Data transmission and reception method in a wireless communication system and wireless communication terminal using the same.

Abstract

The present invention discloses a method and apparatus for operating a wireless communication terminal. Specifically, the wireless communication terminal according to the present invention transmits a request frame for multi-access point (AP) coordinating to a first terminal, the frame including channel information indicating a specific channel to be used for transmitting and receiving low-latency data within a specific interval. The terminal receives a response frame as a response to the frame and can transmit and receive the low-latency data with a second terminal within the specific interval. At this time, the transmission and reception of the low-latency data via the specific channel within the specific interval is guaranteed by the frame, the specific channel is not occupied by the first terminal during the specific interval and is used for transmitting and receiving the low-latency data with the second terminal.

Description

Technical Field

[0001] The present invention relates to a method for obtaining a transmission opportunity (TXOP) and channel occupancy for improving the efficiency of a wireless LAN.

Background Art

[0002] Recently, as the spread of mobile devices has expanded, wireless LAN technology that can provide fast wireless Internet services to them has been in the spotlight. Wireless LAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, and embedded devices to be wirelessly connected to the Internet at home, in enterprises, or in a specific service-providing area based on wireless communication technology.

[0003] Since IEEE (Institute of Electronics Engineers) 802.11 supported the initial wireless LAN technology using a frequency of 2.4 GHz, various technology standards have been put into practical use or are under development. First, IEEE 802.11b uses a frequency in the 2.4 GHz band and supports a communication speed of up to 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses a frequency in the 5 GHz band instead of the 2.4 GHz band, thereby reducing the impact on interference compared to the rather congested 2.4 GHz band frequency, and improving the communication speed up to 54 Mbps using OFDM technology. However, IEEE 802.11a has a disadvantage in that its communication distance is shorter than that of IEEE 802.11b. And IEEE 802.11g uses the same 2.4 GHz band frequency as IEEE 802.11b to implement a maximum communication speed of 54 Mbps and satisfies backward compatibility, receiving considerable attention, but is also superior to IEEE 802.11a in terms of communication distance.

[0004] Furthermore, IEEE 802.11n is a technical standard established to overcome the limitations in communication speed that had been pointed out as a vulnerability in wireless LANs. The purpose of IEEE 802.11n is to increase network speed and reliability and extend the operating range of wireless networks. Specifically, IEEE 802.11n supports high throughput (HT) with a data processing speed of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas at both the transmitter and receiver ends to minimize transmission errors and optimize data speed. In addition, this standard uses a coding method that transmits multiple duplicate copies to improve data reliability.

[0005] As the proliferation of wireless LANs accelerates and the applications using them diversify, there is a growing need for new wireless LAN systems that can support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n. Among these, IEEE 802.11ac supports a wide bandwidth (80MHz to 160MHz) at the 5GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5GHz band, early 11ac chipsets are expected to support operation in the 2.4GHz band for backward compatibility with older 2.4GHz band products. Theoretically, this standard allows for a minimum wireless LAN speed of 1Gbps and a maximum single-link speed of 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Another method for transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz band is IEEE 802.11ad. 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, limiting its use to devices in short-range spaces.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is nearing completion as a wireless LAN standard for 802.11ac and 802.11ad and beyond, to provide highly efficient and high-performance wireless LAN communication technology in high-density environments where access points (APs) and terminals are densely packed. In an 802.11ax-based wireless LAN environment, it is necessary to provide highly frequency-efficient communication indoors and outdoors in the presence of high-density stations and APs (Access Points), and various technologies have been developed to realize this.

[0007] Furthermore, in order to support new multimedia applications such as high-definition video and real-time games, development has begun on a new wireless LAN standard to increase the maximum transmission speed. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is currently under development with the goal of supporting a maximum transmission rate of 30 Gbps in the 2.4 / 5 / 6 GHz band through wider bandwidth, increased spatial streams, and multiple AP coordination.

[0008] Recently, discussions have begun on ultra-high reliability (UHR) wireless LAN communication technologies to overcome the reliability issues that have been pointed out as limitations of wireless LANs, as a wireless LAN standard since 802.11be. The ultra-high reliability wireless LAN standard is being developed with the goal of supporting low latency and low jitter for wireless LAN traffic with a high probability (for example, 99.9999% or higher). [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention aims to provide an ultra-high-reliability wireless LAN service for new multimedia applications by enhancing the method of wireless LAN channel occupancy.

[0010] The technical problems to be addressed in this specification are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary skill in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0011] In the wireless communication terminal according to the present invention, the processor transmits a request frame for multi-access point (AP) coordinating to a first terminal, the frame includes channel information indicating a specific channel to be used for transmitting and receiving low-latency data within a specific section, the processor receives a response frame as a response to the frame, transmits and receives the low-latency data with a second terminal within the specific section, the transmission and reception of the low-latency data via the specific channel within the specific section is guaranteed by the frame, the specific channel is not occupied by the first terminal during the specific section and is used for transmitting and receiving the low-latency data with the second terminal.

[0012] Furthermore, in the present invention, if the specified section partially or completely overlaps with the TXOP (Transmission opportunity) section using the NAV (Network allocation vector) setting by the first terminal, the specified channel is used to send and receive the low-latency data with the second terminal during the specified section.

[0013] Furthermore, in the present invention, the requested frame is transmitted in duplicate in units of 20 MHz within the total bandwidth of the wireless communication terminal.

[0014] Furthermore, in the present invention, the processor sends a release request message to the first terminal to release the use of the specific channel due to the multiple AP adjustment, and the use of the specific channel is released within the specific interval based on the release request message.

[0015] Furthermore, in the present invention, the processor transmits a specific frame to the first terminal at regular intervals to inform it of the use of the specific channel.

[0016] Furthermore, in the present invention, if the specific frame is not transmitted to the first terminal within the specified time, the use of the specific channel is canceled within the specified interval, and the specified time, which is the transmission period of the specific frame, is longer than the transmission period of the beacon frame.

[0017] Furthermore, in the present invention, the specified interval is a restricted R-TWT (Restricted-target wake time) interval for transmitting and receiving the low-latency data.

[0018] The present invention also provides a method comprising the steps of: transmitting a request frame for multi-access point (AP) coordinating to a first terminal, wherein the frame includes channel information indicating a specific channel to be used for transmitting and receiving low-latency data within a specific interval; receiving a response frame as a response to the frame; and transmitting and receiving the low-latency data with a second terminal within the specific interval, wherein the transmission and reception of the low-latency data via the specific channel within the specific interval is guaranteed by the frame, the specific channel is not occupied by the first terminal during the specific interval, and is used for transmitting and receiving the low-latency data with the second terminal.

[0019] Furthermore, the present invention provides a wireless communication terminal that receives a frame from a first terminal indicating that a specific channel is unavailable within a specific section, the specific channel is used by a second terminal of another BSS to send and receive low-latency data within the specific section, data is sent and received with the first terminal based on the frame, the transmission and reception of the low-latency data via the specific channel within the specific section is guaranteed by the frame, the specific channel is not occupied by the first terminal during the specific section and is used for sending and receiving the low-latency data with the second terminal.

[0020] In the present invention, when the first primary channel of the second terminal and the second primary channel of the wireless communication terminal are the same channel, among the overall bandwidth, the channel connection procedure between the wireless communication terminal and the first terminal is performed on a sub-channel of an operating channel that does not include the first primary channel.

Advantages of the Invention

[0021] One embodiment of the present invention provides a wireless communication method for efficiently managing TXOP and a wireless communication terminal using the same.

[0022] According to one embodiment of the present invention, through multi-access point (AP) coordination between terminals, data can be transmitted and received on a channel occupied by the TXOP setting of another terminal.

[0023] Also, according to one embodiment of the present invention, through multi-AP coordination between an AP (Access Point) and another AP, since the other AP does not occupy the primary channel of the AP, the AP can perform channel connection for transmitting and receiving low-latency traffic.

[0024] Also, according to one embodiment of the present invention, before the start of the restricted-target wake time (R-TWT) service period (SP) of the AP, the approach of other APs to the band included in the operating bandwidth can be interrupted.

[0025] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those with ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0026] [Figure 1]It is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] It is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] It is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] It is a diagram showing the configuration of an access point according to an embodiment of the present invention. [Figure 5] It is a diagram schematically showing the process in which a STA sets a link with an AP. [Figure 6] It is a diagram showing the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] It is a diagram showing various standard generation-based PPDU (physical layer protocol data unit) formats according to an embodiment of the present invention. [Figure 8] It is a diagram showing the EHT / UHR PPDU format according to an embodiment of the present invention. [Figure 9] It is a diagram showing a transmission / TXOP protection method using RTS frames and CTS frames according to an embodiment of the present invention. [Figure 10] It is a diagram showing a transmission / TXOP protection method using MU-RTS frames and CTS frames according to an embodiment of the present invention. [Figure 11] It is a diagram showing an example in which the transmission of low-latency traffic of another AP is delayed by the TXOP of an AP according to an embodiment of the present invention. [Figure 12] It is a diagram showing the format of elements exchanged between APs for multi-AP cooperative puncturing and the setting status of the operating bandwidth and main channel of an AP to which multi-AP cooperative puncturing is applied according to an embodiment of the present invention. [Figure 13]This figure shows an example of a frame exchange sequence to which Coordinated Puncturing for AP2 according to one embodiment of the present invention is applied. [Figure 14] This figure shows yet another example of a frame replacement sequence to which adjusted puncturing for AP2 according to one embodiment of the present invention is applied. [Figure 15] This figure shows an example of an element format that an AP performing multiple AP cooperative operation according to one embodiment of the present invention transmits to its BSS STA to instruct it on channel access restriction-related information. [Figure 16] This figure shows an example of a method for exchanging dedicated channel information to enhance protection between BSSs (Basic Service Sets) that have undergone Multi-AP Coordination according to one embodiment of the present invention. [Figure 17] This figure shows an example of a method for changing the CCA threshold to enhance protection between BSSs that have undergone multiple AP adjustment according to one embodiment of the present invention. [Figure 18] This figure shows an example of a frame format used in the multiple AP adjustment process according to one embodiment of the present invention. [Figure 19] This figure shows an example of a multiple AP adjustment process between APs according to one embodiment of the present invention. [Figure 20] This figure shows an example of a multiple AP adjustment teardown frame format according to one embodiment of the present invention. [Figure 21] This figure shows an example of the format of the operation information field sent by an AP according to one embodiment of the present invention for changing the disabled subchannel of a BSS. [Figure 22] This figure shows an example of a method by which multiple AP adjustment puncturing is applied to a subchannel other than the primary channel according to one embodiment of the present invention. [Figure 23]This figure shows the positional relationship of puncturing channels between APs performing multiple AP adjustment puncturing negotiations according to one embodiment of the present invention, and an example of the resulting adjustment limitations. [Figure 24] This figure shows an example of a method for specifying PPC and APC for 80MHz, 160MHz, and 320MHz channels according to one embodiment of the present invention. [Figure 25] This flowchart shows an example of a data transmission and reception method performed by a terminal according to one embodiment of the present invention. [Modes for carrying out the invention]

[0027] The terminology used herein has been selected to the greatest extent possible from currently widely used general terms, taking into account the function of the present invention; however, this may differ depending on the intentions, conventions, or emergence of new technologies of the articulate persons. In addition, in certain cases, the applicant has arbitrarily selected some terms, and in such cases, the meaning of these terms will be described in the description of the relevant invention. Therefore, it should be made clear that the terms used herein are not merely names of terms, but should be interpreted based on the substantive meaning of the terms and the overall content of this specification.

[0028] Throughout the specification, when one configuration is described as being "connected" to another, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" with other components in between. Furthermore, when one configuration is described as "containing" a particular component, this means, unless otherwise stated, that it may contain other components rather than excluding them. In addition, limitations such as "greater than or equal to" or "less than or equal to" a specific threshold may be appropriately replaced by "greater than" or "less than" depending on the embodiment.

[0029] In the present invention, the terms "field" and "subfield" may be used interchangeably.

[0030] Figure 1 shows a wireless LAN system according to one embodiment of the present invention.

[0031] A wireless LAN system includes one or more Basic Service Sets (BSS), where a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0032] As shown in Figure 1, the infrastructure BSS BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 which are stations that provide distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0033] A Station (STA) is any device that includes Medium Access Control (MAC) and a Physical Layer interface to a wireless medium in accordance with the IEEE 802.11 standard, and in a broad sense includes not only non-AP stations but also all access points (APs). In this specification, "terminal" is used to refer to non-APs, APs, or both. A station for wireless communication includes a processor and a communication unit, and depending on the embodiment, further includes a user interface unit and a display unit, etc. The processor generates frames to be transmitted over the wireless network or processes frames received over the wireless network, and performs various other processing for controlling the station. The communication unit is functionally connected to the processor and sends and receives frames over the wireless network for the station. In this invention, "terminal" is used as a term that includes user equipment (UE).

[0034] An Access Point (AP) is an individual device that provides connectivity to a distribution system (DS) via a wireless medium for stations associated with it. In infrastructure BSS, communication between non-AP stations is generally conducted via APs, however, direct communication is possible between non-AP stations if a direct link is configured. In this invention, AP is used as a concept that includes PCP (Personal BSS Coordination Point), but in a broader sense, it includes all concepts such as central controllers, base stations (BS), node B, BTS (Base Transceiver System), or site controllers. In this invention, AP is also referred to as a base wireless communication terminal, but in a broader sense, base wireless communication terminal is used as a term that includes APs, base stations, eNBs (eNodeBs), and transmission points (TPs). Furthermore, base wireless communication terminals include various forms of wireless communication terminals that allocate and schedule communication medium resources in communication with multiple wireless communication terminals.

[0035] Multiple infrastructure BSSs are connected to each other via a distribution system DS. In this case, multiple BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0036] Figure 2 shows an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of Figure 2, redundant explanations are omitted for parts that are the same as or corresponding to the embodiment of Figure 1.

[0037] As shown in Figure 2, BSS3 is an independent BSS and does not include APs, so all stations (STA6, STA7) are not connected to APs. 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 one another.

[0038] Figure 3 is a block diagram showing the configuration of a station 100 according to one 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.

[0039] First, the communication unit 120 transmits and receives wireless signals such as wireless LAN packets and may be incorporated into the station 100 or provided externally. According to one 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 of different frequency bands such as 2.4GHz, 5GHz, 6GHz, and 60GHz. According to one embodiment, the station 100 may include a communication module using a frequency band of 7.125GHz or higher and a communication module using a frequency band of 7.125GHz or lower. Each communication module can perform wireless communication with an AP or external station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the station 100, the communication unit 120 may operate only one communication module at a time or operate multiple communication modules together simultaneously. When the station 100 includes multiple communication modules, each communication module may be provided in an independent form, or the multiple modules may be integrated as a single chip. In embodiments of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0040] Next, the user interface 140 includes various forms of input / output means provided in the station 100. In other words, 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. The user interface unit 140 also outputs based on instructions from the processor 110 using various output means.

[0041] Next, the display unit 150 outputs an image to the display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or a user interface based on control instructions from the processor 110. The memory 160 stores control programs used by the station 100 and various data associated with them. Such control programs include connection programs necessary for the station 100 to connect with APs or external stations.

[0042] The processor 110 of the present invention executes various instructions 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 units. According to an embodiment of the present invention, the processor 110 executes a program for connection with the AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information regarding the priority conditions of the station 100 contained in the communication setup message and requests a connection to the AP based on the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling a part of the station 100's configuration, such as the communication unit 120. In other words, the processor 110 may be a modem or a modulator and / or demodulator that modulates and demodulates the wireless signals transmitted and received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. A detailed embodiment relating to this will be described later.

[0043] The station 100 shown in Figure 3 is a block diagram according to one embodiment of the present invention, and the separately shown blocks represent logically distinguished elements of the device. Therefore, the above-described elements of the device are mounted on one chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated and implemented on a single chip, or they may be implemented on separate chips. Furthermore, in the embodiment 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 provided in the station 100.

[0044] Figure 4 is a block diagram showing the configuration of AP200 according to one embodiment of the present invention. As shown, AP200 according to an embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In Figure 4, redundant explanations are omitted for parts of the AP200 configuration that are the same as or correspond to the configuration of station 100 in Figure 3.

[0045] Referring to Figure 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 Figure 3, the communication unit 220 of the AP 200 can also include a plurality of communication modules using different frequency bands. That is, the AP 200 according to an embodiment of the present invention can 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 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can communicate wirelessly with the station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the AP 200, the communication unit 220 can operate only one communication module at a time or operate multiple communication modules together simultaneously. In an embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0046] Next, the memory 260 stores the control program used by the AP200 and various data associated with it. Such a control program includes a connection program that manages the connection of stations. The processor 210 controls each unit of the AP200 and controls the transmission and reception of data between units. According to one embodiment of the present invention, the processor 210 executes the program for connecting with stations stored in the memory 260 and transmits a communication setting message to one or more stations. In this case, the communication setting message includes information regarding the connection priority conditions of each station. The processor 210 also performs connection settings in response to connection requests from stations. According to one embodiment, the processor 210 is a modem or modulation / demodulation unit that modulates and demodulates the wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations of wireless signal transmission and reception of the AP200 according to the embodiment of the present invention. A detailed embodiment relating thereto will be described later.

[0047] Figure 5 is a schematic diagram illustrating the process by which STA establishes a link with AP.

[0048] Referring to Figure 5, the link between STA100 and AP200 is established through three main steps: scanning, authentication, and association. First, the scanning step is the step in which STA100 obtains connection information for the BSS operated by AP200. There are two methods for performing scanning: passive scanning, which obtains information using only the beacon message S101 that AP200 periodically transmits, and active scanning, in which STA100 transmits a probe request S103 to the AP, receives a probe response S105 from the AP, and obtains connection information.

[0049] In the scanning step, STA100, having successfully received wireless connection information, transmits an authentication request (S107a), receives an authentication response from AP200 (S107b), and performs the authentication step. After the authentication step is performed, STA100 transmits an association request (S109a), receives an association response from AP200 (S109b), and performs the association step. In this specification, "association" basically means wireless coupling, but the present invention is not limited to this, and in a broad sense, coupling includes both wireless and wired coupling.

[0050] On the other hand, an additional 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are performed. In Figure 5, Server 300 is a server that processes authentication between STA100 and the 802.1X-based system, and may be physically connected to AP200 or exist as a separate server.

[0051] Figure 6 shows the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0052] A terminal performing wireless LAN communication checks whether a channel is busy or occupied by performing carrier sensing before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to that channel. This process is called Clear Channel Assessment (CCA), and the level at which the detection of the signal is determined is called the CCA threshold. If a wireless signal above the CCA threshold is received by the terminal and the terminal is the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel, or if a wireless signal below the CCA threshold is detected, the channel is determined to be idle.

[0053] If a channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after a time period determined by the status of each terminal, such as an IFS (Inter Frame Space), AIFS (Arbitration IFS), PIFS (PCF IFS), etc. In this embodiment, the AIFS is used as a replacement for the conventional DIFS (DCF IFS). Each terminal waits, decreasing a slot time equal to a random number determined for that terminal during the interval of idle state of the channel, and the terminal that has exhausted all of its slot time attempts to access the channel. The period in which each terminal performs this backoff procedure is called the competition window period. At this time, the random number can be called the backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number acquired by the terminal. If a terminal senses that a channel is idle during the slot time, the terminal can decrease the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be allowed to access the channel. Therefore, terminal transmission may be permitted when the channel is idle during the AIFS time and the backoff counter slot time.

[0054] If a specific terminal successfully accesses the channel, it transmits data through the channel. However, if a terminal attempting access collides with another terminal, the colliding terminals are each assigned a new random number and perform a further backoff procedure. In one embodiment, the random number newly assigned to each terminal is determined within a range twice the range (competition window, CW) of the random number previously assigned to that terminal (2*CW). Meanwhile, each terminal attempts access again in the next competition window interval by performing a further backoff procedure, but this time, each terminal performs the backoff procedure from the slot time remaining in the previous competition window interval. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0055] <Examples of various PPDU formats> Figure 7 shows various standard generational PPDU (physical layer protocol data unit) formats according to embodiments of the present invention.

[0056] 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. Figure 7(d) shows the detailed field configuration of L-SIG and RL-SIG commonly used in the aforementioned PPDU formats.

[0057] Referring to Figure 7(a), the legacy PPDU preamble includes L-STF (Legacy Short Training field), L-LTF (Legacy Long Training field), and L-SIG (Legacy Signal field). In embodiments of the present invention, the L-STF, L-LTF, and L-SIG can be referred to as the legacy preamble.

[0058] Referring to Figure 7(b), the HE PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as the HE preamble. The specific configuration of the HE preamble may be modified according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0059] Referring to Figure 7(c), the EHT PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used in only some of the EHT PPDU formats.

[0060] Thus, the PPDU used in the UHR standard may have a format similar to that of the PPDU used in the EHT standard. This is because the EHT PPDU format defined in 802.11be includes a U-SIG field that is promised to be used commonly across multiple wireless LAN generations. In this case, the value of the PHY Version Identifier field in the U-SIG field included in the EHT PPDU is 0, while the value of the PHY Version identifier field in the U-SIG field included in the UHR PPDU may be a non-zero value, such as 1. The EHT PPDU includes an EHT-STF (Extremely High Throughput Short Training field) field in the STF field and an EHT-LTF (Extremely High Throughput Long Training field) field in the LTF field. The UHR PPDU includes a UHR-STF (Ultra High Reliability Short Training field) field in the STF field and a UHR-LTF (Ultra High Reliability Long Training field) field in the LTF field.

[0061] The L-SIG field included in the PPDU preamble is configured with 64 FFT OFDM and consists of a total of 64 subcarriers. Of these, 48 subcarriers, excluding the guard subcarrier, DC subcarrier, and pilot subcarrier, are used for L-SIG data transmission. Since BPSK and a Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information configuration of the L-SIG.

[0062] Referring to Figure 7(d), L-SIG includes the L_RATE field and the L_LENGTH field. The L_RATE field consists of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of a modulation scheme such as BPSK / QPSK / 16-QAM / 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. Combining the information from the L_RATE and L_LENGTH fields allows us to determine the total length of the PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0063] The L_LENGTH field is measured in bytes, with a total of 12 bits allocated, allowing for signaling up to 4095. In combination with the L_RATE field, it can indicate the length of the PPDU. In this case, legacy and non-legacy terminals can parse the L_LENGTH field in different ways.

[0064] First, the method by which a legacy or non-legacy terminal analyzes the length of a PPDU using the L_LENGTH field is as follows: When the L_RATE field is set to 6Mbps, 3 bytes (i.e., 24 bits) may be transmitted in 4us, which is the symbol duration of one 64FFT. Therefore, by adding the 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing this by the transmission amount of one symbol, which is 3 bytes, the number of 64FFT reference symbols after L-SIG is obtained. After multiplying the obtained number of symbols by the symbol duration of one, which is 4us, and then adding the 20us required for transmission of L-STF, L-LTF, and L-SIG, the length of the PPDU, i.e., the reception time (RXTIME), is obtained. This can be expressed mathematically as shown in Equation 1 below.

[0065]

number

[0066] At this time,

number

[0067]

number

[0068] Here, TXTIME is the total transmission time that constitutes the PPDU, as shown in Equation 3 below. In this case, TX represents the transmission time of X.

[0069]

number

[0070] Referring to the formula above, 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 ​​L_LENGTH = {3k+1, 3k+2, 3(k+1)} will indicate the same PPDU length.

[0071] Referring to Figure 7(e), the U-SIG (Universal SIG) field persists in EHT / UHR PPDUs and subsequent generations of wireless LAN PPDUs, playing a role in distinguishing which generation of PPDU it is, including EHT / UHR. Furthermore, the U-SIG field can facilitate the spatial reuse of EHT / UHR and subsequent generations of wireless LANs. The U-SIG is a 64FFT-based OFDM 2 symbol capable of transmitting a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits for CRC / Tail, are divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0072] The VI bit maintains its current bit configuration into the future, allowing current EHT / UHR terminals to obtain information about a PPDU through its VI field even when subsequent generations of PPDUs are defined. For this purpose, the VI field consists of the PHY version, UL / DL, BSS Color, TXOP, and Reserved fields. The PHY version ID field is 3 bits and is responsible for sequentially classifying EHT / UHR and subsequent generations of wireless LAN standards into versions. The PHY version ID field of an EHT (11be) PPDU has a value of 000b, while the PHY version ID field of a UHR PPDU has a value other than 000b. The UL / DL field distinguishes whether the PPDU is an uplink or downlink PPDU. BSS Color refers to the BSS-specific identifier defined in 11ax and has a value of 6 bits or more. TXOP stands for Transmit Opportunity Duration, which was communicated in the MAC header. By adding it to the PHY header, the length of the TXOP containing the MPDU can be inferred without needing to decode the MPDU, and it has a value of 7 bits or more.

[0073] The VD field of the EHT is signaling information useful only for 11be version PPDUs and may consist of fields that are common to all PPDU formats, such as the PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a distinguisher that differentiates between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDU, etc.

[0074] The BW field signals five basic PPDU BW options (BWs that can be expressed in the form of 20*2 exponential values) at 20, 40, 80, 160(80+80), and 320(160+160) MHz, and various remaining PPDU BWs composed of preamble puncturing. Furthermore, after being signaled at 320 MHz, some 80 MHz may be signaled in a punctured form. The punctured and deformed channel form may be signaled directly in the BW field, or it may be signaled using the BW field together with a field appearing after the BW field (e.g., a field within 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 we assume the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0075] The VD field of a UHR is a field that indicates signaling information useful only for a UHR PPDU. However, the information indicated by each field included in the VD field of a UHR PPDU may be identical to, or in a more extended form of, the information indicated by the field that plays the same role as the VD field of an EHT (11be). For example, a field indicating a puncturing pattern included in the VD field of a UHR PPDU can indicate a wider variety of patterns than a field indicating a puncturing pattern included in the VD field of an EHT PPDU. Alternatively, a field indicating a puncturing pattern included in the VD field of a UHR PPDU may be analyzed in combination with a BW field. This allows for the indication of a wider variety of puncturing patterns.

[0076] Figure 8 shows the EHT / UHR PPDU format according to an embodiment of the present invention.

[0077] The EHT / UHR PPDU format may be indicated by the PPDU Format field in the U-SIG field of the PPDU. Figure 8(a) shows an EHT / UHR SU PPDU according to an embodiment of the present invention. The EHT / UHR SU PPDU is a PPDU used for single-user transmission between an AP and a single station and may include an EHT-SIG-A field for additional signaling after U-SIG.

[0078] Figure 8(b) shows an EHT / UHR Trigger-based PPDU according to an embodiment of the present invention. The EHT / UHR Trigger-based PPDU is an uplink PPDU used for transmission, which is a response to a trigger frame, and does not require a separate EHT / UHR-SIG-A field after U-SIG.

[0079] Figure 8(c) shows an EHT / UHR MU PPDU according to an embodiment of the present invention. The EHT / UHR MU PPDU is a PPDU used for transmission to one or more terminals. The EHT / UHR MU PPDU format may include HE-SIG-B after the U-SIG field.

[0080] Figure 8(d) shows an EHT / UHR ER SU PPDU according to an embodiment of the present invention. The EHT / UHR ER SU PPDU is used for single-user transmission to stations in an extended range. The EHT / UHR ER SU PPDU format may have U-SIG repeated over time.

[0081] The EHT / UHR MU PPDU described using Figure 8(c) may be used by an AP to perform downlink transmissions to multiple stations. In this case, the EHT / UHR MU PPDU may include scheduling information for multiple stations to receive the PPDU simultaneously. In this case, the EHT / UHR MU PPDU can transmit the AID information of the receiver or sender of the PPDU via the user-specific field of EHT / UHR-SIG-B. A station that receives the EHT / UHR MU PPDU can perform spatial reuse operations based on the AID information obtained in the PPDU's preamble. More specifically, the resource unit allocation (RA) field of EHT / UHR-SIG-B may include information about the resource unit (RU) division configuration in a specific bandwidth (e.g., 20 MHz) in the frequency domain. Furthermore, information about the stations assigned to each divided resource unit may be transmitted via the user-specific field of EHT / UHR-SIG-B. The user-specific field may include one or more user fields corresponding to each of the divided resource units.

[0082] Among the plurality of divided resource units, the AID of the recipient or the sender may be inserted into the user field corresponding to the resource unit where data transmission is performed. The pre-specified Null STA ID may be inserted into the user field corresponding to the remaining resource units where data transmission is not performed.

[0083] Two or more PPDUs described in FIG. 8 may be indicated in the same PPDU format. For example, the value of the U-SIG PPDU format subfield indicating the EHT / UHR SU PPDU and the value of the U-SIG PPDU format subfield indicating the EHT / UHR MU PPDU may be the same.

[0084] Some fields or some information of the fields included in the format of the above-described PPDU may be omitted. This can be called the compression mode or the compressed mode.

[0085] <Wi-Fi Terminal Channel Access Method> Since a Wi-Fi terminal (AP, non-AP STA, etc.) communicates using an unlicensed band, before transmitting a frame, it checks whether the channel it intends to transmit on is being used by other devices. CSMA (Carrier Sense Multiple Access) is a channel access method in which a terminal attempting to transmit a packet performs carrier sense to check whether the channel is being used by other devices, and transmits only when it is determined (IDLE) that the channel is not being used by other devices. A terminal using CSMA can perform an operation of not attempting to transmit at least when it is confirmed that another device is using the medium (channel) (when it is determined as BUSY), so the transmission that started first can be protected from other devices.

[0086] However, multiple terminals that recognize that the medium has been occupied by another device will experience a transmission collision when they simultaneously attempt to transmit packets once they confirm that the other device has ceased occupying the medium (the medium changes to IDLE). In other words, when a specific terminal attempts to transmit a packet, multiple other terminals attempt to transmit packets at the same time, and the terminal that is supposed to receive the packet transmitted by the specific terminal is unable to correctly receive and decode the packet due to interference that started from the transmissions made by the multiple other terminals.

[0087] CSMA / CA (CSMA with collision avoidance), as described above, is a channel access mechanism that prevents multiple terminals from simultaneously attempting to transmit packets after sensing that the medium has changed to IDLE. When a terminal approaches a medium (channel) using CSMA / CA, it waits for a random amount of time after observing that the state of the medium has changed to IDLE before attempting to transmit. This random amount of time may be an aslottime equal to a random number (random backoff counter) generated by each terminal attempting to transmit (generally 9us). In other words, terminals approaching a medium using CSMA / CA attempt to transmit after waiting for different random amounts of time from each other, so unlike when using CSMA alone, they will attempt to transmit at different times. In this case, if a specific terminal that waited the shortest random amount of time after the medium changed to IDLE attempts to transmit first, the other terminals can then abandon the channel approach procedure after realizing that the medium has been occupied (changed to BUSY) by that specific terminal. At this time, the specified terminal performs an operation to decrease the backoff counter it maintains by 1 each aslottime while the medium is maintained as IDLE, but it may attempt to transmit when the backoff counter becomes 0, or when the backoff counter becomes 0 and aslottime has elapsed. At this time, the specified terminal that performed the transmission may generate a new random number (new backoff counter) after the transmission is completed, and attempt to transmit again when the new random number becomes 0, or after it becomes 0.

[0088] The CSMA / CA and random backoff procedures briefly explained above are both applied to DCF (Distributed Coordination Function) and EDCAF (Enhanced Distributed Channel Access), which are basic functions used by Wi-Fi terminals when attempting channel access. These are well-known and widely used methods for accessing unlicensed bandwidth channels, and a detailed explanation will be omitted.

[0089] The DCF and EDCAF used by the MAC of a Wi-Fi terminal evaluate the channel status by considering not only the channel status (IDLE / BUSY) confirmed by each terminal itself through a physical CS (Carrier Sense), but also the results of a virtual CS (Virtual CS). Furthermore, even if the result of a physical CS performed on a channel is idle, if the virtual CS result is busy, the Wi-Fi terminal will consider the channel status to be busy. In this case, the virtual CS is a channel evaluation method that determines the channel to be busy if the NAV (Network allocation vector) is not 0. The NAV may be a value maintained for future traffic that is expected to occupy the medium. Furthermore, when a Wi-Fi MAC receives an RTS / CTS frame, it may set a NAV (NAV count) based on the duration information of the received frame, such as the value of the duration field, and maintain a non-zero value for the expected time the medium will be occupied after the RTS / CTS frame exchange. In other words, the value maintained as NAV decreases over time. If the NAV value of a particular MAC is 0, it may be interpreted that the future traffic that the particular MAC was aware of will not occupy the medium any further. If the NAV is 0, the MAC can determine that the virtual CS result is idle. In this case, the Wi-Fi MAC can also set the NAV based on duration values ​​obtained not only from RTS / CTS frames but also from other MAC frames that it has received.

[0090] The channel evaluation method that considers both the physical CS and virtual CS results (determine the state of the medium), as briefly explained above, is also a well-known Wi-Fi MAC function, so a detailed explanation will be omitted.

[0091] <EDCAとTXOP> EDCA provides a mechanism for differentiating and managing traffic into four types of access categories (ACs) based on their characteristics. These four ACs are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best Effort), and AC_BK (AC Background), and each AC may have different contention window (CW), transmit opportunity (TXOP), and AIFSN parameters. Simply put, EDCA is a mechanism that differentiates the CW, TXOP, and AIFSN parameters for the four types of ACs and adjusts the transmission priority of traffic transmitted using each AC. To this end, EDCA can map the traffic (MSDU) that a MAC should service to one of the four ACs using a traffic category (TC) or traffic stream (TS). The traffic mapped to one of the four ACs by EDCA is then managed in four separate queues for each AC. These four queues may not be physically separated but logically separated.

[0092] AC_VO is an AC that can be used for traffic that is not as large in absolute volume as voice traffic but is vulnerable to transmission delays. It has relatively small CW and AIFSN parameter values ​​to increase the probability that it will be served preferentially over traffic of other ACs. The TXOP parameters of AC_VO are limited to smaller values ​​than the TXOP parameters of other ACs, and a shorter transmission time is guaranteed compared to other ACs.

[0093] AC_VI is an AC that is more robust to transmission delays than voice traffic, but still requires low-latency transmission and can be used for video traffic that needs to handle large volumes of traffic. AC_VI has larger CW and AIFSN parameter values ​​than AC_VO but smaller than other ACs, and its TXOP is about twice as long as AC_VI's.

[0094] AC_BE is an AC that can be used for traffic that is robust to transmission delays, and most general traffic, excluding voice data and streaming video data, can be classified as AC_BE. AC_BE uses larger values ​​for CW and AIFSN parameters compared to AC_VO and AC_VI. Also, AC_BE does not have a separate TXOP. Therefore, traffic that falls under AC_BE cannot be used in a TXOP transmission sequence where a PPDU is sent, an ACK response is received, and another PPDU is sent after SIFS.

[0095] AC_BK is a type of AC that is similar to AC_BE in that it is robust to transmission delays, but can be used for traffic with a lower priority than BE traffic. AC_BK uses the same CW parameter values ​​as AC_BE, but uses higher AIFSN parameter values ​​than AC_BE. Also, traffic corresponding to AC_BK does not have a separate TXOP, just like AC_BE, and cannot be used in TXOP transmission sequences.

[0096] The four types of EDCA AC described above are mapped to 802.1D UP (user-priority), and the EDCA AC is determined by the UP value of the wired traffic or the TID of the MSDU instructed from the upper layer. In this case, if the TID of the MSDU indicates a value between 0 and 7, the value indicated by the TID may correspond one-to-one with UP.

[0097] Furthermore, the four types of EDCA ACs mentioned above each have default CW (CWmin, CWmax), AIFSN, and TXOP parameters defined in the standard. The parameter values ​​for each AC can be changed by the AP, and different values ​​can be used for each BSS.

[0098] By utilizing the EDCA mechanism, Wi-Fi traffic is stored in one of four queues corresponding to four ACs, and is only transmitted to the target device if the AC containing the traffic wins a channel access competition with other ACs. In this case, during channel access competition between ACs, each AC uses its assigned access parameters (CW[AC], AIFSN[AC]) to compete, and the channel access competition behavior performed by each AC is the same as that of DCF. In this case, if a particular AC has no traffic to send to its queue, that particular AC does not need to participate in the competition.

[0099] However, as mentioned above, since each AC utilizes different CW and AIFSN parameter values, AC_VO, which has the smallest CW and AIFSN parameters, has a higher probability of winning channel access competition with other ACs, and therefore, AC_VO's traffic is more likely to be served with priority over the traffic of other ACs.

[0100] Furthermore, the EDCA mechanism stipulates internal competition rules, such as the higher-priority AC winning when an internal collision occurs and increasing the CW of the other AC that caused the collision, as well as rules that include the traffic of other ACs that did not win the competition (primary AC) in the PPDU. However, these are not significantly related to the proposed invention, so a detailed explanation will be omitted.

[0101] As mentioned above, EDCA provides the EDCA Transmission Opportunity (EDCA TXOP) function, along with the ability to operate differentiated ACs based on the type of traffic (frames, packets, etc.) for QoS enhancement. EDCA TXOP refers to the time during which a particular AC's EDCAF (EDCA Function) can control the medium without interference from other devices when it acquires a channel access opportunity, i.e., becomes a TXOP holder. At this time, EDCA TXOP may be limited by an advertised TXOP limit set by the AP. The TXOP holder must complete its own transmission and the transmission of response frames that are responded to its transmission within the TXOP limit.

[0102] A TXOP holder can transmit multiple frames (multiple PPDUs) within an EDCA TXOP interval. As long as each frame is transmitted within the acquired TXOP interval, the TXOP holder can transmit multiple frames consecutively without performing a separate channel access procedure, such as a backoff procedure, between each frame transmission. In this case, if the multiple frames are MPDUs or A-MPDUs (Aggregated MAC protocol data units) that do not request an immediate acknowledgment, the transmission of multiple frames may occur at SIFS (short interframe space) or RIFS (reduced interframe space) intervals. In this case, if there is an MPDU or A-MPDU among the multiple frames that requests an immediate acknowledgment, the TXOP holder can transmit the frame requesting the immediate acknowledgment, receive the acknowledgment, and then transmit the next frame after SIFS.

[0103] In this case, traffic (packets, frames, etc.) from other ACs that are not the specific AC that holds the TXOP may also be transmitted together within the TXOP acquired by the TXOP holder (specific AC) when certain conditions are met. The transmission of traffic from other ACs that are not the TXOP holder within the TXOP may be due to TXOP sharing between ACs, and the details related to the aforementioned specific conditions are omitted as they are not relevant to the present invention.

[0104] As described above, a TXOP holder can transmit consecutive frames within the TXOP without performing a separate channel access procedure. This operation may be achievable when other terminals understand and protect the TXOP segment acquired by the TXOP holder. In other words, in order for the TXOP holder to acquire medium control authority over the EDCA TXOP segment, a procedure may be required to notify other terminals that the acquired TXOP segment is identifiable.

[0105] For this reason, a terminal (AC) that has become a TXOP holder or has started transmitting after completing the channel access procedure may attempt to make the TXOP segment known to other terminals by transmitting an RTS frame. In this case, an RTS frame means a frame in which the Type subfield (the 4th bit (B3) and 3rd bit (B2) of the Frame Control field) of the MAC frame header is set to 01b (Type=Control frame), and the Subtype subfield (the 8th bit (B7), 7th bit (B6), 6th bit (B5), and 5th bit (B4) of the Frame Control field) is set to 1011b. Other terminals that receive an RTS frame from a TXOP holder may set the NAV based on the duration-related information contained in the RTS frame, such as the value of the Duration field. The set NAV may be maintained at a non-zero value during the time corresponding to the TXOP holder's TXOP. However, a terminal designated as the target device for an RTS frame must respond with a CTS frame instead of setting the NAV based on the information in the RTS frame. In this case, the target device of the RTS frame sent to initiate TXOP is the TXOP responder and must send a CTS frame as a response to RTS (after receiving the RTS frame and SIFS). In this case, the Duration field of the responding CTS frame is set to a value calculated as: value indicated in the Duration field of the received RTS frame - CTS frame transmission time - SIFS. The terminal that receives the CTS frame can set the NAV based on the duration-related information contained in the CTS frame (e.g., the value of the Duration field).

[0106] Therefore, the NAV of the terminal that receives an RTS frame from the TXOP holder and the terminal that receives a CTS frame from the TXOP responder are set to 0 after the TXOP acquired by the TXOP holder has ended. This allows the Wi-Fi MAC mechanism to protect the TXOP holder and the TXOP responder from exchanging multiple frames in the TXOP without interference.

[0107] However, if a TXOP holder transmits an RTS frame as a non-HT duplicate PPDU across the primary 80MHz bandwidth, but the CTS frame (non-HT duplicate PPDU) responded to by the TXOP responder is only in the primary 40MHz bandwidth, the TXOP holder may use only the primary 40MHz or less primary bandwidth, for example, primary 20MHz, for frame exchange in the acquired TXOP. The CH_BANDWIDTH (a type of TXVECTOR parameter) of the PPDU transmitted by the TXOP holder must be set to a value equal to or less than the CH_BANDWIDTH_IN-NON_HT (a type of RXVECTOR parameter) of the received CTS frame. In this case, the RTS frame may be an RTS frame that allows the CTS frame to be responded to with a bandwidth smaller than the bandwidth from which the RTS frame was transmitted. The RTS frame may be an RTS frame transmitted with DYN_BANDWIDTH_IN_NON_HT (a type of TXVECTOR parameter) set to Dynamic. If DYN_BANDWIDTH_IN_NON_HT is set to static and an RTS frame is sent from the TXOP holder, the TXOP responder may respond with a CTS frame using the same bandwidth as the RTS frame was received.

[0108] Figure 9 shows a transmission / TXOP protection method using RTS frames and CTS frames according to an embodiment of the present invention.

[0109] Before transmitting a PPDU, the first station (STA1) transmits an RTS frame to the second station (STA2), which is the destination device of the PPDU. After the second station (STA2) recognizes that the received RTS frame is an RTS frame targeted at itself, it responds with a CTS frame after SIFS.

[0110] After receiving the RTS frame transmitted by the first station (STA1), the neighboring station (Neighbor STA) of the first station (STA1), namely STA1_Neighbor, sets the NAV based on the value indicated by the Duration field of the RTS frame. After receiving the CTS frame transmitted by the second station (STA2), the neighboring station of the second station (STA2), namely STA2_Neighbor, sets the NAV based on the information indicated by the Duration field of the CTS frame. After receiving the RTS / CTS frames, STA1_Neighbor and STA2_Neighbor determine that the virtual CS is busy while the set NAV (counter) remains a non-zero value and perform operations such as not decreasing the backoff counter. As a result, the neighboring terminals that receive the RTS / CTS frames do not attempt to transmit during the period when the NAV remains a non-zero value. Therefore, the first station (STA1) and the second station (STA2) are not interfered with by neighboring terminals while exchanging the PPDU and Ack frames.

[0111] Even if there is a hidden relationship where signals from the transmissions between the first station (STA1) and STA2_Neighbor are not detected, STA2_Neighbor can perform operations considering that the channel (channel, WM, Wireless medium) is in use while the first station (STA1) transmits the PPDU.

[0112] <TXOP Protection Using MU-RTS Trigger Frame> 11ax (6th generation Wi-Fi, Wi-Fi 6, HEW, High Efficiency WLAN) defines the MU-RTS Trigger / CTS frame exchange procedure and adds a function that allows APs to initiate TXOP using MU-RTS trigger frames (hereinafter referred to as MU-RTS, MU-RTS frames) and protect the TXOP frame exchange procedure. The MU-RTS frame is a type of trigger frame, and a station that receives a MU-RTS frame and whose AID12 (LSB 12 bits of the Association ID) is indicated from the User field contained in the MU-RTS frame simultaneously responds with a CTS frame. When an AP protects TXOP using MU-RTS frames, multiple stations respond with CTS frames, so TXOP can be protected from each peripheral device of multiple stations that are the target devices of DL MU PPDU (Down link multi-user PPDU). In addition, MU-RTS frames may be used to protect UL MU PPDU. More specifically, before requesting a Trigger-based PPDU (TB) from multiple stations using a trigger frame, the AP may send a MU-RTS frame, causing the multiple stations responding with a TB PPDU to respond with a CTS frame. In this case, the CTS frames responded by the multiple stations will guide each station's surrounding stations to configure NAVs that protect the TB PPDU and the Ack frames (Ack, Block Ack, etc.) sent after the TB PPDU. This means that legacy stations (STAs) that cannot recognize (parse, decode) the trigger frame and TB PPDU do not need to access the channel during the packet exchange sequence (or TXOP) initiated by the trigger frame.

[0113] Figure 10 shows a transmission / TXOP protection method using MU-RTS frames and CTS frames according to an embodiment of the present invention.

[0114] In the embodiment shown in Figure 10, prior to transmitting the MU PPDU, the AP transmits MU-RTS frames to the first station (STA1) and second station (STA2), which are the target devices for the MU PPDU. The first station (STA1) and second station (STA2) receive the MU-RTS frames and, after SIFS, respond to the MU-RTS frames with CTS frames, respectively.

[0115] Station STA1_Neighbor, a neighboring station of Station 1 (STA1), sets the NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by Station 1 (STA1). Station STA2_Neighbor, a neighboring station of Station 2 (STA2), sets the NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by Station 2 (STA2). After receiving the CTS frame, STA1_Neighbor and STA2_Neighbor perform actions such as determining that the Virtual Carrier Sense (CS) is busy and not decreasing the backoff counter while the set NAV (counter) is maintained at a non-zero value. Therefore, a peripheral terminal that has received the CTS frame will not attempt to transmit during the interval in which the NAV is maintained at a non-zero value. As a result, the AP will not be interfered with by peripheral terminals while it is transmitting the MU PPDU and Station 1 (STA1) and Station 2 (STA2) are transmitting the Ack frame.

[0116] The aforementioned trigger frame is a frame type defined in 11ax, where the Type (4th bit (B3) and 3rd bit (B2)) and Subtype (8th bit (B7), 7th bit (B6), 6th bit (B5), and 5th bit (B4)) subfields of the Frame Control field are set to 01b and 0010b, respectively. A trigger frame is a Control Type frame where the Type subfield of the Frame Control field is 01b, and the Subtype value 0010 indicates that it is a Trigger frame type. In 11ax, trigger frames are defined to allow an AP to request response frames from multiple stations at once, and MU-RTS frames are used by an AP to request CTS frames from multiple stations (non-AP STAs). Other trigger types besides the MU-RTS frame include the Basic Tigger frame which requests UL MU PPDU, the BRP trigger frame which requests Beamforming Report (Beamforming Report Poll Tigger frame), the MU-BAR Tigger frame (BlockAck request), the BSRP trigger frame which requests Buffer Status Report (Buffer Status Report Poll Tigger frame), the GCR MU-BAR trigger frame, the BQRP (Bandwidth Query Report Poll) trigger frame, and the NDP Feedback Report Ball (Poll) trigger frame. Since other trigger types besides the MU-RTS frame are not related to the content of this invention, a detailed explanation is omitted.

[0117] <Transmission delay problem caused by the time the media is occupied> As mentioned above, in conventional Wi-Fi, an STA (AP and non-AP STA) that has acquired channel access rights can send and receive frames with other STAs without interference from other STAs during the acquired transmission opportunity (TXOP) interval. TXOP protection, which allows STAs to send and receive frames without interference from other STAs, can be achieved by maintaining a non-zero value in the time interval corresponding to such a TXOP through a network allocation vector (NAV).

[0118] In conventional Wi-Fi, the NAV configuration method, designed to guarantee the authority of an STA (i.e., TXOP holder) that has acquired a TXOP through NAV settings, has aspects that make it difficult to achieve the target low-latency transmission in UHR. Specifically, an STA's channel access procedure for low-latency traffic may be interrupted by a NAV configured by a frame transmitted by another STA. This results in a delay in the transmission of low-latency traffic. In other words, the conventional Wi-Fi channel access mechanism, which aborts the channel access procedure to protect another STA's TXOP, can become a factor that hinders the transmission of low-latency traffic that should be completed in a short time. Also, if a PPDU transmitted by a particular STA occupies the medium for a very long time, that is, if a particular STA transmits a large PPDU, other STAs' channel access will be restricted during the time that the PPDU occupies the medium. If the channel access procedure of an STA that must transmit low-latency traffic is delayed by a long PPDU transmitted by another STA, the low-latency traffic may not be transmitted in a timely manner.

[0119] Therefore, in order to enhance UHR's support for low-latency traffic, methods must be introduced to address channel access delay issues caused by other STAs occupying the medium.

[0120] Figure 11 shows an example in which the transmission of low-latency traffic from other APs is delayed by TXOP of an AP according to an embodiment of the present invention.

[0121] Referring to Figure 11, the transmission from AP2 and AP3 may be delayed by the TXOP set by the frame transmitted from AP1 (e.g., an RTX frame).

[0122] Specifically, as shown in Figure 11, after AP1 acquires channel access rights, it can send an RTS frame to STA1 and become a TXOP holder after receiving a CTS frame response from STA1. AP1 can send a DL PPDU to STA1 in TXOP and receive an Ack frame. During the time interval in which AP1 acquires TXOP, AP2 and AP3 have NAVs set by the RTS frame and CTS frame, respectively, and therefore the NAV will not reach 0 until AP1's TXOP ends. Consequently, after AP2 receives the RTS frame, it generates LL traffic packets (traffic packets requesting low latency), but its channel access is restricted until AP1's TXOP ends, and it cannot process the low latency traffic. Similarly, after AP3 receives the CTS frame, it is unable to process the generated low latency traffic packets until AP1's TXOP ends.

[0123] <Multi-AP collaborative operation> The reason for introducing the TXOP concept in conventional Wi-Fi was to ensure that an STA that has acquired channel access rights can continue the frame exchange sequence without interference from other STAs for a certain period of time. This allows each STA to secure the frame exchange time it desires within the maximum time limit (TXOP limit) when it acquires channel access rights. This is a method that allows for more energy-efficient operation for each STA by ensuring the minimum amount of processing that can be obtained through a single channel access procedure. However, in terms of supporting low-latency transmission, which is the goal of UHR, the phenomenon of other STAs' channel access being restricted when a TXOP acquired by a particular STA can become a problem that makes it difficult to support low-latency transmission. Therefore, in UHR, it is necessary to appropriately adjust the conventional TXOP acquisition method and operation method in order to ensure that each STA's low-latency transmission is performed in a timely manner.

[0124] In the next-generation standard, UHR, the operation of each AP to enhance its service to its own BSS through coordination between APs, or to enhance service to STAs located at the edge of a specific AP's coverage where signal attenuation is high, is being considered. In particular, methods are being explored to increase wireless LAN efficiency and improve stability at the same time by sharing wireless resources (frequency resource and / or time resource) and / or coordinated transmission (cooperative transmission to a single STA) between APs performing coordinated operation.

[0125] As an example of sharing radio resources between APs, a specific AP can allocate (share) a portion of the frequency resources it has acquired for the duration of a TXOP to another AP, and the other AP can then use the allocated resources to provide services to STAs belonging to its BSS. This may be made possible by requirements-related information exchanged between the specific AP that acquired the TXOP and the other AP. Furthermore, the other AP can inform the specific AP in advance of information related to when it should transmit and the amount of radio resources (such as frequency BW or RU (resource unit)) it needs. When the specific AP acquires a TXOP, it can allocate (share) the radio resources it has acquired to the other AP based on the information it has received in advance from the other AP. In this case, the specific AP that acquired the TXOP (is the TXOP holder) may be called a Sharing AP, and the other AP that has been allocated (shared) radio resources from the specific AP may be called a Shared AP.

[0126] The process by which APs exchange information about mutually required radio resources can be understood as a multiplex AP coordination process. Furthermore, the operation of a specific AP allocating (sharing) its acquired radio resources while considering the requirements of other APs, and the operation of the other APs using these resources for transmission, can be considered a multiplex AP coordinated operation.

[0127] <Multi-AP Cooperation Methods for Low-Latency Traffic Services> Furthermore, multiple APs performing coordination operations can perform further adjustments to support service for low-latency traffic. For example, each AP can request other APs to operate in a manner that takes into account the low-latency traffic it should handle by exchanging information about the amount of low-latency traffic it should serve and its QoS (Quality of Service) requirements, or by exchanging information related to the R-TWT SP that it operates with its own BSS.

[0128] For example, the first AP can instruct the second AP, which is performing the adjustment operation, on information related to the start time and length of the R-TWT SP (Reverse-Turn-Wave SP) it is operating on its own BSS (Block Stop Signal), and the period of the R-TWT SP. In this case, if the second AP acquires a TXOP (Time-Operated Operation), it can terminate the TXOP before the first AP's R-TWT SP begins, thereby allowing the first AP to serve low-latency traffic in the R-TWT SP. That is, when the second AP receives a request frame from the first AP requesting channel adjustment, it can terminate its acquired TXOP before the start of a specific section (e.g., an R-TWT SP section) for the transmission of low-latency traffic by the first AP, based on the start time, length, and set period of that section included in the request frame.

[0129] <Multi-AP Cooperative Puncture Method for Low-Latency Traffic Services> As part of multiple AP cooperative operation, APs occupying a medium can occupy it in a pre-arranged manner. That is, each AP can acquire a TXOP or transmit a PPDU in a manner that does not occupy a specific bandwidth, based on pre-exchanged information, in order to allow other APs to approach the medium.

[0130] In other words, each AP can coordinate with each of the other APs for channel connectivity for sending and receiving traffic for low-latency transmission, and each AP can use the channel for channel connectivity (or traffic transmission / reception) within a specific time (e.g., R-TWT interval) even if the channel has been configured with a TXOP by another AP through the coordination procedure. For example, if the first AP configures a TXOP by sending and receiving frames with the first non-AP STA, the second AP may need to send and receive low-latency traffic with the second non-AP STA within the configured TXOP. In this case, the second AP cannot send or receive low-latency traffic until the TXOP ends because of the TXOP interval already configured by the first AP. However, since low-latency traffic requires a short delay for transmission and reception, a long TXOP can cause problems with traffic transmission and reception. Therefore, in this case, the second AP can send a frame (e.g., a request frame or beacon frame) requesting the first AP not to occupy the channel for sending and receiving low-latency traffic (e.g., the main channel for establishing channel connectivity to serve low-latency traffic). In this case, the request frame may include the BSSID, MAC address, and / or channel information for sending and receiving low-latency traffic of the second AP (e.g., channel information for channel connection). When the first AP receives a frame from the second AP, it does not have to occupy the channel based on the information contained in the frame. In this case, methods for not occupying the channel include using channel puncturing or sending information to the non-AP STA indicating that the channel will be deactivated. The channel for low-latency traffic may be used within the TXOP only in specific sections (e.g., R-TWT sections).In other words, in sections that do not overlap with the TXOP section set by the first AP, the second AP can freely send and receive low-latency traffic. Therefore, in sections within the TXOP that overlap with a specific section, the second AP can use that channel for low-latency traffic through channel coordination with the first AP.

[0131] In other words, through a channel coordination procedure, a specific channel may be prevented from being occupied by the first AP within a specific interval and may be used to serve low-latency traffic by the second AP. To put it another way, even if the first AP is capable of occupying or using a specific channel, if a coordination procedure with the second AP is performed, the first AP will not occupy the channel, and the second AP will be able to use the channel to send and receive low-latency data.

[0132] For example, if AP 1 anticipates that its TXOP will overlap in time with AP 2's R-TWT SP, AP 1 can acquire the TXOP in a way that does not occupy AP 1's primary channel. As a result, even while AP 1's TXOP is in progress, AP 2 does not occupy its primary channel, and can complete its own channel access procedure and then serve low-latency traffic to the R-TWT SP.

[0133] The specific operating procedure will be explained in more detail using an embodiment of the present invention described later. For the sake of explanation, the procedure will be mainly described in relation to the two APs (the first AP and the second AP), but each AP in an AP group containing multiple APs can perform the adjustment operation described later with each AP, or with multiple APs at once. In other words, the adjustment procedure and adjustment operation performed by the first AP and the second AP can be applied identically or similarly to the adjustment procedure and adjustment operation performed between the first AP and multiple second APs.

[0134] The first and second APs can perform a coordinated operation through prior coordination, agreeing not to occupy the BW containing each other's primary channels. Therefore, when the first and second APs acquire a TXOP, they can do so in a manner that they do not occupy a specific BW containing the other AP's primary channel. Such channel occupancy operation of the APs may be applied at all times, regardless of the presence or absence of the other AP's R-TWT SP, or it may be applied based on instructions given in another manner.

[0135] In other words, if the first AP receives instructions from the second AP in another way, it can only acquire a TXOP in a manner that does not occupy a specific bandwidth (BW) containing the second AP's main channel. For this purpose, the first and second APs may need to exchange information in advance regarding the location of each other's main channels. When an AP acquires a TXOP in this way, by not occupying a specific bandwidth (e.g., 80 MHz, 40 MHz, or 20 MHz) containing the other AP's main channel, the other AP can access the channel via its main channel. In this case, the method of not occupying the specific bandwidth containing the other AP's main channel may be to limit the bandwidth of the TXOP acquired by the AP itself (e.g., occupying only the 160 MHz bandwidth when it is possible to occupy the 320 MHz bandwidth) or by puncturing (preamble puncturing) the bandwidth containing the other AP's main channel. In this case, a PPDU transmission method that does not occupy a specific bandwidth containing the other AP's main channel may be understood as a PPDU transmission method that applies adjusted puncturing. In this case, a PPDU configured by a specific AP using coordinated puncturing may have preamble puncturing applied or have a configuration with restricted bandwidth so as not to occupy a specific bandwidth including the main channel of another AP. In this case, coordinated puncturing can be applied at the TXOP level, at the PPDU level, or at the consultation procedure level between two APs.

[0136] In other words, when the first AP acquires a specific TXOP, it is possible to acquire the TXOP excluding a specific BW that includes the second AP's main channel. In other words, when the first AP transmits a specific PPDU, it is possible to transmit the PPDU excluding a specific BW that includes the second AP's main channel. In other words, through consultation with the second AP, the first AP is possible to approach and occupy a channel excluding a specific BW that includes the second AP's main channel.

[0137] When tuned puncturing is applied on a PPDU basis, the first AP can occupy the bandwidth containing the second AP's primary 20MHz channel when acquiring the TXOP, and apply tuned puncturing starting from a specific PPDU transmitted in the middle of the TXOP.

[0138] For example, the first AP can transmit the first PPDU within the TXOP in a manner that occupies the second AP's main channel, and then transmit starting from the second PPDU in a manner that does not occupy a specific bandwidth, including the second AP's main channel. In this case, the second AP can ignore the NAV set by the first PPDU transmitted by the first AP and access the channel via its own main channel while the first AP's TXOP is in progress. This may be an acceptable NAV-ignoring operation because the second AP has coordinated with the first AP in advance. That is, the operation of the second AP ignoring the NAV set by the first AP may be understood as an operation permitted by coordination between the first and second APs. However, the operation of the second AP ignoring the first AP's NAV may only be permitted when the second AP intends to service LL traffic. Furthermore, the operation of the second AP ignoring the first AP's NAV may only be permitted for the R-TWT SP operated by the second AP.

[0139] As another example, the first AP transmits the first PPDU within the TXOP in a manner that occupies the second AP's primary channel, and then transmits the second PPDU in a manner that does not occupy a specific bandwidth including the second AP's primary channel, but it is possible to allocate frequency resources to the second AP via a PPDU transmitted before the second PPDU (e.g., the first PPDU) for the bandwidth including the second AP's primary channel. For example, the first AP can allow the second AP to access the channel by using the first PPDU to allocate a 242 tone size RU located on the second AP's primary 20 MHz channel. The first AP can then transmit the second PPDU using only the bandwidth excluding the bandwidth allocated to the second AP. In this case, the second PPDU may be considered a PPDU to which the adjusted puncturing configured according to one embodiment of the present invention is applied.

[0140] On the other hand, each AP may need to manage its non-AP STAs (Basic Service Assistance Teams) that are members of its BSS (Basic Service Set) to prevent them from occupying a specific bandwidth (BW) that includes the main channel of another AP that has coordinated with it. This means that when coordination occurs between the first and second APs, the member STAs of the BSS operated by the first and second APs will operate in a way that prevents them from approaching a specific BW bandwidth, in accordance with the coordination performed by the APs with which they are associated. This prevents the second AP's channel access from being interfered with by non-AP STAs associated with the first AP.

[0141] One method is for each AP to set a specific bandwidth containing the main channel of a remote AP as a disabled subchannel of its BSS (Basic Service Set) in order to prevent its own non-AP STAs from interfering with the remote AP's channel access. In this case, a disabled subchannel is a subchannel that the BSS instructs not to use, and if an AP instructs a member STA that a specific subchannel is disabled, the member STA will not approach that subchannel. In other words, the first AP can guide the BSS's non-AP STA to not approach the bandwidth containing the second AP's main channel by instructing the BSS's STA to set a subchannel in the bandwidth containing the second AP's main channel as a disabled subchannel. In this case, the method by which the AP instructs the non-AP STA about the disabled subchannel may be by using the Disabled Subchannel Bitmap subfield included in the EHT Operation element or by using the Disabled Subchannel Bitmap subfield included in the UHR Operation element. In this case, the action taken by a non-AP STA upon receiving information about a subchannel deactivated by the Disabled Subchannel Bitmap subfield may be the same as the action taken by an EHT non-AP STA for a subchannel indicated as disabled by the Disabled Subchannel Bitmap subfield. That is, it may be the application of preamble puncturing to the 20MHz subchannel indicated by the Disabled Subchannel Bitmap.

[0142] In another embodiment, each AP can instruct its BSS (Basic Service Set) non-AP STA with information related to subchannels whose access is restricted by adjustment operations and the time period (time, period, duration, etc.) during which access is restricted. In this case, the BSS STA must not access the channel instructed by the AP during the specified time interval. This operation, where the AP instructs information and time information on specific subchannels whose access is restricted by adjustment operations, and the non-AP STA refrains from accessing those specific subchannels based on this, is a new operation for UHR non-AP STA that was not defined in conventional Wi-Fi. The non-AP STA must not access the specific subchannel instructed by the AP during the specified time interval, and for this reason, preamble puncturing for the specific subchannel must be applied to the PPDU transmitted during the specified time interval. Alternatively, instead of using preamble puncturing, the non-AP STA can transmit without occupying the specific subchannel by transmitting a BW PPDU that does not occupy the specific subchannel. In this case, the specific subchannel that the AP instructs its BSS STA to include may be a subchannel that includes the primary subchannel of another AP performing multiplex AP coordination. In this case, the time interval that the AP instructs its BSS STA to include (information related to the time when access to the specific subchannel is restricted) may be the same as that instructed by the other AP performing multiplex AP coordination based on the R-TWT SP. More specifically, the time interval instructed by the AP may be the same time interval as the R-TWT SP of the other AP, or a time interval that includes the R-TWT SP.

[0143] In the context of multiple AP cooperative operation, an AP that designates at least one subchannel within the BSS's Operating BW as a Disabled / Coordinated subchannel must set the Disabled Subchannel Bitmap bit of the EHT Operation element corresponding to the designated subchannel to 1.

[0144] Furthermore, when a specific bit in the Disabled Subchannel Bitmap included in the UHR Operation element is set to 1, the AP must also set the bit in the Disabled Subchannel Bitmap of the corresponding EHT Operation element for the subchannel to which the specific bit corresponds to 1. In other words, a subchannel that is indicated as disabled by the UHR Operation element must also be indicated as disabled by the EHT Operation element.

[0145] However, a subchannel that is indicated as not disabled by the UHR Operation element may be indicated as disabled by the EHT Operation element. This may occur when a subchannel that is indicated as disabled only by the EHT Operation element is a subchannel whose access is restricted by the multiple AP cooperative operation. Furthermore, an AP may indicate that a specific subchannel is not disabled by the Disabled Subchannel Bitmap subfield included in the UHR Operation element, but may indicate that the said specific subchannel is disabled by the Disabled Subchannel Bitmap subchannel of the EHT Operation element. In this case, the said specific subchannel may be a subchannel that is indicated as disabled only by the EHT STA for the purpose of multiple AP coordination operation. In this case, the reason why the AP indicates that the said specific subchannel is disabled only by the EHT STA is that it is impossible for the EHT STA to adjust its access to the said specific subchannel in response to the coordination operation.

[0146] As a specific example of coordinated puncturing operation, when a first AP and a non-AP STA coupled to the first AP (an STA that is a member of the BSS operated by the first AP) transmit an initial frame (e.g., an RTS or MU-RTS frame) to acquire a TXOP, they may transmit in a manner that does not occupy a specific bandwidth containing the primary channel of the second AP. In this case, the first AP can determine the location and width of the specific bandwidth based on primary channel information and / or minimum bandwidth information (information instructed by the second AP to request that the first AP not occupy it) that has been previously instructed by the second AP. In this case, the method by which the first AP and the non-AP STA coupled to the first AP do not occupy a specific bandwidth containing the primary channel of the second AP may be to not transmit a duplicated PPDU in the specific bandwidth when transmitting a non-HT duplicated PPDU, or to apply preamble puncturing to the specific bandwidth. In this case, the above operation may only be permissible if the primary channels of the first AP and the second AP are different 20 MHz channels. In this case, the first AP and the second AP can pre-tune the position of the main channel in order to perform the operations described above. In this case, the operations described above may only be utilized when the main channel of the second AP exists among the 20MHz subchannels included in the operating bandwidth of the first AP.

[0147] An R-TWT SP is a TWT SP that is committed to prioritizing low-latency traffic, and APs and non-AP STAs send / receive frames with TIDs defined as low-latency traffic within the R-TWT SP interval. Additionally, the start of an R-TWT SP is set to overlap with a Quiet interval, and is characterized by being an interval where channel access for Legacy STAs is restricted.

[0148] An R-TWT SP is a type of Broadcast TWT that may be operated on each link, and a non-AP STA can join each R-TWT SP as a member STA. The broadcast TWT element sent to establish an R-TWT SP includes a Restricted TWT Parameter Set field, which includes a TID indicator that is considered low-latency traffic at that TWT SP.

[0149] Puncture refers to a technique for transmitting a PPDU without using certain subchannels located within the bandwidth (BW) from which the PPDU is transmitted. For example, an 80MHz PPDU can be transmitted without occupying a specific 20MHz bandwidth located within the 80MHz bandwidth from which the 80MHz PPDU is transmitted. This allows an STA to transmit an 80MHz PPDU even if a 20MHz subchannel is already occupied by another STA within the 80MHz bandwidth. In this case, the 80MHz PPDU transmitted by the STA is transmitted in a form in which the 20MHz subchannel occupied by the other STA is punctured. That is, the subcarrier located in the specific 20MHz bandwidth is not utilized for PPDU transmission. Therefore, even if a subchannel is included in the bandwidth of the PPDU transmitted by a particular STA, if puncture is applied to that subchannel, it can be identified as idle by other STAs. Preamble puncturing means that the puncturing technique described above has been applied to the PPDU preamble in a way that prevents the PPDU preamble from appearing for a specific 20 MHz subchannel.

[0150] At this time, the specific AP performing the adjusted puncturing and the non-AP STA of the specific AP transmit the PPDU by setting the bit corresponding to the specific BW in the TXVECTOR parameter INACTIVE_SUBCHANNEL to 1, in order to transmit a PPDU that does not occupy the specific BW, including the main channel of other APs.

[0151] Figure 12 shows the format of elements exchanged between APs for multiplexed AP cooperative puncturing, and the operating bandwidth and main channel settings of the APs to which multiplexed AP cooperative puncturing is applied, according to one embodiment of the present invention.

[0152] The names of the subfields described herein are for illustrative purposes only, and the names of each subfield are not limited to these and may be used by other names. Therefore, even if the names of each subfield differ from one another, they may be considered the same subfield in the embodiments of the present invention as long as the purpose and function of transmission are the same.

[0153] Figure 12(a) shows the element format exchanged between APs to perform multiple AP cooperative puncturing.

[0154] The Coordinated Puncturing Required subfield indicates whether the AP that transmitted the element requests the AP receiving the element to assist with coordinated puncturing. That is, when the first AP transmits the element to the second AP, it can transmit an element with the Coordinated Puncturing Required subfield set to 1 to request the second AP to apply coordinated puncturing to the bandwidth including its main channel.

[0155] Furthermore, the Coordinated Puncturing Required subfield can provide additional information regarding the conditions for coordinated puncturing support. For example, a value of 0 in the Coordinated Puncturing Required subfield means that support is not required; a value of 1 means that coordinated puncturing support is required based on the R-TWT SP; and a value of 2 means that coordinated puncturing support is always required. These values ​​can have different meanings.

[0156] In the example above, if a specific AP transmits an element whose subfield is designated as 1, other APs will have to apply adjusted puncturing when they acquire a TXOP that is expected to overlap with the R-TWT SP of the said AP. In this case, the element whose subfield is designated as 1 has a configuration that includes a TWT element.

[0157] In the example above, if a specific AP transmits an element instructed to have a subfield of 2, other APs will always have to apply adjusted puncturing until they receive an element in which the subfield is set to 0 or 1.

[0158] In the example above, if the subfield is set to a value that indicates no adjusted puncturing assistance is needed (e.g., 0), the remaining subfields described later can be reserved or omitted. That is, only when the subfield is set to a value that requests adjusted puncturing assistance can the subfields described later be included in the element or parsed in their original sense (not reserved).

[0159] The Primary Channel Info (Information) subfield indicates information related to the primary channel location of the AP transmitting the element. The Primary Channel Info subfield can be configured in the same way as the Channel Number field, which is parsed by the Global operating classes table.

[0160] The Minimum BW Info (Information) subfield contains information about the minimum BW that the AP transmitting the element requests from the AP receiving the element. More specifically, the Minimum BW Info subfield indicates the BW size of the bandwidth containing the primary 20MHz channel that the coordinated puncturing operation attempts to secure. For example, if the AP transmitting the element wishes to secure only the primary 20MHz bandwidth, it can set the Minimum BW Info subfield to a value that represents the 20MHz bandwidth. In this case, the AP receiving the element can help secure the primary 20MHz channel by sending a PPDU that does not occupy the primary 20MHz bandwidth of the AP transmitting the element. As another example, if the AP transmitting the element wishes to secure the primary 80MHz bandwidth, it can set the Minimum BW Info subfield to a value that represents the 80MHz bandwidth. In this case, the AP receiving the element can help secure the 80MHz bandwidth by sending a PPDU that does not occupy the primary 80MHz bandwidth (the 80MHz bandwidth including the primary 20MHz subchannel) of the AP transmitting the element.

[0161] If an element exchanged between APs for multiplexed AP cooperative puncturing includes a TWT element, the TWT element indicates information related to the R-TWT SP that the AP transmitting the element is operating in its BSS. Other APs receiving an element exchanged between APs for multiplexed AP cooperative puncturing from a particular AP will have to perform puncturing adjusted to take into account the R-TWT SP of the particular AP if the element includes a TWT element. In this case, the TWT element may only be included in the element if the Coordinated Puncturing Required subfield is indicated to a specific value.

[0162] Figure 12(b) shows the Operating BW and primary subchannel settings for AP1 and AP2, which are in a relationship that enables multiple AP cooperative puncturing.

[0163] Referring to Figure 12(b), AP1 and AP2 each have an Operating BW corresponding to 320 MHz. The primary 160 MHz bandwidth of AP1 and the primary 160 MHz bandwidth of AP2 are the same, while the primary 80 MHz bandwidth of AP1 and the primary 80 MHz bandwidth of AP2 are different. In this case, if AP2 instructs AP1 to use the Minimum BW Info subfield (see Figure 12(a)) to specify a value corresponding to the 80 MHz bandwidth, AP1 can apply the puncturing adjusted when acquiring TXOP and operate without occupying the overlapping bandwidth (AP1's secondary 80 MHz) with AP2's primary 80 MHz bandwidth. As a result, even during the time interval in which AP1 acquired TXOP, AP2 can perform channel approach procedures on the primary 20 MHz subchannel and then approach the frequency resources of the primary 80 MHz and secondary 160 MHz bandwidths.

[0164] Figure 13 shows an example of a frame exchange sequence to which Coordinated Puncturing for AP2 according to one embodiment of the present invention is applied.

[0165] AP1 and AP2 in Figure 13 are APs that have the same Operating BW and main channel settings as AP1 and AP2 shown in Figure 12(b).

[0166] AP2 sends a Coordination Request frame to AP1 in its primary 160MHz band. This Coordination Request frame has a configuration including the elements shown in Figure 12(a), and through this, AP2 requests AP1 to apply coordinated puncturing to its primary 80MHz band. After receiving the Coordination Request frame from AP2, AP1 responds with a Coordination Response frame accepting the requested coordination operation.

[0167] Therefore, in order for AP1 to not occupy AP2's primary 80MHz bandwidth when acquiring TXOP, AP1 occupies it in a 160+80MHz configuration, which is a punctured 80MHz bandwidth from the 320MHz PPDU. In this case, the punctured 80MHz bandwidth is the same as AP2's primary 80MHz bandwidth. Thus, AP1's TXOP is acquired and proceeds without occupying AP2's primary 80MHz bandwidth, and even during the process in which AP1 transmits a DL PPDU to STA1 and receives a BA (BlockAck) frame in response, AP2 can acquire channel access rights through EDCA performed on the primary 20MHz subchannel.

[0168] LL traffic, which should support low latency, is generated while AP1's TXOP is in progress, but AP2 can process the LL traffic in the primary 80MHz bandwidth without delaying its transmission until AP1's TXOP is complete.

[0169] Furthermore, even though AP1's TXOP is in progress, AP2 can apply puncturing operation adjusted by AP1 to match the R-TWT SP, allowing it to transmit / receive LL traffic in the P80MHz band that is not occupied.

[0170] Figure 14 shows yet another example of a frame exchange sequence to which adjusted puncturing for AP2 according to one embodiment of the present invention is applied.

[0171] AP1 and AP2 in Figure 14 are APs with the same Operating BW and main channel settings as AP1 and AP2 shown in Figure 12(b).

[0172] AP2 sends a Coordination Request frame to AP1 in its primary 160MHz band. This Coordination Request frame has a configuration including the elements shown in Figure 12(a), and AP2 is requesting AP1 to apply coordinated puncturing to its primary 80MHz band. After receiving the Coordination Request frame from AP2, AP1 responds with a Coordination Response frame accepting the requested coordination operation.

[0173] AP1 transmits the RTS frame and DL PPDU#1 across the 320MHz bandwidth because DL PPDU#1 does not overlap temporally with AP2's R-TWT SP in order to obtain TXOP. However, since DL PPDU#2 overlaps with AP2's R-TWT SP, AP1 transmits DL PPDU#2 in the form of a 160+80MHz PPDU, thereby maintaining TXOP without occupying AP2's primary 80MHz bandwidth.

[0174] AP2 can transmit / receive LL traffic in the P80MHz band in the R-TWT SP section because AP1 has applied puncturing operation adjusted to match the R-TWT SP, even though AP1's TXOP is in progress.

[0175] In this case, AP2 ignores the NAV set by the RTS frame DL PPDU#1 transmitted by AP1, even if the NAV is not 0, and approaches its own P80MHz band. This is AP2's NAV-ignoring operation, taking into account that AP1, the TXOP holder, is the device that coordinated with itself.

[0176] Figure 15 shows an example of an element format that an AP performing multiple AP cooperative operation according to one embodiment of the present invention transmits to its BSS STA to instruct it on channel access restriction-related information.

[0177] Figure 15(a) shows the UHR Operation Parameters field format. The Disabled Subchannel Bitmap Present subfield indicates whether the UHR Operation element contains a Disabled Subchannel Bitmap subfield. The Disabled Subchannel Bitmap Present subfield is set to 1 when the UHR Operation element contains a Disabled Subchannel Bitmap subfield, and to 0 when it does not. The Disabled Subchannel Bitmap Resolution subfield indicates how many 20MHz subchannels each bit of the Disabled Subchannel Bitmap contained in the UHR Operation element corresponds to. The Disabled Subchannel Bitmap Resolution subfield is Reserved when the Disabled Subchannel Bitmap Present subfield is indicated as 0. When the Disabled Subchannel Bitmap Resolution subfield is set to 0, it means that each bit of the Disabled Subchannel Bitmap contained in the UHR Operation element corresponds to one 20MHz subchannel; when set to 1, it means that each bit of the Disabled Subchannel Bitmap contained in the UHR Operation element corresponds to two 20MHz subchannels; and when set to 2, it means that each bit of the Disabled Subchannel Bitmap contained in the UHR Operation element corresponds to four 20MHz subchannels.In this case, the setting and meaning of the Disabled Subchannel Bitmap Resolution subfield are for illustrative purposes only, and it is possible to indicate / interpret it in other ways, such as 1 meaning one 20MHz subchannel, 2 meaning two 20MHz subchannels, and 3 meaning four 20MHz subchannels.

[0178] Figure 15(b) shows the UHR Operation element format. The UHR Operation element includes a Disabled Subchannel Bitmap subfield, where each bit of the Disabled Subchannel Bitmap subfield corresponds to each subchannel in the Operating BW. In this case, a particular bit of the Disabled Subchannel Bitmap subfield can correspond to multiple subchannels, which may be determined by the Disabled Subchannel Bitmap Resolution subfield, as explained using Figure 15(a). The Disabled Subchannel Bitmap subfield can have a size of 1, 2, or 4 octets. In this case, the size of the Disabled Subchannel Bitmap subfield is determined based on the Operating BW size of the BSS and the Resolution information indicated in the Disabled Subchannel Bitmap Resolution subfield.

[0179] For example, if the BSS Operating BW is 640MHz, a 4-octet Disabled Subchannel Bitmap consisting of 32 bits corresponding to each of the 32 20MHz subchannels included in the 640MHz may be specified. In this case, the Disabled Subchannel Bitmap Resolution subfield is set to a value that means each bit of the Disabled Subchannel Bitmap corresponds to one 20MHz subchannel. If the Disabled Subchannel Bitmap Resolution subfield indicates that each bit of the Disabled Subchannel Bitmap corresponds to two 20MHz subchannels, the Disabled Subchannel Bitmap transmitted by an AP of a BSS with a 640MHz operating BW will have a size of 2 octets. If the Disabled Subchannel Bitmap Resolution subfield indicates that each bit of the Disabled Subchannel Bitmap corresponds to four 20MHz subchannels, the Disabled Subchannel Bitmap transmitted by an AP of a BSS with a 640MHz operating BW will have a size of 1 octet.

[0180] As another example, if the BSS Operating BW is 320MHz, a 2-octet Disabled Subchannel Bitmap may be specified, consisting of 16 bits corresponding to each of the 16 20MHz subchannels included in the 320MHz. Therefore, for an AP of a BSS with a 320MHz operating BW, the Disabled Subchannel Bitmap subfield cannot be configured with a size of 4 octets. If the Disabled Subchannel Bitmap Resolution subfield indicates that each bit of the Disabled Subchannel Bitmap corresponds to two 20MHz subchannels, then the Disabled Subchannel Bitmap transmitted by an AP of a BSS with a 320MHz operating BW will have a size of 1 octet.

[0181] The UHR Operation Parameters field and UHR Operation element described above may be transmitted as part of a Beacon frame, Probe Response frame, or combined Response frame sent by the AP, or as part of a frame sent by the AP to change the Operating Mode.

[0182] Figure 15(c) shows the Coordinated Puncturing element format. The Coordinated Puncturing Subchannel Bitmap subfield is a subfield that indicates the information of the subchannel to which puncturing coordinated by multiple AP cooperative operation should be applied. The number of bits contained in the Coordinated Puncturing Subchannel Bitmap subfield is (maximum operating BW supported by UHR / 20MHz). For example, if the maximum operating BW supported by UHR is 640MHz, the Coordinated Puncturing Subchannel Bitmap subfield may consist of 32 bits.

[0183] The first bit of the Coordinated Puncturing Subchannel Bitmap subfield corresponds to the lowest-positioned 20MHz subchannel on the frequency axis among the subchannels included in the Operating BW, and the x-th bit corresponds to the x-th 20MHz subchannel on the frequency axis among the subchannels included in the Operating BW. Therefore, when the Operating BW of the BSS is limited, only the first x bits of the Coordinated Puncturing Subchannel Bitmap subfield correspond to each 20MHz subchannel, and the bits from x+1 onwards do not need to correspond to a subchannel. Consequently, bits of the Coordinated Puncturing Subchannel Bitmap subfield for which there is no corresponding 20MHz subchannel are set to the already set value (e.g., 0).

[0184] When a specific bit in the Coordinated Puncturing Subchannel Bitmap subfield is set to 1, it means that the subchannel corresponding to that specific bit is a subchannel to which coordinated puncturing must be applied. Therefore, if a specific bit in the Coordinated Puncturing Subchannel Bitmap subfield received from an AP is indicated as 1, a non-AP STA should transmit a PPDU without occupying the subchannel corresponding to that specific bit. In other words, when a non-AP STA is indicated as having a specific bit in the Coordinated Puncturing Subchannel Bitmap subfield set to 1, it must set the bit in the TXVECTOR parameter INACTIVE_SUBCHANNEL of the PPDU it transmits that corresponds to that specific bit (the bit corresponding to the same subchannel) to 1.

[0185] The Coordinated Puncturing Offset subfield indicates information related to when coordinated puncturing must be applied. The Coordinated Puncturing Offset subfield is parsed together with the Coordinated Puncturing Interval subfield to indicate when coordinated puncturing should be applied. Specifically, the value indicated by the Coordinated Puncturing Offset subfield means that coordinated puncturing must be applied starting from the same time as the TSF (Timing Synchronization Function) %Interval (the value indicated by the Coordinated Puncturing Interval subfield). In this case, the % symbol in the formula above represents the modulation operator (remainder operator). That is, the Coordinated Puncturing Offset subfield and the Coordinated Puncturing Interval subfield play a role in indicating a TSF timer value with an interval indicated by the Coordinated Puncturing Interval subfield, and it means that PPDUs sent starting from the same time as the TSF timer value indicated must have coordinated puncturing applied. For example, if the Coordinated Puncturing Offset subfield is set to a value meaning 100 and the Coordinated Puncturing Interval subfield is set to a value meaning 1000, the TSF values ​​indicated by both subfields will be 100, 1100, 2100, 3100, and so on.

[0186] The Coordinated Puncturing Duration subfield indicates how long coordinated puncturing should be applied based on the TSF timer values ​​identified by the Coordinated Puncturing Offset and Coordinated Puncturing Interval subfields. In other words, a non-AP STA must instruct coordinated puncturing to be applied to PPDUs transmitted over the time interval indicated by the Coordinated Puncturing Duration subfield, starting from the point indicated by the Coordinated Puncturing Offset and Coordinated Puncturing Interval subfields. For example, if the Coordinated Puncturing Offset subfield is set to a value meaning 100, the Coordinated Puncturing Interval subfield is set to a value meaning 1000, and the Coordinated Puncturing Duration is instructed to be 30, then a non-AP STA must apply coordinated puncturing when sending PPDUs at points in time with TSF values ​​of 100 to 130, 1100 to 1130, 2100 to 2130, and 3100 to 3130.

[0187] In this context, TSF refers to the local timer used by Wi-Fi devices to achieve timing sync. The AP indicates its local timer value in the Time Stamp field of the Beacon frame, and the non-AP STA adjusts its TSF timer based on the Time Stamp value received from the AP.

[0188] <Method for enhancing protection between BSSs using Multi-AP Coordination> As described above, each AP can configure a disabled subchannel for its own BSS through adjustment, thereby ensuring that the main BSS channels of other APs remain in an idle state even when a particular AP's BSS occupies the medium.

[0189] After performing a channel access procedure (e.g., EDCA) on the primary channel, a Wi-Fi STA decides whether to approach a subchannel by considering whether the subchannel was previously identified as idle in PIFS duration. For example, if the CCA result of a specific subchannel performed by a particular STA is BUSY, the STA must transmit in a manner that does not occupy that subchannel. This is a very basic method of channel access by Wi-Fi STAs, and a detailed explanation is omitted.

[0190] In short, the CCA method for subchannels defined in Wi-Fi is based on whether the signal measured on the subchannel is above a specific threshold (e.g., -62dBm or -72dBm), and does not utilize NAV information. Due to these limitations, Wi-Fi STA can only provide a lower level of protection for frame exchange sequences that do not occupy its primary channel compared to frame exchange sequences that do occupy its primary channel.

[0191] Therefore, when a first BSS uses a subchannel to which multiple AP-coordinated puncturing has been applied, an STA that performs channel access procedures such as EDCA does not know in advance that other subchannels are occupied by the first BSS when the channel access procedure is completed on the subchannel (the STA's main channel). Instead, it must directly determine whether the subchannel is busy or idle using PHY layer CCA. If the CCA result performed by the STA on the subchannel is idle, the STA may attempt to access the subchannel, potentially interfering with the transmission of the first BSS, which was previously occupying the subchannel. This problem may arise because the operation of conventional Wi-Fi STAs to evaluate the idle / busy state of subchannels relies solely on the results of PHY layer CCA without utilizing NAV (Network Allocation Vector). Consequently, a situation may occur where the transmission of a BSS that has disabled a specific subchannel through multiple AP coordination fails due to interference from another BSS that has completed the channel access procedure on that specific subchannel.

[0192] As briefly explained in the example above, if a BSS transmission using multiple AP-coordinated puncturing fails due to interference from other coordinated BSSs, contrary to the original intention of multiple AP-coordinated puncturing to achieve more harmonious operation, a side effect may occur in which each coordinated BSS experiences more transmission failures.

[0193] <Sharing information on exclusive channels to enhance protection> Two BSSs performing multiple AP-coordinated puncturing would exchange information with each other regarding the channels occupied by the frame exchange sequence taking place within their own BSSs. Based on this exchanged information, they would need to determine whether or not a secondary channel (another subchannel other than the primary channel, e.g., a secondary channel) is occupied by the other BSS, and then decide whether or not to approach the secondary channel.

[0194] According to one embodiment of the present invention, a subchannel disabled by multiplexed AP-coordinated puncturing may be permitted to transmit frames of a specific format. More specifically, a subchannel disabled by multiplexed AP-coordinated puncturing may be permitted to transmit ICFs (Initial Control frames, e.g., RTS / MU-RTS / BlockAck Request frames and / or other types of Control frames) and ICRs (Initial Control Response frames, e.g., CTS / BlockAck frames, etc.), while the transmission of data frames (PPDUs including Data frames) may be restricted. That is, the puncturing applied by multiplexed AP-coordinated puncturing may apply only to data frames (Data PPDUs). In this case, the specific frame includes information related to the channel (BW information and / or subchannel information and / or puncturing pattern) occupied by the frame exchange sequence in which the STA that transmitted the frame participates. Therefore, an STA that receives the specific frame can determine which subchannel the TXOP of the BSS to which the STA that sent the specific frame belongs is occupying, and can consider a subchannel occupied by another BSS's TXOP to be busy (virtual busy) until the TXOP ends. In other words, even if the PHY layer CCA result of a specific subchannel is idle, it is possible to determine that the specific subchannel is busy (virtual busy) during the interval when another BSS is using that subchannel, thereby protecting the transmission of the other BSS.

[0195] Figure 16 shows an example of a method for exchanging dedicated channel information to enhance protection between BSSs (Basic Service Sets) that have undergone Multi-AP Coordination according to one embodiment of the present invention.

[0196] Referring to Figure 16, BSS1 and BSS2 are BSSs that have undergone multiple AP coordination to utilize multiple AP-coordinated puncturing. Considering that the main channel of BSS1 is Ch_1, BSS2 has set Ch_1 as the disabled subchannel of the BSS. The STA of BSS2 transmits an ICF to start the frame exchange sequence in a form that occupies the disabled subchannel Ch_1, and the STA of BSS1 receives the ICF or the ICR, which is the response frame to the ICF. The ICF and ICR transmitted by the STA of BSS2 contain information related to the channels occupied by the frame exchange sequence performed by the STA of BSS2, and in the example in Figure 16, it indicates that the regions corresponding to Ch_3 and Ch_4 will be occupied by the frame exchange sequence. The STA of BSS1 that receives the ICF and / or ICR recognizes that the frame exchange sequence of BSS2 will be performed on Ch_3 and Ch_4, and determines that Ch_3 and Ch_4 are Virtual BUSY for the time interval in which the frame exchange sequence will be performed. At this time, information about the time interval in which the frame exchange sequence takes place is indicated in the Duration ID field of the ICF and ICR frames. Therefore, the STA of BSS1 completes the channel approach procedure on Ch_1, which is idle, but starts the frame exchange sequence in a way that does not occupy Ch_3 and Ch_4, considering that the virtual CCA results for Ch_3 and Ch_4 are busy.

[0197] <Channel occupancy time sharing for enhanced protection> Another way to enhance protection between coordinated BSSs may be to modify the channel access method to secondary subchannels, taking into account the time that other BSSs occupy the channel.

[0198] Frames transmitted on a subchannel disabled by multiple AP-adjusted puncturing can serve to cause an STA receiving the frame on the subchannel to set a specific timer value. In this case, the specific timer is used to determine the threshold used for the subchannel's CCA. More specifically, an STA with a specific timer of 0 can use a first value as the CCA threshold when performing PHY layer CCA on the subchannel, while an STA with a specific timer that is not 0 can use a second value as the CCA threshold when performing PHY layer CCA on the subchannel. In this case, the first value is greater than the second value. For example, the first value may be -62 dBm or -72 dBm, and the second value may be -82 dBm. That is, an STA with a specific timer that is not 0 would have to determine a secondary subchannel that is considered IDLE when the timer is 0 as BUSY.

[0199] For this purpose, the first AP, which has performed M-AP coordination for puncturing coordinated with the second AP and multiple APs, can make known to its member STAs of the first BSS it operates information for identifying the second BSS operated by the second AP (e.g., the MAC address of the second AP and / or the BSS Color of the second BSS). When an STA of the first BSS receives a frame it has received from the STA of the second BSS, it sets its own specific timer based on the Duration / ID field of the received frame. The method of setting the specific timer may be to set the value of the specific timer as the time indicated by the Duration / ID field. However, if the existing value of the specific timer is greater than the value indicated by the Duration / ID field of the newly received frame, the value of the specific timer is not reset. When an STA with a specific timer value that is not 0 performs a CCA on a secondary subchannel, it applies a lower value as the CCA threshold than when the specific timer value is 0.

[0200] As described above, if a specific BSS's STA modifies and uses the CCA threshold for its secondary subchannel, the likelihood of that specific BSS's STA interfering with the frame exchange sequence of another BSS in progress on its subchannel is reduced, thus resulting in reduced interference between BSSs of APs that have undergone multiple AP coordination.

[0201] Figure 17 shows an example of a method by which the CCA threshold is modified to enhance protection between BSSs that have undergone multiple AP adjustment according to one embodiment of the present invention.

[0202] Referring to Figure 17, BSS1 and BSS2 are BSSs that have undergone multiple AP adjustment to utilize multiple AP-adjusted puncturing. Considering that the primary channel of BSS1 is Ch_1, BSS2 has set Ch_1 as the disabled subchannel of the BSS. The STA of BSS2 transmits an ICF to initiate the frame exchange sequence, occupying the disabled subchannel Ch_1, and the STA of BSS1 receives the ICF or the ICR, which is the response frame to the ICF. Upon receiving the ICF and / or ICR transmitted by the STA of BSS2, the STA of BSS1 changes the CCA threshold for the subchannel from x dBm to y dBm. In this case, y is a value smaller than x, meaning that the subchannel CCA threshold of the BSS1 STA is set lower during the period when the frame exchange sequence of BSS2 is in progress. The STA of BSS1 completes the channel approach procedure on Ch_1, which is idle, and determines that Ch_3 and Ch_4, among the subchannels to which a low CCA threshold is applied, are busy. Therefore, the STA of BSS1 starts the frame exchange sequence in a way that does not occupy the subchannels used by BSS2.

[0203] On the other hand, two BSSs that have performed multiple AP coordination to perform multiple AP coordinated puncturing can ignore the NAV set on the other BSS and continue the channel access procedure. In other words, the STA of the first BSS, which has set the NAV (Basic NAV) based on a frame transmitted by the STA of the second BSS, can determine the virtual CCA result for the main channel as IDLE and proceed with the channel access procedure, even if the NAV timer set by the second BSS is not 0.

[0204] In other words, the STAs of two BSSs that have performed multiple AP coordination to use multiple AP coordinated puncturing will not determine the virtual CCA result for the main channel as busy, even if the Basic NAV (Inter-BSS NAV) is set by each other. This is because the NAV set by the other BSS is the NAV set by a frame transmitted on the other BSS's deactivated subchannel, and the transmitted frame was sent only to indicate the occupation status of the subchannel, not to set the NAV for the main channel. As an example, when the STA of the first BSS receives a frame transmitted by the STA of the second BSS, it sets a timer for its own subchannel (information about the time interval during which the subchannel should be considered busy) based on the Duration / ID field value of the received frame and the channel information contained in the received frame, and either does not set a timer for the main channel (NAV timer, Basic / Inter-BSS NAV timer) or ignores it after setting it. This allows for the exchange of occupied channel and occupied time information between the STA of the first BSS and the STA of the second BSS, and the frame exchange sequence of each BSS can be performed without interfering with the channel approach procedure of other BSSs. In this case, the STA of a particular BSS does not need to set the (Basic / Inter-BSS)NAV timer when it receives a frame transmitted by another BSS.

[0205] Thus, when each BSS's STA receives a frame from another BSS, it can decide whether or not to set a NAV, or to ignore the NAV after setting it, based on whether or not the other BSS is a BSS that has performed multiple AP coordination for multiple AP-coordinated puncturing with its own BSS. To help each STA distinguish frames received from other BSSs, an AP can provide its BSS's STA with a list of APs (or BSSs) with which it has performed multiple AP coordination for multiple AP-coordinated puncturing. For example, a first AP that has performed M-AP coordination for multiple AP-coordinated puncturing with a second AP can make information related to the second BSS operated by the second AP (e.g., the MAC address of the second AP and / or the BSS Color of the second BSS) public to the member STA of the first BSS it operates. If the STA of the first BSS determines that a frame it has received was sent from the STA of the second BSS, it may choose not to set a NAV (Inter-BSS NAV or Basic NAV), or it may ignore the NAV set by the frame sent by the second BSS and perform channel access (determining the virtual CCA result of the main channel as IDLE). In this case, the STA of the first BSS may perform actions based on the BSS Color information of the PPDU containing the received frame (information obtained by the BSS Color field of the Preamble) or the TA field or RA field information of the received frame in order to determine which BSS sent the received frame. In one embodiment, if the TA field or RA field of the received frame matches the AP MAC address of another BSS specified by the AP, the STA of the first BSS does not need to set a NAV based on the received frame. In another embodiment, if the TA field or RA field of the received frame matches the AP MAC address of another BSS specified by the AP, the STA of the first BSS may ignore the NAV set in the received frame.

[0206] <Method and Procedure for Adjustment between APs> Among the methods for adjusting the AP to transmit and receive low-latency traffic between the AP and the non-AP STA within the TXOP set by other APs described in FIGS. 11 to 17, the AP attempting to perform the adjustment exchanges information necessary for the adjustment operation (e.g., primary channel information, minimum puncturing BW information, R-TWT SP information), etc., and then operates its own TXOP (acquires the TXOP and determines the subchannels for acquiring the TXOP (applies puncturing, BW restrictions, etc.)) based on the information indicated by the peer AP.

[0207] Therefore, the APs performing the adjustment operation need to be able to send / receive the necessary information to each other. In this case, a method different from the information exchange by the STAs belonging to the same BSS may be utilized. Further, since the STAs belonging to the same BSS use the same primary channel, they can exchange information with each other by utilizing the primary channel or the frequency resources including the primary channel. However, the information exchange between the APs of BSSs using different subchannels as the primary channel may be restricted using the primary channel. As an example, when the first AP using the first subchannel as the primary channel and the second AP using the second subchannel as the primary channel attempt to exchange information, the first AP and the second AP must exchange information on the primary channel of their own BSS and / or the primary channel of the peer AP's BSS, respectively. That is, a predefined method for information exchange between APs using different subchannels as the primary channel is required.

[0208] In addition, a procedure for two different APs using different subchannels as the primary channel to discover each other for multi-AP adjustment also needs to be predefined. This is to prevent a situation where a specific AP discovers the peer AP but the peer AP cannot discover the specific AP.

[0209] For reference, in conventional Wi-Fi, to help non-AP STAs easily obtain information about other APs, each AP sometimes included a Neighbor Report element and a Reduced Neighbor Report element in the beacon frames it transmitted. In this case, the elements transmitted by each AP contained information such as the operating channel / class information and TSF (timing synchronization function) offset information of the Neighbor AP known to the AP transmitting the element. Therefore, a non-AP STA that received the element from a specific AP could obtain information (main channel information and beacon transmission timing information) for receiving beacon frames from other APs. In other words, a non-AP STA could discover other APs using the Neighbor Report element and / or Reduced Neighbor Report element received from a specific AP.

[0210] However, conventional Wi-Fi standards did not specify how each AP should verify Neighbor AP information when transmitting the element. Therefore, each AP could omit information about its own Neighbor APs from the element, even if it had one. As a result, each AP had no reason to perform a thorough discovery operation to verify its Neighbor APs, and could operate by including only information about Neighbor APs it was aware of in the element. In other words, even if a non-AP STA receives a Neighbor Report element and / or Reduced Neighbor Report element from a specific AP, it is impossible to verify whether the Neighbor APs verified by the element represent all of the specific AP's Neighbor APs.

[0211] Thus, while APs that adhere to conventional Wi-Fi standards may acquire / instruct information about their Neighbor APs, they may not take action to acquire information about all Neighbor APs, and the actions taken to identify Neighbor APs may differ from one another. As a result, the first AP may recognize the second AP as its Neighbor AP, but the second AP may not recognize the first AP as its Neighbor AP (i.e., not recognize the existence of the first AP). This asymmetrical Neighbor AP recognition phenomenon is not a major problem in conventional Wi-Fi operation that is only used to provide information about Neighbor APs to non-AP STAs, but if this phenomenon occurs between APs attempting M-AP coordination, it can cause coordination failure. Generally, APs that use the same subchannel as their primary channel are likely to be in a "Discovered" state because they can receive beacon frames transmitted by each other, while APs that use different subchannels as their primary channels are less likely to be aware of each other because they cannot receive each other's beacon frames.

[0212] For example, the first access point (AP) may discover the second AP by receiving a Measurement Report frame from a non-AP STA associated with it, and then attempt to perform M-AP coordination with the second AP. However, if the second AP is unaware of the first AP's existence, the series of steps taken by the first AP to perform M-AP coordination with the second AP will be wasted without being recognized by the second AP. In other words, the M-AP coordination procedure introduced by the next-generation standard to improve the efficiency of wireless LANs will instead result in the unnecessary use of resources.

[0213] Therefore, procedures need to be introduced to ensure that APs attempting to perform M-AP coordination are aware of each other's presence (Discovery) and can send / receive frames for M-AP coordination.

[0214] According to one embodiment of the present invention, an AP can induce a receiving AP to perform coordination with it by transmitting a frame that indicates its intention to perform multiplex AP coordination (hereinafter referred to as M-AP coordination) or its capability to perform M-AP coordination. In this case, the frame may be a beacon frame or another type of management frame. In this case, the frame may be transmitted in non-HT duplicated PPDU format or in a form in which 20MHz UHR PPDU is duplicated. That is, an AP transmitting the frame on a 160MHz BW can transmit a 20MHz non-HT PPDU or a 20MHz UHR PPDU on each of the eight 20MHz subchannels included in the 160MHz BW.

[0215] Thus, the reason why frames transmitted by an AP for M-AP adjustment should be transmitted in duplicate PPDU format is to allow a device receiving the PPDU on any of the subchannels included in the BW on which the PPDU is transmitted (for example, a partner AP or a non-AP STA associated with a partner AP) to receive the frames included in the PPDU on its own primary 20MHz channel. Furthermore, if a specific AP transmits a frame for M-AP adjustment in 20MHz duplicated PPDU format, a device using each subchannel occupied by the PPDU as its primary channel can verify the frame transmitted by that specific AP by receiving only the 20MHz PPDU (part of the duplicated PPDU) that is received occupying its own primary channel. In other words, a BSS device (AP and / or non-AP STA) that uses a subchannel other than the primary channel of the AP that transmitted the frame as its primary channel can also verify (decode) the frame transmitted by the AP through 20MHz PPDU reception.

[0216] In this way, each AP can transmit its own M-AP adjustment frame in a 20MHz duplicated PPDU, allowing it to be received by BSS equipment (APs and / or non-AP STAs) that use different subchannels as their primary channels. Thus, it is possible to exchange M-AP adjustment frames between BSS APs that use different subchannels as their primary channels.

[0217] A specific AP that receives a frame for M-AP adjustment transmitted by another AP can discover the existence of the other AP and recognize that the other AP intends to perform M-AP adjustment. If the specific AP also intends to perform M-AP adjustment with the other AP, it can transmit a frame for M-AP adjustment on an RU located on the main channel of the other AP when transmitting a PPDU that occupies the main channel of the other AP. In this case, the specific AP can transmit the PPDU that occupies the main channel of the other AP in a format that is a non-HT duplicated PPDU or a duplicated 20MHz UHR PPDU.

[0218] As described above, frames transmitted by an AP to allow other APs to recognize its presence have a similar function to beacon frames transmitted by an AP to allow non-AP STAs to recognize its presence and capabilities. For the sake of brevity, in this invention, frames transmitted by an AP to be discovered by other APs are named M-AP beacon frames.

[0219] An M-AP beacon frame may contain basic information about the AP that transmits the frame and the BSS operated by that AP. In this case, the M-AP beacon frame includes information that helps the receiving AP that receives the M-AP beacon frame to understand whether the AP that transmitted the M-AP beacon frame and the receiving AP (the receiving AP) are in a relationship where they can perform coordination. In other words, an AP that receives an M-AP beacon frame can determine whether it and the AP that transmitted the M-AP beacon frame can perform M-AP coordination operations based on the information indicated in the M-AP beacon frame.

[0220] In this case, the specific method by which an AP that receives an M-AP beacon frame can determine whether it and the other AP (the AP that sent the M-AP beacon frame) are in a relationship where they can perform M-AP coordination operations is based on whether the main channel of the AP that sent the M-AP beacon frame is a subchannel included in its own Operating BW. Furthermore, if the main channel of the AP that sent the M-AP beacon frame is a subchannel not included in its own Operating channel, the AP that receives the M-AP beacon frame must determine that M-AP coordination between itself and the AP that sent the M-AP beacon frame is impossible. The reason why the main channel of the first AP that received the M-AP beacon frame is not checked to see whether it is included in the Operating channel of the second AP that sent the M-AP beacon frame is because the situation in which the M-AP beacon frame sent by the second AP is received by the first AP only occurs when the operating channel of the second AP (the BSS operated by the second AP) includes a subchannel corresponding to the main channel of the first AP.

[0221] Furthermore, even if an AP that receives an M-AP beacon frame confirms that the primary channel of the AP that sent the frame is included in its own operating channel, it must also confirm whether the other AP will support the M-AP coordination operation it intends to perform. The M-AP coordination operations that can be used between APs may include at least one of the following: 1. Multi-AP Spatial Reuse 1) A spatial reuse method that uses information exchanged in advance between APs performing adjustments. 2) Each AP can adjust its transmit power for spatial reuse. 3) A Shared AP, having identified the target device for transmission by the Sharing AP (which is the TXOP holder), can reuse its spatial capabilities based on previously acquired interference-related information. 2.Multi-AP Coordinated resource sharing 1) Coordinated TDMA: A Sharing AP, which is a TXOP holder, allocates a portion of the time interval included in the TXOP it has acquired to a Shared AP. The Shared AP then uses the allocated time interval to service the non-AP STA of the BSS it operates (by sending DL PPDUs or trigger frames). 2) Coordinated OFDMA: A Sharing AP, which is the TXOP holder, can allocate some of the RUs included in the BW that acquired the TXOP to the Shared AP, and the Shared AP can use the allocated RUs to send DL PPDUs or trigger frames. 3.Multi-AP R-TWT protection (R-TWT adjustment, Coordinated R-TWT) 1) The adjusted APs exchange R-TWT (restricted-TWT) information operated on their respective BSSs. Each AP restricts the TXOP length or the subchannels from which it acquires a TXOP, taking into account when the R-TWT SP of other APs begins. This allows each AP to access the channel at the start of the R-TWT SP. 4.Multi-AP joint sounding / transmission 1) The adjusted AP will perform sounding with the STA belonging to the BSS operated by each AP, thereby enabling joint transmission. 2) When a joint transmission occurs, the transmissions of the specific AP and other APs may be transmitted simultaneously to the specific STA associated with the specific AP. 3) When a joint transmission occurs, if the specific AP transmits to a specific STA that it has associated with, other APs can perform nulling (MIMO technology) to reduce interference to the specific STA. 5.Multi-AP Coordinated Puncturing 1) APs that have performed M-AP adjustment apply puncturing to each other's main channels to prevent a situation where transmissions from their own BSS prevent other APs' BSS from accessing the channel. This is the operation provided in the present invention described above, and a detailed explanation is omitted.

[0222] As described above, when multiple M-AP coordination operations are defined, each AP can support all M-AP coordination operations or only some of them. Therefore, each AP must determine whether or not to perform M-AP coordination after confirming, based on the information indicated by the M-AP beacon frame of the other AP, whether the other AP will support the M-AP coordination operation it intends to perform with the other AP. For example, an AP that receives an M-AP beacon frame transmitted from another AP will determine, based on the information contained in the received M-AP beacon frame, whether the other AP will support the M-AP coordination it intends to perform with the other AP. Only if the other AP supports the M-AP coordination will the AP proceed with the procedure to perform M-AP coordination with the other AP. On the other hand, if it is determined that the other AP will not support the M-AP coordination it intends to perform with the other AP, the AP does not need to attempt M-AP coordination with the other AP. In this case, the action that an AP takes to perform M-AP coordination with the sender of the M-AP beacon frame it received may be to send its own M-AP beacon frame to a bandwidth that occupies the bandwidth including the main channel of the other AP. In this case, the action that an AP takes to perform M-AP coordination with the sender of the M-AP beacon frame it received may be to send its own M-AP coordination request frame to a bandwidth that occupies the bandwidth including the main channel of the other AP. In this case, the M-AP coordination request frame is a frame that contains information instructing the M-AP coordination operation that it supports and / or information instructing the M-AP coordination operation that it intends to perform with the other AP. Furthermore, the M-AP coordination request frame may have a configuration that includes an indicator of the other AP with which it intends to perform M-AP coordination. In this case, the AP that receives the M-AP coordination request frame can recognize that the AP that sent the M-AP coordination request frame intends to perform M-AP coordination with it, and can recognize what type of M-AP operation coordination is being requested.

[0223] An AP that sends an M-AP adjustment request frame can enable the AP that receives the frame to recognize that an M-AP adjustment request has been made to it by sending a PPDU containing an indicator related to the AP it intends to adjust to. At this time, the AP that sends the M-AP adjustment request frame can enable the other AP to recognize that an M-AP adjustment has been requested to it by indicating the MAC address of the other AP in the RA field (Receiver address field) of the M-AP adjustment request frame. At this time, the AP that sends the M-AP adjustment request frame can enable the other AP to recognize that an M-AP adjustment has been requested to it by indicating the color of the BSS operated by the other AP in the BSS Color field included in the Preamble of the 20MHz duplicated UHR PPDU it sends. If an AP sending an M-AP adjustment request frame instructs the BSS Color of the PPDU to be the color of the BSS operated by the other AP, a non-AP STA, which is a member of the BSS operated by the other AP, will recognize the PPDU as an intra-PPDU, and as a result the M-AP adjustment frame will receive a higher level of protection from the non-AP STA (this has effects such as preventing the non-AP STA from attempting spatial reuse operations based on the BSS color, but this is not directly related to the main concept that this invention aims to provide, so a detailed explanation will be omitted).

[0224] The process by which APs having different main channels discover each other, recognize the type of M-AP adjustment supported by the other AP, and perform M-AP adjustment will be explained in detail in the embodiments of the present invention described later.

[0225] Figure 18 shows an example of a frame format used in the multiplex AP adjustment process according to one embodiment of the present invention.

[0226] The frame designations described in Figure 18 are for illustrative purposes only, and each frame is not limited to these; other designations may be used. Furthermore, the designations of each field included in each frame may be changed, or some fields may be omitted. Moreover, the functional aspects of each frame, as described by the AP discovery / M-AP adjustment procedure according to the present invention, should be understood as the content of the invention.

[0227] Figure 18(a) shows the M-AP beacon frame format.

[0228] An M-AP beacon frame contains an AP identifier, which is used to identify the AP that sent the frame. Specifically, an M-AP beacon frame may include an AP ID field. The AP ID field indicates the BSS Color value of the BSS operated by the AP that sent the M-AP beacon frame. Alternatively, the AP ID field may indicate the MAC address of the AP that sent the M-AP beacon frame. In other words, the AP ID field is a field that helps a receiving device of an M-AP beacon frame to recognize the AP that sent the frame, and it may instead indicate other types of information that can identify the sending AP.

[0229] An M-AP beacon frame may be a type of Broadcast frame.

[0230] An M-AP beacon frame contains information about the operating channel of the BSS operated by the AP that transmits the frame. Specifically, an M-AP beacon frame includes an Operating Class field. The Operating Class indicated by the Operating Class field can be used to obtain Channel starting frequency information, Channel spacing information, and Channel set information. Therefore, a device that receives an M-AP beacon frame can determine the operating channel information (Channel set and BW (bandwidth)) of the BSS operated by the AP that transmitted the M-AP beacon frame.

[0231] An M-AP beacon frame contains information about the primary channel of the BSS operated by the AP that transmits the frame. Specifically, an M-AP beacon frame includes a Channel Number field. The Channel Number field is parsed in conjunction with the operating channel information (indicated in the Operating Class field) and has the function of identifying one of the subchannels included in the operating channel (the primary channel).

[0232] An M-AP beacon frame contains information related to the TSF value of the AP that sends the frame. Specifically, an M-AP beacon frame includes a Timestamp field. The Timestamp field indicates the TSF timer value of the STA (AP STA and / or non-AP STA) that sends the frame. The Timestamp field included in an M-AP beacon frame may be the same size as, or smaller than, the Timestamp field (8 octets) included in a typical beacon frame. The Timestamp field is used when an AP that receives an M-AP beacon frame calculates its own TSF offset in relation to the AP that sent the M-AP beacon frame. An AP attempting to synchronize timing with the AP that sent the M-AP beacon frame can adjust its own TSF timer using the Timestamp field of the received M-AP beacon frame.

[0233] An M-AP beacon frame indicates the type of M-AP coordination operation supported by the AP sending the frame. Specifically, an M-AP beacon frame may include an M-AP Coordination Support Bitmap field. Each bit in the M-AP Coordination Support Bitmap may be set to indicate whether or not a particular M-AP coordination function is supported. For example, the first bit of the M-AP Coordination Support Bitmap field (e.g., B0) can be set to 1 to indicate support for a particular M-AP coordination function, or to 0 to indicate that the particular M-AP coordination function is not supported.

[0234] Figure 18(b) shows the M-AP Coordination Request frame format.

[0235] An M-AP adjustment request frame is a frame sent by an AP that intends to perform M-AP adjustment with a remote AP. Its basic function is to instruct the remote AP on the type of M-AP adjustment it intends to perform.

[0236] An M-AP adjustment request frame may be a type of action frame.

[0237] The M-AP Coordination Request frame contains an AP identifier used to identify the AP that sent the frame. Specifically, the M-AP Coordination Request frame may include an AP ID field. The AP ID field indicates the BSS Color value of the BSS operated by the AP that sent the M-AP Coordination Request frame. This is the same as the AP ID field included in the M-AP beacon frame described above, and therefore, a redundant explanation is omitted.

[0238] An M-AP coordination request frame may include a Dialog Token field. The Dialog Token field is used to determine which M-AP coordination request frame a response frame is for when a response frame is received after sending multiple M-AP coordination request frames. In other words, APs that send M-AP coordination request frames configured in different ways must set the Dialog Token field of each request frame to a different value, and when a response frame is received, they must determine which M-AP coordination request frame it is a response to by checking the value of the Dialog Token field in the received frame.

[0239] The M-AP Coordination Request frame includes the Operating Class field, Channel Number field, Timestamp field, and M-AP Coordination Support Bitmap. These fields have the same settings / analysis methods and functions as the fields with the same names included in the M-AP beacon frame, and therefore, redundant explanations are omitted.

[0240] An M-AP coordination request frame includes a Requested M-AP Coordination field. The Requested M-AP Coordination field instructs the AP sending the frame to perform an M-AP coordination operation with the other AP. The Request M-AP Coordination field may be composed of a Bitmap, and each bit in the Request M-AP Coordination field may correspond to the same M-AP coordination as the bit at the same position in the M-AP Coordination Support Bitmap field. That is, a specific M-AP coordination corresponding to a bit at a specific position in the M-AP Coordination Support Bitmap corresponds to the bit at the same position in the Requested M-AP Coordination field. For example, if bit B0 of the M-AP Coordination Support Bitmap corresponds to M-AP Coordinated Puncturing, then bit B0 of the Requested M-AP Coordination field also corresponds to M-AP Coordinated Puncturing. Each bit in the Request M-AP Coordination field indicates whether or not the AP intends to coordinate the corresponding M-AP function with the other AP. In other words, an AP sending an M-AP coordination request frame can set a specific bit in the Request M-AP Coordination field to 1 to request coordination of a specific M-AP function with the other AP, or set the specific bit to 0 to not request coordination for the specific M-AP function. In this case, each bit in the Request M-AP Coordination field may be set to 1 only if the bit in the corresponding M-AP Coordination Support Bitmap is set to 1. In other words, an AP sending an M-AP coordination request frame must only request coordination for the M-AP coordination functions it supports from the other AP. Furthermore, an AP sending an M-AP coordination request frame should only request coordination for M-AP coordination functions that the other AP has indicated it supports.In other words, an AP sending an M-AP coordination request frame must only request coordination for M-AP coordination functions that both it and the other AP support. An AP sending a Requested M-AP Coordination field can request coordination for multiple M-AP coordination functions at once by setting one or more bits in that field to 1.

[0241] Figure 18(c) shows the M-AP Coordination Response frame format.

[0242] An M-AP adjustment response frame is a response frame sent by an AP that has received an M-AP adjustment request frame.

[0243] The M-AP coordinated response frame includes a Dialog Token field, which serves to distinguish which request frame the response frame is for. In other words, the AP sending the response frame sets the Dialog Token field of the response frame to the same value as the value indicated in the Dialog Token field of the target request frame to which it is sending the response.

[0244] The M-AP Coordination Response Frame includes a Control field. The Control field indicates what types of M-AP Coordination Information fields are included in the frame (M-AP Info field in Figure 16(c)). In other words, the configuration of the M-AP Info field changes depending on the setting of the Control field.

[0245] The M-AP Info field may contain multiple M-AP Coordination Information fields. Each M-AP Coordination Information field indicates the information necessary when making adjustments to each M-AP adjustment function. For example, the M-AP Coordination Information field associated with M-AP Coordinated Puncturing may include information regarding the minimum puncturing BW. The information necessary for adjusting each M-AP adjustment function may differ from one another, and in this invention, the provided frame format does not specify the adjustment method for each M-AP adjustment function but rather relates to a general M-AP adjustment procedure and frame format, and a detailed explanation of the configuration of the M-AP Coordination Information fields is omitted.

[0246] Each M-AP Coordination Information field included in the M-AP Info field of the M-AP Coordination Response Frame relates to the M-AP coordination function requested by the corresponding M-AP Coordination Request Frame. However, an AP responding with an M-AP Coordination Response Frame does not need to include M-AP Coordination Information fields for M-AP coordination functions it does not intend to coordinate in the M-AP Info field. In other words, an AP sending an M-AP Coordination Response Frame can selectively accept only the M-AP coordinations it intends to perform from among those requested by the request frame it received. In this case, the selective acceptance method may include the M-AP coordination to be accepted and its associated M-AP Coordination Information fields in the M-AP Info field of the response frame, but may not include the M-AP coordinations to be not accepted and their associated M-AP Coordination Information fields. Therefore, if an AP that has sent an M-AP adjustment request frame and has received an M-AP adjustment response frame finds that the type of M-AP adjustment function to be adjusted, as confirmed by the received M-AP adjustment response frame, is different from the type it desires, it may refuse to perform the M-AP adjustment indicated in the response frame.

[0247] Alternatively, an AP that has sent an M-AP adjustment request frame to another AP and then received an M-AP adjustment response frame can request a different form of M-AP adjustment than the one instructed by the M-AP adjustment response frame it received by sending an M-AP adjustment response frame (a response in the same format) as a reply to the M-AP adjustment response frame. In other words, an AP performing M-AP adjustment can refuse to accept the M-AP adjustment function requested by the other AP and send an M-AP adjustment response frame to the other AP to instruct it to perform the M-AP adjustment function it desires.

[0248] Furthermore, the M-AP Info field may include M-AP Coordination Information fields for M-AP coordination functions not requested in the request frame. If the M-AP Info field further includes M-AP Coordination Information fields for M-AP coordination functions not requested in the request frame, the M-AP coordination functions corresponding to the further included M-AP Coordination Information fields may be understood as having been requested for coordination by the AP sending the response frame to the AP sending the request frame. In other words, the AP sending the M-AP coordination response frame can request coordination for M-AP coordination functions that were not requested by the AP sending the M-AP coordination request frame. The types of M-AP coordination functions that the AP sending the response frame can request from the AP sending the request frame are limited to the M-AP coordination functions supported by both APs.

[0249] Figure 18(d) shows the M-AP Coordination Confirm frame format.

[0250] The M-AP Coordination Confirm frame is a frame sent by an AP that has received an M-AP Coordination Response frame when it intends to accept or reject the establishment of the M-AP coordination instructed by the received M-AP Coordination Response frame. The M-AP Coordination Confirm frame includes a Dialog Token field, which is set to the same value as the Dialog Token field of the M-AP Coordination Response frame that the M-AP Coordination Confirm frame intends to accept / reject. The M-AP Coordination Confirm frame also includes a Status Code field, which may indicate Accept or Reject (Refuse). Therefore, the AP that sent the M-AP Coordination Response frame can confirm whether the M-AP coordination it instructed has been accepted or rejected by the other AP based on the Status Code value of the returned M-AP Coordination Confirm frame. If the Status Code field indicates acceptance of an M-AP adjustment, the M-AP Coordination Confirm frame may include an M-AP Coordination Information field for the M-AP adjustment being adjusted. If the Status Code field indicates rejection of an M-AP adjustment, the M-AP Coordination Confirm frame may include information regarding the reason for rejection (e.g., Reason Code).

[0251] Figure 19 shows an example of a multiple AP adjustment process between APs according to one embodiment of the present invention.

[0252] Referring to Figure 19, AP1 transmits M-AP beacon frames not only on its primary 20MHz channel but also on other subchannels included in its operating channel. By receiving the M-AP beacon frames transmitted by AP1 via its main channel, AP2 can obtain information about AP1's operating channel, main channel information, and the M-AP adjustment functions supported by AP1, along with the fact that AP1 is present.

[0253] AP2 transmits an M-AP adjustment request frame on a subchannel included in its operating channel for the purpose of performing M-AP adjustment with AP1. Upon receiving the M-AP adjustment request frame transmitted by AP2, AP1 obtains information such as AP2's operating channel, main channel information, the M-AP adjustment functions supported by AP2, and the type of M-AP adjustment requested by AP2.

[0254] AP1 sends an M-AP Coordination Response frame in response to the M-AP Coordination Request frame requested by AP2. After AP2 receives the M-AP Coordination Response frame from AP1, it sends an M-AP Coordination Confirm frame to complete the M-AP Coordination procedure. Although not shown in Figure 17, AP1 sends an Ack response to the M-AP Coordination Confirm frame, and AP2 considers the M-AP coordination to be complete (set) when it receives an Ack response to the M-AP Coordination Confirm frame it sent. In other words, the M-AP coordination is completed when the successful transmission of M-AP Coordination Confirm frames is confirmed between both APs.

[0255] <Removal of multiple AP adjustments (Delete, teardown, expired)> As in the embodiment of the present invention described above, the AP confirms the M-AP adjustment function supported by the other AP and performs M-AP adjustment with the other AP through a series of processes.

[0256] According to one embodiment of the present invention, an M-AP adjustment established between two APs can be modified or canceled by a pre-agreed procedure. For example, an AP that has performed an M-AP adjustment can cancel the established M-AP adjustment by sending a frame requesting the cancellation of the M-AP adjustment to the other AP. In this case, the AP that receives the request to cancel the M-AP adjustment from the other AP must always accept the request. This means that the M-AP adjustment is a procedure that is performed / completed through consultation between both APs, and therefore, if one AP does not intend to conduct consultation, the other AP cannot continue to apply the M-AP adjustment.

[0257] In other words, if a specific channel (e.g., the primary channel) becomes available for use in a specific section (e.g., the R-TWT section) through a coordination procedure with other APs to serve low-latency traffic within a TXOP configured by another AP, the use of that specific channel through such a coordination procedure may be terminated by a procedure agreed upon between the AP or the other AP. That is, an AP or another AP can perform a coordination termination procedure by sending a termination request frame to the other AP requesting the termination of use of the specific channel in a specific section. Upon receiving the termination request frame, the AP can accept the termination request, and once the termination request is accepted, the use of that channel ends.

[0258] In addition to the procedure for canceling the above adjustment, if a specific frame that should be periodically transmitted from an AP requesting the use of a specific channel is not received within a certain period, other APs can determine that the AP does not intend to use the specific channel and cancel the use of that channel. In other words, if an AP is deemed inoperable, such as when the power to the other AP is shut down, other APs do not need to continue permitting the AP to use the specific channel and can cancel the adjustment for that channel. For example, an AP that can use a specific channel within a specific interval through an adjustment procedure must transmit a specific frame to other APs at regular intervals to inform them of the use of the specific channel. If this specific frame is not transmitted within a certain period, other APs can consider that the adjustment procedure for the specific channel has been completed and can cancel the adjustment for that channel. In this case, the transmission period of the specific frame may be longer than the transmission period of a general beacon frame. Also, the specific frame must be transmitted at least once within a certain period, or within a certain time after a previously transmitted specific frame has been transmitted. In this case, the specific frame may be a beacon frame (for example, an M-AP (multi-AP) beacon frame).

[0259] On the other hand, if adjustments have been made to multiple M-AP adjustment functions between the two APs, it is possible to cancel only some of the M-AP adjustments. For example, if the first AP and the second AP have made adjustments to the first M-AP adjustment function and the second M-AP adjustment function, the first AP can request the cancellation of only the first M-AP adjustment function or the second M-AP adjustment function.

[0260] Also, this may occur when one of the power supplies of the APs that have performed M-AP adjustment ends, or when the operation mode of one of the APs is changed, and the previously established M-AP adjustment no longer functions effectively. When such a situation occurs, an AP that believes the M-AP adjustment is still valid has an unnecessary burden of having to perform operations for M-AP adjustment and manage information in the absence of a peer AP. To solve such a problem, each AP that has performed M-AP adjustment can consider that the M-AP adjustment established with the peer AP is no longer valid and has ended if a frame transmitted from the peer AP is not confirmed within a certain period (e.g., M-AP Timeout). That is, if an AP no longer receives a frame transmitted from the peer AP, it can perform operations considering that the M-AP adjustment established with the peer AP has expired (expire, teardown).

[0261] Therefore, each AP must manage so that the M-AP adjustment established with the peer AP is not released by transmitting at least one PPDU in a form that occupies the primary channel of the peer AP within the above-mentioned certain period. At this time, the frame included in the PPDU may be an M-AP beacon frame.

[0262] FIG. 20 shows an example of a multiple AP adjustment teardown frame format according to an embodiment of the present invention.

[0263] An AP can end the M-AP adjustment performed with a peer AP by transmitting an M-AP Coordination Teardown frame to the peer AP.

[0264] An M-AP Coordination Teardown frame may include an AP ID field. The AP ID field of an Individually Addressed M-AP Coordination Teardown frame indicates the ID (BSS Color or the AP's MAC address) of the receiving AP of the M-AP Coordination Teardown frame. The AP ID field of a Broadcast M-AP Coordinated Teardown frame indicates the ID (BSS Color or the AP's MAC address) of the AP sending the M-AP Coordination Teardown frame. A Broadcast M-AP Coordination Teardown frame is used when the AP sending the frame intends to tear down the coordination with all APs with which it has performed M-AP coordination. That is, an AP that receives a Broadcast M-AP Coordination Teardown frame can cancel the M-AP coordination it performed with the AP indicated in the AP ID field. In this case, the RA field (Receiver Address, Address 1 field) of the Individually Addressed M-AP Coordination Teardown frame indicates a frame with the MAC address of a specific AP. In this case, the Broadcast address M-AP Coordination Teardown frame means a frame in which the RA field of the frame is set to a predetermined specific value (for example, each bit is set to 1) and all STAs are instructed to receive it.

[0265] The M-AP Coordination Teardown frame may include a Teardown All field (1 bit) that indicates whether to release all established M-AP coordinations. The AP that transmits the M-AP Coordination Teardown frame can set the Teardown All field to 1 and request the deletion of all M-AP coordination functions that have been coordinated with the peer AP. When the Teardown All field is set to 0, the M-AP coordination functions to be released are specified by the M-AP Coordination Bitmap field. However, if there is only one M-AP coordination function that has been coordinated by the AP transmitting the M-AP Coordination Teardown frame with the peer AP, the Teardown All field must always be set to 1.

[0266] The M-AP Coordination Teardown frame has a configuration that includes the M-AP Coordination Bitmap field when the Teardown All field is indicated as 0. Each bit of the M-AP Coordination Bitmap field corresponds to an M-AP coordination function. The AP that transmits the M-AP Coordination Teardown frame indicates which M-AP coordination function it desires to release by setting to 1 the bit of the M-AP Coordination Bitmap field corresponding to the M-AP coordination function for which release is requested among the M-AP coordination functions that have been coordinated with the peer AP.

[0267] <Maintenance of Multiple AP Coordination> Traditionally, Wi-Fi APs can change the operating parameters of the BSS they manage at any time while the BSS is running. For example, an AP can decide to change the BSS's operating channel or change the EDCA parameter set. In this case, the AP takes steps to notify non-AP STAs belonging to the BSS so that they can recognize the changed BSS parameters and change their operation appropriately. In particular, if a parameter considered important is changed, the AP manages it as a critical update and takes actions to make non-AP STAs aware that the update has occurred (or is scheduled to occur). Specifically, the AP helps non-AP STAs recognize whether a critical update has occurred by including a Check Beacon field in the TIM (Traffic Indication Map) frame it transmits. STAs that recognize a critical update from the TIM frame must receive a beacon frame to obtain (update) information related to the parameter affected by the critical update. The situation in which an AP manages something as a critical update is when any one of the following elements included in the beacon frame undergoes the following changes: (Wi-Fi 6 standard) a)Inclusion of a Channel Switch Announcement element b)Inclusion of an Extended Channel Switch Announcement element c)Modification of the EDCA parameters element d)Inclusion of a Quiet element e)Modification of the DSSS Parameter Set f)Modification of the HT Operation element g)Inclusion of a Wide Bandwidth Channel Switch element h)Inclusion of a Channel Switch Wrapper element i)Inclusion of an Operating Mode Notification element j)Inclusion of a Quiet Channel element k)Modification of the VHT Operation element l)Modification of the HE Operation element m)Insertion of a Broadcast TWT element n)Inclusion of the BSS Color Change Announcement element o)Modification of the MU EDCA Parameter Set element p)Modification of the Spatial Reuse Parameter Set element q)Modification of the UORA Parameter Set element r)Insertion of an Index Adjustment Factor field in a Multiple BSSID Configuration element

[0268] Thus, when a critical update occurs (or is scheduled to occur) in the BSS it operates, the AP must recognize the changed parameters and provide information so that member STAs can operate correctly. This allows both APs and non-AP STAs to operate in a unified manner regarding operating channels, operating modes, channel access rules, channel quieting, etc.

[0269] Conventionally, Wi-Fi only required parameter management between the AP and the BSS member STA operated by the AP. However, as considered in one embodiment of the present invention, when adjustments are made between APs, parameter management between APs also becomes necessary. In other words, if an AP that has performed M-AP adjustment changes a specific parameter, the other AP that has also performed M-AP adjustment must be aware of this and act accordingly. Therefore, a procedure is needed for APs to notify each other that their parameters have been changed (or are scheduled to be changed). At this time, the already established M-AP adjustment can be updated based on the changed parameter.

[0270] For example, if one of two APs performing M-AP Coordinated Puncturing changes the main channel of the BSS, the other AP can assist in puncturing the changed main channel of the aforementioned AP. In other words, a subchannel that has been statically punctured (disabled subchannel) by M-AP Coordinated Puncturing can be changed to another subchannel by the other AP's change of main channel.

[0271] As another example, if one of two APs performing M-AP coordinated puncturing operates a new R-TWT SP, the other AP can support coordinated puncturing for the new R-TWT SP interval. In other words, the time interval in which puncturing occurs through M-AP coordinated puncturing can be extended by the addition of the other AP's R-TWT SP. Conversely, the time interval in which puncturing occurs through M-AP coordinated puncturing can be reduced by the deletion (removal) of the other AP's R-TWT SP.

[0272] As another example, if one of two APs performing M-AP Coordinated Resource Sharing changes the Operating BW of its BSS, the other AP must consider the changed Operating BW of that AP when deciding which resources to share with it. For example, if the other AP reduces its Operating BW from the existing 80MHz to 40MHz, the AP must allocate resources to the other AP only for the 40MHz band including the other AP's primary channel, and not to any other bands in the 80MHz band other than the primary 40MHz.

[0273] Therefore, just as a conventional Wi-Fi AP instructs non-AP STAs, which are members of its BSS, to recognize BSS parameter updates, when an AP that has performed M-AP adjustments intends to change its own BSS parameters, it will need to instruct the other AP to recognize its BSS parameter update. In this case, the types of M-AP critical updates that an AP that has performed M-AP adjustments must instruct to change its BSS parameters may include at least one of a) to e) described below. An AP that has experienced an M-AP critical update must transmit a frame containing the element that caused the critical update on its operating channel in a 20MHz duplicated format so that the other AP can recognize the content of its critical update.

[0274] As an example, an AP that has undergone a major update due to (a) described below must transmit a frame containing a Channel Switch Announcement element (Channel Switch Announcement frame) in a 20MHz duplicated format so that the other AP can become aware of its channel switch plan.

[0275] As another example, an AP that has undergone a major update due to a) to e) described below must transmit beacon frames on all subchannels (IDLE subchannels) included in the operating channel, not just the main channel, every TBTT. In other words, the beacon frames must be transmitted as 20MHz duplicated PPDU (20MHz non-HT duplicated PPDU or 20MHz duplicated UHR PPDU). a) When you plan to change the operating channel of BSS (1) That is, the beacon frame that it transmits contains a Channel Switch Announcement element, (2) when an Extended Channel Switch Announcement element is included, (3) when a Wide Bandwidth Channel Switch element is included, or (4) when a Channel Switch Wrapper element is included b) when planning to add / change the BSS's Quiet duration (1) that is, when the Beacon frame transmitted by itself includes a Quiet element, or (2) when a Quiet Channel element is included c) when planning to change the BSS's Operating BW (1) that is, when changing the HT Operation element and / or VHT Operation element and / or HE Operation element and / or EHT Operation element and / or UHR Operation element included in the Beacon frame transmitted by itself to a value different from the existing one d) when planning to change the BSS's color (1) that is, when the BSS Color Change Announcement element is included in the Beacon frame transmitted by itself e) when planning to change (such as adding / removing) the R-TWT SP operating in the BSS (1) that is, when the Beacon frame transmitted by itself includes a Broadcast TWT element indicating a new R-TWT SP or removing an existing R-TWT SP

[0276] In the case of a) described above, the AP's Operating class / channel (the frequency position of the operating channel and / or the position of the main channel) is changed. This change in the AP's operating channel either makes it impossible to perform further coordinated operation with the other AP that has undergone M-AP adjustment, or it causes a change in the channel to which the adjustment operation is applied.

[0277] For example, if the first AP, which has performed M-AP coordination with the second AP, changes its operating channel, the operating channels of the first and second APs may not overlap at all. In this case, there are no actions that the first and second APs can take for M-AP coordination, and therefore, the M-AP coordination established between the two APs must be terminated. At this time, the first AP should notify the second AP of its planned operating channel change, and the second AP can consider the M-AP coordination established with the first AP to be terminated at the time the first AP changes its operating channel.

[0278] As another example, if the first AP, which has made adjustments for M-AP coordinated puncturing with the second AP, changes its main channel, the subchannel to which the second AP must apply puncturing (the subchannel corresponding to the first AP's main channel) may change. In this case, the first AP can instruct the second AP to change its main channel, so that the second AP performs coordinated puncturing on its changed main channel.

[0279] In case b), this applies when an AP sets a Quiet duration for channel measurement or R-TWT SP. If a partner AP recognizes that a specific AP has set a Quiet duration, it can set the same Quiet duration as the specific AP in its own BSS. In other words, an AP that has performed M-AP adjustments can help each STA perform more accurate channel measurement or obtain channel access rights at the start of R-TWT SP by adjusting its own Quiet duration to the same time interval.

[0280] In case c), the AP changes the BSS's Operating BW, which can result in a situation where further coordinated operation with the partner AP that has performed M-AP adjustments becomes impossible, or it can cause a change in the types of RUs (Resource units) that can be allocated through resource sharing.

[0281] For example, if the first AP, which has performed M-AP coordination with the second AP, changes its Operating BW, the operating channels of the first and second APs may not overlap at all. In this case, there are no actions that the first and second APs can take for M-AP coordination, and therefore, the M-AP coordination established between the two APs must be terminated. At this time, the first AP should inform the second AP of its Operating BW change plan so that it can be recognized, and the second AP can consider the M-AP coordination established with the first AP to have ended at the time the first AP changes its Operating BW.

[0282] As another example, as a result of the first AP adjusting for the second AP and M-AP Coordinated Resource Sharing and changing its Operating BW, the types of RUs that the second AP can allocate to the first AP may increase or decrease (increase in the types of RUs when the BW increases, and decrease in the types of RUs when the BW decreases). In this case, the first AP can help the second AP perform resource sharing considering its changed Operating BW by instructing the second AP of its Operating BW change plan.

[0283] In cases d) and e), they are BSS parameter changes that trigger changes to the method and timing of applying M-AP coordinated spatial reuse and M-AP Coordinated R-TWT respectively, and detailed explanations are omitted. At this time, M-AP Coordinated R-TWT means an M-AP adjustment method that ends the TXOP before the R-TWT SP of the partner AP starts after exchanging the information of the R-TWT SP between APs.

[0284] <M-AP Adjusted Puncturing Management Method> When the main channel of the partner AP is changed, the AP that performs M-AP Coordinated Puncturing must manage so that the non-AP STA associated with itself does not occupy the changed main channel of the partner AP by changing the deactivated (Disabled) subchannels set for its own BSS.

[0285] The channel change procedure defined in Wi-Fi may be performed using the Channel Switch Announcement element and the Extended Channel Switch Announcement element, and information related to the primary channel change of the other AP that an AP can obtain from the other AP can also be obtained using the aforementioned elements or other elements of a similar format. In other words, an AP can plan to change the disabled subchannel set for its BSS in conjunction with the channel switch (including primary channel change) of the other AP that has performed M-AP coordinated puncturing.

[0286] The (Extended)Channel Switch Announcement element is transmitted when an AP attempts to change the operating channel of a BSS, and contains information about the new operating channel and information about when the channel switch will begin. Specifically, the (Extended)Channel Switch Announcement element includes fields such as Channel Switch Mode (Extended Channel Switch Announcement element), New Operating Class, New Channel Number, and Channel Switch Count. The New Operating Class and New Channel Number fields indicate information about the new operating channel, and the Channel Switch Count field indicates information about when the channel switch will begin. The Channel Switch Count field indicates the number of BSS TBTT (Target Beacon Transmission Time) remaining until the channel switch begins, so that the BSS STA can know how many beacons have been transmitted before the channel switch will begin.

[0287] When one of the APs performing M-AP-adjusted puncturing is scheduled to perform a channel switch, the AP that receives information related to the channel switch may attempt to change the disabled subchannels it has set for its BSS to coincide with the scheduled channel switch time of the other AP (the AP scheduled to perform the channel switch). In this case, the AP can include the information of the newly disabled subchannel bitmap to be applied to the BSS in the Operation element it sends. In this case, the AP can also include a Counter in the Operation element it sends that indicates the time when the new disabled subchannel setting will be applied to the BSS. That is, the AP can send an Operation element that includes a Disabled Subchannel Bitmap subfield indicating the disabled subchannel currently applied to the BSS, a New Disabled Subchannel Bitmap subfield indicating the new disabled subchannel, and a Disabled Subchannel Change Count subfield indicating the time when the new disabled subchannel will be applied. Upon receiving the operation element from the AP, a non-AP STA that receives the New Disabled Subchannel subfield and the Disabled Subchannel Change Count subfield must act in a manner that considers the disabled subchannel setting indicated by the New Disabled Subchannel subfield to be applied to the BSS at the time specified by the Disabled Subchannel Change Count subfield.In other words, static puncturing must be applied to existing disabled subchannels before the point in time identified by the Disabled Subchannel Change Count subfield, and static puncturing must be applied to subchannels designated as disabled by the New Disabled Subchannel Bitmap subfield from the point in time identified by the Disabled Subchannel Change Count subfield onward. When AP sets the New Disabled Subchannel Bitmap subfield for the BSS, it must set the puncturing pattern indicated by that subfield to one of the defined non-OFDMA puncturing patterns.

[0288] Figure 21 shows an example of the format of the operation information field that an AP according to one embodiment of the present invention sends for the modification of a disabled subchannel of a BSS.

[0289] Referring to Figure 21, the UHR Operation Information field includes the Control subfield, CCFS0 subfield, CCFS1 subfield, Disabled Subchannel Bitmap subfield, Disabled Subchannel Change Count subfield, and New Disabled Subchannel subfield.

[0290] The Control subfield includes the Channel Width subfield and the New Disabled Subchannel Information Present subfield. The Channel Width subfield is set to 0, indicating a UHR BSS bandwidth of 20 MHz; set to 1, indicating a 40 MHz UHR BSS bandwidth; set to 2, indicating an 80 MHz UHR BSS bandwidth; set to 3, indicating a 160 MHz UHR BSS bandwidth; and set to 4, indicating a 320 MHz UHR BSS bandwidth.

[0291] The CCFS0 and CCFS1 subfields indicate information related to the center frequency of the BSS operating channel. More specifically, CCFS0 indicates the channel center frequency index of the 20, 40, or 80 MHz channel where the operating channel is located, when the BSS bandwidth is 20, 40, or 80 MHz. When the BSS bandwidth is 160 MHz, CCFS0 indicates the channel center frequency index of the primary 80 MHz channel, and when the BSS bandwidth is 320 MHz, CCFS0 indicates the channel center frequency index of the primary 160 MHz channel. CCFS1 is set to 0 when the BSS bandwidth is 20, 40, or 80 MHz. When the BSS bandwidth is 160 MHz, CCFS1 indicates the channel center frequency index of the 160 MHz channel corresponding to the operating channel, and when the BSS bandwidth is 320 MHz, CCFS1 indicates the channel center frequency index of the 320 MHz channel corresponding to the operating channel.

[0292] The Disabled Subchannel Bitmap subfield indicates the disabled subchannels currently applied to the BSS. The first bit of the Disabled Subchannel Bitmap subfield corresponds to the 20MHz subchannel with the lowest frequency among the subchannels included in the BSS operating channel, the second bit corresponds to the 20MHz subchannel with the second lowest frequency, and the third bit corresponds to the 20MHz subchannel with the third lowest frequency. If the BSS Operating BW is 320MHz, the above method is applied sequentially up to the 16th bit. If the BSS Operating BW is 160MHz, bits 9 through 16 are reserved because there are no corresponding subchannels.

[0293] The Disabled Subchannel Change Count subfield indicates a value related to the number of TBTTs remaining until a disabled subchannel applied to the BSS is changed. Specifically, the Disabled Subchannel Change Count subfield may be set to the number of TBTTs remaining until a disabled subchannel of the BSS is changed, or the number of TBTTs minus 1.

[0294] The New Disabled Subchannel Bitmap subfield indicates the newly disabled subchannel to be applied to the BSS, starting from the point indicated by the Disabled Subchannel Change Count subfield. Each bit in the New Disabled Subchannel Bitmap subfield is set in the same way as the Disabled Subchannel Bitmap subfield described above. However, the disabled subchannel indicated by the Disabled Subchannel Bitmap subfield and the disabled subchannel indicated by the New Disabled Subchannel Bitmap subfield are different from each other and cannot be identical. In other words, the AP must not send a New Disabled Subchannel Bitmap subfield that indicates the same subchannel as an existing disabled subchannel as a disabled subchannel.

[0295] The Disabled Subchannel Change Count subfield and the New Disabled Subchannel Bitmap subfield are subfields that are included in the UHR Operation Information field when a specific field in the UHR Operation parameters field (included in the UHR Operation element) is set to 1, and are not included in the UHR Operation Information field when the specific field is set to 0. In this case, the specific field may be the New Disabled Subchannel Information Present subfield.

[0296] <Method for applying M-AP-adjusted puncturing to channel access procedures using subchannels other than the primary channel> A UHR STA (AP STA and / or non-AP STA) can access a channel using a subchannel other than the primary channel while the primary channel is occupied by OBSS. For example, an STA on a 160MHz UHR BSS can attempt to access a channel using a 20MHz subchannel (a non-primary channel) located in the secondary 80MHz band, even when the primary channel (primary 20MHz channel) is occupied by OBSS. Attempting to access a channel using a non-primary channel means performing an operation similar to that of a conventional Wi-Fi terminal, which accesses a channel based on the IDLE / BUSY status of the primary 20MHz channel, i.e., performs a backoff procedure (according to DCF and EDCA rules), but using the IDLE / BUSY status of the non-primary channel. After completing channel access using a non-primary channel, the UHR STA can perform frame exchange using the remaining IDLE subchannels other than the subchannel occupied by OBSS (including the primary 20MHz channel). In other words, it can obtain a TXOP on the non-primary channel.

[0297] Thus, a UHR STA can initiate transmission after accessing a channel using a subchannel other than the primary 20MHz channel, and may attempt to prevent the non-primary channel used for channel access from being occupied by M-AP Coordinated Puncturing. In this case, an AP performing M-AP Coordinated Puncturing can help the other AP access the channel on a non-primary channel by applying static puncturing to the non-primary channel used by the other AP when accessing the channel. In other words, the M-AP Coordinated Puncturing procedure described above can be applied not only to the bandwidth containing the primary channel, but also to the bandwidth containing the non-primary channel used for channel access.

[0298] For example, if the primary channel of the first AP (or non-AP STA) is occupied by the second AP (or second non-AP STA) of OBSS, the first AP can move to another channel (non-primary channel) and establish a channel connection. In this case, even if the second AP is within the TXOP interval set by the second AP for the channel on which the first AP is establishing a channel connection, the second AP can perform puncturing without occupying the channel on which the first AP is establishing a channel connection, allowing the first AP to establish a channel connection on that channel. At this time, the first AP can establish a channel connection on that channel and send and receive low-latency traffic, and within the interval for sending and receiving low-latency traffic on that channel (e.g., R-TWT), traffic can be sent and received even if that interval is within the TXOP interval set by the second AP.

[0299] Thus, if a subchannel used for channel access on a channel that is not the primary channel is punctured by M-AP adjustment between both APs, then the M-AP-adjusted puncturing operation may also be performed between the APs of both BSSs that use the same subchannel as the primary channel.

[0300] For the sake of explanation, the subchannel that the UHR BSS STA uses for channel access when the main channel is occupied by the OBSS will be named the Auxiliary 20MHz subchannel (A20).

[0301] An AP performing adjustments for M-AP-adjusted puncturing instructs the other AP with information about its own (its BSS) A20. The method for instructing the A20 information can be the same or similar as the method for instructing the main channel information in the embodiment shown in Figure 12, and a detailed explanation is omitted. Information on the minimum BW (bandwidth including A20) that requires puncturing can also be instructed in the same or similar manner as in Figure 12.

[0302] Based on the information about A20 provided by the other AP, each AP can help the other AP access the channel on A20 during the time that it and / or the STA of its BSS are exchanging frames by setting disabled subchannels of the BSS it operates or determining which subchannels it does not occupy when it acquires a TXOP. In other words, the M-AP tuned puncturing operation of the present invention described above may be applied identically to the other AP's (or BSS's) A20 (a 20MHz subchannel that is not the primary 20MHz channel but is used for channel access) instead of the other AP's (or BSS's) P20 (primary 20MHz channel).

[0303] Furthermore, two APs performing M-AP-tuned puncturing can apply M-AP-tuned puncturing to both P20 and A20 of the BSS operated by the other AP. In other words, the subchannels to which puncturing is applied by M-AP-tuned puncturing can be the entire bandwidth including P20 and the entire bandwidth including A20.

[0304] The procedure of the present invention described above for P20 may also be applied identically to the method by which an AP that has performed M-AP tuned puncturing sets a disabled subchannel of its own BSS, and to the method of applying puncturing that takes into account SPs promised between the two APs, such as R-TWT SPs, and the explanation is omitted to avoid repetition.

[0305] Figure 22 shows an example of how multiple AP adjustment puncturing is applied to a subchannel other than the primary channel according to one embodiment of the present invention.

[0306] Figure 22(a) shows the operating channels, primary 20MHz channel (P20), and channel access channel (A20, Auxiliary 20MHz, non-primary channel) locations for the BSS operated by AP1 and AP2, respectively. It is assumed that the operating channels of the BSS operated by AP1 and AP2 are fully overlapping, and the primary channel locations for both BSSs are the same.

[0307] Figure 22(b) shows how AP1 assists AP2 in performing non-primary channel access (channel access using A20) by puncturing the region containing AP2's A20 channel during the process of AP1 acquiring a TXOP. Referring to Figure 22(b), AP2 transmits information related to its own A20 to AP1. This figure symbolically illustrates the procedure for M-AP coordination between APs, as explained earlier in one embodiment of Figure 12, and shows that information regarding A20 is also indicated during this coordination process. AP1 acquires a TXOP after completing the channel access procedure performed on P20. The PPDU transmitted after acquiring the TXOP is transmitted in a form in which puncturing is applied to the bandwidth containing AP2's A20. AP2 switches to non-primary channel access mode after confirming that the TXOP of OBSS (AP1's BSS) has started while performing the channel access procedure on the P20 channel. That is, it performs the channel access procedure on A20. Since A20 is a channel that AP1 did not occupy when acquiring the TXOP, AP2 determines A20 to be idle, reduces the backoff counter, and then accesses the channel. Through this process, AP1 operates its TXOP in a way that allows AP2 to access the channel on A20. Although not shown in Figure 20, AP1 can also induce its BSS member STA not to occupy the bandwidth including A20 when accessing the channel by setting the bandwidth including AP2's A20 as a disabled subchannel of its BSS.

[0308] <BSS Management Method for Smooth M-AP Negotiation> As demonstrated by the aforementioned embodiment of the present invention, two BSSs performing coordinated puncturing can access the primary channel, which remains idle even while the TXOP of the other BSS is in progress.

[0309] However, each AP can decide whether or not to coordinate with the other AP, taking into consideration whether the primary channel location of the BSS operated by the other AP is appropriate to be designated as a disabled subchannel of the BSS operated by the AP itself. In other words, an AP can decide whether or not to conduct coordinated puncturing consultation with the other AP, taking into consideration the effects that occur when the primary channel of the BSS operated by the other AP is set as a disabled subchannel of the BSS operated by the AP itself. This is related to the constraint that when setting a disabled subchannel of a BSS, the configuration of the remaining bandwidth excluding the subchannel designated as a disabled subchannel within the operating bandwidth should have a defined non-OFDMA puncturing pattern.

[0310] A simplified explanation of the non-OFMDA puncturing pattern defined in 11be is as follows:

[0311] This configuration involves puncturing 20MHz within an 80MHz bandwidth. Specifically, it's 40MHz + 20MHz (484 tone size RU + 242 tone size RU).

[0312] A configuration in which 20MHz or 40MHz is punctured within the 160MHz bandwidth. However, the punctured 40MHz bandwidth is limited to one of the defined 40MHz channels. That is, 80MHz + 40MHz + 20MHz or 80MHz + 40MHz (996 tone size RU + 484 tone size RU + 242 tone size RU, or 996 tone size RU + 484 tone size RU)).

[0313] This configuration involves puncturing 40MHz or 80MHz, or one 40MHz and one 80MHz simultaneously, within a 320MHz bandwidth. However, when one 40MHz and one 80MHz are punctured simultaneously, the puncturing is applied to the 80MHz bandwidth located on one side of the 320MHz bandwidth's outer edge. That is, 160MHz + 80MHz + 40MHz or 160MHz + 80MHz or 160MHz + 40MHz or 120MHz + 80MHz (996x2 tone size RU + 996 tone size RU + 484 tone size RU or 996x2 tone size RU + 996 tone size RU or 996x2 tone size RU + 484 tone size RU or 996 + 484 tone size RU + 996 tone size RU)

[0314] The limitation of the various forms of puncturing patterns defined above is that only a single hole, i.e., a single continuous band (e.g., 20 / 40 / 80 MHz), is allowed within a continuous non-punctured band. As a concrete example of this limitation, a form in which two 20 MHz subchannels are punctured in an 80 MHz PPDU is not defined, nor are puncturing patterns in which two spaced-out 20 MHz bands are punctured in a 160 MHz PPDU, or two spaced-out 40 MHz bands are punctured in a 320 MHz PPDU.

[0315] Therefore, an AP attempting to perform multi-AP coordination with a partner AP can decide whether or not to perform M-AP coordination by considering whether its own puncturing pattern, when puncturing is applied to the primary channel of the BSS operated by the partner AP, is one of the defined non-OFDMA puncturing patterns. In other words, each AP conducting negotiations for multi-AP coordinated puncturing must decide whether or not to conduct M-AP coordinated puncturing negotiations with the partner AP based on the correlation between the disabled subchannel location of its own BSS and the subchannel used by the partner AP's BSS as the primary channel.

[0316] Figure 23 shows an example of the positional relationship of puncturing channels between APs performing multiple AP adjustment puncturing negotiations according to one embodiment of the present invention, and the resulting adjustment limitations.

[0317] Referring to Figure 23, BSS1, BSS2, and BSS3 are all BSSs with an operating bandwidth of 160 MHz. However, each BSS uses a different channel as its primary channel.

[0318] When AP1 of BSS1, which uses Ch_1 as its primary channel, negotiates with AP2 for M-AP tuned puncturing, the S20 channel of BSS1 is disabled. When AP1 negotiates with AP3 for M-AP tuned puncturing, the S40_H channel of BSS1 is disabled. Since a puncturing pattern using only P20, S40_L, and S80 is not defined for 160MHz, it is impossible for AP1 to negotiate for M-AP tuned puncturing with both AP2 and AP3. Therefore, AP1 can only negotiate for the use of M-AP tuned puncturing with either AP2 or AP3.

[0319] When AP2 of BSS2, which uses Ch_2 as its main channel, negotiates with AP1 for M-AP tuned puncturing, the S20 channel of BSS2 is disabled. When AP2 negotiates with AP3 for M-AP tuned puncturing, the S40_H channel of BSS2 is disabled. Since a puncturing pattern using only P20, S40_L, and S80 is not defined for 160MHz, it is impossible for AP2 to negotiate for M-AP tuned puncturing with both AP1 and AP3. Therefore, AP2 can only negotiate for M-AP tuned puncturing with either AP1 or AP3.

[0320] AP3 of BSS3, which uses Ch_3 as its primary channel, can negotiate with both AP1 and AP2 for M-AP coordinated puncturing. This is because AP3 can deactivate the primary channels of both BSS1 and BSS2 by deactivating its own S40 channel, and a puncturing pattern that punctures only S40 is defined for the 160MHz bandwidth.

[0321] As a result, AP1, AP2, and AP3 have the same or different numbers of negotiable APs depending on the relative positions of the channels that each BSS uses as its primary channel.

[0322] As confirmed in the aforementioned embodiment, an AP conducting negotiations for M-AP coordinated puncturing can decide whether or not to perform M-AP coordination depending on the primary channel position of the other AP. The AP's decision should be respected for the efficient operation of the BSS operated by the AP, and therefore it is unlikely that other APs will make a decision that is unfavorable to a particular AP's request.

[0323] However, to increase the likelihood of coordination between APs and to enhance the effectiveness of any coordination performed between APs, each AP may be advised to set its BSS's primary channel (and other subchannels used for channel access (non-primary channels in the example above)) according to already agreed-upon rules. As a simple example, if, among several BSSs with overlapping operating channels, half of the BSSs use a specific subchannel as their primary channel and the other half use another specific subchannel as their primary channel, each AP can complete coordinated puncturing negotiations with the other half of the BSSs (APs) by setting one subchannel as a disabled subchannel. In other words, the success or failure of M-AP coordination between two APs is influenced by the initial conditions (i.e., the primary channel location) of the two APs.

[0324] Therefore, an AP intending to negotiate with an adjacent AP for M-AP coordinated puncturing can increase the probability of successful coordination by determining the primary channel of its BSS as a subchannel at a location suitable for the negotiating AP to apply puncturing to (set as a deactivated subchannel). In this case, the primary channel selection method performed by the AP may be to select a subchannel at a pre-specified location as the primary channel.

[0325] According to one embodiment of the present invention, one subchannel from each 80MHz channel is designated as the Preferred Puncturing Channel (PPC, a provisional name, which may be defined by another name), and the AP supporting M-AP-tuned puncturing must set up the BSS by setting the subchannel designated as the PPC as the primary channel. In other words, the AP supporting M-AP-tuned puncturing must designate (set) the PPC from among the subchannels included in its primary 80MHz band as the primary 20MHz subchannel. In this case, the PPC may be designated for an 80MHz channel included in the 5GHz band and an 80MHz channel included in the 6GHz band.

[0326] As a specific example, an AP operating a BSS with an operating bandwidth (BW) of 160MHz would decide on one of the two 80MHz subchannels included in the 160MHz band as the primary 80MHz band. However, of the four subchannels included in the primary 80MHz band, the subchannel that matches the PPC (Power Point Control) must be designated and used as the primary 20MHz subchannel. As another specific example, an AP operating a BSS with an operating bandwidth of 320MHz would decide on one of the four 80MHz subchannels included in the 320MHz band as the primary 80MHz band. However, of the four subchannels included in the primary 80MHz band, the subchannel that matches the PPC must be designated and used as the primary 20MHz subchannel. Furthermore, an AP operating a BSS with an operating bandwidth of 80MHz must set the subchannel that matches the PPC among the four subchannels included in the operating bandwidth as the primary 20MHz subchannel.

[0327] However, each 80MHz channel may also be further designated as an Alternate Primary Channel (APC, a provisional name, which may be defined by a different name), which can use only BSSs with an operating BW of 80MHz as the primary channel. The APC of a particular 80MHz channel is designated as a subchannel different from the PPC of the same particular 80MHz channel. An AP of a BSS using the APC of a particular 80MHz channel as its primary channel can negotiate for M-AP coordinated puncturing with an AP of a BSS using the PPC of the same particular 80MHz channel as its primary channel. In other words, within an 80MHz channel, there are two different subchannels that can be used as primary channels by BSSs with an operating channel of 80MHz, and M-AP coordinated puncturing negotiations can be conducted between APs using different subchannels as primary channels. In this case, the PPC and APC of a particular 80MHz channel are located consecutively in one of the two 40MHz channels included in the particular 80MHz channel. In other words, the PPC and APC designated for a specific 80MHz channel are designated as different 20MHz subchannels included in the specific 40MHz band. The reason why the PPC and APC are included in the specific 40MHz band is to allow the AP of a BSS having an operating bandwidth of 160MHz or 320MHz to designate the specific 40MHz band as a disabled subchannel (punctured band) and to conduct consultations for M-AP coordinated puncturing with the AP of a BSS using the specific 80MHz band as an operating channel. In this case, the APC may be designated for an 80MHz channel included in the 5GHz band and an 80MHz channel included in the 6GHz band.

[0328] As described above, if the primary channel of the BSS operated by each AP is restricted to a subchannel that matches the PPC (or APC), then it becomes more likely that multiple BSSs adjacent to each BSS will use the same subchannel as their primary channel. Therefore, when the AP of the BSS performs M-AP coordination with the APs of the multiple BSSs, it can complete the coordination by setting only a number of subchannels smaller than the number of APs being coordinated as punctured (deactivated) subchannels.

[0329] Furthermore, the PPC for the 6GHz band may be designated as a subchannel that matches the PSC (Preferred Scanning Channel). The PSC is a subchannel that is recommended to be used as the primary channel by 6GHz-only APs (6GHz APs that do not share a co-located AP set with APs operating in the 2.4GHz and 5GHz bands). However, 6GHz APs attempting to perform M-AP coordinated puncturing are subject to the constraint that, even if they are not 6GHz-only APs or belong to an AP MLD, they must increase their coordination probability with other APs by setting the primary 20MHz channel of the BSS to a channel that matches the PPC.

[0330] Figure 24 shows an example of a PPC and APC specification method for 80MHz, 160MHz, and 320MHz channels according to one embodiment of the present invention.

[0331] For the 80MHz channel, one PPC and one APC are designated. The PPC and APC are designated as adjacent channels and reside within a specific 40MHz channel. For the 160MHz channel, two PPCs are designated, each located in a different 80MHz band. For the 320MHz channel, four PPCs are designated, each located in a different 80MHz band.

[0332] A simplified explanation of how M-AP coordination is performed between APs using PPCs is as follows: APs operating on 160MHz BSS (APs supporting M-AP coordinated puncturing) adopt one of the two types defined for 160MHz to configure the BSS operating channel. That is, all 160MHz BSS APs supporting M-AP coordinated puncturing use one of the two PPCs included in the 160MHz channel as the primary channel. Therefore, when an AP of a BSS using Type 1 coordinates with multiple APs of a BSS using Type 2, the coordination can be completed by disabling (puncturing) only one subchannel (20MHz subchannel or 40MHz channel), and when an AP of a BSS using Type 2 coordinates with multiple APs of a BSS using Type 1, the coordination can be completed by disabling only one subchannel (20MHz subchannel or 40MHz channel).

[0333] Figure 25 is a flowchart showing an example of a data transmission and reception method performed by a terminal according to one embodiment of the present invention.

[0334] Referring to Figure 25, if a terminal has coordinated with other terminals and a TXOP interval has been set by the NAV settings of another terminal, the terminal can send and receive data within the TXOP interval for a specific period.

[0335] Specifically, the terminal sends a request frame for multi-access point (AP) coordinating to the first terminal (S25010). The frame may include channel information indicating a specific channel to be used for sending and receiving low-latency data in a particular section.

[0336] Subsequently, the terminal receives a response frame from the first terminal as a response to the frame (S25020), and can transmit and receive the low-latency data with the second terminal within the specified interval (S25030). The transmission and reception of the low-latency data via the specified channel within the specified interval may be guaranteed by the frame. Furthermore, the specified channel is not occupied by the first terminal within the specified interval and is used for transmitting and receiving the low-latency data with the second terminal.

[0337] When a specific section partially or completely overlaps with a TXOP (Transmission opportunity) section using the NAV (Network allocation vector) setting by the first terminal, the specific channel in the specific section is used to transmit and receive the low-latency data with the second terminal. Request frames are transmitted duplicated in 20MHz units within the total bandwidth of the wireless communication terminal.

[0338] The terminal can send a release request message to the first terminal to cancel the use of the specific channel due to the multiplex AP adjustment, and the use of the specific channel via the specific channel is canceled within the specific interval based on the release request message.

[0339] Furthermore, the terminal transmits a specific frame to the first terminal at regular intervals to inform it of the use of the specific channel.

[0340] If the specific frame is not transmitted to the first terminal within the specified time, the use of the specific channel is canceled within the specified interval, and the specified time, which is the transmission period of the specific frame, is longer than the transmission period of the beacon frame.

[0341] The aforementioned specific interval is a restricted R-TWT (Restricted-target wake time) interval for transmitting and receiving the low-latency data.

[0342] The above description of the present invention is illustrative, and a person with ordinary skill in the art to which the invention pertains will understand that it can be easily modified into other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in any respect. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0343] The scope of the present invention is indicated by the claims described below, rather than by the detailed description above, and all modified or altered forms derived from the meaning and scope of the claims and the concept of equivalents should be considered to be included within the scope of the present invention.

Claims

1. A wireless communication terminal, Transmitter / receiver unit, Includes a processor, The aforementioned processor, A request frame for Multiple Access Point (AP) Coordinating is sent to the first terminal. The frame includes channel information indicating a specific channel used for transmitting and receiving low-latency data during a specific interval. A response frame is received as a response to the aforementioned frame. The second terminal and the specified section perform transmission and reception of the low-latency data. The transmission and reception of the low-latency data via the specific channel within the specified interval is guaranteed by the frame. The specified channel is not occupied by the first terminal during the specified interval and is used for sending and receiving the low-latency data with the second terminal, and is a wireless communication terminal.

2. The wireless communication terminal according to claim 1, wherein, when the specified section partially or completely overlaps with a TXOP (Transmission Opportunity) section using the NAV (Network allocation vector) setting by the first terminal, the specified channel is used to transmit and receive the low-latency data with the second terminal during the specified section.

3. The wireless communication terminal according to claim 1, wherein the request frame is transmitted in duplicate in units of 20 MHz within the total bandwidth of the wireless communication terminal.

4. The aforementioned processor, A release request message to the first terminal is sent to release the use of the specific channel due to the multiplex AP adjustment. The wireless communication terminal according to claim 1, wherein the use of the specific channel is terminated within the specific interval based on the termination request message.

5. The aforementioned processor, The wireless communication terminal according to claim 1, which transmits a specific frame to the first terminal at regular intervals to indicate the use of the specific channel.

6. If the specific frame is not transmitted to the first terminal within the aforementioned time period, the use of the specific channel within the aforementioned interval is terminated. The wireless communication terminal according to claim 5, wherein the constant time, which is the transmission period of the specific frame, is longer than the transmission period of the beacon frame.

7. The wireless communication terminal according to claim 1, wherein the specified section is a restricted-target wake time (R-TWT) section for transmitting and receiving the low-latency data.

8. A method performed by a wireless communication terminal, the method is The first terminal receives a request frame for Multiple Access Point (AP) Coordinating, The frame includes a step that includes channel information indicating a specific channel used for transmitting and receiving low-latency data during a specific interval, The step of receiving a response frame as a response to the aforementioned frame, This includes the step of transmitting and receiving the low-latency data with the second terminal within the specified section, The transmission and reception of the low-latency data via the specific channel within the specified interval is guaranteed by the frame. A method wherein the specified channel is not occupied by the first terminal during the specified interval and is used for sending and receiving the low-latency data with the second terminal.

9. The method according to claim 8, wherein, when the specified section partially or completely overlaps with a TXOP (Transmission Opportunity) section using the NAV (Network allocation vector) setting by the first terminal, the specified channel is used to transmit and receive the low-latency data with the second terminal during the specified section.

10. The method according to claim 8, wherein the request frame is transmitted in duplicate in units of 20 MHz within the total bandwidth of the wireless communication terminal.

11. The aforementioned method, The process further includes sending a release request message to the first terminal to cancel the use of the specific channel due to the multiplex AP adjustment, The method according to claim 8, wherein the use of the specified channel is terminated within the specified interval based on the termination request message.

12. The aforementioned method, The method according to claim 8, further comprising the step of transmitting a specific frame to the first terminal at regular intervals to indicate the use of the specific channel.

13. If the specific frame is not transmitted to the first terminal within the aforementioned time period, the use of the specific channel within the aforementioned interval is terminated. The method according to claim 12, wherein the constant time, which is the transmission period of the specific frame, is longer than the transmission period of the beacon frame.

14. The method according to claim 8, wherein the specified section is a restricted-target wake time (R-TWT) section for transmitting and receiving the low-latency data.

15. A wireless communication terminal, Transmitter / receiver unit, Includes a processor, The aforementioned processor, The first terminal receives a frame indicating that the use of a specific channel within a specific section is unavailable. The aforementioned specific channel is used by a second terminal of another BSS to send and receive low-latency data during a specific interval. Based on the frame, data is transmitted and received with the first terminal. The transmission and reception of the low-latency data via the specific channel within the specified interval is guaranteed by the frame. The specified channel is not occupied by the first terminal during the specified interval and is used for sending and receiving the low-latency data with the second terminal, and is a wireless communication terminal.

16. The wireless communication terminal according to claim 15, wherein, when the first primary channel of the second terminal and the second primary channel of the wireless communication terminal are the same channel, the channel connection procedure between the wireless communication terminal and the first terminal is performed on a subchannel of the operating channel that does not include the first primary channel, out of the total bandwidth.

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