information.
  • AID Association Identifier
  • MCS Modulation and Coding Scheme
  • different indexes may be assigned to resource units assignable to the STA in an 80 MHz channel, and the resource allocation information may indicate an index assigned to the resource unit allocated to the STA.
  • bit size for indicating the index in the resource allocation information may be a total of 7 bits.
  • the trigger frame corresponds to a random access trigger frame for indicating random access
  • the random access trigger frame indicates a predetermined AID and a resource unit corresponding to the predetermined AID
  • the STA includes the Random access to a resource unit may be performed
  • the UL MU PPDU may be transmitted using the resource unit based on a result of performing the random access.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • FIG. 5 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 6 is a diagram illustrating a frame control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • FIG. 7 is a diagram conceptually illustrating a channel sounding method in a wireless communication system to which the present invention can be applied.
  • FIG. 8 is a diagram illustrating a VHT NDPA frame in a wireless communication system to which the present invention can be applied.
  • FIG. 9 is a diagram illustrating an NDP PPDU in a wireless communication system to which the present invention can be applied.
  • FIG. 10 is a diagram illustrating a VHT compressed beamforming frame format in a wireless communication system to which the present invention can be applied.
  • FIG. 11 is a diagram illustrating a beamforming report poll frame format in a wireless communication system to which the present invention can be applied.
  • FIG. 12 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 13 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 14 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • 15 is a diagram illustrating an ACK frame in a wireless communication system to which the present invention can be applied.
  • FIG. 16 is a diagram illustrating a Block Ack Request frame in a wireless communication system to which the present invention can be applied.
  • FIG. 17 illustrates a BAR information field of a block ACK request frame in a wireless communication system to which an embodiment of the present invention may be applied.
  • FIG. 18 is a diagram illustrating a block ACK frame in a wireless communication system to which the present invention can be applied.
  • FIG. 19 is a diagram illustrating a BA Information field of a block ACK frame in a wireless communication system to which the present invention can be applied.
  • FIG. 20 is a diagram illustrating a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • HE High Efficiency
  • 21 through 23 are diagrams illustrating an HE format PPDU according to an embodiment of the present invention.
  • 24 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.
  • 25 to 27 illustrate a resource allocation unit in an OFDMA multi-user transmission scheme according to an embodiment of the present invention.
  • 29 illustrates a DL MU PPDU according to a second embodiment of the present invention.
  • FIG. 30 is a view showing a trigger frame structure of the present invention.
  • FIG. 31A illustrates a Common Info field included in a broadcast trigger frame
  • FIG. 31B illustrates a Per User Info field included in a broadcast trigger frame.
  • FIG. 32A illustrates a Common Info field included in a unicast trigger frame
  • FIG. 32B illustrates a Per User Info field included in a unicast trigger frame.
  • 33 is a diagram illustrating a signaling method of resource unit allocation information according to the first embodiment of the present invention.
  • 34 is a diagram illustrating a signaling method of resource unit allocation information according to the second embodiment of the present invention.
  • 35 is a diagram illustrating a case where an 80 MHz channel is divided into at least one resource unit according to an embodiment of the present invention.
  • 36 is a diagram illustrating a signaling method of individual resource unit allocation information according to an embodiment of the present invention.
  • FIG. 37 is a table illustrating an index indicating a stream number and a starting stream together according to an embodiment of the present invention.
  • 40 is a diagram illustrating a Per User Info field format according to an embodiment of the present invention.
  • 41 is a diagram illustrating a method of allocating a resource unit and a random access area according to an embodiment of the present invention.
  • FIG. 42 is a flowchart illustrating a UL MU PPDU transmission method of an STA device according to an embodiment of the present invention.
  • each STA apparatus is a block diagram of each STA apparatus according to an embodiment of the present invention.
  • CDMA code division multiple access
  • FDMA frequency division multiple access
  • TDMA time division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single carrier frequency division multiple access
  • GSM global system for mobile communications
  • GPRS general packet radio service
  • EDGE enhanced data rates for GSM evolution
  • OFDMA may be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like.
  • UTRA is part of a universal mobile telecommunications system (UMTS).
  • 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.
  • LTE-A evolution of 3GPP LTE.
  • Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • the IEEE 802.11 structure may be composed of a plurality of components, and a wireless communication system supporting a station (STA) station mobility that is transparent to a higher layer may be provided by their interaction.
  • STA station
  • a basic service set (BSS) may correspond to a basic building block in an IEEE 802.11 system.
  • FIG. 1 there are three BSSs (BSS 1 to BSS 3) and two STAs are included as members of each BSS (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are BSS 2. Included in, and STA 5 and STA 6 are included in BSS 3) by way of example.
  • an ellipse representing a BSS may be understood to represent a coverage area where STAs included in the BSS maintain communication. This area may be referred to as a basic service area (BSA).
  • BSA basic service area
  • the most basic type of BSS in an IEEE 802.11 system is an independent BSS (IBSS).
  • the IBSS may have a minimal form consisting of only two STAs.
  • BSS 3 of FIG. 1, which is the simplest form and other components are omitted, may correspond to a representative example of the IBSS. This configuration is possible when STAs can communicate directly.
  • this type of LAN may not be configured in advance, but may be configured when a LAN is required, which may be referred to as an ad-hoc network.
  • the membership of the STA in the BSS may be dynamically changed by turning the STA on or off, the STA entering or exiting the BSS region, or the like.
  • the STA may join the BSS using a synchronization process.
  • the STA In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association may be set up dynamically and may include the use of a Distribution System Service (DSS).
  • DSS Distribution System Service
  • the direct STA-to-STA distance in an 802.11 system may be limited by physical layer (PHY) performance. In some cases, this distance limit may be sufficient, but in some cases, communication between STAs over longer distances may be required.
  • a distribution system (DS) may be configured to support extended coverage.
  • the DS refers to a structure in which BSSs are interconnected. Specifically, instead of the BSS independently as shown in FIG. 1, the BSS may exist as an extended type component of a network composed of a plurality of BSSs.
  • DS is a logical concept and can be specified by the characteristics of the Distribution System Medium (DSM).
  • DSM Distribution System Medium
  • the IEEE 802.11 standard logically distinguishes between wireless medium (WM) and distribution system medium (DSM). Each logical medium is used for a different purpose and is used by different components.
  • the definition of the IEEE 802.11 standard does not limit these media to the same or to different ones.
  • the plurality of media are logically different, and thus the flexibility of the structure of the IEEE 802.11 system (DS structure or other network structure) can be described. That is, the IEEE 802.11 system structure can be implemented in various ways, the corresponding system structure can be specified independently by the physical characteristics of each implementation.
  • the DS may support mobile devices by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.
  • the AP means an entity that enables access to the DS through the WM to the associated STAs and has STA functionality. Data movement between the BSS and the DS may be performed through the AP.
  • STA 2 and STA 3 illustrated in FIG. 1 have a functionality of STA, and provide a function of allowing associated STAs STA 1 and STA 4 to access the DS.
  • all APs basically correspond to STAs, all APs are addressable entities.
  • the address used by the AP for communication on the WM and the address used by the AP for communication on the DSM need not necessarily be the same.
  • Data transmitted from one of the STAs associated with an AP to the STA address of that AP may always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity.
  • transmission data (or frame) may be transmitted to the DS.
  • a wireless network of arbitrary size and complexity may be composed of DS and BSSs.
  • this type of network is referred to as an extended service set (ESS) network.
  • the ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include a DS.
  • the ESS network is characterized by what appears to be an IBSS network at the Logical Link Control (LLC) layer. STAs included in the ESS may communicate with each other, and mobile STAs may move from one BSS to another BSS (within the same ESS) transparently to the LLC.
  • LLC Logical Link Control
  • BSSs can be partially overlapped, which is the form generally used to provide continuous coverage.
  • the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs.
  • the BSSs can be located at the same physical location, which can be used to provide redundancy.
  • one (or more) IBSS or ESS networks may be physically present in the same space as one or more ESS networks. This may be necessary if the ad-hoc network is operating at the location of the ESS network, if the IEEE 802.11 networks are physically overlapped by different organizations, or if two or more different access and security policies are required at the same location. It may correspond to an ESS network type in a case.
  • an STA is a device that operates according to Medium Access Control (MAC) / PHY regulations of IEEE 802.11. As long as the function of the STA is not distinguished from the AP individually, the STA may include an AP STA and a non-AP STA. However, when communication is performed between the STA and the AP, the STA may be understood as a non-AP STA. In the example of FIG. 1, STA 1, STA 4, STA 5, and STA 6 correspond to non-AP STAs, and STA 2 and STA 3 correspond to AP STAs.
  • MAC Medium Access Control
  • Non-AP STAs generally correspond to devices that users directly handle, such as laptop computers and mobile phones.
  • a non-AP STA includes a wireless device, a terminal, a user equipment (UE), a mobile station (MS), a mobile terminal, and a wireless terminal.
  • WTRU wireless transmit / receive unit
  • MTC machine-type communication
  • M2M machine-to-machine
  • the AP is a base station (BS), Node-B (Node-B), evolved Node-B (eNB), and Base Transceiver System (BTS) in other wireless communication fields.
  • BS base station
  • Node-B Node-B
  • eNB evolved Node-B
  • BTS Base Transceiver System
  • downlink means communication from the AP to the non-AP STA
  • uplink means communication from the non-AP STA to the AP.
  • the transmitter may be part of an AP and the receiver may be part of a non-AP STA.
  • a transmitter may be part of a non-AP STA and a receiver may be part of an AP.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • the layer architecture of the IEEE 802.11 system may include a MAC sublayer and a PHY sublayer.
  • the PHY sublayer may be divided into a Physical Layer Convergence Procedure (PLCP) entity and a Physical Medium Dependent (PMD) entity.
  • PLCP Physical Layer Convergence Procedure
  • PMD Physical Medium Dependent
  • the PLCP entity plays a role of connecting a data frame with a MAC sublayer
  • the PMD entity plays a role of wirelessly transmitting and receiving data with two or more STAs.
  • Both the MAC sublayer and the PHY sublayer may include a management entity, which may be referred to as a MAC sublayer management entity (MLME) and a PHY sublayer management entity (PLME), respectively.
  • MLME MAC sublayer management entity
  • PLME PHY sublayer management entity
  • These management entities provide layer management service interfaces through the operation of layer management functions.
  • the MLME may be connected to the PLME to perform management operations of the MAC sublayer, and likewise the PLME may be connected to the MLME to perform management operations of the PHY sublayer.
  • a Station Management Entity may be present in each STA.
  • the SME is a management entity independent of each layer.
  • the SME collects layer-based state information from MLME and PLME or sets values of specific parameters of each layer.
  • the SME can perform these functions on behalf of general system management entities and implement standard management protocols.
  • the XX-GET.request primitive is used to request the value of a Management Information Base attribute (MIB attribute), and the XX-GET.confirm primitive, if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with an error indication in the status field.
  • MIB attribute Management Information Base attribute
  • the XX-SET.request primitive is used to request that a specified MIB attribute be set to a given value. If the MIB attribute is meant for a particular action, this request requests the execution of that particular action. And, if the state is 'SUCCESS' XX-SET.confirm primitive, it means that the specified MIB attribute is set to the requested value. In other cases, the status field indicates an error condition. If this MIB attribute means a specific operation, this primitive can confirm that the operation was performed.
  • MIB attribute Management Information Base attribute
  • XX-GET.confirm primitive if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with
  • the MAC sublayer includes a MAC header and a frame check sequence (FCS) in a MAC Service Data Unit (MSDU) or a fragment of an MSDU received from an upper layer (eg, an LLC layer).
  • FCS frame check sequence
  • MSDU MAC Service Data Unit
  • MPDU MAC Protocol Data Unit
  • A-MSDU aggregated MSDU
  • a plurality of MSDUs may be merged into a single A-MSDU (aggregated MSDU).
  • the MSDU merging operation may be performed at the MAC upper layer.
  • the A-MSDU is delivered to the PHY sublayer as a single MPDU (if not fragmented).
  • the PHY sublayer generates a physical protocol data unit (PPDU) by adding an additional field including information required by a physical layer transceiver to a physical service data unit (PSDU) received from the MAC sublayer. . PPDUs are transmitted over wireless media.
  • PPDU physical protocol data unit
  • the PSDU is substantially the same as the MPDU since the PHY sublayer is received from the MAC sublayer and the MPDU is transmitted by the MAC sublayer to the PHY sublayer.
  • A-MPDU aggregated MPDU
  • a plurality of MPDUs may be merged into a single A-MPDU.
  • the MPDU merging operation may be performed at the MAC lower layer.
  • A-MPDUs may be merged with various types of MPDUs (eg, QoS data, Acknowledge (ACK), Block ACK (BlockAck), etc.).
  • the PHY sublayer receives the A-MPDU as a single PSDU from the MAC sublayer. That is, the PSDU is composed of a plurality of MPDUs.
  • A-MPDUs are transmitted over the wireless medium in a single PPDU.
  • PPDU Physical Protocol Data Unit
  • IEEE 802.11 WLAN system to which the present invention can be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • Non-HT PPDUs may also be referred to as legacy PPDUs.
  • the non-HT format PPDU includes an L-STF (Legacy (or Non-HT) Short Training field), L-LTF (Legacy (or, Non-HT) Long Training field) and It consists of a legacy format preamble and a data field composed of L-SIG (Legacy (or Non-HT) SIGNAL) field.
  • L-STF Legacy (or Non-HT) Short Training field
  • L-LTF Legacy (or, Non-HT) Long Training field
  • L-SIG Legacy (or Non-HT) SIGNAL
  • the L-STF may include a short training orthogonal frequency division multiplexing symbol (OFDM).
  • L-STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. .
  • the L-LTF may include a long training orthogonal frequency division multiplexing symbol.
  • L-LTF may be used for fine frequency / time synchronization and channel estimation.
  • the L-SIG field may be used to transmit control information for demodulation and decoding of the data field.
  • the L-SIG field consists of a 4-bit Rate field, 1-bit Reserved bit, 12-bit Length field, 1-bit parity bit, and 6-bit Signal Tail field. Can be.
  • the rate field contains rate information, and the length field indicates the number of octets of the PSDU.
  • FIG. 3B illustrates an HT-mixed format PPDU (HTDU) for supporting both an IEEE 802.11n system and an IEEE 802.11a / g system.
  • HTDU HT-mixed format PPDU
  • the HT mixed format PPDU includes a legacy format preamble including an L-STF, L-LTF, and L-SIG fields, an HT-SIG (HT-Signal) field, and an HT-STF (HT Short). Training field), HT-formatted preamble and data field including HT-LTF (HT Long Training field).
  • L-STF, L-LTF, and L-SIG fields mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields. Even if the L-STA receives the HT mixed PPDU, the L-STA may interpret the data field through the L-LTF, L-LTF, and L-SIG fields. However, the L-LTF may further include information for channel estimation that the HT-STA performs to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.
  • the HT-STA may know that it is an HT-mixed format PPDU using the HT-SIG field following the legacy field, and may decode the data field based on the HT-STA.
  • the HT-LTF field may be used for channel estimation for demodulation of the data field. Since IEEE 802.11n supports Single-User Multi-Input and Multi-Output (SU-MIMO), a plurality of HT-LTF fields may be configured for channel estimation for each data field transmitted in a plurality of spatial streams.
  • SU-MIMO Single-User Multi-Input and Multi-Output
  • the HT-LTF field includes data HT-LTF used for channel estimation for spatial streams and extension HT-LTF (additional used for full channel sounding). It can be configured as. Accordingly, the plurality of HT-LTFs may be equal to or greater than the number of spatial streams transmitted.
  • the L-STF, L-LTF, and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the HT-SIG field is transmitted for demodulation and decoding of data transmitted for the HT-STA.
  • the HT-SIG field is transmitted without performing beamforming so that the L-STA and HT-STA can receive the corresponding PPDU to acquire data, and then the HT-STF, HT-LTF and data fields transmitted are precoded. Wireless signal transmission is performed through.
  • the HT-STF field is transmitted to allow the STA to perform precoding to take into account the variable power due to precoding, and then the plurality of HT-LTF and data fields after that.
  • Table 1 below is a table illustrating the HT-SIG field.
  • FIG. 3 (c) illustrates an HT-GF format PPDU (HT-GF) for supporting only an IEEE 802.11n system.
  • the HT-GF format PPDU includes HT-GF-STF, HT-LTF1, HT-SIG field, a plurality of HT-LTF2 and data fields.
  • HT-GF-STF is used for frame timing acquisition and AGC.
  • HT-LTF1 is used for channel estimation.
  • the HT-SIG field is used for demodulation and decoding of the data field.
  • HT-LTF2 is used for channel estimation for demodulation of data fields. Similarly, since HT-STA uses SU-MIMO, channel estimation is required for each data field transmitted in a plurality of spatial streams, and thus HT-LTF2 may be configured in plural.
  • the plurality of HT-LTF2 may be configured of a plurality of Data HT-LTF and a plurality of extended HT-LTF similarly to the HT-LTF field of the HT mixed PPDU.
  • the data field is a payload, and includes a service field, a SERVICE field, a scrambled PSDU field, tail bits, and padding bits. It may include. All bits of the data field are scrambled.
  • the service field has 16 bits. Each bit is assigned from 0 to 15, and transmitted sequentially from bit 0. Bits 0 to 6 are set to 0 and used to synchronize the descrambler in the receiver.
  • the IEEE 802.11ac WLAN system supports downlink multi-user multiple input multiple output (MU-MIMO) transmission in which a plurality of STAs simultaneously access a channel in order to efficiently use a wireless channel.
  • MU-MIMO downlink multi-user multiple input multiple output
  • the AP may simultaneously transmit packets to one or more STAs that are paired with MIMO.
  • DL MU transmission (downlink multi-user transmission) refers to a technology in which an AP transmits a PPDU to a plurality of non-AP STAs through the same time resource through one or more antennas.
  • the MU PPDU refers to a PPDU that delivers one or more PSDUs for one or more STAs using MU-MIMO technology or OFDMA technology.
  • the SU PPDU means a PPDU having a format in which only one PSDU can be delivered or in which no PSDU exists.
  • control information transmitted to the STA may be relatively large compared to the size of 802.11n control information for MU-MIMO transmission.
  • An example of control information additionally required for MU-MIMO support includes information indicating the number of spatial streams received by each STA, information related to modulation and coding of data transmitted to each STA, and the like. Can be.
  • the size of transmitted control information may be increased according to the number of receiving STAs.
  • control information required for MU-MIMO transmission is required separately for common control information common to all STAs and specific STAs.
  • the data may be transmitted by being divided into two types of information of dedicated control information.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • VHT format PPDU VHT format PPDU
  • a VHT format PPDU includes a legacy format preamble including a L-STF, L-LTF, and L-SIG fields, a VHT-SIG-A (VHT-Signal-A) field, and a VHT-STF ( A VHT format preamble and a data field including a VHT Short Training field (VHT-LTF), a VHT Long Training field (VHT-LTF), and a VHT-SIG-B (VHT-Signal-B) field.
  • VHT-LTF VHT Short Training field
  • VHT-LTF VHT Long Training field
  • VHT-SIG-B VHT-Signal-B
  • L-STF, L-LTF, and L-SIG mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields.
  • the L-LTF may further include information for channel estimation to be performed to demodulate the L-SIG field and the VHT-SIG-A field.
  • the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field may be repeatedly transmitted in 20 MHz channel units. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field are repeatedly transmitted on every 20 MHz channel. Can be.
  • the VHT-STA may know that it is a VHT format PPDU using the VHT-SIG-A field following the legacy field, and may decode the data field based on the VHT-STA.
  • the L-STF, L-LTF and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the VHT-SIG-A field is transmitted for demodulation and decoding of data transmitted for the VHT-STA.
  • the VHT-SIG-A field is a field for transmitting control information common to the AP and the MIMO paired VHT STAs, and includes control information for interpreting the received VHT format PPDU.
  • the VHT-SIG-A field may include a VHT-SIG-A1 field and a VHT-SIG-A2 field.
  • the VHT-SIG-A1 field includes information on channel bandwidth (BW) used, whether space time block coding (STBC) is applied, and group identification information for indicating a group of STAs grouped in MU-MIMO.
  • Group ID Group Identifier
  • NSTS space-time streams
  • Partial AID Partial Association Identifier
  • Transmit power save forbidden information can do.
  • the Group ID means an identifier assigned to the STA group to be transmitted to support MU-MIMO transmission, and may indicate whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.
  • Table 2 is a table illustrating the VHT-SIG-A1 field.
  • the VHT-SIG-A2 field contains information on whether a short guard interval (GI) is used, forward error correction (FEC) information, information on modulation and coding scheme (MCS) for a single user, and multiple information.
  • GI short guard interval
  • FEC forward error correction
  • MCS modulation and coding scheme
  • Information on the type of channel coding for the user beamforming-related information, redundancy bits for cyclic redundancy checking (CRC), tail bits of convolutional decoder, and the like. Can be.
  • Table 3 is a table illustrating the VHT-SIG-A2 field.
  • VHT-STF is used to improve the performance of AGC estimation in MIMO transmission.
  • VHT-LTF is used by the VHT-STA to estimate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF may be set as many as the number of spatial streams in which a PPDU is transmitted. In addition, if full channel sounding is supported, the number of VHT-LTFs may be greater.
  • the VHT-SIG-B field includes dedicated control information required for a plurality of MU-MIMO paired VHT-STAs to receive a PPDU and acquire data. Therefore, the VHT-STA decodes the VHT-SIG-B field only when common control information included in the VHT-SIG-A field indicates that the currently received PPDU indicates MU-MIMO transmission. It can be designed to. On the other hand, if the common control information indicates that the currently received PPDU is for a single VHT-STA (including SU-MIMO), the STA may be designed not to decode the VHT-SIG-B field.
  • the VHT-SIG-B field includes a VHT-SIG-B length field, a VHT-MCS field, a reserved field, and a tail field.
  • the VHT-SIG-B Length field indicates the length of the A-MPDU (before end-of-frame padding).
  • the VHT-MCS field includes information on modulation, encoding, and rate-matching of each VHT-STA.
  • the size of the VHT-SIG-B field may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.
  • FIG. 4 (b) illustrates the VHT-SIG-B field according to the PPDU transmission bandwidth.
  • the VHT-SIG-B bits are repeated twice.
  • the VHT-SIG-B bits are repeated four times and pad bits set to zero are attached.
  • VHT-SIG-B bits are repeated four times, as with the 80 MHz transmission, with pad bits set to zero attached. Then, all 117 bits are repeated again.
  • information indicating a bit size of a data field constituting the PPDU and / or indicating a bit stream size constituting a specific field May be included in the VHT-SIG-A field.
  • the L-SIG field may be used to effectively use the PPDU format.
  • a length field and a rate field included in the L-SIG field and transmitted may be used to provide necessary information.
  • MPDU MAC Protocol Data Unit
  • A-MPDU Aggregate MAC Protocol Data Unit
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the STA Since the formats of various PPDUs are mixed and used as described above, the STA must be able to distinguish the formats of the received PPDUs.
  • the meaning of distinguishing a PPDU may have various meanings.
  • the meaning of identifying the PPDU may include determining whether the received PPDU is a PPDU that can be decoded (or interpreted) by the STA.
  • the meaning of distinguishing the PPDU may mean determining whether the received PPDU is a PPDU supported by the STA.
  • the meaning of distinguishing the PPDU may also be interpreted to mean what information is transmitted through the received PPDU.
  • FIG. 5 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • a MAC frame (ie, an MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • MAC Header includes Frame Control field, Duration / ID field, Address 1 field, Address 2 field, Address 3 field, Sequence control It is defined as an area including a Control field, an Address 4 field, a QoS Control field, and an HT Control field.
  • the Frame Control field includes information on the MAC frame characteristic. A detailed description of the Frame Control field will be given later.
  • the Duration / ID field may be implemented to have different values depending on the type and subtype of the corresponding MAC frame.
  • the Duration / ID field is an AID (association identifier) of the STA that transmitted the frame. It may be set to include. Otherwise, the Duration / ID field may be set to have a specific duration value according to the type and subtype of the corresponding MAC frame.
  • the Duration / ID fields included in the MAC header may be set to have the same value.
  • the Address 1 to Address 4 fields include a BSSID, a source address (SA), a destination address (DA), a transmission address (TA) indicating a transmission STA address, and a reception address indicating a destination STA address (TA).
  • SA source address
  • DA destination address
  • TA transmission address
  • TA reception address indicating a destination STA address
  • RA It is used to indicate Receiving Address.
  • the address field implemented as a TA field may be set to a bandwidth signaling TA value, in which case, the TA field may indicate that the corresponding MAC frame contains additional information in the scrambling sequence.
  • the bandwidth signaling TA may be represented by the MAC address of the STA transmitting the corresponding MAC frame, but the Individual / Group bit included in the MAC address may be set to a specific value (for example, '1'). Can be.
  • the Sequence Control field is set to include a sequence number and a fragment number.
  • the sequence number may indicate a sequence number allocated to the corresponding MAC frame.
  • the fragment number may indicate the number of each fragment of the corresponding MAC frame.
  • the QoS Control field contains information related to QoS.
  • the QoS Control field may be included when indicating a QoS data frame in a subtype subfield.
  • the HT Control field includes control information related to the HT and / or VHT transmission / reception schemes.
  • the HT Control field is included in the Control Wrapper frame. In addition, it exists in the QoS data frame and the management frame in which the order subfield value is 1.
  • the frame body is defined as a MAC payload, and data to be transmitted in a higher layer is located, and has a variable size.
  • the maximum MPDU size may be 11454 octets
  • the maximum PPDU size may be 5.484 ms.
  • FCS is defined as a MAC footer and is used for error detection of MAC frames.
  • the first three fields (Frame Control field, Duration / ID field and Address 1 field) and the last field (FCS field) constitute the minimum frame format and are present in every frame. Other fields may exist only in a specific frame type.
  • FIG. 6 is a diagram illustrating a frame control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • the Frame Control field includes a Protocol Version subfield, a Type subfield, a Subtype subfield, a To DS subfield, a From DS subfield, and more fragments.
  • the Protocol Version subfield may indicate the version of the WLAN protocol applied to the corresponding MAC frame.
  • the Type subfield and the Subtype subfield may be set to indicate information for identifying a function of a corresponding MAC frame.
  • the type of the MAC frame may include three frame types: a management frame, a control frame, and a data frame.
  • Each frame type may be further divided into subtypes.
  • control frames include request to send (RTS) frames, clear-to-send (CTS) frames, acknowledgment (ACK) frames, PS-Poll frames, content free (End) frames, CF End + CF-ACK frame, Block Acknowledgment request (BAR) frame, Block Acknowledgment (BA) frame, Control Wrapper (Control + HTcontrol) frame, VHT null data packet notification (NDPA) It may include a Null Data Packet Announcement and a Beamforming Report Poll frame.
  • Management frames include beacon frames, announcement traffic indication message (ATIM) frames, disassociation frames, association request / response frames, reassociation requests / responses Response frame, Probe Request / Response frame, Authentication frame, Deauthentication frame, Action frame, Action No ACK frame, Timing Advertisement It may include a frame.
  • ATIM announcement traffic indication message
  • disassociation frames association request / response frames
  • reassociation requests / responses Response frame Probe Request / Response frame
  • Authentication frame Deauthentication frame
  • Action frame Action No ACK frame
  • Timing Advertisement It may include a frame.
  • the To DS subfield and the From DS subfield may include information necessary to interpret the Address 1 field or the Address 4 field included in the corresponding MAC frame header.
  • both the To DS subfield and the From DS subfield are set to '0'.
  • the To DS subfield and the From DS subfield are set to '1' and '0' in order if the frame is a QoS Management frame (QMF), and in order if the frame is not QMF. Both can be set to '0', '0'.
  • QMF QoS Management frame
  • the More Fragments subfield may indicate whether there is a fragment to be transmitted following the corresponding MAC frame. If there is another fragment of the current MSDU or MMPDU, it may be set to '1', otherwise it may be set to '0'.
  • the Retry subfield may indicate whether the corresponding MAC frame is due to retransmission of a previous MAC frame. In case of retransmission of the previous MAC frame, it may be set to '1', otherwise it may be set to '0'.
  • the power management subfield may indicate a power management mode of the STA. If the value of the Power Management subfield is '1', the STA may indicate switching to the power save mode.
  • the More Data subfield may indicate whether there is an additional MAC frame to be transmitted. If there is an additional MAC frame to be transmitted, it may be set to '1', otherwise it may be set to '0'.
  • the Protected Frame subfield may indicate whether the frame body field is encrypted. If the Frame Body field includes information processed by the encryption encapsulation algorithm, it may be set to '1', otherwise it may be set to '0'.
  • each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • SU-MIMO technology in which a beamformer assigns all antennas to one beamformee and communicates, increases channel capacity through diversity gain and stream multiplexing using space-time. .
  • SU-MIMO technology can contribute to improving the performance of the physical layer by increasing the number of antennas by increasing the number of antennas compared to when the MIMO technology is not applied.
  • the MU-MIMO technology in which a beamformer allocates antennas to a plurality of beamformees, provides a link layer protocol for multiple access of a plurality of beamformees connected to the beamformer. It can improve performance.
  • Sounding means using the corresponding training field to measure the channel for purposes other than data demodulation of the PPDU including the preamble training field.
  • Beamformer may instruct feedback of channel state information through the HT control field included in the MAC header, or Beamformee may report channel state information through the HT control field included in the MAC frame header (see FIG. 8).
  • the HT control field may be included in a control frame or a QoS data frame in which the Order subfield of the MAC header is set to 1, and the management frame.
  • FIG. 7 is a diagram conceptually illustrating a channel sounding method in a wireless communication system to which the present invention can be applied.
  • FIG. 7 illustrates a method for feeding back channel state information between a Beamformer (eg, an AP) and a Beamformee (eg, a non-AP STA) based on a sounding protocol.
  • the sounding protocol may refer to a procedure for receiving feedback on channel state information.
  • the channel state information sounding method between the beamformer and the beamformee based on the sounding protocol may be performed by the following steps.
  • the beamformer transmits a VHT NDPA (VHT Null Data Packet Announcement) frame indicating a sounding transmission for feedback of the beamformee.
  • VHT NDPA VHT Null Data Packet Announcement
  • the VHT NDPA frame refers to a control frame used to indicate that channel sounding is started and that NDP (Null Data Packet) will be transmitted.
  • NDP Null Data Packet
  • the VHT NDPA frame may include AID (association identifier) information, feedback type information, etc. of the Beamformee to transmit the NDP. A more detailed description of the VHT NDPA frame will be given later.
  • the VHT NDPA frame may be transmitted in a different transmission method when data is transmitted using MU-MIMO and when data is transmitted using SU-MIMO. For example, when performing channel sounding for MU-MIMO, a VHT NDPA frame is transmitted in a broadcast manner, but when channel sounding for SU-MIMO is performed, a VHT NDPA frame is transmitted to one target STA. Can be transmitted in a unicast manner.
  • NDP has a VHT PPDU structure excluding data fields.
  • Beamformees receiving the VHT NDPA frame may check the value of the AID12 subfield included in the STA information field, and may determine whether the beamformee is a sounding target STA.
  • the beamformees may know the feedback order through the order of the STA Info field included in the NDPA.
  • 11 illustrates a case in which the feedback order is performed in the order of Beamformee 1, Beamformee 2, and Beamformee 3.
  • Beamformee 1 obtains downlink channel state information based on a training field included in the NDP, and generates feedback information to be transmitted to the beamformer.
  • Beamformee 1 transmits a VHT compressed beamforming frame including feedback information to the beamformer after SIFS after receiving the NDP frame.
  • the VHT Compressed Beamforming frame may include an SNR value for a space-time stream, information about a compressed beamforming feedback matrix for a subcarrier, and the like. A more detailed description of the VHT Compressed Beamforming frame will be described later.
  • the beamformer After receiving the VHT Compressed Beamforming frame from Beamformee 1, the beamformer transmits a Beamforming Report Poll frame to Beamformee 2 to obtain channel information from Beamformee 2 after SIFS.
  • the Beamforming Report Poll frame is a frame that performs the same role as the NDP frame, and Beamformee 2 may measure a channel state based on the transmitted Beamforming Report Poll frame.
  • Beamformee 2 transmits the VHT Compressed Beamforming frame including feedback information to the beamformer after SIFS.
  • the beamformer After receiving the VHT Compressed Beamforming frame from Beamformee 2, the beamformer transmits a Beamforming Report Poll frame to Beamformee 3 to obtain channel information from Beamformee 3 after SIFS.
  • Beamformee 3 transmits the VHT Compressed Beamforming frame including feedback information to the beamformer after SIFS.
  • FIG. 8 is a diagram illustrating a VHT NDPA frame in a wireless communication system to which the present invention can be applied.
  • the VHT NDPA frame may include a frame control field, a duration field, a receiving address field, a transmitting address field, a sounding dialog token field, It may be composed of a STA Info 1 field, a STA Info n field, and an FCS.
  • the RA field value indicates a receiver address or STA address for receiving a VHT NDPA frame.
  • the RA field value has the address of the STA identified by the AID in the STA Info field. For example, when transmitting a VHT NDPA frame to one target STA for SU-MIMO channel sounding, the AP transmits the VHT NDPA frame to the target STA by unicast.
  • the RA field value has a broadcast address.
  • the AP when transmitting a VHT NDPA frame to at least one target STA for MU-MIMO channel sounding, the AP broadcasts a VHT NDPA frame.
  • the TA field value represents a transmitter address for transmitting a VHT NDPA frame or an address of a transmitting STA or a bandwidth for signaling a TA.
  • the Sounding Dialog Token field may be referred to as a sounding sequence field.
  • the Sounding Dialog Token Number subfield in the Sounding Dialog Token field contains a value selected by the Beamformer to identify the VHT NDPA frame.
  • the VHT NDPA frame includes at least one STA Info field. That is, the VHT NDPA frame includes a STA Info field that includes information about the sounding target STA. One STA Info field may be included for each sounding target STA.
  • Each STA Info field may be composed of an AID12 subfield, a feedback type subfield, and an Nc index subfield.
  • Table 4 shows subfields of the STA Info field included in the VHT NDPA frame.
  • each field described above may follow the definition of the IEEE 802.11 system.
  • each field described above corresponds to an example of fields that may be included in a MAC frame, and may be replaced with another field or further fields may be included.
  • FIG. 9 is a diagram illustrating an NDP PPDU in a wireless communication system to which the present invention can be applied.
  • the NDP may have a format in which a data field is omitted from the VHT PPDU format shown in FIG. 4.
  • the NDP may be precoded based on a specific precoding matrix and transmitted to the sounding target STA.
  • the length field indicating the length of the PSDU included in the data field is set to '0'.
  • the Group ID field indicating whether the transmission scheme used for NDP transmission is MU-MIMO or SU-MIMO is set to a value indicating SU-MIMO transmission.
  • the data bits of the VHT-SIG-B field of the NDP are set to a fixed bit pattern for each bandwidth.
  • the sounding target STA When the sounding target STA receives the NDP, the sounding target STA estimates a channel based on the VHT-LTF field of the NDP and obtains channel state information.
  • FIG. 10 is a diagram illustrating a VHT compressed beamforming frame format in a wireless communication system to which the present invention can be applied.
  • the VHT compressed beamforming frame is a VHT action frame for supporting the VHT function and includes an action field in the frame body.
  • the Action field is included in the Frame Body of the MAC frame to provide a mechanism for specifying extended management operations.
  • the Action field includes the Category field, the VHT Action field, the VHT MIMO Control field, the VHT Compressed Beamforming Report field, and the MU Exclusive Beamforming. Report) field.
  • the Category field is set to a value indicating a VHT category (ie, a VHT Action frame), and the VHT Action field is set to a value indicating a VHT Compressed Beamforming frame.
  • the VHT MIMO Control field is used to feed back control information related to beamforming feedback.
  • the VHT MIMO Control field may always be present in the VHT Compressed Beamforming frame.
  • the VHT Compressed Beamforming Report field is used to feed back information about a beamforming metric including SNR information about a space-time stream used to transmit data.
  • the MU Exclusive Beamforming Report field is used to feed back SNR information on a spatial stream when performing MU-MIMO transmission.
  • the presence and content of the VHT Compressed Beamforming Report field and the MU Exclusive Beamforming Report field are determined by the Feedback Type subfield, the Remaining Feedback Segments subfield, and the First Feedback Segment of the VHT MIMO Control field. Feedback Segment) may be determined according to the value of the subfield.
  • VHT MIMO Control field the VHT Compressed Beamforming Report field
  • VHT Compressed Beamforming Report field the VHT Compressed Beamforming Report field
  • MU Exclusive Beamforming Report field the VHT MIMO Control field
  • the VHT MIMO Control field includes an Nc Index subfield, an Nr Index subfield, a Channel Width subfield, a Grouping subfield, a Codebook Information subfield, Feedback Type Subfield, Remaining Feedback Segments Subfield, First Feedback Segment Subfield, Reserved Subfield, and Sounding Dialog Token Number Sub It consists of fields.
  • Table 5 shows subfields of the VHT MIMO Control field.
  • the Nc Index subfield, Channel Width subfield, Grouping subfield, Codebook Information subfield, Feedback Type subfield, and Sounding Dialog Token Number subfield Is set to a preliminary field
  • the First Feedback Segment subfield is set to '0'
  • the Remaining Feedback Segments subfield is set to '7'.
  • the Sounding Dialog Token Number subfield may be called a Sounding Sequence Number subfield.
  • the VHT compressed beamforming report field contains explicit feedback in the form of angles of the compressed beamforming feedback matrix 'V' which the transmitting beamformer uses to determine the steering matrix 'Q'. It is used to convey information.
  • Table 6 shows subfields of the VHT compressed beamforming report field.
  • the VHT compressed beamforming report field may include an average SNR for each space-time stream and a compressed beamforming feedback matrix 'V' for each subcarrier.
  • the compressed beamforming feedback matrix is used to calculate a channel matrix (ie, steering matrix 'Q') in a transmission method using MIMO as a matrix including information on channel conditions.
  • Nr scidx () means a subcarrier through which the Compressed Beamforming Feedback Matrix subfield is transmitted.
  • Ns denotes the number of subcarriers through which the compressed beamforming feedback matrix is transmitted to the beamformer.
  • Beamformee can reduce the number of Ns through which the compressed beamforming feedback matrix is transmitted using a grouping method. For example, the number of compressed beamforming feedback matrices fed back may be reduced by grouping a plurality of subcarriers into one group and transmitting the compressed beamforming feedback matrix for each group.
  • Ns may be calculated from the Channel Width subfield and the Grouping subfield included in the VHT MIMO Control field.
  • Table 7 illustrates an average SNR of Space-Time (SNR) Stream subfield of a space-time stream.
  • an average SNR for each space-time stream is calculated by calculating an average SNR value for all subcarriers included in a channel and mapping the value to a range of -128 to +128.
  • the MU Exclusive Beamforming Report field is used to convey explicit feedback information in the form of delta SNR.
  • Information in the VHT Compressed Beamforming Report field and the MU Exclusive Beamforming Report field may be used by the MU Beamformer to determine the steering matrix 'Q'.
  • Table 8 shows subfields of an MU Exclusive Beamforming Report field included in a VHT compressed beamforming frame.
  • the MU Exclusive Beamforming Report field may include an SNR per space-time stream for each subcarrier.
  • Each Delta SNR subfield has an increment of 1 dB between -8 dB and 7 dB.
  • scidx denotes subcarrier (s) in which the Delta SNR subfield is transmitted, and Ns denotes the number of subcarriers in which the Delta SNR subfield is transmitted to the beamformer.
  • FIG. 11 is a diagram illustrating a beamforming report poll frame format in a wireless communication system to which the present invention can be applied.
  • the Beamforming Report Poll frame includes a Frame Control field, a Duration field, a Receiving Address (RA) field, a Transmitting Address (TA) field, and a Feedback Segment Retransmission Bitmap. ) Field and the FCS.
  • the RA field value indicates the address of the intended recipient.
  • the TA field value indicates an address of an STA transmitting a Beamforming Report Poll frame or a bandwidth signaling a TA.
  • the Feedback Segment Retransmission Bitmap field indicates a feedback segment requested in a VHT Compressed Beamforming report.
  • Downlink MU- MIMO Frame (DL MU- MIMO Frame)
  • FIG. 12 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • a PPDU includes a preamble and a data field.
  • the data field may include a service field, a scrambled PSDU field, tail bits, and padding bits.
  • the AP may aggregate the MPDUs and transmit a data frame in an A-MPDU (aggregated MPDU) format.
  • the scrambled PSDU field may be configured as an A-MPDU.
  • An A-MPDU consists of a sequence of one or more A-MPDU subframes.
  • the A-MPDU is zero after the last A-MPDU subframe to fit the A-MPDU to the last octet of the PSDU. And three to three octets of an end-of-frame (EOF) pad.
  • EEF end-of-frame
  • the A-MPDU subframe consists of an MPDU delimiter, and optionally an MPDU may be included after the MPDU delimiter.
  • an MPDU may be included after the MPDU delimiter.
  • a pad octet is attached after the MPDU to make the length of each A-MPDU subframe a multiple of 4 octets.
  • the MPDU Delimiter is composed of a Reserved field, an MPDU Length field, a cyclic redundancy check (CRC) field, and a delimiter signature field.
  • CRC cyclic redundancy check
  • the MPDU Delimiter may further include an end-of-frame (EOF) field. If the MPDU Length field is 0 and the A-MPDU subframe used for padding or the A-MPDU subframe carrying the MPDU when the A-MPDU consists of only one MPDU, the EOF field is set to '1'. do. Otherwise it is set to '0'.
  • EEF end-of-frame
  • the MPDU Length field contains information about the length of the MPDU.
  • An A-MPDU subframe whose MPDU Length field has a value of '0' is used when padding the corresponding A-MPDU to match the A-MPDU to the octets available in the VHT PPDU.
  • the CRC field includes CRC information for error checking
  • the Delimiter Signature field includes pattern information used to search for an MPDU delimiter.
  • the MPDU is composed of a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • FIG. 13 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 13 shows that the number of STAs receiving the PPDU is three and the number of spatial streams allocated to each STA is 1, but the number of STAs paired to the AP and the number of spatial streams allocated to each STA are illustrated in FIG. Is not limited to this.
  • the MU PPDU includes L-TFs field (L-STF field and L-LTF field), L-SIG field, VHT-SIG-A field, VHT-TFs field (VHT-STF field and VHT-LTF). Field), VHT-SIG-B field, Service field, one or more PSDU, padding field, and Tail bit. Since the L-TFs field, the L-SIG field, the VHT-SIG-A field, the VHT-TFs field, and the VHT-SIG-B field are the same as in the example of FIG. 4, detailed descriptions thereof will be omitted.
  • Information for indicating the duration of the PPDU may be included in the L-SIG field.
  • the PPDU duration indicated by the L-SIG field is the symbol assigned to the VHT-SIG-A field, the symbol assigned to the VHT-TFs field, the field assigned to the VHT-SIG-B field, and the Service field.
  • the STA receiving the PPDU may obtain information about the duration of the PPDU through the information indicating the duration of the PPDU included in the L-SIG field.
  • Group ID information and space-time stream number information per user are transmitted through the VHT-SIG-A, and a coding method and MCS information are transmitted through the VHT-SIG-B.
  • the beamformees may check the VHT-SIG-A and the VHT-SIG-B, and may know whether the beamformees belong to the MU MIMO frame. Therefore, the STA that is not a member STA of the corresponding Group ID or the member of the corresponding Group ID or the number of allocated streams is '0' reduces power consumption by setting to stop receiving the physical layer from the VHT-SIG-A field to the end of the PPDU. can do.
  • the Group ID can receive the Group ID Management frame transmitted by the Beamformer in advance, so that the MU group belonging to the Beamformee and the user of the group to which the Beamformee belongs, that is, the stream through which the PPDU is received.
  • each VHT A-MPDU may be transmitted in a different stream.
  • each A-MPDU may have a different bit size.
  • null padding may be performed such that the time when the transmission of the plurality of data frames transmitted by the beamformer is the same as the time when the transmission of the maximum interval transmission data frame is terminated.
  • the maximum interval transmission data frame may be a frame in which valid downlink data is transmitted by the beamformer for the longest period.
  • the valid downlink data may be downlink data that is not null padded.
  • valid downlink data may be included in the A-MPDU and transmitted.
  • Null padding may be performed on the remaining data frames except the maximum interval transmission data frame among the plurality of data frames.
  • the beamformer may encode and fill one or more A-MPDU subframes located in temporal order in the plurality of A-MPDU subframes in the A-MPDU frame with only the MPDU delimiter field.
  • An A-MPDU subframe having an MPDU length of 0 may be referred to as a null subframe.
  • the EOF field of the MPDU Delimiter is set to '1'. Accordingly, when the MAC layer of the receiving STA detects the EOF field set to 1, power consumption may be reduced by setting the physical layer to stop reception.
  • FIG. 14 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • MU-MIMO is defined in downlink from the AP to the client (ie, non-AP STA).
  • client ie, non-AP STA.
  • a multi-user frame is simultaneously transmitted to multiple receivers, but acknowledgments should be transmitted separately in the uplink.
  • Block Ack Request is sent in response to a frame.
  • the AP transmits a VHT MU PPDU (ie, preamble and data) to all receivers (ie, STA 1, STA 2, and STA 3).
  • the VHT MU PPDU includes a VHT A-MPDU transmitted to each STA.
  • STA 1 Receiving a VHT MU PPDU from the AP, STA 1 transmits a block acknowledgment (BA) frame to the AP after SIFS.
  • BA block acknowledgment
  • the AP After receiving the BA from the STA 1, the AP transmits a block acknowledgment request (BAR) frame to the next STA 2 after SIFS, and the STA 2 transmits a BA frame to the AP after SIFS.
  • BAR block acknowledgment request
  • the AP receiving the BA frame from STA 2 transmits the BAR frame to STA 3 after SIFS, and STA 3 transmits the BA frame to AP after SIFS.
  • the AP transmits the next MU PPDU to all STAs.
  • an ACK frame is used as a response to the MPDU, and a block ACK frame is used as a response to the A-MPDU.
  • 15 is a diagram illustrating an ACK frame in a wireless communication system to which the present invention can be applied.
  • an ACK frame is composed of a frame control field, a duration field, an RA field, and an FCS.
  • the RA field may be a second address field of a data frame, a management frame, a block ACK request frame, a block ACK frame, or a PS-Poll frame received immediately before. It is set to the value of.
  • the ACK frame is transmitted by the non-QoS STA, the More Fragments subfield in the Frame Control field of the data frame or management frame received immediately before If '0', the duration value is set to '0'.
  • the duration value may include a data frame, a management frame, a block ACK request frame, a block received immediately before.
  • the duration / ID field of the ACK (Block Ack) frame or the PS-Poll frame the time required for transmitting the ACK frame and the SIFS interval are set to a value (ms). If the calculated duration value is not an integer value, it is rounded up.
  • FIG. 16 is a diagram illustrating a Block Ack Request frame in a wireless communication system to which the present invention can be applied.
  • a block ACK request (BAR) frame includes a frame control field, a duration / ID field, a reception address field, a transmission address field, a BAR control ( BAR control field, BAR information field and frame check sequence (FCS).
  • BAR block ACK request
  • FCS frame check sequence
  • the RA field may be set to the address of the STA that receives the BAR frame.
  • the TA field may be set to an address of an STA that transmits a BAR frame.
  • the BAR control field includes a BAR Ack Policy subfield, a Multi-TID subfield, a Compressed Bitmap subfield, a Reserved subfield, and a TID Information (TID_Info) subfield. It includes.
  • Table 9 is a table illustrating a BAR control field.
  • the BAR Information field contains different information according to the type of the BAR frame. This will be described with reference to FIG. 17.
  • FIG. 17 illustrates a BAR information field of a block ACK request frame in a wireless communication system to which an embodiment of the present invention may be applied.
  • FIG. 17A illustrates a BAR Information field of a Basic BAR frame and a Compressed BAR frame
  • FIG. 17B illustrates a BAR Information field of a Multi-TID BAR frame.
  • the BAR Information field includes a Block Ack Starting Sequence Control subfield.
  • the Block Ack Starting Sequence Control subfield includes a fragment number subfield and a starting sequence number subfield.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Number subfield includes the sequence number of the first MSDU in which the corresponding BAR frame is transmitted.
  • the Starting Sequence Control subfield includes the sequence number of the first MSDU or A-MSDU for which the corresponding BAR frame is to be transmitted.
  • the BAR Information field may include a TID Info subfield and a Block Ack Starting Sequence Control subfield. Stars are repeated.
  • the Per TID Info subfield includes a reserved subfield and a TID value subfield.
  • the TID Value subfield contains a TID value.
  • the Block Ack Starting Sequence Control subfield includes the Fragment Number and Starting Sequence Number subfields as described above.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Control subfield includes the sequence number of the first MSDU or A-MSDU for which the corresponding BAR frame is to be transmitted.
  • FIG. 18 is a diagram illustrating a block ACK frame in a wireless communication system to which the present invention can be applied.
  • a block ACK (BA) frame includes a frame control field, a duration / identifier (Duration / ID) field, a reception address (RA) field, a transmission address (TA) field, and a BA control (BA). control field, BA Information field, and frame check sequence (FCS).
  • BA frame check sequence
  • the RA field may be set to the address of the STA requesting the block ACK.
  • the TA field may be set to an address of an STA that transmits a BA frame.
  • the BA control field includes a BA Ack Policy subfield, a Multi-TID subfield, a Compressed Bitmap subfield, a Reserved subfield, and a TID Information (TID_Info) subfield. It includes.
  • Table 10 is a table illustrating a BA control field.
  • the BA Information field includes different information according to the type of the BA frame. This will be described with reference to FIG. 19.
  • FIG. 19 is a diagram illustrating a BA Information field of a block ACK frame in a wireless communication system to which the present invention can be applied.
  • FIG. 19 (a) illustrates a BA Information field of a Basic BA frame
  • FIG. 19 (b) illustrates a BA Information field of a Compressed BA frame
  • FIG. 19 (c) illustrates a BA Information field of a Multi-TID BA frame. To illustrate.
  • the BA Information field includes a Block Ack Starting Sequence Control subfield and a Block ACK Bitmap subfield.
  • the Block Ack Starting Sequence Control subfield includes a Fragment Number subfield and a Starting Sequence Number subfield as described above.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Number subfield includes the sequence number of the first MSDU for transmitting the corresponding BA frame and is set to the same value as the Basic BAR frame received immediately before.
  • the Block Ack Bitmap subfield consists of 128 octets and is used to indicate the reception status of up to 64 MSDUs.
  • a value of '1' in the Block Ack Bitmap subfield indicates that the MPDU corresponding to the corresponding bit position was successfully received, and a value of '0' indicates that the MPDU corresponding to the corresponding bit position was not successfully received.
  • the BA Information field includes a Block Ack Starting Sequence Control subfield and a Block ACK Bitmap subfield.
  • the Block Ack Starting Sequence Control subfield includes a Fragment Number subfield and a Starting Sequence Number subfield as described above.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Number subfield includes the sequence number of the first MSDU or A-MSDU for transmitting the corresponding BA frame, and is set to the same value as the Basic BAR frame received immediately before.
  • the Block Ack Bitmap subfield is 8 octets long and is used to indicate the reception status of up to 64 MSDUs and A-MSDUs.
  • a value of '1' in the Block Ack Bitmap subfield indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successfully received.
  • a value of '0' indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successful. Indicates that it has not been received.
  • the BA Information field includes a TID Info subfield, a Block Ack Starting Sequence Control subfield, and a block ACK bit.
  • the Block Ack Bitmap subfield is repeatedly configured for one or more TIDs, and is configured in the order of increasing TIDs.
  • the Per TID Info subfield includes a reserved subfield and a TID value subfield.
  • the TID Value subfield contains a TID value.
  • the Block Ack Starting Sequence Control subfield includes the Fragment Number and Starting Sequence Number subfields as described above.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Control subfield contains the sequence number of the first MSDU or A-MSDU for which the corresponding BA frame is to be transmitted.
  • the Block Ack Bitmap subfield consists of 8 octets in length.
  • a value of '1' in the Block Ack Bitmap subfield indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successfully received.
  • a value of '0' indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successful. Indicates that it has not been received.
  • New frames for next-generation WLAN systems 802.11ax systems, with increasing attention from vendors in various fields for next-generation WiFi and increased demand for high throughput and quality of experience (QoE) after 802.11ac.
  • QoE quality of experience
  • IEEE 802.11ax is a next-generation WLAN system that supports higher data rates and handles higher user loads.
  • One of the recently proposed WLAN systems is known as high efficiency WLAN (HEW: High). Called Efficiency WLAN).
  • the IEEE 802.11ax WLAN system may operate in the 2.4 GHz frequency band and the 5 GHz frequency band like the existing WLAN system. It can also operate in the higher 60 GHz frequency band.
  • IEEE 802.11ax the existing IEEE 802.11 OFDM system (IEEE 802.11a, 802.11n) is used for outdoor throughput transmission for average throughput enhancement and inter-symbol interference in outdoor environment. , 4x larger FFT size for each bandwidth than 802.11ac. This will be described with reference to the drawings below.
  • the description of the non-HT format PPDU, the HT-mixed format PPDU, the HT-greenfield format PPDU, and / or the VHT format PPDU described above will be described in HE format unless otherwise noted. May be incorporated into the description of the PPDU.
  • FIG. 20 is a diagram illustrating a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • HE High Efficiency
  • FIG. 20A illustrates a schematic structure of an HE format PPDU
  • FIGS. 20B to 20D illustrate more specific structures of an HE format PPDU.
  • a HE format PPDU for HEW may be largely composed of a legacy part (L-part), an HE part (HE-part), and a data field (HE-data).
  • L-part legacy part
  • HE-part HE part
  • HE-data data field
  • the L-part is composed of an L-STF field, an L-LTF field, and an L-SIG field in the same manner as the conventional WLAN system maintains.
  • the L-STF field, L-LTF field, and L-SIG field may be referred to as a legacy preamble.
  • the HE-part is a part newly defined for the 802.11ax standard and may include an HE-STF field, an HE-SIG field, and an HE-LTF field.
  • FIG. 25A the order of the HE-STF field, the HE-SIG field, and the HE-LTF field is illustrated, but may be configured in a different order.
  • HE-LTF may be omitted.
  • the HE-SIG field may be collectively referred to as HE-preamble.
  • L-part and HE-part may be collectively referred to as a physical preamble (PHY).
  • PHY physical preamble
  • the HE-SIG may include information for decoding the HE-data field (eg, OFDMA, UL MU MIMO, Enhanced MCS, etc.).
  • information for decoding the HE-data field eg, OFDMA, UL MU MIMO, Enhanced MCS, etc.
  • the L-part and the HE-part may have different fast fourier transform (FFT) sizes (ie, subcarrier spacing), and may use different cyclic prefixes (CP).
  • FFT fast fourier transform
  • CP cyclic prefixes
  • 802.11ax systems can use FFT sizes that are four times larger than legacy WLAN systems. That is, the L-part may have a 1 ⁇ symbol structure, and the HE-part (particularly, HE-preamble and HE-data) may have a 4 ⁇ symbol structure.
  • 1 ⁇ , 2 ⁇ , 4 ⁇ size FFT means relative size with respect to legacy WLAN system (eg, IEEE 802.11a, 802.11n, 802.11ac, etc.).
  • the FFT size used for the L-part is 64, 128, 256, and 512 at 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively
  • the FFT size used for the HE-part is 256 at 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively. , 512, 1024, 2048.
  • the FFT size is larger than that of the legacy WLAN system, the number of subcarriers per unit frequency is increased because the subcarrier frequency spacing is smaller, but the OFDM symbol length is longer.
  • the use of a larger FFT size means that the subcarrier spacing becomes narrower, and similarly, an Inverse Discrete Fourier Transform (IDFT) / Discrete Fourier Transform (DFT) period is increased.
  • IDFT Inverse Discrete Fourier Transform
  • DFT Discrete Fourier Transform
  • the IDFT / DFT period may mean a symbol length excluding the guard period (GI) in the OFDM symbol.
  • the subcarrier spacing of the HE-part is 1/4 of the subcarrier spacing of the L-part.
  • the ID-FT / DFT period of the HE-part is four times the IDFT / DFT period of the L-part.
  • the GI can be one of 0.8 ⁇ s, 1.6 ⁇ s, 3.2 ⁇ s, so the OFDM symbol length (or symbol interval) of the HE-part including the GI is 13.6 ⁇ s, 14.4 ⁇ s, 16 according to the GI. It can be
  • the HE-SIG field may be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-SIG-A field having a length of 12.8 kHz, a HE-STF field of 1 OFDM symbol, one or more HE-LTF fields, and a HE-SIG-B field of 1 OFDM symbol. It may include.
  • the FFT having a size four times larger than the existing PPDU may be applied from the HE-STF field. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively.
  • the HE-SIG when the HE-SIG is transmitted by being divided into the HE-SIG-A field and the HE-SIG-B field as shown in FIG. 20 (b), the positions of the HE-SIG-A field and the HE-SIG-B field are shown in FIG. May be different from 25 (b).
  • the HE-SIG-B field may be transmitted after the HE-SIG-A field
  • the HE-STF field and the HE-LTF field may be transmitted after the HE-SIG-B field.
  • an FFT of 4 times larger than a conventional PPDU may be applied from the HE-STF field.
  • the HE-SIG field may not be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-STF field of one OFDM symbol, a HE-SIG field of one OFDM symbol, and one or more HE-LTF fields.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively.
  • the HE-SIG field is not divided into the HE-SIG-A field and the HE-SIG-B field, and the HE-LTF field may be omitted.
  • the HE-part of the HE format PPDU may include a HE-STF field of 1 OFDM symbol and a HE-SIG field of 1 OFDM symbol.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 160 MHz, respectively.
  • the HE format PPDU for the WLAN system according to the present invention may be transmitted on at least one 20 MHz channel.
  • the HE format PPDU may be transmitted in a 40 MHz, 80 MHz, or 160 MHz frequency band through a total of four 20 MHz channels. This will be described in more detail with reference to the drawings below.
  • 21 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • 21 illustrates a PPDU format when 80 MHz is allocated to one STA (or OFDMA resource units are allocated to a plurality of STAs within 80 MHz) or when different streams of 80 MHz are allocated to a plurality of STAs, respectively.
  • L-STF, L-LTF, and L-SIG may be transmitted as OFDM symbols generated based on 64 FFT points (or 64 subcarriers) in each 20MHz channel.
  • the HE-SIG B field may be located after the HE-SIG A field.
  • the FFT size per unit frequency may be larger after the HE-STF (or HE-SIG B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG A field may include common control information that is commonly transmitted to STAs that receive a PPDU.
  • the HE-SIG A field may be transmitted in one to three OFDM symbols.
  • the HE-SIG A field is copied in units of 20 MHz and includes the same information.
  • the HE-SIG-A field informs the total bandwidth information of the system.
  • Table 11 is a table illustrating information included in the HE-SIG A field.
  • each field illustrated in Table 11 may follow the definition of the IEEE 802.11 system.
  • each field described above corresponds to an example of fields that may be included in the PPDU, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included. Another embodiment of the information included in the HE-SIG A field will be described later with reference to FIG. 34.
  • HE-STF is used to improve the performance of AGC estimation in MIMO transmission.
  • the HE-SIG B field may include user-specific information required for each STA to receive its own data (eg, PSDU).
  • PSDU user-specific information required for each STA to receive its own data
  • the HE-SIG B field may be transmitted in one or two OFDM symbols.
  • the HE-SIG B field may include information on the modulation and coding scheme (MCS) of the corresponding PSDU and the length of the corresponding PSDU.
  • MCS modulation and coding scheme
  • the L-STF, L-LTF, L-SIG, and HE-SIG A fields may be repeatedly transmitted in units of 20 MHz channels. For example, when a PPDU is transmitted on four 20 MHz channels (ie, an 80 MHz band), the L-STF, L-LTF, L-SIG, and HE-SIG A fields may be repeatedly transmitted on every 20 MHz channel. .
  • legacy STAs supporting legacy IEEE 802.11a / g / n / ac may not be able to decode the HE PPDU.
  • the L-STF, L-LTF, and L-SIG fields are transmitted through a 64 FFT on a 20 MHz channel so that the legacy STA can receive them.
  • the L-SIG field may occupy one OFDM symbol, one OFDM symbol time is 4 ms, and a GI may be 0.8 ms.
  • the FFT size for each frequency unit may be larger from the HE-STF (or HE-SIG A). For example, 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel. As the FFT size increases, the number of OFDM subcarriers per unit frequency increases because the interval between OFDM subcarriers becomes smaller, but the OFDM symbol time becomes longer. In order to improve the efficiency of the system, the length of the GI after the HE-STF may be set equal to the length of the GI of the HE-SIG A.
  • the HE-SIG A field may include information required for the HE STA to decode the HE PPDU.
  • the HE-SIG A field may be transmitted through a 64 FFT in a 20 MHz channel so that both the legacy STA and the HE STA can receive it. This is because the HE STA can receive not only the HE format PPDU but also the existing HT / VHT format PPDU, and the legacy STA and the HE STA must distinguish between the HT / VHT format PPDU and the HE format PPDU.
  • FIG. 22 illustrates an HE format PPDU according to an embodiment of the present invention.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-B field may include information specific to each STA, but may be encoded over the entire band (ie, indicated by the HE-SIG-A field). That is, the HE-SIG-B field includes information on all STAs and is received by all STAs.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band.
  • the HE-SIG-B may be allocated 20 MHz for STA 1, 20 MHz for STA 2, 20 MHz for STA 3, and 20 MHz for STA 4.
  • STA 1 and STA 2 may allocate 40 MHz, and STA 3 and STA 4 may then allocate 40 MHz.
  • STA 1 and STA 2 may allocate different streams, and STA 3 and STA 4 may allocate different streams.
  • the HE-SIG C field may be added to the example of FIG. 27.
  • information on all STAs may be transmitted over the entire band, and control information specific to each STA may be transmitted in units of 20 MHz through the HE-SIG-C field.
  • the HE-SIG-B field may be transmitted in units of 20 MHz similarly to the HE-SIG-A field without transmitting over the entire band. This will be described with reference to the drawings below.
  • FIG. 23 illustrates an HE format PPDU according to an embodiment of the present invention.
  • the HE-SIG-B field is not transmitted over the entire band, but is transmitted in 20 MHz units as in the HE-SIG-A field. However, at this time, the HE-SIG-B is encoded and transmitted in 20 MHz units differently from the HE-SIG-A field, but may not be copied and transmitted in 20 MHz units.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-A field is duplicated and transmitted in units of 20 MHz.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band. Since the HE-SIG-B field includes information about each STA, information about each STA may be included for each HE-SIG-B field in units of 20 MHz. In this case, in the example of FIG. 23, 20 MHz is allocated to each STA. For example, when 40 MHz is allocated to the STA, the HE-SIG-B field may be copied and transmitted in units of 20 MHz.
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the HE format PPDU as shown in FIGS. 21 to 23 may be identified through a RL-SIG (Repeated L-SIG) field, which is a repetition symbol of the L-SIG field.
  • the RL-SIG field is inserted before the HE SIG-A field, and each STA may identify the format of the received PPDU as the HE format PPDU using the RL-SIG field.
  • DL MU transmission downlink multi-user transmission
  • UL MU transmission uplink multi-user transmission
  • Such DL MU transmission or UL MU transmission may be multiplexed in the frequency domain or the spatial domain.
  • different frequency resources eg, subcarriers or tones
  • OFDMA orthogonal frequency division multiplexing
  • different spatial streams may be allocated as downlink or uplink resources for each of the plurality of STAs.
  • a transmission expression through different spatial streams may be referred to as 'DL / UL MU MIMO' transmission.
  • overlap between frequency resources used for transmitting uplink data by a plurality of STAs may occur. For example, when oscillators of the plurality of STAs are different, frequency offsets may appear differently. If each of a plurality of STAs having different frequency offsets simultaneously performs uplink transmission through different frequency resources, some of frequency regions used by each of the plurality of STAs may overlap.
  • the AP may receive signals of different power from each of the plurality of STAs. In this case, a signal arriving at a weak power may be difficult to be detected by the AP relative to a signal arriving at a strong power.
  • the present invention proposes a UL MU transmission method in a WLAN system.
  • 24 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.
  • an AP instructs STAs participating in UL MU transmission to prepare for UL MU transmission, receives UL MU data frames from corresponding STAs, and responds to an UL MU data frame with an ACK frame ( Transmits a Block Ack (BA) frame.
  • BA Block Ack
  • the AP transmits a UL MU Trigger frame 2410 to instruct STAs to transmit UL MU data to prepare for UL MU transmission.
  • the UL MU scheduling frame may be referred to as a term of a 'UL MU scheduling frame'.
  • the UL MU trigger frame 2410 may include control information such as STA identifier (ID) / address information, resource allocation information to be used by each STA, duration information, and the like.
  • ID STA identifier
  • the UL MU trigger frame 2410 may include control information such as STA identifier (ID) / address information, resource allocation information to be used by each STA, duration information, and the like.
  • the STA ID / address information means information on an identifier or an address for specifying each STA that transmits uplink data.
  • the resource allocation information is assigned to uplink transmission resources allocated to each STA (for example, frequency / subcarrier information allocated to each STA in case of UL MU OFDMA transmission, and stream index allocated to each STA in case of UL MU MIMO transmission). Means information.
  • Duration information means information for determining a time resource for transmission of an uplink data frame transmitted by each of a plurality of STAs.
  • the duration information may include interval information of a TXOP (Transmit Opportunity) allocated for uplink transmission of each STA or information (eg, bits or symbols) about an uplink frame length. Can be.
  • TXOP Transmit Opportunity
  • information eg, bits or symbols
  • the UL MU trigger frame 2410 may further include control information such as MCS information, coding information, etc. to be used when transmitting the UL MU data frame for each STA.
  • the above control information is the HE-part (eg, HE-SIG A field or HE-SIG B field) of the PPDU carrying the UL MU trigger frame 2410 or the control field (eg, the UL MU trigger frame 2410).
  • the frame control field of the MAC frame may be transmitted.
  • the PPDU carrying the UL MU trigger frame 2410 has a structure starting with L-part (eg, L-STF field, L-LTF field, L-SIG field, etc.).
  • legacy STAs may perform Network Allocation Vector (NAV) setting through L-SIG protection from the L-SIG field.
  • NAV Network Allocation Vector
  • legacy STAs may calculate an interval (hereinafter, referred to as an 'L-SIG guard interval') for NAV setting based on data length and data rate information in the L-SIG.
  • the legacy STAs may determine that there is no data to be transmitted to them during the calculated L-SIG protection period.
  • the L-SIG guard interval may be determined as the sum of the MAC duration field value of the UL MU trigger frame 2410 and the remaining interval after the L-SIG field of the PPDU carrying the UL MU trigger frame 2410. Accordingly, the L-SIG guard period may be set to a value up to a period for transmitting the ACK frame 2430 (or BA frame) transmitted to each STA according to the MAC duration value of the UL MU trigger frame 2410.
  • the first field may distinguish and indicate UL MU OFDMA transmission and UL MU MIMO transmission.
  • '0' may indicate UL MU OFDMA transmission
  • '1' may indicate UL MU MIMO transmission.
  • the size of the first field may consist of 1 bit.
  • the second field (eg, STA ID / address field) informs STA ID or STA addresses to participate in UL MU transmission.
  • the size of the second field may be configured as the number of bits to inform the STA ID ⁇ the number of STAs to participate in the UL MU. For example, when the second field consists of 12 bits, the ID / address of each STA may be indicated for every 4 bits.
  • the third field (eg, resource allocation field) indicates a resource region allocated to each STA for UL MU transmission.
  • the resource region allocated to each STA may be sequentially indicated to each STA in the order of the second field.
  • the first field value is '0', this indicates frequency information (eg, frequency index, subcarrier index, etc.) for UL MU transmission in the order of STA ID / address included in the second field.
  • frequency information eg, frequency index, subcarrier index, etc.
  • MIMO information eg, stream index, etc.
  • the size of the third field may be configured in a plurality of bits (or bitmap format).
  • ⁇ It may be configured as the number of STAs to participate in the UL MU transmission.
  • the second field is set in the order of 'STA 1' and 'STA 2'
  • the third field is set in the order of '2', '2'.
  • STA 1 when the first field is '0', STA 1 may be allocated frequency resources from the upper (or lower) frequency domain, and STA 2 may be sequentially allocated the next frequency resource. For example, in case of supporting 20 MHz OFDMA in an 80 MHz band, STA 1 may use a higher (or lower) 40 MHz band, and STA 2 may use a next 40 MHz band.
  • STA 1 may be allocated an upper (or lower) stream, and STA 2 may be sequentially allocated the next stream.
  • the beamforming scheme according to each stream may be specified in advance, or more specific information about the beamforming scheme according to the stream may be included in the third field or the fourth field.
  • Each STA transmits UL MU data frames 2421, 2422, and 2423 to the AP based on the UL MU trigger frame 2410 transmitted by the AP.
  • each STA may transmit the UL MU data frames 2421, 2422, 2423 to the AP after SIFS after receiving the UL MU trigger frame 2410 from the AP.
  • Each STA may determine a specific frequency resource for UL MU OFDMA transmission or a spatial stream for UL MU MIMO transmission based on resource allocation information of the UL MU trigger frame 2410.
  • each STA may transmit an uplink data frame on the same time resource through different frequency resources.
  • each of STA 1 to STA 3 may be allocated different frequency resources for uplink data frame transmission based on STA ID / address information and resource allocation information included in the UL MU trigger frame 2410.
  • STA ID / address information may sequentially indicate STA 1 to STA 3
  • resource allocation information may sequentially indicate frequency resource 1, frequency resource 2, and frequency resource 3.
  • the STA 1 to STA 3 sequentially indicated based on the STA ID / address information may be allocated the frequency resource 1, the frequency resource 2, and the frequency resource 3 sequentially indicated based on the resource allocation information. That is, STA 1 may transmit uplink data frames 2421, 2422, and 2423 to the AP through frequency resource 1, STA 2, frequency resource 2, and STA 3 through frequency resource 3.
  • each STA may transmit an uplink data frame on the same time resource through at least one different stream among a plurality of spatial streams.
  • each of STA 1 to STA 3 may be allocated a spatial stream for uplink data frame transmission based on STA ID / address information and resource allocation information included in the UL MU trigger frame 2410.
  • STA ID / address information may sequentially indicate STA 1 to STA 3
  • resource allocation information may sequentially indicate spatial stream 1, spatial stream 2, and spatial stream 3.
  • the STA 1 to STA 3 sequentially indicated based on the STA ID / address information may be allocated to the spatial stream 1, the spatial stream 2, and the spatial stream 3 sequentially indicated based on the resource allocation information. That is, STA 1 may transmit uplink data frames 2421, 2422, and 2423 to the AP through spatial stream 1, STA 2, spatial stream 2, and STA 3.
  • the PPDU carrying the uplink data frames 2421, 2422, and 2423 can be configured in a new structure without the L-part.
  • the L-part of the PPDU carrying the uplink data frames 2421, 2422, and 2423 is SFN type (that is, all STAs are the same). L-part configuration and contents can be sent simultaneously).
  • the L-part of the PPDU carrying the uplink data frames 2421, 2422, and 2423 has a L-part of 20 MHz in the band allocated to each STA. Can be sent.
  • the HE-SIG field in the PPDU carrying the uplink data frames 2421, 2422, and 2423 (that is, how the data frame is constructed). (Area for transmitting the control information) may not be necessary.
  • the HE-SIG-A field and / or the HE-SIG-B may not be transmitted.
  • the HE-SIG-A field and the HE-SIG-C field may be transmitted, and the HE-SIG-B field may not be transmitted.
  • the AP may transmit an ACK frame 2430 (or BA frame) in response to the uplink data frames 2421, 2422, and 2423 received from each STA.
  • the AP may receive uplink data frames 2421, 2422, and 2423 from each STA, and transmit an ACK frame 2430 to each STA after SIFS.
  • the existing ACK frame may be configured to include the AID (or Partial AID) of the STAs participating in the UL MU transmission in the RA field having a size of 6 octets.
  • a new structure of the ACK frame can be configured in the form for DL SU transmission or DL MU transmission.
  • the AP may transmit only the ACK frame 2430 for the UL MU data frame that has been successfully received to the corresponding STA.
  • the AP may inform whether the reception was successful through the ACK frame 2430 as an ACK or a NACK. If the ACK frame 2430 includes NACK information, the ACK frame 2430 may also include information on the reason for the NACK or information thereafter (eg, UL MU scheduling information).
  • the PPDU carrying the ACK frame 2430 may be configured in a new structure without the L-part.
  • the ACK frame 2430 may include STA ID or address information. However, if the order of STAs indicated in the UL MU trigger frame 2410 is applied in the same manner, the STA ID or address information may be omitted.
  • the TXOP (that is, the L-SIG guard interval) of the ACK frame 2430 is extended to include a frame for the next UL MU scheduling or a control frame including correction information for the next UL MU transmission. It may be.
  • an adjustment process such as synchronization between STAs may be added for UL MU transmission.
  • 25 to 27 illustrate a resource allocation unit in an OFDMA multi-user transmission scheme according to an embodiment of the present invention.
  • a plurality of resource units may be defined in units of n tones (or subcarriers) within a PPDU bandwidth.
  • the resource unit means an allocation unit of frequency resources for DL / UL OFDMA transmission.
  • One or more resource units may be allocated to one STA as DL / UL frequency resources, and different resource units may be allocated to the plurality of STAs, respectively.
  • 25 illustrates a case where the PPDU bandwidth is 20 MHz.
  • Seven DC tones may be located in the center frequency region of the 20 MHz PPDU bandwidth.
  • six left guard tones and five right guard tones may be located at both sides of the 20 MHz PPDU bandwidth.
  • one resource unit may consist of 26 tones.
  • one resource unit may be composed of 52 tones or 26 tones.
  • one resource unit may be composed of 106 tones or 26 tones.
  • one resource unit may be configured with 242 tones.
  • a resource unit consisting of 26 tones may include two pilot tones, a resource unit consisting of 52 tones may include four pilot tones, and a resource unit consisting of 106 tones may include four pilot tones. .
  • up to nine STAs may be supported for DL / UL OFDMA transmission in a 20 MHz band.
  • up to five STAs may be supported for DL / UL OFDMA transmission in the 20 MHz band.
  • up to three STAs may be supported for DL / UL OFDMA transmission in the 20 MHz band.
  • a 20 MHz band may be allocated to one STA.
  • the resource unit configuration method of FIG. 25 (a) to FIG. 25 (d) may be applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA.
  • the resource unit configuration scheme in which FIGS. 25A to 25D are combined may be applied.
  • FIG. 26 exemplifies a case where the PPDU bandwidth is 40 MHz.
  • DC tones may be located in the center frequency region of the 40 MHz PPDU bandwidth.
  • 12 left guard tones and 11 light guard tones may be located at both sides of the 40 MHz PPDU bandwidth.
  • one resource unit may consist of 26 tones.
  • one resource unit may consist of 52 tones or 26 tones.
  • one resource unit may be configured of 106 tones or 26 tones.
  • one resource unit may be configured with 242 tones.
  • one resource unit may be configured with 484 tones.
  • a resource unit consisting of 26 tones may include two pilot tones, a resource unit consisting of 52 tones may include four pilot tones, and a resource unit consisting of 106 tones may include four pilot tones.
  • a resource unit consisting of 242 tones may include eight pilot tones, and a resource unit consisting of 484 tones may include sixteen pilot tones.
  • up to 18 STAs may be supported for DL / UL OFDMA transmission in a 40 MHz band.
  • up to 10 STAs may be supported for DL / UL OFDMA transmission in a 40 MHz band.
  • a resource unit is configured as shown in FIG. 26C up to six STAs may be supported for DL / UL OFDMA transmission in a 40 MHz band.
  • the resource unit is configured as shown in 26 (d) up to two STAs may be supported for DL / UL OFDMA transmission in the 40 MHz band.
  • the corresponding resource unit may be allocated to one STA for SU DL / UL transmission in the 40 MHz band.
  • the resource unit configuration method of FIG. 26 (a) to FIG. 26 (e) may be applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA.
  • the resource unit configuration scheme in which FIGS. 26 (a) to 26 (e) are combined may be applied.
  • Seven DC tones may be located in the center frequency region of the 80 MHz PPDU bandwidth. However, when 80 MHz PPDU bandwidth is allocated to one STA (that is, when a resource unit composed of 996 tones is allocated to one STA), five DC tones may be located in the center frequency region. In addition, 12 left guard tones and 11 light guard tones may be located at both sides of the 80 MHz PPDU bandwidth.
  • one resource unit may consist of 26 tones.
  • one resource unit may be composed of 52 tones or 26 tones.
  • one resource unit may include 106 tones or 26 tones.
  • one resource unit may be configured of 242 tones or 26 tones.
  • one resource unit may consist of 484 tones or 26 tones.
  • one resource unit may be configured with 996 tones.
  • a resource unit consisting of 26 tones may include two pilot tones, a resource unit consisting of 52 tones may include four pilot tones, and a resource unit consisting of 106 tones may include four pilot tones.
  • a resource unit consisting of 242 tones may include 8 pilot tones
  • a resource unit consisting of 484 tones may include 16 pilot tones
  • a resource unit consisting of 996 tones may include 16 pilot tones. have.
  • up to 37 STAs may be supported for DL / UL OFDMA transmission in an 80 MHz band.
  • up to 21 STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band.
  • up to 13 STAs may be supported for DL / UL OFDMA transmission in an 80 MHz band.
  • up to five STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band.
  • the resource unit when the resource unit is configured as shown in 27 (e), up to three STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band. In addition, when a resource unit is configured as shown in 27 (f), the corresponding resource unit may be allocated to one STA for SU DL / UL transmission in the 80 MHz band.
  • the resource unit configuration method of FIG. 27 (a) to FIG. 27 (f) may be applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA.
  • the resource unit configuration scheme in which FIGS. 27 (a) to 27 (f) are combined may be applied.
  • the bandwidth of the 160MHz PPDU may have a structure in which the 80MHz PPDU bandwidth described above in FIG. 32 is repeated twice.
  • Only some resource units may be used for DL / UL OFDMA transmission among all resource units determined according to the above-described resource unit configuration. For example, when a resource unit is configured as shown in FIG. 30 (a) within 20 MHz, one resource unit may be allocated to less than nine STAs, and the remaining resource units may not be allocated to any STAs.
  • the data field of the PPDU is multiplexed and transmitted in a frequency domain in units of resource units allocated to each STA.
  • the data field of the PPDU may be configured in units of resource units allocated to each STA and transmitted simultaneously to the AP.
  • each STA simultaneously transmits a PPDU it may be recognized that a data field of a PPDU transmitted from each STA is multiplexed and transmitted in a frequency domain from an AP as a receiving end.
  • one resource unit may consist of a plurality of streams in a spatial domain.
  • one or more streams may be allocated to one STA as DL / UL spatial resources, and different streams may be allocated to the plurality of STAs, respectively.
  • a resource unit composed of 106 tones in FIG. 27C may be configured of a plurality of streams in a spatial domain to simultaneously support DL / UL OFDMA and DL / UL MU-MIMO.
  • a new control frame format carrying main information for identifying STAs transmitting the UL MU PPDU and resource allocation information for transmission of the UL MU PPDU may be defined, which may be referred to as a 'trigger frame'.
  • the trigger frame may consist of one (or at least one) MPDU.
  • the trigger frame may correspond to a type of a MAC control frame or a MAC management frame.
  • the trigger frame type may be newly defined.
  • the trigger frame may be configured as a frame including a HT-Control field in the MAC header (eg, a HT-Control wrapper frame).
  • information ie, trigger information
  • the HE-Control field newly defined in the HE format (ie, the VHT / HT control field of the HE format (or HE variant)) in the corresponding frame. It may be.
  • the HE-Control field may be newly defined in the 802.11ax system in a manner similar to the HT-Control field defined in the existing HT format. Accordingly, the HE-Control field may be included in the MAC header in a manner similar to the manner in which the HT-Control field is included in the MAC header.
  • Trigger frames may be classified into two types, as shown in FIGS. 28 and 29, according to a method included in the DL MU PPDU.
  • a data field of a DL MU PPDU may be configured in an A-MPDU format (see FIGS. 12 and 13) in which a plurality of MPDUs are aggregated.
  • at least one MPDU of the A-MPDUs may correspond to a trigger frame, and the remaining MPDUs may correspond to DL MU frames. That is, the trigger frame and the DL MU frame may be included in the A-MPDU format in the same data field received by one STA.
  • the data field of the DL MU PPDU may be configured in an MPDU format including one MPDU.
  • one MPDU constituting the data field may correspond to a trigger frame.
  • the AP may include and transmit at least one MPDU (ie, trigger frame) including the trigger information in the data field allocated to the STA.
  • the trigger information may be included in a MAC header or a MAC frame body in the corresponding MPDU.
  • the AID information of the STA that receives each data field of the DL MU PPDU may be included in a PHY header (eg, the HE-SIG A / B / C field) and transmitted.
  • trigger information may be transmitted to each STA individually.
  • a trigger frame individually transmitted to each STA may be referred to as a “unicast trigger frame” or an individually addressed trigger frame.
  • the unicast trigger frame for one user may be included as an A-MPDU format in a DL MU PPDU transmitted before xIFS based on the UL MU transmission time points of STAs.
  • 29 illustrates a DL MU PPDU according to a second embodiment of the present invention.
  • one data field in a DL MU PPDU may include at least one MPDU (ie, trigger frame) corresponding to a trigger frame.
  • information ie, trigger information
  • UL MU transmission may be included in a MAC header or a MAC frame body in a corresponding MPDU.
  • the specific data field including the trigger frame may be transmitted in a broadcast manner. Therefore, the AID of the specific data field may be set to the broadcast AID, and the trigger frame of the specific data field may include AIDs of STAs for which UL MU transmission is triggered. Accordingly, at least one MPDU (or trigger frame included in the MPDU) included in a specific data field may be referred to as a 'broadcast trigger frame'.
  • the MPDU corresponding to the trigger frame is included in a specific data field of the DL MU PPDU, it is necessary to inform the STA that a specific data field including the trigger frame exists.
  • the PHY header for example, the HE-SIG A / B / C field
  • the corresponding data field includes a trigger indicator or ID indicating that the trigger frame is included in the corresponding data field. There may be.
  • a 1-bit trigger indicator indicating whether a specific data field including trigger information is included may be included in a PHY header (eg, an HE-SIG A / B / C field).
  • the PHY header eg, the HE-SIG A / B / C field
  • the broadcast AID as identification information for the corresponding data field for broadcast transmission of the specific data field.
  • the STA may recognize that a specific data field including a trigger frame exists through broadcast identification information included in a PHY header (eg, the HE-SIG A / B / C field).
  • the broadcast trigger frame transmitted on a subchannel (or resource unit (RU)) of a DL OFDMA includes resource allocation information for STAs that receive a frame transmitted on another subchannel (or resource unit (RU)) of a corresponding DL OFDMA. (Or a Per User Info field), and the information about the subchannel (or resource unit (RU)) through which the broadcast trigger frame is transmitted may be a specific field (eg, PHY header, etc.) as described above. May be signaled).
  • the structure of the DL MU PPDU according to the embodiments of the present invention has been described above.
  • the above-described first and second embodiments may be applied independently or in combination according to circumstances.
  • the specific data field of the DL MU PPDU may include at least one MPDU corresponding to the trigger frame, and the other data field may include the trigger frame and the DL MU frame. It can be included as an MPDU format.
  • FIG. 30 is a view showing a trigger frame structure of the present invention.
  • a trigger frame includes a Frame control (FC) field, a Duration field, a RA (A1) field, a TA (A2) field, a Common Info field (or a common information field), a Per User (STA) Info N field ( Or may include a user-specific field, STA Info 1 to n), and an FCS.
  • FC Frame control
  • A1 RA
  • A2 TA
  • A2 TA
  • Common Info field or a common information field
  • STA Per User
  • N field Or may include a user-specific field, STA Info 1 to n
  • FCS Per User
  • the present invention is not limited thereto, and some fields may be excluded or new fields may be added.
  • the RA (A1) field indicates the address of the receiving STA that receives the trigger frame.
  • the RA field may be included or excluded in the trigger frame according to an embodiment.
  • the TA (A2) field indicates the address of the AP / STA transmitting the trigger frame.
  • the Common Info field represents a field including information received in common for STAs receiving a trigger frame.
  • the common info field may include a trigger type subfield, a trigger common info field, and / or a type-specific common info field.
  • the trigger type subfield may indicate a trigger type of a trigger frame for triggering transmission of a specific frame (eg, UL MU data frame, Ack / BA frame, NDPA frame, MU-BAR frame, etc.).
  • a specific frame eg, UL MU data frame, Ack / BA frame, NDPA frame, MU-BAR frame, etc.
  • the Trigger common Info subfield may indicate common information for transmission of the UL MU PPDU, for example, UL PPDU (maximum) length information, BW information, GI information, and the like.
  • the Type-specific common Info subfield may be optionally included in a trigger frame, and may indicate type specific information and user common information required for a specific trigger type. That is, the Type-specific common Info subfield may be selectively included in the trigger frame according to the trigger frame type, and the indicating information / content may also be configured differently according to the trigger frame type.
  • the subfields included in the Common Info field may be different according to the type / type / transmission method of the trigger frame including the Common Info field, which will be described later with reference to FIGS. 31 and 32.
  • the Per User Info field indicates a field including information received individually at each STA. Therefore, the Per User Info field may be included in the trigger frame as many as the number of STAs.
  • the Per User Info field may include a Trigger Per User Info N subfield and / or a Type-specific Per User Info N subfield.
  • the Trigger Per User Info N subfield is user individual information (or user-specific information) for UL MU PPDU transmission, for example, AID information of the STA, the STA is UL MCS information used to generate / transmit the MU frame, and resource unit allocation information allocated to each STA may be included.
  • the Type-specific Per User Info N subfield may be optionally included in a trigger frame, and may indicate type specific information and user specific / individual information required for a specific trigger type. That is, the Type-specific Per User Info N subfield may be selectively included in the trigger frame according to the trigger frame type, and the indicating information / content may also be configured differently according to the trigger frame type.
  • Subfields included in the Per User Info field may be different depending on the type / type / transmission method of the trigger frame including the Per User Info field, which will be described later with reference to FIGS. 31 and 32.
  • FIG. 31 is a diagram illustrating a Common Info field and a Per User Info field included in a broadcast trigger frame.
  • FIG. 31A illustrates a Common Info field included in a broadcast trigger frame
  • FIG. 31B illustrates a Per User Info field included in a broadcast trigger frame.
  • the Common Info field (or common information) of the broadcast trigger frame includes trigger type information, UL PPDU maximum length information (9 bits), BW information (2 bits), GI information (1 bit), and LTF type. Information (3 bits), LTF Num (number) information (3 bits), and / or common resource unit allocation (RU) information. In this specification, information may be replaced with the term field or subfield.
  • the trigger type information indicates a type of a frame to be UL transmitted in response to a trigger frame by STAs such as a UL MU data frame, an Ack / BA frame, a random access (RA) frame, and the like.
  • the UL (MU) PPDU maximum length information indicates the maximum length of the UL (MU) PPDU triggered by the trigger frame. STAs receiving the maximum length information may perform padding up to the maximum length for the corresponding UL (MU) PPDU when the length of the UL (MU) PPDU to be transmitted is shorter than the indicated maximum length (or insert a padding bit). Can be).
  • the BW information may indicate the transmission bandwidth / channel of the UL MU PPDU.
  • the BW information may optionally include a Common Info field. That is, the BW information may or may not be included (or signaled) in the Common Info field.
  • the STAs may transmit the UL MU PPDU on the transmission bandwidth / channel indicated by the BW information.
  • the STAs may transmit the UL MU PPDU on the same transmission bandwidth / channel as that of the DL MU PPDU carrying the trigger frame.
  • the GI information may indicate the length of the guard interval (or the length of the guard interval used when generating the UL MU PPDU) applied / used to the UL MU PPDU.
  • the LTF type information indicates the LTF type of the UL MU PPDU
  • the LTF Num information may indicate the number of streams (or the number of HE-LTFs) used for the UL MU PPDU transmission.
  • the (common) resource unit allocation information may include information about a resource unit allocated to each STA for UL MU frame transmission. Such resource allocation information may be included in the Common Info field as shown in the figure or in the Per User Info field described below. When included in the Per User Info field, the resource unit allocation information may individually indicate a resource unit allocated to a specific STA that receives the Per User Info field.
  • information about parameters included in the common field (or common block field) of the HE-SIG A field or the HE-SIG B field of the UL MU PPDU may be further included.
  • the Per User Info field (or Per user information) of the broadcast trigger frame includes AID information (or reserved bits) (11 bits), user resource unit allocation (User RU allocation). Information, MCS information (4 bits), coding type information (1 bit), and / or SU / MU MIMO information (1 bit). In this specification, information may be replaced with the term field or subfield.
  • the AID information may indicate the AIDs of STAs that will transmit the UL MU frame / PPDU. In other words, it may indicate AIDs of STAs that will trigger UL MU transmission.
  • the AID information may be a reserved bit when the trigger type of the broadcast trigger frame is a random access type.
  • the (user) resource unit allocation information may separately indicate resource unit allocation information for a specific STA that receives a Per User Info field among STAs performing UL MU transmission. Such resource allocation information may be included in the Common Info field and transmitted as described above. In this case, the resource allocation information may commonly indicate resource allocation information for all STAs for which UL MU transmission is triggered.
  • the MCS information may indicate MCS information to be applied to the UL MU frame / PPDU.
  • Coding type information indicates whether STAs use low-density parity check (LDPC) or binary convolutional coding (BCC) for UL MU PPDU transmission / generation.
  • LDPC low-density parity check
  • BCC binary convolutional coding
  • SU / MU MIMO information indicates SU MIMO transmission or MU MIMO transmission of the UL MU PPDU.
  • the Per User Info field may include at least one of stream number (Nsts) information (3 bits), transmission beamforming (TxBF) information (1 bit), and STBC information (1 bit). It may further include.
  • the Per User Info field may further include index information (5 bits) indicating the number of streams (Nsts) and a start stream.
  • information about parameters included in the user specific field of the HE-SIG B field of the UL MU PPDU may be further included.
  • FIG. 32 is a diagram illustrating a Common Info field and a Per User Info field included in a unicast trigger frame. More specifically, FIG. 32 (a) illustrates a Common Info field included in a unicast trigger frame, and FIG. 32 (b) illustrates a Per User Info field included in a unicast trigger frame.
  • the Common Info field and the Per User Info field of the unicast trigger frame may be configured similarly to the Common Info field and the Per User Info field of the broadcast trigger frame. Therefore, the description of the information included in the broadcast trigger frame can be equally applied to the unicast trigger frame, and the following description will focus on differences between the broadcast trigger frame and the unicast trigger frame.
  • the Common Info field (or common information) of the unicast trigger frame includes reserved bits, UL PPDU maximum length information (9 bits), BW information (2 bits), GI information (1 bit), and LTF type information. (3bits), LTE Num information (3bits), and / or Common RU allocation information, and may not include trigger type information and user resource unit allocation information.
  • the Per User Info field of the unicast trigger frame includes reserved bits (11 bits), user resource unit allocation information, MCS information (4 bits), coding type information (1 bit), and / or SU / MU MIMO. It may include information (1 bit), and may not include AID information.
  • the Per User Info field may include at least one of stream number (Nsts) information (3 bits), transmission beamforming (TxBF) information (1 bit), and STBC information (1 bit). It may further comprise.
  • the Per User Info field may further include an index of the stream Nsts and index information (5 bits) of the starting stream.
  • Trigger type (2 ⁇ 3bits)
  • the trigger frame may be defined as a plurality of trigger types for triggering various UL frames.
  • a trigger frame including an AID field may be transmitted to trigger general data and control frames.
  • the STA may transmit a UL MU PPDU including (or configured) data and / or control frames, such as an Ack / BA frame or a Buffer status report frame, through its allocated resources.
  • the UL MU PPDU transmitted may exclude a frame requiring additional signaling information such as an NDPA trigger frame.
  • the NDPA trigger frame may refer to a frame in which an NDPA frame and a trigger frame are combined.
  • the AID (or STA address) of the STA to trigger the UL MU transmission may be included in the Per User Info field.
  • the HE-SIG B field or the RA field of the broadcast trigger frame may include a broadcast AID (or STA MAC address).
  • the AID (or STA MAC address) of the STA to trigger the UL MU transmission may be included in the HE-SIG B field or the RA field of the unicast trigger frame.
  • a trigger frame for triggering random access there may be a trigger frame for triggering random access.
  • the trigger frame may not include the AID field.
  • a trigger frame for triggering random access may be generated and transmitted in the form of a broadcast trigger frame type.
  • a trigger frame for triggering a DL Channel State Information (CSI) report request frame (or NDPA frame).
  • CSI Channel State Information
  • NDPA frame DL Channel State Information report request frame
  • Such trigger frame may require signaling of additional information regarding a CSI reporting method and a measuring method.
  • various trigger types such as an e-RTS (extended-RTS) frame may be additionally present.
  • e-RTS extended-RTS
  • Resource unit allocation information / fields-relating to field location and signaling content
  • the resource unit allocation information may be included in a common info field or a per user info field.
  • each STA since the resource unit allocation information included in the Common Info field indicates resource allocation in common to STAs receiving the trigger frame (that is, since each STA is not directly instructed), each STA has a total resource allocation information and There is a problem in that it is necessary to directly obtain / calculate what resource unit is allocated to itself based on its order. That is, there is a disadvantage in that the burden on the STA is increased in that the STA must directly find out what resource unit is allocated to the UL MU transmission.
  • the signaling overhead may increase, but each STA may directly know the resource unit allocated to it, thereby reducing the burden.
  • a uniform frame design can be designed between the broadcast trigger frame and the unicast trigger frame, thereby reducing the system complexity.
  • resource unit allocation information is signaled per STA (or per user).
  • the resource unit allocation information may include unit information (eg, 26/52/106 tone resource unit / full BW, etc.) or common resource unit allocation information of resource units for random access of STAs. Can be directed.
  • the common resource unit allocation information may correspond to information on frequency resources to be randomly accessed by STAs in common.
  • the resource unit allocation information may be located in the Common Info field or the Per User Info field of the trigger frame for random access.
  • 33 is a diagram illustrating a signaling method of resource unit allocation information according to the first embodiment of the present invention.
  • the resource unit allocation information may include a resource unit index (RU index) and a bandwidth / channel index (BC index).
  • RU index resource unit index
  • BC index bandwidth / channel index
  • the RU index may indicate a combination (or size) of the resource unit, and the AP may signal, as resource unit allocation information, the RU index corresponding to the resource unit combination to be allocated to the STA.
  • the bit value of the RU index is as follows.
  • 0x1111 It may indicate a resource unit corresponding to the entire UL transmission bandwidth (that is, 242 ton resource unit for the 20MHz channel, 484 ton resource unit for the 40MHz channel, or 996 ton resource unit for the 80MHz channel), respectively.
  • the RU index is 0x1111
  • the resource unit corresponding to the entire UL transmission bandwidth is indicated. Therefore, the size of the resource unit indicated by the BC index, which will be described later, may vary.
  • the BC index may indicate the bandwidth / channel in which the resource unit allocated to the STA is located (or included), and the AP may use the BC index indicating the bandwidth / channel in which the resource unit to be allocated to the STA is located. May be signaled as:
  • the bit value of the BC index is
  • 0x100 to 0x101 first 40 MHz channel to second 40 MHz channel
  • each channel indicates the order and position within a specific 80 MHz channel, as shown in FIG.
  • the resource unit allocation information is the first 26 ton resource unit of the fourth 20 MHz channel of the 80 MHz channel, as shown in FIG. 3310 may be indicated.
  • the resource unit allocation information may indicate the first 484 tone resource unit 3320 of the first 40 MHz channel of the 80 MHz channel. have.
  • all resource units present in a particular channel e.g., an 80 MHz channel.
  • a method of assigning an index and signaling an index assigned to a resource unit to be allocated as resource allocation information is possible.
  • such a resource unit allocation scheme will be referred to as an 'per user RU allocation scheme'.
  • 34 is a diagram illustrating a signaling method of resource unit allocation information according to the second embodiment of the present invention.
  • the resource unit allocation information may be signaled to indicate an index assigned to each resource unit as the second embodiment. If an index is assigned to a resource unit existing in an 80 MHz channel as in the example of this figure, since there are a total of 68 indexes, resource unit allocation information indicating an index may be signaled with a total bit size of 7 bits.
  • a common resource unit allocation method for allocating the divided resource units for each STA (Common RU allocation)
  • the combination of resource units constituting the entire channel may be signaled as common resource unit allocation information and information about resource units allocated to each STA as individual resource unit allocation information, which is related to FIGS. 35 and 36. This will be described later.
  • 35 is a diagram illustrating a case where an 80 MHz channel is divided into at least one resource unit according to an embodiment of the present invention.
  • 36 is a diagram illustrating a signaling method of individual resource unit allocation information according to an embodiment of the present invention.
  • an 80 MHz channel is 242 ton resource unit / 106 ton resource unit / 26 ton resource unit / 484 ton according to the common resource unit allocation method. Assume a case in which resource units are distinguished.
  • the common resource unit allocation information about the resource unit divided for resource allocation in the 80 MHz channel may be included in the Trigger Common Info subfield of the trigger frame.
  • the common resource unit allocation information may be signaled in various ways. As shown in FIG. 35, when indexes are provided for each of various combinations of resource units constituting a specific channel, common resource unit allocation information may be signaled to indicate a specific combination of resource units. Alternatively, the common resource unit allocation information may indicate a specific combination of resource units in the same / similar manner to the resource unit allocation information included in the common field (or common block field) of the HE-SIG B field.
  • individual resource unit allocation information about the STA to which each resource divided in the 80 MHz channel is allocated may be set in the Trigger Per User Info subfield (or Per User Info field) in the case of a broadcast trigger frame, or in the case of a unicast trigger frame. Can be included in each User Info field.
  • 36 (a) is a diagram illustrating a method for signaling individual resource unit allocation information in a broadcast trigger frame according to the first embodiment of the present invention.
  • a trigger per user info subfield may exist in the broadcast trigger frame as many resource units as are allocated to each STA. That is, in the example of FIG. 35, since five resource units are divided into one (242 ton resource unit, two 106 ton resource units, one 26 ton resource unit, and one 484 ton resource unit), five trigger per users An Info subfield (or Per User Info field) may be included in the broadcast trigger frame. Accordingly, the number of Trigger Per User Info subfields (or Per User Info fields) included in the broadcast trigger frame indicates the number of resource units that can be implicitly allocated.
  • the Trigger Per User Info subfields (or Per User Info fields) sequentially listed may correspond to resource units sequentially positioned in an 80 MHz channel.
  • the first Trigger Per User Info subfield may correspond to the 242 tone resource unit located first in the 80 MHz channel.
  • the AP may allocate each resource unit by including an AID of an STA to which a resource unit corresponding to the corresponding subfield is included in each Trigger Per User Info subfield (or Per User Info field).
  • the Trigger Per User Info subfield (or Per User Info field) may include AID information, and it may be interpreted that the STA indicated by the AID information has been allocated a resource unit corresponding to the subfield.
  • the Trigger Per User Info subfield (or Per User Info field) corresponding to the unassigned resource unit may include a null AID (AID to which the STA is not assigned). have. Therefore, the STA that receives the Trigger Per User Info subfield (or Per User Info field) including the null AID may ignore the subfield.
  • the Trigger Per User Info subfield configured to indicate individual resource unit allocation information may be as shown in FIG. 36 (a). That is, the first to fifth Trigger Per User Info subfields (or Per User Info fields) may include AID1 to 3, Null AID, and AID4, respectively.
  • the first 242-tone resource unit of the 80 MHz channel is in the STA having AID 1
  • the second 106-tone resource unit is in the STA having AID 2
  • the third 106-tone resource unit is in the STA having AID 3
  • the tone resource unit may be allocated to the STA having AID 4, respectively
  • the fourth 26 tone resource unit may be interpreted as not being allocated to the STA.
  • the information about the unallocated resource unit may not be signaled as individual resource unit allocation information but may be signaled as common resource unit allocation information.
  • each STA that receives the corresponding trigger frame needs to accumulate its own order to determine the location of the resource unit allocated to the STA. Therefore, the following proposes a method of explicitly indicating, without implicitly indicating individual resource unit allocation information as in the above-described embodiment.
  • 36 (b) is a diagram illustrating a method for signaling individual resource unit allocation information in a broadcast trigger frame according to the second embodiment of the present invention.
  • the Trigger Per User Info subfield (or Per User Info field) of the broadcast trigger frame explicitly states the AID of the STA and the position / order of resource units to be allocated to the STA. Can be directed.
  • the Trigger Per User Info subfield (or Per User Info field) does not need to include the AID of a specific STA according to the location of the resource unit, and Null AID is also unnecessary. Do.
  • 36C is a diagram illustrating a method of signaling individual resource unit allocation information in a unicast trigger frame according to an embodiment.
  • a common resource unit allocation scheme may be used for a uniform trigger frame format with the broadcast trigger frame.
  • the unicast trigger frame includes trigger information for one STA, the second embodiment described above with reference to FIG. 36 (b) may be applied.
  • the unicast trigger frame (in particular, the Per User Info field of the unicast trigger frame) may explicitly indicate the AID of the STA and the position / order of the resource unit to be allocated to the STA. Can be. Alternatively, the AID of the STA may be omitted in the unicast trigger frame.
  • the signaling method / format of the broadcast / unicast trigger frame has been described through a common resource unit allocation scheme.
  • a method of using the 'common resource unit allocation method' and the 'individual resource unit allocation method' described above with reference to FIG. 34 may be mixed as follows.
  • the AP may use a common resource unit allocation scheme when transmitting a broadcast trigger frame, and may use an individual resource unit allocation scheme when transmitting a unicast trigger frame.
  • Resource unit allocation information is always included in the Common Info field of the trigger frame, but its interpretation can be changed for each broadcast / unicast trigger frame.
  • the Common Info field is configured in a manner of implicitly indicating resource unit allocation information according to the common resource unit allocation scheme (for example, FIG. 36 (a)), and unicast.
  • the resource allocation information explicitly indicates resource unit allocation information according to an individual resource unit allocation scheme (FIG. 36 (c)), and may insert the corresponding information into the common info field instead of the per user info field. .
  • Common resource unit allocation schemes and individual resource unit allocation schemes have advantages and disadvantages, respectively.
  • the smaller the number of triggering STAs is advantageous to the individual resource unit allocation scheme, but the larger the number of STAs is advantageous to the common resource unit allocation scheme.
  • the AP may select a resource allocation method in a direction in which signaling overhead is reduced in consideration of the number of STAs to be triggered, and may additionally transmit an indication bit for indicating the selected allocation method to the STA.
  • the Common Info field of the trigger frame may include a resource unit allocation indication bit (1 bit).
  • the indication bit value is '0', it indicates that the common resource unit allocation scheme is indicated, and when it is '1', it can be interpreted as indicating an individual resource unit allocation scheme.
  • the AP may select an appropriate one of two allocation methods in consideration of the number of STAs triggered as described above, and may indicate the selected allocation method through an indication bit. .
  • the AP may use only individual resource unit allocation schemes.
  • a broadcast trigger frame is transmitted, a common resource unit allocation method is used, and when a unicast trigger frame is transmitted, an individual resource unit allocation method is used. May be used to distinguish a broadcast trigger frame from a unicast trigger frame.
  • the bandwidth information / field for indicating the total transmission bandwidth / channel of the UL MU PPDU may or may not be included in the trigger frame according to the following two options.
  • Option 1 If the (transmission) bandwidth / channel of the UL MU PPDU is set to follow the transmission bandwidth of the trigger frame (or the bandwidth of the UL MU PPDU is set to the DL MU PPDU including the trigger frame).
  • the bandwidth information / field may not be included (or may not be signaled) in the trigger frame).
  • the (transmission) bandwidth of the UL MU PPDU may be included (or signaled) in the trigger frame.
  • the transmission bandwidth / channel of the PHY header may follow the entire transmission bandwidth / channel of the UL MU PPDU. That is, the bandwidth / channel of the PHY header may be equal to the total transmission bandwidth / channel of the UL MU PPDU.
  • the transmission bandwidth / channel of the PHY header may correspond to at least one 20 MHz channel including a frequency part / region in which data of the UL MU PPDU is transmitted.
  • the transmission bandwidth / channel of the PHY header may be determined as the first 20 MHz channel.
  • Option 2 For an STA that does not transmit its PHY header over the entire transmission bandwidth, it is preferable to apply Option 2 rather than Option 1.
  • the SU / MU MIMO information of the trigger frame indicates MU MIMO
  • STBC information and TxBF information may not be required for the trigger frame. Instead, starting stream index information may be needed. That is, additionally necessary information differs depending on whether the trigger frame indicates SU MIMO or MU MIMO. Therefore, in this specification, it is proposed to interpret information included in a following field differently depending on which MIMO information indicates SU / MU MIMO information.
  • the following fields may be interpreted as indicating stream number (Nsts) information, transmission beamforming (TxBF) information, and STBC information, respectively.
  • the following field may be interpreted as indicating an index indicating the stream number and the starting stream.
  • FIG. 37 is a table illustrating an index indicating a stream number and a starting stream together according to an embodiment of the present invention.
  • an index may be configured to indicate the stream number and the starting stream together.
  • the number of streams and the starting stream indicated by each index are expressed in binary, and the number of streams corresponds to the number of bits having a value of '1' and the stream corresponding to the first bit position having a value of '1'. .
  • the bit size (or number of bits) of the (combined) index may be determined based on the maximum number of STAs (or users) and the maximum number of streams that can be allocated per STA. If the maximum number of STAs is 4 and the maximum number of streams per STA is 4, a total of 26 combinations are derived. Therefore, the bit size of the (combined) index for indicating the number of streams and the starting stream together may be determined as 5 bits.
  • a unified trigger frame format that can be commonly applied to broadcast trigger frames and unicast trigger frames is proposed.
  • This use of a unified trigger frame format between broadcast trigger frames and unicast trigger frames has the advantage of reducing system complexity.
  • a unified trigger frame includes a Frame control (FC) field, a Duration field, a RA (A1) field, a TA (A2) field, a Common Info field (or a common information field), and a Per User (STA) Info N.
  • Field or User-Specific field, STA Info 1 ⁇ n field
  • FCS Per User
  • the Common Info field includes a first subfield (3bits), a UL PPDU maximum length subfield (9bits), a BW subfield (2bits), a GI subfield (1bit), an LTF type subfield (3bits), and an LTF Num subnumber. Field (3 bits) and / or reserved bits (3 bits). However, the present invention is not limited thereto, and some subfields may be excluded or a new subfield may be added. In the present specification, a subfield may be replaced with the term field or information.
  • a unified trigger frame when transmitted as a broadcast trigger frame, it may be interpreted as indicating trigger type information, and when it is transmitted as a unicast trigger frame, it may be interpreted as a reserved bit.
  • the Per User Info N field (or STA Info 1 to n fields) includes a reserved bit (3 bits), a second subfield (11 bits), a resource unit allocation subfield (7 bits), an MCS subfield (4 bits), and a coding type subfield ( 1 bit), a SU / MU MIMO subfield (1 bit) and / or a third subfield (5 bits).
  • a subfield may be replaced with the term field or information.
  • a unified trigger frame when transmitted as a broadcast trigger frame, it may be interpreted to indicate AID information of the STA, and a unicast trigger frame (or a broadcast trigger frame not including AID information) If transmitted as), it can be interpreted as a reserved bit.
  • the trigger frame may additionally include Tx Power information / value (or Tx Power parameter) recommended by the AP to STAs performing UL MU transmission. .
  • the AP may transmit transmit power information (Tx Power) / value (or Tx Power parameter) recommended by the AP to each STA in a trigger frame (particularly, a Per User Info field of the trigger frame).
  • Tx Power transmit power information
  • Tx Power parameter Transmission Power parameter
  • the AP may transmit a specific value (for example, 0x000) to the STA as transmission power information / value (or Tx Power parameter).
  • the STA receiving the corresponding value may transmit the UL Frame / PPDU at the transmission power determined by the STA.
  • the AP may add recommended transmission power information / value (or Tx Power parameter) to the trigger frame.
  • the STA may allow the STA to determine the transmission power by itself. That is, when the AP instructs the STA to SU MIMO through the trigger frame, the AP does not add the recommended transmission power information / value (or Tx Power parameter) to the trigger frame or instructs the STA to determine the transmission power by itself. Power information / values (or Tx Power parameters) can be added.
  • transmission power information / value (or Tx Power parameter) is included in a trigger frame, but is not limited thereto.
  • the transmission power information / value (or Tx Power parameter) is DL MU PPDU. It may be included in the HE-SIG field (eg, the HE-SIG A / B / C field) and transmitted.
  • the trigger frame may further include Rx Power information / value (or Rx Power parameter) recommended by the AP to STAs performing UL MU transmission.
  • Rx Power information / value or Rx Power parameter
  • the STA can estimate a path loss from the STA to the AP through a beacon frame of the AP or a frame previously received.
  • the AP may receive Rx Power information / value (or Rx Power parameter) in the trigger frame (especially, the Common Info field of the trigger frame) so that the STAs can receive the Frame / PPDU at the recommended reception power. It can be transmitted by including.
  • the received power (Rx Power) information / value (or Rx Power parameter) is transmitted (or not transmitted) at a specific value
  • the STA itself transmits the received power by itself. You can decide.
  • the above-described transmission power information / value (or Tx Power parameter) and reception power (Rx Power) information / value (or Rx Power parameter) may be included in the trigger frame only when the trigger frame indicates MU MIMO.
  • the trigger frame format has been described generally.
  • the Common Info field and the Per User Info field included in the trigger frame will be described in detail.
  • the common info field may include a trigger type subfield, a trigger common info subfield, and / or a type-specific common info subfield.
  • the Trigger type subfield indicates a trigger frame type (or trigger type) for transmission of a specific frame (eg, UL MU data frame, Ack / BA frame, NDPA frame, MU-BAR frame, etc.). Can be directed.
  • a specific frame eg, UL MU data frame, Ack / BA frame, NDPA frame, MU-BAR frame, etc.
  • the Trigger type subfield may indicate a general trigger frame type (or trigger frame type for transmission of UL MU data / control frame).
  • a trigger frame of the general trigger frame type (including the AID of the STA) may trigger transmission of general data (ie, UL MU data) / control frame of the STA.
  • a trigger frame for random access which will be described later, may correspond to the present trigger frame type, which will be described later.
  • the trigger type subfield may indicate a DL NDPA frame type.
  • a trigger frame of the DL NDPA frame type may trigger transmission of a UL feedback frame of an STA for DL CSI.
  • a Type-specific common Info subfield and / or a Type-specific Per user Info subfield for indicating a sounding token and / or a feedback method may be added to the trigger frame.
  • the trigger type subfield may indicate the MU BAR frame type.
  • a trigger frame of the MU BAR frame type may trigger transmission of an UL MU BA frame of the STA.
  • a Type-specific common Info subfield and / or a Type-specific Per user Info subfield for indicating BAR control information and / or BAR information may be added to the trigger frame.
  • the trigger type subfield may indicate the MU RTS frame type.
  • a trigger frame of the MU RTS frame type may trigger transmission of an UL MU CTS frame of the STA.
  • trigger frame types such as a UL NDPA frame type for triggering transmission of a UL NDP frame may be defined, and are not limited to the above-described trigger frame type.
  • a trigger type subfield and a type-specific info subfield may not be necessary. This is because trigger information indicating UL transmission, such as an NDPA frame, an MU BAR frame, or an MU RTS frame, is transmitted only through a "broadcast trigger frame.”
  • the trigger common Info subfield may include common information for UL MU PPDU allocation / transmission of the STA.
  • the Trigger common Info subfield may include UL PPDU maximum length information (9 bits), BW information (2 bits), GI information (1 bit), PE (Packet Extension) information (3 bits), LTF type information (1 bit), and LTF Num. (Number) information (3 bits) and / or LDPC extra symbol information (1 bit) may be included.
  • information may be replaced with the term field or subfield.
  • the resource unit allocation information may be included in the Trigger common info subfield of the broadcast trigger frame or the Trigger Per User info subfield of the unicast trigger frame.
  • the resource unit allocation information proposes a format included in the Trigger Per User info subfield.
  • 40 is a diagram illustrating a Per User Info field format according to an embodiment of the present invention.
  • the Per User Info field may include a Trigger Per User Info N subfield and / or a Type-specific Per User Info N subfield.
  • the Trigger Per User Info N subfield may include user individual / specific information for UL MU PPDU allocation / transmission of the STA.
  • the Trigger Per User Info N field may include AID information (or reserved bits) (11 bits), resource unit allocation (User RU allocation) information (7 bits), transmission information (for example, MCS information (4 bits), and coding type).
  • Transmission beamforming (TxBF) information and STBC information may be needed as information for triggering UL SU transmission.
  • information may be replaced with the term field or subfield, and detailed description of each information is as described above with reference to FIGS. 31 and 32.
  • Trigger frame for random access TF-R
  • This TF-R may be referred to as a trigger frame for random access.
  • Transmission of a general UL MU PPDU may be triggered by a trigger frame including an AID of an STA to transmit the corresponding UL MU PPDU.
  • the transmission of the random access frame may be triggered by a trigger frame including a specific AID (eg, AID 0) (ie, AID for random access).
  • a Type Specific subfield may be additionally required to indicate additional information such as a random access back-off parameter and a random access classification (traffic class, group).
  • the TF-R may be used for random access for buffer status reporting or association request.
  • each random access region includes at least one resource unit.
  • each random access region includes at least one resource unit.
  • Information about this random access region may be indicated (or included) by the Per User Info field of the TF-R.
  • the random access region may be used interchangeably with a resource unit.
  • the AP may designate different random access classifications for each traffic type in order to prevent many STAs from performing random access to the same frequency domain at once. For example, the AP may designate a region to be randomly accessed for each group by creating a group for each traffic type, and may transmit information about the information to the TF-R.
  • the AP may simultaneously indicate trigger information for UL MU transmission of the data / control frame and trigger information for random access using a trigger frame of a general trigger type that triggers transmission of a general data / control frame.
  • the AP may transmit a “cascade trigger frame” in which a general trigger frame and a trigger frame for random access are cascaded to trigger transmission and random access of a data / control frame.
  • the Type specific common info subfield of the cascade trigger frame may include various indication information for triggering a UL frame and random access.
  • the Type specific common info subfield of a cascade trigger frame may include a cascade trigger frame indicator (TF indication) indicating a cascaded trigger frame format, full numerical information of a back-off unit for the cascade trigger frame, It may include at least one of the random access back-off parameter and / or the number information of the random access region.
  • TF indication cascade trigger frame indicator
  • the Trigger Per User Info subfield of the cascade trigger frame may include random access region information.
  • the Type specific Per User Info subfield of the cascade trigger frame may include random access type information, number information of resource units constituting (or included) a random access region, and / or size / size information of the resource unit.
  • the random access region may indicate a random access region indicated by random access region information included in the preceding Trigger Per User Info subfield.
  • 41 is a diagram illustrating a method of allocating a resource unit and a random access area according to an embodiment of the present invention.
  • the Trigger Per User Info subfield of the cascade trigger frame indicates allocation of resource units for each of STAs 1 and 2 and assigns allocation of random access regions for each of random access (RA) types 1 and 2. Can be directed. Furthermore, the Type specific (Per User) info subfield of the cascade trigger frame indicates the number of resource units (3 (RU1 to RU3)) included in the random access region allocated for RA type 1 and the size of the corresponding resource unit. can do. Similarly, the Type specific (Per User) info subfield of the cascade trigger frame indicates the number of resource units (5 (RU1 to RU5)) included in the random access region allocated for RA type 2 and the size of the corresponding resource unit. Can be directed.
  • STAs 1 and 2 may transmit UL MU frames using resource units allocated to them.
  • other STAs that receive the cascade trigger frame may select a resource unit that matches their back off count and perform random access to the corresponding resource unit.
  • the size / size of the resource unit included in the random access region is signaled in the Type specific (Per User) Info subfield, but the present invention is not limited thereto, and the size / size of the resource unit is not separately signaled. Can be fixed / set to a predetermined size (e.g., 26 ton resource unit).
  • FIG. 42 is a flowchart illustrating a UL MU PPDU transmission method of an STA device according to an embodiment of the present invention.
  • the embodiments described above with reference to the flowchart can be equally applied. Therefore, hereinafter, redundant description will be omitted.
  • a STA may first receive a DL MU PPDU (S4210).
  • the received DL MU PPDU may include a trigger frame including trigger information for triggering / supporting UL MU transmission of the STA.
  • the trigger frame may correspond to a unicast trigger frame for one STA transmitted in an Aggregated (MP) -MPDU or a broadcast trigger frame transmitted through a subchannel of the DL OFMDA.
  • the unicast trigger frame or broadcast trigger frame may be configured in a unified frame format to reduce system complexity and signaling overhead, and include a common info field and a user info field. It may include in common.
  • This unified trigger frame format is as described above with respect to FIG. In addition to the description of the Common Info field and the User Info field is the same as described above with reference to FIGS. 31-32 and 38-40.
  • the broadcast trigger frame transmitted in the subchannel (or resource unit (RU)) of the DL OFDMA is a resource for STAs that receive the frame transmitted in another subchannel (or resource unit (RU)) of the DL OFDMA. It may not include allocation information (or a Per User Info field).
  • allocation information or a Per User Info field.
  • the resource unit allocation information for may not be included.
  • the trigger frame may correspond to a trigger frame for random access for indicating a random access of the STA, the detailed description thereof has been described above with reference to FIG. 41.
  • the STA may transmit a UL MU PPDU as a response to the received DL MU PPDU (S4220).
  • the STA may transmit the UL MU PPDU based on the trigger information of the trigger frame in the received DL MU PPDU.
  • each STA apparatus is a block diagram of each STA apparatus according to an embodiment of the present invention.
  • the STA apparatus 4310 may include a memory 4312, a processor 4311, and an RF unit 4313.
  • the STA device may be an AP or a non-AP STA as an HE STA device.
  • the RF unit 4313 may be connected to the processor 4311 to transmit / receive a radio signal.
  • the RF unit 4313 may up-convert data received from the processor 4311 into a transmission / reception band to transmit a signal.
  • the processor 4311 may be connected to the RF unit 4313 to implement a physical layer and / or a MAC layer according to the IEEE 802.11 system.
  • the processor 4311 may be configured to perform an operation according to various embodiments of the present disclosure according to the above-described drawings and descriptions.
  • a module implementing the operation of the STA 4310 according to various embodiments of the present invention described above may be stored in the memory 4312 and executed by the processor 4311.
  • the memory 4312 is connected to the processor 4311 and stores various information for driving the processor 4311.
  • the memory 4312 may be included in the processor 4311 or may be installed outside the processor 4311 to be connected to the processor 4311 by a known means.
  • the STA apparatus 4310 may include a single antenna or multiple antennas.
  • the specific configuration of the STA apparatus 4310 of FIG. 43 may be implemented so that the above-described matters described in various embodiments of the present invention may be independently applied or two or more embodiments may be simultaneously applied.
  • each component or feature is to be considered optional unless stated otherwise.
  • Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention.
  • the order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.
  • Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof.
  • an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.
  • ASICs application specific integrated circuits
  • DSPs digital signal processors
  • DSPDs digital signal processing devices
  • PLDs programmable logic devices
  • FPGAs field programmable gate arrays
  • processors controllers, microcontrollers, microprocessors, and the like.
  • an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above.
  • the software code may be stored in memory and driven by the processor.
  • the memory may be located inside or outside the processor, and may exchange data with the processor by various known means.
  • the frame transmission scheme in the wireless communication system of the present invention has been described with reference to the example applied to the IEEE 802.11 system, but it is possible to apply to various wireless communication systems in addition to the IEEE 802.11 system.

Abstract

Conformément à un mode de réalisation, la présente invention concerne un procédé pour une transmission multiutilisateur de liaison montante par une station (STA) dans un système de réseau local sans fil (WLAN), lequel procédé comprend les étapes consistant : à recevoir une unité de données de protocole de couche physique (PPDU) multiutilisateur (MU) de liaison descendante (DL), la PPDU MU DL comprenant une trame de déclenchement comprenant des informations de déclenchement pour une transmission MU de liaison montante (UL); et à transmettre une PPDU MU UL sur la base des informations de déclenchement, la trame de déclenchement correspondant à une trame de déclenchement de monodiffusion comprise et transmise dans une A-MPDU pour la STA ou à une trame de déclenchement de diffusion transmise par l'intermédiaire d'un sous-canal d'un accès multiple par répartition orthogonale de la fréquence (OFDMA) DL; la trame de déclenchement de monodiffusion ou la trame de déclenchement de diffusion étant configurée dans un format de trame unifié et comprenant un champ d'informations commun et un champ d'informations d'utilisateur en commun; et le champ d'informations d'utilisateur pouvant comprendre des informations d'attribution d'unité de ressource indiquant une unité de ressource attribuée à la STA.
PCT/KR2016/008975 2015-08-19 2016-08-16 Procédé pour transmettre une trame de déclenchement dans un système de communication sans fil, et dispositif associé WO2017030342A1 (fr)

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US20180242293A1 (en) * 2015-02-27 2018-08-23 Intel IP Corporation Joint encoding of wireless communication allocation information
US10602501B2 (en) * 2015-02-27 2020-03-24 Intel IP Corporation Joint encoding of wireless communication allocation information
US10624085B2 (en) 2015-04-30 2020-04-14 Huawei Technologies Co., Ltd. WLAN system resource indication method and apparatus
US11818690B2 (en) 2015-04-30 2023-11-14 Huawei Technologies Co., Ltd. WLAN system resource indication method and apparatus
US11178659B2 (en) 2015-04-30 2021-11-16 Huawei Technologies Co., Ltd. WLAN system resource indication method and apparatus
WO2018194723A1 (fr) * 2017-04-17 2018-10-25 Intel Corporation Trames de déclenchement améliorées pour communications sans fil
WO2018231719A1 (fr) * 2017-06-12 2018-12-20 Intel Corporation Type de trame de déclenchement améliorée pour une communication sans fil
US11641237B2 (en) 2018-03-26 2023-05-02 Lg Electronics Inc. Method and apparatus for transmitting PPDU on basis of S-TDMA in wireless LAN system
WO2019190150A1 (fr) * 2018-03-26 2019-10-03 엘지전자 주식회사 Procédé et appareil de transmission d'unité ppdu sur la base d'un accès s-tdma dans un système de réseau lan sans fil
WO2019190151A1 (fr) * 2018-03-26 2019-10-03 엘지전자 주식회사 Procédé et appareil de transmission d'une ppdu sur la base d'un s-tdma dans un système lan sans fil
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WO2019194516A1 (fr) * 2018-04-06 2019-10-10 엘지전자 주식회사 Procédé et dispositif de transmission de ppdu sur la base d'un fdr dans un système lan sans fil
US11581997B2 (en) 2018-04-06 2023-02-14 Lg Electronics Inc. Method and device for transmitting PPDU on basis of FDR in wireless LAN system
CN114128158A (zh) * 2019-07-30 2022-03-01 松下电器（美国）知识产权公司 基站、发送方法及接收方法
EP4007407A4 (fr) * 2019-07-30 2022-08-17 Panasonic Intellectual Property Corporation of America Station de base, procédé de transmission et procédé de réception
CN114303335B (zh) * 2019-09-13 2024-04-09 松下电器（美国）知识产权公司 用于混合自动重复请求操作的通信装置和通信方法
CN114303335A (zh) * 2019-09-13 2022-04-08 松下电器（美国）知识产权公司 用于混合自动重复请求操作的通信装置和通信方法
CN114424493A (zh) * 2019-09-30 2022-04-29 夏普株式会社 终端装置、基站装置以及通信方法
CN114424493B (zh) * 2019-09-30 2024-03-29 夏普株式会社 终端装置、基站装置以及通信方法
CN113692049A (zh) * 2020-05-06 2021-11-23 联发科技股份有限公司 无线通信终端及无线通信方法
CN116017729A (zh) * 2020-05-28 2023-04-25 华为技术有限公司 通信方法及装置
US11832263B2 (en) 2020-05-28 2023-11-28 Huawei Technologies Co., Ltd. Communication method and apparatus
EP4149192A4 (fr) * 2020-06-05 2023-11-01 Huawei Technologies Co., Ltd. Procédé d'envoi de trame de déclenchement, procédé de réception de trame de déclenchement et appareil de communication
WO2022108327A1 (fr) * 2020-11-18 2022-05-27 엘지전자 주식회사 Trame de déclenchement améliorée
CN117014274A (zh) * 2020-12-09 2023-11-07 华为技术有限公司 定义触发帧中忽略比特的比特源及释放冗余波束成形比特

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