Wireless communication methods that support bandwidth expansion are compatible with wireless communication terminals that utilize this method.

Abstract

The invention relates to a wireless communication station. The station comprises: a transceiver; and a processor. The processor determines whether the subchannel is not included in the transmission opportunity frequency band (TXOP) in the TXOP received by the station in the extended state, and performs frame exchange in the TXOP frequency band and the subchannel included frequency band when the subchannel is in the extended state.

Description

Wireless communication method supporting adaptive bandwidth expansion and wireless communication terminal using the same

[0001] The present invention relates to a wireless communication method supporting adaptive bandwidth expansion and a wireless communication terminal using the same.

[0002] With the recent proliferation of mobile devices, wireless LAN (WLAN) technology, which can provide them with fast wireless Internet service, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly connect to the Internet at home, in businesses, or in specific service areas.

[0003] Since supporting the initial wireless LAN technology using the 2.4 GHz frequency, IEEE (Institute of Electrical and Electronics Engineers) 802.11 has been commercializing or developing various technology standards. First, IEEE 802.11b supports a communication speed of up to 11 Mbps while using the 2.4 GHz band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz band instead of the 2.4 GHz band, thereby reducing the impact of interference compared to the considerably crowded 2.4 GHz band. It also uses OFDM (orthogonal frequency division multiplexing) technology to increase the communication speed to up to 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication range than IEEE 802.11b. And IEEE 802.11g, like IEEE 802.11b, uses the 2.4GHz band to achieve a communication speed of up to 54Mbps and satisfies backward compatibility, which has garnered considerable attention. It is also superior to IEEE 802.11a in terms of communication distance.

[0004] And to overcome the limitations of communication speed, which has been pointed out as a vulnerability in wireless LAN, there is IEEE 802.11n, a technical standard established. IEEE 802.11n aims to increase the speed and reliability of networks and extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT) with data processing speeds of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. In addition, this standard can use a coding method that transmits multiple redundant copies to increase data reliability.

[0005] As wireless LAN becomes more widespread and applications diversify, the need for new wireless LAN systems that support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n has arisen. 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 for the 5GHz band, early 11ac chipsets will also support operation in the 2.4GHz band to ensure backward compatibility with existing 2.4GHz band products. Theoretically, according to this specification, multi-station wireless LAN speeds can reach at least 1Gbps and a maximum single-link speed of at least 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, such as wider radio frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256 QAM). In addition, there is IEEE 802.11ad, which transmits data using the 60 GHz band instead of the existing 2.4 GHz / 5 GHz. IEEE 802.11ad is a transmission standard that provides speeds of up to 7 Gbps using beamforming technology, making it suitable for streaming high-bitrate video such as large amounts of data or uncompressed HD video. However, the 60 GHz frequency band has a disadvantage in that it has difficulty passing through obstacles, so it can only be used between devices in short distances.

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

[0007] Additionally, development of new wireless LAN standards has begun to increase maximum transmission speeds to support emerging multimedia applications such as high-definition video and real-time gaming. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is currently under development with the goal of supporting transmission rates of up to 30 Gbps in the 2.4 / 5 / 6 GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation.

[0008] Recently, discussions have begun on Ultra High Reliability (UHR) wireless LAN communication technology, a successor to the 802.11be standard, to overcome reliability issues that have been identified as limitations of wireless LAN. The UHR standard is currently under development with the goal of supporting low latency and low jitter in wireless LAN traffic with a high probability (e.g., greater than 99.9999%).

[0009] An embodiment of the present invention aims to provide a wireless communication method supporting adaptive bandwidth expansion and a wireless communication terminal using the same.

[0010] According to one embodiment of the present invention, a station for wireless communication includes a transceiver; and a processor. The processor determines whether a subchannel not included in a frequency band of a TXOP (transmit opportunity) acquired by the station is expandable, and if the subchannel is expandable, performs frame exchange in the frequency band of the TXOP and a frequency band including the subchannel.

[0011] The processor may perform an enhanced distributed channel access function (EDCAF) backoff procedure on a primary channel, and upon success of the EDCAF backoff procedure, may perform frame exchange in a frequency band including the TXOP and the secondary channel based on whether the secondary channel is idle for a predetermined time period.

[0012] The above processor may perform the EDCAF backoff using the minimum value (CWmin) of the contention window for the AC (access category) corresponding to the EDCAF when performing the EDCAF backoff.

[0013] When performing the EDCAF backoff, the processor may reset the QSRC (QoS (quality of service) STA Retry Counter) value of the AC corresponding to the EDCAF.

[0014] The processor may perform a clear channel assessment (CCA) on the primary channel and the secondary channel without performing an enhanced distributed channel access function (EDCA) backoff procedure on the primary channel within the TXOP. In addition, the processor may perform frame exchange on the band of the TXOP and the secondary channel that is idle for the predetermined time period as a result of the CCA, if the primary channel is idle for the predetermined time period as a result of the CCA.

[0015] The processor may perform CCA on the subchannel and the primary channel even if retransmission is not required within the TXOP.

[0016] In frame exchanges performed within the above TXOP, the interval between any two frames may be greater than SIFS (short inter-frame space).

[0017] The processor may transmit a PPDU for transmitting at least one of the two frames with a duration shorter than a pre-specified duration.

[0018] Even if the above subchannel is expandable, the duration of the above TXOP may not be extended.

[0019] According to an embodiment of the present invention, a method of operating a station for wireless communication includes the steps of: determining whether a subchannel not included in a frequency band of a TXOP (transmit opportunity) acquired by the station is in an expandable state; and, if the subchannel is in an expandable state, performing frame exchange in a frequency band of the TXOP and a frequency band including the subchannel.

[0020] The step of determining whether the above sub-channel is in an expandable state may include a step of performing an enhanced distributed channel access function (EDCAF) backoff procedure on the primary channel.

[0021] When the subchannel is in an expandable state, the step of performing frame exchange in the frequency band of the TXOP and the frequency band including the subchannel may include the step of performing frame exchange in the frequency band of the TXOP and the frequency band including the subchannel based on whether the subchannel is idle for a predetermined time period when the EDCAF backoff procedure is successful.

[0022] The step of performing the EDCAF backoff procedure in the above primary channel may include the step of performing the EDCAF backoff using the minimum value (CWmin) of the contention window for the AC (access category) corresponding to the EDCAF when performing the EDCAF backoff.

[0023] The step of performing the EDCAF backoff procedure in the above primary channel may include a step of resetting a QSRC (QoS (quality of service) STA Retry Counter) value of an AC corresponding to the EDCAF when performing the EDCAF backoff.

[0024] The step of determining whether the subchannel is in an expandable state may include a step of performing a clear channel assessment (CCA) on the primary channel and the subchannel without performing an enhanced distributed channel access function (EDCA) backoff procedure on the primary channel within the TXOP. If the subchannel is in an expandable state, the step of performing frame exchange in a frequency band of the TXOP and a frequency band including the subchannel may include a step of performing frame exchange in a band of the TXOP and a subchannel that is idle for the predetermined time period as a result of the CCA, if the primary channel is idle for the predetermined time period as a result of the CCA.

[0025] The step of performing the CCA on the main channel and the sub-channel may perform the CCA on the sub-channel and the main channel even if retransmission is not required within the TXOP.

[0026] In frame exchanges performed within the above TXOP, the interval between any two frames may be greater than SIFS (short inter-frame space).

[0027] The above operating method may further include a step of transmitting a PPDU for transmitting at least one of the two frames with a duration shorter than a pre-specified duration.

[0028] Even if the above subchannel is expandable, the duration of the above TXOP may not be extended.

[0029] One embodiment of the present invention provides a wireless communication method for efficiently supporting relay communication and a wireless communication terminal using the same.

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

[0031] Figure 2 illustrates a wireless LAN system according to another embodiment of the present invention.

[0032] Figure 3 shows the configuration of a station according to one embodiment of the present invention.

[0033] Figure 4 shows the configuration of an access point according to one embodiment of the present invention.

[0034] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0035] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0036] FIG. 7 shows various standard generation-specific physical layer protocol data unit (PPDU) formats according to an embodiment of the present invention.

[0037] Figure 8 shows an EHT / UHR PPDU format according to an embodiment of the present invention.

[0038] FIG. 9 shows a transmission / TXOP protection method using an RTS frame and a CTS frame according to an embodiment of the present invention.

[0039] FIG. 10 shows a transmission / TXOP protection method using an MU-RTS frame and a CTS frame according to an embodiment of the present invention.

[0040] Figure 11 shows the format of a trigger frame according to an embodiment of the present invention.

[0041] Figure 12 shows the format of the Common Info field of a trigger frame according to an embodiment of the present invention.

[0042] Figure 13 shows the format of the User Info field of a trigger frame according to an embodiment of the present invention.

[0043] FIG. 14 illustrates an example of a frame exchange sequence between STAs performed during a TXOP according to an embodiment of the present invention.

[0044] FIG. 15 illustrates an example of a frame exchange sequence in which an STA transfers TXOP acquisition rights to another STA after completing a backoff procedure according to one embodiment of the present invention.

[0045] FIG. 16 illustrates an example of a frame exchange sequence for transferring TXOP acquisition rights and NAV states of other STAs after a backoff procedure of an STA according to one embodiment of the present invention.

[0046] FIG. 17 illustrates an example of the format of an initiating frame and a trigger frame according to one embodiment of the present invention.

[0047] FIG. 18 illustrates an example of a TXOP sharing and bandwidth (BW) expansion procedure between STAs according to an embodiment of the present invention.

[0048] FIG. 19 illustrates an example of a TXOP sharing procedure and a TXOP holder operation of an STA according to an embodiment of the present invention.

[0049] FIG. 20 illustrates an example of a format for a frame for transferring TXOP acquisition rights or sharing TXOP according to one embodiment of the present invention.

[0050] FIG. 21 illustrates an example of a method for performing channel access using a subchannel according to an embodiment of the present invention.

[0051] FIG. 22 illustrates another example of a method for performing channel access using a subchannel according to an embodiment of the present invention.

[0052] FIG. 23 illustrates an example of a method for initiating a channel access procedure using a subchannel according to one embodiment of the present invention.

[0053] FIG. 24 illustrates an example of a method for obtaining a shared transmission opportunity (TXOP) using a TXOP according to an embodiment of the present invention.

[0054] FIG. 25 illustrates an example of a format of a parameter set element for TXOP sharing according to one embodiment of the present invention.

[0055] FIG. 26 illustrates an example of the configuration and connection status of an AP MLD and a non-AP MLD according to one embodiment of the present invention.

[0056] FIG. 27 illustrates an example of an element for sharing a TXOP according to an embodiment of the present invention.

[0057] FIG. 28 illustrates an example of a frame including elements for sharing a TXOP according to one embodiment of the present invention.

[0058] FIG. 29 illustrates an example of a response frame format for a frame for sharing TXOP according to an embodiment of the present invention.

[0059] FIG. 30 illustrates an example of a method for minimizing performance degradation of an overlapping basic service set (OBSS) of APs when expanding the bandwidth of a shared TXOP according to an embodiment of the present invention.

[0060] FIG. 31 illustrates an example of an operation of an AP in which TXOP sharing is performed between APs according to one embodiment of the present invention and BW expansion is performed during the shared TXOP.

[0061] Figure 32 shows an example of the operation of a station according to one embodiment of the present invention.

[0062] FIG. 33 shows a method for a station to expand bandwidth according to a bandwidth expansion rule according to an embodiment of the present invention.

[0063] FIG. 34 shows an operation of expanding the bandwidth of TXOP according to another embodiment of the present invention.

[0064] FIG. 35 shows an operation of expanding the bandwidth of TXOP according to another embodiment of the present invention.

[0065] Figure 36 shows the types and location information of RUs that can be included in an EHT PPDU with an 80 MHz bandwidth.

[0066] Figure 37 shows an rRU and a dRU according to an embodiment of the present invention.

[0067] Figure 38 is a combination of dRUs that can be configured using tones contained in a 20MHz channel.

[0068] FIG. 39 shows a TB PPDU of a station responding to a TB PPDU with a signal having the same symbol length, according to an embodiment of the present invention.

[0069] FIG. 40 shows that a TB PPDU is transmitted as a signal having the same symbol length within a frequency band segment according to an embodiment of the present invention.

[0070] FIG. 41 illustrates a method for setting dRUs of different tone sizes to have the same tone spacing and a method for allocating dRUs of different tone sizes at once according to an embodiment of the present invention.

[0071] The terms used in this specification have been selected from widely used and current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, customs, or the emergence of new technologies. Furthermore, in certain cases, the applicant may arbitrarily select terms, in which case their meanings will be described in the description of the relevant invention. Therefore, it should be noted that the terms used in this specification should be interpreted based on their substantive meaning and the overall content of this specification, rather than simply their names.

[0072] Throughout the specification, when a component is said to be "connected" to another component, this includes not only the case where the component is "directly connected," but also the case where the component is "electrically connected" with another component intervening therebetween. Furthermore, when a component is said to "include" a particular component, this does not exclude the other component, but rather allows the inclusion of other components, unless specifically stated otherwise. Furthermore, the terms "more than" or "less than" with respect to a specific threshold may be appropriately replaced with "greater than" or "less than", respectively, depending on the embodiment.

[0073] Hereinafter, in the present invention, fields and subfields may be used interchangeably.

[0074] Figure 1 illustrates a wireless LAN system according to one embodiment of the present invention.

[0075] A wireless LAN system includes one or more Basic Service Sets (BSSs), which represent a collection of devices that have successfully synchronized and can communicate with each other. BSSs can generally be categorized as infrastructure BSSs and independent BSSs (IBSSs). Figure 1 illustrates an infrastructure BSS.

[0076] As illustrated in FIG. 1, the infrastructure BSS (BSS1, BSS2) includes one or more stations (STA1, STA2, STA3, STA4, STA5), an access point (AP-1, AP-2) that provides a distribution service, and a distribution system (DS) that connects multiple access points (AP-1, AP-2).

[0077] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium that complies with the IEEE 802.11 standard, and broadly includes both non-access point (AP) stations and access points (APs). In addition, the term "terminal" in this specification may refer to a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface unit and a display unit, depending on the embodiment. The processor may generate a frame to be transmitted through a wireless network or process a frame received through the wireless network, and may perform various other processes for controlling the station. In addition, the communication unit is functionally connected to the processor and transmits and receives frames through the wireless network for the station. In the present invention, a terminal may be used as a term that includes a user equipment (UE).

[0078] An Access Point (AP) is an entity that provides access to a distribution system (DS) via a wireless medium for stations associated with it. In an infrastructure BSS, communication between non-AP stations is in principle performed via the AP, but direct communication is also possible between non-AP stations when a direct link is established. Meanwhile, in the present invention, the AP is used as a concept including a Personal BSS Coordination Point (PCP), and in a broad sense, it can include concepts such as a centralized controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller. In the present invention, the AP may also be referred to as a base wireless communication terminal, and the base wireless communication terminal may be used as a term including, in a broad sense, an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal may include various types of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with multiple wireless communication terminals.

[0079] Multiple infrastructure BSSs can be interconnected via a distribution system (DS). Multiple BSSs connected via the distribution system are referred to as an Extended Service Set (ESS).

[0080] FIG. 2 illustrates an independent BSS, a wireless LAN system, according to another embodiment of the present invention. In the embodiment of FIG. 2, portions identical or corresponding to those in the embodiment of FIG. 1 will be omitted for duplicative description.

[0081] BSS3, illustrated in Figure 2, is an independent BSS and does not include an AP. Therefore, all stations (STA6, STA7) are not connected to an AP. An independent BSS does not allow access to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) can be directly connected to another.

[0082] FIG. 3 is a block diagram showing the configuration of a station (100) according to one embodiment of the present invention. As illustrated, the station (100) according to the embodiment of the present invention may include a processor (110), a communication unit (120), a user interface unit (140), a display unit (150), and a memory (160).

[0083] First, the communication unit (120) transmits and receives wireless signals such as wireless LAN packets, and may be built into or externally installed in the station (100). According to an embodiment, the communication unit (120) may include at least one communication module using different frequency bands. For example, the communication unit (120) may include communication modules of different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to one embodiment, the station (100) may 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 may perform wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (120) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the station (100). When the station (100) includes multiple communication modules, each communication module may be provided in an independent form, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit (120) may represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0084] Next, the user interface unit (140) includes various types of input / output means provided in the station (100). That is, the user interface unit (140) can receive user input using various input means, and the processor (110) can control the station (100) based on the received user input. In addition, the user interface unit (140) can perform output based on a command of the processor (110) using various output means.

[0085] Next, the display unit (150) outputs an image on the display screen. The display unit (150) can output various display objects, such as content executed by the processor (110) or a user interface based on the control commands of the processor (110). In addition, the memory (160) stores a control program used in the station (100) and various data corresponding thereto. Such a control program may include a connection program required for the station (100) to connect to an AP or an external station.

[0086] The processor (110) of the present invention can execute various commands or programs and process data within the station (100). In addition, the processor (110) can control each unit of the above-described station (100) and control data transmission and reception between the units. According to an embodiment of the present invention, the processor (110) can execute a program for connection to an AP stored in the memory (160) and receive a communication setup message transmitted by the AP. In addition, the processor (110) can read information on the priority conditions of the station (100) included in the communication setup message and request connection to the AP based on the information 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), and according to an embodiment, may refer to a control unit for individually controlling some components of the station (100), such as the communication unit (120). That is, the processor (110) may be a modem or modulator and / or demodulator that modulates and / or demodulates wireless signals transmitted and received from the communication unit (120). The processor (110) controls various operations of transmitting and receiving wireless signals of the station (100) according to an embodiment of the present invention. A specific embodiment thereof will be described later.

[0087] The station (100) illustrated in FIG. 3 is a block diagram according to one embodiment of the present invention, and the blocks shown separately are logically distinguished elements of the device. Accordingly, the elements of the above-described device may be mounted as one chip or as multiple chips depending on the design of the device. For example, the processor (110) and the communication unit (120) may be implemented by being integrated into one chip or may be implemented as separate chips. In addition, 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).

[0088] Fig. 4 is a block diagram illustrating the configuration of an AP (200) according to one embodiment of the present invention. As illustrated, the AP (200) according to the embodiment of the present invention may include a processor (210), a communication unit (220), and a memory (260). In Fig. 4, redundant descriptions of portions of the configuration of the AP (200) that are identical or corresponding to the configuration of the station (100) of Fig. 3 will be omitted.

[0089] Referring to FIG. 4, the AP (200) according to the present invention has a communication unit (220) for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit (220) of the AP (200) may also include a plurality of communication modules that utilize different frequency bands. That is, the AP (200) according to the embodiment of the present invention may include two or more communication modules for different frequency bands, such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP (200) may include a communication module that utilizes a frequency band of 7.125 GHz or higher and a communication module that utilizes a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with a station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (220) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the AP (200). In an embodiment of the present invention, the communication unit (220) may represent an RF communication module that processes an RF (Radio Frequency) signal.

[0090] Next, the memory (260) stores the control program used in the AP (200) and various data according to the control program. This control program may include a connection program that manages the connection of the station. In addition, the processor (210) controls each unit of the AP (200) and may control data transmission and reception between the units. According to an embodiment of the present invention, the processor (210) may execute a program for connection with a station stored in the memory (260) and transmit a communication setup message to one or more stations. At this time, the communication setup message may include information on the connection priority conditions of each station. In addition, the processor (210) performs connection setup according to a connection request from a station. According to one embodiment, the processor (210) may be a modem or a modulator and / or demodulator that modulates and demodulates a wireless signal transmitted and received from the communication unit (220). The processor (210) controls various operations of wireless signal transmission and reception of the AP (200) according to an embodiment of the present invention. Specific examples of this will be described later.

[0091] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0092] Referring to FIG. 5, the link between STA (100) and AP (200) is largely established through three stages: scanning, authentication, and association. First, the scanning stage is a stage in which STA (100) acquires access information of the BSS operated by AP (200). Methods for performing scanning include a passive scanning method in which information is acquired only by utilizing a beacon message (S101) periodically transmitted by AP (200), and an active scanning method in which STA (100) acquires access information by transmitting a probe request to AP (S103) and receiving a probe response from AP (S105).

[0093] The STA (100) that successfully receives wireless access information in the scanning step transmits an authentication request (S107a) and receives an authentication response from the AP (200) (S107b) to perform the authentication step. After the authentication step is performed, the STA (100) transmits an association request (S109a) and receives an association response from the AP (200) (S109b) to perform the association step. In this specification, association basically means wireless association, but the present invention is not limited thereto, and association in a broad sense may include both wireless association and wired association.

[0094] Meanwhile, an additional 802.1X-based authentication step (S111) and an IP address acquisition step (S113) via DHCP may be performed. In Fig. 5, the authentication server (300) is a server that processes STA (100) and 802.1X-based authentication, and may be physically connected to the AP (200) or may exist as a separate server.

[0095] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0096] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether the channel is busy. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to the channel. This process is called clear channel assessment (CCA), and the level that determines whether the signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by the terminal is intended for the terminal, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected on the channel or a wireless signal with a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0097] When the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an IFS (Inter Frame Space) time, such as AIFS (Arbitration IFS) or PIFS (PCF IFS), depending on the status of each terminal. In some embodiments, the AIFS may be used as a configuration to replace the existing DIFS (DCF IFS). Each terminal waits while decreasing the slot time by a random number determined for the terminal during the idle interval of the channel, and a terminal that has exhausted all slot times attempts to access the channel. The period during which each terminal performs the backoff procedure is called a contention window period. At this time, the random number may be referred to as a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal may decrease the backoff counter by 1. Additionally, if the backoff counter reaches 0, the terminal may be permitted to perform channel access on the corresponding channel. Accordingly, transmission by the terminal may be permitted if the channel is idle during the AIFS time and the slot time of the backoff counter.

[0098] If a specific terminal successfully accesses the channel, the terminal can transmit data through the channel. However, if the terminal attempting access collides with another terminal, the collided terminals are each assigned a new random number and perform a backoff procedure again. According to one embodiment, the random number newly assigned to each terminal may be determined within a range twice (2*CW) of the random number range (contention window, CW) previously assigned to the terminal. Meanwhile, each terminal performs the backoff procedure again in the next contention window period to attempt access, and at this time, each terminal performs the backoff procedure starting from the slot time remaining in the previous contention window period. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0099] <Various PPDU format examples>

[0100] FIG. 7 shows various standard generation-specific physical layer protocol data unit (PPDU) formats according to an embodiment of the present invention.

[0101] More specifically, FIG. 7(a) illustrates an embodiment of a legacy PPDU format based on 802.11a / g, FIG. 7(b) illustrates an embodiment of a HE PPDU format based on 802.11ax, and FIG. 7(c) illustrates an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. In addition, FIG. 7(d) illustrates a detailed field configuration of L-SIG and RL-SIG commonly used in the above PPDU formats.

[0102] Referring to FIG. 7(a), the preamble of a legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0103] Referring to FIG. 7(b), the preamble of the HE PPDU additionally 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 an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF may be referred to as a 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.

[0104] Referring to FIG. 7(c), the preamble of the EHT PPDU additionally includes, in addition to the legacy preamble, an RL-SIG (Repeated Legacy Short Training field), a U-SIG (Universal Signal field), an EHT / UHR-SIG-A (Extremely High Throughput / Ultra High Reliability Signal A field), an EHT / UHR-SIG-A (Extremely High Throughput / Ultra High Reliability Signal B field), an EHT-STF (Extremely High Throughput Short Training field), and an EHT-LTF (Extremely High Throughput Long Training field). In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B can only be used in some of the EHT PPDU formats.

[0105] In this way, the PPDU used in the UHR standard may have a format similar to the PPDU format used in the EHT standard. This is because the EHT PPDU format defined in 802.11be includes a U-SIG field that multiple wireless LAN generations have agreed to use in common. At this time, the value of the PHY Version Identifier field of the U-SIG field included in the EHT PPDU may be 0, and the value of the PHY Version identifier field of the U-SIG field included in the UHR PPDU may have 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.

[0106] The L-SIG field included in the PPDU preamble applies 64FFT 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 L-SIG applies BPSK, Rate=1 / 2 Modulation and Coding Scheme (MCS), it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of L-SIG.

[0107] Referring to Fig. 7(d), L-SIG includes an L_RATE field and an 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 combine modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and inefficiencies such as 1 / 2, 2 / 3, and 3 / 4. Combining the information in the L_RATE field and the L_LENGTH field can indicate the total length of the corresponding PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0108] The L_LENGTH field is allocated in bytes, with a total of 12 bits, allowing for signaling up to 4095. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. At this time, legacy and non-legacy terminals may interpret the L_LENGTH field in different ways.

[0109] First, the method by which a legacy terminal or non-legacy terminal interprets the length of the PPDU using the L_LENGTH field is as follows. If the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4 us, which is the duration of one symbol of 64 FFT. Therefore, by adding 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of symbols based on 64 FFT after L-SIG is obtained. Multiplying the obtained number of symbols by 4 us, which is the duration of one symbol, and then adding 20 us 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 as a formula as shown in Mathematical Expression 1 below.

[0110]

[0111] At this time, represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU can be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as in Mathematical Expression 2 below.

[0112]

[0113] Here, TXTIME is the total transmission time that constitutes the corresponding PPDU, as shown in mathematical expression 3 below. In this case, TX represents the transmission time of X.

[0114]

[0115] Referring to the above formulas, the length of the PPDU is calculated based on the rounded value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0116] Referring to Fig. 7(e), the U-SIG (Universal SIG) field continues to exist in EHT / UHR PPDUs and subsequent generation wireless LAN PPDUs, and serves to distinguish which generation of PPDU it is, including EHT / UHR. In addition, the U-SIG field can serve to facilitate spatial reuse of EHT / UHR and subsequent generation wireless LANs. U-SIG is an OFDM 2 symbol based on 64FFT and can convey a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits of CRC / Tail, are largely divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0117] The VI bit maintains its current bit configuration in the future so that even if a subsequent generation PPDU is defined, current EHT / UHR terminals can obtain information about the PPDU through the VI fields of the PPDU. For this purpose, the VI field consists of PHY version, UL / DL, BSS Color, TXOP, and Reserved fields. The PHY version ID field is 3 bits and sequentially distinguishes EHT / UHR and subsequent generation wireless LAN standards by version. The PHY version ID field of the EHT (11be) PPDU has a value of 000b, and the PHY version ID field of the UHR PPDU has a value other than 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS Color means an identifier for each BSS defined in 11ax and has a value of 6 bits or more. TXOP stands for Transmit Opportunity Duration transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the corresponding PPDU can be inferred without having to decode the MPDU, and has a value of 7 bits or more.

[0118] The VD field of EHT is signaling information that is only useful for PPDUs of version 11be. It can be composed of fields that are commonly used in any PPDU format, such as PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a delimiter that distinguishes EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs.

[0119] The BW field largely signals five basic PPDU BW options of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz (a BW that can be expressed in the form of an exponential of 20*2 can be called the basic BW), and various remaining PPDU BWs configured through Preamble Puncturing. In addition, some 80 MHz can be signaled in a punctured form after being signaled at 320 MHz. In addition, the punctured and modified channel form can be signaled directly in the BW field, or by using the BW field together with a field that appears after the BW field (for example, a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signaling is possible, so only a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signaling is possible, so the puncturing mode can signal up to 11.

[0120] The VD field of the UHR is a field that indicates signaling information that is only useful for the UHR PPDU. However, the information indicated by each field included in the VD field of the UHR PPDU may be identical to or more extended than the information indicated by the field that plays the same role as the VD field of the EHT (11be). For example, the field indicating the puncturing pattern included in the VD field of the UHR PPDU may indicate a wider variety of patterns than the field indicating the puncturing pattern included in the VD field of the EHT PPDU. Alternatively, the field indicating the puncturing pattern included in the VD field of the UHR PPDU may be interpreted in conjunction with the BW field. This allows for indicating a wider variety of puncturing patterns.

[0121]

[0122] Figure 8 shows an EHT / UHR PPDU format according to an embodiment of the present invention.

[0123] The EHT / UHR PPDU format can be indicated by the PPDU Format field of the U-SIG field of the PPDU. Fig. 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 the U-SIG.

[0124] FIG. 8(b) illustrates an EHT / UHR Trigger-based PPDU according to an embodiment of the present invention. An EHT / UHR Trigger-based PPDU is an uplink PPDU used for transmission in response to a trigger frame, and may not have a separate EHT / UHR-SIG-A field after the U-SIG.

[0125] Figure 8(c) illustrates an EHT / UHR MU PPDU according to an embodiment of the present invention. An EHT / UHR MU PPDU is a PPDU used for transmission to one or more terminals. The EHT / UHR MU PPDU format may include a HE-SIG-B field after the U-SIG field.

[0126] Figure 8(d) illustrates 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 allows the U-SIG to be repeated along the time axis.

[0127] The EHT / UHR MU PPDU described through (c) of FIG. 8 can be used by an AP to perform downlink transmission to multiple stations. At this time, the EHT / UHR MU PPDU can include scheduling information for multiple stations to simultaneously receive the PPDU. At this time, the EHT / UHR MU PPDU can convey AID information of the receiver or transmitter of the corresponding PPDU through the user specific field of EHT / UHR-SIG-B. A station that receives the EHT / UHR MU PPDU can perform a spatial reuse operation based on the AID information obtained from the preamble of the PPDU. More specifically, the resource unit allocation (RA) field of EHT / UHR-SIG-B can include information on a resource unit (RU) partitioning form in a specific bandwidth (e.g., 20 MHz) in the frequency domain. Additionally, information about the station assigned to each partitioned resource unit may be conveyed via a user-specific field of EHT / UHR-SIG-B. The user-specific field may include one or more user fields corresponding to each partitioned resource unit.

[0128] Among the multiple resource units divided, the AID of the receiver or sender may be inserted into the user field corresponding to the resource unit in which data transmission is performed. A pre-specified null STA ID may be inserted into the user field corresponding to the remaining resource units in which data transmission is not performed.

[0129] Two or more PPDUs described through FIG. 8 may be indicated by the same PPDU format. For example, the value of the U-SIG PPDU format subfield indicating an EHT / UHR SU PPDU and the value of the U-SIG PPDU format subfield indicating an EHT / UHR MU PPDU may be the same.

[0130] Some fields or some information within a field included in the PPDU format described above may be omitted. This may be referred to as compression mode or compressed mode.

[0131]

[0132] <Wi-Fi 단말의 채널 액세스 방법>

[0133] Wi-Fi terminals (APs, non-AP STAs, etc.) perform communication using unlicensed bands, so before transmitting a frame, they check whether the channel they want to transmit is in use by another device. CSMA (Carrier Sense Multiple Access) is a channel access method in which a terminal that wants to transmit a packet performs carrier sense to check whether the channel is in use by another device, and transmits only if the channel is determined to be idle. Since a terminal using CSMA can perform an action of not attempting transmission at least when it is determined that another device is using the medium (channel) (when it is determined to be busy), the transmission that was initiated first can be protected from other devices.

[0134] However, multiple terminals that recognize that the medium is occupied by another device experience a transmission collision by simultaneously attempting to transmit packets when it is confirmed that the medium occupation from the other device has ended (the medium has changed to Idle). That is, as multiple other terminals simultaneously attempt to transmit packets when a specific terminal attempts to transmit a packet, a terminal that is supposed to receive the packet transmitted by the specific terminal is unable to properly receive and decode the packet that it is supposed to receive due to interference caused by the transmissions performed by the multiple other terminals.

[0135] CSMA / CA (CSMA with collision avoidance) is a channel access mechanism that prevents multiple terminals from simultaneously attempting packet transmission when the medium has changed to Idle, as described above. Terminals accessing the medium (channel) using CSMA / CA attempt to transmit after waiting for a random amount of time when the state of the medium they observe changes to Idle. The random amount of time may be an aslottime (typically 9 microseconds) equal to a random number (random backoff counter) generated by each terminal attempting to transmit. In other words, terminals accessing the medium using CSMA / CA attempt to transmit after waiting for different random amounts of time, so they attempt to transmit at different times, unlike when CSMA alone is used. In this case, when a specific terminal that waited for the shortest random amount of time after the medium changed to Idle attempts to transmit first, other terminals can recognize that the medium has been occupied (changed to busy) by the specific terminal and abort the channel access procedure. At this time, the specific terminal may perform an operation of decreasing the backoff counter maintained by it by 1 every aslottime while the medium is maintained as Idle, and may attempt transmission when the backoff counter becomes 0, or when the aslottime has passed after the backoff counter becomes 0. At this time, the specific terminal that performed the transmission may generate a new random number (new backoff counter) after the transmission is finished, and may attempt transmission when the new random number becomes 0 again, or after it becomes 0.

[0136] The CSMA / CA and random backoff procedures briefly explained above are applied to DCF (Distributed coordination function) and EDCAF (Enhanced distributed channel access function), which are the basic functions used by Wi-Fi terminals when attempting to access a channel. Since these are well-known and widely used unlicensed band channel access methods, a more detailed explanation will be omitted.

[0137]

[0138] The DCF and EDCAF utilized by the MAC of the Wi-Fi terminal evaluate the channel status by considering not only the channel status (idle / busy) confirmed by each terminal performing its own physical CS (Carrier Sense) but also the results of a virtual CS. In more detail, even if the result of the physical CS performed on the channel is idle, if the result of the virtual CS is busy, the Wi-Fi terminal considers the channel status to be busy. At this time, 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 predicted to occupy the medium. To explain in more detail, when the MAC of Wi-Fi receives an RTS / CTS frame, it can set the NAV (NAV count) based on the duration information of the received frame, for example, the value of the duration field, and maintain the NAV as a non-zero value for the expected time that 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 specific MAC is 0, it can be interpreted that the future traffic recognized by the specific MAC is no longer occupying the medium. If the NAV is 0, the MAC can determine the virtual CS result as Idle. At this time, the MAC of Wi-Fi can also set the NAV based on the duration value obtained from not only the RTS / CTS frame but also other received MAC frames.

[0139] The channel estimation method (determine the state of the medium) that considers the results of the physical CS and virtual CS briefly described above is also one of the well-known Wi-Fi MAC functions, so a detailed explanation is omitted.

[0140]

[0141] <EDCA와 TXOP>

[0142] EDCA provides a mechanism to differentiate and manage traffic into four types of ACs (access categories) according to the characteristics of the traffic. At this time, the four types of ACs are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best effort), and AC_BK (AC Background), and each AC can have different CW (contention window), TXOP (transmit opportunity), and AIFSN parameters. Simply put, EDCA is a mechanism that differentiates the CW, TXOP, and AIFSN parameters for the four types of ACs and controls the transmission priority of traffic transmitted using each AC. To this end, EDCA can map traffic (MSDU) that the MAC must service to one of the four ACs according to the TC (traffic category) or TS (traffic stream). At this time, the traffic mapped to one of the four ACs by EDCA is divided and managed into four queues for each AC. At this time, the four queues may be logically separated rather than physically separated.

[0143] AC_VO is an AC that can be utilized for traffic that is vulnerable to transmission delays, although the absolute volume of traffic, such as voice traffic, is not large. It has relatively small CW and AIFSN parameter values ​​to increase the probability of being serviced preferentially over traffic from other ACs. The TXOP parameter of AC_VO is limited to a relatively small value compared to the TXOP parameters of other ACs, ensuring only a shorter transmission time than other ACs.

[0144] AC_VI is an AC that is more delay-tolerant than voice traffic, but can still be utilized for traffic such as video that requires low-latency transmission and high traffic volume. AC_VI has larger CW and AIFSN parameter values ​​than AC_VO but smaller than other ACs, and its TXOP is approximately twice as long as AC_VI.

[0145] AC_BE is an AC that can be utilized 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 CW and AIFSN parameters with values ​​greater than AC_VO and AC_VI. In addition, AC_BE does not have a separate TXOP. Therefore, traffic corresponding to AC_BE cannot be utilized in the TXOP transmission sequence, which transmits a PPDU, receives an ACK in response, and then transmits a PPDU again after SIFS.

[0146] AC_BK, similar to AC_BE, is a delay-tolerant traffic, but can be utilized for lower-priority traffic than BE traffic. AC_BK utilizes the same CW parameter values ​​as AC_BE, and the AIFSN parameter values ​​are larger than those of AC_BE. In addition, traffic corresponding to AC_BK does not have a separate TXOP like AC_BE, so it cannot be utilized in the TXOP transmission sequence.

[0147] The four types of EDCA AC described above are mapped to the UP (user-priority) of 802.1D, and the EDCA AC is determined based on the UP value of the traffic received through the wire or the TID of the MSDU indicated from the upper layer. At this time, if the TID of the MSDU indicates a value between 0 and 7, the value indicated by the TID can correspond one-to-one with the UP.

[0148] In addition, the four types of EDCA AC described above have default CW (CWmin, CWmax), AIFSN, and TXOP parameters defined in the standard, and the parameter values ​​of each AC can be changed by the AP, so that different values ​​can be used for each BSS.

[0149]

[0150] Using the EDCA mechanism, Wi-Fi traffic is stored in one of four queues corresponding to four ACs, and can be transmitted to the destination device only if the AC containing the traffic wins the channel access competition with other ACs. At this time, in the channel access competition between ACs, each AC competes using its assigned access parameters (CW[AC], AIFSN[AC]), and the channel access competition operation performed by each AC is identical to DCF. At this time, if a specific AC does not have any traffic to transmit in its queue, the specific AC may not participate in the competition.

[0151] However, as described above, since the CW and AIFSN parameter values ​​utilized by each AC are different, the AC_VO with the smallest CW and AIFSN parameters is more likely to win the channel access competition with other ACs, and thus the traffic of AC_VO is more likely to be serviced with priority over the traffic of other ACs.

[0152] In addition, the EDCA mechanism stipulates internal competition rules such as when an (internal) collision occurs between ACs, the AC with a higher priority wins, and increases the CW of the other AC that caused the collision, and rules for composing a PPDU including traffic from an AC other than the AC that won the competition (primary AC), but a detailed description is omitted because it is not closely related to the proposal of the present invention.

[0153] As described above, EDCA provides the EDCA TXOP (EDCA Transmission Opportunity) function along with the function of operating differentiated ACs according to the type of traffic (frames, packets, etc.) to enhance QoS. EDCA TXOP refers to the time during which the EDCAF (EDCA Function) of a specific AC can control the medium without being disturbed by other devices during the TXOP period (duration) when it obtains a channel access opportunity, i.e., becomes a TXOP holder. At this time, the EDCA TXOP may be limited by the TXOP limit advertised by the AP. The TXOP holder must ensure that its own transmission and the transmission of the response frame responded to by its own transmission can be terminated within the TXOP limit.

[0154] A TXOP holder can transmit multiple frames (multiple PPDUs) during an EDCA TXOP period. If the transmission of each frame is performed within the acquired TXOP period, the TXOP holder can transmit multiple frames continuously without performing a separate channel access procedure, such as a backoff procedure, between transmissions of each frame. At this time, if the multiple frames are MPDUs or A-MPDUs (Aggregated MAC protocol data units) that do not request an immediate ack, the transmission of the multiple frames can be performed at an interval of a short interframe space (SIFS) or a reduced interframe space (RIFS). At this time, if there is an MPDU or A-MPDU requesting an immediate ack among the multiple frames, the TXOP holder can transmit a frame requesting an immediate ack, receive the ack, and transmit the next frame after an SIFS.

[0155] At this time, traffic (packets, frames, etc.) of other ACs other than the specific AC that is the TXOP holder may also be transmitted together within the TXOP acquired by the TXOP holder (specific AC) when certain conditions are satisfied. The transmission of traffic of other ACs other than the TXOP holder within the TXOP may be an operation due to TXOP sharing between ACs, and detailed information regarding the above-mentioned certain conditions is omitted because it is not related to the present invention.

[0156]

[0157] As described above, a TXOP holder can perform continuous frame transmission without performing a separate channel access procedure within the TXOP. This may be an operation that can be achieved when other terminals understand and protect the TXOP interval acquired by the TXOP holder. In other words, in order for the TXOP holder to acquire medium control authority for the EDCA TXOP interval, a procedure may be required to notify other terminals of the acquired TXOP interval so that they can recognize it.

[0158] To this end, a terminal (AC) that becomes a TXOP holder or initiates transmission after completing a channel access procedure may attempt to allow other terminals to recognize the TXOP section by transmitting an RTS frame. At this time, the RTS frame means a frame in which the Type subfield (the fourth bit (B3), the third bit (B2) of the Frame Control field) of the Frame Control field of the MAC frame header is set to 01b (Type = Control frame) and the Subtype subfield (the eighth bit (B7), the seventh bit (B6), the sixth bit (B5), the fifth bit (B4) of the Frame Control field) is set to 1011b. Another terminal that receives an RTS frame from a TXOP holder may set an NAV based on information related to the duration included in the RTS frame, for example, the value of the Duration field. The set NAV may be maintained as a non-zero value for a time corresponding to the TXOP of the TXOP holder. However, the terminal indicated as the destination device of the RTS frame must respond with a CTS frame instead of setting the NAV based on the information in the RTS frame. At this time, the destination device of the RTS frame transmitted to start TXOP is a TXOP responder and must transmit a CTS frame in response to the RTS (SIFS after the RTS frame is received). At this time, the Duration field of the responding CTS frame is set to a value calculated as the value indicated in the Duration field of the received RTS frame - the CTS frame transmission time - SIFS. The terminals receiving the CTS frame can set the NAV based on information related to the duration included in the CTS frame (e.g., the value of the Duration field).

[0159] Therefore, the NAV of the terminal that received the RTS frame from the TXOP holder and the terminal that received the CTS frame from the TXOP responder are set to 0 after the TXOP acquired by the TXOP holder ends. This allows the Wi-Fi MAC mechanism to protect the TXOP holder and the TXOP responder from exchanging multiple frames without interruption during the TXOP.

[0160] However, if the TXOP holder transmits an RTS frame as a non-HT duplicate PPDU over the primary 80 MHz band, but the CTS frame (non-HT duplicate PPDU) responded to by the TXOP responder is responded to only in the primary 40 MHz band, the TXOP holder may use only the bandwidth of the primary 40 MHz or less than the primary 40 MHz, for example, the primary 20 MHz, for frame exchange during the acquired TXOP. The CH_BANDWIDTH (a type of TXVECTOR parameter) of the PPDU transmitted by the TXOP holder shall be set to a value equal to or smaller 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 in a BW smaller than the BW in which the RTS frame was transmitted. An 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 the RTS frame is transmitted from a TXOP holder, the TXOP responder may have to respond with a CTS frame with the same BW as the BW in which the RTS frame was received.

[0161]

[0162] FIG. 9 shows a transmission / TXOP protection method using an RTS frame and a CTS frame according to an embodiment of the present invention.

[0163] Before transmitting a PPDU, the first station (STA1) transmits an RTS frame to the second station (STA2), which is the destination of the PPDU, and the second station (STA2) recognizes that the received RTS frame is an RTS frame destined for itself and responds with a CTS frame after SIFS.

[0164] STA1_Neighbor, a neighbor station of the first station (STA1), sets the NAV based on the value indicated by the Duration field of the RTS frame after receiving the RTS frame transmitted by the first station (STA1). STA2_Neighbor, a neighbor station of the second station (STA2), sets the NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the second station (STA2). STA1_Neighbor and STA2_Neighbor determine that the virtual CS is busy while the set NAV (counter) is maintained at a non-zero value after receiving the RTS / CTS frame, and perform actions such as not decreasing the backoff counter. As a result, the neighboring terminals that received the RTS / CTS frame do not attempt transmission during the period in which the NAV is maintained at a non-zero value. Therefore, the first station (STA1) and the second station (STA2) may not be disturbed by surrounding terminals while exchanging PPDU and Ack frames.

[0165] Even if the first station (STA1) and STA2_Neighbor are in a relationship where signals due to each other's transmissions are not detected (hidden), STA2_Neighbor can perform an operation that takes into account that the channel (channel, WM, Wireless medium) is in use while the first station (STA1) transmits a PPDU.

[0166]

[0167] <MU-RTS 트리거 프레임을 이용한 TXOP 보호>

[0168] 11ax (6th generation Wi-Fi, Wi-Fi6, HEW, High Efficiency WLAN) defines the MU-RTS Trigger / CTS frame exchange procedure, and adds a function that enables the AP to start TXOP and protect the TXOP frame exchange procedure using the MU-RTS trigger frame (hereinafter referred to as MU-RTS, MU-RTS frame). The MU-RTS frame is a type of trigger frame. When the MU-RTS frame is received, the station whose AID12 (the LSB 12 bits of the Association ID) is indicated in the User field included in the MU-RTS frame simultaneously responds with a CTS frame. When the AP protects the TXOP using the MU-RTS frame, since multiple stations respond with CTS frames, the TXOP can be protected from the peripheral devices of each of the multiple stations that are the destination devices of the DL MU PPDU (Down link multi-user PPDU). In addition, the MU-RTS frame can be used to protect the UL MU PPDU. In more detail, before requesting a TB (Trigger based) PPDU from multiple stations through a trigger frame, the AP can transmit an MU-RTS frame to cause multiple stations that will respond to the TB PPDU to respond with a CTS frame. At this time, the CTS frames responded to by the multiple stations induce the surrounding stations of each station to set a NAV that protects the TB PPDU and the Ack frame (Ack, Block Ack, etc.) to be transmitted after the TB PPDU, and through this, legacy stations STAs that cannot recognize (interpret, decode) the trigger frame and TB PPDU may not perform channel access during the packet exchange sequence period (or TXOP) initiated through the trigger frame.

[0169]

[0170] FIG. 10 shows a transmission / TXOP protection method using an MU-RTS frame and a CTS frame according to an embodiment of the present invention.

[0171] In the embodiment of FIG. 10, before transmitting an MU PPDU, the AP transmits an MU-RTS frame to the first station (STA1) and the second station (STA2), which are the destination devices of the MU PPDU, and the first station (STA1) and the second station (STA2) receive the MU-RTS frame and, after SIFS, each respond to the MU-RTS frame with a CTS frame.

[0172]

[0173] STA1_Neighbor, a neighboring station of the first station (STA1), sets its NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the first station (STA1). STA2_Neighbor, a neighboring station of the second station (STA2), sets its NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the second station (STA2). STA1_Neighbor and STA2_Neighbor perform actions such as not decreasing the backoff counter, assuming that the Virtual CS (Virtual Carrier Sense) is busy while the NAV (counter) set after receiving the CTS frame remains at a non-zero value. Therefore, neighboring terminals that have received the CTS frame do not attempt to transmit during the period in which the NAV remains at a non-zero value. This allows the AP to transmit MU PPDUs and the first station (STA1) and the second station (STA2) to transmit Ack frames without being interrupted by surrounding terminals.

[0174] The trigger frame described above is a frame type defined in 11ax, and is a frame type in which the Type (fourth bit (B3) and third bit (B2)) and Subtype (eighth bit (B7), seventh bit (B6), sixth bit (B5), and fifth bit (B4)) subfields of the Frame Control field are set to 01b and 0010b, respectively. A trigger frame is a frame of Control Type in which 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, a trigger frame is defined so that an AP can request a response frame for multiple stations at once, and an MU-RTS frame is used so that an AP can request a CTS frame for multiple stations (non-AP STAs). Trigger Types other than the MU-RTS frame include the Basic Tigger frame requesting UL MU PPDU, the Beamforming Report Poll Tigger frame requesting Beamforming Report, the MU-BAR Tigger frame (BlockAck request), the BSRP trigger frame requesting Buffer Status Report, the GCR MU-BAR trigger frame, the Bandwidth Query Report Poll (BQRP) trigger frame, and the NDP Feedback Report Poll trigger frame. Trigger Types other than the MU-RTS frame are not related to the content of the present invention, so a detailed description thereof is omitted.

[0175]

[0176]

[0177] Figure 11 shows the format of a trigger frame according to an embodiment of the present invention.

[0178] The trigger frame includes a MAC header including a Frame Control field, a Common Info field, a User Info List field, a Padding field, and an FCS field.

[0179] The Frame Control field contains Type and Subtype subfields, and a trigger frame has the values ​​of these two subfields set to 01b and 0010b, respectively.

[0180] The Common Info field includes a Trigger Type subfield for indicating the type of trigger frame, a UL Length subfield for indicating the length of the UL transmission being responded to, and more details are described in detail through an embodiment of FIG. 12.

[0181] The User Info List field may include a User Info field containing information for indicating the target device of the trigger frame. In this case, in addition to the information for indicating the target device, the User Info field also includes information regarding parameters used by the target device when transmitting a response frame after receiving the trigger frame, such as UL DCM or UL MCS, depending on the Type of the Trigger frame. The User Info field is described in detail with reference to FIG. 13.

[0182] The Padding field is a field set to secure time for the station receiving the trigger frame to prepare to transmit a response frame, such as a UL TB PPDU or CTS frame. The AP transmitting the trigger frame can adjust the length of the Padding field considering the performance of the target devices. In addition, in 11be (Wi-Fi 7, EHT), the end time of the PPDU containing the trigger frame may be added / adjusted to align it with other PPDUs, but a detailed explanation is omitted.

[0183] The FCS (Frame Check Sequence) field contains a 32-bit CRC (Cyclic Redundancy Code), calculated from the MAC header and Frame Body fields. The function and setting method of the FCS field in the trigger frame are identical to those of the FCS field in a conventional MAC frame. A separate description thereof will be omitted.

[0184]

[0185] Figure 12 shows the format of the Common Info field of a trigger frame according to an embodiment of the present invention.

[0186] The Trigger Type subfield indicates the type (type, variant) of the trigger frame. If the value of the Trigger Type subfield is 0, the Trigger Type subfield indicates a basic trigger frame. If the value of the Trigger Type subfield is 1, the Trigger Type subfield indicates a BFRP (Beamforming Report Poll) trigger frame. If the value of the Trigger Type subfield is 2, the Trigger Type subfield indicates an MU-BAR frame. If the value of the Trigger Type subfield is 3, the Trigger Type subfield indicates an MU-RTS frame. If the value of the Trigger Type subfield is 4, the Trigger Type subfield indicates a BSRP frame. If the value of the Trigger Type subfield is 5, the Trigger Type subfield indicates a GCR MU-BAR frame. If the value of the Trigger Type subfield is 6, the Trigger Type subfield indicates a Bandwidth Query Report Poll (BQRP) frame. If the value of the Trigger Type subfield is 7, the Trigger Type subfield indicates an NFRP (NDP Feedback Report Poll) frame.

[0187] The UL Length subfield indicates the value to be set in the L-SIG LENGTH field of the TB PPDU responded to via the trigger frame.

[0188] The More TF subfield indicates whether there are more trigger frames to be transmitted after the trigger frame containing the More TF subfield.

[0189] The CS Required subfield indicates whether the destination device of the trigger frame must perform CS (Physical & Virtual CS, ED & NAV) when transmitting a response frame. If the value of the CS Required subfield is 1, the station that receives the trigger frame containing the CS Required subfield must perform CS before transmitting a response frame to the trigger frame.

[0190] The UL BW subfield indicates the value of the BW field that an STA responding with a TB PPDU after receiving a trigger frame must set in the preamble, e.g., HE-SIG-A or U-SIG.

[0191] The GI And HE / EHT-LTF Type subfield indicates the GI (Guard interval) and HE (EHT)-LTF values ​​of the TB PPDU to be responded to.

[0192] The MU-MIMO HE(EHT)-LTF Mode subfield indicates information regarding the HE(EHT)-LTF mode that should be applied to the TB PPDU to be responded to.

[0193] If the value of the Doppler subfield is 0, the Number Of HE(EHT / UHR)-LTF Symbols And Midamble Periodicity subfield indicates the number of HE(EHT)-LTF symbols that should be applied to the TB PPDU. If the value of the Doppler subfield is 1, the Number Of HE(EHT / UHR)-LTF Symbols And Midamble Periodicity subfield indicates information related to the number of HE(EHT)-LTF symbols and the periodicity of the midamble.

[0194] The UL STBC subfield indicates whether STBC encoding should be applied to the TB PPDU that is a response to a trigger frame containing the UL STBC subfield. If STBC encoding should be applied, the value of the UL STBC subfield is set to 1. The value of the UL STBC subfield of the trigger frame that triggers the EHT / UHR TB PPDU is reserved.

[0195] The LDPC Extra Symbol Segment subfield indicates whether an LDPC extra symbol segment should appear in the TB PPDU that is a response to a trigger frame containing the LDPC Extra Symbol Segment subfield. If the value of the LDPC Extra Symbol Segment subfield is 1, the TB PPDU that is a response to a trigger frame containing the LDPC Extra Symbol Segment subfield contains an LDPC extra symbol segment.

[0196] The AP Tx Power subfield indicates a value related to the transmission power used by the AP that transmitted the trigger frame when transmitting the trigger frame. A station that receives the trigger frame can adjust the transmission power of the response frame to the trigger frame based on the value indicated by the AP Tx Power subfield.

[0197] The Pre-FEC Padding Factor and PE Disambiguity subfields indicate whether the Pre-FEC Padding Factor is 1, 2, 3, or 4, and provide information to clarify the length of the PE (Packet Extension).

[0198] The UL Spatial Reuse subfield contains four Spatial Reuse subfields and indicates the value to be set in the Spatial Reuse field of a TB PPDU that is a response to a trigger frame containing a UL Spatial Reuse subfield.

[0199] The Doppler subfield indicates whether a midamble is included in the TB PPDU, which is a response to a trigger frame containing a Doppler subfield. A trigger frame that triggers an EHT / UHR TB PPDU may have the value of the Doppler subfield set to reserved. In this case, setting the subfield to reserved may indicate that the station operates without considering the presence and value of the Doppler subfield after receiving the trigger frame.

[0200] The Special User Info Field Present subfield indicates whether the User Info field, among the User Info fields, represents a User Info field whose AID12 subfield is indicated as 2007 or a predefined value.

[0201] The Trigger Dependent Common Info subfield is a field included in a trigger frame only when the type of trigger frame indicated by the Trigger Type field is a basic trigger frame or an NFRP trigger frame.

[0202]

[0203] Figure 13 shows the format of the User Info field of a trigger frame according to an embodiment of the present invention.

[0204] The AID12 subfield indicates information regarding which station the User Info field containing the AID12 subfield is for. A station with an AID equal to the AID indicated by the AID12 subfield can determine that a trigger frame containing the AID12 subfield includes the station as a destination. In this case, the AID12 subfield can be set to 1 to 2006 (1 to 2007 if the trigger frame is a HE Trigger) when indicating one associated station.

[0205] At this time, if the value of the AID12 subfield is 0, the AID12 subfield may indicate that one or more RA-RUs (Random Access RUs) are allocated to a station associated with the AP that transmitted the trigger frame. If the trigger frame received by the station associated with the AP that transmitted the trigger frame does not have a User Info field including an AID12 subfield indicating the AID of the station, and has a User Info field with a value of 0 in the AID12 subfield, the station may attempt to transmit a TB PPDU using RA-RU.

[0206] Additionally, if the value of the AID12 subfield is 2045, the AID12 subfield may indicate that one or more RA-RUs (Random Access RUs) are allocated to a station that is not associated with the AP that transmitted the trigger frame. A station that is not associated with an AP may attempt to transmit a TB PPDU using RA-RUs if the trigger frame received by the station includes a User Info field with the value of the AID12 subfield being 2045.

[0207] Additionally, if the value of the AID12 subfield is 4095, the station receiving the trigger frame may determine that a padding field starts from the AID12 subfield. In this case, the station may not attempt to parse the remaining portion of the MAC frame after the AID12 subfield with the value 4095.

[0208] Additionally, when the value of the AID12 subfield is 2046, the AID12 subfield may indicate that the User Info field containing the AID12 subfield indicates information about an unallocated RU, which is an RU that is not allocated to any station.

[0209] Except for the MU-RTS trigger frame, the RU Allocation subfield of other trigger frames indicates the size and location information of the RU (Resource Unit) / MRU (Multiple Resource Unit) allocated to the destination device of the User Info field including the RU Allocation subfield. The station can determine the information of the RU / MRU allocated to the station by interpreting the RU Allocation subfield and the PS160 subfield included in the User Info field together. The station can determine the information of the RU / MRU allocated to the station by interpreting the RU Allocation subfield and the PS160 subfield and PS320 subfield included in the User Info field together. At this time, the PS320 subfield indicates whether the allocated RU is included in the primary 320 MHz band or the secondary 320 MHz band among the 640 MHz band. The PS160 subfield indicates whether the RU is allocated within a 160 MHz band located higher on the frequency axis or within a 160 MHz band located lower on the frequency axis within the 320 MHz band indicated by the PS320 subfield (primary 320 MHz or secondary 320 MHz). However, if the 320 MHz band indicated by the PS320 subfield is the primary 320 MHz, the information indicated by the PS160 subfield may indicate whether it is the primary 160 MHz or the secondary 160 MHz, rather than the high / low on the frequency axis. Specifically, the 320 MHz band indicated by the PS320 subfield may be the primary 320 MHz. In this case, if the value of the PS160 subfield is 0, the PS160 subfield may indicate that the allocated RU is included in the primary 160 MHz band.When the value of the PS160 subfield is 1, the PS160 subfield may indicate that the allocated RU is included in the secondary 160 MHz band. In this case, the value of the PS160 subfield is an example. When the value of the PS160 subfield is 1, the PS160 subfield may indicate that the allocated RU is included in the primary 160 MHz band. When the value of the PS160 subfield is 0, the PS160 subfield may indicate that the allocated RU is included in the secondary 160 MHz band.

[0210] Within each 160 (and 320) MHz band indicated in this manner, the method of indicating the location of the allocated RU may be the same as or similar to the method of indicating the RU Allocation subfield of the trigger frame defined in EHT.

[0211] The RU Allocation subfield of the MU-RTS indicates the channel on which the destination device in the User Info field responds to the CTS frame. Specifically, the RU Allocation subfield of the MU-RTS frame indicates whether the destination device transmits the CTS frame only on the primary 20 MHz channel, or on the primary 40 MHz channel, primary 80 MHz channel, primary 160 MHz channel, 80 + 80 MHz channel, primary 320 MHz channel, or primary Primary 640 MHz channel when transmitting the CTS frame. At this time, MRU represents an RU that is a combination of two or more RUs, and 52+26, 106+26, 484+242, 996+484, 996+484+242, 2x996+484, 3x996, 3x996+484, 4x996, 4x996+4x996-tone size MRUs can be used in UHR.

[0212] The UL FEC Coding Type subfield indicates the code type of the TB PPDU to be responded to. If the value of the UL FEC Coding Type subfield is 0 and the value of BCC (binary convolution coding) is 1, the UL FEC Coding Type subfield indicates LDPC (low density parity check).

[0213] The UL EHT / UHR-MCS subfield indicates the EHT / UHR-MCS to be applied to the TB PPDU transmission in response to the trigger frame.

[0214] The SS Allocation / RA-RU Information subfield can be used as the SS Allocation subfield when the AID12 subfield is not allocated an RA-RU. The 6 bits of the SS Allocation subfield can include a 4-bit Starting Spatial Stream subfield and a 2-bit Number Of Spatial Streams subfield. When the value of the AID12 subfield is 0, 2044, or 2045, the User Info field containing the AID12 subfield indicates information about the RA-RU.

[0215]

[0216] The UL Target Receive Power subfield indicates the predicted signal strength (power) that the TB PPDU, which is a response to the trigger frame, will receive at the AP's antenna side. When a station transmits a TB PPDU, the station can adjust the transmission power of the TB PPDU according to the value of the UL Target Receive Power subfield. This allows the AP to receive the TB PPDU at the power it expects.

[0217] The PS160 subfield, together with the RU Allocation subfield, indicates information about the location and size of the RU / MRU allocated by the User Info field containing the PS160 subfield.

[0218] The Trigger Dependent User Info (sub) field does not appear in the MU-RTS frame, so a detailed description is omitted.

[0219]

[0220] Limitations of Existing Channel Access Methods

[0221] As mentioned above, in Wi-Fi, an AP can instruct multiple non-AP STAs to simultaneously transmit DL PPDUs by using the signaling field included in the preamble to indicate information related to the RU that each non-AP STA should receive. In addition, multiple non-AP STAs can transmit UL PPDUs based on a trigger frame transmitted from the AP. In this way, the frame exchange sequence (frame exchange sequence) performed by the AP as the center and multiple non-AP STAs is an evolution of Wi-Fi wireless LAN technology designed to more efficiently utilize limited radio frequency resources.

[0222] However, the AP's operation of transmitting a DL MU PPDU or instructing / triggering UL MU PPDU transmission through a trigger frame has a limitation in that it can only be used when the AP has acquired a TXOP. When a non-AP STA has acquired a TXOP, a 1:1 frame exchange sequence is performed in which the non-AP STA transmits a UL PPDU and the AP responds to it (Ack, Block Ack, etc.), which is the same as the frame exchange sequence used in older versions of WLAN. In other words, since the Multi-User operation of the recently defined Wi-Fi standard can only be used in the TXOP acquired by the AP, there is a limitation in that it is difficult to expect an improvement in WLAN utilization efficiency due to MU operation when a non-AP STA has acquired a TXOP.

[0223]

[0224] When a non-AP STA acquires a TXOP, in addition to not being able to perform highly efficient MU operations (operations utilizing DL MU PPDU and UL MU PPDU), it has more limitations compared to when an AP acquires a TXOP.

[0225] For example, the amount of frequency resources available for frame exchange is limited. Generally, non-AP STAs have lower capabilities compared to APs, and therefore their operating BW is likely to be narrower than that of the AP. In other words, the BW of the TXOP acquired by a non-AP STA after performing channel access is relatively higher than the BW that can acquire the TXOP when the AP performs channel access. For example, if the AP supports operation for 320 MHz BW, but the non-AP STA only supports operation for 80 MHz BW, the non-AP STA will acquire the TXOP for only 80 MHz and then perform frame exchange with the AP. In this case, the AP cannot utilize the capabilities that it could support through the remaining 240 MHz of the 320 MHz BW, excluding 80 MHz, which means that the opportunity to support services for more traffic may be lost due to the TXOP acquired by the non-AP STA.

[0226] Another example is the limited number of spatial streams available for frame exchange. Typically, non-AP STAs have configurations that include fewer antennas than APs, resulting in a smaller number of available antennas. This means that even if the AP still has available antennas, the ability to perform more efficient operations utilizing those available antennas is limited during the time period in which the non-AP STA acquires a TXOP.

[0227] Even if it is not an example related to the BW and number of antennas described above, it is easy to understand that the expected utilization of the TXOP obtained by the AP is higher than the TXOP obtained by the non-AP STA, so a detailed explanation will be omitted.

[0228] FIG. 14 illustrates an example of a frame exchange sequence between STAs performed during a TXOP according to an embodiment of the present invention.

[0229] Referring to FIG. 14, after the AP acquires channel access rights (completes the backoff procedure), it acquires a TXOP for 320 MHz by transmitting a CTS-to-self frame across the 320 MHz band. During the TXOP it acquired, the AP transmits a 320 MHz DL PPDU and can use a trigger frame to cause a UL MU PPDU (TB PPDU) to respond across the 320 MHz band. In other words, the AP performs an MU operation utilizing the 320 MHz band during its TXOP, and this process utilizes a multi-antenna transmission / reception technology utilizing the eight antennas that the AP has.

[0230] On the other hand, after obtaining channel access, a non-AP STA transmits an RTS frame across the 80 MHz band and receives a CTS frame. Unlike the AP, which obtained a TXOP for the 320 MHz band, the non-AP STA obtains a TXOP only for the 80 MHz band due to capability limitations. The non-AP STA transmits a UL PPDU during the TXOP it has obtained and receives a BA in response. During this process, although the AP has eight antennas, the non-AP STA only uses two spatial streams because it has two antennas.

[0231] As a result, the TXOP acquired by the AP is efficiently utilized through MU PPDU exchange using a wide bandwidth and a large number of antennas, whereas the TXOP acquired by the non-AP STA is relatively less efficient because it utilizes a relatively narrow bandwidth and a small number of antennas.

[0232] That is, an AP can perform UL / DL transmission by acquiring a TXOP more efficiently than a non-AP STA can perform UL / DL transmission by acquiring a TXOP. Therefore, the present invention proposes a method for efficiently using a TXOP through a procedure for sharing the right to acquire a TXOP or the acquired TXOP between STAs.

[0233] Specifically, an STA (e.g., a non-AP STA or AP) that has acquired the right to acquire a TXOP through a back-off procedure or has already acquired a TXOP can share the acquired right or TXOP with another STA (e.g., a non-AP STA or AP) through a specific frame (e.g., an initiating frame). In this case, the other STA can transmit and receive PPDUs using the right to acquire a TXOP or the acquired TXOP. If a non-AP STA can share the right to acquire a TXOP or the acquired TXOP with an AP of an associated BSS. The non-AP STA can transmit its own information (e.g., an access category related to the back-off procedure for acquiring a TXOP, the length of the TXOP, and buffer information) in a frame for acquiring the right to acquire a TXOP or sharing the acquired TXOP. An AP that has the right to acquire a TXOP or has shared a TXOP can transmit and receive PPDUs, and can instruct non-AP STAs to perform uplink transmission by transmitting a trigger frame. If the AP instructs a non-AP STA with the right to acquire a TXOP or with which it has shared a TXOP to perform uplink transmission through a trigger frame, a user information field including information such as the AID of the allocated resource for the corresponding non-AP STA may be located at the very first among the user information fields included in the user-specific field. A non-AP STA with the right to acquire a TXOP or with which it has shared a TXOP may perform channel access using EDCA parameters regardless of the value of the MU-EDCA timer.

[0234] After a TXOP ends, the AP can select a new backoff counter for channel access within the contention window. In this case, the contention window size for selecting a new backoff counter can be either the minimum value or the size of the contention window for the current connection category.

[0235] In the present invention, the length of the shared TXOP may be equal to or shorter than the length of the TXOP acquired by the sharing STA. That is, the STA may share all or part of the TXOP acquired through the backoff procedure.

[0236] Hereinafter, the method for obtaining a TXOP or sharing an acquired TXOP according to the present invention can be applied not only to a method in which a non-AP STA shares with an AP, but also between a non-AP STA and a non-AP STA, an AP and a non-AP STA, and an AP and an AP.

[0237] <non-AP STA의 개시를 기초로 수행되는 AP의 채널 액세스>

[0238] As mentioned above, in order to efficiently utilize wireless resources, it is advantageous for the AP to acquire a TXOP rather than for a non-AP STA to acquire a TXOP, and increasing the proportion of APs acquiring TXOPs is important for efficient utilization of wireless LAN resources in the BSS and the entire network.

[0239] According to one embodiment of the present invention, after obtaining channel access rights, a non-AP STA can induce an AP to obtain a TXOP instead of obtaining a TXOP itself. In other words, the non-AP STA can transfer / cede the TXOP acquisition opportunity it has obtained to an (associated) AP.

[0240] More specifically, a non-AP STA can acquire channel access (complete the backoff procedure) by performing a backoff procedure via DCF or EDCA. Subsequently, the non-AP STA can instruct the AP that it has acquired channel access through a pre-arranged procedure, thereby allowing the AP to acquire a TXOP. Through this process, the AP can acquire a TXOP (become a TXOP holder) based on the non-AP STA's acquisition of channel access.

[0241] Here is a simple sequence of operations in which a non-AP STA performs channel access and yields a TXOP acquisition opportunity to the AP. (See 1. to 5. below. Additional operations and considerations that can be applied to each sequence are A, B, etc.) However, the sequence of operations described below is only one embodiment, and it should be considered that the main idea of ​​the present invention is a method in which the AP acquires a TXOP through a series of processes after the non-AP STA acquires the TXOP acquisition right (channel access right, i.e., completion of the backoff procedure). In addition, it should be understood that the method in which the acquired TXOP is utilized similarly to the TXOP in which the AP is the TXOP holder (i.e., the AP transmits a DL MU PPDU or transmits a trigger frame to solicit a UL MU PPDU response, etc.) after the non-AP STA acquires the TXOP, and the method in which the AP utilizes a BW larger than the BW of the TXOP acquired by the non-AP STA are the same as the main function to be provided by the present invention, except that only the subject of acquisition of the TXOP is different.

[0242] The procedure for an STA (AP or non-AP) to acquire TXOP rights or share TXOPs from an STA (AP or non-AP STA) is as follows. Hereinafter, the procedure for an AP to acquire TXOP rights or share TXOPs from a non-AP STA is described as an example, but the present invention is not limited thereto and can be applied to a procedure for granting TXOP acquisition rights or sharing TXOPs between STAs.

[0243] 1. Non-AP STA performs backoff procedure through DCF or EDCA.

[0244] 2. Instead of transmitting a frame to initiate its own TXOP, a non-AP STA that has completed the backoff procedure transmits a pre-arranged frame to its associated AP to yield the AP the opportunity to acquire a TXOP. (An associated AP refers to an AP of the BSS of which it is a member.)

[0245] 3. The AP that receives the TXOP initiating frame from the non-AP STA transmits a frame for TXOP acquisition on the channel identified as IDLE as a result of CCA within its operating bandwidth.

[0246] 4. After the AP acquires the TXOP, it transmits a trigger frame.

[0247] 5. After the AP acquires a TXOP or when the TXOP ends, it creates a new backoff counter.

[0248] (1. Performing back-off procedures through DCF or EDCA)

[0249] A non-AP STA can acquire the right to acquire a TXOP through a back-off procedure. In this case, the non-AP STA can perform the back-off procedure using DCF, EDCA parameters, or MU EDCA parameters. If the non-AP STA wants to share the TXOP acquisition right or the acquired TXOP with an associated AP, it can perform the back-off procedure using EDCA parameters regardless of the value of the MU EDCA timer. In other words, a non-AP STA that wants to share the TXOP acquisition right or the acquired TXOP with an associated AP can perform the back-off procedure using EDCA parameters even if the value of the MU EDCA timer does not become '0' when performing the back-off procedure. In other words, a non-AP STA that wants to share the TXOP acquisition right or the acquired TXOP with an associated AP can perform the back-off procedure using EDCA parameters at any time regardless of the value of the MU EDCA timer.

[0250] That is, a non-AP STA that intends to share a TXOP with the AP after acquiring it or to transfer the TXOP acquisition opportunity to the AP can perform channel access using EDCA parameters regardless of the value of the MU EDCA timer. In addition, a non-AP STA can transfer the TXOP acquisition opportunity to the AP or share the acquired TXOP even if it performs a backoff procedure through MU EDCA. If the MU EDCA timer of a conventional Wi-Fi non-AP STA is not 0, the non-AP STA must perform channel access using the MU EDCA parameters, but if it intends to yield the TXOP acquisition opportunity to the AP, it can perform the backoff procedure by applying the EDCA parameters. This may be an operation considered to ensure that a non-AP STA that transfers the TXOP acquisition opportunity to the AP has channel access rights under the same conditions as a legacy non-AP STA that does not perform UL MU (Uplink multi-user) operation when performing channel access.

[0251] (2. Transmission of frames for TXOP acquisition or TXOP sharing)

[0252] A non-AP STA that has completed the backoff procedure may transmit a specific frame to grant (or share) the right (or opportunity) to acquire a TXOP to the AP instead of transmitting a frame to initiate a TXOP. At this time, the AP receiving the specific frame is an AP associated with the non-AP STA, that is, an AP of a BSS of which the non-AP STA is a member. The specific frame may be called an initiating frame, but is not limited thereto and may be called by various names. Alternatively, the initiating frame may be an existing frame, in which case the frame for granting the right to acquire a TXOP may be configured in a different manner. For example, the initiating frame may be an RTS frame or a trigger frame. In this case, the RTX frame or trigger frame for granting the right to acquire a TXOP may be configured in a different manner from the existing configuration method. For example, the format or field values ​​may be configured differently. That is, the initiation frame can be classified as a frame of the same type (and subtype) as the frame defined in conventional Wi-Fi, but can be set up in a different way when used to grant the AP the right to acquire the TXOP it has acquired.

[0253] The initiation frame may include at least one of Duration / ID information, AC information, buffer status information, and / or at least one parameter (e.g., MCS, PPDU BW (RU size), PPDU length) related to PPDU transmission of a non-AP STA that has acquired TXOP acquisition authority.

[0254] i. If the initiation frame is a CTS-to-AP frame, the CTS-to-AP frame refers to a CTS frame with the RA field set to the MAC address of the AP. At this time, the Duration / ID of the CTS-to-AP frame can be set to a length that includes the trigger frame to be transmitted by the AP that received the initiation frame.

[0255] ii. The initiation frame may include information related to an Access Category (AC) related to a back-off procedure for obtaining TXOP acquisition rights by a non-AP STA and / or information related to the length of TXOP that could be acquired after completing the back-off procedure. Information related to the length of TXOP may be set to a length that includes a trigger frame to be transmitted by an AP receiving the initiation frame in the Duration / ID field of the initiation frame. That is, the Duration / ID field may be set to a value that takes into account the length of the trigger frame when an AP granted TXOP acquisition rights from a non-AP STA transmits the trigger frame. Alternatively, information related to the length of TXOP may be indicated by being included in a Frame body field rather than a MAC header of the initiation frame.

[0256] iii. The initiation frame may include information (e.g., buffer status information) related to the buffer status of the non-AP STA transmitting the initiation frame (i.e., granting the right to acquire a TXOP or sharing the acquired TXOP).

[0257] iv. The initiation frame may include information related to parameters (e.g., MCS, PPDU bandwidth (RU size), PPDU length, etc.) that the non-AP STA transmitting the initiation frame (i.e., granting the right to acquire a TXOP or sharing the acquired TXOP) intends to use when transmitting an uplink PPDU.

[0258] v. The initiation frame may have a configuration including a user information field that a non-AP STA wants to receive through the trigger frame (a configuration identical (or similar) to the user information field included in the trigger frame). In this case, the AP may transmit a trigger frame including a user information field identical to the user information field included in the initiation frame to at least one non-AP STA, including a non-AP STA that grants the right to acquire a TXOP or shares the acquired TXOP.

[0259] vi. The initiation frame can be transmitted as a non-HT PPDU or a non-HT duplicated PPDU. That is, a non-AP STA can transmit the initiation frame as a non-HT or a non-HT duplicated PPDU.

[0260] The initiation frame may include information (e.g., channel state information) related to an idle channel identified by a non-AP STA transmitting the frame. More specifically, the initiation frame may have a configuration including a field indicating whether each subchannel identified by the STA transmitting the frame is IDLE / BUSY. In this case, whether each subchannel is IDLE or BUSY may be information utilized by an AP transmitting a trigger frame after receiving the frame. For example, when the AP allocates an RU to an STA that transmitted the initiation frame via the trigger frame, the AP may allocate an RU included in the subchannel(s) that the STA indicated as IDLE. That is, when selecting an RU to allocate to an STA that transmitted the initiation frame, the AP may need to allocate an RU included in a subchannel that the STA that transmitted the frame indicated as IDLE.

[0261] The Duration / ID field of the initiation frame may be set in a predetermined manner. More specifically, the Duration / ID field of the initiation frame may be set to a value indicating a time point before the start time of the TB PPDU responded to by the trigger frame transmitted by the AP that received the frame. That is, even if the second STA that received the initiation frame transmitted by the first STA sets the NAV (network allocation vector) based on the frame, the NAV is released at the time of responding with the TB PPDU for the trigger frame transmitted by the AP. Through this process, an unassociated non-AP STA can respond with a TB PPDU to the RA-RU (Random access RU) indicated by the trigger frame of the AP (through the UORA (UL OFDMA-based random access) procedure).

[0262] The Duration / ID field of the initiation frame may be set based on information previously instructed by the AP. That is, the AP may notify non-AP STAs of the value to be set in the Duration / ID field of the initiation frame through the Management frame. This may be a value determined by considering the time it takes for the AP to attempt to acquire a TXOP after receiving the initiation frame. For example, the AP may intend to adjust the length of a frame (e.g., an MU-RTS frame) transmitted to acquire a TXOP after receiving the initiation frame, and may notify the Duration / ID field value determined by considering the adjusted transmission length. As a more specific example, the AP may include padding in the initial frame transmitted after receiving the initiation frame, taking into account the mode transition time (eMLSR / low-power mode => normal operation mode) of non-AP STAs operating in eMLSR mode or low-power listening mode. In this case, the time taken by the AP to transmit the first trigger frame after acquiring the TXOP may be slightly longer than when transmitting a short initial frame (without padding). Therefore, in order to ensure MAC level protection until the non-AP STA that transmitted the initiation frame performs a TB PPDU response to the trigger frame, the Duration / ID field value of the initiation frame needs to be appropriately adjusted, and for this purpose, the AP should announce the Duration / ID field value. Alternatively, the AP may need to keep the length of the initial frame transmitted after receiving the initiation frame less than a pre-agreed length.In this case, the Duration / ID field value of the initiation frame is set in a pre-promised manner, and the initial frame sequence and the length of the initial frame must be adjusted in consideration of the time that the AP is protected by the Duration / ID field value.

[0263] A non-AP STA may need to transmit a CF-END frame if it does not receive a frame transmitted by the AP within a preset time interval after transmitting an initiation frame (a frame transmitted by the AP to acquire a TXOP or a frame following the initiation frame transmitted according to a pre-arranged frame exchange sequence). This may be a procedure (CF-END frame transmission) to release the NAV of STAs whose NAVs were set due to the initiation frame when the procedure for transferring the TXOP to the AP through the initiation frame fails.

[0264] A non-AP STA may be required to transmit an initiation frame if the time it acquires channel access (the time it completes the backoff procedure) is within the R-TWT SP (Restricted-TWT (target wake time) Service period). R-TWT SP refers to an SP set to transmit low-latency traffic with priority, and refers to TWT, a type of Broadcast TWT. The start time of an R-TWT SP has the characteristic of having the same start time as the overlapping quiet interval (1 TU length).

[0265] For 20 MHz-only non-AP STAs that only support 20 MHz operation, a restriction may be applied that requires them to transmit an initiation frame when the backoff procedure is completed. In other words, a 20 MHz-only non-AP STA may not be a TXOP holder itself and must hand over the TXOP to the AP. This may be an operational restriction for 20 MHz-only non-AP STAs considered to prevent the performance of the BSS from being degraded due to the limited performance of the 20 MHz-only non-AP STA.

[0266] (3. Attempt to acquire TXOP by obtaining TXOP acquisition authority or by AP that shares TXOP)

[0267] An AP that has received an initiation frame to obtain TXOP acquisition rights from a non-AP STA or to share an acquired TXOP can transmit a specific frame for TXOP acquisition on a channel identified as idle based on the result of CCA within its operating bandwidth (BW).

[0268] i. At this time, the method by which the AP determines whether each channel is IDLE through CCA may be based on the CCA result during the PIFS after the initiation frame is received. (Including Virtual CCA) At this time, the channel on which the initiation frame is received may be excluded from the determination of IDLE. Alternatively, the method by which the AP determines whether each channel is IDLE through CCA may be based on whether the channel maintained the IDLE state during the PIFS or SIFS after the initiation frame was received (Including Virtual CCA). At this time, the channel on which the initiation frame was received may be excluded from the determination of IDLE. Alternatively, the method by which the AP determines whether each channel is IDLE through CCA may be based on whether the channel maintained the IDLE state during the PIFS before the initiation frame was received (Including Virtual CCA).

[0269] ii. The AP can transmit a frame for acquiring TXOP on a channel other than the channel occupied by the PPDU including the initiation frame received from the non-AP STA (an idle channel). That is, the AP's TXOP acquisition procedure can proceed through a PPDU having a larger BW than the PPDU including the initiation frame. In this case, the AP's TXOP can be acquired for a BW larger than the BW in which the non-AP STA transmitted the initiation frame. In addition, even if the non-AP STA transmitting the initiation frame determines the subchannel to be busy and does not transmit the initiation frame (a channel that is included in the BW of the PPDU transmitted by the non-AP STA but is punctured), the AP can acquire the AP's TXOP because the AP determines the subchannel to be idle. In this case, the AP can use the RU of the subchannel (the subchannel not occupied by the initiation frame) for frame exchange with other non-AP STAs without allocating it to the non-AP STA. However, even if the subchannel is determined to be Idle by the AP, the AP does not attempt to acquire TXOP for a subchannel that the BSS has decided not to use (a disabled subchannel). After receiving an initiation frame, an AP attempting to acquire TXOP for a BW larger than the BW of the PPDU including the initiation frame may attempt BW expansion considering the Resolution of the BW expansion and / or the IDLE subchannel ratio for the additional BW. More specifically, an AP attempting to acquire TXOP for a BW larger than the BW of the PPDU including the initiation frame may attempt BW expansion only when a certain percentage or more of the subchannels included in the expanded BW are determined to be IDLE. In this case, the certain percentage may be, for example, 50%.For example, an AP that receives an initiation frame via an 80 MHz PPDU may attempt to acquire TXOP for 160 MHz BW only if two or more subchannels among the four subchannels included in the Secondary 80 MHz BW are determined to be IDLE. That is, if only one subchannel among the four subchannels included in the Secondary 80 MHz BW is determined to be IDLE, the AP may not attempt to acquire TXOP for 160 MHz BW. However, if six or more subchannels among the twelve subchannels included in the Secondary 80 MHz and Secondary 160 MHz bands are IDLE, the AP may attempt to acquire TXOP for the 320 MHz band. However, even in this case, if less than 4 of the 8 subchannels included in the Secondary 160 MHz band are idle, the AP cannot attempt to expand the BW for the Secondary 160 MHz band. The example considering the 50% ratio above is for illustration purposes only, and the specific ratio value can be changed to any other value. In other words, whether or not the AP is allowed to expand the BW is determined based on whether the gain obtainable through the expanded BW is sufficient, and the specific criteria for whether the gain is sufficient can be applied in any other way or based on any other criteria.

[0270] iii. The frame for acquiring TXOP transmitted by the AP may be a CTS-to-Self frame, an MU-RTS frame, an RTS frame, or a trigger frame.

[0271] iv. The PPDU including the frame for TXOP acquisition transmitted by the AP is transmitted after the last SIFS or PIFS of the PPDU including the initiation frame received from the non-AP STA. That is, the AP that received the initiation frame transmits the frame for TXOP acquisition after the SIFS or PIFS. At this time, the inter-frame space used when the AP transmits the frame for TXOP acquisition after receiving the initiation frame may be the same as the inter-frame space used by the AP to determine whether each subchannel is IDLE / BUSY. That is, the AP can perform CCA (PHY CCA, ED (energy detection)) on its operating bandwidth during the SIFS or PIFS immediately after receiving the initiation frame, and perform channel access for subchannels determined to be IDLE.

[0272] v. The Duration / ID field of the frame for acquiring TXOP transmitted by the AP can be set based on the received initiation frame. For example, the Duration / ID field of the frame for acquiring TXOP transmitted by the AP can be set to a value equal to or smaller than the value of 'Duration / ID field of initiation frame' - 'SIFS or PIFS' - 'length of the frame for acquiring TXOP transmitted by the AP'. Alternatively, the AP may need to determine the length of the TXOP that it is attempting to acquire based on information indicated by other fields included in the initiation frame. That is, the length of the TXOP that the AP can acquire can be determined (limited) based on other fields (fields other than the Duration / ID field) included in the initiation frame.

[0273] vi. The frame for acquiring TXOP transmitted by the AP may be transmitted in a non-HT PPDU or non-HT duplicated PPDU format. That is, after receiving the initiation frame, the AP must attempt to acquire TXOP using a non-HT or non-HT duplicated PPDU format.

[0274] (4. Transmission of trigger frame by AP)

[0275] When an AP acquires a TXOP by performing channel access after receiving an initiation frame transmitted by a non-AP STA, the AP may be required to transmit at least one trigger frame within the TXOP. In this case, the trigger frame may be a trigger frame that solicits a UL PPDU (TB PPDU) by allocating an RU to the non-AP STA that transmitted the initiation frame. However, if it is determined that the non-AP STA that transmitted the initiation frame does not need to perform transmission based on information included in the initiation frame, the AP may not be required to transmit the trigger frame within the acquired TXOP.

[0276] When an AP transmits a trigger frame to a non-AP STA that has transmitted an initiation frame, the AP may transmit a trigger frame to instruct uplink transmission to at least one non-AP STA within the acquired TXOP after acquiring a TXOP from the non-AP STA. At this time, at least one non-AP STA may include a non-AP STA that has been granted TXOP acquisition authority or has shared the acquired TXOP. If a trigger frame for uplink transmission is transmitted to a non-AP STA that has been granted TXOP acquisition authority or has shared the acquired TXOP (hereinafter, a TXOP-sharing non-AP STA), a user information field for the TXOP-sharing non-AP STA may be located at the very first of at least one user field included in a user-specific field of the trigger frame. This is to compensate the non-AP STA that has been granted TXOP acquisition authority or has shared the acquired TXOP to the AP.

[0277] i. The trigger frame has a configuration including a user information field corresponding to the AID of the TXOP-sharing non-AP STA that transmitted the initiation frame. At this time, among the user information fields included in the trigger frame, the user information field corresponding to the TXOP-sharing non-AP STA that transmitted the initiation frame may be indicated first. (The first except for the Special User Information field (the User Info field whose AID subfield is 2007 or a pre-promised value))

[0278] ii. The AP may set the user information field for the TXOP-sharing non-AP STA included in the trigger frame based on the information indicated through the initiation frame. That is, the User Info field corresponding to the non-AP STA that transmitted the initiation frame may be set based on various parameters (MCS, UL Length, BW / RU size information, etc.) included in the initiation frame. For example, the AP may set the UL Length subfield included in the trigger frame based on the information indicated by the TXOP-sharing non-AP STA. If the non-AP STA indicates information related to the length of the TB PPDU that it wants to transmit, the AP may set the UL Length field of the trigger frame to be equal to the indicated length or to a length longer than the indicated length. When the AP receives an initiation frame from a non-AP STA and transmits a trigger frame during the acquired TXOP, the AP can prioritize scheduling STAs that have transmitted / are scheduled to transmit the initiation frame (when soliciting a TB PPDU response). At this time, the AP can determine whether each STA is an STA that has transmitted / is scheduled to transmit the initiation frame based on whether a preset time has passed since the non-AP STA transmitted the initiation frame. Alternatively, the AP can determine whether each STA is an STA that has transmitted / is scheduled to transmit the initiation frame based on whether the STA has set the Capability or Operating element related to transmission of the initiation frame to true (or 1). When the AP allocates RUs to a TXOP-sharing non-AP STA that has transmitted an initiation frame, the AP must allocate only RUs in the band occupied by the PPDU including the initiation frame transmitted by the TXOP-sharing non-AP STA.That is, the AP must not allocate RUs in a band not occupied by the initiation frame (or the PPDU containing the initiation frame) to the TXOP-sharing non-AP STA that transmitted the initiation frame. This may be a RU allocation restriction that considers that the band not occupied by the initiation frame (or the PPDU containing the initiation frame) is a band that the non-AP STA that transmitted the initiation frame has determined as BUSY in the CCA result or a band outside the operating bandwidth of the non-AP STA. Accordingly, the size and position of the RU allocated to the non-AP STA that transmitted the initiation frame may be allocated differently from what the non-AP STA requested, depending on the CCA result of each subchannel confirmed by the AP.

[0279] vi. The AP shall determine the location of the RU to be allocated to the non-AP STA that has transmitted the initiation frame by considering the location of the Primary 20 MHz channel. More specifically, the AP shall allocate an RU within the Primary 20 MHz channel, or including an RU of the Primary 20 MHz channel, to the non-AP STA that has transmitted the initiation frame.

[0280] (5. Backoff counter generation by AP)

[0281] An AP that has acquired a TXOP can generate (or select) a new backoff counter after acquiring the TXOP or at the end of the TXOP. In this case, the AC for generating the backoff counter can be determined based on the AC indicated by the initiation frame. In other words, the backoff counter generated after acquiring the TXOP or at the end of the TXOP can generate a backoff counter of the same (or similar) AC as the AC indicated by the initiation frame. For example, if the AP determines that AC_BE is indicated based on the information indicated through the initiation frame, it can generate a new backoff counter for AC_BE. When generating a new backoff counter, the AP may need to generate the new counter using the CW_min (minimum contention window) of the corresponding AC. Alternatively, the AP may need to generate the new counter using the current CW of the corresponding AC. Alternatively, if the AP acquires a TXOP based on the initiation frame, the backoff counters of the EDCAFs may not be changed. Alternatively, the AC for which the AP generates a new backoff counter may be the AC with the smallest remaining backoff counter among all ACs. That is, when selecting an AC for which to regenerate a backoff counter, the AP may determine the AC for which to regenerate the backoff counter based on the backoff counter size of each AC. This can be understood as a backoff regeneration method that considers that the AP may use any AC during the process of performing channel access to transmit a trigger frame. At this time, if there are two or more ACs with the smallest backoff counters (i.e., two or more ACs have the same backoff counter), the AP may select one of the two ACs with the smallest backoff counters to regenerate the backoff counter of that AC. Alternatively, the AP may determine any AC for which to generate a new backoff counter.This could also be a backoff regeneration method that takes into account that the AP can use any AC during the process of performing Channel Access to transmit a trigger frame. When generating a new backoff counter, the AP can generate a new random number using CWmin and add up the remaining backoff counters of the corresponding AC to determine the new backoff counter. That is, when the AP regenerates a new backoff counter in a situation where the backoff counter of AC[VO] is 2, the AP can determine the new backoff counter of AC[VO] by adding 2 to the random number generated using CWmin[VO] (a natural number between 0 and CWmin[VO]).

[0282] FIG. 15 illustrates an example of a frame exchange sequence in which an STA transfers TXOP acquisition rights to another STA after completing a backoff procedure according to one embodiment of the present invention.

[0283] Referring to Figure 15, a non-AP STA acquires channel access to the 80 MHz band after completing the backoff procedure. Instead of acquiring a TXOP, the non-AP STA transmits an initiation frame to the AP. The initiation frame may have the same configuration as described in Figure 14.

[0284] An AP that receives an initiation frame from a non-AP STA checks the CCA results of channels within its operating bandwidth as well as the 80 MHz band in which the initiation frame was received, and transmits a CTS-to-self frame to obtain a TXOP for the 320 MHz band. In the example of Fig. 15, some of the bands in which the AP obtained a TXOP were determined to be BUSY through CCA results and were punctured by the AP.

[0285] After transmitting a CTS-to-self frame, the AP transmits a trigger frame to allocate RUs to one or more non-AP STAs. At this time, the AP allocates RUs in the band occupied by the PPDU including the initiation frame to the non-AP STA that transmitted the initiation frame. The non-AP STAs that receive the trigger frame (including the non-AP STA that transmitted the initiation frame) respond with a TB PPDU, and the AP transmits a BlockAck to indicate whether reception was successful.

[0286] FIG. 16 illustrates an example of a frame exchange sequence for transferring TXOP acquisition rights and NAV states of other STAs after a backoff procedure of an STA according to one embodiment of the present invention.

[0287] Referring to FIG. 16, non-AP STA1 transmits an initiation frame to the AP. At this time, non-AP STA1 is a non-AP STA that has acquired channel access rights (frame transmission rights) according to the EDCA procedure. The initiation frame has a Duration / ID field setting for setting the NAV for the section including the trigger frame transmitted after the AP acquires the TXOP or to acquire the TXOP. Accordingly, as illustrated in FIG. 16, the NAV for the 40 MHz band in which the initiation frame is transmitted is set. That is, the NAVs of the STAs that have received the frame within the 40 MHz band in which the initiation frame is transmitted are set.

[0288] In the situation illustrated in FIG. 16, the AP, having received a 40 MHz initiation frame, transmits a trigger frame in the 320 MHz band to attempt to acquire a TXOP, and the Duration / ID field of the trigger frame is set to the period including the TB PPDU responded to by the trigger frame. Therefore, the NAV for the 320 MHz band is set through the trigger frame, and the AP can operate the TXOP without being disturbed by other STAs (such as OBSS STAs) within the acquired TXOP.

[0289] FIG. 17 illustrates an example of the format of an initiating frame and a trigger frame according to one embodiment of the present invention.

[0290] Referring to FIG. 17, non-AP STA1 transmits an initiation frame to the AP, and the initiation frame has a structure including a Duration 1 and / or Duration 2 field. Duration 1 includes information related to the length of TXOP that the AP that received the initiation frame can obtain. Therefore, the AP obtains the TXOP based on the information identified in the Duration 1 field of the received initiation frame. In one embodiment of FIG. 17, considering that the Duration 1 field directly indicates the length of the obtainable TXOP, a situation is illustrated in which the TXOP duration of the AP is determined to be x when the Duration 1 field is indicated as x. However, the information indicated in the Duration 1 field may be information related to the AC (access category) that the STA that transmitted the initiation frame used for channel access or other types of information. In addition, the AP may only obtain a TXOP of a length shorter than the TXOP length identified based on the Duration 1 field.

[0291] Additionally, the initiation frame may have a configuration including a User Info field. At this time, the User Info field included in the initiation frame may be a field including information related to the configuration of the TB PPDU that the non-AP STA that transmitted the initiation frame intends to transmit. That is, the User Info field may be a field including information related to the MCS to be applied to the TB PPDU, the size and / or location information of the RU to be transmitted the TB PPDU, the number of antennas (Spatial Streams) to be used, etc. At this time, the names of each field used in the present invention are only for example, and the actual field names may be different, or each of the information described as being included in the field may be indicated through a separate field. Additionally, information related to the length of the TB PPDU to be transmitted may be included, and the Duration field 2 illustrated in one embodiment of FIG. 17 may be a field including information related to the response length of the TB PPDU. At this time, information related to the response length of TB PPDU can be a direct time length or the amount of traffic to be transmitted through TB ​​PPDU (queue size, buffer status, etc.).

[0292] As a result, it is possible for two different Duration-related information (information related to the obtainable TXOP length and information related to the length of the TB PPDU) to be indicated through the initiation frame. At this time, at least one of the two different Duration-related information may be indicated through the Duration / ID field of the MAC header. Alternatively, the two different Duration-related information may be indicated in the frame body, and the Duration / ID field may be utilized for other purposes (such as NAV management of the OBSS).

[0293] In this case, the value indicated by the Duration 1 field among the two different duration-related information may be greater than the value indicated by the Duration 2 field.

[0294] The AP acquires a TXOP based on the information included in the received initiation frame and then transmits a trigger frame. At this time, the length of the TXOP acquired by the AP is determined (limited) based on the Duration-related information included in the initiation frame. In one embodiment of FIG. 17, the AP acquires a TXOP of length x based on x indicated in Duration field 1 included in the initiation frame.

[0295] Additionally, the AP transmits a trigger frame to the non-AP STA that transmitted the initiation frame based on the information included in the initiation frame. In one embodiment of FIG. 17, the AP transmits a trigger frame in which the User Info field corresponding to AID12 of the non-AP STA1 that transmitted the initiation frame is indicated first, and the User Info field is set based on the information indicated through the initiation frame. Consequently, the non-AP STA that transmitted the initiation frame responds with a TB PPDU in the manner that it requested from the AP by receiving the trigger frame.

[0296] <2-step channel access procedure>

[0297] According to one embodiment of the present invention described above, after a non-AP STA completes a backoff procedure, it can instruct the AP to initiate a TXOP acquisition procedure by transmitting an initiation frame to the AP. At this time, the procedure for the AP to acquire a TXOP can be appropriately replaced with a procedure for the AP to share the TXOP. In other words, the above-described series of procedures can be changed to a procedure in which a non-AP STA, which is a TXOP holder, shares its TXOP with the AP by transmitting an initiation frame to the AP.

[0298] To briefly explain how the TXOP sharing procedure is applied, it is a series of processes in which a non-AP STA acquires a TXOP after completing a backoff procedure and shares the acquired TXOP with its AP by transmitting an initiation frame.

[0299] At this time, the AP is allowed to perform operations similar to those of a TXOP holder during the shared TXOP. That is, the AP can perform operations such as transmitting a DL MU PPDU during the shared TXOP, transmitting a trigger frame to respond to a UL MU PPDU, or transmitting an RTS / MU-RTS frame to protect the subsequent frame exchange sequence. To this end, a series of operations defined to be performed by a TXOP holder in existing Wi-Fi can be allowed to be performed by the AP that has shared the TXOP. That is, the AP can also transmit a CF-End frame to terminate the TXOP during the shared TXOP.

[0300] Therefore, the above-described TXOP acquisition opportunity transfer method can be appropriately changed to the TXOP sharing procedure below.

[0301] 1. Non-AP STA attempts to acquire TXOP after performing backoff procedure through DCF or EDCA.

[0302] 2. A non-AP STA that has acquired a TXOP transmits a pre-arranged frame (hereinafter referred to as a TXOP sharing frame) to its Associated AP to share the TXOP it has acquired with the AP. (An Associated AP refers to an AP of the BSS of which it is a member.)

[0303] 3. An AP that receives a TXOP shared frame from a non-AP STA attempts TXOP BW extension for a channel identified as IDLE by CCA within its operating bandwidth.

[0304] 4. The AP transmits a Trigger frame or DL ​​(MU) PPDU using the extended BW during the shared TXOP.

[0305] 5. The AP can create a new backoff counter after the shared TXOP ends.

[0306] The operations and applicable restrictions performed in steps 1 through 5, which are shared with the AP after the Non-AP STA acquires the TXOP, are identical / similar to the TXOP transfer method described above, so redundant descriptions are omitted. However, since these operations are performed in a situation where the AP is not the TXOP holder, additional management methods for operations performed in a situation where the AP is not the TXOP holder may be applied as follows.

[0307] Non-AP STAs (such as the second and third STAs) that can recognize that another non-AP STA (the first STA) within the BSS is a TXOP holder can process frames transmitted by the AP after it has shared the TXOP in the same way as they process frames received during the TXOP for which the AP is the TXOP holder. That is, the non-AP STAs can ignore the NAV (Intra-BSS NAV) during the TXOP shared with the AP. In addition, the AP can ignore the NAV set by the non-AP STA that transmitted the TXOP shared frame.

[0308] More specifically, non-AP STAs (such as the second and third STAs) that are not TXOP holders can perform a response to the RTS / MU-RTS frame transmitted by the AP even if the NAV is set by a frame transmitted by another non-AP STA (such as the first STA). That is, a non-AP STA (such as the second and third STAs) that receives an RTS / MU-RTS frame transmitted by the AP during a TXOP shared by the AP from another non-AP STA (such as the first STA) can perform a CTS response to the RTS / MU-RTS frame even if the TXOP holder that it recognizes is not the AP. In this case, a method for determining whether to perform a response when a non-AP STA receives a frame requesting a response, such as an RTS / MU-RTS / Trigger frame received from an AP, may be determined based on whether the Virtual CCA result confirmed by the basic NAV is IDLE. That is, a non-AP STA whose basic NAV is identified as IDLE (basic NAV is 0) can respond to the RTS / MU-RTS / Trigger frame transmitted by the AP even if its intra-BSS NAV is identified as Busy (intra-BSS NAV is not 0) and the TXOP holder is identified as another STA other than the AP. This may be an additional exception to the existing Wi-Fi CTS frame response condition that allows the first STA that received the RTS frame to respond with a CTS frame only when the second STA that transmitted the RTS frame is identified as the TXOP holder or when the NAV is 0 (i.e., NAV indicates idle).

[0309] For reference, intra-BSS NAV refers to a NAV set after receiving a PPDU classified as an intra-BSS PPDU, and basic NAV refers to a NAV set after receiving a PPDU that is not classified as an intra-BSS PPDU. Intra-BSS PPDU refers to a PPDU classified as an inter-BSS PPDU according to the Intra-BSS and inter-BSS PPDU classification rules, and the classification method is defined as a method using information such as BSS color or the address field of the frame included in the PPDU. Since the method of classifying Intra-PPDU is not related to the TXOP assignment / sharing for the AP to be provided in the present invention, a detailed description thereof will be omitted.

[0310] In summary, the TXOP holder of a TXOP is a non-AP STA, and the non-AP STA can transmit a frame in a pre-arranged format to the AP for the purpose of sharing the TXOP it has acquired with the AP. The AP, which has received a frame in the pre-arranged format from a non-AP STA, may be permitted to perform operations similar to those of the TXOP holder during the TXOP of the non-AP STA. That is, the AP may perform operations such as transmitting a DL MU PPDU or transmitting a Trigger frame, even though it is the TXOP of the non-AP STA. In addition, when the AP receives a frame in the pre-arranged format from a non-AP STA, the AP may attempt to access an additional Idle subchannel other than the BW in which the non-AP STA acquired the TXOP. In this case, the channel access procedure performed by the AP after receiving the frame in the pre-arranged format (TXOP shared frame) may be understood as a secondary channel access procedure for BW expansion. That is, the primary channel access procedure is the process of obtaining a TXOP after a non-AP STA completes the backoff procedure, and the secondary channel access procedure may refer to the BW extension procedure performed by the AP that received the frame from the STA that obtained the TXOP. At this time, it is easy to understand that the CCA procedure performed to extend the BW and the AP's operation performed during the shared TXOP may be similar to the TXOP transfer described above, so a detailed description is omitted.

[0311] In addition, the above-described procedure can be utilized to share a TXOP with another AP not only when a non-AP STA has completed the backoff procedure, but also when an AP has completed the backoff procedure. For example, after completing the backoff procedure, AP1 can instruct AP2 to perform a sharing operation during the same time period as the TXOP it has acquired by transmitting an initiation frame (or another frame transmitted for TXOP sharing). At this time, AP2 can perform an operation similar to that of being a TXOP holder through the sharing operation. That is, AP2 can perform an operation such as transmitting a DL PPDU or a Trigger frame to its Associated STAs during the time period shared from AP1. Therefore, even if the embodiments of the present invention described above or below are described as operation procedures that a non-AP STA performs with its AP after completing the backoff procedure, it should be understood that a similar operation procedure can be equally applied between APs.

[0312] FIG. 18 illustrates an example of a TXOP sharing and bandwidth (BW) expansion procedure between STAs according to an embodiment of the present invention.

[0313] Referring to FIG. 18, a non-AP STA transmits an RTS frame to the AP after completing the backoff procedure, and becomes a TXOP holder by receiving a CTS frame in response. Thereafter, the non-AP STA transmits a TXOP sharing frame to the AP to share the TXOP it has acquired. The AP, which has received the TXOP sharing frame, performs CCA for its operating channels and attempts BW extension for subchannels determined to be IDLE. At this time, the AP performs the same operation as if it were the TXOP holder, although the TXOP is not acquired by it. The diagram illustrated in one embodiment of FIG. 18 illustrates a procedure in which the AP transmits a CTS-to-Self frame and a trigger frame to request a response to a UL MU PPDU.

[0314] FIG. 19 illustrates an example of a TXOP sharing procedure and a TXOP holder operation of an STA according to an embodiment of the present invention.

[0315] Referring to Figure 19, after completing the backoff procedure, non-AP STA1 transmits an RTS frame to the AP and receives a CTS frame in response, thereby becoming a TXOP holder. Thereafter, non-AP STA1 transmits a TXOP sharing frame to the AP to share the TXOP.

[0316] At this time, non-AP STA2 and OBSS STAs can recognize that the TXOP holder is non-AP STA1 after receiving the RTS frame transmitted by non-AP STA1 or the CTS frame transmitted by the AP. In addition, the NAV is set until the TXOP of non-AP STA1 ends.

[0317] After receiving a TXOP shared frame from non-AP STA1, the AP transmits a trigger frame, which is one of the operations performed as a TXOP holder. The trigger frame is a trigger frame that requests a response of TB PPDU from not only non-AP STA1 but also non-AP STA2, and non-AP STA2 responds with a TB PPDU even though it is confirmed that the TXOP holder is non-AP STA1. In other words, non-AP STA1 can respond to frames received from the AP while ignoring the NAV, which is the TXOP holder.

[0318] The time period during which the AP performs frame exchange during the shared TXOP is protected by the NAV of the OBSS STAs established through the frames exchanged during the process of non-AP STA1 becoming the TXOP holder.

[0319] <TXOP 개시 / 공유 절차에 활용되는 프레임 format>

[0320] According to the aforementioned embodiments of the present invention, when a non-AP STA completes a backoff procedure, it may transmit a frame for transferring a TXOP acquisition opportunity to the AP. Furthermore, after acquiring a TXOP, the non-AP STA may transmit a frame for sharing the acquired TXOP with the AP.

[0321] In this way, the action of a non-AP STA transferring the opportunity to acquire a TXOP to the AP or sharing the acquired TXOP may not be advantageous from the perspective of the non-AP STA's operation. This is because, from the perspective of the non-AP STA, it is advantageous for it to acquire a TXOP and finish transmitting the frames it wants to transmit during the TXOP as quickly as possible, and the additional sequence performed to transfer or share the TXOP may be an unreasonable action with no expected benefit. Therefore, a non-AP STA that transfers the opportunity to acquire a TXOP to the AP or shares the acquired TXOP with the AP should be sufficiently compensated.

[0322] The first consideration is that a non-AP STA that has completed the backoff procedure must be guaranteed the same frame throughput as if it had acquired and utilized the TXOP itself. In other words, even if a non-AP STA cedes the opportunity to acquire a TXOP to the AP or shares the TXOP it has acquired, it must be able to process the same amount of traffic as if it had acquired and utilized the TXOP itself. To achieve this, the non-AP STA must be instructed to the AP regarding the traffic and / or traffic volume it intends to process. Based on this information, the AP may need to allocate sufficient resources to the non-AP STA.

[0323] FIG. 20 illustrates an example of a format for a frame for transferring TXOP acquisition rights or sharing TXOP according to one embodiment of the present invention.

[0324] Referring to FIG. 20, the initiation frame may include a subfield related to TXOP limit or AC. The subfield related to TXOP limit or AC may be a field set based on the Access Category for which the non-AP STA transmitting the frame has completed the backoff procedure. The AP may determine the length of the acquired TXOP based on the information indicated in the field. The TXOP limit field may be a field used to indicate the section of the TXOP that the non-AP STA wishes to share with the AP when included in a TXOP sharing frame. The time indicated by the field must be the same as or earlier than the end time of the TXOP acquired by the non-AP STA.

[0325] The UL Length field is a field that indicates the frame length of the TB PPDU that the non-AP STA transmitting the corresponding frame wants to transmit. After receiving the TXOP Initiating / Shared frame, the AP that transmits the trigger frame to the non-AP STA may need to transmit the trigger frame with the UL Length field set to the same value as indicated in the UL Length field of the TXOP Initiating / Shared frame.

[0326] The Number of Spatial Streams field indicates the number of Spatial Streams that the non-AP STA that transmitted the TXOP Initiating / Shared frame intends to utilize when transmitting the TB PPDU. An AP that transmits a trigger frame to a non-AP STA after receiving the TXOP Initiating / Shared frame may need to transmit trigger frames allocated to the non-AP STA as many as the number of Spatial Streams indicated in the Number of Spatial Streams field of the TXOP Initiating / Shared frame. That is, when transmitting a trigger frame, the AP must set the SS Allocation subfield of the User Info field having the AID12 value indicating the non-AP STA to the same value as the Number of Spatial Streams field included in the TXOP Initiating / Shared frame transmitted by the non-AP STA.

[0327] The MCS field indicates the MCS (Modulation and Coding Scheme) that the non-AP STA that transmitted the TXOP Initiating / Shared frame intends to utilize when transmitting the TB PPDU. An AP that transmits a trigger frame to a non-AP STA after receiving the TXOP Initiating / Shared frame may need to transmit trigger frames allocated to the non-AP STAs as many as the number of Spatial Streams indicated in the Number of Spatial Streams field of the TXOP Initiating / Shared frame. That is, when transmitting a trigger frame, the AP must set the (HE / EHT / UHR) MCS field of the User Info field having the AID12 value indicating the non-AP STA to the same value as the MCS field included in the TXOP Initiating / Shared frame transmitted by the non-AP STA.

[0328] The Buffer Status field indicates information related to the amount of buffered traffic held by the non-AP STA that transmitted the TXOP Initiating / Sharing frame. Alternatively, the field may be replaced with a field containing information related to the size and / or position of the BW or RU to which the non-AP STA requests to respond with a TB PPDU. After receiving the TXOP Initiating / Sharing frame, the AP may set the RU Allocation subfield (and PS 160, PS 320 subfield, etc.) of the User Info field corresponding to the non-AP STA that transmitted the TXOP Initiating / Sharing frame based on the information indicated in the Buffer Status field of the TXOP Initiating / Sharing frame in the trigger frame transmitted.

[0329] The Channel Info. Bitmap field is a field that indicates whether the subchannels confirmed when a non-AP STA that transmitted a TXOP Initiating / Shared frame performed channel access are IDLE / BUSY. Each bit of the Channel Info. Bitmap field corresponds to a different subchannel, and is set to 1 (or 0) if the corresponding subchannel is confirmed as IDLE, and is set to 0 (or 1) if the corresponding subchannel is confirmed as BUSY. Among the bits of the Channel Info. Bitmap field, the bits corresponding to subchannels for which the non-AP STA setting the corresponding field could not determine whether they are IDLE / BUSY are set in a preset manner. In this case, a method of setting a bit corresponding to a subchannel for which IDLE / BUSY cannot be determined may be to set the bits to the same value as the setting value of the bits corresponding to the BUSY subchannel. That is, the Channel Info. When the Bitmap field is composed of 16 bits and corresponds to each of the 16 20 MHz subchannels included in the 320 MHz band, a non-AP STA performing 80 MHz operation indicates the Channel info. Bitmap field by setting the IDLE / BUSY status for 4 subchannels (or 3 subchannels excluding the primary 20 MHz subchannel) to 1 / 0, respectively, and setting the IDLE / BUSY status for the remaining 12 subchannels to 0. After receiving a TXOP Initiating / Shared frame and transmitting a trigger frame, the AP must allocate to the non-AP STA only the RUs included in the subchannels that the non-AP STA that transmitted the frame indicated as being determined to be IDLE.

[0330] The second thing to consider is that there must be a sufficient number of non-AP STAs that follow the TXOP transfer / sharing procedure provided by the present invention. If there is no non-AP STA among the non-AP STAs that are members of the BSS that can perform the TXOP transfer / sharing procedure, the BSS cannot obtain the effect that the present invention intends to provide. Therefore, the AP can induce the non-AP STAs to actively support the TXOP transfer / sharing procedure by preferentially performing services for the non-AP STAs that can support the TXOP transfer / sharing procedure among the non-AP STAs that are members of the BSS. In this process, the AP can preferentially perform scheduling (for DL / UL frame exchange) for the non-AP STAs that support the TXOP transfer / sharing procedure during the (shared) TXOP acquired through the TXOP transfer / sharing procedure. That is, the AP may be allowed to apply preferential scheduling to non-AP STAs that support TXOP transfer (transferring the TXOP acquisition opportunity after a non-AP STA completes the backoff procedure) or TXOP sharing (sharing the TXOP acquired by a non-AP STA) procedures.

[0331] Although the above-described embodiments of the present invention were written considering that a non-AP STA transmits a TXOP Initiating / Sharing frame to an associated AP, the same operation can be performed between APs. In other words, it is possible for a first AP to transmit a TXOP sharing frame to a second AP to share the TXOP after acquiring a TXOP, and it is also possible for the BW to be expanded by AP2 during this process. In addition, if the BW in which the first AP acquires the TXOP is smaller than the operating bandwidth of the second AP, the first AP can induce the second AP to perform frame exchange in a band in which the first AP itself did not acquire the TXOP through the initiation frame it transmits. At this time, the TXOP sharing frame that the first AP transmits to the second AP can be a frame classified as an MU-RTS type. At this time, the TXOP shared frame transmitted by the first AP to the second AP may be a frame that instructs the second AP to provide an RU that is not included in the BW acquired by the first AP.

[0332] A frame transmitted by a non-AP STA to share a TXOP with an AP may be an MU-RTS TXS (MU-RTS TXOP sharing) trigger frame. At this time, the MU-RTS TXS trigger frame means a trigger frame in which the Triggered TXOP sharing Mode subfield included in the Common Info field of the trigger frame is not 0. When a non-AP STA transmits an MU-RTS TXS trigger frame to an AP, it may be required to include only one User Info field. At this time, the User Info field may indicate TB PPDU related parameters that the non-AP STA itself wants to receive from the AP, as considered in the embodiments of the present invention described above.

[0333] Channel Access Procedure for Bandwidth (BW) Expansion

[0334] As described above, according to one embodiment of the present invention, when an AP receives a control frame (initiating frame and / or sharing frame) transmitted by a non-AP STA after obtaining channel access rights, the AP may attempt to access a wider band than the band in which the control frame was received. In other words, an AP that receives a control frame (initiating frame and / or sharing frame) transmitted by a non-AP STA may attempt to access a subchannel not occupied by the control frame.

[0335] However, an AP accessing an additional subchannel other than the subchannel occupied by the control frame may need to perform a procedure to obtain access to the subchannel.

[0336] In the embodiments described above, when the AP accesses additional subchannels other than the subchannels on which control frames are received, it has been considered that additional access to the subchannels is performed when each subchannel is determined to be IDLE as a result of a CCA performed during an SIFS or PIFS. This procedure of accessing additional subchannels based on the result of a CCA performed during an SIFS or PIFS may be considered similar to the procedure by which an STA that has completed a backoff procedure on a primary channel accesses secondary channels, but may be an operation that causes fairness issues with heterogeneous devices.

[0337] More specifically, some heterogeneous devices perform independent LBT (listen before talk, similar to the backoff procedure in Wi-Fi) for each 20 MHz subchannel to access it, and then perform channel access only for the subchannels for which channel access was obtained through LBT. Therefore, the behavior of the AP performing only SIFS / PIFS CCA after receiving a control frame and then accessing additional subchannels can be viewed as a somewhat more aggressive channel access method than that of the heterogeneous devices.

[0338] Additionally, other heterogeneous devices use a channel access method to access additional subchannels that are judged as IDLE when they have completed LBT (acquired channel access rights) on a specific 20 MHz subchannel (main channel), similar to how Wi-Fi accesses a BW exceeding 20 MHz. However, the condition for these other heterogeneous devices to access the additional subchannels is limited to when they have acquired channel access rights on a specific 20 MHz subchannel, and therefore, the act of the AP accessing the additional subchannel when receiving a control frame may be perceived as an aggressive channel access method compared to the other heterogeneous devices.

[0339] Therefore, in order to operate harmoniously with heterogeneous devices that share the unlicensed band, an AP that receives a control frame from a non-AP STA and accesses an additional subchannel according to one embodiment of the present invention may also need to access the additional subchannel after completing a backoff procedure.

[0340] The channel access method for BW expansion described below is a specific method in which an AP accesses not only the subchannel occupied by a control frame received from a non-AP STA but also an additional subchannel, and is a method that can be performed without fairness issues with heterogeneous devices. In this case, the meaning of BW expansion includes obtaining channel access rights to a BW wider than the BW of the PPDU containing the control frame, or obtaining channel access rights to an additional subchannel other than the subchannel occupied by the control frame. In other words, even if the BW obtained by the AP receiving the control frame is the same as the BW of the PPDU containing the control frame, if the subchannel for which channel access rights are obtained is larger than the subchannel occupied by the control frame, the BW can be considered to have been expanded.

[0341] According to an embodiment of the present invention, when the entire bandwidth is composed of one primary channel block (or primary channel) and one or more secondary channel blocks (or secondary channels), a station (non-AP STA or AP) may select one secondary channel block among one or more secondary channel blocks other than a primary subchannel included in the primary channel block, perform a channel access procedure through a secondary subchannel constituting the selected secondary channel block, and obtain a TXOP. That is, the station may perform channel access through a secondary subchannel other than a primary subchannel, and obtain a TXOP.

[0342] In another embodiment of the present invention, when a TXOP is acquired through a secondary subchannel using the above method, the frequency axis range in which the TXOP is acquired may be limited to a secondary channel block including the secondary subchannel on which the channel access procedure is performed. That is, a station that has performed a channel access procedure through a secondary subchannel can transmit and receive only within the secondary channel including the secondary subchannel within the acquired TXOP.

[0343] In another embodiment of the present invention, when a station (e.g., an AP or a non-AP STA) receives a TXOP (a first TXOP) shared from another station (e.g., a non-AP STA or an AP), the station can perform a channel access procedure through the shared TXOP. However, when a primary subchannel of a primary channel block is occupied by another station (e.g., an OBSS STA) within the shared TXOP, the station cannot perform a channel access procedure on the primary subchannel. In this case, the station selects one of the secondary channel blocks supported among the entire bandwidth other than the primary subchannel of the primary channel, performs a channel access procedure through the secondary subchannel included in the selected secondary channel block, and can obtain a TXOP (a second TXOP). In this case, the first TXOP can be used for frame transmission and reception up to a frequency range supported by other stations that share the first TXOP on the frequency axis, but the frequency range in which the second TXOP is acquired can be limited to a subchannel including a sub-subchannel on which channel access is performed.

[0344] In another embodiment of the present invention, the second TXOP obtained through the above method may end at the same time as the first TXOP, and the second TXOP may be considered as a frequency axis extension of the first TXOP. That is, when the first TXOP is shared, the station may extend the frequency axis range of the first TXOP to the second TXOP through a channel access procedure through a secondary subchannel. In this case, other stations may not support the secondary channel for obtaining the second TXOP. For example, the total bandwidth may be 320 MHz, and the total bandwidth may be composed of one primary channel of 80 MHz and secondary channels of 80 MHz and 160 MHz. In this case, the 160 MHz secondary channel may be divided into a low 80 MHz channel and a high 80 MHz channel. In this case, one of the four 80MHz bands may be a primary bandwidth (or primary channel) including a primary subchannel for channel access, and the remaining three may be secondary bandwidths (or secondary channels). A first station (e.g., an AP or a non-AP STA) may support up to 320MHz, and a second station may support only 160MHz. The second station may perform a channel access procedure (a first channel access procedure) through a primary subchannel of the primary band, and may obtain a TXOP (a first TXOP) through the first channel access procedure and share it with the first station. The first station may transmit and receive frames through the shared first TXOP. However, if the primary subchannel within the first TXOP is occupied by another station (e.g., an OBSS station), the first station may not perform channel access and frame transmission and reception through the primary subchannel.Accordingly, the first station can change the channel to an idle sub-band among the three sub-bands that is not occupied by other stations, and perform a channel access procedure (second channel access procedure) through a sub-channel of the changed sub-band to obtain a TXOP (second TXOP). In this case, the frequency axis range in which the first TXOP is obtained is up to 160 MHz including the primary band that the second station can support, and the frequency axis range in which the second TXOP is obtained is up to 80 MHz, which is a sub-band including the sub-channel on which the first station performed the second channel access (or up to a secondary channel of 160 MHz including the corresponding sub-band). In addition, the second TXOP can be considered as an extension of the first TXOP, and ends at the same time as the end time of the first TXOP.

[0345] In another embodiment of the present invention, if the first station acquires a TXOP by performing a channel access procedure through a secondary band that the second station does not support (e.g., the second station supports only Primary 160MHz out of 320MHz and the first station performs channel access in the low 80MHz out of secondary 160MHz, etc.) through the above method, the first station may instruct the second station to move to the secondary 160MHz and operate in order to change the operating channel of the second station. For example, the first station may transmit a frame (e.g., a trigger frame) instructing the second station to change the operating channel within the acquired second TXOP, and the second station, upon receiving the frame, may move to the channel indicated in the frame (e.g., Low 80MHz out of secondary 160MHz) and receive a downlink frame indicated through the frame or transmit an uplink frame.

[0346] <1. Performing backoff procedure for each 20 MHz subchannel> In the channel access method according to the present embodiment, when an AP performs a backoff procedure simultaneously on a plurality of subchannels (including a primary channel) included in an operating bandwidth (BW), and a control frame is received from a non-AP STA, channel access can be performed on the subchannels occupied by the PPDU including the control frame and the idle subchannels for which the backoff procedure has been completed. In this case, performing the backoff procedure simultaneously on the plurality of subchannels means that a separate backoff procedure is performed on each of the plurality of subchannels, and this is performed in parallel in time.

[0347] Specifically, the AP performs a backoff procedure on multiple subchannels within its operating bandwidth. For example, an AP with an operating bandwidth of 80 MHz performs a backoff procedure on each of the four 20 MHz subchannels within the 80 MHz band. At this time, if the AP has completed the backoff procedure on the Primary 20 MHz channel, the AP can obtain channel access rights for the subchannels identified as Idle among the four subchannels within the 80 MHz band according to conventional Wi-Fi operation.

[0348] However, even if the backoff procedure on a subchannel other than the primary 20 MHz channel has been completed, the AP cannot access the other subchannel. This may be a limitation that applies because the AP has not yet acquired channel access to the primary 20 MHz channel and cannot perform transmissions that do not occupy the primary 20 MHz channel.

[0349] Therefore, the AP can wait until it obtains access to the Primary 20 MHz channel while it has acquired channel access rights (completed backoff procedures) for other subchannels (subchannels other than the primary 20 MHz subchannel) for which the backoff procedure has been completed. At this time, the AP can maintain the backoff counter as 0 when the backoff counter of the backoff performed on a subchannel other than the primary 20 MHz subchannel becomes 0 until it obtains access to the primary channel. In other words, the AP may not initiate transmission while the backoff counter of a subchannel other than the primary 20 MHz subchannel is 0. At this time, the operation of the AP not initiating transmission may continue until it obtains channel access rights for the Primary 20 MHz channel.

[0350] As considered in the above-described embodiment of the present invention, a non-AP STA that has acquired channel access rights can share the TXOP it has acquired with the AP by transmitting a control frame (TXOP sharing frame) to the AP. At this time, since the non-AP STA performs the channel access procedure only in the Primary 20 MHz subchannel, the channel access rights acquired by the non-AP STA include the channel access rights for the Primary 20 MHz subchannel. Accordingly, when the non-AP STA transmits a control frame to the AP and the channel access rights for the Primary 20 MHz subchannel are shared with the AP, the AP can initiate access to the Primary 20 MHz channel.

[0351] At this time, the AP accessing the primary channel using the TXOP shared by the non-AP STA can also initiate channel access to subchannels for which it has already acquired channel access rights (for which the backoff procedure has been completed). In other words, when the AP accesses the primary channel using the TXOP acquired by the non-AP STA, it can also initiate channel access to additional subchannels for which the backoff procedure has already been completed.

[0352] That is, according to the present embodiment, an AP that extends BW performs a backoff procedure in parallel for each 20 MHz subchannel, and when channel access rights for a primary channel acquired by a non-AP STA are shared from a non-AP STA, accesses the primary channel using the shared rights, and accesses other subchannels for which channel access rights have been acquired through the backoff procedure (backoff procedure completed, red backoff counter is 0), thereby completing the channel access procedure for BW extension.

[0353] However, performing parallel backoff for each 20 MHz subchannel may result in excessive power consumption by the AP during the channel access process. For example, an AP with an operating bandwidth of 320 MHz must perform a backoff procedure for each of the 16 20 MHz subchannels for channel access, so a simple calculation predicts that the power consumption of the channel access procedure will be 16 times more. This may be because, unlike the operation of existing APs, which perform CCA of other subchannels only after the backoff procedure performed on the primary 20 MHz subchannel is completed, the parallel backoff operation requires determining the IDLE / BUSY state of each subchannel for each slot.

[0354] Therefore, the AP can secure channel access by performing parallel backoff for each 20 MHz subchannel, while shortening the period during which the parallel backoff is performed. A specific method for shortening the period during which the AP performs parallel backoff may be to initiate the AP's parallel backoff only when the AP receives a control frame transmitted by a non-AP STA.

[0355] To be more specific, the AP may perform a backoff procedure only on the Primary 20 MHz channel, and when a control frame is received from a non-AP STA, the AP may initiate / perform a 20 MHz channel access procedure (backoff procedure) for each additional subchannel to obtain channel access rights for the additional subchannel. In this case, the non-AP STA may add padding to the PPDU containing the control frame it transmits, thereby helping the AP's backoff procedure (performed on a subchannel other than the primary channel) to be completed during the time secured by the padding. The amount of padding included may be a preset length or a length set based on a value indicated by the AP. The padding may be PHY and / or MAC padding. The meaning of padding may mean anything that increases the length of the PPDU other than the control frame transmitted for TXOP sharing. That is, a non-AP STA can place a control frame as the first frame and aggregating other frames (UL traffic) to induce the other frames to play a role similar to padding.

[0356] Alternatively, the AP can perform the backoff procedure for the band larger than 20 MHz without performing the backoff procedure for each 20 MHz subchannel. For example, in addition to the backoff procedure performed on the Primary 20 MHz subchannel, the AP can perform the backoff procedure for the Secondary 80 MHz, the Low 80 MHz of the Secondary 160 MHz, and the High 80 MHz of the Secondary 160 MHz. Therefore, the AP can obtain channel access in 80 MHz units when accessing bands other than the Primary 80 MHz band. This may be a channel access method to consider because the operating bandwidth of a Wi-Fi AP may have a rather large number of subchannels, and performing the backoff procedure for each 20 MHz subchannel would excessively increase the operational complexity on the AP side. In other words, the AP can apply a single backoff procedure to the band larger than 20 MHz, thereby obtaining channel access for the band larger than 20 MHz.

[0357] Alternatively, the AP may select a specific 20 MHz subchannel for performing the channel access procedure at each predetermined bandwidth interval and perform the channel access procedure (backoff procedure) through that subchannel. More specifically, the AP may select one 20 MHz subchannel for performing the channel access procedure for each of the four 80 MHz bands within the 320 MHz BW. At this time, among the four 80 MHz bands, the primary 20 MHz subchannel may always be selected for the primary 80 MHz band. In addition, when the AP operates in the 6 GHz band, the AP may perform the channel access procedure for each 80 MHz band on a channel that must be used as the primary according to the 6 GHz rule among each 80 MHz band. At this time, the channel that must be used as the primary according to the 6 GHz rule refers to the preferred scanning channel (PSD) of the non-AP STA. At this time, the preferred scanning channel of the non-AP STA is one 20 MHz subchannel within each 80 MHz BW of the 6 GHz band, which means a subchannel with a center frequency of (Channel starting frequency - 55 + (80 x n)) MHz. At this time, n has a value of 1 to 15.

[0358] In this case, when the AP initiates transmission on the Primary 20 MHz channel, it can additionally access the IDLE channel of each 80 MHz if the channel access procedure performed on a specific 20 MHz subchannel of each 80 MHz has already been completed. At this time, the operation of the AP initiating transmission on the Primary 20 MHz channel may be performed by utilizing the TXOP shared by the non-AP STA. If the channel access procedure performed on a specific 20 MHz subchannel of a specific 80 MHz band has not been completed, the AP cannot access the subchannels of the specific 80 MHz band when it initiates transmission on the Primary 20 MHz channel. At this time, the method of selecting a specific 20 MHz subchannel (a subchannel performing the channel access procedure) for each 80 MHz band is for example only, and it is also possible for a specific 20 MHz subchannel to be selected for each 160 MHz band or 320 MHz band. Even if the specific 20 MHz subchannels performing the channel access procedure are selected one per bandwidth rather than one per 80 MHz band, channel access rights for each IDLE subchannel can be obtained in the same / similar manner, so a repeated explanation is omitted.

[0359] FIG. 21 illustrates an example of a method for performing channel access using a subchannel according to an embodiment of the present invention.

[0360] Referring to FIG. 21, after an AP receives a control frame from a non-AP STA, it can access the channel by utilizing an additional subchannel for which channel access rights have been secured.

[0361] Specifically, the AP and non-AP STA perform a backoff procedure on the primary channel to gain channel access. A non-AP STA that completes the backoff procedure faster than the AP transmits a control frame (Ctrl frame) to the AP. This control frame is a frame that the non-AP STA transmits to share the TXOP it has acquired with the AP.

[0362] At this time, the AP was performing backoff procedures for channel access not only for the main channel (P_20) but also for other subchannels, and the backoff procedures performed on two subchannels had already been completed (S_20 and L_20 of S_40).

[0363] An AP that receives a control frame from a non-AP STA on the primary channel sends a response frame not only to the primary channel (P_20) occupied by the control frame, but also to additional subchannels (S_20 and L_20 of S_40) for which channel access has already been secured (backoff procedure completed). At this time, among the subchannels for which the AP transmitted the response frame, the TXOP of the AP starts for subchannels other than the primary channel occupied by the control frame. That is, the AP accesses the primary channel with the shared TXOP through the control frame transmitted by the non-AP STA, and simultaneously accesses the additional subchannels for which it has already completed the backoff procedure.

[0364] FIG. 22 illustrates another example of a method for performing channel access using a subchannel according to an embodiment of the present invention.

[0365] Referring to FIG. 22, after an AP receives a control frame from a non-AP STA, it can access the channel by utilizing an additional subchannel for which channel access rights have been secured.

[0366] To avoid repetition, the same content as described in Fig. 21 above may be omitted.

[0367] Specifically, the AP performs a backoff procedure not only on the primary 20 MHz channel but also on additional subchannels. The additional subchannels are among the subchannels included in the AP's operating bandwidth.

[0368] The AP receives a control frame transmitted by a non-AP STA before the backoff procedure performed on the Primary 20 MHz channel is completed, and shares the TXOP for the subchannels occupied by the control frame with the non-AP STA through this. The AP accesses the channel using the shared TXOP, and simultaneously accesses an additional subchannel for which channel access rights have already been secured. At this time, a method for the AP to secure channel access rights for the additional subchannel may be to access the subchannels identified as IDLE based on the results of the CCA performed during the PIFS prior to accessing the additional subchannel for which the backoff procedure has already been completed. That is, the AP accesses the primary channel using the shared TXOP through the control frame transmitted by the non-AP STA, and simultaneously accesses the primary channel and an additional subchannel for which it has already completed the backoff procedure, and performs PIFS access for the additional subchannels.

[0369] Therefore, the AP accesses the Primary 80 MHz band occupied by the PPDU of the control frame transmitted by the non-AP STA using the TXOP shared by the non-AP STA, and simultaneously accesses the additional subchannels for which it has secured channel access rights through the backoff procedure and PIFS CCA performed on the additional subchannel. That is, the AP responds with a Resp frame for the control frame not only through the P_80 channel but also through all of the remaining additional subchannels for which the channel access procedure has been completed. (i.e., responding for the 320 MHz band in FIG. 22)

[0370] FIG. 23 illustrates an example of a method for initiating a channel access procedure using a subchannel according to one embodiment of the present invention.

[0371] Referring to FIG. 23, after an AP receives a control frame from a non-AP STA, it may initiate a channel access procedure to access an additional subchannel.

[0372] To avoid repetition, the same content as described in Figures 21 and 22 above may be omitted.

[0373] Specifically, the AP and non-AP STAs perform a backoff procedure on the primary channel to gain channel access. A non-AP STA that completes the backoff procedure faster than the AP transmits a control frame (Ctrl frame) to the AP. At this time, the PPDU containing the control frame additionally includes padding.

[0374] An AP that receives a control frame from a non-AP STA initiates a backoff procedure for each of the additional subchannels to secure channel access rights for the additional subchannels not occupied by the control frame. At this time, the backoff procedure initiated by the AP for each additional subchannel is performed for the time required due to the padding added to the PPDU containing the control frame, and the AP completes the backoff procedure performed for the S_20, L_20 of S_40, and H_20 of S_40 subchannels.

[0375] Therefore, the AP accesses the Primary 20 MHz subchannel (P_20) occupied by the PPDU of the control frame transmitted by the non-AP STA using the TXOP shared by the non-AP STA, and simultaneously accesses additional subchannels for which it has secured channel access rights through the backoff procedure. That is, the AP responds with a Response frame for the control frame not only through the P_20 channel but also through all of the remaining additional subchannels for which the channel access procedure has been completed. (i.e., responding for the 80 MHz band in FIG. 23)

[0376] That is, the AP accesses the primary channel with a shared TXOP through a control frame transmitted by a non-AP STA, and simultaneously accesses additional subchannels for which it has already completed the backoff procedure.

[0377] <2. Performing channel access procedures during the TXOP period shared by non-AP STAs>

[0378] Alternatively, the AP may perform a channel access procedure (backoff procedure) on the Primary 20 MHz subchannel during the shared TXOP period with the non-AP STA, and when the channel access (backoff procedure) procedure is completed, the AP may access the Primary 20 MHz subchannel and additional subchannels identified as IDLE. That is, the AP may become a TXOP holder of the TXOP including the Primary 20 MHz subchannel and additional subchannels. In this case, the AP may determine whether the additional subchannels other than the Primary 20 MHz subchannel are IDLE / BUSY based on the CCA results identified during PIFS (SIFS (16 us) + aSlotTime (9 us), i.e., 25 us) on each subchannel.

[0379]

[0380] Such a channel access procedure may be achieved by the AP ignoring the NAV set by the frame transmitted by the non-AP STA during the shared TXOP period with the non-AP STA. That is, when the AP receives a frame from the non-AP STA that shares the TXOP acquired by the non-AP STA, the AP may determine the Virtual CCA result of the primary channel (simply put, a CCA method that determines BUSY when the NAV is not 0) as IDLE regardless of the value of the NAV set by the frame transmitted by the non-AP STA. That is, the AP may ignore the NAV set by the non-AP STA during the shared TXOP with the non-AP STA and perform the channel access procedure on the Primary 20 MHz channel.

[0381] When the AP completes the channel access procedure on the Primary 20 MHz channel (i.e., the backoff procedure is completed and channel access is obtained) during the TXOP shared by the non-AP STA with the AP, the AP may attempt channel access to additional subchannels identified as IDLE, including the Primary 20 MHz channel. In this case, the TXOP of the non-AP STA may be terminated and the TXOP of the AP may be initiated. That is, the TXOP acquired by the non-AP STA is terminated when the AP completes the channel access procedure during the shared time, and the TXOP of the AP is initiated.

[0382]

[0383] This can be considered as an AP channel access method that applies the same / similar method to the channel access method of other heterogeneous devices described above, where they access additional subchannels that are judged to be IDLE when completing LBT on a specific 20 MHz subchannel (the primary channel). However, there is a difference in that the AP's channel access can proceed within the TXOP acquired by a non-AP STA.

[0384] That is, when a non-AP STA shares a TXOP it has acquired with an AP, it can be understood that it performs TXOP sharing with the understanding that the AP's TXOP is initiated after the AP acquires channel access rights within the TXOP it has acquired.

[0385] At this time, the control frame (TXOP sharing frame) that the non-AP STA transmits to the AP to share the TXOP it has acquired includes a function that induces the Wi-Fi STAs that have received the frame to set the NAV. Therefore, other STAs that have received the control frame transmitted by the non-AP STA must determine that the Virtual CCA result of the Primary 20 MHz channel is BUSY until the NAV set by the frame is released (becomes 0), and as a result, channel access is restricted.

[0386] Additionally, when an AP receives a control frame (TXOP shared frame) from a non-AP STA, it can transmit a response frame. At this time, the response frame transmitted by the AP includes a function that induces the STAs that received the response frame to set the NAV. Therefore, other STAs that received the response frame transmitted by the AP must determine that the Virtual CCA result of the Primary 20 MHz channel is BUSY until the NAV set by the frame is released (becomes 0), and as a result, channel access is restricted.

[0387]

[0388] That is, channel access of STAs of the BSS and nearby STAs is restricted due to the NAV set through the control frame transmitted by the non-AP STA and the response frame transmitted by the AP, and only the AP can ignore the NAV set by the non-AP STA (the STA that transmitted the control frame) and complete the channel access procedure. At this time, completing the channel access procedure means acquiring channel access rights (the backoff counter becomes 0) by performing operations such as calling the backoff procedure for channel access and decreasing the backoff counter.

[0389]

[0390] At this time, the NAV set by the control frame transmitted by the non-AP STA can be set through a method identical / similar to the Duration / ID setting method considered in the embodiments of the present invention described above, so a detailed description is omitted. However, when setting the Duration / ID field of the control frame, the non-AP STA may additionally consider the time required for the AP to complete the channel access procedure.

[0391]

[0392] In addition, the AP may invoke / proceed with the backoff procedure only when the TXOP shared from the non-AP STA is longer than (or equal to or longer than) the agreed-upon time. That is, the AP may be restricted from performing a series of operations to obtain channel access by invoking the backoff procedure when the TXOP shared from the non-AP STA is shorter than (or shorter than or equal to) the agreed-upon time. Alternatively, a similar restriction may be applied to the non-AP STA. That is, the non-AP STA may need to transmit a control frame to share the TXOP with the AP only when the TXOP that it can share with the AP is longer than the agreed-upon time.

[0393] In addition, if the AP determines that there is an additional subchannel that is identified as IDLE in addition to the subchannels occupied by the control frame received from the non-AP STA (i.e., if it determines that there is an additional accessible subchannel), it can attempt to acquire its own TXOP by performing a channel access procedure. In other words, the AP can perform a channel access procedure during the shared TXOP from the non-AP STA only if it determines that it can secure an additional subchannel through the channel access procedure (such as invoking, proceeding, and completing a backoff procedure) performed during the shared TXOP. At this time, the method for the AP to determine that there is an additional accessible subchannel may be that at least one subchannel other than the subchannel occupied by the control frame received from the non-AP STA is determined to be accessible among the subchannels included in its operating bandwidth. That is, if the AP determines that at least one additional subchannel is accessible in addition to the subchannels occupied by the control frame when a control frame is received, it can initiate a channel access procedure to acquire channel access rights for the additional subchannel.

[0394] At this time, the method for determining whether there are additional subchannels accessible to the AP may be based on whether the CCA result of each subchannel confirmed during the PIFS before the control frame is received is IDLE. Alternatively, the method for determining whether there are additional subchannels accessible to the AP may be based on whether the CCA result of each subchannel confirmed during the SIFS or PIFS immediately after the control frame is received is IDLE. At this time, the AP may apply different rules to determine whether each subchannel is accessible. What is important is that after determining whether each subchannel is accessible, the channel access procedure is initiated only when it is determined that an additional subchannel other than the subchannel occupied by the control frame is accessible. The specific method for determining whether each subchannel is accessible may not be important.

[0395] As described above, after receiving a control frame for TXOP sharing from a non-AP STA, the AP can decide whether to initiate a channel access procedure.

[0396] An AP can make a non-AP STA that transmitted a control frame aware of this by acting differently when it decides to access an additional subchannel by initiating a channel access procedure and when it decides not to initiate a channel access procedure.

[0397] More specifically, when the AP decides to access an additional subchannel by initiating a channel access procedure after receiving a control frame, the AP may transmit a first response frame to the non-AP STA in response to the control frame. At this time, the first response frame may have the meaning of a response to the received control frame, as well as a meaning of notifying that the AP that responded to the first response frame will proceed with the channel access procedure. That is, the non-AP STA that transmitted the control frame (TXOP shared frame) can recognize that the control frame was normally received by the AP and that the AP initiated the channel access procedure when the first response frame is received from the AP. Therefore, the non-AP STA should determine that its TXOP has ended and should not perform operations such as TXOP recovery. At this time, the first response frame may be an individually addressed frame transmitted to the non-AP STA that transmitted the control frame, or a broadcast (group addressed) frame. This may be an addressing method to be considered because the first response frame may include a function that allows other STAs that have received the frame to recognize the operational intent of the AP that transmitted the first response frame. That is, the AP that transmitted the first response frame has the intention to perform a frame exchange sequence with STAs existing in its BSS by becoming a TXOP holder, and non-AP STAs (STAs that are members of the BSS) that have received the first response frame transmitted by its AP may recognize that the TXOP of the AP is about to start and prepare to participate in the frame exchange (e.g., maintain the Awake state without switching to Doze).Therefore, since the first response frame transmitted by the AP has both the meaning of a response to the non-AP STA that transmitted the control frame (TXOP shared frame) and the function of notifying the existence of its own TXOP to be initiated later, it is also possible for the AP to transmit the frame as a broadcast (group addressed) frame. However, even if the first response frame is transmitted as an individually addressed frame, it is possible for the member STAs of the BSS to recognize that the AP's TXOP will be initiated soon based on the format of the first response frame.

[0398] At this time, the format of the first response frame can be CTS or CTS-to-Self (RA addressed is set to AP's MAC addressed). If the AP responds with a CTS-to-Self frame as the first response frame, the TXOP acquired by the AP thereafter is subject to the TXOP limit from the start of transmission of the CTS-to-Self frame.

[0399] More specifically, if the AP decides not to initiate a channel access procedure after receiving a control frame, it can respond with a second response frame. When the AP transmits a second response frame, it can continue the frame exchange sequence using only the subchannels occupied by the control frame. This may be because the AP responds with a second response frame because it determines that there are no additional subchannels within its operating bandwidth where it can obtain channel access.

[0400] Therefore, when the AP decides not to initiate a channel access procedure after receiving a control frame, it can continue the frame exchange sequence using the subchannels occupied by the control frame and notify this to the non-AP STA by responding with a second response frame. At this time, the second response frame may be a trigger frame indicating a response to a TB PPDU. At this time, the trigger frame may be a trigger frame indicating a TB PPDU response to the non-AP STA that transmitted the control frame (TXOP shared frame). At this time, the second response frame may be an MU-RTS frame. STAs that receive the MU-RTS frame, which is the second response frame, can respond with a CTS frame to the MU-RTS frame, which is the second response frame transmitted by the AP, even if the NAV set by the control frame is not 0. That is, other non-AP STAs that have set NAVs by a specific non-AP STA that has shared TXOP with the AP can ignore the NAV set by the specific non-AP STA when responding to a frame transmitted by the AP.

[0401] FIG. 24 illustrates an example of a method for obtaining a shared transmission opportunity (TXOP) using a TXOP according to an embodiment of the present invention.

[0402] Referring to FIG. 24, when an AP receives a TXOP from a non-AP STA, it can perform a backoff procedure within the shared TXOP and obtain the TXOP.

[0403] To avoid repetition, the same content as described in Figures 21, 22 and 23 above may be omitted.

[0404] Specifically, the AP and non-AP STA each perform a backoff procedure to obtain channel access, and the non-AP STA's backoff procedure is completed first. After the backoff procedure is completed, the non-AP STA shares the TXOP it has acquired with the AP by transmitting a control frame to the AP.

[0405] After receiving a control frame transmitted by a non-AP STA, the AP transmits a response frame to encourage other STAs to set their NAVs. The AP then ignores the NAV set by the non-AP STA and invokes and completes the backoff procedure during the TXOP it has shared.

[0406] An AP that has completed a backoff procedure during a shared TXOP from a non-AP STA obtains channel access rights for subchannels identified as IDLE during the PIFS from the time the backoff procedure was completed, and initiates its own TXOP for those subchannels.

[0407] At this time, other STAs can recognize that the channel access procedure was interrupted due to the NAV set by the control frame transmitted by the non-AP STA and / or the NAV set by the response frame transmitted by the AP, and that the TXOP holder has become the AP after the AP receives a frame to initiate its own TXOP.

[0408] As considered in one embodiment of the present invention described above, operations that help an AP initiate a TXOP after a non-AP STA obtains channel access rights can be understood as channel reservation or TXOP reservation operations performed by a non-AP STA to obtain a TXOP of the AP.

[0409] In addition, in one embodiment of the present invention, although the frame transmitted by the non-AP STA to share the TXOP with the AP is considered to be an MU-RTS TXS frame, the frame transmitted by the non-AP STA to allow the AP to acquire the TXOP may be a different type of control frame. More specifically, the frame transmitted by the non-AP STA that has acquired the TXOP (acquired the channel access right) to allow the AP to perform the TXOP acquisition procedure may be a new type of trigger frame (a trigger frame of a type not defined in IEEE 802.11be, i.e., EHT).

[0410] <TXOP 공유 / 개시 절차를 위한 채널 액세스 절차>

[0411] According to the procedure provided in the present invention, an AP can acquire a TXOP with the help of a non-AP STA. That is, when a non-AP STA acquires channel access rights after completing a channel access procedure, the TXOP can be transferred / shared with the AP. An AP associated with multiple non-AP STAs can acquire a TXOP whenever at least one non-AP STA among the non-AP STAs acquires channel access rights. This may cause fairness issues with legacy BSSs and other BSSs that cannot utilize the procedure provided in the present invention.

[0412] To address fairness issues, the AP can instruct non-AP STAs to apply different EDCA parameters than the standard channel access procedure when performing channel access to initiate TXOP sharing / initiation procedures. Specifically, the AP can designate separate EDCA parameters to be used for TXOP sharing / initiation procedures, taking into account factors such as the presence of other BSSs and the number of STAs within a BSS, and instruct / guide non-AP STAs to follow these parameters.

[0413] To this end, the AP can differentiate the EDCA parameters used by non-AP STAs when accessing a channel to transmit a TXOP sharing / initiation frame by including a TXOP sharing EDCA parameter Set element in the management frames it transmits (e.g., beacon, probe response, association response frame, and operation mode indication, etc.). More specifically, the AP can indicate the EDCA parameters to be used by non-AP STAs that intend to transmit the AP TXOP sharing / initiation frame when performing a channel access procedure. The EDCA parameters can include at least one of CWmin, CWmax, and AIFSN. In this case, CWmin, CWmax, and AIFSN can be indicated for each AC (access category).

[0414] A non-AP STA that intends to transmit a TXOP Share / Initiate frame must perform channel access using different CWmin, CWmax, and AIFSN parameters than when it does not intend to transmit a TXOP Share / Initiate frame.

[0415] For example, a non-AP STA may update CWmin[AC], CWmax[AC], and AIFSN[AC] using the values ​​indicated via the TXOP sharing EDCA parameters Set element when the AP indicates that it will transmit a TXOP initiation / sharing frame, and may update CWmin[AC], CWmax[AC] and AIFSN[AC] using the values ​​indicated via the EDCA parameters Set element when the AP indicates that it will not transmit a TXOP initiation / sharing frame. However, a non-AP STA whose MUEDCATimer[AC] is not 0 at the time when the AP indicates that it will not transmit a TXOP initiation / sharing frame may update CWmin[AC], CWmax[AC], and AIFSN[AC] using the values ​​indicated via the MU EDCA parameters Set element.

[0416] Additionally, it is also possible to indicate the TXOP limit of each Access Category through the TXOP shared EDCA parameter Set element. In this case, the TXOP limit for each AC means the maximum length of the TXOP acquired through the EDCA of the corresponding AC. However, a non-AP STA that has acquired channel access rights through an AC for which the TXOP limit is indicated as 0 through the TXOP shared EDCA parameter Set element may be required to transmit the first frame as a TXOP sharing / initiation frame. In other words, a non-AP STA for which the EDCA of an AC with a TXOP limit of 0 is the TXOP holder must support the TXOP initiation of the AP (share the TXOP with the AP) through the first frame.

[0417] In addition, a non-AP STA that has transmitted a TXOP initiation / share frame to an AP may attempt a TXOP recovery procedure if a response (e.g., a CTS frame) to the frame it transmitted is not received from the AP. That is, if a response to the TXOP initiation / share frame is not performed from the AP, the non-AP STA may perform a procedure such as performing PIFS recovery, performing a new backoff procedure, or waiting until the TXNAV timer expires. This can be understood as a recovery procedure performed by a non-AP STA as a TXOP holder, because the point in time when the AP does not perform a response to the TXOP initiation / share frame transmitted by the non-AP STA is the point in time when the non-AP STA is still a TXOP holder.

[0418] <TXOP 공유 / 개시 절차와 관련한 시그널링>

[0419] As described above, after a non-AP STA acquires a TXOP, the procedure of transferring the TXOP to the AP (i.e., transmitting a TXOP sharing / initiation frame, etc.) may be an operation performed only when necessary by the AP. This is because if there is not much traffic queued on the AP side or the AP does not intend to perform coordination operations with other APs, the AP may not intend to perform transmission using the TXOP acquired by the non-AP STA or to acquire the TXOP. Therefore, the AP can induce non-AP STAs to allow or not allow the non-AP STAs to transmit TXOP sharing / initiation frames to it by notifying non-AP STAs that it intends to acquire or share the TXOP.

[0420] That is, the AP can indicate to the STAs of the BSS whether it wants to be given the TXOP (i.e., whether it wants to receive the TXOP sharing / initiation frame), and this must be done in a way agreed upon in advance between the AP and the STAs.

[0421] The method by which an AP instructs non-AP STAs to perform a TXOP sharing / initiation procedure may include at least one of the following methods.

[0422] - The AP can, through a beacon frame, indicate whether non-AP STAs that have obtained channel access rights during the time period until the next TBTT (Target beacon Transmit Time) should transmit a TXOP share / initiate frame. At this time, if the AP does not indicate whether or not to transmit a TXOP share / initiate frame through a specific beacon frame, it can be interpreted that the indication performed through a beacon frame transmitted before the specific beacon frame is maintained. In other words, rather than indicating whether or not to transmit a TXOP share / initiate frame in every beacon frame, the AP can also perform the indication through a beacon frame only when it intends to change the indication regarding whether or not to transmit the frame. Therefore, a non-AP STA should interpret that when the first beacon frame includes an indication as to whether or not to transmit a TXOP share / initiate frame, and the second beacon frame does not include an indication as to whether or not to transmit a TXOP share / initiate frame, the same indication as indicated through the first beacon frame continues to be maintained.

[0423] - The AP may indicate whether to transmit a TXOP sharing / initiation frame via a probe response frame and / or an association response frame. A non-AP STA that has received an indication to transmit a TXOP sharing / initiation frame via a probe response / association response frame received from the AP must transmit a TXOP sharing / initiation frame to the AP when it has obtained channel access rights after completing the channel access procedure.

[0424] - The AP can instruct the non-AP STA to transmit a TXOP sharing / initiation frame through a response frame transmitted to the non-AP STA.

[0425] --> For example, when an AP receives an RTS frame from a non-AP STA, the AP can instruct the non-AP STA that transmitted the RTS frame to transmit a TXOP share / initiate frame by responding by setting a specific bit of the CTS frame for the RTS frame to a specific value (e.g., 1). That is, the non-AP STA must transmit a TXOP share / initiate frame to the AP if a specific bit of the CTS frame received in response to the RTS frame transmitted to the AP is set to a specific value. At this time, the specific bit of the CTS frame may be a bit included in the frame control field of the CTS frame. At this time, the specific bit may be one of the bits corresponding to the To DS, From DS, More Fragments, Retry, Power Management, More Data, Protected frame, and +HTC subfield.

[0426] --> As another example, the AP can instruct the non-AP STA to transmit a TXOP sharing / initiation frame by setting a specific bit of the Ack / BlockAck frame that responds to the frame received from the non-AP STA to a specific value (e.g., 1). That is, the non-AP STA must transmit the TXOP sharing / initiation frame to the AP if the specific bit of the Ack / BlockAck frame responded to by the AP is set to a specific value. At this time, the specific bit may be set for the above-described purpose only when the non-AP STA is a TXOP holder. At this time, the specific bit of the Ack / BlockAck frame may be a bit included in the frame control field. At this time, the specific bit may be one of the bits corresponding to the To DS, From DS, More Fragments, Retry, Power Management, More Data, Protected frame, and +HTC subfield.

[0427] - The AP can transmit an AP Priority Access Enable frame to instruct non-AP STAs to transmit a TXOP share / initiate frame. The AP Priority Access Enable frame is a frame that the AP transmits when it intends to proactively manage the TXOP acquired within the BSS. Non-AP STAs that receive the frame from the Associated AP must perform a procedure (such as transmitting a TXOP share / initiate frame) to transfer the TXOP to the AP when they acquire channel access rights (TXOP). Thereafter, the AP can transmit an AP Priority Access Disable frame to instruct non-AP STAs not to transmit a TXOP share / initiate frame. At this time, the AP Priority Access Enable frame may include and be instructed information related to the time at which transmission of the TXOP share / initiate frame is required. For example, if 100ms is indicated through an AP Priority Access Enable frame transmitted by an AP, non-AP STAs may be required to transmit a TXOP share / initiate frame to the AP if they obtain channel access rights within 100ms of receiving the frame. The AP Priority Access Disable frame is a frame transmitted when the AP does not need assistance from non-AP STAs, and non-AP STAs that receive the frame from the Associated AP do not perform the procedure for transferring the TXOP to the AP when they obtain channel access rights (TXOP). In this case, the AP Priority Access Enable / Disable frame is a frame named for convenience of explanation, and other frames with the same / similar functions can be used for the same / similar purposes.

[0428] In this way, the AP can, depending on operational purposes, instruct / request the non-AP STAs of the BSS to transmit TXOP sharing / initiation frames, or instruct / request not to transmit TXOP sharing / initiation frames. Non-AP STAs can decide whether to transmit TXOP sharing / initiation frames based on the most recently received instructions from the AP.

[0429] In addition, if the AP and the non-AP STA are devices each belonging to an MLD (Multi-Link Device), the above-described AP indication can also be indicated through another AP of the MLD to which the AP belongs. For example, it is possible for the STAs associated with AP1 to be indicated through a beacon frame transmitted by AP2 belonging to the same MLD as AP1 as to whether they should transmit a TXOP sharing / initiation frame. In this case, the non-AP STA1 associated with AP1 can determine / decide whether it should transmit a TXOP sharing / initiation frame to AP1 based on information obtained through the non-AP STA2, which is another STA in the MLD. The concept of MLD is described in more detail through an embodiment of FIG. 26.

[0430] FIG. 25 illustrates an example of a format of a parameter set element for TXOP sharing according to one embodiment of the present invention.

[0431] Referring to FIG. 25, the TXOP shared EDCA parameter Set element transmitted by the AP may include AC_BE Parameter Record, AC_BK Parameter Record, AC_VI Parameter Record, and AC_VO Parameter Record fields. At this time, the AC_BE Parameter Record, AC_BK Parameter Record, AC_VI Parameter Record, and AC_VO Parameter Record fields of the TXOP shared EDCA parameter Set element include AIFSN, CWmin, CWmax, and TXOP limit information that a non-AP STA that intends to transmit a TXOP shared / initiation frame must use when performing a channel access procedure.

[0432] The CWmin and CWmax values ​​are indicated through the 4-bit ECWmin and ECWmax subfields, respectively. ECWmin is set so that the value 2^(ECWmin)-1 is the CWmin value it intends to indicate. That is, the ECWmin subfield of the Parameter Record field that indicates CWmin as 15 is indicated as 4. Similarly, ECWmax is set so that the value 2^(ECWmax)=1 is the CWmax value it intends to indicate. That is, the ECWmax subfield of the Parameter Record field that indicates CWmax as 1023 is indicated as 10.

[0433] The TXOP Limit subfield indicates the maximum length of the TXOP obtained using the values ​​of the corresponding Parameter set.

[0434] FIG. 26 illustrates an example of the configuration and connection status of an AP MLD and a non-AP MLD according to one embodiment of the present invention.

[0435] An MLD is a logical entity to which one or more STAs are affiliated. A device in which each STA affiliated to an MLD functions as an AP is an AP MLD, and a device in which each affiliated STA functions as a non-AP STA is a non-AP MLD.

[0436] Each STA within an MLD can operate on a different link (channel). In other words, STAs within an MLD can operate on multiple different channels. For example, STAs within an MLD can operate on channels in different bands, such as 2.4 GHz, 5 GHz, and 6 GHz. This allows MLD to gain benefits in channel access and improve overall network performance.

[0437] Additionally, it is possible to refer to MLD operation as multi-link operation, MLD operation, or multi-band operation. While existing wireless LANs operate on a single link, MLD operation utilizes multiple links to obtain more channel access opportunities or can operate efficiently on multiple links by considering channel conditions.

[0438] As illustrated in FIG. 26, two MLDs can be connected via multiple Links. An AP MLD including AP1, AP2, and AP3 and an MLD non-AP MLD including non-AP STA1, non-AP STA2, and non-AP STA3 can each be connected via three Links. When multiple Links are connected between MLDs, the connection between the AP and the non-AP STA in each Link unit supports the same connection state as the connection state between single Link devices. In addition, information can be exchanged between STAs belonging to the same MLD via the MLD, and therefore, information received by AP1 can be transmitted to AP2, and information received by non-AP STA1 can also be transmitted to non-AP STA2.

[0439] Through this, AP MLD can transmit changes related to AP1 to non-AP STA1 via AP2. That is, as considered in one embodiment of the present invention, if AP2 instructs AP1 to transmit a TXOP share / initiate frame via Link2, non-AP STA1 can transmit a TXOP share / initiate frame to AP1 based on the information acquired by non-AP STA2 via Link2.

[0440] <non-AP가 개시하는 TXOP sharing 절차에 대한 AP의 시그널링>

[0441] As described above, a non-AP STA may transmit a specific frame (e.g., a kind of control frame (which may be a trigger type frame) that may be named a TXOP sharing request frame) to the AP to share the TXOP it has acquired with the AP.

[0442] If there is no traffic that the AP wants to transmit on the AP side (i.e., the AP's transmission queue is empty) and there is no scheduling target device that the AP recognizes (i.e., a non-AP STA that must solicit a TB PPDU via a trigger frame), the AP may not have an action to perform during the TXOP shared with the non-AP STA. In this case, the TXOP shared by the non-AP STA to the AP cannot be used for any purpose other than transmitting the non-AP STA's TB PPDU, and therefore, it can be understood that unnecessary TXOP sharing has been performed.

[0443] Accordingly, the AP can announce to non-AP STAs in the BSS whether it should or should not share TXOPs. This announcement by the AP can be understood as an action by the AP to instruct non-AP STAs whether to initiate a TXOP sharing procedure.

[0444] A simple method for instructing non-AP STAs to perform TXOP sharing may be to have the AP instruct non-AP STAs to use the TXOP sharing procedure by transmitting a specific frame, a specific element, or a specific field. In this case, the non-AP STAs may share the TXOP they have acquired with the AP when they are instructed to share the TXOP they have acquired with the AP through the specific frame, the specific element, or the specific field received from the AP. That is, the non-AP STA may share the TXOP with the AP when it has acquired the TXOP when it is instructed to perform TXOP sharing in the specific frame / element / field most recently received. However, the non-AP STA may first transmit low-latency traffic through the TXOP it has acquired, taking into account the latency requirement of the traffic it wants to transmit, and then share the remaining TXOP with the AP. Here, the non-AP STA sharing a TXOP with the AP means the operation of transmitting the above-described TXOP sharing / initiation frame to the AP. That is, it was used to mean both the non-AP STA transferring a TXOP to the AP or initiating the AP's TXOP acquisition procedure, and in the embodiments of the present invention described below, when it is explained that the non-AP STA 'shares' the TXOP it has acquired with the AP, it should be interpreted to mean both the TXOP being 'transferred' to the AP or the AP's TXOP being 'initiated' by the non-AP STA. That is, it should be understood that the TXOP of the non-AP STA is shared with the AP when the AP controls (manages, i.e. transmits a DL PPDU, requests a TB PPDU response, etc.) the medium during the time period (TXOP) in which the non-AP STA acquired authority by completing the channel access procedure.

[0445] The method by which an AP instructs non-AP STAs whether a non-AP STA should perform TXOP sharing is described in more detail through an embodiment of FIG. 27.

[0446] FIG. 27 illustrates an example of an element for sharing a TXOP according to an embodiment of the present invention.

[0447] The element that the AP transmits to non-AP STAs to indicate whether the non-AP STAs should share the TXOPs they have acquired with it may have the format shown in FIG. 27.

[0448] Specifically, as illustrated in FIG. 27, the TXOP shared element includes a TXOP shared control field. In addition, the TXOP shared element may further include a TXOP shared EDCA Parameter Set field.

[0449] At this time, whether the TXOP shared element further includes a TXOP shared EDCA Parameter Set field is indicated through the TXOP shared EDCA Parameter Set bit included in the TXOP shared control field. More specifically, the TXOP shared EDCA Parameter Set field is included in the TXOP shared element when the TXOP shared EDCA Parameter Set bit included in the TXOP shared control field is set / indicated to 1.

[0450] The TXOP sharing control field includes a Policy subfield. The Policy subfield indicates whether non-AP STAs should share the acquired TXOP with the AP when they acquire the TXOP. If the Policy subfield of the TXOP sharing element transmitted by the AP is indicated by a specific value (e.g., 0), non-AP STAs may not perform TXOP sharing with the AP when they acquire the TXOP. On the other hand, if the Policy subfield of the TXOP sharing element transmitted by the AP is indicated by a different value (e.g., 1), non-AP STAs must perform TXOP sharing with the AP when they acquire the TXOP. That is, non-AP STAs must transmit the TXOP sharing / initiation frame of the present invention described above to the AP. At this time, the non-AP STAs must determine whether to perform TXOP sharing based on the TXOP sharing element most recently received from the AP.

[0451] That is, the two types of policies indicated through the Policy subfield can be understood as normal and AP Priority. That is, if the Policy subfield is indicated with the specific value (e.g., 0), the 'normal' policy is applied, in which case non-AP STAs perform channel access through a conventional channel access method (e.g., EDCA or DCF, etc.) and then perform a conventional frame exchange sequence. At this time, the conventional frame exchange sequence means an operation such as transmitting a UL PPDU as a TXOP holder without sharing the TXOP with the AP. On the other hand, if the Policy subfield is indicated with another value (e.g., 1), the 'AP Priority' policy is applied, in which case non-AP STAs must acquire a TXOP and then share (transfer) the TXOP they have acquired to the AP.

[0452] Meanwhile, when the 'AP priority' policy is applied, non-AP STAs can perform channel access procedures in a different way than when the 'normal' policy is applied. In this case, performing the channel access procedure in a different way may mean using different values ​​for the backoff-related parameters used when performing channel access. That is, when the 'normal' policy is indicated, non-AP STAs perform channel access using parameters indicated through the EDCA Parameter Set element or the MU EDCA Parameter Set element, whereas when the 'AP priority' policy is indicated, non-AP STAs that intend to initiate a TXOP sharing procedure must perform channel access using parameters indicated through the TXOP sharing EDCA Parameter Set field of the TXOP sharing element, or the TXOP sharing EDCA Parameter Set element included in the Beacon frame, etc.

[0453] At this time, a non-AP STA that performs channel access with the intention of initiating a TXOP sharing procedure performs channel access (EDCA) using the parameters (TXOP sharing EDCA parameters) indicated through the TXOP sharing EDCA Parameter Set field, regardless of the MU EDCA timer value.

[0454] The R-TWT SP subfield is a subfield that indicates whether the acquired TXOP for the overlapping section with the R-TWT SP should be shared with the AP. If the R-TWT SP subfield is indicated with a specific value (e.g., 0), a non-AP STA may not share the TXOP with the AP when it acquires the TXOP for the overlapping section with the R-TWT SP. However, if the R-TWT SP subfield is set to another value (e.g., 1), the non-AP STA may be required to share the acquired TXOP for the overlapping section with the AP. That is, for the overlapping section with the R-TWT SP, the non-AP STA must ensure that the AP can control (manage, i.e., transmit DL PPDU or solicit TB PPDU, etc.) the Medium. Therefore, if the R-TWT SP subfield is set to another value (e.g., 1), the non-AP STA must share the acquired TXOP for the section overlapping with the R-TWT SP with the AP, regardless of the policy indicated through the Policy subfield.

[0455] At this time, the information indicated through the R-TWT SP subfield can be indicated through the Policy subfield. In other words, as in the example of FIG. 27, the Policy subfield and the R-TWT SP subfield are not separately indicated, and it is possible to indicate through the Policy subfield whether or not to share the acquired TXOP for the section overlapping with the R-TWT SP. That is, if the Policy subfield is indicated with a specific value (e.g., 2), it can be indicated / interpreted that the "AP priority" policy is applied during the R-TWT SP. That is, if the Policy subfield is indicated with the specific value (e.g., 2), the non-AP STA may have to decide whether to share with the AP based on whether the TXOP it has acquired overlaps with the R-TWT SP scheduled by the AP. At this time, the non-AP STA performs TXOP sharing with the AP if the TXOP it has acquired overlaps with the R-TWT SP scheduled by the AP. At this time, a non-AP STA may not perform TXOP sharing with the AP if the TXOP it has acquired does not overlap with the R-TWT SP scheduled by the AP.

[0456] The TXOP Shared EDCA Parameter Set field is a field that includes an EDCA parameter set that a non-AP STA that performs channel access (EDCA) with the intention of performing TXOP sharing must use. Information included in the TXOP Shared EDCA Parameter Set field may be similar to information included in the EDCA Parameter Set element and the MU EDCA Parameter Set element. More specifically, the TXOP Shared EDCA Parameter Set field may include an ACI / AIFSN field, an ECWmin / ECWmax field, and a TXOP limit field. Although FIG. 27 illustrates that the TXOP Shared EDCA Parameter Set field includes one ACI / AIFSN, ECWmin / ECWmax, TXOP limit, and Shared TXOPlimit subfield, the TXOP Shared EDCA Parameter Set field may repeatedly include up to four ACI / AIFSN, ECWmin / ECWmax, TXOP limit, and Shared TXOPlimit subfields. That is, the TXOP shared EDCA Parameter Set field illustrated in FIG. 27 includes the ACI / AIFSN, ECWmin / ECWmax, TXOP limit, and Shared TXOPlimit subfields only once, and the same configuration can be repeatedly included up to four times. In this case, the number of times the ACI / AIFSN, ECWmin / ECWmax, TXOP limit, and Shared TXOPlimit subfields are repeated in the TXOP shared EDCA Parameter Set field can be indicated through the TXOP shared control field.For example, the TXOP Shared EDCA Parameter Set Present subfield of one embodiment of FIG. 27 indicates whether a TXOP Shared EDCA Parameter Set field is included in a TXOP Shared element including the corresponding subfield, and further, it is possible to indicate information related to the size of the TXOP Shared EDCA Parameter Set field (information related to how many times the ACI / AIFSN, ECWmin / ECWmax, TXOP limit, and Shared TXOPlimit subfields appear).

[0457] ACI / AIFSN subfield and ECWmin / ECWmax, TXOP limit subfield can be set / interpreted in the same way as the fields of the same name included in the EDCA Parameter Set element of the existing Wi-Fi, so a detailed description is omitted. (Refer to 9.4.2.28 (EDCA Parameter Set element) of Draft P802.11REVme_D2.0)

[0458] The Shared TXOPlimit subfield indicates information related to the minimum time that must be observed when sharing a TXOP acquired through the AC (the Access Category indicated by the corresponding ACI / AIFSN subfield) with the AP. For example, if AC_VO is indicated through the ACI / AIFSN subfield and 2 ms is indicated through the corresponding Shared TXOPlimit subfield, a non-AP STA must share the TXOP acquired through AC_VO with the AP for at least 2 ms. That is, the Shared TXOPlimit subfield for a specific AC indicates the minimum time that a non-AP STA that acquired a TXOP through the specific AC must share with the AP. If the Shared TXOPlimit subfield for a specific AC is set to 0, a non-AP STA may be required to transmit a TXOP sharing / initiation frame when attempting channel access (transmitting the first frame) through the specific AC. That is, an AC in which the Shared TXOPlimit subfield is set to 0 may mean that a non-AP STA must acquire a TXOP through the AC and share the TXOP with the AP at the same time.

[0459] The TXOP shared element described through Figure 27 can be transmitted through frames transmitted by the AP, and non-AP STAs must use the policies and parameters indicated through the most recently received TXOP shared element.

[0460] If the information (values ​​of each subfield) of the TXOP shared element indicated by the AP differs from the information indicated through the previously transmitted TXOP shared element, it can be considered a critical update for the BSS parameters. In other words, when the information indicated through the TXOP shared element is set differently from the information it previously indicated, the AP must consider this to be a critical update and take action accordingly. In other words, the AP must increase the Check Beacon field value of the next TIM frame it transmits by 1.

[0461] FIG. 28 illustrates an example of a frame including elements for sharing a TXOP according to one embodiment of the present invention.

[0462] Referring to FIG. 28, the AP may transmit a TXOP sharing element via a Beacon and / or (ML) Probe Response and / or (Re)Association Response, TXOP sharing Notification frame.

[0463] Non-AP STAs must follow the Channel access policy indicated through the most recently received TXOP shared element, and if the 'AP priority' policy is applied, they must perform the Channel Access Procedure (EDCA) using the parameters indicated through the TXOP shared EDCA Parameter Set field.

[0464] The method of including elements in the Beacon, (ML) Probe Response, and (Re)Association Response frames is the same as including various elements in the same frame in conventional Wi-Fi, so a separate explanation is omitted.

[0465] The TXOP Share Notification frame is an Action frame, and can be a frame transmitted by the AP to change instructions related to TXOP sharing. In this case, the TXOP Share Notification frame can be an Action No Ack frame. That is, non-AP STAs that receive the frame may not respond with a Response frame.

[0466] The Category field of the TXOP shared Notification frame is a field that indicates that the corresponding Action frame is a TXOP shared Notification frame, and non-AP STAs can recognize that the corresponding frame is a TXOP shared Notification frame when the Category field is set to a specific value.

[0467] The Category field of the TXOP shared Notification frame indicates that the corresponding Action frame is a (Protected) UHR Action frame. At this time, the value indicated by the Category field can be set to 38 to indicate that it is a UHR Action frame, or 39 to indicate that it is a Protected UHR Action frame.

[0468] The (Protected) UHR Action field of the TXOP shared Notification frame is a field that indicates that the Action frame is a TXOP shared Notification frame, and non-AP STAs can recognize that the frame is a TXOP shared Notification frame when the (Protected) UHR Action field is set to a specific value.

[0469] The Dialog Token field is set to a non-zero value and is used to distinguish this transaction from other transactions.

[0470] The TXOP shared field contains a TXOP shared element (see Figure 27).

[0471] <Various response frame examples>

[0472] As explained above, when a non-AP STA shares a TXOP with an AP through a TXOP sharing / initiation procedure, there may be cases where the AP does not have an operation to perform using the shared TXOP. In this case, the AP can transmit a response frame to the control frame (TXOP sharing / initiation frame) received from the non-AP STA, indicating that it does not need to share the TXOP. In addition, when the AP intends to perform a service for multiple non-AP STAs using the TXOP shared from the non-AP STA, the multiple non-AP STAs may need to prepare an operation that takes into account that the AP will perform transmission to them.

[0473] That is, when a control frame for TXOP sharing is received from a non-AP STA, the AP can instruct other STAs about whether it will perform transmission / reception through the shared TXOP and / or about prior information regarding the operation to be performed using the shared TXOP. At this time, the instruction can be performed through a response frame (TXOP sharing response frame) transmitted by the AP in response to the control frame.

[0474] The information that the AP indicates through the response frame can be broadly divided into two types: 1. The frame exchange sequence will be performed using the TXOP shared by the Non-AP STA, and 2. There is no action to be performed using the TXOP shared by the Non-AP STA.

[0475] The method by which the AP indicates whether to perform an operation using the TXOP (hereinafter, shared TXOP) shared by the non-AP STA through the response frame may be by using the format of the response frame or by setting a specific subfield (bit) included in the response frame to a specific value.

[0476] To explain the instruction method using the frame format more specifically, when the AP intends to perform a follow-up operation using the shared TXOP (such as transmitting a DL MU PPDU or requesting a UL TB PPDU response by transmitting a trigger frame), it can respond with a TXOP sharing response frame in response to a TXOP sharing / initiation frame received from a non-AP STA. At this time, the TXOP sharing response frame can be a trigger frame or an MU-RTS (Trigger) frame. Alternatively, the TXOP sharing response frame can be a frame of another type of predetermined format. Therefore, after transmitting a TXOP sharing / initiation frame to the AP, the non-AP STA that received the TXOP sharing response frame in response must not perform transmission without the AP's triggering during the remaining TXOP. In other words, when the non-AP STA receives a TXOP sharing response frame in response from the AP, the non-AP STA must perform an operation recognizing that the AP has become a TXOP holder. That is, the NAV (Intra-BSS NAV, Basic NAV) must be set based on the Duration / ID field value of the frame transmitted by the AP. At this time, the non-AP STA can stop the channel access procedure (keep the Virtual NAV busy) by setting the NAV timer to the same value as its remaining TXNAV timer when it receives a TXOP sharing response frame from the AP. At this time, the non-AP STA can set its TXNAV to 0 when it receives a TXOP sharing response frame from the AP. TXNAV refers to a timer that the TXOP holder initializes to the value indicated through the Duration / ID field of the frame that it most recently successfully transmitted. At this time, the meaning of the successfully transmitted frame means that the frame in question is a frame in which a response frame for the frame is received.

[0477] When the AP does not intend to perform subsequent operations using the shared TXOP (such as transmitting a DL MU PPDU or requesting a UL TB PPDU response by transmitting a trigger frame), it is possible to respond with a CTS frame in response to the TXOP sharing / initiation frame. That is, when a non-AP STA receives a CTS frame in response to its transmitted TXOP sharing / initiation frame, it can recognize that the AP does not intend to use the TXOP it has shared. In this case, the non-AP STA can perform operations such as transmitting a UL PPDU or a P2P PPDU using its remaining TXOP. That is, when the non-AP STA's TXOP sharing with the AP is rejected (suspended), the non-AP STA can continue the operation it wants to perform during its TXOP as a TXOP holder.

[0478] To explain in more detail how to use a specific subfield (bit) included in a response frame, when an AP receives a TXOP share / initiate frame from a non-AP STA, the AP can set a specific subfield (bit) of the response frame in a different way depending on whether it intends to perform a subsequent operation using the shared TXOP. For a simple example, when the AP intends to transmit a DL MU PPDU or receive a UL TB PPDU in response using the Shared TXOP, the AP can set the specific subfield to a specific value, and when it does not intend to perform an operation using the Shared TXOP, the AP can set the specific subfield to a different value. Accordingly, after transmitting a TXOP share / initiate frame to the AP, the non-AP STA can determine whether the AP intends to perform an operation using the Shared TXOP based on the specific subfield value of the received response frame.

[0479] At this time, when the non-AP STA determines that the AP has no intention of performing an operation using the Shared TXOP, the non-AP STA can operate as a TXOP holder by transmitting a UL PPDU or / and a P2P PPDU during the remaining TXOP, similar to the case of the instruction method using the frame format described above.

[0480] At this time, when the non-AP STA recognizes that the AP intends to perform an operation using the Shared TXOP through the specific subfield, the non-AP STA must perform operations such as setting the NAV based on the frame transmitted by the AP and resetting its TXNAV timer, similar to the case of the instruction method using the above-described frame format. That is, the non-AP STA that recognizes that the AP intends to perform an operation using the Shared TXOP through the specific subfield of the TXOP shared response frame to which the AP responded must function as if it is not a TXOP holder during the section corresponding to the shared TXOP.

[0481] In this way, an AP that has received a TXOP sharing / initiation frame can indicate through a response frame whether it will perform an operation utilizing the shared TXOP, and a non-AP STA that has transmitted the TXOP sharing / initiation frame can determine whether it will function as a TXOP holder for the remaining TXOP based on the responded TXOP sharing response frame.

[0482] Furthermore, the AP can instruct non-AP STAs that it wishes to perform frame exchange using the Shared TXOP through the TXOP Shared Response frame. In other words, the AP can instruct non-AP STAs other than the non-AP STA that transmitted the TXOP Shared / Initiate frame regarding operations to be performed during the Shared TXOP through the TXOP Shared Response frame. At this time, the AP can also perform the same instruction through a frame transmitted following the TXOP Shared Response frame (the next frame transmitted with an SIFS interval from the TXOP Shared Response frame) rather than the TXOP Shared Response frame. The following description is written assuming that the instruction to non-AP STAs is performed through the TXOP Shared Response frame, but it should be understood that the same instruction can also be performed through a frame transmitted following the TXOP Shared Response frame.

[0483] More specifically, the AP may transmit information indicating non-AP STAs that wish to perform transmission / reception during the Shared TXOP via a TXOP shared response frame. At this time, the information indicating the non-AP STAs may mean a field indicating an Association ID (AID) of the non-AP STA. That is, the AP may transmit one or more AID fields via the TXOP shared response frame, and each AID field indicates an AID (such as AID11 or AID12) of a target non-AP STA that is to transmit a DL MU PPDU via the Shared TXOP and / or a target non-AP STA that is to request a TB PPDU response via a trigger frame. Accordingly, non-AP STAs whose AIDs are indicated through the TXOP sharing response frame transmitted by the AP (a response frame to a TXOP sharing / initiation frame transmitted by a specific non-AP STA) can recognize that the AP will transmit a DL PPDU to them or request a response to a TB PPDU. In this case, the non-AP STAs can perform a waiting operation for reception of DL PPDUs and response to TB PPDUs to be performed in the future without switching to Power Save mode. At this time, the number of AID fields included in the TXOP sharing response frame is indicated through another (sub)field included in the TXOP sharing response frame. At this time, the other field may be a control field. Therefore, non-AP STAs can recognize how many AID fields are included in the corresponding TXOP sharing response frame based on the value indicated in the control field (or another subfield included in the control field (e.g., Number Of AIDs subfield)) of the received TXOP sharing response frame. At this time, the control field may be set to the number of AID fields included in the corresponding TXOP shared response frame - 1.That is, the subfield related to the number of AID fields can be set to 0 through the control field of the TXOP shared response frame including one AID field. At this time, the control field may be set to the number of AID fields included in the corresponding TXOP shared response frame. That is, the subfield related to the number of AID fields can be set to 1 through the control field of the TXOP shared response frame including one AID field. However, it is possible that the AID of a specific non-AP STA that transmitted the TXOP shared / initiate frame is not indicated through the AID field. This may be an applicable exception because the AP will transmit at least one trigger frame to the specific non-AP STA (the non-AP STA that transmitted the TXOP shared / initiate frame) during the Shared TXOP. That is, since the non-AP STA that transmitted the TXOP sharing / initiation frame is aware that at least one trigger frame will be received from the AP during the shared TXOP, the AP does not need to indicate the AID of the non-AP STA through the AID field.

[0484] Meanwhile, when performing operations using Shared TXOP, the AP may intend to change the operating channel of some non-AP STAs to the secondary channel in order to increase the utilization of the secondary channel.

[0485] As an example of the present invention, as described above, a station (e.g., an AP, etc.) can transmit a specific frame (e.g., a trigger frame, etc.) to change the operating channel of another station to a channel not supported by another station (e.g., a non-AP STA, etc.), and another station that receives the specific frame can change the operating channel to the channel indicated by the specific frame and transmit and receive the frame.

[0486] For example, if the total bandwidth is 320MHz, the AP can support and use all of 320MHz, but non-AP STAs may only support the bandwidth of the primary 160MHz (or lower) and not support the remaining secondary 160MHz. In this case, the operating bandwidth of the non-AP STAs is the primary 160MHz, and the remaining secondary 160MHz is not supported by the non-AP STAs, so the secondary 160MHz may not be used by the non-AP STAs. In order to use the secondary 160MHz (e.g., to transmit or receive frames in the secondary 160MHz), the AP can transmit a frame to the non-AP STAs to instruct them to change the operating bandwidth to the secondary 160MHz, and the non-AP STAs that receive the frame can change the operating bandwidth to the secondary 160MHz instructed by the frame and operate.

[0487] In another embodiment of the present invention, in the above embodiment, the AP can obtain a TXOP in a secondary channel through the method described in “Channel access procedure for bandwidth expansion”, and can perform a procedure for changing the operating bandwidth for non-AP STAs within the obtained TXOP.

[0488] In another embodiment of the present invention, the method for changing the operating channels of the above non-AP STAs and the method for performing channel access by the AP on a secondary channel can be performed together with a method for sharing a TXOP. Specifically, a first STA (e.g., an AP or a non-AP STA) can receive a TXOP (first TXOP) from a second STA (e.g., a non-AP STA or an AP) through the TXOP sharing procedure described above. At this time, the second STA can support only Primary 160MHz or Primary 80MHz out of a total bandwidth of 320MHz, and can perform a channel access procedure (first channel access procedure) using the primary subchannel of Primary 160MHz or Primary 80MHz, thereby obtaining the first TXOP. The frequency axis range in which the first TXOP is obtained can be up to the Primary 160MHz or Primary 80MHz range. The first STA can transmit and receive frames within the shared first TXOP. However, if the primary subchannel of Primary 160MHz or Primary 80MHz is occupied by another STA (e.g., OBSS STA), the channel access procedure cannot be performed through the Primary subchannel. Therefore, the first STA can select one of the remaining channels other than Primary 160MHz or Primary 80MHz (e.g., Secondary 160MHz or Secondary 80MHz when the total bandwidth is 320MHz), perform the channel access procedure (second channel access procedure) through the subchannel of the selected channel, and obtain a TXOP (second TXOP).In this case, the frequency range over which the second TXOP is acquired may be limited to the channel on which the channel access procedure was performed (e.g., Secondary 160MHz or Secondary 80MHz), and the second TXOP may be considered as an extension of the frequency band of the first TXOP. Accordingly, the second TXOP may be terminated at the same time as the first TXOP. In this case, the first STA may transmit a specific frame (e.g., a trigger frame, etc.) to the other STAs to change the operating channel of the other STAs to the Secondary 160MHz or Secondary 80MHz on which the second channel access procedure was performed. At this time, the other STAs may support only the Primary 160MHz or Primary 80MHz in the same or similar manner as the second STA. Other STAs that have received a specific frame from the first STA can change their operating bandwidth to Secondary 160MHz or Secondary 80MHz by expanding the bandwidth, and can transmit and receive frames using Secondary 160MHz or Secondary 80MHz.

[0489] For example, there may be a situation where an AP plans to operate a BW of 320 MHz for frame exchange using Shared TXOP. In this case, if all non-AP STAs to which the AP wishes to transmit are non-AP STAs that have set only the Primary 160 MHz band as their Operating BW, the AP cannot utilize the Secondary 160 MHz band. In this case, the reason the operating BW of the non-AP STAs is limited to the Primary 160 MHz may be because the operating bandwidth of the non-AP STAs is limited to 160 MHz. In this case, in order to utilize the Secondary 160 MHz band, the AP may request some non-AP STAs to change to operate on the Secondary 160 MHz band. Non-AP STAs that have been requested to change to the secondary 160 MHz band by the AP can receive DL PPDUs or respond with TB PPDUs using RUs included in the secondary 160 MHz band until the frame exchange sequence performed with the AP is completed. In other words, non-AP STAs do not support transmission / reception on the primary channel, but change their operation mode to support transmission / reception on the secondary channel.

[0490] As in the example above, the behavior of non-AP STAs changing their operating BW to a subchannel rather than the primary channel of the BSS may be similar to the Subchannel Selective Transmission (SST) behavior defined in 11ax. However, the non-AP STAs may have a difference in that, when the AP transmits a frame indicating a change to a subchannel to them, they operate on the indicated subchannel only during a continuous frame exchange sequence including the frame. In this case, the continuous frame exchange sequence refers to frame exchange sequences performed within a single TXOP. In this case, each frame (PPDU) of the continuous frame exchange sequence has an SIFS or PIFS interval.

[0491] In this way, when a non-AP STA changes its operation mode to support transmission / reception in a band other than the primary channel (a band including a sub-channel), it may require a time period depending on the capability of the non-AP STA. That is, each non-AP STA may have a time period required to change to the sub-channel operation mode, and the operation mode change time may be indicated as the Capability of the non-AP STA through the process of associating the AP and the non-AP STA. At this time, the value indicated by the non-AP STA through the Capability may be a transition time required to change to the sub-channel operation mode and / or a minimum padding field length that must be included in a frame (a frame transmitted by the AP) indicating to change to the sub-channel operation mode. Accordingly, when an AP instructs a specific non-AP STA to change to the sub-channel operation mode, it must operate while taking into consideration the time period required for the specific non-AP STA to change to the sub-channel operation mode. That is, when an AP instructs a specific non-AP STA to change to a sub-channel operation mode, the AP may include a padding field that is equal to or longer than the minimum padding field length indicated by the specific non-AP STA in the frame transmitted to instruct the change. In this case, the padding field may mean a field included after the AID field indicating the AID of the specific non-AP STA.

[0492] In this way, the AP can instruct the non-AP STA to switch to the side-channel operation mode, and the non-AP STA can perform frame exchange on the side-channel by switching to the side-channel operation mode when the AP performs the instruction to do so. To this end, the AP and the non-AP STA can perform prior negotiation on the side-channel operation mode. More specifically, the AP can request the non-AP STA to activate the side-channel operation mode, and operation through the change of the side-channel operation mode of the non-AP STA can be possible only if the non-AP STA accepts the request. Additionally, the AP can instruct the non-AP STA about the side-channel to which it should move, and the non-AP STA can accept the side-channel instructed by the AP or instruct the AP to select a different side-channel. Once an agreement on the side-channel is completed between the AP and the non-AP STA, the non-AP STA can switch to a state in which operation is possible for the agreed-upon side-channel when switching to the side-channel operation mode.

[0493] Accordingly, when the AID of another non-AP STA operating in the sub-channel operation mode is indicated through a TXOP shared response frame transmitted after receiving a TXOP shared / initiate frame received from a specific non-AP STA, the other non-AP STA can switch to the operation mode for the sub-channel previously agreed upon with the AP. That is, the TXOP shared response frame transmitted by the AP may not only have the function of indicating a target non-AP STA that wishes to perform transmission / reception through the shared TXOP, but also have the function of indicating switching to the sub-channel operation mode of the indicated non-AP STA. In this case, the AP may set a specific bit (or a specific subfield) included in the TXOP shared response frame to a pre-agreed value in order to indicate whether the TXOP shared response frame indicates switching to the sub-channel operation mode. For example, an AP can instruct non-AP STAs whose AIDs are indicated through the AID field included in the TXOP shared response frame to switch to the subchannel operation mode by setting the Secondary Subchannel Operation subfield included in the response frame to 1. If the Secondary Subchannel Operation subfield of the TXOP shared response frame is set to 0, non-AP STAs will not switch to the subchannel operation mode even if their AIDs are indicated through the AID field.

[0494] FIG. 29 illustrates an example of a response frame format for a frame for sharing TXOP according to an embodiment of the present invention.

[0495] The Duration / ID field of the TXOP sharing response frame indicates a later time than the time indicated by the Duration / ID field of the TXOP sharing / initiation frame received by the AP. In other words, the time indicated by the Duration / ID field of the TXOP sharing response frame transmitted in response to the TXOP sharing / initiation frame is a future time than the time indicated by the Duration / ID field of the TXOP sharing / initiation frame. This is a Duration / ID field setting rule designed to allow STAs that have set a NAV after receiving a TXOP sharing / initiation frame to set the NAV again after receiving a TXOP sharing response frame. STAs that set a NAV again after receiving a TXOP sharing response frame recognize that the STA that transmitted the TXOP sharing response frame, i.e., the AP, is the TXOP holder. To this end, a non-AP STA transmitting a TXOP share / initiate frame must set the Duration / ID field of the TXOP share / initiate frame to a value smaller than a specific value (the maximum value that can be indicated considering the TXOP limit). At this time, the non-AP STA transmitting the TXOP share / initiate frame may need to set the Duration / ID field to a preset value. At this time, the preset value may be a value pre-specified by the AP or the standard to be set in the Duration / ID field of the TXOP share / initiate frame. However, when the AP transmits a TXOP share response frame indicating that it does not intend to use Shared TXOP, the Duration / ID field of the TXOP share response frame may be set to indicate the same time as the time indicated by the Duration / ID field of the TXOP share / initiate frame.

[0496] The Accept / Refuse field indicates whether the AP that received the TXOP Share / Initiate frame intends to perform an operation using the Shared TXOP. If the Accept / Refuse field is indicated with a specific value (e.g., 1), it means that the AP plans to utilize the Shared TXOP, i.e., it will take over the Shared TXOP. If the Accept / Refuse field is indicated with another value (e.g., 0), it indicates that the AP does not plan to utilize the Shared TXOP. In this case, the non-AP STA that transmitted the TXOP Share / Initiate frame can function as a TXOP holder (i.e., transmit UL PPDU and / or P2P PPDU and receive Ack / BlockAck frames, etc.) for the remaining TXOP.

[0497] The following fields are included only in the response frame transmitted by the AP to indicate that it will utilize Shared TXOP.

[0498] The Secondary Subchannel Operation field indicates whether non-AP STAs that support the sub-channel operation mode among the non-AP STAs whose AIDs are indicated through the corresponding TXOP sharing response frame should switch to the sub-channel operation mode. If the Secondary Subchannel Operation field is set to 1, non-AP STAs that support the sub-channel operation mode among the non-AP STAs whose AIDs are indicated through the AID field must switch to the sub-channel operation mode. If the Secondary Subchannel Operation field is set to 0, even non-AP STAs whose AIDs are indicated through the AID field may participate in the subsequent frame exchange sequence without switching to the sub-channel operation mode. In this case, the Secondary Subchannel Operation field may be a field that is meaningful only for non-AP STAs that support the sub-channel operation mode and have completed consultation with the AP regarding the sub-channel operation. In other words, non-AP STAs that do not support the sub-channel operation mode among the non-AP STAs do not perform any separate operation depending on the value of the Secondary Subchannel Operation field.

[0499] The control field indicates the number of AID fields included in the TXOP shared response frame. The control field can be set to the number of AID fields - 1. Alternatively, the control field can be set to the number of AID fields.

[0500] The AID field indicates the AIDs of non-AP STAs that the AP transmitting the TXOP shared response frame intends to transmit / receive during the shared TXOP. Therefore, non-AP STAs whose AIDs are indicated through the AID field must perform operations that consider that the AP will transmit at least one DL PPDU to them or transmit at least one trigger frame (i.e., request a TB PPDU response) during the shared TXOP. In other words, they must maintain the Awake state without transitioning to the Doze state during the period corresponding to the shared TXOP.

[0501] The padding field is a field set based on the minimum padding length indicated by non-AP STAs that change to the side-channel operation mode. More specifically, the padding field is set to a length that is equal to or longer than the length indicated by the non-AP STA that indicated the largest minimum padding length among the non-AP STAs that were instructed to switch to the side-channel operation mode by the TXOP sharing response frame. For example, if the minimum padding lengths indicated by three non-AP STAs that perform the switch to the side-channel operation mode by a specific TXOP sharing response frame are 10 us, 20 us, and 30 us, respectively, the AP sets the padding field of the TXOP sharing response frame to have a length of 30 us or longer than 30 us.

[0502] <Overlapping BSS와의 조화로운 동작을 위한 BW 확장 규칙>

[0503] According to one embodiment of the present invention described above, an AP that receives a TXOP sharing / initiation frame from a non-AP STA can access subchannels identified as Idle among the subchannels not occupied by the received TXOP sharing / initiation frame. In this case, it has been mentioned that the AP must call / perform / complete an additional backoff procedure during the Shared TXOP in order to obtain access rights to the subchannels identified as Idle.

[0504] Even if the AP performs an additional backoff procedure during the Shared TXOP to obtain access to the Idle subchannel, the fairness issue may be raised regarding the operation of expanding the BW during the TXOP itself. For example, if a non-AP STA shares the TXOP acquired for the 80 MHz (Primary 80 MHz) band with the AP, and then the AP accesses an additional 80 MHz band (Secondary 80 MHz) to perform operations utilizing the 160 MHz band, this may result in interfering with the channel access of the OBSS (Overlapping BSS (basic service set)) operating in the additional 80 MHz band. According to the embodiments of the present invention described above, the AP performs an additional backoff procedure to obtain access to a subchannel, and performs procedures for fair competition, such as confirming that the CCA result for the additional subchannels is IDLE. However, in the case of Legacy BSSs that do not have a BW expansion opportunity, such operations may still be accepted as unreasonable operations.

[0505] Therefore, an AP that wants to obtain channel access to additional BW (BW and idle subchannels) during a Shared TXOP can perform operations that further protect the operating channel of the OBSS in order to minimize performance degradation of the OBSS. For a simple example, an AP that obtains channel access to additional BW during a Shared TXOP may only have access to subchannels among idle subchannels that do not correspond to the Operating BW of the OBSS. In other words, an AP that performs channel access to additional BW during a Shared TXOP may not perform channel access to subchannels included in the Operating BW of the OBSS, even if the subchannel is identified as idle. However, the AP's access to channels occupied by the TXOP sharing / initiation frame is not subject to restrictions related to the OBSS. In this case, the meaning of channel access performed during a Shared TXOP refers to the channel access procedure performed after the AP, which received the TXOP sharing / initiation frame, responds with a TXOP sharing response frame.

[0506] That is, when the AP expands the BW during the Shared TXOP, it may not access the subchannels included in the Operating BW of the OBSS. At this time, the AP may perform Preamble Puncturing to avoid accessing the subchannels included in the Operating BW of the OBSS. Preamble Puncturing refers to a technique of transmitting without loading a signal on a specific subchannel (a subchannel that is not to be occupied) in order to not occupy some of the subchannels included in the PPDU BW. For example, when an STA transmits a 320 MHz PPDU with Preamble puncturing applied, it may perform transmission in a manner that does not occupy a specific 80 MHz band among the 320 MHz band spanned by the 320 MHz PPDU. At this time, the signal of the 320 MHz PPDU is not detected in the specific 80 MHz band. Since the Preamble puncturing technology is a conventional technology introduced in 11ax and 11be, further detailed description will be omitted.

[0507] In this way, the channel access of the AP that extends the BW during the Shared TXOP is restricted to all subchannels included in the Operating BW of the OBSS.

[0508] In this case, the performance gains achieved through the AP's BW expansion procedure can be severely limited. To address this issue, APs expanding their BW during a shared TXOP must be conditionally granted access to specific subchannels, even if those subchannels are part of the OBSS's operating BW.

[0509] For example, it is possible that an AP extending BW during a Shared TXOP is allowed to access subchannels other than the Primary channel of the OBSS. More specifically, an AP extending BW during a Shared TXOP can access a subchannel of the OBSS when the subchannel is confirmed as Idle. However, access to the Primary channel of the OBSS is not permitted even if the CCA result confirms it as IDLE. In this case, the Primary channel of the OBSS refers to a channel including the Primary 20 MHz subchannel of the OBSS. That is, the Primary channel of the OBSS may be the Primary 20 MHz subchannel of the OBSS. That is, the Primary channel of the OBSS may be two subchannels corresponding to the Primary 40 MHz of the OBSS. That is, the Primary channel of the OBSS may be four subchannels corresponding to the Primary 80 MHz of the OBSS.

[0510] As another example, an AP extending BW during a Shared TXOP may be permitted to access subchannels included in the Operating BW of the OBSS, but may be recommended to perform Multi-AP Coordination operations that take into account the Requirements of the OBSS. In this case, an AP extending BW during a Shared TXOP may perform channel access to the Operating BW of the OBSS, and must perform Multi-AP Coordination operations that share RUs (Resource Units) or TXOPs with the OBSS as needed. Multi-AP operations refer to a series of operations in which APs exchange each other's Requirement information, etc., and harmoniously divide and use frequency resources and / or TXOPs considering each other's Requirements. At this time, an AP that allocates (shares) frequency resources or allocates (shares) TXOPs to other APs may be referred to as a sharing / Coordinating AP. In the case of one embodiment of the present invention described above, it can be understood that an operation is applied in which an AP that expands BW during a Shared TXOP functions as a sharing / coordinating AP and performs BW expansion in a form that minimizes performance degradation of the OBSS by allocating (sharing) RU (frequency resource, Resource Unit) and / or TXOP to the AP of the OBSS.

[0511] At this time, the AP expanding BW during Shared TXOP may attempt to expand BW for the IDLE subchannel with different rules depending on whether the OBSS is a Legacy BSS or a UHR BSS, such as not accessing the subchannel included in the Operating BW of the Legacy BSS if the OBSS is a Legacy BSS, and performing RU / TXOP allocation (sharing) to the UHR BSS, which is an OBSS, through Multi-AP operation if the OBSS is a UHR BSS. In addition, even if the OBSS is a UHR BSS, if it does not perform Multi-AP operation with the OBSS, it may not access the subchannel included in the Operating BW of the OBSS. That is, if the UHR BSS of the relationship that does not perform Multi-AP operation is an OBSS, the Operating BW of the UHR BSS must be considered in the same way as that of the Legacy BSS.

[0512] FIG. 30 illustrates an example of a method for minimizing performance degradation of an overlapping basic service set (OBSS) of APs when expanding the bandwidth of a shared TXOP according to an embodiment of the present invention.

[0513] Referring to the Operating BW of the BSSs in FIG. 30, the Operating BW of the 320 MHz BSS includes four 80 MHz segments corresponding to 80_1 to 80_4. At this time, the Operating BW of the UHR BSS, which is an OBSS, is the third and fourth 80 MHz segments, and the Operating BW of the Legacy BSS, which is an OBSS, is the fourth 80 MHz segment.

[0514] After receiving the Ctrl frame (TXOP sharing / initiation frame) transmitted by the non-AP STA, the AP responds with a response frame (TXOP sharing response frame). The AP initiates an additional channel access procedure (channel access performed during the shared TXOP) to perform operations utilizing a wider BW during the shared TXOP, since the Ctrl frame occupies only the primary 80 MHz band.

[0515] The AP confirms that the entire 320 MHz band included in the Operating BW of the BSS it operates is idle, but does not access the fourth 80 MHz segment because the fourth 80 MHz segment is included in the Operating BW of the Legacy OBSS. At this time, the AP transmits a 320 MHz PPDU and punctures the subchannels corresponding to the fourth 80 MHz segment to avoid accessing the fourth 80 MHz segment.

[0516] The AP obtains channel access rights for the first, second, and third 80 MHz segment bands by transmitting an M-AP coordination frame in the bands corresponding to the first, second, and third 80 MHz segments. However, considering the requirements of the UHR OBSS, the AP allocates (shares) the RU located in the primary 80 MHz band of the UHR BSS (the third 80 MHz segment of the BSS) to the AP of the UHR BSS.

[0517] As described above, the embodiments provided by the present invention were written considering that a non-AP STA transmits a TXOP Initiating / Sharing frame to an associated AP, but the same operation can be performed between APs. In other words, it is possible for a first AP to transmit a TXOP sharing frame to a second AP to share the TXOP after acquiring a TXOP, and it is also possible for the BW to be expanded by AP2 during this process. In addition, if the BW in which the first AP acquired the TXOP is smaller than the Operating BW of the second AP, the first AP can induce the second AP to perform frame exchange in a band in which the first AP itself did not acquire the TXOP through the TXOP initiation frame it transmits. At this time, the TXOP sharing frame transmitted by the first AP to the second AP may be a frame classified as an MU-RTS type. At this time, the frame transmitted by the first AP to the second AP may be a frame transmitted for multi-AP operation.

[0518] However, when TXOP sharing is performed between two APs, only TXOP sharing can be performed for a band in which the Operating BWs of the two APs overlap. For example, when AP1 uses a 320 MHz band including a first 160 MHz band and a second 160 MHz band as its Operating BW, and AP2 uses a 320 MHz band including a second 160 MHz band and a third 160 MHz band as its Operating BW, the band in which the first AP can share its TXOP with the second AP may be limited to the second 160 MHz band. This may be because it is impossible for the first AP to obtain channel access rights to the third 160 MHz band included in the Operating BW of the second AP. Therefore, when TXOP sharing is performed between two APs, only TXOP sharing can be performed for a frequency region in which the Operating BWs of the two APs overlap. At this time, the above-described AP2 can obtain channel access rights to the third 160 MHz band by performing additional channel access during the shared TXOP allocated (shared) from AP1. The method by which AP2 performs additional channel access during the time allocated (shared) from AP1 can be performed in the same / similar manner as the method by which an AP performs additional channel access during the time allocated (shared) from a non-AP STA, so a detailed description thereof is omitted.

[0519] In addition, the condition for a specific AP to share TXOP with another AP is that the Primary 20 MHz channel of the other AP must exist within the Operating BW of the specific AP. This is because, if the Primary 20 MHz channel of the other AP is not included within the Operating BW of the specific AP, the other AP cannot receive the frame (e.g., TXS trigger frame) transmitted by the specific AP.

[0520] FIG. 31 illustrates an example of an operation of an AP in which TXOP sharing is performed between APs according to one embodiment of the present invention and BW expansion is performed during the shared TXOP.

[0521] Referring to FIG. 31, the Operating BW of AP1 is 160 MHz corresponding to the 1st 80 MHz Segment and the 2nd 80 MHz Segment, and the Operating BW of AP2 is a 320 MHz band including the 1st 80 MHz Segment, the 2nd 80 MHz Segment, the 3rd 80 MHz Segment, and the 4th 80 MHz Segment.

[0522] AP1 acquires a TXOP by transmitting a CTS-to-Self frame for its primary 80 MHz band, the 1st 80 MHz Segment. AP1 transmits a control frame (TXS trigger frame in FIG. 31) to AP2 to share (allocate) the TXOP it acquired. At this time, since the control frame that AP1 transmitted to AP2 occupies only the 1st 80 MHz Segment, AP2 also responds with a response frame that occupies only the 1st 80 MHz Segment, and through this, the TXOP for 80 MHz corresponding to the 1st 80 MHz Segment is allocated to AP2.

[0523] AP2 invokes / initiates / completes a new backoff procedure to obtain access to a wider bandwidth during the Shared TXOP. Through this, AP2 additionally obtains channel access rights for the 2nd 80 MHz Segment, 3rd 80 MHz Segment, and 4th 80 MHz Segment, which are determined to be IDLE. AP2 acts as a TXOP holder for the four 80 MHz segments during the Shared TXOP. That is, during the time allocated by AP1 (Shared TXOP), AP2 can perform frame exchange with STAs of its own BSS using not only the 1st 80 MHz segment to which AP1 allocated (shared) the TXOP, but also the 2nd, 3rd, and 4th 80 MHz Segments to which it obtained channel access rights through the channel access procedure it performed using the Shared TXOP. At this time, AP2 can transmit a DL PPDU occupying its entire Operating BW (320 MHz) or receive a TB PPDU in response during the Shared TXOP allocated (shared) from AP1. In other words, it can allocate an RU in the 320 MHz band using a trigger frame.

[0524] Figure 32 shows an example of the operation of a station according to one embodiment of the present invention.

[0525] Referring to Figure 32, a station can perform a channel access procedure through a sub-channel rather than a primary channel.

[0526] Specifically, the station can perform a first channel access procedure through a specific secondary subchannel included in a specific secondary channel (S32010). In this case, the entire bandwidth supported by the wireless communication terminal can be composed of one primary channel and one or more secondary channels including the specific secondary subchannel.

[0527] Thereafter, the station can acquire a first transmission opportunity (TXOP) through a first channel access procedure (S32020). At this time, the first channel access procedure and the first TXOP may be channel access and TXOP through the sub-channel described above, and the frequency axis range in which the first TXOP is acquired may be limited to the specific sub-sub-channel.

[0528] The first channel access procedure may be performed when the channel status of a primary subchannel included in the one primary channel is busy and / or when the primary subchannel is occupied by an overlapping basic set (OBSS) terminal.

[0529] A station may transmit a trigger frame to one or more terminals during a TXOP, instructing transmission of a frame through a plurality of sub-channels constituting the particular sub-channel.

[0530] When one or more terminals are operating on the primary channel, the trigger frame may indicate a change from the primary channel to the specific subchannel. In addition, the one or more terminals may indicate that the bandwidth of the specific subchannel is not supported as an operating bandwidth, and the trigger frame may include a field indicating a change from the primary channel to the specific subchannel.

[0531] A station can receive a frame for sharing a second TXOP from a specific terminal, and the second TXOP can be obtained by a second channel access procedure of the specific terminal in a primary subchannel included in the one primary channel.

[0532] The range on the frequency axis in which the second TXOP is obtained is the entire bandwidth, and the end points of the first TXOP and the second TXOP may be the same.

[0533]

[0534] FIG. 33 shows a method for a station to expand bandwidth according to a bandwidth expansion rule according to an embodiment of the present invention.

[0535] When a station acquires a TXOP, the station can use a secondary channel as well as the primary channel with a bandwidth of 20 MHz during the acquired TXOP if the secondary channel is idle during the PIFS. Therefore, the station cannot utilize a secondary channel that is temporarily busy when the station acquires the TXOP but will soon become idle. In (a) of Fig. 33, the station acquires a TXOP with a bandwidth of 40 MHz (P20, S20) through a channel access procedure. This is because in (a) of Fig. 33, when the station acquires the TXOP, the secondary channel (S40) with a bandwidth of 40 MHz is busy. However, after the station starts frame exchange, the secondary channel (S40) with a bandwidth of 40 MHz becomes idle. In (a) of Fig. 33, the station can perform frame exchange only in the bands (P20, S20) with a bandwidth of 40 MHz. In Figure 33 (b), the station performs the backoff procedure again to use a slightly wider bandwidth even if the backoff counter reaches 0 in the first backoff procedure. However, in Figure 33 (b), during the second backoff procedure, the 40 MHz bandwidth (P20, S20) that the station was able to acquire in the first backoff procedure also becomes busy, preventing the station from acquiring a TXOP. In this way, if the decision on whether to use subchannels is confirmed upon acquiring a TXOP, the station may not be able to utilize the wireless medium to its full potential. Therefore, a procedure to expand the bandwidth within the TXOP acquired by the station may be necessary. This will be described with reference to Figures 34 and 35.

[0536]

[0537] FIGS. 34 and 35 illustrate a station performing a bandwidth extension procedure within an acquired TXOP according to another embodiment of the present invention.

[0538] In another embodiment of the present invention, a station may extend the bandwidth of an acquired TXOP when a pre-specified condition is satisfied within the acquired TXOP. For example, if a pre-specified condition is satisfied after the station acquires a TXOP with a bandwidth of 40 MHz, the station may perform frame exchange using an 80 MHz bandwidth. At this time, when the bandwidth is extended, it may be considered that the previously acquired TXOP ends and a new TXOP begins. At this time, it may be considered that two consecutive TXOPs are performed. In this embodiment, a station that is a TXOP holder may not update TXNAV when acquiring a second TXOP. Therefore, after acquiring the first TXOP, the sum of the durations of the second TXOP cannot be greater than the duration of the first TXOP, as indicated by the Duration / ID field of the MAC header. The pre-specified condition may be the success of the bandwidth extension procedure described below. In this specification, a station acquiring a TXOP may mean that the station acquires a TXOP from any one EDCAF.

[0539] A station can determine whether the subchannels it wants to include in its bandwidth within the acquired TXOP are scalable.

[0540] Specifically, the station performs EDCAF on the primary channel within the acquired TXOP, and if the EDCAF is successful, the station can extend the bandwidth of the TXOP to a subchannel that is idle during a pre-designated time period, for example, a PIFS or DIFS, when the EDCAF is successful. At this time, if at least one channel among the subchannels that the station intends to include in the bandwidth within the acquired TXOP, for example, a channel in units of 20 MHz, is idle during a pre-designated time period, for example, a PIDFS, the station can initiate a backoff procedure of the EDCAF on the primary channel. In addition, the station can initiate EDCAF for traffic other than the low-latency traffic after completing transmission for the low-latency traffic. In this case, the low-latency traffic may be traffic designated as the low-latency traffic. In addition, the bandwidth extension is used to determine whether the bandwidth can be extended, and may be allowed only for the AC of the EDCAF that has acquired a new TXOP. In another specific embodiment, the bandwidth extension may be allowed only for the AC that has currently acquired the TXOP. Specifically, the station may perform the backoff procedure of the EDCAF for the AC that has currently acquired the TXOP, and may not perform the backoff procedure of the EDCAF for the remaining ACs. At this time, the station may determine that the primary 20 MHz channel is busy for ACs other than the AC that has currently acquired the TXOP. For example, if the station succeeds in the backoff procedure in the EDCAF for AC_BE and acquires the current TXOP, the station may not perform the backoff procedure for the EDCAFs of AC_VO, AC_VI, and AC_BK, excluding AC_BE, in the bandwidth extension procedure. At this time, the station may determine that the value of the TXNAV timer of the EDCAFs of AC_VO, AC_VI, and AC_BK is not 0. In addition, the station may ignore the value of the TXNAV timer of AC_BE even if it is not 0.This is because the bandwidth expansion procedure is for expanding the bandwidth of a previously acquired TXOP, so it may be unfair to use an AC that was not used for TXOP acquisition.

[0541] Additionally, when a station performs the backoff procedure of EDCAF in a bandwidth expansion procedure, the station can acquire a backoff counter within CWmin[AC]. Additionally, when a station performs the backoff procedure of EDCAF in a bandwidth expansion procedure, the station can reset the value of QSRC (QoS (quality of service) STA Retry Counter)[AC].

[0542] If a station fails the EDCAF backoff procedure, the station may lose any TXOPs it has previously acquired.

[0543] In another specific embodiment, if a station performs a CCA and a subchannel to be included in the bandwidth within a TXOP is idle for a predetermined time period, the station may extend the bandwidth of the TXOP to the corresponding subchannel. The predetermined time period may be PIFS or DIFS. Specifically, if a station performs a CCA and a subchannel to be included in the bandwidth is idle for a predetermined time period consecutively from the end time of the immediately preceding exchanged PPDU, the station may extend the bandwidth of the TXOP to the corresponding subchannel. In these embodiments, a random backoff counter-based backoff procedure may not be performed on the subchannel other than performing the CCA for the predetermined time period. Specifically, in these embodiments, the station performs a CCA on the primary channel and the subchannel, and if the primary channel is idle for the predetermined time period, among the subchannels on which the CCA was performed, the subchannel that is idle for the predetermined time period as a result of the CCA may be included in the bandwidth. In this case, if the primary channel is not idle for a predetermined time period, the station may lose the previously acquired TXOP. These embodiments can prevent the bandwidth expansion procedure from taking a long time and causing the channel to be included in the bandwidth to be occupied by another device. In another specific embodiment, when the station performs a CCA for a secondary channel to be included in the bandwidth, the station may not perform a random backoff counter-based backoff procedure or CCA for the primary channel.

[0544] To determine whether a subchannel to be included in the bandwidth is expandable, a station seeking to expand the bandwidth within the acquired TXOP may maintain the interval between frames within the TXOP to be greater than the short inter-frame space (SIFS). In this case, the station may maintain the interval between frames to be greater than the SIFS and less than the PIFS. In another specific embodiment, the station may maintain the interval between frames to be PIFS (PCF (point coordination function) inter-frame space).

[0545] In another specific embodiment, regardless of the inter-frame spacing, a station may determine whether a subchannel to be included in the bandwidth is scalable. In this case, the inter-frame spacing may be maintained as SIFS.

[0546] Accordingly, the station can transmit a short PPDU according to the intervals of the embodiments described above. In this case, the short PPDU may refer to a PPDU having a pre-specified PPDU format. Specifically, the pre-specified PPDU format may have certain fields omitted or reduced. In addition, the short PPDU may be a PPDU having a duration shorter than the pre-specified duration. In this case, the pre-specified duration may be 1 ms. In addition, when the station transmits a PPDU that does not include a frame requesting an immediate response, the station may maintain the interval between frames as PIFS.

[0547] Additionally, in the embodiments described above, the station may maintain the interval between frames to be greater than SIFS even when retransmission is not required.

[0548] If the remaining TXOP is less than the threshold, the station may not be allowed to determine whether a subchannel to be included in the bandwidth within the acquired TXOP is scalable. In this case, the threshold may be specified by the AP operating the BSS to which the station belongs. In another specific embodiment, the threshold may be a value predefined in the 802.11 standard. In another specific embodiment, the threshold may be a value determined by the station. Through this embodiment, the bandwidth expansion procedure may be prevented from being performed when the gain that can be obtained from the bandwidth expansion is small. In addition, if it is not allowed to determine whether a subchannel to be included is scalable, the embodiments of maintaining the interval between frames greater than SIFS described above may not be applied. Therefore, the embodiment of short PPDU transmission described above may not be applied either.

[0549] After the judgment procedure described above, the station can transmit an initial frame on a subchannel determined to be included in the bandwidth. At this time, the format of the initial frame may be a pre-specified format. For example, the initial frame may be an RTS frame, an MU-RTS frame, or a CTS-to-Self frame. If a response to the frame transmitted by the station is received, the station may determine that it has acquired a new TXOP through the bandwidth extension procedure. At this time, the response frame to the initial frame may be a CTS frame. In addition, the station may determine that it has acquired a TXOP for the subchannel on which the response frame to the initial frame was received. In addition, the station may determine that it has not acquired a TXOP for the subchannel on which the response frame to the initial frame was not received. However, the station may determine that it has acquired a new TXOP for the channel even if a response frame to the initial frame is not received on a channel included in the bandwidth of the first TXOP.

[0550] Additionally, a station may set the Duration / ID field of the initiation frame to a value that does not extend the first TXOP. Specifically, the station may set the Duration / ID field of the initiation frame to a value corresponding to the expiration of the first TXOP. This is so that the station, as the TXOP holder, does not update TXNAV when acquiring the second TXOP.

[0551] If, according to the embodiments described above, a station acquires a TXOP for a subchannel that is not included in the bandwidth of the first TXOP, the station may determine that the bandwidth expansion procedure is successful.

[0552] A station may indicate that it will perform a bandwidth extension procedure in the first PPDU transmitted in the first TXOP. At this time, the station receiving the PPDU may determine that the frame interval within the TXOP can be set to be greater than SIFS. Furthermore, the station receiving the PPDU may determine that the bandwidth extension procedure will be performed and an initiation frame will be transmitted. At this time, in order to receive the initiation frame, the station may determine whether a subchannel within the operating bandwidth is idle.

[0553] In the previously described embodiments, when a station expands its bandwidth, it is described as acquiring a new TXOP. In another specific embodiment, when a station expands its bandwidth, the bandwidth of the previously acquired TXOP may be considered to be expanded. In this case, even if the bandwidth is expanded, the duration of the previously acquired TXOP may not be extended.

[0554] FIG. 34 shows an operation of expanding the bandwidth of TXOP according to another embodiment of the present invention.

[0555] In the embodiment of Fig. 34, the station acquires a TXOP for a band (P20, S20) with a bandwidth of 40 MHz. The station performs frame exchange in the band (P20, S20) with a bandwidth of 40 MHz and performs a backoff procedure for a bandwidth extension procedure. Through the backoff procedure, the station acquires a TXOP for a subchannel with a bandwidth of 40 MHz and performs frame exchange in the band (P20, S20, S40) with a total bandwidth of 80 MHz.

[0556]

[0557] FIG. 35 shows an operation of expanding the bandwidth of TXOP according to another embodiment of the present invention.

[0558] In the embodiment of FIG. 35, the station acquires a TXOP for a band (P20, S20) having a bandwidth of 40 MHz. The station performs frame exchange in the band (P20, S20) having a bandwidth of 40 MHz and performs a bandwidth expansion procedure. At this time, the bandwidth expansion procedure may include a subchannel determined to be idle by the station performing a CCA during the PIFS, as shown in the dotted line of FIG. 35, into the TXOP band. To secure space for performing the CCA, the station may transmit a short PPDU. At this time, the format of the short PPDU may follow the embodiments described above. The station transmits a first short PPDU (short PPDU1) and determines that the 40 MHz subchannel (S40) is busy in the first bandwidth expansion procedure attempted. Therefore, the station determines that the first bandwidth expansion procedure has failed. The station transmits a second short PPDU (short PPDU2), and determines that the 40MHz subchannel (S40) is idle during the second attempted bandwidth extension procedure. Therefore, the station transmits an RTS frame. Furthermore, the station determines that it has acquired a TXOP on the channel (P20, S20, S40) on which it received a CTS frame for the RTS frame. The station performs frame exchange in the band (P20, S20, S40) with a total bandwidth of 80MHz.

[0559]

[0560] The RU setting method is explained through Figs. 36 to 41.

[0561] Figure 36 shows the types and location information of RUs that can be included in an EHT PPDU with an 80 MHz bandwidth.

[0562] An 80MHz EHT PPDU can be transmitted over a frequency band with various combinations of RUs, such as one 996-tone RU, two 484-tone RUs, or four 242-tone RUs. Each tone within the frequency band over which the 80MHz PPDU is transmitted can be contained and used in a 26-tone RU, or contained in a 52 / 106 / 242 / 484 / 996-tone RU. In this case, each RU within the entire frequency band over which the PPDU is transmitted can be set to various sizes. For example, the first 20MHz subchannel located at the leftmost position can be composed of a 26-tone RU and a 52-tone RU, the second 20MHz subchannel can be composed of two 106-tone RUs and one 26-tone RU, and the third and fourth 20MHz subchannels can be composed of 484-tone RUs. At this time, each RU can be used alone or combined with other RUs (Multiple RU, MRU). For example, a 26-tone size RU and a 52-tone size RU can be combined to form a 52+26-tone size RU. In this case, the tones contained in the two combined RUs are used together. As another example, a 242-tone size RU and a 484-tone size RU can be combined to form a 484+242-tone size RU. There are restrictions on the combination of RUs that can be utilized as MRUs. Specifically, only one 26-tone RU can be combined with a 52-tone size RU. In addition, the combined 26-tone RU is limited to a 26-tone RU located in the same 20 MHz subchannel where the 52-tone RU is located. Additionally, small size RUs, 26, 52, and 106-tone size RUs can only be combined with other small size RUs. Large size RUs, 242, 484, and 996-tone size RUs can only be combined with other large size RUs.

[0563] For 26-tone RU, 52-tone RU, and 106-tone RU, tones are contained only in frequency regions corresponding to approximately 2 MHz, 5 MHz, and 10 MHz, respectively. A terminal transmitting via a 26-tone RU occupies only the 2 MHz band. Therefore, to meet the transmission power constraints stipulated by the PSD regulation, even a terminal transmitting via a 106-tone RU can only use half the transmission power when transmitting a 20 MHz PPDU.

[0564] The range of a wireless signal is determined by the transmission power of the signal, and as the transmission power decreases, the range of the wireless signal decreases.

[0565] Distributed-tone RU (dRU) is a method of setting RU tones to increase transmission efficiency within the transmission power regulation according to the PSD described above. The dRU can increase transmission power by using RUs that occupy the widest possible frequency band. The PSD regulation stipulates that the maximum transmission power (-1 dBm / MHz for a station) increases in proportion to the width of the occupied frequency band. When a station transmits a TB PPDU in a 26-tone RU with a 20 MHz bandwidth, the station can use 10 times more transmission power than when it transmits a TB PPDU in a 26-tone RU with a 2 MHz bandwidth as shown in FIG. 36. In this specification, an RU that uses continuous tones as illustrated in FIG. 36 is referred to as an rRU (regular RU), and an RU that distributes tones to occupy a wide frequency band is referred to as a dRU (distributed(-tone) RU).

[0566]

[0567] Figure 37 shows an rRU and a dRU according to an embodiment of the present invention.

[0568] Figure 37 (a) shows nine 26-tone rRUs located within a 20MHz channel. The first 26-tone rRU contains 26 consecutive tones located in the lowest frequency range. The second 26-tone rRU contains 26 consecutive tones located in the lowest frequency range among the remaining tones excluding the tones included in the first 26-tone rRU. The tones included in the 20MHz channel are divided into nine equal parts, sequentially forming each 26-tone rRU.

[0569] Figure 37(b) shows nine 26-tone dRUs located within a 20MHz channel. The first 26-tone dRU contains one tone located in the lowest frequency range, and the 1 + Nx9 (N= 0 to 25)-th tones, such as the 10th (1+9) tone, the 19th tone (1+ 2x9), and the 28th tone (1+ 3x9). The second 26-tone dRU contains the 2nd + Nx9 (N= 0 to 25), and the third 26-tone dRU contains the 3 + Nx9 (N= 0 to 25)-th tones. The tone interval included in the 26-tone dRU is nine times wider than the tone interval included in the 26-tone rRU. In this way, each tone constituting the dRU is not positioned consecutively but is positioned at regular intervals, and a tone included in another dRU is positioned between two tones included in the dRU.

[0570] Comparing (a) of Fig. 37 with (b) of Fig. 15, the tones of the 26-tone rRU are placed in a frequency region corresponding to 1 / 9 of the 20 MHz channel, and the tones of the 26-tone dRU are evenly placed throughout the frequency region of the 20 MHz channel.

[0571] 52-tone size rRUs and dRUs not included in FIG. 37 can also be configured in the same manner as the 26-tone rRUs and dRUs. The 52 tones located in the lowest frequency band in a 20 MHz channel constitute the first 52-tone rRU, and the second 52-tone rRU is configured with the 52 tones located in the lowest frequency band among the remaining tones excluding the tones included in the first 52-tone rRU. The first 52-tone dRU is configured with 1+Nx(4 or 5) (N= 0 to 51), the second 52-tone dRU is configured with 2+Nx(4 or 5), the third 52-tone dRU is configured with 3+Nx(4 or 5), and the fourth 52-tone dRU is configured with 4+Nx(4 or 5). Here, (4 or 5) indicates that the tones included in a specific 52-tone dRU exist every 4 tones or every 5 tones, and the tone interval is 4 or 5 times larger than the tone interval of the 52-tone rRU. Here, the 52-tone dRU may be configured by combining the tones included in two 26-tone rRUs. For example, the tones included in the first 52-tone dRU may be configured by combining the tones included in the first 26-tone dRU and the fifth 26-tone dRU. As another example, the tones included in the first 52-tone dRU may be configured by combining the tones included in the first 26-tone dRU and the sixth 26-tone dRU.

[0572] Also, although not illustrated in the example of FIG. 37, each tone of a 52-tone dRU can be placed in a 40 MHz channel or an 80 MHz channel. When a dRU of a specific tone size, for example, a 52-tone size, is configured, the dRU can be configured by selecting tones evenly distributed over a frequency band in which the dRU is to be placed, for example, a 40 MHz or 80 MHz band, thereby defining dRUs of various tone sizes for various frequency bands. Specific examples of combinations of dRUs and frequency bands are omitted because they are not related to the main inventive idea that the present invention seeks to provide.

[0573] In this way, the dRU has a configuration that is distributed over a wider frequency band than the rRU. Therefore, a station transmitting a TB PPDU using a dRU can transmit the TB PPDU with a higher transmit power than when transmitting the TB PPDU using an rRU containing the same tone. A station transmitting a TB PPDU using a 26-tone size rRU must keep the transmit power of the TB PPDU below approximately 2 dBm according to the PSD regulation. However, a station transmitting a TB PPDU using a 26-tone size dRU can transmit the TB PPDU with an output power of 10 dBm or more without violating the PSD regulation.

[0574]

[0575] <dRU를 이용한 전송의 특징>

[0576] As explained above, dRU has tones distributed over a wide frequency range, and the interval (spacing) of each tone (subcarrier) is larger than that of rRU with the same number of tones.

[0577] In the case of wireless signals, as the tone spacing on the frequency increases, the symbol length of the wireless signal transmitted over the wireless medium becomes shorter. Therefore, the symbol length of the signal transmitted by a station that responds to a TB PPDU using a dRU is different from the symbol length of the signal transmitted by a station that responds to a TB PPDU using an rRU. Specifically, the symbol length of the signal transmitted by a station that uses a dRU is shorter than the symbol length of the signal transmitted by a station that uses an rRU.

[0578] Additionally, the symbol length may further vary depending on the subcarrier spacing of the dRU used by the station. For example, the tone spacing included in a 26-tone dRU deployed in the 20 MHz band is different from the tone spacing included in a 52-tone dRU deployed in the 20 MHz band. Therefore, the symbol length used by a station transmitting a TB PPDU using a 26-tone dRU to transmit the TB PPDU is different from the symbol length used by a station responding to the TB PPDU using a 52-tone dRU to transmit the TB PPDU.

[0579] After receiving a trigger frame, if the stations responding to the TB PPDU use dRUs with different tone intervals to respond to the TB PPDU, the AP will receive signals with different symbols transmitted by multiple stations, overlapping. These signals with different symbol lengths that are received overlappingly are OFDMA signals that conventional Wi-Fi APs do not support receiving. Therefore, the Wi-Fi AP may not be able to normally receive the TB PPDUs responded by each station.

[0580]

[0581] Figure 38 is a combination of dRUs that can be configured using tones contained in a 20MHz channel.

[0582] The tones included in a 20MHz channel can be used to configure two 26-tone dRUs, one 52-tone dRU, and one 106-tone dRU. Although the 26-tone dRUs dRU1 and dRU2 include different tones, the intervals between the tones constituting each dRU are the same. The 52-tone dRU dRU3 is configured by utilizing some of the tones excluding the tones constituting dRU1 and dRU2, and since it includes more tones than the 26-tone dRU, the intervals between the tones included in the 52-tone dRU are shorter than those in the 26-tone dRU. The 106-tone dRU dRU4 is configured by using the remaining tones suggested by the tones constituting dRU1, dRU2, and dRU3. Each tone of dRU4 has the shortest tone interval among the dRUs illustrated in FIG. 38.

[0583] Although the tones constituting each dRU are described as being equally spaced within a 20MHz channel, the specific spacing of the tones constituting each dRU may be set differently from what was previously described. Even in this case, the tone spacing (subcarrier spacing) of a 52-tone dRU deployed in a 20MHz channel is larger than the tone spacing (subcarrier spacing) of a 26-tone dRU deployed in a 20MHz channel, and the tone spacing of a 106-tone dRU deployed in a 20MHz channel is larger than the tone spacing of a 52-tone dRU deployed in a 20MHz channel.

[0584] Even dRUs of different sizes can be combined if the tones constituting each dRU are different. For example, an AP can transmit a trigger frame and assign dRU1, dRU2, dRU3, and dRU4 to four stations, respectively.

[0585] As in Fig. 38, if stations that simultaneously respond to TB PPDUs use dRUs with different tone intervals, the AP must simultaneously receive TB PPDUs with different symbol lengths. For example, the AP may have a different symbol length for a signal from a station transmitting a TB PPDU via a 26-tone dRU and a different symbol length for a signal from another station transmitting a TB PPDU via a 52-tone dRU. In this case, the AP must simultaneously receive and parse TB PPDUs transmitted via signals with different symbol lengths. In addition, if signals with different symbol lengths are simultaneously received, synchronization using a cyclic prefix may not be possible.

[0586] A method is needed to prevent symbol length mismatch problems that may arise when using dRUs in uplink transmission using OFDMA. An AP according to an embodiment of the present invention can configure dRUs allocated via a trigger frame to have identical subcarrier spacing. Only dRUs with identical subcarrier spacing can be allocated via a single trigger frame. Within this restriction, a station responding to a TB PPDU transmits a signal with the same symbol length.

[0587] According to another embodiment of the present invention, when two dRUs assigned to different stations are deployed in separate frequency bands, the dRUs assigned to the two different stations may have different tone spacings. If the two dRUs assigned to different stations are deployed in the same frequency segment, they may have the same tone spacing, and if they are deployed in different frequency segments, they may have different tone spacings. When the first dRU is configured with a tone located in the first frequency segment and the second dRU is configured with a tone located in the second frequency segment, if the first frequency segment and the second frequency segment are non-overlapping segments, the first dRU and the second dRU may be dRUs having different tone spacings. When multiple stations transmit TB PPDUs in separate frequency bands after receiving a trigger frame from an AP, it may be acceptable for the multiple stations to have different symbol lengths of signals.

[0588] According to another embodiment of the present invention, multiple dRUs including tones within a specific frequency unit band (e.g., 20 MHz, 40 MHz, 80 MHz or 160 MHz) may be restricted to be all set to the same tone spacing. The AP may use the trigger frame to trigger transmission of a TB PPDU such that multiple stations transmitting dRUs within the same frequency unit band simultaneously respond to the trigger frame so that the symbol length of the signal used is the same. For example, two dRUs positioned within a first 80 MHz segment of the trigger frame may have the same tone spacing, and two dRUs positioned within a second 80 MHz segment may be the same as or different from two dRUs positioned within the first 80 MHz segment. Even dRUs that are allocated together through the trigger frame may be positioned in different frequency segments. In this case, the dRUs may have different tone spacings.

[0589] Two dRUs having equal tone spacing may be at least one of dRUs having the same number of tones defined for the same frequency range or two dRUs having equal tone spacings contained in the dRUs. Only the first 26-tone dRU and the second 26-tone dRU defined in the 20 MHz band may be dRUs having equal tone spacings. A 26-tone dRU defined in the 20 MHz band and a 52-tone dRU defined for the 40 MHz band may have equal tone spacings.

[0590]

[0591] <dRU를 이용한 UL OFDMA 수행 방법 및 제한>

[0592] As previously explained, if each station responding to a TB PPDU uses a dRU with a different tone interval, the AP may fail to receive the TB PPDU. Therefore, the AP can take this into account when allocating RUs to each station.

[0593] An AP can assign the same RU type to each station via a trigger frame. This method of assigning the same RU type may include at least one of the following methods. The methods described below can be applied together. For example, the rules A and B described below can be applied together.

[0594] A. All RUs allocated through trigger frames are set to rRUs or dRUs.

[0595] i. However, the types of RUs in different 80MHz segments may be different. It may be permissible for the first 80MHz or 160MHz segment to be allocated entirely to rRUs, and for the second 80MHz or 160MHz segment to be allocated entirely to dRUs.

[0596] B. How to set all dRUs allocated through trigger frames to dRUs with the same tone size

[0597] i. A method in which all stations allocated dRUs through a single trigger frame are allocated dRUs of the same size.

[0598] ii. At this time, dRUs of the same tone size have the same number of tones and are dRUs with the same tone interval.

[0599] iii. However, stations responding to TB PPDUs in different 80MHz segments may be allowed to be allocated dRUs of different sizes.

[0600] C. How all dRUs allocated through trigger frames have the same tone interval

[0601] i. All stations allocated a dRU through a single trigger frame respond with a TB PPDU of the same symbol length.

[0602] ii. At this time, dRUs of different tone sizes that are allocated together are dRUs that are placed in different frequency regions.

[0603] 1. A 26-tone dRU with a 20 MHz bandwidth, a 52-tone dRU with a 40 MHz bandwidth, and a 106-tone dRU with an 80 MHz bandwidth can be allocated together using a single trigger frame. A 26-tone dRU spanning 20 MHz and a 52-tone dRU spanning 20 MHz cannot be allocated together. The configuration method of dRUs that can be allocated together is explained in more detail in the <Method of Configuring dRUs with Different Tone Sizes and Same Tone Intervals> described below.

[0604] D. How to align the symbol boundaries of each STA responding to a TB PPDU through a trigger frame.

[0605] i. When the AP assigns dRUs with different tone spacings to each station, the AP can set the GIs of stations using different tone spacings to different values ​​so that the boundaries of symbols responded by each station end at the same point in time.

[0606] 1. At this time, the symbol lengths of the TB PPDUs transmitted by the two stations may be the same.

[0607] 2. At this time, the symbol lengths of the TB PPDUs transmitted by the two stations may be multiples of each other. Specifically, the symbol length of the TB PPDU transmitted by one station may be an integer multiple of the symbol length of the TB PPDU transmitted by the other station, for example, 2, 3, or 4 times longer.

[0608] FIG. 39 shows a TB PPDU of a station responding to a TB PPDU with a signal having the same symbol length, according to an embodiment of the present invention.

[0609] In Figure 39, the TB PPDU occupies four frequency band segments. Each of the four frequency band segments can be a 20MHz channel, a 40MHz channel, or an 80MHz channel. The different patterns depicted in Figure 39 represent signals from different stations, and TB PPDUs transmitted by different stations are transmitted in each segment.

[0610] Multiple TB PPDU signals transmitted by occupying the first segment include a cyclic prefix (CP) of the same length. Each station transmits symbols with the same guard interval (GI). At this time, signals occupying different segments also have the same CP. This is because all stations indicate the same GI when the AP transmits a trigger frame. Each station responds to the TB PPDU using a dRU containing the same tone, and the dRU to which each station responds to the TB PPDU can be configured with some of the tones within each segment.

[0611]

[0612] FIG. 40 shows that a TB PPDU is transmitted as a signal having the same symbol length within a frequency band segment according to an embodiment of the present invention.

[0613] In Figure 40, a TB PPDU occupies four frequency band segments. The four frequency band segments may be 20MHz channels, 40MHz channels, or 80MHz channels. The different patterns depicted in Figure 40 represent signals from different stations, and TB PPDUs transmitted by different stations are transmitted in each segment.

[0614] The signal occupying the 1st segment is 1 / 4 shorter than the symbol length of the signal occupying the 3rd segment and the 4th segment, and the signal occupying the 2nd segment is 1 / 2 shorter than the symbol length of the signal occupying the 3rd segment and the 4th segment. The signals occupying each segment have a length difference of an integer multiple. Therefore, the point in time when the symbol of the signal occupying the 3rd segment and the 4th segment ends is the same as the point in time when the symbol of the signal occupying the 1st segment and the 2nd segment ends. At this time, the symbol length of the signal occupying the 1st segment and the 2nd segment is shorter than the symbol length of the signal occupying the 2nd segment, the 3rd segment, and the 4th segment. This is because the tone interval of the dRU assigned to the station responding to the TB PPDU through the 1st segment is larger than the tone interval of the dRU assigned to the station responding to the TB PPDU through the 2nd segment, the 3rd segment, and the 4th segment.

[0615] FIG. 41 illustrates a method for setting dRUs of different tone sizes to have the same tone spacing and a method for allocating dRUs of different tone sizes at once according to an embodiment of the present invention.

[0616] In Fig. 49, two 26-tone dRUs are located in the 1st 20 MHz channel, and tones included in one 52-tone dRU distributed in the 40 MHz channel are located. However, since the 52-tone dRU has the same tone interval as the 26-tone dRU, 26 tones, which are half of the 52 tones included in the 52-tone dRU, are located in the 1st 20 MHz channel. The remaining 26 tones of the 52-tone dRU are located in the 2nd 20 MHz channel, and the 2nd 20 MHz channel includes the 26-tone dRU of the 1st 20 MHz channel and two other 26-tone dRUs.

[0617] In this way, although the number of tones included in the 26-tone dRU and the 52-tone dRU is different, the tones included in the 52-tone dRU are distributed over a wider frequency range, so that the spacing between the tones constituting each dRU can be maintained the same.

[0618]

[0619] <How to configure dRUs with different tone sizes and the same tone interval>

[0620] A simple way to configure dRUs with different tone sizes but the same tone spacing is as follows.

[0621] A 40MHz 52-tone dRU having the same tone spacing as a 26-tone size dRU distributed in 20MHz can be configured by combining two 26-tone dRUs of the same index defined for two 20MHz channels included in 40MHz. The 52-tone dRU of the first 40MHz channel can be configured by combining the tones constituting the first 26-tone dRU configured using the tones included in the first 20MHz channel and the second 26-tone dRU configured using the tones included in the second 20MHz channel. In this case, the first 26-tone dRU and the second 26-tone dRU are configured using frequency tones that are spaced apart by 20MHz. When a 20MHz frequency offset is applied to the frequency of each tone constituting the first 26-tone dRU, it matches the tones constituting the second 26-tone dRU.

[0622] B. A 26-tone size dRU distributed at 20MHz, an 80MHz-tone dRU having the same tone spacing as the 52-tone dRU of the above-described A. can be configured by combining two 52-tone dRUs of a 40MHz channel configured through the process of the above-described A. It is possible to configure a 106-tone dRU of the first 80MHz channel by combining the tones constituting the first 52-tone dRU configured using the tones included in the first 40MHz channel and the second 52-tone dRU configured using the tones included in the second 40MHz channel. At this time, the first 52-tone dRU and the second 52-tone dRU are configured using frequency tones spaced apart by 40MHz. When a 40MHz frequency offset is applied to the frequency of each tone constituting the first 52-tone dRU, it matches the tones constituting the second 52-tone dRU. In addition, the 106-tone dRU has a configuration that additionally includes two tones that are not included in the first and second 52-tone dRUs. In this case, the two tones additionally included in the 106-tone dRU are determined as two of the tones located between the first 52-tone dRU and the second 52-tone dRU. Referring to the tone plan illustrated in FIG. 36, among the 23 DC tones located between the two 484-tone rRUs, two of the remaining 18 tones, excluding the five DC tones located in the middle of the 996-tone rRU, are included in the 106-tone dRU distributed in the 80 MHz band.

[0623] In the process of configuring dRUs (20 MHz 26-tone dRU, 40 MHz 52-tone dRU, 80 MHz 106-tone dRU) having the same tone spacing, in addition to the method of configuring a larger dRU by combining dRUs with relatively small tone sizes as described above, a method of determining separate tone positions may be applied. Specifically, the positions of each tone configuring the 80 MHz 106-tone dRU may be determined regardless of the tone positions of the 26-tone and 52-tone dRUs. At this time, the positions of the tones of each dRU may be determined so as to be evenly distributed with respect to the frequency range in which each dRU is distributed, and may be determined so that each tone has the same spacing (the spacing between tones configuring different dRUs) even if tones included in dRUs with different tone sizes exist together within a specific frequency band. In this way, when determining a new tone for a dRU, the position of the tone constituting each dRU may be mathematically determined based on the spanning frequency range and the number of tones of each dRU. Since the tone position of each dRU, which is determined based on the number of tones and the frequency range in which the tones are distributed, is determined mathematically and does not have any additional features provided by the invention, a more detailed description thereof will be omitted. ...

Claims

1. At a station communicating wirelessly, Transmitter and receiver; and Contains a processor, The above processor The station determines whether a subchannel not included in the frequency band of the TXOP (transmit opportunity) acquired by the station is expandable, If the above sub-channel is in an expandable state, frame exchange is performed in the frequency band of the TXOP and the frequency band including the above sub-channel. Station.

2. In paragraph 1, The above processor Performing an enhanced distributed channel access function (EDCAF) backoff procedure on a primary channel, and when the EDCAF backoff procedure is successful, performing frame exchange in a frequency band including the TXOP and the secondary channel based on whether the secondary channel is idle for a predetermined time period. Station.

3. In paragraph 2, The above processor When performing the EDCAF backoff, the minimum value (CWmin) of the contention window for the AC (access category) corresponding to the EDCAF is used to perform the EDCAF backoff. Station.

4. In paragraph 2, The above processor When performing the above EDCAF backoff, the QSRC (QoS (quality of service) STA Retry Counter) value of the AC corresponding to the above EDCAF is reset. Station.

5. In paragraph 1, The above processor Within the above TXOP, without performing the EDCAF (enhanced distributed channel access function) backoff procedure on the primary channel, CCA (clear channel assessment) is performed on the primary channel and the secondary channel, If the primary channel is idle for a predetermined time interval as a result of the CCA, frame exchange is performed on the band of the TXOP and the secondary channel that is idle for the predetermined time interval as a result of the CCA. Station.

6. In paragraph 5, The above processor Performing CCA on the subchannel and the main channel even if retransmission is not required within the above TXOP. Station.

7. In paragraph 1, In the frame exchange performed within the above TXOP, the interval between any two frames is greater than SIFS (short inter-frame space). Station.

8. In paragraph 7, The above processor Transmitting a PPDU for transmitting at least one of the above two frames with a duration shorter than a pre-specified duration. Station.

9. In paragraph 1, Even if the above subchannel is expandable, the duration of the above TXOP is not extended. Station.

10. In the operation method of the station communicating wirelessly A step of determining whether a sub-channel not included in the frequency band of the TXOP (transmit opportunity) acquired by the station is expandable; and If the sub-channel is in an expandable state, the step of performing frame exchange in the frequency band of the TXOP and the frequency band including the sub-channel is included. How it works.

11. In paragraph 10, The step of determining whether the above sub-channel is expandable is comprising a step of performing an enhanced distributed channel access function (EDCAF) backoff procedure on the primary channel; If the above sub-channel is in an expandable state, the step of performing frame exchange in the frequency band of the TXOP and the frequency band including the above sub-channel When the EDCAF backoff procedure is successful, a step of performing frame exchange in the frequency band of the TXOP and the frequency band including the subchannel is based on whether the subchannel is idle for a predetermined time period. How it works.

12. In paragraph 11, The step of performing the EDCAF backoff procedure on the above primary channel is When performing the EDCAF backoff, the step of performing the EDCAF backoff using the minimum value (CWmin) of the contention window for the AC (access category) corresponding to the EDCAF is included. How it works.

13. In paragraph 11, The step of performing the EDCAF backoff procedure on the above primary channel is When performing the EDCAF backoff, a step of resetting the QSRC (QoS (quality of service) STA Retry Counter) value of the AC corresponding to the EDCAF is included. How it works.

14. In paragraph 10, The step of determining whether the above sub-channel is expandable is Including a step of performing CCA (clear channel assessment) on the primary channel and the secondary channel without performing an EDCAF (enhanced distributed channel access function) backoff procedure on the primary channel within the TXOP, If the above sub-channel is in an expandable state, the step of performing frame exchange in the frequency band of the TXOP and the frequency band including the above sub-channel A step of performing frame exchange on the band of the TXOP and the idle subchannel during the predetermined time interval as a result of the CCA, when the primary channel is idle for a predetermined time interval as a result of the CCA. How it works.

15. In paragraph 14, The step of performing the CCA in the above main channel and the above sub channel Performing CCA on the subchannel and the main channel even if retransmission is not required within the above TXOP. Station.

16. In paragraph 1, In the frame exchange performed within the above TXOP, the interval between any two frames is greater than SIFS (short inter-frame space). How it works.

17. In paragraph 16, The above method of operation is Further comprising a step of transmitting a PPDU for transmitting at least one of the above two frames with a duration shorter than a pre-specified duration. How it works.

18. In paragraph 10, Even if the above subchannel is expandable, the duration of the above TXOP is not extended. How it works.

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