KR20160048012A - Transmission method for multi user in wireless local area network - Google Patents

Abstract

Disclosed is a multi-user transmission method in a wireless LAN. An operation method of a first station comprises the following steps of: receiving a trigger frame from a second station wherein the trigger frame includes resource information allocated for multi-user transmission and TA related information for a PPDU transmitted through a resource indicated by the resource information; and transmitting the PPDU to the second station in case of indication by the TA related information. Therefore, performance of a wireless LAN system can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-user transmission method in a wireless local area network (WLAN)

The present invention relates to wireless LAN technology and, more particularly, to multi-user transmission.

With the development of information and communication technology, various wireless communication technologies are being developed. Among them, a wireless local area network (WLAN) may be a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), a smart phone A smart phone, a tablet PC, or the like, to wirelessly connect to the Internet in a home, an enterprise, or a specific service providing area.

The standard for wireless LAN technology is being developed as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. As the spread of wireless LANs is activated and applications using the wireless LANs are diversified, there is a growing need for new wireless LAN technologies that support higher throughput than existing wireless LAN technologies. Very high throughput (VHT) Wireless LAN technology is a proposed technology to support data rates of over 1Gbps. Among them, the wireless LAN technology according to the IEEE 802.11ac standard is a technology for providing an ultra high throughput in a band below 6 GHz, and the wireless LAN technology according to the IEEE 802.11ad standard is a technology for providing an ultra high throughput in a 60 GHz band.

In addition, standards for various wireless LAN technologies have been defined and technology development is under way. Typically, the wireless LAN technology according to the IEEE 802.11af standard is a technology defined for operation of a wireless LAN in a TV idle band, and the wireless LAN technology according to the IEEE 802.11ah standard operates at a low power in a band below 1 GHz The wireless LAN technology according to the IEEE 802.11ai standard is a technology defined for fast initial link setup (FILS) in a wireless LAN system. Recently, IEEE 802.11ax standardization for the purpose of improving frequency efficiency in a dense environment in which a plurality of base stations and terminals exist is proceeding.

In a system based on such a wireless LAN technology, multiuser (MU) transmission can be performed. The multi-user transmission may include uplink and downlink transmission based on orthogonal frequency division multiple access (OFDMA), and uplink and downlink transmission based on MU-MIMO (multi user-multiple input multiple output). When multi-user transmission is performed between stations, information necessary for multi-user transmission can be signaled to the corresponding station.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of operating a station supporting multi-user transmission in a wireless LAN.

According to an aspect of the present invention, there is provided a method of operating a first station in a wireless LAN, the method comprising: receiving information on resources allocated for multi-user transmission and TA related information for PPDUs transmitted through the resource; Receiving from the second station a trigger frame including the PPDU, and transmitting the PPDU to the second station at a time point indicated by the TA related information.

Here, the multi-user transmission may be OFDMA-based transmission or MU-MIMO based transmission.

Here, the time indicated by the TA related information may be set such that each of the PPDUs is received in the second station within a predetermined time range.

Here, at least two stations among the plurality of stations participating in the multi-user transmission may use different TA values, and the plurality of stations may include the first station.

Here, the TA related information may indicate a relative ratio of the TA value to the reference TA value.

Here, the TA related information may indicate an increase / decrease of the TA value with respect to the reference TA value.

According to another aspect of the present invention, there is provided a method of operating a station in a wireless LAN, the method including receiving information on resources allocated for multi-user reception and TA related information for PPDUs received through the resource, Generating a trigger frame, and transmitting the trigger frame.

Here, the time indicated by the TA related information may be set to receive the PPDUs within a predetermined time range.

According to another aspect of the present invention, there is provided a method of operating a first station in a wireless local area network (WLAN), the method including receiving information on resources allocated for multi-user transmission and guard subcarriers for PPDUs transmitted through the resources, Comprising the steps of: receiving a trigger frame from a second station, the trigger frame including pertinent information, and transmitting a PPDU to a second station via a subcarrier excluding a guard subcarrier indicated by the guard subcarrier- To the station.

Here, the multi-user transmission may be OFDMA-based transmission or MU-MIMO based transmission.

Herein, the guard subcarriers indicated by the guard subcarrier related information may be set such that the second station receives each of the PPDUs through a predetermined frequency band.

Here, each of the plurality of stations participating in the multi-user transmission may use the same number of guard subcarriers, and the plurality of stations may include the first station.

At least two stations among the plurality of stations participating in the multi-user transmission may use different numbers of guard subcarriers, and the plurality of stations may include the first station.

Here, the guard sub-carrier related information may indicate a relative ratio of the number of guard sub-carriers to the number of guard guard sub-carriers.

Here, the guard sub-carrier related information can instruct the increase / decrease in the number of guard sub-carriers with respect to the number of reference guard sub-carriers.

According to another aspect of the present invention, there is provided a method of operating a station in a wireless local area network (WLAN), including: receiving information on resources allocated for multi-user reception and guard subcarrier related information for PPDUs received through the resource; Generating a trigger frame including the trigger frame, and transmitting the trigger frame.

Here, the guard subcarriers indicated by the guard subcarrier related information may be set to receive the PPDUs through a predetermined frequency band.

According to another aspect of the present invention, there is provided a method of operating a first station in a wireless local area network (WLAN), the method comprising receiving information on resources allocated for multi-user transmission and transmission power of PPDUs transmitted through the resources Receiving a trigger frame containing information from a second station, and transmitting the PPDU to the second station at a transmit power indicated by the transmit power related information.

Here, the multi-user transmission may be OFDMA-based transmission or MU-MIMO based transmission.

Here, the transmission power indicated by the transmission power related information may be set such that the reception power of each of the PPDUs in the second station falls within a predetermined reception power range.

Here, each of the plurality of stations participating in the multi-user transmission may use the same transmission power, and the plurality of stations may include the first station.

Here, at least two stations among the plurality of stations participating in the multi-user transmission may use transmission power of different sizes, and the plurality of stations may include the first station.

Here, the transmission power related information may indicate a relative ratio of the transmission power to the reference transmission power.

Here, the transmission power related information may indicate an increase / decrease of transmission power with respect to a reference transmission power.

According to another aspect of the present invention, there is provided a method of operating a station in a wireless LAN, the method comprising: receiving information on resources allocated for multi-user reception and information on transmission power of PPDUs received through the resource; Generating a trigger frame including the trigger frame, and transmitting the trigger frame.

Here, the transmission power indicated by the transmission power related information may be set such that the reception power of each of the PPDUs falls within a preset reception power range.

In accordance with the present invention, an access point may be configured to perform uplink transmission when performing multi-user transmission (e.g., orthogonal frequency division multiple access (OFDMA) transmission, multiuser-multiple input multiple output (MU-MIMO) (E.g., cyclic prefix (CP) related information, timing advance (TA) related information, and the like) necessary to mitigate or alleviate the inconsistency in the reception timing of the link PPDU (physical layer convergence procedure (PLCP) Information necessary for mitigating or eliminating the mismatch of the frequency band in which the uplink PPDU is received (for example, guard subcarrier related information, etc.), information necessary for mitigating or eliminating the mismatch between the received power of the uplink PPDU Related information of the uplink PPDU to the stations participating in the multi-user transmission.

Each of the stations participating in the multi-user transmission can generate an uplink PPDU based on the information received from the access point, and can transmit the generated uplink PPDU to the access point. The access point may receive an uplink PPDU from each of the stations. According to the above-described method, inconsistencies in the reception time points of the uplink PPDUs, mismatches in the reception frequency bands, mismatches in the reception power strengths, and the like can be mitigated or eliminated, and the access point can successfully decode the uplink PPDUs. Therefore, the performance of the WLAN system can be improved.

1 is a block diagram showing the structure of a wireless LAN device.
2 is a schematic block diagram illustrating a transmission signal processing unit in a wireless LAN.
3 is a schematic block diagram illustrating a received signal processing unit in a wireless LAN.
FIG. 4 is a diagram showing a relationship between frames. FIG.
5 is a conceptual diagram for explaining a frame transmission procedure according to the CSMA / CA scheme for avoiding collision between frames in a channel.
6 is a conceptual diagram showing an embodiment of a topology of a wireless local area network (WLAN).
7 is a flowchart illustrating an uplink multi-user method according to an embodiment of the present invention.
8 is a block diagram illustrating a trigger frame according to an embodiment of the present invention.
9 is a block diagram illustrating a UL MU PPDU according to an embodiment of the present invention.
10 is a flowchart illustrating an uplink multi-user method according to another embodiment of the present invention.
11 is a flowchart illustrating an uplink multi-user method according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and like parts are denoted by similar reference numerals throughout the specification.

A basic service set (BSS) in a wireless local area network (WLAN) (hereinafter referred to as "wireless LAN") includes a plurality of wireless LAN devices. The WLAN device may include a medium access control (MAC) layer and a physical (PHY) layer according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. At least one of the plurality of wireless LAN devices may be an access point (AP), and the remaining wireless LAN device may be a non-AP station (non-AP STA). Or ad-hoc networking, a plurality of wireless LAN devices may all be non-AP stations. In general, a station (STA) is also used when collectively referred to as an access point (AP) and a non-AP station, but for simplicity, the non-AP station is also abbreviated as a station (STA).

1 is a block diagram showing the structure of a wireless LAN device.

1, a wireless LAN device 1 includes a baseband processor 10, a radio frequency (RF) transceiver 20, an antenna unit 30, a memory 40, an input interface unit 50, An output interface unit 60, and a bus 70, The baseband processor 10 performs the baseband related signal processing described herein, and may include a MAC processor 11, a PHY processor 15, and the like.

In one embodiment, the MAC processor 11 may include a MAC software processing unit 12 and a MAC hardware processing unit 13. At this time, the memory 40 includes software (hereinafter referred to as "MAC software") including some functions of the MAC layer, and the MAC software processing unit 12 implements some functions of the MAC by driving the MAC software , The MAC hardware processing unit 13 may implement the remaining functions of the MAC layer as hardware (MAC hardware), but the present invention is not limited thereto. The PHY processor 15 may include a transmission signal processing unit 100 and a reception signal processing unit 200.

The baseband processor 10, the memory 40, the input interface unit 50 and the output interface unit 60 can communicate with each other via the bus 70. [ The RF transceiver 20 may include an RF transmitter 21 and an RF receiver 22. In addition to the MAC software, the memory 40 may store an operating system, an application, etc., and the input interface unit 50 acquires information from the user, and the output interface unit 60 acquires information from the user Output.

The antenna unit 30 may include one or more antennas. When using multiple-input multiple-output (MIMO) or multi-user MIMO (MU-MIMO), the antenna unit 30 may include a plurality of antennas.

2 is a schematic block diagram illustrating a transmission signal processing unit in a wireless LAN.

2, the transmission signal processing unit 100 includes an encoder 110, an interleaver 120, a mapper 130, an inverse Fourier transformer 140, and a guard interval (GI) inserter 150 can do.

Encoder 110 encodes the input data and may be, for example, a forward error correction (FEC) encoder. The FEC encoder may include a binary convolutional code (BCC) encoder, in which case a puncturing device may be included. Alternatively, the FEC encoder may include a low-density parity-check (LDPC) encoder.

The transmission signal processing unit 100 may further include a scrambler scrambling the input data before encoding the input data to reduce the probability that a long same sequence of 0's or 1's occurs. If a plurality of BCC encoders are used as the encoder 110, the transmission signal processing unit 100 may further include an encoder parser for demultiplexing the scrambled bits into a plurality of BCC encoders. When an LDPC encoder is used as the encoder 110, the transmission signal processing unit 100 may not use the encoder parser.

The interleaver 120 interleaves the bits of the stream output from the encoder 110 to change the order. Interleaving may be applied only when a BCC encoder is used as the encoder 110. [ The mapper 130 maps the bit stream output from the interleaver 120 to constellation points. When an LDPC encoder is used as the encoder 110, the mapper 130 may perform LDPC tone mapping in addition to the property store mapping.

When MIMO or MU-MIMO is used, the transmission signal processing unit 100 may use a plurality of interleavers 120 and a plurality of mappers 130 corresponding to the number of spatial streams N _SS . The transmission signal processing unit 100 may further include a stream parser that divides outputs of a plurality of BCC encoders or LDPC encoders into a plurality of blocks to be provided to different interleavers 120 or a mapper 130. In addition, the transmission signal processing unit 100 includes a space-time block code (STBC) encoder for spreading a property point from N _SS spatial streams to N _STS space-time streams, and a spatial mapper for mapping the received signals to transmit chains. The spatial mapper can use direct mapping, spatial expansion, beamforming, or the like.

The inverse Fourier transformer 140 transforms a sex store block output from the mapper 130 or the spatial mapper into an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT) Domain block, that is, a symbol. When the STBC encoder and the spatial mapper are used, the inverse Fourier transformer 140 may be provided for each transmission chain.

When MIMO or MU-MIMO is used, the transmission signal processing unit 100 may insert a cyclic shift diversity (CSD) before or after the inverse Fourier transform to prevent unintended beamforming. The CSD may be specified for each transport chain or for each space-time stream. Or CSD may be applied as part of a spatial mapper. Further, when using MU-MIMO, some blocks before the space mapper may be provided for each user.

The GI inserter 150 inserts a GI in front of the symbol. The transmission signal processing unit 100 can smoothly window the edge of the symbol after inserting the GI. The RF transmitter 21 converts the symbol into an RF signal and transmits it via the antenna. When MIMO or MU-MIMO is used, the GI inserter 150 and the RF transmitter 21 can be provided for each transmission chain.

3 is a schematic block diagram illustrating a received signal processing unit in a wireless LAN.

3, the received signal processing unit 200 may include a GI eliminator 220, a Fourier transformer 230, a demapper 240, a deinterleaver 250, and a decoder 260. The RF receiver 22 receives the RF signal through the antenna and converts it into a symbol, and the GI remover 220 removes the GI from the symbol. When using MIMO or MU-MIMO, the RF receiver 22 and the GI remover 220 may be provided for each receive chain.

The Fourier transformer 230 transforms symbols, i.e., time domain blocks, into discrete Fourier transforms (DFTs) or fast Fourier transforms (FFTs) into frequency domain ghost points. Fourier transformer 230 may be provided for each receive chain. If MIMO or MU-MIMO is used, it may include a spatial demapper that transforms the Fourier transformed reception chain into a spatiotemporal stream, and an STBC decoder that despreads the span stream from the space-time stream to the spatial stream. have.

The dem mapper 240 demaps the block of the sex store output from the Fourier transformer 230 or the STBC decoder into a bit stream. If the received signal is LDPC encoded, demapper 240 may perform further LDPC tone demapping before property demapping. The deinterleaver 250 deinterleaves the bits of the stream output from the demapper 240. Deinterleaving can be applied only when the received signal is BCC encoded.

In case of using MIMO or MU-MIMO, the received signal processing unit 200 may use a plurality of demapper 240 and a plurality of deinterleavers 250 corresponding to the number of spatial streams. At this time, the received signal processing unit 200 may further include a stream deparser that combines the streams output from the plurality of deinterleavers 250.

The decoder 260 decodes the stream output from the deinterleaver 250 or the stream decoder, and may be, for example, an FEC decoder. The FEC decoder may include a BCC decoder or an LDPC decoder. The received signal processing unit 200 may further include a descrambler for descrambling the decoded data by the decoder 260. When a plurality of BCC decoders are used as the decoder 260, the received signal processing unit 200 may further include an encoder deparser for multiplexing the decoded data. When the LDPC decoder is used as the decoder 260, the received signal processing unit 200 may not use the encoder de-parser.

FIG. 4 is a diagram showing an interframe space (IFS) relationship. FIG.

Referring to FIG. 4, a data frame, a control frame, and a management frame may be exchanged between the wireless LAN devices. A data frame is a frame used for transmission of data forwarded to an upper layer. The data frame is transmitted after performing a backoff after a distributed coordination function IFS (DIFS) from when the medium becomes idle.

The management frame is used for exchange of management information that is not forwarded to the upper layer, and is transmitted after backoff after IFS such as DIFS or PIFS (point coordination function IFS). The subtype frame of the management frame includes Beacon, Association request / response, probe request / response, and authentication request / response. A control frame is a frame used for controlling access to a medium. Subtype frames of the control frame include RTS, CTS, and ACK. The control frame is transmitted after backoff after DIFS elapses when it is not a response frame of another frame, and is transmitted without backoff after SIFS (short IFS) if it is a response frame of another frame. The type and subtype of the frame can be identified by a type field and a subtype field in the frame control field.

Meanwhile, the QoS (Quality of Service) STA can transmit an arbitration IFS (AIFS) for an access category (AC) to which a frame belongs, i.e., a frame after the backoff after the AIFS [AC] elapses. At this time, a frame in which AIFS [AC] can be used may be a control frame, not a data frame, a management frame, and a response frame.

5 is a conceptual diagram for explaining a frame transmission procedure according to a carrier sense multiple access (CSMA) / collision avoidance (CA) scheme for avoiding collision between frames in a channel.

Referring to FIG. 5, a first station STA1 denotes a transmitting station to which data is to be transmitted, and a second station STA2 denotes a receiving station that receives data transmitted from the first station STA1. The third station STA3 may be located in an area capable of receiving a frame transmitted from the first station STA1 and / or a frame transmitted from the second station STA2.

The first station STA1 can determine whether a channel is being used through carrier sensing. The first station STA1 can determine the occupation state of the channel based on the magnitude of the energy existing in the channel or the correlation of the signal or can use the NAV (network allocation vector) The occupied state can be judged.

The first station STA1 transmits a request to send (RTS) frame to the second station after performing the backoff if it is determined that the channel is not used by another station during DIFS (i.e., when the channel is idle) (STA2). When receiving the RTS frame, the second station STA2 may transmit a clear to send (CTS) frame, which is a response to the RTS frame, to the first station STA1 after SIFS.

On the other hand, when receiving the RTS frame, the third station STA3 transmits the frame transmission period (for example, SIFS + CTS frame + SIFS + data) continuously transmitted subsequently using duration information included in the RTS frame Frame + SIFS + ACK frame). Alternatively, when receiving the CTS frame, the third station STA3 may use the duration information included in the CTS frame to transmit a frame transmission period (for example, SIFS + data frame + SIFS + ACK frame) You can set the NAV timer for. The third station STA3 can update the NAV timer using the duration information included in the new frame when the new frame is received before the expiration of the NAV timer. The third station STA3 does not attempt to access the channel until the NAV timer expires.

When receiving the CTS frame from the second station STA2, the first station STA1 may transmit the data frame to the second station STA2 after SIFS from the completion of reception of the CTS frame. When the second station STA2 successfully receives the data frame, the second station STA2 can transmit an ACK frame, which is a response to the data frame, to the first station STA1 after SIFS.

The third station STA3 can determine whether the channel is being used through carrier sensing when the NAV timer expires. If the third station STA3 determines that the channel has not been used by another station during the DIFS since the expiration of the NAV timer, the third station STA3 may attempt to access the channel after the contention window CW due to the random backoff has passed.

6 is a conceptual diagram showing an embodiment of a topology of a wireless local area network (WLAN).

6, each of the first station 610 and the second station 620 may be located within the cell coverage of the access point 600 and may be associated with an access point 600, have. The first station 610 may be located closer to the access point 600 than the second station 620. The second station 620 may be located away from the liquid point 600 relative to the first station 610.

Each of the access point 600, the first station 610 and the second station 620 may perform multi-user (MU) transmission. The multi-user transmission includes uplink transmission based on orthogonal frequency division multiple access (OFDMA), downlink transmission based on OFDMA, uplink transmission based on multi user-multiple input multiple output (MIMO) -MIMO based downlink transmission, and the like. Hereinafter, "UL MU transmission" may refer to OFDMA based uplink transmission or MU-MIMO based uplink transmission, and may be referred to as "UL MU PPDU (physical layer convergence procedure data unit) "may refer to PPDUs transmitted / received by uplink multi-user transmission. "DL MU PPDU" may refer to an OFDMA-based downlink transmission or an MU-MIMO based downlink transmission, and a "DL MU PPDU " . ≪ / RTI >

Each of the access points 600, the first station 610 and the second station 620 can perform multi-user transmission in a bandwidth of 20 MHz units (for example, bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz units, Or a unit of bandwidth less than 20 MHz (e.g., in a 10 MHz bandwidth, 5 MHz, 2.5 MHz bandwidth, etc.). When the subcarrier spacing is 312.5 kHz, 156.25 kHz, or 78.125 kHz, the frequency band having a bandwidth of 20 MHz may include 64, 128, or 256 subcarriers, respectively, and a bandwidth of 10 MHz, 5 MHz, A multi-user transmission can be performed.

Meanwhile, when uplink multi-user transmission is performed, the first station 610 may transmit UL MU PPDU-1 to the access point 600 through a frequency band having a bandwidth of 20 MHz, and the second station 620 may transmit UL MU PPDU- 1 to the access point 600 through the frequency band used by the STA1 and the frequency band of the continuous bandwidth of 20 MHz. Reception of UL MU PPDU-1 at access point 600 due to difference in propagation delay time and difference in delay spread between UL MU PPDU-1 and UL MU PPDU-2, respectively, And the reception timing of the UL MU PPDU-2 may not coincide with each other. The inter-symbol interference (ISI) for the UL MU PPDU may be increased due to the inconsistency of the reception time point, in which case the access point 600 may not successfully decode each of the UL MU PPDU-1 and UL MU PPDU- have.

In addition, due to the doppler effect, the offset of the carrier frequency for each of UL MU PPDU-1 and UL MU PPDU-2 may be increased. In this case, UL The inter carrier interference (ICI) for the MU PPDU can be increased. Thus, the access point 600 may not be able to successfully decode UL MU PPDU-1 and UL MU PPDU-2, respectively. In addition, due to the difference in distance between the first station 610 and the second station 620 and the access point 600, and the obstacles located in the communication path, the path to each of UL MU PPDU-1 and UL MU PPDU- The path loss may be different. If the received power strength of each of the UL MU PPDU-1 and UL MU PPDU-2 is less than a preset reference due to the path loss, the access point 600 transmits UL MU PPDU-1 and UL MU PPDU- It may not be able to decode successfully.

Therefore, when multi-user transmission is performed, there is a need for a method for mitigating or eliminating inconsistencies in the reception timing of UL MU PPDUs (or DL MU PPDUs), inconsistencies in reception frequency bands, mismatches in received power strengths, and the like. Hereinafter, a method for mitigating or alleviating mismatches in the reception timing of the UL MU PPDUs, mismatches in the reception frequency bands, mismatches in the received power intensity, etc. when uplink multi-user transmission is performed will be described. However, The inconsistency of the reception timing of the DL MU PPDU, the inconsistency of the reception frequency band, the inconsistency of the received power intensity, etc., may be alleviated or eliminated.

The uplink multi-user transmission can be largely performed in three ways. In the first scheme, the access point can trigger transmission of the UL MU PPDU by transmitting a trigger frame to a plurality of stations, and each of the plurality of stations receiving the trigger frame transmits information included in the trigger frame Based UL MU PPDU can be generated and the generated UL MU PPDU can be transmitted to the access point. In the second scheme, an access point can transmit a DL MU PPDU to a plurality of stations, and each of a plurality of stations receiving a DL MU PPDU can generate a UL MU PPDU based on the information contained in the DL MU PPDU And can transmit the generated UL MU PPDU to the access point. In the third scheme, each of the plurality of stations can generate UL MU PPDUs independent of the trigger frame and DL MU PPDUs described above, and can transmit the generated UL MU PPDUs to the access point. In the first method described above, a method for mitigating or eliminating the inconsistency in the reception timing of the UL MU PPDU, the inconsistency of the reception frequency band, and the inconsistency in the received power intensity is as follows.

7 is a flowchart illustrating an uplink multi-user method according to an embodiment of the present invention.

Referring to FIG. 7, an access point (AP) may generate a trigger frame (S700). The trigger frame may be used to trigger transmission of the UL MU PPDU. The trigger frame may include information necessary for uplink multi-user transmission. The trigger frame can have the following structure.

8 is a block diagram illustrating a trigger frame according to an embodiment of the present invention.

8, the trigger frame 800 includes a frame control field 801, a duration field 802, a common information field 803, at least one station-specific information fields 804-1, ..., 804 -N) and a frame check sequence (FCS) field 805. The fields included in the trigger frame 800 are not limited to the contents described above, and the trigger frame 800 may further include other fields as needed. The common information field 803 may include information commonly used by a plurality of stations among the information required for uplink multi-user transmission.

The number of station-specific information fields 804-1, ..., and 804-N may be the same as the number of stations participating in uplink multi-user transmission. For example, if the number of the plurality of stations participating in the uplink multi-user transmission is three, the trigger frame 800 may include three station-specific information fields 804-1, ..., 804-N. have. Each of the station-specific information fields 804-1, ..., 804-N may include information used by a particular station participating in the uplink multi-user transmission. For example, the per-station information-1 field 804-1 may include information used by a first station participating in an uplink multi-user transmission.

Referring again to FIG. 7, the trigger frame includes identification information indicating each of a plurality of stations (STAs) involved in uplink multi-user transmission, resource allocation information indicating a resource to which the UL MU PPDU is transmitted, FFT / IFFT structure information indicating an FFT / IFFT structure used for Fourier transform in the transmission / reception step, MCS information indicating a modulation and coding scheme (MCS) used for modulation and coding of UL MU PPDU, UL MU PPDU Payload information indicating the size of the payload to be included, and the like.

The identification information may include a MAC address, an association identifier (AID), a partial ID (PAID), a group ID, and the like. The identification information may be included in the common information field 803 of the trigger frame 800 or the station-specific information fields 804-1, ..., 804-N. The identification information is not limited to the contents described above, and the identification information can be set variously. The resource allocation information may refer to frequency band information, time domain information, and the like allocated to each of a plurality of stations (STAs) participating in uplink multi-user transmission. For example, if uplink multi-user transmission is performed over a frequency band with a bandwidth of 80 MHz, a first frequency band with a bandwidth of 20 MHz may be indicated by a binary number "00 " The second frequency band may be indicated by the binary number "01 ", the third frequency band with a bandwidth of 20 MHz contiguous with the second frequency band may be indicated by the binary number" 10 & The fourth frequency band of 20 MHz can be indicated by the binary number "11 ". At this time, when a plurality of stations (STAs) participating in uplink multi-user transmission are STA1, STA2, STA3 and STA4, resource allocation information set to binary number "01 11 10 00" is transmitted to STA1, STA2, STA3 and STA4 The second frequency band, the fourth frequency band, the third frequency band, and the first frequency band are allocated. The resource allocation information may be included in the common information field 803 of the trigger frame 800 or the station specific information fields 804-1, ..., 804-N. The method of setting the resource allocation information is not limited to that described above, and the resource allocation information can be set in various ways.

The FFT / IFFT structure information can indicate the size of the FFT / IFFT used in the transmission / reception phase of the UL MU PPDU. For example, the FFT / IFFT structure information set to binary numbers "00", "01", "10" and "11" respectively has 32-point, 62- The branch may indicate an FFT / IFFT. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses FFT / IFFT of the same size, the FFT / IFFT structure information may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use different sizes of FFT / IFFT structures, the FFT / IFFT structure information is transmitted to station-specific information fields of the trigger frame 800 804-1, ..., 804-N. The method of setting the FFT / IFFT structure information is not limited to that described above, and the FFT / IFFT structure information can be set in various ways.

The MCS information may indicate the MCS used in the transmission / reception phase of the UL MU PPDU. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses the same MCS, the MCS information may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use different MCSs, the MCS information is transmitted to the station-specific information fields 804-1, ..., 804 of the trigger frame 800 -N). ≪ / RTI > The payload information may indicate the size of the payload included in the UL MU PPDU. When each of a plurality of stations (STAs) participating in uplink multi-user transmission transmits a payload of the same size, the payload information may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of STAs participating in uplink multi-user transmission transmit payloads of different sizes, the payload information is transmitted to station-specific information fields 804-1 , ..., 804-N.

In addition, the trigger frame may include information (e. G., Cyclic prefix (CP) related information, timing advance (TA) related information, etc.) for mitigating or eliminating a reception time inconsistency of the UL MU PPDU. The CP related information may include CP length information indicating the CP length included in the UL MU PPDU, and may further include an indicator indicating whether to use the CP length indicated by the CP length information. Here, the access point (AP) transmits a separate frame (for example, "data frame-ACK frame", "RTS frame-CTS frame", " ) Frame (e.g., an authentication request frame, an association request frame, etc.), a response frame (e.g., an authentication response frame, a connection response frame, Time, delay spread, etc., and the CP length included in the UL MU PPDU can be determined based on the measured information. The manner of determining the CP length is not limited to that described above, and the CP length can be determined through various methods.

The CP length information can directly indicate the CP length. Here, the CP length may be 0.4 mu s, 0.8 mu s, 1.6 mu s, 3.2 mu s, or the like. Alternatively, the CP length indicated by the CP length information may be represented by two bits. For example, CP length information set to binary numbers "00", "01", "10", and "11" may indicate a CP having a length of 0.4 μs, 0.8 μs, 1.6 μs, and 3.2 μs. Alternatively, the CP length information may indicate a relative ratio of the CP length to the reference CP length. For example, if the reference CP length is 0.8 mu s and the relative proportions of the CP lengths indicated by the CP length information are 1/2, 1, 2 and 4, then this is 0.4 mu s, 0.8 mu s, 1.6 mu s, Lt; RTI ID = 0.0 > CP < / RTI > Alternatively, the CP length information may indicate an increase or a decrease in the CP length relative to the reference CP length. For example, when the reference CP length is 0.8 占 퐏, the CP length information set to the binary number "0 " may indicate the use of the reference CP length, and the CP length information set to binary number " 1 " CP length (e.g., 1.6 占 퐏, 3.2 占 퐏, and the like) may be used. As another example, when the reference CP length is 0.8 占 퐏, the CP length information set to the binary number "0" may indicate that the reference CP length is used, and the CP length information set to binary number "1" (For example, 0.4 mu sec or the like) may be used. An access point (AP) may instruct the use of a CP length equal to or less than a reference CP length when uplink multi-user transmission is performed indoors, The use of a CP length that is longer than the CP length.

Here, the reference CP length may be preset between the access point (AP) and a plurality of stations (STAs). If the reference CP length is not set in advance, the information indicating the reference CP length may be included in the common information field 803 of the trigger frame 800. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses the same CP length (or relative ratio of CP length, increase / decrease of CP length, etc.), the CP length information is common to the trigger frame 800 May be included in the information field 803. When at least two stations among a plurality of stations participating in uplink multi-user transmission use different CP lengths (or a relative ratio of CP lengths, increase / decrease of CP lengths) May be included in the station-specific information fields 804-1, ..., 804-N of the trigger frame 800. [

An indicator set to a binary number "0 " may indicate that the CP length indicated by the CP length information is not used, and an indicator set to binary" 1 " may indicate that the CP length indicated by the CP length information is to be used . When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses an indicator indicating the same information, the indicator may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use an indicator for indicating different information, the station-specific indicator is used for the station-specific information field 804-1 , ..., 804-N. The CP length information and the setting method of each indicator are not limited to the above-described contents, and each of the CP length information and the indicator can be set in various ways.

Meanwhile, the TA related information may include TA value information indicating a transmission time point of the UL MU PPDU, and may further include an indicator indicating whether to use the TA value indicated by the TA value information. Here, the access point (AP) is configured to transmit a separate frame (e.g., "data frame-ACK frame", "RTS frame-CTS frame", " (E.g., authentication request frame, connection request frame, etc.) - response frame (e.g., authentication response frame, connection response frame, etc.) The TA value indicating the transmission time point of the UL MU PPDU can be determined based on the received information. The manner of determining the TA value is not limited to that described above, and the TA value can be determined through various methods.

The TA value information can directly indicate the TA value. For example, the TA value indicated by the TA value information may be represented by two bits. The TA value may be expressed in units of time or length of symbols. For example, the TA value information set to binary numbers "00", "01", "10", and "11" may indicate that the TA values are 0.05 ms, 0.1 ms, 0.15 ms, and 0.2 ms. Alternatively, the TA value information may indicate a relative ratio of the TA value to the reference TA value. For example, when the reference TA value is 0.1 ms and the relative ratios of the TA values indicated by the TA value information are 1/2, 1, 3/2 and 2, respectively, this means that the TA values are 0.05 ms, 0.1 ms, 0.15 ms and 0.2 ms, respectively. Alternatively, the TA value information may indicate an increase or decrease of the TA value relative to the reference TA value. For example, when the reference TA value is 0.1 ms, the TA value information set to the binary number "0 " may indicate the use of the reference TA value, and the TA value information set to binary number " 1 " TA value (e.g., 0.15 ms, 0.2 ms, etc.). As another example, when the reference TA value is 0.1 ms, the TA value information set to the binary number "0" may indicate the use of the reference TA value, and the TA value information set to binary number " 1 " Value (e.g., 0.05 ms, etc.) may be used. Herein, the access point (AP) can instruct the use of the TA value below the reference TA value when the uplink multi-user transmission is performed indoors, and can use the TA value that is larger than the reference TA value when the uplink multi- The use of the TA value can be instructed.

Here, the reference TA value can be set in advance between the access point (AP) and a plurality of stations (STAs). If the reference TA value is not set in advance, the information indicating the reference TA value may be included in the common information field 803 of the trigger frame 800. [ When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses the same TA value (or a relative ratio of TA values, increase / decrease of TA values, etc.), the TA value information is shared among the trigger frames 800 May be included in the information field 803. When at least two stations among a plurality of stations participating in uplink multi-user transmission use different TA values (or a relative ratio of TA values, increase / decrease of TA values, etc.), the TA value information per station May be included in the station-specific information fields 804-1, ..., 804-N of the trigger frame 800. [

An indicator set to binary "0 " may indicate that the TA value indicated by the TA value information is not used, and an indicator set to binary" 1 " may indicate that the TA value indicated by the TA value information is used . When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses an indicator for indicating the same information, the indicator may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use an indicator for indicating different information, the station-specific indicator is used for the station-specific information field 804-1 , ..., 804-N. The TA value information and the setting method of each of the indicators are not limited to those described above, and each of the TA value information and the indicators can be set in various ways.

The trigger frame may also include information (e. G., Information related to guard subcarriers (or guard tones), etc.) to mitigate or mitigate the inconsistency of the received frequency band with the UL MU PPDU have. Here, the guard subcarrier may mean a subcarrier not used for transmission of the UL MU PPDU among the subcarriers constituting the resource indicated by the resource allocation information. The guard subcarrier related information may include guard subcarrier setting information indicating the number of guard subcarriers, and may further include an indicator indicating whether to use guard subcarriers indicated by the guard subcarrier setting information . The guard subcarrier setting information can indicate not only the number of guard subcarriers but also the position of guard subcarriers. Here, the access point (AP) is configured to transmit a separate frame (e.g., "data frame-ACK frame", "RTS frame-CTS frame", " (E.g., an authentication request frame, a connection request frame, etc.) - a response frame (e.g., an authentication response frame, a connection response frame, etc.) The number and position of guard subcarriers for uplink multi-user transmission can be determined. The manner of determining the number and position of guard subcarriers is not limited to that described above, and the number and position of guard subcarriers can be determined through various methods.

The guard subcarrier setting information can directly indicate the number and position of guard subcarriers. For example, 2 bits out of the guard subcarrier setting information can indicate the number of guard subcarriers. The guard subcarrier setting information set to binary numbers "00", "01", "10" and "11" can indicate that the number of guard subcarriers is 2, 4, 6 and 8, respectively. One bit of the guard subcarrier setting information can indicate the position of the guard subcarrier. The guard subcarrier setting information set to the binary number "0 " may indicate that the guard subcarrier is located at the boundary of the frequency band, and the guard subcarrier setting information set to binary number & In the region of < / RTI >

Alternatively, the guard subcarrier setting information may indicate a relative ratio of the number of guard subcarriers to the number of guard guard subcarriers. For example, when the number of reference guard subcarriers is 2, and the relative ratios indicated by the guard subcarrier setting information are 1, 2, 3 and 4, this means that the number of guard subcarriers is 2, 4, 6 and 8 You can tell. Alternatively, the guard subcarrier setting information may indicate an increase or decrease in the number of guard subcarriers relative to the number of reference guard subcarriers. For example, when the number of reference guard subcarriers is 4, the guard subcarrier setting information set to binary number "0 " can indicate the use of the same number of guard subcarriers as the reference guard subcarrier, (E.g., six guard subcarriers, etc.) that is greater than the number of reference guard subcarriers can be used. As another example, when the number of reference guard subcarriers is 4, the guard subcarrier setting information set to binary number "0 " can indicate the use of the same number of guard subcarriers as the reference guard subcarrier, The set guard subcarrier setting information can indicate that a guard subcarrier (e.g., two guard subcarriers, etc.) smaller than the reference guard subcarrier number is used. An access point (AP) can instruct the use of guard subcarriers smaller than the number of guard subcarriers or reference guard subcarriers equal to the number of guard subcarriers when the uplink multi-user transmission is performed indoors, When multi-user transmission is performed outdoors, it may indicate the use of a larger number of guard subcarriers than a reference guard subcarrier.

Here, the number of reference guard subcarriers may be set in advance between the access point (AP) and the plurality of stations (STAs). If the number of reference guard subcarriers is not set in advance, the number of reference guard subcarriers may be included in the common information field 803 of the trigger frame 800. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses the same number of guard subcarriers (or a relative ratio of the number of guard subcarriers, the number of guard subcarriers, increase / decrease in the number of guard subcarriers, etc.) The guard subcarrier setting information may be included in the common information field 803 of the trigger frame 800. At least two stations among a plurality of stations participating in uplink multi-user transmission are different in guard subcarrier number (or guard subcarrier position, relative ratio of guard subcarriers, increase / decrease in the number of guard subcarriers ), The station-specific guard subcarrier setting information may be included in the station-specific information fields 804-1, ..., 804-N of the trigger frame 800. [

An indicator set to binary number "0 " may indicate that the guard subcarrier number and position indicated by the guard subcarrier setting information is not used, and an indicator set to binary number " 1 " The number of guard subcarriers and the position may be used. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses an indicator indicating the same information, the indicator may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use an indicator indicating different information, the station-specific indicator may be stored in the station information fields 804-1, ..., 804-N. Each of the guard subcarrier setting information and the indicators are not limited to the contents described above, and each of the guard subcarrier setting information and the indicators can be set in various ways.

In addition, the trigger frame may include information necessary to mitigate or alleviate mismatch in the received power of the UL MU PPDU (e.g., transmission power related information of the UL MU PPDU). The transmission power related information may include transmission power estimation information indicating the transmission power intensity of the UL MU PPDU or transmission power estimation information used to estimate transmission power intensity of the UL MU PPDU, Transmission power indicator indicating whether to use the transmission power strength indicated by the transmission power estimation information). In addition, the transmission power related information may include information indicating a maximum transmission power strength of each of a plurality of stations (STAs) involved in uplink multi-user transmission. On the other hand, the access point (AP) determines whether information indicating the maximum transmission power strength of each of a plurality of stations (STAs) from a plurality of stations participating in uplink multi-user transmission and maximum transmission power strength And can receive an indicator to indicate. The access point AP may set the transmission power intensity indicated by the transmission power related information to be equal to or less than the maximum transmission power strength of each of a plurality of stations (STAs) participating in the uplink multi-user transmission.

Here, the access point (AP) is configured to transmit a separate frame (e.g., "data frame-ACK frame", "RTS frame-CTS frame", " (E.g., authentication request frame, connection request frame, etc.) - response frame (e.g., authentication response frame, connection response frame, etc.) The transmission power of the UL MU PPDU can be determined based on the received information. The manner of determining the transmission power intensity is not limited to that described above, and the transmission power can be determined through various methods.

On the other hand, when uplink multi-user transmission is performed based on OFDMA, the bandwidth of a frame used for estimation of transmission power intensity (for example, a frame transmitted by each of a plurality of stations (STAs) A plurality of stations (STAs) participating in user transmission may be different from a bandwidth of a frame to be transmitted. In this case, the access point (AP) can notify the plurality of stations (STA) participating in the uplink multi-user transmission through the trigger frame in consideration of the difference in bandwidth, or transmit power intensity So that a plurality of stations (STA) participating in uplink multi-user transmission can notify the difference in bandwidth through the trigger frame.

Alternatively, when uplink multi-user transmission is performed based on MU-MIMO, transmission power is determined based on a frame to which beamforming is not applied (for example, a frame transmitted by each of a plurality of stations (STAs) Can be estimated. In this case, when a frame to which beamforming is applied in uplink multi-user transmission is transmitted, an access point (AP) transmits transmission power considering beamforming through a trigger frame to a plurality of stations (STA ). If it is determined that the transmission power intensity considering the beamforming can not be estimated or the previously performed beamforming sounding procedure is not valid, the access point (AP) performs a beamforming sounding procedure Can be performed.

The transmit power intensity information can directly indicate the transmit power strength of the UL MU PPDU. For example, the transmit power intensity information may include a reference transmit power strength and a transmit power offset per station, through which the transmit power intensity of the per station UL MU PPDU may be directly indicated. For example, if the reference transmission power strength is 20dB and the transmission power offset per station is + 5dB, this may indicate that the transmission power strength of the UL MU PPDU is 25dB.

Alternatively, the transmission power intensity information may indicate a relative ratio of the transmission power intensity to the reference transmission power intensity. For example, if the transmit power strength is 20 dB and the relative ratios indicated by the transmit power intensity information are 1/4, 1/2, 1, 2 and 4, then the transmit power strength is 14 dB, 17 dB, 20 dB, 23 dB And 26 dB, respectively. Alternatively, the transmit power intensity information may indicate an increase or a decrease in transmit power intensity relative to a reference transmit power intensity. For example, if the reference transmit power intensity is 20 dB, the transmit power intensity information set to binary "0" may indicate to use the reference transmit power intensity, and the transmit power intensity information set to binary & It may be instructed to use a transmit power intensity (e.g., 23 dB, etc.) that is greater than the power intensity. In another example, when the reference transmit power is 20 dB, the transmit power intensity information set to binary "0" may indicate using the reference transmit power intensity, and the transmit power intensity information set to binary "1 " (E.g., 17 dB) that is less than the intensity.

Alternatively, the transmission power estimation information may indicate a reference transmission power intensity and a bandwidth offset corresponding to the reference bandwidth (or a relative ratio of the bandwidth to the reference bandwidth, increase or decrease of the bandwidth to the reference bandwidth, and the like). For example, if the reference bandwidth is 20 MHz, the reference transmit power strength is 20 dB, and the bandwidth offset is 20 MHz, the transmit power estimate information indicates to use a transmit power strength corresponding to a bandwidth of 40 MHz (e.g., 23 dB) can do. Alternatively, if the reference bandwidth is 20 MHz, the reference transmit power is 20 dB, and the relative ratio of bandwidth is 1/2, then the transmit power estimate information uses the transmit power strength (e.g., 17 dB) corresponding to a bandwidth of 10 MHz . Alternatively, if the reference bandwidth is 20 MHz, the reference transmit power strength is 20 dB, and the increased bandwidth is used, then the transmit power estimate information may be a transmit power intensity corresponding to an increased bandwidth (e.g., 40 MHz) 23dB) may be used.

The transmission power estimation information may include the transmission power strength of the trigger frame including the reception power strength and the transmission power estimation information of the UL MU PPDU required by the access point (AP). Each of the plurality of stations (STAs) can estimate the path loss of the trigger frame based on the received power level and transmit power strength of the trigger frame when receiving the trigger frame including the transmission power estimation information, AP) of the UL MU PPDU required by the UL MU PPDU + path loss "can be estimated as the transmission power intensity of the UL MU PPDU. An access point (AP) may indicate the use of a transmission power intensity less than or equal to a reference transmission power intensity when uplink multi-user transmission is performed indoors, It can direct the use of large transmission power.

Here, the reference transmission power intensity can be preset between the access point (AP) and the plurality of stations (STAs). If the reference transmit power strength is not predetermined, information indicating the reference transmit power strength may be included in the common information field 803 of the trigger frame 800. [ (STAs) participating in the uplink multi-user transmission can use the same transmission power strength (or a relative ratio of transmission power strength, increase / decrease of transmission power strength, bandwidth offset, relative ratio of bandwidth, The transmission power estimation information (or the transmission power estimation information) when using the reception power strength of the UL MU PPDU requested by the AP, the transmission power intensity of the trigger frame including the transmission power estimation information, May be included in the common information field 803 of the mobile terminal 800. At least two stations among a plurality of stations participating in uplink multi-user transmission may transmit different transmission power intensities (or a relative ratio of transmission power intensities, increase / decrease of transmission power intensities, bandwidth offsets, (Or transmission power intensity of a trigger frame including transmission power estimation information, etc.), which is required by the access point (AP), is used, Power estimation information) may be included in the station-specific information fields 804-1, ..., 804-N of the trigger frame 800. [

The indicator set to binary number "0 " may indicate that the transmission power intensity indicated by the transmission power intensity information (or transmission power estimation information) is not used, and the indicator set to binary" 1 " Or transmission power estimation information) may be used. When each of a plurality of stations (STAs) participating in uplink multi-user transmission uses an indicator indicating the same information, the indicator may be included in the common information field 803 of the trigger frame 800. When at least two stations among a plurality of stations participating in uplink multi-user transmission use an indicator for indicating different information, the station-specific indicator is used for the station-specific information field 804-1 , ..., 804-N. The transmission power intensity information, the transmission power estimation information, and the setting method of each indicator are not limited to the above-described contents, and each of the transmission power intensity information, transmission power estimation information, and indicators may be set in various ways.

Meanwhile, the access point AP may transmit the trigger frame to a plurality of stations (STAs) (S710). Here, when uplink multi-user transmission is performed in a bandwidth of 20 MHz units (for example, bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and the like), the access point AP transmits a duplicated trigger frame To a plurality of stations (STAs) participating in uplink multi-user transmission. Alternatively, if uplink multi-user transmission is performed in units of bandwidth less than 20 MHz (e.g., bandwidths of 10 MHz, 5 MHz, 2.5 MHz, etc.), the access point (AP) Lt; / RTI >

Each of the plurality of stations (STAs) may receive a trigger frame from an access point (AP). Each of the plurality of stations (STAs) can determine that the UE itself participates in the uplink multi-user transmission when its identification information exists in the trigger frame, and the UL MU PPDU is transmitted through the resource allocation information included in the trigger frame The resource to be transmitted can be confirmed. In addition, each of the plurality of stations (STAs) can ascertain the offset of the carrier frequency for the received trigger frame and adjust its carrier frequency based on the identified offset. Each of the plurality of stations (STAs) can generate UL MU PPDU based on the information included in the trigger frame (S720).

If the trigger frame includes CP-related information (or if the trigger frame contains CP-related information and the indicator indicates that the CP length indicated by the CP-related information is to be used), a plurality of stations STAs) may generate an UL MU PPDU having a CP length indicated by CP related information. UL MU PPDUs can be generated based on the same CP length or different CP lengths. If the trigger frame includes TA related information (or if the trigger frame contains TA related information and the indicator indicates that the TA value indicated by the TA related information is to be used), a plurality of stations STAs) can determine the transmission time point of the UL MU PPDU based on the TA value indicated by the TA related information. When both the CP related information and the TA related information are included in the trigger frame, each of the plurality of stations (STAs) uses only one of the CP related information and the TA related information, or both the CP related information and the TA related information Can be used.

If the trigger frame includes guard subcarrier related information (or the number and position of the guard subcarriers indicated by the guard subcarrier related information are included in the trigger frame and the indicator is used for the guard subcarrier related information) ), Each of the plurality of stations (STAs) can confirm the number, position, etc. of guard subcarriers through the guard subcarrier related information, and confirm that the UL MU PPDU is not transmitted through the confirmed guard subcarrier Able to know.

When the trigger frame includes the transmission power related information of the UL MU PPDU (or if the trigger frame includes the transmission power related information of the UL MU PPDU and the indicator is the transmission indicated by the transmission power related information of the UL MU PPDU , The plurality of stations (STAs) can confirm the transmission power intensity indicated by the transmission power related information of the UL MU PPDU. Alternatively, each of the plurality of stations (STAs) can measure the received signal strength of the trigger frame, estimate the path loss based on the measured received signal strength and the transmitted signal strength of the trigger frame included in the trigger frame , The sum of the estimated path loss and the received signal strength of the UL MU PPDU required by the access point (AP) included in the trigger frame can be determined as the transmission power strength of the UL MU PPDU.

In addition, the transmission power related information of the UL MU PPDU includes a minimum transmission power intensity (hereinafter referred to as "minimum transmission power intensity") among the maximum transmission power strengths of a plurality of stations (STAs) participating in uplink multi- As shown in FIG. In this case, each of the plurality of stations (STAs) participating in the uplink multi-user transmission transmits a transmission power control signal to each of the plurality of stations (STAs) in the UL MU PPDU, The transmit power offset that can mitigate or mitigate interference). When the trigger frame includes the FFT / IFFT structure information, each of the plurality of stations (STAs) can confirm the size of the FFT / IFFT used for the Fourier transform of the UL MU PPDU. When MCS information is included in the trigger frame, each of a plurality of stations (STAs) can confirm the MCS used for modulation and coding of the UL MU PPDU. When the trigger frame includes the payload information of the UL MU PPDU, each of the plurality of stations (STAs) can check the size of the payload of the UL MU PPDU and generate a payload to correspond to the confirmed size have.

Each of the plurality of stations (STAs) is configured to transmit UL (UL) transmission power indicated by the transmission power intensity information through a frequency resource excluding a guard subcarrier indicated by guard subcarrier related information at a transmission time point indicated by the TA- The MU PPDU may be transmitted to the access point AP (S730). Here, the UL MU PPDU may be as follows.

9 is a block diagram illustrating a UL MU PPDU according to an embodiment of the present invention.

Referring to FIG. 9, the UL MU PPDU 900 may be transmitted over a frequency band with a bandwidth of 80 MHz. When a plurality of stations (STAs) participating in uplink multi-user transmission are STA1, STA2 and STA3, STA1 can use a frequency band having a bandwidth of 40 MHz in a bandwidth of 80 MHz, STA2 can use a frequency band And STA3 can use a frequency band having a bandwidth of 20 MHz continuous with the frequency band used by STA2. The UL MU PPDU 900 may include a legacy preamble, a high efficiency (HE) preamble (or a high efficiency WLAN) preamble, and a payload. The legacy preamble may include a legacy-short training field (L-STF), a long training field (L-LTF), and an L-SIG (signal) field. When the UL MU PPDU 900 is transmitted over a frequency band with a bandwidth of 80 MHz, the legacy preamble can be copied and transmitted in units of 20 MHz bandwidth.

The HE preamble may include an HE-SIG A field, at least one HE-STF, at least one HE-LTF, and a HE-SIG B field. When the UL MU PPDU 800 is transmitted over a frequency band with a bandwidth of 80 MHz, the HE-SIG A field may be copied and transmitted in units of 20 MHz bandwidth. The HE-SIG A field may include information commonly used by a plurality of stations (STA1, STA2, STA3) participating in uplink multi-user transmission. When each of a plurality of stations STA1, STA2, and STA3 participating in uplink multi-user transmission uses the same MCS, payload size, CP length, TA value, transmission power strength, number of guard subcarriers, and location, The HE-SIG A field may contain such information.

 The HE-STF, HE-LTF, and HE-SIG B fields and payloads may be transmitted over a bandwidth assigned to each of a plurality of stations (STA1, STA2, STA3) involved in uplink multi-user transmission. For example, STA1 can transmit HE-STF, HE-LTF, HE-SIG B field and payload over a frequency band of 40 MHz bandwidth. The HE-SIG B field transmitted by STA1 may contain information specific for STA1. STA2 can transmit HE-STF, HE-LTF, HE-SIG B field and payload over a frequency band with a bandwidth of 20 MHz. The HE-SIG B field transmitted by STA2 may contain information specific for STA2. STA3 can transmit HE-STF, HE-LTF, HE-SIG B field and payload over a frequency band with a bandwidth of 20 MHz. The HE-SIG B field transmitted by STA3 may contain information specific for STA3.

Alternatively, the HE-SIG B field may be copied and transmitted in units of 20 MHz bandwidth. In this case, the HE-SIG B field includes a first region including information commonly used by the stations STA1, STA2, and STA3 participating in the uplink multi-user transmission and a first region including information used by the stations participating in the uplink multi- STA1, STA2, and STA3). When each of a plurality of stations (STA1, STA2, STA3) participating in uplink multi-user transmission uses the same MCS, payload size, CP length, TA value, transmission power strength, guard subcarrier number and location The information may be included in the first area of the HE-SIG B field. At least two stations among a plurality of stations STA1, STA2, and STA3 participating in uplink multi-user transmission may transmit different MCSs, payload size, CP length, TA value, transmission power strength, The corresponding information may be included in the second area of the HE-SIG B field.

Referring again to FIG. 7, an access point (AP) may receive UL MU PPDUs from each of a plurality of stations (STAs) participating in an uplink multi-user transmission. When an access point (AP) transmits a trigger frame including information (e.g., CP related information, TA related information, and the like) used for mitigating or eliminating a mismatch in reception timing of the UL MU PPDU, UL MU PPDUs may be received from each of a plurality of stations (STAs) participating in uplink multiuser transmission within a range of time. Thus, the ISI for the UL MU PPDU can be reduced.

When an access point (AP) transmits a trigger frame including information (for example, guard sub-carrier related information, etc.) used for eliminating a mismatch in the reception frequency band of the UL MU PPDU, And may receive UL MU PPDUs with offsets of decodable subcarriers from each of a plurality of participating stations (STAs). Thus, the ICI for the UL MU PPDU can be reduced. When an access point (AP) transmits a trigger frame including information (for example, transmission power related information, etc.) used for eliminating a mismatch in received power intensity of the UL MU PPDU, the receiving power of the UL MU PPDU Lt; RTI ID = 0.0 > MU PPDU < / RTI > can be successfully decoded.

In the second scheme described above, a method for mitigating or eliminating mismatches in reception timing of the UL MU PPDUs, inconsistencies in the reception frequency bands, mismatches in received power, and the like are as follows.

10 is a flowchart illustrating an uplink multi-user method according to another embodiment of the present invention.

Referring to FIG. 10, an access point (AP) may transmit a DL MU PPDU to a plurality of stations (STAs) (S1000). The DL MU PPDU (e.g., at least one of the HE-SIG A field and the HE-SIG B field included in the DL MU PPDU) includes identification information indicating each of a plurality of stations (STAs), UL MU PPDU Resource allocation information indicating a resource, FFT / IFFT structure information indicating an FFT / IFFT structure used for Fourier transform in the UL MU PPDU transmission / reception step, MCS indicating an MCS used for modulation and coding of UL MU PPDU, Payload information indicating the size of the payload included in the UL MU PPDU, information (e.g., CP related information, TA related information) for mitigating or eliminating a mismatch at the receiving time of the UL MU PPDU, UL MU (E. G., Information related to guard subcarriers) for mitigating or eliminating discrepancies in the reception frequency bands of the PPDUs, information for mitigating or eliminating discrepancies in received power of UL MU PPDUs Transmission power related information of PPDU ), And the like.

Here, each of the identification information, the resource allocation information, the FFT / IFFT structure information, the MCS information, the payload information, the CP related information, the TA related information, the guard subcarrier related information, . ≪ / RTI > The HE-SIG B field of the DL MU PPDU includes a first region including information commonly used by a plurality of stations (STAs) participating in uplink multi-user transmission, and a first region including information used in uplink multi- And a second area containing information specific to each of the stations (STAs) of the mobile station. In this case, when each of the plurality of stations (STAs) uses the same FFT / IFFT structure information, MCS information, payload information, CP related information, TA related information, guard subcarrier related information, This information may be included in the first area of the HE-SIG B field. At least two stations among the plurality of stations use different FFT / IFFT structure information, MCS information, payload information, CP related information, TA related information, guard sub carrier related information, transmission power related information, , The corresponding information may be included in the second area of the HE-SIG B field.

Each of the plurality of stations (STAs) can receive a DL MU PPDU from an access point (AP), and when the identification information of the DL MU PPDU exists in its own, it can determine that it participates in uplink multi-user transmission And can confirm the resource to which the UL MU PPDU is to be transmitted through the resource allocation information included in the DL MU PPDU. Each of the plurality of stations (STAs) may generate UL MU PPDU based on the information included in the UL MU PPDU (S1010). The manner in which the UL MU PPDU is generated may be the same as the step S720 described above. Each of the plurality of stations (STAs) transmits a UL MU (UL MU) indicating a transmission power intensity indicated by the transmission power intensity information through a frequency resource excluding a subcarrier indicated by guard subcarrier related information at a transmission time point indicated by the TA- The PPDU may be transmitted to the access point AP (S1020).

An access point (AP) may receive UL MU PPDUs from each of a plurality of stations (STAs). When an access point (AP) transmits a DL MU PPDU including information (e.g., CP related information, TA related information, etc.) used for mitigating or eliminating a discrepancy in reception time of the UL MU PPDU, It is possible to receive UL MU PPDUs from each of a plurality of stations (STAs) participating in uplink multi-user transmission within a range of a reception time point. When an access point (AP) transmits a DL MU PPDU including information (e.g., guard subcarrier related information, etc.) used for mitigating or eliminating a mismatch in the reception frequency band of the UL MU PPDU, And may receive UL MU PPDUs with offsets of decodable subcarriers from each of a plurality of stations (STAs) participating in user transmissions. When the access point AP transmits a DL MU PPDU including information (e.g., transmission power related information, etc.) used to mitigate or alleviate the mismatch in the received power intensity of the UL MU PPDU, Mismatches in received power can be mitigated or eliminated.

In the third scheme described above, a method for mitigating or eliminating mismatches in reception timing of the UL MU PPDU, inconsistency in the reception frequency band, and inconsistency in received power intensity is as follows.

11 is a flowchart illustrating an uplink multi-user method according to another embodiment of the present invention.

Referring to FIG. 11, each of a plurality of stations (STAs) transmits an uplink multi-user transmission (for example, a trigger frame, a procedure for transmitting / receiving a separate frame other than the DL MU PPDU, (UL MU PPDU), resource allocation information indicating a resource to which the UL MU PPDU is transmitted, and an FFT / IFFT structure used for Fourier transform in the UL MU PPDU transmission / reception step MCS information indicating the MCS used for modulation or coding of the UL MU PPDU, payload information indicating the size of the payload included in the UL MU PPDU, inconsistency in the reception timing of the UL MU PPDU (E.g., CP related information, TA related information) for mitigating or eliminating the mismatch in the reception frequency band of the UL MU PPDU, information for mitigating or eliminating the mismatch in the reception frequency band of the UL MU PPDU (E.g., information related to transmission power of the UL MU PPDU) or the like for mitigating or eliminating the discrepancy of the received power of the UL MU PPDU from the access point AP (S 1100) .

Each of the plurality of stations (STAs) can determine that the UE participates in uplink multi-user transmission when its own identification information matches the acquired identification information, and the UL MU PPDU transmits You can identify the resource to be Each of the plurality of stations (STAs) may generate an UL MU PPDU based on the obtained information (S1110). The manner in which the UL MU PPDU is generated may be the same as the step S720 described above. Each of the plurality of stations (STAs) is configured to transmit UL (UL) transmission power indicated by the transmission power intensity information through a frequency resource excluding a guard subcarrier indicated by guard subcarrier related information at a transmission time point indicated by the TA- The MU PPDU may be transmitted to the access point AP (S1120).

An access point (AP) may receive UL MU PPDUs from each of a plurality of stations (STAs). (AP related information, TA related information, and the like) used to mitigate or alleviate a mismatch in reception timing of the UL MU PPDU is transmitted to each of a plurality of stations (STAs), the access point (AP) Can receive UL MU PPDUs from each of a plurality of stations (STAs) participating in uplink multi-user transmission within a range of decodable reception times. When information (e.g., guard subcarrier related information, etc.) used to mitigate or alleviate mismatches in the reception frequency band of the UL MU PPDU is transmitted to each of a plurality of stations (STAs), the access point UL MU PPDUs having offset of a decodable subcarrier from each of a plurality of stations (STAs) participating in uplink multi-user transmission. When information (for example, transmission power related information, etc.) used for eliminating a mismatch between received power levels of UL MU PPDUs is transmitted to each of a plurality of stations (STAs) Discrepancies can be mitigated or eliminated.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (26)

A method of operating a first station in a wireless local area network,
From a second station, a trigger frame including information on resources allocated for multi-user transmission and timing advance (TA) related information for PPDUs (physical layer convergence procedure (PLCP) protocol data units Receiving; And
And transmitting the PPDU to the second station at a time point indicated by the TA related information. The method according to claim 1,
Wherein the multi-user transmission is an orthogonal frequency division multiple access (OFDMA) transmission or a multi-user multiple input multiple output (MU-MIMO) transmission. The method according to claim 1,
Wherein the time point indicated by the TA related information is set such that each of the PPDUs is received at the second station within a predetermined time range. The method according to claim 1,
Wherein at least two stations among the plurality of stations participating in the multi-user transmission use different TA values, and the plurality of stations comprise the first station. The method according to claim 1,
Wherein the TA related information indicates a relative ratio of a TA value to a reference TA value. The method according to claim 1,
Wherein the TA related information indicates an increase / decrease of a TA value relative to a reference TA value. A method of operating a station in a wireless local area network,
Generating a trigger frame including information on resources allocated for multi-user reception and TA (timing advance) related information for PPDU (physical layer convergence procedure (PLC) protocol data units (PLCDs) received via the resource); And
And transmitting the trigger frame. The method of claim 7,
And the time point indicated by the TA related information is set to receive the PPDUs within a predetermined time range. A method of operating a first station in a wireless local area network,
From a second station, a trigger frame including information on resources allocated for multi-user transmission and guard subcarrier related information for PPDUs (physical layer convergence procedure (PLCP) protocol data units step; And
And transmitting a PPDU to the second station via a subcarrier excluding a guard subcarrier indicated by the guard subcarrier related information among the subcarriers constituting the resource. The method of claim 9,
Wherein the multi-user transmission is an orthogonal frequency division multiple access (OFDMA) transmission or a multi-user multiple input multiple output (MU-MIMO) transmission. The method of claim 9,
Wherein the guard subcarriers indicated by the guard subcarrier related information are set such that the second station receives each of the PPDUs on a predetermined frequency band. The method of claim 9,
Wherein each of the plurality of stations participating in the multiuser transmission uses the same number of guard subcarriers and the plurality of stations comprises the first station. The method of claim 9,
Wherein at least two of the plurality of stations participating in the multiuser transmission use a different number of guard subcarriers and the plurality of stations comprise the first station. The method of claim 9,
Wherein the guard subcarrier related information indicates a relative ratio of the number of guard subcarriers to the number of guard guard subcarriers. The method of claim 9,
Wherein the guard subcarrier related information indicates an increase / decrease in the number of guard subcarriers relative to the number of guard guard subcarriers. A method of operating a station in a wireless local area network,
Generating a trigger frame including information on resources allocated for multi-user reception and guard subcarrier related information for PPDU (physical layer convergence procedure (PLC) protocol data units (PLCD)) received through the resource; And
And transmitting the trigger frame. 18. The method of claim 16,
Wherein the guard subcarriers indicated by the guard subcarrier related information are set to receive the PPDUs on a predetermined frequency band. A method of operating a first station in a wireless local area network,
Receiving from the second station a trigger frame including information on resources allocated for multi-user transmission and transmission power related information of PPDUs (physical layer convergence procedure (PLC) protocol data units (PLCDs) transmitted via the resource); And
And transmitting a PPDU to the second station at a transmit power indicated by the transmit power related information. 19. The method of claim 18,
Wherein the multi-user transmission is orthogonal frequency division multiple access (OFDMA) based transmission or multi-user multiple input multiple output (MU-MIMO) based transmission. 19. The method of claim 18,
Wherein the transmission power indicated by the transmission power related information is set such that the reception power of each of the PPDUs in the second station falls within a predetermined reception power range. 19. The method of claim 18,
Wherein each of the plurality of stations participating in the multi-user transmission uses the same transmit power, and the plurality of stations comprise the first station. 19. The method of claim 18,
Wherein at least two stations among the plurality of stations participating in the multi-user transmission use different sizes of transmission power, and the plurality of stations comprise the first station. 19. The method of claim 18,
Wherein the transmission power related information indicates a relative ratio of transmission power to a reference transmission power. 19. The method of claim 18,
Wherein the transmission power related information indicates an increase or decrease in transmission power relative to a reference transmission power. A method of operating a station in a wireless local area network,
Generating a trigger frame including information on resources allocated for multi-user reception and transmission power related information of PPDUs (physical layer convergence procedure (PLC) protocol data units (PLCDs) received via the resource); And
And transmitting the trigger frame. 26. The method of claim 25,
Wherein the transmission power indicated by the transmission power related information is set such that the reception power of each of the PPDUs falls within a predetermined reception power range.

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