Wireless communication method using multiple links, and wireless communication terminal using the same

Abstract

To provide a multi-link device using a plurality of links.SOLUTION: A processor is configured to: receive, in any one of the links, a first physical layer protocol data unit (PPDU) including access category (AC) constraint signaling and a reverse direction (RD) grant from a station which is a transmission opportunity (TXOP) holder or a service period (SP) source; and transmit, in the one link, a second PPDU to the station in response to the first PPDU on the basis of the AC constraint signaling. The AC constraint signaling indicates whether a traffic identifier (TID) or AC of a frame included in the second PPDU is constrained.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method using multilinks and a wireless communication terminal using the same. [Background technology]

[0002] Recently, as the popularity of mobile devices has increased, wireless LAN technology, which can provide them with high-speed wireless Internet services, has been gaining attention. Wireless LAN technology is a technology that uses short-range wireless communication technology to enable mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, embedded devices, etc. to connect to the Internet wirelessly at home, in business, or in specific service areas.

[0003] Since supporting early wireless LAN technology using the 2.4 GHz frequency band, IEEE (Institute of Electronics Engineers) 802.11 has since implemented or is currently developing various other technology standards. IEEE 802.11b uses the 2.4 GHz frequency band and supports a maximum communication speed of 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz frequency band instead of the 2.4 GHz band, reducing the impact of interference compared to the significantly more congested 2.4 GHz frequency band, and uses OFDM technology to improve communication speeds to a maximum of 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. IEEE 802.11g, like IEEE 802.11b, uses the 2.4GHz band and achieves a maximum transmission speed of 54Mbps, and has attracted considerable attention for its backward compatibility, but it also has an advantage over IEEE 802.11a in terms of communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been identified as a weakness of wireless LANs. IEEE 802.11n aims to increase network speed and reliability and extend the operating distance of wireless networks. Specifically, IEEE 802.11n supports high throughput (HT) of up to 540 Mbps and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas on both the transmitting and receiving ends to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As WLAN adoption continues to grow and applications become more diverse, the need for new WLAN systems is emerging to support data throughput rates (Very High Throughput, VHT) higher than those supported by IEEE 802.11n. Among these, IEEE 802.11ac supports wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard is defined only in the 5GHz band, initial 802.11ac chipsets are expected to support operation in the 2.4GHz band as well for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, there is IEEE 802.11ad, a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, making it suitable for streaming large amounts of data and high-bitrate video, such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage of being difficult to pass through obstacles and can only be used between devices in close proximity.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard is being developed and is nearing completion as the successor to 802.11ac and 802.11ad in order to provide high-efficiency and high-performance WLAN communication technology in high-density environments where APs and terminals are densely packed. In an 802.11ax-based WLAN environment, high-frequency-efficient communication must be provided both indoors and outdoors in the presence of a high density of stations and APs (Access Points), and various technologies are being developed to achieve this.

[0007] Additionally, development of a new WLAN standard has begun to increase maximum transmission speeds to support new multimedia applications such as high-definition video and real-time gaming. IEEE 802.11be (Extremely High Throughput, EHT), the seventh generation WLAN standard, is currently being developed with the goal of supporting transmission rates of up to 30Gbps in the 2.4 / 5 / 6GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of one embodiment of the present invention is to provide a wireless communication method using multilinks and a wireless communication terminal using the same. [Means for solving the problem]

[0009] According to an embodiment of the present invention, a multi-link device using a plurality of links includes a transceiver and a processor. The processor receives a first physical layer protocol data unit (PPDU) including access category (AC) restriction signaling and a reverse direction (RD) grant from a station that is a transmission opportunity (TXOP) holder or a service period (SP) source over one of the plurality of links, and transmits a second PPDU to the station over the one of the links in response to the first PPDU based on the AC restriction signaling. The AC restriction signaling indicates whether a traffic identifier (TID) or AC of a frame included in the second PPDU is restricted.

[0010] An AC or a TID is mapped to one of the plurality of links, and the multi-link device can transmit frames based on the mapped AC or TID through the one of the links. In this case, the processor can, when the AC restriction signaling indicates that any TID of a data frame included in the second PPDU is acceptable, not include in the second PPDU a data frame corresponding to a TID not mapped to the one of the links, and include in the second PPDU a data frame corresponding to a TID mapped to the one of the links.

[0011] An AC or TID may be mapped to one of the plurality of links, and the multi-link device may transmit frames based on the mapped AC or TID through the one of the links. In this case, the processor may, when the AC restriction signaling indicates that an AC or TID of a frame included in the second PPDU is restricted, not include in the second PPDU a data frame that is not mapped to the one of the links or corresponds to a TID or AC with a lower priority than the priority of the AC or TID of a frame received from the station, and may include in the second PPDU a data frame that is mapped to the one of the links and corresponds to a TID or AC with a priority equal to or higher than the priority of the AC or TID of a frame received from the station.

[0012] When the multilink device receives a plurality of frames from the station, the priority of the AC or TID of the frame received from the station may be the lowest priority among the priorities of the plurality of frames.

[0013] The processor can consider the AC of the management frame to be a pre-specified value.

[0014] When the multilink device includes a BlockAck frame in the second PPDU, the processor can determine the AC of the BlockAck frame based on a TID field of the BlockAck frame. Also, when the multilink device includes a BlockAckReq frame in the second PPDU, the processor can determine the AC of the BlockAckReq frame based on a TID field of the BlockAckReq frame.

[0015] The AC restriction signaling may be included in a medium access control (MAC) header of a frame included in a PPDU that includes the RD grant.

[0016] A method for operating a multi-link device using a plurality of links according to an embodiment of the present invention includes receiving, via any one of the plurality of links, a first physical layer protocol data unit (PPDU) including access category (AC) restriction signaling and a reverse direction (RD) grant from a station that is a transmission opportunity (TXOP) holder or a service period (SP) source; and transmitting, via the any one of the links, a second PPDU to the station in response to the first PPDU based on the AC restriction signaling. The AC restriction signaling indicates whether a traffic identifier (TID) or AC of a frame included in the second PPDU is restricted.

[0017] An AC or a TID is mapped to one of the plurality of links, and the multi-link device can transmit frames based on the AC or TID mapped to the one of the links. In this case, transmitting the second PPDU to the station can include, when the AC restriction signaling indicates that any TID of a data frame included in the second PPDU is acceptable, not including in the second PPDU a data frame corresponding to a TID not mapped to the one of the links, and including in the second PPDU a data frame corresponding to a TID mapped to the one of the links.

[0018] An AC or TID may be mapped to one of the plurality of links, and the multilink device may transmit frames based on the mapped AC or TID through the one of the links. In this case, transmitting the second PPDU to the station may include, when the AC restriction signaling indicates that an AC or TID of a frame included in the second PPDU is restricted, not including in the second PPDU a data frame that is not mapped to the one of the links or corresponds to a TID or AC with a lower priority than a priority of an AC or TID of a frame received from the station, and including in the second PPDU a data frame that is mapped to the one of the links and corresponds to a TID or AC with a priority equal to or higher than a priority of an AC or TID of a frame received from the station, if the AC restriction signaling indicates that an AC or TID of a frame included in the second PPDU is restricted.

[0019] When the multilink device receives a plurality of frames from the station, the priority of the AC or TID of the frame received from the station may be the lowest priority among the priorities of the plurality of frames.

[0020] The step of transmitting the second PPDU to the station may include the step of regarding an AC of a management frame as a pre-specified value.

[0021] The step of transmitting the second PPDU to the station may include determining an AC of the BlockAck frame based on a TID field of the BlockAck frame if the multilink device includes a BlockAck frame in the second PPDU, and determining an AC of the BlockAckReq frame based on a TID field of the BlockAckReq frame if the multilink device includes a BlockAckReq frame in the second PPDU. The AC restriction signaling may be included in a medium access control (MAC) header of a frame included in the PPDU including the RD grant. [Effects of the Invention]

[0022] An embodiment of the present invention provides a wireless communication method that efficiently uses multilinks and a wireless communication terminal that uses the same. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an access point according to an embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a process in which a STA establishes a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7]1 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8] 1 illustrates various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 shows a multi-link device according to an embodiment of the present invention; [Figure 10] 10 illustrates a frame exchange between a non-AP multilink device and an AP multilink device when TID-to-link mapping is configured according to an embodiment of the present invention. [Figure 11] 3 illustrates a frame exchange according to a reverse direction (RD) protocol according to an embodiment of the present invention. [Figure 12] 1 illustrates AC-limited signaling according to an embodiment of the present invention. [Figure 13] 1 shows a frame format and a format of a signaling field of the frame according to an embodiment of the present invention. [Figure 14] According to one embodiment of the present invention, RD exchange without AC restrictions is performed on a link to which TID-to-link mapping is applied. [Figure 15] According to yet another embodiment of the present invention, RD exchange is performed in which AC restrictions are not applied on a link to which TID-to-link mapping is applied. [Figure 16] According to yet another embodiment of the present invention, no AC restriction is set when RD exchange is performed on a link to which TID-to-link mapping is applied. [Figure 17] According to yet another embodiment of the present invention, it is shown that RD exchange is performed when AC restrictions are applied on the link to which TID-to-link mapping is applied. [Figure 18]According to yet another embodiment of the present invention, it is shown that RD exchange is performed when AC restrictions are applied on the link to which TID-to-link mapping is applied. [Figure 19] 10 illustrates signaling information about AC restrictions used in RD initiator RD responses, according to an embodiment of the present invention. [Figure 20] 1 shows that an RD exchange is performed when a PPDU whose transmission ends are synchronized is transmitted over multiple links according to an embodiment of the present invention. [Figure 21] 1 shows the RU configuration that can be allocated to one station in IEEE 802.11ax and the RU configuration that can be allocated to one station according to an embodiment of the present invention. [Figure 22] 1 illustrates an OFDMA DL PPDU used in the IEEE 802.11ax standard and in embodiments of the present invention. [Figure 23] It will be shown that the backoff procedure is performed using sub-channels other than the 20 MHz primary channel according to an embodiment of the present invention. [Figure 24] According to an embodiment of the present invention, when a station successfully accesses a subchannel other than the 20 MHz primary channel and transmits a PPDU, the length of the PPDU is limited. [Figure 25] In accordance with an embodiment of the present invention, when the 20 MHz primary channel is not idle, a station may access the channel via a sub-channel of a segment other than the primary segment. [Figure 26] According to an embodiment of the present invention, a first AP of a multi-link device signals via a second AP that the first AP can receive on a sub-channel other than the 20 MHz main channel. [Figure 27] This shows that an AP of an AP multi-link device according to an embodiment of the present invention allows a station parked on a segment other than the 80 MHz primary channel to perform a backoff procedure for upstream transmission on the segment on which the station is parked. DETAILED DESCRIPTION OF THE INVENTION

[0024] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of engineers in the relevant technical field, customs, or the emergence of new technologies. In addition, in certain cases, the applicant may have arbitrarily selected terms, and in such cases, the meanings thereof will be described in the relevant description of the invention. Therefore, it is made clear that the terms used in this specification should be interpreted not simply as names of terms, but based on the substantive meanings of the terms and the overall content of this specification.

[0025] Throughout this specification, when a component is referred to as being "connected" to another component, this includes not only when the component is "directly connected" to another component, but also when the component is "electrically connected" to another component via another component in between. Furthermore, when a component is referred to as "comprising" a specific component, this does not mean that the component may exclude the other component, but may further include the other component, unless otherwise specified. In addition, limitations such as "greater than" or "less than" based on a specific critical value may be appropriately substituted with "exceeds" or "less than," respectively, depending on the embodiment.

[0026] Hereinafter, in the present invention, the terms field and subfield may be used interchangeably.

[0027] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0028] A wireless LAN system includes one or more Basic Service Sets (BSSs), which are a set of devices that can synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0029] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 that are stations providing distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0030] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard. In a broad sense, the term "station" encompasses not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface and a display unit, depending on the embodiment. The processor generates frames to be transmitted over a wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The communication unit is functionally connected to the processor and transmits and receives frames over the wireless network for the station. In this specification, the term "terminal" encompasses user equipment (UE).

[0031] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for associated stations. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP. However, if a direct link is established, direct communication is also possible between non-AP stations. Meanwhile, in the present invention, the term AP is used as a concept including a personal BSS coordination point (PCP), but in a broader sense, it also includes concepts such as a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller. In the present invention, an AP is also referred to as a base wireless communication terminal, but in a broader sense, the term base wireless communication terminal is used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal includes various types of wireless communication terminals that allocate communication medium resources and perform scheduling for communication with multiple wireless communication terminals.

[0032] A plurality of infrastructure BSSs are connected to each other via a distribution system DS, and the plurality of BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0033] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0034] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so none of the stations (STA6, STA7) are connected to an AP. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0035] 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention. As shown, the station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0036] First, the communication unit 120 transmits and receives wireless signals such as WLAN packets and may be incorporated into or external to the station 100. According to an embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules using different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with an AP or an external station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 120 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided independently, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit 120 may represent a radio frequency (RF) communication module that processes RF signals.

[0037] Next, the user interface 140 includes various types of input / output means provided in the station 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0038] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as a user interface, based on the contents processed by the processor 110 or the control commands of the processor 110. The memory 160 also stores control programs and various data used by the station 100. The control programs include a connection program required for the station 100 to connect to an AP or an external station.

[0039] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information about the station 100's preferences contained in the communication setup message and requests connection to the AP based on the information about the station 100's preferences. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the communication unit 120. That is, the processor 110 may be a modem that modulates and demodulates wireless signals transmitted and received by the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0040] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in embodiments of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively included in the station 100.

[0041] 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention. As shown, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, duplicated descriptions of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in FIG. 3 will be omitted.

[0042] Referring to FIG. 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 may also include multiple communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention may include two or more communication modules using different frequency bands, for example, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with a station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 220 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF (Radio Frequency) communication module that processes RF signals.

[0043] The memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a connection program that manages station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. The communication setup message includes information regarding connection preferences for each station. The processor 210 also performs connection setup in response to a station connection request. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals by the AP 200 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0044] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0045] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information for the BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0046] The STA 100 that successfully receives wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs the authentication step (S107b). After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs the association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0047] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, server 300 is a server that processes 802.1X-based authentication with STA 100, and may be physically connected to AP 200 or may exist as a separate server.

[0048] FIG. 6 is a diagram showing a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0049] A terminal performing WLAN communication performs carrier sensing to check whether a channel is occupied before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not a signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold is received by the terminal and the terminal is the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal with a strength below the CCA threshold is detected, the channel is determined to be idle.

[0050] If the channel is determined to be idle, each terminal having data to transmit performs a backoff procedure after an Inter Frame Space (IFS), such as an Arbitration IFS (AIFS) or a PCF IFS (PIFS), depending on the status of each terminal. In some embodiments, the AIFS is used as a configuration replacing the conventional DCF IFS (DIFS). Each terminal waits while decrementing a slot time equal to a random number determined for the corresponding terminal during the idle interval of the channel, and a terminal that has exhausted all of its slot time attempts to access the corresponding channel. The period during which each terminal performs the backoff procedure is called a contention window period. In this case, the random number can be called a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal can decrement the backoff counter by 1. If the backoff counter reaches 0, the terminal may be allowed to perform channel access on the corresponding channel. Therefore, if the channel is idle during the AIFS time and the backoff counter slot time, the terminal may be allowed to transmit.

[0051] If a specific terminal successfully accesses the channel, it transmits data over the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are assigned new random numbers and perform a backoff procedure again. According to one embodiment, the new random numbers assigned to each terminal are determined within a range (2*CW) twice the range of the random numbers previously assigned to the terminal (contention window, CW). Meanwhile, each terminal attempts access by performing a backoff procedure again in the next contention window period. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, terminals communicating over a wireless LAN can avoid collisions with each other on a specific channel.

[0052] <Examples of various PPDU formats>

[0053] Figure 7 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. More specifically, Figure 7(a) shows an example of a legacy PPDU format based on 802.11a / g, Figure 7(b) shows an example of an HE PPDU format based on 802.11ax, and Figure 7(c) shows an example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Also, Figure 7(d) shows detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0054] 7(a), the preamble of the legacy PPDU includes a Legacy Short Training field (L-STF), a Legacy Long Training field (L-LTF), and a Legacy Signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0055] Referring to FIG. 7(b), the preamble of the HE PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a High Efficiency Signal A field (HE-SIG-A), a High Efficiency Signal B field (HE-SIG-B), a High Efficiency Short Training field (HE-STF), and a High Efficiency Long Training field (HE-LTF) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as an HE preamble. The specific configuration of the HE preamble may vary depending on the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0056] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a Universal Signal field (U-SIG), an Extremely High Throughput Signal A field (EHT-SIG-A), an Extremely High Throughput Signal B field (EHT-SIG-A), an Extremely High Throughput Short Training field (EHT-STF), and an Extremely High Throughput Long Training field (EHT-LTF) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may vary depending on the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some EHT PPDU formats.

[0057] The L-SIG field included in the PPDU preamble is configured with a total of 64 subcarriers using 64 FFT OFDM. Of these, 48 subcarriers, excluding guard subcarriers, DC subcarriers, and pilot subcarriers, are used for L-SIG data transmission. BPSK and Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, so it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of the L-SIG.

[0058] Referring to FIG. 7(d), the L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field is composed of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission rates of 6, 9, 12, 18, 24, 36, 48, or 54 Mbps, which is a combination of a modulation scheme such as BPSK, QPSK, 16-QAM, or 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. The combined information in the L_RATE and L_LENGTH fields indicates the total length of the PPDU. In a non-legacy PPDU format, the L_RATE field is set to the minimum rate of 6 Mbps.

[0059] The unit of the L_LENGTH field is byte, and a total of 12 bits are allocated, allowing signaling up to 4095. In combination with the L_RATE field, the length of the PPDU can be indicated. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0060] First, a legacy or non-legacy terminal analyzes the length of the PPDU using the L_LENGTH field as follows. When the L_RATE field is set to 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted at 4 us, which is the duration of one symbol of the 64FFT. Therefore, by adding 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the amount of transmission of one symbol, the number of 64FFT reference symbols after the L-SIG is obtained. The obtained number of symbols is multiplied by 4 us, which is the duration of one symbol, and then 20 us, which is required to transmit the L-STF, L-LTF, and L-SIG, is added to obtain the length of the PPDU, i.e., the reception time (RXTIME). This can be expressed mathematically as shown in Equation 1 below.

[0061]

number

[0062] At this time,

[0063]

number

[0064] represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU may be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as shown in Equation 2 below.

[0065]

number

[0066] Here, TXTIME is the total transmission time constituting the PPDU, and is expressed as the following equation 3. In this case, TX represents the transmission time of X.

[0067]

number

[0068] Referring to the above formula, the length of the PPDU is calculated based on the rounded up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0069] Referring to Figure 7(e), the U-SIG (Universal SIG) field remains in the EHT PPDU and subsequent generation WLAN PPDUs, and serves to distinguish which generation of PPDU it is, including 11be. The U-SIG is two 64FFT-based OFDM symbols and can transmit a total of 52 bits of information. Of these, 43 bits excluding 9 bits of CRC / tail are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0070] The VI bit will maintain its current bit configuration, so even if a subsequent generation PPDU is defined, current 11be UEs can obtain information about the PPDU from the VI field of the PPDU. To this end, the VI field consists of the PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits long and serves to sequentially distinguish between 11be and subsequent generations of WLAN standards. 11be has a value of 000b. The UL / DL field identifies whether the PPDU is an uplink or downlink PPDU. The BSS color represents a BSS identifier defined in 11ax and has a value of 6 or more bits. The TXOP represents the transmit opportunity duration (Transmit Opportunity Duration) transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the MPDU, and has a value of 7 or more bits.

[0071] The VD field, which is signaling information useful only for 11be version PPDUs, may consist of fields commonly used in any PPDU format, such as the PPDU format and BW, as well as fields defined differently for each PPDU format. The PPDU format is a separator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs. The BW field broadly signals five basic PPDU BW options: 20, 40, 80, 160 (80 + 80), and 320 (160 + 160) MHz (BWs that can be expressed in the form of a power of 20 * 2 can be called basic BWs), as well as various remaining PPDU BWs formed by preamble puncturing. After signaling at 320 MHz, a portion of 80 MHz may be punctured. In addition, the punctured and modified channel shape may be signaled directly in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (for example, a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0072] The fields located after the BW field vary depending on the type and format of the PPDU. MU PPDUs and SU PPDUs may be signaled using the same PPDU format, and a field for distinguishing between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, requiring additional signaling. Both SU PPDUs and MU PPDUs include an EHT-SIG field, but some fields not required for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or may have a reduced size compared to the size of the original fields included in the MU PPDU. For example, the SU PPDU may have a different configuration, such as the common fields of the EHT-SIG being omitted or replaced, or the user-specific fields being replaced or reduced to one.

[0073] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (eg, the RA field) may be omitted depending on the value of the compression field.

[0074] When a portion of the EHT-SIG field of the SU PPDU is compressed, the information included in the compressed field may be signaled together in an uncompressed field (e.g., a common field). In the case of an MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU was sent to it. Therefore, the AP must transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the MCS, which is the modulation method. The EHT-SIG field may include information on the size and location of the RU assigned to each user.

[0075] In the case of an SU PPDU, a STA may be assigned multiple RUs, and the multiple RUs may be contiguous or discontinuous. If the RUs assigned to the STA are not contiguous, the STA can efficiently receive the SU PPDU only by recognizing punctured RUs in between. Therefore, the AP can transmit the SU PPDU including information on punctured RUs among the RUs assigned to the STA (e.g., puncturing pattern of the RUs). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and the puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field can signal the type of discontinuous channels appearing within the bandwidth.

[0076] The type of signaled discontinuous channel is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, since the SU PPDU is a PPDU transmitted only to a single UE, the STA can recognize its allocated bandwidth from the BW field included in the PPDU and can recognize punctured resources within the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the UE can receive the PPDU in the remaining resource units excluding specific channels of the punctured resource units. In this case, multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0077] The reason why only limited discontinuous channel types are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed for each 20 MHz subchannel, if puncturing is performed on a BW having multiple 20 MHz subchannels, such as 80, 160, or 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered discontinuous) must be signaled by expressing whether or not each of the remaining 15 20 MHz subchannels excluding the primary channel is in use. Using 15 bits to signal the discontinuous channel type for single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0078] This invention proposes a method for signaling the discontinuous channel type of an SU PPDU and illustrates the discontinuous channel type determined by the proposed method. It also proposes a method for signaling the primary 160 MHz and secondary 160 MHz puncturing types in a 320 MHz BW configuration of an SU PPDU. The discontinuous channel types allowed when the above discontinuous channel type definition method is applied and a method for signaling the discontinuous channel type with 3 bits are shown in Figures 17 to 19.

[0079] In addition, one embodiment of the present invention proposes a method of varying the PPDU configuration indicated by the preamble puncturing BW value depending on the PPDU format signaled in the PPDU format field. Assuming that the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, an EHT-SIG-A symbol can be further signaled after the U-SIG, or no EHT-SIG-A can be signaled at all. Taking this into consideration, up to 11 puncturing modes must be fully signaled using only the BW field of the U-SIG. However, in the case of an EHT MU PPDU, an EHT-SIG-B symbol is further signaled after the U-SIG, so up to 11 puncturing modes can be signaled in a different manner than in the case of an SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20 MHz or 10 MHz bandwidth. Detailed puncturing patterns for each PPDU type will be described in detail below with reference to FIGS. 11 and 12.

[0080] Figure 7(f) shows the format-specific field configuration of the VD field when the PPDU format field of the U-SIG indicates an EHT MU PPDU. For an MU PPDU, SIG-B, a signaling field for simultaneous reception by multiple users, is required. SIG-B may be transmitted after the U-SIG without a separate SIG-A. For this purpose, the U-SIG must signal information for decoding SIG-B. These fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, and number of EHT-LTF symbols.

[0081] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention.

[0082] 8, a PPDU may be configured with a preamble and a data portion, and the format of one type, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is EHT PPDU may be indicated based on a PPDU format field included in the U-SIG field.

[0083] 8(a) shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

[0084] 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. The EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used for responding to the trigger frame. Unlike the EHT SU PPDU, the EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0085] 8(c) shows an example of an EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit a PPDU to one or more STAs. In the EHT MU PPDU format, an HE-SIG-B field may be located after the U-SIG field.

[0086] 8(d) shows an example of an EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission with STAs in a wider range than the EHT SU PPDU described in FIG. 8(a), and the U-SIG field may be repeated on the time axis.

[0087] The EHT MU PPDU described in (c) of Figure 8 can be used by the AP for downlink transmission to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive the PPDU transmitted from the AP. The EHT MU PPDU can convey AID information of the receiver and / or sender of the transmitted PPDU to the STA through the user specific field of the EHT-SIG-B. Therefore, multiple terminals receiving the EHT MU PPDU can perform spatial reuse based on the AID information of the user specific field included in the preamble of the received PPDU.

[0088] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information regarding the configuration of resource units (e.g., the division type of resource units) in a specific bandwidth (e.g., 20 MHz) on the frequency axis. That is, the RA field may indicate the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU so that the STA can receive the PPDU. Information about the STA allocated (or designated) to each divided resource unit may be included in a user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field may include one or more user fields corresponding to each divided resource unit.

[0089] For example, among the multiple divided resource units, the user field corresponding to at least one resource unit used for data transmission may include the AID of the receiver or sender, and the user field corresponding to the remaining resource units not used for data transmission may include a previously set null STA ID.

[0090] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0091] When a single wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be improved. In this case, a link is a physical path and may be configured as a single wireless medium that can be used to transmit an MSDU (MAC service data unit). For example, when the frequency band of one link is being used by another wireless communication device, the wireless communication device can continue communication using another link. In this way, the wireless communication device can effectively use multiple channels. Furthermore, when a wireless communication device simultaneously communicates using multiple links, the overall throughput can be improved. However, existing wireless LANs are specified on the assumption that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is needed. A wireless communication method for a wireless communication device using multiple links will be described with reference to FIGS. 9 to 26. First, a specific embodiment of a wireless communication device using multiple links will be described with reference to FIG. 9.

[0092] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0093] A multi-link device (MLD) may be defined for the wireless communication method using multiple links described above. The multi-link device may represent a device having one or more affiliated stations. Depending on a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. The multi-link device may also exchange multi-link elements. The multi-link element includes information about one or more stations or one or more links. The multi-link element may include a multi-link setup element, which will be described later. In this case, the multi-link device may be a logical entity. Specifically, the multi-link device may have multiple affiliated stations. The multi-link device may be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one medium access control service access point (SAP) up to a logical link control (LLC). The MLD may also have one MAC data service.

[0094] Multiple stations included in a multilink device can operate on multiple links. Also, multiple stations included in a multilink device can operate on multiple channels. Specifically, multiple stations included in a multilink device can operate on different links or different channels. For example, multiple stations included in a multilink device can operate on different channels, such as 2.4 GHz, 5 GHz, and 6 GHz.

[0095] The operation of the multilink device can be referred to as multilink operation, MLD operation, or multi-band operation. If the station associated with the multilink device is an AP, the multilink device can be referred to as AP MLD. If the station associated with the multilink device is a non-AP station, the multilink device can be referred to as non-AP MLD.

[0096] FIG. 9 shows the operation of communication between non-AP MLD and AP-MLD. Specifically, non-AP MLD and AP-MLD each communicate using three links. AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). Non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via a first link (Link1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via a second link (Link2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via a third link (Link3).

[0097] Multilink operation may include a multilink setup operation. Multilink setup corresponds to the association operation of the single-link operation described above and must be performed prior to frame exchange in the multilink. A multilink device can obtain information required for multilink setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multilink. In this case, the capability information may include information indicating whether one of multiple devices included in the multilink device can transmit and the other devices can receive at the same time. The capability information may also include information about links available to each station included in the MLD. The capability information may also include information about channels available to each station included in the MLD.

[0098] Multilink configuration may be established through negotiation between peer stations. Specifically, multilink configuration may be established through communication between stations without communication with an AP. Multilink configuration may also be established through any one of the links. For example, even if the first to third links are established through multilink, multilink configuration may be established through the first link.

[0099] Additionally, a mapping between TIDs (traffic identifiers) and links may be set, which will be explained with reference to FIG.

[0100] FIG. 10 illustrates frame exchange between a non-AP multilink device and an AP multilink device when TID-to-link mapping is configured according to an embodiment of the present invention.

[0101] Specifically, frames corresponding to a specific TID value may be exchanged only through a pre-specified link. The mapping between TIDs and links may be configured on a directional basis. For example, when multiple links are configured between a first multilink device and a second multilink device, the first multilink device may be configured to transmit frames with a first TID to the multiple first links, and the second multilink device may be configured to transmit frames with a second TID to the first links. Furthermore, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to TIDs on each link according to a default setting. In this case, the default setting may be that all TIDs are exchanged on any one link.

[0102] The TID will be described in detail. The TID is an ID for classifying traffic and data to support quality of service (QoS). The TID may be used and assigned in a layer higher than the MAC layer. The TID may indicate a traffic category (TC) or a traffic stream (TS). There may be 16 distinct TIDs. For example, the TID may be designated as any one of 0 to 15. Different TID values ​​may be designated depending on an access policy, a channel access method, or a medium access method. For example, when enhanced distributed channel access (EDCA) or hybrid coordination function contention-based channel access (HCAF) is used, the TID may be assigned a value ranging from 0 to 7. When EDCA is used, the TID may indicate a user priority (UP). In this case, the UP may be designated by the TC or the TS. The UP may be assigned in a layer higher than the MAC. Furthermore, when HCCA (HCF controlled channel access) or SPCA is used, the TID may be assigned a value in the range of 8 to 15. When HCCA or SPCA is used, the TID may indicate a TSID. Furthermore, when HEMM or SEMM is used, the TID may be assigned a value in the range of 8 to 15. When HEMM or SEMM is used, the TID may indicate a TSID.

[0103] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in EDCA channel contention. QoS stations can guarantee QoS using AC. AC may include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may indicate background, best effort, video, and voice, respectively. AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI may be further subdivided into AC_VI primary and AC_VI alternate. AC_VO may be further subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to an AC. For example, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may have decreasing priority in that order. That is, 1 may have a lower priority, and 7 may have a higher priority. Therefore, the order of priority may be AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO can correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to the characteristics of TID, the mapping between TID and link can represent the mapping between AC and link.The mapping between links and ACs can also represent the mapping between TIDs and links.

[0104] As described above, a TID may be mapped to each of multiple links. The mapping may specify the links through which traffic corresponding to a specific TID or AC can be exchanged. Furthermore, the TID or AC that can be transmitted for each transmission direction within a link may be specified. As described above, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to the TID on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on any one link. At any given time, any TID or AC may be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0105] When a link is mapped to a TID or AC, frames may be transmitted on the link based on the TID or AC mapped to the link. Specifically, when a link is mapped to a TID or AC, only frames corresponding to the TID or AC mapped to the link may be transmitted on the link. When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to the link may be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames not corresponding to a TID or AC not mapped to the link may not be transmitted on the link. When a link is mapped to a TID or AC, an ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a Block ACK agreement may be determined based on the mapping between the TID and the link. In yet another specific embodiment, the mapping between the TID and the link may be determined based on the Block ACK agreement. Specifically, a Block ACK agreement may be set for a TID mapped to a specific link.

[0106] In the embodiment of FIG. 10, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are associated via a first link (Link1), and the second AP (AP2) and the second station (STA2) are associated via a second link (Link2). All TIDs are mapped to the first link (Link1), and AC_VO or TIDs corresponding to AC_VO are mapped to the second link (Link2). In this case, all TIDs may be exchanged in the first link (Link1), and TIDs corresponding to AC_VO may be exchanged in the second link (Link2). Furthermore, exchange of data not corresponding to AC_VO may not be permitted in the second link (Link2).

[0107] The above-described TID-to-link mapping may ensure QoS. Specifically, a high-priority AC or TID may be mapped to a link where a relatively small number of stations are active or where channel conditions are good. The above-described TID-to-link mapping may also allow stations to remain in a power-saving state for a longer period of time.

[0108] FIG. 11 illustrates a frame exchange according to a reverse direction (RD) protocol according to an embodiment of the present invention.

[0109] According to an embodiment of the present invention, frames may be exchanged according to a reverse direction protocol. Specifically, a station that is a transmit opportunity (TXOP) holder may transmit a frame to a responder, and the responder may be allowed to transmit a frame to a station that is a TXOP holder. When a station that is not the TXOP holder receives a RD grant (RDG) from a station that is a TXOP holder, the station that is not the TXOP holder may transmit a frame to the station that is the TXOP holder within the TXOP. That is, a station that receives the RDG may transmit a frame to the station that is the TXOP holder without a separate contention procedure-based channel access or backoff procedure. In this case, a station that transmits the RDG may be referred to as an RD initiator, and a station that receives the RDG may be referred to as an RD responder. Furthermore, exchanging frames according to the RD protocol may be referred to as an RD exchange or an RD exchange sequence. HT stations, VHT stations, HE stations, EHT stations, DMG stations, and S1G (Sub 1 GHz) stations can support RD exchange.

[0110] A station can signal whether it can act as an RD responder. Specifically, a station can signal whether it can act as an RD responder using a subfield of the HT Extended Capabilities field of the HE Capabilities element. In this case, the subfield can be referred to as an RD Responder field. In yet another specific embodiment, a station can signal whether it can act as an RD responder using a 6 GHz Band Capabilities element or a subfield of the 6 GHz Band Capabilities element. If a station signals that it cannot act as an RD responder, the station may not be allowed to send an RD grant.

[0111] A station may signal information related to RD exchange using at least one of an RDG / More PPDU subfield and an AC constraint subfield. In this case, the RDG / More PPDU subfield and the AC constraint subfield may be included in the HTC field. The HTC field may be a high throughput control field. A frame including an HTC field may be referred to as a +HTC frame. An MPDU corresponding to a frame including an HTC field may be referred to as a +HTC MPDU. The CAS Control subfield may include at least one of an RDG / More PPDU subfield and an AC Constraint subfield.

[0112] The RD exchange may be performed as follows.

[0113] The RD initiator can send a PPDU including an RDG to the RD responder. In this case, the RD initiator can be a TXOP holder or a service period (SP) source. Whether an RDG is included can be signaled by the RDG / More PPDU subfield. If the RDG / More PPDU subfield has a value of 1, the RDG / More PPDU subfield can indicate that the PPDU including the RDG / More PPDU subfield includes an RDG. If the RDG / More PPDU subfield has a value of 0, the RDG / More PPDU subfield can indicate that the PPDU including the RDG / More PPDU subfield does not include an RDG.

[0114] A station that receives an RDG can transmit a PPDU immediately after the PPDU containing the RDG. That is, a station that receives an RDG can transmit a PPDU without a separate contention procedure-based channel access. In this case, the interval between the PPDU containing the RDG and the PPDU transmitted by the station that received the RDG may be SIFS (short interframe space) or RIFS (reduced interframe space). In this specification, "immediately after" and "immediately" may refer to a pre-specified time interval. In this case, the pre-specified time interval may be SIFS or RIFS.

[0115] In these embodiments, a station that receives an RDG can transmit a PPDU to the RD initiator. That is, the PPDU transmitted by the station that receives the RDG can include a frame for which the RD initiator is the intended recipient. Also, a station that receives an RDG can transmit multiple PPDUs. One or more PPDUs transmitted by a station that receives an RDG after receiving a PPDU containing the RDG can be referred to as an RD response or an RD response burst. Also, a station that receives an RDG and transmits a PPDU, i.e., a station that transmits an RD response or an RD response, can be referred to as an RD responder. As described above, an RD responder can transmit multiple PPDUs consecutively after receiving an RDG. An RD responder can transmit one PPDU and then immediately transmit a PPDU. In this case, the RD responder can signal, in the frame containing the PPDU, whether a further PPDU will be transmitted immediately after the PPDU containing the frame. That is, the RD responder can signal, in the frame containing the PPDU, whether a further PPDU will be transmitted at an interval of SIFS or RIFS from the PPDU containing the frame. In this case, the RD responder can use the RDG / More PPDU subfield described above. Specifically, the RDG / More PPDU subfield transmitted by the RD initiator may indicate RDG, and the RDG / More PPDU subfield transmitted by the RD responder may indicate whether an additional PPDU is to be transmitted after the PPDU containing the RDG / More PPDU. In addition, the RD response may include up to one immediate BlockACK frame or ACK frame.

[0116] The RD initiator that receives the RD response can send an ACK (acknowledgment) to the RD responder. Specifically, the RD initiator can send an ACK to the RD responder immediately after the RD response.

[0117] Multiple RD exchange sequences may be included in one TXOP or SP. In this case, the RD initiators of the multiple RD exchange sequences may be the same, and the RD responders of the multiple RD exchange sequences may be different. In such an embodiment, one RD responder can participate in multiple RD exchange sequences.

[0118] The RD responder can transmit a PPDU to be transmitted to multiple stations as an RD response. For example, if the RD responder is a VHT AP, the RD response can include a VHT MU PPDU. If the RD responder is a HE AP, the RD response can include a HE MU PPDU. If the RD responder is an EHT AP, the RD response can include an EHT MU PPDU. The RD responder can also transmit an RD response including a trigger frame. In this case, the trigger frame may be limited to a trigger frame that triggers the transmission of the RD initiator. The trigger frame in this specification can also refer to a frame including a TRS (triggered response scheduling) field. A station that receives the trigger frame can transmit a trigger-based (TB) PPDU in response to the PPDU including the trigger frame. In this case, the interval between the PPDU including the trigger frame and the TB PPDU may be SIFS.

[0119] The AC or TID of a frame that the RD responder can transmit in the RD response may be restricted. In this case, the RD initiator can signal whether the AC or TID of a frame that the RD responder can transmit in the RD response or RD response burst is restricted. Specifically, the RD initiator can signal whether the AC or TID of a frame that the RD responder can transmit in the RD response is restricted using the AC Constraint subfield. Also, when the RD initiator obtains a TXOP through enhanced distributed channel access (EDCA) channel access, the AC or TID of a frame that the RD responder can transmit in the RD response may be restricted. The RD initiator may not be allowed to request frames other than frames for acknowledgement (ACK) from the RD responder. Therefore, the RD initiator may not request frames other than frames for acknowledgement (ACK) from the RD responder. In this case, the frame for acknowledgement (ACK) may include at least one of an ACK frame, a compressed BlockAck frame, an Extended Compressed Block frame, and a Multi-STA BlockAck frame.

[0120] If the RD responder signals that it will not send an additional PPDU, the RD initiator can send a PPDU immediately after the RD response. Specifically, if the RD initiator receives a frame that may include an HT control field from the RD responder and the frame does not include an HT control field, the RD initiator can send a PPDU immediately after the RD response. In yet another specific embodiment, if the RD initiator receives a frame requesting an immediate response from the RD responder, the RD initiator can send a PPDU immediately after the RD response.

[0121] Furthermore, if the RD initiator fails to receive an RD response to a PPDU containing RDG, the RD initiator can transmit a PPDU. Specifically, if the RD initiator fails to receive a response to a PPDU containing RDG within a predetermined time, the RD initiator can transmit a PPDU after a predetermined time from the PPDU containing RDG. Specifically, the RD initiator can transmit a PPDU PIFS after transmitting the PPDU containing RDG. Furthermore, the RD initiator can perform channel sensing before transmitting a PPDU, and transmit the PPDU only if the channel is idle. This may be part of the RD initiator's error recovery operation.

[0122] An RD responder may make an RD response within the following conditions:

[0123] Also, when the RD responder sends the RD response, the RD responder can send the RD response regardless of the set NAV (network allocation vector).

[0124] In addition, the RD responder can only perform an RD response within the TXOP or SP acquired by the RD initiator. The RD responder can obtain the TXOP duration or SP duration from the MAC header of the frame included in the PPDU including the RDG. Specifically, the RD responder can obtain the TXOP duration or SP duration from the Duration / ID field of the MAC header of the frame included in the PPDU including the RDG.

[0125] In addition, the frames that the RD responder can transmit as the RD response may be limited. Specifically, the frames that the RD responder can transmit as the RD response may be limited to a frame for acknowledgement (ACK), a QoS data frame, a QoS Null frame, a management frame, and a basic trigger frame. In this case, the frame for acknowledgement (ACK) may include at least one of an ACK frame, a compressed BlockAck frame, an Extended Compressed Block frame, and a Multi-STA BlockAck frame.

[0126] In addition, the intended recipient of at least one frame included in the RD response may be limited to the RD initiator. The intended recipient of the frame may be indicated by a MAC address. Specifically, a station corresponding to the MAC address indicated by the Address1 field of the frame may be the intended recipient of the frame. In yet another specific embodiment, the station whose transmission is triggered by the trigger frame may be the intended recipient of the trigger frame.

[0127] In addition, when the RD responder transmits an RD response, it can only transmit PPDUs with a width equal to or smaller than the channel width of the PPDU containing the RDG. In this case, the RD responder can determine the channel width of the PPDU containing the RDG from the value of CH_BANDWIDTH of the RXVECTOR obtained when receiving the PPDU containing the RDG.

[0128] When a PPDU including an RDG requests an immediate block ACK response, the RD responder may include a BlockAck frame in the first PPDU of the RD response. As described above, when the RD responder transmits multiple PPDUs as an RD response, the RD responder may signal that additional PPDUs will be transmitted in a PPDU other than the last PPDU of the RD response. Specifically, the RD responder may set the value of the RDG / More PPDU field of a PPDU other than the last PPDU of the RD response to indicate that additional PPDUs will be transmitted. The RD responder may also set the value of the RDG / More PPDU field of a PPDU other than the last PPDU of the RD response to indicate that additional PPDUs will not be transmitted. In this case, a value of 1 in the RDG / More PPDU field may indicate that additional PPDUs will be transmitted. A value of 0 in the RDG / More PPDU field may indicate that additional PPDUs will not be transmitted. In addition, the RD responder may not be permitted to transmit additional PPDUs after transmitting a PPDU including a frame requesting an immediate response. Therefore, when transmitting a PPDU containing a frame requesting a response, the RD responder can signal that no additional PPDUs will be transmitted, and after the RD responder signals that no additional PPDUs will be transmitted, the RD responder does not need to transmit any additional PPDUs as an RD response.

[0129] When the RD responder transmits a trigger frame, the RD responder may set a field in the trigger frame so that channel sensing is not required when responding to the trigger frame. Specifically, the RD responder may set the CS Required field in the trigger frame to 1. In this case, the trigger frame may be a basic trigger frame.

[0130] As described above, the TID or AC of a frame included in a PPDU transmitted by the RD responder as an RD response may be restricted. When the RD initiator signals that the AC or TID of a frame that the RD responder can transmit is restricted, the RD responder can include a frame corresponding to the same AC as the AC of a frame including an RDG in the RD response PPDU. Specifically, when the RD initiator sets the RDG / More subfield to 1 and the AC constraint subfield to 1, the RD responder can include a frame corresponding to the same AC as the AC of a frame including an RDG in the RD response PPDU. Also, when the RD initiator signals that the AC or TID of a frame that the RD responder can transmit is restricted, the RD responder can set the Preferred AC subfield of the trigger frame included in the RD response to indicate the same AC as the AC of the frame including an RDG. The Preferred AC subfield can indicate a recommended AC of an MPDU included in a PPDU transmitted in response to a frame including the Preferred AC subfield. Specifically, the Preferred AC subfield may indicate the AC with the lowest priority among ACs recommended as an AC for an MPDU included in a PPDU transmitted in response to a frame including the Preferred AC subfield. As described above, the Preferred AC subfield may be included in a trigger frame. Specifically, the Preferred AC subfield may be included in a basic trigger frame.

[0131] In the example of Figure 11, the first station (STA A) is the RD initiator, and the second station (STA B) and the third station (STA C) may be RD responders. In the example of Figure 11, eight PPDU exchanges are performed during the TXOP.

[0132] In the first PPDU exchange (a), a first station (STA A) transmits a PPDU including a QoS data frame for which a second station (STA B) is the intended recipient. The Ack Policy field of the QoS data frame, which indicates the response policy for the data frame, may be set to implicit BlockAck Request, indicating that an immediate response using a BlockAck frame is requested. The RDG / More PPDU subfields of the two QoS data frames included in the PPDU indicate RDG. The Duration / ID fields of the QoS data frames indicate the duration of the remaining TXOP.

[0133] In the second PPDU exchange (b), the second station (STA B) sends a PPDU containing a BlockAck frame, which is a +HTC frame, to the first station (STA A). The RDG / More PPDU field of the BlockAck frame is set to 1 to signal that an additional PPDU will be transmitted immediately after the transmission of the PPDU containing the BlockAck frame.

[0134] In the third PPDU exchange (c), the second station (STA B) transmits a PPDU containing a QoS data frame to the first station (STA A), where the second station (STA B) sets the RDG / More PPDU subfield value of the QoS data frame to 0 to signal that no additional PPDUs will be transmitted immediately after transmitting the PPDU containing the BlockAck frame.

[0135] In the fourth PPDU exchange (d), the first station (STA A) regains control of the TXOP and transmits a PPDU containing a BlockAck frame to the second station (STA B). The BlockAck frame can then contain an ACK for the QoS data frames transmitted in the second and third PPDU exchanges.

[0136] In the fifth PPDU exchange (e), the first station (STA A) transmits a PPDU including a QoS data frame for which the third station (STA C) is the intended recipient. The Ack Policy field of the QoS data frame may be set to implicit BlockAck Request. The first station (STA A) also signals RDG by setting the RDG / More PPDU subfields of the two QoS data frames included in the PPDU to 1. The Duration / ID fields of the QoS data frames indicate the duration of the remaining TXOP.

[0137] In the sixth PPDU exchange (f), the third station (STA C) transmits a PPDU to the first station (STA A) that includes a BlockAck frame, which is a +HTC frame, and a QoS data frame. At this time, the third station (STA C) sets the Ack policy field of the QoS data frame to implicit BlockAck Request. The third station (STA C) also sets the RDG / More PPDU subfield value of the QoS data frame to 0, signaling that no additional PPDUs will be transmitted immediately after the transmission of the PPDU that includes the BlockAck frame.

[0138] In the seventh PPDU exchange (g), the first station (STA A) regains control of the TXOP. The first station (STA A) transmits a PPDU including a BlockAck frame to the third station (STA C). In this case, the BlockAck frame can include an ACK for the QoS data frame transmitted in the sixth PPDU exchange. The first station (STA A) signals RDG by setting the RDG / More PPDU subfield of the BlockAck frame included in the PPDU to 1.

[0139] In the eighth PPDU exchange (h), the third station (STA C) transmits a PPDU containing two QoS data frames, which are +HTC frames, to the first station (STA A). At this time, the third station (STA C) sets the Ack policy field of the QoS data frame to implicit BlockAck Request. The third station (STA C) also sets the RDG / More PPDU subfield value of the QoS data frame to 0, signaling that no additional PPDUs will be transmitted immediately after transmitting the PPDU containing the BlockAck frames.

[0140] In the ninth PPDU exchange (i), the first station (STA A) transmits to the third station (STA C) a PPDU including a BlockAcK frame containing an ACK for the QoS data frame transmitted in the eighth PPDU exchange.

[0141] It has already been explained that in the RD protocol, the AC or TID of a frame included in a PPDU transmitted by an RD responder as an RD response is restricted. This may be in consideration of fairness with other stations, since a TXOP holder may obtain a TXOP using channel access parameters corresponding to a specific AC. The AC or TID restriction of a frame included in a PPDU transmitted as an RD response will be specifically explained with reference to FIG. 12. For convenience of explanation, the AC or TID restriction of a frame included in a PPDU transmitted as an RD response will be referred to as an AC constraint.

[0142] FIG. 12 illustrates AC limitation signaling according to an embodiment of the present invention.

[0143] The AC restriction signaling may indicate that the TID of a data frame included in the RDG response PPDU is not restricted. That is, the AC restriction signaling may signal that a data frame of any TID may be included in the RDG response PPDU. The AC restriction signaling may also indicate that the AC or TID of a frame included in the RDG response PPDU may be restricted. Specifically, the AC restriction signaling may restrict the AC or TID of a frame included in the RDG response PPDU to an AC or TID value specified by the RD initiator. In yet another specific embodiment, the AC restriction signaling may indicate that the AC or TID of a data frame included in the RDG response PPDU is restricted to a value set based on the TID or AC of a frame received from the RD initiator. For example, the AC restriction signaling may indicate that the AC or TID of a data frame included in the RDG response PPDU is restricted to the TID or AC of a frame received from the RD initiator. Furthermore, the AC restriction signaling may indicate that the ACs or TIDs of frames included in the RDG response PPDU are restricted to TIDs or ACs with the same or higher priority than the priority of the TIDs or ACs of frames received from the RD initiator. In such an embodiment, the frame received from the RD initiator may represent the frame last received from the RD initiator. In yet another specific embodiment, when the RD responder receives multiple frames from the RD initiator, the frame received from the RD initiator may represent the TID or AC with the lowest priority among the TIDs or ACs of frames received from the RD initiator.

[0144] The RD responder can regard the AC of the management frame as a pre-specified value. In this case, the pre-specified value may be AC_VO. The RD responder can also determine the AC of the BlockAckReq frame based on the TID field of the BlockAckReq frame and determine the AC of the BlockAck frame as the basis indicated by the TID field of the BlockAck frame. Specifically, the RD responder can determine the AC of the BlockAckReq frame as the AC of the TID indicated by the TID field of the BlockAckReq frame and determine the AC of the BlockAck frame as the AC of the TID indicated by the TID field of the BlockACk frame. In this case, the TID fields of the BlockACk frame and the BlockACkReq frame can indicate the TID for which the Ack is transmitted. Furthermore, if the RD initiator transmits a frame for which the AC cannot be determined, the RD initiator may not be allowed to set the RDG for that frame. Specifically, when an RD initiator transmits a frame for which the AC cannot be determined, the RD initiator may not be allowed to set the RDG / More PPDU field of the frame to 1.

[0145] The AC constraint signaling may be indicated by the aforementioned AC Constraint subfield. Specifically, when the value of the AC Constraint subfield is 0, the AC Constraint subfield may indicate that the TID of a data frame included in the PPDU of the RDG response is not restricted. Also, when the value of the AC Constraint subfield is 1, the AC Constraint subfield may indicate that the TID or AC of a frame included in the PPDU of the RDG response is restricted.

[0146] In the embodiment of Figure 12, the RD initiator transmits a QoS data frame with AC_BE to the RD responder using a PPDU including an RDG. At this time, the RD initiator sets the value of the AC restriction field to 1, indicating that the TID or AC of the data frame included in the RD response PPDU is restricted. Since the TID or AC of the data frame included in the RD response PPDU is restricted, the RD responder includes a QoS data frame corresponding to AC_BE in the RD response PPDU.

[0147] FIG. 13 shows a frame format and a format of a signaling field of the frame according to an embodiment of the present invention.

[0148] 13(a) shows the format of a MAC frame. The MAC frame can include a MAC header, a Frame Body, and an FCS. The MAC header can include at least one of the RDG / More PPDU subfield and the AC Constraint subfield.

[0149] Specifically, the MAC header may include a Frame Control field, a Duration / ID field, a MAC address field, a Sequence Control field, a QoS Control field, and an HT Control field. The Frame Control field may include a Type subfield and a Subtype subfield. The Type subfield and Subtype subfield may indicate the frame type and subtype, respectively. The Frame Control field may also include a +HTC subfield, which may indicate whether the frame containing the Frame Control field includes an HT Control field. The Duration / ID field may indicate the duration. If the frame containing the Duration / ID field is not a PS-Poll frame, the Duration / ID field indicates the duration. A station receiving a MAC frame may set its NAV based on the duration indicated by the Duration / ID field. The Duration / ID field may indicate an ID, such as an AID. If the MAC frame containing the Duration / ID field is a PS-Poll frame, the Duration / ID field may indicate the ID.

[0150] The MAC address field may include one or more address fields. The address field indicates a MAC address. The address field may include at least one of a basic service set identifier (BSSID) field, a source address (SA) field, a destination address (DA) field, a transmitting STA address or transmitter address (TA) field, and a receiving STA address or receiver address (RA) field. The Sequence Control field may indicate a fragment number or a sequence number corresponding to a MAC frame including the Sequence Control field. The QoS Control field may indicate at least one of the TID of the MAC frame including the QoS Control field, an Ack Policy corresponding to the MAC frame including the QoS Control field, a TXOP limit, a buffer status of a station transmitting the MAC frame including the QoS Control field, and a queue size of a station transmitting the MAC frame including the QoS Control field. The QoS Control field may include at least one of the RDG / More PPDU subfield and the AC Constraint subfield. For example, the QoS Control field included in the DMG PPDU may include the above-mentioned RDG / More PPDU subfield and AC Constraint subfield.

[0151] The HT Control field may include at least one of the RDG / More PPDU subfield and the AC Constraint subfield. The HT Control field may be configured with 4 octets, i.e., 32 bits.

[0152] The MAC header and the fields contained in the MAC header may have a preset length.

[0153] The Frame Body field contains the contents of the MAC frame, for example, the Frame Body field may contain information corresponding to the frame type and subtype.

[0154] The FCS field indicates the frame check sequence (FCS) of the MAC frame in which it is included. The value of the FCS field may be an FCS obtained based on the values ​​of the MAC header and Frame Body field. A station that receives an MCA frame can determine whether it has successfully received the MAC frame based on the value of the FCS field.

[0155] 13(b) shows the format of the HT Control field, which may include at least one of an AC Constraint subfield and an RDG / More PPDU subfield.

[0156] For example, the HT Control field may be composed of 32 bits (B0 to B31). In this case, B30 and B31 may be an AC Constraint subfield and an RDG / More PPDU subfield, respectively. The format of the HT Control field may vary depending on the format of the PPDU in which the HT Control field is included. First, the HT Control field described above may be an HT variant included in an HT PPDU or a VHT variant included in a VHT PPDU. Furthermore, the format of the HT Control field may include an HE variant included in an HE PPDU or an EHT variant included in an EHT PPDU. In this case, the HE variant may represent a variant of the HT Control field included in a PPDU introduced in a version of the 802.11ax standard or later. The HT Control field may include signaling indicating the variant of the HT Control field. For example, some bits of the HT Control field may indicate the variant of the HT Control field. When the value of B0 is 0, B0 can indicate that the HT Control field is an HT variant. When the value of B0 is 1, B0 can indicate that the HT Control field is a VHT variant, an HE variant, or an EHT variant. When the value of B0 is 1 and the value of B1 is 0, B0 and B1 can indicate that the HT Control field is a VHT variant. When the value of B0 is 1 and the value of B1 is 1, B0 and B1 can indicate that the HT Control field is an HE variant or an EHT variant.In yet another specific embodiment, when B0 has a value of 1 and B1 has a value of 1, B0 and B1 may indicate that the HT Control field is an HE variant, an EHT variant, or a variant of the HT Control field included in a PPDU introduced after the 802.11be standard. Also, when the HT Control field is an HE variant, an EHT variant, or a variant of the HT Control field included in a PPDU introduced after the 802.11be standard, the HT Control field may include an A (aggregated control)-Control subfield. For example, HT Control fields B2 to B31 may be A-Control subfields. The A-Control subfield may include control information.

[0157] Figure 13(c) shows the A-Control subfield of Figure 13(b). The A-Control subfield may include a Control List subfield and a Padding subfield. The Control List subfield may include one or more control information. The Control List subfield may include one or more Control subfields. The A-Control subfield may or may not include a Padding subfield. For example, the remainder of the A-Control subfield, excluding the Control List subfield, may be the Padding subfield. In a specific embodiment, the Padding subfield may be set to a predetermined value. Alternatively, the Padding subfield may start with a predetermined value.

[0158] Figure 13(d) shows the format of the Control subfield in Figure 13(c). The Control subfield may include a Control ID subfield and a Control Information subfield.

[0159] The Control ID subfield may indicate what content is included in the Control Information subfield or what control information is included in the Control subfield including the Control ID subfield. A station can determine the length of the Control Information subfield based on the value of the Control ID subfield. The Control ID subfield may be 4 bits long. The Control subfield may include the above-mentioned triggered response scheduling (TRS) control. The Control subfield may include TRS, which is information that triggers transmission by a station that receives the Control subfield. The Control ID value corresponding to TRS may be 0. The Control subfield may also include information about an operating mode (OM). The Control ID value corresponding to OM may be 1. The Control subfield may also include information about link adaptation. The Control ID value corresponding to link adaptation information may be 2. The Control subfield may also include information about a buffer. The buffer information may be a buffer status report (BSR). The Control ID value corresponding to a BSR may be 3. In addition, the Control subfield may include information about uplink power headroom. The information about uplink power headroom may indicate how much additional transmittable power is available or may be a value used for power pre-correction. The value of Control ID corresponding to the information about uplink power headroom may be 4. In addition, the Control subfield may include signaling indicating the state of a subchannel.The signaling indicating the status of the subchannel may include a bandwidth query report (BQR). The Control ID value corresponding to the BQR may be 5. For example, the BQR may indicate whether the subchannel is available for use. The Control subfield may also include information about command and status (CAS). The Control ID value corresponding to CAS may be 6.

[0160] 13(e) shows the format of the Control Information subfield when the Control subfield includes CAS. According to an embodiment of the present invention, the A-Control subfield may include an AC Constraint subfield and an RDG / More PPDU subfield. Specifically, when the A-Control subfield includes CAS, the Control Information subfield corresponding to CAS may include an AC Constraint subfield and an RDG / More PPDU subfield. For example, the first and second bits of the Control Information subfield corresponding to CAS may be the AC Constraint subfield and the RDG / More PPDU subfield, respectively. In addition, the CAS may include a PSRT PPDU subfield. The PSRT subfield may indicate whether a PPDU including the PSRT subfield is a PSRT (parameterized spatial reuse transmission) PPDU. In addition, a PSRT PPDU is a PPDU transmitted using a parameterized spatial reuse (PSR) opportunity. In addition, when the Control subfield includes CAS, the Control Information subfield may include a Reserved field.

[0161] The AC Constraint subfield and RDG / More PPDU subfield described in FIG. 13 may be the AC Constraint subfield and RDG / More PPDU subfield described in previous figures.

[0162] The above-mentioned TID-to-link mapping may also be applied when RD exchange is performed. In this case, AC restrictions may also be applied to the RD exchange. Therefore, when RD exchange is performed on a link to which TID-to-link mapping is applied, the range of frames that the RD responder can transmit in the RD response may become an issue. This will be described with reference to Figures 14 to 20.

[0163] FIG. 14 illustrates an example in which RD exchange is performed on a link to which TID-to-link mapping is applied, without AC restrictions, according to an embodiment of the present invention.

[0164] When an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can perform an RD response based on the TID or AC mapped to the link. Specifically, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can transmit a frame corresponding to one of the TIDs or ACs mapped to the link in the RD response. In this case, the RD responder may select any AC or TID from the TIDs or ACs mapped to the link and transmit a data frame corresponding to the selected AC or TID in the RD response. Specifically, the RD responder may include a data frame corresponding to a TID mapped to the link in a PPDU transmitted in response to a PPDU containing an RDG, but may not include a data frame corresponding to a TID not mapped to the link. In other words, even if no AC restriction is applied, the RD responder may not be allowed to transmit a frame corresponding to a TID mapped to the link, a TID that is not an AC, a TID corresponding to an AC, or an AC.

[0165] In yet another specific embodiment, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can transmit, in the RD response, data frames corresponding to TIDs or ACs with the same or higher priority than the TIDs or ACs mapped to the link. Specifically, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can transmit, in the RD response, data frames corresponding to TIDs or ACs with a higher priority than the lowest priority among the TIDs or ACs mapped to the link. Therefore, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder may not transmit, in the RD response, data frames corresponding to TIDs or ACs with the lowest priority among the TIDs or ACs mapped to the link.

[0166] In the above-described embodiment, the TID-to-link mapping may indicate the TID-to-link mapping applied when the RD responder transmits, because the TID-to-link mapping applied to the RD initiator does not apply to the RD responder. This embodiment may also be applied when the RD responder transmits to multiple stations in the RD response.

[0167] In the embodiment of FIG. 14, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). All TIDs are mapped to the first link (Link1). The second AP (AP2) can transmit all TIDs via the second link (Link2). However, when the second station (STA2) transmits a data frame via the second link (Link2), the TID-to-link mapping allows the second station (STA2) to transmit data frames corresponding to AC_VO and AC_VI via the second link (Link2).

[0168] The second AP (AP2) sends an RDG to the second station over the second link (Link2). At this time, the second AP (AP2) sets the AC Constraint subfield to 0 to signal that AC constraints are not applied. The second station (STA2) sends data frames corresponding to AC_VI or AC_VO in the RD response. In addition, the second station (STA2) cannot send data frames that do not correspond to AC_VI or AC_VO in the RD response.

[0169] FIG. 15 shows that RD exchange is performed in a link to which TID-to-link mapping is applied, without AC restrictions, according to yet another embodiment of the present invention.

[0170] When an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can perform the RD response regardless of the TID-to-link mapping. Specifically, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can transmit a data frame corresponding to any TID in the RD response regardless of the TID-to-link mapping. In a specific embodiment, when an RD exchange is performed on a link to which TID-to-link mapping is applied and no AC restriction is applied in the RD exchange, the RD responder can transmit a data frame corresponding to an AC or TID that is not mapped to the link in the RD response.

[0171] In the above-described embodiment, the TID-to-link mapping may represent the TID-to-link mapping applied when the RD responder transmits, because the TID-to-link mapping applied to the RD initiator does not apply to the RD responder. This embodiment may also be applied when the RD responder transmits to multiple stations in the RD response.

[0172] In the embodiment of FIG. 15, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device also includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). All TIDs are mapped to the first link (Link1). The second AP (AP2) can transmit all TIDs via the second link (Link2). However, according to the TID-to-link mapping applied to the second link (Link2), when the second station (STA2) transmits a data frame via the second link (Link2), the second station (STA2) can transmit data frames corresponding to AC_VO and AC_VI via the second link (Link2).

[0173] The second AP (AP2) sends an RDG to the second station over the second link (Link2). At this time, the second AP (AP2) sets the AC Constraint subfield to 0 to signal that no AC constraints apply. In the RD response, the second station (STA2) can send data frames corresponding to any TID regardless of the TID-to-link mapping applied to the second link (Link2). Therefore, in the RD response, the second station (STA2) sends a QoS data frame corresponding to AC_BE, an AC that is not mapped to the second link (Link2).

[0174] FIG. 16 shows that no AC restriction is set when RD exchange is performed on a link to which TID-to-link mapping is applied according to yet another embodiment of the present invention.

[0175] If the TID or AC of a frame that the RD initiator transmits using a PPDU including an RDG is not mapped to a link that the RD responder uses for the RD response, the RD initiator may not be allowed to apply AC restrictions. That is, if the TID or AC of a frame that the RD initiator transmits using a PPDU including an RDG is not mapped to a link that the RD responder uses for the RD response, the RD initiator may not apply AC restrictions. In this case, the RD initiator can signal that AC restrictions are not applied.

[0176] In yet another specific embodiment, if a TID or AC with a higher priority than the priority of a TID or AC of a frame transmitted by the RD initiator using a PPDU including an RDG is not mapped to a link used by the RD responder for the RD response, the RD initiator may not be allowed to apply AC restriction. That is, if a TID or AC with a higher priority than the priority of a TID or AC of a frame transmitted by the RD initiator using a PPDU including an RDG is not mapped to a link used by the RD responder for the RD response, the RD initiator may not apply AC restriction. In this case, the RD initiator can signal that AC restriction is not applied.

[0177] In the above-described embodiment, the TID or AC of a frame transmitted by the RD initiator using a PPDU including RDG may be the lowest priority TID or AC among the TIDs or ACs of frames transmitted by the RD initiator using a PPDU including RDG. In yet another specific embodiment, the TID or AC of a frame transmitted by the RD initiator using a PPDU including RDG may be the lowest priority TID or AC among the TIDs or ACs of frames received by the RD responder from a PPDU including RDG. In yet another specific embodiment, the TID or AC of a frame transmitted by the RD initiator using a PPDU including RDG may be the TID or AC of the last frame received by the RD responder from a PPDU including RDG. In yet another specific embodiment, the TID or AC of a frame transmitted by the RD initiator using a PPDU including RDG may be the TID or AC of the last frame received by the RD responder from a PPDU including RDG.

[0178] In the above-described embodiment, the TID-to-link mapping may represent the TID-to-link mapping applied when the RD responder transmits, because the TID-to-link mapping applied to the RD initiator does not apply to the RD responder. This embodiment may also be applied when the RD responder transmits to multiple stations in the RD response.

[0179] In the embodiment of FIG. 16, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device also includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). All TIDs are mapped to the first link (Link1). The second AP (AP2) can transmit all TIDs via the second link (Link2). However, when the second station (STA2) transmits a data frame via the second link (Link2), the TID-to-link mapping allows the second station (STA2) to transmit frames corresponding to AC_VO and AC_VI via the second link (Link2).

[0180] The second AP (AP2) transmits an RDG to the second station over the second link (Link2). At this time, the second AP (AP2) sets the value of the AC Constraint subfield to 0 to signal that AC constraints are not applied. This is because the second AP (AP2) transmits a QoS data frame corresponding to AC_BE using a PPDU including the RDG, and AC_BE is not mapped to the TID that the second station (STA2) transmits over the second link (Link2). The second station (STA2) can perform an RD response according to any one of the embodiments described above with reference to FIGS. 14 and 15.

[0181] FIG. 17 illustrates RD exchange when AC restrictions are applied to a link to which TID-to-link mapping is applied according to yet another embodiment of the present invention.

[0182] If the RD initiator signals in the RD response that an AC is restricted, the RD responder may be allowed to transmit a frame corresponding to a TID or AC that is not mapped to the link on which the RD response is made. In this case, the RD responder may determine the TID or AC of the frame to be transmitted in the RD response based on the TID or AC of the frame received from the PPDU including the RDG. Specifically, the RD responder may determine the TID or AC of the frame to be transmitted in the RD response to be the same as the TID or AC of the frame received from the PPDU including the RDG. In yet another specific embodiment, the RD responder may determine the TID or AC of the frame to be transmitted in the RD response to be an AC or TID that is the same as or has a higher priority than the priority of the TID or AC of the frame received from the PPDU including the RDG. The TID or AC of the frame received from the PPDU including the RDG may be the TID or AC of the frame last received from the PPDU including the RDG. Also, as in the previous embodiment, exceptional transmission of TID-to-link mapping may be allowed only for RD exchanges where AC restrictions are signaled.

[0183] In the above-described embodiment, the TID-to-link mapping may represent the TID-to-link mapping applied when the RD responder transmits, because the TID-to-link mapping applied to the RD initiator does not apply to the RD responder. This embodiment may also be applied when the RD responder transmits to multiple stations in the RD response.

[0184] In the embodiment of Figure 17, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device also includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). All TIDs are mapped to the first link (Link1). The second AP (AP2) can transmit all TIDs via the second link (Link2), but the second station (STA2) can only transmit frames corresponding to AC_VO and AC_VI via the second link (Link2) due to the TID-to-link mapping applied to the second link (Link2).

[0185] The second AP (AP2) sends an RDG to the second station over the second link (Link2). At this time, the second AP (AP2) sets the AC Constraint subfield to 1 to signal that AC constraints are applied. The second AP (AP2) also sends a QoS data frame corresponding to AC_BE using a PPDU containing the RDG. The second station (STA2) does not map AC_BE to the second link (Link2), but sends a frame corresponding to AC_BE in the RD response.

[0186] FIG. 18 illustrates RD exchange when AC restrictions are applied on a link to which TID-to-link mapping is applied, according to yet another embodiment of the present invention.

[0187] In yet another embodiment, if the RD initiator signals that AC is restricted in the RD response and TID-to-link mapping applies to the link on which the RD response is made, the RD responder can send any TID in the RD response. That is, if the RD initiator signals that AC is restricted in the RD response and TID-to-link mapping applies to the link on which the RD response is made, the RD responder can send the RD response as in the embodiment described in FIG. 15.

[0188] In the embodiment of FIG. 18, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device also includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). All TIDs are mapped to the first link (Link1). The second AP (AP2) can transmit all TIDs via the second link (Link2). However, when the second station (STA2) transmits a data frame via the second link (Link2), the TID-to-link mapping allows the second station (STA2) to transmit data frames corresponding to AC_VO and AC_VI via the second link (Link2).

[0189] The second AP (AP2) sends an RDG to the second station over the second link (Link2). At this time, the second AP (AP2) signals that the AC constraint is applied by setting the AC Constraint subfield to 1. In the RD response, the second station (STA2) can send data frames corresponding to any TID, including TIDs that do not correspond to the ACs or TIDs mapped to the second link.

[0190] When an RD exchange is performed on a link to which TID-to-link mapping is applied and AC restrictions are applied in the RD exchange, the RD responder can perform an RD response based on the TID or AC mapped to the link. Specifically, when an RD exchange is performed on a link to which TID-to-link mapping is applied and AC restrictions are applied in the RD exchange, the RD responder can transmit a data frame corresponding to an AC or TID with the same or higher priority as the AC or TID of the frame received from the RD initiator and corresponding to one of the TIDs or ACs mapped to the link in the RD response. For convenience of explanation, a PPDU transmitted in response to a PPDU containing an RDG is referred to as an RD response PPDU. Specifically, when the RD responder transmits a data frame in the RD response, the RD responder may not include in the RD response PPDU a data frame corresponding to a TID or AC with a lower priority than the TID or AC of the frame received from the RD initiator or a TID or AC not mapped to the link. In this case, the RD responder can include a data frame corresponding to a TID or AC that is the same as or has a higher priority than the priority of the TID or AC of the frame received from the RD responder and that is mapped to the link in the PPDU (RD response PPDU) sent in response to the PPDU containing the RDG.

[0191] The frame received from the RD initiator may represent the frame last received by the RD responder from the RD initiator. In yet another specific embodiment, when the RD responder receives multiple frames from the RD initiator, the frame received from the RD initiator may indicate the TID or AC with the lowest priority among the TIDs or ACs of the frames received from the RD initiator. In this case, the multiple frames may be multiple frames included in the PPDU last received by the RD responder from the RD initiator.

[0192] FIG. 19 illustrates signaling information regarding AC restrictions used in the RD initiator RD response according to an embodiment of the present invention.

[0193] The RD initiator may signal information about the AC restriction applied in the RD exchange. For convenience of explanation, this signaling is referred to as AC restriction information signaling. The RD responder may determine the AC or TID of the frame to be transmitted in the RD response based on the AC restriction information signaling. The information about the AC restriction applied in the RD exchange may be the information used in the embodiments described with reference to FIGS. 11 to 18. For example, the information about the AC restriction may indicate the AC restriction method in the embodiments described with reference to FIGS. 11 to 18. For example, the AC restriction information signaling may indicate whether TID-to-link mapping should be applied in the RD response. When the AC restriction information signaling is a pre-specified first value and the AC Constraint subfield indicates that the TID or AC is not restricted, the RD responder may transmit the RD response regardless of the TID-to-link mapping. When the AC restriction information signaling is a pre-specified second value and the AC Constraint subfield indicates that the TID or AC is not restricted, the RD responder may transmit the RD response with the TID-to-link mapping. Specifically, when the AC restriction information signaling is a pre-specified second value and the AC Constraint subfield indicates that the TID or AC is not restricted, the RD responder can make an RD response using only the TID or AC mapped to the link on which the RD response is made by the TID-to-link mapping.

[0194] If the AC Constraint subfield indicates that the TID or AC is restricted, the RD responder can determine whether to apply TID-to-link mapping to perform the RD response based on the AC restriction information signaling.

[0195] The AC restriction information signaling may be included in the A-Control subfield. In yet another specific embodiment, the AC restriction information signaling may be included in the CAS. FIG. 19 shows a Control Information subfield of the CAS according to one embodiment of the present invention. At this time, the Control Information subfield includes the AC restriction information signaling (AC Indication subfield). In yet another specific embodiment, the AC restriction information signaling may be included in the Reserved field of the Control Information subfield described in FIG. 13(e).

[0196] FIG. 20 illustrates RD exchange when PPDUs with synchronized transmission ends are transmitted over multiple links according to an embodiment of the present invention.

[0197] A multilink device can synchronize PPDUs transmitted over multiple links. Specifically, a multilink device can synchronize the ends of PPDUs transmitted over multiple links. In yet another specific embodiment, a multilink device can synchronize the beginnings of PPDUs transmitted over multiple links. This operation may be applied when the transmission / reception capabilities of a multilink device receiving a PPDU over at least one of multiple links are limited. This operation may be applied when a multilink device receiving a PPDU over at least one of multiple links cannot simultaneously receive and transmit over any one of the links. If a multilink device can receive over one link and transmit over another link, it is called an STR (simultaneous transmit and receive; simultaneous transmission and reception) multilink device. If a multilink device cannot transmit over one link and receive over another link, it is called a non-STR multilink device. Therefore, a multilink device transmitting over multiple links to a non-STR multilink device can transmit synchronized PPDUs.

[0198] The RD exchange may be configured depending on whether a synchronized PPDU is transmitted or not.

[0199] When a synchronized PPDU is transmitted over multiple links, the multilink device may transmit an RDG over only one of the multiple links. In this case, an RD response may be transmitted only over the link on which the RDG was transmitted. For example, when a multilink device transmits synchronized PPDUs over a first link and a second link, the multilink device may include an RDG in the PPDU transmitted over the first link. In this case, the PPDU transmitted in response to the synchronized PPDU over the first link may be a first PPDU, and the PPDU transmitted in response to the synchronized PPDU over the second link may be a second PPDU. A first frame may be transmitted over the first PPDU, and a second frame may be transmitted over the second PPDU. The length of the first frame may be longer than the length of the second frame. For example, the first frame may include a data frame, and the second frame may include an ACK. In this case, padding may need to be included in the second PPDU to synchronize the first PPDU and the second PPDU. This may increase transmission inefficiency.

[0200] When a synchronized PPDU is transmitted over multiple links, RDG may be transmitted over all of the multiple links, or RDG may not be transmitted. When a multi-link device transmits a synchronized PPDU over multiple links, the multi-link device may set the values ​​of the RDG / More PPDU subfields transmitted over the multiple links to the same value. When a multi-link device transmits a synchronized PPDU over multiple links, the multi-link device may set the values ​​of the RDG / More PPDU subfields transmitted over the multiple links to either all 1 or all 0. This can improve transmission efficiency.

[0201] In yet another specific embodiment, RDG may be transmitted on all or none of the multiple links, regardless of whether they transmit synchronized PPDUs.

[0202] In yet another specific embodiment, if a multilink device receiving a PPDU over multiple links is a non-STR multilink device, RDG may be transmitted over all of the multiple links, or none of the multiple links. If a multilink device receiving a PPDU over multiple links is a non-STR multilink device, the multilink device may set the values ​​of the RDG / More PPDU subfields transmitted over the multiple links to the same value. If a multilink device receiving a PPDU over multiple links is a non-STR multilink device, the multilink device may set the values ​​of the RDG / More PPDU subfields transmitted over the multiple links to either 1 or 0. This is because if RD exchange with a non-STR multilink device is performed over only one link, transmission over the other links may be restricted.

[0203] In the embodiment of Figure 20, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The no-AP multilink device includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link2). In this case, the first AP (AP1) and the second AP (AP2) transmit synchronized PPDUs and set the RDG / More PPDU subfield to the same value. Specifically, the first AP (AP1) and the second AP (AP2) set the RDG / More PPDU subfield to 1 and transmit synchronized PPDUs. In addition, the first station (STA1) and the second station (STA2) set the RDG / More PPDU subfield to 1 and transmit synchronized PPDUs. The first station (STA1) and the second station (STA2) set the value of the RDG / More PPDU subfield to 0 and transmit synchronized additional PPDUs.

[0204] Furthermore, when a multilink device initiates RD exchange on multiple links and performs error recovery on multiple links, the error recovery may be performed simultaneously on the multiple links. That is, error recovery may be performed on all of the multiple links, or may not be performed on all of the multiple links. This embodiment may be applied when the RD initiator is a non-STR multilink device or the RD responder is a non-STR device. This is because it is difficult to transmit synchronized PPDUs on multiple links if error recovery is performed on only one link.

[0205] When the RD initiator is a multilink device and the RD responder is also a multilink device, and signaling related to the RD exchange is transmitted over one of the links, the signaling related to the RD exchange may be applied to the remaining links of the multiple links in addition to the corresponding link. In this case, the signaling related to the RD exchange may include at least one of the above-described RDG, information about the additional PPDU, and AC restriction signaling information. In this case, the information about the RDG and the additional PPDU may be transmitted in the above-described RDG / More PPDU subfield. For example, the RD initiator, which is a multilink device, and the RD responder, which is a multilink device, may be connected over a first link and a second link. In this case, when the RDG is transmitted over the first link, it may be considered that the RDG is transmitted over the second link. Furthermore, when it is signaled that an additional PPDU is to be transmitted over the first link, it may be considered that an additional PPDU is also to be transmitted over the second link. This embodiment may be applied when synchronized PPDUs are transmitted. Furthermore, even if frame reception is successful on one link and reception fails on another link, signaling related to RD exchange may be applied to the remaining links in addition to the link in question, so that RD exchange may be performed stably on multiple links even if transmission fails on one link.

[0206] The IEEE 802.11be standard supports a maximum bandwidth of 320 MHz, which is twice the maximum bandwidth of 160 MHz supported by the previous 802.11 standard. In addition, previous standards, such as IEEE 802.11be, only allowed preamble puncturing in the downlink (DL) MU PPDU, and the resource unit (RU) allocated to each station was limited to one contiguous RU (996 × 2 tone size). In IEEE 802.11be, preamble puncturing is also allowed in uplink (UL) transmission, and each station may be assigned two or more non-contiguous RUs. However, some RU combinations may not be allowed due to implementation difficulties and efficiency considerations.

[0207] FIG. 21 shows the RU configuration that can be allocated to one station in IEEE 802.11ax and the RU configuration that can be allocated to one station according to an embodiment of the present invention.

[0208] The IEEE 802.11be standard also supports small RUs, which are RUs with a size of less than 20 MHz and 242 tones. Specifically, the IEEE 802.11be standard allows stations to be assigned 26+52 tone-size RUs, 26+52 tone-size RUs, and 26+52 tone-size RUs. Small RUs are omitted from Figure 21.

[0209] Figure 21(a) shows the 996-tone-size RU in an 80 MHz channel and the 996 x 2-tone-size RU in a 160 MHz channel in the IEEE 802.11ax standard. In IEEE 802.11ax, when an AP triggers a station to transmit UL using a bandwidth greater than 40 MHz using a trigger frame, it can only allocate contiguous 80 MHz RUs or contiguous 160 MHz RUs to the station. In this case, when the AP triggers a station to transmit UL OFDMA and allocates a bandwidth greater than 40 MHz to the station, the AP can only allocate 80 MHz RUs to the station. In addition, in IEEE 802.11ax, when an AP uses RUs greater than 40 MHz while performing DL OFDMA, only 80 MHz RUs are allowed.

[0210] Figure 21(b) shows four types of 60 MHz (242 + 484 tone size) RUs permitted within an 80 MHz channel in the IEEE 802.11be standard, and four types of 120 MHz (484 + 996 tone size) RUs permitted within a 160 MHz channel. In the IEEE 802.11be standard, when an AP allocates RUs over 40 MHz to a station using a trigger frame, the AP can allocate not only an 80 MHz RU but also four types of 60 MHz RUs to the station. The AP can also allocate four types of 120 MHz RUs or four types of 160 MHz RUs to the station. These various types of RUs can be used not only for UL transmission but also for DL ​​PPDUs using OFDMA. The effects obtained when using these various types of RUs are described using Figure 22.

[0211] FIG. 22 shows an OFDMA DL PPDU used in the IEEE 802.11ax standard and in an embodiment of the present invention.

[0212] In FIG. 22, an AP transmits an OFDMA DL PPDU to a first station (STA1) and a second station (STA2). The OFDMA DL PPDU is composed of a first PPDU (PPDU1) and a second PPDU (PPDU2). This illustrates a case where the frequency bandwidths allocated to the first PPDU (PPDU1) and the second PPDU (PPDU2) differ due to differences in the modulation and coding schemes (MCSs) used when encoding the first PPDU (PPDU1) and the second PPDU (PPDU2). When the frequency bandwidths allocable to the multiple PPDUs transmitted together differ, it is efficient to use minimal padding for the multiple PPDUs. However, when the number of selectable RUs is limited, transmission to one station may be abandoned or excessive padding may be required.

[0213] Figure 22(a) shows an example in which an AP transmits an OFDMA DL PPDU using only the RU allocation allowed by the IEEE 802.11ax standard. The AP transmits a first PPDU (PPDU1) and a second PPDU (PPDU2) to both a first station (STA1) and a second station (STA2) using 80 MHz RUs. Therefore, a large amount of padding is used in the transmission of the first PPDU (PPDU1).

[0214] Figure 22(b) shows that the AP transmits an OFDMA DL PPDU using only the RU allocation allowed by the IEEE 802.11ax standard. Because RUs with various bandwidths can be allocated, less padding is used in Figure 22(b) than in Figure 22(a). When RUs with various bandwidths are used in the TB PPDU as well as the OFDMA DL PPDU described in Figure 22, transmission efficiency can be improved.

[0215] In the existing 802.11 standard, a backoff procedure is performed based on CCA of a 20 MHz primary channel (herein, a 20 MHz primary channel refers to a primary channel with a bandwidth size of 20 MHz). Specifically, even when accessing a channel above 20 MHz, a channel other than the 20 MHz primary channel can be accessed only if the CCA result of the 20 MHz primary channel is idle. The larger the maximum bandwidth available to a station, the greater the inefficiency of such a channel access method. Therefore, a method is needed that allows channel access on a channel other than the 20 MHz primary channel even when the 20 MHz primary channel is busy.

[0216] In a specific embodiment, a station can perform a backoff procedure using a subchannel instead of the 20 MHz primary channel. In this case, the station can perform a backoff procedure using a subchannel instead of the 20 MHz primary channel only if the 20 MHz primary channel is detected as busy. Specifically, if the 20 MHz primary channel is detected as busy and the destination station of a PPDU transmitted on the 20 MHz primary channel is not the station, the station can perform a backoff procedure using a subchannel instead of the 20 MHz primary channel. Therefore, the station can perform a backoff procedure using a subchannel instead of the 20 MHz primary channel only if the station decodes the preamble of a PPDU received on the 20 MHz primary channel. Furthermore, the station can determine the STA-ID of the EHT-SIG by decoding the preamble of the PPDU. In yet another specific embodiment, the station can determine the intended recipient of the MAC frame by decoding the first MAC frame of the PPDU. Furthermore, only when a station determines that a PPDU received on the 20 MHz primary channel is transmitted from a BSS other than the station's own BSS, i.e., an inter-BSS PPDU, can the station perform the backoff procedure using a subchannel instead of the 20 MHz primary channel. To do this, the station can determine the BSS color of the HE-SIG or U-SIG by decoding the PPDU preamble. If the station determines that a PPDU transmitted on the 20 MHz primary channel is an inter-BSS PPDU, the station may skip the procedure for determining whether the station is the intended recipient of the PPDU.

[0217] Also, a station may initiate a backoff procedure using a subchannel other than the 20 MHz primary channel if the subchannel on which channel access is made is idle in the DIFS.

[0218] An embodiment may be applied to compensate for the time required to decode the preamble of a PPDU transmitted on a 20 MHz primary channel. Using a subchannel instead of the 20 MHz primary channel, the backoff procedure can be initiated by decrementing the backoff counter by a pre-specified number. The pre-specified number may be determined based on the time required to decode the preamble of the PPDU. For example, if the time required to decode the preamble of the PPDU is 3 slots (e.g., 27 us), the pre-specified number may be 3. In still another specific embodiment, the backoff procedure may be performed without such compensation. A backoff procedure method using a subchannel instead of the 20 MHz primary channel will be described with reference to FIGS. 23 to 27.

[0219] FIG. 23 shows that an embodiment of the present invention performs a backoff procedure using a sub-channel rather than the 20 MHz primary channel.

[0220] In the backoff procedure, a station performs CCA on a slot-by-slot basis. If the CCA result indicates that the channel is idle, the station decrements the backoff counter value by 1. If the CCA result indicates that the channel is not idle, the station maintains the backoff counter value. As mentioned above, slot-by-slot CCA may also be performed when the backoff procedure is performed on a subchannel rather than the 20 MHz primary channel. In addition, the bandwidth of subchannels other than the 20 MHz primary channel may also be 20 MHz.

[0221] The number of channels other than the 20 MHz primary channel on which a station performs a backoff procedure may be two or more. For example, if a station operates in an 80 MHz channel, the station may perform channel access based on a backoff procedure on three 20 MHz subchannels. The number of subchannels other than the 20 MHz primary channel on which a station may perform a backoff procedure may be determined according to the capability of the station. In yet another specific embodiment, the number of subchannels other than the 20 MHz primary channel on which a station may perform a backoff procedure may be a pre-specified number. In this case, the pre-specified number may be one or two.

[0222] A station can separately set and manage backoff counters for the 20 MHz primary channel and subchannels other than the 20 MHz primary channel. Specifically, the station can change the backoff counter for each channel depending on the channel access result for each channel. That is, if the station successfully transmits on a channel, the station can obtain a new backoff counter for that channel within the CW_min for the backoff counter for that channel. If the station fails to transmit on a channel, the station can either double the CW value for the backoff counter for that channel or obtain a new backoff counter for that channel within the CWmax. Figure 23(b) shows how backoff counter values ​​are set and managed for each subchannel. In Figure 23(b), the station sets the initial value of the backoff counter for the 20 MHz primary channel (P20) to 4 and the initial value of the backoff counter for the first subchannel (S20_1) to 5. After the station transmits the PPDU on the first subchannel (S20_1), the second subchannel (S20_2), and the third subchannel (S20_3), the station accesses the 20 MHz primary channel again, using the same backoff counter for the 20 MHz primary channel.

[0223] The station can set and manage a single backoff counter shared by the 20 MHz primary channel and subchannels other than the 20 MHz primary channel. Figure 23(a) shows how the station uses a single common backoff counter for the 20 MHz primary channel and subchannels other than the 20 MHz primary channel. In Figure 23(a), the station sets the initial value of the backoff counter to 5 for the 20 MHz primary channel (P20). Because the 20 MHz primary channel (P20) is idle for three slots in the primary channel, the station decrements the backoff counter by 3. Then, because the 20 MHz primary channel (P20) is not idle and the first subchannel (S20_1) is idle in the DIFS, the station begins the backoff procedure on the first subchannel (S20_1). At this time, since the first subchannel (S20_1) is idle for three slots and the second and third subchannels (S20_2) and (S20_3) are idle in the PIFS, the station transmits a PPDU on the first subchannel (S20_1), the second subchannel (S20_2), and the third subchannel (S20_3). The station then obtains a new backoff counter and performs channel access. Unlike the embodiment of FIG. 20(a), if the first subchannel (S20_1) is also detected as not idle and the station can perform a backoff procedure on the second subchannel (S20_2), the station can perform a backoff procedure on the second subchannel (S20_2). If the station cannot perform a backoff procedure on the second subchannel (S20_2), the station may wait until the 20 MHz primary channel (P20) or the first subchannel (S20_1) becomes idle.

[0224] When a station successfully accesses a channel on a subchannel other than the 20 MHz primary channel and transmits a PPDU, the length of the PPDU may be limited. First, while a station accesses a channel and transmits via a subchannel rather than the 20 MHz primary channel, the AP associated with the station cannot transmit or receive on the 20 MHz primary channel. Therefore, scanning, etc., performed via the 20 MHz primary channel may not be performed. Furthermore, an inter-BSS PPDU transmitted via the 20 MHz primary channel cannot be received, and a NAV cannot be set based on the inter-BSS PPDU. Therefore, when a station successfully accesses a channel on a subchannel rather than the 20 MHz primary channel and transmits a PPDU, the length of the PPDU must be limited. Furthermore, for fairness with stations conforming to existing standards, the length of the PPDU must be limited when a station successfully accesses a channel on a subchannel rather than the 20 MHz primary channel and transmits a PPDU. Furthermore, as described above, the number of subchannels on which a station can perform a backoff procedure may be limited. These embodiments will be described in detail with reference to FIG. 24.

[0225] FIG. 24 shows that, according to an embodiment of the present invention, when a station transmits a PPDU after successfully accessing a sub-channel rather than the 20 MHz primary channel, the length of the PPDU is limited.

[0226] When a station successfully accesses a channel on a subchannel rather than the 20 MHz primary channel and transmits a PPDU, the station can complete the transmission of the PPDU within the time determined based on the transmission of the Inter-BSS PPDU transmitted on the 20 MHz primary channel. In this case, the time determined based on the transmission of the Inter-BSS PPDU may be the end time of the Inter-BSS PPDU. In yet another specific embodiment, the time determined based on the transmission of the Inter-BSS PPDU may be the time when the ACK for the transmission of the Inter-BSS PPDU is completely transmitted. The station can determine the time determined based on the transmission of the Inter-BSS PPDU based on the value of the length field in the L-SIG of the Inter-BSS PPDU. Alternatively, the station can determine the time determined based on the transmission of the Inter-BSS PPDU based on the value of the TXOP field in the signaling field of the Inter-BSS PPDU.

[0227] In the example of FIG. 24, a station transmits a PPDU via a first subchannel (S20_1), a second subchannel (S20_2), and a third subchannel (S20_3) within the Inter-BSS PPDU (OBSS PPDU) length transmitted on a 20 MHz primary channel (P20).

[0228] When a station is allowed channel access on a subchannel other than the 20 MHz primary channel, the AP must detect the PPDU on the subchannel in addition to the 20 MHz primary channel to receive the PPDU. Specifically, when an Inter-BSS PPDU is transmitted on the 20 MHz primary channel, the AP can detect the PPDU on subchannels other than the 20 MHz primary channel. The PPDU detection may involve searching for the PPDU preamble. In this embodiment, the AP can search for the PPDU on a subchannel on which the Inter-BSS PPDU is not transmitted. In this case, the order of the subchannels in which the AP searches for the PPDU may be predetermined. For example, when an Inter-BSS PPDU having a 40 MHz bandwidth is transmitted on the 20 MHz primary channel, the AP can search for the PPDU on a subchannel 40 MHz away from the 20 MHz primary channel.

[0229] Thus, additional processing is required for the station to receive PPDUs transmitted on channels that do not include the 20 MHz primary channel. Therefore, a station may not support reception of PPDUs transmitted on channels that do not include the 20 MHz primary channel. A station can signal whether it supports reception of PPDUs transmitted on channels that do not include the 20 MHz primary channel. Specifically, a station can signal to the AP using the Capability element whether it supports reception of PPDUs transmitted on channels that do not include the 20 MHz primary channel. When the AP configures a PPDU on a channel that does not include the 20 MHz primary channel, the AP can include in the PPDU only frames whose recipients are only stations that have signaled that they support reception of PPDUs transmitted on channels that do not include the 20 MHz primary channel.

[0230] The IEEE 802.11be standard specifies that segments may be divided into 80 MHz units, which can be called 80 MHz segments. Also, it specifies that different signaling fields, such as EHT-SIG or U-SIG, are transmitted for each 80 MHz segment within one PPDU. Figure 25 illustrates a case where a station accesses a channel in a segment that does not include a 20 MHz primary channel.

[0231] FIG. 25 shows that when the 20 MHz primary channel is not idle, a station performs channel access on a sub-channel of a segment other than the primary segment according to an embodiment of the present invention.

[0232] As described above, a station can perform channel access in a segment that does not include the 20 MHz primary channel. Specifically, if the 20 MHz primary channel is not idle, the station can perform channel access in a segment that does not include the 20 MHz primary channel.

[0233] In yet another specific embodiment, a station may be configured by an AP to receive and decode a preamble via a subchannel other than the 20 MHz primary channel. In this case, the station can perform channel access in a segment that does not include the 20 MHz primary channel. In this embodiment, the station can perform channel access in a segment that does not include the 20 MHz primary channel without detecting whether a PPDU is transmitted in the 20 MHz primary channel. Such transmission using a segment that does not include the 20 MHz primary channel can be referred to as subchannel selective transmission (SST). Furthermore, a station that receives the preamble and PPDU of a PPDU in a segment that does not include the 20 MHz primary channel can be referred to as a parked station.

[0234] One sub-channel for channel access may be designated for each segment. If the 20 MHz primary channel is not idle, a station may access the sub-channel designated for channel access in a segment that does not include the 20 MHz primary channel.

[0235] In the example of FIG. 25, an AP detects an Inter-BSS PPDU having a 40 MHz bandwidth transmitted on a 20 MHz primary channel (P20). The AP performs a backoff procedure on a first subchannel (S20_1) of a second segment (Segment 2). The first subchannel (S20_1) may be a designated channel on which the backoff procedure is performed when the backoff procedure is performed on the second segment (Segment 2). A station parked on the second segment (Segment 2) detects the preamble of the PPDU on the first subchannel (S20_1). The station parked on the second segment (Segment 2) can wait to receive the PPDU on the first subchannel (S20_1) regardless of whether the AP performed the backoff procedure on the 20 MHz primary channel (P20) or the first subchannel (S20_1). In addition, a station parked in the second segment (Segment 2) detects the preamble of the HE MU PPDU or EHT MU PPDU in the first subchannel (S20_1), and a station parked in the second segment (Segment 2) can decode the preamble of the PPDU in a subchannel other than the first subchannel (S20_1) of the second segment (Segment 2) to determine the special stream and RU of the PPDU transmitted to the station.

[0236] The AP may transmit a PPDU not only in the second segment (Segment 2) but also over a subchannel that was idle during the previous PIFS at the time of terminating the backoff procedure in the second segment (Segment 2). In this case, the AP may determine whether to transmit a PPDU in each segment depending on whether a channel designated for a backoff procedure to be performed in each segment during the PIFS prior to the time of terminating the backoff procedure is idle. Specifically, if a channel designated for a backoff procedure to be performed in each segment during the PIFS prior to the time of terminating the backoff procedure is idle, the AP may transmit a PPDU in the segment. If a channel designated for a backoff procedure to be performed in each segment during the PIFS prior to the time of terminating the backoff procedure is not idle, the AP does not need to transmit a PPDU in the segment.

[0237] In the example of Figure 25, during the PIFS before the end of the backoff procedure in the second segment (Segment 2), it is detected that the second subchannel (S20_2), which is the subchannel on which the backoff procedure is performed in the third segment (Segment 3), is not idle. Also, during the PIFS before the end of the backoff procedure in the second segment (Segment 2), it is detected that the third subchannel (S20_3), which is the subchannel on which the backoff procedure is performed in the fourth segment (Segment 4), is idle. Therefore, the AP transmits PPDUs in the second segment (Segment 2) and the fourth segment (Segment 4).

[0238] Thus, constraints may be applied to the length of the PPDU transmitted, the intended recipient of the MAC frame contained in the PPDU, and the RUs allocated to the station receiving the PPDU.

[0239] Although the above embodiment has been described using AP transmission as an example, the above embodiment may also be applied to non-AP stations, which will be described in detail with reference to FIG.

[0240] FIG. 26 illustrates a first AP in a multi-link device signaling via a second AP that the first AP can receive on a sub-channel other than the 20 MHz primary channel, according to an embodiment of the present invention.

[0241] When a first AP of a multi-link device detects that the 20 MHz primary channel of the first AP is not idle, the first AP can signal through a second AP, another AP of the multi-link device, that it will perform a backoff procedure on a sub-channel other than the 20 MHz primary channel. In this case, the first AP can indicate the sub-channel on which the backoff procedure will be performed through the second AP. In yet another specific embodiment, the first AP does not need to signal through the second AP the sub-channel on which the backoff procedure will be performed. In this case, the station can perform the backoff procedure on a pre-designated sub-channel.

[0242] Furthermore, the first AP may signal, via the second AP, the time the first AP will wait for reception on a subchannel other than the 20 MHz primary channel. The station may determine the length of the UL PPDU based on the signaled wait time. Specifically, the station may determine the length of the UL PPDU so that transmission of the UL PPDU does not continue beyond the signaled wait time. In yet another specific example, the station may determine the length of the UL PPDU so that a response, e.g., an ACK, to the UL PPDU is completed beyond the signaled wait time.

[0243] In this embodiment, the second AP may transmit a control frame including information regarding reception standby, for example, information regarding a subchannel other than the 20 MHz primary channel of the first AP, and information regarding a standby time. In this case, the recipient address of the control frame may be a MAC address of a specific station. Only stations corresponding to the recipient address may perform a backoff procedure on the subchannel, not the 20 MHz primary channel. In yet another specific embodiment, the recipient address may be a group address. Only stations corresponding to the group address may perform a backoff procedure on the subchannel, not the 20 MHz primary channel. In this case, multiple stations may compete for channel access. In yet another specific embodiment, the recipient address may be a broadcast address. Stations not corresponding to the recipient address may maintain a power-saving state during the reception standby time.

[0244] In the above-described embodiment, only one control frame containing information about waiting for reception may be transmitted, or multiple control frames may be transmitted. The control frame containing information about waiting for reception may be transmitted alone. In yet another specific embodiment, the control frame containing information about waiting for reception may be transmitted together with a data frame, another control frame, or a management frame.

[0245] In addition, the second AP can signal information about TIDs that can be transmitted based on the backoff procedure of subchannels other than the 20 MHz primary channel. Specifically, the control frame described above can include information about TIDs that can be used in uplink transmissions that are transmitted based on the backoff procedure of subchannels other than the 20 MHz primary channel. In this case, the information about TIDs can be indicated by an 8-bit field. Specifically, each bit in the 8-bit field can correspond to a TID value from 0 to 7. If the value of each bit is 1, it can indicate that the TID corresponding to that bit is allowed. If the value of the subfield is 11111111 2b In another specific embodiment, the value of the subfield is 11111111. 2b If the value of each bit is 1, it can indicate that transmission of all TIDs is permitted. In yet another specific embodiment, information about TIDs can be represented by a 16-bit field. Specifically, each bit of the 16-bit field can correspond to a TID value from 0 to 15. If the value of each bit is 1, it can indicate that the TID corresponding to that bit is permitted.

[0246] In addition, the second AP may signal EDCA parameters to be used in the backoff procedure of a subchannel other than the 20 MHz primary channel. Specifically, the control frame may include information regarding the EDCA parameters to be used in the backoff procedure of a subchannel other than the 20 MHz primary channel. The first station (STA1) performs the backoff procedure on a subchannel rather than the 20 MHz primary channel using the signaled backoff parameters. In a specific embodiment, even if the first station (STA1) is using the MU EDCA parameters, the first station (STA1) may perform the backoff procedure on a subchannel rather than the 20 MHz primary channel using the signaled backoff parameters. In this case, after the first station (STA1) completes the backoff procedure on a subchannel other than the 20 MHz primary channel or when performing the backoff procedure on the 20 MHz primary channel, the first station (STA1) may perform the backoff procedure again using the MU-EDCA parameters.

[0247] In the embodiment of FIG. 26, the AP multilink device includes a first AP (AP1) and a second AP (AP2). The non-AP multilink device includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) are connected via a first link (Link1), and the second AP (AP2) and the second station (STA2) are connected via a second link (Link1). At this time, it is detected that the 20 MHz primary channel of the first AP (AP1) is not idle. The second AP (AP2) transmits information about the first AP's (AP1) reception standby, for example, information about the reception standby subchannel and reception standby time, to the second station (STA2). At this time, the second AP (AP2) transmits the reception standby information using a control frame over the second link (Link2). At this time, the recipient address of the control frame may be the first station (STA1). In yet another specific embodiment, the recipient address of the control frame may be the MAC address of a non-AP multilink device including the first station (STA1) and the second station (STA2). In yet another specific embodiment, the recipient address of the control frame may be a group address. The first station (STA1) performs a backoff procedure on a subchannel other than the 20 MHz primary channel (P20). After the backoff procedure is successful, it transmits a PPDU to the first AP (AP1).

[0248] According to an embodiment of the present invention, an AP may park a station associated with the AP in a segment other than the 80 MHz primary channel. In this case, the station associated with the AP can operate as if a subchannel in the segment in which the station is parked were a 20 MHz primary channel. Specifically, the station associated with the AP can search for a preamble of a PPDU in the segment in which the station is parked. Furthermore, even if the AP transmits a PPDU with a 320 MHz bandwidth, the station associated with the AP can receive it as if it were a PPDU with an 80 MHz bandwidth or a 160 MHz bandwidth. This is because, as described above, the signaling field of the PPDU, e.g., the U-SIG field and the EHT-SIG field, may be transmitted with different content for each segment. Furthermore, because the signaling field may be transmitted with different content for each segment, excessive increase in the length of the signaling field can be prevented.

[0249] A subchannel used by stations associated with an AP like a 20 MHz primary channel in a parked segment is called a virtual primary channel. In this case, preamble puncturing may not be performed on the virtual primary channel. One virtual primary channel may be designated for each segment. Specifically, the lowest 20 MHz channel in a segment may be designated as the virtual primary channel. If the AP is unable to transmit a PPDU preamble on the virtual primary channel in a segment, the AP may puncture the segment. In yet another specific embodiment, if the AP is unable to transmit a PPDU preamble on the virtual primary channel in a segment, the AP may transmit a PPDU to stations not parked in the segment. In other words, if the AP is unable to transmit a PPDU preamble on the virtual primary channel in a segment, the stations parked in the segment may not receive the PPDU. Furthermore, when the AP punctures a segment, the AP does not trigger uplink transmission of stations parked in the segment. Specifically, the AP does not need to send a trigger frame that allocates RUs for uplink transmission to stations parked in that segment.

[0250] When a station parked in a segment other than the 80 MHz primary channel is restricted to channel access on a 20 MHz primary channel other than the virtual primary channel, the AP may use a different channel for transmission and a different channel for detecting the PPDU preamble. Furthermore, a station may also use a different channel for backoff for uplink transmission and a different channel for detecting the PPDU preamble. Therefore, while the AP performs backoff for a station parked in a segment other than the 80 MHz primary channel, it may not be able to receive the PPDU transmitted by the station parked in a segment other than the 80 MHz primary channel. Therefore, the AP may allow a station parked in a segment other than the 80 MHz primary channel to perform a backoff procedure for uplink transmission on the segment in which the station is parked. This will be described with reference to FIG. 27.

[0251] Figure 27 shows that an AP of an AP multi-link device according to an embodiment of the present invention allows a station parked on a segment other than the 80 MHz primary channel to perform a backoff procedure for uplink transmission on the segment on which the station is parked.

[0252] A station that detects that an Inter-BSS PPDU is transmitted on the 20 MHz primary channel can allow stations parked on segments other than the 80 MHz primary channel to perform backoff procedures for uplink transmission on the virtual primary channel. In this case, the AP can determine the segment on which the station will perform the backoff procedure for uplink transmission based on the bandwidth of the Inter-BSS PPDU transmitted on the 20 MHz primary channel. Specifically, the AP can determine the segment on which the Inter-BSS PPDU is not transmitted as the segment on which the station will perform the backoff procedure for uplink transmission. In this case, the AP can allow the stations parked on the determined segment to perform the backoff procedure using the virtual primary channel of the determined segment. In this case, the AP can allow only some of the stations parked on the determined segment to perform the backoff procedure using the virtual primary channel. For example, if an Inter-BSS PPDU with a 160 MHz bandwidth is transmitted on two segments, the AP can allow the stations parked on the remaining two segments to perform the backoff procedure using the virtual primary channel. In this case, the AP can allow only stations parked in one of the two segments to perform backoff using the virtual primary channel.

[0253] Furthermore, the AP can signal a segment for which a backoff procedure is permitted using the virtual primary channel using a 2-bit subfield. For convenience of explanation, a segment for which a backoff procedure is permitted using the virtual primary channel is referred to as a designated segment. In this case, the subfield can indicate an index of the designated segment. For example, if the value of the subfield is 0, the subfield can indicate that the segment corresponding to the lowest frequency band is the designated segment. If the value of the subfield is 3, the subfield can indicate that the segment corresponding to the highest frequency band is the designated segment. In yet another specific embodiment, if the value of the subfield is 0, the subfield can indicate that the segment corresponding to the 80 MHz primary channel is the designated segment. If the value of the subfield is 1, the subfield can indicate that the segment corresponding to the 80 MHz secondary channel is the designated segment. If the value of the subfield is 2 or 3, the subfield can indicate that each of the two segments corresponding to the 160 MHz secondary channel is the designated segment.

[0254] In addition, the AP may signal to the station PPDU reception waiting time information, which is information about the time the AP waits to receive a PPDU on the virtual primary channel. Specifically, the AP may signal the PPDU reception waiting time information to the station along with a designated segment. At this time, the station may determine the length of the PPDU to be transmitted based on the PPDU reception waiting time information. Specifically, the station may determine the PPDU length so that the time to complete PPDU transmission does not exceed the PPDU reception waiting time. In yet another specific embodiment, the station may determine the PPDU length so that the time to complete the PPDU and the response to the PPDU does not exceed the PPDU reception waiting time. At this time, the response to the PPDU may be an ACK, for example, an ACK frame or a BlockACK frame.

[0255] The AP may also signal to the station the type of traffic to be transmitted based on the backoff procedure on the virtual primary channel. Specific operations of the AP and station may be the same as those of the AP and station in the embodiment described in FIG. 26. The AP may also signal to the station EDCA parameters to be used when the station performs the backoff procedure on the virtual primary channel. Specific operations of the AP and station may be the same as those of the AP and station in the embodiment described in FIG. 26. In this case, the EDCA parameters used when the station performs the backoff procedure on the 20 MHz primary channel may be independent of the EDCA parameters used when the station performs the backoff procedure on the virtual primary channel. For example, the backoff counter used when the station performs the backoff procedure on the 20 MHz primary channel may be independent of the backoff counter used when the station performs the backoff procedure on the virtual primary channel.

[0256] Additionally, the AP multilink device can transmit the above information to a station coupled to the first AP via the second AP of the AP multilink device.

[0257] Furthermore, stations parked in segments other than the segment including the virtual primary channel for which the AP has permitted the backoff procedure to be performed can enter a power-saving state of the power-saving operation based on the above-described reception standby time information. Specifically, stations parked in segments other than the segment including the virtual primary channel for which the AP has permitted the backoff procedure to be performed can maintain a power-saving state during the reception standby time.

[0258] In the embodiment of Figure 27, the AP multilink device includes a first AP and a second AP. The first AP detects that an Inter-BSS PPDU is being transmitted on its 20 MHz primary channel (P20). The first AP (AP1) signals to the second AP (AP2) that a backoff procedure for uplink transmission is permitted on the virtual primary channel of the second segment (Segment 2) that is not the first segment (Segment 1) including the 20 MHz primary channel (P20). The first AP (AP1) also signals that a backoff procedure for uplink transmission is permitted on the second segment (Segment 2), along with the link on which the first AP (AP1) operates, the uplink transmission wait time (time limit), the TID of the traffic to be transmitted in the uplink transmission, and the EDCA parameters to be used in the backoff procedure for the uplink transmission.

[0259] Although the present invention has been described above with reference to wireless LAN communication, the present invention is not limited thereto and may be equally applied to other communication systems such as cellular communication. Furthermore, although the method, apparatus, and system of the present invention have been described in relation to specific embodiments, some or all of the components and operations of the present invention may be implemented using a computer system having a general-purpose hardware architecture.

[0260] The features, structures, effects, etc. described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by a person skilled in the art to which the embodiment belongs. Therefore, content related to such combinations and modifications should be interpreted as being included within the scope of the present invention.

[0261] The above description has focused on the embodiments, but these are merely examples and do not limit the present invention. Those skilled in the art will understand that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the present invention. For example, each component specifically illustrated in the embodiments can be modified and implemented. Differences related to such modifications and applications should be construed as being included within the scope of the present invention as defined by the appended claims.

Claims

1. A multi-link device using multiple links, a transceiver; and a processor; The processor: receiving a first physical layer protocol data unit (PPDU) including access category (AC) restriction signaling and a reverse direction (RD) grant from a station that is a transmission opportunity (TXOP) holder or a service period (SP) source via any one of the plurality of links; transmitting a second PPDU to the station in response to the first PPDU based on the AC limitation signaling over the one link; The AC restriction signaling indicates whether a traffic identifier (TID) or AC of a frame included in the second PPDU is restricted.

2. An AC or a TID is mapped to any one of the plurality of links, and the multi-link device transmits a frame based on the mapped AC or TID through the any one of the links; The processor:

2. The multi-link device of claim 1, wherein the AC restriction signaling indicates that any TID of a data frame included in the second PPDU is acceptable, and when the multi-link device includes a data frame in the second PPDU, the multi-link device does not include in the second PPDU a data frame corresponding to a TID that is not mapped to any one of the links, and includes in the second PPDU a data frame corresponding to a TID that is mapped to any one of the links.

3. An AC or a TID is mapped to any one of the plurality of links, and the multi-link device transmits a frame based on the mapped AC or TID through the any one of the links; The processor:

2. The multi-link device of claim 1, wherein the AC restriction signaling indicates that the AC or TID of a frame included in the second PPDU is restricted, and when the multi-link device includes a data frame in the second PPDU, the multi-link device does not include in the second PPDU a data frame that is not mapped to any one of the links or that corresponds to a TID or AC with a lower priority than the priority of the AC or TID of the frame received from the station, and includes in the second PPDU a data frame that is mapped to any one of the links and that corresponds to a TID or AC with the same or higher priority than the priority of the AC or TID of the frame received from the station.

4. 4. The multi-link device according to claim 3, wherein when the multi-link device receives a plurality of frames from the station, the priority of the AC or TID of the frame received from the station is the lowest priority among the priorities of the plurality of frames.

5. 2. The multi-link device according to claim 1, wherein said processor regards AC of a management frame as a pre-specified value.

6. The processor: If the second PPDU includes a BlockAck frame, determining an AC of the BlockAck frame based on a TID field of the BlockAck frame; 2. The multi-link device according to claim 1, wherein when a BlockAckReq frame is included in the second PPDU, the AC of the BlockAckReq frame is determined based on a TID field of the BlockAckReq frame.

7. 2. The multi-link device of claim 1, wherein the AC restriction signaling is included in a medium access control (MAC) header of a frame included in a PPDU that includes the RD grant.

8. 1. A method of operating a multi-link device using multiple links, comprising: receiving a first physical layer protocol data unit (PPDU) including access category (AC) restriction signaling and a reverse direction (RD) grant from a station that is a transmission opportunity (TXOP) holder or a service period (SP) source over any one of the plurality of links; and transmitting a second PPDU to the station in response to the first PPDU based on the AC limitation signaling over any one of the links; The AC restriction signaling indicates whether a traffic identifier (TID) or AC of a frame included in the second PPDU is restricted.

9. An AC or a TID is mapped to any one of the plurality of links, and the multi-link device transmits a frame based on the mapped AC or TID through the any one of the links; The step of transmitting the second PPDU to the station comprises:

9. The method of claim 8, wherein the AC restriction signaling indicates that any TID of a data frame included in the second PPDU is acceptable, and when the multi-link device includes a data frame in the second PPDU, the method includes not including a data frame corresponding to a TID that is not mapped to any one of the links in the second PPDU, and including a data frame corresponding to a TID that is mapped to any one of the links in the second PPDU.

10. An AC or a TID is mapped to any one of the plurality of links, and the multi-link device transmits a frame based on the mapped AC or TID through the any one of the links; The step of transmitting the second PPDU to the station comprises:

9. The method of claim 8, wherein the AC restriction signaling indicates that an AC or TID of a frame included in the second PPDU is restricted, and when the multi-link device includes a data frame in the second PPDU, the method includes not including in the second PPDU a data frame that is not mapped to any one of the links or that corresponds to a TID or AC with a lower priority than the priority of the AC or TID of the frame received from the station, and including in the second PPDU a data frame that is mapped to any one of the links and that corresponds to a TID or AC with a higher priority than or the same as the priority of the AC or TID of the frame received from the station.

11. 11. The method of claim 10, wherein when the multilink device receives multiple frames from the station, the priority of the AC or TID of the frame received from the station is the lowest priority among the priorities of the multiple frames.

12. The step of transmitting the second PPDU to the station comprises:

9. A method according to claim 8, including the step of assuming that the AC of the management frame is a pre-specified value.

13. The step of transmitting the second PPDU to the station comprises: determining an AC of the BlockAck frame based on a TID field of the BlockAck frame when the second PPDU includes the BlockAck frame; The method of claim 8 , further comprising determining an AC of the BlockAckReq frame based on a TID field of the BlockAckReq frame when the second PPDU includes the BlockAckReq frame.

14. The method of claim 8 , wherein the AC restriction signaling is included in a medium access control (MAC) header of a frame included in a PPDU that includes the RD grant.

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