KR20200096471A - Method for transmitting and receiving data in wireless local area network and apparatus for the same - Google Patents

Abstract

Disclosed are a method for transmitting and receiving data in a wireless local area network (WLAN) and an apparatus thereof. According to the present invention, a frame transmission method comprises the steps of: acquiring a channel for transmitting a first data unit by a first terminal; when a data unit to be transmitted to at least one terminal other than the first terminal exists in an access point, generating a physical layer convergence procedure (PLCP) protocol data unit (PPDU) including the first data unit and the data unit to be transmitted to the at least one terminal; and transmitting the PPDU to the first terminal and the at least one terminal. Accordingly, the performance of the WLAN can be increased.

Description

Method and device for transmitting and receiving data in wireless LAN {METHOD FOR TRANSMITTING AND RECEIVING DATA IN WIRELESS LOCAL AREA NETWORK AND APPARATUS FOR THE SAME}

The present invention relates to a wireless LAN technology, and more particularly, to a technology for transmitting and receiving frames including multiplexed data units.

With the development of information and communication technologies, various wireless communication technologies are being developed. Among them, wireless local area network (WLAN) is a personal digital assistant (PDA), laptop computer, portable multimedia player (PMP), and smart device based on radio frequency technology. It is a technology that enables wireless access to the Internet in a home, business, or specific service area using a portable terminal such as a smart phone or a tablet PC.

The standard for wireless LAN technology is being developed as the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard. The WLAN technology according to the IEEE 802.11a standard operates based on an orthogonal frequency division multiplexing (OFDM) method, and can provide a maximum transmission rate of 54 Mbps in a 5GHz band. The WLAN technology according to the IEEE 802.11b standard operates based on a direct sequence spread spectrum (DSSS) scheme and can provide a maximum transmission rate of 11 Mbps in the 2.4 GHz band. The wireless LAN technology according to the IEEE 802.11g standard operates based on the OFDM method or the DSSS method, and can provide a maximum transmission rate of 54Mbps in the 2.4GHz band.

The WLAN technology according to the IEEE 802.11n standard operates in the 2.4GHz band and the 5GHz band based on the OFDM scheme, and when using the multiple input multiple output-OFDM (MIMO-OFDM) scheme, four spatial streams ( spatial stream) can provide a maximum transmission rate of 300Mbps. Wireless LAN technology according to the IEEE 802.11n standard can support a channel bandwidth of up to 40 MHz, and in this case, a maximum transmission rate of 600 Mbps can be provided.

As the widespread use of such a wireless LAN is activated and applications using the same are diversified, the need for a new wireless LAN technology to support a throughput higher than the data processing speed supported by IEEE 802.11n is increasing. Very high throughput (VHT) wireless LAN technology is one of the IEEE 802.11 wireless LAN technologies proposed to support a data processing speed of 1 Gbps or higher. Among them, IEEE 802.11ac is being developed as a standard for providing ultra-high throughput in a band below 5 GHz, and IEEE 802.11ad is being developed as a standard for providing ultra high throughput in a band of 60 GHz.

Recently, the number of stations associated with a basic service set (BSS) of a wireless LAN is rapidly increasing, and accordingly, collisions between stations within a BSS are increasing. In this environment, there is a need for a transmission/reception scheme for efficiently transmitting and receiving data between stations.

An object of the present invention for solving the above problems is to provide a method of transmitting and receiving multiplexed data.

Another object of the present invention for solving the above problems is to provide an apparatus for transmitting and receiving multiplexed data.

A frame transmission method performed at an access point according to an embodiment of the present invention for achieving the above object includes: acquiring a channel for transmitting a first data unit of a first terminal, at least one terminal other than the first terminal When a data unit to be transmitted to the access point exists in the access point, generating a PPDU including the first data unit and a data unit to be transmitted to the at least one terminal, and the PPDU to the first terminal and the at least one And transmitting to the terminal of.

Here, the PPDU may further include at least one of a length of a data unit, a receiver identifier of a data unit, a channel through which the data unit is transmitted, a transmission period, and a space.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed on a frequency in the PPDU.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed in time in the PPDU.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed in space in the PPDU.

Here, the data unit may be an MPDU or MSDU.

Here, the frame transmission method may further include receiving an ACK frame that is a response to reception of the PPDU from the first terminal and the at least one terminal.

A frame reception method performed in a terminal according to another embodiment of the present invention for achieving the above object includes receiving a PPDU multiplexed with a plurality of data units from an access point, and the terminal through a signal field included in the PPDU. Determining whether a first data unit of is present in the PPDU, and receiving the first data unit through a resource indicated by the signal field when the first data unit is present in the PPDU.

Here, the signal field may include at least one of a length of a data unit, a receiver identifier of a data unit, a channel through which the data unit is transmitted, a transmission period, and a space.

Here, the plurality of data units may be multiplexed on a frequency in the PPDU.

Here, the plurality of data units may be multiplexed in time in the PPDU.

Here, the plurality of data units may be spatially multiplexed in the PPDU.

Here, the frame reception method may further include transmitting an ACK frame, which is a response to reception of the first data unit, to the access point.

An access point according to an embodiment of the present invention for achieving the other object includes a processor and a memory in which at least one instruction executed through the processor is stored, and the at least one instruction is a first terminal of a first terminal. Acquiring a channel for data unit transmission, when a data unit to be transmitted to at least one terminal other than the first terminal exists in the access point, a data unit to be transmitted to the first data unit and the at least one terminal It may be executed to perform the step of generating a PPDU including a and transmitting the PPDU to the first terminal and the at least one terminal.

Here, the PPDU may include at least one of a length of a data unit, a receiver identifier of a data unit, a channel through which the data unit is transmitted, a transmission period, and a space.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed on a frequency in the PPDU.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed in time in the PPDU.

Here, the first data unit and the data unit to be transmitted to the at least one terminal may be multiplexed in space in the PPDU.

Here, the data unit may be an MPDU or MSDU.

Here, the at least one command may be executable to further perform the step of receiving an ACK frame that is a response to reception of the PPDU from the first terminal and the at least one terminal.

According to the present invention, the performance of a wireless LAN can be improved.

1 is a block diagram showing an embodiment of a station performing methods according to the present invention.
2 is a conceptual diagram showing an embodiment of a configuration of a wireless LAN system according to IEEE 802.11.
3 is a conceptual diagram illustrating an embodiment of a frame transmission/reception method in a wireless LAN.
4 is a block diagram showing a PPDU composed of A-MPDUs.
5 is a block diagram showing a PPDU composed of A-MSDUs.
6 is a conceptual diagram illustrating another embodiment of a method for transmitting and receiving frames in a wireless LAN.
7 is a flowchart illustrating a method of transmitting and receiving a frame according to an embodiment of the present invention.
8 is a flowchart illustrating a step of generating a PPDU in a method of transmitting and receiving a frame according to an embodiment of the present invention.
9 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed on a frequency.
10 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed in frequency and time.
11 is a block diagram illustrating an embodiment of a PPDU composed of MPDUs multiplexed in time.
12 is a block diagram showing an embodiment of a PPDU composed of MSDUs multiplexed in time.
13 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed in frequency, time, and space.
14 is a conceptual diagram illustrating an embodiment of a method of transmitting and receiving a PPDU composed of data units multiplexed on a frequency.
15 is a conceptual diagram illustrating an embodiment of a method for transmitting and receiving a PPDU composed of data units multiplexed in frequency and time.
16 is a conceptual diagram illustrating an embodiment of a method for transmitting and receiving a PPDU composed of data units multiplexed in frequency, time and space.
17 is a block diagram showing the configuration of an access point according to an embodiment of the present invention.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail.

However, this is not intended to limit the present invention to a specific embodiment, it is to be understood as including all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it is directly connected to or may be connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof does not preclude in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate an overall understanding, the same reference numerals are used for the same elements in the drawings, and duplicate descriptions for the same elements are omitted.

Throughout the specification, a station (STA) is a medium access control (MAC) and a physical layer for a wireless medium in accordance with the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard. It means any functional medium including an interface. The station STA may be classified into a station STA that is an access point (AP) and a station STA that is a non-AP. A station (STA) that is an access point (AP) may be simply referred to as an access point (AP), and a station (STA) that is a non-access point (AP) may simply be referred to as a terminal.

The station STA may include a processor and a transceiver, and may further include a user interface and a display device. The processor refers to a unit designed to generate a frame to be transmitted through a wireless network or to process a frame received through a wireless network, and may perform various functions for controlling the station (STA). The transceiver is functionally connected to the processor and refers to a unit designed to transmit and receive frames through a wireless network for a station (STA).

The access point (AP) is a centralized controller, a base station (BS), a radio access station, a node B, an evolved node B, a relay, and a mobile mobile station (MMR). It may refer to a multihop relay)-BS, a base transceiver system (BTS), or a site controller, and may include some or all functions thereof.

The terminal (i.e., non-access point) is a wireless transmit/receive unit (WTRU), user equipment (UE), user terminal (UT), access terminal (AT), Refers to a mobile station (MS), a mobile terminal, a subscriber unit, a subscriber station (SS), a wireless device, or a mobile subscriber unit. You can do it, and you can include some or all of them.

Here, the terminal is a desktop computer capable of communication, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, and a smart watch. (smart watch), smart glass, e-book reader, PMP (Portable Multimedia Player), portable game console, navigation device, digital camera, DMB (digital multimedia broadcasting) player, digital voice Digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player ), etc.

1 is a block diagram showing an embodiment of a station performing methods according to the present invention.

Referring to FIG. 1, a station 100 may include at least one processor 110, a memory 120, and a network interface device 130 connected to a network to perform communication. In addition, the station 100 may further include an input interface device 140, an output interface device 150, and a storage device 160. Each component included in the station 100 may be connected by a bus 170 to communicate with each other.

The processor 110 may execute a program command stored in the memory 120 and/or the storage device 160. The processor 110 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to the present invention are performed. The memory 120 and the storage device 160 may be formed of a volatile storage medium and/or a nonvolatile storage medium. For example, the memory 120 may be composed of read only memory (ROM) and/or random access memory (RAM).

Embodiments of the present invention are applied to a wireless LAN system according to IEEE 802.11, and can be applied to other communication systems as well as a wireless LAN system according to IEEE 802.11.

For example, embodiments of the present invention are mobile Internet such as wireless personal area network (WPAN), wireless body area network (WBAN), wireless broadband internet (WiBro), or world interoperability for microwave access (WiMax), global system for mobile communication) or 2G mobile communication network such as code division multiple access (CDMA), wideband code division multiple access (WCDMA) or 3G mobile communication network such as cdma2000, high speed downlink packet access (HSDPA) or high speed uplink (HSUPA) packet access), a 4G mobile communication network such as long term evolution (LTE) or LTE-Advanced, a 5G mobile communication network, and the like.

2 is a conceptual diagram showing an embodiment of a configuration of a wireless LAN system according to IEEE 802.11.

Referring to FIG. 2, a wireless LAN system according to IEEE 802.11 may include at least one basic service set (BSS). BSS refers to a set of stations (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2), STA6, STA7, STA8) that can communicate with each other by successfully synchronizing, and does not mean a specific area. .

The BSS can be classified into an infrastructure BSS (infrastructure BSS) and an independent BSS (IBSS). Here, BSS1 and BSS2 refer to infrastructure BSS, and BSS3 refers to IBSS.

BSS1 is a distribution system that connects a first terminal (STA1), a first access point (STA2 (AP1)) providing a distribution service, and a plurality of access points (STA2 (AP1), STA5 (AP2)) ( distribution system, DS). In BSS1, the first access point STA2 (AP1) may manage the first terminal STA1.

BSS2 connects a third terminal (STA3), a fourth terminal (STA4), a second access point (STA5 (AP2)) providing a distribution service, and a plurality of access points (STA2 (AP1), STA5 (AP2)). It may include a distribution system (DS). In BSS2, the second access point STA5 (AP2) may manage the third terminal STA3 and the fourth terminal STA4.

BSS3 refers to IBSS operating in an ad-hoc mode. In BSS3, there is no access point, which is a centralized management entity. That is, in BSS3, the terminals STA6, STA7, and STA8 are managed in a distributed manner. In BSS 3, all the terminals STA6, STA7, and STA8 may mean a mobile terminal, and access to the distribution system (DS) is not permitted, thus forming a self-contained network.

The access points STA2 (AP1) and STA5 (AP2) may provide access to the distributed system DS through a wireless medium for the terminals STA1, STA3, and STA4 coupled to them. Communication between the terminals STA1, STA3, and STA4 in BSS1 or BSS2 is generally performed through an access point (STA2 (AP1), STA5 (AP2)), but when a direct link is established, the terminals ( Direct communication between STA1, STA3, and STA4 is possible.

A plurality of infrastructure BSSs may be interconnected through a distribution system (DS). A plurality of BSSs connected through the distribution system (DS) is referred to as an extended service set (ESS). Entities included in the ESS (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2)) can communicate with each other, and any terminal (STA1, STA3, STA4) within the same ESS communicates without interruption. You can move from one BSS to another BSS.

Distribution system (DS) is a mechanism for one access point to communicate with another access point.Accordingly, the access point transmits frames for terminals coupled to the BSS managed by itself or moves to another BSS. Frames can be transmitted for any terminal. In addition, the access point can transmit and receive frames with an external network such as a wired network. Such a distribution system (DS) does not necessarily have to be a network, and there is no limitation on its form as long as it can provide a predetermined distribution service specified in the IEEE 802.11 standard. For example, the distribution system may be a wireless network such as a mesh network, or a physical structure that connects access points to each other.

3 is a conceptual diagram illustrating an embodiment of a frame transmission/reception method in a wireless LAN.

Referring to FIG. 3, a first station STA1 to transmit data may determine a channel occupation state based on clear channel assessment (CCA), which is a wireless LAN standard sensing technology. As a result of CCA, when the channel is in an idle state, the first station STA1 is a contention window (CW) according to a distributed coordination function (DIFS) inter frame space (DIFS) and random backoff ( For example, if the channel is in an idle state during CW=4), a transmit opportunity (TXOP) for transmission of the data frame 300 may be obtained. Here, the random backoff refers to a procedure for additionally waiting for a time corresponding to the product of the contention window (CW) and the slot time (aSlotTime).

The first station STA1 may complete data transmission within the acquired TXOP. For example, the first station STA1 may transmit the data frame 300 to the second station. When the second station receives the data frame 300, the second station may transmit the acknowledgment (ACK) frame 301 to the first station STA1 after a short inter frame space (SIFS) from the end of reception of the data frame 300. . When the first station STA1 receives the ACK frame 301, it may determine that the data frame 300 has been successfully received by the second station. The first station STA1 may transmit the data frame 302 to the second station STA2 after SIFS from the time when the reception of the ACK frame 301 ends. When receiving the data frame 302, the second station may transmit the ACK frame 303 to the first station STA1 after SIFS from the time when the reception of the data frame 302 ends. When the first station STA1 receives the ACK frame 303, it may determine that the data frame 302 has been successfully received by the second station.

The first station STA1 may obtain the TXOP again when additional data to be transmitted exists. The first station STA1 may check the occupancy status of the channel based on the CCA. As a result of the CCA, when the channel is in an idle state, the first station STA1 may acquire a TXOP for transmission of the data frame 304 when the channel is in an idle state during DIFS and contention window (CW=2). The first station STA1 may transmit the data frame 304 to the second station in the TXOP. When receiving the data frame 304, the second station may transmit the ACK frame 305 to the first station STA1 after SIFS from the time when the reception of the data frame 304 ends.

When the first station STA1 receives the ACK frame 305, it may determine that the data frame 304 has been successfully received by the second station. The first station STA1 may transmit the data frame 306 to the second station STA2 after SIFS from the time when the reception of the ACK frame 305 ends. When receiving the data frame 306, the second station may transmit the ACK frame 307 to the first station STA1 after SIFS from the time when the reception of the data frame 306 ends. When the first station STA1 receives the ACK frame 307, it may determine that the data frame 306 has been successfully received by the second station.

Here, since the ACK frames 301, 303, 305, 307 must be transmitted whenever each of the data frames 300, 302, 304, 306 is transmitted, the ACK frames 301, 303, 305, 307 Due to repetitive transmission, the overhead of the WLAN may increase. Also, since the MAC headers included in each of the data frames 300, 302, 304, and 306 overlap each other, overhead of the WLAN may increase.

In order to solve this problem, A (aggregate)-MPDU (MAC protocol data unit) and A-MSDU (MAC service data unit) are specified in the IEEE 801.11n standard.

4 is a block diagram showing a physical layer convergence procedure (PPDU) protocol data unit (PPDU) composed of A-MPDU.

Referring to FIG. 4, the PPDU 400 may include a PHY header 410, a service field 420, and an A-MPDU 430. In addition, the PPDU 400 may further include at least one of a pad bit 440 and a tail bit 450. The A-MPDU 430 may include at least one MPDU 431 and 432. The first MPDU 431 may include a MAC header 431-1 and an MSDU 431-2. The second MPDU 432 may include a MAC header 432-1 and an MSDU 432-2. When the PPDU 400 configured with the A-MPDU 430 is used, transmission of repetitive ACK frames can be minimized.

5 is a block diagram showing a PPDU composed of A-MSDUs.

Referring to FIG. 5, the PPDU 500 may include a PHY header 510, a service field 520, and an A-MSDU 530. In addition, the PPDU 500 may further include at least one of a pad bit 540 and a tail bit 550. The A-MSDU 530 may include a MAC header 531 and at least one MSDU 532, 533, 534. When the PPDU 500 composed of the A-MSDU 530 is used, transmission of repetitive ACK frames and MAC headers can be minimized.

6 is a conceptual diagram illustrating another embodiment of a method for transmitting and receiving frames in a wireless LAN.

Referring to FIG. 6, a first station STA1 to transmit data may determine the occupancy state of a channel based on CCA. As a result of CCA, when the channel is in the idle state, the first station STA1 acquires a TXOP for transmission of the A-MPDU 600 including at least one MPDU if the channel is in the idle state during DIFS and contention window (CW=4). can do. That is, the first station STA1 may transmit the A-MPDU 600 to the second station (not shown) within the TXOP. When receiving the A-MPDU 600, the second station may transmit a block ACK (BA) frame 601 to the first station STA1 after SIFS from the time when the reception of the A-MPDU 600 ends. . When the first station STA1 receives the BA frame 601, it may determine that the A-MPDU 600 has been successfully received by the second station.

The first station STA1 may obtain the TXOP again when additional data to be transmitted exists. That is, the first station STA1 may determine the occupied state of the channel based on the CCA. As a result of CCA, when the channel is in the idle state, the first station STA1 acquires a TXOP for transmission of the A-MSDU 602 including at least one MSDU if the channel is in the idle state during DIFS and contention window (CW=2). can do. That is, the first station STA1 may transmit the A-MSDU 602 to the second station in the TXOP. When receiving the A-MSDU 602, the second station may transmit the BA frame 603 to the first station STA1 after SIFS from the time when the reception of the A-MSDU 602 ends. When the first station STA1 receives the BA frame 603, it may determine that the A-MSDU 602 has been successfully received by the second station.

When an A-MPDU or A-MSDU is used, transmission of repetitive ACK frames and MAC headers can be minimized. However, since the A-MPDU or A-MSDU is transmitted only to one station, the use of the A-MPDU or A-MSDU may be inefficient when there are many stations in one BSS. If the data to be transmitted to a specific station is very large, transmission may not be completed in the current TXOP. In this case, data to be transmitted to a specific station may be continuously transmitted in the next TXOP after waiting again for a time equal to'DIFS + contention window (CW)' after CCA is performed. In addition, data to be transmitted to other stations in the same BSS may be transmitted in the next TXOP after waiting again for the amount of'DIFS + contention window (CW)' after performing CCA as described above. That is, when data to be transmitted is large or the number of stations in one BSS is large, temporal overhead may occur due to a time required for channel access (eg, DIFS, contention window, etc.). Therefore, the performance of the wireless LAN may be degraded.

In addition, the number of associated stations per BSS in the city center is rapidly increasing, and accordingly, collisions between stations within the BSS and collisions with stations connected to neighboring BSSs are increasing. In this environment, there is a need for a transmission scheme for efficiently transmitting data to many stations connected to one BSS.

7 is a flowchart illustrating a method of transmitting and receiving a frame according to an embodiment of the present invention, and FIG. 8 is a flowchart illustrating a step of generating a PPDU in a method of transmitting and receiving a frame according to an embodiment of the present invention.

7 and 8, an access point (AP) may form a BSS. Each of the terminals STA1, STA2, STA3, and STA4 may belong to a BSS and may be associated with an access point (AP). The access point AP that intends to transmit the first data unit DU1 to the first terminal STA1 may determine the occupied state of the channel based on the CCA. As a result of the CCA, when the channel is in an idle state, the access point AP may acquire a TXOP for transmission of the first data unit DU1 when the channel is in the idle state during DIFS and the contention window (S700). Here, the data unit may mean MPDU or MSDU.

After obtaining the TXOP, the access point AP may generate a PPDU composed of multiplexed data units (S710). Specifically, the access point (AP) transmits a data unit to be transmitted to other terminals (STA2, STA3, STA4) other than the first terminal (STA1) among terminals connected to it (STA1, STA2, STA3, STA4). ), it may be determined whether it exists in (S711). If the data unit to be transmitted to other terminals STA2, STA3, and STA4 does not exist in the transmission queue, S720 may be performed as a next step.

On the other hand, when a data unit to be transmitted to another terminal (STA2, STA3, STA4) exists in the transmission queue, the access point (AP) may multiplex the data units on a frequency, and a PPDU composed of the multiplexed data units is It can be generated (S712). The PPDU composed of data units multiplexed over frequency is as follows.

9 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed on a frequency.

9, the PPDU may include a PHY header and a payload. The access point (AP) may allocate the first data unit (DU1) to be transmitted to the first terminal (STA1) to the first subcarrier (SC1) among the entire band, and transmit it to the second terminal (STA2). The second data unit DU2 to be transmitted may be allocated to the second subcarrier SC2 among the entire band, and the third data unit DU3 to be transmitted to the third terminal STA3 is assigned to the fourth subcarrier ( SC4), and the fourth data unit DU4 to be transmitted to the fourth terminal STA4 may be allocated to the third subcarrier SC3 among the entire band.

Here, in order to match the payload size of each of the subcarriers SC1, SC2, SC3, SC4 to the same, the access point AP has a pad bit in each of the data units DU1, DU2, DU3, and DU4. At least one of (eg, a MAC pad bit, a PHY pad bit) and a tail bit may be added.

Referring back to FIGS. 7 and 8, after multiplexing data units on a frequency, the access point AP is a terminal other than the first terminal STA1 among terminals connected to it (STA1, STA2, STA3, STA4). It may be determined whether a data unit to be transmitted to (STA2, STA3, STA4) exists in the transmission queue (S713). If the data unit to be transmitted to other terminals STA2, STA3, and STA4 does not exist in the transmission queue, S720 may be performed as a next step. That is, the access point (AP) may transmit a PPDU composed of data units multiplexed on a frequency.

On the other hand, even when data units are multiplexed on a frequency basis, if a data unit to be transmitted to other terminals (STA2, STA3, STA4) exists in the transmission queue, the access point (AP) may multiplex the data units on frequency and time. In addition, a PPDU composed of multiplexed data units may be generated (S714). The PPDU composed of data units multiplexed in frequency and time is as follows.

10 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed in frequency and time.

Referring to FIG. 10, a PPDU may include a PHY header and a payload. The access point AP includes a first data unit DU1 to be transmitted to the first terminal STA1 to the first subcarrier SC1, a data unit DU2 to be transmitted to the second terminal STA2, and 3 A third data unit DU3 to be transmitted to the terminal STA3 may be allocated. The access point (AP) allocates a data unit (DU2) to be transmitted to the second terminal (STA2) and a third data unit (DU3) to be transmitted to the third terminal (STA3) to the second subcarrier (SC2) among the entire band. can do. The access point (AP) allocates a data unit (DU4) to be transmitted to the fourth terminal (STA4) and a first data unit (DU1) to be transmitted to the first terminal (STA1) to the third subcarrier (SC3) among the entire band. can do. The access point (AP) allocates a data unit (DU3) to be transmitted to the third terminal (STA3) and a fourth data unit (DU4) to be transmitted to the fourth terminal (STA4) to the fourth subcarrier (SC4) among the entire bands. can do.

Here, in order to match the payload size of each of the subcarriers SC1, SC2, SC3, and SC4 to the same, the access point AP pads the last data units DU1, DU2, DU3, and DU4 included in the payload. At least one of a bit (eg, a MAC pad bit, a PHY pad bit) and a tail bit may be added.

Meanwhile, a PPDU composed of MPDUs multiplexed in time and a PPDU composed of MSDUs multiplexed in time are as follows.

11 is a block diagram illustrating an embodiment of a PPDU composed of MPDUs multiplexed in time.

Referring to FIG. 11, the PPDU 1100 may include a PHY header 1101, a service field 1102, an MPDU-1 1103, an MPDU-2 1104, and an MPDU-3 1105. In addition, the PPDU 1100 may further include at least one of a pad bit 1106 and a tail bit 1107. Each of the MPDUs 1103, 1104, and 1105 included in the PPDU 1100 may represent different user data units. For example, MPDU-1 (1103) may mean a data unit to be transmitted to the first terminal (STA1), MPDU-2 (1104) can mean a data unit to be transmitted to the second terminal (STA2). In addition, the MPDU-3 1105 may mean a data unit to be transmitted to the third terminal STA3.

12 is a block diagram showing an embodiment of a PPDU composed of MSDUs multiplexed in time.

12, the PPDU 1200 includes a PHY header 1201, a service field 1202, a MAC header 1203, MSDU-1 1204, MSDU-2 1205, and MSDU-3 1206. Can include. In addition, the PPDU 1200 may further include one of a pad bit 1207 and a tail bit 1208. Each of the MSDUs 1204, 1205, and 1206 included in the PPDU 1200 may represent different user data units. For example, MSDU-1 1204 may refer to a data unit to be transmitted to the first terminal (STA1), and MSDU-2 (1205) may refer to a data unit to be transmitted to the second terminal (STA2). In addition, MSDU-3 1206 may refer to a data unit to be transmitted to the third terminal STA3.

Referring back to FIGS. 7 and 8, after multiplexing the data units in terms of frequency and time, the access point AP is in addition to the first terminal STA1 among terminals connected to it (STA1, STA2, STA3, STA4). It may be determined whether a data unit to be transmitted to other terminals STA2, STA3, and STA4 exists in the transmission queue (S715). If the data unit to be transmitted to other terminals STA2, STA3, and STA4 does not exist in the transmission queue, S720 may be performed as a next step. That is, the access point (AP) may transmit a PPDU composed of data units multiplexed in frequency and time.

On the other hand, even when data units are multiplexed in terms of frequency and time, if data units to be transmitted to other terminals STA2, STA3, and STA4 are present in the transmission queue, the access point (AP) selects the data units in frequency, time, and space. It can be multiplexed onto the phase, and a PPDU composed of multiplexed data units can be generated (S716). A PPDU composed of data units multiplexed in frequency, time, and space is as follows.

13 is a block diagram illustrating an embodiment of a PPDU composed of data units multiplexed in frequency, time, and space.

Referring to FIG. 13, a PPDU may include a PHY header and a payload. The first space SP1 and the second space SP2 may be orthogonal to each other. The access point AP may allocate data units to the first space SP1. That is, the access point AP has a first data unit DU1 to be transmitted to the first terminal STA1 to the first subcarrier SC1 among the entire band, and a second data unit to be transmitted to the second terminal STA2 ( DU2) and a third data unit DU3 to be transmitted to the third terminal STA3 may be allocated. The access point (AP) allocates a data unit (DU2) to be transmitted to the second terminal (STA2) and a third data unit (DU3) to be transmitted to the third terminal (STA3) to the second subcarrier (SC2) among the entire band. can do. The access point (AP) allocates a data unit (DU4) to be transmitted to the fourth terminal (STA4) and a first data unit (DU1) to be transmitted to the first terminal (STA1) to the third subcarrier (SC3) among the entire band. can do. The access point (AP) allocates a data unit (DU3) to be transmitted to the third terminal (STA3) and a fourth data unit (DU4) to be transmitted to the fourth terminal (STA4) to the fourth subcarrier (SC4) among the entire bands. can do.

Also, the access point AP may allocate data units to the second space SP2. The access point AP includes a first data unit DU1 to be transmitted to the first terminal STA1 to the first subcarrier SC1 and a second data unit DU2 to be transmitted to the second terminal STA2. And a third data unit DU3 to be transmitted to the third terminal STA3 may be allocated. The access point (AP) allocates a data unit (DU2) to be transmitted to the second terminal (STA2) and a third data unit (DU3) to be transmitted to the third terminal (STA3) to the second subcarrier (SC2) among the entire band. can do. The access point (AP) allocates a data unit (DU4) to be transmitted to the fourth terminal (STA4) and a first data unit (DU1) to be transmitted to the first terminal (STA1) to the third subcarrier (SC3) among the entire band. can do. The access point (AP) allocates a data unit (DU3) to be transmitted to the third terminal (STA3) and a fourth data unit (DU4) to be transmitted to the fourth terminal (STA4) to the fourth subcarrier (SC4) among the entire bands. can do.

Here, in order to match the payload size of each of the subcarriers SC1, SC2, SC3, and SC4 to the same, the access point AP pads the last data units DU1, DU2, DU3, and DU4 included in the payload. At least one of a bit (eg, a MAC pad bit, a PHY pad bit) and a tail bit may be added.

Meanwhile, an access point (AP) may generate a PPDU composed of data units multiplexed in space for two main purposes. First, the access point (AP) repeatedly transmits a PPDU composed of data units (DU1, DU2, DU3, DU4) multiplexed in frequency and time in order to obtain a spatial diversity gain. I can. Second, the access point (AP) can generate different PPDUs composed of data units (DU1, DU2, DU3, DU4) multiplexed in frequency and time to improve transmission capacity, and can generate different PPDUs. Can be transmitted in an independent space.

Referring back to FIGS. 7 and 8, frequency multiplexing, frequency-time multiplexing, and frequency-time-space multiplexing are sequentially performed according to the state of the transmission queue (eg, the state of the transmission queue after multiplexing) in step S710. It was described as being. In addition, according to another embodiment of the present invention, the access point (AP) may generate a PPDU based on at least one of frequency multiplexing, temporal multiplexing, and spatial multiplexing according to a state of a transmission queue. That is, the AP may generate a PPDU composed of multiplexed data units based on the size of data currently stored in the transmission queue without considering the state of the transmission queue after multiplexing. For example, when there are many data units currently stored in the transmission queue, the access point AP may generate a PPDU composed of data units multiplexed in frequency-time-space. Alternatively, the AP may generate a PPDU composed of data units multiplexed in frequency, time, or space when there are few data units currently stored in the transmission queue.

Meanwhile, the signal (SIG) field of the PPDU includes the length of the data unit, the receiver identifier of the data unit (eg, association identifier (AID), partial AID (PAID), group ID, etc.), and the data unit. It may further include at least one of a transmitted channel, a transmission period, and a space. Here, the signal field may mean a high throughput (HT)-SIG A field or an HT-SIG B field specified in the IEEE 802.11n standard. Alternatively, the signal field may mean a very high throughput (VHT)-SIG A field or a VHT-SIG B field specified in the IEEE 802.11ac standard. For example, the receiver identifier of the data unit may be set in the group ID field included in the VHT-SIG A field. The space in which the data unit is transmitted may be set in a number of spatial-time stream (NSTS) field included in the VHT-SIG A field.

After generating the PPDU, the AP may transmit the PPDU to the corresponding terminals STA1, STA2, STA3, and STA4 (S720). Each of the terminals STA1, STA2, STA3, and STA4 may acquire the SIG field included in the PPDU when receiving the PPDU (S730-1, S730-2, S730-3, S730-4). Each of the terminals STA1, STA2, STA3, and STA4 can know whether their own data unit exists in the PPDU based on information included in the SIG field. Each of the terminals (STA1, STA2, STA3, and STA4) has its own data unit based on the information included in the SIG field when its data unit is present in the PPDU, which resource (i.e., frequency resource, time resource, spatial resource). ). Each of the terminals STA1, STA2, STA3, and STA4 may acquire a data unit through a resource indicated by the SIG field (S740-1, S740-2, S740-3, and S740-4). Each of the terminals STA1, STA2, STA3, and STA4 may transmit an ACK frame to the AP after SIFS from the time when the PPDU reception ends when the data unit is successfully received (S750).

In this case, each of the terminals STA1, STA2, STA3, and STA4 may transmit a BA frame to the access point AP in response to reception of the data unit. Here, each of the terminals STA1, STA2, STA3, and STA4 may transmit an ACK frame to the access point (AP) through a resource corresponding to a resource to which their data unit is transmitted. For example, when the terminal (STA1, STA2, STA3, STA4) receives the data unit through the second transmission period in the first subcarrier among the PPDUs received from the fourth antenna, the ACK frame, which is a response to the data unit, is provided. It can be set in the second transmission period in the first subcarrier among PPDUs to be transmitted through 4 antennas.

14 is a conceptual diagram illustrating an embodiment of a method of transmitting and receiving a PPDU composed of data units multiplexed on a frequency.

Referring to FIG. 14, an access point (AP) that intends to transmit a first data unit (DU1) for a first terminal (STA1) may determine the occupancy state of a channel based on a CCA. As a result of the CCA, when the channel is in the idle state, the access point (AP) may acquire the TXOP if the channel is in the idle state during DIFS and contention window (CW=4). The access point (AP) determines whether a data unit to be transmitted to other terminals (STA2, STA3, STA4) other than the first terminal (STA1) among the terminals (STA1, STA2, STA3, and STA4) connected to it exists in the transmission queue. can do.

If a data unit to be transmitted to other terminals STA2, STA3, and STA4 exists in the transmission queue, the access point AP is the data units DU1 and DU2 of each of the terminals STA1, STA2, STA3, and STA4. , DU3, DU4) can be multiplexed on a frequency. For example, the first data unit DU1 for the first terminal STA1 may be allocated to the first subcarrier SC1, and the second data unit DU2 for the second terminal STA2 is 2 may be allocated to the subcarrier SC2, and the fourth data unit DU4 for the fourth terminal STA4 may be allocated to the third subcarrier SC3, and the third terminal STA3 The three data unit DU3 may be allocated to the fourth subcarrier SC4.

The access point AP may transmit a PPDU composed of data units DU1, DU2, DU3, and DU4 multiplexed over frequency to the terminals STA1, STA2, STA3, and STA4. Each of the terminals STA1, STA2, STA3, and STA4 can receive a PPDU, and whether their own data unit (DU1, DU2, DU3, DU4) exists in the PPDU based on information included in the SIG field of the PPDU. You can check. Each of the terminals (STA1, STA2, STA3, and STA4) has its own data unit (DU1, DU1, DU4) based on information included in the SIG field of the PPDU when its own data unit (DU1, DU2, DU3, DU4) exists in the PPDU. DU2, DU3, DU4) can check the transmitted resource.

Each of the terminals STA1, STA2, STA3, and STA4 may receive their own data units DU1, DU2, DU3, and DU4 through resources indicated by the SIG field of the PPDU. When each of the terminals STA1, STA2, STA3, and STA4 successfully receives the data units DU1, DU2, DU3, and DU4, they may transmit an ACK frame to the access point (AP) after SIFS from the end of reception of the PPDU. . At this time, each of the terminals STA1, STA2, STA3, and STA4 may transmit an ACK frame to the access point (AP) through a resource corresponding to a resource to which their data unit (DU1, DU2, DU3, DU4) is transmitted. .

15 is a conceptual diagram illustrating an embodiment of a method for transmitting and receiving a PPDU composed of data units multiplexed in frequency and time.

Referring to FIG. 15, an access point (AP) that intends to transmit a first data unit (DU1) for a first terminal (STA1) may determine the occupancy state of a channel based on a CCA. As a result of the CCA, when the channel is in the idle state, the access point (AP) may acquire the TXOP if the channel is in the idle state during DIFS and contention window (CW=4). The access point (AP) determines whether a data unit to be transmitted to other terminals (STA2, STA3, STA4) other than the first terminal (STA1) among the terminals (STA1, STA2, STA3, and STA4) connected to it exists in the transmission queue. can do.

If a data unit to be transmitted to other terminals STA2, STA3, and STA4 exists in the transmission queue, the access point AP is the data units DU1 and DU2 of each of the terminals STA1, STA2, STA3, and STA4. , DU3, DU4) can be multiplexed in frequency and time. For example, a first data unit DU1 for a first terminal STA1, a second data unit DU2 for a second terminal STA2, and a third data unit DU3 for a third terminal STA3. ) May be allocated to the first subcarrier SC1. The second data unit DU2 for the second terminal STA2 and the third data unit DU3 for the third terminal STA3 may be allocated to the second subcarrier SC2. The fourth data unit DU4 for the fourth terminal STA4 and the first data unit DU1 for the first terminal STA1 may be allocated to the third subcarrier SC3. The third data unit DU3 for the third terminal STA3 and the fourth data unit DU4 for the fourth terminal STA4 may be allocated to the fourth subcarrier SC4.

The access point AP may transmit a PPDU composed of data units DU1, DU2, DU3, and DU4 multiplexed in frequency and time to the terminals STA1, STA2, STA3, and STA4. Each of the terminals STA1, STA2, STA3, and STA4 can receive a PPDU, and whether their own data unit (DU1, DU2, DU3, DU4) exists in the PPDU based on information included in the SIG field of the PPDU. You can check. Each of the terminals (STA1, STA2, STA3, and STA4) has its own data unit (DU1, DU1, DU4) based on information included in the SIG field of the PPDU when its own data unit (DU1, DU2, DU3, DU4) exists in the PPDU. DU2, DU3, DU4) can check the transmitted resource.

Each of the terminals STA1, STA2, STA3, and STA4 may receive their own data units DU1, DU2, DU3, and DU4 through resources indicated by the SIG field of the PPDU. When each of the terminals STA1, STA2, STA3, and STA4 successfully receives the data units DU1, DU2, DU3, and DU4, they may transmit an ACK frame to the access point (AP) after SIFS from the end of reception of the PPDU. . At this time, each of the terminals STA1, STA2, STA3, and STA4 may transmit an ACK frame to the access point (AP) through a resource corresponding to a resource to which their data unit (DU1, DU2, DU3, DU4) is transmitted. .

16 is a conceptual diagram illustrating an embodiment of a method for transmitting and receiving a PPDU composed of data units multiplexed in frequency, time and space.

Referring to FIG. 16, an access point AP that intends to transmit a first data unit DU1 for a first terminal STA1 may determine a channel occupancy state based on a CCA. As a result of the CCA, when the channel is in the idle state, the access point (AP) may acquire the TXOP if the channel is in the idle state during DIFS and contention window (CW=4). The access point (AP) determines whether a data unit to be transmitted to other terminals (STA2, STA3, STA4) other than the first terminal (STA1) among the terminals (STA1, STA2, STA3, and STA4) connected to it exists in the transmission queue. can do.

If a data unit to be transmitted to other terminals STA2, STA3, and STA4 exists in the transmission queue, the access point AP is the data units DU1 and DU2 of each of the terminals STA1, STA2, STA3, and STA4. , DU3, DU4) can be multiplexed in frequency, time and space. For example, a first data unit DU1 for a first terminal STA1, a second data unit DU2 for a second terminal STA2, and a third data unit DU3 for a third terminal STA3. ) May be allocated to the first subcarrier SC1 of the first space SC1. The second data unit DU2 for the second terminal STA2 and the third data unit DU3 for the third terminal STA3 may be allocated to the second subcarrier SC2 of the first space SC1. have. The fourth data unit DU4 for the fourth terminal STA4 and the first data unit DU1 for the first terminal STA1 may be allocated to the third subcarrier SC3 of the first space SC1. have. The third data unit DU3 for the third terminal STA3 and the fourth data unit DU4 for the fourth terminal STA4 may be allocated to the fourth subcarrier SC4 of the first space SC1. have.

In addition, the first data unit DU1 for the first terminal STA1, the second data unit DU2 for the second terminal STA2, and the third data unit DU3 for the third terminal STA3 are It may be allocated to the first subcarrier SC1 of the second space SC2. The second data unit DU2 for the second terminal STA2 and the third data unit DU3 for the third terminal STA3 may be allocated to the second subcarrier SC2 of the second space SC2. have. The fourth data unit DU4 for the fourth terminal STA4 and the first data unit DU1 for the first terminal STA1 may be allocated to the third subcarrier SC3 of the second space SC2. have. The third data unit DU3 for the third terminal STA3 and the fourth data unit DU4 for the fourth terminal STA4 may be allocated to the fourth subcarrier SC4 of the second space SC2. have.

The access point (AP) may transmit a PPDU composed of data units (DU1, DU2, DU3, DU4) multiplexed in frequency, time and space to the terminals STA1, STA2, STA3, and STA4. Each of the terminals STA1, STA2, STA3, and STA4 can receive a PPDU, and whether their own data unit (DU1, DU2, DU3, DU4) exists in the PPDU based on information included in the SIG field of the PPDU. You can check. Each of the terminals (STA1, STA2, STA3, and STA4) has its own data unit (DU1, DU1, DU4) based on information included in the SIG field of the PPDU when its own data unit (DU1, DU2, DU3, DU4) exists in the PPDU. DU2, DU3, DU4) can check the transmitted resource.

Each of the terminals STA1, STA2, STA3, and STA4 may receive their own data units DU1, DU2, DU3, and DU4 through resources indicated by the SIG field of the PPDU. When each of the terminals STA1, STA2, STA3, and STA4 successfully receives the data units DU1, DU2, DU3, and DU4, they may transmit an ACK frame to the access point (AP) after SIFS from the end of reception of the PPDU. . At this time, each of the terminals STA1, STA2, STA3, and STA4 may transmit an ACK frame to the access point (AP) through a resource corresponding to a resource to which their data unit (DU1, DU2, DU3, DU4) is transmitted. .

17 is a block diagram showing the configuration of an access point according to an embodiment of the present invention.

Referring to FIG. 17, the access point 1700 includes a channel connection unit 1701, a transmission queue confirmation unit 1702, a signal transmission unit 1703, a band division unit 1704, a frame combination unit 1705, and an antenna arrangement unit. (1706) may be included. The processor 110 described above with reference to FIG. 1 includes a channel transmission unit 1701, a transmission queue confirmation unit 1702, a signal transmission unit 1703, a band division unit 1704, a frame combination unit 1705, and an antenna. The function of the placement unit 1706 may be performed.

The channel connection unit 1701 may attempt to access a channel based on a DCF method or an enhanced distributed channel access (EDCA) method. In this case, a station to access the channel may be determined based on an access category (AC) of a data unit and a size of a contention window (CW). When a channel is accessed by the channel connection unit 1701, the transmission queue checking unit 1702 may determine whether a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue. If a data unit for a terminal other than the terminal currently connected to the channel does not exist in the transmission queue, the signal transmission unit 1703 may transmit a PPDU composed of only data units for the terminal currently connected to the channel.

On the other hand, when a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue, the band division unit 1704 may multiplex the data units for the terminals on a frequency basis. Thereafter, the transmission queue checking unit 1702 may determine whether a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue. If a data unit for a terminal other than the terminal currently connected to the channel does not exist in the transmission queue, the signal transmission unit 1703 may transmit a PPDU composed of data units multiplexed on a frequency.

On the other hand, when a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue, the band division unit 1704 and the frame combination unit 1705 may multiplex the data units for the terminals in frequency and time. I can. That is, the frame combination unit 1705 may reconstruct a frame by adding a data unit for another terminal to each of the subcarriers. Thereafter, the transmission queue checking unit 1702 may determine whether a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue. If a data unit for a terminal other than the terminal currently connected to the channel does not exist in the transmission queue, the signal transmission unit 1703 may transmit a PPDU composed of data units multiplexed in frequency and time.

On the other hand, when a data unit for a terminal other than the terminal currently connected to the channel exists in the transmission queue, the band division unit 1704, the frame combination unit 1705, and the antenna arrangement unit 1706 may configure the data units for the terminals. It can be multiplexed over frequency, time and space. That is, the antenna placement unit 1706 may reconstruct a frame by overlapping data units for terminals in space. The signal transmission unit 1703 may transmit a PPDU composed of data units multiplexed in frequency, time, and space.

Previously, a method of multiplexing data units in time, frequency, and space has been described in detail. Since only one station occupying the channel in the existing wireless LAN has exclusively used the entire channel during the entire TXOP, other stations have no choice but to wait during the corresponding TXOP. In addition, since many stations attempt to access a channel after the TXOP has elapsed, the problem of channel access delay inevitably occurs continuously. In order to solve this problem, methods according to the present invention have been proposed.

According to the present invention, transmission opportunities can be frequently given to many stations in one BSS. Through this, the waiting time for data transmission may be reduced, and thus the performance of the wireless LAN (eg, communication quality, transmission stability, etc.) may be improved.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for embodiments of the present invention, or may be known and usable to those skilled in computer software.

The computer-readable medium may mean a hardware device specially configured to store and execute program commands, such as ROM, RAM, flash memory, and the like. The hardware device may be configured to operate as at least one software module to perform an operation according to the embodiments of the present invention, and vice versa. The program instruction may mean a high-level language code that can be executed in a computer based on an interpreter, as well as a machine language code created by a compiler.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention described in the following claims. I will be able to.

Claims (11)

As a frame transmission method performed in an access point (access point),
Generating a first physical layer convergence procedure (PPDU) protocol data unit (PPDU) including one or more data units;
Generating a second PPDU comprising one or more data units; And
And transmitting the first PPDU and the second PPDU to a plurality of terminals in a multiple input multiple output (MIMO) method,
Each of the first PPDU and the second PPDU further includes information on spaces used for transmission based on the MIMO scheme. The method according to claim 1,
The first PPDU is transmitted to a first terminal among the plurality of terminals, the first PPDU further includes an identifier of the first terminal, and the second PPDU is transmitted to a second terminal among the plurality of terminals. And, the second PPDU further comprises an identifier of the second terminal, frame transmission method. The method according to claim 1,
When the first PPDU includes a plurality of data units, the plurality of data units are multiplexed on a frequency. The method of claim 3,
The first PPDU further includes information indicating a channel through which each of the plurality of data units is transmitted. The method of claim 3,
The frame transmission method, wherein padding is added to at least one data unit among the plurality of data units in order to equalize the end points of the plurality of data units. As a frame reception method performed in a first terminal,
Receiving a first physical layer convergence procedure (PPDU) protocol data unit (PPDU) from an access point in a first space among a plurality of spaces orthogonal to each other;
Comparing an identifier included in the first PPDU with an identifier of the first terminal; And
If the identifier included in the first PPDU is the same as the identifier of the first terminal, acquiring one or more data units included in the first PPDU. The method of claim 6,
The first PPDU further includes information indicating the first space in which the first PPDU is transmitted. The method of claim 6,
In a second space orthogonal to the first space among the plurality of spaces, a second PPDU is transmitted from the access point to a second terminal, and the second PPDU includes an identifier of the second terminal. . The method of claim 6,
When the first PPDU includes a plurality of data units, the plurality of data units are multiplexed on a frequency. The method of claim 9,
The first PPDU further includes information indicating a channel through which each of the plurality of data units is transmitted. The method of claim 9,
A method of receiving a frame, wherein padding is added to at least one data unit among the plurality of data units in order to equalize the end points of the plurality of data units.

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