WO2016186310A1

WO2016186310A1 - Method for transmitting data in wireless communication system and device for same

Info

Publication number: WO2016186310A1
Application number: PCT/KR2016/003161
Authority: WO
Inventors: 천진영; 류기선; 김정기; 최진수; 조한규
Original assignee: 엘지전자(주)
Priority date: 2015-05-21
Filing date: 2016-03-28
Publication date: 2016-11-24

Abstract

A method for a station (STA) device for uplink (UL) multi-user (MU) transmission comprising the steps of: receiving a downlink (DL) MU PPDU including a physical preamble and a data field, wherein the data field includes at least one MPDU, wherein the at least one MPDU includes a trigger frame or a MAC header, wherein the trigger frame or the MAC header includes scheduling information for UL MU transmission of an ACK frame; and transmitting, as a reply to the DL MU PPDU, the UL MU PPDU including the ACK frame, based on the scheduling information, wherein the scheduling information may include UL MU PPDU length information and resource allocation information related to a resource unit used for the UL MU transmission of the ACK frame.

Description

Method for transmitting data in wireless communication system and apparatus therefor

The present invention relates to a wireless communication system, and more particularly, to a data transmission method for supporting multi-user ACK frame transmission and an apparatus supporting the same.

Wi-Fi is a Wireless Local Area Network (WLAN) technology that allows devices to access the Internet in the 2.4 GHz, 5 GHz, or 60 GHz frequency bands.

WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. The Wireless Next Generation Standing Committee (WNG SC) of IEEE 802.11 is an ad hoc committee that considers the next generation wireless local area network (WLAN) in the medium to long term.

IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT), which provides up to 600 Mbps data rate, and also supports both transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology using multiple antennas.

As the popularity of WLAN and the applications diversify using it, the next generation WLAN system supporting Very High Throughput (VHT) is the next version of the IEEE 802.11n WLAN system. IEEE 802.11ac supports data processing speeds of 1 Gbps and higher via 80 MHz bandwidth transmission and / or higher bandwidth transmission (eg 160 MHz) and operates primarily in the 5 GHz band.

Recently, there is a need for a new WLAN system to support higher throughput than the data throughput supported by IEEE 802.11ac.

The scope of IEEE 802.11ax, often discussed in the next-generation WLAN task group, also known as IEEE 802.11ax or High Efficiency (HEW) WLAN, includes: 1) 802.11 physical layer and MAC in the 2.4 GHz and 5 GHz bands; (medium access control) layer enhancement, 2) spectral efficiency and area throughput improvement, 3) environments with interference sources, dense heterogeneous network environments, and high user loads. Such as improving performance in real indoor environments and outdoor environments, such as the environment.

Scenarios considered mainly in IEEE 802.11ax are dense environments with many access points (APs) and stations (STAs), and IEEE 802.11ax discusses spectral efficiency and area throughput improvement in such a situation. . In particular, there is an interest in improving the performance of the indoor environment as well as the outdoor environment, which is not much considered in the existing WLAN.

In IEEE 802.11ax, we are interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment. There is a discussion about improving system performance in dense environments with many STAs.

In the future, IEEE 802.11ax improves system performance in outdoor basic service set (OBSS) environment, outdoor environment performance, and cellular offloading rather than single link performance in one basic service set (BSS). Discussion is expected to be active. The directionality of IEEE 802.11ax means that next-generation WLANs will increasingly have a technology range similar to that of mobile communication. Considering the situation where mobile communication and WLAN technology are recently discussed in the small cell and direct-to-direct communication area, the technical and business of next-generation WLAN and mobile communication based on IEEE 802.11ax Convergence is expected to become more active.

An object of the present invention is to propose a method for transmitting / receiving an uplink / downlink multi-user ACK frame in a wireless communication system.

It is also an object of the present invention to propose an efficient signaling method of scheduling information for UL MU transmission of an ACK frame.

It is also an object of the present invention to propose an efficient signaling method of resource allocation information for UL MU transmission of an ACK frame.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In order to solve the above technical problem, an STA apparatus and a data transmission method of the STA apparatus of a WLAN system according to an embodiment of the present invention are proposed.

In a method of transmitting uplink (UL) multi-user (MU) of a STA (Station) device in a wireless LAN (WLAN) system according to an embodiment of the present invention, a physical preamble and data Receiving a downlink (DL) MU Physical Protocol Data Unit (PPDU) including a field; The data field includes at least one Mac Protocol Data Unit (MPDU), wherein the at least one MPDU includes a trigger frame or a MAC header, and the trigger frame or the medium access control (MAC) header is an ACK ( Acknowledgment) comprising the scheduling information for transmitting the UL MU, and transmitting the UL MU PPDU containing the ACK frame as a response to the DL MU PPDU based on the scheduling information; The scheduling information may include resource unit allocation information on a resource unit used for UL MU transmission of the ACK frame and the UL MU PPDU length information.

The scheduling information may further include Modulation and Coding Scheme (MCS) level information applied to the ACK frame and transport channel information of the UL MU PPDU.

The resource allocation information may include a plurality of bits sequentially corresponding to 26 ton resource units allocated for UL MU transmission of the ACK frame, and a bit value of each of the plurality of bits corresponds to a corresponding 26 ton. As the STA to which the resource unit is allocated is changed to another STA, it may be switched to a bit value different from the bit value of the previous bit.

In the transmitting of the UL MU PPDU, when the resource allocation information indicates allocation of a 26-tone resource unit to the STA, the ACK frame using two 13-tone resource units discontinuously located on a frequency axis. It may be a step of transmitting the included UL MU PPDU.

In addition, the resource allocation information includes a plurality of bits sequentially corresponding to the remaining 26-tone resource units except for a specific 26-tone resource unit of the 26-tone resource units allocated for UL MU transmission of the ACK frame, The bit value of each of the plurality of bits may be switched to a bit value different from the bit value of the previous bit as the STA to which the corresponding 26 tone resource unit is allocated is changed to another STA.

The specific 26-tone resource unit is a 26-tone resource unit located in the center of the 20 MHz channel when the transmission channel of the UL MU PPDU is a 20 MHz channel, and 52 ton when the transmission channel of the UL MU PPDU is a 40 MHz channel. A 26-ton resource unit located between resource units or between 106-tone resource units, and when the transmission channel of the UL MU PPDU is an 80 MHz channel, may be a 26-tone resource unit located in the center of the 80 MHz channel.

The resource allocation information may indicate that the specific resource unit is allocated to an STA not indicated by the resource allocation information when the number of STAs indicated by the resource allocation information is smaller than the number of STAs receiving the DL MU PPDU. When the number of STAs indicated by resource allocation information is the same as the number of STAs receiving the DL MU PPDU, the specific resource unit may indicate not-used.

In addition, when a resource allocation method for UL MU transmission is defined in a table for each index, the resource allocation information may include index information corresponding to a specific resource allocation method for UL MU transmission of the ACK frame.

In addition, STA (Station) device of a wireless LAN (WLAN) system according to another embodiment of the present invention, RF unit for transmitting and receiving radio signals; And a processor for controlling the RF unit; And a downlink (DL) MU Physical Protocol Data Unit (PPDU) including a physical preamble and a data field, wherein the data field comprises at least one MPDU (Mac Protocol). Data unit), wherein the at least one MPDU includes a trigger frame or a MAC header, wherein the trigger frame or the medium access control (MAC) header includes scheduling information for UL MU transmission of an acknowledgment (ACK) frame. And a UL MU PPDU including the ACK frame as a response to the DL MU PPDU based on the scheduling information, wherein the scheduling information is used to transmit the UL MU PPDU length information and the UL MU transmission of the ACK frame. Resource unit allocation information about a resource unit used may be included.

In addition, when the resource allocation information instructs the STA to allocate the 26-tone resource unit, the UL MU PPDU including the ACK frame using two 13-tone resource units discontinuously located on a frequency axis. Can be transmitted.

According to an embodiment of the present invention, since a transmission format of an ACK frame is indicated, collisions due to transmission of ACK frames of different formats by STAs can be prevented.

In addition, according to an embodiment of the present invention, since scheduling information for UL MU transmission of an ACK frame is signaled in various ways, there is an effect that an efficient signaling method can be selectively applied according to a situation.

In addition, other effects of the present invention will be further described in the following embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.

1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.

2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.

3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.

4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.

5 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.

FIG. 6 is a diagram illustrating a frame control field in a MAC frame in a wireless communication system to which the present invention can be applied.

7 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention can be applied.

8 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.

9 is a diagram illustrating a downlink multi-user PPDU format in a wireless communication system to which the present invention can be applied.

10 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.

11 is a diagram illustrating an ACK frame in a wireless communication system to which the present invention can be applied.

12 is a diagram illustrating a block ACK request frame in a wireless communication system to which the present invention can be applied.

FIG. 13 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.

14 is a diagram illustrating a block ACK (block Ack) frame in a wireless communication system that can be applied to the present invention.

FIG. 15 is a diagram illustrating a BA Information field of a block ACK frame in a wireless communication system to which the present invention can be applied.

16 illustrates an HE format PPDU according to an embodiment of the present invention.

17 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.

18 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.

19 is a diagram illustrating an uplink multi-user transmission procedure according to an embodiment of the present invention.

20 to 22 are diagrams illustrating resource allocation in an OFDMA multi-user transmission scheme according to an embodiment of the present invention.

FIG. 23 illustrates an UL MU ACK frame for a DL MU frame. FIG.

FIG. 24 (a) is a diagram illustrating an implicit resource allocation scheme, and FIG. 24 (b) is a diagram illustrating an explicit resource allocation scheme.

FIG. 25 (a) is a diagram illustrating a method of allocating UL MU transmission resources of an ACK frame in a subchannel of a predetermined size, and FIG. 25 (b) is an ACK frame in all transport channels of a DL / UL MU PPDU. A diagram illustrating a method of allocating UL MU transmission resources.

FIG. 26A illustrates an ACK frame when MCS level “0” is uniformly applied, and FIG. 26B illustrates uniformly the MCS level “3” (16 QAM modulation and 1/2 code rate). It is a figure which illustrates the ACK frame in case of application.

27 (a) is a diagram illustrating a signaling method of scheduling information according to the first embodiment of the present invention.

27 (b) is a diagram illustrating a signaling method of scheduling information according to a second embodiment of the present invention.

FIG. 27C is a diagram illustrating a signaling method of scheduling information according to a third embodiment of the present invention. FIG.

FIG. 28 (a) is a diagram illustrating an embodiment in which resource allocation information is signaled by a toggle method.

28 (b) is a diagram illustrating a distributed allocation method according to an embodiment of the present invention.

FIG. 28 (c) is a diagram illustrating a resource allocation method according to the preset tone plan of FIG. 20 (c).

29 is a flowchart illustrating a UL MU transmission method of an STA apparatus according to an embodiment of the present invention.

30 is a block diagram of each STA apparatus according to an embodiment of the present invention.

The terminology used herein is a general term that has been widely used as far as possible in consideration of the functions in the present specification, but may vary according to the intention of a person skilled in the art, convention or the emergence of a new technology. In addition, in certain cases, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in the description of the corresponding embodiment. Therefore, it is to be understood that the terminology used herein is to be interpreted based not on the name of the term but on the actual meaning and contents throughout the present specification.

Moreover, although the embodiments will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, the present invention is not limited or restricted to the embodiments.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The following techniques are code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and NOMA It can be used in various radio access systems such as non-orthogonal multiple access. CDMA may be implemented by a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may 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). OFDMA may be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (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, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

For clarity, the following description focuses on IEEE 802.11 systems, but the technical features of the present invention are not limited thereto.

시스템 일반System general

The IEEE 802.11 structure may be composed of a plurality of components, and a wireless communication system supporting a station (STA) station mobility that is transparent to a higher layer may be provided by their interaction. . A basic service set (BSS) may correspond to a basic building block in an IEEE 802.11 system.

In FIG. 1, there are three BSSs (BSS 1 to BSS 3) and two STAs are included as members of each BSS (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are BSS 2. Included in, and STA 5 and STA 6 are included in BSS 3) by way of example.

In FIG. 1, an ellipse representing a BSS may be understood to represent a coverage area where STAs included in the BSS maintain communication. This area may be referred to as a basic service area (BSA). When the STA moves out of the BSA, the STA cannot directly communicate with other STAs in the BSA.

The most basic type of BSS in an IEEE 802.11 system is an independent BSS (IBSS). For example, the IBSS may have a minimal form consisting of only two STAs. In addition, BSS 3 of FIG. 1, which is the simplest form and other components are omitted, may correspond to a representative example of the IBSS. This configuration is possible when STAs can communicate directly. In addition, this type of LAN may not be configured in advance, but may be configured when a LAN is required, which may be referred to as an ad-hoc network.

The membership of the STA in the BSS may be dynamically changed by turning the STA on or off, the STA entering or exiting the BSS region, or the like. In order to become a member of the BSS, the STA may join the BSS using a synchronization process. In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association may be set up dynamically and may include the use of a Distribution System Service (DSS).

The direct STA-to-STA distance in an 802.11 system may be limited by physical layer (PHY) performance. In some cases, this distance limit may be sufficient, but in some cases, communication between STAs over longer distances may be required. A distribution system (DS) may be configured to support extended coverage.

DS refers to a structure in which BSSs are interconnected. Specifically, instead of the BSS independently as shown in FIG. 1, the BSS may exist as an extended type component of a network composed of a plurality of BSSs.

DS is a logical concept and can be specified by the characteristics of the Distribution System Medium (DSM). In this regard, the IEEE 802.11 standard logically distinguishes between wireless medium (WM) and distribution system medium (DSM). Each logical medium is used for a different purpose and is used by different components. The definition of the IEEE 802.11 standard does not limit these media to the same or to different ones. In this way, the plurality of media are logically different, and thus the flexibility of the structure of the IEEE 802.11 system (DS structure or other network structure) can be described. That is, the IEEE 802.11 system structure can be implemented in various ways, the corresponding system structure can be specified independently by the physical characteristics of each implementation.

The DS may support mobile devices by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.

The AP means an entity that enables access to the DS through the WM to the associated STAs and has STA functionality. Data movement between the BSS and the DS may be performed through the AP. For example, STA 2 and STA 3 illustrated in FIG. 1 have a functionality of STA, and provide a function of allowing associated STAs STA 1 and STA 4 to access the DS. In addition, since all APs basically correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM need not necessarily be the same.

Data transmitted from one of the STAs associated with an AP to the STA address of that AP may always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity. In addition, when a controlled port is authenticated, transmission data (or frame) may be transmitted to the DS.

A wireless network of arbitrary size and complexity may be composed of DS and BSSs. In an IEEE 802.11 system, this type of network is referred to as an extended service set (ESS) network. The ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include a DS. The ESS network is characterized by what appears to be an IBSS network at the Logical Link Control (LLC) layer. STAs included in the ESS may communicate with each other, and mobile STAs may move from one BSS to another BSS (within the same ESS) transparently to the LLC.

In the IEEE 802.11 system, nothing is assumed about the relative physical location of the BSSs in FIG. 1, and all of the following forms are possible.

Specifically, BSSs can be partially overlapped, which is the form generally used to provide continuous coverage. Also, the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs. In addition, the BSSs can be located at the same physical location, which can be used to provide redundancy. In addition, one (or more) IBSS or ESS networks may be physically present in the same space as one or more ESS networks. This may be necessary if the ad-hoc network is operating at the location of the ESS network, if the IEEE 802.11 networks are physically overlapped by different organizations, or if two or more different access and security policies are required at the same location. It may correspond to an ESS network type in a case.

In a WLAN system, an STA is a device that operates according to Medium Access Control (MAC) / PHY regulations of IEEE 802.11. As long as the function of the STA is not distinguished from the AP individually, the STA may include an AP STA and a non-AP STA. However, when communication is performed between the STA and the AP, the STA may be understood as a non-AP STA. In the example of FIG. 1, STA 1, STA 4, STA 5, and STA 6 correspond to non-AP STAs, and STA 2 and STA 3 correspond to AP STAs.

Non-AP STAs generally correspond to devices that users directly handle, such as laptop computers and mobile phones. In the following description, a non-AP STA includes a wireless device, a terminal, a user equipment (UE), a mobile station (MS), a mobile terminal, and a wireless terminal. ), A wireless transmit / receive unit (WTRU), a network interface device (network interface device), a machine-type communication (MTC) device, a machine-to-machine (M2M) device, or the like.

In addition, the AP is a base station (BS), Node-B (Node-B), evolved Node-B (eNB), and Base Transceiver System (BTS) in other wireless communication fields. , A concept corresponding to a femto base station (Femto BS).

Hereinafter, in the present specification, downlink (DL) means communication from the AP to the non-AP STA, and uplink (UL) means communication from the non-AP STA to the AP. In downlink, the transmitter may be part of an AP and the receiver may be part of a non-AP STA. In uplink, a transmitter may be part of a non-AP STA and a receiver may be part of an AP.

Referring to FIG. 2, the layer architecture of the IEEE 802.11 system may include a MAC sublayer and a PHY sublayer.

The PHY sublayer may be divided into a Physical Layer Convergence Procedure (PLCP) entity and a Physical Medium Dependent (PMD) entity. In this case, the PLCP entity plays a role of connecting a data frame with a MAC sublayer, and the PMD entity plays a role of wirelessly transmitting and receiving data with two or more STAs.

Both the MAC sublayer and the PHY sublayer may include a management entity, which may be referred to as a MAC sublayer management entity (MLME) and a PHY sublayer management entity (PLME), respectively. have. These management entities provide layer management service interfaces through the operation of layer management functions. The MLME may be connected to the PLME to perform management operations of the MAC sublayer, and likewise the PLME may be connected to the MLME to perform management operations of the PHY sublayer.

In order to provide correct MAC operation, a Station Management Entity (SME) may be present in each STA. The SME is a management entity independent of each layer. The SME collects layer-based state information from MLME and PLME or sets values of specific parameters of each layer. The SME can perform these functions on behalf of general system management entities and implement standard management protocols.

MLME, PLME and SME can interact in a variety of ways based on primitives. Specifically, the XX-GET.request primitive is used to request the value of a Management Information Base attribute (MIB attribute), and the XX-GET.confirm primitive, if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with an error indication in the status field. The XX-SET.request primitive is used to request that a specified MIB attribute be set to a given value. If the MIB attribute is meant for a particular action, this request requests the execution of that particular action. And, if the state is 'SUCCESS' XX-SET.confirm primitive, it means that the specified MIB attribute is set to the requested value. In other cases, the status field indicates an error condition. If this MIB attribute means a specific operation, this primitive can confirm that the operation was performed.

The operation in each sublayer is briefly described as follows.

The MAC sublayer includes a MAC header and a frame check sequence (FCS) in a MAC Service Data Unit (MSDU) or a fragment of an MSDU received from an upper layer (eg, an LLC layer). A sequence is attached to generate one or more MAC Protocol Data Units (MPDUs). The generated MPDU is delivered to the PHY sublayer.

When an aggregated MSDU (A-MSDU) scheme is used, a plurality of MSDUs may be merged into a single A-MSDU (aggregated MSDU). The MSDU merging operation may be performed at the MAC upper layer. The A-MSDU is delivered to the PHY sublayer as a single MPDU (if not fragmented).

The PHY sublayer generates a physical protocol data unit (PPDU) by adding an additional field including information required by a physical layer transceiver to a physical service data unit (PSDU) received from the MAC sublayer. . PPDUs are transmitted over wireless media.

The PSDU is substantially the same as the MPDU since the PHY sublayer is received from the MAC sublayer and the MPDU is transmitted by the MAC sublayer to the PHY sublayer.

When an aggregated MPDU (A-MPDU) scheme is used, a plurality of MPDUs (where each MPDU may carry an A-MSDU) may be merged into a single A-MPDU. The MPDU merging operation may be performed at the MAC lower layer. A-MPDUs may be merged with various types of MPDUs (eg, QoS data, Acknowledge (ACK), Block ACK (BlockAck), etc.). The PHY sublayer receives the A-MPDU as a single PSDU from the MAC sublayer. That is, the PSDU is composed of a plurality of MPDUs. Thus, A-MPDUs are transmitted over the wireless medium in a single PPDU.

PPDUPPDU (Physical Protocol Data Unit) 포맷Physical Protocol Data Unit Format

Physical Protocol Data Unit (PPDU) refers to a block of data generated at the physical layer. Hereinafter, a PPDU format will be described based on an IEEE 802.11 WLAN system to which the present invention can be applied.

3A illustrates a non-HT format PPDU for supporting an IEEE 802.11a / g system. Non-HT PPDUs may also be referred to as legacy PPDUs.

Referring to (a) of FIG. 3, the non-HT format PPDU includes an L-STF (Legacy (or Non-HT) Short Training field), L-LTF (Legacy (or, Non-HT) Long Training field) and It is configured to include a legacy format preamble (or legacy preamble) and a data field composed of an L-SIG (Legacy (or Non-HT) SIGNAL) field.

The L-STF may include a short training orthogonal frequency division multiplexing symbol (OFDM). L-STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. .

The L-LTF may include a long training orthogonal frequency division multiplexing symbol. L-LTF may be used for fine frequency / time synchronization and channel estimation.

The L-SIG field may be used to transmit control information for demodulation and decoding of the data field.

The L-SIG field consists of a 4-bit Rate field, 1-bit Reserved bit, 12-bit Length field, 1-bit parity bit, and 6-bit Signal Tail field. Can be.

The rate field contains rate information, and the length field indicates the number of octets of the PSDU.

3B illustrates an HT-mixed format PPDU (HTDU) for supporting both an IEEE 802.11n system and an IEEE 802.11a / g system.

Referring to FIG. 3B, the HT mixed format PPDU includes a legacy format preamble including an L-STF, L-LTF, and L-SIG fields, an HT-SIG (HT-Signal) field, and an HT-STF (HT Short). Training field), HT-formatted preamble and data field including HT-LTF (HT Long Training field).

Since the L-STF, L-LTF, and L-SIG fields mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields. Even if the L-STA receives the HT mixed PPDU, the L-STA may interpret the data field through the L-LTF, L-LTF and L-SIG fields. However, the L-LTF may further include information for channel estimation that the HT-STA performs to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.

The HT-STA may know that it is an HT-mixed format PPDU using the HT-SIG field following the legacy field, and may decode the data field based on the HT-STA.

The HT-LTF field may be used for channel estimation for demodulation of the data field. Since IEEE 802.11n supports Single-User Multi-Input and Multi-Output (SU-MIMO), a plurality of HT-LTF fields may be configured for channel estimation for each data field transmitted in a plurality of spatial streams.

The HT-LTF field includes data HT-LTF used for channel estimation for spatial streams and extension HT-LTF (additional used for full channel sounding). It can be configured as. Accordingly, the plurality of HT-LTFs may be equal to or greater than the number of spatial streams transmitted.

In the HT-mixed format PPDU, the L-STF, L-LTF, and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the HT-SIG field is transmitted for demodulation and decoding of data transmitted for the HT-STA.

The HT-SIG field is transmitted without performing beamforming so that the L-STA and HT-STA can receive the corresponding PPDU to acquire data, and then the HT-STF, HT-LTF and data fields transmitted are precoded. Wireless signal transmission is performed through. In this case, the HT-STF field is transmitted to allow the STA to perform precoding to take into account the variable power due to precoding, and then the plurality of HT-LTF and data fields after that.

Table 1 below is a table illustrating the HT-SIG field.

3 (c) illustrates an HT-GF format PPDU (HT-GF) for supporting only an IEEE 802.11n system.

Referring to FIG. 3C, the HT-GF format PPDU includes HT-GF-STF, HT-LTF1, HT-SIG field, a plurality of HT-LTF2 and data fields.

HT-GF-STF is used for frame timing acquisition and AGC.

HT-LTF1 is used for channel estimation.

The HT-SIG field is used for demodulation and decoding of the data field.

HT-LTF2 is used for channel estimation for demodulation of data fields. Similarly, since HT-STA uses SU-MIMO, channel estimation is required for each data field transmitted in a plurality of spatial streams, and thus HT-LTF2 may be configured in plural.

The plurality of HT-LTF2 may be configured of a plurality of Data HT-LTF and a plurality of extended HT-LTF similarly to the HT-LTF field of the HT mixed PPDU.

In (a) to (c) of FIG. 3, the data field is a payload, and includes a service field, a SERVICE field, a scrambled PSDU field, tail bits, and padding bits. It may include. All bits of the data field are scrambled.

3 (d) shows a service field included in a data field. The service field has 16 bits. Each bit is assigned from 0 to 15, and transmitted sequentially from bit 0. Bits 0 to 6 are set to 0 and used to synchronize the descrambler in the receiver.

The IEEE 802.11ac WLAN system supports downlink multi-user multiple input multiple output (MU-MIMO) transmission in which a plurality of STAs simultaneously access a channel in order to efficiently use a wireless channel. According to the MU-MIMO transmission scheme, the AP may simultaneously transmit packets to one or more STAs that are paired with MIMO.

DL MU transmission (downlink multi-user transmission) refers to a technology in which an AP transmits a PPDU to a plurality of non-AP STAs through the same time resource through one or more antennas.

Hereinafter, the MU PPDU refers to a PPDU that delivers one or more PSDUs for one or more STAs using MU-MIMO technology or OFDMA technology. The SU PPDU means a PPDU having a format in which only one PSDU can be delivered or in which no PSDU exists.

The size of control information transmitted to the STA may be relatively large compared to the size of 802.11n control information for MU-MIMO transmission. An example of control information additionally required for MU-MIMO support includes information indicating the number of spatial streams received by each STA, information related to modulation and coding of data transmitted to each STA, and the like. Can be.

Therefore, when MU-MIMO transmission is performed to simultaneously provide data services to a plurality of STAs, the size of transmitted control information may be increased according to the number of receiving STAs.

In order to efficiently transmit the increased size of the control information, a plurality of control information required for MU-MIMO transmission is required separately for common control information common to all STAs and specific STAs. The data may be transmitted by being divided into two types of information of dedicated control information.

4 (a) illustrates a VHT format PPDU (VHT format PPDU) for supporting an IEEE 802.11ac system.

Referring to FIG. 4A, a VHT format PPDU includes a legacy format preamble including a L-STF, L-LTF, and L-SIG fields, a VHT-SIG-A (VHT-Signal-A) field, and a VHT-STF ( A VHT format preamble and a data field including a VHT Short Training field (VHT-LTF), a VHT Long Training field (VHT-LTF), and a VHT-SIG-B (VHT-Signal-B) field.

Since L-STF, L-LTF, and L-SIG mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields. However, the L-LTF may further include information for channel estimation to be performed to demodulate the L-SIG field and the VHT-SIG-A field.

The L-STF, L-LTF, L-SIG field, and VHT-SIG-A field may be repeatedly transmitted in 20 MHz channel units. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field are repeatedly transmitted on every 20 MHz channel. Can be.

The VHT-STA may know that it is a VHT format PPDU using the VHT-SIG-A field following the legacy field, and may decode the data field based on the VHT-STA.

In the VHT format PPDU, the L-STF, L-LTF and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the VHT-SIG-A field is transmitted for demodulation and decoding of data transmitted for the VHT-STA.

The VHT-SIG-A field is a field for transmitting control information common to the AP and the MIMO paired VHT STAs, and includes control information for interpreting the received VHT format PPDU.

The VHT-SIG-A field may include a VHT-SIG-A1 field and a VHT-SIG-A2 field.

The VHT-SIG-A1 field includes information on channel bandwidth (BW) used, whether space time block coding (STBC) is applied, and group identification information for indicating a group of STAs grouped in MU-MIMO. Group ID (Group Identifier), information about the number of space-time streams (NSTS) / Partial AID (Partial Association Identifier) and Transmit power save forbidden information. can do. Here, the Group ID means an identifier assigned to the STA group to be transmitted to support MU-MIMO transmission, and may indicate whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.

Table 2 is a table illustrating the VHT-SIG-A1 field.

The VHT-SIG-A2 field contains information on whether a short guard interval (GI) is used, forward error correction (FEC) information, information on modulation and coding scheme (MCS) for a single user, and multiple information. Information on the type of channel coding for the user, beamforming-related information, redundancy bits for cyclic redundancy checking (CRC), tail bits of convolutional decoder, and the like. Can be.

Table 3 is a table illustrating the VHT-SIG-A2 field.

VHT-STF is used to improve the performance of AGC estimation in MIMO transmission.

VHT-LTF is used by the VHT-STA to estimate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF may be set as many as the number of spatial streams in which a PPDU is transmitted. In addition, if full channel sounding is supported, the number of VHT-LTFs may be greater.

The VHT-SIG-B field includes dedicated control information required for a plurality of MU-MIMO paired VHT-STAs to receive a PPDU and acquire data. Therefore, the VHT-STA decodes the VHT-SIG-B field only when common control information included in the VHT-SIG-A field indicates that the currently received PPDU indicates MU-MIMO transmission. It may be designed to. On the other hand, if the common control information indicates that the currently received PPDU is for a single VHT-STA (including SU-MIMO), the STA may be designed not to decode the VHT-SIG-B field.

The VHT-SIG-B field includes a VHT-SIG-B length field, a VHT-MCS field, a reserved field, and a tail field.

The VHT-SIG-B Length field indicates the length of the A-MPDU (before end-of-frame padding). The VHT-MCS field includes information on modulation, encoding, and rate-matching of each VHT-STA.

The size of the VHT-SIG-B field may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.

4 (b) illustrates the VHT-SIG-B field according to the PPDU transmission bandwidth.

Referring to FIG. 4B, in the 40 MHz transmission, the VHT-SIG-B bits are repeated twice. For an 80 MHz transmission, the VHT-SIG-B bits are repeated four times and pad bits set to zero are attached.

For 160 MHz transmission and 80 + 80 MHz, first the VHT-SIG-B bits are repeated four times, as with the 80 MHz transmission, and pad bits set to zero are attached. Then, all 117 bits are repeated again.

In order to transmit a PPDU of the same size to STAs paired to an AP in a system supporting MU-MIMO, information indicating a bit size of a data field constituting the PPDU and / or indicating a bit stream size constituting a specific field May be included in the VHT-SIG-A field.

However, the L-SIG field may be used to effectively use the PPDU format. In order to transmit the same size PPDU to all STAs, a length field and a rate field included in the L-SIG field and transmitted may be used to provide necessary information. In this case, since the MAC Protocol Data Unit (MPDU) and / or Aggregate MAC Protocol Data Unit (A-MPDU) are set based on the bytes (or octets) of the MAC layer, additional padding is applied at the physical layer. May be required.

In FIG. 4, the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.

Since the formats of various PPDUs are mixed and used as described above, the STA must be able to distinguish the formats of the received PPDUs.

Here, the meaning of distinguishing a PPDU (or meaning of distinguishing a PPDU format) may have various meanings. For example, the meaning of identifying the PPDU may include determining whether the received PPDU is a PPDU that can be decoded (or interpreted) by the STA. In addition, the meaning of distinguishing the PPDU may mean determining whether the received PPDU is a PPDU supported by the STA. In addition, the meaning of distinguishing the PPDU may also be interpreted to mean what information is transmitted through the received PPDU.

MAC 프레임 포맷MAC frame format

Referring to FIG. 5, a MAC frame (ie, an MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).

MAC Header includes Frame Control field, Duration / ID field, Address 1 field, Address 2 field, Address 3 field, Sequence control It is defined as an area including a Control field, an Address 4 field, a QoS Control field, and an HT Control field.

The Frame Control field includes information on the MAC frame characteristic. A detailed description of the Frame Control field will be given later.

The Duration / ID field may be implemented to have different values depending on the type and subtype of the corresponding MAC frame.

If the type and subtype of the corresponding MAC frame is a PS-Poll frame for power save (PS) operation, the Duration / ID field is an AID (association identifier) of the STA that transmitted the frame. It may be set to include. Otherwise, the Duration / ID field may be set to have a specific duration value according to the type and subtype of the corresponding MAC frame. In addition, when the frame is an MPDU included in an A-MPDU format, the Duration / ID fields included in the MAC header may be set to have the same value.

The Address 1 to Address 4 fields include a BSSID, a source address (SA), a destination address (DA), a transmission address (TA) indicating a transmission STA address, and a reception address indicating a destination STA address (TA). RA: It is used to indicate Receiving Address.

Meanwhile, the address field implemented as a TA field may be set to a bandwidth signaling TA value, in which case, the TA field may indicate that the corresponding MAC frame contains additional information in the scrambling sequence. The bandwidth signaling TA may be represented by the MAC address of the STA transmitting the corresponding MAC frame, but the Individual / Group bit included in the MAC address may be set to a specific value (for example, '1'). Can be.

The Sequence Control field is set to include a sequence number and a fragment number. The sequence number may indicate a sequence number allocated to the corresponding MAC frame. The fragment number may indicate the number of each fragment of the corresponding MAC frame.

The QoS Control field contains information related to QoS. The QoS Control field may be included when indicating a QoS data frame in a subtype subfield.

The HT Control field includes control information related to the HT and / or VHT transmission / reception schemes. The HT Control field is included in the Control Wrapper frame. In addition, it exists in the QoS data frame and the management frame in which the order subfield value is 1.

The frame body is defined as a MAC payload, and data to be transmitted in a higher layer is located, and has a variable size. For example, 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 are present in every frame. Other fields may exist only in a specific frame type.

Referring to FIG. 6, the Frame Control field includes a Protocol Version subfield, a Type subfield, a Subtype subfield, a To DS subfield, a From DS subfield, and more fragments. A subfield, 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 corresponding MAC frame.

The Type subfield and the Subtype subfield may be set to indicate information for identifying a function of a corresponding MAC frame.

The type of the MAC frame may include three frame types: a management frame, a control frame, and a data frame.

Each frame type may be further divided into subtypes.

For example, control frames include request to send (RTS) frames, clear-to-send (CTS) frames, acknowledgment (ACK) frames, PS-Poll frames, content free (End) frames, CF End + CF-ACK frame, Block Acknowledgment request (BAR) frame, Block Acknowledgment (BA) frame, Control Wrapper (Control + HTcontrol) frame, VHT null data packet notification (NDPA) It may include a Null Data Packet Announcement and a Beamforming Report Poll frame.

Management frames include beacon frames, announcement traffic indication message (ATIM) frames, disassociation frames, association request / response frames, reassociation requests / responses Response frame, Probe Request / Response frame, Authentication frame, Deauthentication frame, Action frame, Action No ACK frame, Timing Advertisement It may include a frame.

The To DS subfield and the From DS subfield may include information necessary to interpret the Address 1 field or the Address 4 field included in the corresponding MAC frame header. In the case of a control frame, both the To DS subfield and the From DS subfield are set to '0'. For a Management frame, the To DS subfield and the From DS subfield are set to '1' and '0' in order if the frame is a QoS Management frame (QMF), and in order if the frame is not QMF. Both can be set to '0', '0'.

The More Fragments subfield may indicate whether there is a fragment to be transmitted following the corresponding MAC frame. If there is another fragment of the current MSDU or MMPDU, it may be set to '1', otherwise it may be set to '0'.

The Retry subfield may indicate whether the corresponding MAC frame is due to retransmission of a previous MAC frame. In case of retransmission of the previous MAC frame, it may be set to '1', otherwise it may be set to '0'.

The power management subfield may indicate a power management mode of the STA. If the value of the Power Management subfield is '1', the STA may indicate switching to the power save mode.

The More Data subfield may indicate whether there is an additional MAC frame to be transmitted. If there is an additional MAC frame to be transmitted, it may be set to '1', otherwise it may be set to '0'.

The Protected Frame subfield may indicate whether the frame body field is encrypted. If the Frame Body field includes information processed by the encryption encapsulation algorithm, it may be set to '1', otherwise it may be set to '0'.

Information included in each field described above may follow the definition of the IEEE 802.11 system. In addition, each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.

Referring to FIG. 7, the HT Control field includes a VHT subfield, an HT Control Middle subfield, an AC Constraint subfield, and a Reverse Direction Grant (RDG) / More PPDU (More PPDU). It may consist of subfields.

The VHT subfield indicates whether the HT Control field has the format of the HT Control field for the VHT (VHT = 1) or has the format of the HT Control field for the HT (VHT = 0). The HT Control field for the VHT may be referred to as a VHT Control field.

The HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield. A more detailed description of the HT Control Middle subfield will be given later.

The AC Constraint subfield indicates whether a mapped AC (Access Category) of a reverse direction (RD) data frame is limited to a single AC.

The RDG / More PPDU subfield may be interpreted differently depending on whether the corresponding field is transmitted by the RD initiator or the RD responder.

When transmitted by the RD initiator, the RDG / More PPDU field is set to '1' if the RDG exists, and set to '0' if the RDG does not exist. When 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 set to '0' when another PPDU is transmitted.

As described above, the HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield.

The HT Control Middle subfield of the HT Control field for VHT includes a reserved bit, a Modulation and Coding Scheme feedback request (MRQ) subfield, and an MRQ Sequence Identifier (MSI). Space-time block coding (STBC) subfield, MCS feedback sequence identifier (MFSI) / Least Significant Bit (LSB) of Group ID (LSB) subfield, MCS Feedback (MFB) Subfield, Group ID Most Significant Bit (MSB) of Group ID (MSB) Subfield, Coding Type Subfield, Feedback Transmission Type (FB Tx Type: Feedback transmission type) subfield and a voluntary MFB (Unsolicited MFB) subfield.

Table 4 shows a description of each subfield included in the HT Control Middle subfield of the VHT format.

In addition, the MFB subfield may include a VHT number of space time streams (NUM_STS) subfield, a VHT-MCS subfield, a bandwidth (BW) subfield, and a signal to noise ratio (SNR). It may include subfields.

The NUM_STS subfield indicates the number of recommended spatial streams. The VHT-MCS subfield indicates a recommended MCS. The BW subfield indicates bandwidth information related to the recommended MCS. The SNR subfield indicates the average SNR value on the data subcarrier and spatial stream.

하향링크 MU-Downlink MU- MIMOMIMO 프레임(DL MU- Frame (DL MU- MIMOMIMO Frame) Frame)

Referring to FIG. 8, a PPDU includes a physical preamble and a data field. The data field may include a service field, a scrambled PSDU field, tail bits, and padding bits.

The AP may aggregate the MPDUs and transmit a data frame in an A-MPDU (aggregated MPDU) format. In this case, the scrambled PSDU field may be configured as an A-MPDU.

An A-MPDU consists of a sequence of one or more A-MPDU subframes.

For the VHT PPDU, since the length of each A-MPDU subframe is a multiple of four octets, the A-MPDU is zero after the last A-MPDU subframe to fit the A-MPDU to the last octet of the PSDU. And three to three octets of an end-of-frame (EOF) pad.

The A-MPDU subframe consists of an MPDU delimiter, and optionally an MPDU may be included after the MPDU delimiter. In addition, except for the last A-MPDU subframe in one A-MPDU, a pad octet is attached after the MPDU to make the length of each A-MPDU subframe a multiple of 4 octets.

The MPDU Delimiter is composed of a Reserved field, an MPDU Length field, a cyclic redundancy check (CRC) field, and a delimiter signature field.

In the case of a VHT PPDU, the MPDU Delimiter may further include an end-of-frame (EOF) field. If the MPDU Length field is 0 and the A-MPDU subframe used for padding or the A-MPDU subframe carrying the MPDU when the A-MPDU consists of only one MPDU, the EOF field is set to '1'. do. Otherwise it is set to '0'.

The MPDU Length field contains information about the length of the MPDU.

If the MPDU does not exist in the corresponding A-MPDU subframe, it is set to '0'. An A-MPDU subframe whose MPDU Length field has a value of '0' is used when padding the corresponding A-MPDU to match the A-MPDU to the octets available in the VHT PPDU.

The CRC field includes CRC information for error checking, and the Delimiter Signature field includes pattern information used to search for an MPDU delimiter.

The MPDU is composed of a MAC header, a frame body, and a frame check sequence (FCS).

9 assumes that the number of STAs receiving the PPDU is three and the number of spatial streams allocated to each STA is 1, but the number of STAs paired to the AP and the number of spatial streams allocated to each STA are shown in FIG. Is not limited to this.

9, the MU PPDU includes an L-TFs field (L-STF field and L-LTF field), an L-SIG field, a VHT-SIG-A field, a VHT-TFs field (VHT-STF field and VHT-LTF). Field), VHT-SIG-B field, Service field, one or more PSDU, padding field, and Tail bit. Since the L-TFs field, the L-SIG field, the VHT-SIG-A field, the VHT-TFs field, and the VHT-SIG-B field are the same as in the example of FIG. 4, detailed descriptions thereof will be omitted.

Information for indicating the duration of the PPDU may be included in the L-SIG field. Within the PPDU, the PPDU duration indicated by the L-SIG field is the symbol assigned to the VHT-SIG-A field, the symbol assigned to the VHT-TFs field, the field assigned to the VHT-SIG-B field, and the Service field. And bits constituting the bits, bits constituting the PSDU, bits constituting the padding field, and bits constituting the Tail field. The STA receiving the PPDU may obtain information about the duration of the PPDU through the information indicating the duration of the PPDU included in the L-SIG field.

As described above, Group ID information and space-time stream number information per user are transmitted through the VHT-SIG-A, and a coding method and MCS information are transmitted through the VHT-SIG-B. Accordingly, the beamformees may check the VHT-SIG-A and the VHT-SIG-B, and may know whether the beamformees belong to the MU MIMO frame. Therefore, the STA that is not a member STA of the corresponding Group ID or the member of the corresponding Group ID or the number of allocated streams is '0' reduces power consumption by setting to stop receiving the physical layer from the VHT-SIG-A field to the end of the PPDU. can do.

The Group ID can receive the Group ID Management frame transmitted by the Beamformer in advance, so that the MU group belonging to the Beamformee and the user of the group to which the Beamformee belongs, that is, the stream through which the PPDU is received.

All MPDUs transmitted in the VHT MU PPDU based on 802.11ac are included in the A-MPDU. In the data field of FIG. 18, each VHT A-MPDU may be transmitted in a different stream.

In FIG. 9, since the size of data transmitted to each STA may be different, each A-MPDU may have a different bit size.

In this case, null padding may be performed such that the time when the transmission of the plurality of data frames transmitted by the beamformer is the same as the time when the transmission of the maximum interval transmission data frame is terminated. The maximum interval transmission data frame may be a frame in which valid downlink data is transmitted by the beamformer for the longest period. The valid downlink data may be downlink data that is not null padded. For example, valid downlink data may be included in the A-MPDU and transmitted. Null padding may be performed on the remaining data frames except the maximum interval transmission data frame among the plurality of data frames.

For null padding, the beamformer may encode and fill one or more A-MPDU subframes located in temporal order in the plurality of A-MPDU subframes in the A-MPDU frame with only the MPDU delimiter field. An A-MPDU subframe having an MPDU length of 0 may be referred to as a null subframe.

As described above, in the null subframe, the EOF field of the MPDU Delimiter is set to '1'. Accordingly, when the MAC layer of the receiving STA detects the EOF field set to 1, power consumption may be reduced by setting the physical layer to stop reception.

블록 block ACKACK (Block (Block AckAck ) 절차) step

In 802.11ac, MU-MIMO is defined in downlink from the AP to the client (ie, non-AP STA). In this case, a multi-user frame is simultaneously transmitted to multiple receivers, but acknowledgments should be transmitted separately in the uplink.

Since all MPDUs transmitted in the VHT MU PPDU based on 802.11ac are included in the A-MPDU, the response to the A-MPDU in the VHT MU PPDU, rather than the immediate response to the VHT MU PPDU, is a block ACK request by the AP (BAR). : Block Ack Request) is sent in response to a frame.

First, the AP transmits a VHT MU PPDU (ie, physical preamble and data) to all receivers (ie, STA 1, STA 2, and STA 3). The VHT MU PPDU includes a VHT A-MPDU transmitted to each STA.

Receiving a VHT MU PPDU from the AP, STA 1 transmits a block acknowledgment (BA) frame to the AP after SIFS. The BA frame will be described later in more detail.

After receiving the BA from the STA 1, the AP transmits a block acknowledgment request (BAR) frame to the next STA 2 after SIFS, and the STA 2 transmits a BA frame to the AP after SIFS. The AP receiving the BA frame from STA 2 transmits the BAR frame to STA 3 after SIFS, and STA 3 transmits the BA frame to AP after SIFS.

If this process is performed for all STAs, the AP transmits the next MU PPDU to all STAs.

ACKACK (Acknowledgement)/블록 (Acknowledgement) / block ACKACK (Block (Block ACKACK ) 프레임) frame

In general, an ACK frame is used as a response to the MPDU, and a block ACK frame is used as a response to the A-MPDU.

Referring to FIG. 11, an ACK frame is composed of a frame control field, a duration field, an RA field, and an FCS.

The RA field may be a second address field of a data frame, a management frame, a block ACK request frame, a block ACK frame, or a PS-Poll frame received immediately before. It is set to the value of.

When the ACK frame is transmitted by the non-QoS STA, the More Fragments subfield in the Frame Control field of the data frame or management frame received immediately before If '0', the duration value is set to '0'.

In an ACK frame that is not transmitted by a non-QoS STA, the duration value may include a data frame, a management frame, a block ACK request frame, a block received immediately before. In the Duration / ID field of the ACK (Block Ack) frame or the PS-Poll frame, the time required for transmitting the ACK frame and the SIFS interval are set to a value (ms). If the calculated duration value is not an integer value, it is rounded up.

Hereinafter, a block ACK (request) frame will be described.

Referring to FIG. 12, a block ACK request (BAR) frame includes a frame control field, a duration / ID field, a reception address field, a transmission address field, a BAR control ( BAR control field, BAR information field and frame check sequence (FCS).

The RA field may be set to the address of the STA that receives the BAR frame.

The TA field may be set to an address of an STA that transmits a BAR frame.

The BAR control field includes a BAR Ack Policy subfield, a Multi-TID subfield, a Compressed Bitmap subfield, a Reserved subfield, and a TID Information (TID_Info) subfield. It includes.

Table 5 is a table illustrating a BAR control field.

The BAR Information field contains different information according to the type of the BAR frame. This will be described with reference to FIG. 13.

FIG. 13A illustrates a BAR Information field of a Basic BAR frame and a Compressed BAR frame, and FIG. 13B illustrates a BAR Information field of a Multi-TID BAR frame.

Referring to FIG. 13A, in the case of a Basic BAR frame and a Compressed BAR frame, the BAR Information field includes a Block Ack Starting Sequence Control subfield.

The Block Ack Starting Sequence Control subfield includes a fragment number subfield and a starting sequence number subfield.

The Fragment Number subfield is set to zero.

In the case of a Basic BAR frame, the Starting Sequence Number subfield includes the sequence number of the first MSDU in which the corresponding BAR frame is transmitted. In the case of a compressed BAR frame, the Starting Sequence Control subfield includes the sequence number of the first MSDU or A-MSDU for which the corresponding BAR frame is to be transmitted.

Referring to FIG. 13 (b), in the case of a Multi-TID BAR frame, the BAR Information field may include a TID Info subfield and a Block Ack Starting Sequence Control subfield. Stars are repeated.

The Per TID Info subfield includes a reserved subfield and a TID value subfield. The TID Value subfield contains a TID value.

The Block Ack Starting Sequence Control subfield includes the Fragment Number and Starting Sequence Number subfields as described above. The Fragment Number subfield is set to zero. The Starting Sequence Control subfield includes the sequence number of the first MSDU or A-MSDU for which the corresponding BAR frame is to be transmitted.

Referring to FIG. 14, a block ACK (BA) frame includes a frame control field, a duration / ID field, a reception address field, a transmission address field, and a BA control BA. control field, BA Information field, and frame check sequence (FCS).

The RA field may be set to the address of the STA requesting the block ACK.

The TA field may be set to an address of an STA that transmits a BA frame.

The BA control field includes a BA Ack Policy subfield, a Multi-TID subfield, a Compressed Bitmap subfield, a Reserved subfield, and a TID Information (TID_Info) subfield. It includes.

Table 6 is a table illustrating a BA control field.

The BA Information field includes different information according to the type of the BA frame. This will be described with reference to FIG. 15.

15 (a) illustrates a BA Information field of a Basic BA frame, FIG. 15 (b) illustrates a BA Information field of a Compressed BA frame, and FIG. 15 (c) illustrates a BA Information field of a Multi-TID BA frame. To illustrate.

Referring to FIG. 15 (a), in the case of a Basic BA frame, the BA Information field includes a Block Ack Starting Sequence Control subfield and a Block ACK Bitmap subfield.

The Block Ack Starting Sequence Control subfield includes a Fragment Number subfield and a Starting Sequence Number subfield as described above.

The Fragment Number subfield is set to zero.

The Starting Sequence Number subfield includes the sequence number of the first MSDU for transmitting the corresponding BA frame and is set to the same value as the Basic BAR frame received immediately before.

The Block Ack Bitmap subfield consists of 128 octets and is used to indicate the reception status of up to 64 MSDUs. A value of '1' in the Block Ack Bitmap subfield indicates that the MPDU corresponding to the corresponding bit position was successfully received, and a value of '0' indicates that the MPDU corresponding to the corresponding bit position was not successfully received.

Referring to FIG. 15B, in the case of a compressed BA frame, the BA Information field includes a block ACK starting sequence control subfield and a block ACK bitmap subfield.

The Fragment Number subfield is set to zero.

The Starting Sequence Number subfield includes the sequence number of the first MSDU or A-MSDU for transmitting the corresponding BA frame, and is set to the same value as the Basic BAR frame received immediately before.

The Block Ack Bitmap subfield is 8 octets long and is used to indicate the reception status of up to 64 MSDUs and A-MSDUs. A value of '1' in the Block Ack Bitmap subfield indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successfully received. A value of '0' indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successful. Indicates that it has not been received.

Referring to FIG. 15 (c), in the case of a Multi-TID BA frame, the BA Information field includes a TID Info subfield, a Block Ack Starting Sequence Control subfield, and a block ACK bit. The Block Ack Bitmap subfield is repeatedly configured for one or more TIDs, and is configured in the order of increasing TIDs.

The Block Ack Starting Sequence Control subfield includes the Fragment Number and Starting Sequence Number subfields as described above. The Fragment Number subfield is set to zero. The Starting Sequence Control subfield contains the sequence number of the first MSDU or A-MSDU for which the corresponding BA frame is to be transmitted.

The Block Ack Bitmap subfield consists of 8 octets in length. A value of '1' in the Block Ack Bitmap subfield indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successfully received. A value of '0' indicates that a single MSDU or A-MSDU corresponding to the corresponding bit position was successful. Indicates that it has not been received.

상향링크 다중 사용자 전송 방법Uplink multi-user transmission method

New frames for next-generation WLAN systems, 802.11ax systems, with increasing attention from vendors in various fields for next-generation WiFi and increased demand for high throughput and quality of experience (QoE) after 802.11ac. There is an active discussion of format and numerology.

IEEE 802.11ax is a next-generation WLAN system that supports higher data rates and handles higher user loads. One of the recently proposed WLAN systems is known as high efficiency WLAN (HEW: High). Called Efficiency WLAN).

The IEEE 802.11ax WLAN system may operate in the 2.4 GHz frequency band and the 5 GHz frequency band like the existing WLAN system. It can also operate at higher 60 GHz frequency bands.

In IEEE 802.11ax system, the existing IEEE 802.11 OFDM system (IEEE 802.11a, 802.11n) is used for outdoor throughput transmission for average throughput enhancement and inter-symbol interference in outdoor environment. , 4x larger FFT size for each bandwidth than 802.11ac. This will be described with reference to the drawings below.

Hereinafter, in the description of the HE format PPDU in the present invention, the description of the non-HT format PPDU, the HT-mixed format PPDU, the HT-greenfield format PPDU, and / or the VHT format PPDU described above will be described in HE format unless otherwise noted. May be incorporated into the description of the PPDU.

FIG. 16 illustrates a PPDU format when 80 MHz is allocated to one STA (or OFDMA resource units are allocated to a plurality of STAs within 80 MHz) or when different streams of 80 MHz are allocated to a plurality of STAs.

Referring to FIG. 16, L-STF, L-LTF, and L-SIG may be transmitted as OFDM symbols generated based on 64 FFT points (or 64 subcarriers) in each 20MHz channel.

The HE-SIG A field may include common control information that is commonly transmitted to STAs that receive a PPDU. The HE-SIG A field may be transmitted in one to three OFDM symbols. The HE-SIG A field is copied in units of 20 MHz and includes the same information. In addition, the HE-SIG-A field informs the total bandwidth information of the system.

Table 7 is a table illustrating information included in the HE-SIG A field.

Information included in each field illustrated in Table 7 may follow the definition of the IEEE 802.11 system. In addition, each field described above corresponds to an example of fields that may be included in the PPDU, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included. Another embodiment of the information included in the HE-SIG A field will be described later with reference to FIG. 34.

The HE-SIG B field may include user-specific information required for each STA to receive its own data (eg, PSDU). The HE-SIG B field may be transmitted in one or two OFDM symbols. For example, the HE-SIG B field may include information on the modulation and coding scheme (MCS) of the corresponding PSDU and the length of the corresponding PSDU.

The L-STF, L-LTF, L-SIG, and HE-SIG A fields may be repeatedly transmitted in units of 20 MHz channels. For example, when a PPDU is transmitted on four 20 MHz channels (ie, an 80 MHz band), the L-STF, L-LTF, L-SIG, and HE-SIG A fields may be repeatedly transmitted on every 20 MHz channel. .

As the FFT size increases, legacy STAs supporting legacy IEEE 802.11a / g / n / ac may not be able to decode the HE PPDU. In order for the legacy STA and the HE STA to coexist, the L-STF, L-LTF, and L-SIG fields are transmitted through a 64 FFT on a 20 MHz channel so that the legacy STA can receive them. For example, the L-SIG field may occupy one OFDM symbol, one OFDM symbol time is 4 ms, and a GI may be 0.8 ms.

HE-STF is used to improve the performance of AGC estimation in MIMO transmission.

The FFT size for each frequency unit may be larger from the HE-STF (or HE-SIG A). For example, 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel. As the FFT size increases, the number of OFDM subcarriers per unit frequency increases because the interval between OFDM subcarriers becomes smaller, but the OFDM symbol time becomes longer. In order to improve the efficiency of the system, the length of the GI after the HE-STF may be set equal to the length of the GI of the HE-SIG A.

The HE-SIG A field may include information required for the HE STA to decode the HE PPDU. However, the HE-SIG A field may be transmitted through a 64 FFT in a 20 MHz channel so that both the legacy STA and the HE STA can receive it. This is because the HE STA can receive not only the HE format PPDU but also the existing HT / VHT format PPDU, and the legacy STA and the HE STA must distinguish between the HT / VHT format PPDU and the HE format PPDU.

In FIG. 17, it is assumed that 20 MHz channels are allocated to different STAs (eg, STA 1, STA 2, STA 3, and STA 4).

Referring to FIG. 17, the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B). For example, from the HE-STF (or HE-SIG-B), 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel.

Since the information transmitted in each field included in the PPDU is the same as the example of FIG. 21, a description thereof will be omitted.

The HE-SIG-B field may include information specific to each STA, but may be encoded over the entire band (ie, indicated by the HE-SIG-A field). That is, the HE-SIG-B field includes information on all STAs and is received by all STAs.

The HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band. For example, in FIG. 22, the HE-SIG-B may be allocated with 20 MHz for

STA

1, 20 MHz for

STA

2, 20 MHz for

STA

3, and 20 MHz for STA 4. In addition, STA 1 and STA 2 may allocate 40 MHz, and STA 3 and STA 4 may then allocate 40 MHz. In this case, STA 1 and STA 2 may allocate different streams, and STA 3 and STA 4 may allocate different streams.

In addition, by defining the HE-SIG-C field, the HE-SIG C field may be added to the example of FIG. 22. In this case, in the HE-SIG-B field, information on all STAs may be transmitted over the entire band, and control information specific to each STA may be transmitted in units of 20 MHz through the HE-SIG-C field.

In addition, unlike the example of FIGS. 16 and 17, the HE-SIG-B field may 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 drawings below.

In FIG. 18, it is assumed that 20 MHz channels are allocated to different STAs (eg, STA 1, STA 2, STA 3, and STA 4).

Referring to FIG. 18, the HE-SIG-B field is not transmitted over the entire band, but is transmitted in 20 MHz units in the same manner as the HE-SIG-A field. However, at this time, the HE-SIG-B is encoded and transmitted in 20 MHz units differently from the HE-SIG-A field, but may not be copied and transmitted in 20 MHz units.

In this case, the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B). For example, from the HE-STF (or HE-SIG-B), 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel.

Since the information transmitted in each field included in the PPDU is the same as the example of FIG. 16, a description thereof will be omitted.

The HE-SIG-A field is duplicated and transmitted in units of 20 MHz.

The HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band. Since the HE-SIG-B field includes information about each STA, information about each STA may be included for each HE-SIG-B field in units of 20 MHz. In this case, in the example of FIG. 29, 20 MHz is allocated to each STA. For example, when 40 MHz is allocated to the STA, the HE-SIG-B field may be copied and transmitted in units of 20 MHz.

It may be more preferable not to transmit the HE-SIG-B field over the entire band as in the case of allocating a part of the bandwidth having a low interference level from the adjacent BSS to the STA in a situation in which different bandwidths are supported for each BSS. .

Hereinafter, the HE format PPDU of FIG. 18 will be described for convenience of description. In addition, hereinafter, the HE-SIG A field, the HE-SIG B field, the HE-STF, and the HE-LTF may be collectively referred to as an HE preamble. In addition, the legacy preamble and the HE preamble may be referred to as a "physical preamble".

16 to 18, the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.

다중 사용자(multi-user) 상향링크 전송 방법Multi-user uplink transmission method

The manner in which an AP operating in a WLAN system transmits data to a plurality of STAs on the same time resource may be referred to as DL MU transmission (downlink multi-user transmission). In contrast, a scheme in which a plurality of STAs operating in a WLAN system transmit data to an AP on the same time resource may be referred to as UL MU transmission (uplink multi-user transmission).

Such DL MU transmission or UL MU transmission may be multiplexed in the frequency domain or the spatial domain.

When multiplexing on the frequency domain, different frequency resources (eg, subcarriers or tones) may be allocated as downlink or uplink resources for each of a plurality of STAs based on orthogonal frequency division multiplexing (OFDMA). Can be. In this same time resource, a transmission scheme using different frequency resources may be referred to as 'DL / UL MU OFDMA transmission'.

When multiplexing on a spatial domain, different spatial streams may be allocated as downlink or uplink resources for each of the plurality of STAs. In this same time resource, a transmission expression through different spatial streams may be referred to as 'DL / UL MU MIMO' transmission.

Current WLAN systems do not support UL MU transmission due to the following limitations.

Current WLAN systems do not support synchronization of transmission timing of uplink data transmitted from a plurality of STAs. For example, assuming that a plurality of STAs transmit uplink data through the same time resource in an existing WLAN system, in the current WLAN system, each of the plurality of STAs may know transmission timing of 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 the plurality of STAs.

In addition, in a current WLAN system, overlap between frequency resources used for transmitting uplink data by a plurality of STAs may occur. For example, when oscillators of the plurality of STAs are different, frequency offsets may appear differently. If each of a plurality of STAs having different frequency offsets simultaneously performs uplink transmission through different frequency resources, some of frequency regions used by each of the plurality of STAs may overlap.

In addition, power control for each of the plurality of STAs is not performed in the existing WLAN system. Depending on the distance between the plurality of STAs and the AP and the channel environment, the AP may receive signals of different power from each of the plurality of STAs. In this case, a signal arriving at a weak power may be difficult to be detected by the AP relative to a signal arriving at a strong power.

Accordingly, the present invention proposes a UL MU transmission method in a WLAN system.

Referring to FIG. 19, the AP instructs STAs participating in UL MU transmission to prepare for UL MU transmission, receives UL MU data frames from the STAs, and responds to the UL MU data frame with an ACK frame ( Transmits a Block Ack (BA) frame.

First, the AP transmits a UL MU Trigger frame (1910) to instruct STAs to transmit UL MU data to prepare for UL MU transmission. Here, the UL MU trigger frame may be referred to as a term of a 'UL MU scheduling frame'.

Here, the UL MU trigger frame 1910 may include control information such as STA identifier (ID) / address information, resource allocation information to be used by each STA, duration information, and the like.

The STA ID / address information means information on an identifier or an address for specifying each STA that transmits uplink data.

The resource allocation information is assigned to uplink transmission resources allocated to each STA (for example, frequency / subcarrier information allocated to each STA in case of UL MU OFDMA transmission, and stream index allocated to each STA in case of UL MU MIMO transmission). Means information.

Duration information means information for determining a time resource for transmission of an uplink data frame transmitted by each of a plurality of STAs.

For example, the duration information may include interval information of a TXOP (Transmit Opportunity) allocated for uplink transmission of each STA or information (eg, bits or symbols) about an uplink frame length. Can be.

In addition, the UL MU trigger frame 1910 may further include control information such as MCS information, coding information, etc. to be used when transmitting the UL MU data frame for each STA.

The above control information is the HE-part (for example, HE-SIG A field or HE-SIG B field) of the PPDU carrying the UL MU trigger frame 1910 or the control field (for example, UL MU trigger frame 1910). For example, the frame control field of the MAC frame) may be transmitted.

The PPDU carrying the UL MU trigger frame 1910 has a structure starting with L-part (eg, L-STF field, L-LTF field, L-SIG field, etc.). Accordingly, legacy STAs may perform Network Allocation Vector (NAV) setting through L-SIG protection from the L-SIG field. For example, legacy STAs may calculate an interval (hereinafter, referred to as an 'L-SIG guard interval') for NAV setting based on data length and data rate information in the L-SIG. The legacy STAs may determine that there is no data to be transmitted to them during the calculated L-SIG protection period.

For example, the L-SIG guard interval may be determined as the sum of the MAC duration field value of the UL MU trigger frame 1910 and the remaining interval after the L-SIG field of the PPDU carrying the UL MU trigger frame 1910. Accordingly, the L-SIG guard interval may be set to a value up to an interval for transmitting the ACK frame 1930 (or BA frame) transmitted to each STA according to the MAC duration value of the UL MU trigger frame 1910.

Hereinafter, a resource allocation method for UL MU transmission to each STA will be described in more detail. For convenience of description, fields including control information are divided and described, but the present invention is not limited thereto.

The first field may distinguish and indicate UL MU OFDMA transmission and UL MU MIMO transmission. For example, '0' may indicate UL MU OFDMA transmission and '1' may indicate UL MU MIMO transmission. The size of the first field may consist of 1 bit.

The second field (eg, STA ID / address field) informs STA ID or STA addresses to participate in UL MU transmission. The size of the second field may be configured as the number of bits to inform the STA ID × the number of STAs to participate in the UL MU. For example, when the second field consists of 12 bits, the ID / address of each STA may be indicated for every 4 bits.

The third field (eg, resource allocation field) indicates a resource region allocated to each STA for UL MU transmission. In this case, the resource region allocated to each STA may be sequentially indicated to each STA in the order of the second field.

If the first field value is '0', this indicates frequency information (eg, frequency index, subcarrier index, etc.) for UL MU transmission in the order of STA ID / address included in the second field. When the value of the 1 field is '1', it indicates MIMO information (eg, stream index, etc.) for UL MU transmission in the order of STA ID / address included in the second field.

In this case, since a plurality of indexes (ie, frequency / subcarrier indexes or stream indexes) may be informed to one STA, the size of the third field may be configured in a plurality of bits (or bitmap format). × It may be configured as the number of STAs to participate in the UL MU transmission.

For example, it is assumed that the second field is set in the order of 'STA 1' and 'STA 2', and the third field is set in the order of '2', '2'.

In this case, when the first field is '0', STA 1 may be allocated frequency resources from the upper (or lower) frequency domain, and STA 2 may be sequentially allocated the next frequency resource. For example, in case of supporting 20 MHz OFDMA in an 80 MHz band, STA 1 may use a higher (or lower) 40 MHz band, and STA 2 may use a next 40 MHz band.

On the other hand, when the first field is '1', STA 1 may be allocated an upper (or lower) stream, and STA 2 may be sequentially allocated the next stream. In this case, the beamforming scheme according to each stream may be specified in advance, or more specific information about the beamforming scheme according to the stream may be included in the third field or the fourth field.

Each STA transmits a UL MU data frame (UL MU Data frame, 1921, 1922, 1923) to the AP based on the UL MU trigger frame 1910 transmitted by the AP. Here, each STA may transmit the UL MU data frames 1921, 1922, 1923 to the AP after SIFS after receiving the UL MU trigger frame 1910 from the AP.

Each STA may determine a specific frequency resource for UL MU OFDMA transmission or a spatial stream for UL MU MIMO transmission based on resource allocation information of the UL MU trigger frame 1910.

Specifically, in the case of UL MU OFDMA transmission, each STA may transmit an uplink data frame on the same time resource through different frequency resources.

Here, each of STA 1 to STA 3 may be allocated different frequency resources for uplink data frame transmission based on STA ID / address information and resource allocation information included in the UL MU trigger frame 1910. For example, STA ID / address information may sequentially indicate STA 1 to STA 3, and resource allocation information may sequentially indicate frequency resource 1, frequency resource 2, and frequency resource 3. In this case, the STA 1 to STA 3 sequentially indicated based on the STA ID / address information may be allocated the frequency resource 1, the frequency resource 2, and the frequency resource 3 sequentially indicated based on the resource allocation information. That is, STA 1 can transmit uplink data frames 1921, 1922, and 1923 to the AP through frequency resource 1, STA 2, frequency resource 2, and STA 3 through frequency resource 3.

In addition, in the case of UL MU MIMO transmission, each STA may transmit an uplink data frame on the same time resource through at least one different stream among a plurality of spatial streams.

Here, each of STA 1 to STA 3 may be allocated a spatial stream for uplink data frame transmission based on STA ID / address information and resource allocation information included in the UL MU trigger frame 1910. For example, STA ID / address information may sequentially indicate STA 1 to STA 3, and resource allocation information may sequentially indicate spatial stream 1, spatial stream 2, and spatial stream 3. In this case, the STA 1 to STA 3 sequentially indicated based on the STA ID / address information may be allocated to the spatial stream 1, the spatial stream 2, and the spatial stream 3 sequentially indicated based on the resource allocation information. That is, STA 1 may transmit uplink data frames 1921, 1922, and 1923 to the AP through spatial stream 1, STA 2 through spatial stream 2, and STA 3 through spatial stream 3.

The PPDU carrying the uplink data frames 1921, 1922, and 1923 can be configured in a new structure without the L-part.

In addition, in the case of the UL MU MIMO transmission or the UL MU OFDMA transmission of the subband type of less than 20 MHz, the L-part of the PPDU carrying the uplink data frames 1921, 1922, and 1923 has an SFN form (that is, all STAs are identical). L-part configuration and contents can be sent simultaneously). On the other hand, in the case of UL MU OFDMA transmission having a subband type of 20 MHz or more, the L-part of the PPDU carrying the uplink data frames 1921, 1922, and 1923 has a L-part of 20 MHz in the band allocated to each STA. Can be sent.

If the uplink data frame can be sufficiently configured with the information of the UL MU trigger frame 1910, the HE-SIG field in the PPDU carrying the uplink data frames 1921, 1922, 1923 (that is, how the data frame is constructed). (Area for transmitting the control information) may not be necessary. For example, the HE-SIG-A field and / or the HE-SIG-B may not be transmitted. In addition, the HE-SIG-A field and the HE-SIG-C field may be transmitted, and the HE-SIG-B field may not be transmitted.

The AP may transmit an ACK frame (ACK frame) 1930 (or BA frame) in response to the uplink data frames 1921, 1922, 1923 received from each STA. Here, the AP may receive uplink data frames 1921, 1922, 1923 from each STA, and transmit an ACK frame 1930 to each STA after SIFS.

If using the same structure of the existing ACK frame, it may be configured to include the AID (or Partial AID) of the STAs participating in the UL MU transmission in the RA field having a size of 6 octets.

Or, if a new structure of the ACK frame can be configured in the form for DL SU transmission or DL MU transmission.

The AP may transmit only the ACK frame 1930 for the UL MU data frame that has been successfully received to the corresponding STA. In addition, the AP may inform whether the reception was successful through the ACK frame 1930 to the ACK or NACK. If the ACK frame 1930 includes NACK information, the ACK frame 1930 may also include information on the reason for the NACK or a subsequent procedure (for example, UL MU scheduling information).

Alternatively, the PPDU carrying the ACK frame 1930 may be configured in a new structure without the L-part.

The ACK frame 1930 may include STA ID or address information. However, if the order of STAs indicated in the UL MU trigger frame 1910 is applied in the same manner, the STA ID or address information may be omitted.

In addition, the TXOP (that is, the L-SIG guard interval) of the ACK frame 1930 is extended to include a frame for the next UL MU scheduling or a control frame including correction information for the next UL MU transmission. It may be.

Meanwhile, an adjustment process such as synchronization between STAs may be added for UL MU transmission.

자원 할당Resource allocation

When a DL / UL OFDMA transmission scheme is used, a plurality of resource units may be defined in units of n tones (or subcarriers) within a PPDU bandwidth.

The resource unit means an allocation unit of frequency resources for DL / UL OFDMA transmission.

One or more resource units may be allocated to one STA as DL / UL frequency resources, and different resource units may be allocated to the plurality of STAs, respectively.

20 illustrates a case where the PPDU bandwidth is 20 MHz.

Seven DC tones may be located in the center frequency region of the 20 MHz PPDU bandwidth. In addition, six left guard tones and five right guard tones may be located at both sides of the 20 MHz PPDU bandwidth.

According to the resource unit configuration method as shown in FIG. 20A, one resource unit may be configured of 26 tones (26 ton resource units). In this case, four leftover tones may be present in the 20 MHz PPDU bandwidth as shown in FIG. In addition, according to the resource unit configuration method as shown in FIG. 20B, one resource unit may be configured of 52 tones (52 ton resource unit) or 26 tones. In this case, four leftover tones may be present in the 20 MHz PPDU bandwidth as shown in FIG. 20 (b) adjacent to the 26 ton / 52 ton resource unit. In addition, according to the resource unit configuration method as shown in FIG. 25C, one resource unit may be configured of 106 tones (106 ton resource units) or 26 tones. In addition, according to the resource unit configuration method as shown in FIG. 20 (d), one resource unit may be configured of 242 tones (242 ton resource unit).

When a resource unit is configured as shown in FIG. 20 (a), up to nine STAs may be supported for DL / UL OFDMA transmission in a 20 MHz band. In addition, when the resource unit is configured as shown in FIG. 20 (b), up to five STAs may be supported for DL / UL OFDMA transmission in the 20 MHz band. In addition, when the resource unit is configured as shown in FIG. 20 (c), up to three STAs may be supported for DL / UL OFDMA transmission in the 20 MHz band. In addition, when a resource unit is configured as shown in 20 (d), the 20 MHz band may be allocated to one STA.

The resource unit configuration scheme of FIG. 20 (a) to FIG. 20 (d) may be applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA. Alternatively, the resource unit configuration method in which FIGS. 20 (a) to 20 (d) are combined may be applied.

21 illustrates a case where the PPDU bandwidth is 40 MHz.

Five DC tones may be located in the center frequency region of the 40 MHz PPDU bandwidth. In addition, 12 left guard tones and 11 light guard tones may be located at both sides of the 40 MHz PPDU bandwidth.

According to the resource unit configuration method as shown in FIG. 21 (a), one resource unit may consist of 26 tones. In this case, 16 leftover tones may be present in the 40 MHz PPDU bandwidth as shown in FIG. 21A adjacent to the 26-tone resource unit. In addition, according to the resource unit configuration method as shown in FIG. 21 (b), one resource unit may be composed of 52 tones or 26 tones. In this case, 16 leftover tones may be present in the 40 MHz PPDU bandwidth as shown in FIG. 21 (b) adjacent to the 26 ton / 52 ton resource unit. In addition, according to the resource unit configuration method as shown in FIG. 21C, one resource unit may be composed of 106 tones or 26 tones. In this case, eight leftover tones may be present in the 40 MHz PPDU bandwidth as shown in FIG. 21C adjacent to the 26 ton / 106 ton resource unit. In addition, according to the resource unit configuration method as shown in FIG. 21 (d), one resource unit may be configured with 242 tones. In addition, according to the resource unit configuration method as shown in FIG. 21E, one resource unit may be configured of 484 tones (484 ton resource unit).

When a resource unit is configured as shown in FIG. 21A, up to 18 STAs may be supported for DL / UL OFDMA transmission in a 40 MHz band. In addition, when the resource unit is configured as shown in FIG. 21 (b), up to 10 STAs may be supported for DL / UL OFDMA transmission in the 40 MHz band. In addition, when a resource unit is configured as shown in FIG. 21C, up to six STAs may be supported for DL / UL OFDMA transmission in a 40 MHz band. In addition, when the resource unit is configured as shown in 21 (d), up to two STAs may be supported for DL / UL OFDMA transmission in the 40 MHz band. In addition, when a resource unit is configured as shown in 21 (e), the corresponding resource unit may be allocated to one STA for SU DL / UL transmission in the 40 MHz band.

The resource unit configuration method of FIG. 21 (a) to FIG. 21 (e) may be applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA. Alternatively, the resource unit configuration scheme in which FIGS. 21A to 21E are combined may be applied.

22 illustrates a case where the PPDU bandwidth is 80 MHz.

Seven DC tones may be located in the center frequency region of the 80 MHz PPDU bandwidth. However, when 80 MHz PPDU bandwidth is allocated to one STA (that is, when a resource unit composed of 996 tones is allocated to one STA), five DC tones may be located in the center frequency region. In addition, 12 left guard tones and 11 light guard tones may be located at both sides of the 80 MHz PPDU bandwidth.

According to the resource unit configuration method as shown in FIG. 22 (a), one resource unit may consist of 26 tones. In this case, 32 leftover tones may be present in the 80 MHz PPDU bandwidth as shown in FIG. 22 (a) adjacent to the 26-tone resource unit. In addition, according to the resource unit configuration method as shown in FIG. 22 (b), one resource unit may consist of 52 tones or 26 tones. In this case, 32 leftover tones may be present in the 80 MHz PPDU bandwidth as shown in FIG. 27 (b) adjacent to the 26 tone / 52 tone resource unit. In addition, according to the resource unit configuration method as shown in FIG. 22C, one resource unit may be composed of 106 tones or 26 tones. In this case, 16 leftover tones may be present in the 80 MHz PPDU bandwidth as shown in FIG. 22C adjacent to the 26 ton / 106 ton resource unit. In addition, according to the resource unit configuration method as shown in FIG. 22 (d), one resource unit may be composed of 242 tones or 26 tones. According to the resource unit configuration method as shown in FIG. 22 (e), one resource unit may consist of 484 tones or 26 tones. According to the resource unit configuration method as shown in FIG. 22 (f), one resource unit may be configured with 996 tones.

When a resource unit is configured as shown in FIG. 22A, up to 37 STAs may be supported for DL / UL OFDMA transmission in an 80 MHz band. In addition, when a resource unit is configured as shown in FIG. 22 (b), up to 21 STAs may be supported for DL / UL OFDMA transmission in an 80 MHz band. In addition, when the resource unit is configured as shown in FIG. 22C, up to 13 STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band. In addition, when the resource unit is configured as shown in 22 (d), up to five STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band. In addition, when the resource unit is configured as shown in 22 (e), up to three STAs may be supported for DL / UL OFDMA transmission in the 80 MHz band. In addition, when a resource unit is configured as shown in 22 (f), the corresponding resource unit may be allocated to one STA for SU DL / UL transmission in the 80 MHz band.

The resource unit configuration scheme of FIG. 22 (a) to FIG. 22 (f) is applied based on the number of STAs participating in DL / UL OFDMA transmission and / or the amount of data transmitted or received by the STA, or the like. Alternatively, the resource unit configuration scheme in which FIGS. 22 (a) to 22 (f) are combined may be applied.

In addition, although not shown in the figure, a configuration method of a resource unit when the PPDU bandwidth is 160 MHz may be proposed. In this case, the bandwidth of the 160MHz PPDU may have a structure in which the 80MHz PPDU bandwidth described above in FIG. 22 is repeated twice.

Only some resource units may be used for DL / UL OFDMA transmission among all resource units determined according to the above-described resource unit configuration. For example, when a resource unit is configured as shown in FIG. 20A within 20 MHz, one resource unit may be allocated to less than nine STAs, and the remaining resource units may not be allocated to any STA.

In the case of DL OFDMA transmission, the data field of the PPDU is multiplexed and transmitted in a frequency domain in units of resource units allocated to each STA.

On the other hand, in the case of UL OFDMA transmission, the data field of the PPDU may be configured in units of resource units allocated to each STA and transmitted simultaneously to the AP. As described above, since each STA simultaneously transmits a PPDU, it may be recognized that a data field of a PPDU transmitted from each STA is multiplexed (or frequency multiplexed) in the frequency domain from the viewpoint of the AP.

In addition, when DL / UL OFDMA transmission and DL / UL MU-MIMO transmission are simultaneously supported, one resource unit may consist of a plurality of streams in a spatial domain. In addition, one or more streams may be allocated to one STA as DL / UL spatial resources, and different streams may be allocated to the plurality of STAs, respectively.

For example, a resource unit composed of 106 tones in FIG. 22C may be configured of a plurality of streams in a spatial domain to simultaneously support DL / UL OFDMA and DL / UL MU-MIMO.

Also, although not shown in the figure, the 26-ton resource unit has two pilot tones, the 52-ton and 106-tone resource units have four pilot tones, and the 242-tone resource unit has eight pilot tones, 484 ton and 996 ton, respectively. The resource unit may include sixteen pilot tones each.

Hereinafter, for convenience of description, a resource unit composed of n tones will be referred to as an 'n tone resource unit' (n is a natural number). For example, in the following, a resource unit consisting of 26 tones is referred to as a '26 ton resource unit '.

UL MU UL MU ACKACK /Of BABA 시그널링Signaling 정보( Information( 스케쥴링Scheduling 정보) Information)

When the AP transmits DL MU frames to the plurality of STAs, each STA that receives the DL MU frame may transmit an ACK / BA frame to the AP as a response to the received DL MU frame. In this case, scheduling information (or signaling information and trigger information) may be required to prevent collision between ACK / BA frames transmitted from UL MUs from STAs. Here, the scheduling information may indicate various information necessary for transmitting the ACK / BA frame UL MU. Such scheduling information may be configured with minimal information for preventing collision with other ACK / BA frames and reducing overhead of the ACK / BA frames. Information constituting the scheduling information will be described in detail below with reference to the drawings.

Hereinafter, for convenience of description, the ACK frame and the BA frame will be collectively referred to as an 'ACK frame'.

1. PPDU Length Information

FIG. 23 illustrates an UL MU ACK frame for a DL MU frame. FIG. In this figure, the common preamble indicates a generic name of L-STF to HE-LTF regardless of structure.

Referring to FIG. 23, the lengths of ACK frames (or UL OFDMA Ack frames) that are UL MU transmitted as a response to a DL MU frame may include a resource unit allocated for transmission of an ACK frame, an ACK frame format, and / or an MCS level. Accordingly, it may be different for each STA. Therefore, in order to equally match the length of ACK frames transmitted UL MU for each STA, length information of the ACK frame having the longest length, that is, (UL MU) PPDU length information is required. Accordingly, the PPDU length information may be signaled in various ways and DL transmitted to each STA.

In an embodiment, the PPDU length information may be indicated by an implicit signaling scheme or directly as scheduling information by an explicit signaling scheme.

In the case of an implicit signaling scheme, the STA may obtain PPDU length information through a Duration field of a MAC frame in the received DL MU frame. For example, the STA may calculate (or estimate) the PPDU length by substituting the time included in the Duration field into Equation 1 below.

However, in the case of a cascade structure in which DL MU frames and UL MU frames (frames including other UL information as well as ACK frames) are continuously transmitted, resource allocation information of the UL MU frame is already included in the DL MU frame (including PPDU length information). Since is included, the PPDU length according to Equation 1 can be calculated only for an STA transmitting only an ACK frame. The STA acquiring the PPDU length may transmit a UL MU by inserting a padding bit after the ACK frame according to the acquired PPDU length.

In the case of an explicit signaling scheme, the AP may directly transmit DL signaling to each STA as scheduling information by signaling PPDU length information, and each STA may transmit a UL MU by inserting a padding bit according to the received PPDU length information. In this case, unlike the implicit signaling scheme, there is an advantage that the overhead is reduced because the STA does not need to calculate the PPDU length separately.

Therefore, the present specification proposes to follow an explicit signaling scheme in which the AP directly transmits PPDU length information as scheduling information.

2. Resource Allocation Information

There are two methods of allocating UL MU transmission frequency resources (or resource units) to transmit an ACK frame to each STA, an implicit resource allocation method and an explicit resource allocation method.

The explicit resource allocation method indicates a method in which an AP directly allocates a resource unit for UL MU transmission of an ACK frame to each STA. Therefore, in this case, the AP may separately signal resource unit allocation information for UL MU transmission of the ACK frame and transmit DL to each STA as scheduling information.

The implicit resource allocation scheme indicates a manner in which the STA uses the same resource unit as the resource unit used for transmission of the DL MU frame as a frequency resource for UL MU transmission of the ACK frame. Therefore, in this case, the AP does not need to separately signal resource unit allocation information for UL MU transmission of the ACK frame and transmit the scheduling information to each STA as scheduling information.

To illustrate the drawings, it is assumed that an AP transmits DL frames by DL MU to STAs 1 to 3. In this case, the DL frame for STA 1 is a first 106-tone resource unit of a 20 MHz channel, the DL frame for STA 2 is a 26-tone resource unit of a 20 MHz channel, and the DL frame for STA 3 is a second 106-tone resource unit of a 20 MHz channel. It is assumed that DL MU has been transmitted using.

In this case, according to the implicit resource allocation scheme (see FIG. 24 (a)), the STAs 1 to 3 may transmit the UL MU by using the transmission frequency resources of the received DL frame as they are, and separate resources. No allocation information is required. Accordingly, STA 1 receives the first 106-tone resource unit of the 20-MHz channel that is the transmission frequency resource of the received DL frame, STA 2 receives the 26-tone resource unit of the 20-MHz channel that is the transmission frequency resource of the received DL frame, and STA 3 receives The ACK frame may be UL MU transmitted using the second 106-tone resource unit of the 20 MHz channel, which is a transmission frequency resource of one DL frame.

In this case, MCS level “0” (BPSK modulation and 1/2 code rate) may be applied to the ACK frame transmitted by the STAs 1 to 3, and in this case, the length of the ACK frame of the STA 2 may be about 426.4 ms. Accordingly, the remaining

STA

1 and 3 may additionally insert a padding bit of about 259.2 ms in length after the ACK frame in accordance with the ACK frame length of the longest STA 2. A method of calculating the ACK frame length will be described later in more detail with reference to FIG. 26.

Or, according to the explicit resource allocation scheme (see FIG. 24 (b)), the STAs 1 to 3 may transmit the UL MU using the resource unit allocated to the UL MU according to the received scheduling information.

For example, as a frequency resource for UL MU transmission of an ACK frame, STA 1 is allocated a first 52 tone resource unit of a 20 MHz channel, STA 2 is assigned a second 52 tone resource unit, and STA 3 is assigned a 106 tone resource unit Can be. Such resource allocation information may be signaled as scheduling information and transmitted to STAs 1 to 3. Upon receiving the scheduling information, the STAs 1 to 3 may transmit UL MUs to each of the ACK frames using resource units allocated to the STAs 1 to 3. Accordingly, STA 1 uses a first 52-tone resource unit of a 20 MHz channel, STA 2 uses a second 52-tone resource unit of a 20 MHz channel, and STA 3 uses an 106-tone resource unit of a 20 MHz channel to generate an ACK frame. UL MU can be transmitted.

In this case, MCS level “0” (BPSK modulation and 1/2 code rate) may be applied to the ACK frame transmitted by the STAs 1 to 3, in which case the length of the ACK frame of the

STAs

1 and 2 is approximately 239.2 ms. have. Therefore, the remaining STA 3 may further insert a padding bit after the ACK frame in accordance with the ACK frame length of the

longest STA

1 and 2. A method of calculating the ACK frame length will be described later in more detail with reference to FIG. 26.

Considering the above, the implicit resource allocation scheme has an advantage of not needing to separately transmit scheduling information. However, there is a disadvantage in that the overhead of the implicit resource allocation scheme is very large compared to the explicit resource allocation scheme. 24 (a) and 24 (b), the implicit resource allocation scheme incurs an overhead of about 190 ms (about 13 symbols) more than the explicit resource allocation scheme.

In the explicit resource allocation scheme, the AP may directly allocate frequency resources to each STA efficiently (or in a direction of minimizing overhead) in consideration of the length of the ACK frame and the MCS level. In contrast, in the implicit resource allocation scheme, since the STAs transmit ACK frames using the same frequency resources of the received DL frame, regardless of the length of the ACK frame and the MCS level, the implicit resources are transmitted even if the same ACK frame is transmitted. The allocation method has a large overhead compared to the explicit resource allocation method.

Therefore, in this specification, to reduce such overhead, it is proposed to follow an explicit resource allocation scheme as a resource allocation scheme for UL MU transmission of an ACK frame. Accordingly, the AP may separately signal resource allocation information for UL MU transmission of the ACK frame and transmit the DL as scheduling information.

3. Bandwidth (or channel) information

Frequency resources for the UL MU transmission of the ACK frame is allocated to the STAs within a sub-channel (eg, 20 MHz channel) (or bandwidth) of a predetermined size and the STA within the entire transmission channel of the UL / DL MU PPDU. There may be a way to assign them.

Before describing the drawings, it is assumed that the AP transmits DL MU DL frames to STAs 1 to 4. In this case, the DL frame for STA 1 is a first 106-tone resource unit of a 40 MHz channel, the DL frame for STA 2 is a 26-tone resource unit of a 40 MHz channel, and the DL frame for STA 3 is a second 106-tone resource unit of a 40 MHz channel. The DL frame for STA 4 is assumed to be DL MU transmitted using a 242-tone resource unit of a 40 MHz channel.

In this case, the frequency resource for the UL MU transmission of the ACK frame may be allocated to STA 1 to 4 in a sub-channel (eg, 20 MHz channel) of a predetermined size, as shown in FIG. 25 (a). . For example, STAs 1 to 3 may be allocated frequency resources within the first 20 MHz sub-channel of the 40 MHz channel (UL / DL MU PPDU transmission channel), STA 4 is frequency within the second 20 MHz sub-channel of the 40 MHz channel Resources may be allocated. That is, STA 1 has a first 52-tone resource unit of the first 20 MHz sub-channel among the 40 MHz channels, STA 2 has a second 52-tone resource unit of the first 20 MHz sub-channel among the 40 MHz channels, and STA 3 has a first 20-MHz subunit among the 40 MHz channels. Each 106-tone resource unit of the channel may be allocated. In addition, STA 4 may be allocated a 242 tone resource unit of the second 20 MHz sub-channel of the 40 MHz channel.

In this case, MCS level “0” (BPSK modulation and 1/2 code rate) may be applied to the ACK frame transmitted by the STAs 1 to 4, in which case the length of the ACK frame of the

STAs

1 and 2 is approximately 239.2 ms. have. Accordingly, the remaining

STAs

3 and 4 may further insert padding bits after the ACK frame in accordance with the length of the ACK frame of the longest STA 2.

Alternatively, frequency resources for UL MU transmission of the ACK frame may be allocated to STAs 1 to 4 in the entire transmission channel of the UL / DL MU PPDU, as shown in FIG. 25 (b). For example, STA 1 to 4 may be allocated one each of four 106 tone resource units in a 40 MHz channel.

In this case, MCS level “0” (BPSK modulation and 1/2 code rate) may be applied to the ACK frame transmitted by the STAs 1 to 4, and in this case, the ACK frame lengths of the STAs 1 to 4 may be about 152.8 ms. Can be.

According to the above description, it is noted that the case in which the frequency resource for UL MU transmission of the ACK frame is allocated in a subchannel of a predetermined size has a larger overhead due to the padding bit insertion than when allocated in the entire transmission channel. Able to know. Referring to FIGS. 25A and 25B, when a frequency resource of an ACK frame is allocated within a subchannel (FIG. 25A) is allocated within an entire transport channel (FIG. 25B). More overhead of about 90 ms (about 6 symbols) occurs.

Therefore, in this specification, to reduce such overhead, it is proposed to follow a method of allocating resources within the entire transmission channel of the UL / DL MU PPDU as a resource allocation method for UL MU transmission of an ACK frame. Accordingly, the AP may separately signal all transmission channel information (or bandwidth information) of the UL / DL MU PPDU for UL MU transmission of the ACK frame and transmit the DL as scheduling information.

4. MCS Level Information

The MCS level to be applied to the ACK frame transmitted by the UL MU may be determined in various embodiments.

In one embodiment, the STA may determine the MCS level to be applied to the ACK frame to the same level as the MCS level of the received DL frame. Therefore, in this case, the AP does not need to separately transmit MCS level information to the STA to be applied to the ACK frame. However, for robust transmission of the ACK frame, since the MCS level of the ACK frame needs to be lower than the MCS level of the DL frame, the following embodiments may be further proposed.

As another embodiment, the STA may uniformly apply a preset MCS level (eg, MCS level “0”) to generate an ACK frame for robust transmission of the ACK frame. Even in this case, the AP does not need to separately transmit the MCS level information to be applied to the ACK frame to the STA. However, there is a problem that the UL MU transmission resources are unnecessarily wasted if the MCS level is always fixed to a certain level.

Referring to FIGS. 26A and 26B, the length of the physical preamble (or preamble) of the UL MU PPDU including the ACK frame may be determined by Equation 2.

Referring to Equation 2, when the legacy preamble consists of L-STF (8 ms), L-LTF (8 ms), and L-SIG field (4 ms), the length of the legacy preamble is 8 + 8 + 4 = 20. It can be In addition, when the HE preamble consists of an R (Repeated) L-SIG (4 ms), a HE-SIG-A field (4 ms), an HE-STF (8 ms) and an HE-LTF (16 ms), The length may be 4 + 4 + 8 + 16 = 32 mm 3. Since the physical preamble includes a legacy preamble and an HE preamble, the physical preamble may have a total length of 20 ms + 32 ms = 52 ms.

In addition, the bit size of the MAC frame may be determined by Equation 3 below.

Referring to Equation 3, the MAC frame is a service field (2 octets), MPDU delimiter (4 octets), MAC header (16 octets), BA control field (2 octets), BA information field (10 octets), FCS (4 octets) and tail (1 octet), the bit size of the MAC frame may be 2 + 4 + 16 + 2 + 10 + 4 + 1 = 39 octets = 312bits. In addition, one symbol length may be 12.8 + 1.6 = 14.4 ms.

Therefore, when MCS level "0" (BPSK modulation and 1/2 code rate) is applied to the MAC frame (Fig. 26 (a)),

The length of the ACK frame transmitted through the 26-tone resource unit is 374.4 ms.

The length of the ACK frame transmitted on a 52-ton resource unit is 187.2 ㎲.

The length of the ACK frame transmitted via the 106-ton resource unit is 100.8 ms.

The length of the ACK frame transmitted through the 242-tone resource unit may be 43.2 ms.

In addition, when MCS level "3" (16 QAM modulation and 1/2 code rate) is applied to the MAC frame (Fig. 26 (b)),

The length of the ACK frame transmitted through the 26-ton resource unit is 100.8 ms.

The length of the ACK frame transmitted through the 52-ton resource unit is 57.6 ms.

The length of the ACK frame transmitted via the 106-tone resource unit is 28.8 ms.

The length of the ACK frame transmitted through the 242-tone resource unit may be 14.4 ms.

Comparing Figs. 26 (a) and 26 (b), the length of the ACK frame transmitted through the 26-tone resource unit is about 275 ms when the MCS level "0" is applied than when the MCS level "3" is applied. You can see that it is longer. In addition, it can be seen that the length of the ACK frame transmitted through the 52-tone resource unit is about 130 ms longer when the MCS level "0" is applied than when the MCS level "3" is applied. Therefore, when the MCS level "0" is collectively applied, a problem may arise that the time resources are unnecessarily wasted as the length of the ACK frame is too long (that is, the overhead is large).

Accordingly, the present specification proposes a method in which an AP directly determines an MCS level applied to an ACK frame according to channel conditions and informs each STA of the MCS level. To this end, the AP may separately signal MCS level information to be applied to the ACK frame and transmit DL to each STA as scheduling information. In this case, the AP may indicate a lower level than the MCS level applied to the DL MU frame for robust UL MU transmission as the MCS level to be applied to the ACK frame.

As described above with reference to FIGS. 23 to 26, in the present specification, as scheduling information for UL MU transmission of an ACK frame, 1. PPDU length information, 2. resource allocation information 3. bandwidth (or channel) information, and 4. MCS level information Suggest signaling. That is, scheduling information for UL MU transmission of an ACK frame may include 1. PPDU length information, 2. resource allocation information, 3. bandwidth (or channel) information, and 4. MCS level information. However, the present invention is not limited thereto. In some embodiments, some of the above-described information may be omitted or new information may be added to the scheduling information.

Such scheduling information may be signaled in various ways, which will be described later in detail.

Signaling method of scheduling information

27 is a diagram illustrating a signaling method of scheduling information according to an embodiment of the present invention.

1. First embodiment-unicast signaling

Referring to FIG. 27A, the scheduling information may be carried in a unicast manner by being included in (or included in) at least one MPDU in a MAC header or DL MU frame. In particular, when the scheduling information is included in the MAC header, the scheduling information may be included in the HE control field (that is, the HT control field of the HE format) of the MAC header.

In the present embodiment, the same MCS level as the DL MU frame is applied to the scheduling information. Therefore, in this embodiment, the scheduling information can be transmitted less robustly than the second and third embodiments to be described later. Therefore, in case the STA fails to decode the scheduling information (or fails to receive the scheduling information), an additional error recovery procedure may be necessary.

2. Second Embodiment-Broadcast Signaling

Referring to FIG. 27B, the scheduling information may be transmitted in a DL MU by being broadcast in a broadcast trigger frame (or broadcast MPDU) received in common to all STAs receiving the DL MU PPDU. . To this end, all the STAs receiving the DL MU PPDU can simultaneously receive the DL MU frame (or A-MPDU) and the broadcast trigger frame allocated thereto.

3. Third embodiment

FIG. 27C is a diagram illustrating a signaling method of scheduling information according to a third embodiment of the present invention. FIG. Referring to FIG. 27C, the scheduling information may be included in (or included in) the HE-SIG B field and transmitted in a DL MU. However, the present invention is not limited to this figure, and the scheduling information may be included in (or included) the DL-MU transmission in the HE-SIG A field.

As such, the scheduling information may be transmitted in a DL MU according to any one of the first to third embodiments. Accordingly, the information included in the scheduling information may be transmitted in the same manner as the DL MU according to any one of the first to third embodiments.

However, the present invention is not limited thereto, and the DL MU may be transmitted according to different embodiments for each information included in the scheduling information.

For example, PPDU length information (and / or resource allocation information) of the scheduling information may be transmitted by (1) broadcast signaling or (2) implicit signaling.

(1) broadcast signaling scheme of PPDU length information (and / or resource allocation information)

As an embodiment, the PPDU length information (or the length information of the maximum Ack / BA frame) among the scheduling information may be included in the common HE-SIG B field (or the common field in the HE-SIG B field) and transmitted.

Here, the common HE-SIG B field may indicate an HE-SIG B field including trigger information. Here, the trigger information refers to configuration information (information for transmitting the UL MU frame such as frequency / time / space axis resource allocation information and coding, MCS) for the UL MU frame. That is, the AP may configure a common HE-SIG B field for UL MU frame transmission and include the PPDU length information therein.

Alternatively, the common HE-SIG B field may include a user-specific HE-SIG B field (a field including user specific allocation information for receiving a DL MU frame) (or HE-SIG B user content). It may indicate a HE-SIG B field (or HE-SIG B common content) transmitted prior to a user-specific HE-SIG B field for reading (called individual HE-SIG B coding). That is, the PPDU length information may be included in the common HE-SIG B field including common information on the configuration of the DL MU frame.

(2) unicast signaling scheme of PPDU length information (and / or resource allocation information)

In another embodiment, the PPDU length information may be included in the user specific HE-SIG B field and transmitted. Alternatively, the PPDU length information may be included in a MAC header, a MAC payload of a DL MU frame.

The remaining information other than the above-described PPDU length information (and / or resource allocation information) of the scheduling information is included in the user-specific HE-SIG B field (or user-specific field of the HE-SIG B field) to be included in the DL MU. Can be sent.

In addition to the above-described embodiments, the information included in the scheduling information may be signaled according to any one of the first to third embodiments or a combination of the first to the third embodiments and transmitted according to the type. .

In the above, various embodiments regarding the signaling method of the scheduling information have been described. The above-described embodiments may be appropriately applied in consideration of the effects of the embodiments.

On the other hand, in relation to the signaling method of the scheduling information, the scheduling information of the general trigger information (for example, trigger information for transmission of the UL MU frame, that is, information for transmission of other UL MU frame except the UL MU ACK frame) Cases recognized as one type and cases not otherwise may be considered.

If the scheduling information is recognized as a type of general trigger information, the AP may signal the scheduling information in the same manner according to the signaling method of the trigger information included in the DL MU frame (eg, a trigger frame or a cascade frame). have. That is, since the trigger information includes the scheduling information, the scheduling information is also signaled as the trigger information is signaled. Therefore, it is not necessary to excessively reduce the amount of scheduling information in order to reduce overhead caused by signaling scheduling information separately from trigger information.

On the contrary, when the scheduling information is not recognized as a type of general trigger information, the scheduling information may be separately signaled using at least one of the above-described first to third embodiments. In particular, at least one of the first to third embodiments may be used as an efficient signaling method for scheduling information for a cascade frame having a combination of a UL MU (data) frame and a UL MU ACK frame. In this case, since the scheduling information is signaled separately from the trigger information, it is necessary to minimize the amount of information included in the scheduling information in order to reduce overhead. In this case, as described above, the scheduling information may include, as minimum information, 1. PPDU length information, 2. resource allocation information, 3. bandwidth (or channel) information, and 4. MCS level information.

In the above, the signaling method of the scheduling information for the UL MU ACK frame transmission has been described. Hereinafter, a signaling method of “resource allocation information” included in the scheduling information will be described in more detail.

자원 할당 정보의 Of resource allocation information 시그널링Signaling 방법 Way

As described above with reference to FIGS. 20 to 22, the AP may allocate an 'n tone resource unit' to each STA as a frequency resource for transmitting a UL MU ACK frame, and transmit resource DL information as scheduling information for the DL MU. have.

In this case, the AP may signal the resource allocation information by toggling the bit value (or by switching the bit value to another value according to the STA change) and expressing (or signaling) (“toggling method”).

For example, in the case of resource allocation for a 20 MHz channel, resource allocation information may be represented by 9 bits, and each bit may correspond to nine 26 tone resource units in the 20 MHz channel, respectively. At this time, the LSB (least significant bit) corresponding to the first 26-ton resource unit located in the 20 MHz channel starts with a predetermined bit value (for example, '0'), and the 26-ton resource unit located later is allocated. When the STA is changed to another STA, the bit value corresponding to the 26-tone resource unit allocated to the other STA may be toggled (that is, switched from '0' to '1').

Referring to FIG. 28 (a), within a 20 MHz channel, the first to fourth 26 ton resource units are in STA 1, the fifth to sixth 26 ton resource units are in STA 2, and the seventh to ninth 26 ton resource units. It may be assumed that the case is allocated to STA 3. In this case, the resource allocation information may be represented (or signaled) as '000011000' according to the above toggling method. That is, the first to fourth bit values corresponding to the 26-tone resource unit allocated to STA 1 may be represented by '0', and the fifth and sixth bit values corresponding to the 26-tone resource unit allocated to STA 2. Can be toggled from the previous bit value '0' to '1', and the seventh through ninth bit values corresponding to the 26-tone resource unit allocated to STA 3 are represented by the previous bit value '1' to '0'. Can be toggled to.

In the case of the present embodiment, frequency resources may be allocated in units of 26 ton resource units. That is, in the above-described example, STA 1 may be allocated 26 ton resource unit # 4, STA 2 to 26 ton resource unit # 2, and STA 3 to 26 ton resource unit # 3. Accordingly, since a frequency resource of a size different from that of the size defined in FIGS. 20 to 22 (for example, 26 tone resource unit # 3) may be allocated to the STA, a new interleaver may be required.

This embodiment may be useful when the AP allocates frequency resources for the UL MU ACK frame in a distributed allocation scheme. For example, when the STA is assigned only one 26-tone resource unit, when the frequency interval of the allocated 26-tone resource unit falls into deep fading, UL MU transmission of the ACK frame through the 26-tone resource unit fails. Accordingly, the STA may interpret the 26-tone resource unit as a logical allocation, and may interpret it as physically allocated two discontinuous 13-tone resource units in the frequency domain. As a result, the STA may obtain a frequency diversity gain.

Referring to FIG. 28 (b), in a 20 MHz channel, a 9x26 ton resource unit may be distinguished into two 9x13 ton resource units, and a 26 ton resource unit, which is a resource allocation unit, includes two 13 ton resources discontinuously located in the frequency domain. It may consist of units. Accordingly, the STA allocated the first 26 ton resource unit can be interpreted as being allocated the first 13 ton resource unit and the 10 th 13 ton resource unit, and can transmit the UL MU using the corresponding 13 ton resource units.

Unlike the embodiment in FIG. 28 (b), the AP may allocate frequency resources according to the tone plan defined in FIGS. 20 to 22. That is, the AP may allocate the 26/52/106/242 tone resource unit to the STA according to the predefined tone plan of the 20 MHz channel. In this case, consecutive bits having the same bit value may mean a resource unit of a specific size. For example, two consecutive bits having the same bit value are 52 ton resource units, 4 bits are 106 ton resource units, and 9 bits are 242 ton resource units, and one bit having a different bit value from a neighboring bit value is a 26 ton resource. It may mean a unit.

In the present embodiment, since frequency resources must be allocated in accordance with the resource allocation interval of the tone plan in FIGS. 20 to 22, the allocation as in the example of FIGS. 28 (a) and 28 (b) is not possible.

Referring to FIG. 28 (c), STA 1 may be assigned a 106-tone resource unit 26 * 4, STA 2 may be a 26-tone resource unit, and STA 3 may be assigned a 106-tone resource unit 26 * 4. In this case, Resource allocation information for the STA 1 to 3 may be represented (or signaled) as '000010000'.

In the case of the embodiment of FIG. 28 (c), unlike the embodiment of FIG. 28 (b), an existing interleaver can be used as it is.

According to this embodiment, the STA may interpret the resource allocation information to match the preset tone plan, even if the resource allocation scheme indicated by the received resource allocation information does not match the preset tone plan (or allocation rule).

For example, when the AP allocates a 106-tone resource unit only to STAs 1 and 3, respectively, the resource allocation information may be represented (or signaled) as '000001111'. This resource allocation information indicates that a 106-tone resource unit and a 26-tone resource unit are allocated to STA 1, but this does not match the tone plan preset in FIG. 20 (c). Accordingly, the STA 1 that has received the corresponding resource allocation information can be interpreted as actually receiving a 106-tone resource unit.

Alternatively, when the AP allocates a 106-tone resource unit to STA 1 and a 26-tone resource unit to STA 2, the resource allocation information may be expressed as “000010000”. In this case, STAs 1 and 2 may interpret that the STA using the last 106 tone resource unit does not exist.

Resource allocation information represented (or signaled) in the manner proposed in FIG. 28 may be transmitted through the HE-SIG B field (or the HE-SIG A field). More specifically, if the HE-SIG B field is encoded and transmitted differently for each STA, to read (or decode) information encoded for each STA at the beginning of the HE-SIG A field or the HE-SIG B field. Common information (the number of STAs, etc.) may be transmitted, and resource allocation information may be included in the common information and transmitted. The STA may know (though, implicitly or explicitly) the STA by decoding up to the HE-SIG B field, and accordingly, the STA may identify itself through bits of positions corresponding to its order in the resource allocation information for the UL MU ACK frame. It can know the resource unit allocated to.

For example, in the example of FIG. 28 (a), the STA 2 may know whether the STA is the second STA through the HE-SIG B field, and accordingly the position '11' in the received resource allocation information ('000011000'). It can be seen that the corresponding fourth and fifth 26 ton resource units are resource units allocated to them.

In FIG. 28, the case of 20 MHz channel transmission is limited. However, the above-described embodiments may be extended and applied to the case of 40 MHz, 80 MHz, and 160 MHz channel transmission, and may be interpreted as follows.

If the HE-SIG B field is encoded in 20 MHz units, the resource allocation information of the UL MU ACK frame may also be transmitted in 20 MHz units. Accordingly, the resource allocation information may be transmitted in 9 bits according to the toggling representation (or signaling) scheme. On the contrary, if the HE-SIG B field is encoded in the full band, resource allocation information of the UL MU ACK frame may also be transmitted over the full band. Accordingly, the resource allocation information may be transmitted in 9 bits in a 20 MHz channel, 18 bits in a 40 MHz channel, 37 bits in an 80 MHz channel, and 74 bits in a 160 MHz channel according to a toggling expression (or signaling) scheme.

In the embodiment of FIG. 28, a signaling scheme of resource allocation information has been described on the assumption that all resource units are allocated to the STA. However, some 26 ton resource units, for example, 26 ton resource units located in the center of a 20 MHz channel (or adjacent to a DC tone), 26 to 52 ton resource units in a 40 MHz channel or between 106 ton resource units There is a limitation that a tone resource unit, a 26-tone resource unit located in the center of an 80 MHz channel (or adjacent to a DC tone) and the like cannot be allocated with a neighboring resource unit.

Therefore, when the resource allocation for the UL MU ACK frame, the AP may preferentially signal resource allocation information for the remaining resource units except for the resource units. For example, the resource allocation information for the 20 MHz channel may be configured with allocation information for the remaining eight 26 ton resource units, except for 26 tons located in the center. In this case, the resource allocation information may be configured with a size of 8 bits.

In this case, the AP may explicitly indicate whether or not to allocate the resource unit excluded from the allocation by leaving 1 bit separately. Alternatively, the AP may implicitly indicate whether to allocate the resource unit excluded from the allocation by adjusting the number of STAs (or toggling counts) for which the allocation information is indicated through the resource allocation information.

For example, if the number of STAs (or the number of toggles) indicated by the resource allocation information is smaller than the number of STAs that receive the DL MU frame (or the number of STAs to which the UL MU ACK frame is transmitted), the STAs may include the excluded resource units. It can be implicitly known to be allocated to a specific STA. For example, it may be assumed that resource allocation information of '00001100' is received by four STAs. In this case, three STAs can grasp the allocation status of the remaining resource units except the central 26-tone resource unit through the received resource allocation information, and the other STA knows that the central 26-tone resource unit is allocated to itself. Can be.

Or, if the number of STAs receiving the DL MU frame (or the number of STAs to transmit the UL MU ACK frame) and the number of STAs indicated by the resource allocation information (or the number of toggled times) are the same, the STAs are resource units excluded from the allocation. It may be implicitly known that this is not-used. For example, it may be assumed that resource allocation information of '00110011' is received by four STAs. In this case, the STAs may know which resource unit is allocated to them according to the received resource allocation information, and the 26-tone resource unit located at the center may know that it is not-used.

This embodiment extends not only specific resource units (e.g., 26 tone resource units located in the center of a 20 MHz channel), but also that any resource units present in the channel are not used for UL MU transmission of ACK frames and are not-used. In this case, information about not-used may be explicitly signaled separately.

In the above, the method of signaling the resource allocation information by the toggle method has been described.

As another method of signaling the resource allocation information, there may be a method of table assignable combinations of resource units as shown in Table 8.

Accordingly, the AP may signal an index corresponding to the resource unit combination that it intends to allocate as resource allocation information and transmit it to the STAs.

Using this method has an advantage of reducing the number of signaling bits of resource allocation information. Here, even if some resource units (for example, 26-tone resource units located in the center of the 20 MHz channel) are not allocated, the table may be included. That is, some resource units may be expressed (or processed) as not-used at a specific index. Alternatively, not-used information for some resource units may be separately signaled and transmitted without being tabled.

Although the above embodiments have been limited to the signaling method of resource allocation information for UL MU transmission of an ACK frame, the embodiments may be extended to a signaling method of general resource allocation information for UL OFDMA (MU) frame transmission. Of course.

In addition, although the above has been described with reference to a signaling method of resource allocation information, the above embodiments may be applied to the same / similarly to other information included in the scheduling information. In addition, in the above embodiments, only the case where the resource allocation information is included in the HE-SIG B field and transmitted is described. However, as described with reference to FIG. 27, since the resource allocation information also corresponds to the scheduling information, a trigger frame and at least one MPDU may be used. Or it may be included in the MAC header and transmitted.

29 is a flowchart illustrating a UL MU transmission method of an STA apparatus according to an embodiment of the present invention. The above-described embodiments can be equally applied to the description related to the present flowchart. Therefore, hereinafter, redundant description is omitted.

Referring to FIG. 29, the STA may receive a DL MU PPDU (S2910). In more detail, the STA may receive a DL MU PPDU including a physical preamble and a data field from the AP. In this case, the data field includes at least one MPDU, wherein the at least one MPDU includes a trigger frame or a MAC header, and the trigger frame or the MAC header includes scheduling information for UL MU transmission of an acknowledgment (ACK) frame. Include.

In this case, the scheduling information may include resource unit allocation information for OFDMA transmission of the ACK frame and length information of the UL MU PPDU including the ACK frame. Furthermore, the scheduling information may further include MCS level information applied to the UL MU ACK frame and transport channel information of the UL MU PPDU including the ACK frame.

Next, the STA may transmit a UL MU PPDU including an ACK frame as a response to the received DL MU PPDU based on the scheduling information (S2920).

Further, although not shown in the flowchart, the resource allocation information may be signaled as various embodiments, as described above with reference to FIG. 28.

In FIG. 30, the STA apparatus 3000 may include a memory 3010, a processor 3020, and an RF unit 3030. As described above, the STA device may be an AP or a non-AP STA as an HE STA device.

The RF unit 3030 may be connected to the processor 3020 to transmit / receive a radio signal. The RF unit 3030 may up-convert data received from the processor 3020 into a transmission / reception band to transmit a signal.

The processor 3020 may be connected to the RF unit 3030 to implement a physical layer and / or a MAC layer according to the IEEE 802.11 system. The processor 3020 may be configured to perform an operation according to various embodiments of the present disclosure according to the drawings and description described above. In addition, a module implementing the operation of the STA 3000 according to various embodiments of the present disclosure described above may be stored in the memory 3010 and executed by the processor 3020.

The memory 3010 is connected to the processor 3020 and stores various information for driving the processor 3020. The memory 3010 may be included in the processor 3020 or may be installed outside the processor 3020 and connected to the processor 3020 by known means.

In addition, the STA apparatus 3000 may include a single antenna or multiple antennas.

The detailed configuration of the STA apparatus 3000 of FIG. 30 may be implemented such that the matters described in the above-described various embodiments of the present invention are applied independently or two or more embodiments are simultaneously applied.

In the method of transmitting UL MU data of the STA apparatus 3000 illustrated in FIG. 30, not only the description related to the flowchart of FIG. 29 but also the description of the above specification may be applied.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in memory and driven by the processor. The memory may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

Embodiments for carrying out the invention have been described in the best mode for carrying out the invention.

The frame transmission scheme in the wireless communication system of the present invention has been described with reference to the example applied to the IEEE 802.11 system, but it is possible to apply to various wireless communication systems in addition to the IEEE 802.11 system.

Claims

In a wireless LAN (WLAN) system, an uplink (UL) multi-user (MU) transmission method of a STA (Station) device,

Receiving a downlink (DL) MU Physical Protocol Data Unit (PPDU) including a physical preamble and a data field; as,

The data field includes at least one Mac Protocol Data Unit (MPDU),

The at least one MPDU comprises a trigger frame or a MAC header, wherein the trigger frame or the medium access control (MAC) header includes scheduling information for UL MU transmission of an acknowledgment (ACK) frame, and

Transmitting a UL MU PPDU including the ACK frame as a response to the DL MU PPDU based on the scheduling information; Including,

The scheduling information,

UL MU PPDU length information and resource unit allocation (Resource Unit allocation) information for the resource unit used for the UL MU transmission of the ACK frame, UL MU transmission method.
The method of claim 1,

The scheduling information further includes Modulation and Coding Scheme (MCS) level information applied to the ACK frame and transmission channel information of the UL MU PPDU.
The method of claim 1,

The resource allocation information includes a plurality of bits sequentially corresponding to 26 tone resource units allocated for UL MU transmission of the ACK frame,

The bit value of each of the plurality of bits is switched to a bit value different from the bit value of the previous bit as the STA to which the corresponding 26-tone resource unit is assigned is changed to another STA.
The method of claim 3, wherein

Transmitting the UL MU PPDU,

When the resource allocation information indicates the allocation of the 26-tone resource unit to the STA, transmitting a UL MU PPDU including the ACK frame by using two 13-tone resource units discontinuously located on a frequency axis; UL MU transmission method.
The method of claim 1,

The resource allocation information includes a plurality of bits sequentially corresponding to the remaining 26 tone resource units except for a specific 26 tone resource unit among 26 tone resource units allocated for UL MU transmission of the ACK frame,

The bit value of each of the plurality of bits is switched to a bit value different from the bit value of the previous bit as the STA to which the corresponding 26-tone resource unit is assigned is changed to another STA.
The method of claim 5,

The specific 26 ton resource unit,

When the transmission channel of the UL MU PPDU is a 20MHz channel, it is a 26-ton resource unit located in the center of the 20MHz channel,

When the transmission channel of the UL MU PPDU is a 40 MHz channel, it is a 26 ton resource unit located between 52 ton resource units or between 106 ton resource units,

When the transmission channel of the UL MU PPDU is an 80 MHz channel, the UL MU transmission method of 26 ton resource unit located in the center of the 80 MHz channel.
The method of claim 5,

The resource allocation information,

When the number of STAs indicated by the resource allocation information is smaller than the number of STAs receiving the DL MU PPDU, it indicates that the specific resource unit is allocated to an STA not indicated by the resource allocation information.

If the number of STAs indicated by the resource allocation information is the same as the number of STAs receiving the DL MU PPDU, indicating that the specific resource unit is not-used.
The method of claim 1,

When a resource allocation method for the UL MU transmission is defined in a table for each index,

The resource allocation information, the UL MU transmission method including index information corresponding to a specific resource allocation method for the UL MU transmission of the ACK frame.
In the STA (Station) device of a wireless LAN (WLAN) system,

An RF unit for transmitting and receiving wireless signals; And

A processor for controlling the RF unit; Including,

The processor,

Receives a downlink (DL) MU Physical Protocol Data Unit (PPDU) including a physical preamble and a data field,

The data field includes at least one Mac Protocol Data Unit (MPDU), and the at least one MPDU includes a trigger frame or a MAC header, wherein the trigger frame or the medium access control (MAC) header is an acknowledgment (ACK). Scheduling information for UL MU transmission of the frame, and

In response to the DL MU PPDU, a UL MU PPDU including the ACK frame is transmitted based on the scheduling information.

The scheduling information,

And resource unit allocation information about a resource unit used for UL MU transmission of the ACK frame.
The method of claim 9,

The scheduling information further includes Modulation and Coding Scheme (MCS) level information applied to the ACK frame and transport channel information of the UL MU PPDU.
The method of claim 9,

The resource allocation information includes a plurality of bits sequentially corresponding to 26 tone resource units allocated for UL MU transmission of the ACK frame,

The bit value of each of the plurality of bits is switched to a bit value different from the bit value of the previous bit as the STA to which the corresponding 26-tone resource unit is allocated is changed to another STA.
The method of claim 11,

The processor,

When the resource allocation information indicates the 26-tone resource unit allocation to the STA, STA device for transmitting a UL MU PPDU including the ACK frame by using two 13-tone resource units discontinuously located on the frequency axis .
The method of claim 9,

The resource allocation information includes a plurality of bits sequentially corresponding to the remaining 26 tone resource units except for a specific 26 tone resource unit among 26 tone resource units allocated for UL MU transmission of the ACK frame,

The bit value of each of the plurality of bits is switched to a bit value different from the bit value of the previous bit as the STA to which the corresponding 26-tone resource unit is allocated is changed to another STA.
The method of claim 13,

The specific 26 ton resource unit,

When the transmission channel of the UL MU PPDU is a 20MHz channel, it is a 26-ton resource unit located in the center of the 20MHz channel,

When the transmission channel of the UL MU PPDU is a 40 MHz channel, it is a 26 ton resource unit located between 52 ton resource units or between 106 ton resource units,

If the transmission channel of the UL MU PPDU is an 80MHz channel, 26 STA resource unit located in the center of the 80MHz channel, STA device.
The method of claim 13,

The resource allocation information,

When the number of STAs indicated by the resource allocation information is smaller than the number of STAs receiving the DL MU PPDU, it indicates that the specific resource unit is allocated to an STA not indicated by the resource allocation information.

And when the number of STAs indicated by the resource allocation information is the same as the number of STAs receiving the DL MU PPDU, indicating that the specific resource unit is not-used.
The method of claim 9,

When a resource allocation method for the UL MU transmission is defined in a table for each index,

The resource allocation information, the STA apparatus including index information corresponding to a specific resource allocation method for the UL MU transmission of the ACK frame.