Method and wireless communication terminal for transmitting and receiving frames in a wireless communication system

Abstract

A method of transmitting a frame of a wireless communication system is disclosed. A non-AP STA receives a beacon frame including a request type field from an AP, and receives a downlink frame or transmits an uplink frame according to a value included in a special field of the beacon frame. In this case, the request type field includes a special field showing a target wake time (TWT) for a low latency operation, and when a value of the special field is set to a first special value, a broadcast TWT service period (SP) is a TWT SP for the low latency operation.

Description

TECHNICAL FIELD

[0001] The present application relates to a wireless communication system, and more particularly, to a communication method, apparatus and system for transmitting and receiving a frame requiring a low-delay operation. BACKGROUND

[0002] In recent years, as the supply of mobile devices expands, a wireless LAN technology capable of providing a fast wireless Internet service to the mobile devices has been highlighted. The wireless LAN technology allows mobile devices including smart phones, smart pads, laptop computers, portable multimedia players, embedded devices, etc. to wirelessly access the Internet based on a short-range wireless communication technology in a home or a company or a special service providing area.

[0003] Since the initial wireless LAN technology using a 2.4 GHz frequency band, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 has commercialized or developed various technology standards. First, the IEEE 802.11b supports a communication speed of a maximum of 11 Mbps when using a 2.4 GHz frequency band. In comparison with the 2.4 GHz frequency band, which is significantly congested, the IEEE 802.11a, which was commercialized after the IEEE 802.11b, uses a 5 GHz frequency band, not a 2.4 GHz frequency band, to reduce the influence of interference, and increases a communication speed to a maximum of 54 Mbps by using an OFDM technology. However, the IEEE 802.11a has a disadvantage in that a communication distance is shorter than that of the IEEE 802.11b. In addition, like the IEEE 802.11b, the IEEE 802.11g uses a 2.4 GHz frequency band to achieve a communication speed of a maximum of 54 Mbps and satisfies backward compatibility to significantly attract attention, and further, is superior to the IEEE 802.11a in terms of a communication distance.

[0004] Further, as a technical standard established in order to overcome the limitation of the communication speed pointed out as a weak point in the wireless LAN, IEEE 802.11η has been provided. IEEE 802.11η aims at improving the speed and reliability of the network and extending the working distance of the wireless network. In more detail, IEEE 802.11η supports a high throughput (HT) in which the data processing speed is maximum 540 Mbps or more, and further, based on a multiple inputs and multiple outputs (MIMO) technique in which a plurality of antennas are used on both sides of a transmission unit and a reception unit to minimize transmission errors and optimize data speed. Further, this standard can use a coding scheme in which a plurality of copies of a transmission are superimposed on each other in order to increase data reliability.

[0005] With the active supply of the wireless LAN and further, with the diversification of applications using the wireless LAN, a demand for a new wireless LAN system supporting a higher throughput (Very High Throughput (VHT)) than the data processing speed supported by IEEE 802.11η has been focused on. Among them, IEEE 802.11ac supports a bandwidth (80 to 160 MHz) in a 5 GHz frequency. The IEEE 802.11ac standard is defined only in the 5 GHz band, but the initial 11ac chipset even supports operation in the 2.4 GHz band for backward compatibility with existing 2.4 GHz band products. In theory, according to this standard, it is possible to enable a wireless LAN speed of a plurality of stations to be a minimum of 1 Gbps, and to enable a maximum single link speed to be a minimum of 500 Mbps. This is achieved by extending the concept of a wireless interface received by 802.11η, such as a wider wireless frequency bandwidth (maximum 160 MHz), more MIMO spatial streams (maximum 8), multi-user MIMO, and high density modulation (maximum 256 QAM). Further, as a scheme for transmitting data by using a 60 GHz band instead of the existing 2.4 GHz / 5 GHz, IEEE 802.11ad has been provided. IEEE 802.11ad is a transmission standard providing a speed of maximum 7 Gbps by using a beamforming technique, and is suitable for high bit rate moving image streaming, such as large-scale data or uncompressed HD video. However, since the 60 GHz band is difficult to penetrate obstacles, it has a disadvantage in that the 60 GHz band can be used only among devices in a near distance space.

[0006] As a wireless LAN standard after 802.11ac and 802.11ad, IEEE 802.11ax (High Efficiency WLAN (HEW)) standard for providing a high-efficiency and high-performance wireless LAN communication technology in a high-density environment of APs and terminal sets is in the process of being completed. In a wireless LAN environment based on 802.11ax, in the presence of high-density stations and access points (APs), communication with high frequency efficiency should be provided indoors / outdoors, and various technologies for implementing such communication have been developed.

[0007] In order to support new multimedia applications such as high-definition video and real-time games, a new wireless LAN standard has been developed to increase the maximum transmission rate. In IEEE 802.11be Extremely High Throughput (EHT) as the 7th generation wireless LAN standard, development of the standard is underway with the aim of supporting a transmission rate of up to 30 Gbps in 2.4 / 5 / 6 GHz bands through a wider bandwidth, increased spatial streams, multi-AP cooperation, etc. In IEEE 802.11be, technologies such as 320 MHz bandwidth, multi-link operation, multi-access point (Multi-AP) operation, and hybrid automatic repeat request (HARQ) are proposed.

[0008] The multi-link operation can be operated in various types according to its operation method and implementation method. In this case, since problems that can occur in the existing IEEE 802.11-based wireless LAN communication operation can occur, it is necessary to define detailed operation methods in the multi-link operation.

[0009] On the other hand, the background art of the present invention is written in order to improve the understanding of the background, and thus can include contents that are not prior art known to those skilled in the art to which the technology pertains. SUMMARY

[0010] TECHNICAL PROBLEM

[0011] An object of the present invention is to provide a method, apparatus, and system for multi-link transmission operation using a wireless LAN, so that a wireless access point efficiently performs transmission and reception of frames requiring low delay time.

[0012] In addition, an object of the present invention is to provide a method, apparatus, and system for setting an interval for transmission and reception of a limit, so that frames requiring low delay time are transmitted and received.

[0013] Further, an object of the present application is to provide a method, apparatus and system for efficiently performing frame transmission operation when a wireless access point or station cannot perform simultaneous transmission and reception operation in multiple links in a multi-link operation.

[0014] The technical problems to be solved in the present specification are not limited to the above-mentioned technical problems, and other technical problems not mentioned can be clearly understood by those skilled in the art on the basis of the following description.

[0015] Technical method

[0016] A multi-link device (MLD) of a wireless communication system includes a communication module; a processor controlling the communication module, the processor: receiving a beacon frame including a request type field from an AP, the request type field including a special field for showing a target wake time (TWT) for a low latency operation, receiving a downlink frame or transmitting an uplink frame according to a value of the special field, the TWT service period (SP) for the low latency operation being a TWT SP for the low latency operation when the value of the special field is set to a first special value.

[0017] Further, in the present application, when the TWT SP for the low latency operation is set, only frames requiring low latency can be transmitted during the TWT SP for the low latency operation.

[0018] Further, in the present application, the beacon frame further includes a quiet information element for protecting the TWT SP for the low latency operation.

[0019] Further, in the present application, an interval set by the quiet information element is the same as a start time of the TWT SP for the low latency operation.

[0020] Further, in the present application, when an interval set by the quiet information element overlaps with part or all of the TWT SP for the low latency operation, the overlapping part or all of the interval set by the quiet information element is ignored.

[0021] Further, in the present application, an interval set by the quiet information element is used for at least one STA to set a network allocation vector (NAV).

[0022] Further, in the present application, the NAV is set during the interval set by the quiet element.

[0023] Further, in the present application, when the value of the special field is set to a second special value, the special field shows that transmission is limited only by the type of response frame to a downlink frame.

[0024] Further, in the present application, the beacon frame further includes a parameter field including a broadcast TWT information field including information related to a traffic identifier (TID) for transmission of a TWT limit frame for the low latency operation.

[0025] Further, in the present application, when the non-AP STA constitutes a multi-link device (MLD), the MLD cannot transmit a frame through other links during reception of the beacon frame.

[0026] Further, in the present application, a frame transmission operation is ended before a start time of a TWT SP for the low latency operation.

[0027] Advantageous Effects

[0028] According to an embodiment of the present application, a frame requiring a low latency can be effectively transmitted.

[0029] Further, according to an embodiment of the present application, a frame requiring a low latency can be effectively transmitted by setting an interval for limiting transmission of a frame.

[0030] According to the present application, when an Access Point (AP) MLD including an AP and a plurality of wireless access points supports a transmission and reception operation of a frame requiring a low latency time, a special interval in which only a frame requiring a low latency time can be transmitted is defined and notified through a broadcast frame. When a wireless local area network station (STA) wants to transmit and receive a frame satisfying the corresponding requirement, a process of negotiation is performed so as to perform a corresponding operation with the AP or the AP MLD. Here, interval information for the low latency time is notified through a beacon frame or a probe response frame, etc. Here, the interval notification and negotiation method for the low latency time are performed in the same or similar method as a negotiation method of a Target Wake Time (TWT) operation. In order to efficiently perform the corresponding operation, the AP or the AP MLD allows access of a terminal supporting the corresponding operation only to a link in use. As the corresponding low latency transmission operation is used, when a terminal or an AP wants to transmit a frame requiring a low latency time, transmission and reception of the corresponding frame are stably performed, thereby having an effect of improving communication efficiency.

[0031] Effects obtainable from the present application are not limited to the above-mentioned effects and other effects not mentioned herein will become apparent to those skilled in the art from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A wireless LAN system according to an embodiment of the present application is illustrated.

[0033] Figure 2 A wireless LAN system according to another embodiment of the present application is illustrated.

[0034] Figure 3 A configuration of a station according to an embodiment of the present application is illustrated.

[0035] Figure 4 A configuration of an access point according to an embodiment of the present application is illustrated.

[0036] Figure 5 A process in which a station and an access point set up a link is schematically illustrated.

[0037] Figure 6 A Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication is illustrated.

[0038] Figure 7 Embodiments of a format of a PLCP Protocol Data Unit (PPDU) for each of various standards generations are illustrated.

[0039] Figure 8 Examples of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats according to an embodiment of the present application and a method for indicating the format are illustrated.

[0040] Figure 9 A configuration diagram illustrating an internal layer structure of a STA according to an embodiment of the present application is illustrated.

[0041] Figure 10 A conceptual diagram illustrating an AP MLD and STA MLD structure performing a multi-link operation according to an embodiment of the present application is illustrated.

[0042] Figure 11 A conceptual diagram illustrating an access procedure between an AP MLD and a STA or a STA MLD according to an embodiment of the present application is illustrated.

[0043] Figure 12FIG. 13 illustrates a first embodiment of an operation of limiting an access procedure of a terminal for performing a low latency function according to an embodiment of the present application.

[0044] Figure 13 FIG. 14 illustrates a second embodiment of an operation of limiting an access procedure of a terminal for performing a low latency function according to an embodiment of the present application.

[0045] Figure 14 FIG. 15 illustrates a block diagram of a link state information element including transmission state information in a corresponding link according to an embodiment of the present application.

[0046] Figure 15 FIG. 16 illustrates a first embodiment of a structure of a low latency operation request frame requesting a low latency operation using a Target Wake Time (TWT) function according to an embodiment of the present application.

[0047] Figure 16 FIG. 17 illustrates a second embodiment of a structure of a low latency operation request frame requesting a low latency operation using a TWT function according to an embodiment of the present application.

[0048] Figure 17 FIG. 18 illustrates a block diagram of a low latency operation response frame as a response to a request frame requesting a low latency operation using a TWT function according to an embodiment of the present application.

[0049] Figure 18 FIG. 19 illustrates a first embodiment of a procedure in which an AP or an AP MLD and a STA perform a low latency operation using a TWT function according to an embodiment of the present application.

[0050] Figure 19 FIG. 20 illustrates a second embodiment of a procedure in which an AP or an AP MLD and a STA perform a low latency operation using a TWT function according to an embodiment of the present application.

[0051] Figure 20 FIG. 21 illustrates an operation in which a TWT time for a low latency operation is not protected according to an embodiment of the present application.

[0052] Figure 21 FIG. 22 illustrates an operation in which a parameter is changed at the same time point when an AP MLD performs a low latency operation using a TWT operation according to an embodiment of the present application.

[0053] Figure 22 FIG. 23 illustrates an embodiment of an operation in which an AP MLD additionally transmits a protection frame protecting a corresponding period at a start time point of a TWT time for a low latency operation in order to protect the TWT time according to an embodiment of the present application.

[0054] Figure 23FIG. 13 illustrates an embodiment of a process in which a STA incapable of AP MLD and STR operation performs a low-latency operation using a TWT function according to an embodiment of the present application.

[0055] Figure 24 FIG. 14 illustrates a conceptual diagram of an AP MLD and a STA MLD structure performing a multi-link operation according to an embodiment of the present application.

[0056] Figure 25 FIG. 15 illustrates a timing diagram of an access procedure and a negotiation procedure between an AP MLD and a STA MLD for a multi-link operation according to an embodiment of the present application.

[0057] Figure 26 FIG. 16 illustrates a timing diagram of a transmission method using a multi-link according to an embodiment of the present application.

[0058] Figure 27 FIG. 17 illustrates an embodiment of a frame transmission and reception operation of a receiving MLD incapable of STR operation in some or all links and a transmitting MLD capable of STR operation according to an embodiment of the present application.

[0059] Figure 28 FIG. 18 illustrates a first embodiment of an operation of protecting frame transmission and reception through an MU-RTS frame and CTS frame exchange procedure between an AP and a plurality of STAs according to an embodiment of the present application.

[0060] Figure 29 FIG. 19 illustrates a first embodiment of a structure of an MU-RTS frame according to an embodiment of the present application.

[0061] Figure 30 FIG. 20 illustrates a second embodiment of a structure of an MU-RTS frame according to an embodiment of the present application.

[0062] Figure 31 FIG. 21 illustrates a second embodiment of an operation of protecting frame transmission and reception through an MU-RTS frame and CTS frame exchange procedure between an AP and a plurality of STAs according to an embodiment of the present application.

[0063] Figure 32 FIG. 22 illustrates a third embodiment of a structure of an MU-RTS frame according to an embodiment of the present application.

[0064] Figure 33 FIG. 23 illustrates a third embodiment of an operation of protecting frame transmission and reception through an MU-RTS frame and CTS frame exchange procedure between an AP and a plurality of STAs according to an embodiment of the present application.

[0065] Figure 34 FIG. 24 illustrates a fourth embodiment of a structure of an MU-RTS frame according to an embodiment of the present application.

[0066] Figure 35An embodiment of a channel reservation procedure by a MU-RTS frame and CTS frame exchange procedure in operation of a plurality of terminals according to an embodiment of the present application is illustrated.

[0067] Figure 36 An operation in which a CTS frame to a MU-RTS frame cannot be transmitted in a special 20MHz channel according to an embodiment of the present application is illustrated.

[0068] Figure 37 A first embodiment of an operation in which transmission of a MU-RTS frame is omitted in an AP MLD adding an additional condition according to an embodiment of the present application is illustrated.

[0069] Figure 38 A second embodiment of an operation in which transmission of a MU-RTS frame is omitted in an AP MLD adding an additional condition according to an embodiment of the present application is illustrated.

[0070] Figure 39 An embodiment of an operation in which a MU-RTS frame is transmitted in an AP MLD according to an added additional condition according to an embodiment of the present application is illustrated.

[0071] Figure 40 A first embodiment of an operation for avoiding a situation in which a CTS frame in a special 20MHz cannot be transmitted due to operation of a corresponding STA MLD according to an embodiment of the present application is illustrated.

[0072] Figure 41 A second embodiment of an operation for avoiding a situation in which a CTS frame in a special 20MHz cannot be transmitted due to operation of a corresponding STA MLD according to an embodiment of the present application is illustrated.

[0073] Figure 42 A third embodiment of an operation for avoiding a situation in which a CTS frame in a special 20MHz cannot be transmitted due to operation of a corresponding STA MLD according to an embodiment of the present application is illustrated.

[0074] Figure 43 A first embodiment of an operation in which frame transmission is continued even if a CTS frame to a MU-RTS frame is not received in a special 20MHz channel according to an embodiment of the present application is illustrated.

[0075] Figure 44 A second embodiment of an operation in which frame transmission is continued even if a CTS frame to a MU-RTS frame is not received in a special 20MHz channel according to an embodiment of the present application is illustrated.

[0076] Figure 45 An operation of a soft AP according to an embodiment of the present application is illustrated.

[0077] Figure 46A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0078] Figure 47 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0079] Figure 48 A non-STR soft AP multi-link device performs channel access on the required link and the optional link according to embodiments of the application.

[0080] Figure 49 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0081] Figure 50 A non-STR soft AP multi-link device performs channel access on the required link and the optional link according to embodiments of the application.

[0082] Figure 51 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0083] Figure 52 Embodiments of the application are applicable when a portion of the multiple links of an AP multi-link device operation is a non-STR link pair according to embodiments of the application.

[0084] Figure 53 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0085] Figure 54 An AP multi-link device operates with stations not included in the station combination of the multi-link device according to embodiments of the application.

[0086] Figure 55 An AP multi-link device operates with stations included in the station combination of the multi-link device according to embodiments of the application.

[0087] Figure 56 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0088] Figure 57 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0089] Figure 58 A non-STR soft AP multi-link device transmits PPDUs on the required link and the optional link according to embodiments of the application.

[0090] Figure 59FIG. illustrates channel access of a multi-link device according to an embodiment of the present application when one non-AP multi-link device is connected to all non-STR link pairs.

[0091] Figure 60 FIG. illustrates channel access of a multi-link device according to an embodiment of the present application when one non-AP multi-link device is connected to all non-STR link pairs.

[0092] Figure 61 FIG. illustrates transmission operation of a non-AP multi-link device according to an embodiment of the present application when one non-AP multi-link device is connected to all links of non-STR link pairs of an AP multi-link device, and the AP multi-link device performs transmission at a certain link.

[0093] Figure 62 FIG. illustrates transmission operation of a non-AP multi-link device according to an embodiment of the present application when one non-AP multi-link device is connected to all links of non-STR link pairs of an AP multi-link device, and the non-AP multi-link device transmits an intra-BSS frame transmitted by another station at a certain link.

[0094] Figure 63 FIG. illustrates transmission operation of a non-AP multi-link device according to another embodiment of the present application when one non-AP multi-link device is connected to all links of non-STR link pairs of an AP multi-link device, and the non-AP multi-link device transmits an intra-BSS frame transmitted by another station at a certain link.

[0095] Figure 64 FIG. illustrates a flowchart of an example of a method of transmitting a frame according to the present application. DETAILED DESCRIPTION

[0096] The terms used in the present specification are used to express the general technical terms that are widely used at present, in consideration of the functions in the present application, but the terms can vary according to the intention of those skilled in the art, customs, or the advent of new technologies. Also, in special cases, the terms selected by the applicant can be arbitrarily selected, and in this case, the meanings of the terms will be described in the corresponding description portion of the present application. Therefore, it should be understood that the terms used in the present specification, should be analyzed based on the meaning of the terms and the content throughout the present specification, rather than the name of the terms alone.

[0097] Throughout the specification, when it is stated that an element is "coupled" to another element, the element can be "directly coupled" to the other element, or "electrically coupled" to the other element via a third element. Also, unless explicitly stated to the contrary, the word "comprises" will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, a limitation such as "or more" or "or less" based on a specific threshold can be replaced with "greater than" or "less than" as appropriate. Hereinafter, in the present invention, a field and a subfield can be used interchangeably.

[0098] Figure 1 A wireless LAN system according to an embodiment of the present invention is illustrated.

[0099] The wireless LAN system includes one or more Basic Service Sets (BSSs), and the BSSs represent a set of devices that successfully synchronize with each other to communicate with each other. Generally, the BSSs can be classified into an infrastructure BSS and an Independent BSS (IBSS), and Figure 1 An infrastructure BSS is shown between them.

[0100] As Figure 1 shown, the infrastructure BSSs (BSS1 and BSS2) include one or more stations (STA1, STA2, STA3, STA4, and STA5), access points (AP-1 and AP-2) that are stations providing a Distribution Service, and a Distribution System (DS) connecting the access points (AP-1 and AP-2).

[0101] A station (STA) is a predetermined device including a Medium Access Control (MAC) complying with the provisions of IEEE 802.11 standards and a Physical Layer interface for a wireless medium, and broadly includes both a non-access point (non-AP) station and an access point (AP). Also, in the present specification, the term "terminal" can be used to refer to either a non-AP STA or an AP, or both terms. A station for wireless communication includes a processor and a communication unit, and according to an embodiment, can further include a user interface unit and a display unit. The processor can generate a frame to be transmitted via a wireless network, or process a frame received via a wireless network, and in addition, perform various processes for controlling the station. Also, the communication unit is functionally connected with the processor, and transmits and receives frames via a wireless network for the station. According to the present application, a terminal can be used as a term including a user equipment (UE).

[0102] An access point (AP) is an entity that provides access to a distribution system (DS) via a wireless medium for stations associated therewith. In an infrastructure BSS, communication among non-AP stations is in principle performed via the AP, but direct communication among non-AP stations is even allowed when a direct link is configured. Meanwhile, in the present application, the AP is used as a concept including a Personal BSS Coordination Point (PCP), and can broadly include a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a station controller, etc. In the present application, the AP can also be referred to as a base station wireless communication terminal. The base station wireless communication terminal can be used as a term broadly including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). Also, the base station wireless communication terminal can include various types of wireless communication terminals that allocate a communication medium resource and perform scheduling in communication with a plurality of wireless communication terminals.

[0103] A plurality of infrastructure BSSs can be connected to each other via a distribution system (DS). In this case, a plurality of BSSs connected via a distribution system is referred to as an Extended Service Set (ESS).

[0104] Figure 2 A stand-alone BSS according to another embodiment of the present application is illustrated, which is a wireless LAN system. In Figure 2 In an embodiment of the present application, the same or corresponding parts of the embodiment of the present application will be omitted. Figure 1 Figure 1

[0105] Since the BSS 3 illustrated in FIG. 1 is an independent BSS and does not include an AP, the stations STA6 and STA7 are not connected to the AP. The independent BSS is not allowed to access a distribution system and forms a self-contained network. In the independent BSS, the respective stations STA6 and STA7 can be directly connected to each other. Figure 2

[0106] Figure 3 FIG. 1 illustrates a block diagram of a configuration of a station 100 according to an embodiment of the present application. As illustrated in FIG. 1, the station 100 according to an embodiment of the present application can include a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160. Figure 3

[0107] First, the communication unit 120 transmits and receives a wireless signal such as a wireless LAN packet, and can be embedded in the station 100 or provided as an external device. According to an embodiment, the communication unit 120 can include at least one communication module using different frequency bands. For example, the communication unit 120 can include communication modules having different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 can include a communication module using a frequency band of 7.125 GHz or more, and a communication module using a frequency band of 7.125 GHz or less. Each communication module can perform wireless communication with an AP or an external station according to a wireless LAN standard of a frequency band supported by the respective communication module. The communication unit 120 can operate one communication module at a time according to the performance and requirements of the station 100, or simultaneously operate a plurality of communication modules together. When the station 100 includes a plurality of communication modules, each communication module can be implemented by independent elements, or a plurality of modules can be integrated into one chip. In an embodiment of the present application, the communication unit 120 can represent a Radio Frequency (RF) communication module for processing an RF signal.

[0108] Second, the user interface unit 140 includes various types of input / output devices provided in the station 100. That is, the user interface unit 140 can receive a user input by using various input devices, 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 by using various output devices.

[0109] ​​​​Next, the display unit 150 outputs an image on a display screen. The display unit 150 can output various display objects such as contents executed by the processor 110 or a user interface, etc. based on a control command of the processor 110. Also, the memory 160 stores a control program and various data used in the station 100. The control program can include an access program required for the station 100 to access an AP or an external station.

[0110] The processor 110 of the present application can execute various commands or programs and process data in the station 100. Also, the processor 110 can control various units of the station 100 and control data transmission / reception among the units. According to an embodiment of the present application, the processor 110 can execute a program for accessing an AP stored in the memory 160 and receive a communication configuration message transmitted by the AP. Also, the processor 110 can read information about a priority condition of the station 100 included in the communication configuration message and request access to the AP based on the information about the priority condition of the station 100. The processor 110 of the present application can represent a main control unit of the station 100 and, according to an embodiment, the processor 110 can represent a control unit for separately controlling certain components (e.g., the communication unit 120, etc.) of the station 100. That is, the processor 110 can be a modem or a modulator and / or demodulator for modulating a wireless signal transmitted to the communication unit 120 and demodulating a wireless signal received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission / reception of the station 100 according to an embodiment of the present application. Detailed embodiments thereof will be described below.

[0111] The station 100 illustrated in Figure 3 is a block diagram according to an embodiment of the present application, in which separate blocks are illustrated as elements of logically distinguished devices. Accordingly, the elements of the devices can be mounted in a single chip or in a plurality of chips according to the design of the devices. For example, the processor 110 and the communication unit 120 can be implemented when integrated as a single chip or as separate chips. Also, in an embodiment of the present application, certain components of the station 100, e.g., the user interface unit 140 and the display unit 150, etc. can be selectively provided in the station 100.

[0112] Figure 4 A block diagram illustrating a configuration of an AP 200 according to an embodiment of the present application is illustrated. As illustrated in Figure 4 , the AP 200 according to an embodiment of the present application can include a processor 210, a communication unit 220, and a memory 260. In Figure 4 , among the components of the AP 200, the components identical to or corresponding to those of the station 100 of Figure 2 are not described in detail. Figure 2 Repeated descriptions of parts of station 100 will be omitted.

[0113] Reference Figure 4 The AP 200 according to the invention includes a communication unit 220 that operates a BSS in at least one frequency band. (As in...) Figure 3 As illustrated in the embodiments, the communication unit 220 of AP 200 may also include multiple communication modules using different frequency bands. That is, an AP 200 according to an embodiment of the present invention may together include two or more communication modules in different frequency bands (e.g., 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz). Preferably, AP 200 may include communication modules using frequency bands of 7.125 GHz or higher, and communication modules using frequency bands of 7.125 GHz or lower. Each communication module can perform wireless communication with the station according to the wireless LAN standard of the frequency band supported by the respective communication module. Communication unit 220 may operate only one communication module at a time, or operate multiple communication modules simultaneously, depending on the performance and requirements of AP 200. In embodiments of the present invention, communication unit 220 may represent a radio frequency (RF) communication module for processing RF signals.

[0114] Next, memory 260 stores the control program and various result data used in AP 200. The control program may include an access program for accessing the management station. Furthermore, processor 210 can control the various units of AP 200 and control data transmission / reception within the units. According to one embodiment of the invention, processor 210 can execute the program for accessing the station stored in memory 260 and transmit communication configuration messages for one or more stations. In this case, the communication configuration message may include information about the access priority conditions of each station. Furthermore, processor 210 performs access configuration according to the access request of a station. According to one embodiment, processor 210 may be a modem or modulator / demodulator for modulating wireless signals transmitted to communication unit 220 and demodulating wireless signals received from communication unit 220. Processor 210 controls various operations, such as wireless signal transmission / reception of AP 200, according to an embodiment of the invention. Detailed embodiments thereof will be described below.

[0115] Figure 5 This is a diagram illustrating the process of setting up a link between a STA and an AP.

[0116] Reference Figure 5, broadly, a link between the STA 100 and the AP 200 is set via three steps of scanning, authentication, and association. First, the scanning step is a step in which the STA 100 obtains access information of a BSS operated by the AP 200. Methods for performing scanning include a passive scanning method in which the AP 200 obtains information by using a beacon message (S101) periodically transmitted, and an active scanning method in which the STA 100 transmits a probe request to the AP (S103), and obtains access information by receiving a probe response from the AP (S105).

[0117] The STA 100 that successfully receives wireless access information in the scanning step performs the authentication step by transmitting an authentication request (S107a) and receiving an authentication response (S107b) from the AP 200. After performing the authentication step, the STA 100 performs the association step by transmitting an association request (S109a) and receiving an association response (S109b) from the AP 200. In the present specification, association basically refers to wireless association, but the present application is not limited thereto, and association can broadly include both wireless association and wired association.

[0118] Meanwhile, an 802.1X-based authentication step (S111) and an IP address acquisition step (S113) via DHCP can be additionally performed. In the 802.1X-based authentication step (S111), the STA 100 transmits an EAP request (S111a) to the AP 200, and the AP 200 transmits an EAP request (S111b) to the authentication server 300. The authentication server 300 transmits an EAP response (S111c) to the AP 200, and the AP 200 transmits an EAP response (S111d) to the STA 100. Figure 5 The authentication server 300 is a server that processes 802.1X-based authentication of the STA 100, and can exist in physical association with the AP 200, or as a separate server.

[0119] Figure 6 is a diagram illustrating a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0120] A terminal performing wireless LAN communication confirms whether a channel is in a busy state by performing carrier sensing before transmitting data. When a wireless signal having a strength or more than a pre-set strength is sensed, the corresponding channel is determined to be in a busy state and the terminal delays access to the corresponding channel. This process is called Clear Channel Assessment (CCA), and the level at which it is decided whether a corresponding signal is sensed is called a CCA threshold. When a wireless signal having a CCA threshold or more is received by a terminal, the terminal processes the received wireless signal. Meanwhile, when no wireless signal is detected in the corresponding channel or a wireless signal having a strength less than the CCA threshold is detected, the channel is determined to be in an idle state.

[0121] When the channel is determined to be idle, each terminal having data to be transmitted performs a backoff process after an Inter Frame Space (IFS) time, which depends on the situation of each terminal, e.g., an Arbitration IFS (AIFS), a PCF IFS (PIFS), etc. According to this embodiment, the AIFS can be used as a component instead of the existing DCF IFS (DIFS). Each terminal waits for a time slot time as long as a random number determined by the corresponding terminal during an interval in which the channel is in an idle state, and the terminal that completely exhausts the time slot time attempts to access the corresponding channel. In this way, the interval in which each terminal performs a backoff process is called a contention window interval.

[0122] When a special terminal succeeds in channel access, the corresponding terminal can transmit data through the channel. However, when terminals attempting access collide with another terminal, the terminals colliding with each other are respectively allocated new random numbers to perform a backoff process again. According to the embodiment, the random number newly allocated to each terminal can be determined within a range (2*CW) that is twice a range (contention window CW) of the random number previously allocated to the corresponding terminal. Meanwhile, each terminal attempts access by performing a backoff process again in the next contention window interval, and in this case, each terminal performs a backoff process from the time slot time remaining in the previous contention window interval. Through this method, the terminals performing wireless LAN communication can avoid mutual collision of a special channel.

[0123] Hereinafter, in the present invention, a terminal can be called a non-AP STA, an AP STA, a STA, a reception device, or a transmission device, and the present invention is not limited thereto. Also, in the present invention, an AP STA can be called an AP.

[0124] <Examples of various PPDU formats>

[0125] Figure 7 Figures illustrating examples of formats of PLCP Protocol Data Units (PPDUs) for each of various standards generations. More specifically, Figure 7 (a) of FIG. 1 illustrates an embodiment of a legacy PPDU format based on 802.11a / g, Figure 7 (b) of FIG. 1 illustrates an embodiment of a HE PPDU format based on 802.11ax, and Figure 7 (c) of FIG. 1 illustrates an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Figure 7 (d) of FIG. 1 illustrates detailed field configurations of RL-SIG and L-SIG commonly used in PPDU formats.

[0126] Referring to Figure 7 (a) of FIG. 1, the preamble of the legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In embodiments of the present disclosure, the L-STF, the L-LTF, and the L-SIG can be referred to as a legacy preamble.

[0127] Referring to Figure 7 (b) of FIG. 1, the preamble of the HE PPDU further includes a repeated legacy short training field (RL-SIG), a high efficiency signal A field (HE-SIG-A), a high efficiency signal B field (HE-SIG-B), a high efficiency short training field (HE-STF), and a high efficiency long training field (HE-LTF) in the legacy preamble. In embodiments of the present disclosure, the RL-SIG, the HE-SIG-A, the HE-SIG-B, the HE-STF, and the HE-LTF can be referred to as an HE preamble. Detailed configurations of the HE preamble can be modified according to the HE PPDU format. For example, the HE-SIG-B can be used only in the HE MU PPDU format.

[0128] Referring to Figure 7 (c), the EHT PPDU further includes a repeated legacy short training field (RL-SIG), a universal signal field (U-SIG), and an extremely high throughput signal A field (EHT-SIG-A), an extremely high throughput signal B field (EHT-SIG-B), an extremely high throughput short training field (EHT-STF), and an extremely high throughput long training field (EHT-LTF) in the legacy preamble. In an embodiment of the disclosure, the RL-SIG, the EHT-SIG-A, the EHT-SIG-B, the EHT-STF, and the EHT-LTF can be referred to as an EHT preamble. The specific configuration of the non-legacy preamble can be modified according to the EHT PPDU format. For example, the EHT-SIG-A and the EHT-SIG-B can be used only in a part of the EHT PPDU format.

[0129] The 64-FFT OFDM is applied to the L-SIG field included in the preamble of the PPDU, and the L-SIG field includes a total of 64 subcarriers. Among the 64 subcarriers, 48 subcarriers other than a guard subcarrier, a DC subcarrier, and a pilot subcarrier are used for transmission of L-SIG data. A modulation and coding scheme (MCS) of BPSK and a code rate = 1 / 2 is applied to the L-SIG, and thus the L-SIG can include a total of 24 bits of information. Figure 7 FIG. 13 illustrates a configuration of the 24 bits of information of the L-SIG according to (d) of the related art.

[0130] Referring to Figure 7The L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field includes 4 bits, and indicates an MCS used for data transmission. Specifically, the L_RATE field indicates one of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps transmission rates obtained by combining a modulation scheme such as BPSK / QPSK / 16-QAM / 64-QAM, etc. with non-efficiency such as 1 / 2, 2 / 3, 3 / 4, etc. The total length of the corresponding PPDU can be indicated by combining the information of the L_RATE field and the information of the L_LENGTH field. In the non-legacy PPDU format, the L_RATE field is configured as a minimum rate of 6 Mbps.

[0131] The unit of the L_LENGTH field can be allocated a total of 12 bits, can signal up to 4095, and can indicate the length of the corresponding PPDU by combination with the L_RATE field. In this case, the legacy terminal and the non-legacy terminal can use different methods to interpret the L_LENGTH field.

[0132] First, the method in which the legacy terminal or the non-legacy terminal analyzes the length of the corresponding PPDU using the L_LENGTH field is as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4us which is one symbol duration of 64 FFT. Accordingly, 3 bytes corresponding to the SVC field and the tail field are added to the value of the field L_LENGTH, and the added value is divided by 3 bytes which is the transmission amount of one symbol, thereby obtaining the number of symbols based on 64 FFT after the L-SIG. The obtained number of symbols is multiplied by 4us (i.e., the length of one symbol), and then 20us required for transmission of the L-STF, the L-LTF, and the L-SIG is added, thereby obtaining the length of the corresponding PPDU, i.e., the reception time RXTIME. This can be expressed by Equation 1 below.

[0133] [Equation 1]

[0134]

[0135] In this case, denotes the minimum 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 up to 5.464ms. The non-legacy terminal transmitting the PPDU should set the L_LENGTH field as shown in Equation 2 below.

[0136] [Equation 2]

[0137]

[0138] Here, TXTIME is the total transmission time of the corresponding PPDU, and is expressed by Equation 3 below. In this case, TX denotes the transmission time of X.

[0139] [Equation 3]

[0140] TXTIME(us) = T L-STF + T L-LTF + T L-SIG + T RL-SIG + T U-SIG + (T EHT-SIG-A ) + (T EHT-SIG-B ) + T EHT-STF + N EHT-LTF T EHT-LTF + T DATA

[0141] Referring to the above equation, the length of the PPDU is calculated based on the upward rounding value of L_LENGTH / 3. Therefore, for a random value of k, three different values of L_LENGTH = {3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0142] Referring to Figure 7 (e), the Universal SIG (U-SIG) field continues to exist in the EHT PPDUs and wireless LAN PPDUs of the subsequent generations, and is used to classify the generations of the PPDUs including 11be. The U-SIG is an OFDM 2 symbol based on 64 FFT, and can transmit a total of 52 bits of information. Among the 52 bits, 43 bits other than 9 bits of CRC / Tail are mainly divided into a Version Independent (VI) field and a Version Dependent (VD) field.

[0143] The VI bit enables the current bit configuration to be maintained subsequently, so that even if a next-generation PPDU is defined, the current 11be terminal can obtain information about the PPDU through the VI field of the PPDU. To this end, the VI field includes a PHY version, UL / DL, BSS color, TXOP, and a reserved field. The PHY version field is 3 bits, and is used to sequentially classify 11be and a subsequent generation wireless LAN standard into each version. The value of 11be is 000b. The UL / DL field identifies whether the PPDU is an uplink / downlink PPDU. The BSS color indicates an identifier of each BSS defined in 11ax, and has a value of 6 bits or more. The TXOP indicates a transmit opportunity duration (Transmit Opportunity Duration) transmitted in the MAC header, in which the PPDU can infer the length of the TXOP included therein by adding the TXOP to the PHY header without having to decode the MPDU, and the TXOP has a value of 7 bits or more.

[0144] The VD field is signaling information useful only for the 11be version of the PPDU, and can include a field commonly used in any PPDU format such as a PPDU format and BW, and a field differently defined for each PPDU format. The PPDU format is a classifier classifying EHT Single User (SU), EHT Multiple User (MU), EHT Trigger-based (TB), EHT Extended Range (ER) PPDU, etc. The BW field signals five basic PPDU BW options (BW, which can be expressed in the type of an exponential power of 20*2, can be referred to as a basic BW) of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz, and various remaining PPDU BWs configured via preamble puncturing. After being signaled in 320 MHz, signaling can be performed in the type of some 80 MHz punctured. The punctured and modified channel type can be directly signaled in the BW field, or can be signaled using the BW field with a field (for example, a field within the EHT-SIG field) that occurs after the BW field. If the BW field is configured to 3 bits, a total of 8 BW signaling can be performed, and thus up to 3 signaling can be performed only in a puncturing mode. If the BW field is configured to 4 bits, a total of 16 BW signaling can be performed, and thus up to 11 signaling can be performed in a puncturing mode.

[0145] Fields located after the BW field vary according to the type and format of the PPDU, and the MU PPDU and the SU PPDU can be signaled in the same PPDU format, a field for classifying between the MU PPDU and the SU PPDU can be located before the EHT-SIG field, and additional signaling can be performed on the field. The SU PPDU and the MU PPDU both include the EHT-SIG field, but some fields that are not required in the SU PPDU can be compressed. Information about the fields on which compression has been applied can be omitted or can have a size smaller than that of the original field included in the MU PPDU. For example, in the case of the SU PPDU, the common field of the EHT-SIG can be omitted or replaced, or the SU PPDU can have a different configuration in which the user-specific field is replaced, reduced to one, or the like.

[0146] Alternatively, the SU PPDU can further include a compression field indicating whether compression is performed, and a part of a field (e.g., the RA field, etc.) can be omitted according to the value of the compression field.

[0147] If a part of the EHT-SIG field of the SU PPDU is compressed, information to be included in the compressed field can also be signaled in an uncompressed field (e.g., the common field, etc.). The MU PPDU corresponds to a PPDU format for simultaneous reception by a plurality of users, and thus requires transmission of the EHT-SIG field after the U-SIG field, and the amount of information transmitted can vary. That is, a plurality of MU PPDUs are transmitted to a plurality of STAs, so that each STA should recognize the position of the RU in which the MU PPDU is transmitted, the STA to which the RU is respectively allocated, and whether the transmitted MU PPDU has been transmitted to the STA itself. Therefore, the AP should transmit the information by including the above information in the EHT-SIG field. To this end, information for efficient transmission of the EHT-SIG field is signaled in the U-SIG field, and this can correspond to the MCS as a modulation method and / or the number of symbols in the EHT-SIG field. The EHT-SIG field can include information about the size and position of the RU allocated to each user.

[0148] In the case of the SU PPDU, a plurality of RUs can be allocated to the STA, and the plurality of RUs can be continuous or discontinuous. If the RUs allocated to the STA are discontinuous, the STA should recognize the punctured RUs in the middle in order to effectively receive the SU PPDU. Accordingly, the AP can transmit the SU PPDU including information of the punctured RUs among the RUs allocated to the STA (e.g., a puncturing pattern of the RUs, etc.). That is, in the case of the SU PPDU, the EHT-SIG field can include a puncturing pattern field including information indicating a puncturing pattern in a bitmap format, etc., and whether the puncturing pattern is applied, and the puncturing pattern field can signal a discontinuous channel type occurring within the bandwidth.

[0149] The signaled discontinuous channel type is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, the SU PPDU is a PPDU transmitted to only a single terminal, so that the STA can recognize the bandwidth allocated to itself via the BW field included in the PPDU, and the SU PPDU can recognize the punctured resources in the allocated bandwidth via the puncturing pattern field of the EHT-SIG field or the U-SIG field included in the PPDU. In this case, the terminal can receive the PPDU in the remaining resource units after excluding the special channel of the punctured resource units. The plurality of RUs allocated to the STA can be configured by different frequency bands or tones.

[0150] In order to reduce the signaling overhead of the SU PPDU, only a limited discontinuous channel type is signaled. The puncturing can be performed for each 20 MHz subchannel, so that if the puncturing is performed for a BW having a large number of 20 MHz subchannels, such as 80, 160, and 320 MHz, in the case of 320 MHz, the discontinuous channel (if the puncturing of only the edge 20 MHz is also considered discontinuous) type should be signaled by representing whether each of the remaining 15 20 MHz subchannels after excluding the primary channel is used. In this way, considering the low transmission rate of the signaling part, allocating 15 bits to signal the discontinuous channel type of a single user transmission can act as excessive signaling overhead.

[0151] The present application proposes a technology for signaling the discontinuous channel type of the SU PPDU, and illustrates the discontinuous channel type determined according to the proposed technology. The present application also proposes a technology for signaling each of the puncturing types of the primary 160 MHz and the secondary 160 MHz in the 320 MHz BW configuration of the SU PPDU.

[0152] Further, in an embodiment of the present application, a technique of differently configuring a PPDU indicated by a preamble puncturing BW value according to a PPDU format signaled in a PPDU format field is proposed. Assuming that the BW field is 4 bits, and in the case of an EHT SU PPDU or TB PPDU, 1 symbol of EHT-SIG-A can be additionally signaled after U-SIG, or EHT-SIG-A can not be signaled at all, thus, considering this, it is necessary to completely signal up to 11 puncturing patterns only via the BW field of U-SIG. However, in the case of an EHT MU PPDU, EHT-SIG-B is additionally signaled after U-SIG, so that up to 11 puncturing patterns can be signaled in a method different from that of the SU PPDU. In the case of an EHT ER PPDU, the BW field can be configured as 1 bit to signal whether the EHT ER PPDU is a PPDU using a 20 MHz band or a 10 MHz band.

[0153] Figure 7 (f) illustrates a configuration of a Format-specific field of a VD field when an EHT MU PPDU is indicated in a PPDU format field of U-SIG. In the case of an MU PPDU, SIG-B, which is a signaling field for simultaneous reception by a plurality of users, is necessarily required, and SIG-B can be transmitted after U-SIG without a separate SIG-A. For this, information for decoding SIG-B should be signaled in U-SIG. These fields include SIG-B MCS, SIG-B DCM, the number of SIG-B symbols, SIG-B compression, and the number of EHT-LTF symbols, etc.

[0154] Figure 8 FIGS. 1 to 6 illustrate examples of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats according to an embodiment of the present application, and a method for indicating the formats.

[0155] Referring to Figure 8 , a PPDU can include a preamble and a data portion, and can be classified as an EHT PPDU format as a PPDU type according to a U-SIG field included in the preamble. Specifically, based on a PPDU format field included in the U-SIG field, it can be indicated whether the format of the PPDU is an EHT PPDU.

[0156] Figure 8(a) of FIG. 1 shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU for a single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling can be located after a U-SIG field.

[0157] Figure 8 (b) of FIG. 1 shows an example of an EHT trigger-based PPDU format corresponding to an EHT PPDU based on a trigger frame transmission. The EHT trigger-based PPDU is an EHT PPDU based on a trigger frame transmission, and is an uplink PPDU for a response to a trigger frame. Unlike the EHT SU PPDU, an EHT-SIG-A field is not located after a U-SIG field in the EHT PPDU.

[0158] Figure 8 (c) of FIG. 1 shows an example of an EHT MU PPDU format corresponding to an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU for transmitting a PPDU to one or more STAs. In the EHT MU PPDU format, an HE-SIG-B field can be located after a U-SIG field.

[0159] Figure 8 (d) of FIG. 1 shows an example of an EHT ER SU PPDU format for a single user transmission with a STA in an extended range. Unlike the EHT SU PPDU explained in (a) of FIG. 1, the EHT ER SU PPDU can be used for a single user transmission with a wider range of STAs, and a U-SIG field can be repeatedly located in a time axis. Figure 8

[0160] Figure 8 The EHT MU PPDU explained in (c) of FIG. 1 can be used by an AP to perform a downlink transmission toward multiple STAs. Here, the EHT MU PPDU can include scheduling information so that the multiple STAs can simultaneously receive a PPDU transmitted from the AP. The EHT MU PPDU can transmit AID information of a transmitter and / or a receiver of a PPDU transmitted via a user specific field of an EHT-SIG-B to the STAs. Accordingly, the multiple terminals that have received the EHT MU PPDU can perform a spatial reuse operation based on the AID information of the user specific field included in a preamble of the received PPDU.

[0161] ​Specifically, a resource unit allocation (RA) field of an HE-SIG-B field included in the HE MU PPDU can include information on a configuration (e.g., a division type of resource units) of resource units in a special bandwidth (e.g., 20 MHz, etc.) of a frequency axis. That is, the RA field can indicate a configuration of resource units divided in a bandwidth for transmission of the HE MU PPDU in order for the STA to receive the PPDU. Information on a STA allocated (or designated) to each of the divided resource units can be included in a user-specific field of the EHT-SIG-B in order to be transmitted to the STA. That is, the user-specific field can include one or more user fields corresponding to the respective divided resource units.

[0162] For example, a user field corresponding to at least one resource unit for data transmission among the plurality of divided resource units can include an AID of a receiver or a transmitter, and a user field corresponding to a remaining resource unit not used for data transmission can include a pre-configured Null STA ID.

[0163] Figure 8 Two or more PPDUs shown in Table 1 can be indicated as a value representing the same PPDU format. That is, two or more PPDUs can be indicated in the same PPDU format by the same value. For example, an EHT SU PPDU and an EHT MU PPDU can be indicated by the U-SIG PPDU format subfield with the same value. In this case, the EHT SU PPDU and the EHT MU PPDU can be distinguished by the number of STAs receiving the PPDU. For example, a PPDU receiving only one STA can be recognized as an EHT SU PPDU, and when the number of STAs is set to receive two or more STAs, the PPDU can be recognized as an EHT MU PPDU. In other words, two or more PPDU formats shown in Table 1 can be indicated by the same subfield value. Figure 8 two or more PPDU formats.

[0164] In addition, part of the fields or part of the information of the fields shown in Table 1 can be omitted, and the case where part of the fields or part of the information of the fields is omitted can be defined as a compression mode or a compressed mode. Figure 8

[0165] In an aspect, when an AP and a STA request a low latency operation for special traffic requiring a low latency time. At this time, traffic requiring a low latency time can be delivered at a MAC layer as follows.

[0166] Figure 9 ​FIG. 1 is a diagram illustrating an internal layer structure of a STA according to an embodiment of the present application.

[0167] Referring to Figure 9 The communication device included in the STA is configured of an application layer performing various operations at the topmost layer, a transport layer guaranteeing end-to-end transmission reliability, a network layer finding a route to a destination communication node and transmitting a signal in a corresponding direction, a data link layer performing a transmission operation in a communication link between terminals, and a physical layer performing a transmission operation through an actual physical signal. At this time, the data link layer can include a logical link control (LLC) and a medium access control (MAC).

[0168] On the other hand, each layer can transmit data and additional parameters for data transmission to an upper or lower layer of a corresponding layer through a service access point (SAP). For example, the LLC layer can receive information on data, a source address, a destination address, etc. from an upper layer through a link service access point (LSAP). In addition, the MAC layer can deliver received data to an upper layer through a MAC SAP, and can receive data to be transmitted and additional parameters for data transmission from the upper layer.

[0169] When data to be transmitted in the layer structure is data requiring a low delay time, the MAC layer can receive corresponding data and related parameters from an upper layer in the type of MA-UNITDATA.request. At this time, if the data to be transmitted is data requiring a low delay time, a corresponding indicator can be included when the data is transmitted from the upper layer to the MAC layer through the MAC SAP. For example, it can be delivered in the MA-UNITDATA.request including data requiring a low delay time. When the indicator of a corresponding low delay time is included, the corresponding MA-UNITDATA.request can include a meter as shown in Table 1 below.

[0170] [Table 1]

[0171]

[0172] Each parameter included in the DA-UNITDATA.request can be as shown in Table 2 below.

[0173] [Table 2]

[0174]

[0175] Alternatively, a separate traffic stream (TS) can be defined for data requiring a low delay time. At this time, in order to manage data belonging to a special TS, a MAC layer management entity SAP (MLME SAP) can receive Quality of Service (QoS) information required for an ID of a special traffic stream from a station management entity (SME). At this time, the MAC layer can receive information on the corresponding TS from the SME in the type of MLME-ADDTS.request.

[0176] In one aspect, when the AP or the STA supports a low delay transmission operation for frames requiring a low delay time, an internal variable can be designated in the corresponding terminal. For example, one of the Management Information Base (MIB) values showing whether a low delay operation is activated can be managed in the terminal. At this time, the corresponding MIB value can be dot11rTWTActivated. At this time, the low delay operation is an operation for delay-sensitive traffic (e.g., delay-sensitive traffic) or a frame for transmitting a frame, and the delay-sensitive traffic or frame can be a preset traffic or frame. For example, the delay-sensitive traffic or frame can be indicated by a TID (or Access Category (AC)) indicating that the corresponding traffic or frame is delay-sensitive traffic or a frame.

[0177] In one aspect, the AP can be an AP included in an AP Multi-link Device (MLD). The STA can be a STA included in a STA MLD. The AP MLD and the STA MLD can be configured as described below in Figure 10

[0178] Figure 10 A conceptual diagram illustrating an AP MLD and a STA MLD structure performing a multi-link operation according to an embodiment of the present application.

[0179] Referring to Figure 10 ​, an AP Multi-link Device (MLD) can be a device including one or more wireless Access Points (APs) and can be a device connected to an upper layer through one interface. That is, an AP MLD can be connected to a Logical Link Control (LLC) layer through one interface. The plurality of APs included in the AP MLD can share some functions of the MAC layer. Each of the APs in the AP MLD can operate on a different link. An STA MLD can be a device including one or more non-AP STAs and can be a device connected to an upper layer through one interface. That is, an STA MLD can be connected to an LLC layer through one interface. The plurality of STAs included in the STA MLD can share some functions of the MAC layer. In addition, the STA MLD can be referred to as a non-AP MLD. At this time, the AP MLD and the STA MLD can perform a multi-link operation using a plurality of separate links. That is, when the AP MLD includes a plurality of APs, each AP constituting a separate link can perform a frame transmission / reception operation using a plurality of links with each terminal included in the STA MLD. In this case, each link can operate in a 2.4 GHz, 5 GHz, or 6 GHz band, and a bandwidth extension operation can be performed in each link. For example, when the AP MLD sets one link in a 2.4 GHz band and two links in a 5 GHz band, a frame transmission of 40 MHz bandwidth can be performed in a bandwidth extension manner in the 2.4 GHz band, and a frame transmission of a maximum of 320 MHz bandwidth can be performed using a non-continuous bandwidth in each link using the 5 GHz band.

[0180] On the other hand, in the AP MLD or the STA MLD, due to an interference problem inside the device, another terminal can not perform a reception operation during a transmission operation of one terminal inside the MLD. In this case, when one AP or terminal in the MLD performs a transmission operation, another AP or terminal in the MLD performs a reception operation, which is referred to as Simultaneous Transmit and Receive (STR). The AP MLD can perform an STR operation for all links. Alternatively, the STR operation can not be performed in some links of the AP MLD. The AP MLD can access a terminal MLD capable of performing the STR operation and can access an MLD incapable of performing the STR operation for some or all links. In addition, in the AP included in the AP MLD, a terminal not belonging to the MLD (for example, an IEEE 802.11a / b / g / n / ac / ax terminal or an IEEE 802.11be terminal not of the MLD type) can be additionally accessed.

[0181] The AP MLD and the STA MLD can perform a negotiation procedure for multi-link operation. At this time, the negotiation procedure for multi-link operation can be performed in the Figure 5 described scanning and access procedure. The AP MLD and the STA MLD can perform a negotiation procedure for multi-link operation in the Figure 5 described scanning and access procedure. When the negotiation procedure for multi-link operation is performed in the access procedure, the AP MLD and the STA MLD can operate as follows.

[0182] Figure 11 A conceptual diagram illustrating an access procedure between an AP MLD and a STA or a STA MLD according to an embodiment of the present application is shown. In Figure 11 , a description repeated with the access procedure described in Figure 5 will be omitted.

[0183] Referring to Figure 11 , the AP MLD and the STA MLD can perform a negotiation procedure for multi-link operation in the scanning and access procedure. For example, in the scanning procedure described in Figure 5 , the AP included in the AP MLD can transmit a beacon frame including an indicator indicating available multi-link operation, the number of available links, available multiple link information, etc. Alternatively, when the AP MLD transmits a probe response frame of a broadcast frame type, the corresponding probe response frame can be transmitted including an indicator indicating available multi-link operation, the number of available links, available multiple link information, etc. The terminal belonging to the STA MLD can transmit a probe request frame including an indicator indicating available multi-link operation. When the STA MLD is to perform a negotiation procedure for multi-link operation, operation information about all APs belonging to the AP MLD can be additionally requested. When the STA belonging to the STA MLD requests information about all APs belonging to the AP MLD, the probe request frame can be transmitted including a corresponding request indicator. The AP belonging to the AP MLD can confirm the corresponding request indicator in the probe request frame, and transmit a probe response frame including all parameters for multi-link operation use (e.g., information of the corresponding AP and information of other APs belonging to the corresponding AP MLD, etc.). In this case, the number of available links, link information, etc. at the time of multi-link operation can be included in the all parameters.

[0184] In the scanning process, the STA MLD which confirms whether the AP MLD is operating in the multi-link operation and uses the link information can perform an access procedure with the AP MLD. At this time, the AP MLD and the STA MLD can simultaneously perform a negotiation procedure for the multi-link operation. That is, an indicator indicating that the multi-link operation of an arbitrary terminal (e.g., STA1) belonging to the STA MLD is available and a request indicator requesting the multi-link operation can be transmitted while the access request frame is transmitted from the arbitrary AP (e.g., AP1) belonging to the AP MLD. The AP receiving the access request frame from the terminal can confirm the indicator requesting the multi-link operation, and when the AP can operate in the multi-link operation, an access response frame allowing the multi-link operation including the link information for the multi-link operation and the parameters used in each link, etc. can be transmitted to the corresponding terminal. The parameters for the multi-link operation can include one or more of the frequency band of each link used, the bandwidth extension direction, the target beacon transmission time (TBTT), and whether the STR operation is available. The AP MLD and the STA MLD which exchange the access request frame and the response frame and confirm the use of the multi-link operation can perform a frame transmission operation using the plurality of links included in the plurality of APs of the AP MLD and the plurality of terminals included in the STA after the corresponding access procedure.

[0185] In an aspect, when the AP or the AP MLD supports a low-delay transmission operation for a frame requiring a low-delay time, one or more links can be limited to access only to a terminal capable of performing the corresponding operation. That is, in order to effectively perform a channel reservation procedure and a transmission procedure for a low-delay operation, access of only a terminal which decodes and understands the corresponding operation can be allowed in a special link. In this case, the low-delay transmission operation can be a low-delay transmission operation using a TWT operation. For example, when a target wake time service period (TWT SP) is included in a beacon to transmit a reservation time for a low-delay terminal, in a STA supporting a low-delay operation using a TWT function, the STA can not be able to perform a channel contention procedure for frame transmission when the STA is not reserved at the corresponding TWT SP time. Conversely, a STA not supporting the corresponding function can also perform a channel access procedure for frame transmission in the corresponding TWT SP. At this time, due to the channel access operation of the STA not supporting the low-delay function using the TWT operation, a situation in which the transmission of a frame reserved to be transmitted to the corresponding TWT SP is suspended or collided can occur. Thus, the required delay time of the frame requiring a low-delay time can not be satisfied. In order to prevent such a situation, the AP and the AP MLD can designate a special link to be used only for a terminal performing a channel reservation procedure according to a low-delay operation.

[0186] On the other hand, when the AP or the AP MLD designates a link for terminals supporting only low latency operation, an access request of an STA not supporting a corresponding function can be rejected as follows.

[0187] In this case, the low latency operation is an operation for transmitting a latency sensitive traffic (e.g., latency sensitive traffic) or frame, and the latency sensitive traffic or frame can be a preset traffic or frame. For example, the latency sensitive traffic or frame can be indicated by a TID (or Access Category (AC)) as a traffic or frame for which a corresponding traffic or frame is latency sensitive. Alternatively, the latency sensitive traffic or frame can mean a traffic or frame to be transmitted within a certain latency time, and can be indicated by a TID (or Access Category (AC)).

[0188] The TWT schedules STAs to operate at different times so that the STAs can remain awake for BSS management activities in order to minimize contention and reduce the time required for STAs using power save mode to remain awake. The TWT operation can be an individual TWT set by the AP individually or a broadcast TWT. That is, the AP can set whether to perform the TWT operation individually per STA or set whether to perform the TWT operation for a plurality of STAs through the broadcast TWT and transmit to a non-AP STA, and the non-AP STA receives a schedule for performing the TWT operation from the AP, the TWT operation can be performed during an interval of a TWT service period (SP).

[0189] In this case, when the broadcast TWT operation is used for the low latency operation, it can be referred to as a restricted TWT operation. That is, the broadcast TWT operation is performed as the restricted TWT operation by the non-AP STA supporting the restricted TWT operation by a special parameter of a capability element (e.g., when a special element is set to "1") and by the corresponding beacon frame set as a frame for the restricted TWT operation by a special field of a beacon frame. In this case, the SP set for the broadcast TWT can be for the restricted TWT operation.

[0190] In this case, the restricted TWT as the TWT operation for requesting transmission of a low latency frame can be used for improved medium access protection for a latency sensitive frame and for supporting resource reservation.

[0191] A non-AP STA configured with a TWT SP by an AP STA cannot transmit, within the TWT SP, frames to the AP STA other than frames agreed upon by the individual TWT.

[0192] Hereinafter, the restricted TWT operation for low latency operation can be referred to as TWT operation.

[0193] Figure 12 A first embodiment of an operation of restricting an access procedure of a terminal for performing a low latency function according to an embodiment of the present application is illustrated. In Figure 12 In the following description, the description of the same procedure as the access procedure described in Figure 5 and Figure 11 will be omitted.

[0194] Referring to Figure 12 , the AP MLD can include a plurality of APs, and each of the APs can operate a link. At this time, the AP MLD can designate one or more of the operated links as a link for a terminal supporting only a low latency operation. For example, among the APs belonging to the AP MLD, the link operated by the AP 1 can be designated as a link for a terminal supporting only a low latency operation. Alternatively, an AP not belonging to the AP MLD can operate only for a terminal supporting a low latency operation.

[0195] The AP or the AP MLD can include an indicator indicating whether a low latency operation is supported in a probe response frame transmitted in the type of a beacon frame or a broadcast frame. The low latency operation can be a low latency operation using the TWT function described in Figures 18 to 19 and Figures 21 to 23 .

[0196] For example, when the corresponding AP or AP MLD supports the low latency operation, a field indicating whether the low latency operation is supported is represented as 1 and transmitted in the capability element included in the corresponding beacon frame and broadcast probe response frame. In addition, the beacon frame and the broadcast probe response frame are transmitted including an indicator indicating that the corresponding link is a link for low latency terminals only. For example, the corresponding beacon frame or broadcast probe response frame contains an EHT operation information element, and the corresponding EHT operation information element contains an indicator (e.g., an rTWT field required, etc.) informing that support for the low latency operation is required. Alternatively, the IBSS STA subfield and the ESS subfield values in the capability information field of the corresponding beacon frame or broadcast probe response frame are both set to 1, so that an existing STA that does not support the low latency operation cannot recognize the BSS type of the corresponding AP. As still another example, the beacon frame or the broadcast probe response frame can further include an Interworking information element, and the Interworking information element can indicate that the link belonging to the access network type subfield in the access network option field is a link for the low latency operation. In the case of a STA MLD or a STA that does not belong to the STA MLD, in which the low latency operation is not supported, the indicator indicating that the corresponding beacon frame or broadcast probe response frame is a link for low latency terminals only can be confirmed, and the STA or the STA MLD that confirms the corresponding indicator can not perform an active scanning procedure and an access procedure with the corresponding AP or AP MLD.

[0197] The STA MLD or the STA that does not belong to the STA MLD can attempt a scanning and access procedure with the AP or the AP MLD as described. Figure 5 For example, the STA MLD or the STA can transmit a probe request frame to the AP or the AP MLD. In this case, the STA or the STA MLD can include function information supported by the corresponding STA or STA MLD in the corresponding probe request frame. For example, when the corresponding STA or STA MLD supports the low latency operation, an indicator field indicating that the corresponding function is supported can be set to 1 and transmitted to the capability element of the corresponding probe request frame. Conversely, when the corresponding STA or STA MLD does not support the corresponding function, a field indicating whether the low latency operation is supported can be set to 0 and transmitted to the capability element of the probe request frame.

[0198] The AP or AP MLD can receive the respective probe request frame from the STA or STA MLD and can confirm whether the respective STA or STA MLD supports the low latency operation. When it is confirmed that the STA or STA MLD does not support the low latency operation, the AP or AP MLD can not transmit the probe response frame as a response to the probe request frame. Alternatively, the AP or AP MLD can indicate that the respective AP is an AP supporting only low latency terminals while transmitting the probe response frame as a response to the probe request frame. The indicator indicating the AP supporting only low latency terminals can be an indicator indicating a link for only low latency terminals as described above. If the STA or STA MLD does not support the low latency operation, the indicator indicating the link for only low latency terminals can be confirmed in the probe response frame, and the respective AP or AP MLD can not perform an access procedure with the STA.

[0199] On the other hand, when the STA supports the low latency operation or when the indicator of the beacon frame and the probe response frame cannot be deciphered, the STA can transmit an access request frame to the AP based on the result of performing scanning as shown in FIG. 6. Figure 5 The AP in which the access request is received can transmit an access response frame as a response to the access request frame. If the STA transmitting the access request frame supports the low latency operation, the access response frame can include an indicator for receiving the access request. Conversely, if the STA transmitting the access request frame does not support the low latency operation, the access response frame can include an indicator for rejecting the access request. At this time, the AP can indicate that the access request is rejected due to the respective STA not supporting the low latency operation in a status code field of the access response frame rejecting the access request. For example, the probe response frame can be transmitted by setting a field value (e.g., 133, etc.) indicating LOW_LATENCY_SUPPORT_NEEDED in the status code field. When the AP included in the AP MLD rejects the respective access request as a response to the access request frame, other link information for proposing access to other links can also be included. Information for not a link for only low latency terminals but a general link can be transmitted in a type of a neighbor report information element. The neighbor report information element can include at least one of a BSSID, a channel, and an operation category, and timing information.

[0200] In the STA receiving the access response frame including the rejection indicator from the AP, the content of the received access response frame can be confirmed and it can be confirmed that the access request is rejected. At this time, the STA can confirm that the corresponding link requires support for low latency operation by confirming the value of the status code field in the access response frame, and can confirm whether the corresponding access response frame contains the proximity report information element. If the proximity report information element is contained in the response frame, the STA can confirm the proposed BSS information by confirming the corresponding content. The STA can confirm other link information included in the proximity report information element, and move to the channel indicated in the corresponding information, and perform the access procedure described above with the AP of the corresponding link. Figure 5 or Figure 11 the access procedure described above.

[0201] On the other hand, when the low latency operation is based on the TWT operation of the wireless LAN operation, the AP or the AP MLD constituting the link for only the low latency terminal can exceptionally allow access of the terminal supporting the TWT function for low power consumption operation. When access of the existing wireless LAN terminal supporting the TWT function is allowed, the AP or the AP MLD can receive or reject the access request of the STA as follows.

[0202] Figure 13 A second embodiment of the operation for performing the access procedure of the low latency restricted terminal according to an embodiment of the present application will be illustrated. In Figure 13 the connection procedure described in Figure 5 , Figure 11 and Figure 12 will be omitted.

[0203] Referring to Figure 13 , the AP MLD can include a plurality of APs, and each AP can operate a link. At this time, the AP MLD can designate one or more operated links as a link for only a terminal supporting a low latency operation using a TWT function. For example, among the APs belonging to the AP MLD, the link operated by the AP 1 can be designated as a link for only a terminal supporting a low latency operation using a TWT function. Alternatively, an AP not belonging to the AP MLD can be operated for only a terminal supporting a low latency operation using a TWT function.

[0204] The AP or the AP MLD can transmit a probe response frame including an indicator indicating support for low latency operation using the TWT function in the type of a beacon frame or a broadcast frame. For example, an indicator indicating whether low latency operation using the TWT function is supported is set to 1 and transmitted to a capability element in the beacon frame or the broadcast probe response frame. In addition, the beacon frame or the broadcast probe response frame includes an indicator indicating that the corresponding link is a link for terminals supporting only the TWT function and is transmitted. For example, the corresponding beacon frame or broadcast probe response frame includes an EHT operation information element, and the corresponding EHT operation information element includes an indicator indicating that TWT operation support is required (e.g., a TWT operation required field, etc.) and is transmitted. Alternatively, as described in Figure 12 the support for the TWT function can be requested through an access network type subfield in an access network option field in a capability information field or an interworking information element. In the case of a STA MLD or a STA not belonging to the STA MLD, which is a STA not supporting the TWT operation, an indicator indicating that the link is for terminals supporting only the TWT function in the corresponding beacon frame or broadcast probe response frame can be confirmed, and the STA or the STA MLD confirming the indicator can not perform an active scanning procedure and an access procedure with the corresponding AP or AP MLD. On the other hand, the AP or the AP MLD sets the required TWT field in the HE operation information element in the beacon frame or the broadcast probe response frame to 1, so that it can be indicated to a STA or a STA MLD supporting the TWT function itself but not supporting low latency operation using the TWT function that a negotiation procedure for the TWT operation is required.

[0205] The STA MLD or the STA not belonging to the STA MLD can attempt a scanning and access procedure with the AP or the AP MLD, as Figure 5described above. For example, the STA MLD or STA can transmit a probe request frame to the AP or AP MLD. In this case, the STA or STA MLD can include the function information supported by the corresponding STA or STA MLD in the corresponding probe request frame. For example, if the corresponding STA or STA MLD supports TWT, an indicator field (e.g., TWT Requester Support field) indicating that the corresponding function is supported is set to 1 and transmitted into the HE Capabilities element in the corresponding probe request frame. In addition, when the corresponding STA or STA MLD supports a low latency operation using the TWT function, an indicator indicating that the corresponding function is supported can be additionally included and transmitted to the corresponding probe request frame. For example, the indicator field indicating that the corresponding function is supported is set to 1 and transmitted into the EHT Capabilities element of the probe request frame. Conversely, if the corresponding STA or STA MLD does not support the corresponding function, the field indicating whether the TWT function is supported and the field indicating whether the low latency operation using the TWT function is supported are set to 0 and transmitted in the HE Capabilities element and the EHT Capabilities element in the probe request frame.

[0206] The AP or AP MLD can receive the corresponding probe request frame from the STA or STA MLD, and can confirm whether the corresponding STA or STA MLD supports the TWT function and the low latency operation using the TWT function. If it is confirmed that the STA or STA MLD does not support the TWT function, the AP or AP MLD can not transmit a probe response frame as a response to the probe request frame. Alternatively, the AP or AP MLD can indicate that the corresponding AP needs to support the TWT function while transmitting the probe response frame as a response to the probe request frame. The indicator indicating that the TWT function needs to be supported can be an indicator indicating that the TWT operation described above needs to be supported. If the STA or STA MLD does not support the TWT function, the indicator requesting the TWT function in the probe response frame can be confirmed, and the access procedure can not be performed with the corresponding AP or AP MLD. At the same time, the AP or AP MLD sets the required TWT field in the HE Operation Information element of the probe response frame to 1, so that it can be indicated to the STA or STA MLD that supports the TWT function itself but does not support the low latency operation using the TWT function that a negotiation procedure for the TWT operation is required.

[0207] On the other hand, if the STA or STA MLD supports the TWT function, or the indicator in the beacon frame and the probe response frame cannot be decoded, the STA performs an access procedure based on the function information supported by the corresponding STA or STA MLD, as described above. Figure 5The STA can transmit an access request frame to the AP as a result of the illustrated execution of the scan. The AP that receives the access request can transmit an access response frame as a response to the access request. The access response frame can include an indicator for receiving the access request if the STA that transmitted the access request frame supports the TWT operation. At this time, by setting the required TWT field in the HE operation information element in the access response frame to 1, it is possible to indicate to the STA or STA MLD that supports the TWT function itself but does not support the low-delay operation using the TWT function that the negotiation procedure for the TWT operation is required. Conversely, if the STA that transmitted the access request frame does not support the TWT operation, the access response frame can include an indicator that rejects the access request. At this time, the AP can indicate in the status code field of the access response frame that rejects the access request that the access request is rejected due to the corresponding STA not supporting the TWT function. For example, the probe response frame can be transmitted with a field value (e.g., 134) representing TWT_REQUESTER_SUPPORT_NEEDED set in the status code field. When the AP included in the AP MLD rejects the corresponding access request as a response to the access request frame, as Figure 12 indicated, it can also include other link information in order to propose access to other links. Information for a general link, not only a link for a low-delay terminal, can be transmitted in a type of proximity report information element. The proximity report information element can include at least one of a BSSID, a channel, and an operation category and timing information.

[0208] The STA that receives the access response frame including the rejection indicator from the AP can confirm the contents of the received access response frame and can confirm that the access request is rejected. At this time, the STA can confirm that the corresponding link requires support for the TWT operation by confirming the value of the status code field in the access response frame, and can confirm whether the corresponding access response frame contains a proximity report information element. If the response frame contains the proximity report information element, the STA can confirm the corresponding contents as Figure 12 indicated and perform an access procedure with the AP indicated in the corresponding information element.

[0209] On one hand, the AP or AP MLD can set the TWT requirement field in the HE operation element of the transmission to 1. In this case, if the STA MLD or a STA that is not a STA MLD supports TWT functionality but not low-latency operation using TWT functionality, a negotiation process for TWT operation can be recognized after the access procedure with the corresponding AP or AP MLD. Therefore, the corresponding STA or STA MLD can perform a negotiation process for TWT operation with the AP during or after the access procedure. After negotiating the corresponding TWT operation, frame transmission operation can be omitted outside the time specified in the negotiated TWT SP. Simultaneously, when both the STA and STA MLD support TWT operation and low-latency operation using TWT functionality, a separate negotiation process for TWT operation can be omitted after the access procedure. In this case, the STA or STA MLD can confirm the TWT SP for low-latency operation transmitted by the AP in the beacon frame or broadcast probe response frame, and can end the frame transmission process before the start time of the corresponding TWT SP. That is, if a STA or STA MLD supporting low-latency operation does not negotiate with the AP in advance, it may not perform frame transmission during the TWT SP time period used for low-latency operation. In other words, frame transmission can be terminated before the start time of the TWT SP used for low-latency operation.

[0210] On one hand, an AP MLD, or an AP not belonging to an AP MLD, can measure information about the frame transmission delay time for the links it uses. The specific transmission delay time can be periodically updated and stored in the AP for a certain period of time (e.g., 100ms). In the case of an AP MLD that supports low-latency transmission operation, it can provide statistical information related to the transmission delay time of frames transmitted on each link used by the corresponding AP MLD. That is, each AP belonging to an AP MLD can provide statistical information related to the transmission delay time of frames transmitted by the corresponding AP and other APs belonging to the same AP MLD. The statistical information can include and be transmitted in the AP MLD, such as beacon frames, probe response frames, access response frames, etc. If a frame requests low latency, the STA that confirms the statistical information can use the corresponding information to... Figure 5 and 12 to Figure 13 The operation involves the AP performing the access procedure, which is part of the AP MLD. Simultaneously, when the STA MLD confirms the statistical information and has a frame requesting low latency, it uses the corresponding information to... Figure 5 and Figures 11 to 13 The STA MLD can perform access procedures with the AP MLD and negotiation procedures for multi-link operations. Additionally, the STA MLD can determine, based on relevant information, which link to transmit frames requiring low latency.

[0211] The statistical information can be transmitted in the type of a Measurement Report information element. The information element related to the transmission delay time can be STA statistics in which a measurement type field of the Measurement Report information element is set to 7, in which an average channel access time (Access Delay) of each access category (AC) can be included in the corresponding BSS. Or, the number of retransmissions according to each user priority (UP) value can be included. Or, the Measurement Report information element can include the average transmission time and the transmission success probability of each AC as described below.

[0212] Figure 14 A block diagram illustrating a link state information element including transmission state information in a corresponding link according to an embodiment of the present application.

[0213] Reference Figure 14 The Measurement Report information element including the transmission state information on the link can include an element ID field, a length field, a field indicating the type of information of the measurement, a field indicating the period of the measurement, a field indicating the measurement group information, and a field indicating the data information of the measurement, etc. At this time, the element ID field, the length field, the field indicating the type of information of the measurement, etc. can be set to be the same as or similar to the STA statistics. The measurement group information field can be set to 17 to be displayed as the information on the transmission delay time transmitted from the corresponding AP. The measurement information includes at least one of the average transmission time of all frames transmitted on the corresponding link, the average transmission time of each AC of the frames transmitted on the corresponding link, the dispersion of the average transmission time of each AC of the frames transmitted on the corresponding link, the upper 95% value in the transmission time of each AC of the frames transmitted on the corresponding link, the transmission failure probability of all frames transmitted on the corresponding link, and the transmission failure probability of each AC of the frames transmitted on the corresponding link. In this case, the transmission time can be calculated from the time when the frame to be transmitted is generated from the corresponding AP to the reception time of the ACK frame according to the completion of the transmission of the corresponding frame. Or, when the ACK frame according to the completion of the transmission of the corresponding frame is received from the time when the frame to be transmitted is generated from the corresponding AP, the transmission time can be calculated as the transmission end time of performing the transmission or performing the retransmission before the corresponding ACK is received. The transmission failure probability can be calculated by "(the number of times of failing in the transmission exceeding the frame retransmission limit number) / (the number of times of receiving the ACK for the frame transmission + the number of times of failing in the transmission exceeding the frame retransmission limit number)" in the corresponding measurement period.

[0214] In an aspect, the STA or STA MLD that wants to transmit a frame requiring a low delay time can indicate information for a requested delay time, etc. of the corresponding frame to the AP or AP MLD. At this time, the frame having a low delay time can be specified as a special Traffic Stream (TS). If the frame requiring a low delay time is data allocated to a special TS, the STA or STA MLD can perform a negotiation procedure for adding a TS for the corresponding data with the AP or AP MLD. For example, in the STA, a TS addition request frame for adding a TS for traffic requiring a low delay time is transmitted to the AP, and in the AP, as a response to the corresponding TS addition request frame, a procedure of transmitting a TS addition response frame can be performed. Through the corresponding TS addition negotiation operation, the STA transmits one or more of delay time information of data request for the TS that wants to be added, data size, requested transmission rate of the corresponding data to the AP.

[0215] The STA or STA MLD that wants to transmit a frame requiring a low delay time can perform a negotiation procedure for a low delay operation with the AP or AP MLD. The negotiation procedure for a low delay operation can be performed identically or similarly to the negotiation procedure for a TWT operation. That is, when the STA transmits a request frame for performing a low delay operation to the AP, the corresponding request frame can be a TWT request frame. A response frame for a low delay operation transmitted from the AP to the STA can be a TWT response frame.

[0216] In an aspect, information including a requested delay time, etc. of a frame that wants to be transmitted can be transmitted to a request frame for a low delay operation. When the low delay operation request frame includes a requested delay time and frame generation information, the corresponding low delay request frame can be in the following Figure 15 will be described.

[0217] Figure 15 FIG. 1 illustrates a structure of a low delay operation request frame requesting a low delay operation using a Target Wake Time (TWT) function according to an embodiment of the present application.

[0218] Reference will now be made to Figure 15, the frame requesting the low latency operation can be configured by the type of the TWT request frame. Accordingly, the corresponding request frame can include a TWT information element. The TWT information element included in the low latency operation request frame can include an element ID field, a length field, a control field, and a parameter field for the low latency operation using the TWT operation. As fields regarding the channel measurement operation, an NDP paging indicator field, a field indicating whether to switch the PS mode of the TWT responder, a field indicating the TWT negotiation type, a field indicating that the TWT schedule adjustment is possible, a field showing the request delay time unit, etc. can be included. In the control field, other fields than the field showing the unit of the request delay time can be set in the same setting manner as when the broadcast TWT operation is negotiated. For example, in the TWT request frame for the low latency operation, the NDP paging indicator field can be set to 0, the field indicating whether to switch the PS mode of the TWT responder can be set to 0, thereby being set not to use the corresponding function. The field indicating the TWT negotiation type is set to 3, so that the corresponding TWT operation is a request frame for negotiating the broadcast TWT type in the beacon frame can indicate the type of the TWT SP for transmitting the low latency terminal as periodic. The unit field of the request delay time indicates the unit of the maximum delay time requested by the frame on average for the corresponding low latency operation, and indicates the unit of 256 µs when the corresponding field is 0, and the unit of 32 µs when 1.

[0219] The parameter field for the low latency operation using the TWT operation can include one or more of a request type field, a field indicating a time point at which low latency traffic is predicted to occur, a required delay time field, a valid number field of a low latency time period of the TWT operation based on the request, and a broadcast TWT information field.

[0220] The request type field can include a field showing whether it is a TWT request frame, a TWT setup indication field, a trigger field, an operation type field, an operation manner field during a broadcast TWT time (or a broadcast TWT SP), an index field for a period of a required low delay time, a field indicating that the corresponding TWT operation is a TWT for a low delay operation, etc. For example, the request type field can include a special field indicating that the TWT operation of the corresponding frame is a restricted TWT operation. In this case, according to the value of the special field, the frame that can be transmitted during the TWT SP according to the TWT operation can be restricted to a special frame for a downlink frame, or a broadcast SP can be set as a restricted TWT SP. That is, if the value of the special field (e.g., a broadcast TWT recommendation field) is '1', the frame that can be transmitted during the TWT SP is restricted to a special frame for a downlink frame, and the value of the special field is '4', the broadcast TWT SP can be set as a restricted TWT SP.

[0221] At this time, in the request type field, for other fields except for the operation manner field during the broadcast TWT time, the index field for a period of a required low delay time, and the field indicating that the corresponding TWT operation is a TWT for a low delay operation, the same type as the TWT information element included in the existing broadcast TWT request frame can be set.

[0222] The operation manner field during the broadcast TWT time is used when frame transmission during the corresponding TWT SP time is to be restricted. For example, when only a type of a response frame to a downlink frame (e.g., an ACK or BlockAck frame to a downlink data frame, or an uplink frame transmitted in response to a trigger frame) is to be transmitted during the corresponding TWT SP, the corresponding field can be set to 1.

[0223] In addition, when requesting an AC to be restricted during a TWT SP of a corresponding low latency terminal, the corresponding field can be set to 4. When requesting an additional protection operation (e.g., a Quiet Time Setup frame or an RTS frame or an MU-RTS frame, etc.) for protecting a corresponding SP at a TWT SP start time point of a corresponding low latency terminal, the corresponding field can be set to 5. Alternatively, when requesting that communication between STAs can be made during a corresponding TWT SP, the corresponding field can be set to 6. An index field for a period of a requested low latency time can be displayed together with the above-described effective number field for a period of a low latency time to show an SP period for a requested TWT-based low latency operation. For example, an SP period for a requested TWT-based low latency operation can be expressed as "(effective number field value for a period of a low latency time) x 2^(index field value for a period of a low latency time)". Further, when a field indicating that a corresponding TWT operation is a TWT for a low latency operation is set to 1, it can be indicated that the corresponding TWT information element is for a low latency operation.

[0224] That is, when a TWT SP is scheduled, a non-AP STA transmits and receives only limited frames (e.g., frames requiring a low latency or being sensitive to a latency) during the TWT SP and does not transmit and receive other frames, or preferentially transmits and receives limited frames (e.g., the limited frames can have a high repair order).

[0225] Meanwhile, a field indicating a time point at which low latency traffic is predicted to occur can indicate a time point at which a frame requiring a corresponding low latency time is predicted to occur. A delay time field requiring a delay time as a maximum delay time required in a corresponding frame can be expressed together with the above-described unit field for a delay time required to indicate a delay time required in uplink and downlink for a corresponding type of frame. A broadcast TWT information field is set in the same manner as a field setting manner in a conventional broadcast TWT operation. Alternatively, when a corresponding TWT operation requests a TWT SP allowing only a special AC and an AC having a higher priority order than this (e.g., when an operation manner field of a TWT time period is set to 4), the broadcast TWT information field can include an AC or a TID to be restricted, instead of a broadcast TWT ID field.

[0226] That is, the broadcast TWT information field can include information related to a TID, a TWT of which is restricted by transmission of a TWT frame for a low latency operation.

[0227] Specifically, the broadcast TWT information field can include a field including information related to a TID. The field including information related to a TID can include a control field, a DL bitmap (or a restricted TWT DL TID bitmap) field, and a UL bitmap (or a restricted TWT UL TID bitmap) field.

[0228] The control field can include a DL bitmap valid field (or a DL TID bitmap valid field), a UL bitmap valid field (or a UL TID bitmap valid field), and a reserved field.

[0229] The DL bitmap valid field, as a field indicating validity of the DL bitmap field, when set to '0', indicates that downlink frames for all TIDs are delay-sensitive traffic, and when set to '1', downlink traffic for a TID corresponding to a value of '1' of the DL bitmap is delay-sensitive traffic, and downlink traffic for a TID corresponding to a value of '0' is shown as delay-insensitive traffic.

[0230] The UL bitmap valid field, as a field indicating validity of the UL bitmap field, when set to '0', indicates that uplink frames for all TIDs are delay-sensitive traffic, and when set to '1', uplink traffic for a TID corresponding to a value of '1' of the UL bitmap is delay-sensitive traffic, and uplink traffic for a TID corresponding to a value of '0' is shown as delay-insensitive traffic. Meanwhile, information on a low-delay period based on a TWT operation can be set to a generation period of a frame requiring a low-delay time to be transmitted in a corresponding low-delay operation.

[0231] On the other hand, if the TS negotiation of traffic requiring a low-delay time is ended before the negotiation process of a low-delay operation using the TWT function described above, the negotiation process of the low-delay operation does not include a request for a delay time or the like. In this case, the low-delay operation request frame of the corresponding low-delay operation can be configured as shown in the following Figure 16

[0232] Figure 16 FIG. 13 illustrates a structure of a low-delay operation request frame requesting a low-delay operation using a TWT function according to a second embodiment of the present application. In Figure 16 the same description as Figure 15 in FIG. 12 is omitted.

[0233] Reference will now be made to Figure 16 ​, the delay operation request frame requesting low latency operation using the TWT function can be constituted similarly to the TWT operation request frame for negotiating broadcast TWT operation. Accordingly, the TWT information element can be included in the corresponding frame, and the TWT information element can include an element ID field, a length field, a control field, and a TWT parameter information field. At this time, the element ID field, the length field, and the control field can be set the same as those set for the request frame for negotiating broadcast TWT.

[0234] The TWT parameter information field can include a request type field, a TWT field, a minimum time for which a STA remains awake during a TWT time, a valid number of intervals between TWT SPs, and broadcast TWT information. In the request field, other fields except for the operation mode field during the TWT time and the field indicating that the corresponding TWT operation is a TWT for low latency operation can be set the same as in the existing broadcast TWT setting method. The operation mode field during the TWT time and the field indicating that the corresponding TWT operation is a TWT for low latency operation can be set as shown in Figure 15 . Alternatively, when the exchange of the corresponding TWT operation request frame is transmitted after the negotiation process for adding a TS, a TWT SP limited to a special traffic stream ID (TSID) can be requested. At this time, the operation mode field during the TWT time can be set to 7. As described in Figure 15 , an indication field indicating that the corresponding TWT request frame is a TWT request frame for low latency operation can be added to the request field. The broadcast TWT information field can be set the same as in the low latency operation request frame using the TWT described in Figure 15 . Alternatively, when the corresponding TWT operation request frame requests to provide a TWT SP limited to a special TSID (for example, when the operation mode field during the TWT time is set to 7), the broadcast TWT information field can include lower 3 bits of the TSID to be limited, instead of the broadcast TWT ID field.

[0235] Meanwhile, as described in Figure 15Or 16, the AP or the AP MLD can confirm the contents of the low-delay operation request frame using the TWT function. According to the request delay time and traffic generation period information confirmed in the request frame, one of the broadcast TWTs for low-delay operation allocated by the AP can be allocated. Alternatively, a TWT SP for low-delay operation can be allocated by generating a new broadcast TWT for only the corresponding traffic. When the broadcast TWT is allocated in the described manner for a low-delay operation request using the corresponding TWT operation, a low-delay operation response frame can be transmitted as a response to the low-delay operation request frame using the TWT operation. Alternatively, when the low-delay operation request cannot be received, a low-delay operation response frame rejecting the request can be transmitted. At this time, the low-delay operation response frame can be configured as follows.

[0236] Figure 17 A block diagram illustrating a low-delay operation response frame as a response to a request frame requesting low-delay operation using the TWT function is illustrated. At this time, descriptions of parts having the same configuration as the request frame requesting low-delay operation using the TWT function in Figure 15 and Figure 16 may be omitted.

[0237] Referring to Figure 17 , the low-delay operation response frame using the TWT can be constituted similarly to the response frame for the broadcast TWT operation. That is, the TWT information element included in the response frame for the broadcast TWT operation can be included. The TWT information element can include an element ID field, a length field, a control field, and a TWT parameter information field. At this time, the settings of the element ID field, the length field, and the control field can be the same as those set for the response frame for negotiating the broadcast TWT.

[0238] The TWT parameter information field can include a request type field, a TWT field, a minimum time for which a STA remains awake during a TWT time, a valid number of intervals between TWT SPs, and broadcast TWT information. In the request field, other fields except for the operation mode field during the TWT time and the field indicating that the corresponding TWT operation is a TWT for low-delay operation can be set in the same manner as the existing broadcast TWT setting manner. The field indicating that the corresponding TWT operation is a TWT for low-delay operation can be set in the same manner as Figure 15 and Figure 16 . As Figure 15 and Figure 16As shown, the operation mode field during the broadcast TWT time is used when limiting transmission during the corresponding TWT SP time. For example, when limiting transmission only to the type of response frame to the downlink frame (e.g., ACK or BlockAck frame to the downlink data frame, or uplink frame for transmission of response to the trigger frame) during the negotiated TWT SP period prompted by the corresponding response frame, the corresponding field can be set to 1. In addition, when setting the AC limiting transmission during the TWT SP period of the corresponding low latency terminal, the corresponding field can be set to 4. When performing an additional protection operation (e.g., Quiet Time Setup frame or RTS frame or MU-RTS frame, etc.) for protecting the corresponding SP at the TWT SP start time point of the corresponding low latency terminal, the corresponding field can be set to 5. Alternatively, when allowing communication between STAs during the corresponding TWT SP period, the corresponding field can be set to 6. Alternatively, when transmitting negotiation of the corresponding TWT operation after the negotiation process for adding TS, TWT SP limited to special traffic stream ID (Traffic Stream ID, TSID) can be requested. At this time, the operation mode field during the TWT time can be set to 7. As Figures 15 to 16 As described in the middle, the indication field indicating that the corresponding TWT request frame is a TWT request frame for low latency operation can be added to the request field. The broadcast TWT information field can be set to be the same as the response frame for the existing broadcast TWT negotiation. Alternatively, when limiting transmission only of frames having a special AC or higher priority order during the TWT SP period for the corresponding TWT operation (e.g., when the operation mode field during the TWT time is set to 4), the broadcast TWT information field of the response frame can also include the AC to be limited. Alternatively, if a special TSID (e.g., the operation mode field during the TWT time is set to 7) of the frame that can be transmitted to the corresponding TWT SP is to be limited, the broadcast TWT information field of the response frame can also include the TSID for limiting.

[0239] The negotiation process and operation process of the low latency operation using the TWT operation through the low latency operation request frame and the low latency operation response frame can be performed as follows.

[0240] Figure 18 A first embodiment of a process in which an AP or AP MLD and a STA perform a low latency operation using a TWT function according to an embodiment of the present application is illustrated.

[0241] Reference Figure 18The execution procedure of the low latency operation for the TWT operation can include a step of confirming the function of the low latency operation by the STA and the AP, a step of transmitting a low latency operation request frame from the STA, a step of transmitting a corresponding low latency operation response frame at the AP, thereby negotiating the use of the low latency operation using the corresponding TWT operation, and a step of performing the low latency operation from the AP to the broadcast probe response frame and the beacon frame, etc. allocating the TWT SP for the low latency operation. In this case, a step of additionally including the negotiation for the additional TS between the STA and the AP can be additionally included before the step of negotiating the use of the low latency operation using the corresponding TWT operation. In addition, a negotiation step for exchanging the period of the beacon frame in which the TWT SP allocated at the STA negotiation can be additionally included after the step of negotiating the use of the low latency operation using the TWT operation.

[0242] The step of confirming the function of the low latency operation can be performed in a scanning and access procedure between the AP or the AP MLD and the STA or the STA MLD. The scanning and access procedure can be performed through the procedure of Figure 5 and Figures 11 to 13 At this time, the AP and the STA can include an indicator of whether to support the low latency operation using the TWT function in the capability element and transmit. In addition, the AP or the AP MLD can include statistical information related to the transmission time of the frame transmitted on the corresponding link and transmit for all links applied to the beacon frame and the probe response frame, etc. The statistical information can be a measurement report information element. Alternatively, the statistical information can be a measurement report information element as shown in Figure 14 The STA or the STA MLD can confirm the statistical information transmitted by the AP or the AP MLD, and based on the information, the STA or the STA MLD can perform an access procedure with the AP or the AP MLD.

[0243] The negotiation procedure for performing the low latency operation using the TWT operation after the scanning and access procedure can start with the procedure of the STA transmitting a low latency operation request frame using the TWT operation to the AP. At this time, the low latency operation request frame using the TWT operation can be configured as shown in Figures 15 to 16 The corresponding request frame can be an action frame. The AP supporting the low latency operation can receive the low latency operation request frame using the TWT operation from the STA, and based on the received content, can confirm that the STA requests the TWT SP allocation for the frame requiring the low latency time. If the AP can allocate the TWT SP belonging to the request frame, the low latency operation response frame using the TWT can be transmitted from the AP as a response to the corresponding request frame. At this time, the TWT operation response frame can be configured as shown in Figure 17

[0244] ​Or, when the STA and the AP perform the negotiation procedure for adding the TS, in order to support that the corresponding TS can transmit a low-delay operation response frame using the unrequested TWT operation from the AP. In this case, the STA does not transmit a separate request frame after performing the negotiation for adding the TS, and can transmit a frame requiring a low-delay time to the corresponding TWT SP. At this time, if the STA does not perform the low-delay operation according to the parameters included in the unrequested low-delay operation response frame, the low-delay operation is released by a TWT release frame, and a low-delay operation request frame using a new TWT operation is transmitted, and the low-delay operation based on the TWT operation can be requested to the AP.

[0245] When the low-delay operation negotiation procedure using the TWT operation ends, the AP can allocate a broadcast TWT ID to the TWT SP to be allocated to the corresponding STA. The broadcast TWT ID can be received through the low-delay operation response frame described in the Figure 17 At this time, a plurality of STAs can be allocated the same TWT ID. The low-delay operation method using the TWT operation can be performed similarly to the operation method of the broadcast TWT. That is, the TWT element of the broadcast TWT SP for all broadcast TWT IDs set in the corresponding AP can be transmitted to the beacon frame and the broadcast probe response frame. In this case, some of the broadcast TWT IDs can be the TWT SP for the low-delay operation. The STA that completes the low-delay operation negotiation through the corresponding TWT operation can confirm the allocated broadcast TWT ID through the low-delay operation response frame, and can confirm that the TWT parameter including the allocated broadcast TWT ID is included in the TWT element of the beacon. The frame requiring the low-delay time can be transmitted and received at the time point indicated by the corresponding TWT parameter. Conversely, when the STA that is not allocated the corresponding broadcast TWT ID confirms that the TWT SP shown in the TWT element is the TWT SP for the low-delay operation, the frame transmission operation can not be performed during the corresponding TWT SP.

[0246] In this case, the TWT element can be included in a control frame or a management frame such as a beacon frame and a probe response frame, etc. and be transmitted.

[0247] At this time, in order to additionally protect the transmission of frames for low latency operation, the AP can additionally transmit an information element for protecting the corresponding time to the beacon frame. For example, when the TWT SP for low latency operation is transmitted to the beacon frame, one or more quiet information elements set to the same time for some or all of the TWT SPs for low latency operation among the corresponding TWT SPs can be additionally transmitted. Among the STAs receiving the corresponding quiet information elements, the STAs to which the TWT SP is not allocated at the same time point as the corresponding time can set the NAV during the time included in the quiet information element and not perform frame transmission. At this time, if the TWT SP time indicated by the TWT parameter including the allocated broadcast TWT ID coincides with the time of the received quiet information element, the corresponding STA ignores the quiet information element and can perform frame transmission operation during the corresponding time. Through the corresponding procedure, the STA to which the TWT SP for low latency operation is allocated can transmit frames requiring low latency time during the corresponding time without interference from other terminals.

[0248] That is, the beacon frame can further include a quiet information element for protecting the TWT SP. The at least one non-AP STA in which the TWT operation is not set can set the NAV based on the quiet information element. In other words, the at least one non-AP STA can set the NAV during the time indicated in the quiet information element so that frames can not be transmitted. For example, the at least one STA in which the TWT operation is not set can set the NAV by the same value as the time indicated by the quiet information element (or quiet element). Alternatively, the legacy STA (e.g., VHT non-AP STA, etc.) can set the NAV by the same value as the time indicated by the quiet information element (or quiet element).

[0249] In this case, the quiet information element component is included in the beacon frame and also included in the control frame and / or management frame (e.g., probe response frame) and transmitted.

[0250] In the non-AP STA, the TWT SP and the quiet information element are set together, and when the interval set by the quiet information element overlaps with part or all of the TWT SP for low latency operation, the part or all of the overlap of the interval set by the quiet information element can be ignored. That is, the non-AP STA can be operated as if there is no quiet interval, which is the interval set by the quiet information element overlapping with the TWT SP for low latency limited.

[0251] The interval set by the quiet information element and the start time of the TWT SP for the low latency operation can be the same. That is, when the interval set by the quiet information element and the TWT SP for the low latency operation overlap, the interval set by the quiet information element and the start time of the TWT SP for the low latency operation can be the same.

[0252] Meanwhile, after the process of negotiating the low latency operation using the TWT function, a process of negotiating the transmission time point of the beacon frame including the broadcast TWT ID negotiated between the STA and the AP can be additionally performed. The corresponding process can be performed by exchanging the broadcast TWT request frame and the broadcast TWT response frame. At this time, the TWT field can be set to the time point of the transmission of the corresponding beacon frame. At this time, the field showing the period between TWT SPs can be set to the period of the beacon frame including the corresponding broadcast TWT ID.

[0253] Meanwhile, the negotiation process for the low latency operation using the TWT function can be performed in the access process between the corresponding STA and the AP. Accordingly, the STA to perform the low latency operation can not go through a separate negotiation process after accessing the AP. At this time, the negotiation and operation processes using the TWT operation can be performed as follows.

[0254] Figure 19 A second embodiment of a process in which an AP or an AP MLD and a STA perform a low latency operation using a TWT function according to an embodiment of the present application is illustrated. At this time, descriptions that are repetitive with descriptions of Figure 18 will be omitted.

[0255] Reference Figure 19 The execution process of the low latency operation for the TWT operation can include a step of confirming the function of the low latency operation by the STA and the AP, a step of transmitting a low latency operation request frame from the STA, a step of transmitting a corresponding low latency operation response frame at the AP, thereby negotiating the low latency operation using the corresponding TWT operation, and a step of performing the low latency operation from the AP allocating a TWT SP for the low latency operation to the broadcast probe response frame and the beacon frame, etc. In this case, a step of additionally negotiating the TS between the STA and the AP can be additionally included before the step of negotiating the low latency operation using the corresponding TWT operation. In addition, a negotiation step for exchanging the period of the beacon frame allocating the TWT SP negotiated at the STA can be additionally included after the step of negotiating the low latency operation using the TWT operation.

[0256] The step of confirming the function of the low latency operation can be performed in the scanning and access process between the AP or the AP MLD and the STA or the STA MLD. The negotiation process for the low latency operation using the TWT function can be performed by exchanging the low latency operation request frame and the low latency operation response frame. Figure 5 and Figures 11 to 13the process to perform the scanning and access procedure. At this time, the AP can include and transmit an indicator showing whether or not the low latency operation using the TWT function is supported in the capability element within the beacon frame, broadcast probe response frame, and probe response frame. The STA can receive the corresponding beacon frame, broadcast probe response frame, and probe response frame to confirm that the AP supports the low latency operation using the TWT operation. In addition, the AP or AP MLD can include and transmit statistical information related to the transmission time of the frame transmitted from the corresponding link in all links using the beacon frame and probe response frame. The statistical information can be a measurement report information element. Alternatively, the statistical information can be Figure 14 the measurement report information element shown in FIG. 10. On the other hand, the STA can include and transmit an indicator showing whether or not the low latency operation using the TWT function is supported in the capability element of the probe request frame and access request frame. The AP can confirm that the corresponding STA performs the low latency operation function using the TWT operation by the probe request frame and access request frame received from the STA.

[0257] The STA that confirms that the AP supports the function by the beacon frame, broadcast probe response frame, and probe response frame received from the AP can include a low latency operation request indicator using the TWT function that requests the use of the corresponding function in the access request frame when the frame requiring the low latency time occurs. At this time, the low latency operation request indicator using the TWT function can be the TWT information element described in FIG. 10. The AP can receive the access request frame from the STA and can confirm the low latency operation request indicator using the TWT function included in the frame. The AP can confirm that the STA requests the TWT SP allocation for the frame requiring the low latency time based on the content of the confirmed request indicator. If the AP can allocate the TWT SP corresponding to the request frame, the low latency operation response indicator using the TWT operation as a response to the corresponding request frame is included in the access response frame and transmitted from the AP. In this case, the low latency response indicator using the TWT operation can be the TWT information element described in FIG. 10. Figures 16 to 17 Figure 17 On the other hand, if the STA confirms that the STA supports the low latency operation using the TWT function by the transmitted probe request frame and access request frame, the AP can transmit a low latency operation response indicator using the TWT operation that does not request from the access response frame. In this case, the STA can transmit the frame requiring the low latency time to the corresponding TWT SP without transmitting a separate request frame. At this time, if the STA does not want to perform the low latency operation according to the parameters included in the low latency operation response frame that does not request, the corresponding low latency operation is released by the TWT release frame, and the low latency operation request frame using the new TWT operation is transmitted, and the low latency operation can be requested to the AP.

[0258]

[0259] ​​When the low latency operation negotiation procedure using the TWT operation ends, the AP can allocate a broadcast TWT ID for a TWT SP to be allocated to the corresponding STA. The STA can receive the broadcast TWT ID through the low latency operation response frame described in the Figure 17 The low latency operation method using the TWT operation can be performed as described in the Figure 18 That is, in the case where the beacon frame includes the TWT SP for the corresponding low latency operation, and the low latency operation can be performed in the corresponding TWT SP. In addition, in order to additionally protect the transmission of the frame for the low latency operation, the AP can additionally transmit an information element for protecting the corresponding time to the beacon frame. After the procedure for negotiating the low latency operation using the TWT function, a procedure for including the transmission time point of the beacon frame of the broadcast TWT ID negotiated between the STA and the AP can be additionally performed.

[0260] Meanwhile, in the case where the terminal accessing to the corresponding link cannot perform the STA operation in the low latency operation execution using the TWT operation, the following problem can occur.

[0261] Figure 20 It is illustrated that in the case where the STA MLD performing the low latency operation with the AP MLD cannot perform the STR operation, the beacon frame cannot be received, resulting in the loss of the TWT information element, and thus the TWT time for the low latency operation is not protected.

[0262] Referring to Figure 20 , the AP MLD can include two or more APs. At this time, each AP can operate a separate link. For example, the AP MLD can include an AP 1 and an AP 2, the AP 1 can operate in a link 1, and the AP 2 can operate in a link 2. Meanwhile, the STA MLD can include a STA 1 and a STA 2. The STA MLD can perform a multi-link operation with the AP MLD using the link 1 and the link 2. At this time, the STA MLD can not perform the STR operation in the link 1 and the link 2. That is, the STA 1 of the STA MLD can not perform the channel sensing operation and the frame reception operation in the link 2 due to interference caused by the corresponding transmission in the process of performing the frame transmission operation in the link 1. Or, the STA 2 of the STA MLD can not perform the channel sensing operation and the frame reception operation in the link 1 due to interference caused by the corresponding transmission in the process of performing the frame transmission operation in the link 2.

[0263] A characteristic that STR operation is not possible in a corresponding STA MLD can hinder a low latency transmission operation using a TWT operation. For example, when a low latency transmission operation using a TWT terminal is performed in Link 1, a corresponding TWT SP can be indicated in a beacon frame. At this time, when a frame transmission operation is performed in a STA MLD using Link 2, a beacon frame transmitted from Link 1 can not be received, and a TWT SP for a low latency operation included in the beacon frame can not be identified. The STA 1 of the STA MLD that cannot identify the TWT SP for the low latency terminal can perform a channel access operation for frame transmission in a corresponding TWT SP, and cannot protect a frame requiring a low latency time in the corresponding TWT SP.

[0264] To solve the above problem, the AP MLD can perform an update operation of a TWT-related parameter for a low latency operation at the same time point as shown below.

[0265] Figure 21 It is illustrated that when the AP MLD performs a low latency operation using a TWT operation, a parameter change operation is made at the same time point.

[0266] Reference Figure 21 For a TWT SP for all low latency terminals allocated in the AP MLD, a parameter change time point can be identically set. For example, a TWT SP-related parameter for a low latency terminal can be allowed to change only in a beacon frame including a Delivery Traffic Indication Map (DTIM). That is, in order to transmit a TWT SP allocated for a low latency terminal in a beacon frame, a broadcast TWT maintenance field of all TWT parameter information fields for a low latency terminal included in a TWT information element can be set to the same value. Except for a beacon frame transmitted at a special time point (for example, a DTIM beacon frame), a TWT SP for a low latency terminal can occur periodically after the same time from a TBTT time point. Meanwhile, at a time point at which a beacon frame (for example, a DTIM beacon frame) transmitted at a corresponding special time point is transmitted, a STA MLD that cannot perform an STR operation cannot perform a frame transmission operation through other links. Through the corresponding procedure, even if a STA MLD that cannot perform an STR operation does not receive a special beacon frame, it can confirm a TWT SP framework for a low latency terminal based on the contents of a TWT information element included in a previously transmitted beacon.

[0267] That is, when the non-AP STA constitutes a multi-link device (MLD), the MLD cannot transmit frames through other links during the period of receiving the beacon frame. In other words, if a STA included in the non-AP MLD successfully acquires a TXOP on one of the NSTR link pairs before the TBTT of the other link, the corresponding STA ends the TXOP before the TBTT of the other link on which the beacon frame is expected to be received.

[0268] Alternatively, to solve the above problem, an additional protection frame for protecting the corresponding TWT SP can be transmitted at the start time point of the corresponding TWT SP. The transmission operation of the corresponding protection frame can be performed as follows.

[0269] Figure 22 An embodiment illustrating an operation of the AP MLD to additionally transmit a protection frame for protecting the corresponding period at the start time point of the TWT time for low latency operation is illustrated.

[0270] Reference Figure 22 To prevent terminals not allocated to the TWT SP for low latency terminals from performing frame transmission at the corresponding time, a reservation frame can be transmitted from the AP at the start time point of the corresponding TWT SP. The reservation frame can be an un-agreed quiet time setting frame. The duration field value of the corresponding quiet time setting frame is designated as the corresponding TWT SP time to prevent un-negotiated STAs from performing a channel contention process during the TWT SP for the corresponding low latency terminal. Conversely, STAs negotiated with the AP for performing frame transmission during the corresponding TWT SP can perform frame transmission requiring a low latency time during the corresponding period.

[0271] Alternatively, the TWT SP can first perform a channel reservation procedure between the AP and the corresponding STA. For example, at the start of the TWT SP, an MU-RTS frame is transmitted from the AP, and the allocated STA can perform an operation of transmitting a CTS frame. At this time, the MU-RTS frame can include an AID allocated to the STA of the corresponding TWT SP. At this time, the NAV value set in the MU-RTS can designate an end point of time of the corresponding TWT SP. The STA allocated to the TWT SP can receive the MU-RTS frame and can confirm that the channel reservation procedure is performed in the corresponding MU-RTS frame. Thus, the plurality of STAs can simultaneously transmit the CTS frame in response to the MU-RTS frame. At this time, the end point of time of the NAV set in the transmitted CTS frame can be set as the end point of time of the corresponding TWT SP. After the exchange procedure of the corresponding MU-RTS and CTS frames, the STA allocated to the TWT SP can perform frame transmission through a channel contention procedure. Conversely, the STA not allocated to the TWT SP can set the NAV during the corresponding TWT SP, and thus can not perform the frame transmission operation.

[0272] On the other hand, when the STA MLD that cannot perform the STR operation performs a low-delay operation using the TWT function, when frame transmission is performed on the other link during the TWT SP time for the low-delay operation, the frame requiring a low-delay time cannot be transmitted during the corresponding TWT SP. That is, when the frame transmission operation is performed on the other link where the STR operation is not possible during the corresponding TWT SP time, the transmission operation of the frame requiring a low-delay time can not be performed due to interference influence caused by the corresponding transmission. To solve this problem, when the STA MLD performing a low-delay operation using the TWT cannot perform the STR operation, the frame transmission on the other link can be restricted as follows.

[0273] Figure 23 An embodiment in which the STA that cannot perform the AP MLD and the STR operation performs a low-delay operation using the TWT function is illustrated. In this case, the description overlapping with the description of Figures 18 to 19 and Figure 22 may be omitted.

[0274] Reference Figure 23, the STA MLD which cannot perform the STR operation can also perform the low latency operation using the AP MLD and the TWT function using the partial link. For example, the STA MLD can perform the multi-link operation with the AP MLD using the link 1 and the link 2. At this time, the STA MLD cannot perform the STR operation in the link 1 and the link 2. That is, the STA 1 of the STA MLD cannot perform the channel sensing operation and the frame reception operation in the link 2 during the process in which the STA 1 performs the frame transmission operation in the link 1 due to the interference effect caused by the corresponding transmission. Or, the STA 2 of the STA MLD cannot perform the channel sensing operation and the frame reception operation in the link 1 during the process in which the STA 2 performs the frame transmission operation in the link 2 due to the interference effect caused by the corresponding transmission. At this time, the TWT operation for the low latency operation in the link 1 of the AP MLD can be negotiated with the STA MLD. The access procedure and the negotiation procedure for the MLD operation can be performed in the manner of Figures 11 to 13 . At this time, when the STA MLD wants to perform the low latency operation using the TWT operation for the partial link, the negotiation procedure for performing the low latency operation using the TWT operation with the AP MLD can be performed in the manner of Figures 18 to 19 . For example, in order for the STA 1 belonging to the STA MLD to perform the low latency operation using the TWT operation in the link 1, the negotiation procedure can be performed with the AP 1 of the AP MLD.

[0275] According to the contents of the negotiation, the AP 1 belonging to the AP MLD can allocate the broadcast TWT ID to the STA 1, and can transmit the beacon frame including the TWT parameter indicated by the corresponding broadcast TWT ID. The TWT parameter can include the start time of the TWT SP. The STA 1 of the STA MLD which cannot perform the STR operation can receive the corresponding beacon frame and can confirm the TWT SP for the low latency operation belonging to the allocated broadcast TWT ID included in the received beacon frame. Or, as described in Figure 21 , the TWT SP for the low latency operation belonging to the allocated broadcast TWT ID can be inferred from the TBTT of the corresponding beacon frame based on the TWT SP included in the previously transmitted beacon frame.

[0276] The STA 1 of the STA MLD which recognizes the TWT SP for the low latency operation can perform the frame transmission operation requiring the low latency time after the start time point of the corresponding TWT SP. At this time, in order to prevent the transmission of the frame requiring the low latency time from being delayed, the STA 1 operating in the link 1 and the STA 2 which cannot perform the STR operation can end the transmission operation of the frame to be transmitted before the start time point of the corresponding TWT SP. The STA 2 can not perform the frame transmission during the TWT SP time for the low latency operation recognized by the corresponding STA MLD.

[0277] Figure 24 FIG. 2 is a conceptual diagram illustrating an AP MLD and a STA MLD structure performing a multi-link operation according to an embodiment of the present application.

[0278] Referring to Figure 24 , an AP multi-link device (MLD) can be a device including one or more wireless access points (APs) and can be a device connected through one interface as an upper layer. That is, the AP MLD can be connected to a logical link control (LLC) layer through one interface. A plurality of APs included in the AP MLD can share part of the functions of the MAC layer. Each of the APs in the AP MLD can operate in other links. The STA MLD can be a device including one or more non-AP STAs and can be a device connected to an upper layer through one interface. That is, the STA MLD can be connected to the LLC layer through one interface. A plurality of STAs included in the STA MLD can share part of the functions of the MAC layer. In addition, the STA MLD can be referred to as a non-AP MLD. At this time, the AP MLD and the STA MLD can perform a multi-link operation using a plurality of separate links. That is, when the AP MLD includes a plurality of APs, each of the APs can configure a separate link and can perform frame transmission and reception operations using a multi-link with each of the terminals included in the STA MLD. In this case, each of the links can operate in a 2.4 GHz, 5 GHz, or 6 GHz band, and a bandwidth extension operation can be performed in each of the links. For example, when the AP MLD configures one link in a 2.4 GHz band and two links in a 5 GHz band, frame transmission can be performed by a bandwidth of 40 MHz in the 2.4 GHz band through a bandwidth extension method, and in each of the links using the 5 GHz band, frame transmission can be performed by a bandwidth of up to 320 MHz by using a non-continuous bandwidth.

[0279] Meanwhile, for some or all APs or terminals belonging to an AP MLD or STA MLD, due to internal interference, while one AP or terminal is performing a transmission operation, other APs or terminals in the same device may be unable to perform a receiving operation. Thus, the operation of other APs or terminals in the MLD receiving data while one AP or terminal is performing a transmission operation is called Simultaneous Transmit and Receive (STR). An AP MLD can perform STR operations on all links. Alternatively, STR operations may not be possible on some links of the AP MLD. If STR operations are not possible on some links, then while one AP is performing a transmission operation on the corresponding multiple links, other APs may not be able to perform a receiving operation. A STA MLD capable of STR operations can be connected to an AP MLD, and for some or all links, a STA MLD that cannot perform STR operations can be connected. When a STA MLD that cannot perform STR operations is connected to some or all links, for the links where STR operations are not possible on the STA MLD, while one terminal is transmitting on the corresponding link, other links may not be able to perform a receiving operation. In addition, the AP included in the AP MLD can additionally connect to terminals that are not part of the MLD (e.g., IEEE 802.11a / b / g / n / ac / ax terminals).

[0280] Figure 25 The figure shows a timing diagram of the access and negotiation processes between the AP MLD and STA MLD for multi-link operation according to an embodiment of the present invention.

[0281] refer to Figure 25 AP MLD and STA MLD can be Figure 5 The described scanning and access process includes a negotiation process for multi-link usage operations. For example, in Figure 5 During the described scanning process, the AP MLD includes the APs transmitting information in the beacon frame, including indicators indicating the availability of multiple links, the number of available links, the multiple available links, and information about the APs using the corresponding links. At this time, among the APs belonging to the AP MLD, only a portion of the information for APs that do not transmit corresponding beacon frames can be transmitted. In this case, the information for APs that do not transmit beacon frames can be transmitted using the Reduced Neighbor Report (RNR) information element. The RNR information element can include one or more of the following information about the APs included in the corresponding information element: the link ID of the link operated by the corresponding AP, the channel and operating class, and a counter indicating the update status of parameters used by the corresponding AP.

[0282] Meanwhile, the terminal belonging to the STA MLD can receive the beacon frame and confirm that the AP which transmitted the corresponding beacon frame is the AP belonging to the AP MLD. In addition, it can confirm partial information (e.g., link ID, used channel information, parameter update counter in the corresponding AP, etc.) of the AP belonging to the corresponding AP MLD to other APs. Alternatively, the terminal belonging to the STA MLD can transmit a probe request frame including an indicator indicating that the multi-link operation is available in the scanning process shown in FIG. 9, and the AP belonging to the AP MLD can include an indicator indicating that the multi-link operation is available in the probe response frame. In this case, the AP can additionally include the number of links available at the time of the multi-link operation, link information, and information of the AP operating the corresponding link, etc. in the corresponding probe response frame and transmit it. Figure 5 The AP is the AP belonging to the AP MLD, and the STA MLD which confirms the partial information of the AP belonging to the corresponding AP MLD to other APs can transmit a multi-link probe request frame requesting all information of the other APs of the corresponding AP MLD to the AP in order to perform the multi-link operation. The multi-link probe request frame can indicate the required information of the AP which the corresponding STA MLD wants to receive from the AP MLD. At this time, the required information can include one or more of an HT capability element, an HT operation element, a VHT capability element, a VHT operation element, an HE capability element, an HE operation element, an EHT capability element, an EHT operation element, a target beacon transmission time (TBTT), EDCA parameter set information, channel information of the operation of the corresponding AP, and bandwidth information supported by the corresponding AP. The STA MLD can request information of one or more special APs in the multi-link probe request frame. Alternatively, the STA MLD can request information of all APs operated by the corresponding AP MLD.

[0283] The AP is the AP belonging to the AP MLD, and the STA MLD which confirms the partial information of the AP belonging to the corresponding AP MLD to other APs can transmit a multi-link probe request frame requesting all information of the other APs of the corresponding AP MLD to the AP in order to perform the multi-link operation. The multi-link probe request frame can indicate the required information of the AP which the corresponding STA MLD wants to receive from the AP MLD. At this time, the required information can include one or more of an HT capability element, an HT operation element, a VHT capability element, a VHT operation element, an HE capability element, an HE operation element, an EHT capability element, an EHT operation element, a target beacon transmission time (TBTT), EDCA parameter set information, channel information of the operation of the corresponding AP, and bandwidth information supported by the corresponding AP. The STA MLD can request information of one or more special APs in the multi-link probe request frame. Alternatively, the STA MLD can request information of all APs operated by the corresponding AP MLD.

[0284] The AP MLD can receive the multi-link probe request frame from the STA MLD, and the STA MLD can confirm that partial or all of the information elements related to the operation of the corresponding AP are requested for partial or all of the APs belonging to the corresponding AP MLD. The AP MLD which confirms the corresponding requested information includes the information requested by the STA MLD, and can be transmitted to the corresponding STA MLD by the type of the multi-link probe request frame. In this case, transmission of information overlapping with the information used in the AP which transmits the multi-link probe response frame can be omitted. Meanwhile, since the multi-link probe response frame is transmitted to the STA MLD which transmitted the multi-link probe request frame, the information of the AP MLD which is not requested by the STA MLD can be omitted. Figure 5The probe response frame of the STA MLD includes more information, so the STA MLD can occupy the channel for more time when transmitting the corresponding multi-link probe response frame. Therefore, in order to prevent excessive channel occupation due to the transmission of too many multi-link probe response frames, the transmission of a response to a multi-link probe request frame received from the same STA MLD can not be performed when a special STA MLD has already transmitted a multi-link probe response frame. Meanwhile, the AP MLD can transmit a multi-link probe response frame including information of all APs belonging to the corresponding AP MLD in the type of a broadcast frame. The multi-link probe response frame transmitted in the type of the corresponding broadcast frame can be transmitted for more than a special period. In this case, if a multi-link probe response frame is transmitted in the type of a broadcast frame within a special time before a multi-link probe request frame is received from a STA MLD, the transmission of a multi-link probe response frame can not be performed. In this case, the special time can be a point in time at which a STA belonging to the corresponding STA MLD transmits a multi-link probe request frame. Figure 5

[0285] The STA MLD receives a multi-link probe response frame from the AP MLD and can confirm the operation parameters of the APs belonging to the AP MLD, etc., and can perform an access procedure and a negotiation procedure for a multi-link operation with the AP MLD. In this case, the negotiation procedure for a multi-link operation can be performed during an access procedure between an AP belonging to the AP MLD and a terminal belonging to the STA MLD. That is, an arbitrary terminal (e.g., STA1) belonging to the STA MLD can transmit an access request frame to an arbitrary AP (e.g., AP1) belonging to the AP MLD while indicating an indicator that the multi-link operation of the terminal is available and a request indicator that requests the performance of a multi-link operation. At this time, the STA MLD transmits the access request frame including link information to be used in the AP MLD and capability information of the terminal related to the corresponding link (e.g., information indicating whether STR with other links is possible, a maximum bandwidth that can be transmitted, or a maximum number of spatial streams that can be used, etc.). The AP receiving the access request frame from the terminal can confirm the indicator requesting a multi-link operation, and when the AP can perform a multi-link operation, can transmit an access response frame allowing the multi-link operation to the corresponding terminal, including link information to be used for a multi-link operation, parameters for each link usage, etc. The parameters for a multi-link operation can include one or more of a link ID, a MAC address, a frequency band, a bandwidth extension direction, a target beacon transmission time (TBTT), and STR operation or not. The AP MLD and the STA MLD that exchange the access request frame and the response frame and confirm the use of a multi-link operation can perform a frame transmission operation using a plurality of links after the corresponding access procedure. ​

[0286] Figure 26 A timing diagram illustrating a transmission method using multiple links according to an embodiment of the present application.

[0287] Referring to Figure 28 When the multi-link operation is performed in the independent transmission method of each link, each AP or terminal belonging to the AP MLD or the STA MLD independently performs a channel contention procedure for frame transmission in each link and performs frame transmission in each link. In this case, the transmission start point and the transmission end point of the frame transmitted from each link can not be the same. When the independent transmission method is performed, the transmission opportunity (TXOP) obtained in each link by the channel contention procedure can be independently obtained in each link.

[0288] In the case of performing the independent transmission method, since the channel access is independently performed for each link according to the channel occupancy state, it has an advantage that each link can be more efficiently performed. In this case, if the interval between the operating bands of each AP of the AP MLD is not sufficient to cause the AP MLD or the STA MLD to be unable to perform the STR operation, the multi-link operation cannot be performed by the independent transmission method.

[0289] Meanwhile, when the receiving MLD is not possible to perform the STR operation in some or all of the links, the frame transmission and reception procedure using the link in which the STR operation is not possible can be performed as follows.

[0290] Figure 27 An embodiment of the operation of the frame transmission and reception of the receiving MLD in which the STR operation is not possible in some or all of the links and the transmission MLD in which the STR operation is possible according to an embodiment of the present application is illustrated.

[0291] Referring to Figure 27a, when STR operation is not possible in the MLD, frame transmission operation is performed in one link, and frame reception operation is not possible in the other link. For example, AP1 and AP2 belong to an AP MLD, AP1 can use link 1, and AP2 can use link 2. STA1 and STA2 belong to a STA MLD, and STA1 can access AP1 and STA2 can access AP2 through a negotiation procedure for multi-link operation. At this time, the STA MLD can not perform STR operation in link 1 and link 2. That is, when STA1 performs frame transmission operation in link 1, STA2 can not perform operation in link 2. Conversely, when STA2 performs frame transmission operation in link 2, STA1 can not perform frame reception operation in link 1. The case where STR operation is not possible can be because of interference within the device that occurs during frame transmission operation in one link. Thus, when the STA MLD can not perform STR operation in some links, frame transmission operation is performed in one link in the corresponding link, and channel sensing operation is not possible in the other link. For example, STA2 can not perform channel sensing operation for frame transmission in link 2 during transmission of a frame to STA1 in link 1. Thus, STA2 can not start frame transmission operation after channel contention procedure in link 2 during frame transmission by STA1 in link 1. That is, even when one of the transmitting MLD and the receiving MLD can not perform STR operation in the corresponding link, the other MLD can perform multi-link communication operation through independent transmission mode in the corresponding link. Figure 11 Multi-link communication operation in independent transmission mode in

[0292] When STR operation is not possible in the AP MLD or the STA MLD in multiple links (e.g., when bandwidth interval between links is not sufficient to perform multi-link operation), the AP MLD and the STA MLD perform multi-link communication operation as in Figure 12The b of the b can perform a multi-link operation in a type of simultaneous transmission operation. The simultaneous transmission operation can be performed through a process of matching the transmission start time or the transmission end time of the frames transmitted in each link to be the same. At this time, the transmission start time or the transmission end time of the frame can be referred to as the transmission start time and the transmission end time of the PPDU including the frame. That is, when the frame length transmitted by the AP or the terminal to each link is different, in order to match the corresponding transmission end time point, padding or padding bits can be added and transmitted. In addition, the TXOP time for frame transmission in each link can be matched to be the same. In this case, the multi-link operation of the simultaneous transmission type can include a negotiation step for simultaneous transmission in multiple links and a step of performing simultaneous transmission using multiple links. The negotiation step for simultaneous transmission can include a step of transmitting a request frame for a TXOP for simultaneous transmission to one or more links at the same time point in an MLD (for example, an AP MLD or an STA MLD) having data to be transmitted, and a step of transmitting a corresponding frame after a short interframe space (SIFS) from the time point of completing the reception of the request frame in the MLD receiving data. In this case, the response frame can be transmitted simultaneously in one or more links receiving the request frame. The request frame can be a control frame. For example, the request frame can be an RTS or a multi-user (MU)-RTS frame, and the response frame can be a CTS frame. Meanwhile, when the channel of one link is in a state of being occupied during channel contention for performing a simultaneous transmission operation, a channel access procedure for performing a simultaneous transmission operation can be performed or a frame transmission operation using only a link having an empty channel can be performed.

[0293] The channel access procedure for the simultaneous transmission operation can be performed in various ways. For example, a backoff procedure is performed in multiple links performing simultaneous transmission, carrier sensing is performed in all links, and when the channel in all links is empty as a result of the carrier sensing, the simultaneous transmission method using multiple links can be performed. Or, if the channel of the other link is empty during a specific time (for example, AIFS, DIFS, or PIFS) before the end of the backoff after performing a backoff operation in one link, the channel using the empty link can perform the simultaneous transmission method using multiple links.

[0294] On the other hand, when the STR operation cannot be performed in the corresponding link by the transmission MLD, if the channel of the other link is empty at a specific time (for example, AIFS, DIFS, or PIFS) before the end of the backoff after performing a backoff operation in one link, the channel using the empty link can perform the simultaneous transmission method using multiple links. Figure 10 If the channel state of one or some of the links in the channel access procedure for frame transmission in the b of the b is busy, one of the following methods can be used:

[0295] 1) After the end of the corresponding occupation period, carrier sensing is performed on the channels of both links during a special time (e.g., PIFS, AIFS, or AIFS + backoff time) to confirm that the channels of both links are empty, after which simultaneous transmission is performed by the b method of Figure 12

[0296] 2) Transmission operation is performed only on the link whose channel is empty

[0297] In the case of performing the above 2) operation, even after the end of the occupation time of the link whose channel state is occupied, the backoff operation for frame transmission is not performed at the transmission end time point of the link performing transmission.

[0298] On the other hand, when the transmission MLD can perform the STR operation on the corresponding link, and the reception MLD cannot perform the STR operation on the corresponding link, if the channel state of one or some of the links in the channel access procedure for frame transmission is busy in b of Figure 12

[0299] 1) After the end of the corresponding occupation period, carrier sensing is performed on the channels of both links during a special time (e.g., PIFS, AIFS, or AIFS + backoff time) to confirm that the channels of both links are empty, after which simultaneous transmission is performed by the b method of Figure 12

[0300] 2) Transmission operation is performed only on the link whose channel is empty

[0301] In the case of performing the above 2) operation, even after the end of the occupation time of the link whose channel state is occupied, the backoff operation for frame transmission is not performed at the transmission end time point of the link performing transmission.

[0302] Meanwhile, when the transmission MLD can perform the STR operation and the reception MLD cannot perform the STR operation on the corresponding link, the transmission start time point and the transmission end time point of the frame transmitted from the transmission MLD through multiple links can not be the same. That is, as shown in c of Figure 12 Figure 12 ​​​​In the case where the channel state of the link 2 is the busy state in performing the channel access procedure for the frame transmission in the b of the above-described example, the AP 1 of the AP MLD can perform the frame transmission operation in the link 1 first. Since the AP MLD can perform the STR operation, the AP 2 can perform the channel contention procedure for the frame transmission in the link 2 while the AP 1 transmits the frame in the link 1. After completing the channel contention procedure and the channel access operation, the AP 2 can perform the frame transmission operation using the link 2. Since the STA MLD does not perform the frame transmission in the link 1, the STA 2 can receive the frame transmitted by the AP 2 in the link 2. On the other hand, if one or more of the frames transmitted by the transmission MLD require the immediate response (e.g., BlockAck frame, etc.) from the reception MLD, the transmission of the corresponding response frame can be performed in the process in which the reception is performed in the other link. In this case, the frame reception operation in the other link can not be smoothly performed due to the transmission of the response frame. In order to prevent this, when the transmission of the corresponding frame is required from one or more of the frames transmitted by the transmission MLD, the transmission end time point of the PPDU of the frame transmitted in the multiple links can be identical.

[0303] Meanwhile, when the frame transmission and reception operation between the AP and the STA is performed, in order to protect the corresponding frame transmission and reception operation, the channel reservation procedure can be performed. The channel reservation procedure can be performed through the procedure of transmitting the Request to Send (RTS) frame from the transmission STA which desires to transmit the frame to the reception STA and transmitting the Clear to Send (CTS) from the reception STA. At this time, the reception STA performs the channel sensing operation during the SIFS time after receiving the RTS frame, so that the CTS is transmitted only when the corresponding channel is in the idle state.

[0304] Meanwhile, when the channel is to be reserved by the AP and the multiple STAs for the multi-user transmission, the exchange procedure of the Multi-user-MU-RTS frame and the CTS frame can be performed. The exchange procedure of the MU-RTS frame and the CTS frame between the AP and the multiple STAs can be performed as follows.

[0305] Figure 28 FIG. 1 illustrates a first embodiment of an operation of protecting the frame transmission and reception by the exchange procedure of the MU-RTS frame and the CTS frame between the AP and the multiple STAs according to an embodiment of the present application.

[0306] Reference Signs Figure 28When the AP wants to transmit frames to a plurality of STAs, in order to protect the frame transmission operation before the corresponding frame transmission, an exchange procedure of a MU-RTS frame and a CTS frame can be performed. The MU-RTS frame can be transmitted using one of a primary 20MHz channel, a primary 40MHz channel, a primary 80MHz channel, a primary 160MHz or 80+80MHz channel, a primary 240MHz or primary 160+80MHz channel, a primary 320MHz or 160+160MHz channel. At this time, the MU-RTS can be indicated of an ID (e.g., an Association ID) of a STA which is to transmit a CTS, a channel (e.g., a primary 20MHz channel, a primary 40MHz channel, a primary 80MHz channel, a primary 160MHz or 80+80MHz channel, a primary 240MHz or primary 160+80MHz channel, a primary 320MHz or 160+160MHz channel) which each STA is to transmit a CTS frame, and the like. The MU-RTS frame can be transmitted in a type of trigger frame. Alternatively, the MU-RTS frame can be transmitted as a frame of a type of a request for a simultaneous transmission of a CTS frame from a plurality of STAs as described later. Figure 14 or Figure 17 constituted. The MU-RTS frame can be a frame which requests a simultaneous transmission of a CTS frame from a plurality of STAs. In this case, the plurality of STAs can include an HE STA defined in IEEE 802.11ax and can include an EHT STA defined in IEEE 802.11be.

[0307] The plurality of STAs receiving the MU-RTS frame from the AP can confirm the information included in the MU-RTS frame. The plurality of STAs can confirm the information of the received MU-RTS frame, and can confirm the AID value included in one or more user information fields in the corresponding MU-RTS frame. At this time, if the AID value coincides with the AID value allocated from the corresponding STA, the STA can confirm that the transmission of the CTS frame is requested from the MU-RTS frame to the corresponding STA. After receiving the MU-RTS frame, the STA including the AID of the MU-RTS frame can perform a channel sensing operation on the channel indicated in the MU-RTS frame during the SIFS time. At this time, the channel can be one of a primary 20 MHz channel, a primary 40 MHz channel, a primary 80 MHz channel, a primary 160 MHz / 80+80 MHz channel, a primary 240 MHz / 160+80 MHz channel, and a primary 320 MHz / 160+160 MHz channel. At this time, if the STA receiving the MU-RTS frame is an HE STA, the bandwidth of the channel in which the CTS frame is transmitted can reach 160 MHz or 80+80 MHz. If the STA receiving the MU-RTS frame is an EHT STA, the maximum bandwidth of the channel in which the CTS frame is transmitted can be 320 MHz or 160+160 MHz. The channel sensing operation can include a physical sensing, a virtual sensing, and a Network Allocation Vector (NAV) confirmation procedure.

[0308] If the channel indicated during the SIFS time after the STA receives the MU-RTS frame is in a channel idle state, the plurality of STAs indicated from the MU-RTS frame can simultaneously transmit CTS frames after the SIFS from the transmission end time point of the PPDU containing the MU-RTS frame. At this time, in the indicated channel, the CTS frame can be transmitted in a non-HT PPDU type or a non-HT duplicated PPDU type repeated per 20 MHz band. At this time, the CTS frames of the plurality of STAs transmitted can be identically configured. Therefore, from the perspective of the AP, as shown in a of Figure 28

[0309] At this time, the reception power of the CTS frame received per 20 MHz channel can be different. When the AP receives the CTS frame as a response to the MU-RTS, the AP can perform the MU-OFDMA or MU-MIMO operation with the plurality of STAs based on the bandwidth of the received CTS frame. Figure 13 ​b, if the channel on which the CTS frame is indicated to be transmitted from the MU-RTS frame is the primary 20 MHz channel, the STA1 can transmit the CTS frame only after performing the channel sensing operation on the corresponding primary 20 MHz channel. At this time, the corresponding CTS frame can be transmitted in the type of non-HT PPDU. The STA1, after transmitting the CTS frame, can receive the downlink frame within the corresponding 20 MHz channel.

[0310] Referring to Figure 28 c, when the channel on which the CTS frame is indicated to be transmitted from the MU-RTS frame is the primary 40 MHz channel, the STA (e.g., STA2) indicated in the user info field of the corresponding MU-RTS frame can transmit the CTS frame only after performing the channel sensing operation on the corresponding primary 40 MHz channel. At this time, the corresponding CTS frame can be transmitted in the type of non-HT duplicate PPDU. The STA2, after transmitting the CTS frame, can receive the downlink frame within the corresponding 40 MHz channel.

[0311] Referring to Figure 28 d, when the channel on which the CTS frame is indicated to be transmitted from the MU-RTS frame is the primary 80 MHz channel, the STA (e.g., STA3) indicated in the user info field of the corresponding MU-RTS frame can transmit the CTS frame only after performing the channel sensing operation on the corresponding primary 80 MHz channel. At this time, the corresponding CTS frame can be transmitted in the type of non-HT duplicate PPDU. The STA3, after transmitting the CTS frame, can receive the downlink frame within the corresponding 80 MHz channel.

[0312] The MU-RTS frame for the MU-RTS frame and CTS frame exchange procedure can be constituted as follows.

[0313] Figure 29 FIG. 1 illustrates a structure of a MU-RTS frame according to an embodiment of the present application.

[0314] Referring to Figure 29, the MU-RTS frame can be constituted in the type of trigger frame, and can be constituted with a common field and one or more user information fields. The common field includes a trigger type field, an indication field of whether to attach a transmission trigger frame after the corresponding frame, a field indicating whether a carrier sensing operation of a receiving terminal is required, an uplink frame bandwidth field, an uplink frame bandwidth extension field, and a reservation field. The common field can further include a MU-RTS type field. Alternatively, the MU-RTS type field can be included in the user information field. The trigger type field can be set to 3 to indicate that the corresponding trigger frame is a MU-RTS frame. In addition, when the trigger frame is a MU-RTS frame, the MU-RTS type field can be included in the trigger frame. When the corresponding MU-RTS frame is transmitted below a bandwidth of 160 MHz and the EHT STA is not set with a separate type of user information field, the MU-RTS type field can be set to 00. When the MU-RTS frame is transmitted with a bandwidth exceeding 160 MHz, it can be set to 10. The field indicating whether a carrier sensing operation is required can be set to 1 to indicate that the STA receiving the MU-RTS frame performs a carrier sensing operation. The uplink frame bandwidth field and the bandwidth extension field can indicate the bandwidth of the CTS frame that the AP transmitting the corresponding MU-RTS frame wishes to receive. That is, when a plurality of STAs transmit CTS frames of a, the AP can indicate the bandwidth of the CTS frame to be finally received. The bandwidth field can indicate as shown in Table 3 below. Figure 13

[0315] [Table 3]

[0316] Bandwidth field value illustrate 0 20MHz 1 40MHz 2 80MHz 3 160MHz or 80+80MHz and above

[0317] The bandwidth extension field is displayed only when the MU-RTS type field is not 00, and when the bandwidth field value is 2 or less, the corresponding bandwidth extension field is set to 0. When the bandwidth field value is 3, the bandwidth extension field can be set as shown in Table 4 below.

[0318] [Table 4]

[0319] Bandwidth extension field value illustrate 0 160MHz or below 80+80MHz 1 320MHz or 160+160MHz

[0320] Meanwhile, when the STA receiving the MU-RTS frame is an HE STA, the value of the MU-RTS type field and the bandwidth extension field in the common field of the MU-RTS frame can not be decrypted. Therefore, when the MU-RTS frame is transmitted from the AP, the bandwidth of the CTS frame transmitted from the HE STA can be indicated as a maximum of 160 MHz or 80+80 MHz regardless of the bandwidth extension field value. If the STA receiving the MU-RTS frame is an EHT STA, the bandwidth of the CTS frame to be transmitted can be confirmed by confirming the bandwidth field and the bandwidth extension field value of all the MU-RTS frames.

[0321] ​The user information field can be constructed differently according to the MURTS type field value of the common field and whether the terminal receiving the corresponding MU-RTS frame is an HE STA or an EHT STA. When the MURTS type field value is 00, the user information field can be constructed of a 12-bit AID field and an 8-bit resource unit (RU) allocation field. When the MURTS type field is 10, if the user information field indicates an HE STA, it can be constructed of a 12-bit AID field and an 8-bit resource unit (RU) allocation field. When the MURTS type field value is 10 and the user information field indicates an EHT STA, it can be constructed of a 12-bit AID field and a 9-bit resource unit (RU) allocation field. Alternatively, regardless of the MURTS type field value, the user information field can be different based on whether the receiving terminal is an HE STA or an EHT STA. For example, when the user information field belongs to an HE STA, the user information field can include a 12-bit AID field and an 8-bit RU allocation field. In addition, when the user information field belongs to an EHT STA, the user information field can include a 12-bit AID field and a 9-bit RU allocation field.

[0322] When the resource unit (RU) allocation field is constructed of 8 bits, if the B0 value of the corresponding RU allocation field is 1, it can indicate that a CTS frame for which a transmission using a 160 MHz or 80+80 MHz bandwidth is requested. If the B0 value of the least significant bit (LSB) of the RU allocation field is 0, it can indicate that a CTS frame for which a 20 MHz, 40 MHz, or 80 MHz transmission is requested by the STA indicated in the corresponding user field.

[0323] The specific location of the transmission bandwidth and the transmission band of the CTS frame can be transmitted in B7-B1 of the RU allocation field, that is, the 7 upper bits of the RU allocation field. At this time, the B7-B1 value of the RU allocation field can be set as shown in Table 5 below.

[0324] [Table 5]

[0325]

[0326] When the RU allocation field is constructed of 9 bits, if the B1-B0, that is, the two least significant bits of the RU allocation field can divide a 320 MHz bandwidth channel into 4 80 MHz channel segments, it can indicate the segment position of the 80 MHz band in which the corresponding CTS frame is transmitted.

[0327] The transmission bandwidth of the CTS frame and the location in the 80MHz segment can be indicated in B8-B2 of the RU allocation field. At this time, the B8-B2 values of the RU allocation field can be set as shown in Table 6 below.

[0328] [Table 6]

[0329]

[0330] In one aspect, when the B8-B2 values indicate a 320MHz or 160+160MHz primary channel, the B1-B0 values of the RU allocation field can be indicated as 11.

[0331] In one aspect, when the length of the RU allocation field within the user info field transmitted to the EHT STA is also maintained at 8 bits, the MU-RTS frame can be constructed as follows.

[0332] Figure 30 A second embodiment of the structure of the MU-RTS frame according to an embodiment of the present application is illustrated. At this time, the description of the same or similar parts of the structure of the MU-RTS frame of Figure 28 will be omitted.

[0333] Referring to Figure 30 , the MU-RTS frame can be constructed in the type of a trigger frame and can be constructed with a common field and one or more user info fields. The common field includes a trigger type field, an indication field of whether a transmission trigger frame is additionally attached after the corresponding frame, a field indicating whether a carrier sensing operation of the receiving terminal is required, an uplink frame bandwidth field, an uplink frame bandwidth extension field, and a reservation field. The common field can further include a MU RTS type field. The remaining fields other than the MU RTS type field can be constructed identically to the MU-RTS frame of Figure 28 . When the corresponding MU-RTS frame is transmitted below a 160MHz bandwidth and the EHT STA is not set with a separate type of user info field, the MU RTS type field can be set to 00. When the MU-RTS frame is transmitted with a bandwidth exceeding 160MHz, it can be set to 10.

[0334] The user info field can be constructed with a 12-bit AID field, an 8-bit RU allocation field, and a reservation field. When the AID field of the user info field indicates an HE STA, or when the bandwidth field and the bandwidth extension field of the common field indicate a bandwidth less than or equal to 160MHz and the MU RTS type field is 00, the 8-bit RU allocation field can be set identically to the 8-bit RU allocation field of Figure 13 . That is, B0 of the RU allocation field shows whether it is transmitted with a 160MHz or an 80+80MHz bandwidth, and B7-B1 of the RU allocation field can be constructed as shown in Table 3.

[0335] When the MU-RTS frame is transmitted with a bandwidth of more than 160 MHz and the MU RTS type field is 10, the RU allocation field within the user info field of the EHT STA can be configured as follows. When the B1-B0 of the RU allocation field, i.e., the two least significant bits, divide the 320 MHz bandwidth channel into four 80 MHz channel segments, the segment in which the primary channel of the transmission corresponding to the CTS frame is located can be indicated.

[0336] The transmission bandwidth of the CTS frame and the position in the 80 MHz segment can be indicated by B7-B2 of the RU allocation field. At this time, the B7-B2 value of the RU allocation field can be set as shown in Table 7 below.

[0337] [Table 7]

[0338]

[0339] In one aspect, when the B7-B2 value indicates a 320 MHz or 160+160 MHz primary channel, the B1-B0 value of the RU allocation field can be indicated as 11.

[0340] The exchange process of the MU-RTS frame and the CTS frame can be performed using the primary 20 MHz channel, the primary 40 MHz channel, the primary 80 MHz channel, the primary 160 MHz / 80+80 MHz channel, the primary 240 MHz / 160+80 MHz channel, and the primary 320 MHz / 160+160 MHz channel. Alternatively, when a special 20 MHz channel other than the primary 20 MHz channel is in an occupied state, the corresponding 20 MHz channel can be emptied, and only the remaining channels can be used for execution. The exchange operation of the MU-RTS frame and the CTS frame using the preamble puncturing operation of the operation of transmitting a frame using the emptied part of the 20 MHz channel can be performed as follows.

[0341] Figure 31 A second embodiment of an operation of protecting frame transmission and reception through the MU-RTS frame and CTS frame exchange process between an AP and a plurality of STAs according to an embodiment of the present application is illustrated. At this time, the same or similar description as the operation of Figure 28 will be omitted.

[0342] Reference Figure 31, the AP can perform frame transmission and reception processes with multiple STAs simultaneously. The process of simultaneously transmitting and receiving frames with multiple STAs can be performed through MU-OFDMA or MU-MIMO operation. At this time, in order to protect the corresponding frame transmission and reception processes, the AP can perform an exchange process of a MU-RTS frame and a CTS frame before transmitting the corresponding frames. The MU-RTS frame can be transmitted using one of a primary 20 MHz channel, a primary 40 MHz channel, a primary 80 MHz channel, a primary 160 MHz or 80+80 MHz channel, a primary 240 MHz or primary 160+80 MHz channel, a primary 320 MHz or 160+160 MHz channel. At this time, if one or more 20 MHz channels other than the primary 20 MHz channel are in an occupied state, or the corresponding 20 MHz channel is not desired to be used, the corresponding one or more 20 MHz channels are cleared, and the MU-RTS frame is transmitted using only the remaining channels. That is, when the MU-RTS frame is transmitted using the primary 80 MHz channel, the primary 160 MHz or 80+80 MHz channel, the primary 240 MHz or primary 160+80 MHz channel, the primary 320 MHz or 160+160 MHz channel, the MU-RTS frame can not be transmitted in a special 20 MHz channel. For example, when the MU-RTS frame is to be transmitted using the primary 80 MHz channel, if the 20 MHz channel within the sub 40 MHz channel is in an occupied state, the corresponding channel is cleared, and the MU-RTS frame is transmitted using only the remaining channel.

[0343] In the MU-RTS can indicate the ID (e.g., association ID) of the STA to transmit the CTS, each of the STAs to transmit the CTS frame, a channel (e.g., primary 20 MHz channel, primary 40 MHz channel, primary 80 MHz channel, primary 160 MHz or 80+80 MHz channel, primary 240 MHz or primary 160+80 MHz channel, primary 320 MHz or 160+160 MHz channel) to transmit the CTS frame, etc. At this time, the 20 MHz channel (punctured channel) not transmitting the MU-RTS and cleared can be additionally indicated. The MU-RTS frame can be constituted as described later. Figure 17 The MU-RTS frame can be a frame requesting the simultaneous transmission of CTS frames from multiple STAs. In this case, the multiple STAs can include HE STAs defined in IEEE 802.11ax and can include EHT STAs defined in IEEE 802.11be.

[0344] Referring to Figure 31a, the AP can transmit the MU-RTS frame to a plurality of STAs, and can receive CTS frames simultaneously transmitted from the STAs from a point of time at which transmission of the PPDU including the corresponding MU-RTS frame ends to after a SIFS time. The CTS frame can be a type repeatedly transmitted per 20 MHz channel. The CTS frame can be a non-HT duplicate PPDU type. At this time, the CTS frames transmitted by the plurality of STAs can be identically constituted. Accordingly, the AP can receive the CTS frame at each of the 20 MHz channels at a point of time. At this time, the received power of the CTS frame received at each of the 20 MHz channels can be different. When the AP receives the CTS frames as responses to the MU-RTS, the AP can perform the MU-OFDMA or MU-MIMO operation with the plurality of STAs based on the bandwidths of the received CTS frames.

[0345] Meanwhile, as described above, the transmission bandwidths of the CTS frames transmitted by the STAs that receive the MU-RTS frame can be respectively different. For example, referring to Figure 16 b, when the channel from which the CTS frame is transmitted is indicated as a primary 20 MHz channel from the MU-RTS frame, the STA1 can perform a channel sensing operation only on the corresponding primary 20 MHz channel. The channel sensing operation can be performed during a SIFS time. When the primary 20 MHz channel is in an idle state, the CTS frame can be transmitted. At this time, the corresponding CTS frame can be transmitted in a non-HT PPDU type. The STA1 can receive a downlink frame within the corresponding 20 MHz channel after the transmission of the CTS frame. In this case, the STA that transmits the CTS frame can be an HE STA or an EHT STA.

[0346] Referring to Figure 31 c, when the channel from which the CTS frame is transmitted is indicated as a primary 40 MHz channel from the MU-RTS frame, the STA (e.g., the STA2) indicated in the user info field of the corresponding MU-RTS frame can perform a channel sensing operation only on the corresponding primary 40 MHz channel. The channel sensing operation can be performed during a SIFS time. When the primary 40 MHz channel is in an idle state, the CTS frame can be transmitted. At this time, the corresponding CTS frame can be transmitted in a non-HT duplicate PPDU type. The STA2 can receive a downlink frame within the corresponding 40 MHz channel after the transmission of the CTS frame. In this case, the STA that transmits the CTS frame can be an HE STA or an EHT STA.

[0347] Referring to Figure 31d, when the channel on which the CTS frame is transmitted from the MU-RTS frame is the primary 80MHz channel and the special 20MHz channel is the clear type, the STA (e.g., STA3) indicated in the user info field of the corresponding MU-RTS frame can perform a channel sensing operation only in the other channels of the corresponding primary 80MHz channel except for the 20MHz channel indicated to be cleared. As a result of the channel sensing, when the corresponding channel is in an idle state, the CTS frame can be transmitted. At this time, the corresponding CTS frame can be transmitted in a non-HT duplicate PPDU type. The STA3 can receive a downlink frame in the channel in which the MU-RTS frame and the CTS frame are exchanged after transmitting the CTS frame. The STA that transmits the CTS frame can be an EHT STA.

[0348] The MU-RTS frame used in the MU-RTS frame and CTS frame exchange process can be constructed by adding a field indicating a punctured channel to the existing MU-RTS frame. Alternatively, the corresponding MU-RTS frame can be constructed as follows.

[0349] Figure 32 A third embodiment of the structure of the MU-RTS frame according to an embodiment of the present application is illustrated. At this time, the description of the same configuration as the MU-RTS frame of Figure 29

[0350] Referring to Figure 32 , the MU-RTS frame can be constructed in the type of a trigger frame, and can be constructed with a common field and one or more user info fields. The common field includes a trigger type field, an indication field of whether a transmission trigger frame is attached after the corresponding frame, a field indicating whether a carrier sensing operation of a receiving terminal is required, an uplink frame bandwidth field, an uplink frame bandwidth extension field, and a reservation field. The common field can further include a MU RTS type field. In addition, the common field can further include a punctured channel field. At this time, the remaining fields except for the MU RTS type field and the punctured channel field can be set the same as in the Figure 14 MU-RTS frame. The field indicating the MU RTS type field can indicate the type of the MU-RTS frame transmitted after clearing a part of the 20MHz channel. For example, the MU RTS type field can be set to 11. When the MU RTS type field is set to 11, the punctured channel field can be included. The MU RTS punctured channel field can be constructed of 16 bits. In this case, each bit of the 16 bits can indicate one 20MHz channel. Accordingly, when the corresponding bit position is set to 0, it can be indicated that the MU-RTS frame is transmitted in the 20MHz channel belonging to the position of the bit. For example, if only the second least significant bit (e.g., B1) is set to 1 and the remaining bits are set to 0 among the 16 bits, only the 20MHz channel of the lower frequency band is the punctured channel, and it can be indicated that the frame is transmitted in the other channels. At this time, it is not possible to set the primary 20MHz channel to 1.​

[0351] The user info field can be configured similarly to Figure 29 or Figure 30 For example, when the corresponding MU-RTS frame is transmitted in a 160 MHz band and the MU RTS type field of the common field is 11, B0 of the RU allocation field within the user info field indicates whether it is a 160 MHz or 80+80 MHz bandwidth, and B7-B1 can be indicated as shown in Table 3. If the corresponding MU-RTS frame is transmitted in a bandwidth exceeding the 160 MHz band and the MU RTS type field is 11, the RU allocation field within the user info field can be configured by 8 bits or 9 bits. When the corresponding RU allocation field is 9 bits, it can be configured as shown in Figure 14 . When the corresponding RU field is 8 bits, it can be configured as shown in Figure 30 .

[0352] When the MU RTS type field is 11, the EHT STA receiving the corresponding MU-RTS frame from the AP can confirm the bandwidth field and the bandwidth extension field to determine the bandwidth in which the corresponding MU-RTS frame is transmitted. The channel to be cleared at the time of CTS transmission can be confirmed through the punctured channel field. In addition, the bandwidth to be transmitted by the corresponding STA can be confirmed through the RU allocation field. The interpretation method of the corresponding RU allocation field can be different according to the bandwidth in which the MU-RTS frame is transmitted and the MU RTS type field. The EHT STA interpreting the RU allocation field according to the bandwidth in which the MU-RTS frame is transmitted and the MU RTS type field clears the 20 MHz channel indicated in the punctured channel field, and can transmit a CTS frame to the remaining channel according to the value indicated to the RU allocation field.

[0353] Meanwhile, the HE STA receiving the corresponding MU-RTS frame can not be able to decode the punctured channel field. Accordingly, the corresponding HE STA can not clear the special 20 MHz channel to transmit a CTS frame to the channel indicated by the RU allocation field.

[0354] Meanwhile, during the exchange of the MU-RTS frame and the CTS frame, the CTS frame can be transmitted only in one or more 20 MHz channels. In this case, the exchange operation of the MU-RTS and the CTS frame can be performed as follows.

[0355] Figure 33 FIG. 13 illustrates a third embodiment of an operation of protecting frame transmission and reception through the exchange of the MU-RTS frame and the CTS frame between the AP and the plurality of STAs according to an embodiment of the present application. At this time, the description identical or similar to the operation of Figure 28 and Figure 31 may be omitted.

[0356] Referring to Figure 33, the AP can perform frame transmission and reception processes with multiple STAs simultaneously. The process of transmitting and receiving frames with multiple STAs simultaneously can be performed through MU-OFDMA or MU-MIMO operation. At this time, in order to protect the corresponding frame transmission and reception processes, the AP can perform an exchange process of a MU-RTS frame and a CTS frame before transmitting the corresponding frames. The MU-RTS frame can be transmitted using one of a primary 20 MHz channel, a primary 40 MHz channel, a primary 80 MHz channel, a primary 160 MHz or 80+80 MHz channel, a primary 240 MHz or primary 160+80 MHz channel, a primary 320 MHz or 160+160 MHz channel. At this time, if the channel state in the 20 MHz channel other than the primary 20 MHz channel is in an occupied state, or the corresponding 20 MHz channel is not desired to be used, only the corresponding 20 MHz channel is cleared, and the remaining channel is used for transmission. For example, when the MU-RTS frame is to be transmitted using the primary 80 MHz channel, if one 20 MHz channel within the sub 40 MHz channel is in an occupied state, the corresponding channel is cleared, and only the remaining channel is used to transmit the MU-RTS frame.

[0357] In the MU-RTS, the ID (for example, association ID) of the STA to be transmitted with the CTS can be indicated, and the channel on which each STA is to transmit the CTS frame. The channel on which the CTS frame is to be transmitted can be a special 20 MHz channel or a plurality of 20 MHz channels. At this time, the type of the plurality of 20 MHz channels can be restricted. In addition, the 20 MHz channel to be cleared (punctured channel) can be additionally indicated without transmitting the MU-RTS. The MU-RTS frame can be configured as shown in the following Figure 34 The MU-RTS frame can be a frame requesting simultaneous transmission of a CTS frame from a plurality of STAs. In this case, the plurality of STAs can include an HE STA defined in IEEE 802.11ax and can include an EHT STA defined in IEEE 802.11be. At this time, the HE STA cannot indicate a channel other than a primary 20 MHz channel, a primary 40 MHz channel, a primary 80 MHz channel, or a primary 160 MHz channel or a primary 80+80 channel to transmit the CTS frame.

[0358] Referring to Figure 33In this configuration, the AP can transmit MU-RTS frames to multiple STAs, and from the end time of the transmission of the PPDU including the corresponding MU-RTS frame to the SIFS time, it can receive CTS frames simultaneously transmitted from the STAs. The CTS frames can be of the type repeatedly transmitted every 20MHz channel. The CTS frames can be of the non-HT replicated PPDU type. In this case, the CTS frames transmitted by multiple STAs can be identically constructed. Therefore, the AP can receive CTS frames on each 20MHz channel at any given time. The received power of the CTS frames received on each 20MHz channel may differ. When the AP receives a CTS frame in response to the MU-RTS, the AP can perform MU-OFDMA or MU-MIMO operations with multiple STAs based on the bandwidth of the received CTS frame.

[0359] Furthermore, as mentioned above, the transmission bandwidth of the CTS frame transmitted by the STA receiving the MU-RTS frame can be different. For example, refer to... Figure 18 b) When the channel indicating the transmission of the CTS frame from the MU-RTS frame is the primary 20MHz channel, STA1 can perform channel sensing operation only on the corresponding primary 20MHz channel. Channel sensing operation can be performed during the SIFS time period. When the primary 20MHz channel is idle, the CTS frame can be transmitted. In this case, the corresponding CTS frame can be transmitted in a non-HT PPDU type. STA1 can receive downlink frames on the corresponding 20MHz channel after transmitting the CTS frame. In this case, the STA transmitting the CTS frame can be an HE STA or an EHT STA.

[0360] refer to Figure 33 c) When the channel indicating the transmission of the CTS frame from the MU-RTS frame is the second lowest 20MHz channel, the STA (e.g., STA2) indicated in the user information field of the corresponding MU-RTS frame can perform channel sensing operation only on the corresponding 20MHz channel. The channel sensing operation can be performed during the SIFS time. When the corresponding 20MHz channel is idle, the CTS frame can be transmitted. At this time, the corresponding CTS frame can be transmitted as a non-HT-replicated PPDU. STA2 can receive downlink frames on the corresponding 20MHz channel after transmitting the CTS frame. In this case, the STA transmitting the CTS frame can be an HE STA.

[0361] refer to Figure 33d, when the channel on which the CTS frame is instructed to be transmitted from the MU-RTS frame is the primary 80MHz channel and the special 20MHz channel is a clear type, the STA (e.g., STA3) indicated in the user info field of the corresponding MU-RTS frame can be instructed to perform a channel sensing operation on the other channel except for the 20MHz channel in the primary 80MHz channel. As a result of the channel sensing, when the corresponding channel is in an idle state, the CTS frame can be transmitted. At this time, the corresponding CTS frame can be transmitted in a non-HT duplicate PPDU type. The STA3 can receive a downlink frame in the channel on which the MU-RTS frame and the CTS frame are exchanged after transmitting the CTS frame. The STA that transmits the CTS frame can be an EHT STA.

[0362] The MU-RTS frame used in the MU-RTS frame and CTS frame exchange process can be of a type in which the RU allocation field of the existing MU-RTS frame can indicate a plurality of 20MHz band deformation. At this time, a field indicating a punctured channel can be added to the corresponding MU-RTS frame. Alternatively, the corresponding MU-RTS frame can be configured as follows.

[0363] Figure 34 A fourth embodiment of the structure of the MU-RTS frame according to an embodiment of the present application is illustrated. At this time, the description of the part configured the same as the MU-RTS frame of Figure 29 or 32 can be omitted.

[0364] Referring to Figure 34 , the MU-RTS frame can be configured in a type of trigger frame, and can be configured with a common field and one or more user info fields. The common field includes a trigger type field, an indication field of whether a transmission trigger frame is attached after the corresponding frame, a field indicating whether a carrier sensing operation of a receiving terminal is required, an uplink frame bandwidth field, an uplink frame bandwidth extension field, and a reservation field. The common field can further include a MU RTS type field. At this time, the fields other than the field indicating the MU RTS type field in the common field can be set the same as the MU-RTS frame of Figure 14 . The field indicating the MU RTS type field can indicate that the MU-RTS frame is of a type transmitted after a part of the 20MHz channel is cleared. For example, the MU RTS type field can be set to 11. Meanwhile, the common field can further include a punctured channel field. When the MU RTS type field is set to 11, the punctured channel field can be included. When the punctured channel field is included, the corresponding field can be set the same as the MU-RTS frame of Figure 17 .

[0365] The user info field can be constituted differently according to whether the terminal indicated by the corresponding field is an HE STA or an EHT STA. When the user info field indicates an HE STA, the corresponding user info field can be constituted by a 12-bit AID field and an 8-bit RU allocation field. At this time, B0 of the RU allocation field indicates whether the bandwidth is 160 MHz or 80+80 MHz, and B7-B1 can be indicated as shown in Table 3. When the corresponding user info field indicates an EHT STA, the corresponding user info field can be constituted by a 12-bit AID field and an 8-bit or 9-bit RU allocation field. If the corresponding RU allocation field is 9 bits, B1-B0 of the RU allocation field can indicate the segment position of the 80 MHz band in which the main channel transmitting the corresponding CTS frame is located when a 320 MHz bandwidth channel is divided into 4 80 MHz channel segments. At this time, B0 can designate the segment position of the 80 MHz band. For example, when B0 is set to 0, it can indicate that the corresponding 80 MHz segment is included in the 160 MHz channel of the lower frequency band in the low 320 MHz or 160+160 MHz main channel. When B0 is set to 1, it can indicate that the corresponding 80 MHz segment is included in the 160 MHz channel of the high frequency band in the low frequency 320 MHz or 160+160 MHz main channel.

[0366] The transmission bandwidth of the CTS frame and the position in the 80 MHz segment can be indicated by B8-B2 of the RU allocation field. At this time, the B8-B2 values of the RU allocation field can be set as shown in Table 8 below.

[0367] [Table 8]

[0368]

[0369]

[0370] Values other than Table 8 of the RU allocation field cannot be used.

[0371] On the other hand, when the B8-B2 values indicate a 320 MHz or 160+160 MHz main channel, or indicate a plurality of RUs within the 320 MHz or 160+160 MHz, the B1-B0 values of the RU allocation field can be set to 11.

[0372] On the other hand, when the RU allocation field is constituted by 8 bits, B1-B0 of the RU allocation field can indicate the segment position of the 80 MHz band in which the main channel transmitting the corresponding CTS frame is located when a 320 MHz bandwidth channel is divided into 4 80 MHz channel segments.

[0373] The transmission bandwidth of the CTS frame and the location in the 80MHz segment can be indicated in B8-B2 of the RU allocation field. At this time, the B7-B2 values of the RU allocation field can be set as shown in Table 9 below.

[0374] [Table 9]

[0375]

[0376]

[0377]

[0378] Values other than those of Table 9 of the RU allocation field cannot be used.

[0379] On the other hand, when the B8-B2 values indicate a 320MHz or 160+160MHz primary channel, or indicate a plurality of RUs within the 320MHz or 160+160MHz, the B1-B0 values of the RU allocation field can be set to 11.

[0380] When the MU RTS type field is 11, the EHT STAs receiving the corresponding MU-RTS frame from the AP can confirm the bandwidth field and the bandwidth extension field to confirm the bandwidth of the MU-RTS frame transmitted. In addition, one or more 20MHz channels to which the corresponding STAs are to transmit the CTS frame can be confirmed through the RU allocation field. The interpretation method of the corresponding RU allocation field can differ according to the type of the terminal (e.g., whether it is an HE STA or an EHT STA) receiving the MU-RTS frame and the MU RTS type field. The EHT STAs confirming the RU allocation field interpreted according to the MU RTS type field can transmit the CTS frame to the one or more 20MHz channels indicated in the RU allocation field. In this case, if the punctured channel field is added to the MU-RTS frame, reference can be made thereto to transmit the CTS frame to the one or more 20MHz channels indicated in the RU allocation field.

[0381] Meanwhile, the HE STAs receiving the corresponding MU-RTS frame can not be able to decode the added punctured channel field. Accordingly, the corresponding HE STAs can transmit the CTS frame on the channels indicated in the RU allocation field without emptying the special 20MHz channel.

[0382] Meanwhile, an indicator requesting the transmission of the CTS frame on the primary 20MHz channel can be added to the MU-RTS frame of Equation 1. Figure 19 When the indicator for transmitting the CTS frame on the primary 20MHz channel is set, even if the primary 20MHz channel is not indicated in the RU allocation field, the STAs receiving the MU-RTS frame can transmit the CTS frame to the plurality of 20MHz channels including the primary 20MHz channel.

[0383] Meanwhile, the exchange procedure of the MU-RTS frame and the CS frame illustrated in Figure 13 , Figure 16 or Figure 18 may also be performed between an AP belonging to an AP MLD and terminals belonging to a STA MLD. At this time, the STA MLD can not be able to perform the STR operation on some links. Therefore, in other links of the terminals belonging to the corresponding STA MLD, the AP MLD transmits the MU-RTS to a plurality of terminals including other terminals of the corresponding STA MLD, and thus the exchange operation of the MU-RTS frame and the CTS frame can be started in one link of the AP MLD. At this time, the operation between the AP MLD and the STA MLD can be performed as follows.

[0384] Figure 35 FIG. 11 illustrates an embodiment of a channel reservation procedure through the exchange procedure of the MU-RTS frame and the CTS frame for operation of a plurality of terminals according to an embodiment of the present application.

[0385] Referring to Figure 35 , even for the MU-RTS frame transmitted from the AP belonging to the AP MLD, some STAs cannot transmit the CTS frame due to the characteristic that the STR operation cannot be performed, and when the CTS frame is transmitted by other STAs in the corresponding channel, the corresponding AP can perform the channel reservation procedure through the exchange procedure of the MU-RTS frame and the CTS frame. For example, a plurality of APs can belong to the AP MLD. At this time, each AP can operate each link. For example, AP1 and AP2 can belong to the AP MLD. AP1 can operate link 1, and AP2 can operate link 2. The STA MLD or the STA not belonging to the STA MLD can access the APs in the AP MLD. For example, STA1-1 and STA1-2 included in the STA MLD1 can access the AP MLD. At this time, STA1-1 can access AP1, and STA1-2 can access AP2. STA2-1 and STA2-2 included in the STA MLD2 can access AP1 and AP2, respectively. At this time, STA1-1 and 1-2 belonging to the STA MLD1 can not be able to perform the STR operation. That is, when STA1-1 performs the transmission operation in the process of link 1, STA1-2 can not be able to perform the reception operation. STA2-1 and STA2-2 belonging to the STA MLD2 can perform the STR operation. In addition, STA3 not belonging to the STA MLD can access AP1.

[0386] Referring to Figure 35The AP 1 belonging to the AP MLD can perform frame transmission and reception operations with a plurality of terminals accessing to the corresponding AP. For example, the AP 1 can transmit downlink frames to the STA 1-1, the STA 2-1, and the STA 3 simultaneously using OFDMA operation. At this time, in order to protect the corresponding frame transmission and reception operations, the exchange process of the MU-RTS frame and the CTS frame can be performed with the corresponding plurality of terminals.

[0387] Meanwhile, when the STR operation is possible between the APs belonging to the AP MLD, the channel access operation for frame transmission can be independently performed at the AP 2 during the frame transmission and reception operation is performed at the AP 1. After the corresponding channel access operation is performed, the frame transmission and reception operation with a plurality of terminals can be performed. For example, when having downlink data to be transmitted to a plurality of terminals, the AP 2 can transmit frames simultaneously using downlink MIMO operation with the STA 1-2 and the STA 2-2 or using downlink OFDMA operation. At this time, in order to protect the corresponding frame transmission and reception operations, the MU-RTS frame can be transmitted to the corresponding plurality of terminals to perform the exchange process of the MU-RTS frame and the CTS frame.

[0388] At this time, referring to Figure 35 of b, since the STA MLD 1, which is not possible to perform the STR operation at the link 1 and the link 2, receives a frame from the link 1, even if the MU-RTS frame is received from the link 2, the CTS frame as a response thereto cannot be transmitted. At this time, referring to Figure 35 of c, the STA that can perform the transmission of the CTS frame as a response to the MU-RTS frame can transmit the CTS frame using the channel indicated in the MU-RTS. At this time, the STA that transmits the CTS frame can be the STA MLD that does not transmit a frame at the link 1 at the point of time of reception at the link 2, the STA MLD that can perform the STR operation at the link 1 and the link 2, or the STA that does not belong to the STA MLD. The operation of transmitting the CTS frame as a response to the MU-RTS can be performed as shown in Figure 13 , Figure 16 or Figure 18 .

[0389] Referring to Figure 35of a, even if a STA MLD of the AP MLD cannot receive a CTS frame from a STA MLD of the STA that cannot perform a STR operation with respect to a transmitted MU-RTS frame, it can be determined that the exchange of the MU-RTS frame and the CTS frame is successful when other terminals indicated to transmit the CTS frame using the same frequency band transmit the CTS frame. Accordingly, the AP 2 of the AP MLD can transmit a downlink frame to a terminal that cannot perform a STA operation and thus cannot transmit a CTS frame. At this time, since a frame transmitted to a terminal that cannot perform a STR operation is included, when a frame transmitted from the link 1 or the link 2 requests transmission of a response frame such as an ACK frame or a BlockAck frame, the transmission end time point of the downlink frame transmitted from the link 1 and the link 2 is identical.

[0390] Meanwhile, referring again to Figure 35 of b, since the STA 1-2 that cannot perform a STR operation and thus cannot transmit a CTS response with respect to the MU-RTS frame received in the link 2, it can receive a downlink frame transmitted from the AP 2 of the corresponding link according to the transmission of the CTS frame by other terminals (for example, the STA 2-2) to the corresponding channel.

[0391] On the other hand, when an MLD that cannot perform a STR operation participates in the exchange process of the MU-RTS frame, there can be no CTS frame transmitted to a special channel according to the inability to transmit a CTS frame with respect to the MU-RTS received in the following situation.

[0392] Figure 36 An operation in which a CTS frame with respect to a MU-RTS frame cannot be transmitted in a special 20 MHz channel according to an embodiment of the present application is illustrated.

[0393] Referring to Figure 36 of a, as illustrated in Figure 13 when a channel extension operation is performed in order to transmit a MU-RTS frame, if the STAs indicated to transmit a CTS frame using an extended channel include only STAs that receive a downlink frame from a link that cannot perform a STR operation, the CTS frame can not be transmitted to the corresponding extended channel. That is, the AP MLD can perform an exchange operation of a MU-RTS frame and a CTS frame using an extended channel after completing a channel access operation in the other link during the transmission of a frame in one link. At this time, the MU-RTS frame can be transmitted using one of a primary 40 MHz channel, a primary 80 MHz channel, a primary 160 MHz or 80+80 MHz channel, a primary 240 MHz or 160+80 MHz channel, or a primary 320 MHz or 160+160 MHz channel. At this time, in the case of a STA that can perform a STA operation or does not receive a frame in the other link, it can be determined that the exchange of the MU-RTS frame and the CTS frame is successful when other terminals indicated to transmit the CTS frame using the same frequency band transmit the CTS frame. Figure 20the CTS frame to the received MU-RTS frame. Conversely, in the case of a STA whose other link on which the STA operation is not possible has received the frame, as shown in Figure 35 the CTS frame cannot be transmitted as a response to the received MU-RTS. At this time, as shown in Figure 35 the CTS frame cannot be transmitted as a response to the received MU-RTS. At this time, as shown in AP1 and AP2 can belong to an AP MLD. AP1 can use a link 1, and AP2 can use a link 2. STA1-1 and STA1-2 can belong to a STA MLD1. STA2-1 and STA2-2 can belong to a STA MLD2. STA1-1, STA2-1, and STA3 can access to AP1, and STA1-2 and STA2-2 can access to AP2. At this time, STA1-1 and STA1-2 of the STA MLD1 can not perform the STR operation on the link 1 and the link 2. At this time, AP1 can transmit a downlink frame to STA1-1, STA2-1, and STA3 through a multi-user OFDMA operation. Alternatively, AP1 can transmit a downlink frame to STA1-1. In order to protect the downlink frame, AP1 can additionally perform an exchange procedure of an RTS frame or a MU-RTS frame and a CTS frame. Meanwhile, when AP1 performs a frame transmission and reception operation with STA1-1 or a plurality of terminals including STA1-1, AP2 can complete a channel contention procedure for frame transmission on the link 2.

[0394] At this time, AP2 can want to transmit a downlink frame to a plurality of terminals including STA1-2. For example, it can want to transmit a downlink frame to STA1-2 and STA2-2. At this time, in order to protect the transmission operation of the downlink frame, the exchange operation of the MU-RTS frame and the CTS frame can be performed before the transmission of the corresponding frame. The transmission of the MU-RTS frame can be transmitted using the same bandwidth as the bandwidth of the downlink frame. For example, when the downlink frame is to be transmitted through the primary 80 MHz channel, the MU-RTS frame can also be transmitted using the primary 80 MHz bandwidth. The transmission bandwidth of the CTS frame transmitted by STA2-2 can be designated as the primary 40 MHz channel, and the transmission bandwidth of the CTS frame transmitted by STA1-2 can be designated as the primary 80 MHz channel. At this time, since STA1-1 receives a frame at link 1, STA1-2 can not be able to transmit a CTS frame as a response to the MU-RTS frame received at link 2. Meanwhile, STA2-2 can transmit a CTS frame as a response to the MU-RTS frame. Meanwhile, since AP2 receives a CTS frame for the MU-RTS frame transmitted by the 80 MHz band only in the 40 MHz band, the downlink frame can be transmitted using only the 40 MHz band. That is, in a sub 40 MHz channel that is not the primary 40 MHz channel, even if the actual channel is in an idle state, frame transmission and reception operations can not be performed.

[0395] In addition, even in the case where the exchange operation of the MU-RTS frame and the CTS frame is performed by emptying the special 20 MHz channel as shown in Figure 31 or Figure 33 , the situation where the CTS frame cannot be received can occur for the MU-RTS frame transmitted to the special 20 MHz channel. Referring to the b of Figure 36 , as shown in the a of Figure 36 , AP1 and AP2 can belong to the AP MLD, STA1-1 and STA1-2 can belong to the STA MLD1, and STA2-1 and STA2-2 can belong to the STA MLD2. At this time, AP1 and AP2 can operate link 1 and link 2, respectively, and STA1-1 and STA1-2 can not be able to perform the STR operation at link 1 and link 2. At this time, AP1 can perform an operation of transmitting a downlink frame to STA1-1 or a plurality of terminals including STA1-1. During the transmission of the corresponding frame, the channel access operation of AP2 for frame transmission can be completed at link 2. At this time, in order to protect the downlink frame to be transmitted, AP2 can additionally perform the exchange operation of the MU-RTS frame and the CTS frame. The receiving STA of the corresponding MU-RTS frame can be the STA that receives the downlink frame. For example, when AP2 wants to transmit a downlink frame to STA1-2 and STA2-2, the MU-RTS frame can be transmitted to the corresponding terminals. At this time, AP2 can transmit the MU-RTS frame as shown in Figure 16 or Figure 18 The MU-RTS frame is transmitted after the special 20MHz band is emptied. In the STA1-2 and STA 2-2 that receive the MU-RTS frame, the CTS frame can be transmitted as a response to the received MU-RTS frame. At this time, as shown in Figure 18 The CTS frame can be transmitted only on the channel on which the MU-RTS frame indicates the transmission of the CTS frame. At this time, since STA1-1 receives the frame on link 1, STA1-2 can not be able to transmit the CTS frame for the MU-RTS frame. STA2-2 can transmit the CTS frame as a response to the MU-RTS frame. At this time, when only STA1-2 is instructed to transmit the CTS frame for the special 20MHz channel, the corresponding 20MHz channel can be in a state in which the CTS transmission is not performed. AP2 that does not receive the CTS frame as a response to the MU-RTS frame in the corresponding 20MHz band can empty the corresponding 20MHz channel and transmit the downlink frame even if the corresponding 20MHz channel is actually in an idle state. At this time, if the channel for which the CTS response for the MU-RTS frame is not received is the primary 20MHz channel, AP2 cannot perform the downlink transmission and reception operation with STA1-2 and STA2-2 even if the CTS frame is received on the other link for the corresponding MU-RTS frame. In addition, when the CTS response for the MU-RTS frame is received at least on the primary 20MHz channel, the transmission of the downlink frame after the reception of the CTS response can be performed.

[0396] Alternatively, when a part of STAs communicating with the AP temporarily changes the primary channel, the phenomenon that the CTS frame for the MU-RTS frame cannot be transmitted can also occur. Referring to Figure 36 As shown in a of Figure 36 In the case where the AP MLD transmits a frame to the STA MLD1 and the STA MLD2, when the primary channel of the STA2-2 is temporarily moved to another channel that is not the primary channel of the AP before the AP2 transmits a frame to link 2, the corresponding STA2 can transmit a CTS response for the received MU-RTS frame based on the STA2-2de primary channel. For example, when the STA2-2de primary channel is changed to the 20MHz channel of the AP2, the STA2-2de primary channel can be changed to the 20MHz channel of the AP2, and the STA2-2de primary channel can be changed to the 20MHz channel of the AP2. Figure 14 or Figure 15When the MU-RTS frame indicates transmission of the CTS frame by the bandwidth of 40MHz, as a response to the received MU-RTS frame from the AP 2, the corresponding STA 2-2 transmits the CTS frame using the primary 40MHz channel of the STA 2-2. Meanwhile, the STA 1-2 can use the same primary channel as the AP 2. At this time, since the STA 1-1 and the STA 1-2 cannot perform the STR operation, and the STA 1-1 receives the frame from the link 1, the STA 1-2 cannot transmit the CTS frame as a response to the received MU-RTS frame. At this time, for the special 20MHz channel, only the STA 1-2 is instructed to transmit the CTS frame, and the corresponding 20MHz channel can be in a state of not performing the CTS transmission. At this time, if the channel on which the CTS response to the MU-RTS frame is not received is the primary 20MHz channel, the AP 2 is not possible to perform the transmission and reception operation of the downlink frame with the STA 1-2 and the STA 2-2 even if the CTS frame is received on the other channel for the corresponding MU-RTS frame.

[0397] In the present application, in the process of transmitting the downlink frame to the STA belonging to the MLD which cannot perform the STR operation, when the channel access is completed on the other link and the frame is transmitted with the other STA belonging to the corresponding MLD, the transmission operation of the downlink frame can be performed as described below.

[0398] Figure 37 FIG. 1 illustrates a first embodiment of an operation of adding an additional condition to omit the transmission of the MU-RTS frame in the AP MLD according to an embodiment of the present application.

[0399] Reference Figure 37When the AP MLD completes a channel access operation for frame transmission on other links while performing a frame transmission process on one link, if a terminal that does not perform a CTS response in the transmission of an MU-RTS frame is included in the corresponding link and transmits a downlink frame, the transmission of the corresponding MU-RTS frame can be omitted. That is, even when the length of a PHY Service Data Unit (PSDU) to be transmitted on the corresponding link exceeds a specific value (e.g., dot11RTSThreshold) and requires the transmission of an RTS frame or an MU-RTS frame, the exchange process of the MU-RTS frame and the CTS frame can be omitted. For example, AP1 and AP2 can belong to an AP MLD. AP1 can use link 1 and AP2 can use link 2. STA1-1 and STA1-2 can belong to STA MLD1. STA2-1 and STA2-2 can belong to STA MLD2. STA1-1, STA2-1, and STA3 can access AP1 and STA1-2 and STA2-2 can access AP2. At this time, STA1-1 and STA1-2 of STA MLD1 can not perform an STR operation on link 1 and link 2. At this time, AP1 can transmit a downlink frame to STA1-1, STA2-1, and STA3 through a multi-user OFDMA operation. Alternatively, AP1 can transmit a downlink frame to STA1-1. In order to protect the downlink frame, AP1 can additionally perform an exchange process of an RTS frame or an MU-RTS frame and a CTS frame. Meanwhile, when AP1 performs a frame transmission and reception operation with STA1-1 or a plurality of terminals including STA1-1, AP2 can complete a channel contention process for frame transmission on link 2. AP2 can want to transmit a downlink frame to a plurality of terminals including STA1-2. At this time, if one or more of the receiving STAs of the frame to be transmitted belong to a STA MLD that cannot perform an STR operation with link 1, and the STAs belonging to the corresponding MLD receive a frame on link 1, an exchange operation of an MU-RTS frame and a CTS frame is not performed to transmit a downlink frame. At this time, if the completion time point of the channel contention process is before the transmission end time point of the CTS frame on link 1, even when a channel access operation is completed on link 2, a channel sensing operation is performed at the start time point of a PPDU including a downlink frame on link 1, and then a frame transmission operation can be performed according to the corresponding time point.

[0400] Meanwhile, when the completion time point of the channel contention process on link 2 occurs in the transmission time of the downlink frame on link 1, an operation is performed according to the remaining transmission time of the PPDU including the downlink frame on link 1 as follows.

[0401] Figure 38FIG. 13 illustrates a second embodiment of an operation of adding an additional condition to omit transmission of a MU-RTS frame in an AP MLD according to an embodiment of the present application.

[0402] Referring to Figure 38 When the AP MLD completes a channel access operation for frame transmission in one link in a frame transmission operation in other links, if a terminal that does not perform a CTS response in the corresponding link is included in the transmission of the MU-RTS frame, the transmission of the corresponding MU-RTS frame can be omitted. At this time, when the point in time at which the channel access operation is completed is included in the transmission time of the PPDU of the downlink frame in the other link, the transmission operation of the MU-RTS frame and the CTS frame can be omitted at the corresponding channel access completion point in time and the downlink frame can be transmitted. That is, when the length of the PHY Service Data Unit (PSDU) to be transmitted in the corresponding link exceeds a specific value (for example, dot11RTSThreshold) and requires transmission of an RTS frame or a MU-RTS frame, the exchange process of the MU-RTS frame and the CTS frame can also be omitted. For example, as Figure 22 illustrated, when the AP1 belonging to the AP MLD performs a frame transmission and reception operation with a plurality of terminals including the STA1-1 or the STA1-2, the AP2 can complete a channel contention process for frame transmission in the link 2. In addition, the AP2 can have data to be transmitted to a plurality of STAs including the STA1-2. At this time, while the AP1 performs a process of transmitting a PPDU containing a downlink frame on the link 1, the AP2 completes the channel contention in the link 2, and at the corresponding completion point in time, it can be confirmed that the remaining transmission time of the PPDU transmitted from the link 1. At this time, when the remaining transmission time of the PPDU transmitted from the link 1 is equal to or longer than a specific time, the AP2 omits the exchange process of the MU-RTS and CTS frames and transmits a downlink frame to the terminals including the STA1-2. The specific time can be a value stored in the AP. Alternatively, the specific time can be exchanged in a negotiation process for multi-link operation between the AP MLD and the STA MLD.

[0403] Meanwhile, when the channel contention completion point in time in the link 2 occurs in the transmission time process of the downlink frame in the link 1, and the remaining transmission time of the PPDU transmitted from the link 1 is within the specific time, as Figure 23 illustrated, the transmission of the downlink frame is matched with the end point in time of the transmission of the PPDU of the corresponding frame in the link 1. Alternatively, the exchange process of the MU-RTS frame and the CTS frame can be performed as

[0404] Figure 39An embodiment of an operation of an AP MLD transmitting a MU-RTS frame according to an additional condition added according to an embodiment of the present application is illustrated. At this time, a repeated description of Figure 37 and Figure 38 may be omitted.

[0405] Referring to Figure 39 , when an AP MLD completes a channel access operation for frame transmission in other links while performing a frame transmission procedure in one link, and the time from the corresponding completion time point to the PPDU transmission end time point on the link on which the frame has been transmitted is within a special time, the AP MLD can perform a transmission operation of a MU-RTS frame. For example, one of the APs (e.g., AP1) belonging to the AP MLD can transmit a downlink frame. At this time, the downlink frame can be transmitted to a plurality of terminals. For example, AP1 operates in link 1 and can transmit a downlink frame to STA1-1, STA2-1, and STA3. At this time, STA1-1 and STA1-2 belong to the STA MLD1, and STA1-1 and STA1-2 can not be able to perform an STR operation. Another AP (e.g., AP2) belonging to the same AP MLD as the AP1 transmitting a downlink frame in link 1 can complete a channel access operation for frame transmission. In this case, the STAs from the frame to be transmitted by the AP2 can be a plurality of STAs, one or more of which can be STAs receiving a frame in link 1. For example, the downlink frame transmitted by AP2 in link 2 can be transmitted to STA1-2 and STA2-2. At this time, if the AP2 requires a transmission operation of a MU-RTS frame according to the length of the PSDU to be transmitted at the time point at which the AP2 completes a channel access operation in link 2, including the remaining transmission time of the PPDU of the frame transmitted from link 1, is within a special time, the AP2 can transmit a MU-RTS frame. Alternatively, in order to protect the downlink frame to be transmitted by the AP2, a exchange procedure of a MU-RTS frame and a CTS frame can be performed. In this case, padding bits can be added to the MU-RTS frame to match the downlink frame transmitted from link 1 and the transmission end time point. Alternatively, a channel sensing operation can be additionally performed so that the transmission end time point of the MU-RTS frame coincides with the PPDU transmission end time point in link 1.

[0406] Meanwhile, the plurality of STAs receiving the MU-RTS frame can acknowledge the MU-RTS frame and transmit a CTS frame after performing a channel sensing on the channel indicated from the MU-RTS frame. The AP receiving the CTS frame can transmit a downlink frame to the plurality of STAs. At this time, when a portion of the STAs incapable of the STR operation on the link 1 transmits an uplink response frame (e.g., a BlockAck frame), the downlink transmission can be deferred until the end of the transmission of the PPDU of the response frame included in the corresponding link (e.g., the link 1). At this time, a channel sensing operation can be performed during the defer time to confirm whether the corresponding channel is occupied by other terminals during the corresponding time.

[0407] Meanwhile, when one or more terminals transmit a CTS frame in response to the MU-RTS frame on the special channel, the AP can determine that the transmission operation of the MU-RTS frame is successful. Accordingly, the one or more STAs can be directed to transmit a CTS frame on all channels of the 20MHz band in which the MU-RTS frame is transmitted by the following operation.

[0408] Figure 40 FIG. 1 illustrates an operation for avoiding a situation in which a CTS frame cannot be transmitted in a special 20MHz due to an operation of a corresponding STA MLD according to an embodiment of the present application.

[0409] Reference Figure 40 When the AP belonging to the AP MLD wants to transmit a downlink frame to a plurality of terminals including STAs incapable of transmitting a CTS frame due to a situation in which the STR operation is impossible, a channel can be indicated to the STAs incapable of CTS transmission so as to transmit a CTS frame to a primary 20MHz channel or a portion of a channel including the primary 20MHz channel. At this time, a frame can be transmitted to other STAs from an extended channel. The other STAs can be indicated to transmit a CTS frame including the corresponding primary channel and the extended channel. That is, a frequency band used in the STAs in which the transmission of the CTS frame is impossible can cause the other STAs to transmit a CTS frame. For example, AP1 and AP2 can belong to the AP MLD. AP1 can operate a link 1 and AP2 can operate a link 2. STAs MLD or STAs not belonging to the STA MLD can access the APs in the AP MLD. For example, STA1-1 and STA1-2 included in the STA MLD1 can access the AP1 and the AP2, respectively. STA2-1 and STA2-2 included in the STA MLD2 can access the AP1 and the AP2, respectively. At this time, the STAs 1-1 and 1-2 belonging to the STA MLD1 can be impossible to perform the STR operation. The STAs 2-1 and 2-2 belonging to the STA MLD2 can perform the STR operation. In addition, STA3 can additionally access the AP1.

[0410] The AP 1 can transmit a downlink frame after completing the channel access operation in the link 1. At this time, the downlink frame can be transmitted to the STA 1-1 or to a plurality of terminals including the STA 1-1. At this time, in order to protect the frame transmission operation of the link 1, the exchange operation of the RTS or MU-RTS frame and the CTS frame can be additionally performed.

[0411] In the process that the AP 1 transmits the downlink frame, the AP 2 can complete the channel access operation for transmitting the downlink frame. At this time, the AP 2 can have data to be transmitted to a plurality of STAs including the STA 1-2. At this time, the AP 2 can transmit a downlink frame to a plurality of terminals including the STA 1-2. At this time, since the length of the PSDU including the downlink frame is equal to or longer than the special length, the exchange operation of the RTS frame or the MU-RTS frame and the CTS frame can be required. At this time, the AP can transmit the MU-RTS frame to a plurality of STAs. At this time, the STA (for example, the STA 1-2) which cannot transmit the CTS frame regardless of the STR operation can indicate the transmission of the CTS frame to the primary 20MHz channel or the partial channel including the primary channel. At this time, the STA capable of the STR operation or the STA which does not receive the frame in the link 1 can indicate the transmission of the CTS frame to the extended channel in the channel in which the MU-RTS frame is transmitted. The STA capable of the STR operation can be the STA belonging to the STA MLD capable of the STR operation. Or, it can be the STA belonging to the STA MLD which does not perform the frame reception operation in the link 1. Or, it can be the STA which does not belong to the STA MLD. At this time, each of the STAs can transmit the CTS frame according to the operation of Figure 13 or Figure 16 Thus, even if the STA 1-2 which cannot perform the STR operation does not transmit the CTS frame, the other STAs transmit the CTS frame to a plurality of channels including the primary channel, so that the AP 2 can receive the CTS frame for the transmitted MU-RTS frame. The AP 2 which receives the CTS frame for the MU-RTS frame can determine that the transmission operation of the MU-RTS frame has been successful. Thus, the AP 2 can transmit the downlink frame to a plurality of terminals.

[0412] On the other hand, if the STR operation cannot be performed due to the interference inside the device, so that the CTS response for the MU-RTS frame received by the partial STA cannot be transmitted, the other STAs can be requested to transmit the CTS frame to the entire band as described below.

[0413] Figure 41 A second embodiment of an operation for avoiding a situation in which the CTS frame in the special 20MHz cannot be transmitted due to the operation of the corresponding STA MLD according to the embodiment of the present application is illustrated. At this time, the description which is repeated with the description of Figure 40 will be omitted.

[0414] Reference Figure 41 When an AP belonging to an AP MLD wants to transmit a downlink frame to a plurality of terminals including STAs that cannot transmit a CTS frame due to a condition in which an STR operation cannot be performed, the AP can instruct a STA capable of CTS transmission to transmit a CTS frame by the entire band. For example, as shown in FIG. 11, STA MLD1, STA MLD2, and STA3 can access an AP MLD. At this time, AP1 completes a channel access operation in link 1 and transmits a downlink frame to a plurality of terminals including STA1-1. At this time, in order to protect the frame transmission operation in link 1, an exchange operation of an RTS or MU-RTS frame and a CTS frame can be additionally performed. Figure 25

[0415] During the transmission of a downlink frame by AP1, AP2 can complete a channel access operation for the transmission of a downlink frame. At this time, AP2 can have data to be transmitted to a plurality of STAs including STA1-2. At this time, AP2 can transmit a downlink frame to a plurality of terminals including STA1-2. At this time, since the length of a PSDU including a downlink frame is equal to or longer than a specific length, an exchange operation of an RTS frame or a MU-RTS frame and a CTS frame can be required. At this time, the AP can transmit a MU-RTS frame to a plurality of STAs. At this time, a terminal that cannot perform an STR operation cannot transmit a CTS frame as a response to the MU-RTS frame. When it is determined that a part of the terminals cannot transmit a CTS frame so that a CTS frame cannot be transmitted in a specific 20 MHz channel, AP2 can request other terminals capable of transmitting a CTS frame to include the corresponding channel and transmit a CTS frame. The other STAs can be STAs belonging to an STA MLD capable of an STR operation. Or, it can be an STA belonging to an STA MLD that does not perform a frame reception operation in link 1. Or, it can be an STA that does not belong to an STA MLD. For example, AP2 can transmit a downlink frame to STA2-2 only in a primary 40 MHz channel. At this time, in a secondary 40 MHz channel, a downlink frame can be transmitted to STA1-2. At this time, STA1-1 receives a frame, and thus STA1-2 cannot transmit a CTS frame as a response to the MU-RTS. At this time, AP2 can request STA2-2 to transmit a CTS frame corresponding to the MU-RTS frame using the entire band. STA2-2 that receives the MU-RTS frame can transmit a CTS frame through all the bands in which the MU-RTS frame is received. Thereby, AP2 can receive a CTS frame for the transmitted MU-RTS frame. AP2 that receives the CTS frame for the MU-RTS frame can determine that the transmission operation of the MU-RTS frame has been successful. Thereby, AP2 can transmit a downlink frame to a plurality of terminals.

[0416] ​On the other hand, if the STA MLD incapable of the STR operation can not perform the STR operation only in part of the channels, the AP MLD can perform an operation of confirming whether the channel in each of the STAs is clear without replacing the RTS or MU-RTS frame and the CTS exchange operation. The corresponding operation is performed in the process in which the AP transmits a Bandwidth Query Report Poll (BQRP) frame to a plurality of STAs and the plurality of STAs transmit a Bandwidth Query Report (BQR) frame. In this case, the channel in which each of the STAs transmits the BQR frame can be different from the channel in which the downlink data is transmitted. The operation of confirming whether the channel is clear through the transmission of the BQR frame can be performed as follows.

[0417] Figure 42 A third embodiment of an operation for avoiding a situation in which a CTS frame in a special 20 MHz cannot be transmitted due to the operation of the corresponding STA MLD according to an embodiment of the present application is illustrated. At this time, the repeated description of the first and second embodiments can be omitted. Figure 40 and Figure 41

[0418] Referring to Figure 42 When the AP belonging to the AP MLD wants to transmit a downlink frame to a plurality of terminals including a STA incapable of transmitting a CTS frame due to a situation in which the STR operation is not possible, a request for confirming whether the channel is occupied or not for each 20 MHz channel to each of the STAs can be made without replacing the channel reservation process through the MU-RTS frame and the CTS frame. At this time, the channel state confirmed in the plurality of STAs can be transmitted through a BQR frame. The frame requesting the transmission of the BQR can be a BQRP frame. For example, as shown in Figure 25 STA MLD1, STA MLD2, and STA3 can access the AP MLD. At this time, the AP1 completes the channel access operation in the link 1 and transmits a downlink frame to a plurality of terminals including the STA1-1. At this time, in order to protect the frame transmission operation of the link 1, the exchange operation of the RTS or MU-RTS frame and the CTS frame can be additionally performed.

[0419] ​During the transmission of downlink frames by AP1, AP2 can complete the channel access operation for transmitting downlink frames. At this time, AP2 can transmit data to multiple STAs, including STA1-2. AP2 can also transmit downlink frames to multiple terminals, including STA1-2. Since the length of the PSDU containing the downlink frame is equal to or longer than the special length, an exchange operation between RTS frames or MU-RTS frames and CTS frames may be required. When STA1-2 can perform STR operation on STA1-1 and the special channel, AP2 can confirm whether the multiple STAs receiving the downlink frame are occupied by the channel, without performing channel protection operation instead of transmitting via MU-RTS frames. The operation of confirming channel status with multiple STAs can be performed by transmitting request frames to multiple STAs to confirm channel occupancy for each 20MHz channel. The request frame can be a frame requesting confirmation of channel status from multiple STAs. The request frame can be a Bandwidth Query Report Poll (BQRP) frame. The BQRP frame can be a frame requesting the transmission of BQR to multiple STAs. At this point, each STA can indicate the channel on which to transmit BQR frames. When STA1-2 can transmit frames on a partial channel, AP2 can designate the channel on which STA1-2 transmits BQR frames as the corresponding channel.

[0420] Multiple STAs receiving BQRP frames from AP2 can use BQRP to acknowledge and request the transmission of BQR frames. This allows multiple STAs to perform channel sensing across all frequency bands they are capable of operating on. In this way, the occupancy of each 20MHz channel can be confirmed. Each STA confirming the occupancy of each 20MHz channel can then transmit a BQR frame through the channel indicated by the BQRP frame. At this time, the PPDU transmitting the BQR frame can be transmitted as either an HE TB PPDU or an EHT TB PPDU.

[0421] AP2, which receives BQR frames from multiple STAs, can confirm channel occupancy for all frequency bands at each STA. AP2 can transmit downlink frames through channels indicated as clear in the BQR frames. In this case, the channels through which AP2 receives BQR frames from each STA and the channels through which it transmits downlink frames to the corresponding STAs can be different channels.

[0422] On the other hand, if STR operations cannot be performed due to internal interference in the equipment, and if... Figure 21 If the AP does not receive CTS frames of MU-RTS frames transmitted by the AP on some channels other than the main channel, the AP can extend the channel and transmit frames after receiving CTS frames on some channels.

[0423] Figure 43 FIG. 1 illustrates a first embodiment of an operation of continuing frame transmission even if a CTS frame is not received in response to a MU-RTS frame in a special 20MHz channel according to an embodiment of the present application. At this time, a description repeated with that of FIG. 1 can be omitted. Figure 40

[0424] Referring to FIG. 2, a description of a process of transmitting a CTS frame in response to an RTS frame is omitted. Figure 43 When an AP belonging to an AP MLD wants to transmit a downlink frame to a plurality of terminals including a STA that cannot transmit a CTS frame due to a condition that an STR operation cannot be performed, the AP can instruct a STA capable of CTS transmission to transmit a CTS frame in the entire bandwidth. For example, as illustrated in FIG. 3, an STA MLD1, an STA MLD2, and an STA3 can access an AP MLD. At this time, an AP1 can complete a channel access operation in a link 1 and transmit a downlink frame to a plurality of terminals including an STA1-1. At this time, in order to protect a frame transmission operation in the link 1, an exchange operation of an RTS or MU-RTS frame and a CTS frame can be additionally performed. Figure 25

[0425] ​​While the AP 1 transmits the downlink frame, the AP 2 can complete the channel access operation for transmitting the downlink frame. At this time, the AP 2 can transmit the downlink frame to a plurality of terminals including the STAs 1-2. At this time, since the length of the PSDU including the downlink frame is equal to or longer than the special length, the exchange operation of the RTS frame or the MU-RTS frame and the CTS frame can be required. At this time, the AP 2 can transmit the MU-RTS frame to a plurality of STAs including the STAs 1-2. Among the STAs receiving the MU-RTS frame, the STAs which can transmit the CTS frame can transmit the CTS frame after performing the carrier sensing on the channel indicated in the MU-RTS. At this time, the STAs (for example, the STAs 1-2) which cannot transmit the CTS frame to the MU-RTS frame cannot transmit the CTS frame as a response to the MU-RTS frame. The STAs 1-2 cannot transmit the CTS frame due to the case where the STR operation cannot be performed, and thus the special 20 MHz channel cannot transmit the CTS frame to the transmitted MU-RTS. Meanwhile, the AP 2 can recognize that the CTS frame cannot be transmitted in the special 20 MHz channel due to the characteristic of the STAs 1-2 which cannot perform the STR operation after the STAs 1-2 transmit the MU-RTS frame. In this case, even if the CTS frame is not received in the corresponding 20 MHz band, the downlink frame can be transmitted to the corresponding 20 MHz band when the CTS frame is received in the other band. For example, when the STA 2-2 indicates that the CTS frame is transmitted in the primary 40 MHz channel and the STA 1-2 indicates that the CTS frame is transmitted in the primary 80 MHz channel with respect to the MU-RTS frame, even if the CTS frame is not received with respect to the sub 40 MHz channel, the AP 2 can transmit the downlink frame to the STAs 1-2 and 2-2 using the 80 MHz channel. At this time, the AP 2 can additionally perform the channel sensing operation with respect to the channel in which the CTS frame is not received during the special time. The channel sensing operation can include only the energy detection (ED) operation for confirming the reception energy level. In this case, the reference energy level for determining whether the channel is occupied in the ED operation can be set to be lower than the energy level for determining whether the channel is occupied in the infinite LAN operation. For example, the reference energy level for determining whether the channel is occupied in the ED operation can be set to -82 dBm. The special time can be a time point from the end time point of the transmission of the MU-RTS frame to the time point before the transmission of the downlink frame. Alternatively, the special time can be a special IFS time (for example, SIFS, PIFS, or AIFS).

[0426] Meanwhile, even if a part of the receiving STAs of the downlink frame cannot transmit the MU-RTS frame due to the STR feature, the AP 2 can recognize that the CTS frame cannot be received. At this time, the AP 2 can perform only the MU-RTS frame and CTS frame exchange procedure for the other frequency band and omit the transmission procedure of the MU-RTS frame to the frequency band in which the frame is transmitted to the corresponding STA, as described below.

[0427] Figure 44 A second embodiment illustrating the operation of continuing the frame transmission even if the CTS frame for the MU-RTS frame is not received in a special 20 MHz channel according to an embodiment of the present application. At this time, the repeated description of Figure 40 and Figure 43 may be omitted.

[0428] Referring to Figure 44 , when the AP belonging to the AP MLD wants to transmit the downlink frame to a plurality of terminals including the STA which cannot transmit the CTS frame due to the condition that the STR operation cannot be performed, the STA which can perform the CTS transmission can be instructed to transmit the CTS frame in the entire bandwidth. For example, as illustrated in Figure 25 , the STA MLD1, the STA MLD2, and the STA3 can access the AP MLD. At this time, the AP1 can complete the channel access operation in the link 1 and transmit the downlink frame to a plurality of terminals including the STA1-1. At this time, in order to protect the frame transmission operation in the link 1, the exchange operation of the RTS or MU-RTS frame and the CTS frame can be additionally performed.

[0429] While the AP 1 transmits the downlink frame, the AP 2 can complete a channel access operation for transmission of the downlink frame. At this time, the AP 2 can have data to be transmitted to a plurality of STAs including the STAs 1-2. At this time, the AP 2 can transmit a downlink frame to a plurality of terminals including the STAs 1-2. At this time, since the length of the PSDU including the downlink frame is equal to or longer than the special length, an exchange operation of an RTS frame or a MU-RTS frame and a CTS frame can be required. At this time, even if the STAs 1-2 include the MU-RTS frame and transmit the MU-RTS frame, according to the fact that the STAs 1-2 cannot perform the STR operation, the AP 2 can recognize that the CTS frame cannot be transmitted in the special 20 MHz channel. In this case, the AP 2 clears the channel recognized as being unable to transmit the CTS frame, and performs a channel reservation procedure through the exchange of the MU-RTS frame and the CTS frame only for the other in. For example, in the case where the downlink frame is transmitted from the primary 40 MHz channel in the STA 2-2 and the downlink frame is transmitted using the sub 80 MHz channel in the STA 1-2, the AP 2 transmits the MU-RTS frame to the primary 40 MHz channel and receives the CTS frame. At this time, the AP 2 extends the use channel from the primary 80 MHz channel after receiving the CTS frame in the primary 40 MHz channel and transmits the frame to the STAs 1-2 and 2-2. At this time, the AP 2 can perform a channel sensing operation on the sub 40 MHz channel during a special time. The channel sensing operation can include only an energy detection (ED) operation for confirming a reception energy level. In this case, the reference energy level for determining whether the channel is occupied in the ED operation can be set to be lower than that for determining whether the channel is occupied in the infinite LAN operation. For example, the reference energy level for determining whether the channel is occupied in the ED operation can be set to -82 dBm. The special time can be a time point after a transmission end time point of the MU-RTS frame to a time point before the transmission of the downlink frame. Alternatively, the special time can be a special IFS time (e.g., SIFS, PIFS, or AIFS).

[0430] Figure 45 FIG. 1 illustrates an operation of a soft AP according to an embodiment of the present application.

[0431] The soft AP can be an AP station. Further, the soft AP can be an AP included in a multi-link device. In this case, the soft AP can be included in a non-STR multi-link device. When the non-STR multi-link device includes the soft AP, the multi-link device can be referred to as a non-STR soft AP multi-link device.

[0432] When the non-STR soft AP multi-link device operates in multiple links, the multiple links can be classified into a mandatory link and an optional link. Specifically, the multiple links can include at least one mandatory link. The operation of the non-STR soft AP multi-link device with a legacy station or a single-link station can be limited to be performed only in the mandatory link. Specifically, the association and the authentication between the non-STR soft AP multi-link device and the legacy station or the single-link station can be limited to be performed in the mandatory link. In this case, the single-link station can be a station that cannot operate in multiple links.

[0433] The mandatory link and the optional link of the non-STR soft AP multi-link device can be designated by the non-STR soft AP multi-link device. Specifically, the mandatory link and the optional link can be set up when the multi-link is set up between the non-STR soft AP multi-link device and a non-AP multi-link device. For example, when the mandatory link is designated in the multiple links, the link other than the mandatory link can be the optional link.

[0434] According to a specific embodiment, the multiple links can be designated as the mandatory link. In this case, the multiple links designated as the mandatory link can be links that can be STRed with each other. For example, when the multiple links in which the non-STR soft AP multi-link device operates include a first link and a second link, and the non-STR soft AP multi-link device performs transmission in the first link, the second link performs reception. In this case, the first link and the second link can be the mandatory link. The mandatory link can be limited to be set identically in the multiple devices that communicate with the non-STR soft AP multi-link device. Specifically, the multiple devices that communicate with the non-STR soft AP multi-link device can not be allowed to set different mandatory links.

[0435] In addition, the optional link of the non-STR soft AP multi-link device can be used only for communication between the non-STR soft AP multi-link device and a multi-link device. The optional link can not be used for communication between the non-STR soft AP multi-link device and a legacy station or a single-link station. In addition, the association and the authentication between the non-STR soft AP multi-link device and the multi-link device can be performed in the mandatory link.

[0436] In Figure 45In an embodiment of the present application, a non-STR soft AP multi-link device (soft AP, non-STR AP MLD) operates in a first link (Link 1) and a second link (Link 2). The first link (Link 1) is a mandatory link, and the second link (Link 2) is an optional link. The non-STR soft AP multi-link device (soft AP, non-STR AP MLD) communicates with a non-AP multi-link device (Non-AP MLD) through the second link (Link 2). Specifically, the non-STR soft AP multi-link device (soft AP, non-STR AP MLD) connects and authenticates with the non-AP multi-link device (Non-AP MLD) through the second link (Link 2). The non-STR soft AP multi-link device (soft AP, non-STR AP MLD) communicates with a legacy STA (Legacy STA) and a single link STA (Single link STA) through the first link (Link 1). The non-STR soft AP multi-link device (soft AP, non-STR AP MLD) connects and authenticates with the legacy STA (Legacy STA) and the single link STA (Single link STA) through the first link (Link 1).

[0437] The channel access method in the mandatory link and the channel access method in the optional link can be different. For this, in the non-STR soft AP multi-link device (soft AP, non-STR AP MLD), the channel access method in the mandatory link and the channel access method in the optional link can be different. Figures 45 to 47 This will be further described.

[0438] Figure 46 FIG. 1 illustrates a non-STR soft AP multi-link device transmitting a PPDU on a mandatory link and an optional link according to an embodiment of the present application.

[0439] In the case of performing channel access independently on the mandatory link and the optional link described above, when the non-STR soft AP multi-link device performs transmission on the optional link, reception cannot be performed on the mandatory link. In order to prevent these problems, whether transmission is performed on the optional link can be determined according to whether transmission is performed on the mandatory link. The non-STR soft AP multi-link device can determine whether transmission is performed on the optional link based on whether transmission is performed on the mandatory link. Specifically, when the non-STR soft AP multi-link device performs transmission, the non-STR soft AP multi-link device performs necessary transmission on the mandatory link. In addition, the non-AP multi-link device connected with the non-STR soft AP multi-link device can determine whether transmission is performed on the optional link based on whether transmission is performed on the mandatory link. Specifically, when the non-AP multi-link device connected with the non-STR soft AP multi-link device performs transmission, the non-AP multi-link device performs necessary transmission on the mandatory link.

[0440] Accordingly, the non-STR soft AP multi-link device can perform transmission on the optional link only when the non-STR soft AP multi-link device performs transmission on the essential link. The non-STR soft AP multi-link device can not be allowed to perform transmission on the optional link when the non-STR soft AP multi-link device does not perform transmission on the essential link.

[0441] When performing channel access based on random backoff, the following embodiments can be applied. Even when the backoff counter reaches 0 in the optional link, the non-STR soft AP multi-link device can not perform transmission on the optional link when the backoff counter does not reach 0 in the essential link. Specifically, the non-STR soft AP multi-link device can wait until the backoff counter reaches 0 in the essential link. The non-STR soft AP multi-link device can start transmission on the optional link when the backoff counter reaches 0 in the essential link or when the essential link is performing transmission.

[0442] When performing channel access based on the result of channel sensing during a time interval of a fixed length, the following embodiments can be applied. Even when the non-STR soft AP multi-link device detects that the channel of the optional link is idle during a predetermined time interval, the non-STR soft AP multi-link device can not be allowed to start transmission on the optional link when the non-STR soft AP multi-link device does not perform transmission on the essential link. In this case, the predetermined time interval can be PIFS. In other specific embodiments, the non-STR soft AP multi-link device performs channel sensing on the optional link during a predetermined time interval only when the non-STR soft AP multi-link device performs transmission on the essential link to perform channel access.

[0443] The non-STR soft AP multi-link device can align the end of the PPDU transmitted on the necessary link with the segment of the PPDU transmitted on the optional link. The simultaneous ending of the transmission of multiple PPDUs can be referred to as aligning the ends of the PPDUs. In addition, when the difference between the ending time points of the transmission of multiple PPDUs is less than or equal to a threshold, it can be considered that the ends of the multiple PPDUs are aligned. In this case, the threshold can be a predetermined value. Specifically, the threshold can be a value set based on SIFS. In addition, the threshold can be a value set based on SIFS and the length of signal extension. For example, the threshold can be a value of the sum of SIFS and the length of signal extension divided by 2. At this time, the threshold can be 8us. When the PPDU transmitted on one of the necessary link and the optional link does not include a frame that directs an immediate response, the non-STR soft AP multi-link device can be allowed not to align the ends of the PPDUs. Specifically, the non-STR soft AP multi-link device aligns the end of the PPDU including the frame that directs the immediate response with the end of the PPDU not including the frame that directs the immediate response, or sets the end of the PPDU including the frame that directs the immediate response as a segment of the PPDU. For example, not aligning the ends of the PPDUs can mean that the end of the PPDU not including the frame that directs the immediate response is the same in time as or earlier than the end of the PPDU including the frame that directs the immediate response.

[0444] In Figure 46 In an embodiment of the disclosure, the non-STR soft AP multi-link device includes a first AP (AP1) and a second AP (AP2). The first AP (AP1) and the second AP (AP2) operate on a first link (Link1) as a necessary link and a second link (Link2) as an optional link, respectively. The first AP (AP1) and the second AP (AP2) are combined with a first station (STA1) and a second station (STA2) included in the non-STR multi-link device, respectively. When the second AP (AP2) transmits data (Data 1) to the second station (STA2), if the first station (STA1) transmits data (Data 2) to the first AP (AP1), the first AP (AP1) can not receive the data (Data 2).

[0445] As described in the above embodiment, when the first AP (AP1) and the second AP (AP2) transmit PPDUs simultaneously, the ends of the PPDUs of the first AP (AP1) and the second AP (AP2) are arranged. When the first AP (AP1) transmits a PPDU containing data (Data 3) and the second AP (AP2) transmits a PPDU containing data (Data 4), the ends of the PPDUs of the first AP (AP1) and the second AP (AP2) are arranged. Furthermore, if the PPDU transmitted on either link does not include a frame that prompts an immediate response, it is permissible not to arrange the ends of the PPDUs of the first AP (AP1) and the second AP (AP2). Since the data (Data 5) transmitted by the first AP (AP1) does not prompt an immediate response, the first AP (AP1) can terminate PPDU transmission earlier than the second AP (AP2).

[0446] The above-described embodiment of channel access operation for non-STR soft AP multi-link devices can also be applied to non-AP multi-link devices connected to non-STR soft AP multi-link devices.

[0447] In the above embodiments, if the exception of unordered PPDUs is allowed, a non-STR soft AP multi-link device may need to receive data from other links during the transmission of PPDUs on any link. For example, Figure 45 As shown, when the second AP (AP2) transmits a PPDU including data (Data6), the first AP (AP1) receives a PPDU including data (Data7) from the first station. At this time, due to the transmission of the PPDU including data (Data6), the first AP (AP1) may be unable to receive the PPDU including data (Data7). Therefore, as described above, a method may be needed that does not interfere with receiving PPDUs on either link.

[0448] Figure 47 The illustration shows a non-STR soft AP multi-link device according to an embodiment of the present invention transmitting PPDUs on necessary and optional links.

[0449] Non-STR soft AP multi-link devices can determine whether to prioritize PPDUs based on which link (necessary and optional) the PPDU, including the frame that prompts an immediate response, is transmitted on. Specifically, when a non-STR soft AP multi-link device transmits a PPDU that includes a frame that prompts an immediate response on an optional link, it may need to prioritize PPDUs transmitted on both the necessary and optional links. That is, when a non-STR soft AP multi-link device transmits a PPDU that does not include a frame that prompts an immediate response on an optional link, it may be allowed not to prioritize PPDUs transmitted on either the necessary or optional links.

[0450] In Figure 47 In an embodiment, the non-STR soft AP multi-link device includes a first AP (AP1) and a second AP (AP2). The first AP (AP1) and the second AP (AP2) operate on a first link (Link1) as a required link and a second link (Link2) as an optional link, respectively. The first AP (AP1) and the second AP (AP2) are combined with a first station (STA1) and a second station (STA2) included in the non-STR multi-link device, respectively. When the second AP (AP 2) transmits data (Data 1) to the second station (STA2), if the first station (STA 1) transmits data (Data 2) to the first AP (AP 1), it is impossible for the first AP (AP 1) to receive the data (Data 2). As in the above-described embodiment, when the first AP (AP 1) transmits a PPDU including data (Data 1) that does not induce an immediate response in the process of the required link, the second AP (AP 2) transmits a PPDU including data (Data 2) that induces an immediate response, the first AP (AP1) and the second AP (AP2) align the ends of the PPDUs. When the second AP (AP2) transmits a PPDU not including data (Data 4) that induces an immediate response, the first AP (AP1) and the second AP (AP2) do not align the ends of the PPDUs. Specifically, the second AP (AP2) can end the transmission of the PPDU before the end of the transmission of the PPDU of the first AP (AP1).

[0451] As in the above-described embodiment, the operation of the non-STR soft AP multi-link device can be the same as that of a non-AP multi-link device in communication.

[0452] Even if the multi-link device establishes a plurality of links, it is not possible to support simultaneous transmission or simultaneous reception on the plurality of links. Such a multi-link device can perform transmission or reception on a plurality of links with the condition of a type of frame or PPDU for which transmission or reception is limited. In this case, the type of frame or PPDU for which transmission or reception is limited can be a type of frame for which transmission is limited, an MCS for which transmission is limited, a number of special streams for which transmission is limited, and a frequency bandwidth for which transmission is limited. The operation of such a multi-link device can be referred to as an enhanced multi-link operation. In the enhanced multi-link operation, the multi-link device can concentrate the processing or transmission capability for one or more links to one or more other links. The non-STR soft AP multi-link device can not perform the enhanced multi-link device operation. Specifically, in the plurality of links set by the non-STR soft AP multi-link device, the enhanced multi-link device operation can not be allowed. For example, the non-STR soft AP multi-link device can not configure the enhanced multi-link device operation of the multi-link device operating in the plurality of links set by the non-STR soft AP multi-link device. Specifically, the non-STR soft AP multi-link device can signal rejection or non-support of the enhanced multi-link operation. This is because, when the enhanced multi-link operation is performed, transmission cannot be performed on the necessary link when transmission is performed on the optional link.

[0453] Figure 48 The non-STR soft AP multi-link device according to an embodiment of the present application performs channel access on the necessary link and the optional link.

[0454] In the process in which the non-STR soft AP multi-link device performs reception on the optional link, the non-STR soft AP multi-link device can defer channel access on the necessary link. This is because, when the non-STR soft AP multi-link device performs reception on the necessary link in the process in which the non-STR soft AP multi-link device performs reception on the optional link, reception on the optional link is hindered. The channel access defer can not perform channel access during the defer. In addition, even if the backoff counter reaches zero, the channel access defer can not start transmission. In addition, the non-STR soft AP multi-link device can defer channel access until an identifier or address of a transmitter of a PPDU received on the optional link is identified. At this time, the channel access defer can continue until reception on the optional link ends.

[0455] In Figure 48In an embodiment, the non-STR soft AP multi-link device includes a first AP (AP1) and a second AP (AP2). The first AP (AP1) and the second AP (AP2) operate on a first link (Link1) as a required link and a second link (Link2) as an optional link, respectively. The first AP (AP1) and the second AP (AP2) are associated with a first station (STA1) and a second station (STA2) included in the non-STR multi-link device, respectively. The first AP (AP1) transmits data (Data 1) not soliciting an immediate response to the first station (STA1), and the second AP (AP2) transmits data (Data 2) soliciting an immediate response to the second station (STA2). The first AP (AP1) defers channel access during a period in which the second AP (AP2) receives a response to the data (Data 2) from the second station (STA2). In addition, the first AP (AP1) transmits data (Data 3) soliciting an immediate response to the first station (STA1), and the second AP (AP2) transmits data (Data 4) soliciting an immediate response to the second station (STA2). The first AP (AP1) receives a response to the data (Data 3) from the first station (STA1), and the second AP (AP2) receives a response to the data (Data 4) from the second station (STA2). The first AP (AP1) defers channel access during a period in which the second AP (AP2) receives a response to the data (Data 4) from the second station (STA2).

[0456] In another specific embodiment, the non-STR soft AP multi-link device can not transmit a PPDU including a frame soliciting an immediate response on the optional link during a period in which the required link transmits a PPDU including a frame not soliciting an immediate response.

[0457] Figure 49 FIG. 1 illustrates a non-STR soft AP multi-link device transmitting a PPDU on a required link and an optional link according to an embodiment of the present application.

[0458] If the non-STR soft AP multi-link device transmits a PPDU not including a frame soliciting an immediate response on both the required link and the optional link, the non-STR soft AP multi-link device can transmit a PPDU on the optional link not later than the end of the PPDU transmission on the required link. That is, in this case, the end of the PPDU transmission on the optional link can be earlier than or equal to the end of the PPDU transmission on the required link. This is because the PPDU transmission on the required link can interfere with transmission from the required link to a station of the non-STR soft AP multi-link device when the PPDU transmission on the required link ends earlier than the PPDU transmission on the optional link.

[0459] In Figure 49In an embodiment, the non-STR soft AP multi-link device includes a first AP (AP1) and a second AP (AP2). The first AP (AP1) and the second AP (AP2) operate on a first link (Link1) as a required link and a second link (Link2) as an optional link, respectively. The first AP (AP1) and the second AP (AP2) are associated with a first station (STA1) and a second station (STA2) included in the non-STR multi-link device, respectively.

[0460] If a multi-link device communicating with the non-STR soft AP multi-link device transmits a PPDU not including a frame of a probe response first on the required link and the optional link, the multi-link device can end transmission on the optional link before the PPDU of the required link. In this case, the non-STR soft AP multi-link device can also perform reception from other stations transmitting to the non-STR soft AP multi-link device on the optional link.

[0461] The AP multi-link device and the non-AP multi-link device can negotiate the use of the multiple links in the scanning and association procedures described above. Figure 5 The use of the multiple links is negotiated in the scanning and association procedures described above. In the scanning procedure, the AP of the AP multi-link device can signal information about the multiple links. Specifically, the AP of the AP multi-link device can include at least any one of an indicator showing that the multiple links are operable, the number of available links, and information about the multiple links in a beacon frame. Further, in the scanning procedure, the station of the non-AP multi-link device can signal information about the multiple links. Specifically, the station of the non-AP multi-link device can include an indicator showing that the multiple links are operable in a probe frame. Further, the station of the non-AP multi-link device can include at least any one of the number of available links and information about the multiple links in the probe frame.

[0462] In the scanning process, a multi-link operation of an AP multi-link device and a non-AP multi-link device using link information can be connected with the AP multi-link device. At this time, the AP multi-link device and the non-AP multi-link device can start a negotiation process for a multi-link operation. The negotiation for the multi-link operation can be performed in an access process between an AP of the AP multi-link device and a station of the non-AP multi-link device. When the station of the non-AP multi-link device transmits an access request frame to the AP of the AP multi-link device, the station of the non-AP multi-link device can transmit an indicator indicating that a multi-link operation can be used and a request indicator requesting to perform the multi-link operation. The AP receiving the access request frame from the station can confirm the indicator requesting the multi-link operation. At this time, if the AP is capable of the multi-link operation, the AP can transmit an access response frame including link information to be used for the multi-link operation and parameters used in each link, etc. to the corresponding station, and allow the multi-link operation. The parameters for the multi-link operation can include at least one of a frequency band of each of a plurality of links used in the multi-link operation, a bandwidth extension direction of each frequency band of the plurality of links, a target beacon transmission time (TBTT), and an STR operation. The AP multi-link device and the non-AP multi-link device using the multi-link operation are confirmed by exchanging the access request frame and the access request response frame after the corresponding access process, and can perform a frame transmission operation using the plurality of links.

[0463] Figure 50 FIG. 1 illustrates that transmission is independently performed in each of a plurality of links according to an embodiment of the present application.

[0464] The AP multi-link device and the non-AP multi-link device completing the negotiation for the multi-link operation can independently perform transmission and reception for each link, or can simultaneously perform transmission and reception in the plurality of links. When transmission and reception are independently performed in each of the plurality of links, the AP of the AP multi-link device and the non-AP station of the non-AP multi-link device independently perform channel contention for transmission. Accordingly, a transmission start point and a transmission end point of each link can not be the same. In addition, a transmission opportunity (TXOP) obtained in a channel access process of each link can also be independently obtained.

[0465] In Figure 50In an embodiment, an AP multi-link device (AP MLD) includes a first AP (AP1) and a second AP (AP2), the first AP (AP1) and the second AP (AP2) operating on a first link (Link 1) and a second link (Link 2), respectively. A non-AP multi-link device (STA MLD) includes a first station (STAl) and a second station (STA2), the first station (STAl) and the second station (STA2) each operating on the first link (Link 1) and the second link (Link 2). The first AP (AP1) and the second AP (AP2) each independently perform channel access on the first link (Link 1) and the second link (Link 2). Each of the first station (STAl) and the second station (STA2) also independently perform channel access on the first link (Link 1) and the second link (Link 2). Thus, the AP multi-link device (AP MLD) and the non-AP multi-link device (STA MLD) can perform reception on the other link during the time the AP multi-link device (AP MLD) and the non-AP multi-link device (STA MLD) perform transmission on one link.

[0466] This embodiment can improve the transmission efficiency on each link. However, when the non-AP multi-link device or the AP multi-link device does not support STR, such a channel access performed independently on each of the multiple links can not be allowed. When the non-AP multi-link device or the AP multi-link device does not support STR, other embodiments can be applied. This is described by way of Figure 50

[0467] Figure 51 Figure 1 illustrates an operation of a multi-link device performing transmission in a non-STR link pair.

[0468] The non-STR multi-link device that does not support STR cannot perform reception on the other link when it performs transmission on one link. Thus, when the non-STR multi-link device performs channel access independently on each of the multiple links, transmission failure can occur. In Figure 50 In an embodiment, an AP multi-link device (AP MLD) includes a first AP (AP1) and a second AP (AP2), the first AP (AP1) and the second AP (AP2) operating on a first link (Link 1) and a second link (Link 2), respectively. A non-AP multi-link device (STA MLD) includes a first station (STAl) and a second station (STA2), the first station (STAl) and the second station (STA2) each operating on the first link (Link 1) and the second link (Link 2). The first AP (AP1) and the second AP (AP2) each independently perform channel access on the first link (Link 1) and the second link (Link 2). Each of the first station (STAl) and the second station (STA2) also independently perform channel access on the first link (Link 1) and the second link (Link 2). Thus, the AP multi-link device (AP MLD) and the non-AP multi-link device (STA MLD) can perform reception on the other link during the time the AP multi-link device (AP MLD) and the non-AP multi-link device (STA MLD) perform transmission on one link.

[0469] ​When there is a pair of non-STR links, a multi-link device performing transmission on the non-STR links can align a transmission start time point and a transmission end time point of frames transmitted on the pair of non-STR links. The transmission start time point and the transmission end time point of the frames can be a transmission start time point and a transmission end time point of a PPDU containing the frames. To this end, the multi-link device can use padding or padding bits. To perform such simultaneous transmission, negotiation for the simultaneous transmission can be performed. The negotiation for the simultaneous transmission can include a frame exchange for obtaining a TXOP for the simultaneous transmission. Specifically, the multi-link device can transmit a plurality of link transmission request frames for obtaining the TXOP. The multi-link device receiving the request frames can transmit a response frame for the request frames with a short interframe space (SIFS) interval. The request frames can be control frames. Further, the request frames can be request to send (RTS) frames or multi-user (MU)-RTS frames. Further, the response frames can be clear to send (CTS) frames. When either of the links is not idle while transmitting the above-described request frames or the response frames, the multi-link device can transmit the request frames or the frames on an idle link among the plurality of links. In Figure 50 In an embodiment of b, as described in a of Figure 50 The first AP (AP1) and the second AP (AP2) operate in the first link (Link 1) and the second link (Link 2), respectively. In addition, the first station (STA1) and the second station (STA2) operate on the first link (Link 1) and the second link (Link 2), respectively. Since the non-AP multi-link device is a non-STR multi-link device, the first AP (AP1) and the second AP (AP2) simultaneously transmit frames. To secure a TXOP, the first AP (AP1) and the second AP (AP2) simultaneously transmit request frames. The first station (STA1) and the second station (STA2) simultaneously transmit response frames as a response to the request frames. Thereafter, within the secured TXOP, the first AP (AP1) and the second AP (AP2) exchange frames with the first station (STA1) and the second station (STA2).

[0470] However, since channel states of the plurality of links are different, the pair of non-STR links can not simultaneously start transmission. In consideration of this, the plurality of stations performing transmission to the non-STR multi-link device can align ends of PPDUs. Specifically, the plurality of stations performing transmission to the non-STR multi-link device can align the ends of the PPDUs even if not aligning starts of the PPDUs. In addition, as described above, if any of the PPDUs transmitted on the pair of non-STR links does not include a frame that leads to an immediate response, the ends of the other PPDUs can not be aligned with the end of the PPDUs including the frame that leads to the immediate response. In Figure 50In the embodiments of b, as described in Figure 50 The first AP (AP1) and the second AP (AP2) operate in the first link (Link 1) and the second link (Link 2), respectively. In addition, the first station (STA1) and the second station (STA2) operate on the first link (Link 1) and the second link (Link 2), respectively. Since the non-AP multi-link device is a non-STR multi-link device, the first AP (AP1) and the second AP (AP2) align the ends of the PPDU when the first AP (AP1) and the second AP (AP2) transmit the PPDU at the same time. When the first AP (AP1) transmits the PPDU that does not include the frame of the leading immediate response, the first AP (AP1) and the second AP (AP2) do not align the ends of the PPDU. When the first AP (AP1) and the second AP (AP2) transmit the PPDU at the same time, the first AP (AP1) and the second AP (AP2) align the ends of the PPDU.

[0471] The non-STR link pair described above means that the STR cannot be performed on the link pair. The non-STR link group means that the plurality of links included in the non-STR link group includes the non-STR link pair. For the embodiments applicable to the case where a part of the plurality of links on which the AP multi-link device operates is the non-STR link pair, it will be described that Figure 51 .

[0472] Figure 52 The embodiments of the present application are applicable when a part of the plurality of links on which the AP multi-link device operates is the non-STR link pair.

[0473] The multi-link device can be associated with the station not included in the multi-link device. At this time, the station not included in the multi-link device has difficulty in determining whether to perform transmission on the other link. In addition, when the stations included in different multi-link devices perform communication in the non-STR link pair, the stations included in different multi-link devices have difficulty in determining whether to perform transmission on the other link other than the link on which the station operates. Referring to Figure 51 , the non-STR AP multi-link device communicates with the first station STA1 and the second station STA2 not included in the multi-link device. In the embodiments of a of Figure 51 , the first AP (AP1) and the second AP (AP2) attempt channel access on the first link (Link 1) and the second link (Link 2), respectively. The first AP (AP1) succeeds in the channel access and thus starts the frame exchange sequence by starting the transmission of the RTS frame. The second AP (AP2) fails in the channel access and thus cannot start the frame exchange sequence. As described above, the second AP (AP2) cannot determine whether to perform transmission on the first link. When the first AP (AP1) transmits data to the first station (STA1) on the first link (Link 1), the second station (STA2) can perform uplink transmission. In Figure 51In the embodiment of FIG. 8B, the first station (STA1) succeeds in channel access and starts a frame exchange sequence with the start of an RTS frame transmission. The second station (STA2) succeeds in channel access and attempts an uplink transmission. While the first AP (AP1) is receiving data transmitted by the first station (STA1) on the first link (Link 1), the transmission of the second station (STA2) can be completed on the second link (Link 2). At this time, since the first AP (AP1) is receiving data transmitted by the first station (STA1) on the first link (Link 1), the second AP (AP2) cannot transmit a response to the transmission of the second station (STA2). In addition, the second station (STA2) cannot confirm whether the transmission of the second station (STA2) is successful. For the embodiment of preventing failure of these frame exchanges, the first AP (AP1) can transmit a response to the transmission of the second station (STA2) on the second link (Link 2) by using the second AP (AP2) as a proxy. In this case, the second AP (AP2) can transmit the response to the transmission of the second station (STA2) on the second link (Link 2) by using the first AP (AP1) as a proxy. In this case, the second AP (AP2) can transmit the response to the transmission of the second station (STA2) on the second link (Link 2) by using the first AP (AP1) as a proxy. Figure 53 This will be described below.

[0474] Figure 53 FIG. 8B illustrates operation of a multi-link device in a plurality of links including a non-STR link pair according to an embodiment of the present application.

[0475] When the multi-link device operates on a plurality of links including a non-STR link pair, the multi-link device can designate at least one of the plurality of links as a basic link. In this case, the basic link can be the necessary link described above. The multi-link device can designate one link of the plurality of links as a basic link. The link of the plurality of links other than the basic link can be referred to as an extension link.

[0476] When the non-AP multi-link device wants to connect to a link included in a non-STR link pair, the AP multi-link device can guide the non-AP multi-link device to connect to all links included in the non-STR link pair. In addition, when a station not included in the non-AP multi-link device wants to connect to a link included in an STR link pair, the AP multi-link device can guide the station not included in the non-AP multi-link device to access the link included in the STR link pair.

[0477] In another specific embodiment, the AP multi-link device can allow connection of the station not included in the non-AP multi-link device only on the basic link. The station not included in the non-AP multi-link device can connect to the AP multi-link device only on the basic link of the AP multi-link device.

[0478] In Figure 53In an embodiment of the above, a non-STR AP MLD operates on a first link (Linkl), a second link (Link2), and a third link (Link3) of a STR capable link pair. The first link (Linkl) and the second link (Link2) are a non-STR link pair, the first link (Linkl) and the third link (Link3) are a STR capable STR link pair, and the second link (Link2) and the third link (Link3) are a STR capable STR link pair. The non-STR AP MLD designates the first link (Linkl) and the third link (Link3) as basic links. In this case, a third station (STA3) not included in the multi-link device can connect to the non-STR MLD on the first link (Linkl) or the third link (Link3). The third station (STA3) cannot connect to the non-STR MLD on the first link (Linkl) or the second link (Link2). The non-STR MLD can direct the third station (STA3) to connect to the non-STR MLD on the third link (Link3).

[0479] In the above embodiment, the channel load of the basic link can be too high. To prevent this, the number of links included in the non-STR link pair can be limited. In this case, the number of links included in the non-STR link pair can be two.

[0480] In the above embodiment, the negotiation AP MLD for multi-link operation can direct connection to the basic link. This is described below. Figure 53

[0481] Figure 54 The operation of the AP MLD according to an embodiment of the present application and a station not included in the multi-link device is illustrated.

[0482] ​When a station not included in the multi-link device requests connection to the extended link to the AP multi-link device, the AP multi-link device can reject the connection request of the station. As a specific method, when the station not included in the multi-link device transmits a probe request frame to the AP multi-link device, the AP multi-link device can not transmit a probe response frame to the station. Also, when the station not included in the multi-link device transmits a frame requesting connection to the extended link to the AP multi-link device, the AP multi-link device can transmit a connection response frame including an indicator rejecting the access request to the station. At this time, the connection response frame can include a field indicating a status code suggesting access to other links. For example, the status code suggesting access to other links can be 82. Also, the connection response frame can include information for the link to which access is suggested. At this time, the information for the link to which access is suggested can be a type of Neighbor Report Information Element. The Neighbor Report Information Element can include at least one of an SSID, a channel, and an operating class, and timing information. The link to which access is suggested can be a basic link included in the STR link pair. The station not included in the multi-link can attempt to connect to the link to which the AP multi-link device suggests access based on the information for the link to which the AP multi-link device suggests access.

[0483] In addition, the AP multi-link device can transmit a beacon frame on the extended link and the basic link at the same time. Also, the AP multi-link device can transmit the beacon frame in a type that a station not included in the multi-link device of the extended link cannot decode. Specifically, for example, the values of the IBSS STA subfield and the ESS subfield in the capability information field within the beacon frame can be set to 1. At this time, the station not included in the multi-link device cannot decode the corresponding beacon, and thus cannot transmit a connection request based on the beacon frame. In this embodiment, the AP multi-link device also transmits a beacon frame on the basic link included in the non-STR link pair in a type that a station not included in the multi-link device cannot decode. Also, the AP multi-link device can set part of the fields in the BSS Load Information Element of the beacon frame transmitted on the extended link to a predetermined value. At this time, the AP multi-link device can set the BSS Load Information Element of the beacon frame transmitted on the extended link to show the maximum value of the channel usage rate. In addition, the AP multi-link device can set the number of stations connected in the BSS Load Information Element transmitted on the extended link to show the maximum value. A station receiving the beacon frame set as described above cannot perform connection on the extended link, or judges that performing connection is inefficient and thus does not attempt connection. In another specific embodiment, the AP multi-link device can not transmit a beacon frame on the extended link.

[0484] The above-described embodiments can be applied not only to the extended link but also to the basic link included in the non-STR link pair. For example, even when a station not included in the multi-link transmits a connection request frame on the basic link included in the non-STR link pair, the AP multi-link device can transmit a frame rejecting connection.

[0485] In Figure 54 embodiments, a station (STA) of a multi-link device does not transmit a probe request frame to a second AP (AP2) operating in an extended link. At this time, the second AP (AP2) does not transmit a probe response frame to the station (STA). A station (STA) of a multi-link device does not transmit a connection request frame to a second AP (AP2) operating in an extended link. At this time, the second AP (AP2) transmits a connection response frame including a status code of rejection of connection to the station (STA). In this case, the connection response frame can include information on a link operated by a third AP (AP3) or a first AP (AP1) as described above. The station (STA) transmits a connection request frame to the third AP (AP3) based on the information on the link operated by the third AP (AP3).

[0486] Figure 55 FIG. illustrates the operation of an AP multi-link device combined with a station of a multi-link device according to an embodiment of the present application.

[0487] A non-AP multi-link device can request information on a link for multi-link operation to an AP multi-link device using a probe request frame. Specifically, the probe request frame can include an indicator requesting link information for multi-link operation. An AP multi-link device receiving the probe request frame including information on a link for multi-link operation can transmit a probe response frame including information on a link for multi-link operation to the non-AP multi-link device. The information on a link for multi-link operation can include at least one of information on an STR link pair, information on a non-STR link pair, and information on a basic link. The non-AP multi-link device can obtain the information on a link for multi-link operation from the probe response frame.

[0488] A non-AP multi-link device can transmit a multi-link operation request to an AP multi-link device using a connection request frame. The connection request frame can include an indicator showing a request for multi-link operation. The AP multi-link device that receives the multi-link operation request can determine whether the multi-link operation is receivable. Specifically, the AP multi-link device can determine whether the multi-link operation is receivable when the connection request frame contains the indicator showing the request for multi-link operation. In a specific embodiment, the AP multi-link device can determine whether the non-AP multi-link device is requesting connection in a non-STR link pair or the non-AP multi-link device is requesting connection in a non-STR link pair. In addition, the AP multi-link device can determine whether the non-AP multi-link device is requesting connection in multiple links. When ...

Claims

1. A non-access point station, non-AP-STA, configured to operate in a wireless communication system, the non-AP-STA comprising: Communication module; and A processor configured to control the communication module. The processor is configured as follows: A management frame is received from the access point (AP). The management frame includes a target wake-up time element related to the scheduled target wake-up time service period (R-TWTSP) and a quiet element related to the quiet interval. The R-TWT SP indicates a TWT SP in which the transmission of delay-sensitive traffic is prioritized. The quiet interval indicates the duration during which no transmission occurs. The TWT element includes a TWT request type field, which includes a special field indicating the type of frame sent during the TWTSP. When the R-TWT SP is configured for the non-AP STA The delay-sensitive traffic is received or sent based on the first special value of the special field. The quiet interval is ignored based on whether it overlaps with the R-TWT SP.

2. The non-AP-STA according to claim 1, wherein, When the quiet interval overlaps with the R-TWT SP, the quiet interval is ignored, and the delay-sensitive traffic is sent or received during the R-TWT SP according to the first special value.

3. The non-AP-STA according to claim 1, wherein, The quiet interval is ignored based on the comparison between the first time point of the R-TWT SP based on the TWT element and the second time point of the quiet interval based on the quiet element.

4. The non-AP-STA according to claim 3, in, The first time point is the start time of the R-TWT SP, and The second time point is the start time of the quiet interval.

5. The non-AP-STA according to claim 3, wherein, When the first time point is the same as the second time point, the quiet interval is ignored.

6. The non-AP-STA according to claim 3, wherein, The non-AP STAs scheduled by the AP for the quiet interval set the network allocation vector (NAV) during the quiet interval.

7. The non-AP-STA according to claim 6, wherein, The first special value indicates that the transmission of the delay-sensitive traffic is prioritized during the R-TWT SP.

8. The non-AP-STA according to claim 1, wherein, The second special value of the special field indicates that the transmission of feedback type frames is prioritized during special TWTSP.

9. The non-AP-STA according to claim 1, wherein, The TWT element also includes a TWT information field, which includes information related to the Traffic Identifier (TID) used for the latency-sensitive traffic.

10. The non-AP-STA according to claim 1, wherein, When the non-AP STA belongs to a multi-link device (MLD), the MLD cannot receive the management frame on a special link while simultaneously sending frames on a link different from the special link.

11. The non-AP-STA according to claim 1, wherein, When a transmission process is performed before the R-TWT SP, the transmission process performed by the non-AP STA ends before the start time of the R-TWT SP.

12. A method for transmitting frames via a non-access point station, non-AP-STA, configured to operate in a wireless communication system, the method comprising: A management frame is received from the access point (AP). The management frame includes a target wake-up time element related to the scheduled target wake-up time service period (R-TWTSP) and a quiet element related to the quiet interval. The R-TWT SP indicates a TWT SP in which the transmission of delay-sensitive traffic is prioritized. The quiet interval indicates the duration during which no transmission occurs. The TWT element includes a TWT request type field, which includes a special field indicating the type of frame sent during the TWTSP. When the R-TWT SP is configured for the non-AP STA The delay-sensitive traffic is received or sent based on the first special value of the special field. The quiet interval is ignored based on whether it overlaps with the R-TWT SP.

13. The method according to claim 12, wherein, When the quiet interval overlaps with the R-TWT SP, the quiet interval is ignored, and the delay-sensitive traffic is sent or received during the R-TWT SP according to the first special value.

14. The method according to claim 12, wherein, The quiet interval is ignored based on the comparison between the first time point of the R-TWT SP based on the TWT element and the second time point of the quiet interval based on the quiet element.

15. The method according to claim 14, in, The first time point is the start time of the R-TWT SP, and The second time point is the start time of the quiet interval.

16. The method of claim 14, wherein, When the first time point is the same as the second time point, the quiet interval is ignored.

17. The method of claim 14, wherein, The non-AP STAs scheduled by the AP for the quiet interval set the network allocation vector (NAV) during the quiet interval.

18. The method according to claim 17, wherein, The first special value indicates that the transmission of the delay-sensitive traffic is prioritized during the R-TWT SP.

19. The method according to claim 12, wherein, The second special value of the special field indicates that the transmission of feedback type frames is prioritized during the special TWT SP.

20. The method according to claim 12, wherein, The TWT element also includes a TWT information field, which includes information related to the Traffic Identifier (TID) used for the latency-sensitive traffic.

21. The method according to claim 12, wherein, When the non-AP STA belongs to a multi-link device (MLD), the MLD cannot receive the management frame on a special link while simultaneously sending frames on a link different from the special link.

22. The method according to claim 12, wherein, When a transmission process is performed before the R-TWT SP, the transmission process performed by the non-AP STA ends before the start time of the R-TWT SP.

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