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

Abstract

The present invention relates to a wireless communication method using a plurality of links and a wireless communication terminal using the same. A station is disclosed that communicates with a single radio multi-link device that includes a plurality of stations that each operate on a plurality of links, but does not support simultaneous transmission or reception of the plurality of stations. The station includes a transceiver and a processor. The processor transmits a control frame to a first station of the single radio multi-link device using the transceiver, receives a response to the control frame from the first station of the single radio multi-link device, and starts a null data packet (NDP) sounding sequence for the first station of the single radio multi-link device.

Description

[0001] This application is a divisional application of Patent Application No. 202180059177.7 (International Application No. PCT / KR2021 / 009812) with the title of "Wireless communication method using multiple links and wireless communication terminal using the same" filed on July 28, 2021, the international application date of which is January 28, 2023. TECHNICAL FIELD

[0002] The present application relates to a wireless communication method using multiple links and a wireless communication terminal using the same. BACKGROUND

[0003] In recent years, as the supply of mobile devices expands, a wireless LAN (Local Area Network) 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, and the like to wirelessly access the Internet in a home or a company or a special service providing area based on a short distance wireless communication technology.

[0004] Since an initial wireless LAN technology supporting the use of a frequency of 2.4 GHz, 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 frequency of a 2.4 GHz band. In comparison with a frequency of a 2.4 GHz band that is significantly congested, the IEEE 802.11a, which is commercialized after the IEEE 802.11b, uses a frequency of a 5 GHz band instead of a 2.4 GHz band to reduce the influence of interference, and by using an OFDM technology, increases a communication speed to a maximum of 54 Mbps. However, the IEEE 802.11a has a disadvantage in that a communication distance is shorter than the IEEE 802.11b. In addition, similar to the IEEE 802.11b, the IEEE 802.11g uses a frequency of a 2.4 GHz band to achieve a communication speed of a maximum of 54 Mbps and satisfies backward compatibility to significantly cause attention, and further, is superior to the IEEE 802.11a in terms of a communication distance.

[0005] 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 to improve the speed and reliability of the network and to extend 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 transmitting unit and a receiving unit to minimize transmission errors and optimize data speed. Further, the standard can use a coding scheme that transmits a plurality of copies of a duplicate in order to increase data reliability.

[0006] With the supply of the wireless LAN being activated, 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 wide 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 the standard, the wireless LAN speed of a plurality of stations can be made to be a minimum of 1 Gbps, and the maximum single link speed can be made to be a minimum of 500 Mbps. This is achieved by expanding the concept of the wireless interface accepted 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 of 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 that provides 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 pass through obstacles, it has a disadvantage in that the 60 GHz band can be used only among devices in a near distance space.

[0007] As a wireless LAN standard after 802.11ac and 802.11ad, IEEE 802.11ax (High Efficiency WLAN (HEW)) standard for providing an efficient and high-performance wireless LAN communication technology in a high-density environment in which APs and terminals are concentrated is in the process of being developed. 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.

[0008] 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 wider bandwidth, increased spatial streams, and multi-AP cooperation, etc. SUMMARY

[0009] TECHNICAL PROBLEM

[0010] Embodiments of the present application are to provide a wireless communication method using multiple links and a wireless communication terminal using the same.

[0011] TECHNICAL SOLUTION

[0012] According to an embodiment of the present application, a station communicating with a single radio multi-link device including a plurality of stations respectively operating on a plurality of links but not supporting simultaneous transmission or reception of the plurality of stations, the station includes a transceiver; and a processor. The processor transmits a control frame to a first station of the single radio multi-link device using the transceiver, receives a response to the control frame from the first station of the single radio multi-link device, and starts a null data packet (NDP) probe sequence for the first station of the single radio multi-link device.

[0013] The control frame can be a MU-RTS frame.

[0014] The control frame can be a trigger frame of a type different from a MU-RTS frame.

[0015] The processor can transmit the control frame in a predetermined physical layer protocol data unit (PPDU) format.

[0016] The predetermined PPDU format can be at least one of a non-HT format or an HT format.

[0017] The processor can transmit the control frame at a predetermined data rate or less.

[0018] The processor can not perform transmission to a second station of the single radio multi-link device while a first station of the single radio multi-link device is performing transmission or reception.

[0019] The processor can not perform transmission to a second station of the single radio multi-link device not only during a frame exchange sequence of the first station is being performed but also for a certain time period from when the frame exchange sequence of the first station is completed.

[0020] During the frame exchange sequence of the first station is being performed, a plurality of RF chains are supported to be used in a link in which the frame exchange sequence of the first station is performed, and the certain time can be determined based on an RF chain change time of the single radio multi-link device.

[0021] When the single radio multi-link device supports a plurality of RF chains to be used in a first link and transitions from not supporting RF chains to be used in a second link to supporting RF chains to be used in the second link, the processor can apply a restriction on channel access for a predetermined time period before performing channel access in the second link.

[0022] The predetermined time can be a predetermined time to which a restriction on channel access is applied due to a time in which channel monitoring is not possible.

[0023] The predetermined time can be a NAVSyncdelay.

[0024] When the single radio multi-link device supports a plurality of RF chains to be used in a first link and does not support RF chains to be used in a second link, a last frame exchange in a frame exchange sequence performed in the first link can be performed using single input single output (SISO) (1x1).

[0025] According to an embodiment of the present invention, a single radio multi-link device including a plurality of stations respectively operating on a plurality of links but not supporting simultaneous transmission or reception of the plurality of stations includes a transceiver; and a processor. When a link in which the processor operates RF chains is changed from a first link to a second link and the link in which the processor operates RF chains is changed again from the second link to the first link, the processor delays performing channel access for a predetermined time period before performing channel access in the first link.

[0026] The predetermined time can be a predetermined time applied when a restriction on channel access is required due to a time in which channel monitoring cannot be performed.

[0027] The predetermined time can be NAVSyncdelay.

[0028] When the single radio multi-link device supports use of multiple RF chains in a first link, and use of RF chains is not supported in a second link, the processor can use single input single output (SISO) (1x1) to transmit a last frame in a frame exchange sequence performed in the first link.

[0029] An operation method of a station in communication with a single radio multi-link device including a plurality of stations respectively operating on a plurality of links but not supporting simultaneous transmission or reception of the plurality of stations according to an embodiment of the present application includes the steps of: transmitting a control frame to a first station of the single radio multi-link device; receiving a response to the control frame from the first station of the single radio multi-link device; and starting a null data packet (NDP) probe sequence for the first station of the single radio multi-link device.

[0030] The control frame can be a MU-RTS frame.

[0031] The control frame can be a trigger frame of a type different from a MU-RTS frame.

[0032] Advantageous effects

[0033] An embodiment of the present application provides a wireless communication method efficiently using a multi-link and a wireless communication terminal using the same. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A wireless LAN system according to an embodiment of the present application is illustrated.

[0035] Figure 2 A wireless LAN system according to another embodiment of the present application is illustrated.

[0036] Figure 3 A configuration of a station according to an embodiment of the present application is illustrated.

[0037] Figure 4 A configuration of an access point according to an embodiment of the present application is illustrated.

[0038] Figure 5 A process in which a station and an access point set a link is schematically illustrated.

[0039] Figure 6A carrier sense multiple access (CSMA) / collision avoidance (CA) method used in wireless LAN communication is illustrated.

[0040] Figure 7 An example of a format of a physical layer protocol data unit (PPDU) for each of various standards generations is illustrated.

[0041] Figure 8 Examples of various extremely high throughput (EHT) physical layer protocol data unit (PPDU) formats and methods for indicating the same according to embodiments of the present application are illustrated.

[0042] Figure 9 A multi-link device according to embodiments of the present application is illustrated.

[0043] Figure 10 Simultaneous transmission of different links in multi-link operation according to embodiments of the present application is illustrated.

[0044] Figure 11 Operation of a multi-link device according to an embodiment of the present application at a link change is illustrated.

[0045] Figure 12 Prevention of channel access by one station of a non-STR multi-link device when the other station of the non-STR multi-link device performs reception is illustrated according to an embodiment of the present application.

[0046] Figure 13 Operation to release channel access prevention when it is identified that an intended receiver of a PPDU received by a station of a non-STR multi-link device is not the station is illustrated.

[0047] Figure 14 Channel access by the station after release of channel access prevention is illustrated according to embodiments of the present application.

[0048] Figure 15 Operation of the station to perform transmission after release of channel access prevention is illustrated according to embodiments of the present application.

[0049] Figure 16 Transmission performed based on a state of a station within a non-STR multi-link device according to embodiments of the present application is illustrated.

[0050] Figure 17 A situation in which interference or collision can occur between links is illustrated.

[0051] Figure 18 Operation of an STR multi-link device to stop transmission to a non-STR multi-link device according to embodiments of the present application is illustrated.

[0052] Figure 19FIG. 1 illustrates processing of a CW value when an STR multi-link device recognizes a transmission conflict between links according to an embodiment of the present invention.

[0053] Figure 20 It illustrates an operation in which an STR multi-link device stops transmission to a non-STR multi-link device and then performs channel access again according to an embodiment of the present invention.

[0054] Figure 21 The diagram illustrates an operation of an STR multi-link device sending a CTS-to-Self frame before transmission to a non-STR multi-link device according to an embodiment of the present invention.

[0055] Figure 22 It is illustrated that transmission is performed by a plurality of APs included in a STR multi-link device to a plurality of stations included in a non-STR multi-link device according to an embodiment of the present invention.

[0056] Figure 23 The diagram illustrates a case where a plurality of APs included in an STR multi-link device perform a plurality of transmissions to a plurality of stations included in a non-STR multi-link device, with transmission ends of the plurality of transmissions being synchronized, according to an embodiment of the present invention.

[0057] Figure 24 The diagram illustrates the exchange of RTS / CTS frames by a multi-link device according to an embodiment of the present invention.

[0058] Figure 25 The diagram shows the reference Figure 24 The embodiments of the present invention are described to solve the hidden node problem that occurs during the RTS / CTS frame exchange process.

[0059] Figure 26 The diagram illustrates RTS / CTS frame exchanges performed by a multi-link device according to an embodiment of the present invention.

[0060] Figure 27 It is illustrated that a response to a control frame is exceptionally transmitted by a multi-link device even in a situation where channel access is prohibited according to an embodiment of the present invention.

[0061] Figure 28 Retransmissions of transmissions to stations that are not STR multilink devices are illustrated.

[0062] Figure 29 Transmission of a control frame according to an embodiment of the present invention through a link in which a station whose channel access is not barred operates instead of a link in which a station whose channel access is barred operates is illustrated.

[0063] Figure 30 The diagram illustrates sending an ACK by a multi-link device according to an embodiment of the present invention.

[0064] Figure 31 Figure illustrates an element field indicating information about support of simultaneous PPDU reception or transmission according to an embodiment of the present application.

[0065] Figure 32 Figure illustrates inter-link TXOP power save mode operation performed by a non-STR multi-link device according to an embodiment of the present application.

[0066] Figure 33 Figure illustrates a station of a non-STR multi-link device entering a sleep state from a synchronization PPDU reception standby according to an embodiment of the present application.

[0067] Figure 34 Figure illustrates a station of a non-STR multi-link device entering a sleep state from a synchronization PPDU reception standby according to another embodiment of the present application.

[0068] Figure 35 Figure illustrates a connection between a single-radio multi-link device and an AP multi-link device according to an embodiment of the present application.

[0069] Figure 36 Figure illustrates a single-radio multi-link device performing MIMO transmission according to an embodiment of the present application.

[0070] Figure 37 Figure illustrates a single-radio multi-link device performing channel access considering a delay time for radio frequency (RF) chain change according to an embodiment of the present application.

[0071] Figure 38 Figure illustrates a Capability element and an Operation element used by a single-radio multi-link device according to an embodiment of the present application.

[0072] Figure 39 Figure illustrates a single-radio multi-link device using MIMO to send a PPDU according to an embodiment of the present application.

[0073] Figure 40 Figure illustrates a station and a single-radio multi-link device performing an NDP sounding procedure according to an embodiment of the present application.

[0074] Figure 41 Figure illustrates a station and a single-radio multi-link device performing a feedback beamforming sounding sequence according to an embodiment of the present application.

[0075] Figure 42 Figure illustrates a station and a single-radio multi-link device performing an NDP sounding procedure according to an embodiment of the present application. DETAILED DESCRIPTION

[0076] By considering the functions of the present application, the terms used in the present specification adopt common general terms which are widely used at present, but the terms can be changed according to the intention of those skilled in the art, customs, and appearance of new technologies. Also, in a special case, there is any selected term by the applicant, and in this case, the meaning thereof will be described in the corresponding description part of the present application. Therefore, it should be understood that the terms used in the present specification will not be analyzed based on only the name of the term, but based on the substantial meaning of the term and the content of the whole specification.

[0077] Throughout the specification, when it is explained 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 "comprise" will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Also, the limitation such as "or more" or "or less" based on a special threshold can be replaced with "greater than" or "less than" respectively, as appropriate.

[0078] Hereinafter, in the present application, a field and a subfield can be used interchangeably.

[0079] Figure 1 FIG. 1 illustrates a wireless LAN system according to an embodiment of the present application.

[0080] The wireless LAN system includes one or more Basic Service Sets (BSSs), and the BSS indicates a set of devices which are successfully synchronized with each other to communicate with each other. Generally, the BSS can be divided into an infrastructure BSS and an Independent BSS (IBSS), and Figure 1 The infrastructure BSS is shown between them.

[0081] As Figure 1 shown, the infrastructure BSS (BSS1 and BSS2) includes one or more stations (STA1, STA2, STA3, STA4, and STA5), access points (AP-1 and AP-2) which are stations providing a Distribution Service, and a Distribution System (DS) connecting a plurality of access points (AP-1 and AP-2).

[0082] A station (STA) is any device that includes a medium access control (MAC) and a physical layer (PHY) interface to the wireless medium in compliance with the provisions of IEEE 802.11 standards, and broadly includes both non-access point (non-AP) stations and access points (APs). Also, in the present specification, the term "terminal" is a term that can be used to refer to either a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a communication unit, and according to embodiments, can further include a user interface unit and a display unit. The processor can generate frames to be transmitted via a wireless network, or process frames received via a wireless network, and in addition, perform various processes for controlling the station. Also, the communication unit is functionally connected to 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).

[0083] 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, an AP is used as a concept including a personal BSS coordination point (PCP), and can broadly include concepts of a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller, etc. In the present application, an AP can also be referred to as a base station wireless communication terminal. A 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, in communication with a plurality of wireless communication terminals, a base station wireless communication terminal can include various types of wireless communication terminals that allocate communication medium resources and perform scheduling.

[0084] 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).

[0085] Figure 2 A stand-alone BSS according to another embodiment of the present application is illustrated, which is a wireless LAN system.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

[0086] Since the BSS 3 illustrated in FIG. 1 is an independent BSS and does not include an AP, all of 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

[0087] Figure 3 is a block diagram illustrating a configuration of a station 100 according to an embodiment of the present application. As illustrated, 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.

[0088] 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 in a separate form, 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.

[0089] 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 means, and the processor 110 can control the station 100 based on the received user input. Further, the user interface unit 140 can perform output based on a command of the processor 110 by using various output means.

[0090] ​​​Next, the display unit 150 outputs an image on a display screen. The display unit 150 can output various display objects such as a content executed by the processor 110 or a user interface based on a control command of the processor 110, etc. Further, 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.

[0091] The processor 110 of the present application can execute various commands or programs and process data in the station 100. Further, 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. Further, 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.

[0092] 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 integrated as a single chip implementation or implemented as separate chips. Further, 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.

[0093] Figure 4 is a block diagram illustrating a configuration of an AP 200 according to an embodiment of the present application. 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 configuration of the AP 200, the same or corresponding elements as those of the station 100 of Figure 3 are illustrated.Figure 3 Repetition of the explanation of parts of the configuration of the station 100 will be omitted.

[0094] Referring to Figure 4 , the AP 200 according to the present application includes a communication unit 220 that operates a BSS in at least one frequency band. As explained in the embodiments of Figure 3 , the communication unit 220 of the AP 200 can also include a plurality of communication modules that use different frequency bands. That is, the AP 200 according to the embodiments of the present application can include two or more communication modules in different frequency bands (e.g., 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz) together. Preferably, the AP 200 can include a communication module that uses a frequency band of 7.125 GHz or above, and a communication module that uses a frequency band of 7.125 GHz or below. Each communication module can perform wireless communication with a station according to a wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit 220 can operate only one communication module at a time according to the performance and requirements of the AP 200, or operate a plurality of communication modules together at the same time. In the embodiments of the present application, the communication unit 220 can represent a Radio Frequency (RF) communication module for processing RF signals.

[0095] Next, the memory 260 stores a control program and various data used in the AP 200. The control program can include an access program for managing access of stations. In addition, the processor 210 can control the respective units of the AP 200, and control data transmission / reception among the units. According to the embodiments of the present application, the processor 210 can execute a program for accessing a station stored in the memory 260, and transmit a communication configuration message for one or more stations. In this case, the communication configuration message can include information on access priority conditions of the respective stations. In addition, the processor 210 performs access configuration according to an access request of a station. According to an embodiment, the processor 210 can be a modem or a modulator and / or demodulator that modulates a wireless signal transmitted to the communication unit 220 and demodulates a wireless signal received from the communication unit 220. The processor 210 controls various operations such as wireless signal transmission / reception of the AP 200 according to the embodiments of the present application. Detailed embodiments thereof will be explained below.

[0096] Figure 5 is a diagram schematically illustrating a process of configuring a link of a station with an access point.

[0097] Referring to 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) transmitted periodically, 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).

[0098] 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.

[0099] 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 response (S111b) to the STA 100. The EAP request and the EAP response are exchanged between the STA 100 and the AP 200, and the AP 200 transmits the EAP response to the authentication server 300 (S111c). 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.

[0100] Figure 6 is a diagram illustrating a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0101] A terminal performing wireless LAN communication checks whether a channel is in a busy state by performing carrier sensing before transmitting data. When a wireless signal having a predetermined strength or greater 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 terminal receives a wireless signal having a CCA threshold or greater, 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.

[0102] When the channel is determined to be idle, each terminal having data to be transmitted performs a backoff procedure after an Inter Frame Space (IFS) time (e.g., Arbitration IFS (AIFS), PCF IFS (PIFS), etc.) depending on the situation of each terminal. According to this embodiment, AIFS can be used as a component instead of the existing DCF IFS (DIFS). Each terminal stands by 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 a 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 procedure is called a contention window interval. In this case, the random number is called a backoff counter. That is, the initial value of the backoff counter can be set by an integer of a random number obtained by the UE. In the case where the UE detects that the channel is idle during the time slot time, the UE can decrease the backoff counter by 1. In addition, in the case where the backoff counter reaches 0, the UE can be allowed to perform channel access in the corresponding channel. Accordingly, in the case where the channel is idle during the AIFS time and the time slot time of the backoff counter, the UE can be allowed to transmit.

[0103] When the special terminal successfully accesses the channel, the corresponding terminal can transmit data through the channel. However, when the terminals attempting access collide with another terminal, the terminals colliding with each other are respectively allocated new random numbers to perform the backoff procedure again. According to an 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 the backoff procedure again in the next contention window interval, and in this case, each terminal performs the backoff procedure from the time of the time slots remaining in the previous contention window interval. Through this method, the respective terminals performing wireless LAN communication can avoid mutual collision of the special channel.

[0104] <Examples of various PPDU formats>

[0105] Figure 7 FIGS. 1 to 4 illustrate examples of formats of a physical layer protocol data unit (PPDU) for each of various standard 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. 2 illustrates an embodiment of an HE PPDU format based on 802.11ax, and Figure 7 (c) of FIG. 3 illustrates an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Figure 7 (d) of FIG. 4 illustrates detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU format.

[0106] Referring to Figure 7 (a), the preamble of the legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In an embodiment of the disclosure, the L-STF, the L-LTF, and the L-SIG can be referred to as a legacy preamble.

[0107] Referring to Figure 7of (b), the preamble of the HE PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a High Efficiency Signal A field (HE-SIG-A), a High Efficiency Signal B field (HE-SIG-B), a High Efficiency Short Training field (HE-STF), and a High Efficiency Long Training field (HE-LTF) in the legacy preamble. In embodiments of the present application, 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. The detailed configuration 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.

[0108] Referring to Figure 7 of (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 embodiments of the present application, 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 detailed 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.

[0109] 64-FFT OFDM is applied to an L-SIG field included in a preamble of a 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 (d) illustrates a configuration of 24 bits of information of the L-SIG.

[0110] Referring to Figure 7 (d), the 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 value among 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps of a transmission rate obtained by combining a modulation scheme of BPSK / QPSK / 16-QAM / 64-QAM, etc. and a code rate such as 1 / 2, 2 / 3, 3 / 4, etc. A total length of a corresponding PPDU can be indicated by combining information of the L_RATE field and information of the L_LENGTH field. In a non-legacy PPDU format, the L_RATE field is configured as a minimum rate of 6 Mbps.

[0111] A unit of the L_LENGTH field can be allocated a total of 12 bits in bytes, up to 4095 can be signaled, and a length of a corresponding PPDU can be indicated by a combination with the L_RATE field. In this case, a legacy terminal and a non-legacy terminal can use different methods to interpret the L_LENGTH field.

[0112] First, a method in which a legacy terminal or a non-legacy terminal analyzes a length of a corresponding PPDU using the L_LENGTH field is as follows. When a value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4 μs that is one symbol duration of 64 FFT. Accordingly, 3 bytes corresponding to an SVC field and a tail field are added to a value of the field L_LENGTH, and the added value is divided by 3 bytes that is a transmission amount of one symbol, thereby obtaining a number of symbols based on 64 FFT after the L-SIG. The obtained number of symbols is multiplied by 4 μs (i.e., a length of one symbol), and then a time of 20 μs required for transmission of L-STF, L-LTF, and L-SIG is added, thereby obtaining a length of a corresponding PPDU, i.e., a reception time RXTIME. This can be expressed by Equation 1 below.

[0113] [Equation 1]

[0114]

[0115] In this case, represents 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 5.484 ms. The non-legacy terminal transmitting the PPDU should set the L_LENGTH field as shown in Equation 2 below.

[0116] [Equation 2]

[0117]

[0118] Here, TXTIME is the total transmission time of the corresponding PPDU, and is represented by Equation 3 below. In this case, TX denotes the transmission time of X.

[0119] [Equation 3]

[0120] TXTIME (us) = T L-STF + T L-LTF + T L-SIG + T RL-SIG + T U-SIC + (T EHT-SIG-A ) + (T EHT-SIG-B ) + T EH-STF + N EHT-LTF · F EHT-LTF + T DATA

[0121] 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 k, three different values of L_LENGTH = {3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0122] Referring to Figure 7 (e), the Universal SIG (U-SIG) field continues to exist in the EHT PPDU and the wireless LAN PPDU of the subsequent generation, and is used to distinguish to which generation including 11be the PPDU belongs. The U-SIG is a 2 symbol of OFDM 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.

[0123] 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 distinguish 11be and a subsequent generation wireless LAN standard by 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 length of the TXOP included in the PPDU can be inferred by adding the TXOP to the PHY header without decoding the MPDU, and the TXOP has a value of 7 bits or more.

[0124] The VD field is signaling information useful only for the 11be version of the PPDU, and can include fields commonly used in any PPDU format such as PPDU format and BW, and fields differently defined for each PPDU format. The PPDU format is a classifier that classifies 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 of 20, 40, 80, 160, (80+80), and 320 MHz (a BW that can be expressed in the form of an exponential power of 20*2 is referred to as a basic BW), and various remaining PPDU BWs configured via preamble puncturing. After being signaled in 320 MHz, it can be signaled in the form 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 that appears after the BW field (for example, a field within the EHT-SIG field). If the BW field is configured to 3 bits, a total of 8 BWs can be signaled, and thus a maximum of 3 puncturing patterns can be signaled. If the BW field is configured to 4 bits, a total of 16 BWs can be signaled, and thus a maximum of 11 puncturing patterns can be signaled.

[0125] 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 distinguishing the MU PPDU and the SU PPDU can be located before the EHT-SIG field, and for this, additional signaling can be performed. Both the SU PPDU and the MU PPDU include the EHT-SIG field, but some fields that are not required in the SU PPDU can be compressed. Information of the fields to which compression is 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, there can be different configurations in which a common field of the EHT-SIG is omitted or replaced, or a user-specific field is replaced, reduced to one, etc.

[0126] Alternatively, the SU PPDU can further include a compression field indicating whether compression is performed, and a part of the field (e.g., the RA field, etc.) can be omitted according to the value of the compression field.

[0127] 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 the 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 the EHT-SIG field to be transmitted after the U-SIG field, and the amount of information transmitted can vary. That is, since a plurality of MU PPDUs are transmitted to a plurality of STAs, 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. For this, information for efficiently transmitting 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 on the size and position of the RU allocated to each user.

[0128] 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, a puncturing mode field including information indicating a puncturing pattern in the form of a bitmap, etc., and whether the puncturing mode is applied can be included in the EHT-SIG field, and the puncturing mode field can signal a discontinuous channel type occurring within the bandwidth.

[0129] The signaled discontinuous channel type is limited, and the BW and the discontinuous channel information of the SU PPDU are indicated in a manner combined with the value of the BW field. For example, the SU PPDU is a PPDU transmitted to only a single terminal, so the STA can recognize the bandwidth allocated to itself through the BW field included in the PPDU, and the SU PPDU can recognize the punctured resources in the allocated bandwidth through the puncturing mode field of the U-SIG field or the EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU in the remaining resource units after excluding the punctured resource units from the special channel. The plurality of RUs allocated to the STA can be configured by different frequency bands or tones.

[0130] 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 if the puncturing is performed for a BW having a plurality of 20 MHz subchannels, such as 80, 160, and 320 MHz, in the case of 320 MHz, the discontinuous channel (puncturing of only the edge 20 MHz is also considered to be 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.

[0131] 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 (Primary) 160 MHz and the secondary (Secondary) 160 MHz in the 320 MHz BW configuration of the SU PPDU.

[0132] 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.

[0133] 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 a SIG-B MCS, a SIG-B DCM, a number of SIG-B symbols, a SIG-B compression, and a number of EHT-LTF symbol fields, etc.

[0134] Figure 7 FIGS. 1 to 6 illustrate examples of various Extremely High Throughput (EHT) Physical Layer Protocol Data Unit (PPDU) formats according to embodiments of the present application, and a method for indicating the same.

[0135] 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.

[0136] 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.

[0137] Figure 8 (b) of FIG. 1 shows an example of an EHT trigger-based PPDU format corresponding to an EHT PPDU transmitted based on a trigger frame. The EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame, and is an uplink PPDU for a response to the trigger frame. Unlike the EHT SU PPDU, the EHT-SIG-A field is not located after the U-SIG field in the EHT PPDU.

[0138] 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, the HE-SIG-B field can be located after the U-SIG field.

[0139] 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 STA in a wider range, and the U-SIG field can be repeatedly located in a time axis. Figure 8

[0140] 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 deliver AID information of a receiver and / or a transmitter of the transmitted PPDU to the STAs through a user specific field of the EHT-SIG-B. Accordingly, the multiple terminals that receive the EHT MU PPDU can perform a spatial reuse operation based on the AID information of the user specific field included in the preamble of the received PPDU.

[0141] ​Specifically, a resource unit allocation (RA) field of an HE-SIG-B field included in the HE MU PPDU can include information about a configuration (e.g., a division form 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 a STA to receive the PPDU. Information about a STA allocated (or designated) to each divided resource unit 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 respective divided resource units.

[0142] For example, a user field corresponding to at least one resource unit for data transmission among the divided plurality of 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.

[0143] For convenience of explanation, in the present specification, a frame or a MAC frame can be used interchangeably with an MPDU.

[0144] When one wireless communication device communicates by using a plurality of links, communication efficiency of the wireless communication device can be improved. In this case, a link can be a physical path and can consist of one wireless medium that can be used to deliver a MAC service data unit (MSDU). For example, in a case where a frequency band of one of the links is used by another wireless communication device, the wireless communication device can continue to perform communication through another link. As such, the wireless communication device can usefully use a plurality of channels. Further, when the wireless communication device simultaneously performs communication by using a plurality of links, total throughput can be increased. However, in the existing wireless LAN, it has been stipulated that one wireless communication device uses one link. Therefore, a WLAN operation method using a plurality of links is required. Will be described Figure 8 A wireless communication method of a wireless communication device using a plurality of links is described. First, will be described Figures 9 to 26 A specific form of a wireless communication device using a plurality of links is described.

[0145] Figure 9 is a diagram illustrating a multi-link device according to an embodiment of the present application.

[0146] A multi-link device (MLD) can be defined for a wireless communication method using the plurality of links. The multi-link device can represent a device having one or more affiliated stations. According to a specific embodiment, the multi-link device can represent a device having two or more affiliated stations. Further, the multi-link device can exchange a multi-link element. The multi-link element includes information about one or more stations or one or more links. The multi-link element can include a multi-link setup element, which will be described later. In this case, the multi-link device can be a logical entity. Specifically, the multi-link device can have a plurality of affiliated stations. The multi-link device can be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device can have one media access control (MAC) service access point (SAP) up to a logical link control (LLC). The MLD can also have one MAC data service.

[0147] The plurality of stations included in the multi-link device can operate on a plurality of links. Further, the plurality of stations included in the multi-link device can operate on a plurality of channels. Specifically, the plurality of stations included in the multi-link device can operate on a plurality of different links or on a plurality of different channels. For example, the plurality of stations included in the multi-link device can operate on a plurality of different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0148] The operation of the multi-link device can be referred to as a multi-link operation, an MLD operation, or a multi-band operation. Further, when a station affiliated with the multi-link device is an AP, the multi-link device can be referred to as an AP MLD. Further, when a station affiliated with the multi-link device is a non-AP station, the multi-link device can be referred to as a non-AP MLD.

[0149] Figure 9 An operation of non-AP MLD and AP-MLD communication is illustrated. Specifically, the non-AP MLD and the AP-MLD communicate by using three links, respectively. The AP MLD includes a first AP AP1, a second AP AP2, and a third AP AP3. The non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP AP1 and the first non-AP STA (non-AP STA1) communicate through a first link Link1. Further, the second AP AP2 and the second non-AP STA (non-AP STA2) communicate through a second link Link2. Further, the third AP AP3 and the third non-AP STA (non-AP STA3) communicate through a third link Link3.

[0150] The multi-link operation can include a multi-link setup operation. The multi-link setup can correspond to an association operation of the single-link operation, and can be first performed in the multi-link for frame exchange. The multi-link device can obtain information required for the multi-link setup from a multi-link setup element. Specifically, the multi-link setup element can include capability information associated with the multi-link. In this case, the capability information can include information indicating whether any one of a plurality of devices included in the multi-link device performs transmission and another device can perform reception at the same time. Further, the capability information can include information about links available for each station included in the MLD. Further, the capability information can include information about channels available for each station included in the MLD.

[0151] The multi-link setup can be set through negotiation between peer stations. Specifically, the multi-link setup can be performed through communication between stations without communication with an AP. Further, the multi-link setup can be set through any one link. For example, even though the first to third links are set through the multi-link, the multi-link setup can be performed through the first link.

[0152] Further, a mapping between a traffic identifier (TID) and a link can be set. Specifically, frames corresponding to a TID of a special value can be exchanged only through a predetermined link. The mapping between the TID and the link can be set based on a direction. For example, when a plurality of links are set between a first multi-link device and a second multi-link device, the first multi-link device can be set to transmit frames of a first TID to a plurality of first links, and the second multi-link device can be set to transmit frames of a second TID to the first link. Further, there can be a default setting for the mapping between the TID and the link. Specifically, in the case where there is no additional setting in the multi-link setup, the multi-link device can exchange frames corresponding to the TID at each link according to the default setting. In this case, the default setting can be to exchange all TIDs in any one link.

[0153] The TID will be described in detail. The TID is an ID for classifying traffic and data in order to support Quality of Service (QoS). Also, the TID can be used or assigned in a layer higher than the MAC layer. Also, the TID can indicate a Traffic Class (TC) or a Traffic Stream (TS). Also, the TID can be classified into 16 types. For example, the TID can be designated as one of values in the range of 0 to 15. The TID value to be used can be variously designated according to an access policy and a channel access or medium access method. For example, in the case of using Enhanced Distributed Channel Access (EDCA) or Hybrid Coordinated Function Competition-based Channel Access (HCAF), values in the range of 0 to 7 can be assigned to the TID. In the case of using EDCA, the TID can indicate a User Priority (UP). In this instance, the UP can be designated based on the TC or the TS. The UP can be assigned in a layer higher than the MAC. Also, in the case of using HCF Controlled Channel Access (HCCA) or SPCA, values in the range of 8 to 15 can be assigned to the TID. In the case of using HCCA or SPCA, the TID can indicate a TSID. Also, in the case of using HEMM or SEMM, values in the range of 8 to 15 can be assigned to the TID. In the case of using HEMM or SEMM, the TID can indicate a TSID.

[0154] The UPs and ACs can be mapped. The ACs can be tags for providing QoS in EDCA. The ACs can be tags for indicating EDCA parameter sets. The EDCA parameters or EDCA parameter sets can be parameters for EDCA channel contention. The QoS stations can use the ACs to guarantee QoS. Also, the ACs can include AC_BK, AC_BE, AC_VI, and AC_VO. The AC_BK, AC_BE, AC_VI, and AC_VO can indicate background, best effort, video, and voice, respectively. Also, each of the AC_BK, AC_BE, AC_VI, and AC_VO can be classified as a dependent AC. For example, the AC_VI can be subdivided into AC_VI primary and AC_VI secondary. Also, the AC_VO can be subdivided into AC_VO primary and AC_VO secondary. Also, the UPs or TIDs can be mapped to the ACs. For example, the UPs or TIDs having values 1, 2, 0, 3, 4, 5, 6, and 7 can be mapped to the AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, the UPs or TIDs having values 1, 2, 0, 3, 4, 5, 6, and 7 can be mapped to the AC_BK, AC_BK, AC_BE, AC_BE, AC_VI secondary, AC_VI primary, AC_VO primary, and AC_VO secondary, respectively. Also, the UPs or TIDs having values 1, 2, 0, 3, 4, 5, 6, and 7 can sequentially have high priority. That is, 1 indicates low priority, and 7 indicates high priority. Thus, the AC_BK, AC_BE, AC_VI, and AC_VO can sequentially have high priority. Also, the AC_BK, AC_BE, AC_VI, and AC_VO can correspond to AC indices (ACIs) 0, 1, 2, and 3, respectively. Due to these characteristics of the TIDs, the mapping between the TIDs and the links can indicate the mapping between the ACs and the links. Also, the mapping between the links and the ACs can indicate the mapping between the TIDs and the links.

[0155] As described above, the TIDs can be mapped to each of the plurality of links. The mapping can designate the links capable of exchanging traffic corresponding to a predetermined TID or AC. Also, the TIDs or ACs transmittable for each transmission direction in the links can be designated. As described above, there can be a default configuration for the mapping between the TIDs and the links. Specifically, in the case where there is no additional configuration for the multi-link configuration, the multi-link device can exchange frames corresponding to the TIDs in each link according to the default configuration. In this instance, the default configuration can exchange all of the TIDs in any one link. Any TID or AC at any point in time can always be mapped to at least any one link. The management frames and control frames can be transmitted in all of the links.

[0156] In case a link is mapped to a TID or an AC, only data frames corresponding to the TIDs or ACs mapped to the corresponding link can be transmitted in the corresponding link. Thus, in case a link is mapped to a TID or an AC, frames not corresponding to the TIDs or ACs mapped to the corresponding link can not be transmitted in the corresponding link. In case a link is mapped to a TID or an AC, ACKs can also be transmitted based on the link to which the TIDs or ACs are mapped. For example, a block ACK protocol can be determined based on the mapping between TIDs and links. According to another embodiment, the mapping between TIDs and links can be determined based on a block ACK protocol. In particular, a block ACK protocol can be set for TIDs mapped to a predetermined link.

[0157] QoS can be guaranteed via the mapping between TIDs and links. In particular, ACs or TIDs having a high priority can be mapped to a link operated by a relatively small number of stations or a link having good channel conditions. Furthermore, via the mapping between TIDs and links, stations can be enabled to maintain a power saving state during a long period of time.

[0158] Figure 9 FIGURE 1 illustrates simultaneous transmission of different links in multi-link operation according to an embodiment of the present disclosure.

[0159] According to implementation of a multi-link device, simultaneous operation can not be supported in multi-link. For example, simultaneous transmission by a multi-link device in multi-link, simultaneous reception in multi-link, or transmission in one link and reception of another link can not be supported. This is because reception or transmission performed in one link can affect reception or transmission performed in another link. In particular, transmission in one link can act as interference to another link. The interference imposed by one multi-link device from one link to another link can be referred to as internal leakage. As the frequency separation between links is small, internal leakage can become large. When internal leakage is not very large, transmission can be performed in another link while transmission is performed in one link. When internal leakage is large, transmission cannot be performed in another link while transmission is performed in one link. As described above, simultaneous operation by a multi-link device in multiple links can be referred to as simultaneous transmission and reception or simultaneous transmission and reception (STR). For example, simultaneous transmission by a multi-link device in multiple links, transmission in one link and reception in another link, or simultaneous reception in multiple links can be referred to as STR.

[0160] As described above, a multi-link device can support STR or support STR only with limitations. Specifically, a multi-link device supports STR under special conditions. For example, when a multi-link device operates as a single radio device, the multi-link device can not perform STR. Further, when a multi-link device operates as a single antenna, STR of the multi-link device can not be performed. When internal leakage having a size greater than or equal to a predetermined size is detected, the multi-link device can not perform STR.

[0161] A station can exchange information about STR capability of the station with another station. Specifically, the station can exchange information about capability of whether to restrict simultaneous transmission in multiple links or simultaneous reception in multiple links with another station. Specifically, the information about capability of whether to restrict transmission or reception in multiple links can indicate whether simultaneous transmission, simultaneous reception, or simultaneous transmission and reception in multiple links can be performed. The information about capability of whether to restrict transmission or reception in multiple links can be information indicated for each step. Specifically, the information about capability of whether to restrict transmission or reception in multiple links can be information indicating a step representing a size of internal leakage. In a detailed embodiment, the information indicating a step representing a size of internal leakage can be information indicating a step representing a size of interference generated due to internal leakage. In another detailed embodiment, the information can be information indicating a step representing a frequency interval between links that can affect internal leakage. The information indicating a step representing a size of internal leakage can be information indicating a relationship between a frequency interval between links and a size of internal leakage.

[0162] In Figure 10 , a first station (STA1) and a second station (STA2) are affiliated to one non-AP multi-link device. A first AP (AP1) and a second AP (AP2) can be affiliated to one non-AP multi-link device. A first link (link1) is configured between the first AP (AP1) and the first station (STA1), and a second link (link2) is configured between the second AP (AP2) and the second station (STA2). In Figure 10In some cases, a non-AP multi-link device can restrictively perform STR. When a second station (STA2) performs transmission in a second link (link2), reception of a first station (STAl) in a first link (linkl) can be interfered by the transmission performed in the second link (link2). For example, reception of the first station (STAl) in the first link (linkl) can be interrupted by the transmission performed in the second link (link2) in the following cases. The second station (STA2) transmits first data (data1) in the second link (link2), and the first AP (AP1) transmits a response to the first data (data1) (ack for data1) to the first station (STAl). The second station (STA2) transmits second data (data2) in the second link (link2). Meanwhile, the transmission time point of the second data (data2) can overlap with the transmission time point of the response to the first data (data1) (ack for data1). The first link (linkl) can be interfered by the transmission to the second station (STA2) in the second link (linkl). Therefore, the first station (STAl) can not receive the response to the first data (data1) (Ack for Data1).

[0163] Operations of a multi-link device performing channel access are described. Operations of a multi-link that are not described in detail can follow the channel access described in reference Figure 10 .

[0164] The multi-link device can perform channel access in the multiple links independently. At this time, the channel access can be backoff-based channel access. When the multi-link device performs channel access in the multiple links independently and the backoff counters in the multiple links reach 0, the multi-link device can perform transmission in the multiple links simultaneously. In a detailed embodiment, when one of the backoff counters of the multi-link reaches 0 and a predetermined condition is satisfied, the multi-link device can not only perform channel access in the link in which the backoff counter reaches 0, but also perform channel access in another link in which the backoff counter does not reach 0. Specifically, when one of the backoff counters of the multi-link reaches 0, the multi-link device can detect energy in another link in which the backoff counter does not reach 0. At this time, when energy having a predetermined size or greater is not detected, the multi-link device can not only perform channel access in the link in which the backoff counter reaches 0, but also perform channel access in the link in which the energy is detected. Accordingly, the multi-link device can perform transmission in the multiple links simultaneously. The size of the threshold for energy detection can be smaller than the size of the threshold for determining whether to reduce the backoff counter. Furthermore, the multi-link device can detect any type of signal as well as a WLAN signal when determining whether to reduce the backoff counter. In energy detection, the multi-link device can detect any type of signal as well as a WLAN signal. A WLAN signal can not be able to detect internal leakage. In this case, the multi-link device can sense a signal detected due to internal leakage through energy detection. Furthermore, as described above, the size of the threshold for energy detection can be smaller than the size of the threshold for determining whether to reduce the backoff counter. Accordingly, even when transmission is performed in one link, the multi-link device can reduce the backoff counter in another link.

[0165] According to the degree of interference between the links used by the multi-link device, the multi-link device can determine whether the stations operating in each link can operate independently. At this time, the degree of interference between the links can be the size of interference detected by another station of the multi-link device when one station performs transmission in one link. When transmission by a first station of the multi-link device in a first link brings interference having a predetermined size or greater to a second station of the multi-link device operating in a second link, the operation of the second station can be limited. Specifically, reception or channel access of the second station can be limited. This is because when interference occurs, the second station can not be able to decode a received signal due to the interference. Furthermore, this is because when interference occurs, when the second station performs channel access using backoff, the second station can determine that the channel is being used.

[0166] The first and second stations can independently operate when the transmission of the first station of the multi-link device in the first link to the second station of the multi-link device operating in the second link brings interference having a size smaller than the predetermined size. Specifically, the first and second stations can independently perform channel access when the transmission of the first station of the multi-link device in the first link to the second station of the multi-link device operating in the second link brings interference having a size smaller than the predetermined size. Further, the first and second stations can independently perform transmission or reception when the transmission of the first station of the multi-link device to the second station of the multi-link device operating in the second link brings interference having a size smaller than the predetermined size. This is because the second station can successfully decode the received signal even though the interference exists when the interference having a size smaller than the predetermined size is generated. Further, this is because the second station can determine that the channel is idle when the second station performs channel access using backoff when the interference having a size smaller than the predetermined size is generated.

[0167] The degree of interference generated between the stations of the multi-link device can vary depending on the hardware characteristics of the multi-link device and the interval between the frequency bands of the links in which the stations operate. For example, the internal interference generated in a multi-link device including expensive radio frequency (RF) devices can be smaller than the internal interference generated in a multi-link device including inexpensive RF devices. Accordingly, the degree of interference generated between the stations of the multi-link device can be determined based on the characteristics of the multi-link device.

[0168] Figure 6 FIG. illustrates that the size of the generated interference varies depending on the interval between the frequency bands of the links and the characteristics of the multi-link device. In Figure 10In an embodiment, a first multi-link device (MLD#1) includes a first station (STAl-1) operating in a first link (linkl) and a second station (STAl-2) operating in a second link (link2). A second multi-link device (MLD#2) includes a first station (STA2-1) operating in the first link (linkl) and a second station (STA2-2) operating in the second link (link2). The frequency separation between the first link (linkl) and the second link (link2) in which the first multi-link device (MLD#1) operates is the same as the frequency separation between the first link (linkl) and the second link (link2) in which the second multi-link device (MLD#2) operates. However, due to the difference between the characteristics of the first multi-link device (MLD#1) and the characteristics of the second multi-link device (MLD#2), the size of the generated interference can be different. Specifically, the size of the generated interference in the first multi-link device (MLD#1) can be greater than the size of the generated interference in the second multi-link device (MLD#2). As described above, the size of the generated interference can vary depending on the characteristics of the multi-link device, and when it is considered that whether the STR is supported is different according to each multi-link device, it can be necessary to exchange information on whether the STR is supported.

[0169] A multi-link device can signal information about whether STR is supported by stations included in the multi-link device. Specifically, an AP multi-link device and a non-AP multi-link device can exchange information about whether STR is supported by an AP included in the AP multi-link device and whether STR is supported by STAs included in the non-AP multi-link device. In such an embodiment, an element indicating whether STR is supported can be used. The element indicating whether STR is supported can be referred to as an STR support element. The STR support element can indicate whether STR is supported by stations of the multi-link device transmitting the STR support element by 1 bit. Specifically, the STR support element can indicate whether STR is supported by each station included in the multi-link device transmitting the STR support element by 1 bit. At this time, when a station supports STR, the value of the bit can be 1, and when a station does not support STR, the value of the bit can be 0. When the multi-link device transmitting the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), the first station (STA1) and the third station (STA3) support STR, and the second station (STA2) does not support STR, the STR support element can include a field having 1011b. It is assumed that stations operating in different frequency bands support STR, and the STR support element can omit signaling indicating whether STR is supported between stations operating in different frequency bands. For example, the first station (STA1) operates in a first link of 2.4 GHz, and the second station (STA2) and the third station (STA3) operate in a second link and a third link of 5 GHz, respectively. The STR support element can indicate that STR is supported between the second station (STA2) and the third station (STA3) by using 1 bit. Furthermore, when the number of stations signaled by the STR support element is 2, the STR support element can include only 1 bit.

[0170] In a detailed embodiment, a relationship between a link located in 2.4 GHz and a link located in 5 GHz or 6 GHz among links of a multi-link device can always be determined as STR. Accordingly, signaling for STR of a link located in 2.4 GHz and a link located in 5 GHz or 6 GHz can be omitted.

[0171] Figure 10 FIG. 1 illustrates an operation of a multi-link device at a time of link change according to an embodiment of the disclosure.

[0172] The STR support element can be changed when the frequency band of the link changes. As described above, this is because whether the STR is supported by the station can change depending on the distance between the frequency bands of the link, and whether the STR is supported by the station can change when the frequency band of the link changes. The change of the frequency band of the link can include at least one of a change of the center frequency, a change of the bandwidth of the frequency band, and a change of the primary channel in 20MHz. The AP and the station can exchange the STR support element through a request and a response. In another detailed embodiment, the STR support element can be exchanged without any separate request when the frequency band of the link changes. Also, in the described embodiment, the change of the frequency band of the link can include a change of the operating channel of the station.

[0173] When the station of the non-AP multi-link device cannot perform the STR, the station of the non-AP multi-link device can request the AP to change the link. Specifically, the station of the non-AP multi-link device can make a request to change at least one of the center frequency, the bandwidth of the frequency band, and the primary channel in 20MHz. The link change request can be transmitted to the AP through the link requested to be changed. In another detailed embodiment, the link change request can be transmitted to the AP through the link not requested to be changed. At this time, the link change request can include information indicating the link requested to be changed. The information indicating the link can be a number for identifying the link. In such an embodiment, the change of the link can be a change of the operating channel within one frequency band. Also, the change of the link can include information on a method of changing the link. Specifically, the link change request can indicate whether to move the center frequency of the link to a frequency higher than the current center frequency or to a frequency lower than the current center frequency. In another detailed embodiment, the link change request can implicitly indicate a change to a frequency band away from an adjacent link. Also, the link change request can indicate a reduction of the bandwidth. The link change request can be a request to change the position of the primary channel. Specifically, the link change request can indicate a change of the position of the primary channel to a channel of a frequency band lower than the position of the primary channel or a channel of a frequency band higher than the position of the primary channel. The AP receiving the link change request can change the link according to the link change request. Also, in a detailed embodiment, the AP receiving the link change request can ignore the link change request.

[0174] In Figure 11In an embodiment, the second station (STA2) and the third station (STA3) of the non-AP multi-link device do not support STR. The non-AP multi-link device transmits a request for changing the third link (link3) to the AP multi-link device. The AP multi-link device receiving the link change request changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating in the third link (link3) to be changed can transmit a change request to the third AP (AP3). In another detailed embodiment, a station not operating in the third link (link3) can transmit a change request to an AP not operating in the third link (link3).

[0175] When the AP changes the link, the AP can broadcast information about the link change through a beacon frame. At this time, the information about the link change can include information about a link frequency. The information about the link frequency can include at least one of a change in an operating bandwidth and a primary channel. In addition, the information about the link change can include information about a link change time point. In addition, when a beacon including the information about the link change is transmitted, the link change can be completed.

[0176] In Figure 11 , the link operated by the third station (STA3) is changed, and thus the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multi-link device can transmit an STR support element to the AP multi-link device and signal information indicating a change in support of STR.

[0177] The link change can not be allowed, or STR can not be supported through the link change. As Figure 11 indicated in an embodiment, the AP multi-link device can support STR, but the non-AP multi-link device can not support STR. This is because it is common to use a relatively expensive device for the AP multi-link device and a relatively inexpensive device for the non-AP multi-link device. Accordingly, in communication between multi-link devices, even when one multi-link device does not support STR, a method of performing efficient communication needs to be performed. At this time, STR can indicate that transmission and reception are simultaneously performed. This will be described with reference to Figure 11 .

[0178] Figure 12 FIG. illustrates limiting channel access of one station of a non-STR multi-link device when reception of another station of the non-STR multi-link device is performed according to an embodiment of the disclosure.

[0179] When transmission of the non-STR multi-link device is performed in one link and reception of the non-STR multi-link device is performed in another link, reception and transmission of the non-STR multi-link device can fail. To solve this problem, when reception of the non-STR multi-link device is performed in one link, channel access of the non-STR multi-link device in another link can be limited. Specifically, when reception of the non-STR multi-link device is performed in one link, backoff of channel access of the non-STR multi-link device in another link can be limited. Accordingly, when reception of the non-STR multi-link device is performed in one link, the non-STR multi-link device can be prevented from starting transmission in another link. In a detailed embodiment, when reception of the non-STR multi-link device starts in one link, backoff of channel access of the non-STR multi-link device in another link can be limited. It can be configured by a special bit of a memory, such as a channel access limitation flag. Whether to limit channel access can be shared by a memory within the multi-link device. Through such an embodiment, channel access limitation can be implemented without separate frame exchange. For ease of description, channel access limitation used in this specification indicates a limitation on channel access or transmission in order to protect transmission or reception of the non-STR multi-link device, unless there is a separate description.

[0180] When channel access is restricted, a station operating in a link where channel access is restricted is not able to perform a backoff procedure regardless of NAV and CCA results. In addition, when channel access is restricted, a station operating in a link where channel access is restricted is not able to perform a transmission regardless of NAV and CCA results. However, even when channel access is restricted, a station operating in a link where channel access is restricted is able to perform reception. In addition, channel access restriction in a second link due to reception performed in a first link can be released based on a point in time when reception in the first link is completed. Specifically, channel access restriction in a second link due to reception performed in a first link can be released when reception in the first link is completed. In another detailed embodiment, channel access restriction in a second link due to reception performed in a first link can be released based on a point in time when an ACK is transmitted after reception in the first link is completed. Specifically, channel access restriction in a second link due to reception performed in a first link can be released at a point in time when an ACK is transmitted after reception in the first link is completed. In another detailed embodiment, channel access restriction in a second link due to reception performed in a first link can be released at a point in time when ACK transmission is completed after reception in the first link is completed. In addition, after channel access restriction is released, a station can immediately decrease a backoff counter without additional sensing. At this time, additional sensing can refer to sensing performed during a DCF interframe space (DIFS). In another detailed embodiment, when a channel is just idle for a predetermined time before channel access restriction is released, the station can immediately decrease a backoff counter without additional sensing. At this time, the predetermined time can be one of a PCF interframe space (PIFS), a short interframe space (SIFS), and an arbitration interframe space (AIFS).

[0181] In Figure 12 In an embodiment, a non-STR multi-link device includes a first station (STA1) operating in a first link (link1) and a second station (STA2) operating in a second link (link2). Intra-device interference is generated when the second station (STA2) performs a transmission in the second link (link2) while the first station (STA1) performs reception in the first link (link1). As described above, when the first station (STA1) operating in the first link (link1) performs reception, channel access of the second station (STA2) performing in the second link (link2) is restricted. After reception of the first station (STA1) in the first link (link1) is completed, the channel access restriction is released. Just after the channel access restriction is released, the second station (STA2) can decrease a value of a previous backoff counter from 3 to 2 without additional sensing.

[0182] For ease of expression, in Figure 12The single block (Tx solid line, Rx dashed line) is used in the drawings used to represent Rx and Tx, and it can be understood that the single block represents the operation including Tx / Ack reception and Rx / Ack transmission, even if the separate Ack block is not shown. This can be equally applied to the following drawings.

[0183] When a station identifies that a received PPDU is not an intended receiver of the station, the station can stop receiving the PPDU. In this case, the operation of releasing the channel access prohibition by the multi-link device is problematic. The intended receiver in this specification is used to have the same meaning as the destination station.

[0184] Figure 12 The operation of releasing the channel access prohibition when it is identified that the intended receiver of a PDDU received by a station of a non-STR multi-link device is not the station is illustrated according to an embodiment of the disclosure.

[0185] When a station identifies that a received PPDU is not an intended receiver of the station, the station can release the channel access prohibition. The station can determine whether the station is an intended receiver of the PPDU based on information of a receiver address of a signaling field indicating the PPDU. At this time, the information of the receiver address of the signaling field indicating the PPDU can be a value of an STA-ID field of an EHT-SIG field. Specifically, the station can determine whether the STA-ID field of the EHT-SIG field indicates the station. In addition, the station can determine whether the station is an intended receiver of the PPDU based on a value of an RA field of a MAC frame included in the PPDU. Specifically, the station can determine whether the RA field of the MAC frame included in the PPDU indicates the station. In Figure 13 In the non-STR multi-link device, a first station (STA1) operating in a first link (link1) and a second station (STA2) operating in a second link (link2) are included. The first station (STA1) receives a PPDU. The first station (STA1) determines that the intended receiver of the received PPDU is not the first station (STA1) and stops receiving the PPDU. At this time, the first station (STA1) can release the channel access prohibition of the second station (STA2). Even if the channel access prohibition of the second station (STA2) is released, the channel access of the second station (STA2) can be delayed according to the NAV configured in the second station (STA2).

[0186] As Figure 13As illustrated, even if the channel access prohibition is released, a station included in a non-STR multi-link device can have channel access opportunities less frequently than a station not included in a multi-link device or a station included in an STR multi-link device. Thus, a method of guaranteeing channel access opportunities of a station included in a non-STR multi-link device can be required to compete fairly with other stations. For example, after the channel access prohibition is released, a station whose channel access is prohibited can decrease a backoff counter by 2 or more. This will be described with reference to Figure 13 Description.

[0187] Figure 14 FIG. illustrates channel access performed by a station after a channel access prohibition is released according to an embodiment of the disclosure.

[0188] After the channel access prohibition is released, a station whose channel access prohibition is released can decrease a backoff counter by 2 or more. This is to balance channel access opportunities with other stations because other stations perform a backoff procedure while the channel access of the station is prohibited.

[0189] In another detailed embodiment, a station whose channel access is prohibited can perform a channel access procedure of decreasing CCA (CSMA) and a backoff counter while the channel access is prohibited. In Figure 14 In the above detailed embodiment, a non-STR multi-link device includes a first station (STA1) operating in a first link (link1) and a second station (STA2) operating in a second link (link2). In Figure 14 In the above detailed embodiment, a channel access of the second station (STA2) is prohibited while the first station (STA1) performs reception. In Figure 14 In (a) of the above detailed embodiment, the second station (STA2) can perform a channel access procedure of decreasing CCA (CSMA) and a backoff counter while the channel access of the second station (STA2) is prohibited. In Figure 14 In (a) of the above detailed embodiment, the second station (STA2) decreases the backoff counter because a channel of the second link (link2) is idle while the channel access of the second station (STA2) is prohibited.

[0190] Further, even if the backoff counter reaches 0 while the channel access is prohibited, a station whose channel access is prohibited can delay transmission without starting transmission. At this time, the station can maintain a value of the backoff counter as 0. Further, although the station delays transmission, the station can maintain a value of a CW. Thus, it can be distinguished from a case where the value of the CW is doubled by the station because a channel accessed by the station is busy. This is because a reason for delaying transmission is not a case where it is determined that the channel is being used. In Figure 14 In (b) of the above detailed embodiment, the second station (STA2) can perform a channel access procedure of decreasing CCA (CSMA) and a backoff counter while the channel access of the second station (STA2) is prohibited. In Figure 14In (b), since the channel of the second link (link2) is idle when the second station (STA2) is prohibited from accessing the channel, the second station (STA2) decrements the backoff counter. When the second station (STA2) is prohibited from accessing the channel, the backoff counter of the second station (STA2) reaches 0. The second station (STA2) delays transmission and starts transmission after releasing the channel access prohibition.

[0191] As described above, channel access prohibition may include prohibiting transmission of a second station when a first station of a non-STR multilink device is transmitting. Additionally, channel access prohibition may include prohibiting transmission of a second station when a first station of a non-STR multilink device is receiving.

[0192] When Figure 14 In the embodiment (b) of FIG. 1 , when the number of stations whose channel access is prohibited is plural, the probability of simultaneously releasing the channel access prohibition of multiple stations and simultaneous transmission of multiple stations is high. Therefore, a method for reducing the probability of transmission collision is required. This will be referred to Figure 14 Provide a description.

[0193] Figure 14 An operation in which a station performs transmission after releasing channel access barring according to an embodiment of the present disclosure is illustrated.

[0194] As described above, transmission is performed in the first link among the multiple links in which the non-STR multi-link device operates, and thus transmission may be prohibited in the second link. When the corresponding transmission is completed in the first link, transmission in the second link may start by RTS / CTS frame exchange. Therefore, when transmission is performed in the first link among the multiple links in which the non-STR multi-link device operates, the non-STR multi-link device may start RTS / CTS frame exchange in the second link. After releasing the channel access prohibition of a station whose transmission is delayed due to channel access prohibition, the station may start request to transmit (RTS) / clear to transmit (CTS) frame exchange before starting delayed transmission. At this time, when the station does not receive the CTS frame, the delayed transmission may not start. Figure 15 In the embodiment of (a), a station whose transmission is delayed due to channel access barring transmits an RTS frame before starting the delayed transmission. The station starts the delayed transmission after receiving a CTS frame in response to the RTS frame.

[0195] In another detailed embodiment, after the channel access prohibition is released for a station whose transmission is delayed due to the channel access prohibition, the station may transmit a frame that includes only some delayed transmissions. In this case, after receiving a response (e.g., ACK) to the frame that includes only some delayed transmissions, the station may transmit the portion of the delayed transmission that has not yet been transmitted. When the station does not receive a response to the frame that includes only some delayed transmissions, the station may not transmit the portion of the delayed transmission that has not yet been transmitted. As described above, after the channel access prohibition is released, the station starts the RTS / CTS exchange or the station transmits only some delayed transmissions, because the collision probability of transmission after the channel access prohibition may be higher than the collision probability of general transmissions. Therefore, the embodiment can be mandatory for transmissions performed after the channel access prohibition is released. In conventional WLAN operations, RTS / CTS frames are used to solve the hidden node problem and can be used based on the size of the transmitted data. In the embodiment, the RTS / CTS frames are used to prevent transmission collisions with stations that perform delayed transmissions in order to protect the transmission or reception of non-STR multilink devices.

[0196] As described above, when one station of a non-STR multi-link device performs reception, the transmission of another station of the non-STR multi-link device may be restricted. In addition, when one station of a non-STR multi-link device performs transmission, it may be difficult to accurately sense the channel state of the link in which another station of the non-STR multi-link device operates. Specifically, when the first station of the non-STR multi-link device performs transmission, the second station of the non-STR multi-link device may determine that the channel state of the link in which the second station operates is always busy. Therefore, even if the channel of the link in which the second station operates is idle, the second station may determine that the channel is busy due to intra-device interference. As described above, when a station whose channel state cannot be determined due to intra-device interference or when one station of a non-STR multi-link device continuously performs transmission, the other station of the non-STR multi-link device is in a blind state. Due to the situation, it may be difficult for the station in the blind state to attempt to transmit through the backoff process. In addition, due to the situation, it may be difficult for the station in the blind state to start receiving the PPDU or to successfully decode it. Therefore, there is a need for a method of performing transmission in consideration of when a station is in a blind state. This will refer to Figure 15 Provide a description.

[0197] Figure 15 Transmissions performed based on the status of stations within a non-STR multi-link device according to an embodiment of the present disclosure are illustrated.

[0198] A station to perform a transmission to a station of a non-STR multi-link device can determine whether to perform the transmission according to whether the station of the non-STR multi-link device is in a blind state. At this time, the station to perform the transmission to the station of the non-STR multi-link device can be a station included in an STR multi-link device. In addition, the station to perform the transmission to the station of the non-STR multi-link device can be an AP included in an AP multi-link device, and the non-STR multi-link device can be a non-AP multi-link device. The station to perform the transmission can determine whether the station of the non-STR multi-link device is in the blind state based on the following description. The station to perform the transmission can determine whether another station of a multi-link device including the station is performing a transmission to a corresponding non-STR multi-link device. When another station of a multi-link device including the station is performing reception from a corresponding non-STR multi-link device, the station can determine that the station of the non-STR multi-link device to receive the transmission of the station is in a blind state. In Figure 16 In an embodiment, an STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). A non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). Accordingly, the second AP (AP2) can inform the first AP (AP1) that reception is being performed from the second station (STA2). Specifically, the second AP (AP2) can inform the first AP (AP1) that a transmission entity to the second AP (AP2) is the second station (STA2). In another detailed embodiment, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is currently performing a transmission. At this time, the first AP (AP1) can determine that the first station (STA1) is in a blind state based on the information.

[0199] A station in a multi-link device can operate through a common MAC. Accordingly, the information exchange between the first AP (AP1) and the second AP (AP2) described above can not be explicitly performed.

[0200] The station can not perform a transmission to a station in a blind state. This is because, even if a transmission is performed to a station in a blind state, the station in the blind state is likely to be unable to start reception or the station in the blind state is unable to decode a PPDU. At this time, the station can cancel the transmission to the station in the blind state, and can perform a transmission to another station.

[0201] When the STR multi-link device performs transmission to the non-STR multi-link device, the STR multi-link device can perform transmission to the non-STR multi-link device in multiple links. Specifically, when the STR multi-link device performs transmission to the non-STR multi-link device in a first link, the STR multi-link device can start transmission to the non-STR multi-link device in a second link. At this time, the STR multi-link device can determine the length of the transmission performed in the second link based on the transmission corresponding to the transmission to the non-STR multi-link device. Specifically, the STR multi-link device can determine the length of the transmission to the non-STR multi-link device in the second link based on the length of the transmission to the non-STR multi-link device in the first link. In a detailed embodiment, the STR multi-link device can end the transmission in the first link and the transmission in the second link at the same time. This is to prevent the transmission to another station of the non-STR multi-link device after the transmission to one of the stations of the non-STR multi-link device ends first, the one of the stations of the non-STR multi-link device transmits a response (e.g., ACK) to the transmission. Through the described embodiment, multiple stations of the non-STR multi-link device can transmit responses to the transmission to the multiple stations at the same time.

[0202] The STR multi-link device cannot determine the status of the stations included in the non-STR multi-link device in real time. Therefore, even if the STR multi-link device operates according to the reference Figure 16 described embodiments, interference or transmission collision can occur between the links in which the non-STR multi-link device operates. For example, in the embodiment of Figure 16 , the first AP (AP1) can start transmission to the first station (STA1) before recognizing that the second station (STA2) is performing transmission to the second AP (AP2). As described above, the probability of inter-link interference or collision can be higher than the probability of intra-link interference or transmission collision. This will be described in more detail with reference to Figure 16 .

[0203] Figure 16 a case in which inter-link interference or collision occurs is illustrated.

[0204] When transmission by the second station of the non-STR station multi-link device to the second AP of the STR AP multi-link device and transmission by the first AP of the STR AP multi-link device to the first station of the non-STR multi-link device start at the same time, transmission collision can occur between the links. Figure 17 (a) illustrates such a case. This is because, as described above, the STR multi-link device cannot determine the status of the stations included in the non-STR multi-link device in real time.

[0205] In addition, even when a transmission by a second station of a non-STR multi-link device to a second AP of an STR AP multi-link device starts earlier than a transmission by a first AP of an STR-AP multi-link device to a first station of a non-STR multi-link device, a transmission collision between links can occur. Figure 17 (b) illustrates this case. This is because the second AP (AP2) informs the first AP (AP1) that the second station (STA2) is performing a transmission requiring time. As described above, since a transmission collision occurs between stations starting transmission at different points in time, the probability of inter-link interference or transmission collision can be higher than the probability of intra-link interference or collision. In addition, since the time taken to identify the transmitter of a PPDU received by an AP of an STR multi-link device is delayed, the probability of inter-link interference or transmission collision can be higher. Therefore, a method of solving this problem is needed. When one station of an STR multi-link device performs reception, another station of the STR multi-link device can not perform channel access. However, when channel access is prohibited, the significance of implementing an STR function can disappear. Therefore, an operating method other than channel access prohibition of an STR multi-link device is needed. This will be described with reference to Figure 17 .

[0206] As described above, it is important to quickly determine a station of a multi-link device that transmits to a multi-link device. A user field of an EHT-SIG of an EHT UL PPDU can show an identifier (STA-ID) of a station that transmits the EHT UL PPDU. Specifically, when a DL / UL field of a signaling field of the EHT PPDU shows that the EHT PPDU is an UL PPDU, the user field of the EHT-SIG of the EHT PPDU can show an identifier of a station that transmits the EHT UL PPDU. A multi-link device that receives the EHT PPDU can identify a station that transmits the EHT PPDU based on the user field of the EHT-SIG of the EHT UL PPDU. Thereby, an AP multi-link device can determine a station that transmits the EHT UL PPDU, and the AP multi-link device can determine a destination device of transmission. Specifically, the AP multi-link device can determine how high the likelihood of a transmission failure to be performed due to an inter-link collision is. In addition, if the likelihood of a transmission failure to be performed by the AP multi-link device is high, the AP multi-link device can delay the transmission to be performed and perform another transmission.

[0207] Figure 17 An operation in which an STR multi-link device stops transmission to a non-STR multi-link device is illustrated according to an embodiment of the disclosure.

[0208] When a station of a STR multi-link device determines that a station of a non-STR multi-link device is in a blind state during a transmission to the station of the non-STR multi-link device, the STR multi-link device can stop the transmission to the station of the non-STR multi-link device in the blind state. Specifically, the STR multi-link device can determine whether the station of the non-STR multi-link device is in the blind state based on a value indicated by a STA (AID)-ID in a signaling field of a received PPDU or a transmission address (TA) field of a MAC frame included in the received PPDU. At this time, the STA-ID can be a value indicating a station that transmitted the UL PPDU. In a detailed embodiment, when the value indicated by the STA (AID)-ID in the signaling field of the received PPDU indicates a first station included in the non-STR multi-link device, the STR multi-link device can determine that a second station included in the non-STR multi-link device is in the blind state. In addition, when the TA field of the MAC frame included in the received PPDU indicates the first station included in the non-STR multi-link device, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in the blind state. Specifically, when the station of the PPDU indicated by the signaling field of the transmitted PPDU is the first station or the TA field of the MAC frame included in the PPDU is the first station, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in the blind state. As such, the STR multi-link device can determine that another station of the non-STR multi-link device is in the blind state by confirming that any one of the stations of the non-STR multi-link device transmits. The operation of the station after the transmission is canceled is described first.

[0209] When leaving the TXOP configured in the station of the non-STR multi-link device, the station that canceled the transmission to the station of the non-STR multi-link device can attempt a transmission to a station different from the station of the non-STR multi-link device. At this time, the station that canceled the transmission to the station of the non-STR multi-link device can perform the transmission to the station different from the station of the non-STR multi-link device without a separate backoff procedure. In a detailed embodiment, when the channel is detected to be idle during a predetermined time interval without a separate backoff procedure after the transmission to the station of the non-STR multi-link device is canceled, the station that canceled the transmission to the station of the non-STR multi-link device can perform the transmission to the station different from the station of the non-STR multi-link device. At this time, the predetermined time interval can be one of SIFS, PDIF, and DIFS.

[0210] When performing the transmission to the station different from the station of the non-STR multi-link device, the station that canceled the transmission to the station of the non-STR multi-link device can transmit a traffic having a priority equal to or higher than that of the traffic of the canceled transmission. This is because the transmission of the traffic having a priority lower than that of the channel access for the canceled transmission is unbalanced. In the described embodiment, the station of the STR multi-link device can be an AP.

[0211] The station that cancels the transmission to the station of the non-STR multi-link device can initiate the configured TXOP. Specifically, the station that cancels the transmission to the station of the non-STR multi-link device can transmit a CF-End frame after cancelling the transmission. It can allow another station operating in the link in which the transmission is scheduled to use the link.

[0212] In Figure 18 In the first embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR non-AP multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state during the transmission to the first station (STA1). Accordingly, the first AP (AP1) stops the transmission to the first station (STA1). In Figure 18 In (a), after stopping the transmission to the first station (STA1), the first AP (AP1) performs a transmission to a station different from the first station (STA1), as described in the first described embodiment. In Figure 18 In (b), after stopping the transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame, as described in the later described embodiment.

[0213] When a station stops a transmission, the station can transmit a fragment that is being transmitted and then can not transmit a subsequent fragment. In a detailed embodiment, the station can immediately stop the transmission of a packet that is being transmitted.

[0214] In the described embodiments, when a transmission to a station of a non-STR multi-link device in a blind state is stopped and a transmission to a station different from the station of the non-STR multi-link device is performed, the STR multi-link device is required to inform that another station can perform a transmission to the other station to stably receive. Methods thereof are described. For ease of description, the station different from the station of the non-STR multi-link device in a blind state is referred to as a different station.

[0215] A station of a STR multi-link device can insert an address of a different station into a MAC frame. Specifically, a station of a STR multi-link device can insert an address of an intended receiver of a MAC frame into a reception address (RA) of the MAC frame and insert an address of a different station into a separate field. In a detailed embodiment, a station of a device can insert an address of a different station into an EHT-SIG. Specifically, a station of a STR multi-link device can insert an address of an intended receiver of a PPDU and an address of a different station into a user field of a signaling field of the PPDU. At this time, the address of the different station can be inserted after the address of the intended receiver of the PPDU in the user field of the signaling field of the PPDU.

[0216] In another detailed embodiment, a station can monitor reception of a PPDU for a predetermined time after recognizing that an intended receiver of the PPDU is not the station. Specifically, the station can monitor whether PPDU reception continues for a predetermined time after recognizing that an intended receiver of a received PPDU is not the station. Accordingly, the station can determine whether to stop transmission of the PPDU and start transmission to the station. In an embodiment, when it is determined that PPDU transmission continues for a predetermined time, the station can enter a sleep state. When it is determined that PPDU transmission does not continue for a predetermined time, the station can remain in an awake state. At this time, when the station receives a new PPDU, the station can decode the PPDU.

[0217] In another detailed embodiment, a station that transmits a PPDU can insert information that signals that PPDU transmission can be stopped into the PPDU. The information that signals that PPDU transmission can be stopped can be a 1-bit subfield. For example, when a value of the subfield that signals that PPDU transmission can be stopped is 1, a station that receives the PPDU can determine that PPDU transmission can be stopped before a point in time indicated by a length field of a signaling field of the PPDU and a duration field of the MAC frame. When the station determines that PPDU transmission can be stopped before the point in time indicated by the length field of the signaling field of the PPDU and the duration field of the MAC frame, the station can postpone entering a sleep state. In addition, the station that transmits the PPDU can insert information that signals that transmission can be stopped into a reserved field of the PPDU.

[0218] As described above, unnecessary channel occupancy can be prevented by transmission cancellation or transmission stop.

[0219] When transmission is stopped or delayed due to transmission collision between links, the value of CW for channel access can be doubled as in general transmission failure. When transmission is stopped or delayed due to transmission collision between links, the value of CW for channel access can not be doubled as in general transmission failure. That is, the station can maintain the value of CW for channel access. Doubling the value of CW is to reduce the probability of transmission collision by increasing the range of numbers that can be the value of the backoff counter. When the station can clearly recognize transmission collision between links, such a need can be low. In addition, when transmission is stopped or delayed due to transmission collision between links, the station doubling the value of CW can delay transmission. However, when both inter-link transmission collision and intra-link collision occur, the station needs to double the value of CW. This will be described with reference to Figure 18

[0220] Figure 18 FIG. 13 illustrates a process of the value of CW when an STR multi-link device recognizes transmission collision between links according to an embodiment of the disclosure.

[0221] As described in the embodiments, when the station cancels transmission due to transmission performed by a non-STR multi-link device, the station can sense the channel state after canceling transmission. When it is sensed that the channel is not idle, the station can double the value of CW. At this time, the doubling can follow the embodiments described with reference to Figure 19 In addition, when it is sensed that the channel is idle, the station can maintain the value of CW. This embodiment is to treat this case as different from transmission success because the possibility of intra-link transmission collision is low even though it is sensed that the channel is idle. Specifically, when the AP of the AP multi-link device fails in transmission to the station of the non-STR multi-link device, the AP of the AP multi-link device can acquire the backoff counter within CW without increasing CW. At this time, if the non-STR multi-link device of the AP multi-link device fails in transmission to the first station, the second station of the non-STR multi-link device performs transmission, the AP of the AP multi-link device can acquire the backoff counter in CW without increasing CW. As described above, in the AP multi-link device, the transmission station of the PPDU indicated based on the signaling field of the PPDU or the station indicated by the TA field of the MAC frame included in the PPDU can determine whether the second station of the non-STR multi-link device performs transmission. When EDCA is applied in the described embodiments, the process regarding CW adjustment and backoff counter generation can be performed by each AC.

[0222] ​In another particular embodiment, the STR multi-link device can determine whether the transmission of the PPDU fails based on whether a response to the PPDU is received. At this time, the STR multi-link device can not consider whether the station that receives the PPDU is included in the non-STR multi-link device. For example, even if a first station that receives the PPDU is included in the non-STR multi-link device and a second station of the non-STR multi-link device transmits so that the first station cannot transmit a response to the PPDU, the STR multi-link device can determine that the transmission of the PPDU fails. Also, when the PPDU transmission of the STR multi-link device fails, the STR multi-link device can increase the value of the CW to the next larger value among possible values of the CW value. At this time, when the value of the CW is the maximum value, the STR multi-link device can maintain the value of the CW as the same value.

[0223] In another detailed embodiment, when the channel is sensed to be idle, the station can configure the value of the CW to be the minimum value of the CW (CW_min). This embodiment is used to treat the case as the same as the transmission success because the possibility of the transmission collision within the link is low when the channel is sensed to be idle. The station can apply the embodiment to the CW of the AC of the traffic included in the cancelled transmission.

[0224] Also, when the transmission is cancelled according to the embodiment, the station can not increase the retry counter. At this time, the retry counter can include at least one of a long retry counter and a short retry counter.

[0225] In this embodiment, the cancelling of the transmission can include at least one of stopping the transmission or delaying the transmission before starting the transmission.

[0226] When the station cancels the transmission after transmitting the CTS-to-Self frame before attempting the transmission, the station can not start the RTS / CTS frame exchange before attempting the transmission after cancelling the transmission. This is because the NAV is configured through the CTS-to-Self frame. Also, when the station leaves the TXOP when attempting the transmission again after cancelling the transmission, the station can attempt the transmission without any backoff procedure.

[0227] In Figure 19In the middle, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STAl) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). The first AP (AP1) determines that the first station (STAl) is in a blind state during the transmission to the first station (STAl). Accordingly, the first AP (AP1) stops the transmission to the first station (STAl). In Figure 6 In (a), the first AP (AP1) determines that the channel of the first link (link1) is idle. At this time, since no TXOP is left, the first AP (AP1) accesses the channel through a backoff procedure. In Figure 19 In (b), the first AP (AP1) determines that the channel of the first link (link1) is not idle. At this time, since a TXOP is left, the first AP (AP1) attempts transmission without a backoff procedure.

[0228] In the described embodiment, when the channel is detected to be idle during a predetermined time interval without a separate backoff procedure after the transmission to the station of the non-STR multi-link device is canceled, the station that canceled the transmission to the station of the non-STR multi-link device can perform transmission to a different station from the station of the non-STR multi-link device. At this time, the duration of the predetermined time interval can be problematic. The station that received the PPDU whose transmission was canceled can not be able to decode the PPDU. At this time, when the channel is sensed to be idle for an extended interframe space (EIFS), the station that failed to decode the PPDU can start a backoff procedure. Accordingly, whether the predetermined time interval is configured to be longer than or equal to the EIFS is problematic. This will be described with reference to Figure 19 .

[0229] Figure 19 FIG. 1 illustrates an operation in which a STR multi-link device performs channel access again after stopping transmission to a non-STR multi-link device according to an embodiment of the disclosure.

[0230] As Figure 20 shown in (a), the predetermined time interval can be DIFS. This assumes that the station of the STR multi-link device acquires a channel access opportunity through a contention procedure, and the acquired channel access opportunity is lost due to transmission collision between links. That is, since the station of the STR multi-link device acquires a channel access opportunity through a contention procedure, the station is provided with higher priority to perform channel access than other stations. When EDCA is applied, AIFS[AC] can be used instead of DIFS.

[0231] In another detailed embodiment, the predetermined time interval can be the EIFS as shown in (b) of Figure 20 This considers that the STR multi-link device can be considered to have exhausted the transmission opportunity and to take into account the fairness with other stations.

[0232] In another detailed embodiment, as shown in (c) of Figure 20 , the predetermined time interval can be the DIFS when signaling the information indicating that the transmission can be stopped in the signaling field of the PPDU. Further, when the station receiving the PPDU detects the stop of the PPDU transmission, the station can sense whether the channel is idle during the DIFS instead of the EIFS. At this time, upon sensing that the channel is idle during the DIFS, the corresponding station can start the backoff procedure. Through this embodiment, the performance of the entire network can be improved and the fairness between stations can be guaranteed. When the EDCA is applied, the DIFS can be replaced with the AIFS[AC].

[0233] As described above, the STR multi-link device can recognize that the transmission collision between links can occur. Specifically, when the first station of the STR multi-link device completes the backoff procedure, the second station of the STR multi-link device can be receiving the PPDU. At this time, when the second station has not completed the decoding of the signaling field of the PPDU, the first station can determine that the transmission collision between links cannot be recognized but the possibility thereof exists. At this time, the first station can insert the information indicating that the transmission can be stopped into the transmitted PPDU, as described above. Further, for stable and efficient transmission, the NSTR multi-link device can transmit the CTS-to-Self frame before transmission to the non-STR multi-link device. This will be described with reference to Figure 20 .

[0234] Figure 20 FIG. illustrates the operation of the STR multi-link device transmitting the CTS-to-Self frame before transmission to the non-STR multi-link device according to an embodiment of the present disclosure.

[0235] A station of a STR multi-link device can transmit a CTS-to-Self frame before a transmission to a non-STR multi-link device. Specifically, when a first station of a STR multi-link device performs reception, a second station of the STR multi-link device attempts to transmit to a non-STR multi-link device, the second station of the STR multi-link device can transmit a CTS-to-Self frame before the transmission to the non-STR multi-link device. Thus, the second station can ensure that the TXOP is used for the transmission to the non-STR multi-link device. Further, before performing the transmission to the non-STR multi-link device, the second station can determine whether a transmission to the first station is performed from a corresponding non-STR multi-link device. The second station can determine a destination station of the transmission according to whether the transmission to the first station is performed from the corresponding non-STR multi-link device. Specifically, when the transmission to the first station is not performed from the corresponding non-STR multi-link device, the second station can perform the transmission to the corresponding non-STR multi-link device. When the transmission to the first station is performed from the corresponding non-STR multi-link device, the second station can perform the transmission to a station not included in the corresponding non-STR multi-link device. For example, when the first station plans to transmit a SU-PPDU for a station of a non-STR multi-link device, a MU-PPDU including data for a station of a non-STR multi-link device, or a PPDU including a trigger frame to trigger a transmission of a station of a non-STR multi-link device, the first station can cancel the planned transmission. At this time, the first station can attempt to transmit a SU-PPDU for a station that is not a station of a non-STR multi-link device, a MU-PPDU not including data for a station of a non-STR multi-link device, or a PPDU including a trigger frame not triggering a transmission of a station of a non-STR multi-link device. At this time, the first station can start the transmission after a time longer than SIFS from the transmission of the CTS-to-Self frame. Specifically, the first station can start the transmission after PIFS from the transmission of the CTS-to-Self frame. A station that transmits the CTS-to-Self frame should start the transmission after SIFS from the transmission of the CTS-to-Self frame. When the planned transmission is cancelled as described in the embodiments and a new transmission is attempted, a processing time for the STR multi-link device to generate an MPDU to be newly transmitted is required. Thus, an exception can be applied to the rule for the time interval between the CTS-to-self frame and the transmission. In an embodiment, the second station exceeds the TXOP acquired by the CTS-to-self, and thus in principle cannot perform the transmission.

[0236] In Figure 21In this case, the STR multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). Since the second AP (AP2) performs reception and the first AP (AP1) plans a transmission to a station of a non-STR multi-link device, the first AP (AP1) transmits a CTS-to-Self frame before the planned transmission. As described above, the first AP (AP1) determines a destination station of the transmission based on a determination of a station that transmits a PPDU received by the second AP (AP2). In addition, the first AP (AP1) performs the transmission after SIFS or PIFS from the transmission of the CTS-to-Self frame.

[0237] The second station can start the RTS / CTS frame exchange procedure by transmitting an RTS frame instead of transmitting a CTS-to-Self frame. Accordingly, the second station can obtain an effect similar to that of the transmission of the CTS-to-Self frame. In the case of the RTS / CTS frame exchange, the second station can obtain a TXOP only when the destination station of the transmission is not in a blind state.

[0238] Figure 21 FIG. illustrates a transmission performed by a plurality of APs included in an STR multi-link device to a plurality of stations included in a non-STR multi-link device according to an embodiment of the present disclosure.

[0239] The plurality of stations included in a non-STR multi-link device can simultaneously perform reception. This is because simultaneous reception of the plurality of stations can cause only a small interference. Figure 21 FIG. illustrates simultaneous reception performed by a plurality of stations included in a non-STR multi-link device. At this time, in order for stable operation of the non-STR multi-link device, a plurality of APs included in an STR multi-link device can perform a plurality of transmissions whose transmission ends are synchronized with the plurality of stations included in the non-STR multi-link device. This will be described with reference to Figure 22 .

[0240] Figure 22 FIG. illustrates a plurality of transmissions performed by a plurality of APs included in an STR multi-link device to a plurality of stations included in a non-STR multi-link device whose transmission ends are synchronized according to an embodiment of the present disclosure.

[0241] When a multi-link device performs a transmission in one of non-STR links, the multi-link device can simplify a channel access procedure for a transmission performed in another link. Specifically, when a first station of the multi-link device completes a backoff channel access procedure in a first link, if a channel is idle during a predetermined time interval within a link of a second station of an STR multi-link device, the second station of the STR multi-link device can start a transmission in a second link.

[0242] In a detailed embodiment, when one station of a STR multi-link device performs a transmission to one station of a non-STR multi-link device, a channel access procedure of another station of the STR multi-link device can be simplified. Specifically, when a first station of the STR multi-link device completes a backoff channel access procedure for a transmission to a first station of a non-STR multi-link device, if a channel is idle during a predetermined time interval within a link of a second station of the STR multi-link device, the second station of the STR multi-link device can start a transmission to a second station of the non-STR multi-link device. At this time, the predetermined time interval can be PIFS. Such an operation can be applied when the first and second stations of the STR multi-link device perform a transmission to stations included in one non-STR multi-link device. In an embodiment, the first and second stations can start the transmission with a difference within a predetermined time interval. The predetermined time interval can be a slot time.

[0243] Further, when the first and second stations of the STR multi-link device perform a transmission to stations included in one non-STR multi-link device, the transmission ends of the first and second stations can be synchronized. At this time, the synchronization of the transmission ends of the first and second stations can indicate that an end of the first station and an end of the second station have a difference within a first predetermined time interval. The first predetermined time interval can indicate an inside of a slot boundary or a symbol boundary.

[0244] The multiple stations of the non-STR multi-link device that receive the synchronized transmission ends can simultaneously perform a subsequent transmission (e.g., a response). At this time, the response can include an ACK. In a conventional WLAN, a transmission after reception is performed after a SIFS from the reception. However, for multiple transmissions that end with a small time difference, performing the subsequent transmissions with a small time difference can make implementation more complex compared to simultaneously performing the subsequent transmissions. Therefore, as described above, the multiple stations of the non-STR multi-link device that receive the synchronized transmission ends can simultaneously perform the subsequent transmissions. At this time, an interval between transmissions following at least one of the multiple transmissions whose transmission ends are synchronized can be a sum of a SIFS and a time within a predetermined time interval. Specifically, a transmission following a first-terminated transmission among the multiple transmissions whose transmission ends are synchronized can be performed at an interval obtained by adding the SIFS and the time within the predetermined time interval from the transmission. At this time, the predetermined time interval can be one of a slot time or a symbol length. Further, the difference within the predetermined time interval can be a difference between an end of a last-terminated transmission among the multiple transmissions whose transmission ends are synchronized and a first-terminated transmission among the multiple transmissions whose transmission ends are synchronized.

[0245] In another detailed embodiment, when the multiple transmissions end with a time difference within a first predetermined time interval, the multiple stations receiving the transmissions can perform the synchronized subsequent transmissions. The multiple subsequent transmissions whose transmission ends are synchronized can indicate the multiple subsequent transmissions performed with a time difference within a second predetermined time interval. Further, the difference within the second predetermined time interval can be the difference between the transmission end of the last ended transmission among the multiple synchronized transmissions and the first ended transmission among the multiple transmissions whose transmission ends are synchronized. At this time, the second predetermined time interval can be smaller than the first predetermined time interval. The PPDU whose transmission ends are synchronized can be referred to as a sync PPDU.

[0246] In Figure 23 , the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). Each of the first AP (AP1) and the second AP (AP2) synchronize the transmission ends to the first station (STA1) and the second station (STA2). That is, after the first station (STA1) ends the transmission, the second station (STA2) ends the transmission within a predetermined time interval from the first station (STA1). The first station (STA1) and the second station (STA2) simultaneously transmit ACKs. At this time, the first station (STA1) transmits the ACK after SIFS from the transmission end to the first station (STA1) and the difference between the transmission end of the first station and the transmission end to the second station (STA2).

[0247] The embodiment can be applied to the transmission whose ACK policy is not configured as No ACK. Specifically, the ACK policy can be applied to the case other than the immediate response. In a detailed embodiment, when the multiple stations of a multi-link device receive the transmission whose transmission end is synchronized, the multiple stations of the multi-link device can simultaneously receive the ACK request and transmit the ACK according to the ACK request. The multiple stations of the multi-link device receiving the transmission whose ACK policy is configured as a value other than No ACK within a predetermined time can simultaneously start the ACK.

[0248] When there is a non-STR multi-link device, the non-STR multi-link device should be considered during the operation of configuring the TXOP by transmitting the RTS / CTS frame and the CTS-to-Self frame. This will be described with reference to Figure 23 .

[0249] Figure 23 FIG. illustrates the exchange of the RTS / CTS frame by the multi-link device according to an embodiment of the disclosure.

[0250] Even when a non-STR multi-link device is present, the RTS / CTS frame exchange process can follow the process defined in conventional WLAN. The RTS / CTS frame can be used to configure the NAV of a station operating in another link. Specifically, a station receiving the RTS / CTS frame can operate in a link different from the link in which the corresponding station operates, and pass the RTS / CTS frame to another station included in the multi-link device including the corresponding station.

[0251] However, as described in the above embodiments, when non-STR multi-link devices exist, channel access or transmission may be restricted. Figures 24 to 29 That is, a station planning a transmission to a first station of a non-STR multilink device may not attempt an RTS / CTS frame exchange if a second station of the non-STR multilink device is performing reception.

[0252] exist Figure 24 In the embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). When the first AP (AP1) transmits an RTS frame to the first station (STA1), the channel access of the second station (STA2) is prohibited. The second AP (AP2) can determine that the channel access of the second station (STA2) is prohibited. Therefore, the second AP (AP2) does not attempt to exchange RTS / CTS frames with the second station (STA2). In this embodiment, a hidden node problem may occur. This will refer to Figure 24 Provide a description.

[0253] Figure 24 The diagram shows the reference Figure 25 The embodiment described herein addresses the hidden node problem that occurs during the RTS / CTS frame exchange process.

[0254] A station performing transmission to a station that is not a STR multi-link device may perform transmission without the CTS / RTS exchange described above. At this time, since TXOP is not configured in the other station, the other station may attempt to transmit, and thus the station that is not a STR multi-link device may not receive the transmission. Figure 25In an embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STAl) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). Due to the transmission of the first AP (AP1) to the first station (STAl), the second AP (AP2) cannot transmit an RTS frame before the transmission. Accordingly, a TXOP for the transmission of the second AP (AP2) is not configured in the stations operating in the second link (link2). Thus, when the second AP (AP2) performs a transmission to the second station (STA2), a station of another BSS (OBSS STA) performs a transmission in the second link (link2). Thereby, the second station (STA2) cannot receive the transmission of the second AP (AP2). To solve the hidden node problem, the following embodiments can be applied.

[0255] In a detailed embodiment, when one station of the non-STR multi-link device performs reception, the station is not allowed to perform a transmission to any station of the non-STR multi-link device. In another detailed embodiment, when a second station of the non-STR multi-link device performs reception while the station performs a transmission to a first station of the non-STR multi-link device, the station can simultaneously perform the transmission and a transmission to the second station. When a second station of the non-STR multi-link device performs reception while the station performs a transmission to a first station of the non-STR multi-link device, the station can synchronize an end of the transmission to the first station and an end of the transmission to the second station. Specifically, when a second station of the non-STR multi-link device performs reception while the station performs a transmission to a first station of the non-STR multi-link device, the station can simultaneously end the transmission to the first station and the transmission to the second station. In an embodiment, the transmission to the second station can be performed by another station of the multi-link device including the station.

[0256] Figure 24 FIG. illustrates an RTS / CTS frame exchange by a multi-link device according to an embodiment of the disclosure.

[0257] In another embodiment of the disclosure, when a second station of the multi-link device transmits an RTS frame to a fourth station of the non-STR multi-link device while a first station of the multi-link device continues to perform a transmission to a third station of the non-STR multi-link device, the first station can end the transmission to the third station before a point in time at which the fourth station transmits the RTS frame. Accordingly, the fourth station can transmit a CTS frame to the second station. Thus, a TXOP for a frame exchange between the second station and the fourth station can be configured. However, it can be difficult to achieve the end of the transmission before the point in time at which the first station transmits the RTS frame to the fourth station.

[0258] In another embodiment of the disclosure, when the first station of the multi-link device continues to perform transmission to the third station of the non-STR multi-link device, the second station of the multi-link device transmits an RTS frame to the fourth station of the non-STR multi-link device, the second station can transmit the RTS frame to the fourth station at the time when the transmission of the first station to the third station ends. To this end, the second station can insert padding in the RTS frame. At this time, the RTS frame can be an RTS frame format for flexibly controlling the length of transmission. For ease of description, the RTS frame format is referred to as a multi-link (ML)-RTS frame. The ML-RTS frame can include a padding field for padding. For example, the ML-RTS frame format can be the same as the RTS frame format shown in FIG. 1. Figure 25 In addition, the first station can insert padding into the transmission of the third station in time to conform to the end of transmission of the RTS frame.

[0259] In an embodiment of the disclosure, Figure 26 The STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second AP (AP2) transmits an ML-RTS frame to the second STA (STA2) in time at the end of transmission of the first station (STA1) to the first AP (AP1). Thereafter, when the first station (STA1) transmits an ACK to the first AP (AP1), the second station (STA2) transmits an ACK to the second AP (AP2). Accordingly, a TXOP for frame exchange between the second AP (AP2) and the second station (STA2) is configured among the stations operating in the channel of the second link.

[0260] In another detailed embodiment, another frame for configuring the NAV can be exchanged instead of the RTS / CTS frame. In the described embodiment, an ACK request frame can be transmitted instead of the RTS frame. The ACK request frame can include duration information related to the end point of transmission. In addition, the frame including the ACK transmitted in response to the ACK request can also include duration information. At this time, the duration information of the frame including the ACK can be configured according to the duration information of the ACK request frame.

[0261] The described embodiments have been described with respect to the RTS / CTS frame exchange, but can also be used for control frame exchange as well as the RTS / CTS frame. At this time, the control frame exchange can include exchange between the PS-Poll frame and the response frame of the PS-Poll.

[0262] Figure 26Figure illustrates exceptional transmission of a response to a control frame by a multi-link device in a case where channel access is prohibited, according to an embodiment of the disclosure.

[0263] As described in the described embodiments, channel access of some stations can be prohibited when there is a non-STR multi-link device. Even if channel access of a station is prohibited, the station can transmit a response to a control frame. Specifically, even if channel access of a station is prohibited, the station can transmit a CTS frame in response to an RTS frame.

[0264] As described above, when a response to a control frame is transmitted as an exception to channel access prohibition, the following embodiments can be applied. A first station transmits a response to a control frame as an exception to channel access prohibition. When the first station transmits a response to a control frame, a third station performs transmission to a second station included in a multi-link device including the first station. In this case, the third station can perform retransmission to the first station. This is because the third station can expect that transmission to the second station fails.

[0265] In an embodiment of Figure 26 , an STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). A non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The first AP (AP) performs transmission to the first station (STA1). The second AP (AP2) transmits an RTS frame to the second station (STA2). Since the first station (STA1) performs reception, channel access of the second station (STA2) is prohibited. However, the second station (STA2) transmits a CTS frame to the second AP (AP2) as an exception to channel access prohibition. The first AP (AP1) can determine that there is a high possibility that transmission of the first AP (AP1) fails due to the second station (STA2) transmitting the CTS frame. Accordingly, the first AP (AP1) performs retransmission to the first station (STA1). Reference will be made to Figure 27 The retransmission method is described in more detail.

[0266] Figure 27 Figure illustrates retransmission of transmission to a station of a non-STR multi-link device.

[0267] In reference to Figure 28In the described retransmission, only some of the packets included in the initial transmission can be retransmitted. Specifically, the station performing the retransmission can retransmit only some of the packets included in the initial transmission. The station performing the retransmission can determine some of the packets included in the initial transmission as packets to be retransmitted based on a time interval in which the station performing the retransmission receives the CTS frame. Specifically, the station performing the retransmission can determine, among the packets included in the initial transmission, packets transmitted in a time interval including a time interval in which the station performing the retransmission receives the CTS frame as packets to be retransmitted. At this time, the station performing the retransmission can retransmit the packets transmitted in the time interval including the time interval in which the station performing the retransmission receives the CTS frame based on a propagation delay. In another detailed embodiment, the station performing the retransmission can retransmit all of the packets included in the initial transmission.

[0268] In addition, the station performing the retransmission can perform the retransmission before receiving an ACK for the transmission. At this time, the station performing the retransmission can receive a block ACK indicating whether the initial transmission and the retransmission are received after the retransmission. To this end, the station performing the retransmission can perform the retransmission before SIFS after the initial transmission. In another detailed embodiment, the station that failed to receive due to the control frame transmitted as an exception to channel access prohibition can defer from receiving the retransmission without transmitting an ACK.

[0269] In Figure 28 In an embodiment, the first AP (AP1) retransmits the fourth packet and the fifth packet in consideration of the interval in which the second AP (AP2) receives the CTS frame and the transmission delay. The first AP (AP1) receives an ACK including whether the retransmission is received after the retransmission.

[0270] Figure 27 FIG. illustrates a control frame transmitted through a link in which a station operating by which channel access is not prohibited rather than a link in which a station operating by which channel access is prohibited according to an embodiment of the disclosure.

[0271] As described in an embodiment shown in Figure 28 As described in an embodiment shown in

[0272] In Figure 29In an embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STAl) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The first AP (AP1) performs a transmission to the first station (STAl). Even though the second AP (AP2) successfully performs a back-off procedure, the second AP (AP2) cannot perform a transmission to the second station (STA2) because the first station (STAl) is receiving the transmission from the first AP (AP1). At this time, the second AP (AP2) requests an RTS frame to the first AP (AP1) for a transmission with the second station (STA2) as a receiver. The first AP (AP1) can insert the RTS frame with the second station (STA2) as a receiver into the transmission performed by the first AP (AP1). In another detailed embodiment, after the first AP (AP1) ends the transmission being performed by the first AP (AP1), the first AP (AP1) can transmit the RTS frame with the second station (STA2) as a receiver in the first link (link1) after a SIFS from the corresponding transmission. The first station (STAl) receives the RTS frame with the second station (STA2) as a receiver and passes the received RTS frame to the second station (STA2). The second station (STA2) performs a CCA during a PIFS. When the channel is idle during the PIFS, the second station (STA2) transmits a CTS-to-Self frame. The first AP (AP1) can stop the transmission to the first station (STAl) during a time interval in which the second station (STA2) is expected to transmit a response to the RTS frame. Further, the first station (STAl) can transmit an ACK to the received transmission when the second station (STA2) transmits a response to the RTS frame. In another detailed embodiment, the first station (STAl) can also transmit a response to the RTS frame when the second station (STA2) transmits a response to the RTS frame. Figure 26 The above description is to help understanding and can be used for controlling the transmission of the frames as well as the RTS frame and the CTS-to-Self frame. Further, another time interval other than the PIFS can be used.

[0273] Figure 29 FIGURE 1 illustrates a transmission of an ACK by a multi-link device according to embodiments of the present disclosure.

[0274] A station of a multi-link device can make a request for a link to transmit an ACK to a station of a non-STR multi-link device. Specifically, the station of the multi-link device can make the request to transmit the ACK in a different link from the link in which the transmission has been performed. In Figure 29In an embodiment of, a first AP (AP1) of a STR multi-link device performs a transmission (TX(#2)) to a first station (STAl) of a non-STR multi-link device. At this time, the first AP (AP1) makes a request to transmit an ACK for the transmission (TX(#2)) through a second link (link2). This is because it is determined that the transmission of the ACK for the transmission (TX(#2)) of the first AP (AP1) is difficult since the transmission (TX(#2)) of the first AP (AP1) ends earlier than the transmission of the second AP (AP2) to the second station (STA2).

[0275] Further, for the ACK transmission, a station can configure an ACK policy as an implicit BAR so as not to transmit an immediate response to the transmission. In another detailed embodiment, a station can configure an ACK policy for a transmission as a BlockAckReq. However, in order to transmit a block ACK, the BlockAckReq should be transmitted, and thus a channel access burden and a transmission delay can be generated. Therefore, a new ACK policy for a multi-link device can be required.

[0276] One station of a multi-link device can also transmit an ACK for a transmission received by another station included in the multi-link device, which is the same as an ACK for a transmission received by the station. The ACK transmission can be referred to as a multi-link (ML)-ACK. Further, the ML-ACK can be configured as an ACK policy. In Figure 30 In an embodiment of, the first AP (AP1) configures the ML-ACK as an ACK policy for the transmission (TX(#2)). The first station (STAl) does not transmit an ACK to the first AP (AP1) after receiving the transmission (TX(#2)). The second station (STA2) completes reception of the transmission from the second AP (AP2), and transmits ACKs for the transmission from the first AP (AP1) and the transmission from the second AP (AP2) together. The non-STR multi-link device can include not only the first station (STAl) and the second station (STA2) but also a third station (STA3), and the STR multi-link device can include not only the first AP (AP1) and the second AP (AP2) but also a third AP (AP3). At this time, the ML-ACK can be configured as an ACK policy for the transmission from the second AP (AP2) to the second station (STA2). When the transmission from the third AP (AP3) to the third station (STA3) is completed later than the transmission from the second AP (AP2) to the second station (STA3), the third station (STA3) can transmit an ACK for the transmission from the first AP (AP1) to the first station (STAl), an ACK from the second AP (AP2) to the second station (STA2), and an ACK for the transmission from the third AP (AP3) to the third station (STA3) to the third AP (AP3).

[0277] Through these embodiments, inter-link interference that can be generated due to ACK transmission can be prevented even if transmissions to stations of non-STR multi-link devices are not completed at the same time. In the described embodiments, the ACK policy can be configured as Block ACK instead of ML-ACK. In another detailed embodiment, the ACK policy can be configured as No ACK instead of ML-ACK.

[0278] When a multi-link device performs traffic transmission, the number of links that acquire a transmission opportunity can increase. At this time, the multi-link device can transmit traffic through a link that acquires a transmission opportunity later, which is scheduled by the multi-link device to be transmitted through a link that acquires a transmission opportunity first. At this time, the NAV configured in the link that acquires a transmission opportunity first of the multi-link device can be configured to be greater than the NAV required to transmit the traffic. When the NAV is configured to be greater than the NAV required to transmit the traffic in the link that acquires a transmission opportunity first of the multi-link device, the multi-link device can transmit a CF-END frame after completing transmission in the link that acquires a transmission opportunity first in order to reset the NAV.

[0279] Reference Figure 28 Reception of a synchronization PPDU and signaling related to reception of a synchronization PPDU are described.

[0280] To receive a synchronization PPDU, a first station of a non-STR multi-link device should determine whether a second station having a non-STR relationship with the first station starts receiving a synchronization PPDU. In addition, the first station should continuously perform preamble detection (PD). When it is considered that channel access of the first station receiving a synchronization PPDU is prohibited by reception of another station of the non-STR multi-link device, such operation of the first station can be unreasonable. Accordingly, the first station can enter a sleep state under a predetermined condition. A synchronization PPDU can be transmitted within a regularly configured TXOP. Accordingly, performance gain that can be obtained by receiving a synchronization PPDU can be determined according to the length of the remaining TXOP. Accordingly, the first station can determine whether to abandon reception of a synchronization PPDU based on the length of the synchronization PPDU. When the first station abandons reception of a synchronization PPDU, the first station can enter a sleep state. Such a power saving operation can be referred to as inter-link TXOP power saving (PS). In inter-link TXOP PS, a station that enters a sleep state can wake up from the sleep state in order to receive frames periodically transmitted from an AP, for example, a beacon frame, a TIM frame, and a DTIM frame. In addition, when a TXOP ends, for example, when a CF-END frame is transmitted, a station that enters a sleep state in inter-link TXOP PS can wake up from the sleep state.

[0281] The TXOP can be changed to a period indicated by a length field of a signaling field of a PPDU or a duration field of a MAC frame. Specifically, in the described embodiment, a station can determine the occupation time of a PPDU based on a period indicated by a length field or a duration field of a MAC frame.

[0282] The non-AP multi-link device can signal information about whether a synchronization PPDU is received and a synchronization PPDU support condition to the AP multi-link device. In addition, the AP multi-link device can signal information about whether the AP multi-link device supports a PPDU transmission to the non-AP multi-link device. At this time, the multi-link device can signal information about whether a synchronization PPDU is supported for each multi-link device. For example, the AP multi-link device can signal information about whether a synchronization PPDU transmission is supported for each AP multi-link device. In another detailed embodiment, the multi-link device can signal information about whether a synchronization PPDU is supported for each station. Specifically, the AP multi-link device can signal information about whether a synchronization PPDU transmission is supported for each AP included in the AP multi-link device. For example, an AP multi-link device including a first AP, a second AP, and a third AP can indicate that the first AP supports a synchronization PPDU transmission, and the second AP and the third AP do not support a synchronization PPDU transmission.

[0283] When information indicating that an AP multi-link device associated with a non-AP multi-link device does not support a synchronization PPDU transmission is indicated, a station of the non-AP multi-link device can enter a sleep state of inter-link PS, and another station of the non-AP multi-link device performs reception. This is because the AP multi-link device associated with the non-AP multi-link device cannot transmit a synchronization PPDU. At this time, the station of the non-AP multi-link device can determine a length of time for which the sleep state is maintained based on a length of a PPDU received by the other station of the non-AP multi-link device.

[0284] Whether a synchronization PPDU transmission or reception is supported can be determined according to an operation policy as well as hardware performance. Therefore, whether a synchronization PPDU transmission or reception is supported can be signaled not only by information about performance but also by information about an operation mode. Reference will be made to Figures 31 to 34 A method of signaling support for a synchronization PPDU transmission or reception is described in detail.

[0285] Figure 31 An element field indicating information about support for a synchronization PPDU reception or transmission according to an embodiment of the disclosure is illustrated.

[0286] As described above, the information indicating whether the synchronous PPDU transmission is supported can be included in an element indicating a capability of the station. For ease of description, the element indicating the capability of the station is referred to as a capability element. Further, in the capability element, a field of the information indicating whether the synchronous PPDU transmission is supported is referred to as a synchronous PPDU Tx support subfield. At this time, the capability element can be a multi-link element, which is an element indicating a capability of a multi-link. Further, the capability element can be an EHT capability element indicating an EHT-related capability. Figure 31 (a) illustrates an example of a capability element.

[0287] When a value of the synchronous PPDU Tx support subfield is 1, the synchronous PPDU Tx support can indicate that a station or a multi-link device indicated by the synchronous PPDU Tx support subfield supports the synchronous PPDU transmission. When the value of the synchronous PPDU Tx support subfield is 0, the synchronous PPDU Tx support can indicate that the station or the multi-link device indicated by the synchronous PPDU Tx support subfield does not support the synchronous PPDU transmission. Further, when the station not included in the multi-link device transmits the capability element, the synchronous PPDU Tx support subfield can signal information that is not information related to whether the synchronous PPDU transmission is supported, or can be used as a reserved field.

[0288] As described above, the information indicating whether the synchronous PPDU reception is supported can be included in an element indicating information related to an operation of the station. For ease of description, the element indicating the information related to the operation of the station is referred to as an operation element. Further, in the operation element, a field of the information indicating whether the synchronous PPDU reception is supported is referred to as a synchronous PPDU Rx disable subfield. Figure 31(b) The operation element illustrates an example. When the value of the support Synchronous PPDU Rx disable subfield is 1, it can indicate that the synchronous PPDU reception is not supported. Specifically, when the value of the support Synchronous PPDU Rx disable subfield is 1, the support Synchronous PPDU Rx disable subfield can indicate that the station which transmits the support Synchronous PPDU Rx disable subfield does not want to pending receive the synchronous PPDU. In the case that the multi-link device configures the value of the support Synchronous PPDU Rx disable subfield as 1, when the first station of the multi-link device performs the reception, the second station of the multi-link device can not perform the PD and CCA. The AP multi-link device associated with the multi-link device which transmits the support Synchronous PPDU Rx disable subfield does not transmit the PPDU to the multiple stations of the multi-link device which transmits the support Synchronous PPDU Rx disable subfield at the same time. The PPDU can be the SU PPDU, the full BW MU PPDU, or the OFDMA MU PPDU which is transmitted through one of the non-HT PPDU format, the HT PPDU format, the VHT PPDU format, the HE PPDU format, and the EHT PPDU format. At this time, the AP multi-link device should not transmit the frame which makes the request for the response (e.g., immediate response). The frame which makes the request for the response can include at least one of the RTS, the multi-user (MU)-RTS, the trigger frame, and the block Ack request (BAR).

[0289] In addition, the operation element can include information related to the minimum length of the synchronous PPDU which can be received by the station or the multi-link device which transmits the operation element. At this time, the subfield which indicates the information related to the minimum length of the synchronous PPDU is referred to as the remaining TXOP threshold subfield. The remaining TXOP threshold subfield can indicate the time. In addition, the remaining TXOP threshold subfield can be expressed in units of us, ms, or symbol. The multi-link device associated with the multi-link device which transmits the remaining TXOP threshold subfield can not be allowed to transmit the synchronous PPDU which is shorter than the length indicated by the remaining TXOP threshold subfield to the multi-link device or the station which transmits the remaining TXOP threshold subfield.

[0290] In addition, when the remaining TXOP threshold subfield is configured as a predetermined value, it can indicate that the multi-link device or the station which transmits the remaining TXOP threshold subfield does not support the synchronous PPDU reception. The predetermined value can be a value which indicates a time which is longer than the maximum time which can be expressed by the remaining TXOP threshold subfield. In another detailed embodiment, the predetermined value can be 0. When the embodiment is applied, the synchronous PPDU Rx disable subfield can be omitted in the operation field.

[0291] Further, in the described embodiments, the synchronization PPDU Rx disable subfield and the remaining TXOP threshold subfield can be signaled by an operation element. The synchronization PPDU Rx disable subfield and the remaining TXOP threshold subfield can be signaled by an element or signaling information other than the operation element. Reference is made to Figure 31 Embodiments are described that implement inter-link TXOP power save mode according to reference Figures 32 to 34 Embodiments are described that implement inter-link TXOP power save mode according to reference

[0292] Figure 31 Figures illustrate inter-link TXOP power save mode operation performed by a non-STR multi-link device according to embodiments of the present disclosure.

[0293] When the information indicating that the non-STR multi-link device does not support synchronization PPDU reception is signaled, the second station of the non-STR multi-link device can enter a sleep state when the first station of the non-STR multi-link device performs reception. At this time, the second station can remain in the sleep state until the end time point of the TXOP indicated by the PPDU received by the first station. As described above, the time point at which the second station expects to receive the frame periodically transmitted from the AP can be before the time point at which the TXOP ends as indicated by the PPDU received by the first station. At this time, the second station can wake up from the sleep state before the time point at which the TXOP ends as indicated by the PPDU received by the first station. As described above, the frame periodically transmitted from the AP can include at least one of a beacon frame, a TIM frame, and a DTIM frame.

[0294] The second station can remain in the sleep state even after the point in time at which the TXOP ends indicated by the PPDU received by the first station. Specifically, the second station can remain in the sleep state even after the point in time at which the TXOP ends indicated by the PPDU received by the first station, based on information received from an AP associated with the second station. At this time, the information received from the AP associated with the second station can be NAV-related information. In addition, the information received from the AP associated with the second station can be operation information of an AP associated with the first station. When a NAV configured by a second AP of an AP multi-link device performing transmission to a second station of a non-AP multi-link device does not expire, a first AP of the AP multi-link device can transmit information about a point in time at which the first AP expects to transmit or receive and a point in time at which the NAV expires, to a first station of the non-AP multi-link device, the first station of the non-AP multi-link device signaling information indicating that the AP multi-link device first AP does not want to receive a synchronization PPDU. When the NAV configured by the second AP of the AP multi-link device performing transmission to the second station of the non-AP multi-link device does not expire, the reception or transmission of the PPDU by the second AP from one station can be included. When the NAV configured by the second AP of the AP multi-link device performing transmission to the second station of the non-AP multi-link device does not expire, the configuration of the NAV in the second AP through the PPDU not transmitted by the second station can be included.

[0295] In an embodiment of the Figure 32 The STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating that reception of a synchronization PPDU is not expected. The first AP (AP1) performs transmission to the first station (STA1). At this time, the second station (STA2) maintains a sleep state until a point in time at which a TXOP ends indicated by a PPDU transmitted by the first AP (AP1) to the first station (STA1).

[0296] Figure 32 A station of a non-STR multi-link device receives a standby into a sleep state from a synchronization PPDU, according to an embodiment of the disclosure is illustrated.

[0297] When the remaining duration of the TXOP indicated by the PPDU received by the first station of the non-STR multi-link device is shorter than or equal to the length indicated by the remaining TXOP threshold subfield transmitted by the non-STR multi-link device, the first station of the non-STR multi-link device can enter the doze state of the inter-link TXOP. At this time, when the remaining duration of the TXOP indicated by the PPDU being received by the first station is longer than the length indicated by the remaining TXOP threshold subfield transmitted by the non-STR multi-link device, the second station can receive a synchronization PPDU transmitted to the second station before entering the doze state. At this time, the second station can receive the synchronization PPDU. To this end, the second station can perform PD and determine whether the intended receiver of the received PPDU is the second station. Specifically, the second station can determine whether the AID indicated by the signaling field of the PPDU or the RA of the MAC frame included in the PPDU indicates the second station.

[0298] In an embodiment of Figure 33 In an embodiment of the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating that a synchronization PPDU is expected to be received. At this time, the non-AP multi-link device also signals 'a', which is the minimum length of the TXOP required for synchronization PPDU reception. The first AP (AP1) performs transmission to the first station (STA1), and the second station (STA2) is on standby to receive the synchronization PPDU. When the TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is equal to or shorter than 'a', the second station (STA2) enters the inter-link TXOP power saving state.

[0299] Figure 33 FIG. illustrates a station of a non-STR multi-link device entering a doze state from synchronization PPDU reception according to another embodiment of the disclosure.

[0300] When a station of a non-STR multi-link device is pending reception of a synchronization PPDU, a transmission of a PPDU that is not a synchronization PPDU is detected in a BSS operated by an AP associated with the station of the non-STR multi-link device, the station of the non-STR multi-link device can enter an inter-link TXOP power save state. At this time, the station can determine that the PPDU having a receiver other than the station is not a synchronization PPDU. In addition, when a transmission of a PPDU that is not a synchronization PPDU is detected in a BSS operated by an AP associated with the station of the non-STR multi-link device in a doze state, the station of the non-STR multi-link device can enter an inter-link TXOP power save state even if a minimum TXOP signaled by the station remains.

[0301] In an embodiment of Figure 34 In an embodiment of, a STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). A non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating that a synchronization PPDU is expected to be received. At this time, the non-AP multi-link device also signals 'a', which is a minimum length of a TXOP required for synchronization PPDU reception. The first AP (AP1) performs transmission to the first station (STA1), and the second station (STA2) is pending reception of a synchronization PPDU. The second station (STA2) detects a transmission of a PPDU that is not a synchronization PPDU in a BSS to which the second station belongs. The TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is greater than 'a', but the second station (STA2) enters an inter-link TXOP power save state.

[0302] <Multi-link single radio (Single Radio) multi-link device service flow>

[0303] As described above, it is considered that the multi-link device adaptively operates when the first station of the non-STR multi-link device performs transmission such that the second station is in a blind state. Specifically, when the multi-link device determines that the station of the non-STR multi-link device is in a blind state, the multi-link device can stop transmission to the station of the non-STR multi-link device. In addition, the station of the non-STR multi-link device can enter a doze state based on the operation, such as transmission and reception, of the other station of the non-STR multi-link device. Thereby, it is possible to solve a problem that can occur when the operation of any one station of the non-STR multi-link device limits the operation of the other station.

[0304] As described above, in the non-STR multi-link device, different stations included in the non-STR multi-link device cannot perform reception and transmission at the same time due to intra-device interference. In addition, due to the limitation of the hardware configuration of the non-STR multi-link device, different stations included in the non-STR multi-link device cannot perform reception and transmission at the same time. Specifically, when a first station of the non-STR multi-link device transmits or receives, the second station of the non-STR multi-link device can be restricted from using the transceiver. For example, the non-STR multi-link device can support only one PPDU procedure. In this case, when the first station of the non-STR multi-link device transmits or receives, the second station of the non-STR multi-link device cannot transmit or receive. As such, a multi-link device including a plurality of stations each operating but not supporting simultaneous transmission or reception of the plurality of stations is referred to as a single-radio multi-link device. Accordingly, when any one station of the single-radio multi-link device transmits / receives, the other stations of the single-radio multi-link device cannot transmit / receive. The operation of the multi-link device as the single-radio multi-link device can be based on the hardware constraint or the definition of the operation mode as described above. Accordingly, in the present specification, the single-radio multi-link device can refer to a multi-link device in which the operation of the stations is limited due to the hardware constraint and a multi-link device in which the operation of the stations is limited according to the definition of the operation mode. Accordingly, the single-radio multi-link device of the present specification includes a multi-link device supporting simultaneous transmission or reception of a plurality of stations of the multi-link device but not supporting simultaneous transmission or reception of the plurality of stations of the multi-link device under a special condition. In this case, the special condition can include a special time point.

[0305] The embodiments regarding the operation of the non-STR multi-link device described above can also be applied to the operation of the single-radio multi-link device. In addition, the embodiments regarding the operation of the station transceiving data with the stations of the non-STR multi-link described above can also be applied to the operation of the station transceiving with the stations of the single-radio multi-link device. For example, when the transmission of the station to the single-radio multi-link device on the first link is determined to fail due to the transmission or reception of the single-radio multi-link device on the second link, the station can not increase the CW of the channel access performed on the first link. Specifically, the station can apply the embodiments described above. At this time, the method in which the transmission of the station to the single-radio multi-link device on the first link is determined to fail due to the transmission or reception of the single-radio multi-link device on the second link can be similar to the method in which the transmission of the station to the stations of the non-STR multi-link is determined to fail due to the operation limitation of the non-STR multi-link device. Figure 34

[0306] Figure 14 FIG. 1 illustrates a connection between a single-radio multi-link device and an AP multi-link device according to an embodiment of the present disclosure.

[0307] ​In this specification, the PHY back-end is collectively referred to as a digital processor of the physical layer, which includes processors that encode and decode PPDUs. In addition, the PHY front-end is collectively referred to as an analog baseband circuit including RF chains.

[0308] The multiple stations of the single radio multi-link device operate on different links. The multiple stations can share one PHY back-end. In this case, when any one station transmits a PPDU, the PHY back-end is used for the encoding of the PPDU. Therefore, at this time, the remaining stations in the multiple stations cannot use the PHY back-end. Therefore, the single radio multi-link device includes multiple stations operating on different links, but can transmit or receive on only one link at a time.

[0309] However, the single radio multi-link device can perform channel access in multiple links. Specifically, the single radio multi-link device can monitor multiple links. Therefore, the single radio multi-link device can perform channel access on multiple links. In this case, the monitoring can include channel sensing. In addition, the channel sensing can include at least one of clear channel assessment (CCA) and preamble detection (PD). Thereby, the single radio multi-link device can reduce channel access delay. Specifically, even if a first station of the single radio multi-link device cannot perform channel access due to channel occupancy by other wireless communication devices on a first link, a second station of the single radio multi-link device performs a backoff procedure on a second link.

[0310] To support these embodiments, the PHY front-end of the single radio multi-link device can independently support channel monitoring from the PHY back-end. In addition, the PHY front-end of the single radio multi-link device can independently support decoding of a preamble of a PPDU for PD from the PHY back-end. In addition, the PHY front-end of the single radio multi-link device can independently support reception of a frame transmitted by a low MCS from the PHY back-end. In this case, the frame transmitted by the low MCS can include at least one of an RTS frame and an MU-RTS frame. Therefore, the PHY front-end can include a MAC processor. In addition, by these embodiments, the processing capability of the PHY back-end can be concentrated for encoding and decoding of data frames.

[0311] In Figure 35In an embodiment of the above, the AP multi-link device comprises a first AP (AP1) and a second AP (AP2). The single-radio multi-link device comprises a first non-AP station (Non-AP STA1) and a second non-AP station (Non-AP STA2). The first AP (AP1) is connected to the first non-AP station (Non-AP STA1) on a first link (Link 1), and the second AP (AP2) is connected to the second non-AP station (Non-AP STA2) on a second link (Link 1). As in the above described embodiment, the first non-AP station (Non-AP STA1) and the second non-AP station (Non-AP STA2) each independently perform channel access using the PHY front end.

[0312] The single-radio multi-link device can use the RF chain of a station that does not participate in transmission or reception for MIMO transmission. Specifically, when a first station of the single-radio multi-link device acquires a channel access opportunity, the first station performs MIMO transmission using not only the RF chain used by the first station but also the RF chain used by a second station of the single-radio multi-link device. This is described in part by Figure 35

[0313] Figure 36 FIG. 1 illustrates a single-radio multi-link device performing MIMO transmission according to an embodiment of the present disclosure.

[0314] In Figure 36 In an embodiment of the above, the AP multi-link device comprises a first AP (AP1) and a second AP (AP2). The single-radio multi-link device comprises a first non-AP station (Non-AP STA1) and a second non-AP station (Non-AP STA2). The first AP (AP1) is connected to the first non-AP station (Non-AP STA1) on a first link (Link 1), and the second AP (AP2) is connected to the second non-AP station (Non-AP STA2) on a second link (Link 1). As in the above described embodiment, the first non-AP station (Non-AP STA1) and the second non-AP station (Non-AP STA2) each independently perform channel access using the PHY front end.

[0315] ​Thus, when the RF chain operating in the first link is changed to operate in the second link, the single-radio multi-link device cannot perform monitoring and channel access in the first link. Further, when the corresponding RF chain operates in the second link again, the single-radio multi-link device can perform channel access in the second link after waiting for a predetermined time period. At this time, channel access of the single-radio multi-link device in the second link is limited from when the RF change is completed to the predetermined time period. Specifically, from when the RF change is completed to when the single-radio multi-link device waits for the predetermined time period, the single-radio multi-link device can perform channel access in the second link. At this time, the channel access can include a backoff procedure. Further, the predetermined time period can be a predetermined time that is applied when channel access needs to be limited due to a time in which channel monitoring cannot be performed. Specifically, the predetermined time can be NAVSyncdelay. Specifically, the single-radio multi-link device can perform the backoff procedure after waiting for the same time as the NAVSyncdelay. This is because the probability that the single-radio multi-link device cannot detect a transmission of another wireless communication terminal being performed in the second link due to a period in which channel monitoring is not performed is high. Further, when the link in which the RF chain operates is changed, a delay time for starting the RF chain operation can be required. Thus, the single-radio multi-link device can perform channel access considering the delay time of the RF chain change. For this, an explanation will be made below. Further, for convenience of explanation, an action in which the RF chain operating in any one link is changed to operate in another link will be referred to as a change of the RF chain. Further, the change of the link can be shown as a change of the RF chain supported by the link. Specifically, in a case where the first link supports the use of a plurality of RF chains, then supports the use of one RF chain, or in a case where the second link does not support the use of one RF chain, then supports the use of one RF chain, the change of the RF chain can be referred to. Figure 36 Further, for convenience of explanation, an action in which the RF chain operating in any one link is changed to operate in another link will be referred to as a change of the RF chain. Further, the change of the link can be shown as a change of the RF chain supported by the link. Specifically, in a case where the first link supports the use of a plurality of RF chains, then supports the use of one RF chain, or in a case where the second link does not support the use of one RF chain, then supports the use of one RF chain, the change of the RF chain can be referred to.

[0316] The station communicating with the single-radio multi-link device using MIMO can be a station included in the multi-link device. Specifically, the station communicating with the single-radio multi-link device using MIMO can be an AP included in the multi-link device. In the absence of a special explanation in the present specification, the station communicating with the single-radio multi-link device using MIMO can be a station included in the multi-link device. In this case, the station included in the multi-link device can be an AP. Further, the operation of the station of the multi-link device explained in the present specification can be expressed as the operation of the multi-link device.

[0317] Figure 37 FIG. 1 illustrates an operation in which a single-radio multi-link device performs channel access considering a delay time of an RF chain change according to an embodiment of the present disclosure.

[0318] A single radio multi-link device can change the RF chain before the expected time point of channel access success. Specifically, the single radio multi-link device can change the RF chain before the time set from the expected time point of channel access success to the delay time based on the RF chain change. For example, the single radio multi-link device can change the RF chain at an early time point from the expected time point of channel access success to the delay time of the RF chain change.

[0319] In Figure 37 In an embodiment of (a), the first station (STA1) of the single radio multi-link device operates on the first link (Link 1), and the second station (STA2) of the single radio multi-link device operates on the second link. The first station (STA1) performs channel access on the first link (Link 1), and the second station (STA2) performs channel access on the second link. When the first station (STA1) succeeds in channel access on the first link (Link 1), the first station (STA1) not only uses the RF chain used for channel access on the first link (Link 1) but also uses the RF chain used for channel access by the second station (STA2) on the second link (Link 2) to perform 2x2 MIMO transmission on the first link (Link 1). In Figure 37 In an embodiment of (a), the single radio multi-link device changes the RF chain at an early time from the expected time point of channel access success (Expected Tx time) to the delay time of the RF chain change (RF chain switching delay).

[0320] In another specific embodiment, the single radio multi-link device can start exchanging RTS frames / CTS frames when it starts transmission after changing the RF chain. In another specific embodiment, the single radio multi-link device can transmit a CTS-to-Self frame when it starts transmission after changing the RF chain. In addition, the single radio multi-link device can transmit a frame with a relatively short length instead of the CTS-to-Self frame. Through these embodiments, the single radio multi-link device can acquire the time required until the RF chain change is completed. In addition, these embodiments are different from the previously described embodiments in that no problem occurs even if channel access is not successful at the predicted time point.

[0321] In Figure 37 In an embodiment of (b), the single radio multi-link device starts transmission by exchanging RTS frames / CTS frames on the first link (Link 1).

[0322] Figure 37The Capability element and the Operation element used by a single radio multi-link device are illustrated according to embodiments of the disclosure.

[0323] The single radio multi-link device can perform transmission or reception by changing the RF chain as shown in Figure 38 . In addition, the single radio multi-link device can perform transmission or reception without changing the RF chain. The single radio multi-link device can select whether to change the RF chain.

[0324] The single radio multi-link device can display in the MIMO Rx support subfield of the Operation element whether to use the RF chain of another link when performing MIMO communication in the corresponding link. For example, when the single radio multi-link device sets the value of the MIMO Rx support subfield of the Operation element to 1, the MIMO Rx support subfield displays that MIMO reception can be performed using a number of spatial streams equal to or less than the value of the Max Rx spatial stream subfield of the Operation element. At this time, the station performing MIMO transmission of the single radio multi-link device performs MIMO transmission using a number of spatial streams equal to or less than the value of the Max Rx spatial stream subfield of the Operation element. In a specific embodiment, the format of the Operation element can be as shown in (a) of FIG. Figures 36 to 37 .

[0325] In addition, the single radio multi-link device can signal the time required for RF chain change in the Capability element. At this time, the switching delay subfield of the Capability element can display the time required for RF chain change. The station performing MIMO transmission of the single radio multi-link device must consider the time required for RF chain change to perform MIMO transmission. Specifically, the station performing MIMO transmission to the single radio multi-link device can start MIMO transmission after the time required for RF chain change from the initial transmission to the single radio multi-link device. In a specific embodiment, the format of the Capability element can be as shown in (a) of FIG. Figure 38 .

[0326] When the single radio multi-link device performs transmission or reception on the first link, the station to which the single radio multi-link device is to transmit can not be allowed to transmit on the link other than the first link. This is because the single radio multi-link device cannot perform reception on the link other than the first link during the transmission or reception on the first link is performed. Specifically, not only during the frame exchange on the first link is performed, but also from when the frame exchange sequence is completed by the single radio multi-link device until a predetermined time elapses, the station to which the single radio multi-link device is to perform transmission can not be allowed to transmit on the link other than the first link. Specifically, the completion of the frame exchange sequence can be determined based on the reception or transmission of the last frame of the frame exchange sequence. At this time, the frame exchange sequence can be performed in the link in which multiple RF chains are available. Specifically, the frame exchange sequence can be performed using MIMO. The predetermined time can be determined based on the required time for the RF chain change. Specifically, the predetermined time can be the time required for the RF chain change.

[0327] Further, the station to which the single radio multi-link device is to transmit in the frame exchange sequence after the RF chain change can determine the format of the PPDU initially transmitted in the frame exchange sequence based on the time required for the RF chain change of the single radio multi-link device. Further, in the first frame exchange sequence starting after the RF chain change, the station to which the single radio multi-link device is to transmit can determine the padding length required for the transmission of the PPDU initially transmitted in the frame exchange sequence based on the time required for the RF chain change of the single radio multi-link device. In this case, the padding can be one of a physical layer padding or a MAC layer padding. Specifically, the station can set the padding to be shorter for the packet transmitted to the single radio multi-link device having a relatively short time required for the RF chain change than for the packet transmitted to the single radio multi-link device having a relatively long time required for the RF chain change.

[0328] Figure 38 FIG. illustrates the single radio multi-link device using MIMO to transmit a PPDU according to an embodiment of the disclosure.

[0329] The station to which the single radio multi-link device is to perform MIMO transmission can start the RTS frame / CTS frame exchange at the time of transmission start after the RF chain change. At this time, the RTS frame can secure the time for the RF chain change and protect the frame exchange thereafter. If it is determined that the RF chain change is not completed even after the RTS frame / CTS frame exchange, the station to which the single radio multi-link device is to perform MIMO transmission can not perform MIMO transmission. At this time, the station to which the single radio multi-link device is to perform MIMO transmission can perform transmission using a single spatial stream.

[0330] When the single radio multi-link device performs transmission or reception on any one link, the single radio multi-link device cannot perform transmission or reception on other links different from the corresponding link. Thus, when the single radio multi-link device performs transmission or reception on any one link, the station operating in a link different from the corresponding link can be considered in a blind state. Thus, when the single radio multi-link device performs transmission or reception on any one link, the AP to transmit to the single radio multi-link device can not transmit to the station operating in a link different from the corresponding link. At this time, the AP to transmit to the single radio multi-link device can stop transmission to the station operating in a link different from the corresponding link.

[0331] When the single radio multi-link device performs transmission or reception on any one link, the AP to transmit or stop transmission to the station of the single radio multi-link device can not increase the CW of the backoff procedure for channel access. Thereafter, when the single radio multi-link device again attempts transmission to the corresponding station, the backoff counter can be obtained in the CW previously used. Thus, when the station to transmit or stop transmission to the station of the single radio multi-link device satisfies a predetermined condition, the CW of the backoff procedure for channel access can not be increased. The predetermined condition can determine which of the stations of the single multi-link device performs transmission or reception according to the above-described embodiments. Specifically, when the station transmitting a PPDU received by other stations of the multi-link device including the station is determined to be included in the single multi-link device, the station can determine any one of the stations of the single multi-link device to perform transmission. In this case, the station can determine the station transmitting the PPDU based on the identifier of the station of the PPDU indicated by the signaling field of the PPDU. At this time, the station can determine which of the stations of the single multi-link device is indicated by the STA-ID of the user field of the HE PPDU. Further, the station can determine which of the stations of the single multi-link device is indicated by the STA-ID of the user field of the EHT PPDU. Further, the station can determine which of the stations of the single multi-link device is indicated by the TA field of the MAC frame included in the PPDU. The MAC frame can be any one of an MSDU, an MPDU, and an A-MPDU. This is similar to the above-described embodiments applicable to transmission of the non-STR multi-link device. Figure 39 Further, in the case of the channel access procedure applicable to EDCA, the above-described CW can show the CW of the AC for channel access.

[0332] In addition, when any one station of the single radio multi-link device causes a transmission failure of the other station of the single radio multi-link device due to transmission or reception, the station performing the transmission of the other station of the single radio multi-link device can not increase the retry counter. In this case, the retry counter can include at least one of a long retry counter and a short retry counter.

[0333] In addition, when the station transmits the MU PPDU to a plurality of stations including the station of the single radio multi-link device, the embodiment regarding maintaining the size of the CW described above can not be applied. Specifically, when the station transmits the MU PPDU to a plurality of stations including the station of the single radio multi-link device and does not receive a response from any one of the plurality of stations, the station transmitting the MU PPDU can increase the size of the CW. At this time, the station transmitting the MU PPDU can increase the value of the CW to the second largest value among the values that the CW value can have. When the value of the CW is the maximum value, the station transmitting the MU PPDU can maintain the value of the CW at the same value.

[0334] In an embodiment of the above Figure 19 In an embodiment of the above

[0335] <Null data packet (NDP) transmission procedure for single radio multi-link device>

[0336] As described above, the single radio multi-link device can perform MIMO through a link in which the RF chain is changed. When the link in which the RF chain is operated is changed, it is necessary to learn the RF characteristics of the changed link before MIMO communication.

[0337] Since channel characteristics for the RF-chains have not been formed, closed-loop multi-antenna technology (beamforming) can not be used. Therefore, channel estimation can be required. Specifically, the single-radio multi-link device can perform channel estimation using an NDP sounding protocol. In an explicit NDP sounding sequence, the beamformer transmits an NDP announcement (NDPA) before transmitting an NDP. At this time, the interval between the NDPA and the NDP is SIFS. A station receiving the NDPA transmits channel state information (CSI) feedback measured when the station receives the NDP to the beamformer if the STA user information list field of the NDPA indicates the station.

[0338] At this time, before performing the NDP sounding protocol, an RTS frame / CTS frame exchange can be performed. Specifically, the single-radio multi-link device and the station to start the NDP sounding protocol can transmit an RTS frame before transmitting the NDPA frame. For convenience of explanation, the single-radio multi-link device and the station to start the NDP sounding protocol are referred to as an NDP sounding protocol initiating station. Through the above-described embodiment, the NDP sounding protocol initiating station can protect the NDP sounding sequence. Further, by this, the time required to change the RF chain can be ensured. Further, the NDP sounding protocol initiating station can perform an exchange procedure of a MU-RTS frame / CTS frame instead of the RTS frame / CTS frame exchange procedure. Further, the NDP sounding protocol initiating station can perform an exchange of a trigger frame of a type different from the MU-RTS frame and a response to the trigger frame instead of the MU-RTS frame / CTS frame exchange procedure. Further, in the present embodiment, the NDP sounding protocol initiating station can transmit the MU-RTS frame, the trigger frame of a type different from the MU-RTS frame, and the NDPA frame in a predetermined PPDU format. Specifically, the predetermined PPDU format can be at least one of a non-HT format and an HT format. Further, the NDP sounding protocol initiating station can transmit the MU-RTS frame, the trigger frame of a type different from the MU-RTS frame, and the NDPA frame at a predetermined data rate or a lower data rate.

[0339] The NDP probe protocol initiator station can adjust the length of the NDP probe sequence based on the time required for RF chain change. The NDP probe protocol initiator station can use a longer NDP probe sequence when exchanging the NDP probe sequence with a single radio multi-link device having a longer time required for RF chain change than when exchanging the NDP probe sequence with a single radio multi-link device having a shorter time required for RF chain change. At this time, the NDP probe protocol initiator station can omit a part of the NDP probe sequence to adjust the length of the NDP probe sequence. In addition, the NDP probe protocol initiator station can adjust the length of the NDP probe sequence by adjusting padding of frames exchanged in the NDP probe sequence. In addition, the NDP probe protocol initiator station can transmit additional frames in the NDP probe sequence to adjust the length of the NDP probe sequence. At this time, the padding can be padding of a physical layer. In addition, the padding can be padding of a MAC layer. Accordingly, in an embodiment explained later, the padding can be physical layer padding or MAC layer padding.

[0340] In addition, when the NDP probe protocol initiator station performs the NDP probe protocol with a plurality of single radio multi-link devices, the NDP probe protocol initiator station can adjust the length of the NDP probe sequence based on the longest time among the times required for RF chain change of the plurality of single radio multi-link devices. It will be described below that the NDP probe protocol initiator station can adjust the length of the NDP probe sequence by adjusting padding of frames exchanged in the NDP probe sequence. Figure 39 A method for adjusting the length of the NDP probe sequence is explained.

[0341] Figures 40 to 42 An NDP probe procedure performed by a station and a single radio multi-link device according to an embodiment of the disclosure is illustrated.

[0342] As described above, the NDP probe protocol initiator station can adjust the length of the NDP probe sequence by adjusting padding of frames exchanged in the NDP probe sequence. If the NDP probe sequence includes RTS frame / CTS frame exchange, the NDP probe protocol initiator station can adjust the length of the NDP probe sequence by inserting padding in the RTS frame. Specifically, when the NDP probe protocol initiator station determines that the RF chain change cannot be completed even after the RTS frame / CTS frame exchange, the NDP probe protocol initiator station can insert padding in the RTS frame.

[0343] In another specific embodiment, if the NDP probe protocol initiator station determines that the RF chain change cannot be completed even after the RTS frame / CTS frame exchange, the NDP probe protocol initiator station can transmit a MU-RTS frame instead of the RTS frame. In this case, the NDP probe protocol initiator station can insert padding into the MU-RTS frame.

[0344] In the above embodiments, the NDP sounding protocol initiating station determines whether the RF chain change is not completed after the RTS frame / CTS frame exchange based on the result of whether the RF chain change is completed from the RTS frame reception completion time point to the time when the length of the CTS frame plus 2X SIFS elapses in the single radio multi-link device. Further, the RTS reception completion time point can be one of the transmission start time point of the PPDU including the RTS frame, the physical layer header transmission completion time point of the PPDU including the RTS frame, the transmission completion time point of the PPDU including the RTS frame, the transmission completion time point of the RTS frame or the A-MPDU including the RTS frame. Further, in the above embodiments in which the MU-RTS frame is used instead of the RTS frame, the MU-RTS frame can be used instead of the RTS frame. Figure 40 (a) of FIG. 14 illustrates the exchange of the NDPA frame, the NDP frame, and the feedback frame after the RTS frame / CTS frame exchange according to the above embodiments. At this time, the NDP sounding protocol initiating station performs the MIMO transmission based on the received feedback frame.

[0345] Further, the NDP sounding protocol initiating station can omit the NDPA frame transmission in the NDP sounding sequence. At this time, the NDP sounding protocol initiating station and the single radio multi-link device can negotiate that the NDP sounding protocol is to be performed without the transmission of the NDPA frame. Accordingly, the station of the single radio multi-link device can defer the NDP reception without receiving the NDPA frame. Specifically, the station of the single radio multi-link device can signal that the NDP reception is possible without the NDPA reception using the capability element. In a specific embodiment, the station of the single radio multi-link device can signal that the NDP frame reception is possible without the NDPA frame reception by setting the NDPA compression support subfield of the capability element to 1. Further, the station of the single radio multi-link device can signal that the NDP frame reception is not possible without the NDPA frame reception by setting the NDPA compression support subfield of the capability element to 0. The NDP sounding protocol initiating station can determine whether to omit the NDPA frame transmission. In this case, the NDP sounding protocol initiating station can omit the NDPA frame transmission for the single radio multi-link device that receives the NDP frame reception is possible without the NDPA frame reception. Further, the above embodiment in which the NDPA frame transmission is omitted in the NDP sounding sequence is applicable only to the case in which the NDP sounding protocol initiating station transmits the NDP to one station as described above. In this case, when the NDP sounding protocol initiating station transmits the NDP to a plurality of stations, the NDPA frame transmission cannot be omitted. Figure 40 (b) of FIG. 14 illustrates the case in which the NDP frame and the feedback frame are exchanged without the NDPA frame after the RTS frame / CTS frame exchange according to the above embodiments. At this time, the NDP sounding protocol initiating station performs the MIMO transmission based on the received feedback frame.

[0346] In the above-described embodiments, since the control frame exchange before the exchange of the NDPA frame, the NDP frame, and the feedback frame is included in the NDP sounding sequence, excessive overhead can occur. In addition, even if the NDPA transmission is omitted, excessive overhead can occur. In order to reduce the excessive overhead, an implicit feedback beamforming sounding sequence can be performed. For this, an explanation will be made below. Figure 40

[0347] Figure 41 FIG. 1 illustrates a station and a single radio multi-link device performing a feedback beamforming sounding sequence according to an embodiment of the disclosure.

[0348] The frame exchange initiating station initiating the frame exchange can not only omit the NDPA frame transmission, but also omit the NDP frame transmission and the feedback frame transmission. At this time, only the frame exchange initiating station can receive the control frame, such as the RTS frame, the MU-RTS frame, and can measure the channel state. The frame exchange initiating station can obtain the steering matrix for the MIMO transmission based on the measured channel state. Specifically, the frame exchange initiating station can obtain the steering matrix based on the measured channel state. The frame exchange initiating station can perform the MIMO transmission using the obtained steering matrix.

[0349] In these embodiments, the frame exchange initiating station can insert the padding into the control frame based on the RF chain change required time as described above. Specifically, the frame exchange initiating station can insert the padding in the control frame based on a value obtained by subtracting the SIFS from the RF chain change required time.

[0350] In addition, the frame exchange initiating station can transmit the QoS data frame instead of the control frame. At this time, as a response to the QoS data frame, the single radio multi-link device can transmit the Ack frame or the Block Ack frame.

[0351] In addition, in the above-described embodiments, the frame exchange initiating station can set the bit of the training request (TRQ) of the control frame and the QoS data frame to 1.

[0352] In addition, in the above-described embodiments, the control frame, such as the MU-RTS frame, even in the control frame capable of setting a plurality of stations as receivers, the receiver of the control frame can be set to one station.

[0353] In Figure 41 ​In an embodiment of (a), the frame exchange initiating station sets the TRQ field to 1 and transmits the MU-RTS frame. The frame exchange initiating station transmits the PPDU including the MU-RTS frame, and the frame exchange initiating station receives the PPDU including the CTS frame as a response to the MU-RTS frame and measures the channel state. The frame exchange initiating station obtains the steering matrix based on the obtained channel state, and performs the MIMO transmission using the obtained steering matrix. In Figure 41 In an embodiment of (b), the frame exchange initiating station transmits the RTS frame instead of the MU-RTS frame. This can be the case where the time required for the RF chain is shorter than the SIFS. Thereafter, the frame exchange initiating station and the stations of the single radio multi-link device operate identically to the embodiment of (a). However, in the embodiment of (b), the stations of the single radio multi-link device transmit the BA frame through the single input single output (SISO). Figure 41 Figure 41 In the embodiment of (b), the stations of the single radio multi-link device transmit the BA frame through the single input single output (SISO).

[0354] In the frame exchange sequence performed immediately after the change of the RF chain, the last frame exchange can be performed through the SISO (1x1). Specifically, the stations of the single radio multi-link device can transmit the last frame of the frame exchange sequence performed immediately after the change of the RF chain in the SISO (1x1). Furthermore, when the MIMO transmission or there is no frame to be received in the frame exchange sequence performed immediately after the change of the RF chain, the stations of the single radio multi-link device can change the RF chain. Specifically, the stations of the single radio multi-link device can start to change the RF chain before the transmission of the last frame of the frame exchange sequence performed immediately after the change of the RF chain.

[0355] Figure 41 FIG. illustrates that the stations and the single radio multi-link device perform the NDP probe procedure according to an embodiment of the disclosure.

[0356] The NDP probe protocol initiating station can determine the MIMO transmission start point based on the time required for the RF chain change of the single radio multi-link device. Specifically, the NDP probe protocol initiating station can delay the MIMO transmission start point to the point in time at which the RF chain change of the single radio multi-link device is completed. For example, if the RF chain change is not completed during the execution of the control frame / response frame to the control frame, for example, the RTS frame / CTS frame or the MU-RTS frame / CTS frame exchange, the NDP probe protocol initiating station can delay the MIMO transmission start point. Specifically, the NDP probe protocol initiating station can transmit the first PPDU after the SISO transmission of the control frame / response to the control frame.

[0357] ​Thus, when the RF chain change is not completed, the MIMO transmission of the NDP probe protocol initiating station can not be allowed. In addition, the explicit and implicit NDP probe protocols described above can also not be allowed until the RF chain change is completed.

[0358] In addition, the NDP probe protocol initiating station can determine whether the RF chain change is completed during the exchange of the control frame / response frame to the control frame based on the time required for the RF chain change indicated by the capability element of the single radio multi-link device transmission.

[0359] When the single radio multi-link device uses SISO transmission, the station performing the frame exchange sequence in the link supporting the use of multiple RF chains can use SISO to transmit the remaining frames in the corresponding frame exchange sequence. For the convenience of description, in the description related to the present embodiment, the station performing the frame exchange sequence in the link supporting the use of multiple RF chains is referred to as the frame exchange sequence performing station. That is, when the single radio multi-link device uses SISO for transmission, the frame exchange sequence performing station can not be allowed to use MIMO to transmit the remaining frames in the corresponding frame exchange sequence. Specifically, when the single radio multi-link device uses SISO to perform ACK to the transmission of the frame exchange sequence performing station, the frame exchange sequence performing station can use SISO to transmit the remaining frames in the corresponding frame exchange sequence. In this case, the ACK can include an ACK frame and a BA frame. Therefore, when the single radio multi-link device uses SISO for transmission of ACK to the frame exchange sequence performing station, the frame exchange sequence performing station cannot use MIMO to transmit the remaining frames in the corresponding frame exchange sequence.

[0360] In the embodiments of (a) and 42(b) of Figure 42 In the embodiments of (a) and 42(b) of Figure 42 In the embodiments of (a) and 42(b) of

[0361] In addition, in the embodiments of (a) and 42(b) of Figure 42 Figure 42In the embodiment of (b), after exchanging the RTS frame and the CTS frame, even the transmission of the PPDU is with SISO. Since the RF chain change is completed after receiving the PPDU, the first station (STA1) of the single-radio multi-link device transmits the BA frame using MIMO (2x2). Since the first station (STA1) of the single-radio multi-link device transmits the BA frame using MIMO (2x2), the NDP probe protocol initiating station determines that MIMO (2x2) transmission is allowed. Therefore, after the NDP probe protocol initiating station receives the BA frame transmitted using MIMO (2x2), the NDP probe protocol initiating station transmits the PPDU using MIMO (2x2).

[0362] As described above, the present application is explained by taking wireless LAN communication as an example, but the present application is not limited to this and can be equally applied to other communication systems such as cellular communication. Furthermore, although the method, apparatus and system of the present application are explained by specific embodiments. But the constituent factors, part or all of the operation of the present application can be realized using a computer system with a general hardware architecture.

[0363] The features, structures, effects, and so on described in the described embodiments contain at least one embodiment of the present application and are not limited to one embodiment. Further, the features, structures, effects, and so on described in each embodiment can be combined or modified by a person skilled in the art with respect to other embodiments. Therefore, the content related to these combinations and changes should be interpreted as included in the scope of the present application.

[0364] Although the above has been described in connection with the embodiments, these are merely examples and do not limit the present application. Those skilled in the art will know that various modifications and applications not exemplified above can be made without departing from the essential characteristics of the present embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. And the differences related to these modifications and applications should be interpreted as included in the scope of the present application defined in the appended claims.

Claims

1. An access point (AP) multi-link device comprising a first AP and a second AP, and communicating with a single-radio non-AP multi-link device comprising a first non-AP station and a second non-AP station, wherein: The first AP and the first non-AP station operate on a first link, and the second AP and the second non-AP station operate on a second link, wherein, when the single-radio non-AP multi-link device operates in a predetermined operation mode, the single-radio non-AP multi-link device does not support transmission or reception by one of the first non-AP station and the second non-AP station while the other of the first non-AP station and the second non-AP station performs frame exchange, the AP multi-link device comprising: transceiver; and processor, wherein the processor is configured to: not perform transmission to the second non-AP station not only while executing the frame exchange sequence of the first non-AP station, but also within a first predetermined time interval from the completion of the frame exchange sequence of the first non-AP station, and sending a control frame to the second non-AP station of the single-radio non-AP multi-link device after the first predetermined time interval, wherein the completion of the frame exchange sequence is determined based on the reception or transmission of the last frame of the frame exchange sequence, The first predetermined time interval is applied based on the radio frequency (RF) chain switching time interval of the single-radio non-AP multi-link device, The RF chain switching time interval is a time interval including a delay required to start a monitoring operation of the RF chain after switching the RF chain, and Wherein, elements including the delay required to initiate operation of an RF chain after switching the RF chain are signaled by the single radio non-AP multi-link device.

2. The AP multi-link device according to claim 1, wherein: The processor sends the control frame in a predetermined physical layer protocol data unit (PPDU) format.

3. The AP multi-link device according to claim 2, wherein: The predetermined PPDU format is a non-high throughput HT format.

4. The AP multi-link device according to claim 1, wherein: The processor transmits the control frame at a data rate equal to or lower than a predetermined data rate.

5. A single-radio non-access point (AP) multi-link device comprising a first non-AP station and a second non-AP station, and communicating with an AP multi-link device comprising a first AP and a second AP, wherein: The first non-AP station and the first AP operate on a first link, and the second non-AP station and the second AP operate on a second link, wherein, when the single-radio non-AP multi-link device operates in a predetermined operation mode, the single-radio non-AP multi-link device does not support transmission or reception by one of the first non-AP station and the second non-AP station while the other of the first non-AP station and the second non-AP station performs frame exchange, the single-radio non-AP multi-link device comprising: transceiver; and processor, wherein the processor is configured to: when the link on which the radio frequency (RF) chain of the single-radio non-AP multi-link device operates switches from the first link to the second link, and the link on which the RF chain operates switches from the second link to the first link again, delay channel access for a predetermined time interval before performing transmission to the first AP on the first link, and Receive control frames, wherein the predetermined time interval is applied based on a radio frequency (RF) chain switching time interval of the single-radio non-AP multi-link device, and The RF chain switching time interval is a time interval including a delay required to start a monitoring operation of the RF chain after switching the RF chain.

6. The single radio non-AP multi-link device of claim 5, wherein: The control frame is sent in a predetermined physical layer protocol data unit (PPDU) format.

7. The single radio non-AP multi-link device of claim 6, wherein: The predetermined PPDU format is a non-HT format.

8. The single radio non-AP multi-link device of claim 5, wherein: The control frame is transmitted at a data rate equal to or lower than a predetermined data rate.

9. A method of operating an access point (AP) multi-link device, the access point (AP) multi-link device comprising a first AP and a second AP, and communicating with a single-radio non-AP multi-link device comprising a first non-AP station and a second non-AP station, wherein: The first AP and the first non-AP station operate on a first link, and the second AP and the second non-AP station operate on a second link, wherein, when the single-radio non-AP multi-link device operates in a predetermined operation mode, when the other of the first non-AP station and the second non-AP station performs frame exchange, the single-radio non-AP multi-link device does not support transmission or reception by one of the first non-AP station and the second non-AP station, the method comprising: performing no transmission to the second non-AP station not only while the frame exchange sequence of the first non-AP station is being performed but also within a first predetermined time interval from the completion of the frame exchange sequence of the first non-AP station, sending a control frame to the second non-AP station of the single-radio non-AP multi-link device after the first predetermined time interval, wherein the completion of the frame exchange sequence is determined based on the reception or transmission of the last frame of the frame exchange sequence, The first predetermined time interval is applied based on the radio frequency (RF) chain switching time interval of the single-radio non-AP multi-link device, wherein the RF chain switching time interval is a time interval including a delay required to start a monitoring operation of the RF chain after switching the RF chain, and Wherein, elements including the delay required to initiate operation of an RF chain after switching the RF chain are signaled by the single radio non-AP multi-link device.

10. The method according to claim 9, wherein: Sending the control frame includes sending the control frame in a predetermined physical layer protocol data unit (PPDU) format.

11. The method according to claim 10, wherein: The predetermined PPDU format is a non-HT format.

12. The method according to claim 9, wherein Transmitting the control frame includes transmitting the control frame at a data rate that is equal to or lower than a predetermined data rate.

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