KR20160057325A - Method for transmitting and receiving frame in wireless local area network and apparatus for the same - Google Patents

Abstract

Disclosed are a method and an apparatus for transmitting/receiving a frame in a wireless LAN. The method comprises: a step of generating a request-to-send (RTS) frame, including a first indicator configured to indicate that multiplexed transmission is performed, raw channel information configured to be used for the multiplexed transmission, and each identifier of a plurality of candidate stations, configured to participate in the multiplexed transmission; a step of transmitting the RTS frame; and a step of receiving a clear-to-send (CTS) frame, which is a response to the RTS frame. Accordingly, performance a wireless LAN may be improved.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a method and apparatus for transmitting / receiving frames in a wireless LAN,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless LAN technology, and more particularly, to orthogonal frequency division multiple access (OFDMA) based frame transmission / reception technology.

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, when a RTS (request to send) -CTS (clear to send) procedure is performed to occupy a resource for downlink (OFDMA) orthogonal frequency division multiple access , And an access point can perform an RTS-CTS procedure with a single station. In this case, it may not be guaranteed that the channel state of all terminals participating in the DL OFDMA is idle. Of the terminals participating in the DL OFDMA, a terminal that has not transmitted a CTS frame may be interfered by a hidden terminal (i.e., a terminal that has not received an RTS frame or a CTS frame).

According to an aspect of the present invention, there is provided an orthogonal frequency division multiple access (OFDMA) frame transmission / reception method and apparatus.

According to an aspect of the present invention, there is provided a frame transmission method performed in a first station, the frame transmission method being performed in a first station includes a first indicator indicating that multiplex transmission is performed, Generating an RTS frame including the source channel information and the identifier of each of a plurality of candidate stations to participate in the multiplex transmission, transmitting the RTS frame, and receiving CTS frames as a response to the RTS frame .

Here, the MAC header of the RTS frame may include first identification information indicating the presence of at least one of the first indicator and the primitive channel information.

Here, the service field of each of the CTS frames may include a second indicator indicating that multiplex transmission is performed and channel state information indicating whether the channel is idle.

Here, the MAC header of each of the CTS frames may include second identification information indicating presence of at least one of the second indicator and the channel status information.

Here, each of the CTS frames may be received in a CDM scheme.

Here, each of the CTS frames may be received at a preset inter-frame interval.

Here, each of the CTS frames may be received in the OFDMA scheme through the channel indicated by the source channel information and the sequence of the identifiers of the plurality of candidate stations included in the RTS frame.

Herein, the frame transmission method includes: determining a plurality of stations participating in multiplex transmission to transmit the CTS frames, determining a number of the plurality of participating stations and an idle state of a channel included in each of the CTS frames, Setting a channel to be allocated to each of the plurality of participating stations based on the channel state information indicating the channel assignment information and transmitting the data frame including the set channel assignment information.

Here, the frame transmission method may further include receiving each response frame for the data frame in a CDM scheme.

Here, the frame transmission method may further include receiving each response frame for the data frame at a preset inter-frame interval.

Here, the frame transmission method may further include receiving each of the response frames for the data frame through the channel indicated by the original channel information or the channel allocation information in the OFDMA scheme.

According to the present invention, a first station (e.g., an access point) may transmit an RTS frame to stations participating in OFDMA, and each station participating in OFDMA may transmit channel status information through a channel indicated by an RTS frame To the first station. That is, since each of the stations participating in OFDMA can transmit a CTS frame, a neighboring station receiving the CTS frame can stop the frame transmission, thereby eliminating the hidden node problem.

Also, the first station can confirm the channel status (i.e., idle or busy) of the stations participating in the OFDMA based on the channel status information included in the CTS frame, OFDMA can be performed. Therefore, all stations participating in OFDMA can successfully transmit and receive frames.

In addition, each of the stations can transmit an uplink frame in an OFDMA or CDMA manner, thereby preventing an excessive occupation of resources by an uplink frame transmitted by each of the stations.

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 timing diagram illustrating a frame transmission / reception method according to an embodiment of the present invention.
7 is a block diagram illustrating an embodiment of an RTS frame.
8 is a block diagram illustrating an embodiment of a CTS frame.
9 is a timing diagram illustrating a frame transmission / reception method according to another embodiment of the present invention.
10 is a timing diagram illustrating a frame transmission / reception method according to another embodiment of the present invention.
11 is a block diagram illustrating an embodiment of a data frame.

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 inter frame 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.

Next, an orthogonal frequency division multiple access (OFDMA) frame transmission / reception procedure in a wireless LAN will be described. In the following description, one station will be described as a procedure for transmitting frames to four stations in the OFDMA scheme. However, the present invention is not limited to this, and one station may transmit frames to four or more stations in the OFDMA scheme. The present invention can be applied to a transmission procedure. Further, even when a method (e.g., transmission or reception of a frame) performed in the first station among the communication entities is described, the corresponding second station is also a method corresponding to the method performed in the first station (E.g., receiving or transmitting a frame). That is, when the operation of the terminal is described, the corresponding access point can perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the access point is described, the corresponding terminal can perform an operation corresponding to the operation of the access point.

6 is a timing diagram illustrating a frame transmission / reception method according to an embodiment of the present invention.

Referring to FIG. 6, the stations STA1, STA2, STA3, STA4, and STA5 may belong to the same BSS and may operate in at least one channel among the first to fourth channels CH1 to CH4. Each of the channels CH1 to CH4 may have a size of 5 MHz, 10 MHz, 20 MHz or 40 MHz. When the first station STA1 wants to transmit the data frames 620-1, 620-2, 620-3, and 620-4 in the OFDMA scheme, the first station STA1 selects a plurality of candidate stations STA2, STA3, STA4). The first station STA1 may transmit the RTS frame 600 through the 20 MHz band if the bandwidth 20 MHz is supported. Also, if the first station STA1 supports 40 MHz, 80 MHz, 160 MHz, etc., the first station STA1 can transmit a duplicated RTS frame 600 every 20 MHz band.

7 is a block diagram illustrating an embodiment of an RTS frame.

7, an RTS frame 600 includes a legacy-short training field (L-STF) 601, a legacy-long training field (L-LTF) 602, an L- 603, a service field 604, and a MAC protocol data unit (MPDU). The MPDU includes a frame control field 605, a duration field 606, a receiver address field 607, a transmitter address field 608, and a frame check sequence (FCS) Field 609. The < / RTI >

The service field 604 includes a scrambler sequence field 604-1 having a size of 7 bits, an indicator field 604-2 having a size of 1 bit, a source channel information field 602 having a size of 2 bits 604-3, and a reserved field 604-4 having a size of 6 bits. Some of the existing spare fields included in the service field 604 may be used as the indicator field 604-2 and other bits may be used as the raw channel information field 604-3. The indicator field 604-2 may indicate an indicator indicating whether to perform OFDMA (e.g., downlink (DL) OFDMA or uplink (OFDMA)). For example, an indicator field 604-2 set to binary 0 may indicate that orthogonal frequency division multiplexing (OFDM) is performed, and an indicator field 604-2 set to binary 1 may indicate that OFDMA is performed. have. The setting of the indicator field 604-2 is not limited to this and may be variously set.

The RAW channel information field 604-3 may include RAW channel information indicating the size of a channel allocated to each of a plurality of candidate stations (STA2, STA3, STA4, STA5) to participate in OFDMA. For example, the RAW channel information field 604-3 set to binary number 00 is configured such that the first station STA1 supports a bandwidth of 20 MHz and a bandwidth of 5 MHz is assigned to each of a plurality of candidate stations STA2, STA3, STA4, and STA5 . The original channel information field 604-3 set to binary number 01 indicates that the first station STA1 supports a bandwidth of 40 MHz and that a bandwidth of 10 MHz is allocated to each of the plurality of candidate stations STA2, STA3, STA4, STA5 have. A primitive channel information field 604-3 set to a binary number of 10 may indicate that the first station STA1 supports a bandwidth of 80 MHz and a bandwidth of 20 MHz is allocated to each of a plurality of candidate stations STA2, STA3, STA4, STA5 have. The source channel information field 604-3 set to binary number 11 can indicate that the first station STA1 supports a bandwidth of 160 MHz and a bandwidth of 40 MHz is assigned to each of the plurality of candidate stations STA2, STA3, STA4, STA5 have.

On the other hand, the indicator and the raw channel information can be set by the scrambler sequence field 604-1 instead of the existing spare field included in the service field 604. [ Table 1 below shows a setting example of the scrambler sequence field 604-1.

The fifth bit B4 (i.e., OFDMA_INDICATION_IN_NON_HT) of the scrambling sequence in Table 1 may perform the same function as the indicator field 604-2. The sixth bit B5 and the seventh bit B6 (i.e., CH_BANDWIDTH_AND_SUB_CH_SIZE_IN_NON_HT) of the scrambling sequence in Table 1 can perform the same function as the original channel information field 604-3.

Meanwhile, the receiver address field 607 may include an identifier of each of a plurality of candidate stations STA2, STA3, STA4, and STA5 to participate in OFDMA. That is, the receiver address field 607 includes a first PAID (partial association identifier) field 607-1 having a size of 9 bits, a second PAID field 607-2 having a size of 9 bits, A fourth PAID field 607-4 having a size of 9 bits, and a spare field 607-5 having a size of 12 bits.

The first PAID field 607-1 located first in the receiver address field 607 uses the first channel CH1 which is the first sub-channel among the bands supported by the first station STA1 (E.g., the PAID, AID, or MAC address of the second station STA2, etc.). Similarly, the second PAID field 607-2, the third PAID field 607-3, or the fourth PAID field 607-4 is the second sub-band of the bands supported by the first station STA1, (I.e., the third station STA3, the second station STA3, the second station STA3, the second station STA3, the third station STA3, the third station STA3, 4 stations (STA4), and a fifth station (STA5).

The MPDU of the RTS frame 600 may include identification information indicating that at least one of the indicator and the raw channel information is present in the service field 604. The identification information is set based on at least one of the To DS field, the From DS field, the More Frag field, the Retry field, the Pwr Mgt field, the More Data field, the Protected Frame field, and the Order field included in the frame control field 605 of the MPDU . For example, if at least one field used for identification information in the frame control field 605 is all set to binary 1 or has a predetermined bit pattern, it is indicated in the service field 604 as an indicator and a primitive May indicate that at least one of the channel information is present.

Referring again to FIG. 6, each of the plurality of candidate stations STA2, STA3, STA4, and STA5 may receive an RTS frame 600 and may receive an MPDU (e.g., a frame control field 605), it can be known that at least one of the indicator and the raw channel information is present in the service field 604. That is, the MAC processor 11 of each of the plurality of candidate stations STA2, STA3, STA4, and STA5 knows that there is at least one of the indicator and the raw channel information in the service field 604 according to the identification information, Thereby obtaining the indicator and the raw channel information from the service field 604.

Each of the plurality of candidate stations STA2, STA3, STA4, and STA5 knows that OFDMA is performed by the indicator, and can know the size of the channel allocated to itself by the source channel information. Also, each of the plurality of candidate stations STA2, STA3, STA4, and STA5 can know the channel assigned to itself based on the order of the primitive channel information and the identifier included in the receiver address field 607. [ For example, the second station STA2, the third station STA3, the fourth station STA4, or the fifth station STA5 may transmit the first channel CH1 among the bands supported by the first station STA1, , The second channel (CH2), the third channel (CH3), or the fourth channel (CH4) are allocated to the first channel.

Each of the plurality of candidate stations STA2, STA3, STA4, and STA5 may determine whether the state of the channel allocated thereto is idle or busy. Each of the candidate stations STA2, STA3, STA4, and STA5 transmits a CTS frame 610-1 through a channel allocated to the candidate stations STA2, STA3, STA4, and STA5 after SIFS from the end of the RTS frame 600, 610-2, 610-3, and 610-4 to the first station STA1. Each of the candidate stations STA2, STA3, STA4, and STA5 transmits CTS frames 610-1, 610-2, 610-3, and 610-4 to the first station (STA1).

8 is a block diagram illustrating an embodiment of a CTS frame.

Referring to FIG. 8, the CTS frame 610 may include an L-STF 611, an L-LTF 612, an L-SIG field 613, a service field 614, and an MPDU. The MPDU may include a frame control field 615, a duration field 616, a receiver address field 617, and an FCS field 618. The service field 614 includes a scrambler sequence field 614-1 having a size of 7 bits, an indicator field 614-2 having a size of 1 bit, a channel state information field 614-3 having a size of 2 bits, And a spare field 614-4 having a size of 6 bits. Alternatively, the service field 614 may be composed of a scrambler sequence field 614-1, a channel state information field 614-3, and a reserved field 614-4 excluding the indicator field 614-2. Some bits of the existing spare field included in the service field 614 may be used as the indicator field 614-2 and other bits may be used as the channel state information field 614-3. Indicator field 614-2 may indicate an indicator indicating whether to perform OFDMA (e.g., DL OFDMA or UL OFDMA). That is, the indicator field 614-2 may perform the same function as the indicator field 604-2 included in the RTS frame 600. [

The channel state information field 614-3 may include channel state information indicating whether the state of the channel allocated to the station that transmitted the corresponding CTS frame 610 is idle or busy. In addition, the channel state information may indicate a state of a channel allocated to the corresponding station as well as a state of an allocated channel and a neighboring channel. For example, the channel state information field 614-3 set to binary number 00 may indicate that the state of the channel allocated to the station that transmitted the corresponding CTS frame 610 is children. The channel state information field 614-3 set to the binary number 01 is a neighboring channel having a frequency higher than a channel allocated to the station that transmitted the corresponding CTS frame 610 and a channel allocated to the station that transmitted the corresponding CTS frame 610 It can indicate that the state of the channel is children. A channel state information field 614-3 set to a binary number of 10 indicates that a channel allocated to a station that transmitted the corresponding CTS frame 610 and a neighboring channel having a frequency lower than that allocated to the station that transmitted the corresponding CTS frame 610 It can indicate that the state of the channel is children. The channel status information field 614-3 set to binary number 11 may indicate that all the channels supported by the first station STA1 are children. The setting of the channel status information field 614-3 is not limited to this and can be variously set.

On the other hand, the indicator and channel state information may be set by the scrambler sequence field 614-1 rather than the existing spare field included in the service field 614. The fifth bit B4 of the scrambling sequence (i.e., OFDMA_INDICATION_IN_NON_HT) can perform the same function as the indicator field 614-2 and the sixth bit B5 and the seventh bit B5 of the scrambling sequence B6) (i.e., SUB_CH_IDLE_INDICATION_IN_OFDMA) can perform the same function as the channel state information field 614-3.

The MPDU of the CTS frame 610 may include identification information indicating that at least one of the indicator and the channel state information is present in the service field 614. The identification information is set based on at least one of a To DS field, a From DS field, a More Frag field, a Retry field, a Pwr Mgt field, a More Data field, a Protected Frame field, and an Order field included in the frame control field 615 of the MPDU . For example, if at least one field used for identification information in the frame control field 615 is all set to binary number 1 or has a preset bit pattern, it is indicated in the service field 614, May indicate that at least one is present.

On the other hand, each of the stations STA2, STA3, STA4, and STA5 transmits a CTS frame 610-1, 610-2, 610-3, 610-4 in a code division multiple access CTS frames 610-1, 610-2, 610-3, and 610-4.

9 is a timing diagram illustrating a frame transmission / reception method according to another embodiment of the present invention.

9, each of the stations STA2, STA3, STA4, and STA5 includes the source channel information included in the RTS frame 600 and the channel information included in each of the candidate stations STA2, STA3, STA4, and STA5 participating in OFDMA When the channel indicated by the identifier order is idle, the CTS frames 610-1, 610-2, 610-3, and 610-4 are transmitted through the first channel to the fourth channel (CH1 to CH4) To the station STA1. Here, it is assumed that each of the stations STA1, STA2, STA3, STA4, and STA5 has information (for example, code information) necessary for transmitting and receiving frames based on CDMA in advance.

In another embodiment, each of the stations STA2, STA3, STA4, and STA5 transmits CTS frames 610-1, 610-2, 610-3, and 610-4 in a sequential manner. 1, 610-2, 610-3, and 610-4.

10 is a timing diagram illustrating a frame transmission / reception method according to another embodiment of the present invention.

10, each of the stations STA2, STA3, STA4, and STA5 includes the source channel information included in the RTS frame 600 and the channel information included in each of a plurality of candidate stations STA2, STA3, STA4, STA5 participating in the OFDMA The CTS frames 610-1, 610-2, 610-3, and 610-4 can be transmitted to the first station STA1 in a sequential manner when the channel indicated by the identifier order is idle. That is, since the second station STA2 has its own identifier in the receiver address field 607 of the RTS frame 600, the second station STA2 transmits the CTS frame 610-1 after SIFS from the end of the RTS frame 600, To the first station STA1. Similarly, the third station STA3 may transmit the CTS frame 610-2 to the first station STA1 after SIFS from the end of the CTS frame 610-1 of the second station STA2, The fourth station STA4 may transmit the CTS frame 610-3 to the first station STA1 after SIFS from the end of the CTS frame 610-2 of the third station STA3, May transmit the CTS frame 610-4 to the first station STA1 after SIFS from the end of the CTS frame 610-3 of the fourth station STA4.

6, the first station STA1 can receive CTS frames 610-1, 610-2, 610-3, and 610-4 from stations STA2, STA3, STA4, and STA5. And that there is at least one of the indicator and the channel state information in the service field 614 based on the identification information included in the MPDU (for example, the frame control field 615) of the CTS frame 610 . That is, the MAC processor 11 of the first stations STA1 knows that there is at least one of the indicator and the channel state information in the service field 614 according to the identification information, Indicator and channel status information. The first station STA1 knows that the OFDMA is performed by the indicator, and can know the state of the channel by the channel state information. In addition, the first station STA1 transmits a plurality of stations (STA2, STA3, STA4, STA5) that transmitted CTS frames 610-1, 610-2, 610-3, Stations. For example, the first station STA1 may determine the second station STA2 and the fourth station STA4 as a plurality of participating stations when receiving the CTS frames 610-1 and 610-3 .

The first station STA1 transmits the channels CH1, CH2, CH3, and CH4, the plurality of participant stations, and the CTSs 610-1, 610-2, 610-3, And a channel to be allocated to a plurality of participating stations based on at least one of the channel state information included in the frame 610. [ That is, the first station STA1 can view the states of the transmitted channels CH1, CH2, CH3, and CH4 by the CTS frames 610-1, 610-2, 610-3, and 610-4 as children Therefore, when the CTS frames 610-1, 610-2, 610-3, and 610-4 are transmitted through the channels CH1, CH2, CH3, and CH4 and the CTS frames 610-1, 610-2, and 610 -3, and 610-4) based on at least one of the channel status information included in the channel status information included in the channel status information.

Thereafter, the first station STA1 allocates the idle channel to each of the plurality of participating stations STA2, STA3, STA4, STA5 in consideration of the number of the participating stations STA2, STA3, STA4, STA5 Can be assigned. For example, if all the bands supported by the first station STA1 are in the idle state and the plurality of participating stations are the second station STA2 and the fourth station STA4, (CH1) or the third channel (CH3) to the second station (STA2) or the fourth station (STA4), respectively. Alternatively, the first station STA1 can allocate the first channel CH1 and the second channel CH2 to the second station STA2, and the third channel CH3 and the fourth channel CH4 4 stations (STA4).

The first station STA1 may generate a data frame 620 including channel allocation information and may transmit data after SIFS from the end of the CTS frames 610-1, 610-2, 610-3, Frame 620 to a plurality of participating stations STA2, STA3, STA4, STA5 in OFDMA manner.

11 is a block diagram illustrating an embodiment of a data frame.

11, the data frame 620 includes an L-STF 621, an L-LTF 622, an L-SIG field 623, a HEW-SIG field 624, a HEW-STF 625, Lt; RTI ID = 0.0 > 626 < / RTI > The HEW-SIG field 624, the HEW-STF 625, or the HEW-LTF 626 may refer to each of the SIG field, STF, or LTF defined in IEEE 802.11ax. The HEW-SIG field 624 may include a channel allocation information field 624-1 and a spare field 624-2 having a size of 7 bits. The channel allocation information field 624-1 may include channel information allocated to each of a plurality of participating stations. The 4 bits of the channel allocation information field 624-1 may indicate the presence or absence of a channel allocated to each of the stations. For example, the first bit, the second bit, the third bit, or the fourth bit of the 4 bits may correspond to the second station STA2, the third station STA3, the fourth station STA4 or the fifth station STA5 May indicate the presence or absence of a channel allocated to the channel. That is, the order of the stations corresponding to each of the 4 bits may be the same as the order of the identifiers of the stations included in the receiver address field 607 of the RTS frame 600. Here, a bit set to a binary 0 in 4 bits may indicate that a channel is not allocated to a station corresponding to the corresponding bit, and a bit set to 1 out of 4 bits indicates that a channel is assigned to a station corresponding to the corresponding bit . 3 bits of the channel allocation information field 626-1 may indicate channel division information for the entire band supported by the first station STA1 as shown in Table 2 below.

For example, a channel allocation information field 626-1 set to a binary number of 1001 100 includes a first channel CH1, which is one-half of the total bandwidth supported by the first station STA1, The third channel CH3 and the fourth channel CH4 which are half of the entire band supported by the first station STA1 may be assigned to the fifth station STA5 Lt; / RTI > As another example, the channel allocation information field 626-1 set to the binary number 0111000 indicates that the second channel CH2 is allocated to the third station STA3, which is one quarter of the entire band supported by the first station STA1 And may indicate that a fourth channel STA4 is assigned a third channel CH3 which is one fourth of the total bandwidth supported by the first station STA1 and that the fifth station STA5 is assigned to the first station STA1, The fourth channel CH4, which is 1/4 of the total bandwidth supported by the STA1, can be allocated. As another example, the channel allocation information field 626-1 set to the binary number 1100001 may include the first channel CH1, which is 1/2 of the total bandwidth supported by the first station STA1, 2 channel CH 2 may be allocated to the third station STA 3 and a third channel CH 3 allocated to the third station STA 3 which is 1/4 of the entire band supported by the first station STA 1 may be allocated.

Referring again to FIG. 6, each of the stations STA2, STA3, STA4, and STA5 is allocated to itself based on the channel allocation information 624-1 included in the HEW-SIG field 624 of the data frame 620 And can decode the MPDU transmitted through the assigned channel. In other words, the second station STA2, the third station STA3, the fourth station STA4 or the fifth station STA respectively have the MPDU1 transmitted through the first channel CH1 allocated thereto, The MPDU 2 transmitted through the second channel CH 2, the MPDU 3 transmitted through the third channel CH 3, or the MPDU 4 transmitted through the fourth channel CH 4. Each of the stations STA2, STA3, STA4, and STA5 transmits ACK frames 630-1, 630-2, 630-3, and 630-4, which are responses thereto, to the RTS frame 600 Or via the channel indicated by the data frame 620. [0064] Each of the stations STA2, STA3, STA4, and STA5 may transmit a block acknowledgment (BA) frame in response to receiving a plurality of MPDUs. At this time, each of the stations STA2, STA3, STA4, and STA5 can transmit a BA frame after receiving a block acknowledgment request (BAR) frame from the first station STA1.

As shown in FIG. 9, each of the stations STA2, STA3, STA4, and STA5 may transmit the ACK frames 630-1, 630-2, 630-3, 630-2, 630-3, and 630-4 through the first through fourth channels CH1 through CH4, respectively. In another embodiment of transmitting ACK frames 630-1, 630-2, 630-3, and 630-4, each of the stations STA2, STA3, STA4, and STA5, as shown in FIG. 10, (630-1, 630-2, 630-3, 630-4).

For example, since the second station STA2 is located at the first position in the receiver address field 607 of the RTS frame 600, the ACK frame 630- 1) to the first station STA1. The third station STA3 determines whether or not there is a channel allocated to the station in the HEW-SIG field 624 of the data frame 620 with its identifier in the receiver address field 607 of the RTS frame 600 secondly The ACK frame 630-2 can be transmitted to the first station STA1 after SIFS from the end of the ACK frame 630-1 of the second station STA2 have. Similarly, the fourth station STA4 or the fifth station STA5 may transmit an ACK frame 630-3 or an ACK frame 630-4 to the first station STA1, respectively. In the HEW-SIG field 624 of the data frame 620, if the second bit of the 4 bits indicating whether or not the channel allocated to the station exists is 1 and the third bit is set to 0, May transmit the ACK frame 630-4 to the first station STA1 after SIFS from the end of the ACK frame 630-2 of the third station STA3.

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 (12)

A frame transmission method performed in a first station,
Generating a request to send (RTS) frame including a first indicator indicating that multiplexing transmission is performed, source channel information used for multiplexing transmission, and an identifier of each of a plurality of candidate stations to participate in multiplex transmission;
Transmitting the RTS frame; And
And receiving clear to send (CTS) frames that are a response to the RTS frame. The method according to claim 1,
Wherein a medium access control (MAC) header of the RTS frame includes first identification information indicating the presence of at least one of the first indicator and the primitive channel information. The method according to claim 1,
Wherein the service field of each of the CTS frames comprises a second indicator indicating that multiplex transmission is performed and channel state information indicating whether the channel is idle. The method of claim 3,
Wherein the MAC header of each of the CTS frames includes second identification information indicating presence of at least one of the second indicator and the channel status information. The method according to claim 1,
Wherein each of the CTS frames is received in a code division multiplexing (CDM) manner. The method according to claim 1,
Wherein each of the CTS frames is received in a preset inter-frame space. The method according to claim 1,
Wherein each of the CTS frames is received on the channel indicated by the source channel information and an identifier sequence of each of a plurality of candidate stations included in the RTS frame. The method according to claim 1,
The frame transmission method includes:
Determining a plurality of stations participating in the multiplex transmission to transmit the CTS frames;
Setting a channel assigned to each of the plurality of participating stations based on the number of the plurality of participating stations and channel state information indicating whether the channel included in each of the CTS frames is idle; And
And transmitting a data frame including the set channel allocation information. The method of claim 8,
The frame transmission method includes:
And receiving each of the response frames for the data frame in a CDM scheme. The method of claim 8,
The frame transmission method includes:
Further comprising receiving each of the response frames for the data frame at a preset inter-frame interval. The method of claim 8,
The frame transmission method includes:
Further comprising receiving each of the response frames for the data frame on the channel indicated by the raw channel information or the channel allocation information. A frame receiving method performed at a first station,
Receiving a request to send (RTS) frame;
Obtaining a first indicator indicating that multiplexing transmission is performed from the RTS frame, primitive channel information used for multiplexing transmission and an identifier of each of a plurality of candidate stations participating in multiplexing transmission; And
And transmitting a clear to send (CTS) frame when the channel indicated by the source channel information and the identifier order of each of a plurality of candidate stations included in the RTS frame is idle. .

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