Wireless communication method using multi-links, and wireless communication terminal using the same

Abstract

To provide a non-access point (AP) multi-link device operating in a first link and a second link.SOLUTION: A non-AP multi-link device comprises a transmission / reception unit and a processor. The processor receives a beacon frame or a probe response frame from an AP multi-link device operating in the first link and the second link, determines a traffic identifier (TID) mapped to the first link and the second link according to TID-to-Link mapping indicated by the beacon frame or the probe response frame, and performs transmission in the first link or the second link according to the TID mapped to the first link and the second link.SELECTED DRAWING: Figure 54

Description

[Technical Field]

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

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

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

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

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

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

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

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

[0009] According to one embodiment of the present invention, a non-AP (access point) multilink device operating on a first link and a second link includes a transceiver unit and a processor. The processor receives a beacon frame or a probe response frame from an AP multilink device operating on the first link and the second link, determines traffic identifiers (TIDs) to be mapped to the first link and the second link according to TID-to-Link mapping indicated by the beacon frame or the probe response frame, and performs transmission on the first link or the second link according to the TIDs mapped to the first link and the second link.

[0010] The non-AP multilink device may not be allowed to reject the TID-to-Link mapping indicated by the beacon frame or the probe response frame.

[0011] The TID-to-Link mapping indicated by the beacon frame or the probe response frame may include deactivating the first link.

[0012] When the TID-to-Link mapping indicated by the beacon frame or the probe response frame does not indicate that the second link is deactivated, the information regarding the TID-to-Link mapping may indicate that all TIDs subject to the TID-to-Link mapping are mapped to the second link.

[0013] When the first link is deactivated and then reactivated, all TIDs that are targets of the TID-to-Link mapping may be mapped to the first link.

[0014] When the first link is deactivated, the station of the non-AP multilink device operating on the first link enters a power-saving state, and when the first link is activated again, when the station of the multilink device wakes up from the power-saving state, NAVSyncDelay-based channel access restrictions may be applied to the station of the non-AP multilink device.

[0015] When the first link is deactivated, the value of the Neighbor AP TBTT offset subfield of the TBTT (target beacon transmission time) Information field corresponding to the first link in the RNR (reduced neighbor report) element transmitted on the second link may be 255.

[0016] When the AP multi-link device is a mobile AP and frame exchange cannot be performed simultaneously on the first link and the second link, the first link may not be the primary link through which the AP multi-link device transmits beacon frames.

[0017] The processor may discard a TID-to-Link mapping established by TID-to-Link mapping negotiation on the first link and the second link before receiving the beacon frame or the probe response frame.

[0018] According to an embodiment of the present invention, an access point (AP) multilink device operating on a first link and a second link includes a transceiver and a processor, wherein the processor transmits a beacon frame or a probe response frame instructing a traffic identifier (TID)-to-link mapping of the first link and the second link to a non-AP multilink device operating on the first link and the second link, and performs transmission on the first link or the second link according to the TID mapped to the first link and the second link.

[0019] The non-AP multilink device may not be allowed to reject the TID-to-Link mapping indicated by the beacon frame or the probe response frame.

[0020] The TID-to-Link mapping indicated by the beacon frame or the probe response frame may include deactivating the first link.

[0021] When the TID-to-Link mapping indicated by the beacon frame or the probe response frame does not indicate that the second link is deactivated, the information regarding the TID-to-Link mapping may indicate that all TIDs that are the subject of the TID-to-Link mapping are mapped to the second link.

[0022] When the first link is deactivated and then reactivated, all TIDs that are targets of the TID-to-Link mapping may be mapped to the first link.

[0023] When the first link is deactivated, the AP of the AP multilink device operating on the first link may enter a power-save state, and when the first link is reactivated and the station of the multilink device wakes up from the power-save state, NAVSyncDelay-based channel access restriction may be applied to the station of the AP multilink device.

[0024] When the first link is deactivated, the processor may transmit a reduced neighbor report (RNR) element on the second link in which the value of the Neighbor AP TBTT offset subfield corresponding to the first link in the target beacon transmission time (TBTT) Information field is set to 255.

[0025] When the AP multi-link device is a mobile AP and frame exchange cannot be performed simultaneously on the first link and the second link, the first link may not be the primary link through which the AP multi-link device transmits beacon frames.

[0026] According to an embodiment of the present invention, a method for operating a non-AP (access point) multi-link device operating on a first link and a second link includes the steps of receiving a beacon frame or a probe response frame from an AP multi-link device operating on the first link and the second link, determining a TID (traffic identifier) ​​to be mapped to the first link and the second link according to a TID-to-Link mapping indicated by the beacon frame or the probe response frame, and transmitting on the first link or the second link according to the TID mapped to the first link and the second link.

[0027] According to an embodiment of the present invention, a method for operating an AP (access point) multi-link device operating on a first link and a second link includes the steps of transmitting a beacon frame or a probe response frame to a non-AP multi-link device operating on the first link and the second link, the beacon frame or the probe response frame indicating a TID (traffic identifier)-to-Link mapping of the first link and the second link, and transmitting on the first link or the second link according to the TID mapped to the first link and the second link. [Effects of the Invention]

[0028] An embodiment of the present invention provides a wireless communication method that efficiently uses multilinks and a wireless communication terminal that uses the same. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an access point according to an embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a process in which a STA establishes a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] 1 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8]1 illustrates various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 shows a multi-link device according to an embodiment of the present invention; [Figure 10] 1 illustrates simultaneous transmission of different links in a multi-link operation according to an embodiment of the present invention. [Figure 11] 10 illustrates the operation of a multi-link device when a link is changed according to one embodiment of the present invention. [Figure 12] 10 shows that, according to one embodiment of the present invention, when any one station in a non-STR multilink device is receiving, channel access by other stations in the non-STR multilink device is prohibited. [Figure 13] 10 shows an operation of canceling channel access prohibition when it is confirmed that the intended recipient of a PPDU received by a station in a non-STR multilink device is not a station according to an embodiment of the present invention. [Figure 14] 10 shows a station according to an embodiment of the present invention accessing a channel after channel access prohibition is lifted. [Figure 15] 10 illustrates an operation of a station transmitting after channel access prohibition is lifted according to an embodiment of the present invention. [Figure 16] 10 illustrates transmissions based on the state of stations in a non-STR multilink device according to an embodiment of the present invention. [Figure 17] This shows the situation where interference or collision between links may occur. [Figure 18] 10 illustrates an operation in which an STR multilink device stops transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 19] 10 shows how the STR multilink device processes the value of CW when it recognizes a transmission collision between links according to an embodiment of the present invention. [Figure 20] 10 illustrates an operation of an STR multilink device accessing a channel again after halting transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 21] 10 illustrates an operation in which an STR multilink device transmits a CTS-to-Self frame before transmitting to a non-STR multilink device according to an embodiment of the present invention. [Figure 22] 1 illustrates that multiple APs included in an STR multilink device transmit to multiple stations included in one non-STR multilink device according to an embodiment of the present invention. [Figure 23] According to an embodiment of the present invention, multiple APs included in an STR multilink device perform multiple transmissions with synchronized end of transmission to multiple stations included in one non-STR multilink device. [Figure 24] 1 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention. [Figure 25] 25 illustrates a hidden node problem that occurs in the RTS / CTS frame exchange procedure according to the embodiment described in FIG. 24. [Figure 26] 1 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention. [Figure 27] 10 shows that a multilink device transmits a response to a control frame exceptionally even when channel access is prohibited according to an embodiment of the present invention. [Figure 28] Indicates that a transmission for a station on a non-STR multilink device should be retransmitted. [Figure 29] 10 shows that a control frame is transmitted on a link on which a station that is not prohibited from channel access operates, rather than on a link on which a station that is prohibited from channel access operates, according to an embodiment of the present invention. [Figure 30] 10 illustrates a multi-link device sending an ACK according to an embodiment of the present invention. [Figure 31]10 illustrates an element field indicating information regarding support for receiving or transmitting a sink PPDU according to an embodiment of the present invention. [Figure 32] 1 illustrates a non-STR multi-link device operating in inter-link TXOP power save mode according to an embodiment of the present invention. [Figure 33] 10 illustrates a station in a non-STR multilink device entering a power-saving state while waiting to receive a synced PPDU according to an embodiment of the present invention. [Figure 34] 10 shows a further embodiment of the present invention in which a station in a non-STR multilink device enters a power-saving state while waiting to receive a sync PPDU. [Figure 35] 1 shows that channel access of a station that has come out of a blind state is restricted according to an embodiment of the present invention. [Figure 36] 10 shows that channel access of stations that have come out of the blind state is restricted according to another embodiment of the present invention. [Figure 37] 10 shows that channel access of stations that have come out of the blind state is restricted according to yet another embodiment of the present invention. [Figure 38] According to yet another embodiment of the present invention, a station that has come out of the blind state is not restricted from accessing the channel if certain conditions are met. [Figure 39] 10 illustrates an Operation element containing information about channel access restriction times according to an embodiment of the present invention. [Figure 40] 10 shows that a station transmits simultaneously with other stations in a non-STR multi-link device in which the station is included in a channel access restricted period according to an embodiment of the present invention. [Figure 41] 10 shows a further embodiment of the present invention in which a station transmits simultaneously with other stations in a channel access restricted section of a non-STR multilink device in which the station is included. [Figure 42]10 illustrates the format of a Basic Multi-Link element that signals parameters that apply to channel access restrictions according to an embodiment of the present invention. [Figure 43] 10 illustrates a station according to an embodiment of the present invention performing a medium access recovery procedure based on information about parameters received from an AP. [Figure 44] 10 shows that a station according to an embodiment of the present invention continuously resets the MediumSyncDelay timer. [Figure 45] 10 illustrates a station according to yet another embodiment of the present invention continuously resetting the MediumSyncDelay timer. [Figure 46] 10 illustrates deactivation-related information transmitted by an AP multilink device according to an embodiment of the present invention. [Figure 47] 10 illustrates a format of signaling information regarding deactivation of a second link transmitted by an AP multi-link device in an embodiment of the present invention over a first link. [Figure 48] 1 illustrates a mapping relationship between UP and AC according to an embodiment of the present invention. [Figure 49] 10 illustrates a multilink device transmitting traffic mapped to each station of the multilink device according to an embodiment of the present invention. [Figure 50] 1 illustrates a multi-link device exchanging frames by TID link mapping according to an embodiment of the present invention. [Figure 51] 10 shows that a basic mapping between TIDs and links is set in an AP multilink device and a non-AP multilink device according to an embodiment of the present invention. [Figure 52] According to an embodiment of the present invention, when any one link is deactivated, the AP multilink device and the non-AP multilink device change the TID-to-Link mapping. [Figure 53]According to an embodiment of the present invention, when any one link is deactivated, the AP multilink device and the non-AP multilink device change the default mapping application to the TID-to-Link mapping of the non-deactivated link. [Figure 54] According to an embodiment of the present invention, when any one link is deactivated, the AP multilink device and the non-AP multilink device apply TID-to-Link mapping to the link that is deactivated and then reactivated. [Figure 55] 10 illustrates the operation of a non-STR mobile AP multi-link device when the non-STR mobile AP multi-link device deactivates a primary link according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of engineers in the relevant technical field, customs, or the emergence of new technologies. In addition, in certain cases, the applicant may have arbitrarily selected terms, and in such cases, the meanings thereof will be described in the relevant description of the invention. Therefore, it is made clear that the terms used in this specification should be interpreted not simply as names of terms, but based on the substantive meanings of the terms and the overall content of this specification.

[0031] Throughout the specification, when a component is "coupled" to another component, this includes not only when it is "directly coupled" to another component, but also when it is "electrically coupled" with another component in between. Furthermore, when a component "comprises" a specific component, this means that it may further include the other component, not excluding the other component, unless otherwise specified. In addition, limitations such as "greater than" or "less than" based on a specific threshold value may be appropriately replaced with "exceed" or "less than," respectively, depending on the embodiment.

[0032] Hereinafter, in the present invention, the terms field and subfield may be used interchangeably.

[0033] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0034] A wireless LAN system includes one or more Basic Service Sets (BSSs), which are a set of devices that can synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0035] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 that are stations providing distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0036] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard. In a broad sense, the term "station" encompasses not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface and a display unit, depending on the embodiment. The processor generates frames to be transmitted over a wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The communication unit is functionally connected to the processor and transmits and receives frames over the wireless network for the station. In this specification, the term "terminal" encompasses user equipment (UE).

[0037] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for associated stations. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP. However, if a direct link is established, direct communication is also possible between non-AP stations. Meanwhile, in the present invention, the term AP is used as a concept including a personal BSS coordination point (PCP), but in a broader sense, it also includes concepts such as a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller. In the present invention, an AP is also referred to as a base wireless communication terminal, but in a broader sense, the term base wireless communication terminal is used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal includes various types of wireless communication terminals that allocate communication medium resources and perform scheduling for communication with multiple wireless communication terminals.

[0038] A plurality of infrastructure BSSs are connected to each other via a distribution system DS, and the plurality of BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0039] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0040] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so none of the stations (STA6, STA7) are connected to an AP. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0041] 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention. As shown, the station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0042] First, the communication unit 120 transmits and receives wireless signals such as WLAN packets and may be incorporated into or external to the station 100. According to an embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules using different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with an AP or an external station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 120 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided independently, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit 120 may represent a radio frequency (RF) communication module that processes RF signals.

[0043] Next, the user interface 140 includes various types of input / output means provided in the station 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0044] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as a user interface, based on the contents processed by the processor 110 or the control commands of the processor 110. The memory 160 also stores control programs and various data used by the station 100. The control programs include a connection program required for the station 100 to connect to an AP or an external station.

[0045] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information about the station 100's preferences contained in the communication setup message and requests connection to the AP based on the information about the station 100's preferences. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the communication unit 120. That is, the processor 110 may be a modem that modulates and demodulates wireless signals transmitted and received by the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0046] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in embodiments of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively included in the station 100.

[0047] 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention. As shown, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, duplicated descriptions of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in FIG. 3 will be omitted.

[0048] Referring to FIG. 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 may also include multiple communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention may include two or more communication modules using different frequency bands, for example, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module can wirelessly communicate with a station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 220 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF (Radio Frequency) communication module that processes RF signals.

[0049] The memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a connection program that manages station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. The communication setup message includes information regarding connection preferences for each station. The processor 210 also performs connection setup in response to a station connection request. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals by the AP 200 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0050] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0051] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information for the BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0052] The STA 100 that successfully receives wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs the authentication step (S107b). After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs the association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0053] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, server 300 is a server that processes 802.1X-based authentication with STA 100, and may be physically connected to AP 200 or may exist as a separate server.

[0054] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0055] A terminal performing WLAN communication performs carrier sensing to check whether a channel is occupied before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not a signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by a terminal is identified as the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal with strength below the CCA threshold is detected, the channel is determined to be idle.

[0056] If the channel is determined to be idle, each terminal having data to transmit performs a backoff procedure after an Inter Frame Space (IFS), such as an Arbitration IFS (AIFS) or a PCF IFS (PIFS), depending on the status of each terminal. In some embodiments, the AIFS is used as a configuration replacing the conventional DCF IFS (DIFS). Each terminal waits while decrementing a slot time equal to a random number determined for the corresponding terminal during the idle interval of the channel, and a terminal that has exhausted all of its slot time attempts to access the corresponding channel. The period during which each terminal performs the backoff procedure is called a contention window period. In this case, the random number can be called a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal can decrement the backoff counter by 1. If the backoff counter reaches 0, the terminal may be allowed to perform channel access on the corresponding channel. Therefore, if the channel is idle during the AIFS time and the backoff counter slot time, the terminal may be allowed to transmit.

[0057] If a specific terminal successfully accesses the channel, it transmits data over the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are assigned new random numbers and perform a backoff procedure again. According to one embodiment, the new random numbers assigned to each terminal are determined within a range (2*CW) twice the range of the random numbers previously assigned to the terminal (contention window, CW). Meanwhile, each terminal attempts access by performing a backoff procedure again in the next contention window period. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, terminals communicating over a wireless LAN can avoid collisions with each other on a specific channel.

[0058] <Examples of various PPDU formats>

[0059] Figure 7 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. More specifically, Figure 7(a) shows an example of a legacy PPDU format based on 802.11a / g, Figure 7(b) shows an example of an HE PPDU format based on 802.11ax, and Figure 7(c) shows an example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Also, Figure 7(d) shows detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0060] 7(a), the preamble of the legacy PPDU includes a Legacy Short Training field (L-STF), a Legacy Long Training field (L-LTF), and a Legacy Signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0061] Referring to FIG. 7(b), the preamble of the HE PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a High Efficiency Signal A field (HE-SIG-A), a High Efficiency Signal B field (HE-SIG-B), a High Efficiency Short Training field (HE-STF), and a High Efficiency Long Training field (HE-LTF) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as an HE preamble. The specific configuration of the HE preamble may vary depending on the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0062] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a Universal Signal field (U-SIG), an Extremely High Throughput Signal A field (EHT-SIG-A), an Extremely High Throughput Signal B field (EHT-SIG-A), an Extremely High Throughput Short Training field (EHT-STF), and an Extremely High Throughput Long Training field (EHT-LTF) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may vary depending on the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some EHT PPDU formats.

[0063] The L-SIG field included in the PPDU preamble is configured with a total of 64 subcarriers using 64 FFT OFDM. Of these, 48 subcarriers, excluding guard subcarriers, DC subcarriers, and pilot subcarriers, are used for L-SIG data transmission. BPSK and Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, so it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of the L-SIG.

[0064] Referring to FIG. 7(d), the L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field is composed of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission rates of 6, 9, 12, 18, 24, 36, 48, or 54 Mbps, which is a combination of a modulation scheme such as BPSK, QPSK, 16-QAM, or 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. The combined information in the L_RATE and L_LENGTH fields indicates the total length of the PPDU. In the non-legacy PPDU format, the L_RATE field is set to the minimum rate of 6 Mbps.

[0065] The unit of the L_LENGTH field is byte, and a total of 12 bits are allocated, allowing signaling up to 4095. In combination with the L_RATE field, the length of the PPDU can be indicated. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0066] First, a legacy or non-legacy terminal analyzes the length of the PPDU using the L_LENGTH field as follows. When the L_RATE field is set to 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted in 4 us, which is the duration of one 64 FFT symbol. Therefore, by adding the 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of 64 FFT reference symbols after the L-SIG is obtained. The obtained number of symbols is multiplied by 4 us, which is the duration of one symbol, and then 20 us, which is required to transmit the L-STF, L-LTF, and L-SIG, is added to obtain the length of the PPDU, i.e., the reception time (RXTIME). This can be expressed mathematically as shown in Equation 1 below.

[0067]

number

[0068] At this time,

number

[0069]

number

[0070] Here, TXTIME is the total transmission time constituting the PPDU, and is expressed as the following equation 3. In this case, TX represents the transmission time of X.

[0071]

number

[0072] Referring to the above formula, the length of the PPDU is calculated based on the rounded up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0073] Referring to Figure 7(e), the U-SIG (Universal SIG) field remains in the EHT PPDU and subsequent generation WLAN PPDUs, and serves to distinguish which generation of PPDU it is, including 11be. The U-SIG is two 64FFT-based OFDM symbols and can transmit a total of 52 bits of information. Of these, 43 bits excluding 9 bits of CRC / tail are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0074] The VI bit will maintain its current bit configuration, so even if a subsequent generation PPDU is defined, current 11be UEs can obtain information about the PPDU from the VI field of the PPDU. To this end, the VI field consists of the PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits long and serves to sequentially distinguish between 11be and subsequent generations of WLAN standards. 11be has a value of 000b. The UL / DL field identifies whether the PPDU is an uplink or downlink PPDU. The BSS color represents a BSS identifier defined in 11ax and has a value of 6 or more bits. The TXOP represents the transmit opportunity duration (Transmit Opportunity Duration) transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the MPDU, and has a value of 7 or more bits.

[0075] The VD field, which is signaling information useful only for 11be version PPDUs, may consist of fields commonly used in any PPDU format, such as the PPDU format and BW, as well as fields defined differently for each PPDU format. The PPDU format is a separator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs. The BW field broadly signals five basic PPDU BW options: 20, 40, 80, 160 (80 + 80), and 320 (160 + 160) MHz (BWs that can be expressed in the form of a power of 20 * 2 can be called basic BWs), as well as various remaining PPDU BWs formed by preamble puncturing. After signaling at 320 MHz, a portion of 80 MHz may be punctured. In addition, the punctured and modified channel shape may be signaled directly in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (for example, a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0076] The fields located after the BW field vary depending on the type and format of the PPDU. MU PPDUs and SU PPDUs may be signaled using the same PPDU format, and a field for distinguishing between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, requiring additional signaling. Both SU PPDUs and MU PPDUs include an EHT-SIG field, but some fields not required for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or may have a reduced size compared to the original field size included in the MU PPDU. For example, the SU PPDU may have a different configuration, such as the common fields of the EHT-SIG being omitted or replaced, or the user-specific fields being replaced or reduced to one.

[0077] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (such as the RA field) may be omitted depending on the value of the compression field.

[0078] When a portion of the EHT-SIG field of the SU PPDU is compressed, the information included in the compressed field may be signaled together in an uncompressed field (e.g., a common field). In the case of an MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU was sent to it. Therefore, the AP must transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the MCS, which is the modulation method. The EHT-SIG field may include information on the size and location of the RU assigned to each user.

[0079] In the case of an SU PPDU, a STA may be assigned multiple RUs, and the multiple RUs may be contiguous or discontinuous. If the RUs assigned to the STA are not contiguous, the STA can efficiently receive the SU PPDU only by recognizing punctured RUs in between. Therefore, the AP can transmit the SU PPDU including information on punctured RUs among the RUs assigned to the STA (e.g., puncturing pattern of the RUs). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and the puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field can signal the type of discontinuous channels appearing within the bandwidth.

[0080] The type of signaled discontinuous channel is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, since the SU PPDU is a PPDU transmitted only to a single UE, the STA can recognize its allocated bandwidth from the BW field included in the PPDU and can recognize punctured resources within the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the UE can receive the PPDU in the remaining resource units excluding specific channels of the punctured resource units. In this case, multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0081] The reason why only limited discontinuous channel types are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed for each 20 MHz subchannel, if puncturing is performed on a BW having multiple 20 MHz subchannels, such as 80, 160, or 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered discontinuous) must be signaled by expressing whether or not each of the remaining 15 20 MHz subchannels excluding the primary channel is in use. Using 15 bits to signal the discontinuous channel type for single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0082] This invention proposes a method for signaling the discontinuous channel type of an SU PPDU and illustrates the discontinuous channel type determined by the proposed method. It also proposes a method for signaling the primary 160 MHz and secondary 160 MHz puncturing types in a 320 MHz BW configuration of an SU PPDU. The discontinuous channel types allowed when the above discontinuous channel type definition method is applied and a method for signaling the discontinuous channel type with 3 bits are shown in Figures 17 to 19.

[0083] In addition, one embodiment of the present invention proposes a method of varying the PPDU configuration indicated by the preamble puncturing BW value depending on the PPDU format signaled in the PPDU format field. Assuming that the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, an EHT-SIG-A symbol can be further signaled after the U-SIG, or no EHT-SIG-A can be signaled at all. Taking this into consideration, up to 11 puncturing modes must be fully signaled using only the BW field of the U-SIG. However, in the case of an EHT MU PPDU, an EHT-SIG-B symbol is further signaled after the U-SIG, so up to 11 puncturing modes can be signaled in a different manner than in the case of an SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20 MHz or 10 MHz bandwidth. Detailed puncturing patterns for each PPDU type will be described in detail below with reference to FIGS. 11 and 12.

[0084] Figure 7(f) shows the format-specific field configuration of the VD field when the PPDU format field of the U-SIG indicates an EHT MU PPDU. For an MU PPDU, SIG-B, a signaling field for simultaneous reception by multiple users, is required. SIG-B may be transmitted after the U-SIG without a separate SIG-A. For this purpose, the U-SIG must signal information for decoding SIG-B. These fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, and number of EHT-LTF symbols.

[0085] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention.

[0086] 8, a PPDU may be configured with a preamble and a data portion, and the format of one type, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is EHT PPDU may be indicated based on a PPDU format field included in the U-SIG field.

[0087] 8(a) shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

[0088] 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. The EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used for responding to the trigger frame. Unlike the EHT SU PPDU, the EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0089] 8(c) shows an example of an EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit a PPDU to one or more STAs. In the EHT MU PPDU format, an HE-SIG-B field may be located after the U-SIG field.

[0090] 8(d) shows an example of an EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission with STAs in a wider range than the EHT SU PPDU described in FIG. 8(a), and the U-SIG field may be repeated on the time axis.

[0091] The EHT MU PPDU described in (c) of Figure 8 can be used by the AP for downlink transmission to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive the PPDU transmitted from the AP. The EHT MU PPDU can convey AID information of the receiver and / or sender of the transmitted PPDU to the STA through the user specific field of the EHT-SIG-B. Therefore, multiple terminals receiving the EHT MU PPDU can perform spatial reuse based on the AID information of the user specific field included in the preamble of the received PPDU.

[0092] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information regarding the configuration of resource units (e.g., the division type of resource units) in a specific bandwidth (e.g., 20 MHz) on the frequency axis. That is, the RA field may indicate the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU so that the STA can receive the PPDU. Information about the STA allocated (or designated) to each divided resource unit may be included in a user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field may include one or more user fields corresponding to each divided resource unit.

[0093] For example, among the multiple divided resource units, the user field corresponding to at least one resource unit used for data transmission may include the AID of the receiver or sender, and the user field corresponding to the remaining resource units not used for data transmission may include a previously set null STA ID.

[0094] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0095] When a single wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be improved. In this case, a link is a physical path and may be configured as a single wireless medium that can be used to transmit an MSDU (MAC service data unit). For example, when the frequency band of one link is being used by another wireless communication device, the wireless communication device can continue communication using another link. In this way, the wireless communication device can effectively use multiple channels. Furthermore, when a wireless communication device simultaneously communicates using multiple links, the overall throughput can be improved. However, existing wireless LANs are specified on the assumption that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is needed. A wireless communication method for a wireless communication device using multiple links will be described with reference to FIGS. 9 to 26. First, a specific embodiment of a wireless communication device using multiple links will be described with reference to FIG. 9.

[0096] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0097] A multi-link device (MLD) may be defined for the wireless communication method using multiple links described above. The multi-link device may represent a device having one or more affiliated stations. Depending on a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. The multi-link device may also exchange multi-link elements. The multi-link element includes information about one or more stations or one or more links. The multi-link element may include a multi-link setup element, which will be described later. In this case, the multi-link device may be a logical entity. Specifically, the multi-link device may have multiple affiliated stations. The multi-link device may be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one medium access control service access point (SAP) up to a logical link control (LLC). The MLD may also have one MAC data service.

[0098] Multiple stations included in a multilink device can operate on multiple links. Also, multiple stations included in a multilink device can operate on multiple channels. Specifically, multiple stations included in a multilink device can operate on different links or different channels. For example, multiple stations included in a multilink device can operate on different channels, such as 2.4 GHz, 5 GHz, and 6 GHz.

[0099] The operation of the multilink device can be referred to as multilink operation, MLD operation, or multi-band operation. If the station associated with the multilink device is an AP, the multilink device can be referred to as AP MLD. If the station associated with the multilink device is a non-AP station, the multilink device can be referred to as non-AP MLD.

[0100] FIG. 9 shows the operation of communication between non-AP MLD and AP-MLD. Specifically, non-AP MLD and AP-MLD each communicate using three links. AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). Non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via a first link (Link1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via a second link (Link2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via a third link (Link3).

[0101] Multilink operation may include a multilink setup operation. Multilink setup corresponds to the association operation of the single-link operation described above and must be performed prior to frame exchange in the multilink. A multilink device can obtain information required for multilink setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multilink. In this case, the capability information may include information indicating whether one of multiple devices included in the multilink device can transmit and the other devices can receive at the same time. The capability information may also include information about links available to each station included in the MLD. The capability information may also include information about channels available to each station included in the MLD.

[0102] Multilink configuration may be established through negotiation between peer stations. Specifically, multilink configuration may be established through communication between stations without communication with an AP. Multilink configuration may also be established through any one of the links. For example, even if the first to third links are established through multilink, multilink configuration may be established through the first link.

[0103] In addition, a mapping between a traffic identifier (TID) and a link may be configured. Specifically, frames corresponding to a specific TID value may be exchanged only through a pre-specified link. The mapping between a TID and a link may be configured on a directional basis. For example, when multiple links are configured between a first multilink device and a second multilink device, the first multilink device may be configured to transmit frames of the first TID to the multiple first links, and the second multilink device may be configured to transmit frames of the second TID to the first links. In addition, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to TIDs on each link according to a default setting. In this case, the default setting may be that all TIDs are exchanged on any one link.

[0104] The TID will be described in detail. The TID is an ID for classifying traffic and data to support quality of service (QoS). The TID may be used and assigned in a layer higher than the MAC layer. The TID may indicate a traffic category (TC) or a traffic stream (TS). There may be 16 distinct TIDs. For example, the TID may be designated as any one of 0 to 15. Different TID values ​​may be designated depending on an access policy, channel access, or medium access method. For example, when enhanced distributed channel access (EDCA) or hybrid coordination function contention-based channel access (HCAF) is used, the TID may be assigned a value ranging from 0 to 7. When EDCA is used, the TID may indicate a user priority (UP). In this case, the UP may be designated by the TC or the TS. The UP may be assigned in a layer higher than the MAC. Furthermore, when HCCA (HCF controlled channel access) or SPCA is used, the TID may be assigned a value in the range of 8 to 15. When HCCA or SPCA is used, the TID may indicate a TSID. Furthermore, when HEMM or SEMM is used, the TID may be assigned a value in the range of 8 to 15. When HEMM or SEMM is used, the TID may indicate a TSID.

[0105] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in EDCA channel contention. QoS stations can guarantee QoS using AC. AC may include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may indicate background, best effort, video, and voice, respectively. AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI may be further subdivided into AC_VI primary and AC_VI alternate. AC_VO may be further subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to an AC. For example, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may have decreasing priority in that order. That is, 1 may have a lower priority, and 7 may have a higher priority. Therefore, the order of priority may be AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO can correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to the characteristics of TID, the mapping between TID and link can represent the mapping between AC and link.The mapping between links and ACs can also represent the mapping between TIDs and links.

[0106] As described above, a TID may be mapped to each of multiple links. The mapping may specify the links through which traffic corresponding to a specific TID or AC can be exchanged. Furthermore, the TID or AC that can be transmitted for each transmission direction within a link may be specified. As described above, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to the TID on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on any one link. At any given time, any TID or AC may be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0107] When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to the link may be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames not corresponding to a TID or AC not mapped to the link may not be transmitted on the link. When a link is mapped to a TID or AC, an ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a Block ACK agreement may be determined based on the mapping between the TID and the link. In yet another specific embodiment, the mapping between the TID and the link may be determined based on the Block ACK agreement. Specifically, a Block ACK agreement may be set for a TID mapped to a specific link.

[0108] The above-described TID-to-link mapping may ensure QoS. Specifically, a high-priority AC or TID may be mapped to a link where a relatively small number of stations are active or where channel conditions are good. The above-described TID-to-link mapping may also allow stations to remain in a power-saving state for a longer period of time.

[0109] FIG. 10 illustrates simultaneous transmission of different links in multi-link operation according to an embodiment of the present invention.

[0110] Depending on the implementation of the multilink device, simultaneous operation of the multilinks may not be supported. For example, a multilink device may not support simultaneous transmission on multiple links, simultaneous reception on multiple links, or transmission on one link while receiving on another link. Reception or transmission on one link may affect reception or transmission on another link. Specifically, transmission on one link may interfere with other links. Interference from one link of a multilink device affecting other links may be called internal leakage. The smaller the frequency spacing between links, the greater the internal leakage. If the internal leakage is not too large, transmission on one link can occur when transmission on another link. If the internal leakage is too large, transmission on one link cannot occur when transmission on another link. This simultaneous operation of a multilink device on multiple links may be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multilink device transmitting on multiple links simultaneously, transmitting on one link while receiving on another link, or receiving on multiple links simultaneously can be referred to as STR.

[0111] As mentioned above, a multilink device may support STR or may support it in a limited manner. Specifically, a multilink device may support STR only under certain conditions. For example, if the multilink device operates with a single radio, the multilink device may not be able to perform STR. Also, if the multilink device operates with a single antenna, the multilink device may not be able to perform STR. Also, if an internal leak is detected to be greater than a predetermined value, the multilink device may not be able to perform STR.

[0112] A station can exchange information about its STR capability with other stations. Specifically, a station can exchange information about whether or not the station has limitations on its ability to simultaneously transmit or receive on multiple links. Specifically, the information about whether or not the station has limitations on its ability to transmit or receive on multiple links can indicate whether or not the station will transmit or receive on multiple links simultaneously, or whether or not transmission and reception are simultaneous. Furthermore, the information about whether or not the station has limitations on its ability to transmit or receive on multiple links can be information indicated in stages. Specifically, the information about whether or not the station has limitations on its ability to transmit or receive on multiple links can be information indicating a stage indicating the magnitude of internal leakage. In a specific embodiment, the information indicating a stage indicating the magnitude of internal leakage can be information indicating a stage indicating the magnitude of interference caused by internal leakage. In yet another specific embodiment, the information indicating a stage indicating the frequency spacing between links that may affect internal leakage can be information indicating a stage indicating the relationship between the frequency spacing between links and the magnitude of internal leakage.

[0113] In FIG. 10, a first station (STA1) and a second station (STA2) are affiliated with one non-AP multilink device. A first AP (AP1) and a second AP (AP2) may also be affiliated with one non-AP multilink device. A first link (link1) is established between the first AP (AP1) and the first station (STA1), and a second link (link2) is established between the second AP (AP2) and the second station (STA2). In FIG. 10, the non-AP multilink device can perform limited STR. When the second station (STA2) transmits on the second link (Link2), the first station (STA1)'s reception on the first link (Link1) may be interrupted by the transmission on the second link (Link2). For example, in the following case, the first station (STA1)'s reception on the first link (Link1) may be interrupted by the transmission on the second link (Link2). The second station (STA2) transmits the first data (Data1) over the second link (Link2), and the first AP (AP1) transmits a response (Ack for Data1) to the first station (STA1). The second station (STA2) transmits the second data (Data2) over the second link (Link2). At this time, the transmission of the second data (Data2) and the transmission of the response (Ack for Data1) to the first data (Data1) may overlap. In this case, the transmission to the second station (STA2) over the second link (Link2) may cause interference to the first link (Link1). As a result, the first station (STA1) may not receive the response (Ack for Data1) to the first data (Data1).

[0114] The operation of the multilink device for channel access will be described below. The multilink operation without a specific description can follow the channel access procedure described in FIG.

[0115] A multilink device can perform channel access independently from multiple links. In this case, the channel access may be backoff-based channel access. When a multilink device performs channel access independently from multiple links and the backoff counters for multiple links reach zero, the multilink device can start transmission simultaneously from multiple links. In a specific embodiment, when one of the backoff counters for multiple links reaches zero and a predetermined condition is met, the multilink device can perform channel access not only for the link whose backoff counter has reached zero but also for other links whose backoff counters have not reached zero. Specifically, when one of the backoff counters for multiple links reaches zero, the multilink device can perform energy sensing on other links whose backoff counters have not reached zero. In this case, if energy greater than or equal to a predetermined magnitude is not detected, the multilink device can perform channel access not only for the link whose backoff counter has reached zero but also for the link for which energy sensing has been performed. This allows the multilink device to start transmission simultaneously from multiple links. The threshold used for energy sensing may be smaller than the threshold used for determining whether to decrement the backoff counter. Furthermore, when determining whether to decrement the backoff counter, the multilink device can sense any type of signal, not just a WLAN signal. Furthermore, in the energy sensing described above, the multilink device can sense any type of signal, not just a WLAN signal. Internal leakage may not be detected as a WLAN signal. In such a case, the multilink device can detect signals detected due to internal leakage through energy sensing. Furthermore, as described above, the threshold used for energy sensing may be smaller than the threshold used to determine whether to decrement the backoff counter. Therefore, even while transmission is occurring on one link, the multilink device can decrement the backoff counter on another link.

[0116] Depending on the degree of interference between links used by the multilink device, the multilink device may determine whether stations operating on each link can operate independently. In this case, the degree of interference between links may be the magnitude of interference perceived by other stations in the multilink device when one station in the multilink device transmits on one of the links. If transmission on the first link of a first station in the multilink device causes interference of a predetermined magnitude or greater to a second station in the multilink device operating on the second link, the operation of the second station may be restricted. Specifically, reception or channel access of the second station may be restricted. If interference occurs, the second station may fail to decode a received signal due to the interference. Furthermore, if interference occurs, the second station may determine that the channel is in use when accessing the channel using backoff.

[0117] Furthermore, if the transmission of a first station in the multilink device through the first link causes interference of less than a predetermined magnitude to a second station in the multilink device operating through the second link, the first station and the second station can operate independently. Specifically, if the transmission of a first station in the multilink device through the first link causes interference of less than a predetermined magnitude to a second station in the multilink device operating through the second link, the first station and the second station can independently access the channel. Also, if the transmission of a first station in the multilink device through the first link causes interference of less than a predetermined magnitude to a second station in the multilink device operating through the second link, the first station and the second station can independently transmit or receive. If interference of less than a predetermined magnitude occurs, the second station can successfully decode the received signal even in the presence of interference. Also, if interference of less than a predetermined magnitude occurs, the second station can determine that the channel is idle when accessing the channel using backoff.

[0118] The degree of interference occurring between stations of a multilink device may vary depending on the interval between the frequency bands of the links on which the stations operate as well as the hardware characteristics of the multilink device. For example, the internal interference occurring in a multilink device including a high RF (radio frequency) device may be smaller than the internal interference occurring in a multilink device including a low RF device. Therefore, the degree of interference occurring between stations of a multilink device may be determined based on the characteristics of the multilink device.

[0119] FIG. 10 shows how the magnitude of interference varies depending on the spacing between link frequency bands and the characteristics of the multilink devices. In the example of FIG. 10, a first multilink device (MLD#1) includes a first station (STA1)-1 operating on a first link (Link1) and a second station (STA1)-2 operating on a second link (Link2). A second multilink device (MLD#2) includes a first station (STA2)-1 operating on a first link (Link1) and a second station (STA2)-2 operating on a second link (Link2). The frequency spacing between the first link (Link1) and the second link (Link2) on which the first multilink device (MLD#1) operates is the same as the frequency spacing between the first link (Link1) and the second link (Link2) on which the second multilink device (MLD#2) operates. However, the magnitude of interference varies depending on the difference between the characteristics of the first multilink device (MLD#1) and the second multilink device (MLD#2). Specifically, the magnitude of interference generated in the second multilink device (MLD#2) may be greater than the magnitude of interference generated in the first multilink device (MLD#1). Considering that the magnitude of interference generated may differ depending on the characteristics of the multilink devices and that the presence or absence of STR support may differ depending on the multilink devices, information regarding whether STR is supported or not needs to be exchanged.

[0120] A multilink device can signal whether or not a station included in the multilink device supports STR. Specifically, an AP multilink device and a non-AP multilink device can exchange whether or not an AP included in the AP multilink device supports STR with whether or not a STA included in the non-AP multilink device supports STR. In this embodiment, an element indicating whether or not STR support is available may be used. The element indicating whether or not STR support is available may be referred to as an STR support element. The STR support element may indicate, with one bit, whether or not a station in the multilink device that transmitted the STR support element supports STR. Specifically, the STR support element may indicate, with one bit, whether or not each station included in the multilink device that transmitted the STR support element supports STR. In this case, if the station supports STR, the bit value may be 1, and if the station does not support STR, the bit value may be 0. If the multilink device that transmitted the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support STR, and the second station (STA2) does not support STR, the STR support element is 101. 1bThe STR support element may include a field having the following information: Stations operating in different frequency bands are assumed to support STR, and the STR support element may omit signaling regarding the presence or absence of STR support between stations operating in different frequency bands. For example, a first station (STA1) operates on a first link of 2.4 GHz, and a second station (STA2) and a third station (STA3) operate on a second link of 5 GHz and a third link of 5 GHz, respectively. In this case, the STR support element may indicate with one bit that STR is supported between the second station (STA2) and the third station (STA3). Alternatively, the STR support element may include only one bit if the STR support element signals two stations.

[0121] In a specific embodiment, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz among the links of a multi-link device may always be determined as STR, and therefore, signaling regarding the presence or absence of STR between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz may be omitted.

[0122] FIG. 11 shows the operation of the multilink device when a link is changed according to one embodiment of the present invention.

[0123] When the frequency band of a link is changed, the STR support element may be exchanged. As described above, whether a station supports STR may vary depending on the distance between the frequency bands of the link, and whether a station supports STR may change when the frequency band of the link is changed. When the frequency band of a link is changed, at least one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a 20 MHz primary channel may be included. The AP and the station may exchange the STR support element through a request and a response. In another specific embodiment, when the frequency band of a link is changed, the STR support element may be exchanged without a separate request. Furthermore, in the above embodiment, when the frequency band of a link is changed, the operating channel of the station may be changed.

[0124] If a station in a non-AP multilink device cannot perform STR, the station in the non-AP multilink device can request a link change from the AP. Specifically, the station in the non-AP multilink device can request at least one of a change in center frequency, a change in frequency band bandwidth, and a change in 20 MHz primary channel. The link change request may be transmitted to the AP through a link for which a change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP through a link for which a change is not requested. In this case, the link change request may include information indicating the link for which a change is requested. The information indicating the link may be a number identifying the link. In this embodiment, the link change may be a change in an operating channel within a frequency band. The link change may also include information regarding a method for changing the link. Specifically, the link change request may indicate whether the center frequency of the link should be moved to a frequency higher than the current center frequency or a frequency lower than the current center frequency. In yet another specific embodiment, the link change request may implicitly indicate a change to a frequency band away from an adjacent link. The link change request may also indicate a reduction in link bandwidth. The link change request may also indicate a change in the location of the primary channel. Specifically, the link change request may indicate a change in the location of the primary channel to a channel in a lower frequency band or a channel in a higher frequency band than the location of the current primary channel. The AP that receives the link change request may change the link in response to the link change request. In a specific embodiment, the AP that receives the link change request may ignore the link change request.

[0125] In the embodiment of Figure 11, the second station (STA2) and the third station (STA3) of the non-AP multilink device cannot support STR. The non-AP multilink device requests the AP multilink device to change the third link (Link3). Upon receiving the link change request, the AP multilink device changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the changed third link (Link3) can send a change request to the third AP (AP3). In yet another specific embodiment, a station not operating on the third link (Link3) can send a change request to the AP not operating on the third link (Link3).

[0126] When an AP changes a link, the AP may broadcast information about the link change using a beacon frame. In this case, the information about the link change may include information about the link frequency. The information about the link frequency may include at least one of a change in the link center frequency, operating bandwidth, and primary channel. The information about the link change may also include information about the time of the link change. The link change may also be completed when a beacon including information about the link change is transmitted.

[0127] In Figure 11, the link on which the third station (STA3) operates is changed, and the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multilink device can send an STR support element to the AP multilink device to signal the presence or absence of changed STR support.

[0128] The above-mentioned link change may not be allowed, or even if the link change occurs, STR may not be supported. Also, as in the embodiment of FIG. 11, an AP multilink device may support STR, but a non-AP multilink device may not support STR. This is because a relatively high-RF device is generally used in an AP multilink device, and a relatively low-RF device is generally used in a non-AP multilink device. Therefore, a method is needed to enable efficient communication between multilink devices even when one of the multilink devices does not support STR. In this case, STR can indicate that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

[0129] FIG. 12 shows that when any one station in a non-STR multilink device is receiving, other stations in the non-STR multilink device are prohibited from accessing the channel according to one embodiment of the present invention.

[0130] When transmission is performed on one link of a non-STR multilink device and reception is performed on another link of the non-STR multilink device, reception and transmission of the non-STR multilink device may fail. To solve this problem, when reception is performed on one link of the non-STR multilink device, channel access may be prohibited on the other links of the non-STR multilink device. Specifically, when reception is performed on one link of the non-STR multilink device, channel access backoff may be prohibited on the other links of the non-STR multilink device. This prevents transmission from starting on the other links of the non-STR multilink device when reception is performed on one link of the non-STR multilink device. In a specific embodiment, when reception begins on one link of the non-STR multilink device, channel access backoff may be prohibited on the other links of the non-STR multilink device. This may be set by a specific bit in memory, such as a channel access prohibition flag. Whether channel access is prohibited may be shared by memory within the multilink device. This embodiment allows channel access prohibition to be implemented without a separate frame exchange. For ease of explanation, unless otherwise specified, channel access prohibition as used herein refers to prohibiting channel access or transmission in order to protect the transmission or reception of non-STR multilink devices.

[0131] When channel access is prohibited, stations operating on the link where channel access is prohibited cannot perform a backoff procedure regardless of the NAV and CCA results. Furthermore, when channel access is prohibited, stations operating on the link where channel access is prohibited cannot transmit regardless of the NAV and CCA results. However, even when channel access is prohibited, stations operating on the link where channel access is prohibited can receive. Furthermore, the prohibition of channel access on the second link due to reception on the first link may be lifted when reception on the first link is completed. Specifically, the prohibition of channel access on the second link due to reception on the first link may be lifted when reception on the first link is completed. In yet another specific embodiment, the prohibition of channel access on the second link due to reception on the first link may be lifted when an ACK is transmitted after reception on the first link is completed. Specifically, the prohibition of channel access on the second link due to reception on the first link may be lifted when an ACK is transmitted after reception on the first link is completed. In yet another specific embodiment, channel access prohibition on the second link due to reception on the first link may be lifted when ACK transmission is completed after reception on the first link is completed. Also, immediately after the channel access prohibition is lifted, the station may immediately decrement the backoff counter without additional sensing. Here, additional sensing may refer to sensing performed during a DCF Interframe Space (DIFS). In yet another specific embodiment, if the channel is idle for a pre-specified time immediately before the channel access prohibition is lifted, the station may immediately decrement the backoff counter without additional sensing. Here, the pre-specified time may be any one of a PCF Interframe Space (PIFS), a DIFS, a Short Interframe Space (SIFS), and an Arbitration Interframe Space (AIFS).

[0132] In the embodiment of FIG. 12, a non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) receives, intra-device interference occurs. As described above, while the first station (STA1) operating on the first link (Link1) receives, the second station (STA2) is prohibited from accessing the channel on the second link (Link2). After the first station (STA1) completes reception on the first link (Link1), the channel access prohibition is lifted. Immediately after the channel access prohibition is lifted, the second station (STA2) can decrement its backoff counter value by 1, from 3 to 2, without additional sensing.

[0133] For convenience of illustration, in Fig. 12, Rx and Tx are represented by a single block (Tx solid line, Rx dotted line), and this single block may be understood to represent an operation including Tx / Ack reception and Rx / Ack transmission even if a separate Ack block is not shown. This may be equally applied to the drawings described later.

[0134] If a station determines that it is not the intended recipient of a PPDU it receives, it may discontinue receiving the PPDU. In such cases, the channel access unblocking operation of the multilink device becomes an issue. In this specification, the intended recipient is used synonymously with the destination station.

[0135] FIG. 13 shows an operation of canceling channel access prohibition when it is confirmed that the intended recipient of a PPDU received by a station in a non-STR multilink device is not a station according to an embodiment of the present invention.

[0136] If the station determines that it is not the intended recipient of the received PPDU, it can lift the channel access prohibition. The station can determine whether it is the intended recipient of the PPDU based on information indicating the recipient address in the signaling field of the PPDU. In this case, the information indicating the recipient address in the signaling field of the PPDU may be the value of the STA-ID field in the EHT-SIG field. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field indicates the station. The station can also determine whether it is the intended recipient of the PPDU based on the value of the RA field in the MAC frame included in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame included in the PPDU indicates the station. In FIG. 13, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first station (STA1) receives a PPDU. The first station (STA1) determines that it is not the intended recipient of the received PPDU and suspends reception of the PPDU. At this time, the first station (STA1) can lift the channel access prohibition for the second station (STA2). Even if the channel access prohibition for the second station (STA2) is lifted, the channel access of the second station (STA2) may be delayed depending on the NAV set for the second station (STA2).

[0137] As shown in FIG. 13, even if channel access prohibition is lifted, stations included in a non-STR multilink device often do not have a channel access opportunity compared to stations not included in the multilink device or stations included in the STR multilink device. Therefore, a method for compensating for channel access opportunities for stations included in a non-STR multilink device is needed to ensure fair competition with other stations. For example, immediately after channel access prohibition is lifted, a station whose channel access prohibition has been lifted may be allowed to decrement its backoff counter by 2 or more. This will be described in FIG. 14.

[0138] FIG. 14 shows a station according to an embodiment of the present invention accessing a channel after channel access prohibition is lifted.

[0139] A station whose channel access prohibition has been lifted can decrement its backoff counter by 2 or more immediately after the channel access prohibition is lifted. This is to ensure fairness in channel access opportunities with other stations, since other stations have performed backoff procedures while the station's channel access was prohibited.

[0140] In yet another specific embodiment, a station whose channel access is prohibited can perform a channel access procedure to decrement the CCA (CSMA) and backoff counter while its channel access is prohibited. In FIG. 14, a non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). In FIG. 14, the second station (STA2) is prohibited from channel access while the first station (STA1) is receiving. In FIG. 14(a), while the second station (STA2)'s channel access is prohibited, the second station (STA2) can perform a channel access procedure to decrement the CCA (CSMA) and backoff counter. In FIG. 14(a), while the second station (STA2)'s channel access is prohibited, the second station (STA2) decrements its backoff counter because the channel of the second link (Link2) is idle.

[0141] In addition, a station whose channel access is prohibited can delay transmission without starting transmission even if its backoff counter reaches 0 while channel access is prohibited. In this case, the station can maintain the backoff counter value at 0. Furthermore, even if the station delays transmission, the station can maintain the CW value as it is. This is different from the station doubling the CW value because the channel it accesses is busy. This is because the reason for delaying transmission is not because the channel is determined to be busy. In FIG. 14(b), while channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure to decrement the CCA (CSMA) and backoff counter. In FIG. 14(b), while channel access of the second station (STA2) is prohibited, the channel of the second link (Link2) is idle, so the second station (STA2) decrements the backoff counter. While 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 resumes transmission after the channel access prohibition is lifted.

[0142] As described above, the channel access prohibition can include prohibiting transmission to a second station when a first station of a non-STR multilink device is transmitting, and can also include prohibiting transmission to a second station when a first station of a non-STR multilink device is receiving.

[0143] In the embodiment illustrated in Figure 14(b), if multiple stations are prohibited from channel access, there is a high possibility that the channel access prohibitions of multiple stations will be lifted simultaneously, causing multiple stations to attempt transmission simultaneously. Therefore, a method is needed to reduce the probability of transmission collisions. This will be explained in Figure 15.

[0144] FIG. 15 shows an operation of a station according to an embodiment of the present invention to transmit after channel access prohibition is lifted.

[0145] As described above, among multiple links operated by a non-STR multilink device, transmission may be performed on a first link and transmission may be prohibited on a second link. When the transmission on the first link is completed, transmission on the second link may begin by exchanging RTS / CTS frames. Therefore, when transmission is performed on a first link among multiple links operated by a non-STR multilink device, the non-STR multilink device may begin exchanging RTS / CTS frames on the second link. After the channel access prohibition of a station whose transmission has been delayed due to channel access prohibition is lifted, the station may begin exchanging RTS / CTS (request to send / clear to send) frames before starting the delayed transmission. In this case, if the station is unable to receive a CTS frame, it may be unable to start the delayed transmission. In the embodiment of FIG. 15(a), a station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before starting the delayed transmission. The station begins the delayed transmission after receiving a CTS frame in response to the RTS frame.

[0146] In yet another specific embodiment, after a station whose transmission has been delayed due to channel access prohibition is released, the station can transmit a frame including only a portion of the delayed transmission. In this case, after the station receives a response, e.g., an ACK, to the frame including only a portion of the delayed transmission, the station can transmit the remaining portion of the delayed transmission. If the station does not receive a response to the frame including only a portion of the delayed transmission, the station may not transmit the remaining portion of the delayed transmission. In this manner, the station initiates an RTS / CTS exchange or transmits only a portion of the delayed transmission after channel access prohibition is released because the collision probability of transmission after channel access prohibition is higher than that of general transmission. Therefore, the above-described embodiment may be mandatory for transmissions performed after channel access prohibition is released. In existing WLAN operations, the RTS / CTS frame is used to solve the hidden node problem and can be used based on the size of the transmission data. In the above-described embodiment, the RTS / CTS frame is used to prevent transmission collisions with stations attempting delayed transmissions to protect the transmission or reception of non-STR multilink devices.

[0147] As described above, when one station in a non-STR multilink device receives, transmissions by other stations in the non-STR multilink device may be restricted. Furthermore, when one station in a non-STR multilink device transmits, other stations in the non-STR multilink device may have difficulty accurately sensing the channel status of the link on which the station operates. Specifically, when a first station in a non-STR multilink device transmits, a second station in the non-STR multilink device may always determine that the channel status of the link on which the second station operates is busy. Therefore, even when the channel of the link on which the second station operates is idle, the second station may determine that the channel is busy due to intra-device interference. In this way, when a station that cannot determine the channel status due to intra-device interference or when one station in a non-STR multilink device is continuing to transmit is said to be in a blind state to other stations in the non-STR multilink device. Due to the above-described situation, a station in a blind state may have difficulty performing a backoff procedure and attempting transmission. In addition, due to the above-mentioned circumstances, it may be difficult for blind stations to start receiving or successfully decode the PPDU. Therefore, a transmission method that takes blind stations into consideration is required. This will be explained in FIG. 16.

[0148] FIG. 16 illustrates transmissions based on the state of stations in a non-STR multilink system according to an embodiment of the present invention.

[0149] A station attempting to transmit to a station in a non-STR multilink device can determine whether to transmit based on whether the station in the non-STR multilink device is in a blind state. In this case, the station attempting to transmit to a station in a non-STR multilink device may be a station included in the STR multilink device. Alternatively, the station attempting to transmit to a station in a non-STR multilink device may be an AP included in the AP multilink device, and the non-STR multilink device may be a non-AP multilink device. A station attempting to transmit to a station in a non-STR multilink device can determine whether the station in the non-STR multilink device is in a blind state. The station attempting to transmit can determine whether other stations in the multilink device that the station is included in are transmitting to the non-STR multilink device. If other stations in the multilink device that the station is included in are receiving from the non-STR multilink device, the station can determine that the station in the non-STR multilink device receiving the station's transmission is in a blind state. In the embodiment of FIG. 16, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can inform the first AP (AP1) that it is receiving from the second station (STA2). Specifically, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is the subject of transmission to the second AP (AP2). In yet another specific embodiment, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is currently transmitting.At this time, the first AP (AP1) can determine based on the notification that the first station (STA1) is in a blind state.

[0150] A station does not need to transmit to a station in a blind state because if it transmits to a station in a blind state, the station in the blind state may not be able to acknowledge reception or may not be able to decode the PPDU. In this case, the station can cancel transmission to the station in the blind state and transmit to another station.

[0151] When an STR multilink device transmits to a non-STR multilink device, the STR multilink device can transmit to the non-STR multilink device over multiple links. Specifically, when the STR multilink device transmits to the non-STR multilink device over a first link, the STR multilink device can begin transmitting to the non-STR multilink device over a second link. In this case, the STR multilink device can determine the length of the transmission over the second link based on the transmission to the non-STR multilink device. Specifically, the STR multilink device can determine the length of the transmission over the second link to the non-STR multilink device based on the length of the transmission over the first link to the non-STR multilink device. In a specific embodiment, the STR multilink device can simultaneously complete transmission over the first and second links. This is to prevent transmission to one of the stations in the non-STR multilink device from completing first, thereby preventing transmission to another station in the non-STR multilink device while one of the stations in the non-STR multilink device is transmitting a response to the transmission, e.g., an ACK. The above-described embodiment allows multiple stations in the non-STR multilink device to simultaneously transmit responses to transmissions to multiple stations.

[0152] An STR multilink device cannot determine the status of stations included in non-STR multilink devices in real time. Therefore, even if an STR multilink device operates according to the embodiment described in FIG. 16, interference or transmission collisions may occur between links on which the non-STR multilink device operates. For example, in the embodiment of FIG. 16, the first AP (AP1) may begin transmitting to the first station (STA1) before recognizing that the second station (STA2) is transmitting to the second AP (AP2). In this way, the probability of inter-link interference or collisions may be greater than the probability of intra-link interference or transmission collisions. This is described in more detail in FIG. 17.

[0153] FIG. 17 shows a situation in which interference or collision between links may occur.

[0154] When a second station in a non-STR station multilink device starts transmitting to a second AP in the STR AP multilink device at the same time as a first AP in the STR AP multilink device starts transmitting to a first station in the non-STR station multilink device, a transmission collision between the links can occur. This is shown in Figure 17(a). As mentioned above, this can occur because the STR multilink device cannot determine the status of the stations included in the non-STR station multilink device in real time.

[0155] Furthermore, even if the transmission of the second station of the non-STR station multilink device to the second AP of the STR AP multilink device begins before the transmission of the first AP of the STR AP multilink device to the first station of the non-STR station multilink device, a transmission collision may occur between the links. This is shown in FIG. 17(b). This is because it may take time for the second AP (AP2) to inform the first AP (AP1) that the second station (STA2) is transmitting. As such, since a transmission collision may occur even between stations that begin transmitting at different times, the probability of inter-device interference or transmission collision may be greater than the probability of intra-link interference or transmission collision. Furthermore, the longer the time it takes for the AP of the STR multilink device to identify the sender of the PPDU it receives, the greater the probability of inter-link interference or transmission collision. Therefore, a method to resolve this issue is needed. When one station of the STR multilink device is receiving, other stations of the STR multilink device may not be allowed to access the channel. However, if channel access is prohibited in this way, the purpose of implementing the STR function may be lost. Therefore, a method of operation that does not inhibit channel access for STR multilink devices is required, which is illustrated in FIG.

[0156] FIG. 18 illustrates an operation in which an STR multilink device stops transmission to a non-STR multilink device according to one embodiment of the present invention.

[0157] If a station in an STR multilink device determines that a station in the non-STR multilink device is in a blind state while transmitting to a station in a non-STR multilink device, the STR multilink device can suspend transmission to the station in the blind state. Specifically, the STR multilink device can determine whether a station in the non-STR multilink device is in a blind state based on a value indicated as an STA(AID)-ID in the signaling field of a received PPDU or a TA (transmitting address) field of a MAC frame included in the received PPDU. In this case, the STA-ID may be a value indicating the station transmitting the UL PPDU in an UL PPDU. In a specific embodiment, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state if a value indicated as an STA(AID)-ID in the signaling field of a received PPDU indicates a first station included in the non-STR multilink device. In addition, if the TA field of the MAC frame included in the received PPDU indicates a first station included in a non-STR multilink device, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state. First, the operation of the station after transmission cancellation will be described.

[0158] If a TXOP set for a station in a non-STR multilink device remains, the station that canceled transmission to the station in the non-STR multilink device can attempt transmission to stations other than the station in the non-STR multilink device. In this case, the station that canceled transmission to the station in the non-STR multilink device can transmit to stations other than the station in the non-STR multilink device without a separate backoff procedure. In a specific embodiment, if the channel is detected as idle for a pre-designated time period without a separate backoff procedure after canceling transmission to the station in the non-STR multilink device, the station that canceled transmission to the station in the non-STR multilink device can transmit to stations other than the station in the non-STR multilink device. In this case, the pre-designated time period may be any one of SIFS, PDIF, and DIFS.

[0159] When a station that has canceled a transmission to a station in a non-STR multilink device transmits to a station other than the station in the non-STR multilink device, the station that canceled the transmission to the station in the non-STR multilink device can transmit traffic with the same priority as the traffic of the canceled transmission or traffic with a higher priority. This is because transmitting traffic with a lower priority than the priority of the traffic used when accessing the channel for the canceled transmission would not be fair. In the above-mentioned embodiment, the station in the STR multilink device may be an AP.

[0160] A station that cancels transmission to a station in a non-STR multilink device can reset the TXOP it set. Specifically, a station that cancels transmission to a station in a non-STR multilink device can send a CF-End frame after canceling transmission, allowing other stations operating on the link scheduled for transmission to use the link.

[0161] In FIG. 18, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). While transmitting to the first station (STA1), the first AP (AP1) determines that the first station (STA1) is in a blind state. Therefore, the first AP (AP1) suspends transmission to the first station (STA1). In FIG. 18(a), after suspending transmission to the first station (STA1), the first AP (AP1) transmits to stations other than the first station (STA1), as in the previously described embodiment. In FIG. 18(b), after suspending transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame as in the embodiment described below.

[0162] When a station suspends transmission, it may not transmit the next fragment after transmitting the fragment that was in transmission. In yet another specific embodiment, the station may immediately stop transmitting the packet that was in transmission.

[0163] In the above-described embodiment, when the STR multilink device suspends transmission to a station of a non-STR multilink device in a blind state and transmits to a station other than the station of the non-STR multilink device in a blind state, it is necessary to notify the other station that transmission to the other station may be performed for stable reception. A method for this will be described. For convenience of explanation, the other station other than the station of the non-STR multilink device in a blind state will be referred to as the other station.

[0164] A station in an STR multilink device can insert the address of another station into a MAC frame. Specifically, the station in the STR multilink device can insert the address of the intended recipient of the MAC frame into the RA (receiving address) of the MAC frame and the address of the other station into a separate field. In yet another specific embodiment, the station in the device can insert the address of the other station into an EHT-SIG. Specifically, the station in the STR multilink device can insert the address of the intended recipient of the PPDU and the address of the other station into the User field of the signaling field of the PPDU. In this case, the address of the other station can be inserted after the address of the intended recipient of the PPDU in the User field of the signaling field of the PPDU.

[0165] In yet another specific embodiment, a station may monitor for reception of a PPDU for a pre-specified time even after determining that the station is not the intended recipient of the received PPDU. Specifically, the station may monitor for continued reception of a PPDU for a pre-specified time even after determining that the station is not the intended recipient of the received PPDU. This allows the station to determine whether PPDU transmission should be stopped and transmission to the station should begin. In this embodiment, if it is determined that PPDU transmission will continue for the pre-specified time, the station may enter a doze state. If it is determined that PPDU transmission will not continue for the pre-specified time, the station may remain awake. In this case, if a new PPDU is received by the station, the station may decode the PPDU.

[0166] In yet another specific embodiment, a station transmitting a PPDU may insert information into the PPDU signaling that the transmission of the PPDU may be interrupted. The information signaling that the transmission of the PPDU may be interrupted may be a 1-bit subfield. For example, if the value of the subfield signaling that the transmission of the PPDU may be interrupted is 1, a station receiving the PPDU may determine that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame. If the station determines that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame, the station may postpone entering a power-saving state. Alternatively, a station transmitting a PPDU may insert information signaling that the transmission may be interrupted into a reserved field of the PPDU.

[0167] In this way, unnecessary channel occupation due to transmission cancellation or transmission interruption can be prevented.

[0168] When transmission is interrupted or postponed due to a transmission collision between links, the CW value used for channel access may be doubled, as in the case of a general transmission failure. When transmission is interrupted or postponed due to a transmission collision between links, unlike the case of a general channel access failure or transmission failure, the CW value used for channel access does not need to be doubled. That is, the station can maintain the CW value used for channel access as it is. Doubling the CW value increases the range of possible backoff counter values ​​and reduces the probability of transmission collision. This need can be reduced if the station can clearly recognize transmission collision between links. Also, when transmission is interrupted or postponed due to a transmission collision between links, doubling the CW value by the station may delay the transmission. However, when inter-link transmission collision and intra-link collision occur simultaneously, the station needs to double the CW value. This is described in FIG. 19.

[0169] FIG. 19 shows how the STR multilink device processes the value of CW when it recognizes a transmission collision between links according to an embodiment of the present invention.

[0170] When a station cancels a transmission due to a transmission performed in a non-STR multilink device, as in the above-described embodiment, the station can sense the channel state after canceling the transmission. If the channel is detected as not idle, the station can double the CW value. In this case, the doubling can be performed according to the embodiment described in FIG. 6. Alternatively, if the channel is detected as idle, the station can maintain the CW value. This embodiment is used to treat a detected channel as idle differently from a successful transmission because the likelihood of a transmission collision within the link is low. In yet another specific embodiment, if the channel is detected as idle, the station can set the CW value to the minimum CW value (CW_min) of the traffic. This embodiment is used to treat a detected channel as idle the same as a successful transmission because the likelihood of a transmission collision within the link is low. The above-described embodiment can be applied to the CW of the AC of the traffic included in the canceled transmission.

[0171] In addition, when a station cancels transmission according to the above-described embodiment, the station may not increment the Retry Counter, which may include at least one of a long retry counter and a short retry counter.

[0172] In the above embodiments, canceling a transmission may include at least one of pausing the transmission and / or delaying the transmission before commencing the transmission.

[0173] If a station sends a CTS-to-Self frame before attempting to transmit and then cancels transmission, the station does not need to initiate an RTS / CTS frame exchange before attempting to transmit after canceling transmission because the NAV has already been set by the CTS-to-Self frame. Also, if a station cancels transmission and still has a TXOP when it attempts to transmit again, the station can attempt transmission without a backoff procedure.

[0174] In FIG. 19, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). While transmitting to the first station (STA1), the first AP (AP1) determines that the first station (STA1) is in a blind state. Therefore, the first AP (AP1) suspends transmission to the first station (STA1). In FIG. 19(a), the first AP (AP1) determines that the channel for the first link (Link1) is idle. At this time, there are no remaining TXOPs, so the first AP (AP1) accesses the channel using the backoff procedure. In Figure 19(b), the first AP (AP1) determines that the channel of the first link (Link1) is not idle. At this time, since there is a TXOP remaining, the first AP (AP1) attempts to transmit without a backoff procedure.

[0175] In the above-described embodiment, if the channel is detected as idle for a pre-specified time interval without a separate backoff procedure after canceling a transmission to a station in a non-STR multilink device, the station that canceled the transmission to the station in the non-STR multilink device can transmit to a station other than the station in the non-STR multilink device. In this case, the duration of the pre-specified time interval can be an issue. A station that receives a PPDU of a canceled transmission may fail to decode the PPDU. In this case, if the channel is detected as idle for an extended interframe space (EIFS), the station that fails to decode the PPDU can initiate a backoff procedure. Therefore, an issue arises as to whether the pre-specified time interval should be set to be longer than or equal to the EIFS. This will be described with reference to FIG. 20.

[0176] FIG. 20 illustrates an operation in which an STR multilink device performs channel access again after halting transmission to a non-STR multilink device according to an embodiment of the present invention.

[0177] As shown in Figure 20(a), the pre-specified time interval may be DIFS. This takes into consideration that a station in an STR multilink device acquires a channel access opportunity through a contention procedure and loses the acquired channel access opportunity due to transmission collision between links. In other words, since a station in an STR multilink device acquires a channel access opportunity through a contention procedure, it is given priority over other stations attempting channel access. When EDCA is applied, DIFS may be replaced with AIFS [AC].

[0178] In yet another specific embodiment, as shown in Figure 20(b), the pre-specified time interval may be EIFS, which is in consideration of the fact that the STR multilink device can assume that it has already used up its transmission opportunities and of fairness with other stations.

[0179] In yet another specific embodiment, as shown in FIG. 20(c), when the signaling field of the PPDU signals that transmission may be interrupted, the pre-specified time interval may be DIFS. Also, when a station receiving a PPDU detects that transmission of the PPDU has been interrupted, the station can detect whether the channel is idle using DIFS instead of EIFS. In this case, if the channel is detected as idle using DIFS, the station can initiate a backoff procedure. This embodiment can improve the performance of the entire network and ensure fairness between stations. When EDCA is applied, DIFS can be replaced with AIFS [AC].

[0180] As described above, the STR multilink device can recognize that a transmission collision between links may occur. Specifically, when a first station of the STR multilink device completes a backoff procedure, a second station of the STR multilink device may be receiving a PPDU. If the second station fails to complete decoding of the signaling field of the PPDU, the first station may not recognize that a transmission collision between links has occurred, but may determine that it is possible. In this case, the first station may insert information indicating that transmission may be interrupted into the PPDU to be transmitted, as described above. Furthermore, the NSTR multilink device may transmit a CTS-to-Self frame before transmitting to a non-STR multilink device for stable and efficient transmission. This will be described with reference to FIG. 21.

[0181] FIG. 21 illustrates an operation in which an STR multilink device transmits a CTS-to-Self frame before transmitting to a non-STR multilink device according to an embodiment of the present invention.

[0182] A station in an STR multilink device can transmit a CTS-to-Self frame before transmitting to a non-STR multilink device. Specifically, if a second station in an STR multilink device attempts to transmit to a non-STR multilink device while a first station in the STR multilink device is receiving, the second station in the STR multilink device can transmit a CTS-to-Self frame before transmitting to the non-STR multilink device. This allows the second station to reserve a TXOP for transmission to the non-STR multilink device. Furthermore, before transmitting to the non-STR multilink device, the second station can determine whether a transmission for the first station is being transmitted from the non-STR multilink device. The second station can determine the destination station of a transmission based on whether a transmission for the first station is being transmitted from the non-STR multilink device. Specifically, if a transmission for the first station is not being transmitted from the non-STR multilink device, the second station can transmit to the non-STR multilink device. When a transmission for a first station is being sent from the non-STR multilink device, a second station may transmit to a station not included in the non-STR multilink device. For example, if the first station plans to transmit a SU-PPDU for a station in the non-STR multilink device, a MU-PPDU containing data for a station in the non-STR multilink device, or a PPDU containing a trigger frame that triggers a transmission for the station in the non-STR multilink device, the first station may cancel the planned transmission. In this case, the first station may attempt to transmit a SU-PPDU for a station other than a station in the non-STR multilink device, a MU-PPDU containing no data for a station in the non-STR multilink device, or a PPDU containing a trigger frame that does not trigger a transmission for the station in the non-STR multilink device.In this case, the first station can begin transmission after a time greater than SIFS from the time it transmits the CTS-to-Self frame. Specifically, the first station can begin transmission PIFS after it transmits the CTS-to-Self frame. The station that transmitted the CTS-to-Self frame must begin transmission SIFS after it transmits the CTS-to-Self frame. As in the above-described embodiment, when canceling a planned transmission and attempting a new transmission, processing time is required from the STR multilink device, such as generating a new MPDU to be transmitted. For this reason, exceptions to the regulations regarding the time interval between a CTS-to-Self frame and a transmission may be applied. In such an embodiment, the second station cannot transmit beyond the TXOP obtained by the CTS-to-Self frame.

[0183] In Figure 21, the STR multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The second AP (AP2) receives and schedules a transmission to a station in the non-STR multi-link device, so the first AP (AP1) transmits a CTS-to-Self frame before the scheduled transmission. As described above, the first AP (AP1) determines the destination station for transmission based on the judgment of the station that transmitted the PPDU received by the second AP (AP2). In addition, the first AP (AP1) transmits after SIFS or PIFS from the time it transmits the CTS-to-Self frame.

[0184] The second station can initiate the RTS / CTS frame exchange procedure by sending an RTS frame instead of a CTS-to-Self frame. This allows the second station to achieve a similar effect to sending a CTS-to-Self frame. In the case of an RTS / CTS frame exchange, the second station can acquire the TXOP only if the destination station is not blinded.

[0185] FIG. 22 illustrates a case in which multiple APs included in an STR multilink device transmit to multiple stations included in one non-STR multilink device according to an embodiment of the present invention.

[0186] Multiple stations included in one non-STR multilink device can receive simultaneously. This is because simultaneous reception by multiple stations causes relatively little interference. Figure 22 shows multiple stations included in one non-STR multilink device receiving simultaneously. In this case, to ensure stable operation of the non-STR multilink device, multiple APs included in the STR multilink device can perform multiple transmissions to multiple stations included in one non-STR multilink device, with the end of transmissions synchronized. This is described in Figure 23.

[0187] FIG. 23 shows an embodiment of the present invention in which multiple APs included in an STR multilink device perform multiple transmissions with synchronized end of transmission to multiple stations included in a single non-STR multilink device.

[0188] In non-STR links, when a multilink device transmits on one link, the multilink device can simplify the channel access procedure for transmissions on other links. Specifically, when a first station in the multilink device completes a backoff channel access procedure on the first link, if the channel is idle for a pre-specified time period in the link of a second station in the STR multilink device, the second station in the STR multilink device can begin transmission on the second link.

[0189] In a specific embodiment, when one station in an STR multilink device transmits to one station in a non-STR multilink device, the channel access procedure for other stations in the STR multilink device can be simplified. Specifically, when a first station in the STR multilink device completes a backoff channel access procedure for transmission to the first station in the non-STR multilink device, if the channel is idle for a pre-specified time interval in the link of the second station in the STR multilink device, the second station in the STR multilink device can begin transmission to the second station in the non-STR multilink device. In this case, the pre-specified time interval may be a PIFS. This operation may be applied when the first and second stations in the STR multilink device transmit to stations included in a single non-STR multilink device. In this embodiment, the first and second stations can begin transmission within a pre-specified time interval. The pre-specified time interval may be a slot time.

[0190] Furthermore, when a first station and a second station in an STR multilink device transmit to a station included in a single non-STR multilink device, the end of transmission of the first station and the second station may be synchronized. In this case, the synchronization of the end of transmission of the first station and the second station may mean that the transmission of the first station and the transmission of the second station end within a first pre-specified time interval. The first pre-specified time interval may mean within a slot boundary or a symbol boundary.

[0191] Multiple stations in a non-STR multilink device that receive synchronized transmission ends can simultaneously transmit subsequent transmissions, for example, responses. In this case, the responses can include an ACK. In conventional WLANs, subsequent transmissions are transmitted SIFS after reception. However, transmitting subsequent transmissions with a slight time difference between multiple transmissions that ended with a slight time difference can be more complex to implement than transmitting subsequent transmissions simultaneously. Therefore, as described above, multiple stations in a non-STR multilink device that receive synchronized transmission ends can simultaneously transmit subsequent transmissions. In this case, the interval between subsequent transmissions following at least one of the multiple transmissions whose transmission ends are synchronized may be the sum of SIFS and a time within a pre-specified time interval. Specifically, the transmission following the first transmission among the multiple transmissions whose transmission ends are synchronized may be transmitted at an interval that is the sum of SIFS and a time within a pre-specified time interval. In this case, the pre-specified time interval may be one of a slot time or a symbol length. Furthermore, the difference within a predetermined time interval may be the difference between the end of the last transmission among a plurality of transmissions whose end is synchronized and the first transmission among a plurality of transmissions whose end is synchronized.

[0192] In yet another specific embodiment, when multiple transmissions end with a time difference within a first pre-specified time interval, multiple stations receiving the transmission can transmit synchronized subsequent transmissions. The multiple subsequent transmissions with synchronized transmission ends can represent multiple subsequent transmissions transmitted with a time difference within a second pre-specified time interval. The difference within the second pre-specified time interval can be the difference between the end of the last completed transmission among the synchronized transmissions and the earliest completed transmission among the synchronized transmission ends. In this case, the second pre-specified time interval can be smaller than the first pre-specified time interval. A PPDU with synchronized transmission ends can be referred to as a sync PPDU.

[0193] In Figure 23, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) and the second AP (AP2) synchronize the end of transmissions to the first station (STA1) and the second station (STA2), respectively. That is, after the first station (STA1) finishes transmission, the second station (STA2) finishes transmission within a time period pre-specified by the first station (STA1). The first station (STA1) and the second station (STA2) simultaneously send ACKs. At this time, the first station (STA1) transmits an ACK after the difference between the end of transmission to the first station (STA1) (SIFS) and the end of transmission to the first station and the end of transmission to the second station (STA2).

[0194] This embodiment may be applied to transmissions for which the ACK policy is not set to No ACK. Specifically, it may also be applied when the ACK policy is not immediate. In a specific embodiment, when multiple stations in a multilink device receive transmissions whose end of transmission is synchronized, the multiple stations in the multilink device can simultaneously receive ACK requests and simultaneously transmit ACKs in response to the ACK requests. Multiple stations in a multilink device that receive transmissions for which the ACK policy is set to a value other than No ACK within a predetermined time period can simultaneously begin ACKs.

[0195] When non-STR multilink devices are present, they must be taken into consideration when transmitting RTS / CTS frames and CTS-to-Self frames to set TXOPs, as will be explained in Figures 24 to 29.

[0196] FIG. 24 shows multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention.

[0197] Even when a non-STR multilink device exists, the RTS / CTS frame exchange procedure can follow the procedure defined in the existing WLAN. The RTS / CTS frame can be used to set the NAV of a station operating on another link. Specifically, a station that receives an RTS / CTS frame can transmit it to other stations operating on links other than the one it operates on and included in the multilink device to which it belongs.

[0198] However, as in the previous embodiment, channel access or transmission may be restricted when a non-STR multilink device is present, which may prevent RTS / CTS transmission as shown in Figure 24. That is, a station planning to transmit to a first station in a non-STR multilink device may not attempt to exchange RTS / CTS frames if a second station in the non-STR multilink device is receiving.

[0199] In FIG. 24, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the first AP (AP1) transmits an RTS frame to the first station (STA1), channel access for the second station (STA2) is prohibited. The second AP (AP2) determines that channel access for 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, as will be described in FIG. 25.

[0200] FIG. 25 illustrates the hidden node problem that occurs in the RTS / CTS frame exchange procedure according to the embodiment described in FIG.

[0201] As described above, a station transmitting to a station in a non-STR multilink device may transmit without being able to exchange CTS / RTS. In this case, because a TXOP is not set for the other station, the other station may attempt to transmit, causing the station in the non-STR multilink device to fail to transmit or receive. In the example of FIG. 25, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). Due to the first AP (AP1) transmitting to the first station (STA1), the second AP (AP2) was unable to send an RTS frame before transmitting. Therefore, a TXOP for the second AP (AP2) transmission is not set for the station operating on the second link (Link2). Therefore, when the second AP (AP2) transmits to the second station (STA2), a station in another BSS (OBSS STA) transmits on the second link (Link2). As a result, the second station (STA2) fails to receive the transmission from the second AP (AP2). To solve this hidden node problem, the following embodiment may be applied.

[0202] In a specific embodiment, if any station in a non-STR multilink device is receiving, the station may not be allowed to transmit to any station in the non-STR multilink device. In yet another specific embodiment, if a station transmits to a first station in a non-STR multilink device and a second station in the non-STR multilink device is receiving, the station may transmit simultaneously with its transmission to the second station. If a station transmits to a first station in a non-STR multilink device and a second station in the non-STR multilink device is receiving, the station may synchronize the end of its transmission to the first station with the end of its transmission to the second station. Specifically, if a station transmits to a first station in a non-STR multilink device and a second station in the non-STR multilink device is receiving, the station may end its transmission to the first station simultaneously with its transmission to the second station. In such an embodiment, transmission to the second station may be performed by another station in the multilink device, including the station.

[0203] FIG. 26 shows multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention.

[0204] In yet another embodiment of the present invention, if a first station in a multilink device continues transmitting to a third station in a non-STR multilink device, and a second station in the multilink device attempts to transmit an RTS frame to a fourth station in the non-STR multilink device, the first station may end its transmission to the third station before the fourth station attempts to transmit the RTS frame. This allows the fourth station to transmit a CTS frame to the second station. This allows TXOP tentative setup for frame exchange between the second and fourth stations. However, it may be difficult for the first station to end its transmission before the fourth station attempts to transmit the RTS frame.

[0205] In yet another embodiment of the present invention, if a second station in the multilink device attempts to transmit an RTS frame to a fourth station in the non-STR multilink device while a first station in the multilink device continues transmitting to a third station in the non-STR multilink device, the second station can transmit the RTS frame to the fourth station to coincide with the end of the first station's transmission to the third station. To do this, the second station can insert padding into the RTS frame. In this case, the RTS frame may have an RTS frame format that allows for flexible adjustment of the transmission length. For convenience of explanation, this RTS frame format is referred to as an ML (multilink)-RTS frame. The ML-RTS frame may include a pad field for padding. For example, the format of the ML-RTS frame may be the same as the RTS frame format shown in FIG. 26. In addition, the first station can insert padding into the transmission to the third station to coincide with the end of the RTS frame.

[0206] In the embodiment of Figure 26, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second AP (AP2) transmits an ML-RTS frame to the second STA (STA2) in synchronization with the end of the first AP's (AP1) transmission to the first station (STA1). 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). As a result, a TXOP for frame exchange between the second AP (AP2) and the second station (STA2) is established in the station operating on the second link channel.

[0207] In yet another specific embodiment, another frame for setting NAV may be substituted for the RTS / CTS frame. In the above-described embodiment, an ACK request frame may be transmitted instead of the RTS frame. The ACK request frame may include duration information related to the transmission end point. In addition, a frame including an ACK transmitted in response to the ACK request may also include duration information. In this case, the duration information of the frame including the ACK may be set according to the duration information of the ACK request frame.

[0208] Although the above-described embodiment has been described for RTS / CTS frame exchange, it may also be used for control frame exchange other than RTS / CTS frames. In this case, the control frame exchange may include the exchange of PS-Poll frames and response frames to PS-Poll.

[0209] FIG. 27 shows that a multilink device transmits a response to a control frame exceptionally even when channel access is prohibited according to an embodiment of the present invention.

[0210] As described in the above embodiment, when a non-STR multilink device is present, channel access of some stations may be prohibited. Even if channel access of a station is prohibited, the station can still send a response to a control frame. Specifically, even if channel access of a station is prohibited, the station can still send a CTS frame in response to an RTS frame.

[0211] In this way, when a response to a control frame is transmitted as an exception to channel access denial, the following embodiment may be applied: A first station transmits a response to a control frame as an exception to channel access denial. When the first station transmits the response to the control frame, a third station transmits to a second station included in the multilink device including the first station. In this case, the third station can retransmit to the first station. The third station can anticipate that the transmission to the second station will fail.

[0212] In the example of FIG. 27, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The first AP (AP) transmits to the first station (STA1). The second AP (AP2) transmits an RTS frame to the second station (STA2). Because the first station (STA1) receives, channel access for the second station (STA2) is prohibited. However, the second station (STA2) transmits a CTS frame to the second AP (AP2) as an exception to the channel access prohibition. The first AP (AP1) can determine that the first AP's (AP1's) transmission is likely to fail due to the second station's (STA2's) CTS frame transmission. Therefore, the first AP (AP1) retransmits to the first station (STA1). The retransmission method is described in more detail in FIG.

[0213] FIG. 28 shows the retransmission of a transmission to a station of a non-STR multilink device.

[0214] In the retransmission described in FIG. 27, only some of the packets included in the initial transmission may be retransmitted. Specifically, the station performing the retransmission may retransmit only some of the packets included in the initial transmission. The station performing the retransmission may determine some of the packets included in the initial transmission to be retransmitted based on the time interval in which the station performing the retransmission received the CTS frame. Specifically, the station performing the retransmission may determine, among the packets included in the initial transmission, packets transmitted in a time interval including the time interval in which the station performing the retransmission received the CTS frame as the packets to be retransmitted. In this case, the station performing the retransmission may retransmit packets transmitted in a time interval including the time interval in which the station performing the retransmission received the CTS frame based on propagation delay. In yet another specific embodiment, the station performing the retransmission may retransmit all of the packets included in the initial transmission.

[0215] In addition, a station performing a retransmission can perform the retransmission before receiving an ACK for the transmission. In this case, after performing the retransmission, the station performing the retransmission can receive a Block ACK indicating whether the initial transmission and the retransmission were received. Therefore, the station performing the retransmission can perform the retransmission before a SIFS after the initial transmission. In yet another specific embodiment, a station that fails to receive a control frame transmitted as an exception to channel access prohibition can wait to receive the retransmission without transmitting an ACK.

[0216] 28, the first AP (AP1) retransmits the fourth and fifth packets, taking into account the interval during which the second AP (AP2) receives the CTS frame and the transmission delay. After the retransmission, the first AP (AP1) receives an ACK indicating whether the retransmission was received or not.

[0217] FIG. 29 shows that a control frame is transmitted on a link where a station that is not prohibited from channel access operates, rather than on a link where a station that is prohibited from channel access operates, according to an embodiment of the present invention.

[0218] As in the embodiment described in FIG. 26, the end of transmission for multiple stations in a non-STR multilink device may be synchronized. However, this may require adjusting an already generated MPDU or generating an MPDU again, which is difficult to implement. Therefore, the multilink device may transmit a control frame over a link in which a station in which channel access is not prohibited operates, rather than a link in which a station in which channel access is prohibited operates. Specifically, the multilink device may transmit a control frame over a link in which a station in the non-STR multilink device is currently receiving from the multilink device. In this case, the control frame may be an RTS frame.

[0219] In the embodiment of FIG. 29, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) transmits to the first station (STA1). Even if the second AP (AP2) successfully completes the backoff procedure, the second AP (AP2) cannot transmit to the second station (STA2) because the first station (STA1) is receiving a transmission from the first AP (AP1). At this time, the second AP (AP2) requests the first AP (AP1) to transmit an RTS frame with the second station (STA2) as the recipient. In this case, the first AP (AP1) may include an RTS frame for which the second station (STA2) is the recipient in the transmission currently being performed by the first AP (AP1). In yet another specific embodiment, after the first AP (AP1) finishes the transmission currently being performed by the first AP (AP1), the first AP (AP1) may transmit an RTS frame for which the second station (STA2) is the recipient via the first link (Link1) SIFS after the transmission. The first station (STA1) receives the RTS frame for which the second station (STA2) is the recipient and transmits the received RTS frame to the second station (STA2). The second station (STA2) performs CCA in the PIFS. If the channel is idle in the PIFS, the second station (STA2) transmits a CTS-to-Self frame. The first AP (AP1) may suspend transmission to the first station (STA1) during a time period in which the second station (STA2) is expected to transmit a response to the RTS frame. Also, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can transmit an ACK for the received transmission. In yet another specific embodiment, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can also transmit a response to the RTS frame.29 is provided to facilitate understanding of the explanation, and may also be used to transmit control frames other than RTS frames and CTS-to-Self frames. Also, time intervals other than PIFS may be used.

[0220] FIG. 30 illustrates a multi-link device sending an ACK according to an embodiment of the present invention.

[0221] A station in a multilink device can request a link for transmitting an ACK to a station in a non-STR multilink device. Specifically, a station in a multilink device can request that an ACK be transmitted on a link other than the link on which the transmission was made. In the example of FIG. 28, a first AP (AP1) in the STR multilink device transmits (Tx(#2)) to a first station (STA1) in a non-STR multilink device. At this time, the first AP (AP1) requests that an ACK for the transmission (Tx(#2)) be transmitted on the second link (Link2). This is because the first AP (AP1)'s transmission (Tx(#2)) to the second station (STA2) from the second AP (AP2) is completed before the first AP (AP1)'s transmission (Tx(#2)) to the second station (STA2) is completed, and it is determined that it is difficult to transmit an ACK for the first AP (AP1)'s transmission (Tx(#2)).

[0222] In addition, for such ACK transmission, the station can set an implicit BAR and ACK policy so as not to send an immediate response to the transmission. In yet another specific embodiment, the station can set the ACK policy for the transmission to BlockAckReq. However, in order to send a Block ACK, a BlockAckReq must be sent, which may result in channel access overhead and transmission delays. Therefore, a new ACK policy for multilink devices is needed.

[0223] A station in a multilink device can transmit both an ACK for a transmission received by the station and an ACK for a transmission received by another station included in the same multilink device. This type of ACK transmission can be called ML (multilink)-ACK. An ACK policy, ML-ACK, can also be configured. In the embodiment of FIG. 30, the first AP (AP1) configures the ACK policy for transmission (Tx(#2)) as ML-ACK. After receiving transmission (Tx(#2)), the first station (STA1) does not transmit an ACK to the first AP (AP1). After completing reception of the transmission from the second AP (AP2), the second station (STA2) transmits to the second AP (AP2) both an ACK for the transmission from the first AP (AP1) and an ACK for the transmission from the second AP (AP2). The non-STR multilink device may include a third station (STA3) in addition to the first station (STA1) and the second station (STA2), and the STR multilink device may include a third AP (AP3) in addition to the first AP (AP1) and the second AP (AP2). In this case, the ACK policy for transmissions from the second AP (AP2) to the second station (STA2) may also be set to ML-ACK. If transmissions from the third AP (AP3) to the third station (STA3) are completed later than transmissions from the second AP (AP2) to the second station (STA3), the third station (STA1) may transmit ACKs for transmissions from the first AP (AP1) to the first station (STA1), ACKs for transmissions from the second AP (AP2) to the second station (STA2), and ACKs for transmissions from the third AP (AP3) to the third station (STA3).

[0224] This embodiment can prevent interference between links that may occur due to ACK transmissions even if transmissions to stations in non-STR multilink devices are not completed simultaneously. In the above-described embodiment, the ACK policy may be set to BlockAck instead of ML-ACK. In yet another specific embodiment, the ACK policy may be set to NoAck instead of ML-ACK.

[0225] While a multilink device transmits traffic, the number of links that have acquired a transmission opportunity may increase. In this case, the multilink device may transmit traffic that was intended to be transmitted on a link that acquired a transmission opportunity earlier on a link that acquired a transmission opportunity later. In this case, the NAV set on the link where the multilink device acquired a transmission opportunity earlier may be set higher than the NAV required to transmit the traffic. If the NAV set on the link where the multilink device acquired a transmission opportunity earlier is higher than the NAV required to transmit the traffic, the multilink device can reset the NAV by transmitting a CF-END frame after completing transmission on the link that acquired a transmission opportunity earlier.

[0226] The above-mentioned reception of the Sync PPDU and signaling related to the reception of the Sync PPDU will be described with reference to FIGS.

[0227] In order for a first station in a non-STR multilink device to receive the Sync PPDU, it must determine whether a second station in a non-STR relationship with the first station has begun receiving the Sync PPDU. Furthermore, the first station must continuously perform preamble detection (PD). Considering that the first station receiving the Sync PPDU is denied channel access due to the reception activity of another station in the non-STR multilink device, this behavior of the first station may be unreasonable. Therefore, the first station can enter a power-saving state within pre-specified conditions. The Sync PPDU may be transmitted within an existing TXOP. Therefore, the performance gain obtained by receiving the Sync PPDU may be determined by the length of the remaining TXOP. Therefore, the first station can determine whether to give up receiving the Sync PPDU based on the length of the Sync PPDU. If the first station gives up receiving the Sync PPDU, the first station can enter a power-saving state. This power-saving operation can be referred to as inter-link TXOP power save (PS). A station that entered the power-save state through an inter-link TXOP PS can wake up from the power-save state to receive frames periodically transmitted from the AP, such as a beacon frame, a TIM frame, and a DTIM frame. Also, when the TXOP ends, for example, when a CF-END frame is transmitted, a station that entered the power-save state through an inter-link TXOP PS can wake up from the power-save state.

[0228] The above-mentioned TXOP may be changed to a period indicated by the length field of the signaling field of the PPDU and the duration field of the MAC frame. Specifically, in the above-mentioned embodiment, the station can determine the time occupied by the PPDU based on the period indicated by the length field and the duration field of the MAC frame.

[0229] A non-AP multilink device can signal to an AP multilink device information regarding whether it supports receiving a sync PPDU and information regarding the conditions for supporting the sync PPDU. Furthermore, an AP multilink device can signal to a non-AP multilink device whether it will transmit a sync PPDU. Here, the multilink device can signal whether it supports a sync PPDU for each multilink device. For example, an AP multilink device can signal whether it supports transmitting a sync PPDU for each AP multilink device. In yet another specific embodiment, a multilink device can signal whether it supports a sync PPDU for each station. Specifically, an AP multilink device can signal whether it supports transmitting a sync PPDU for each AP included in the AP multilink device. For example, an AP multilink device including a first AP, a second AP, and a third AP can indicate that the first AP supports transmitting a sync PPDU and that the second and third APs do not support transmitting a sync PPDU.

[0230] If an AP multilink device associated with a non-AP multilink device signals that it does not support sync PPDU transmission, a station in the non-AP multilink device can enter the inter-link PS power-save state described above while other stations in the non-AP multilink device are receiving. This is because the AP multilink device associated with the non-AP multilink device cannot transmit sync PPDUs. In this case, the station in the non-AP multilink device can determine the length of time to maintain the power-save state based on the length of the PPDU received by other stations in the non-AP multilink device.

[0231] Whether the transmission or reception of the Sync PPDU is supported may be determined by an operation policy in addition to hardware performance. Therefore, whether the transmission or reception of the Sync PPDU is supported may be signaled by information on an operating mode in addition to information on performance. A method for signaling whether the transmission or reception of the Sync PPDU is supported will be described in detail with reference to FIG. 31.

[0232] FIG. 31 shows an element field indicating information regarding support for receiving or transmitting a sink PPDU according to an embodiment of the present invention.

[0233] As described above, information indicating whether Sync PPDU transmission is supported may be included in an element indicating station capabilities. For ease of explanation, the element indicating station capabilities is called a Capability element. Furthermore, the field of the Capability element containing information indicating whether Sync PPDU transmission is supported is called a Supporting Sync PPDU Tx subfield. In this case, the Capability element may be a Multi-Link element indicating multi-link capabilities. Furthermore, the Capability element may be an EHT Capability element indicating EHT-related capabilities. Figure 31(a) shows an example of a Capability element.

[0234] If the value of the Supporting Sync PPDU Tx subfield is 1, it may indicate that the station or multilink device indicated by the Supporting Sync PPDU Tx subfield supports sync PPDU transmission. If the value of the Supporting Sync PPDU Tx subfield is 0, it may indicate that the station or multilink device indicated by the Supporting Sync PPDU Tx subfield does not support sync PPDU transmission. Furthermore, when a station not included in the multilink device transmits a Capability element, the Supporting Sync PPDU Tx subfield may signal information that is not unrelated to whether sync PPDU transmission is supported or may be used as a reserved field.

[0235] As described above, information indicating whether or not sync PPDU reception is supported may be included in an element indicating station operation-related information. For ease of explanation, an element indicating station operation-related information is referred to as an Operation element. Furthermore, a field in the Operation element for information indicating whether or not sync PPDU reception is supported is referred to as a Supporting Sync PPDU Rx Disable subfield. Figure 31(b) shows an example of an Operation element. When the Supporting Sync PPDU Rx Disabled subfield has a value of 1, it may indicate that reception of a sync PPDU is not desired. Specifically, when the Supporting Sync PPDU Rx Disabled subfield has a value of 1, the Supporting Sync PPDU Rx Disabled subfield may indicate that the station transmitting the Supporting Sync PPDU Rx Disabled subfield does not want to wait for reception of a sync PPDU. In a multilink device that sets the Supporting Sync PPDU Rx Disabled subfield to 1, the second station of the multilink device does not need to perform PD and CCA while the first station of the multilink device is receiving. An AP multilink device connected to a multilink device that transmitted the Supporting Sync PPDU Rx Disabled subfield does not simultaneously transmit PPDUs to multiple stations of the multilink device that transmitted the Supporting Sync PPDU Rx Disabled subfield. The PPDU may be an SU PPDU, Full BW MU PPDU, or OFDMA MU PPDU transmitted in any one of non-HT PPDU, HT PPDU, VHT PPDU, HE PPDU, and EHT PPDU formats. In this case, the AP multilink device must not transmit a response, for example, a frame requesting an immediate response.The frame requesting a response may include at least one of an RTS, a Multi-User RTS (MU-RTS), a trigger frame, and a Block Ack Request (BAR).

[0236] The Operation element may also include information related to the minimum length of a sync PPDU that can be received by the station or multilink device that transmitted the Operation element. In this case, a subfield indicating information related to the minimum length of a sync PPDU is referred to as a Remaining TXOP Threshold subfield. The Remaining TXOP Threshold subfield may indicate time. The Remaining TXOP Threshold subfield may also be indicated in us, ms, or symbol units. A multilink device connected to the multilink device that transmitted the Remaining TXOP Threshold subfield may not be allowed to transmit a sync PPDU that is shorter than the length indicated by the Remaining TXOP Threshold subfield to the multilink device or station that transmitted the Remaining TXOP Threshold subfield.

[0237] Furthermore, when the Remaining TXOP Threshold subfield is set to a pre-specified value, it may indicate that the multilink device or station that transmitted the Remaining TXOP Threshold subfield does not support receiving Sync PPDUs. The pre-specified value may be a value indicating a time greater than the maximum time that the Remaining TXOP Threshold subfield can indicate. In yet another specific embodiment, the pre-specified value may be 0. When such an embodiment is applied, the Sync PPDU Rx Disable subfield may be omitted from the Operation element.

[0238] Also, in the above-mentioned embodiment, it has been described that the Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield can be signaled by the Operation element. The Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield can be signaled by an element other than the Operation element or by signaling information. Figures 32 to 34 describe an embodiment in which the inter-link TXOP power save mode is performed by the signaling described in Figure 31.

[0239] FIG. 32 illustrates an inter-link TXOP power save mode operation in a non-STR multi-link device according to an embodiment of the present invention.

[0240] If a non-STR multilink device signals that it does not support sync PPDU reception, a second station in the non-STR multilink device may enter a power-save state while a first station in the non-STR multilink device is receiving. In this case, the second station may maintain the power-save state until the end of the TXOP indicated in the PPDU received by the first station. As described above, the second station may predict that it will receive a frame periodically transmitted from the AP before the end of the TXOP indicated in the PPDU received by the first station. In this case, the second station may wake up from the power-save state before the end of the TXOP indicated in the PPDU received by the first station. As described above, the frame periodically transmitted from the AP may include at least one of a beacon frame, a TIM frame, and a DTIM frame.

[0241] The second station may maintain a power-saving state even after the end of the TXOP indicated by the PPDU received by the first station. Specifically, the second station may determine whether to maintain a power-saving state even after the end of the TXOP indicated by the PPDU received by the first station, based on information received from the AP to which the second station is connected. In this case, the information received from the AP to which the second station is connected may be NAV-related information. Also, the information received from the AP to which the second station is connected may be operation information of the AP to which the first station is connected. If the NAV set by the second AP of the AP multilink device currently transmitting to the second station of the non-AP multilink device has not yet expired, the first AP of the AP multilink device may transmit information regarding the expected end of the first AP's transmission or reception and the expected expiration of the NAV to the first station of the non-AP multilink device that signaled that it does not wish to receive a sync PPDU. If the NAV set by the second AP of the AP multilink device currently transmitting to the second station of the non-AP multilink device has not expired, the second AP may transmit or receive a PPDU from any one of the stations.If the NAV set by the second AP of the AP multilink device currently transmitting to the second station of the non-AP multilink device has not expired, the NAV may be set in the second AP by a PPDU not transmitted by the second station.

[0242] In the embodiment of Figure 32, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The non-STR non-AP multilink device signals that it does not wish to receive a sync PPDU. The first AP (AP1) transmits to the first station (STA1). At this time, the second station (STA2) remains in a power-saving state until the end of the TXOP indicated in the PPDU transmitted by the first AP (AP1) to the first station (STA1).

[0243] FIG. 33 shows a station in a non-STR multilink device entering a power saving state while waiting to receive a sync PPDU according to an embodiment of the present invention.

[0244] A first station in a non-STR multilink device can enter a power-saving state for an inter-link TXOP if the remaining duration of the TXOP indicated in the PPDU being received by the first station in the non-STR multilink device is equal to or shorter than the length indicated in the Remaining TXOP Threshold subfield transmitted by the non-STR multilink device. Before entering the power-saving state, a second station can receive a sync PPDU transmitted to the second station if the remaining duration of the TXOP indicated in the PPDU being received by the first station is greater than the length indicated in the Remaining TXOP Threshold subfield transmitted by the non-STR multilink device. To do so, the second station can perform PD to determine whether the intended recipient of the received PPDU is the second station. Specifically, the second station can determine whether the AID indicated in the signaling field of the PPDU or the RA of the MAC frame included in the PPDU indicates the second station.

[0245] In the embodiment of FIG. 33, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multilink device signals its desire to receive a sink PPDU. At this time, the non-STR non-AP multilink device also signals the minimum TXOP length "a" required to receive the sink PPDU. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sink PPDU. If 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-save state.

[0246] FIG. 34 shows a station in a non-STR multilink device entering a power saving state while waiting to receive a sync PPDU according to yet another embodiment of the present invention.

[0247] If a station in a non-STR multilink device detects a PPDU other than a Sync PPDU from a BSS operated by an AP connected to the station in the non-STR multilink device while waiting to receive a Sync PPDU, the station in the non-STR multilink device can enter the inter-link TXOP power-saving state. In this case, the station can determine that a PPDU that is not the intended recipient of the station is not a Sync PPDU. Also, if a station detects a PPDU other than a Sync PPDU from a BSS operated by an AP connected to the station in the non-STR multilink device even if the minimum TXOP signaled by the station remains, the station in the non-STR multilink device can enter the inter-link TXOP power-saving state.

[0248] In the embodiment of FIG. 34, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multilink device signals its desire to receive a sync PPDU. At this time, the non-STR non-AP multilink device also signals the minimum TXOP length "a" required to receive the sync PPDU. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sync PPDU. The second station (STA2) detects that a PPDU other than the sync PPDU is being transmitted from the BSS to which the second station belongs. Although the TXOP of the PPDU sent by the first AP (AP1) to the first station (STA1) is larger than "a", the second station (STA2) enters the inter-link TXOP power saving state.

[0249] In the above-mentioned blind state, for example, when other stations in a multilink device including a station are transmitting, the station may perform carrier sensing at the physical layer, making it difficult to accurately determine the state of the transmission medium. Specifically, a station in a non-STR multilink device may experience interference due to transmission. Due to the interference, even if a station in a non-STR multilink device performs carrier sensing, it may be difficult to determine the state of the current transmission medium. In this case, carrier sensing may be the above-mentioned CCA. As described above, CCA may include at least one of PD and ED. Therefore, in the blind state, a station may not be able to set its NAV based on a PPDU or frame transmitted by another station. Therefore, if a station exiting the blind state immediately attempts channel access, transmission collision may occur. To prevent this, channel access of a station exiting the blind state may be restricted. In this case, channel access restriction may indicate that a station determines whether a wireless medium is idle using stricter criteria than those used when channel access restriction is not applied. Specifically, when a station's channel access is restricted, the station can determine that the wireless medium is busy because the NAV is set. In the following embodiments, "channel access restriction" may refer to the channel access restriction according to such an embodiment. Specifically, the channel access of a station that has left the blind state may be restricted for a specified time from the time the station leaves the blind state. For convenience of explanation, the specified time is referred to as a channel access restriction time. Also, the time period during which the channel access restriction time is applied is referred to as a channel access restriction period.

[0250] In a specific embodiment, the channel access restriction time may be NAVSyncDelay. The channel access restriction time may be set based on the maximum possible length of a PPDU. For example, the channel access restriction time may be Max PPDU (aPPDUMaxTime) + SIFS + BAtime. Here, Max PPDU (aPPDUMaxTime) represents the maximum possible length of a PPDU. BAtime represents the time required to transmit a BA frame. For example, if the maximum length of an HE PPDU is the longest among the maximum lengths of PPDUs supported by the station, Max PPDU (aPPDUMaxTime) may be 5.484 ms. SIFS may be 16 us. This embodiment can prevent a station in a blind state with no NAV set from attempting channel access immediately after entering the blind state, resulting in a transmission collision. Furthermore, this embodiment can prevent a station from causing a transmission collision even when the station enters a power saving state in the blind state, as described above.

[0251] A station whose channel access is restricted in a channel access restricted section can perform CCA, which allows the station to receive a PPDU and set its NAV based on the received PPDU or a frame included in the PPDU.

[0252] FIG. 35 illustrates how channel access for stations coming out of the blind state is restricted according to an embodiment of the present invention.

[0253] If a station in a non-STR multilink device frequently enters a blind state, the channel access restriction described above may excessively restrict the channel accessibility of the station. In particular, if the channel access restriction time is set to an excessively large value, such as NAVSyncDelay, the channel access restriction may excessively restrict the channel accessibility of the station.

[0254] In the embodiment of FIG. 35, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits an UL PPDU on the first link (Link1), the second station (STA#2) switches to a blind state. As described above, the second station (STA#2) may not be able to perform PD in the blind state. When the second station (STA#2) exits the blind state, the second station (STA#2) performs CCA during the channel access restriction time. In this case, the channel access restriction time may be NAVSyncDelay, as described above. The second station (STA#2) can attempt channel access when the channel access restriction period expires and NAV is not set. In this case, the channel access may include a backoff procedure. Such channel access restriction may be repeated every time the second station (STA#2) switches to and returns from the blind state. If the first station (STA#1) transmits frequently, the channel accessibility of the second station (STA#2) may be excessively restricted.

[0255] To prevent this, the channel access restriction time may be set according to another embodiment other than the above-described embodiment. In a specific embodiment, the channel access restriction time may be set according to the situation to prevent excessive restriction of the channel accessibility of non-STR stations. This will be described with reference to FIG. 36.

[0256] FIG. 36 shows how channel access for stations coming out of the blind state is restricted according to yet another embodiment of the present invention.

[0257] The channel access restriction time of a station may be determined based on the time the station maintained a blind state immediately before channel access. Specifically, the channel access restriction time of a station may be equal to the time the station maintained a blind state immediately before channel access. For example, if a station was in a blind state for 5 ms and then emerged from the blind state, the station's channel access may be restricted for 5 ms. If a station was in a blind state for 1 ms and then emerged from the blind state, the station's channel access may be restricted for 1 ms. In yet another specific embodiment, the channel access restriction time may be the sum of the time the station maintained a blind state, the SIFS, and the time taken to transmit a BA frame. The time taken to transmit an ACK frame may be used instead of the time taken to transmit a BA frame.

[0258] The duration of the blind state can be determined based on the length of the transmission that caused the blind state. That is, the duration of the blind state may be equal to the duration of the transmission that caused the blind state. In yet another specific embodiment, when the channel access restriction time is set to a time shorter than the maximum channel access restriction time, the station can use a value smaller than the ED threshold used after the maximum channel access restriction time has expired as the ED threshold from the time the channel access restriction period expires until the time equal to the maximum channel access restriction time has expired. In this case, the maximum channel access restriction time may be NAVSyncDelay. For example, the station's channel access restriction time may be a time shorter than NAVSyncDelay. In this case, when the station exits the blind state and the channel access restriction period expires, the station can attempt channel access. After the channel access restriction period expires and the station exits the blind state, the station can perform ED at -72 dBm from the time the station exits the blind state until the maximum channel access restriction time has expired. In this case, the station can perform ED at -62 dBm from the time the station exits the blind state and after the maximum channel access restriction time has expired.

[0259] In yet another specific embodiment, the channel access restriction time of the station may be determined as the time the station maintains the blind state plus a pre-specified time, for example, the channel access restriction time of the station may be the sum of the time the station maintains the blind state, the length of the SIFS, and the length of the ACK frame.

[0260] In yet another specific embodiment, the channel access restriction time of a station may be determined as a multiple of the time the station has maintained the blind state. In this way, determining the length of the channel access restriction time based on the time the station has maintained the blind state reflects the fact that the longer the blind state is maintained, the more likely it is that the station will not be able to receive PPDUs transmitted by other stations.

[0261] In the example of FIG. 36, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits a UL PPDU on the first link (Link1), the second station (STA#2) switches to a blind state. The second station (STA#2) maintains the first blind state for x us. Immediately after the first blind state, the channel access of the second station (STA#2) is restricted for x us. In addition, the second station (STA#2) maintains the second blind state for y us. Immediately after the second blind state, the channel access of the second station (STA#2) is restricted for y us. Also, the first station (STA#1) maintains the first blind state for z us. Immediately after the first blind state, the channel access of the first station (STA#1) is restricted for z us.

[0262] The other embodiments described above may be applied to the embodiment of Fig. 36. That is, the channel access restriction time may be the sum of the time the station maintains the blind state, the SIFS, and the time it takes to transmit a BA frame. Instead of the time it takes to transmit a BA frame, the time it takes to transmit an ACK frame may be used.

[0263] In yet another specific embodiment, the channel access restriction time may be determined based on whether the time the station maintains the blind state is within a predetermined threshold. In this case, the threshold may be a value negotiated between the AP of the STR multilink device and the non-STR multilink device. This will be described with reference to FIG. 37.

[0264] FIG. 37 shows how channel access for stations coming out of the blind state is restricted according to yet another embodiment of the present invention.

[0265] If the time that the station maintains the blind state is equal to or less than a pre-specified threshold, the channel access restriction time of the station may be a first pre-specified value. If the time that the station maintains the blind state is greater than the pre-specified threshold, the channel access restriction time of the station may be a second pre-specified value. In this case, the first pre-specified value is smaller than the second pre-specified value.

[0266] In the example of FIG. 37, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits an UL PPDU on the first link (Link1), the second station (STA#2) switches to a blind state. The second station (STA#2) remains in the first blind state for a time greater than a threshold. Therefore, the second station (STA#2) has restricted channel access for a second pre-specified time (Long NAVSyncDelay). The second station (STA#2) remains in the second blind state for a time less than the threshold. Therefore, the second station (STA#2) has restricted channel access for a first pre-specified time (Short NAVSyncDelay).

[0267] In another specific embodiment, the channel access restriction time may be determined depending on which of a plurality of stages the time the station maintains in the blind state corresponds to. Specifically, there are four thresholds for the time the station maintains in the blind state, and five stages may exist depending on the four thresholds. In this case, if the time the station maintains in the blind state corresponds to stage two, the channel access restriction time is set to the two-stage channel access restriction time.

[0268] Also, the channel access restriction time corresponding to the lowest level may be 0. That is, if the time that a station maintains the blind state is equal to or less than a specific value, the channel access restriction may not be applied. This will be explained with reference to FIG.

[0269] FIG. 38 shows that according to yet another embodiment of the present invention, channel access is not restricted when a station that has come out of the blind state meets certain conditions.

[0270] If at least one of pre-specified conditions is satisfied, the station's channel access may not be restricted immediately after the station exits the blind state. That is, if none of the pre-specified conditions is satisfied, the station's channel access may be restricted immediately after the station exits the blind state. This prevents the station's channel accessibility from being excessively restricted. Specifically, as described above, if the time period during which the station maintains the blind state is equal to or less than a specific value, the channel access restriction may not be applied. In this case, the specific value may be determined based on the time required to transmit a specific frame. Specifically, the specific value may be determined based on the length of the specific frame. For example, the specific value may be determined based on the length and transmission rate of the specific frame. In such an embodiment, the specific frame may be at least one of an ACK frame, a BA frame, and a CTS frame. In yet another specific embodiment, if the time period during which the station maintained the blind state is included in the NAV set for the station, the channel access restriction may not be applied to the station after the station exits the blind state. This embodiment, which does not apply channel access restrictions, can prevent excessive restriction of channel accessibility for stations that have left the blind state when relatively short frames, such as ACK frames, BA frames, and CTS frames, are transmitted.

[0271] In yet another specific embodiment, if a station has a NAV set when it exits the blind state, no other channel access restriction other than the NAV may be applied to the station after it exits the blind state. Specifically, if the station switches to the blind state while a NAV is set and then exits the blind state, no other channel access restriction may be applied to the station. That is, the channel access restriction time may be 0. This is because it is highly likely that no other stations are transmitting due to the NAV.

[0272] When a NAV is set in a channel access restriction period, a station can access the channel without channel access restriction during a portion of the channel access restriction period. Specifically, in the above-described embodiment, the NAV set in the station may be the NAV set after the station switches to the blind state. Specifically, the first station may receive a PPDU and switch to the blind state before the first station completes reception of the PPDU. That is, a second station in a non-STR multi-link device including the first station may start transmitting a PPDU while the first station is receiving the PPDU. In this case, the first station may complete reception of the PPDU and set the NAV. Furthermore, completion of reception of the PPDU may represent the generation of a PHY-RXEND.indication primitive. Furthermore, if the first station enters the blind state during reception of the PPDU and fails to complete reception of the PPDU, the first station may set the NAV to the point at which reception of the PPDU is expected to be completed.

[0273] In the above-described embodiment, the NAV may indicate a NAV when a single NAV is operated. The NAV may also indicate a NAV when multiple NAVs are operated. The multiple NAVs may be a basic NAV and an intra-BSS NAV. The intra-BSS NAV is configured by an intra-BSS PPDU. The basic NAV is configured by an inter-BSS PPDU or a PPDU that does not distinguish between an intra-BSS PPDU and an inter-BSS PPDU.

[0274] In the above-described embodiments, "setting the NAV" refers to setting the NAV to a non-zero value. In the above-described embodiments, "setting the NAV" may refer to updating the NAV. A station may obtain duration information from a PPDU or a frame and set the NAV according to the duration information. Specifically, the station may obtain the duration information from the signaling field of the PPDU. In a specific embodiment, the station may obtain the duration information from the HE-SIG-A field or the U-SIG field of the PPDU. Alternatively, the station may obtain the duration information from the Duration / ID field of the MAC header of an MPDU included in the PPDU. Alternatively, the station may set the NAV at the end of the PPDU according to the duration information obtained from the PPDU, or may set the NAV at the end of the PPDU according to the duration information obtained from a frame included in the PPDU. In this case, the station may determine the end of the PPDU based on the L-SIG field included in the PPDU. Specifically, the station obtains the duration of the PPDU using the L_LENGTH field and L_DATARATE field of the L-SIG field, and can determine the end of the PPDU based on the obtained duration.

[0275] Furthermore, if a station switches to a blind state and then exits the blind state while the link on which the station operates is occupied by a PPDU transmitted by another station, channel access restrictions may not be applied to the station after the station exits the blind state. For convenience of explanation, a non-STR multi-link device will be described as including a first station and a second station, with the first station operating on the first link and the second station operating on the second link. While the first link is occupied by a PPDU transmitted by a third station operating on the first link, the first station operating on the first link may switch to the blind state due to transmission by the second station. The first station may exit the blind state before the transmission of the PPDU transmitted by the third station is completed. In this case, the first station may attempt channel access without channel access restrictions. In such an embodiment, channel access restrictions may not be applied to the station after the station exits the blind state only if the recipient address of the PPDU occupying the link does not indicate the station or the station is not the intended recipient of the PPDU. In yet another specific embodiment, channel access restrictions may not be applied to a station after it exits the blind state, regardless of the recipient address or intended recipient of a PPDU occupying a link. In such an embodiment, the station may determine the end of a PPDU based on the L-SIG field as described above. In yet another specific embodiment, the station may determine the end of a PPDU based on information about a TXOP included in the PPDU. Specifically, the station may determine the end of a PPDU based on the TXOP indicated by the signaling field of the PPDU. Alternatively, the station may obtain the duration field of an MPDU included in the PPDU and determine the end of the PPDU based on the TXOP indicated by the duration field.

[0276] In the above embodiment, a station can determine that it has exited the blind state when another station in the non-STR multilink device in which the station is included has finished transmitting.

[0277] In the embodiment of FIG. 38, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits an UL PPDU on the first link (Link1), the second station (STA#2) switches to a blind state. As described above, if the second station (STA#2) satisfies certain conditions, channel access restriction is not applied to the second station (STA#2) after it leaves the blind state. For example, if the time the second station (STA#2) remains in the blind state is shorter than a predetermined time (No NavSyncDelay Threshold), channel access restriction may not be applied even if the second station (STA#2) has just left the blind state. In yet another specific embodiment, if a NAV is set for a second station (STA#2) and the second station (STA#2) remains in a blind state while the NAV is applied, channel access restriction may not be applied even immediately after the second station (STA#2) leaves the blind state.

[0278] If a station's first channel access transmission during a channel access restricted period fails, the station may not be allowed to access the channel for the remaining channel access restricted periods. Specifically, in the above-described embodiments, an embodiment in which channel access restriction is relaxed has been described. That is, an embodiment in which channel access is restricted for a time shorter than the maximum value of the channel access restricted time, or an embodiment in which channel access is not restricted at all, has been described. In these embodiments, if channel access restriction relaxation is applied to a station and a transmission collision occurs due to the station's first transmission after the station has emerged from a blind state, channel access restriction may be applied to the station for a certain period of time. Specifically, if channel access restriction relaxation is applied to a station and the station's first transmission fails after the station has emerged from a blind state, channel access may be restricted for a certain period of time from when the station determines that the transmission of its first frame has failed. In this case, the certain period of time may be determined based on the maximum value of the channel access restricted time. That is, the station may not be allowed to transmit during the channel access restricted period remaining after the station determines that the transmission of its first frame has failed. Therefore, the station does not need to attempt transmission during the channel access restricted period remaining after the station determines that the transmission of its first frame has failed. Also, channel access restriction may be such that a station determines that a NAV is set when determining whether a wireless medium is idle.

[0279] In this case, the first transmission may refer to the first transmission among transmissions performed by EDCA. Therefore, even if a transmission in response to a frame received by the station fails, channel access restriction may not be applied for a certain period of time. The transmission in response to a frame received by the station may include at least one of an ACK frame transmission, a BA frame transmission, a CTS frame transmission, and a TB PPDU. Furthermore, the first transmission may refer to the first transmission before the station receives a frame that sets the station as the destination device or intended recipient. Furthermore, the first transmission may refer to a transmission performed before the maximum channel access restriction time has elapsed since the station left the blind state. In this case, even if the station attempts to transmit after the maximum channel access restriction time has elapsed since the station left the blind state and the transmission fails, the station's channel access is not restricted.

[0280] In the above-described embodiment, not applying channel access restriction may include canceling the channel access restriction after the channel access restriction has been applied. For example, the operation of not applying channel access restriction may be setting the remaining time of the channel access restriction period to 0 when a condition corresponding to an exception to the application of channel access restriction is met after the channel access restriction has been applied.

[0281] FIG. 39 illustrates an Operation element containing information regarding channel access restriction times according to an embodiment of the present invention.

[0282] As described in FIG. 37, the channel access time may be determined based on the time the station maintains the blind state. The AP may signal the threshold for the time the station maintains the blind state used in such an embodiment using an element of a management frame. The AP may also signal the channel access restriction time using an element of a management frame. The AP may also signal whether to adaptively adjust the channel access restriction time based on the time the station maintains the blind state using an element of a management frame. In such an embodiment, the element of the management frame may be an Operation element.

[0283] The station may determine a channel access restriction time based on a threshold value for the time the station has maintained a blind state signaled from the AP associated with the station. The station may also apply channel access restriction based on the channel access restriction time signaled from the AP associated with the station. The station may also apply channel access restriction based on whether to adaptively adjust the channel access restriction time signaled from the AP associated with the station based on the time the station has maintained a blind state.

[0284] In the embodiment of Figure 39, NoNAVSyncDelayThreshold indicates a threshold that determines whether channel access restriction is applied, ShortNAVSyncDelayThreshold indicates a threshold that determines whether a relatively short length of channel access restriction time is applied, and ProportionalNAVSyncDelay indicates whether the channel access restriction time is determined based on the time the station remains in the blind state.

[0285] As an exception to the channel access restriction described above, a station may be permitted to transmit a PPDU in a channel access restricted section whose transmission begins simultaneously with the PPDU transmission of another station in the non-STR multilink device to which the station belongs. In this case, the simultaneous start of transmission of multiple PPDUs may mean that the transmission begins within a predetermined time difference. A PPDU whose transmission begins within a predetermined time difference from the start of transmission of another PPDU is called a Start Sync PPDU. This is described with reference to FIG. 40.

[0286] FIG. 40 illustrates a case in which a station simultaneously transmits with other stations in a non-STR multi-link device in which the station is included in a channel access restricted period according to an embodiment of the present invention.

[0287] When a station in a non-STR multilink device transmits an Initiate Sync PPDU, the transmission end point may differ from that of a synchronized PPDU. In this case, the station may be restricted not to request an immediate response. The immediate response may include at least one of an ACK frame and a BA frame. Specifically, a station that transmits an Initiate Sync PPDU whose transmission ends first may be restricted not to request an immediate response. In this case, the general response rule may not be applied. Furthermore, an immediate response may not be transmitted based on the judgment of the station that received the Initiate Sync PPDU. Specifically, a station that receives the Initiate Sync PPDU may determine whether to transmit an immediate response based on whether the received PPDU is an Initiate Sync PPDU and whether the PPDU that transmitted the Initiate Sync PPDU is a station in a non-STR multilink device.

[0288] Also, assume that a first station and a second station of a non-STR multilink device are operating on the first and second links, respectively. If the first station acquires a transmission opportunity on the first link through a backoff procedure, and the second station detects that the second link is idle in the PIFS at the time of acquiring the transmission opportunity, both the first and second stations can transmit a StartSync PPDU. In this case, the second station can transmit a StartSync PPDU immediately after exiting the blind state, even if channel access restrictions are applied. Even in this embodiment, the second station must detect that the channel is idle in the PIFS. Therefore, if the second station detects that the channel is busy through CCA at the time of transmitting the StartSync PPDU, the second station cannot transmit the StartSync PPDU. In this embodiment, a pre-designated time interval other than the PIFS, such as a DIFS, may be used.

[0289] In addition, the AP can signal to the station whether the station can transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section. In this case, the AP can signal to the station whether the station can transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section using an Operation element. Specifically, the Operation element may include a field indicating whether the station can transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section. For convenience of explanation, this field is referred to as the NAVSyncDelay exception field. If the NAVSyncDelay exception field indicates that the station can transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section, the station can transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section. If the NAVSyncDelay exception field indicates that the station cannot transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section, the station cannot transmit a start sync PPDU as an exception to the channel access restriction in the channel access restricted section.

[0290] In the embodiment of FIG. 40, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits an UL PPDU (UL PPDU#1) on the first link (Link1), the second station (STA#2) switches to a blind state. Channel access restriction is applied to the second station (STA#2) that has emerged from the blind state. During the channel access restriction period, the first station (STA#1) successfully completes a backoff procedure and acquires a transmission opportunity. At this time, the second station (STA#2) senses that the second link (Link2) is idle in the PIFS. Therefore, even if the second station (STA#2) is in a channel access restricted section, the first station (STA#1) and the second station (STA#2) transmit start sync PPDUs (UL PPDU#2_1, UL PPDU#2_2).

[0291] In this way, if a station is allowed to transmit a sync PPDU immediately after waking up from the blind state as an exception to the channel access restriction, it may interfere with the transmission of other wireless communication terminals, especially stations operating in an OBSS. This is because the transmission protection mechanism performed at the MAC level does not apply to a station immediately after waking up from the blind state. Therefore, it is possible to strictly define the conditions for transmitting a sync PPDU immediately after waking up from the blind state as an exception to the channel access restriction. This will be explained with reference to Figure 41.

[0292] FIG. 41 illustrates a case in which a station transmits simultaneously with other stations of a non-STR multi-link device in which the station is included during a channel access restricted period according to yet another embodiment of the present invention.

[0293] A station may receive parameters related to channel sensing, i.e., CCA, from an AP to which the station is associated. The CCA-related parameters may include an ED threshold. The station may perform CCA based on the CCA-related parameters received from the AP. Specifically, the station may perform ED based on the ED threshold received from the AP. This operation may also be applied when a station accesses a channel to transmit a start sync PPDU as an exception to the channel access restriction.

[0294] When a station performs channel sensing in a PIFS to transmit a start sync PPDU as an exception to the channel access restriction, the station may perform ED using stricter conditions than those applied in ED to transmit a start sync PPDU when the channel access restriction does not apply. For convenience of explanation, ED for transmitting a start sync PPDU when the channel access restriction does not apply is referred to as a general sync PPDU ED. Also, ED performed by a station to transmit a start sync PPDU as an exception to the channel access restriction is referred to as an exception sync PPDU ED. For example, a station may perform exception sync PPDU ED using a threshold lower than the threshold used in general sync PPDU ED. When a station performs exception sync PPDU ED, the station may determine whether it is idle for a time interval longer than the time interval used in general sync PPDU ED.

[0295] The AP can also signal to the station whether the conditions for the exception sync PPDU ED are stricter than the conditions for the general sync PPDU ED. Specifically, the AP can signal the conditions for the exception sync PPDU ED to the station. For example, the AP can signal the threshold used in the exception sync PPDU ED to the station. The AP can also signal the length of the idle time interval used in the exception sync PPDU ED to the station. The AP can perform this signaling using an Operation element.

[0296] In addition, the AP may signal whether a station can transmit a start sync PPDU as an exception to the channel access restriction. In this embodiment, a station may transmit a start sync PPDU in a channel access restricted section only if it is signaled that the station can transmit a start sync PPDU as an exception to the channel access restriction. In this case, the station may transmit a start sync PPDU according to the exception sync PPDU ED condition.

[0297] In the example of FIG. 41, a first station (STA#1) and a second station (STA#2) of a non-STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. A first AP (AP#1) and a second AP (AP#2) of the STR multi-link device operate on a first link (Link1) and a second link (Link2), respectively. While the first station (STA#1) transmits an UL PPDU (UL PPDU#1) on the first link (Link1), the second station (STA#2) switches to a blind state. Channel access restriction is applied to the second station (STA#2) that has exited the blind state. During the channel access restriction period, the first station (STA#1) successfully completes a backoff procedure and acquires a transmission opportunity. At this time, the second station (STA#2) detects that the second link (Link2) is idle in the PIFS using a threshold of -82 dBm, which is lower than the threshold used for the general sync PPDU ED. Therefore, even if the second station (STA#2) is in a channel access restricted section, the first station (STA#1) and the second station (STA#2) transmit start sync PPDUs (UL PPDU#2_1, UL PPDU#2_2).

[0298] Such an embodiment can mitigate transmission collisions that may occur even if exceptions to channel access restrictions are applied.

[0299] <Medium access recovery procedure>

[0300] As described above, when a non-STR multilink device exits the blind state, channel access of the station in the multilink device that has exited the blind state may be restricted. In this case, channel access of the station in the multilink device may be restricted during MediumSyncDelay. This may be the case when multiple stations in the multilink device operate on non-STR links. When a first station in the non-STR multilink device transmits on the first link, a second station operating on the second link among the stations in the non-STR multilink device may be in a blind state. Therefore, the second station in the non-STR multilink device exits the blind state when transmission on the second link is completed. In this case, the first and second links may be a non-STR link pair.

[0301] In a specific embodiment, the channel access restriction may be applied when the duration of the time interval during which a station of the multi-link device is in the blind state is greater than a pre-specified threshold, which may be referred to as aMediumSyncThreshold.

[0302] In addition, when the station of the multilink device comes out of the blind state, the station of the multilink device can start the MediumSyncDelay timer. At this time, if the value of the MediumSyncDelay timer is greater than 0, the channel access of the station of the multilink device is restricted. When the value of the MediumSyncDelay timer becomes 0, the channel access restriction of the station of the multilink device is released.

[0303] Also, when channel access of a station of a multilink device is restricted, channel access for all ACs may be restricted. Therefore, the MediumSyncDelay timer of a station of a multilink device may apply to all EDCAFs of the station of the multilink device.

[0304] The aforementioned channel access restrictions may be as follows:

[0305] When channel access restrictions are applied to stations of a multilink device, the type of frame that the station of the multilink device can transmit as the first frame (hereinafter referred to as the start frame) may be restricted. The start frame may be an RTS frame.

[0306] Furthermore, when a channel access restriction is applied to a station of a multilink device, the number of times the station of the multilink device can attempt channel access during the time period to which the channel access restriction is applied may be limited. Specifically, the number of times the station of the multilink device can attempt channel access may be limited until the MediumSyncDelay timer expires. In this case, the channel access attempt may be an attempt to transmit the start frame described above. The maximum number of attempts may be specified by the AP multilink device. For example, if the maximum number of attempts is specified as 1, the station of the multilink device can attempt to transmit an RTS frame once while the MediumSyncDelay timer has a value greater than 0. The maximum number of attempts may be counted regardless of whether the transmission is successful. Furthermore, the maximum number of attempts may not be reset even if the MediumSyncDelay timer is reset. For example, if the maximum number of attempts is 1 and the station of the multilink device attempts channel access for start frame transmission, the MediumSyncDelay timer may be reset before the MediumSyncDelay timer expires. In this case, the station of the multilink device may not be allowed to attempt to transmit the initiation frame again. A station may consider channel access to have failed if it does not receive a response frame to the initiation frame within a pre-specified time. The initiation frame may be an RTS frame, and the response frame may be a CTS frame. The pre-specified time may be a CTS timeout.

[0307] Also, while the channel access restriction is applied, the station of the multilink device can use the CCA-ED threshold as a pre-specified value. In this case, the pre-specified value may be specified by the AP. The pre-specified value may be a value smaller than when the channel access restriction is not applied, for example, a value lower than -62 dBm.

[0308] The channel access restriction may be released when the MediumSyncDelay timer expires, i.e., the value of the MediumSyncDelay timer decreases to 0, or when it is released, i.e., the value of the MediumSyncDelay timer is reset to 0. If a station of the multilink device receives a valid MPDU occupying the primary channel, the station of the multilink device may set the value of the MediumSyncDelay timer to 0. Also, if a station of the multilink device receives a PPDU that sets the TXOP_DURATION of the RXVECTOR to a value other than UNSPECIFIED, the station of the multilink device may set the value of the MediumSyncDelay timer to 0. In such an embodiment, a station of a non-AP multilink device may not be allowed to set the value of the MediumSyncDelay timer to 0 based on an RTS frame transmitted by another non-AP station.

[0309] The value of aMediumSyncThreshold may be set based on at least one of the CTS frame, the RTS frame, and the ACK. Specifically, the value of aMediumSyncThreshold may be set based on the time it takes for the CTS frame, the RTS frame, and the ACK to be transmitted in a non-HT duplicated PPDU format or a non-HT PPDU format. In a specific embodiment, the value of aMediumSyncThreshold may be set based on the time it takes for the CTS frame, the RTS frame, and the ACK to be transmitted in a non-HT duplicated PPDU format or a non-HT PPDU format at a basic rate. In this case, the basic rate may be 6 Mbps. For example, the value of aMediumSyncThreshold may be set to a value equal to or greater than the time it takes for the CTS frame, the RTS frame, and the ACK to be transmitted in a non-HT duplicated PPDU format or a non-HT PPDU format at a basic rate. In addition, the value of aMediumSyncThreshold may be set to a time equal to or greater than the time required for the start frame to be transmitted at the basic rate in a non-HT duplicated PPDU format or a non-HT PPDU format. As described above, the start frame may be an RTS frame, and the value of aMediumSyncThreshold may be 52 us. 52 us is the time required to transmit a non-HT PPDU or a non-HT duplicated PPDU containing an RTS frame. Specifically, the time required for the preamble of a non-HT PPDU or a non-HT duplicated PPDU is 20 us, and the time required for transmitting an RTS frame is 32 us. In this case, 32 us is the time required to transmit 20 octets, 2 octets corresponding to the service field, and 6 bits corresponding to the tail, contained in the RTS frame, at 6 Mbps. In this case, one symbol transmitted at 6 Mbps may contain 24 bits.

[0310] In this way, the reason why the value of aMediumSyncThreshold is set based on the transmission time of the start frame in the above-described embodiment is that when channel access is restricted, a station in the multilink device transmits a start frame to acquire a TXOP. Specifically, when a station in the multilink device transmits a start frame, other stations may enter a blind state. Therefore, if the value of aMediumSyncThreshold is set to a time shorter than the time required to transmit the start frame, stations surrounding the station in the multilink device may be subject to channel access restrictions in a chain reaction. This can be prevented by setting the value of aMediumSyncThreshold based on the transmission time of the start frame.

[0311] In yet another specific embodiment, the transmission rate of a PPDU including a start frame may be determined based on the value of aMediumSyncThreshold. Specifically, a station of a multi-link device may determine the transmission rate of a PPDU including a start frame so that the required transmission time of the PPDU including the start frame is equal to or less than the time of aMediumSyncThreshold. For example, if the value of aMediumSyncThreshold is 44 us and the start frame is an RTS frame, the station of the multi-link device can transmit a non-HT PPDU including an RTS frame using a data rate higher than 6 Mbps. In yet another specific embodiment, the data rate of a PPDU including a start frame may be specified in advance. Specifically, the data rate of a PPDU including a start frame may be specified to be greater than 6 Mbps. Specifically, the data rate of a PPDU including a start frame may be specified to be greater than 12 Mbps.

[0312] In yet another specific embodiment, a station that was unable to perform medium monitoring by transmitting a start frame, i.e., is in a blind state, may not have its channel access restricted when it exits the blind state. Specifically, even if a station has been in the blind state for a duration longer than aMediumSyncThreshold by transmitting a start frame, the station's channel access may not be restricted when it exits the blind state. This prevents a chain reaction of channel access restrictions on multiple stations surrounding the station when the channel access of one station is restricted.

[0313] <Multilink device operation mode setting>

[0314] When any one station of a single-radio multilink device transmits or receives, other stations of the single-radio multilink device cannot transmit or receive. As described above, whether a multilink device operates as a single-radio multilink device may depend on hardware constraints or an operational mode definition. Therefore, in this specification, the term "single-radio multilink device" may refer not only to a multilink device in which station operation is restricted by hardware constraints, but also to a multilink device in which station operation is restricted by an operational mode definition. Therefore, the "single-radio multilink device" in this specification may include a multilink device that supports simultaneous transmission or reception by multiple stations of the multilink device, but does not support simultaneous transmission or reception by multiple stations of the multilink device under certain conditions. In this case, the certain conditions may include a specific time point.

[0315] Furthermore, the operation mode of a multilink device may be applied to each link. For example, a multilink device may include a first station operating on a first link, a second station operating on a second link, and a third station operating on a third link. At a specific time, the EMLSR mode may be applied to the first and second stations of the multilink device, and the third station may not operate. In this case, simultaneous frame exchange between the first and second stations may not be permitted.

[0316] The channel access restrictions described above may be applied to stations that have difficulty performing medium monitoring due to their operating mode.

[0317] In the above-described embodiments, the operations of a station in a multilink device may be replaced by the operations of the multilink device. Also, in the above-described embodiments, the operations of an AP may be replaced by the operations of a non-AP station, and the operations of a non-AP station may be replaced by the operations of an AP. Thus, the operations of an AP in a non-STR multilink device may be replaced by the operations of a non-AP station in a non-STR multilink device, and the operations of a non-AP station in an STR multilink device may be replaced by the operations of an AP in the STR multilink device. Also, the operations of a non-AP station in a non-STR multilink device may be replaced by the operations of an AP in a non-STR multilink device, and the operations of an AP in an STR multilink device may be replaced by the operations of a non-AP station in an STR multilink device.

[0318] <Restrictions on Medium Access Recovery Procedures>

[0319] As described above, when channel access restriction is applied for medium access recovery, the channel access of the station may be restricted by parameters specified by the AP. The parameter values ​​applied to the channel access restriction are described in FIG. 42.

[0320] FIG. 42 illustrates the format of a Basic Multi-Link element that signals parameters that apply to channel access restrictions according to an embodiment of the present invention.

[0321] The parameters applied to the channel access restriction may include at least one of the number of channel access attempts allowed in the channel access restriction time interval, the CCA-ED threshold used to determine whether the channel is idle in the channel access restriction time interval, and the duration of the channel access restriction time interval.

[0322] In this case, the channel access restriction time interval may be a time interval where the value of the MediumSyncDelay timer is greater than 0, as described above. The station may also set the initial value of the MediumSyncDelay timer according to the duration of the channel access restriction time interval instructed by the AP or a default value. In this case, the default value may be aPPDUMaxTime. aPPDUMaxTime may be the longest PPDU transmission time allowed for transmission in the EHT PHY. Therefore, aPPDUMaxTime may be 5.484 ms.

[0323] The CCA-ED threshold used to determine whether a channel is idle during a channel access restriction time interval may be lower than the CCA-ED threshold applied outside the channel access restriction time interval. The CCA-ED threshold outside the channel access restriction time interval is referred to as dot11OFDMEDThreshold, and the CCA-ED threshold during the channel access restriction time interval is referred to as dot11MSDOFDMEDthreshold. The value of dot11OFDMEDThreshold is -62 dBm, and the value of dot11MSDOFDMEDthreshold may be -62 dBm to -72 dBm. When the value of dot11MSDOFDMEDthreshold is not specified by the AP, the value of dot11MSDOFDMEDthreshold may be -72 dBm.

[0324] The maximum number of channel access attempts during the channel access restriction time period may be applied as described above. Also, if the AP does not signal the maximum number of channel access attempts during the channel access restriction time period, the station may consider the default value as the maximum number of channel access attempts. The maximum number of channel access attempts may be 1.

[0325] The AP may signal parameters applied to the channel access restriction using a multi-link-related element. In this case, the multi-link-related element may be a Basic Multi-Link element. Specifically, the Basic Multi-Link element may include a field indicating parameters applied to the channel access restriction. In this case, the field may be referred to as a Medium Synchronization Delay Information field.

[0326] 42(a) shows a Basic Multi-Link element including a Medium Synchronization Delay Information field. A station receives a Basic Multi-Link element including a Medium Synchronization Delay Information field and can obtain the value of a parameter applied to channel access restriction from the Medium Synchronization Delay Information field. At this time, the station can apply the parameter indicated by the last received Medium Synchronization Delay Information field to channel access. After the station associates with an AP, if the station fails to receive a Medium Synchronization Delay Information field from the associated AP, the station can apply the default value of the parameter to channel access restriction.

[0327] 42(b) shows a specific format of the Medium Synchronization Delay Information field. The Medium Synchronization Delay Information field may include a Medium Synchronization Duration subfield indicating the duration of the channel access restriction time interval, a Medium Synchronization OFDM ED Threshold subfield indicating the CCA-ED threshold for the channel access restriction time interval, and a Medium Synchronization Maximum Number Of TXOPs subfield indicating the maximum number of channel access attempts for the channel access restriction time interval. In this case, the Medium Synchronization Duration subfield may be an 8-bit field. The Medium Synchronization OFDM ED Threshold subfield may be a 4-bit field. The Medium Synchronization Maximum Number Of TXOPs subfield may be a 4-bit field.

[0328] The AP may not be allowed to signal a value smaller than the default value in the channel access restriction time interval. As described above, the default value may be aPPDUMaxtime. Specifically, the station may set the duration of the channel access restriction time interval to a value indicated by the value of the Medium Synchronization Duration subfield plus the default value. For example, if the Medium Synchronization duration subfield indicates 100, the station may set the initial value of its MediumSyncDelay timer to aPPDUMaxtime + 100 * 32 us. In this case, the initial value of the MediumSyncDelay timer may be 8.609 ms.

[0329] Figure 42(c) shows how the Medium Synchronization OFDM ED Threshold subfield is set. The value of the Medium Synchronization OFDM ED Threshold subfield may be set to 0 to 10. A station can set the value of dot11MSDOFDMEDthreshold to the value indicated by the Medium Synchronization OFDM ED Threshold subfield plus a default value. For example, if the value of the Medium Synchronization OFDM ED Threshold subfield is 2, a station can set the value of dot11MSDOFDMEDthreshold to -70 dBm.

[0330] The Medium Synchronization Maximum Number Of TXOPs subfield may indicate the maximum number of channel access attempts minus 1. In this case, a station may attempt channel access a number of times equal to the value of the Medium Synchronization Maximum Number Of TXOPs subfield plus 1 during the channel access restricted time period. Also, if the value of the Medium Synchronization Maximum Number Of TXOPs subfield is set to a pre-specified value, the Medium Synchronization Maximum Number Of TXOPs subfield may indicate that there is no limit to the number of times a station may attempt channel access during the channel access restricted time period. In this case, the pre-specified value may be 15.

[0331] FIG. 43 shows a station according to an embodiment of the present invention performing a medium access recovery procedure based on information about parameters received from an AP.

[0332] In the embodiment of FIG. 43, the AP multilink device includes a first AP (AP#1) operating on a first link (Link1) and a second AP (AP#2) operating on a second link (Link2). The non-AP multilink device also includes a first station (STA#1) operating on the first link (Link1) and a second station (STA#2) operating on the second link (Link2). The first station (STA#1) receives information regarding channel access restriction (Medium Synchronization Delay Information field) from the first AP (AP#1). At this time, the second station (STA#2) cannot perform medium monitoring on the second link (Link2) due to the frame exchange (UL PPDU) performed on the first link (Link1). Therefore, the channel access restriction is applied to the second station (STA#2) from the time the first station (STA#1) finishes transmission. At this time, the second station (STA#2) applies the channel access restriction based on the information regarding channel access restriction transmitted by the first AP (AP#1).

[0333] 43, since the value of the Medium Synchronization Duration subfield is X, the second station (STA#2) sets the initial value of the MediumSyncDelay timer to X × 32 us. Also, since the value of the Medium Synchronization OFDM ED subfield is 5, the second station (STA#2) sets the value of the dot11MSDOFDMEDthreshold to −67 dBm.

[0334] In the embodiment of FIG. 43, since the value of the Medium Synchronization Maximum Number Of TXOPs subfield is 0, the second station (STA#2) can attempt channel access once within the channel access restriction time interval. Therefore, when the second station (STA#2) transmits an RTS frame within the channel access restriction time interval and fails to receive a CTS frame within the CTS timeout, the second station (STA#2) cannot attempt channel access within the remaining channel access restriction time interval.

[0335] <MediumSyncDelay Timer Management Method>

[0336] A station may enter the medium monitoring unavailable state again during the channel access restriction period. At this time, the method of applying channel access restriction to the station may become a problem. In a specific embodiment, when the station enters the medium monitoring unavailable state again during the channel access restriction period, channel access restriction may be applied to the station again when the station exits the medium monitoring unavailable state. That is, when the station enters the medium monitoring unavailable state again during the channel access restriction period, the station can set the value of the MediumSyncDelay timer to the initial value when the station exits the medium monitoring unavailable state. When the station sets the MediumSyncDelay timer to the initial value again, it may not be allowed for the station to initialize the number of channel access attempts. This may be to prevent the station from setting the MediumSyncDelay timer to the initial value in order for the station to attempt channel access again.

[0337] In still other specific embodiments, when the station enters the medium monitoring unavailable state again in the channel access restriction period, the station can increase the duration of the channel access restriction period by the duration of the monitoring unavailable time period. Specifically, when the station enters the medium monitoring unavailable state again in the channel access restriction period, the station in the monitoring unavailable state is not allowed to decrease the value of the MediumSyncDelay timer. Or, when the station enters the medium monitoring unavailable state again in the channel access restriction period, the station can increase the value of the MediumSyncDelay timer by the time period of the monitoring unavailable state.

[0338] With such an embodiment, the station can increase the time period to which the channel access restriction is applied and protect the transmissions of surrounding stations.

[0339] <TXOP Acquisition Trial Count Management Method>

[0340] As described above, when the station enters the medium monitoring unavailable state again in the channel access restriction period, the station can set the value of the MediumSyncDelay timer to the initial value when it exits the medium monitoring unavailable state. When the station sets the MediumSyncDelay timer to the initial value again, the station is not allowed to initialize the channel access trial count. However, the station can enter the monitoring unavailable state repeatedly. Each time the channel access trial count is not initialized, the channel access of the station may be overly restricted. This will be described with reference to FIG. 44.

[0341] FIG. 44 shows that the station according to the embodiment of the present invention continuously resets the MediumSyncDelay timer.

[0342] In the example of FIG. 44, the AP multilink device includes a first AP (AP#1) operating on a first link (Link1) and a second AP (AP#2) operating on a second link (Link2). The non-AP multilink device also includes a first station (STA#1) operating on the first link (Link1) and a second station (STA#2) operating on the second link (Link2). At this time, due to the frame exchange (UL PPDU) performed on the second link (Link2), the second station (STA#2) cannot perform medium monitoring on the first link (Link1). Therefore, channel access restrictions are applied to the first station (STA#1) from the moment the second station (STA#2) finishes transmission. At this time, the first station (STA#1) transmits an RTS frame but cannot receive a CTS frame. Thereafter, the first station (STA#1) enters a medium monitoring disabled state before the channel access restriction time interval expires, and the first station (STA#1) sets the MediumSyncDelay timer to its initial value. Since the first station (STA#1) has already attempted channel access and the maximum number of channel access attempts is set to 1, it cannot attempt channel access until the channel access restriction time interval expires. Thereafter, the first station (STA#1) re-enters a medium monitoring disabled state before the channel access restriction time interval expires, and the first station (STA#1) sets the MediumSyncDelay timer to its initial value. Thereafter, the first station (STA#1) re-enters a medium monitoring disabled state before the channel access restriction time interval expires, and the first station (STA#1) sets the MediumSyncDelay timer to its initial value. As a result, the first station (STA#1) cannot attempt channel access for an excessively long time. A method for resolving this issue is described with reference to FIG. 45.

[0343] FIG. 45 shows a station according to yet another embodiment of the present invention continuously resetting the MediumSyncDelay timer.

[0344] When a predetermined time has elapsed since the start of the channel access restriction time interval, the station may attempt channel access more than the number of channel access attempts within the channel access restriction time interval. The predetermined time may be specified by the AP. Alternatively, the predetermined time may be a fixed time, such as aPPDUMAXTime. Alternatively, the predetermined time may be greater than the duration of the channel access restriction time interval. In a specific embodiment, when a predetermined time has elapsed since the start of the channel access restriction time interval, the station may initialize the number of channel access attempts within the channel access restriction time interval. For example, the station may set a channel access attempt count initialization timer at the start of the channel access restriction time interval. The value of the channel access attempt count initialization timer decreases steadily over time. When the channel access attempt count initialization timer reaches 0, the station may set the number of channel access attempts within the channel access restriction time interval to 0. In this case, when the station sets the channel access attempt count initialization timer, the station may set the value of the channel access attempt count initialization timer to be equal to the value of the MediumSyncDelay timer. In yet another specific embodiment, when the station sets the channel access attempt count initialization timer, the station can set the value of the channel access attempt count initialization timer to a value instructed by the AP, and the AP can only set the value of the MediumSyncDelay timer and a larger value as the initial value of the channel access attempt count initialization timer.

[0345] In yet another specific embodiment, when the station's channel access attempt count initialization timer expires, the station may increase the maximum number of channel access attempts. In this case, the station may increase the maximum number of channel access attempts based on the increased duration of the channel access restriction time interval. Specifically, when the station's channel access attempt count initialization timer expires, the station may add an initial value of the maximum number of channel access attempts to the maximum number of channel access attempts.

[0346] Also, when the channel access attempt count initialization timer expires and the MediumSyncDelay timer is set again, the station may set the channel access attempt count initialization timer. In yet another specific embodiment, when the channel access attempt count initialization timer expires, the station may set the channel access attempt count initialization timer.

[0347] Also, if the station has not attempted channel access before the MediumSyncDelay timer is set again, the station may set the channel access attempt count initialization timer when the MediumSyncDelay timer is set again.

[0348] The above-described embodiment regarding the setting of the channel access attempt count initialization timer may be applied only when the initial value of the channel access attempt count is greater than a pre-specified value. For example, the pre-specified value may be 2. In this case, when the initial value of the channel access attempt count is 2, the channel access attempt count initialization timer may not be set. Also, when the initial value of the channel access attempt count is 3, the channel access attempt count initialization timer may be set according to the above-described embodiment.

[0349] Also, when the MediumSyncDelay timer expires, the channel access attempt count initialization timer may be set to 0.

[0350] In the example of FIG. 45, the AP multilink device includes a first AP (AP#1) operating on a first link (Link1) and a second AP (AP#2) operating on a second link (Link2). The non-AP multilink device also includes a first station (STA#1) operating on the first link (Link1) and a second station (STA#2) operating on the second link (Link2). At this time, due to the frame exchange (UL PPDU) performed on the second link (Link2), the second station (STA#2) cannot perform medium monitoring on the first link (Link1). Therefore, channel access restrictions are applied to the first station (STA#1) from the moment the second station (STA#2) finishes transmission. At this time, the first station (STA#1) transmits an RTS frame but cannot receive a CTS frame. Subsequently, the first station (STA#1) enters a medium monitoring disabled state before the channel access restriction time period ends, and the first station (STA#1) sets the MediumSyncDelay timer to its initial value. Since the first station (STA#1) has already attempted channel access and the maximum number of channel access attempts is set to 1, it cannot attempt channel access before the channel access restriction time period ends. At this time, when the first station (STA#1) sets the MediumSyncDelay timer to its initial value, the first station (STA#1) sets the channel access attempt count initialization timer (MediumSyncDelay timer#1'). Therefore, when the channel access attempt count initialization timer (MediumSyncDelay timer#1') expires, the first station (STA#1) attempts channel access again (transmits an RTS frame). The first station (STA#1) receives a CTS frame and restores medium sync.

[0351] <Link Deactivation>

[0352] The multi-link device can deactivate some of the multiple links on which the multi-link device operates. At this time, the stations of the multi-link device operating on the deactivated links can perform a power-saving operation to enter the power-saving state (doze state). Conventionally, in a wireless LAN, an AP was not allowed to enter the power-saving state. This is because the AP needs to periodically transmit management frames such as beacon frames and receive connection requests from new stations. However, the multi-link device includes a plurality of stations operating on different links, and frame exchange on the deactivated links may be very restricted. Therefore, among the APs of the AP multi-link device, the AP operating on the deactivated link can enter the power-saving state. The AP of the AP multi-link device in the power-saving state can support only minimal operations. Specifically, the AP of the AP multi-link device in the power-saving state performs CCA and PD, but does not need to support frame exchange.

[0353] When the AP multi-link device deactivates any one link, it may cause confusion to the stations operating on that link. Therefore, the procedure for the AP multi-link device to deactivate the link must be clearly defined. This will be described in FIGS. 46 and 47.

[0354] <Method for Disabling Links of AP Multi-Link Device>

[0355] When any one link is deactivated, frame exchange on that link may be restricted. Specifically, it may not be allowed to exchange data frames, management frames, and control frames on the deactivated link. However, it may be allowed for a non-AP station to transmit a P2P (peer to peer) PPDU to a P2P peer station on the deactivated link.

[0356] FIG. 46 illustrates deactivation-related information transmitted by an AP multilink device according to an embodiment of the present invention.

[0357] The AP multilink device may signal information related to a time interval during which a link is deactivated using a management frame. The information related to the time interval during which a link is deactivated may include at least one of a start time and a duration of the time interval during which the link is deactivated. Specifically, the AP multilink device may signal information related to the time interval during which a link is deactivated using a Multi-Link element in a management frame. The Multi-Link element may include a time when the link will start to be deactivated and a duration of the time interval during which the link is deactivated. The Common Info field of the Multi-Link element may include a time when the link will start to be deactivated and a duration of the time interval during which the link is deactivated. The management frame may be at least one of a beacon frame and a probe response frame.

[0358] An AP multilink device may signal information regarding the deactivation of a second link over a first link using a management frame. Specifically, the Multi-Link element of the management frame may include a Per-STA profile indicating information about an individual link and an AP operating over the individual link. The AP multilink device may signal information regarding the deactivation of a second link using the Per-STA profile of the Multi-Link element transmitted over the first link. A non-AP multilink device may obtain information regarding the deactivation of a second link from the Per-STA profile of the Multi-Link element transmitted over the first link. The Per-STA profile may include information about the link corresponding to the Per-STA profile, the AP operating over the link corresponding to the Per-STA profile, and the BSS operated by the AP operating over the link corresponding to the Per-STA profile. Specifically, the Per-STA profile may indicate the MAC address of the AP operating over the link corresponding to the Per-STA profile, the non-STR link pair, the beacon period, and DTIM information.

[0359] The AP multilink device can signal whether a link is deactivated using a reduced neighbor report (RNR) element of a management frame. The AP multilink device can also signal whether a link corresponding to the TBTT information field is deactivated using a TBTT information field. Specifically, the TBTT information field can indicate a 1-bit Unavailable Link Indication field indicating whether a link corresponding to the TBTT information field is deactivated. If a link corresponding to the TBTT information field is deactivated, the value of the TBTT information field can be set to 1.

[0360] The AP multilink device indicates the TU difference between the previous TBTT and the next TBTT of a neighbor AP using the Neighbor AP TBTT offset subfield of the TBTT Information field of the RNR element included in the management frame. When the value of the Neighbor AP TBTT offset subfield is set to 255, the Neighbor AP TBTT offset subfield indicates that the TU difference between the previous TBTT and the next TBTT of the AP is unknown. When the TBTT Information field of the RNR element indicates information about an AP operating on a deactivated link, the AP can set the value of the Neighbor AP TBTT offset subfield of the TBTT Information field of the RNR element to 255. This is because beacon frame transmission is not permitted on a deactivated link.

[0361] The AP multilink device may not need to specify the duration of the time period during which the link is inactive. In this case, when the AP multilink device transmits the first frame on a deactivated link, the link may be reactivated. In this case, the type of the first frame may be specified in advance. When the non-AP multilink device receives the first frame on a deactivated link, the non-AP multilink device may determine that the link has been reactivated. For example, the first frame may be a beacon frame or a probe response frame. The first frame may also be transmitted at a basic rate, such as 6 Mbps or 24 Mbps. The first frame may also be transmitted in a non-HT duplicated format. When this embodiment is applied, more stations can decode the first frame.

[0362] The non-AP multilink device may perform channel access based on information related to a time period during which the link is inactive, and may manage TID-to-Link mapping based on information related to a time period during which the link is inactive.

[0363] Figure 46(a) shows the format of the Presence Bitmap subfield of a Basic Multi-Link element. The Presence Bitmap subfield of a Basic Multi-Link element may include a Link Unavailability Parameters Present subfield. If the value of the Link Unavailability Parameters Present subfield is 1, the Common Info field of the Basic Multi-Link element may include a Link Unavailability Parameters field.

[0364] Figure 46(b) shows the format of the Common Info field of a Basic Multi-Link element including the Link Unavailability Parameters field. The Link Unavailability Parameters field may be a three-octet field.

[0365] Figure 46(c) shows the format of the Link Unavailability Parameters field. The Link Unavailability Parameters field may include a Link Unavailability Count subfield indicating when the link corresponding to the Link Unavailability Parameters field is deactivated. In this case, the Link Unavailability Count subfield may be a 1-octet field. If the value of the Link Unavailability Count subfield is 0, it may indicate that the link corresponding to the Link Unavailability Parameters field is deactivated after the management frame including the Link Unavailability Count subfield is transmitted. In addition, the Link Unavailability Count subfield may be set to any one of values ​​0 to 255.

[0366] The Link Unavailability Parameters field may also include a Link Unavailability Duration subfield indicating the duration of the inactive time interval of the link corresponding to the Link Unavailability Parameters field. The Link Unavailability Duration subfield may be a two-octet or one-octet field. If the Link Unavailability Duration subfield is a one-octet field, the value of the Link Unavailability Duration subfield may be set to any one of 0 to 255. If the Link Unavailability Duration subfield is a two-octet field, the value of the Link Unavailability Duration subfield may be set to any one of 0 to 65535. The value of the Link Unavailability Duration subfield may indicate the duration of the inactive time interval of the link in beacon interval units. For example, if the beacon interval is 100 ms and the value of the Link Unavailability Duration subfield is 2, the duration of the inactive time interval of the link may be 200 ms. In yet another specific embodiment, the value of the Link Unavailability Duration subfield may indicate the duration of the link inactivity time period in TU units. If the value of the Link Unavailability Duration subfield is 100, the duration of the link inactivity time period may be 100 TUs. If the value of the Link Unavailability Duration subfield is set to the maximum value that the Link Unavailability Duration subfield can have, the Link Unavailability Duration subfield may indicate that the duration of the link inactivity time period is not specified.In this case, the above-described embodiment in which the AP multilink device does not specify the duration of the link inactivity time period may be applied.

[0367] As previously mentioned, the AP multilink device can signal information regarding the deactivation of the second link over the first link using a management frame.

[0368] FIG. 47 shows a format of signaling information regarding deactivation of a second link transmitted by an AP multi-link device in an embodiment of the present invention over a first link.

[0369] 47(a) shows the format of a BSS Parameters subfield transmitted by an AP multilink device according to an embodiment of the present invention. The AP multilink device can signal whether a link is deactivated using a reduced neighbor report (RNR) element of a management frame. The BSS Parameters subfield of the RNR element may include an Unavailable Link Indication subfield indicating whether a link corresponding to the BSS Parameters subfield is deactivated. If the value of the Unavailable Link Indication subfield is 1, the Unavailable Link Indication subfield can indicate that the link corresponding to the BSS Parameters subfield is deactivated.

[0370] 47(b) illustrates a TBTT Information field including a BSS Parameters subfield according to an embodiment of the present invention. The link corresponding to the BSS Parameters subfield may be a link corresponding to the link ID indicated by the TBTT Information field including the BSS Parameters subfield.

[0371] FIG. 47(c) shows the format of the STA Control field according to an embodiment of the present invention, and FIG. 47(d) shows the format of the STA Info field. Specifically, the Multi-Link element of the management frame may include a Per-STA profile indicating information about an individual link and an AP operating on the individual link. An AP multi-link device can signal information about the deactivation of a second link using the Per-STA profile of the Multi-Link element transmitted on the first link. A non-AP multi-link device can obtain information about the deactivation of a second link from the Per-STA profile of the Multi-Link element transmitted on the first link. The Per-STA profile may include information about the link corresponding to the Per-STA profile, the AP operating on the link corresponding to the Per-STA profile, and the BSS operated by the AP operating on the link corresponding to the Per-STA profile. Specifically, the Per-STA profile may indicate the MAC address of the AP operating on the link corresponding to the Per-STA profile, the non-STR link pair, the beacon period, and DTIM information. The Per-STA profile may be indicated by the STA Control field and the STA info field.

[0372] The STA Control field may include a Link Unavailability Parameters Present subfield that indicates whether the STA info field includes a Link Unavailability Parameters subfield. If the Link Unavailability Parameters Present subfield has a value of 1, the Link Unavailability Parameters Present subfield may indicate that the STA info field includes a Link Unavailability Parameters field. The Link Unavailability Parameters field indicates that the link corresponding to the STA info field is deactivated.

[0373] <How to instruct other links to be deactivated>

[0374] In the above-described embodiment in which the AP multilink device signals information about the deactivation of the second link over the first link using a management frame, a non-AP station may not need to decode a Per-STA profile corresponding to a non-AP station other than the non-AP station. In this case, the non-AP station may not know that the deactivation status of a link on which the non-AP station is not operating has changed. To prevent this, if a Per-STA profile corresponding to a link other than the link for which the management frame is transmitted contains information about link deactivation, the AP multilink device may indicate that a critical update will occur in the TBTT Information field containing the Per-STA profile. Specifically, the AP multilink device may increment the value of the BSS Parameters Change Count subfield in the TBTT Information field corresponding to the Per-STA profile containing information about link deactivation by 1 from its previous value. A station in the non-AP multilink device may determine that the value of the BSS Parameters Change Count subfield in the TBTT Information field received by the non-AP multilink device is different from the value of the BSS Parameters Change Count subfield in the TBTT Information field previously received. In this case, a station in the non-AP multilink device can obtain information corresponding to the critical update by decoding the Per-STA profile in the TBTT Information field. Also, a station in the non-AP multilink device can obtain information corresponding to the critical update by receiving a management frame, for example, a beacon frame, on a link corresponding to the Per-STA profile.

[0375] Conventionally, the following updates have been classified as critical updates in wireless LANs:

[0376] (a)Inclusion of a Channel Switch Announcement element

[0377] (b)Inclusion of an Extended Channel Switch Announcement element

[0378] (c)Modification of the EDCA parameters element

[0379] (d)Inclusion of a Quiet element

[0380] (e)Modification of the DSSS Parameter Set

[0381] (f)Modification of the HT Operation element

[0382] (g)Inclusion of a Wide Bandwidth Channel Switch element

[0383] (h)Inclusion of a Channel Switch Wrapper element

[0384] (i)Inclusion of an Operating Mode Notification element

[0385] (j)Inclusion of a Quiet Channel element

[0386] (k)Modification of the VHT Operation element

[0387] (l)Modification of the HE Operation element

[0388] (m)Insertion of a Broadcast TWT element

[0389] (n)Inclusion of the BSS Color Change Announcement element

[0390] (o)Modification of the MU EDCA Parameter Set element

[0391] (p)Modification of the Spatial Reuse Parameter Set element

[0392] (q)Modification of the UORA Parameter Set element

[0393] The above critical update items may be supplemented with a change to the Link Unavailability Parameters subfield and a change to the Unavailable Link Indication subfield, as described above. In such an embodiment, when the value of the Link Unavailability Parameters subfield or the value of the Unavailable Link Indication subfield is changed, the AP multilink device may increase the value of the BSS Parameter Change Count subfield by 1 compared to the value of the BSS Parameter Change Count subfield previously transmitted.

[0394] If the inactive period of a link is not specified, the non-AP station can determine that the inactive time period has ended based on the Unavailable Link Indication subfield or the BSS Parameter Change Count subfield. Specifically, if the Unavailable Link Indication subfield indicates that the link corresponding to the Unavailable Link Indication subfield will not be deactivated, the non-AP station can determine that the inactive time period of the link corresponding to the Unavailable Link Indication subfield has ended. In this case, if the value of the Unavailable Link Indication subfield is 0, the Unavailable Link Indication subfield can indicate that the link corresponding to the Unavailable Link Indication subfield will not be deactivated. Furthermore, if the value of the BSS Parameter Change Count subfield is different from the value of the BSS Parameter Change Count subfield previously received by the non-AP station, the non-AP station can determine that the inactive time period of the link corresponding to the BSS Parameter Change Count subfield has ended.

[0395] <WLANのQoSサポート>

[0396] Despite the increase in WLAN transmission speeds, transmission delays remain a problem for some services. In particular, WLANs operating in unlicensed bands may be unsuitable for operating services requiring low-latency transmissions because the time required for traffic transmission is difficult to predict. EDCA was introduced to solve this problem. A station supporting EDCA is called a QoS station, an AP supporting EDCA is called a QoS AP, and a BSS supporting EDCA is called a QoS BSS. Hereinafter, for convenience of explanation, a QoS AP is called an AP, a QoS station is called a station, and a QoS BSS is called a BSS. In EDCA, traffic is classified into four access categories (ACs) based on their characteristics. The four ACs are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best Effort), and AC_BK (AC Background). In the backoff procedure described above, the AC determines the value of parameters related to the CW. The AC may also determine the maximum TXOP value. The AC may also determine the value of the AIFSN parameter. This allows the priority of traffic transmission for each AC to be adjusted. Traffic may be mapped to four ACs for each traffic category (TC) or traffic stream (TS). The traffic mapped to the four ACs is managed in four queues operated for each AC.

[0397] AC_VO is an AC for traffic that is not as large in absolute volume as voice traffic but is vulnerable to transmission delays, and is mapped with relatively small CW and AIFSN parameter values. However, the maximum TXOP value of AC_VO is relatively smaller than the maximum TXOP values ​​of other ACs. AC_VI is an AC for video traffic that is more resistant to transmission delays than voice traffic but requires low-delay transmission and must handle a large amount of traffic. AC_VI is mapped with CW and AIFSN parameter values ​​that are larger than AC_VO but smaller than the CW and AIFSN parameters of other ACs. The maximum TXOP value of AC_VO is approximately twice as long as the maximum TXOP value of AC_VI. AC_BE is an AC for traffic that is resistant to transmission delays, and most general traffic except voice data and streaming video data may be classified as AC_BE. The CW and AIFSN parameters of AC_BE are mapped with larger values ​​than the CW and AIFSN parameters of AC_VO and AC_VI. Also, a different TXOP maximum value is not mapped to AC_BE. Transmission using a consecutive transmission sequence is not allowed in AC_BE. AC_BK is an AC for traffic that is similar to AC_BE in that it is resistant to transmission delays, but has a lower priority than BE traffic. AC_BK is mapped with the same CW parameter value as AC_BE, and with an AIFSN parameter value that is larger than the AIFSN parameter of AC_BE. Also, a different TXOP maximum value is not mapped to AC_BK. Transmission using a consecutive transmission sequence is not allowed in AC_BK.

[0398] The four ACs are mapped to 802.1D UP (user priority), and the EDCA AC is determined by the UP value of the traffic received via wire or the TID of the MSDU indicated by the upper layer. In this case, when the TID of the MSDU indicates a value from 0 to 7, the value indicated by the TID has a one-to-one correspondence with the UP.

[0399] FIG. 48 shows a mapping relationship between UP and AC according to an embodiment of the present invention.

[0400] The default CW parameters (CWmin, CWmax), AIFSN parameters, and TXOP max value for each of the four ACs are defined in the 802.11 standard. The AC's CW parameters (CWmin, CWmax), AIFSN parameters, and TXOP max value can be changed by the AP, and different values ​​can be used for each BSS. In EDCA, traffic is stored in one of the four queues corresponding to the traffic's AC. Channel access contention occurs between the four ACs, and the traffic of the AC that wins the contention is transmitted. In channel access contention, AC-specific access parameters (CW[AC], AIFSN[AC]) are used. In this case, the channel access operation is the same as that of DCF.

[0401] As described above, different channel access parameter values ​​may be assigned to different ACs, and different transmission priorities may be applied to different ACs.

[0402] In addition to EDCA, the 802.11 MAC protocol may also employ HCF controlled channel access (HCCA) for QoS management. HCCA provides a centralized / hybrid coordinator function to guarantee TS (Traffic Stream) QoS for applications that require periodic service (such as voice and video). Other features include Service Period Channel Access (SPCA) and dynamic allocation of service periods. However, these are only available to DMG stations.

[0403] A method for enhancing QoS for a multilink device may be needed. Independent transmission queues may be used for each link of the multilink device. In this case, the queues may be logically independent. When traffic is mapped by link, the QoS of the traffic can be enhanced. This is described in FIG. 49.

[0404] FIG. 49 illustrates a multilink device transmitting traffic mapped to each station of the multilink device according to an embodiment of the present invention.

[0405] In Figure 49, the AP multilink device (AP MLD) includes the first AP (AP1) through the fourth AP (AP4). Also, the non-AP multilink device (Non-AP MLD) includes the first station (non-AP STA1) through the fourth station (non-AP STA4). The first station (non-AP STA1) through the fourth station (non-AP STA4) operate on the first link (Link1) through the fourth link (Link1), respectively. The first AP (AP1) through the fourth AP (AP4) operate on the first link (Link1) through the fourth link (Link1), respectively. In this case, traffic is mapped to each of the first AP (AP1) through the fourth AP (AP4) by AC. AC_BK is mapped to the first AP (AP1), AC_BE is mapped to the second AP (AP2), AC_VI is mapped to the third AP (AP3), and AC_VO is mapped to the fourth AP (AP4). Thus, in the AP multilink device (AP MLD), traffic corresponding to AC_BK is transmitted through the first AP (AP1), traffic corresponding to AC_BE is transmitted through the second AP (AP2), traffic corresponding to AC_VI is transmitted through the third AP (AP3), and traffic corresponding to AC_VO is transmitted through the fourth AP (AP4). The channel quality and load status of each link may differ. Furthermore, the performance and operating bandwidth of each station may differ. Therefore, the bandwidth and MCS of the PPDU containing the traffic may vary depending on which traffic the multilink device maps to which link.

[0406] For example, if the first AP (AP1) of an AP multilink device (AP MLD) operates in the 2.4 GHz band, the first AP (AP1) can operate on a 40 MHz operating channel. If the fourth AP (AP4) operates in the 6 GHz band, the fourth AP (AP4) can operate on a maximum 320 MHz operating channel. The AP multilink device (AP MLD) can map traffic that requires high throughput and low latency transmission to the fourth AP (AP4). The multilink device can map traffic to each of multiple links based on the traffic characteristics. This enhances the QoS of traffic transmission.

[0407] To provide fine-grained QoS enforcement, a TID may be mapped to each link, and priority may be given to transmission of traffic corresponding to the TID mapped to that link on each link. This is illustrated in FIG.

[0408] FIG. 50 shows a multilink device exchanging frames using TID link mapping according to an embodiment of the present invention.

[0409] Traffic transmitted over a WLAN is identified by a TID. A MAC frame, such as a data frame or a QoS data frame, uses a TID service field to signal the TID of the traffic included in the MAC frame. The QoS control field may include the TID service field. The TID identifies the traffic included in an MSDU, fragment, or A-MSDU of the MAC frame. The TID corresponds to a UP (user priorities) or a TSID (traffic stream identifier). The TID service field is a 4-bit field and can represent values ​​from 0 to 15. If the value of the TID subfield is one of 0 to 7, the value of the TID subfield indicates the UP of the MSDU included in the frame body of the MAC frame containing the TID subfield. The MAC frame is processed by the MAC entity using AC parameters corresponding to the UP according to EDCA. If the value of the TID subfield is one of 8 to 15, the value of the TID subfield indicates the TSID of the MSDU included in the frame body of the MAC frame containing the TID subfield. The MAC frame is processed by the MAC entity using parameters corresponding to the UP of the TSID indicated in the User Priority service field of the TS Info field of the TSPEC. The UP of the TSID may be indicated in the User Priority field of the TCLAS. The Access Policy of the TSID is indicated by the Access Policy field of the TS Info subfield. The 7th and 8th bits of the Access Policy subfield are set to 10. b EDCA is indicated if b In yet another specific embodiment, TID-to-Link mapping may be applied only when the TID value is between 0 and 7.

[0410] When a multilink device maps the TID of a TS to a link, it can obtain information about the UP of the TS and the alternate queue to be used for TS transmission from the Intra-Access Priority field of the Intra-Access Category Priority element of the ADDTS Request frame used to generate the TS. The multilink device can use the information about the UP and alternate queue obtained when transmitting traffic corresponding to the TID of the TS.

[0411] A TID may be mapped to each of multiple links operated by a multilink device. In this case, the multilink device may signal information about the TID mapped to each link to associated multilink devices. In this case, the multilink device receiving the signaling may accept or reject the TID and link mapping. If no agreement is reached on the TID and link mapping, frames may be exchanged on each link without TID restrictions. In yet another specific embodiment, if no agreement is reached on the TID and link mapping, frames may be exchanged on each link using a default TID and link mapping.

[0412] When a multilink device maps TIDs to links, the multilink device may need to map all TIDs to one or more links. In a specific embodiment, the multilink device may transmit frames containing traffic corresponding to the TIDs mapped to the links through the links, and may not allow transmission of frames containing traffic corresponding to TIDs not mapped to the links. Mapping of TIDs to links may be performed for each multilink device. Furthermore, mapping of TIDs to links may be performed for each transmission direction. For example, the TID mapped to the uplink and the TID mapped to the downlink of a link may be different. Therefore, when a first multilink device and a second link device are connected via the first and second links, the first multilink device may map TID values ​​0 to 3 to the first link, and the second multilink device may map TID values ​​4 to 7 to the first link.

[0413] Furthermore, TID-to-Link mapping may be applied to each transmission direction. Specifically, a TID-to-Link mapping applied to UL transmission and a TID-to-Link mapping applied to DL transmission may be set independently for one link. For example, TID values ​​0 to 3 may be mapped to transmissions from an AP multilink device on the first link, and TID values ​​4 to 7 may be mapped to transmissions from a non-AP multilink device on the first link.

[0414] In this specification, the mapping between TID and link may be replaced with the mapping between AC and link, the mapping between UP and link, the mapping between TC and link, or the mapping between TS and link.

[0415] Additionally, remaining TID values ​​not explicitly indicated in the TID-to-link mapping may be mapped to the remaining links. For example, if it is signaled that TID values ​​0-3 are to be mapped to the first link, the remaining TID values ​​excluding TID values ​​0-3 may be mapped to the second link. In yet another specific embodiment, transmission of traffic corresponding to all TIDs may be permitted on the second link.

[0416] Furthermore, the TID-to-link mapping may be changed during operation as well as when the multilink devices are first connected. When the multilink device disassociates a station from a specific link, the multilink device may change the TID-to-link mapping. In this case, the multilink device may need to disassociate a station from a specific link when the station enters a power-saving mode. Furthermore, the multilink device may request a change in the TID-to-link mapping from the other multilink device. For example, if TID values ​​0 to 3 are mapped to the first link, the non-AP multilink device may request the AP multilink device to map TID values ​​0 to 3 to the second link. Specifically, if the multilink device has difficulty guaranteeing the QoS of the traffic mapped to the link, the multilink device may request a change in the TID-to-link mapping from the other multilink device.

[0417] In addition, if a multilink device rejects a TID-link mapping request, the multilink device that sent the TID-link mapping request may be limited for a pre-specified time from requesting the same TID-link mapping as the previously requested TID-link mapping again. This is to prevent repeated TID-link mapping requests. In this case, the pre-specified time may be a time specified by the AP. Specifically, the AP multilink device may signal the pre-specified time using BSS operation parameters.

[0418] A method for signaling a mapping between a TID and a link will now be described. A multilink device can signal a mapping between a TID and a link using a TID-to-Link Mapping element. The TID-to-Link Mapping element may include a Link ID field. The Link ID field indicates the link that signals the TID-to-Link Mapping element. In addition, the TIDs Info field indicates information about the TID mapped to the link indicated by the Link ID field. The TIDs Info field may include a field indicating the value of the TID mapped to the link indicated by the Link ID field. In this case, the TIDs Info field may include a bitmap indicating the value of the TID mapped to the link indicated by the Link ID field. In this case, each bit of the bitmap is mapped to a specific TID, and when a bit is set to 1, it may indicate that the TID corresponding to that bit is mapped to the link indicated by the Link ID field.

[0419] In the embodiment of FIG. 50, the AP multilink device (AP MLD) plans to transmit traffic with TIDs 0 to 3 to the non-AP multilink device (non-AP MLD) on the first link (Link 1). The AP multilink device (AP MLD) signals to the non-AP multilink device (non-AP MLD) using the TID-to-Link Mapping element that TID values ​​0 to 3 are mapped to the first link (Link 1) and TID values ​​4 to 7 are mapped to the second link (Link 2). The TID-to-Link Mapping element includes two Link ID fields indicating the first and second links, respectively, and two TIDs Info fields indicating information about the TIDs mapped to the first link and the information about the TIDs mapped to the second link, respectively. Each TIDs Info field may include 7 bits indicating TIDs 0 to 7. For example, to indicate TIDs 0 to 3, 8 bits of the TIDs info subfield may be set to 11110000. b and the 8 bits of the TIDs info subfield are set to 00001111 to indicate TIDs 4 to 7. b may be set to

[0420] In yet another specific embodiment, the TIDs Info field may include a Min TID field and a Max TID field. The Min TID field indicates the minimum value of the TIDs mapped to the link corresponding to the TIDs Info field, and the Max TID field indicates the maximum value of the TIDs mapped to the link corresponding to the TIDs Info field. Each of the Min TID field and the Max TID field may be a 3-bit or 4-bit field. For example, if the Min TID field and the Max TID field are each 3 bits and the TIDs Info field indicates 0 to 3, the Min TID field is set to 000 and the Max TID field is set to 011. bAs mentioned above, the TID-to-Link Mapping element signals only the TIDs mapped to the first link, and the TIDs mapped to the second link may be implicitly signaled. Specifically, because the TID-to-Link Mapping element explicitly signals that TIDs 0 through 7 are mapped to the first link, the TID-to-Link Mapping element can implicitly signal that the remaining TIDs are mapped to the second link.

[0421] A non-AP multilink device accepts the TID-to-link mapping indicated by the TID-to-Link Mapping element.

[0422] When multiple TIDs are mapped to one link and the multiple TIDs correspond to two or more ACs, the multilink device can differentiate the ACs using EDCA and transmit traffic. For example, when a TID corresponding to AC_VO and a TID corresponding to AC_BK are mapped to a first link, the multilink device can transmit traffic corresponding to AC_VO with priority over traffic corresponding to AC_BK using EDCA. In addition, all TIDs must be mapped to at least one link, and the multilink device may not accept a link-to-link mapping request for any TID that is not mapped to any link.

[0423] The inactive link may not have any TIDs mapped to it. That is, a deactivated link may be a link to which no TIDs are mapped. Also, if the links operated by a multilink device include a deactivated link, it is not mandatory that all TIDs be mapped to at least one link. Specifically, among the links operated by a multilink device, there may be TID values ​​that are not mapped to activated links.

[0424] FIG. 51 shows that a basic mapping between TIDs and links is set in an AP multilink device and a non-AP multilink device according to an embodiment of the present invention.

[0425] As previously mentioned, the basic TID-to-link mapping applies when no other TID-to-link mapping is configured. In the example of Figure 51, the basic TID-to-link mapping is that all TIDs and TSIDs are mapped to links.

[0426] When one of the multiple links operated by a multilink device is deactivated, it may be necessary to change the TID-to-Link mapping. This is because frames corresponding to the TID mapped to the deactivated link may not be exchanged. Therefore, when one of the multiple links operated by a multilink device is deactivated, it is necessary to adjust the TID-to-Link mapping for the non-deactivated links. This will be described with reference to Figures 52 to 54.

[0427] <Link deactivation and TID-to-Link mapping management>

[0428] When an AP multilink device deactivates a first link, a non-AP multilink device operating on the first link can map the TID mapped to the first link to a second link. In this case, the second link may be a link on which the AP multilink device and the non-AP multilink device operate. When the first link is deactivated, the non-AP multilink device can map the TID mapped to the first link to the second link. When the non-AP multilink device maps the TID mapped to the first link to the second link, the TID mapping may be performed without TID-to-link mapping negotiation. Furthermore, in this embodiment, in addition to TID-to-link mapping for non-AP multilink device transmissions, TID-to-link mapping for AP multilink device transmissions may also be applied.

[0429] In a specific embodiment, the second link may be a pre-designated link, specifically, the second link may be a link designated through negotiation between the non-AP multi-link device and the AP multi-link device before the first link is deactivated.

[0430] FIG. 52 illustrates how an AP multilink device and a non-AP multilink device change TID-to-Link mapping when one of the links is deactivated according to an embodiment of the present invention.

[0431] In FIG. 52(a), an AP multilink device (AP MLD) including a first AP (AP1), a second AP (AP2), and a third AP (AP3) is coupled to a non-AP multilink device (Non-AP MLD) including a first station (Non-AP STA1), a second station (Non-AP STA2), and a third station (Non-AP STA3). The first AP (AP1) and the first station (Non-AP STA1) operate on a first link (Link1). The second AP (AP2) and the second station (Non-AP STA2) operate on a second link (Link2). The third AP (AP3) and the third station (Non-AP STA3) operate on a third link (Link3). TID values ​​0 to 2 are mapped to uplink and downlink transmissions of the first link (Link1). Furthermore, TID values ​​3 to 4 are mapped to the uplink and downlink transmissions of the second link (Link 2), and TID values ​​5 to 7 are mapped to the uplink and downlink transmissions of the third link (Link 3).

[0432] In Figure 52(b), the third link (Link 3) is deactivated. At this time, the AP multilink device (AP MLD) and non-AP multilink device (Non-AP MLD) map the TID values ​​5 to 7 mapped to the third link (Link 3) to the first link (Link 1) and second link (Link 2). As a result, the AP multilink device (AP MLD) and non-AP multilink device (Non-AP MLD) can exchange frames corresponding to TID values ​​5 to 7 even if the third link (Link 3) is deactivated.

[0433] In yet another specific embodiment, when a first link among links between an AP multilink device and a non-AP multilink device is deactivated, default mapping may be applied to all links between the AP multilink device and the non-AP multilink device. In this case, the default mapping may be such that all TIDs that are targets of TID-to-Link mapping are mapped to the link. In a specific embodiment, all TIDs that are targets of TID-to-Link mapping may have TID values ​​of 0 to 7. In yet another specific embodiment, all TIDs that are targets of TID-to-Link mapping may have TID values ​​of 0 to 15. Furthermore, when the first link is deactivated, the TID-to-Link mapping applied to all links between the AP multilink device and the non-AP multilink device may be canceled, and default mapping may be applied. In this case, because the first link is deactivated, default mapping is not applied to the TID-to-Link mapping of the first link.

[0434] Before an AP multilink device deactivates any one of the links, the AP multilink device may need to perform TID-to-link mapping so that no TID is mapped to that link. When an AP multilink device transmits a management frame including information to deactivate any one of the links, the AP multilink device may be obligated to also transmit an element instructing the AP multilink device to perform TID-to-link mapping. Specifically, when an AP multilink device transmits a beacon frame or a probe response frame including information to deactivate any one of the links, the AP multilink device may be obligated to also transmit an element instructing the AP multilink device to perform TID-to-link mapping. Furthermore, when an AP multilink device transmits a management frame including information to deactivate any one of the links, a non-AP multilink device may not be allowed to reject the TID-to-link mapping. Specifically, when an AP multilink device transmits a beacon frame or a probe response frame including information to deactivate any one of the links, a non-AP multilink device may not be allowed to reject the TID-to-link mapping. Furthermore, when an AP multilink device transmits a management frame including information for deactivating one of the links, the management frame may indicate a default mapping for the links other than the deactivated link. Specifically, when an AP multilink device transmits a beacon frame or a probe response frame including information for deactivating one of the links, the beacon frame or the probe response frame may indicate a default TID-to-Link mapping for the links other than the deactivated link. In such an embodiment, the beacon frame or the probe response frame may indicate a default TID-to-Link mapping for the links other than the deactivated link using a TID-to-Link Mapping element.

[0435] In yet another specific embodiment, the AP multilink device may transmit a TID-to-Link teardown frame before deactivating at least one link. Specifically, before deactivating at least one link, the AP multilink device may transmit a TID-to-Link teardown frame to all links operated by the AP multilink device. In the above-described embodiment, a station that receives a TID-to-Link teardown frame may apply a default TID mapping to the TID-to-Link mapping of the link on which the TID-to-Link teardown frame was received before any link is deactivated.

[0436] In yet another specific embodiment, a separate TID-to-Link Mapping Cancellation frame may not be transmitted. In such an embodiment, when any one link is deactivated, a non-AP multilink device that receives a management frame, e.g., a beacon frame or a probe response frame, including information for deactivating any one link may apply a default mapping to the TID-to-Link mapping of the remaining links, excluding the deactivated link, among the links configured in the non-AP multilink device and the AP multilink device. That is, when any one link is deactivated, a default mapping may be applied to the uplink TID-to-Link mapping of the remaining links, excluding the deactivated link, among the links configured in the non-AP multilink device and the AP multilink device. Furthermore, when any one link is deactivated, an AP multilink device that transmits a management frame, e.g., a beacon frame or a probe response frame, including information for deactivating any one link may apply a default mapping to the TID-to-Link mapping of the remaining links, excluding the deactivated link, among the links configured in the non-AP multilink device and the AP multilink device. That is, when any one link is deactivated, a default mapping may be applied to the downlink transmission TID-to-Link mapping of the remaining links, excluding the deactivated link, among the links configured in the non-AP multilink device and the AP multilink device.

[0437] In the above-described embodiment, when a default mapping is applied to a link for which a TID-to-Link mapping has been established through TID-to-Link mapping negotiation, the TID-to-Link mapping established for the link through TID-to-Link mapping negotiation may be discarded before the default mapping is applied.

[0438] Figure 53 shows that according to an embodiment of the present invention, when any one link is deactivated, the AP multi-link device and the non-AP multi-link device change the default mapping application to the TID-to-Link mapping of the non-deactivated link.

[0439] In FIG. 53(a), an AP multilink device (AP MLD) including a first AP (AP1), a second AP (AP2), and a third AP (AP3) is coupled to a non-AP multilink device (Non-AP MLD) including a first station (Non-AP STA1), a second station (Non-AP STA2), and a third station (Non-AP STA3). The first AP (AP1) and the first station (Non-AP STA1) operate on a first link (Link1). The second AP (AP2) and the second station (Non-AP STA2) operate on a second link (Link2). The third AP (AP3) and the third station (Non-AP STA3) operate on a third link (Link3). TID values ​​0 to 2 are mapped to uplink and downlink transmissions on the first link (Link1). Furthermore, TID values ​​3 to 4 are mapped to the uplink and downlink transmissions of the second link (Link 2), and TID values ​​5 to 7 are mapped to the uplink and downlink transmissions of the third link (Link 3).

[0440] In Figure 53(b), when the third link (Link3) is deactivated, the AP multilink device (AP MLD) and the non-AP multilink device (Non-AP MLD) apply default mapping to the TID-to-Link mapping of the first link (Link1) and the second link (Link2), which are not deactivated.

[0441] In the above-described embodiment, a management frame, such as a beacon frame or a probe response frame, containing information to deactivate any one link may be a frame whose recipient address is set to a group address, such as a broadcast address.

[0442] In addition, the embodiment in which default mapping is applied when any one link is deactivated may be applied only when there is a TID mapped only to the deactivated link. Therefore, even if any one link is deactivated, if traffic corresponding to the TID mapped to the deactivated link can be exchanged with another link, the above embodiment may not be applied. In addition, the embodiment in which default mapping is applied when any one link is deactivated may be applied only to uplink transmission. In yet another specific embodiment, it may be applied only to downlink transmission.

[0443] This embodiment can prevent the AP multilink device and the non-AP multilink device from being unable to exchange frames corresponding to a specific TID due to one of the links being inactivated, and can also reduce the complexity of frame exchange and link management between the AP multilink device and the non-AP multilink device.

[0444] Furthermore, when a deactivated link is reactivated, the TID-to-Link mapping that was applied before the link was deactivated may be reapplied. In this case, the TID-to-Link mapping that was applied before the link was deactivated may be set through TID-to-Link mapping negotiation. Before the first link is deactivated, TID value 2 may be mapped to the first link, and when the second link is deactivated, TID value 2 may be mapped to the second link. In this case, when the first link is reactivated, TID value 2 may be mapped to the first link. Also, when the first link is reactivated, TID value 2 may not be mapped to the second link. In the above-described embodiment, the reactivation of a deactivated link may be when the inactivation time interval ends.

[0445] In yet another specific embodiment, when a deactivated link is reactivated, a default mapping may be applied to the TID-to-Link mapping of the link. Specifically, when a deactivated link is reactivated, the default mapping may be applied to the TID-to-Link mapping of the link regardless of the TID-to-Link mapping applied to the link before deactivation. Furthermore, when a deactivated link is reactivated, the TID-to-Link mapping of the link to which the default mapping was applied due to the deactivation of the link may be restored. Specifically, when the inactivation period of the deactivated link ends, the TID-to-Link mapping of the link to which the default mapping was applied due to the deactivation of the link may be restored.

[0446] In yet another specific embodiment, even if one link is deactivated, another TID-to-link mapping change may not be performed. In such an embodiment, even if frames corresponding to one TID cannot be exchanged due to the deactivation of one link, another TID-to-link mapping change may not be performed. In this case, the another TID-to-link mapping change may be to map a TID mapped only to the deactivated link to another link. This embodiment may be applied when the AP multilink device determines that exchange of traffic corresponding to a TID mapped only to the deactivated link may not be permitted. Specifically, in such an embodiment, if the duration of the inactivation time interval is shorter than a predetermined duration, a TID-to-link mapping change to map a TID mapped only to the deactivated link to another link may not be performed. Furthermore, if the duration of the inactivation time interval is specified as unknown, a TID-to-link mapping change to map a TID mapped only to the deactivated link to another link may be performed.

[0447] In addition, information about the Block Ack session managed by a station operating on the deactivated link may also be transferred to another station in the multilink device that includes the station. The information about the Block Ack session may include a scoreboard for Block Ack transmission. In addition, the other station may be a station in the multilink device operating on a link to which the TID mapped only to the deactivated link is newly mapped. This prevents unnecessary retransmissions due to the lack of management of the success or failure of transmission of frames corresponding to a specific TID.

[0448] Figure 54 shows that according to an embodiment of the present invention, when one link is deactivated, the AP multilink device and the non-AP multilink device apply TID-to-Link mapping to the link that is deactivated and then reactivated.

[0449] In FIG. 54, an AP multilink device (AP MLD) including a first AP (AP1), a second AP (AP2), and a third AP (AP3) is coupled to a non-AP multilink device (Non-AP MLD) including a first station (Non-AP STA1), a second station (Non-AP STA2), and a third station (Non-AP STA3). The first AP (AP1) and the first station (Non-AP STA1) operate on a first link (Link1). The second AP (AP2) and the second station (Non-AP STA2) operate on a second link (Link2). The third AP (AP3) and the third station (Non-AP STA3) operate on a third link (Link3). TID values ​​0 to 2 are mapped to uplink and downlink transmissions on the first link (Link1). TID values ​​3 to 4 are mapped to uplink and downlink transmissions on the second link (Link2). Furthermore, TID values ​​5 to 7 are mapped to the upstream and downstream transmissions of the third link (Link 3).

[0450] When the third link (Link 3) is deactivated, the AP MLD and non-AP MLD apply the default mapping to the TID-to-Link mapping of the first and second links (Link 1 and Link 2), which are not deactivated.

[0451] When the third link (Link3) is activated, the TID-to-Link mapping from the first link (Link1) to the third link (Link3) is the TID-to-Link mapping that was applied before the third link (Link3) was deactivated.

[0452] As described above, when any one link is deactivated, a default mapping may be applied to the TID-to-Link mapping of the remaining links established between the AP multilink device and the non-AP multilink device. In this case, it may be prohibited to change the TID-to-Link mapping of the remaining links until the deactivated link is activated. For example, a first link among the links established between the AP multilink device and the non-AP multilink device may be deactivated. In this case, it may be prohibited to change the TID-to-Link mapping of the remaining established links, excluding the first link, until the first link is activated again.

[0453] In yet another specific embodiment, the TID-to-Link mapping of a deactivated link may not be changed until the deactivated link is activated. For example, a first link among the links established between an AP multilink device and a non-AP multilink device may be deactivated. In this case, the TID-to-Link mapping for the first link may not be changed until the first link is activated again. Therefore, during TID-to-Link mapping, the TID to be mapped must be mapped to at least one of the remaining links excluding the deactivated link until the deactivated link is activated. Furthermore, transmission of a TID-to-Link Mapping Request frame that maps a TID only to a deactivated link may not be allowed. Furthermore, the AP multilink device may not be allowed to accept a TID-to-Link Mapping Request that maps a TID to a deactivated link. Furthermore, the AP multilink device may not be allowed to accept a TID-to-Link Mapping Request that maps a TID only to a deactivated link.

[0454] In the above-described embodiment, the TID-to-Link mapping change may include changing the TID-to-Link mapping through TID-to-Link mapping negotiation.

[0455] Furthermore, the limitations according to the above-described embodiments may be commonly applied to non-AP multilink devices and AP multilink devices.

[0456] <Management of deactivated links>

[0457] Because frame exchange is restricted on a deactivated link, operation between an AP and a non-AP station connected via a deactivated link may be postponed or canceled. For example, an individual target wake time (TWT) agreement may be established between an AP and a non-AP station connected via a deactivated link. In this case, the AP must attempt frame exchange with the non-AP station at the agreed-upon time. Also, if a periodic TWT is established between the AP and the non-AP station, the AP must periodically attempt frame exchange with the non-AP station.

[0458] However, when a link connecting an AP and a non-AP station is deactivated, the AP may not attempt to exchange frames with the non-AP station even if a TWT agreement exists between the AP and the non-AP station. Furthermore, even if a TWT agreement exists between the AP and the non-AP station, the non-AP station may determine that the AP is not transmitting frames. In this case, the AP and the non-AP station may determine that the TWT agreement has been suspended. In a specific embodiment, when a deactivated link is reactivated, the AP and the non-AP station may resume the suspended TWT agreement.

[0459] A station that received a radio measurement request frame but failed to transmit a measurement report frame before any one of the links was deactivated may not transmit a measurement report frame during the deactivated time period. In yet another specific embodiment, a station that received a radio measurement request frame but failed to transmit a measurement report frame before any one of the links was deactivated may cancel the radio measurement operation. Specifically, a station that received a radio measurement request frame but failed to transmit a measurement report frame before the link was deactivated may ignore all previously received measurement requests. A station that transmitted a radio measurement request frame but failed to receive a measurement report frame before the link was deactivated may determine that a radio measurement report frame will not be transmitted during the link deactivation period. In such an embodiment, the radio measurement may include at least one of a beacon report, a frame report, a channel load report, and a noise histogram report.

[0460] <Management of legacy non-AP stations bound to deactivated links>

[0461] Even if the AP multilink device deactivates one of the links, the non-AP stations operating on the deactivated link may attempt to exchange frames with the AP multilink device. Therefore, when the AP multilink device deactivates one of the links, the AP multilink device must prepare the non-AP stations operating on the deactivated link for deactivation.

[0462] Before the AP multilink device deactivates one of its links, it can designate a time interval during which the deactivated link is deactivated as a quiet interval. Specifically, the AP multilink device can transmit a quiet element that designates a time interval during which the deactivated link is deactivated as a quiet interval. At this time, the AP multilink device can transmit a management frame or a beacon frame that includes the quiet element. A non-AP station that receives the quiet element maintains a NAV value other than 0 during the quiet interval and does not access the channel. Specifically, a non-AP station that receives the quiet element can set its NAV value according to the duration of the quiet interval designated by the quiet element. This allows legacy non-AP stations to determine that the channel is in a virtual busy state during the quiet interval.

[0463] Furthermore, unlike legacy non-AP stations, non-legacy non-AP stations that receive a quiet element transmitted for a deactivated link can access the channel during the quiet period of the deactivated link and attempt P2P transmission. Specifically, if the quiet element indicates the quiet period of the deactivated link as a quiet period, the non-legacy non-AP station does not need to set a NAV corresponding to the quiet period based on the quiet element. Furthermore, the quiet element transmitted for a deactivated link may be a quiet element transmitted over the deactivated link. In this case, legacy non-AP stations cannot ignore quiet elements transmitted over links other than the deactivated link.

[0464] Before the AP multilink device deactivates one of its links, it can transmit a management frame to legacy non-AP stations that are members of the BSS of the deactivated link, recommending that they move to another BSS. Specifically, before the AP multilink device deactivates one of its links, it can transmit a BSS transition management request frame to legacy non-AP stations that are members of the BSS of the deactivated link. In this case, legacy non-AP stations that receive the BSS transition management request frame can disassociate with the AP of the AP multilink device operating on the deactivated link. The BSS transition management request frame can include a Request Mode field. The Request Mode field can include a BSS Termination Included bit. The BSS Termination Included bit can be the fourth bit of the Request Mode field. When the BSS Termination Included bit is set to 1, the Request Mode field can include a BSS Termination Duration field. In this case, the BSS Termination Duration field may be a 12-octet field. The BSS Termination Duration field may include a Subelement ID field (1-octet), a Length field (1-octet), a BSS Termination TSF field (8-octet), and a Duration field (2-octet). The Subelement ID field may be a 1-octet field. The Length field may be a 1-octet field. The BSS Termination TSF field may be an 8-octet field. The Duration field may be a 2-octet field.The BSS Termination TSF field indicates the time at which the BSS is terminated using a TSF timer. The Duration field indicates the duration of the time interval at which the BSS is terminated in minutes. The AP multilink device can set the TSF corresponding to the deactivation point, which is the point at which the link to be deactivated begins to be deactivated, as the value of the BSS Termination TSF field. The TSF corresponding to the deactivation point may be the TSF at the deactivation point or a TSF value with the smallest error from the deactivation point. The AP multilink device can set the duration of the deactivation point in minutes as the value of the Duration field.

[0465] Furthermore, unlike legacy non-AP stations, non-legacy non-AP stations that receive a BSS transition management frame transmitted for a deactivated link can ignore the BSS transition management frame. Specifically, if the BSS transition management frame indicates that the BSS will terminate during the link's inactivity time interval, the non-legacy non-AP station can ignore the BSS transition management frame. In a specific embodiment, if the difference between the BSS termination time interval indicated by the BSS transition management frame and the link's inactivity time interval is within a predetermined time, the non-legacy non-AP station can ignore the BSS transition management frame. The difference between the BSS termination time interval and the link's inactivity time interval being within a predetermined time may refer to at least one of the difference between the start time of the BSS termination time interval and the start time of the link's inactivity time interval and the difference between the end time of the...

Claims

1. A non-AP (access point) multilink device that communicates with an AP (access point) multilink device via multiple links, a transmitter / receiver; a processor, The processor: receiving a beacon frame or a probe response frame from the AP multilink device; When the beacon frame or the probe response frame establishes a TID (traffic identifier)-to-link mapping between the non-AP multilink device and the AP multilink device, determining TIDs to be mapped to the multiple links according to the TID-to-link mapping established by the beacon frame or the probe response frame; transmitting on at least one link of the plurality of links according to a TID that is mapped to the at least one link of the plurality of links; When the beacon frame or the probe response frame establishes the TID-to-Link mapping between the non-AP multilink device and the AP multilink device, the non-AP multilink device is not allowed to reject the TID-to-Link mapping established by the beacon frame or the probe response frame; The value of a Neighbor AP TBTT Offset subfield corresponding to the deactivated link in a target beacon transmission time (TBTT) Information field included in the beacon frame or the probe response frame is 255; The TID-to-Link mapping set by the beacon frame or the probe response frame includes deactivating at least one link among the plurality of links.

2. 2. The non-AP multi-link device of claim 1, wherein the beacon frame or the probe response frame indicates that all TIDs subject to the TID-to-Link mapping are mapped to links other than the at least one inactivated link among the plurality of links.

3. 3. The non-AP multi-link device of claim 2, wherein when the beacon frame or the probe response frame indicates that any one link to which any one TID is mapped is to be deactivated, the TID-to-Link mapping is applied between the non-AP multi-link device and the AP multi-link device according to the beacon frame or the probe response frame.

4. 2. The non-AP multi-link device of claim 1, wherein when at least one link among the plurality of links is deactivated and then reactivated, all TIDs that are the subject of the TID-to-Link mapping are mapped to the at least one reactivated link among the plurality of links.

5. When the AP multilink device is a mobile AP and a non-STR (nonsimultaneous transmit and receive) multilink device in which transmission on one link of the plurality of links is limited to protect transmission or reception of the non-AP multilink device on another link of the plurality of links, the beacon frame or the probe response frame does not deactivate a primary link of the AP multilink device; The non-AP multi-link device of claim 1 , wherein the primary link is a link through which the AP multi-link device transmits the beacon frame.

6. After receiving the beacon frame or the probe response frame, the processor: Ignoring BSS transition management frames received on a link deactivated by the beacon frame or the probe response frame; The non-AP multi-link device of claim 1 , wherein the BSS transition management frame indicates that a BSS operating on the link deactivated by the beacon frame or the probe response frame is terminated.

7. After at least one link is deactivated by the beacon frame or the probe response frame, the processor:

2. The non-AP multi-link device of claim 1, wherein the non-AP multi-link device does not require a change to the TID-to-Link mapping of the at least one link.

8. After receiving the beacon frame or the probe response frame, the processor:

8. The non-AP multi-link device according to claim 7, wherein the device requests a change in TID-to-Link mapping of at least one link other than the link deactivated by the beacon frame or the probe response frame.

9. When the TID-to-Link mapping between the non-AP multi-link device and the AP multi-link device is applied according to the beacon frame or the probe response frame, the processor:

2. The non-AP multi-link device according to claim 1, wherein the device discards TID-to-Link mappings established for the plurality of links through TID-to-Link mapping negotiation before receiving the beacon frame or the probe response frame.

10. 2. The non-AP multi-link device of claim 1, wherein when at least one link is deactivated, the processor determines that a target wake time (TWT) agreement for the at least one deactivated link has been discontinued.

11. An AP multilink device that communicates with a non-AP (access point) multilink device via multiple links, a transmitter / receiver; a processor, The processor: Transmitting a beacon frame or a probe response frame to the non-AP multilink device to establish a traffic identifier (TID)-to-Link mapping between the AP multilink device and the non-AP multilink device; transmitting on at least one link of the plurality of links according to a TID that is mapped to the at least one link of the plurality of links; When the beacon frame or the probe response frame establishes the TID-to-Link mapping between the AP multilink device and the non-AP multilink device, the non-AP multilink device is not allowed to reject the TID-to-Link mapping established by the beacon frame or the probe response frame; The TID-to-Link mapping established by the beacon frame or the probe response frame includes deactivating at least one link among the plurality of links; The AP multilink device sets a value of a Neighbor AP TBTT Offset subfield corresponding to the deactivated link in a target beacon transmission time (TBTT) Information field included in the beacon frame or the probe response frame to 255.

12. The AP multi-link device of claim 11, wherein the beacon frame or the probe response frame indicates that all TIDs subject to the TID-to-Link mapping are mapped to links other than the at least one inactivated link among the plurality of links.

13. 12. The AP multilink device of claim 11, wherein when the at least one link among the plurality of links is deactivated and then reactivated, all TIDs that are the subject of the TID-to-Link mapping are mapped to the at least one reactivated link among the plurality of links.

14. 12. The AP multi-link device of claim 11, wherein a NAVSyncDelay-based channel access restriction is applied to an AP of the AP multi-link device when the at least one link among the plurality of links is deactivated and the deactivated at least one link among the plurality of links is reactivated.

15. A method for operating a non-AP (access point) multilink device that communicates with an AP (access point) multilink device over multiple links, comprising: receiving a beacon frame or a probe response frame from the AP multilink device; determining TIDs mapped to the plurality of links according to the TID-to-Link mapping established by the beacon frame or the probe response frame when the beacon frame or the probe response frame establishes a TID-to-Link mapping between the non-AP multilink device and the AP multilink device; transmitting on the at least one link of the plurality of links according to a TID that is mapped to the at least one link of the plurality of links; When the beacon frame or the probe response frame establishes the TID-to-Link mapping between the non-AP multilink device and the AP multilink device, the non-AP multilink device is not allowed to reject the TID-to-Link mapping established by the beacon frame or the probe response frame; The value of a Neighbor AP TBTT Offset subfield corresponding to the deactivated link in a target beacon transmission time (TBTT) Information field included in the beacon frame or the probe response frame is 255; The method of operation, wherein the TID-to-Link mapping set by the beacon frame or the probe response frame includes deactivating at least one link of the plurality of links.

16. A method of operating an AP multilink device that communicates with a non-AP (access point) multilink device over multiple links, comprising: transmitting a beacon frame or a probe response frame to the non-AP multilink device, the beacon frame or the probe response frame establishing a traffic identifier (TID)-to-Link mapping between the AP multilink device and the non-AP multilink device; transmitting on the at least one link of the plurality of links according to a TID that is mapped to the at least one link of the plurality of links; When the beacon frame or the probe response frame establishes the TID-to-Link mapping between the AP multilink device and the non-AP multilink device, the non-AP multilink device is not allowed to reject the TID-to-Link mapping established by the beacon frame or the probe response frame; The TID-to-Link mapping established by the beacon frame or the probe response frame includes deactivating at least one link among the plurality of links; A method of operating in which a value of a Neighbor AP TBTT Offset subfield corresponding to the deactivated link in a target beacon transmission time (TBTT) Information field included in the beacon frame or the probe response frame is set to 255.

Images