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WO2016003037A1 - Procédé et dispositif pour transmettre des données multiutilisateur de liaison montante dans un système de communication sans fil - Google Patents

Procédé et dispositif pour transmettre des données multiutilisateur de liaison montante dans un système de communication sans fil Download PDF

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Publication number
WO2016003037A1
WO2016003037A1 PCT/KR2015/000865 KR2015000865W WO2016003037A1 WO 2016003037 A1 WO2016003037 A1 WO 2016003037A1 KR 2015000865 W KR2015000865 W KR 2015000865W WO 2016003037 A1 WO2016003037 A1 WO 2016003037A1
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Prior art keywords
frame
sta
field
ack
transmission
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PCT/KR2015/000865
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English (en)
Korean (ko)
Inventor
천진영
류기선
이욱봉
최진수
임동국
조한규
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엘지전자(주)
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Publication of WO2016003037A1 publication Critical patent/WO2016003037A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile

Definitions

  • the present invention relates to a wireless communication system, and more particularly, to a method and apparatus for supporting uplink data transmission of a multi-user.
  • Wi-Fi is a Wireless Local Area Network (WLAN) technology that allows devices to connect to the Internet in the 2.4 GHz, 5 GHz, or 6 GHz frequency bands.
  • WLAN Wireless Local Area Network
  • WLAN is based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard.
  • IEEE Institute of Electrical and Electronic Engineers
  • the WNG SC Wireless Next Generation Standing Committee
  • IEEE 802.11 is an ad hoc committee that worries about the next generation wireless local area network (WLAN) over the medium to long term.
  • IEEE 802.11n aims to increase the speed and reliability of the network and to extend the operating distance of the wireless network. More specifically, IEEE 802.11n supports high throughput (HT), which provides data rates of up to 600 Mbps. In addition, to minimize transmission errors and optimize data rates, both the transmitter and receiver It is based on Multiple Inputs and Multiple Outputs (MIMO) using multiple antennas.
  • HT high throughput
  • MIMO Multiple Inputs and Multiple Outputs
  • IEEE 802.11ac supports data rates of over 1 Gbps over 80 MHz bandwidth transmissions and / or higher bandwidth transmissions (e.g., 160 MHz) and operates primarily in the 5 GHz band.
  • IEEE 802.11ax which is mainly discussed in the next generation WLAN study group called IEEE 802.11ax or High Efficiency (HEW) WLAN, is as follows: 1) 802.11 PHY (physical) layer in the band of 2.4GHz and 5GHz and MAC (2) improvement of spectrum efficiency and area throughput; (3) environment where interference sources exist; a dense heterogeneous network environment; and high user load And improving performance in real indoor and outdoor environments such as the environment.
  • IEEE 802.11ax The scenarios that are mainly considered in IEEE 802.11ax are dense environments of AP (access point) and STA (station), and IEEE 802.11ax discusses improvement of spectrum efficiency and area throughput in this situation . Especially, it is interested not only in indoor environment but also actual performance improvement in outdoor environment which is not considered much in existing WLAN.
  • IEEE 802.11ax is very interested in scenarios such as wireless office, smart home, stadium, hotspot, building / apartment, A discussion on improving system performance in dense environments with STA is underway.
  • IEEE 802.11ax will not improve the performance of a single link in a basic service set (BSS), but will improve system performance in an overlapping basic service set (OBSS) environment, improve outdoor environment performance, and reduce cellular offloading Discussions are expected to be active.
  • the directionality of IEEE 802.11ax means that the next generation WLAN will have a technology range similar to that of mobile communication. Considering the recent discussion of mobile communication and WLAN technology in the small cell and D2D (direct-to-direct) communication areas, it is expected that the technology and business of the next generation WLAN and mobile communication based on IEEE 802.11ax Fusion is expected to become more active.
  • An object of the present invention is to propose an uplink multi-user transmission method in a wireless communication system.
  • a method for multi-user uplink data transmission in a wireless communication system comprising the steps of: transmitting a frequency band or a spatial stream allocated from an access point (AP) Transmitting an uplink multi-user (UL MU) data frame to the AP through the AP and receiving an acknowledgment (ACK) frame for the UL MU data frame from the AP; ,
  • the ACK frame includes ACK information for a plurality of STAs that have performed UL MU transmission, and the ACK frame may include identification information for identifying that the ACK frame is an ACK frame for UL MU transmission.
  • an STA (Station) apparatus for multi-user uplink data transmission in a wireless communication system
  • the apparatus comprising a Radio Frequency (RF) unit and a processor for transmitting /
  • the processor transmits an uplink multi-user (UL MU) data frame to the AP through a frequency band or a spatial stream allocated from an access point (AP) MU data frame, the ACK frame including ACK information for a plurality of STAs that have performed the UL MU transmission, wherein the ACK frame is configured to transmit the UL MU transmission And an identification information for identifying the ACK frame to be transmitted.
  • UL MU uplink multi-user
  • AP access point
  • a method for multi-user uplink data transmission in a wireless communication system comprising the steps of: transmitting an access point (AP) Receiving an uplink multi-user (UL MU) data frame through a spatial stream, and receiving, by the AP, an ACK (Acknowledge) frame for the UL MU data frame from the STA
  • the ACK frame includes ACK information for a plurality of STAs that have performed UL MU transmission and the ACK frame may include identification information for identifying that the ACK frame is an ACK frame for the UL MU transmission have.
  • an access point (AP) apparatus for multi-user uplink data transmission in a wireless communication system, the apparatus comprising: a radio frequency (RF) unit for transmitting / Wherein the processor receives an uplink multi-user (UL MU) data frame from a STA through a frequency band or a spatial stream allocated to the STA, Wherein the ACK frame is configured to receive an ACK frame for the UL MU data frame from the STA, wherein the ACK frame includes ACK information for a plurality of STAs that have performed UL MU transmission, And identification information for identifying the ACK frame for the UL MU transmission.
  • RF radio frequency
  • BSS basic service set
  • PPDU physical protocol data unit
  • the ACK frame may comprise a Frame Control field, a Duration field, a Receiving Address (RA) field, and a Frame Check Sequence.
  • RA Receiving Address
  • the RA field may include a reduced identifier of one or more STAs to which an ACK is to be transmitted among a plurality of STAs that have performed the UL MU transmission.
  • the reduced identifier of the STA may be part of the STA's Media Access Control (MAC) address or an Association Identifier (AID).
  • MAC Media Access Control
  • AID Association Identifier
  • the RA field may include a representative identifier and a bit indicating ACK or NACK (non-ACK) for each of a plurality of STAs that have performed the UL MU transmission.
  • the representative identifier is an identifier of a first STA among a plurality of STAs that have performed the UL MU transmission, a group identifier of the UL MU transmission, a broadcasting identifier, and a BSS (basic service set) identifier to which the AP belongs It can be one.
  • the ACK frame includes a Frame Control field, a Duration / ID field, a Receiving Address (RA) field, a TA (Transmitting Address) field, a BA control field, a BA information field, and a frame check sequence.
  • RA Receiving Address
  • TA Transmitting Address
  • the BA control field may include information for identifying that the ACK frame is an ACK frame for the UL MU transmission.
  • the BA control field may include information on the number of traffic identifiers (TIDs) of a plurality of STAs that have performed the UL MU transmission.
  • TIDs traffic identifiers
  • the BA information field is repeatedly configured according to a traffic identifier (TID), and the BA information field may include an STA identifier and the TID.
  • TID traffic identifier
  • uplink multi-user transmission can be performed through different spatial streams or frequency resources in a wireless communication system.
  • a response signal (Acknowledgment) for uplink multi-user data can be smoothly transmitted in a wireless communication system.
  • FIG. 1 is a diagram showing 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 can be applied.
  • Figure 3 illustrates a non-HT format PPDU and an HT format PPDU of a wireless communication system to which the present invention may be applied.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention may be applied.
  • FIG. 5 is a diagram illustrating a constellation for identifying a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 7 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. 8 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • FIG. 9 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention may be applied.
  • FIG. 10 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention may be applied.
  • FIG. 11 is a conceptual diagram illustrating a channel sounding method in a wireless communication system to which the present invention can be applied.
  • FIG. 12 is a diagram illustrating a VHT NDPA frame in a wireless communication system to which the present invention can be applied.
  • FIG. 13 is a diagram illustrating an NDP PPDU in a wireless communication system to which the present invention can be applied.
  • FIG. 14 is a diagram illustrating a VHT compressed beamforming frame format in a wireless communication system to which the present invention may be applied.
  • 15 is a diagram illustrating a Beamforming Report Poll frame format in a wireless communication system to which the present invention can be applied.
  • 16 is a diagram illustrating a Group ID Management frame in a wireless communication system to which the present invention can be applied.
  • 17 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 18 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • FIG. 19 is a diagram illustrating a Block Ack Request frame in a wireless communication system to which the present invention can be applied.
  • FIG. 20 is a diagram illustrating a BAR information field of a Block Ack Request frame in a wireless communication system to which the present invention can be applied.
  • FIG. 21 is a diagram illustrating a block ACK (Block Ack) frame in a wireless communication system to which the present invention can be applied.
  • FIG. 22 is a diagram illustrating a BA information field of a block ACK (Block Ack) frame in a wireless communication system to which the present invention can be applied.
  • FIG. 23 is a diagram illustrating an ACK frame in a wireless communication system to which the present invention can be applied.
  • 24 to 28 are diagrams illustrating an HE (High Efficiency) format PPDU according to an embodiment of the present invention.
  • FIG. 30 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.
  • 31 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.
  • 32 to 35 are diagrams illustrating an ACK frame according to an embodiment of the present invention.
  • 36 is a diagram illustrating an ACK frame transmission method according to an embodiment of the present invention.
  • FIG. 37 is a block diagram illustrating a wireless device in accordance with 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- single carrier frequency division multiple access
  • CDMA can be implemented with radio technology such as universal terrestrial radio access (UTRA) or CDMA2000.
  • TDMA can be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE).
  • GSM global system for mobile communications
  • GPRS general packet radio service
  • EDGE enhanced data rates for GSM evolution
  • OFDMA can be implemented with wireless technologies such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and evolved UTRA (E-UTRA).
  • UTRA is part of the universal mobile telecommunications system (UMTS).
  • 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is part of E-UMTS (evolved UMTS) using E-UTRA, adopting OFDMA in downlink and SC-FDMA in uplink.
  • LTE-A (advanced) is the 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, the steps or portions of the embodiments of the present invention that are not described in order to clearly illustrate the technical idea of the present invention can be supported by the documents. In addition, all terms disclosed in this document may be described by the standard document.
  • FIG. 1 is a diagram showing an example of an IEEE 802.11 system to which the present invention can be applied.
  • the IEEE 802.11 architecture may be composed of a plurality of components, and a wireless communication system supporting station (STA: Station) mobility transparent to an upper layer by their interaction may be provided .
  • STA wireless communication system supporting station
  • a Basic Service Set (BSS) may correspond to a basic configuration block in an IEEE 802.11 system.
  • BSS 1 to BSS 3 three BSSs (BSS 1 to BSS 3) exist 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 included in BSS 2 And STA 5 and STA 6 are included in BSS 3).
  • an ellipse representing a BSS may be understood as indicating a coverage area in which STAs included in the corresponding BSS maintain communication. This area can be referred to as a basic service area (BSA). If the STA moves out of the BSA, it will not be able to communicate directly with other STAs in the BSA.
  • BSA basic service area
  • IBSS independent BSS
  • an IBSS may have a minimal form consisting of only two STAs.
  • BSS 3 of FIG. 1, which is the simplest form and the other components are omitted, may be 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 STA's membership in the BSS can be changed dynamically, such as by turning the STA on or off, by the STA entering or leaving the BSS region, and so on.
  • the STA can join the BSS using the synchronization process.
  • the STA In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association can be set dynamically and can 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 the physical (PHY) performance. In some cases, these distances may be sufficient, but in some cases communication between STAs at greater distances may be required.
  • a distribution system (DS) can be configured to support extended coverage.
  • DS means a structure in which BSSs are interconnected. Specifically, instead of the BSSs existing independently as shown in FIG. 1, there may be a BSS 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 a wireless medium (WM) and a distribution system medium (DSM).
  • WM wireless medium
  • DSM distribution system medium
  • Each logical medium is used for different purposes and is used by different components.
  • these media are not limited to the same or different.
  • flexibility of the structure of the IEEE 802.11 system (DS structure or other network structure) can be described in that a plurality of media are logically different. That is, the IEEE 802.11 system structure can be variously implemented, and the system structure can be specified independently according to the physical characteristics of each implementation.
  • the DS may support the mobile device by providing seamless integration of a plurality of BSSs and by providing the logical services necessary to address the destination.
  • An AP refers to an entity that has access to the DS through WM and has STA functionality for the associated STAs. Data movement between the BSS and the DS can be performed through the AP.
  • STA 2 and STA 3 shown in FIG. 1 have a function of the STA and provide a function of allowing the associated STAs (STA 1 and STA 4) to access the DS.
  • all APs are basically STAs, all APs are addressable objects. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same.
  • Data transmitted from one of the STAs associated with the AP to the STA address of the AP is always received at the uncontrolled port and can be processed by the IEEE 802.1X port access entity. Also, when the controlled port is authenticated, the transmitted data (or frame) may be forwarded to the DS.
  • a wireless network with arbitrary size and complexity may be comprised of DS and BSSs.
  • this type of network is referred to as an extended service set (ESS) network.
  • An ESS may correspond to a set of BSSs connected to one DS. However, ESS does not include DS.
  • the ESS network is characterized by its appearance as an IBSS network in a logical link control (LLC) layer. STAs included in the ESS can communicate with each other, and moving STAs can move from one BSS to another (within the same ESS) transparently to the LLC.
  • LLC logical link control
  • BSSs can be partially overlapped, which is a form commonly used to provide continuous coverage.
  • the BSSs may not be physically connected, and there is no limitation on the distance between the BSSs logically.
  • the BSSs can be physically located at the same location, which can be used to provide redundancy.
  • one (or more) IBSS or ESS networks may physically exist in the same space as one or more ESS networks. This may be the case when the ad-hoc network is in a location where the ESS network exists, or when IEEE 802.11 networks physically overlap by different organizations are configured, or when two or more different access and security policies are required at the same location And the ESS network type in the case of the ESS.
  • the STA is a device operating according to the IEEE 802.11 Medium Access Control (MAC) / PHY specification.
  • An STA can include an AP STA and a non-AP STA (non-AP STA), unless the STA's functionality is separately distinguished from the AP.
  • the STA can be understood as a non-AP STA.
  • STA 1, STA 4, STA 5 and STA 6 correspond to non-AP STA
  • STA 2 and STA 3 correspond to AP STA.
  • Non-AP STAs are devices that are typically handled by the user, such as laptop computers and mobile phones.
  • the non-AP STA includes a wireless device, a terminal, a user equipment (UE), a mobile station (MS), a mobile terminal, a wireless terminal ), A wireless transmit / receive unit (WTRU), a network interface device, a machine-type communication (MTC) device, or a machine-to-machine (M2M) device.
  • UE user equipment
  • MS mobile station
  • WTRU wireless transmit / receive unit
  • MTC machine-type communication
  • M2M machine-to-machine
  • the AP may be a base station (BS), a node-B, an evolved Node-B (eNB), a base transceiver system (BTS) , A femto base station (Femto BS), and the like.
  • BS base station
  • eNB evolved Node-B
  • BTS base transceiver system
  • Femto BS A femto base station
  • a DL refers to communication from an AP to a non-AP STA
  • an uplink refers to communication from a non-AP STA to an AP.
  • the transmitter is part of the AP and the receiver can be part of the non-AP STA.
  • the transmitter is part of the non-AP STA and the receiver can be part of the AP.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention can be applied.
  • the hierarchical architecture of the IEEE 802.11 system may include a MAC sublayer 210 and a PHY sublayer 220.
  • the PHY sublayer 220 may be divided into a Physical Layer Convergence Procedure (PLCP) entity and a PMD (Physical Medium Dependent) entity.
  • PLCP Physical Layer Convergence Procedure
  • PMD Physical Medium Dependent
  • the PLCP entity connects the MAC sublayer and the data frame
  • the PMD entity wirelessly transmits and receives data to and from two or more STAs.
  • Both the MAC sublayer 210 and the PHY sublayer 220 may include a Management Entity and each may include a MAC Sublayer Management Entity (MLME) 230 and a PHY Sublayer Management Entity (PLME) Sublayer Management Entity, 240). These management entities 230 and 240 provide the layer management service interface through the operation of the layer management function.
  • the MLME 230 may be connected to the PLME 240 to perform a management operation of the MAC sublayer 210 and the PLME 240 may be connected to the MLME 230 to manage the PHY sublayer 220 A management operation can be performed.
  • a Station Management Entity (SME) 250 may be present in each STA.
  • the SME 250 is a management entity independent of each layer and collects layer-based state information from the MLME 230 and the PLME 240 or sets values of specific parameters of each layer.
  • the SME 250 may perform these functions on behalf of general system management entities, and may implement a standard management protocol.
  • the MLME 230, the PLME 240, and the SME 250 may interact in various ways based on primitives.
  • the XX-GET.request primitive is used to request a value of a management information base attribute (MIB attribute), and if the status is 'SUCCESS', the XX-GET.confirm primitive uses the corresponding MIB attribute value Return, otherwise return an error indication in the status field.
  • the XX-SET.request primitive is used to request that the specified MIB attribute be set to the given value. If the MIB attribute implies a particular action, then this request requests execution of that particular action.
  • the XX-SET.confirm primitive has a status of 'SUCCESS', this means that the specified MIB attribute is set to the requested value. Otherwise, the status field indicates an error condition. If this MIB attribute implies a specific action, this primitive can confirm that the action has been performed.
  • the MAC sublayer 210 transmits a MAC header and a frame check sequence FCS to a MAC Service Data Unit (MSDU) or an MSDU fragment received from an upper layer (e.g., an LLC layer) : Frame Check Sequence) to generate one or more MAC Protocol Data Units (MPDUs).
  • MSDU MAC Service Data Unit
  • MPDU MAC Protocol Data Unit
  • the generated MPDU is delivered to the PHY sublayer 220.
  • A-MSDU aggregated MSDU
  • A-MSDU aggregated MSDU
  • the MSDU merging operation can be performed in the MAC upper layer.
  • the A-MSDU is delivered to the PHY sublayer 220 in a single MPDU (if it is not fragmented).
  • the PHY sublayer 220 adds a supplementary field including information required by a physical layer transceiver to a physical service data unit (PSDU) received from the MAC sublayer 210 to generate a physical protocol data unit (PPDU) Data Unit).
  • PSDU physical service data unit
  • PPDU physical protocol data unit
  • the PPDU is transmitted over a wireless medium.
  • the PSDU is received from the MAC sublayer 210 by the PHY sublayer 220 and the MPDU is transmitted by the MAC sublayer 210 to the PHY sublayer 220 so that the PSDU is substantially the same as the MPDU.
  • a plurality of MPDUs (where each MPDU can carry an A-MSDU) can be merged into a single A-MPDU.
  • the MPDU merging operation can be performed in the MAC lower layer.
  • the A-MPDU may be merged with various types of MPDUs (e.g., QoS data, ACK (Acknowledge), Block ACK (BlockAck), etc.).
  • the PHY sublayer 220 receives the A-MPDU from the MAC sublayer 210 as a single PSDU. That is, the PSDU is composed of a plurality of MPDUs.
  • the A-MPDU is transmitted over a wireless medium within a single PPDU.
  • PPDU Physical Protocol Data Unit
  • a physical protocol data unit means a data block generated in the physical layer.
  • PPDU physical protocol data unit
  • Figure 3 illustrates a non-HT format PPDU and an HT format PPDU of a wireless communication system to which the present invention may be applied.
  • Figure 3 (a) illustrates a non-HT format PPDU for supporting IEEE 802.11a / g systems.
  • a non-HT PPDU may also be referred to as a legacy PPDU.
  • the non-HT format PPDU includes L-STF (Legacy (or Non-HT) Short Training field), L-LTF (Legacy And a legacy format preamble consisting of an L-SIG (Legacy (or Non-HT) SIGNAL) field and a data field.
  • L-STF Legacy (or Non-HT) Short Training field
  • L-LTF Legacy And a legacy format preamble consisting of an L-SIG (Legacy (or Non-HT) SIGNAL) field
  • a data field a data field.
  • the L-STF may comprise a short training orthogonal frequency division multiplexing symbol (OFDM).
  • OFDM orthogonal frequency division multiplexing symbol
  • the L-STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization .
  • the L-LTF may comprise a long training orthogonal frequency division multiplexing symbol (OFDM symbol).
  • L-LTF can 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 may include information on a data rate and a data length.
  • FIG. 3 (b) illustrates an HT mixed format PPDU for supporting both the IEEE 802.11n system and the IEEE 802.11a / g system.
  • the HT mixed format PPDU includes a legacy format preamble, an HT-SIG (HT-Signal) field, an HT-STF (HT Short) field consisting of L-STF, L-LTF and L- A training field, and an HT format pre-amble composed of an HT Long Training field (HT-LTF) and a data field.
  • HT-SIG HTTP-Signal
  • HT-STF HTTP Short field consisting of L-STF, L-LTF and L- A training field
  • HT format pre-amble composed of an HT Long Training field (HT-LTF) and a data field.
  • the L-STF, L-LTF and L-SIG fields refer to the legacy fields for backward compatibility, so that the L-STF to L-SIG fields are the same as the non-HT format.
  • the L-STA can interpret the data field via the L-LTF, L-LTF and L-SIG fields even when receiving the HT mixed PPDU.
  • the L-LTF may further include information for channel estimation to be performed by the HT-STA to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.
  • the HT-STA uses the HT-SIG field following the legacy field to know that it is an HT-mixed format PPDU, and can decode the data field based on this.
  • the HT-LTF field may be used for channel estimation for demodulation of the data field. Since IEEE 802.11n supports SU-MIMO (Single-User Multi-Input and Multi-Output), HT-LTF fields can be composed of a plurality of HT-LTF fields 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 an extended HT-LTF (data HT-LTF) and a supplementary HT-LTF (data HT-LTF) used additionally for data channel estimation for the spatial stream and a full channel sounding, ≪ / RTI >
  • a plurality of HT-LTFs may be equal to or greater than the number of spatial streams to be transmitted.
  • the L-STF, L-LTF, and L-SIG fields are transmitted first to enable the HT-mixed format PPDU to also receive and acquire data from the L-STA.
  • the HT-SIG field is then transmitted for demodulation and decoding of data transmitted for the HT-STA.
  • the wireless signal transmission is performed through the wireless network.
  • the STA transmits the HT-STF field and the plurality of HT-LTFs and the data field thereafter in order to take into account the portion where power is varied by precoding in the STA receiving the precoding.
  • FIG. 3C illustrates an HT-GF format PPDU (HT-greenfield format PPDU) for supporting only the IEEE 802.11n system.
  • the HT-GF format PPDU includes an HT-GF-STF, an HT-LTF1, an HT-SIG field, a plurality of HT-LTF2, and a data field.
  • 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 demodulating and decoding the data field.
  • HT-LTF2 is used for channel estimation for demodulation of the data field.
  • the HT-STA uses SU-MIMO, it requires channel estimation for each data field transmitted in a plurality of spatial streams, so that the HT-LTF2 can be composed of pluralities.
  • the plurality of HT-LTF2 may be composed of a plurality of Data HT-LTFs and a plurality of extended HT-LTFs similar to the HT-LTF field of the HT mixed PPDU.
  • a data field is a payload, which includes a service field, a scrambled PSDU field, tail bits, padding bits, . ≪ / RTI >
  • the IEEE 802.11ac WLAN system supports transmission of a downlink MU-MIMO (Multi User Multiple Input Multiple Output) scheme in which a plurality of STAs concurrently access channels in order to utilize wireless channels efficiently.
  • MU-MIMO Multi User Multiple Input Multiple Output
  • an AP can simultaneously transmit a packet to one or more MIMO-paired STAs.
  • DL downlink multi-user transmission refers to a technique in which an AP transmits PPDUs to a plurality of non-AP STAs through the same time resource through one or more antennas.
  • the MU PPDU means 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 transmitted or a PSDU does not exist.
  • the size of the control information transmitted to the STA may be relatively larger than the size of the 802.11n control information.
  • the control information additionally required for MU-MIMO support information indicating the number of spatial streams received by each STA, modulation and coding related information of data transmitted to each STA, and the like .
  • the size of control information to be transmitted can be increased according to the number of receiving STAs.
  • a plurality of control information required for MU-MIMO transmission includes common control information common to all STAs and individual control information required for each STA individually And dedicated control information, which is transmitted to the mobile station.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention may be applied.
  • VHT format PPDU VHT format PPDU
  • the VHT format PPDU includes a legacy format preamble composed of L-STF, L-LTF, and L-SIG fields, a VHT-SIG-A (VHT- field, a VHT format preamble composed of VHT-SIG-B (VHT-Signal-B) fields, and a data field.
  • L-STF, L-LTF, and L-SIG refer to a legacy field for backward compatibility, so that from the L-STF to the L-SIG field is the same as the non-HT format.
  • the L-LTF may further include information for channel estimation to be performed in order to demodulate the L-SIG field and the VHT-SIG-A field.
  • L-STF, L-LTF, L-SIG field and VHT-SIG-A field can be repeatedly transmitted in units of 20 MHz channels. For example, when a PPDU is transmitted over four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG and VHT- .
  • the VHT-STA can recognize the VHT format PPDU using the VHT-SIG-A field following the legacy field, and can decode the data field based on the VHT-SIG-A field.
  • the L-STF, L-LTF, and L-SIG fields are transmitted first in order to enable the VHT format PPDU to receive and acquire data from the L-STA.
  • the VHT-SIG-A field is then transmitted for demodulation and decoding of data transmitted for the VHT-STA.
  • the VHT-SIG-A field is a field for transmission of control information common to the AP and the paired VHT STAs, which 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 a channel bandwidth (BW) to be used, whether space time block coding (STBC) is applied, group identification information for indicating a group of STAs grouped in the MU-MIMO Group ID, Group Identifier), information on the number of streams of the NSTS / Partial AID (Partial AID) and Transmit power save forbidden can do.
  • the Group ID is an identifier allocated to the STA group to support the MU-MIMO transmission, and may indicate whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.
  • Table 1 is a table illustrating the VHT-SIG-A1 field.
  • VHT SU For PPDU Set to '1' if STBC is used, otherwise set to '0'
  • the space-time stream is 4, 4, and the VHT SU PPDU
  • the upper 3 bits are set as follows. If the space-time stream is 1, '3' for a spatiotemporal stream, '4' for a spatiotemporal stream, '4' for a spatiotemporal stream, '2' for a spatiotemporal stream, 6, '6' for a space-time stream, '7' for a space-time stream, and the lower 9 bits indicate a partial AID (Partial AID).
  • TXOP_PS_NOT_ALLOWED One Set to '0' if the VHT AP permits the non-AP VHT STA to transition to the power save mode during TXOP (transmission opportunity). Otherwise, set to '1'. Non-AP VHT transmitted by the STA.
  • VHT PPDU is set to '1'. Reserved One
  • the VHT-SIG-A2 field includes information on whether or not to use a short guard interval (GI), forward error correction (FEC) information, information on an MCS (Modulation and Coding Scheme) Information on the type of channel coding for the user, information related to beamforming, redundancy bits for CRC (Cyclic Redundancy Checking), tail bits of convolutional decoder, and the like .
  • GI short guard interval
  • FEC forward error correction
  • MCS Modulation and Coding Scheme
  • Table 2 is a table illustrating the VHT-SIG-A2 field.
  • NSTS field of the user whose user position is'0' is set to '0'
  • NSTS field of the user position is' 0 ' 0 '
  • it is set to' 1 'as a spare field LDPC Extra OFDM Symbol
  • LDPC PPDU encoding procedure for SU PPDU
  • at least one LDPC user's PPDU encoding procedure for VHT MU PPDU
  • VHT MCS / MU Coding 4 In case of VHT SU PPDU: Indicates VHT-MCS index.
  • VHT MU PPDU case Instructs coding in order of user position (user position) '1' to '3' in order from upper bit. If the NSTS field of the user is not '1' Indicates the coding used. If BCC is '0', LDPC is set to '1'. Angle If the NSTS field of the user is '0', it is set to '1' as a spare field. Beamformed One VHT SU For PPDU: Set to '1' if beamforming steering matrix is applied to SU transmission. Otherwise set to '0'. VHT MU PPDU case: set as '1' for spare field. Reserved One CRC 8 Contains a CRC to detect errors in the PPDU at the receiver Tail 6 Used for trellis termination of convolutional decoder Set to '0'
  • 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, VHT-LTF can be set to the number of spatial streams to which PPDUs are 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 necessary for a plurality of VHT-STAs paired with MU-MIMO to receive PPDUs and acquire data. Therefore, the VHT-STA can be designed to decode the VHT-SIG-B field only if the PPDU currently received in the VHT-SIG-A field indicates the MU-MIMO transmission . On the other hand, if the common control information indicates that the PPDU currently received 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 contains information on the 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.
  • the L-SIG field may be used to effectively use the PPDU format.
  • a length field and a rate field which are included and transmitted in the L-SIG field so that a PPDU of the same size is transmitted to all STAs, can be used to provide necessary information.
  • MPDU MAC Protocol Data Unit
  • A-MPDU Aggregate MAC Protocol Data Unit
  • the data field is a payload, which may include a SERVICE field, a scrambled PSDU (scrambled PSDU), tail bits, and padding bits.
  • the STA Since the various PPDU formats are mixed and used, the STA must be able to distinguish the format of the received PPDU.
  • the meaning of distinguishing the PPDU may have various meanings.
  • the meaning of distinguishing PPDUs may include the meaning of determining whether a received PPDU is a PPDU that can be decoded (or interpreted) by the STA.
  • the meaning of distinguishing PPDUs may mean that the received PPDUs are judged whether they are PPDUs that can be supported by the STA.
  • the meaning of distinguishing PPDUs can also be interpreted to mean that information transmitted through the received PPDUs distinguishes what information is.
  • FIG. 5 is a diagram illustrating a constellation for identifying a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 5A illustrates a constellation of an L-SIG field included in a non-HT format PPDU
  • FIG. 5B illustrates an example of phase rotation for detecting an HT mixed format PPDU
  • FIG. 5 (c) illustrates phase rotation for VHT format PPDU detection.
  • the constellation of OFDM symbols transmitted after the L-SIG field and the L- Is used. That is, the STA can distinguish the PPDU format based on the phase of the constellation of the OFDM symbol transmitted after the L-SIG field and / or the L-SIG field of the received PPDU.
  • BPSK Binary Phase Shift Keying
  • the STA determines whether it is an L-SIG field. That is, the STA attempts decoding based on the same structure as the example of FIG. 5 (a). If the STA fails to decode the PPDU, it can determine that the PPDU is an HT-GF format PPDU.
  • the constellation phases of OFDM symbols transmitted after the L-SIG field may be used. That is, the modulation method of the OFDM symbol transmitted after the L-SIG field may be different, and the STA can distinguish the PPDU format based on the modulation method for the field after the L-SIG field of the received PPDU.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the HT mixed format PPDU may be used.
  • the phases of the OFDM symbol # 1 and the OFDM symbol # 2 corresponding to the HT-SIG field transmitted after the L-SIG field in the HT mixed format PPDU are all rotated by 90 degrees counterclockwise. That is, QBPSK (Quadrature Binary Phase Shift Keying) is used as the modulation method for OFDM symbol # 1 and OFDM symbol # 2.
  • QBPSK Quadrature Binary Phase Shift Keying
  • the QBPSK constellation may be rotated by 90 degrees in the counterclockwise direction based on the BPSK constellation.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the HT-SIG field transmitted after the L-SIG field of the received PPDU based on the constellation shown in FIG. 5B. If the STA decodes successfully, it determines that the corresponding PPDU is an HT format PPDU.
  • the constellation phases of OFDM symbols transmitted after the L-SIG field can be used.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the VHT format PPDU may be used.
  • phase of the OFDM symbol # 1 corresponding to the VHT-SIG-A field after the L-SIG field in the VHT format PPDU is not rotated, but the phase of the OFDM symbol # 2 is rotated by 90 degrees counterclockwise . That is, BPSK is used as a modulation method for OFDM symbol # 1, and QBPSK is used as a modulation method for OFDM symbol # 2.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the VHT-SIG field transmitted after the L-SIG field of the received PPDU based on the constellation as shown in FIG. 5C. If the STA successfully decodes the PPDU, it can determine that the corresponding PPDU is a VHT format PPDU.
  • the STA can determine that the corresponding PPDU is a non-HT format PPDU.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • a MAC frame (i.e., MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • the MAC Header includes a Frame Control field, a Duration / ID field, an Address 1 field, an Address 2 field, an Address 3 field, a Sequence control field, Control field, an Address 4 field, a QoS control field, and an HT Control field.
  • the Frame Control field contains information on the corresponding MAC frame characteristic. A more 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 indicates an association identifier (AID) of the STA that transmitted the frame. . ≪ / RTI > 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. Also, when the frame is an MPDU included in the aggregate-MPDU (A-MPDU) format, the Duration / ID field included in the MAC header may be set to have the same value.
  • A-MPDU aggregate-MPDU
  • the Address 1 field to the Address 4 field includes a BSSID, a source address (SA), a destination address (DA), a transmission address (TA) indicating a transmission STA address, a reception address RA: Receiving Address).
  • the address field implemented in the TA field may be set to a bandwidth signaling TA value.
  • 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 is set to a specific value (for example, '1') .
  • the Sequence Control field is set to include a sequence number and a fragment number.
  • the sequence number may indicate a sequence number assigned to the corresponding MAC frame.
  • the fragment number can indicate the number of each fragment of the corresponding MAC frame.
  • the QoS Control field contains information related to the QoS.
  • the QoS Control field may be included when indicating a QoS data frame in a subtype subfield.
  • the HT Control field contains control information associated with the HT and / or VHT transceiving scheme.
  • the HT Control field is included in the Control Wrapper frame. Also, a QoS data frame and a management frame having an order subfield value of 1 exist.
  • the frame body is defined as a MAC payload, and data to be transmitted is located in an upper layer and has a variable size.
  • the maximum MPDU size may be 11454 octets and 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 exist in all frames. Other fields may exist only in a specific frame type.
  • FIG. 7 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 sub-field, a Type sub-field, a Subtype sub-field, a To DS sub-field, a From DS sub-field, A retry subfield, a power management subfield, a more data subfield, a protected frame subfield, and an order subfield.
  • the Protocol Version subfield may indicate the version of the WLAN protocol applied to the MAC frame.
  • the Type subfield and Subtype subfield may be set to indicate information identifying the function of the corresponding MAC frame.
  • the type of the MAC frame may include three types of frames: a management frame, a control frame, and a data frame.
  • each frame type can be divided into sub types again.
  • control frames may include a request to send (RTS) frame, a clear-to-send (CTS) frame, an acknowledgment (ACK) frame, a PS-Poll frame, a contention free A block Acknowledgment request (BAR) frame, a block Acknowledgment (BA) frame, a control wrapper (Control + HTcontrol) frame, a VHT null data packet announcement (NDPA : Null Data Packet Announcement, and a Beamforming Report Poll frame.
  • RTS request to send
  • CTS clear-to-send
  • ACK acknowledgment
  • PS-Poll a contention free A block Acknowledgment request
  • BAR block Acknowledgment request
  • BA block Acknowledgment
  • Control + HTcontrol Control + HTcontrol
  • VHT null data packet announcement NDPA : Null Data Packet Announcement
  • Beamforming Report Poll frame a Beamforming Report Poll frame.
  • the management frames include a beacon frame, an announcement traffic indication message (ATIM) frame, a disassociation frame, an association request / response frame, a reassociation request / A Probe Request / Response frame, an Authentication frame, an Deauthentication frame, an Action frame, an Action No ACK frame, a Timing Advertisement frame, Frame.
  • ATIM announcement traffic indication message
  • the To DS subfield and the From DS subfield may include information necessary for interpreting the Address 1 field to 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', respectively, in the order that the corresponding frame is a QoS management frame (QMF). If the frame is not QMF Can be set to '0' and '0', respectively.
  • QMF QoS management frame
  • the More Fragments subfield may indicate whether there is a fragment to be transmitted following the corresponding MAC frame. It may be set to '1' if another fragment of the current MSDU or MMPDU exists, otherwise it may be set to '0'.
  • the Retry sub-field may indicate whether the corresponding MAC frame corresponds to the retransmission of the previous MAC frame. Is set to '1' in case of retransmission of the previous MAC frame, and may be set to '0' otherwise.
  • the Power Management subfield may indicate the power management mode of the STA. If the value of the Power Management subfield is '1', the STA can be instructed to switch to the power save mode.
  • the More Data subfield may additionally indicate whether or not a MAC frame to be transmitted exists. If there is an additional MAC frame to be transmitted, it is set to '1'; otherwise, it can be set to '0'.
  • the Protected Frame subfield may indicate whether or not the Frame Body field is encrypted. It may be set to '1' if the Frame Body field contains information processed by a cryptographic encapsulation algorithm, otherwise it may be set to '0'.
  • each of the above-described fields may follow the definition of the IEEE 802.11 system.
  • Each of the fields described above corresponds to an example of fields that can be included in the MAC frame, but is not limited thereto. That is, each of the fields described above may be replaced with another field, or an additional field may be further included, and all fields may not necessarily be included.
  • IEEE 802.11 communication is fundamentally different from a wired channel environment because it is performed in a shared wireless medium.
  • CSMA / CD carrier sense multiple access / collision detection
  • a CSMA / CA Carrier Sense Multiple Access with Collision Avoidance
  • the CAMA / CA mechanism is also called Distributed Coordination Function (DCF) of the IEEE 802.11 MAC. It basically adopts a listen before talk access mechanism.
  • DCF Distributed Coordination Function
  • the AP and / or the STA may be configured to sense a wireless channel or medium during a predetermined time interval (e.g., DIFS (DCF Inter-Frame Space)) sensing CCA (Clear Channel Assessment). As a result of sensing, if it is determined that the medium is in the idle status, the frame transmission is started through the medium.
  • DIFS DCF Inter-Frame Space
  • the corresponding AP and / or STA does not start its own transmission, and additionally to the DIFS on the assumption that several STAs are already waiting to use the medium It may attempt to transmit a frame after waiting for a delay time for access (e.g., a random backoff period).
  • a delay time for access e.g., a random backoff period
  • HCF Hybrid Coordination Function
  • HCF is based on the DCF and Point Coordination Function (PCF).
  • the PCF is a polling-based, synchronous access scheme that refers to periodically polling all receiving APs and / or STAs to receive data frames.
  • HCF has EDCA (Enhanced Distributed Channel Access) and HCCA (HCF Controlled Channel Access).
  • EDCA Enhanced Distributed Channel Access
  • HCCA HF Controlled Channel Access
  • the EDCA is a contention-based access method for a provider to provide data frames to a large number of users, and the HCCA uses a contention-based channel access method using a polling mechanism.
  • the HCF includes a medium access mechanism for improving the QoS (Quality of Service) of the WLAN, and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).
  • QoS Quality of Service
  • FIG. 8 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • each STA may select a random backoff count and wait for a slot time corresponding thereto, and then try transmission.
  • An arbitrary backoff count has a pseudo-random integer value and can be determined as one of a value ranging from zero to a uniform distribution in a contention window (CW) range.
  • CW is the value of the contention window parameter.
  • the CW parameter is given an initial value of CW min , but can take a value of twice as long as the transmission fails (for example, if the ACK for the transmitted frame is not received).
  • CW parameter value becomes CW max
  • data transmission can be attempted while maintaining the CW max value until the data transmission is successful. If the data transmission is successful, the CW parameter value is reset to the CW min value.
  • the STA When an arbitrary backoff process is initiated, the STA counts down the backoff slot according to the determined backoff count value, and continues to monitor the media while counting down. When the medium is occupied, the countdown is stopped and waited. When the medium is idle, the countdown is resumed.
  • the STA 3 when a packet to be transmitted to the MAC of the STA 3 arrives, the STA 3 can confirm that the medium is idle by DIFS and transmit the frame immediately.
  • each STA monitors and wait for the medium to be in a busy state.
  • data to be transmitted may also occur in each of STA 1, STA 2 and STA 5, and each STA waits for DIFS when the medium is monitored in idle state. Then, according to a random backoff count value selected by each STA, Count down.
  • STA 2 selects the smallest backoff count value
  • STA 1 selects the largest backoff count value. That is, a case where the remaining backoff time of the STA 5 is shorter than the remaining backoff time of the STA 1 at the time when the STA 2 finishes the backoff count and starts the frame transmission is illustrated.
  • STA 1 and STA 5 stop and wait for the countdown while STA 2 occupies the medium. If the media occupation of STA 2 is terminated and the medium becomes idle again, STA 1 and STA 5 wait for DIFS and then resume the stopped back-off count. That is, the frame transmission can be started after counting down the remaining backoff slots by the remaining backoff time. Since the remaining backoff time of STA 5 is shorter than STA 1, frame transmission of STA 5 starts.
  • data to be transmitted may also occur in STA 4 while STA 2 occupies the medium.
  • STA 4 when the medium is idle, the apparatus waits for DIFS and then counts down the backoff slot according to an arbitrary backoff count value selected by the STA 4.
  • the remaining backoff time of STA 5 coincides with the arbitrary backoff count value of STA 4, in which case a collision may occur between STA 4 and STA 5. If a collision occurs, neither STA 4 nor STA 5 will receive an ACK, and data transmission will fail. In this case, STA 4 and STA 5 double the CW value, then select an arbitrary backoff count value and perform a countdown of the backoff slot.
  • the STA 1 waits while the medium is occupied due to the transmission of the STA 4 and the STA 5, waits for the DIFS when the medium is idle, and can start frame transmission after the remaining backoff time.
  • the CSMA / CA mechanism also includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly senses the media.
  • Virtual carrier sensing is intended to compensate for problems that may arise from media access, such as hidden node problems.
  • the MAC of the WLAN system uses a network allocation vector (NAV).
  • the NAV is a value indicating to another AP and / or the STA that the AP and / or the STA that is currently using or authorized to use the medium has remaining time until the media becomes available. Therefore, the value set to NAV corresponds to the period in which the medium is scheduled to be used by the AP and / or the STA that transmits the frame.
  • the AP and / or the STA may perform a procedure of exchanging a request to send (RTS) frame and a clear to send (CTS) frame to indicate that the media is about to be accessed.
  • the RTS frame and the CTS frame contain information indicating a time interval in which the wireless medium necessary for ACK frames to be transmitted and received is reserved for an actual data frame transmission and an acknowledgment (ACK) is supported.
  • Another STA that receives the RTS frame transmitted from the AP and / or the STA to which the frame is to be transmitted or the CTS frame transmitted from the STA to which the frame is to be transmitted, transmits the RTS frame to the STA through a time interval indicated by the information included in the RTS / It can be set not to access the medium. This can be implemented through setting the NAV during the time interval.
  • the time interval between frames is defined as an interframe space (IFS).
  • IFS interframe space
  • the STA can determine whether the channel is used during the IFS time interval through carrier sensing.
  • a plurality of IFSs are defined to provide a priority level for occupying wireless media in an 802.11 WLAN system.
  • FIG. 9 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention may be applied.
  • All timings can be determined by referring to the physical layer interface primitives, namely, the PHY-TXEND.confirm primitive, the PHYTXSTART.confirm primitive, the PHY-RXSTART.indication primitive, and the PHY-RXEND.indication primitive.
  • the frame interval according to IFS type is as follows.
  • the different IFSs are determined from the attributes specified by the physical layer regardless of the bit rate of the STA.
  • the IFS timing is defined as a time gap on the medium. IFS timing except AIFS is fixed for each physical layer.
  • the SIFS may include a PPDU containing a Block ACK (Block Ack) frame, an ACD frame, a CTS frame, a BlockAckReq frame or an immediate response to an A-MPDU, a second or subsequent MPDU of a fragmented burst, Lt; / RTI > is used for transmission of the STA's response to polling by the mobile station and has the highest priority.
  • SIFS may also be used for point coordinators of frames, regardless of the type of frame during the contention-free period (CFP) time. SIFS represents the time from the end of the last symbol of the previous frame or the signal extension (if present) to the start of the first symbol of the preamble of the next frame.
  • SIFS timing is achieved when transmission of consecutive frames begins at the TxSIFS slot boundary.
  • SIFS is the shortest of the IFSs between transmissions from different STAs.
  • the STA occupying the medium may be used when it is necessary to maintain the occupancy of the medium during the period in which the frame exchange sequence is performed.
  • PIFS is used to gain priority to access media.
  • PIFS can be used in the following cases:
  • TIM Traffic Indication Map
  • Hybrid Coordinator that initiates a CFP or Transmission Opportunity (TXOP)
  • An HC or non-AP QoS STA which is a polled TXOP holder for recovering from the absence of expected reception within a controlled access phase (CAP)
  • the HT AP During a PSMP sequence that transmits a power save multi-poll (PSMP) recovery frame, the HT AP
  • a STA using PIFS initiates transmission after a CS (carrier sense) mechanism to determine that the media is idle at the TxPIFS slot boundary, except when performing CCA on the secondary channel of the example listed above.
  • CS carrier sense
  • the DIFS may be used by the STA operating to transmit a data frame (MPDU) and a MAC Management Protocol Data Unit (MMPDU) under the DCF.
  • the STA using the DCF can transmit at the TxDIFS slot boundary if it is determined that the medium is idle through the CS (carrier sense) mechanism after the correctly received frame and backoff time has expired.
  • a correctly received frame means a frame in which the PHY-RXEND.indication primitive does not indicate an error, and the FCS indicates that the frame is error free.
  • the SIFS time ('aSIFSTime') and the slot time ('aSlotTime') can be determined for each physical layer.
  • the SIFS time has a fixed value, but the slot time can change dynamically according to the radio delay time (aAirPropagationTime).
  • Equation (3) Equation (3)
  • the default physical layer parameter is based on 'aMACProcessingDelay' having a value equal to or smaller than 1 ⁇ s.
  • the radio waves are spread at 300 m / s in free space.
  • 3 ⁇ s may be the upper limit of the BSS maximum one-way distance to 450 m (round trip ⁇ 900 m).
  • PIFS and DIFS are defined by the following equations (4) and (5), respectively.
  • Equations (1) to (5) illustrate general values, but the values may vary depending on the STA or the position of the STA.
  • SIFS SIFS
  • PIFS PIFS
  • DIFS DIFS
  • the respective MAC slot boundaries for SIFS, PIFS, and DIFS are defined as shown in Equations (6) to (8) below.
  • the SU-MIMO technique in which a beamformer allocates all antennas to one beamformee and communicates, increases channel capacity through diversity gain and stream multiplexing using time and space .
  • the SU-MIMO technique can contribute to the improvement of the physical layer performance by expanding the spatial freedom by increasing the number of antennas as compared with the case where the MIMO technique is not applied.
  • the MU-MIMO technique in which the beamformer allocates antennas to a plurality of beamformers increases the transmission rate per channel or increases the reliability of the channels through a link layer protocol for multiple accesses of a plurality of beamformers connected to the beamformer, Performance can be improved.
  • the feedback procedure for acquiring channel information can be largely supported by two methods.
  • One is a method using a control frame and the other is a method using a channel sounding procedure in which a data field is not included. Sounding refers to using a corresponding training field to measure a channel for purposes other than data demodulation of a PPDU that includes a preamble training field.
  • the beamformer may instruct the feedback of the channel state information through the HT control field included in the MAC header, or the beamformee may report the channel state information through the HT control field included in the MAC frame header.
  • the HT control field can be included in a control data frame, a management data frame, or a control data frame in which the Order subfield of the MAC header is set to 1.
  • FIG. 10 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention may be applied.
  • the HT Control field includes a VHT subfield, an HT Control Middle subfield, an AC Constraint subfield, and a Reverse Direction Grant (RDG) / Additional PPDU (More PPDU) Field.
  • RDG Reverse Direction Grant
  • More PPDU Additional PPDU
  • the VHT subfield indicates whether the HT Control field has the format of the HT Control field for the VHT or the HT Control field for the HT.
  • an HT control field for VHT is assumed.
  • the HT Control field for VHT can be referred to as the VHT Control field.
  • the HT Control Middle subfield may be implemented to have a different format according to the instructions of the VHT subfield. A more detailed description of the HT Control Middle subfield will be described later.
  • the AC Constraint subfield indicates whether the mapped AC (Access Category) of the reverse direction (RD) data frame is confined to a single AC.
  • the RDG / More PPDU subfield may be interpreted differently depending on whether the corresponding field is sent by an RD initiator or an RD responder.
  • the RDG / More PPDU field When transmitted by an RD initiator, the RDG / More PPDU field is set to '1' if RDG is present and set to '0' if RDG is not present. If it is transmitted by the RD Responder, it is set to '1' if the PPDU including the corresponding subfield is the last frame transmitted by the RD Responder and to '0' if another PPDU is transmitted.
  • the HT Control Middle subfield includes a Reserved bit, a Modulation and Coding Scheme (MRQ) feedback request subfield, a MRQ Sequence Identifier (MSI) / space time block coding (STBC) MCS Feedback Sequence Identifier (MFSI) / Group ID least significant bit (GID-L) Least Significant Bit (LSB) of sub-field, MCS feedback (MFB) ) Sub-field, a group ID most significant bit (GID-H) of a most significant bit (MSB), a coding type sub-field, a feedback transmission type (FB Tx Type) And a voluntary MFB (Unsolicited MFB) subfield.
  • MRQ Modulation and Coding Scheme
  • MSI Modulation and Coding Scheme
  • STBC space time block coding
  • GID-L Group ID least significant bit
  • LSB Least Significant Bit
  • MCS feedback (MFB) MCS feedback
  • Sub-field a group ID most significant bit (GID
  • Table 3 shows a description of each subfield included in the HT Control Middle subfield of the VHT format.
  • Table 3 Subfield meaning Justice MRQ MCS request Set to '1' if MCS feedback (solicited MFB) is requested. Otherwise, set to '0'.
  • MSI MRQ sequence identifier If the Unsolicited MFB subfield is '0' and the MRQ subfield is set to '1', then the MSI subfield contains a sequence number ranging from 0 to 6 identifying the specific request. If the Unsolicited MFB subfield is '1' A compressed MSI (Compressed MSI) subfield (2 bits), and an STBC indication subfield (1 bit).
  • the MFSI / GID-L MFB sequence identifier / LSB of Group ID When the Unsolicited MFB subfield is set to '0', the MFSI / GID-L subfield contains the received value of the MSI contained in the frame related to MFB information. Unsolicited MFB subfield is set to '1' If it is estimated from the PPDU, the MFSI / GID-L subfield contains the least significant 3 bits of the group ID of the PPDU for which the MFB is estimated MFB VHT N_STS, MCS, BW, SNR feedback The MFB subfield contains the recommended MFB.
  • VHT-MCS 15
  • the GID-H subfields are all set to 1 Coding Type Coding type of MFB response
  • the coding type subfield includes a coding type (BCC (binary convolutional code) and LDPC (low-density parity check) 1) of the frame in which the spontaneous MFB is estimated FB Tx Type Transmission type of MFB response
  • BCC binary convolutional code
  • LDPC low-density parity check
  • the FB Tx Type subfield is set to '1' Unsolicited MFB Unsolicited MCS feedback indicator If the MFB is a response to the MRQ, it is set to '1'. If the MFB is not a response to the MRQ, it is set to '0'
  • the MFB subfield includes a VHT-MCS subfield, a bandwidth (BW) subfield, a signal-to-noise ratio (SNR) subfield, Subfields.
  • the NUM_STS subfield indicates the number of recommended spatial streams.
  • the VHT-MCS subfield indicates the recommended MCS.
  • the BW subfield indicates the bandwidth information associated with the recommended MCS.
  • the SNR subfield indicates the average SNR value on the data subcarrier and spatial stream.
  • each of the above-described fields may follow the definition of the IEEE 802.11 system.
  • Each of the fields described above corresponds to an example of fields that can be included in the MAC frame, but is not limited thereto. That is, each of the fields described above may be replaced with another field, or an additional field may be further included, and all fields may not necessarily be included.
  • FIG. 11 is a conceptual diagram illustrating a channel sounding method in a wireless communication system to which the present invention can be applied.
  • FIG. 11 illustrates a method of feeding back channel state information between a Beamformer (for example, AP) and a Beamformee (for example, a non-AP STA) based on a sounding protocol.
  • the sounding protocol may refer to a procedure for receiving information on channel state information.
  • the channel state information sounding method between the beamformer and the beamformee based on the sounding protocol can be performed in the following steps.
  • VHT VHT Null Data Packet Announcement
  • the VHT NDPA frame is a control frame used to notify that channel sounding is started and NDP (null data packet) is to be transmitted.
  • NDP nucleic acid data packet
  • the VHT NDPA frame may include association identifier (AID) information of the beamformee to which the NDP is to be transmitted, feedback type information, and the like. A more detailed description of the VHT NDPA frame will be given later.
  • AID association identifier
  • the VHT NDPA frame can be transmitted using different transmission schemes when data is transmitted using MU-MIMO and when data is transmitted using SU-MIMO. For example, when channel sounding for MU-MIMO is performed, a VHT NDPA frame is transmitted in a broadcast manner, whereas when channel sounding is performed for SU-MIMO, a VHT NDPA frame Can be transmitted in a unicast manner.
  • NDP has a VHT PPDU structure excluding data fields.
  • the Beamformees receiving the VHT NDPA frame can check the AID12 subfield value contained in the STA information field and confirm that the STA is the sounding STA.
  • the beamformers can know the feedback sequence through the sequence of the STA Info field included in the NDPA.
  • FIG. 11 illustrates a case in which the feedback sequence proceeds in the order of Beamformee 1, Beamformee 2, and Beamformee 3.
  • Beamformee 1 acquires 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 the VHT compressed beamforming frame including feedback information after SIFS to the beamformer 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 given 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 performs the same function as the NDP frame, and Beamformee 2 can measure the channel state based on the transmitted Beamforming Report Poll frame.
  • Beamformee 2 transmits the VHT Compressed Beamforming frame including the feedback information to the beamformer after SIFS.
  • the Beamformer receives a VHT Compressed Beamforming frame from Beamformee 2, and 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 the feedback information to the beamformer after SIFS.
  • FIG. 12 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 includes a Frame Control field, a Duration field, a RA (Receiving Address) field, a TA (Transmitting Address) field, a Sounding Dialog Token field, STA information 1 (STA Info 1) field to STA information n (STA Info n) field, and FCS.
  • the RA field value indicates a receiver address or STA address for receiving the 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 a target STA for SU-MIMO channel sounding, the AP transmits the VHT NDPA frame to the target STA in a unicast manner.
  • the RA field value has a broadcast address. For example, 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 indicates the transmitter address transmitting the VHT NDPA frame or the address of the transmitting STA or the bandwidth signaling TA.
  • the Sounding Dialog Token field may also be referred to as a Sounding Sequence field.
  • the Sounding Dialog Token Number The Sounding Dialog Token Number subfield contains the 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 an STA Info field including information on the STA to be sounded.
  • the STA Info field may be included for each STA to be sounded.
  • Each STA Info field may consist of an AID12 subfield, a feedback type subfield, and an Nc index subfield.
  • Table 4 shows the subfields of the STA Info field included in the VHT NDPA frame.
  • the AID12 subfield value is set to '0'.
  • Feedback Type Indicates the type of feedback request for the STA to be sounded. '0' for SU-MIMO, '1' for MU-MIMO, Nc Index
  • the feedback type subfield indicates MU-MIMO, it indicates a value obtained by subtracting 1 from the number Nc of columns of the compressed beamforming feedback matrix.
  • each of the above-described fields may follow the definition of the IEEE 802.11 system.
  • each of the fields described above corresponds to an example of fields that can be included in the MAC frame, and may be replaced with another field, or an additional field may be further included.
  • FIG. 13 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 the data field is omitted in the VHT PPDU format as shown in FIG.
  • the NDP may be precoded based on a specific precoding matrix and transmitted to the STA to be sounded.
  • the length field indicating the length of the PSDU included in the data field in the L-SIG field of the NDP is set to '0'.
  • the Group ID field indicating whether the transmission scheme used for NDP transmission in the VHT-SIG-A field of the NDP 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 Upon receiving the NDP, the sounding target STA estimates the channel based on the VHT-LTF field of the NDP and acquires channel state information.
  • FIG. 14 is a diagram illustrating a VHT compressed beamforming frame format in a wireless communication system to which the present invention may be applied.
  • a VHT compressed beamforming frame is a VHT action frame for supporting a VHT function, and includes an Action field in a frame body.
  • the Action field provides a mechanism for specifying extended management operations included in the frame body of the MAC frame.
  • the Action field includes a Category field, a VHT Action field, a VHT MIMO Control field, a VHT Compressed Beamforming Report field, and an MU Exclusive Beamforming Report) field.
  • the Category field is set to a value indicating the VHT category (i.e., the VHT Action frame), and the VHT Action field is set to a value indicating the VHT Compressed Beamforming frame.
  • the VHT MIMO Control field is used to feedback control information associated with beamforming feedback.
  • the VHT MIMO Control field can always be present in the VHT Compressed Beamforming frame.
  • the VHT Compressed Beamforming Report field is used to feed back information on a beamforming metric including SNR information on a space-time stream used to transmit data.
  • the MU Exclusive Beamforming Report field is used to feedback SNR information on a spatial stream when performing MU-MIMO transmission.
  • VHT Compressed Beamforming Report field and the MU Exclusive Beamforming Report field are set in the feedback type subfield of the VHT MIMO Control field, the Remaining Feedback Segments subfield, the first feedback segment Feedback Segment) sub-field.
  • 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, A Feedback Type subfield, a Remaining Feedback Segments subfield, a First Feedback Segment subfield, a reserved subfield, and a Sounding Dialog Token Number sub-field. Field.
  • Table 5 shows the subfields of the VHT MIMO Control field.
  • .Nr 8, '7' Channel Width 2 '0' for 40 MHz, '1' for 80 MHz, '2', 160 MHz for 40 MHz, and 20 MHz for the measured channel to produce a compressed beamforming feedback matrix.
  • Remaining Feedback Segments 3 Indicates the number of remaining feedback segments for the associated VHT Compressed Beamforming frame. Set to '0' if this is a segment of the last feedback segment of an segmented report or an unsegmented report. 1 'to' 6 'if it is not the first and last feedback segment of the segmented report. If it is a feedback segment that is not the last segment of the segmented report, In the case of a retransmission feedback segment, the field is set to the same value as the associated segment of the original transmission.
  • First Feedback Segment One Set to '1' if this is the first feedback segment of a segmented report or a feedback segment of an unsegmented report If this is not the initial feedback segment or if the VHT Compressed Beamforming Report field and the MU Exclusive Beamforming Report field Is set to '0' if it is not present in the frame
  • the field is set to the same value as the associated segment of the original transmission Sounding Dialog Token Number 6 Sounding Dialog Token of the NDPA frame.
  • 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 also be referred to as a Sounding Sequence Number subfield.
  • the VHT compressed beamforming report field is used to indicate the compassessed beamforming feedback matrix 'V' used by the transmit beamformer to determine the steering matrix 'Q' It is used to convey information.
  • Table 6 shows the subfields of the VHT compressed beamforming report field.
  • an average SNR for each space-time stream and a compressed beamforming feedback matrix 'V' for each subcarrier may be included.
  • the compressed beamforming feedback matrix is used to calculate a channel matrix (i.e., steering matix 'Q') in a transmission method using MIMO as a matrix including information on channel conditions.
  • Nr scidx () means the subcarrier on which the Compressed Beamforming Feedback Matrix subfield is transmitted.
  • Ns denotes the number of subcarriers to which the beamforming feedback matrix compressed is transmitted to the beamformer.
  • the beamformee can use the grouping method to reduce the number of Ns to which the compressed beamforming feedback matrix is transmitted. For example, it is possible to reduce the number of compressed beamforming feedback matrices fed back by bundling a plurality of subcarriers into one group and transmitting a compressed beamforming feedback matrix for each group.
  • Ns can be calculated from the Channel Width subfield and the Grouping subfield included in the VHT MIMO Control field.
  • Table 7 illustrates the average SNR of the space-time stream.
  • the average SNR for each space-time stream is calculated by calculating an average SNR value for the entire subcarriers included in the channel and mapping the SNR 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 a delta ( ⁇ ) SNR.
  • the information in the VHT Compressed Beamforming Report field and the MU Exclusive Beamforming Report field can be used by the MU Beamformer to determine the steering matix 'Q'.
  • Table 8 shows sub-fields of the MU Exclusive Beamforming Report field included in the VHT compressed beamforming frame.
  • an SNR per space-time stream may be included for each subcarrier.
  • Each Delta SNR subfield has a value increased by 1 dB between -8 dB and 7 dB.
  • scidx denotes the subcarrier (s) through which the Delta SNR subfield is transmitted, and Ns denotes the number of subcarriers to which the Delta SNR subfield is transmitted to the beamformer.
  • 15 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 RA (Receiving Address) field, a TA (Transmitting Address) field, a Feedback Segment Retransmission Bitmap ) Field and an FCS.
  • the RA field value indicates the address of the intended recipient.
  • the TA field value indicates the address of the STA transmitting the Beamforming Report Poll frame or the bandwidth for signaling the TA.
  • the Retransmission Bitmap field indicates the feedback segment requested in the VHT Compressed Beamforming report.
  • the AP can simultaneously transmit data frames to at least one STA paired with the MIMO.
  • the AP may simultaneously transmit data to an STA group including at least one STA among a plurality of STAs associated with the AP.
  • the number of paired STAs can be a maximum of four, and when the maximum number of spatial streams is eight, each STA can be assigned a maximum of four spatial streams.
  • a STA to transmit data transmits a PPDU to a plurality of STAs Lt; / RTI >
  • the AP transmits an PPDU to a plurality of STAs according to the MU-MIMO transmission scheme.
  • the AP simultaneously transmits the PPDU to different STAs belonging to the paired STA group through different spatial streams.
  • the VHT-SIG A field of the VHT PPDU format includes group ID information and space-time stream information, so that each STA can confirm whether the PPDU is transmitted to itself.
  • a spatial stream may not be allocated to a specific STA of a transmission target STA group, so that data may not be transmitted.
  • a Group ID Management frame is used to assign or change a user position corresponding to one or more Group IDs. That is, the AP can notify the STAs associated with the specific group ID through the Group ID Management frame before performing the MU-MIMO transmission.
  • 16 is a diagram illustrating a Group ID Management frame in a wireless communication system to which the present invention can be applied.
  • the Group ID Management frame is a VHT Action frame for supporting the VHT function, and includes an Action field in the Frame Body.
  • the Action field provides a mechanism for specifying extended management operations included in the frame body of the MAC frame.
  • the Action field comprises a Category field, a VHT Action field, a Membership Status Array field, and a User Position Array field.
  • the Category field is set to a value indicating the VHT category (i.e., the VHT Action frame), and the VHT Action field is set to a value indicating the Group ID Management frame.
  • the Membership Status Array field consists of 1 bit of Membership Status subfields for each group. If the Membership Status subfield is set to '0', it indicates that the STA is not a member of the corresponding group. If it is set to '1', it indicates that the STA is a member of the group.
  • the STA may be assigned one or more groups by setting one or more Membership Status subfields in the Membership Status Array field to '1'.
  • the STA may have a user position in each group to which it belongs.
  • the user position indicates the position of the STA in the entire spatial stream according to the MU-MIMO transmission when the STA belongs to the corresponding group ID.
  • the User Position Array field consists of 2-bit User Position subfields for each group. Within the group to which it belongs, the user position of the STA is indicated by the User Position subfield in the User Position Array field. The AP can assign the same user position to each different STA in each group.
  • the AP can only send Group ID Management frames if the dot11VHTOptionImplemented parameter is 'true'.
  • the Group ID Management frame is transmitted only to the VHT STA having the MU Beamformee Capable field set to '1' in the VHT Capabilities element field.
  • the Group ID Management frame is transmitted in a frame addressed to each STA.
  • the STA receives a Group ID Management frame having an RA field matching its MAC address.
  • the STA updates the PHYCONFIG_VECTOR parameter GROUP_ID_MANAGEMENT based on the contents of the received Group ID Management frame.
  • the transmission of the Group ID Management frame to the STA and the transmission of the ACK from the STA to the STA are completed before transmitting the MU PPDU to the STA.
  • the MU PPDU is most recently transmitted to the STA and is transmitted to the STA based on the contents of the Group ID Management frame in which the ACK was received.
  • the downlink MU-MIMO frame (DL MU-MIMO Frame)
  • 17 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.
  • FIG. 17 shows the number of STAs receiving the PPDUs and the number of spatial streams allocated to each STA is assumed to be 1, but the number of STAs paired to the AP, the number of spatial streams allocated to each STA
  • the present invention is not limited thereto.
  • the MU PPDU includes an L-TFs field (L-STF field and L-LTF field), L-SIG field, VHT-SIG-A field, VHT-TFs field Field), a VHT-SIG-B field, a Service field, one or more PSDUs, a padding field, and a Tail bit.
  • 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 those in FIG. 4 and will not be described in detail below.
  • the PPDU duration indicated by the L-SIG field includes a symbol assigned a VHT-SIG-A field, a symbol assigned a VHT-TFs field, a field assigned a VHT-SIG-B field, A bit constituting a PSDU, a bit constituting a padding field, and a bit constituting a tail field.
  • the STA receiving the PPDU can obtain information on the duration of the PPDU through the information indicating the PPDU duration included in the L-SIG field.
  • the Group ID information and the number of space-time streams per user are transmitted through VHT-SIG-A, and the coding method and MCS information are transmitted through VHT-SIG-B. Therefore, the beamformers can check VHT-SIG-A and VHT-SIG-B and know whether they are MU MIMO frames to which they belong. Therefore, the STA which is not the member STA of the corresponding Group ID, the member of the corresponding Group ID, or the STA whose number of allocated streams is '0' is set to stop receiving the physical layer from the VHT-SIG-A field to the end of the PPDU, thereby reducing power consumption can do.
  • the Group ID can know which MU group the Beamformee belongs to and how many users are in the group to which the Beamformee belongs, that is, which stream the PPDU is received.
  • All MPDUs transmitted in the VHT MU PPDU based on 802.11ac are included in the A-MPDU.
  • the upper box in the data field of FIG. 17 illustrates a VHT A-MPDU transmitted to the STA 1, a middle box illustrates a VHT A-MPDU transmitted to the STA 2, and a lower box illustrates a VHT A- A-MPDU is illustrated.
  • the A-MPDU comprises one or more consecutive A-MPDU subframes and an EOF padding of 0 to 3 octets in length.
  • Each A-MPDU subframe includes one MPDU delimiter field, and optionally an MPDU may be included later.
  • Each A-MPDU subframe that is not located at the end in the A-MPDU has a padding field such that the length of the subframe is a multiple of four octets.
  • each A-MPDU may have different bit sizes.
  • null padding may be performed so that the transmission time of the plurality of data frames transmitted by the beamformer is equal to the transmission completion time of the maximum-interval transmission data frame.
  • the maximum interval transmission data frame may be a frame in which the valid downlink data is transmitted for the longest interval by the beamformer.
  • the effective downlink data may be null padded downlink data.
  • valid downlink data may be included in the A-MPDU and transmitted.
  • the remaining data frames excluding the maximum interval transmission data frame can perform null padding.
  • the beamformer may encode one or more A-MPDU subframes temporally subordinated to a plurality of A-MPDU subframes in the A-MPDU frame by encoding only the MPDU delimiter field.
  • FIG. 18 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 the downlink from the AP to the client (i.e., non-AP STA). At this time, a multi-user frame is simultaneously transmitted to multiple receivers, but an acknowledgment must be transmitted individually in the uplink.
  • the AP sends a VHT MU PPDU (i.e., preamble and data) to all receivers (i.e., STA 1, STA 2, STA 3).
  • VHT MU PPDU contains the VHT A-MPDU sent to each STA.
  • the STA 1 After receiving the VHT MU PPDU from the AP, the STA 1 transmits a Block Acknowledgment (BA) frame to the AP after SIFS.
  • BA Block Acknowledgment
  • the AP After receiving the BA from STA 1, the AP transmits a BAR (block acknowledgment request) frame to the next STA 2 after SIFS, and the STA 2 transmits the BA frame to the AP after SIFS.
  • the AP After receiving the BA frame from the STA 2, the AP transmits the BAR frame to the STA 3 after the SIFS, and the STA 3 transmits the BA frame to the AP after the SIFS.
  • the AP sends the next MU PPDU to all STAs.
  • FIG. 19 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 Receive Address (RA) field, a Transport Address A BAR control field, a BAR information field, and a frame check sequence (FCS).
  • BAR Block Ack Request
  • FCS frame check sequence
  • the RA field may be set to the address of the STA receiving the BAR frame.
  • the TA field may be set to the address of the STA transmitting the BAR frame.
  • the BAR control field includes a BAR Ack Policy sub-field, a Multi-TID sub-field, a Compressed Bitmap sub-field, a Reserved sub-field, and a TID information (TID_Info) .
  • Table 9 is a table illustrating the BAR control field.
  • the BAR Information field contains different information depending on the type of the BAR frame. This will be described with reference to FIG.
  • FIG. 20 is a diagram illustrating a BAR information field of a Block Ack Request frame in a wireless communication system to which the present invention can be applied.
  • FIG. 20A illustrates a BAR Information field of a Basic BAR frame and a compressed BAR frame
  • FIG. 20B illustrates a BAR Information field of a Multi-TID BAR frame
  • FIG. 20C illustrates a GAR The BAR Information field of the BAR frame is illustrated.
  • 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 contains the sequence number of the first MSDU to which the corresponding BAR frame is transmitted.
  • the Starting Sequence Control subfield contains the sequence number of the first MSDU or A-MSDU to which the corresponding BAR frame is to be transmitted.
  • the BAR Information field includes a Per TID Info sub-field and a Block Ack Starting Sequence Control sub- It is composed repeatedly by TID.
  • the Per TID Info subfield includes a Reserved subfield and a TID Value subfield.
  • the TID Value subfield contains the TID value.
  • the Block Ack Starting Sequence Control subfield includes a Fragment Number and a Starting Sequence Number subfield as shown in FIG. 20 (a).
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Control subfield contains the sequence number of the first MSDU or A-MSDU to which the corresponding BAR frame is to be transmitted.
  • FIG. 21 is a diagram illustrating a block ACK (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 / ID field, a RA field, a TA field, control field, a BA information field, and a frame check sequence (FCS).
  • BA block ACK
  • the RA field may be set to the address of the STA requesting the block ACK.
  • the TA field may be set to the address of the STA transmitting the BA frame.
  • the BA control field includes a BA Ack Policy sub-field, a Multi-TID sub-field, a Compressed Bitmap sub-field, a Reserved sub-field, and a TID information (TID_Info) .
  • Table 10 is a table illustrating the BA control field.
  • the BA Information field includes different information depending on the type of the BA frame. This will be described with reference to FIG.
  • FIG. 22 is a diagram illustrating a BA information field of a block ACK (Block Ack) frame in a wireless communication system to which the present invention can be applied.
  • FIG. 22A illustrates the BA Information field of the Basic BA frame
  • FIG. 22B illustrates the BA Information field of the Compressed BA frame
  • FIG. 22C illustrates the BA of the Multi-TID BA frame. Information field is illustrated.
  • the BA Information field includes a Block Ack Starting Sequence Control sub-field and a Block Ack Bitmap sub-field.
  • the Block Ack Starting Sequence Control subfield includes a Fragment Number subfield and a Starting Sequence Number subfield as shown in FIG.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Number subfield contains the sequence number of the first MSDU to which the corresponding BA frame is to be transmitted and is set to the same value as the basic BAR frame received immediately before.
  • the Block Ack Bitmap subfield is composed of a length of 128 octets and is used to indicate the reception status of a maximum of 64 MSDUs.
  • a value of '1' in the Block Ack Bitmap subfield indicates that the MPDU corresponding to the corresponding bit position has been successfully received, and a value of '0' indicates that the MPDU corresponding to the corresponding bit position has not been 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 shown in FIG.
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Number subfield contains the sequence number of the first MSDU or A-MSDU to which the corresponding BA frame is to be transmitted and is set to the same value as the basic BAR frame received immediately before.
  • the Block Ack Bitmap subfield is composed of 8 octets in length and is used to indicate the reception state 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 bit position has been successfully received, and a value of '0' indicates that a single MSDU or A- Lt; / RTI >
  • the BA Information field includes a TID-specific information (Per TID Info) subfield, a Block Ack Starting Sequence Control subfield, A block Ack Bitmap subfield is constructed by repeating one or more TIDs in order of increasing TID.
  • the Per TID Info subfield includes a Reserved subfield and a TID Value subfield.
  • the TID Value subfield contains the TID value.
  • the Block Ack Starting Sequence Control subfield includes a Fragment Number and a Starting Sequence Number subfield as shown in FIG. 20 (a).
  • the Fragment Number subfield is set to zero.
  • the Starting Sequence Control subfield contains the sequence number of the first MSDU or A-MSDU to which the corresponding BA frame is to be transmitted.
  • the Block Ack Bitmap subfield is composed 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 bit position has been successfully received, and a value of '0' indicates that a single MSDU or A- Lt; / RTI >
  • FIG. 23 is a diagram illustrating an ACK frame in a wireless communication system to which the present invention can be applied.
  • an ACK frame includes a frame control field, a duration field, an RA field, and an FCS.
  • the RA field includes a second address (Address 2) field of a data frame, a management frame, a block ACK request frame, a block ACK (Block Ack) frame, or a PS- .
  • a duration value in an ACK frame other than that transmitted by a non-QoS STA includes a data frame received immediately before, a management frame, a block Ack Request frame, Is set to a value (ms) obtained by subtracting the time required for ACK frame transmission and the SIFS interval in the Duration / ID field of the block ACK (Block Ack) frame or the PS-Poll frame. If the calculated duration value is not an integer value, it is rounded.
  • IEEE 802.11ax is a next-generation WLAN system for supporting higher data rates and handling higher user loads. As one of the recently proposed WLAN systems, it has a so-called high efficiency WLAN (HEW: High Efficiency WLAN).
  • HEW High Efficiency WLAN
  • the IEEE 802.11ax WLAN system can operate in the 2.4 GHz frequency band and the 5 GHz frequency band as the existing WLAN system. It can also operate in the 60 GHz frequency band of 6 GHz or higher.
  • FIG. 24 is a diagram illustrating a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • HE High Efficiency
  • FIG. 24A illustrates a schematic structure of an HE format PPDU
  • FIGS. 24B through 24D illustrate a more specific structure of an HE format PPDU.
  • the HE format PPDU for the HEW can be largely composed of a legacy part (L-part), an HE part (HE-part), and a data field (HE-data).
  • the L-part is composed of the L-STF field, the L-LTF field and the L-SIG field in the same manner as in the conventional WLAN system.
  • the HE-part is a newly defined part for the 802.11ax standard and may include the HE-STF field, the HE-SIG field, and the HE-LTF field.
  • FIG. 24A illustrates the order of the HE-STF field, the HE-SIG field, and the HE-LTF field, but may be configured in a different order. Also, the HE-LTF may be omitted.
  • the HE-SIG may include information for decoding the HE-data field (e.g., OFDMA, UL MU MIMO, enhanced MCS, etc.).
  • information for decoding the HE-data field e.g., OFDMA, UL MU MIMO, enhanced MCS, etc.
  • the L-part and HE-part may have different Fast Fourier Transform (FFT) sizes (i.e., subcarrier spacing) and may use different CPs (Cyclic Prefixes).
  • FFT Fast Fourier Transform
  • the HE-SIG field may be divided into an HE-SIG A field and a HE-SIG B field.
  • the HE-part of the HE format PPDU includes an HE-SIG A field having a length of 12.8 ⁇ s, an HE-STF field of one OFDM symbol, one or more HE-LTF fields and a HE-SIG B field of one OFDM symbol can do.
  • the HE-SIG A field is excluded from the HE-part, and the HE-STF field is 4 times larger than the conventional PPDU. That is, FFTs of 256, 512, 1024 and 2048 sizes can be applied from HE-STF fields of HE format PPDUs of 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.
  • the positions of the HE-SIG A field and HE-SIG B field are b).
  • the HE-SIG A field may be followed by the HE-SIG B field, and the HE-SIG B field followed by the HE-STF and HE-LTF fields may be transmitted.
  • an FFT having a size four times larger than that of the conventional PPDU can be applied from the HE-STF field.
  • the HE-SIG field may not be divided into the HE-SIG A field and the HE-SIG B field.
  • the HE-part of the HE format PPDU may include an 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 can be 4 times larger than the conventional PPDU. That is, FFTs of 256, 512, 1024 and 2048 sizes can be applied from HE-STF fields of HE format PPDUs 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 the HE-STF field of one OFDM symbol and the HE-SIG field of one OFDM symbol.
  • the HE-part can be 4 times larger than the conventional PPDU. That is, FFTs of 256, 512, 1024 and 2048 sizes can be applied from HE-STF fields of HE format PPDUs of 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.
  • a HE format PPDU for a WLAN system may be transmitted over at least one 20 MHz channel.
  • a HE format PPDU may be transmitted in the 40 MHz, 80 MHz, or 160 MHz frequency band over a total of four 20 MHz channels. This will be described in more detail with reference to the following drawings.
  • 25 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 25 illustrates a PPDU format when 80 MHz is assigned to one STA, or when different streams of 80 MHz are assigned to a plurality of STAs, respectively.
  • L-STF, L-LTF, and L-SIG may be transmitted on OFDM symbols generated based on 64 FFT points (or 64 subcarriers) in each 20 MHz channel.
  • the HE-SIG A field may include common control information transmitted in common to STAs receiving PPDUs.
  • 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 contains the same information.
  • the HE-SIG-A field informs the entire bandwidth information of the system.
  • Table 11 is a table illustrating information included in the HE-SIG A field.
  • Bandwidth 2 Indicates the bandwidth over which the PPDU is transmitted. For example, 20 MHz, 40 MHz, 80 MHz, or 160 MHz
  • Group ID (Group ID) 6 Indicates a group of STAs or STAs to receive PPDUs
  • Stream information 12 Indicate the location or number of the spatial stream for each STA or indicate the location or number of the spatial stream for the group of STAs
  • the UL indication (UL indication) One Indicates whether the PPDU is directed to the AP (downlink) or to the STA MU indication
  • One Indicates whether the PPDU is an SU-MIMO PPDU or an MU-MIMO PPDU
  • the guard interval indication (GI indication) One Indicates whether short GI or long GI is used
  • Allocation information 12 Indicates the band or channel (subchannel index or subband index) assigned to each STA in the band in which the PPDU is transmitted.
  • Transmission power 12 Indicates the transmit power for each channel or each STA.
  • each of the fields illustrated in Table 11 may follow the definition of the IEEE 802.11 system.
  • each of the fields described above corresponds to an example of fields that can be included in the PPDU, but the present invention is not limited thereto. That is, each of the fields described above may be replaced with another field, or an additional field may be further included, and all fields may not necessarily be included.
  • the HE-STF is used to improve the performance of AGC estimation in MIMO transmission.
  • the HE-SIG B field may contain user-specific information required for each STA to receive its data (e.g., PSDU).
  • PSDU data
  • the HE-SIG B field may be transmitted in one or two OFDM symbols.
  • the HE-SIG B field may include information about the modulation and coding scheme (MCS) of the PSDU and the length of the PSDU.
  • MCS modulation and coding scheme
  • L-STF, L-LTF, L-SIG, and HE-SIG A fields can be repeatedly transmitted in units of 20 MHz channels.
  • the L-STF, L-LTF, L-SIG and HE-SIG A fields may be repeatedly transmitted on every 20 MHz channel when the PPDU is transmitted over four 20 MHz channels (i.e., 80 MHz band) .
  • the L-STF, L-LTF, and L-SIG fields are transmitted over a 64 FFT on a 20 MHz channel for legacy STA reception.
  • the L-SIG field may occupy one OFDM symbol
  • one OFDM symbol time may be 4 ⁇ ⁇
  • the GI may be 0.8 ⁇ ⁇ .
  • the FFT size for each frequency unit can be larger than HE-STF (or HE-SIG A). For example, a 256 FFT may be used on a 20 MHz channel, a 512 FFT may be used on a 40 MHz channel, and a 1024 FFT may be used on an 80 MHz channel. As the FFT size increases, the interval between OFDM subcarriers decreases, so the number of OFDM subcarriers per unit frequency increases but the OFDM symbol time increases. In order to improve the efficiency of the system, the length of the GI after the HE-STF can be set equal to the length of the GI of the HE-SIG A.
  • the HE-SIG A field may contain the information required by the HE STA to decode the HE PPDU. However, the HE-SIG A field can be transmitted over 64 FFTs on a 20 MHz channel for both legacy STAs and HE STAs to receive. This is because the HE STA can receive the existing HT / VHT format PPDU as well as the HE format PPDU, and the legacy STA and HE STA must distinguish between the HT / VHT format PPDU and the HE format PPDU.
  • 26 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • the FFT size per unit frequency may become larger from HE-STF (or HE-SIG B).
  • HE-STF or HE-SIG B
  • 256 FFTs are used in the 20 MHz channel
  • 512 FFTs are used in the 40 MHz channel
  • 1024 FFTs can be used in the 80 MHz channel.
  • FIG. 27 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • the HE-SIG B field is located after the HE-SIG A field.
  • the FFT size per unit frequency may become larger from HE-STF (or HE-SIG B).
  • HE-STF or HE-SIG B
  • 256 FFTs are used in the 20 MHz channel
  • 512 FFTs are used in the 40 MHz channel
  • 1024 FFTs can be used in the 80 MHz channel.
  • the information transmitted in each field included in the PPDU is the same as the example of FIG. 25, and therefore, the description thereof will be omitted.
  • the HE-SIG B field may contain information specific to each STA, but may be encoded over the entire band (i.e., indicated in 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 indicate frequency bandwidth information allocated to each STA and / or stream information in the corresponding frequency band.
  • HE-SIG-B in FIG. 23 may be assigned 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 can allocate 40 MHz
  • STA 3 and STA 4 can allocate 40 MHz thereafter.
  • STA 1 and STA 2 can allocate different streams
  • STA 3 and STA 4 can allocate different streams.
  • the HE-SIG-C field may be defined, and the HE-SIG C field may be added to the example of FIG.
  • the HE-SIG-B field information on all STAs is 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 can be transmitted in units of 20 MHz in the same manner as the HE-SIG-A field without transmitting over the entire band. This will be described with reference to the following drawings.
  • FIG. 28 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • the HE-SIG B field is located after the HE-SIG A field.
  • the HE-SIG B field is not transmitted over the entire band, but is transmitted in units of 20 MHz in the same manner as the HE-SIG A field.
  • the FFT size per unit frequency may become larger from HE-STF (or HE-SIG B).
  • HE-STF or HE-SIG B
  • 256 FFTs are used in the 20 MHz channel
  • 512 FFTs are used in the 40 MHz channel
  • 1024 FFTs can be used in the 80 MHz channel.
  • the information transmitted in each field included in the PPDU is the same as the example of FIG. 25, and therefore, the description thereof will be omitted.
  • the HE-SIG A field is duplicated and transmitted in units of 20 MHz in the HE-SIG A field.
  • the HE-SIG B field may indicate frequency bandwidth information allocated to each STA and / or stream information in the corresponding frequency band.
  • the HE-SIG B field can be transmitted in units of 20 MHz as in the HE-SIG A field.
  • the HE-SIG B field includes information on each STA, information on each STA may be included in each HE-SIG B field of 20 MHz units.
  • 20 MHz is allocated to each STA in the example of FIG. 28.
  • the HE-SIG-B field may be copied and transmitted in units of 20 MHz.
  • information on all STAs may be included in the HE-SIG B field and may be duplicated and transmitted in units of 20 MHz like the HE-SIG A field.
  • the symbol length is shortened by using 64 FFTs at 20 MHz, If the HE-SIG-B field is located after the HE-STF field and the HE-LTF field, the length of the symbol can be made long by using 256 FFT at 20 MHz.
  • the data field may include a payload, a service field, a scrambled PSDU, tail bits, and padding bits.
  • the phase of three OFDM symbols transmitted after the L-SIG field in the HE format PPDU may be used.
  • the phases of the OFDM symbol # 1 and the OFDM symbol # 2 transmitted after the L-SIG field in the HE format PPDU are not rotated, but the phase of the OFDM symbol # 3 is rotated by 90 degrees counterclockwise . That is, BPSK is used as the modulation method for the OFDM symbol # 1 and the OFDM symbol # 2, and QBPSK can be used as the modulation method for the OFDM symbol # 3.
  • the STA attempts to decode the first to third OFDM symbols transmitted after the L-SIG field of the received PPDU based on the constellation shown in FIG. If the STA successfully decodes the PPDU, it can determine that the PPDU is an HE format PPDU.
  • the HE-SIG A field is transmitted in three OFDM symbols after the L-SIG field, this means that both the OFDM symbols # 1 to # 3 are used to transmit the HE-SIG A field.
  • the manner in which a plurality of STAs operating in the WLAN system transmit data to the AP on the same time resource may be referred to as an " uplink multi-user transmission ".
  • the uplink transmission by each of the plurality of STAs may be multiplexed in the frequency domain or the spatial domain.
  • different frequency resources may be allocated as uplink transmission resources for each of a plurality of STAs based on orthogonal frequency division multiplexing (OFDMA).
  • OFDMA orthogonal frequency division multiplexing
  • each of the plurality of STAs When the uplink transmission by each of the plurality of STAs is multiplexed in the spatial domain, different spatial streams are assigned to each of the plurality of STAs, so that each of the plurality of STAs can transmit uplink data through different spatial streams.
  • the transmission method through these different spatial streams may be referred to as 'UL MU MIMO transmission'.
  • the WLAN system does not support UL MU transmission due to the following limitations.
  • synchronization of transmission timing of uplink data transmitted from a plurality of STAs is not supported. For example, assuming that a plurality of STAs transmit the uplink data through the same time resource in the existing WLAN system, in the current WLAN system, each of the plurality of STAs can know the transmission timing of the uplink data of another STA none. Therefore, it is difficult for the AP to receive uplink data on the same time resource from each of a plurality of STAs.
  • overlapping between frequency resources used for transmitting uplink data by a plurality of STAs may occur. For example, if the oscillator of each of the plurality of STAs is different, the frequency offset may appear differently. If a plurality of STAs having different frequency offsets perform uplink transmission at the same time through different frequency resources, a part of frequency regions used by each of the plurality of STAs may overlap.
  • the AP can receive signals of different powers from each of the plurality of STAs. In such a case, a signal arriving at a weak power may be relatively difficult to detect by the AP compared to a signal arriving at a strong power.
  • the present invention proposes a UL MU transmission method in a WLAN system.
  • FIG. 30 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 transmits an ACK frame in response to an UL MU data frame send.
  • the AP first instructs the STAs to transmit UL MU scheduling (UL MU scheduling) frame 3010 to prepare for UL MU transmission.
  • UL MU scheduling UL MU scheduling
  • the UL MU scheduling frame may be referred to as the term 'UL MU trigger frame' or 'trigger frame'.
  • the UL MU scheduling frame 3010 may include control information such as STA identifier (ID) / address information, resource allocation information, duration information, and the like.
  • ID STA identifier
  • the STA ID / address information indicates an identifier or an address for specifying each STA transmitting the uplink data.
  • the resource allocation information includes uplink transmission resources allocated to each STA (for example, frequency / subcarrier information allocated to each STA in UL MU OFDMA transmission and stream index allocated to each STA in case of UL MU MIMO transmission) .
  • Duration information is information for determining a time resource for transmission of an uplink data frame transmitted by each of a plurality of STAs.
  • the duration information is referred to as 'MAC duration'.
  • the MAC duration may include interval information of TXOP (Transmit Opportunity) allocated for uplink transmission of each STA or information (e.g., a bit or symbol) about the length of an uplink frame.
  • TXOP Transmit Opportunity
  • information e.g., a bit or symbol
  • the UL MU scheduling frame 3010 may further include control information such as MCS information, coding information, and the like to be used for UL MU data frame transmission for each STA.
  • control information such as MCS information, coding information, and the like to be used for UL MU data frame transmission for each STA.
  • the control information may include the HE-SIG A field or the HE-SIG B field of the PPDU carrying the UL MU scheduling frame 3010 or the control field of the UL MU scheduling frame 3010 (e.g., For example, a Frame Control field of a MAC frame).
  • the PPDU that conveys the UL MU scheduling frame 3010 has a structure that starts with an L-part (e.g., L-STF field, L-LTF field, L-SIG field, etc.).
  • the legacy STAs can perform the NAV (Network Allocation Vector) setting from the L-SIG field.
  • the legacy STAs can calculate the interval (hereinafter referred to as 'L-SIG protection interval') for the NAV setting based on the data length and the data rate information in the L-SIG. Then, the legacy STAs can determine that there is no data to be transmitted to the L-SIG during the calculated L-SIG protection period.
  • the L-SIG guard interval may be determined as the sum of the MAC duration value of the UL MU scheduling frame 3010 and the remaining interval after the L-SIG field in the PPDU carrying the UL MU scheduling frame 3010. Accordingly, the L-SIG protection interval may be set to a value up to a transmission interval of the ACK frame 3030 transmitted to each STA according to the MAC duration value of the UL MU scheduling frame 3010.
  • the first field may indicate UL MU OFDMA transmission and UL MU MIMO transmission separately. For example, if '0', UL MU OFDMA transmission is indicated, and if it is '1', UL MU MIMO transmission can be indicated.
  • the size of the first field may be one bit.
  • a second field (e.g., the STA ID / address field) indicates the STA ID or STA addresses to participate in the UL MU transmission.
  • the size of the second field may be composed of the number of bits for informing STA ID times the number of STAs participating in UL MU. For example, if the second field is composed of 12 bits, the ID / address of each STA can be indicated by 4 bits.
  • a third field (e.g., a resource allocation field) indicates a resource area allocated to each STA for UL MU transmission. At this time, the resource area allocated to each STA can be sequentially indicated to each STA according to the order of the second field.
  • the first field value is '0'
  • frequency information for example, frequency index, subcarrier index, etc.
  • MIMO information e.g., stream index, etc.
  • the size of the third field may be a plurality of bits (or a bitmap format) ⁇ UL MU The number of STAs to participate in the 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' and '2'.
  • STA 1 when the first field is '0', STA 1 is allocated a frequency resource from an upper (or lower) frequency domain, and STA 2 can allocate a frequency resource subsequent thereto sequentially.
  • STA 1 can use the upper (or lower) 40 MHz band and STA 2 can use the next 40 MHz band.
  • the beamforming scheme according to each stream is designated in advance, or more specific information about the beamforming scheme according to the stream in the third field or the fourth field may be included.
  • Each STA transmits UL MU data frames 3021, 3022, and 3023 to the AP based on the UL MU scheduling frame 3010 transmitted by the AP.
  • each STA can transmit UL MU data frames 3021, 3022, and 3023 to the AP after SIFS after receiving the UL MU scheduling frame 3010 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 the resource allocation information of UL MU scheduling frame 3010.
  • each STA can transmit an uplink data frame on the same time resource through different frequency resources.
  • STA1 to STA3 may be allocated different frequency resources for uplink data frame transmission based on the STA ID / address information and resource allocation information included in the UL MU scheduling frame 3010, respectively.
  • the STA ID / address information sequentially indicates STA 1 to STA 3
  • the resource allocation information can sequentially indicate the frequency resource 1, the frequency resource 2, and the frequency resource 3.
  • the STA1 to STA3 sequentially designated based on the STA ID / address information can be sequentially allocated the frequency resource 1, the frequency resource 2, and the frequency resource 3, respectively, based on the resource allocation information. That is, the STA 1 can transmit UL data frames 3021, 3022 and 3023 to the AP through the frequency resource 1, the STA 2 through the frequency resource 2, and the STA 3 through the frequency resource 3.
  • each STA can transmit an uplink data frame on the same time resource through at least one different stream among a plurality of spatial streams.
  • Each STA1 to STA3 may be allocated a STA ID / address information included in the UL MU scheduling frame 3010 and a spatial stream for uplink data frame transmission based on the resource allocation information.
  • the STA ID / address information may indicate STA 1 to STA 3 sequentially
  • the resource allocation information may indicate the spatial stream 1, the spatial stream 2, and the spatial stream 3 sequentially.
  • the STA1 to STA3 sequentially designated based on the STA ID / address information can be sequentially assigned the spatial stream 1, the spatial stream 2, and the spatial stream 3, respectively, based on the resource allocation information. That is, the STA 1 can transmit the uplink data frames 3021, 3022, and 3023 to the AP through the spatial stream 1, the STA 2 and the STA 3 through the spatial stream 2 and the spatial stream 3, respectively.
  • the transmission duration (or the transmission end time) of the UL data frames 3021, 3022, and 3023 transmitted by each STA may be determined by the MAC duration information included in the UL MU scheduling frame 3010 have. Accordingly, each STA performs UL MU scheduling on the transmission end points of the UL data frames 3021, 3022, and 3023 (or uplink PPDUs carrying UL data frames) through bit padding or fragmentation And may synchronize based on the MAC duration value included in the frame 3010.
  • the PPDU for transmitting the uplink data frames 3021, 3022, and 3023 can be configured without a L-part or with a new structure.
  • the L-part of the PPDU that carries the UL data frames 3021, 3022 and 3023 is in SFN type (i.e., L-part configuration and contents simultaneously).
  • the L-part of the PPDU for transmitting the UL data frames 3021, 3022 and 3023 is L-part in 20MHz units in the band allocated by each STA Lt; / RTI >
  • the MAC duration value may be set to a value up to a period for transmitting the ACK frame 3030.
  • the L-SIG guard interval may be determined based on the MAC duration value have. Accordingly, the legacy STA can set the NAV to the ACK frame 3030 through the L-SIG field of the UL MU scheduling frame 3010.
  • the SIG field in the PPDU carrying the UL MU scheduling frame 3010 may also be unnecessary.
  • the HE-SIG-A field and / or HE-SIG-B may not be transmitted.
  • the HE-SIG-A and HE-SIG-C fields may be transmitted and the HE-SIG-B field may not be transmitted.
  • the AP may transmit the ACK frame 3030 in response to the uplink data frames 3021, 3022, and 3023 received from each STA.
  • the AP may receive uplink data frames 3021, 3022, and 3023 from each STA, and may transmit an ACK frame 3030 to each STA after SIFS.
  • the RA field having the size of 6 octets can be configured to include the AIDs (or Partial AIDs) of the STAs participating in the UL MU transmission.
  • an ACK frame of a new structure can be configured for DL SU transmission or DL MU transmission. That is, in the case of the DL SU transmission, the ACK frame 3030 can be sequentially transmitted to each STA participating in the UL MU transmission, and in the case of the DL MU transmission, the ACK frame 3030 can transmit the resources allocated to each STA Or stream) to each STA participating in the UL MU transmission.
  • the AP can transmit only the ACK frame 3030 for the UL MU data frame that has succeeded in reception to the corresponding STA.
  • the AP may inform ACK or NACK of the reception success through the ACK frame 3030. If the ACK frame 3030 includes NACK information, it may also include reason for a NACK or information (e.g., UL MU scheduling information, etc.) for subsequent processing.
  • the PPDU carrying the ACK frame 3030 may be configured with a new structure without an L-part.
  • the ACK frame 3030 may include the STA ID or the address information. However, if the order of the STAs indicated in the UL MU scheduling frame 3010 is the same, the STA ID or the address information may be omitted.
  • a TXOP i.e., L-SIG guard interval
  • a control frame including a frame for the next UL MU scheduling or correction information for the next UL MU transmission in the TXOP It is possible.
  • an adjustment process such as synchronizing STAs for UL MU transmission may be added.
  • 31 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.
  • the UL MU data frame is transmitted And transmit an ACK.
  • the AP first instructs the STAs to transmit UL MU scheduling (UL MU scheduling) frame 3110 to prepare for UL MU transmission.
  • UL MU scheduling UL MU scheduling
  • Each STA that receives the UL MU scheduling frame 3110 from the AP transmits sync signals 3121, 3122, and 3123 to the AP.
  • each STA may receive the UL MU scheduling frame 3110 and may transmit synchronization signals 3121, 3122, and 3123 to the AP after SIFS.
  • the AP receiving the synchronization signals 3121, 3122, and 3123 from each STA transmits an adjustment frame 3130 to each STA.
  • the AP may receive the synchronization signals 3121, 3122, and 3123 and may transmit the correction frame 3130 after SIFS.
  • the procedures for transmitting and receiving the synchronization signals 3121, 3122, and 3123 and the correction frame 3130 are procedures for correcting the time / frequency / power and the like among the STAs for transmission of UL MU data frames. That is, STAs transmit their synchronization signals 3121, 3122, and 3123, and the AP transmits correction information for correcting errors such as time / frequency / power based on the values to each STA through a correction frame 3130 So that the value can be corrected and transmitted in the UL MU data frame to be transmitted next.
  • This procedure may also be performed after the UL MU scheduling frame 3110 so that the STA may have time to prepare the data frame configuration according to the scheduling.
  • the STAs indicated in the UL MU scheduling frame 3110 transmit synchronization signals 3121, 3122, and 3123 to the indicated or designated resource areas, respectively.
  • the synchronization signals 3121, 3122, and 3123 transmitted from each STA can be multiplexed by time division multiplexing (TDM), code division multiplexing (CDM), and / or SDM (spatial division multiplexing).
  • the order of the STAs indicated in the UL MU scheduling frame 3110 is STA 1, STA 2, and STA 3, and the synchronization signals 3121, 3122, and 3123 of the STAs are multiplexed into the CDM,
  • the assigned Sequence 1, Sequence 2, and Sequence 3 can be transmitted to the AP.
  • resources e.g., time / sequence / stream, etc.
  • each STA for multiplexing the synchronization signals 3121, 3122, and 3123 of each STA into TDM, CDM, and / Lt; / RTI >
  • the PPDU carrying the synchronization signals 3121, 3122, and 3123 may not include the L-part, or may be transmitted only with the physical layer signal without the configuration of the MAC frame.
  • the AP receiving the synchronization signals 3121, 3122, and 3123 from each STA transmits an adjustment frame 3130 to each STA.
  • the AP can transmit the correction frame 3130 to each STA in the DL SU transmission scheme or to each STA in the DL MU transmission scheme. That is, in the case of the DL SU transmission, the correction frame 3130 may be sequentially transmitted to each STA participating in the UL MU transmission, and in the case of DL MU transmission, the correction frame 3130 may include resources allocated to each STA Or stream) to each STA participating in the UL MU transmission.
  • the correction frame 3130 may include the STA ID or the address information, and may omit the STA ID or the address information if the order of the STAs indicated in the UL MU scheduling frame 3110 is the same.
  • correction frame 3130 may include an adjustment field.
  • the adjustment field may include information for correcting an error such as time / frequency / power.
  • the correction information indicates information that the signal of the STAs received by the AP informs that an error such as time / frequency / power may occur and correct the error gap.
  • any information can be included in the correction frame 3130 as long as it can more accurately correct errors in time, frequency, power, etc. of each STA based on the synchronization signals 3121, 3122, and 3123 received by the AP .
  • PPDUs conveying correction frame 3130 may be constructed with a new structure without L-part.
  • the procedure of transmitting and receiving the synchronization signals 3121, 3122, and 3123 and the correction frame 3130 may be performed before transmitting the UL MU scheduling frame 3110 of each STA.
  • the transmission of the synchronization signals 3121, 3122, and 3123 may be omitted, and the AP may transmit correction information to the UL MU scheduling frame 3110 through implicit measurement.
  • an AP may determine an error such as time / frequency / power between each STA through an NDP or a buffer status / sounding frame transmitted from each STA And transmit the correction information to each STA through the UL MU scheduling frame 3110.
  • the procedure for correcting the time difference may be omitted.
  • the procedure for correcting the frequency difference may be omitted.
  • Each STA transmits UL MU data frames 3141, 3142, and 3143 to the AP based on the UL MU scheduling frame 3110 and the correction frame 3130 transmitted by the AP.
  • each STA may transmit the UL MU data frames 3141, 3142, and 3143 to the AP after SIFS after receiving the correction frame 3130 from the AP.
  • the AP may transmit the ACK frame 3150 in response to the uplink data frames 3141, 3142, and 3143 received from each STA.
  • the AP may receive uplink data frames 3141, 3142, and 3143 from each STA and may transmit an ACK frame 3150 to each STA after SIFS.
  • FIG. 30 proposes an ACK frame configuration and transmission method according to the UL MU transmission illustrated in FIGS. 30 and 31.
  • FIG. 30 proposes an ACK frame configuration and transmission method according to the UL MU transmission illustrated in FIGS. 30 and 31.
  • the configuration of the existing ACK frame transmits an ACK for one STA.
  • the BA frame also allows an STA to send ACKs for multiple TIDs, but sends an ACK for one STA.
  • the AP sends a BAR frame to the STA so that each STA can send ACK sequentially.
  • a traffic identifier is an identifier that can be used by an upper layer entity to classify an MSDU into a MAC entity supporting QoS in the MAC data service. That is, it means an ID allocated to each connection when the STA has multiple connections.
  • the TID is assigned to the MSDU in the upper layer of the MAC.
  • the existing ACK can be transmitted only to one STA.
  • a new ACK transmission method is required because the AP must transmit ACKs for UL MU data received from a plurality of STAs to a plurality of STAs .
  • the AP can simultaneously transmit ACK frames to all STAs that have performed UL MU transmission or transmit ACK frames sequentially for each STA. We will examine each case.
  • the ACK frame for the UL MU transmission according to the present invention may be configured based on the structure of the existing ACK frame or the structure of the existing BA frame.
  • the AP may transmit an ACK frame configured based on the existing ACK frame structure to each STA. Also, if any UL MU data frame of each UL MU data frame of each STA is composed of A-MPDU, the AP can transmit an ACK frame configured based on the existing BA frame structure to each STA. Also, the AP may use an ACK frame based on the existing ACK frame structure and an ACK frame based on the existing BA frame structure.
  • the ACK frame according to the present invention can be variously defined in structure or use, but will be collectively referred to as an ACK frame for convenience of explanation.
  • the ACK frame When transmitting an ACK frame to all STAs at the same time, the ACK frame is transmitted in a single ACK frame including ACK information for all STAs that have performed UL MU transmission, or ACK information for each STA that has performed UL MU transmission A plurality of ACK frames including only the ACK frame may be multiplexed and transmitted.
  • 32 is a diagram illustrating an ACK frame according to an embodiment of the present invention.
  • FIG. 32 (a) conceptually shows an ACK frame for UL MU transmission.
  • an ACK for UL MU transmission can be simultaneously transmitted to all STAs using the configuration of the illustrated ACK frame shown in FIG. 32 (a).
  • the ACK frame may be transmitted in units of 20 MHz or over the entire band used for UL MU transmission or over the entire band (e.g., 20 MHz, 40 MHz, 80 MHz or 160 MHz) supported in the BSS.
  • FIG. 32 (b) illustrates a case where an ACK frame is transmitted with a 20 MHz PPDU.
  • an ACK including ACK information for all STAs in a 20 MHz PPDU through a primary channel Frame can be transmitted.
  • an ACK frame may be transmitted within a 20 MHz PPDU, but the 20 MHz PPDU may be copied to transmit an ACK frame in a frequency band used for UL MU transmission or a full frequency band supported by a BSS.
  • FIG. 32C illustrates a case where an ACK frame is transmitted in the entire band used for UL MU transmission or in the entire band (for example, 80 MHz) supported in the BSS.
  • an ACK frame may be transmitted over an entire band used for UL MU transmission or a full band (for example, 40 MHz, 80 MHz, or 160 MHz) supported by the BSS. For example, if all STAs that have performed UL MU transmissions support 80 MHz channels, they can transmit ACK frames over an 80 MHz PPDU.
  • the HE-part is not shown in FIGS. 32 (b) and 32 (c), if necessary, it may be constituted by a 20 MHz unit or a full band (for example, 40 MHz, 80 MHz or 160 MHz) .
  • all fields may be transmitted in the HE-part, but only some fields (e.g., HE-SIG field) may be transmitted.
  • 33 is a diagram illustrating an ACK frame according to an embodiment of the present invention.
  • an ACK frame according to the present invention may be configured with a frame control field, a duration field, an RA field, and an FCS as in an existing ACK frame.
  • the RA field may be configured differently from the existing ACK frame to include ACK information according to the UL MU transmission.
  • the ACK frame according to the present invention may have the same length as or different from the existing ACK frame.
  • Figs. 33B and 33C are diagrams illustrating the configuration of an RA field when an ACK frame is constructed as shown in Fig. 33A.
  • an ACK frame structure can be constructed by configuring a plurality of RA fields.
  • the RA field for each STA can be configured to be equal to the length of the existing RA field, and the RA field for each STA can be configured to be 12 bits so as not to change the length of the existing RA field have.
  • the RA field for each STA includes the ID of each STA or the reduced STA ID (Reduced STA ID).
  • An example of the STA ID (or the reduced STA ID) may be a MAC address (or a part thereof) or an AID (or a part thereof).
  • the RA field for each STA may be configured such that each STA is the same as the UL MU transmission order, and the UL MU transmission order of each STA may be indicated by the UL MU scheduling frame.
  • the number of RA fields is fixed to the maximum number of STAs capable of participating in the UL MU, the STA IDs receiving ACK are sequentially filled, and the rest are dummy values Can be filled.
  • each RA field includes IDs of STA 1, STA 2, (Or reduced ID), and the rest can be filled with dummy values.
  • the RA field may be composed of one representative ID field and an ACK / NACK field for each STA configured bit by bit.
  • the first STA ID among the STAs participating in the UL MU transmission or the group ID for the UL MU transmission may be applicable.
  • the UL MU scheduling frame may inform the STA participating in the UL MU of the group ID.
  • each STA since each STA knows the order of its own from the UL MU scheduling frame, it reads the representative ID field, identifies the ACK frame for the UL MU transmission participated therein, reads the bit at the position corresponding to its own order ACK or NACK can be confirmed. By transmitting ACK / NACK information through 1 bit, each STA can confirm NACK as well as ACK.
  • the representative ID field can be composed of 48 bits in the same manner as the length of the existing RA field.
  • the representative ID field may be composed of 44 bits so as not to change the length of the existing RA field.
  • the ACK / NACK field for each STA may be composed of two or more bits (for example, four bits each), and may include the reason information of the NACK.
  • the representative ID field may include a broadcast ID or a BSS ID, and the representative ID field may be omitted. That is, since the frame exchange sequence initiated by the UL MU scheduling frame includes up to the ACK frame, it is possible to identify whether the ACK frame is an ACK frame for the UL MU transmission even if the representative ID field is omitted.
  • the ACK frame for the UL MU transmission is configured based on the structure of the existing ACK frame, the ACK frame for the UL MU transmission should be interpreted differently from the existing ACK frame. That is, the STA should be informed of whether the ACK frame is for the MU UL transmission.
  • it may include information indicating an ACK frame for a MU UL transmission in a trigger frame (e.g., an UL MU scheduling frame).
  • a trigger frame e.g., an UL MU scheduling frame
  • the ACK frame is transmitted. That is, when the STA participating in the UL MU transmission transmits an UL MU data frame composed of a single MPDU, the trigger frame indicates that the ACK frame for the corresponding UL MU data frame is configured as shown in FIG. 33 (b) or (c) It may include an indicator for the period.
  • it may include identification information for identifying an ACK frame for MU UL transmission in an ACK frame.
  • 1 bit can be set to '0x1' using a bandwidth signaling RA instead of the representative ID field. And may be configured with an ACK / NACK field for each STA after the first 1 bit.
  • the MSB 1 bit in the existing RA field region is set to '1', ACK / NACK information for each STA is sequentially included in the next RA field region, and the remaining bits are zero padded.
  • the STA can know that the corresponding ACK frame is an ACK frame for multiple STAs (i.e., for UL MU transmission).
  • the RA field of the existing ACK frame is the non-bandwidth signaling TA of the previous frame.
  • Bandwidth signaling TA refers to a bit that indicates the MSB 1 bit (individual / group) of a TA address such as RTS, ACK, BAR, BA, NDPA, Poll, Quot; 1 " to indicate that information about the bandwidth is included.
  • RTS RTS
  • ACK acknowledgement
  • BAR BA
  • NDPA NDPA
  • Poll Quot
  • 1 &quot to indicate that information about the bandwidth is included.
  • the RTS frame is set to '1'
  • it is set to '0' in the CTS frame and transmitted.
  • the ACK frame is set to '0' and transmitted.
  • 34 is a diagram illustrating an ACK frame according to an embodiment of the present invention.
  • an ACK frame includes a frame control field, a duration / ID field such as a conventional multi-TID BA type BA frame, ) Field, a receive address (RA) field, a transmit address (TA) field, a BA control field, a BA information field, and a frame check sequence (FCS).
  • a frame control field such as a conventional multi-TID BA type BA frame
  • a duration / ID field such as a conventional multi-TID BA type BA frame
  • RA receive address
  • TA transmit address
  • BA control field such as a BA control field
  • FCS frame check sequence
  • the BA control field and the BA information field may be configured differently from the existing ACK frame in order to include ACK information according to the UL MU transmission.
  • the ACK frame according to the present invention may have the same or different length from the existing BA frame.
  • FIG. 34 (b) is a diagram illustrating a configuration of a BA control field when an ACK frame is configured as shown in FIG. 34 (a).
  • FIG. 34C is a diagram illustrating the configuration of the BA information field when an ACK frame is configured as shown in FIG. 34A.
  • the BA control field includes a BA Ack Policy subfield, a Multi-TID subfield, a Compressed Bitmap subfield, A subfield, an STA identifier, and TID information (STA ID & TID Info).
  • Table 12 is a table illustrating the BA control field.
  • Multi-TID One (Basic BA) 01: Compressed BA 10: ACK frame for UL MU 11: Indicate the type of BA frame according to the Multi-TID subfield, Compressed Bitmap subfield and CGR subfield value 00: Multiple TID BA (Multi-TID BA) Compressed Bitmap One Reserved 9 STA ID & TID Info 4 For UL MU, n number of STAs to receive ACK (number of TIDs per STA)
  • the corresponding BA frame can indicate that the ACK frame is for UL MU transmission.
  • the value of the Multi-TID sub-field and the compressed bitmap sub-field is' 10 ', it is set to a preliminary value as in the conventional case.
  • the value of the Multi-TID sub field and the compressed bitmap sub field value' It can also be interpreted as a use. That is, when the UL MU is transmitted in response to downlink data other than UL MU transmission, a value of '11' may indicate that the corresponding frame is a multi-TID BA. On the other hand, when transmitted in response to UL MU transmission, a value of '11' may indicate that the frame is an ACK frame for UL MU transmission.
  • the STA ID & TID info subfield may indicate a value of (number of STAs receiving ACK times number of TIDs per STA). That is, it can indicate the number of TIDs of all STAs that have performed UL MU transmission.
  • the BA information field includes a Per TID Info sub-field, a Block Ack Starting Sequence Control, A sub-field, and a block ACK bitmap subfield may be constructed by repeating one or more TIDs.
  • the Per TID Info subfield includes an STA ID (STA ID) subfield and a TID Value (TID Value) subfield.
  • STA ID STA ID
  • TID Value TID Value
  • Table 13 is a table illustrating the Per TID Info sub-field.
  • the STA ID subfield includes the ID of each STA of 12 bits or a reduced STA ID (Reduced STA ID).
  • An example of the STA ID (or the reduced STA ID) may be a MAC address (or a part thereof) or an AID (or a part thereof).
  • the TID Value subfield contains the TID value.
  • the Block Ack Starting Sequence Control subfield may include a Fragment Number subfield and a Starting Sequence Number subfield as shown in FIG.
  • the Fragment Number subfield may be set to zero.
  • the Starting Sequence Number subfield may include the sequence number of the MPDU or the MSDU to which the ACK frame for the corresponding UL MU transmission is to be transmitted.
  • the Block Ack Bitmap subfield may be composed of 8 octets or 128 octets in length.
  • a value of '1' in the Block Ack Bitmap subfield indicates that the MPDU or MSDU corresponding to the corresponding bit position has been successfully received, and if set to '0', the MPDU or MSDU corresponding to the bit position has not been successfully received .
  • the BA information field can be repeatedly configured for each TID.
  • STA 1 is assigned TID '1', '2'
  • STA 2 is assigned TID '3', '4', '5'
  • STA 3 is assigned TID '6'
  • Each BA information field includes a Block Ack Starting Sequence Control subfield and a Block Ack Bitmap subfield.
  • 35 is a diagram illustrating an ACK frame according to an embodiment of the present invention.
  • ACK frames for UL MU data frames of STA 1, STA 2, STA 3 and STA 4 are multiplexed in a frequency domain or a spatial domain and transmitted .
  • the ACK frame transmitted to each STA can be multiplexed according to UL MU transmission. For example, if the UL MU data frame is frequency multiplexed and transmitted, then the ACK frame is also frequency multiplexed and transmitted, and if the UL MU data frame is spatially multiplexed and transmitted, the ACK frame may also be spatially multiplexed and transmitted have.
  • each STA needs to know which resource (i.e., frequency or stream) the ACK frame transmitted to itself is transmitted through.
  • an ACK frame may be transmitted from the same resource as the resource (i.e., frequency or stream) transmitted by each STA to the UL MU data frame. That is, when an ACK frame is frequency-multiplexed and transmitted, an ACK frame can be transmitted in the same frequency domain as the frequency domain in which the UL MU data frame is transmitted from each STA. Likewise, when ACK frames are transmitted in a spatial multiplexing manner, ACK frames can be transmitted in the same stream as the UL MU data frame transmitted from each STA.
  • an ACK frame may be transmitted in a resource different from the resource (i.e., frequency or stream) in which each STA has transmitted the UL MU data frame.
  • the AP transmits resource information (i.e., DL MU OFDMA transmission , And stream information in the case of DL MU MIMO transmission). For example, each STA can be informed via a UL MU scheduling frame.
  • resource information i.e., DL MU OFDMA transmission , And stream information in the case of DL MU MIMO transmission.
  • an ACK frame may be transmitted from resources allocated equally sequentially to each STA. For example, a frequency region in which an ACK frame is transmitted (for example, transmission in an 80 MHz band at 20 MHz for each STA or transmission in a 20 MHz band at 5 MHz for each STA) is predetermined, and each STA The order of the frequency bands through which the ACK frame is transmitted may be determined to be the same as the transmission order of the UL MU data frame. Likewise, a stream area in which an ACK frame is transmitted (for example, four streams, one stream for each STA) is predetermined, and the order of streams in which an ACK frame is transmitted for each STA in the corresponding stream area is UL MU data And can be determined to be the same as the transmission order of the frames.
  • a frequency region in which an ACK frame is transmitted for example, transmission in an 80 MHz band at 20 MHz for each STA or transmission in a 20 MHz band at 5 MHz for each STA
  • the bandwidth of an ACK frame transmitted for each STA may be configured in units of 20 MHz.
  • the bandwidth of ACK frames transmitted for each STA may be configured in units of 20 MHz.
  • the bandwidth for transmitting UL MU data frames is different for each STA, or when each STA transmits UL MU data frames through different streams, the bandwidth of an ACK frame transmitted for each STA is configured in units of 20 MHz It is possible.
  • the STAs participating in the UL MU transmission may be grouped on a certain basis, and one ACK frame may be configured for each STA group.
  • FIG. 35 (b) illustrates a case where a total of eight STAs participating in the UL MU transmission are grouped into four groups of STA 1 and 2, STA 3 and 4, STA 5 and 6, and STA 7 and 8, respectively.
  • the ACK information for the STAs belonging to each group is encoded together to form an ACK frame for each group.
  • An ACK frame may be transmitted in different frequency bands (for example, 20 MHz units) or in different streams.
  • the UL MU data can be grouped by the STA that transmitted the UL MU data in the corresponding 20 MHz band.
  • the UL MU data may be transmitted through different streams in the 20 MHz bandwidth in which the ACK frame is transmitted, or the UL MU data may be transmitted in the 5 MHz or 10 MHz band within the 20 MHz bandwidth in which the ACK frame is transmitted .
  • STA 1 and STA 2 may be the case where UL MU data is transmitted through different streams in the highest 20 MHz band or UL MU data is transmitted through each 10 MHz band in the highest 20 MHz band .
  • grouping may be performed for each STA that transmits UL MU data in the corresponding stream.
  • the UL MU data may be transmitted through different bands in the stream where the ACK frame is transmitted.
  • STA 1 and STA 2 may be the case of transmitting UL MU data through different bands in stream 1.
  • PPDUs that transmit ACK frames for each STA are frequency-multiplexed and transmitted.
  • the MAC format of the ACK frame transmitted to each STA can be the same as that of the existing ACK frame or BA frame, but the structure of the PPDU transmitting the ACK frame can be changed.
  • the MAC format and the PHY format of the existing ACK frame can be used as they are have.
  • the ACK frame is frequency-multiplexed and transmitted in units of 5 MHz in the 20-MHz band, the physical layer characteristics of the existing ACK frame are changed, so that the ACK frame can be transmitted in the same manner as in FIG. 35 (b).
  • an ACK frame can be frequency-multiplexed and transmitted to each STA in units of 5 MHz in the entire 20 MHz band. More specifically, the L-part of the PPDU to which the ACK frame is transmitted is configured in the 20 MHz band as in the conventional case, and the PSDU of each ACK frame is configured in units of 5 MHz. In this case, the MAC frame format of the existing ACK frame can be used equally.
  • the HE-part is not shown, but may be configured in units of 20 MHz or 5 MHz, if necessary, as in the structure of the example of FIGS.
  • all fields may be transmitted in the HE-part, but only some fields (e.g., HE-SIG field) may be transmitted.
  • PPDUs carrying ACK frames for each STA are spatially multiplexed and transmitted.
  • One stream is allocated to each STA, and an ACK frame is spatially multiplexed and transmitted to each STA through the allocated stream.
  • the MAC format of the existing ACK frame can be used equally.
  • the HE-part is not shown, but may be configured in units of 20 MHz as in the case of the example structure shown in Figs. 24 to 28, if necessary.
  • all fields may be transmitted in the HE-part, but only some fields (e.g., HE-SIG field) may be transmitted.
  • the HE-LTF may be included to allow the uplink channel estimation by the number of the entire streams or the number of streams allocated to itself, or may include the number of all streams in the data field or the number of streams allocated to the uplink channel A pilot may be included to enable estimation.
  • 36 is a diagram illustrating an ACK frame transmission method according to an embodiment of the present invention.
  • FIG. 36 (a) illustrates a method of transmitting an ACK frame for UL MU transmission using a BAR frame and a BA frame in DL MU transmission
  • FIG. 36 (b) illustrates an example in which APs sequentially transmit ACK frames or BA Frame is transmitted.
  • xIFS denotes a predetermined time interval (for example, SIFS) at which other signals can not interfere with each other.
  • each STA requests an ACK to an AP in the same manner as a STA that transmitted an UL MU data frame
  • the AP transmits an ACK frame or a BA frame in response thereto.
  • the AP When the first STA requests an AP an ACK frame, the AP sends an ACK frame or a BA frame to the first STA. Similarly, when the second STA and the third STA request an ACK frame to the AP, the AP transmits an ACK frame or a BA frame to the second STA and the third STA.
  • the process by which the first STA requests the AP for the ACK frame may be omitted, assuming that it implicitly indicates in the UL MU data frame transmission
  • a BAR frame may be used to request an ACK frame to the AP, and may have the same structure as the example of FIG. 19.
  • the AP does not transmit the ACK frame to the STA that has not successfully received the UL data frame. Then, the STA corresponding to the next sequence can transmit the BAR frame to the AP if ACK is not received after a predetermined interval. For example, the STA 3 transmits a BAR frame to the AP immediately after the STA 2 transmits the BAR frame and the ACK frame from the AP to the STA 2 is not received after the SIFS.
  • this method is not a method of controlling the procedure of an AP, and thus an error may occur. That is, if the AP does not receive an ACK frame but the next STA fails to receive it, the next STA may immediately send a BAR frame to the AP or the entire procedure may be disrupted if the AP fails to receive the BAR. For example, if an AP transmits an ACK to STA 2 but the STA 3 does not receive the ACK in the next step, it sends a BAR frame to the AP, so that an ACK directed to STA 2 and a BAR frame of STA 3 may collide have.
  • the AP can transmit an ACK frame to each STA at predetermined time intervals (for example, SIFS).
  • predetermined time intervals for example, SIFS
  • the AP can transmit an ACK frame to each STA in the same order as the STA that transmitted the UL MU data frame.
  • the STA can be skipped and the ACK frame can be transmitted to the next STA. For example, if the AP does not receive the data frame transmitted from the STA 2, the AP can transmit the ACK frame to the STA 3 after the SIFS after transmitting the ACK frame to the STA 1.
  • the AP can transmit an ACK frame to each STA regardless of the order of the STA that transmitted the UL MU data frame.
  • an ACK frame or a BA frame includes an RA field, even if an ACK frame is arbitrarily transmitted, it may not be a problem that each STA receives.
  • the STA that has not received the ACK frame may wait for more than a predetermined time interval to distinguish whether it is the last ACK frame or not, and if the signal is not received, the uplink data transmission may be regarded as a failure.
  • the AP may transmit a frame for notifying that transmission of the ACK frame is completed after transmitting the last ACK frame. For example, after the AP transmits all the ACK frames, it can notify each STA through the CF-end frame that the ACK frame transmission is completed.
  • FIG. 37 is a block diagram illustrating a wireless device in accordance with an embodiment of the present invention.
  • an apparatus 3710 may include a processor 3711, a memory 3712, and an RF unit 3713.
  • Apparatus 3710 may be an AP or a non-AP STA for implementing an embodiment in accordance with the present invention.
  • the RF unit 3713 can be connected to the processor 3711 to transmit / receive radio signals.
  • a physical layer according to an IEEE 802.11 system can be implemented.
  • the processor 3711 may be connected to the RF unit 3713 to implement the physical layer and / or the MAC layer according to the IEEE 802.11 system.
  • Processor 3711 may be configured to perform operations in accordance with various embodiments of the invention described above.
  • modules implementing the operations of the AP and / or STA according to various embodiments of the present invention described above may be stored in memory 3712 and executed by processor 3711.
  • the memory 3712 is connected to the processor 3711 and stores various information for driving the processor 3711. [ The memory 3712 may be included inside the processor 3711 or may be installed outside the processor 3711 and connected to the processor 3711 by known means.
  • the device 3710 may have a single antenna or multiple antennas.
  • Embodiments in accordance with 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) 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
  • an embodiment of the present invention may be implemented in the form of a module, a procedure, a function, or the like which performs the functions or operations described above.
  • the software code can be stored in memory and driven by the processor.
  • the memory is located inside or outside the processor and can exchange data with the processor by various means already known.
  • the uplink multi-user transmission scheme has been described with reference to the example applied to the IEEE 802.11 system.
  • the present invention can be applied to various wireless communication systems other than the IEEE 802.11 system.

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Abstract

L'invention concerne un procédé et un dispositif pour transmettre des données multiutilisateur de liaison montante (MU UL) dans un système de communication sans fil, et, plus particulièrement, un procédé pour transmettre des données MU UL dans un système de communication sans fil, le procédé comprenant les étapes suivantes : une station (STA), par l'intermédiaire d'un flux spatial ou d'une bande de fréquences attribuée à partir d'un point d'accès (AP), transmet une trame de données MU UL à l'AP ; et la STA reçoit, à partir de l'AP, une trame d'accusé de réception (ACK) par rapport à la trame de données MU UL, la trame d'ACK comprenant des informations d'ACK concernant une pluralité de STA qui ont réalisé la transmission MU UL et la trame d'ACK pouvant comprendre des informations d'identification pour identifier que la trame d'ACK est une trame d'ACK par rapport à la transmission MU UL.
PCT/KR2015/000865 2014-07-03 2015-01-27 Procédé et dispositif pour transmettre des données multiutilisateur de liaison montante dans un système de communication sans fil WO2016003037A1 (fr)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017179901A1 (fr) * 2016-04-11 2017-10-19 주식회사 윌러스표준기술연구소 Procédé de communication sans fil supportant une transmission en cascade multiutilisateurs et terminal de communication sans fil associé
CN107359960A (zh) * 2016-05-10 2017-11-17 华为技术有限公司 无线帧的发送与接收方法与装置
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