Wireless communication method using multi-link and wireless communication terminal using the same

Abstract

To provide a wireless communication method using a multi-link and a wireless communication terminal using the same.SOLUTION: According to the present disclosure, a non-AP multi-linkDevice (MLD) including a plurality of STAs respectively operating on a plurality of links in a wireless communication system may receive a frame from an APMLD including a plurality of access points (APs) respectively operating on the plurality of links, and may perform processing of each of one or more TBTT information fields based on a TBTT information type subfield and a TBTT information length field included in the frame.SELECTED DRAWING: Figure 47

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 supporting early wireless LAN technology using the 2.4 GHz frequency band, IEEE (Institute of Electronics Engineers) 802.11 has since implemented or is currently developing various other technology standards. IEEE 802.11b uses the 2.4 GHz frequency band and supports a maximum communication speed of 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz frequency band instead of the 2.4 GHz band, reducing the impact of interference compared to the significantly more congested 2.4 GHz frequency band, and uses OFDM technology to improve communication speeds to a maximum of 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 transmitter and receiver 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 continues to grow and applications become more diverse, the 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 bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard is defined only in the 5GHz band, initial 802.11ac chipsets are expected to support operation in the 2.4GHz band as well for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, IEEE 802.11ad is a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz band. 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, development of new WLAN standards has begun to increase maximum transmission speeds 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 under development with the goal of supporting transmission rates of up to 30 Gbps through wider bandwidth in the 2.4 / 5 / 6 GHz bands, increased spatial streams, and multi-AP cooperation. IEEE 802.11be proposes technologies such as a 320 MHz bandwidth, multi-link operation, multi-AP (multi-access point) operation, and hybrid automatic repeat request (HARQ) retransmission. 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.

[0009] The technical problems to be solved by the present specification are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0010] According to the present invention, there is provided a multi-link device (MLD) including a plurality of stations operating on a plurality of links, the multi-link device including a transceiver and a processor, the processor receiving a frame from an AP (Access Point) MLD including a plurality of APs, the frame including a Reduced Neighbor Report (RNR) element including one or more Neighbor AP information fields including information related to other APs included in the AP MLD, the Neighbor AP information field including a target beacon transmission time (TBTT) information field type subfield, a TBTT information length field, and one or more TBTT information fields. and processing each of the one or more TBTT information fields based on the TBTT information type subfield and the TBTT information length field, and when the value of the TBTT information type subfield is '0', each of the one or more TBTT information fields is processed only up to a first octet value or a second octet value by comparing the value of the TBTT information length field with a first threshold value and / or a second threshold value, and when the value of the TBTT information type subfield is '1', each of the one or more TBTT information fields is processed only up to a third octet value by comparing the value of the TBTT information length field with a third threshold value.

[0011] Also, in the present invention, the TBTT information field type subfield is used to indicate the content and / or length of the one or more TBTT information fields, and the TBTT information length field indicates the length of each of the one or more TBTT information fields.

[0012] Also, in the present invention, when the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is smaller than the first threshold value and equal to or larger than the second threshold value, each of the one or more TBTT information fields is processed only up to the second octet value, and the second octet value is smaller than the first octet value.

[0013] In addition, in the present invention, the remaining octets except for the second octet value in each of the one or more TBTT information fields are not processed.

[0014] Also, in the present invention, when the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is equal to or greater than the first threshold value, the one or more TBTT information fields are processed only up to the first octet value, and the second octet value is smaller than the first octet value.

[0015] In addition, in the present invention, the remaining octets except for the first octet value in each of the one or more TBTT information fields are not processed.

[0016] Also, in the present invention, if the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is smaller than the second threshold value, the one or more TBTT information fields are not processed.

[0017] Also, in the present invention, when the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is equal to or greater than the third threshold value, the one or more TBTT information fields are processed only up to the third octet value.

[0018] In addition, in the present invention, the remaining octets except for the third octet value in each of the one or more TBTT information fields are not processed.

[0019] Also, in the present invention, if the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is smaller than the third threshold value, the one or more TBTT information fields are not processed.

[0020] In addition, in the present invention, each of the one or more TBTT information fields includes a Neighbor AP TBTT Offset subfield, which indicates an offset between the TBTT for the AP to transmit a beacon frame and the TBTT for another AP to transmit a beacon frame.

[0021] Also, in the present invention, when the other AP is included in the AP MLD, the offset value indicated by the neighbor AP TBTT offset subfield is set to a value other than a preset value associated with Unknown.

[0022] In the present invention, the preset value is "255."

[0023] The present invention also provides a method for receiving a frame from an AP (Access Point) of an AP MLD including a plurality of APs, the frame including a Reduced Neighbor Report (RNR) element including one or more Neighbor AP information fields including information related to other APs included in the AP MLD, the Neighbor AP information field including a target beacon transmission time (TBTT) information field type subfield, a TBTT information length field, and one or more TBTT information fields. and processing each of the one or more TBTT information fields based on the TBTT information type subfield and the TBTT information length field, wherein if the value of the TBTT information type subfield is '0', each of the one or more TBTT information fields is processed only up to a first octet value or a second octet value by comparing the value of the TBTT information length field with a first threshold value and / or a second threshold value, and if the value of the TBTT information type subfield is '1', each of the one or more TBTT information fields is processed only up to a third octet value by comparing the value of the TBTT information length field with a third threshold value. [Effects of the Invention]

[0024] An embodiment of the present invention provides a wireless communication method that efficiently uses multilinks and a wireless communication terminal that uses the same.

[0025] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0026] [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] 1A and 1B are diagrams illustrating examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8] 1A and 1B are diagrams showing examples of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 is a diagram illustrating a multi-link device according to an embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating an example of a TID-to-link mapping method according to one embodiment of the present invention. [Figure 11] FIG. 10 is a diagram illustrating an example of a multi-link NAV setting operation according to one embodiment of the present invention. [Figure 12] FIG. 10 is a diagram illustrating yet another example of a multi-link NAV setting operation according to one embodiment of the present invention. [Figure 13] FIG. 1 is a diagram illustrating an example of BSS classification and operations based thereon according to an embodiment of the present invention. [Figure 14] FIG. 2 is a diagram illustrating a wireless LAN function according to an embodiment of the present invention. [Figure 15]FIG. 2 is a diagram illustrating an uplink (UL) multi-user (MU) operation according to one embodiment of the present invention. [Figure 16] FIG. 1 is a diagram illustrating a trigger frame format according to one embodiment of the present invention. [Figure 17] A diagram showing a method for indicating a trigger-based PPDU format according to one embodiment of the present invention. [Figure 18] FIG. 10 is a diagram illustrating an example of UL MU operation according to one embodiment of the present invention. [Figure 19] FIG. 10 is a diagram illustrating a power management operation performed by a station according to an embodiment of the present invention. [Figure 20] FIG. 2 is a diagram showing the format of a TIM element according to an embodiment of the present invention. [Figure 21] FIG. 2 is a diagram showing the format of a Multi-Link Traffic element according to an embodiment of the present invention. [Figure 22] 10 illustrates how the Partial Virtual Bitmap subfield of the Multi-Link Traffic element and the TIM element signal buffered traffic to an AP multi-link device according to an embodiment of the present invention. [Figure 23] 1 is a diagram illustrating a method for configuring a Multi-Link Traffic element according to an embodiment of the present invention. [Figure 24] A figure showing a method of setting the Per-Link Traffic Bitmap subfield of the Multi-Link Traffic element when the link set in which an AP multi-link device operates in accordance with an embodiment of the present invention is different from the link set in which a non-AP multi-link device communicating with the AP multi-link device operates. [Figure 25] FIG. 10 is a diagram illustrating signaling associated with a Multi-Link element and MediumSyncDelay according to one embodiment of the present invention. [Figure 26] 1 is a diagram illustrating a multi-link setup process according to an embodiment of the present invention. [Figure 27] FIG. 10 is a diagram illustrating the format of a Reduced Neighbor Report element according to an embodiment of the present invention. [Figure 28] 5 is a diagram illustrating a method for setting an ID of a multi-link device according to an embodiment of the present invention. [Figure 29] 10 is a diagram illustrating a method for allocating AIDs to non-AP stations belonging to a multi-link device according to an embodiment of the present invention. [Figure 30] 10 is a diagram illustrating a method for allocating AIDs to non-AP stations belonging to a multi-link device according to an embodiment of the present invention. [Figure 31] 10 is a diagram illustrating a TID-to-link mapping negotiation in which an AP multi-link device sends a TID-to-link mapping request according to an embodiment of the present invention. [Figure 32] 10 is a diagram illustrating a TID-to-link mapping negotiation in which an AP multi-link device sends a TID-to-link mapping request according to an embodiment of the present invention. [Figure 33] 10 is a diagram illustrating a TID-to-link mapping negotiation when a link set requesting TID-to-link mapping is different from a link set set in a TID-to-link mapping response according to an embodiment of the present invention. [Figure 34] FIG. 2 is a diagram illustrating an example of a TBTT information field format according to an embodiment of the present invention. [Figure 35] FIG. 2 is a diagram illustrating an example of a receiving and processing operation of a Neighbor AP Information field according to an embodiment of the present invention. [Figure 36] FIG. 2 is a diagram illustrating an example of a receiving and processing operation of a Neighbor AP Information field according to an embodiment of the present invention. [Figure 37] 10A and 10B are diagrams illustrating an example of beacon frame transmission and TBTT offset according to an embodiment of the present invention. [Figure 38] 10 is a diagram illustrating an example of the configuration of a multi-link and multi-BSSID set according to an embodiment of the present invention. [Figure 39] 10 is a diagram illustrating another example of the configuration of a multi-link and multi-BSSID set according to one embodiment of the present invention. [Figure 40] 10 is a diagram illustrating yet another example of the configuration of a multi-link and multi-BSSID set according to an embodiment of the present invention. [Figure 41] FIG. 2 illustrates an example of an EHT operating element according to an embodiment of the present invention. [Figure 42] FIG. 10 is a diagram illustrating an example of a traffic indicator virtual bitmap according to an embodiment of the present invention. [Figure 43] FIG. 10 is a diagram illustrating another example of a traffic indicator virtual bitmap according to an embodiment of the present invention. [Figure 44] FIG. 1 illustrates an example of a multiple link setup according to an embodiment of the present invention. [Figure 45] 10A and 10B are diagrams illustrating an example of the configuration of an RNR (Reduced Neighbor Report) element and transmission of a beacon frame according to an embodiment of the present invention. [Figure 46] FIG. 2 illustrates an example of a multiple link element according to an embodiment of the present invention. [Figure 47] FIG. 2 is a diagram illustrating an example of an operation method of an MLD according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] 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.

[0028] Throughout this specification, when a component is referred to as being "connected" to another component, this includes not only when it is "directly connected" to another component, but also when it is "electrically connected" with another component interposed therebetween. 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. Additionally, limitations such as "greater than" or "less than" based on a specific threshold value may be appropriately replaced with "more than" or "less than," respectively, depending on the embodiment.

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

[0030] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0031] 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.

[0032] As shown in FIG. 1, 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.

[0033] 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).

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The display unit 150 then outputs an image on a display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or a user interface based on a control command from 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.

[0042] 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.

[0043] 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 mounted 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 mounted 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 provided in the station 100.

[0044] 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.

[0045] 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 may perform wireless communication 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.

[0046] 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 about 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 modulator / demodulator that modulates and demodulates wireless signals transmitted and received by 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.

[0047] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0048] 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 a 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.

[0049] 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.

[0050] 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.

[0051] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0052] A terminal performing wireless LAN 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 a strength below the CCA threshold is detected, the channel is determined to be idle.

[0053] When a 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. Depending on the embodiment, the AIFS may be used as an alternative to the existing DCF IFS (DIFS). Each terminal waits while decrementing a slot time equal to a random number determined for the terminal during the idle interval of the channel, and a terminal that has used up the slot time attempts to access the channel. The period during which each terminal performs the backoff procedure is called a contention window period. The random number may be used as a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If a terminal detects that the channel is idle during the slot time, the terminal may decrement the backoff counter by 1. Furthermore, if the backoff counter reaches 0, the terminal may be allowed to perform channel access on the channel. Therefore, a terminal may be allowed to transmit if the channel is idle during the AIFS time and the backoff counter slot time.

[0054] If a specific terminal successfully accesses the channel, it transmits data 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.

[0055] <Examples of various PPDU formats>

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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 may 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.

[0060] 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.

[0061] 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 a non-legacy PPDU format, the L_RATE field is set to the minimum rate of 6 Mbps.

[0062] The L_LENGTH field is in bytes, and a total of 12 bits are allocated, allowing a maximum of 4095 to be signaled. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0063] First, a legacy or non-legacy terminal analyzes the length of the corresponding PPDU using the L_LENGTH field as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted during 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, to obtain the length of the corresponding PPDU, i.e., the reception time (RXTIME). This can be expressed mathematically as shown in Equation 1 below.

[0064]

number

[0065] At this time,

number

[0066]

number

[0067] 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.

[0068]

number

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 size of the original fields 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.

[0074] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (eg, the RA field) may be omitted depending on the value of the compression field.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] This invention proposes a method for signaling the discontinuous channel type of the SU PPDU, shows the discontinuous channel type determined by the proposed method, and proposes a method for signaling the primary 160 MHz and secondary 160 MHz puncturing types in the 320 MHz BW configuration of the SU PPDU.

[0080] In addition, one embodiment of the present invention proposes a method of varying the PPDU configuration indicated by the preamble puncturing BW value according to the PPDU format signaled in the PPDU format field. Assuming the length of the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, an EHT-SIG-A symbol of one symbol may be further signaled after the U-SIG, or no EHT-SIG-A may be signaled at all. Taking this into consideration, up to 11 puncturing modes must be 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 may be signaled in a different manner than in the 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0092] 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 composed of 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.

[0093] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0094] A multi-link device (MLD) may be defined for the wireless communication method using multiple links described above. A multi-link device may refer to a device having one or more affiliated stations. Depending on a specific embodiment, a multi-link device may refer to a device having two or more affiliated stations. A multi-link device may also exchange multi-link elements. A multi-link element includes information about one or more stations or one or more links. A multi-link element may include a multi-link setup element, which will be described later. In this case, a multi-link device may be a logical entity. Specifically, a multi-link device may have multiple affiliated stations. A multi-link device may be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). A multi-link device may have one medium access control service access point (SAP) up to a logical link control (LLC). An MLD may also have one MAC data service.

[0095] 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 multiple different links or multiple different channels. For example, multiple stations included in a multilink device can operate on multiple different channels, such as 2.4 GHz, 5 GHz, and 6 GHz.

[0096] 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.

[0097] 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 the first link (Link 1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via the second link (Link 2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via the third link (Link 3).

[0098] The multilink operation may include a multilink setup operation. The multilink setup corresponds to the association operation of the single-link operation described above and may be the first step for frame exchange in the multilink. The multilink device can obtain information required for the multilink setup from the 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 the 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.

[0099] Multilink setting may be performed by negotiation between peer stations. Specifically, multilink setting may be performed by communication between stations without communication with an AP. Multilink setting may also be performed in any one of the links. For example, even if the first to third links are set up by multilink, multilink setting may be performed in the first link.

[0100] 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 on 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 a first TID to the multiple links, and the second multilink device may be configured to transmit frames of a second TID to the first link. In addition, a default setting may exist for the mapping between a TID and a link. Specifically, if no additional settings are configured in the multilink configuration, the multilink device can 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.

[0101] 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 or assigned in a layer higher than the MAC layer. The TID may represent a traffic category (TC) or a traffic stream (TS). The TID may be classified into 16 types. For example, the TID may be designated as any one of 0 to 15. The TID value to be used may be designated separately according to an access policy, a channel access method, or a medium access method. For example, when enhanced distributed channel access (EDCA) or hybrid coordination function contention-based channel access (HCAF) is used, the TID value may be assigned in the range of 0 to 7. When EDCA is used, the TID may represent 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 value may be assigned in the range of 8 to 15. When HCCA or SPCA is used, the TID may represent the TSID. Furthermore, when HEMM or SEMM is used, the TID value may be assigned in the range of 8 to 15. When HEMM or SEMM is used, the TID may represent the TSID.

[0102] UP and AC 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 ACs. AC may include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may represent 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 can be further subdivided into AC_VI primary and AC_VI alternate. AC_VO can be further subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to an AC. For example, UP or TID 1, 2, 0, 3, 4, 5, 6, and 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. UP or TID 1, 2, 0, 3, 4, 5, 6, and 7 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. UP or TID 1, 2, 0, 3, 4, 5, 6, and 7 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 decreasing priority may be AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO may correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to such characteristics of TID, the mapping between TID and link may represent the mapping between AC and link. Also, the mapping between link and AC may represent the mapping between TID and link.

[0103] As described above, a TID may be mapped to each of multiple links. The mapping may involve specifying the links through which traffic corresponding to a specific TID or AC can be exchanged. Furthermore, the TIDs or ACs that can be transmitted for each transmission direction within a link may be specified. As described above, there may be a default setting for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device can exchange frames corresponding to the TIDs 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 point in time, any TID or AC may be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0104] 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 that are mapped to the link but do not correspond to the TID or AC will 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.

[0105] The above-described TID-to-link mapping may ensure QoS. Specifically, a higher priority AC or TID may be mapped to a link where a relatively small number of stations are operating 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.

[0106] FIG. 10 shows a multi-link mapped by the TID-to-link mapping method according to an embodiment of the present invention.

[0107] Referring to Figure 10, there may be a mapping relationship between TIDs and links as described in Figure 9. In addition, in the present invention, the mapping relationship between TIDs and links may be referred to as TID-to-link mapping, TID-to-link mapping, TID mapping, link mapping, etc. The TID may be a traffic identifier. The TID may also be an ID (identifier) ​​that classifies traffic, data, etc. to support quality of service (QoS).

[0108] The TID may be an ID used or assigned in a layer higher than the MAC layer. The TID may indicate traffic categories (TC) or traffic streams (TS). The TID may have 16 possible values, for example, values ​​from 0 to 15. Individual TID values ​​may be used depending on an access policy, channel access, or medium access method. For example, when EDCA (HCF (hybrid coordination function) connection-based channel access, enhanced distributed channel access) is used, the possible TID values ​​may be 0 to 7. When EDCA is used, the TID value may indicate user priority (UP), and the UP may be related to TC or TS. The UP may be a value assigned in a layer higher than the MAC. When HCCA (HCF controlled channel access) or SPCA is used, the possible TID values ​​may be 8 to 15. When HCCA or SPCA is used, the TID may indicate TSID. Furthermore, when HEMM or SEMM is used, the possible TID value may be 8 to 15. Furthermore, when HEMM or SEMM is used, TID may indicate TSID.

[0109] There may also be a mapping relationship between UP and access category (AC). An AC may be a label for providing QoS in EDCA or a label indicating a set of EDCA parameters. The EDCA parameters or a set of EDCA parameters may be used for channel association. An AC may be used in a QoS STA.

[0110] The AC value may be set to one of 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. Furthermore, AC_BK, AC_BE, AC_VI, and AC_VO may be further subdivided. For example, AC_VI may be further subdivided into AC_VI primary and AC_VI alternate. Furthermore, AC_VO may be further subdivided into AC_VO primary and AC_VO alternate. Furthermore, UP values ​​or TID values ​​may be mapped to AC values. For example, UP values ​​or TID values ​​of 1, 2, 0, 3, 4, 5, 6, and 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Alternatively, UP values ​​or TID values ​​1, 2, 0, 3, 4, 5, 6, and 7 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. UP values ​​or TID values ​​1, 2, 0, 3, 4, 5, 6, and 7 may have increasing priorities. That is, 1 may be a lower priority and 7 may be a higher priority. Therefore, the order of increasing priorities may be AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may correspond to ACI (AC index) 0, 1, 2, and 3, respectively.

[0111] Therefore, there may be a relationship between a TID and an AC. Therefore, the TID-to-link mapping of the present invention may be a mapping relationship between an AC and a link. Also, in the present invention, when a TID is mapped, it may mean that an AC is mapped, and vice versa.

[0112] According to one embodiment of the present invention, a TID may be mapped to each link of a multi-link. For example, there may be a mapping of which links a specific TID or a specific AC is allowed to transmit or receive on. Such mapping may be defined separately for each direction of the link. As described above, a default setting may exist for the mapping between TIDs and links. For example, the mapping between TIDs and links may basically map all TIDs to a certain link. According to one embodiment, at a specific time, a certain TID or a certain AC may be mapped to at least one link. Furthermore, management frames or control frames may be transmitted on all links.

[0113] In the present invention, data frames corresponding to TIDs or ACs that are mapped to either direction of the link may be transmitted, and data frames corresponding to TIDs or ACs that are not mapped to either direction of the link may not be transmitted.

[0114] According to one embodiment, the TID-to-link mapping may also be applied to the acknowledgment. For example, a block ack agreement may be based on the TID-to-link mapping. Alternatively, the TID-to-link mapping may be based on the block ack agreement. For example, a block ack agreement may exist for a TID-to-link mapped TID.

[0115] TID-to-link mapping can provide QoS services. For example, by mapping a high-priority AC and TID to a link with good channel conditions or few STAs, data for that AC and TID can be transmitted quickly. Alternatively, TID-to-link mapping can help STAs on a specific link save power (or enter a doze state).

[0116] 10, there may be an AP MLD including AP1 and AP2. There may also be a Non-AP MLD including STA1 and STA2. The AP MLD may also include multiple links, Link1 and Link2. AP1 and STA1 may be associated via Link1, and AP2 and STA2 may be associated via Link2.

[0117] Thus, Link1 may include a link transmitting from AP1 to STA1 and / or a link transmitting from STA1 to AP1, and Link2 may include a link transmitting from AP2 to STA2 and / or a link transmitting from STA2 to AP2, where each link may be mapped with a TID and / or AC.

[0118] For example, all TIDs and all ACs may be mapped to Link1, a link for transmission from AP1 to STA1, and Link1, a link for transmission from STA1 to AP1. Furthermore, only AC_VO or a TID corresponding to AC_VO may be mapped to Link2, a link for transmission from STA2 to AP2. Furthermore, only data of mapped TIDs and / or ACs can be transmitted on the link. Furthermore, data of TIDs or ACs not mapped to a link cannot be transmitted on the link.

[0119] FIG. 11 is a diagram illustrating an example of a multi-link NAV setting operation according to an embodiment of the present invention.

[0120] The simultaneous transmit and receive (STR) operation of MLD may be limited, which may be related to the frequency spacing between multiple links operating in a multi-link.

[0121] Therefore, according to an embodiment of the present invention, simultaneous transmission or reception is restricted when the spacing between links is m MHz, and simultaneous transmission or reception may not be restricted when the spacing between links is n MHz for n greater than m. This embodiment may be intended to solve the problem of simultaneous transmission or reception being restricted, and redundant description may be omitted. This embodiment may also be applied to MLDs that do not support STR.

[0122] According to an embodiment of the present invention, duration information may be shared between links operating as multiple links. As an example, the duration information may be TXOP duration information transmitted in a signaling field of a preamble. The signaling field may be the U-SIG field described above. Alternatively, the signaling field may be the HE-SIG-A field described above. As another example, the duration information may be indicated by a Duration / ID field included in a MAC header. As another example, the duration information may be indicated by a Length field included in an L-SIG field. According to an example, the duration information indicated by the U-SIG field, HE-SIG-A, or Duration / ID field may be a value indicating the TXOP duration. According to an example, the duration information indicated by the L-SIG field may be a value indicating the length of a physical layer protocol data unit (PPDU) including the L-SIG field or an end of a PPDU including the L-SIG field.

[0123] Furthermore, according to an embodiment of the present invention, it is possible to restrict transmission or channel access during a period based on period information shared between links. The method of restricting transmission or channel access may include setting a NAV. Alternatively, the NAV may be reset to resume transmission or channel access. In this case, the NAV may be an intra-BSS NAV. The intra-BSS NAV may be a NAV set by an intra-BSS frame (or PPDU). That is, a STA belonging to an MLD may set its NAV based on a frame (or PPDU) directed to another STA belonging to the MLD.

[0124] According to one embodiment of the present invention, an inter-link NAV may exist. The inter-link NAV may be a NAV used by STAs of multiple links belonging to an MLD when operating with multiple links. For example, transmission on link 2 may be avoided based on the inter-link NAV set based on period information received on link 1. Also, the inter-link NAV may exist or be used for an MLD that does not support STR. For example, when an inter-link NAV is set, the MLD that set the inter-link NAV does not need to transmit or connect channels on multiple links (or all links used by the MLD).

[0125] In addition to the intra-BSS NAV, a basic NAV may also be included as a type of NAV. The basic NAV may be a NAV set by an inter-BSS frame (or a PPDU), and the basic NAV may also be set by a frame (or a PPDU) that does not determine whether it is an intra-BSS or inter-BSS frame (or a PPDU).

[0126] Using a separate inter-link NAV may have advantages over not using an inter-link NAV in situations where the NAV setting is updated. For example, situations may arise where it is acceptable to reset the NAV set by another link. For example, if an inter-link NAV is set based on a certain frame (or PPDU), but it is determined that the frame (or PPDU) is not destined for the same MLD, it may be acceptable to reset the set inter-link NAV. Suppose there is an MLD operating on link 1 and link 2, the NAV for link 1 may be set based on a frame received on link 1. Then, the NAV for link 1 may be updated based on a frame received on link 2. If the NAV for link 2 no longer needs to be maintained, resetting the NAV for link 1 would result in the loss of the NAV information set based on the frame received on link 1. If the inter-link NAV were used together with the NAV for each link, the NAV for each link would be maintained even if the inter-link NAV was reset, thereby resolving the above problem.

[0127] Although the embodiment of the present invention focuses on setting the NAV, the embodiment of the present invention is not limited to this and can also be applied to instructing the physical layer to suspend channel connection or instructing the channel state to be busy. Furthermore, the embodiment is not limited to resetting the NAV and can also be applied to instructing the physical layer to continue channel connection or instructing the channel state to be idle. In this case, a primitive exchanged between the physical layer and the MAC layer may be used. Alternatively, a primitive exchanged between one STA and another STA in the MLD may be used. Alternatively, a primitive exchanged between one MAC layer and another MAC layer in the MLD may be used.

[0128] According to an embodiment of the present invention, when a STA belonging to an MLD starts receiving a PPDU, other STAs belonging to the MLD may have to terminate their channel access. As described above, channel access may be terminated based on the received duration information. However, due to the position of the field containing the duration information or the time required for decoding, there may be a time lag between the start of PPDU reception and the acquisition of the duration information. Therefore, accessing the channel and starting transmission during this time may lead to the above-mentioned problem. Therefore, according to an embodiment of the present invention, an STA in an MLD can terminate its channel access from the time another STA in the MLD starts receiving. Furthermore, after another STA in the MLD starts receiving, it can resume its channel access if it determines that the received frame is not intended for the other STA.

[0129] FIG. 12 is a diagram illustrating yet another example of a multi-link NAV setting operation according to an embodiment of the present invention.

[0130] FIG. 12 embodies the explanation of the specific method of the embodiment explained in FIG. 11, and the duplicated explanation may be omitted.

[0131] As described above, based on a frame or PPDU received by a STA belonging to the same MLD, other STAs belonging to the same MLD can suspend or resume their channel access or transmission. In the present invention, suspending channel access or transmission may include operations such as setting (updating) the NAV, determining the channel as busy, or suspending CCA. Furthermore, resuming channel access or transmission may include operations such as resetting the NAV, canceling the NAV setting, determining the channel as idle, or performing CCA. Hereinafter, these operations may be referred to as suspending and resuming channel access. Hereinafter, it may be described that STA1 and STA2 belong to the MLD and operate on Link1 and Link2, respectively. Furthermore, frames and PPDUs may be indicated interchangeably. Furthermore, the NAV in this case may be the intra-BSS NAV or the inter-link NAV, as described in FIG. 11.

[0132] According to an embodiment of the present invention, when STA1 begins to receive a frame, STA2 may suspend the channel connection. Furthermore, when STA1 acquires duration information from the L-SIG, STA2 may maintain the suspended channel connection. In this case, STA2 can determine that the suspended channel connection will last until the end of the frame received by STA1. Furthermore, if STA1 cannot reliably decode the L-SIG (if the L-SIG is invalid), STA2 can resume the channel connection.

[0133] In addition, STA1 can receive the TXOP duration and BSS color from the U-SIG of the frame received. If the received BSS color indicates intra-BSS or the BSS color is the BSS color corresponding to STA1, the channel connection can be suspended. In one embodiment, the duration for suspending the channel connection may be until the end of the received frame. In this case, there is an advantage that the channel connection can be started sooner after the end of the received frame. In another embodiment, the duration for suspending the channel connection may be the TXOP duration. In this case, the duration of the suspended channel connection may be updated based on the L-SIG. In this case, there is an advantage that the sequence following the received frame can be better protected.

[0134] Alternatively, STA1 may receive the TXOP duration and BSS color from the U-SIG of the received frame, but the received BSS color may indicate that it is not intra-BSS, or the BSS color may not be the BSS color corresponding to STA1. Alternatively, STA1 may not be able to successfully decode the U-SIG. In such cases, STA2 can resume channel connection.

[0135] Alternatively, STA2 can resume the channel connection if information obtained from the U-SIG of a frame received by STA1 indicates that the frame is a frame not received by STA1. For example, STA2 can resume the channel connection if the PHY identifier obtained from the U-SIG is an ID corresponding to a future standard or an unrecognized ID.

[0136] Although the above description is directed to the case where U-SIG is received, the same embodiment can also be applied to the case where HE-SIG-A is received when HE PPDU is received. For example, HE-SIG-A may include TXOP duration and BSS color, and therefore the above-described operations can be performed.

[0137] Also, STA2 may receive a STA-ID from the EHT-SIG of the frame received by STA1. If the received STA-ID is an indicator that STA1 should receive, for example, if the STA-ID indicates STA1, the STA-ID indicates a group to which STA1 belongs, or the STA-ID indicates broadcast, STA2 can maintain the state in which the channel connection is suspended.

[0138] Alternatively, STA1 may receive a STA-ID from the EHT-SIG of the received frame. If the received STA-ID is an indicator that does not correspond to STA1, for example, if the STA-ID does not indicate an indicator that corresponds to STA1, if the STA-ID does not indicate a group to which STA1 belongs, or if the STA-ID does not indicate broadcast, STA2 can resume the channel connection. Alternatively, STA2 can resume the channel connection even if STA1 fails to successfully decode the EHT-SIG.

[0139] Although the case of receiving EHT-SIG has been described, the same embodiment can also be applied to the case of receiving HE-SIG-B when receiving HE PPDU. For example, HE-SIG-B may include STA-ID, and therefore the above-described operation can be performed.

[0140] STA2 may also receive the MAC header of a frame received by STA1. If the RA (receiver address) or DA (destination address) included in the received MAC header indicates a value that STA1 should receive, for example, if the RA or DA indicates STA1, indicates a group to which STA1 belongs, or the STA-ID indicates broadcast, STA2 can maintain the suspended channel connection. In this case, the duration of the suspended channel access may be based on the duration information included in the received MAC header. More specifically, the duration of the suspended channel access may be based on the duration information indicated by the Duration / ID field included in the received MAC header.

[0141] Also, STA1 may have received the MAC header of the frame it received. If the RA or DA included in the received MAC header is an indicator that does not apply to STA1, for example, if the RA or DA does not indicate an indicator that applies to STA1, does not indicate a group to which STA1 belongs, or does not indicate broadcast, STA2 can resume channel connection. Alternatively, STA1 may not have received all of the MAC header. For example, STA1 may fail to receive all of the MPDUs included in the A-MPDU. In this case, STA2 can resume channel connection.

[0142] The channel connection suspension and resumption described in FIG. 12 may be performed in the decoding order as STA1 starts receiving frames (or PPDUs) and sequentially decodes them. The decoding order may be based on the PPDU format, frame format, etc. For example, the L-SIG, U-SIG, EHT-SIG, and MAC header may be decoded in this order (for EHT PPDUs). Alternatively, the L-SIG, HE-SIG-A, and MAC header may be decoded in this order (for HE SU PPDUs and HE TB PPDUs). Alternatively, the L-SIG, HE-SIG-A, HE-SIG-B, and MAC header may be decoded in this order (for HE MU PPDUs). Alternatively, the L-SIG and MAC header may be decoded in this order (for 11a / g PPDUs).

[0143] According to an embodiment of the present invention, the STA-ID mentioned above may be a value indicating an intended recipient of a PPDU or a resource unit (RU). The STA-ID may be included in an EHT-SIG field, an HE-SIG-B field, or the like. The STA-ID may indicate a value corresponding to a single STA. For example, when multiple STAs are included in an MLD, the STA-ID may indicate a value corresponding to one of the multiple STAs. The STA-ID may be a value based on the AID or MAC address of the STA.

[0144] FIG. 13 is a diagram illustrating an example of BSS classification and operations based thereon according to an embodiment of the present invention.

[0145] According to one embodiment of the present invention, a STA can classify (or determine) a BSS based on a received frame or a received PPDU. Classifying a BSS may include an operation of classifying whether a received frame or a received PPDU corresponds to a BSS to which the classifying STA belongs. Alternatively, classifying a BSS may mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the classifying STA belongs. Classifying a BSS may also include an operation of classifying whether a received frame or a received PPDU corresponds to a BSS to which the classifying STA does not belong. Alternatively, classifying a BSS may also mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the classifying STA does not belong. Classifying a BSS may also include an operation of classifying to which BSS a received frame or a received PPDU belongs. Alternatively, classifying a BSS may mean an operation of classifying from which BSS a received frame or a received PPDU is transmitted. According to one embodiment of the present invention, a BSS to which a classification STA belongs may be referred to as an intra-BSS. Alternatively, a BSS including a BSS to which a classification STA belongs may be referred to as an intra-BSS. Furthermore, a BSS that is not an intra-BSS may be referred to as an inter-BSS. Alternatively, a BSS that is not an intra-BSS may be an inter-BSS or an unclassified BSS. Alternatively, an inter-BSS may include an unclassified BSS. Furthermore, a BSS to which a classification STA does not belong may be referred to as an inter-BSS.

[0146] According to an embodiment, if a received frame or a received PPDU corresponds to an intra-BSS or is determined to have been transmitted from an intra-BSS, the received frame or the received PPDU may be referred to as an intra-BSS frame or an intra-BSS PPDU, respectively. Furthermore, if a received frame or a received PPDU corresponds to an inter-BSS or is determined to have been transmitted from an inter-BSS, the received frame or the received PPDU may be referred to as an inter-BSS frame or an inter-BSS PPDU, respectively. Furthermore, a PPDU including an intra-BSS frame may be an intra-BSS PPDU. Furthermore, a PPDU including an inter-BSS frame may be an inter-BSS PPDU.

[0147] According to an embodiment of the present invention, a BSS can be classified based on one or more BSS classification conditions, for example, a BSS can be classified based on whether or not at least one of the one or more BSS classification conditions is satisfied.

[0148] The BSS classification conditions may include a condition based on BSS color. BSS color may be an identifier for a BSS. Also, BSS color may be included in the preamble of a PPDU, more specifically, in the signaling field (e.g., the HE-SIG-A field, the U-SIG field, or the VHT-SIG-A field). Also, BSS color may be included in TXVECTOR, which is transmitted from the MAC layer of the sender to the PHY layer. Also, BSS color may be included in RXVECTOR, which is transmitted from the PHY layer of the receiver to the MAC layer. The parameters included in TXVECTOR and RXVECTOR may be referred to as TXVECTOR parameters and RXVECTOR parameters, respectively. Also, BSS color may be included in the TXVECTOR parameter or RXVECTOR parameter. The AP may notify the STA of the BSS color set by the AP. According to an embodiment, BSSs can be classified based on the BSS color included in the received PPDU. If the BSS color included in a PPDU received by a STA is different from the BSS color of the BSS corresponding to the STA, the received PPDU can be classified as an inter-BSS PPDU. Alternatively, if the BSS color included in a PPDU received by a STA is different from the BSS color of the BSS corresponding to the STA and its value is not 0, the received PPDU can be classified as an inter-BSS PPDU. Furthermore, if the BSS color included in a PPDU received by a STA is the same as the BSS color of the BSS corresponding to the STA, the received PPDU can be classified as an intra-BSS PPDU.

[0149] The BSS classification conditions may include a condition based on a MAC address. The MAC address may be included in the MAC header of the frame. The MAC address may include a receiver address (RA), a transmitter address (TA), a BSSID, a source address (SA), a destination address (DA), etc. According to one embodiment, a BSS may be classified based on a MAC address included in a received frame. If the MAC address included in the received frame is different from the BSSID of the BSS corresponding to the STA, the received frame may be classified as an inter-BSS frame. More specifically, if all of the MAC addresses included in the received frame are different from the BSSID of the BSS corresponding to the STA, the received frame may be classified as an inter-BSS frame. If the MAC address included in the received frame is the same as the BSSID of the BSS corresponding to the STA, the received frame may be classified as an intra-BSS frame. More specifically, if at least one of the MAC addresses included in the received frame is the same as the BSSID of the BSS corresponding to the STA, the received frame may be classified as an intra-BSS frame.

[0150] The corresponding BSS may include a BSS to which the STA is associated. The corresponding BSS may also include a BSS included in the same multiple BSSID set as the BSS to which the STA is associated. The corresponding BSS may also include a BSS included in the same co-hosted BSSID set as the BSS to which the STA is associated. For one or more BSSs included in the same multiple BSSID set or the same co-hosted BSSID set, information about the one or more BSSs may be transmitted in one frame.

[0151] The BSS classification condition may include a condition based on the value of the Partial AID field included in the VHT PPDU. The Partial AID field may be included in the preamble of the VHT PPDU. The Partial AID field may also be included in the VHT-SIG-A field included in the VHT PPDU. According to one embodiment, the Partial AID field may indicate a portion of the BSS color. For example, when the partial BSS color function is used, the Partial AID field may indicate a portion of the BSS color. Alternatively, when an AID assignment rule is used, the Partial AID field may indicate a portion of the BSS color. The AID assignment rule may be a method of assigning an AID based on the BSS color. Furthermore, when the Group ID field included in the VHT-SIG-A field of the VHT PPDU is a pre-set value (e.g., when the Group ID field is set to 63), the Partial AID field may indicate a portion of the BSS color. According to one embodiment, when the Partial AID field of a received PPDU indicates part of a BSS color, if the received Partial AID field value is different from part of the BSS color corresponding to the receiving STA, the received PPDU can be classified as an inter-BSS PPDU.

[0152] Furthermore, when the Partial AID field of a received PPDU indicates a portion of a BSS color, if the value of the received Partial AID field is identical to a portion of the BSS color corresponding to the receiving STA, the received PPDU can be classified as an intra-BSS PPDU. In this case, the portion of the BSS color may be 4 LSBs of the BSS color. According to another embodiment, the Partial AID field may indicate a portion of the BSSID. For example, if the Group ID field included in the VHT-SIG-A field of the VHT PPDU has a pre-set value (e.g., the Group ID field is set to 0), the Partial AID field may indicate a portion of the BSSID. According to one embodiment, when the Partial AID field of a received PPDU indicates a portion of a BSSID, if the value of the received Partial AID field is different from a portion of the BSSID corresponding to the receiving STA, the received PPDU can be classified as an inter-BSS PPDU. Furthermore, if the Partial AID field of a received PPDU indicates a portion of a BSSID, and the received Partial AID field value is identical to a portion of the BSSID corresponding to the receiving STA, the received PPDU can be classified as an intra-BSS PPDU. In this case, the portion of the BSSID can be the 9 MSBs of the BSSID. In addition, the Partial AID field value can be included in the TXVECTOR parameter PARTIAL_AID or the RXVECTOR parameter PARTIAL_AID. In addition, the Group ID field value can be included in the TXVECTOR parameter GROUP_ID or the RXVECTOR parameter GROUP_ID.

[0153] The BSS classification conditions may include conditions under which the AP receives a PPDU of a pre-set condition. For example, the PPDU of the pre-set condition may include a downlink PPDU. According to one embodiment, the downlink PPDU may include a VHT MU PPDU. Also, the downlink PPDU may include a PPDU in which signaling indicating uplink or downlink is set to a pre-set value. The signaling indicating uplink or downlink may be included in the signaling field of the HE PPDU. Alternatively, the signaling indicating uplink or downlink may be included in a U-SIG. The U-SIG may be included in the preamble of an EHT PPDU or a post-EHT standard PPDU.

[0154] In addition, there may be cases where a PPDU cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU. For example, if neither the above-mentioned conditions for classification as an intra-BSS PPDU nor the conditions for classification as an inter-BSS PPDU are met, the PPDU cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU.

[0155] In addition, when classifying BSSs, if the classification results based on multiple conditions do not match, the final result can be determined based on the pre-set conditions. For example, if the result based on the BSS color condition does not match the result based on the MAC address condition, the result based on the MAC address condition takes precedence, or the result based on the MAC address condition can be determined as the final result. Alternatively, if both the conditions for classification as an intra-BSS PPDU and the conditions for classification as an inter-BSS PPDU are met, the PPDU can be classified as an intra-BSS PPDU.

[0156] According to an embodiment of the present invention, a STA may perform an operation based on a classified BSS. The operation based on the classified BSS may include an intra-PPDU power save operation. The intra-PPDU power save operation may be a power save operation based on a received PPDU. The intra-PPDU power save operation can be performed when a pre-defined condition is met. The pre-defined condition may include a condition for classifying a received PPDU as an intra-BSS PPDU. The pre-defined condition may also include a condition that the intended receiver of a received PPDU is not the STA that received the PPDU. For example, if an ID or address included in a PPDU does not correspond to the STA that received the PPDU, the intended receiver of the PPDU may not be the STA that received the PPDU. The ID may be included in the preamble of the PPDU. For example, the ID may be the STA_ID included in the preamble of the PPDU. The STA_ID may be included in an EHT MU PPDU or an EHT PPDU. The address may be the MAC address described above. Furthermore, if the signaling indicating uplink or downlink included in the received PPDU indicates uplink, the intended recipient of the PPDU may not be the STA that received the PPDU. Furthermore, if the configuration of the received PPDU is set to a format that the STA that received the PPDU does not support, the intended recipient of the PPDU may not be the STA that received the PPDU. The configuration of the received PPDU may include the MCS of the PPDU, the number of spatial streams, the channel width, etc. Furthermore, if the STA that received the PPDU does not support the configuration of the received PPDU, a PHY-RXEND.indication(UnsupportedRate) primitive may be received. Furthermore, if the received PPDU is in a pre-configured format, the intended recipient of the PPDU may not be the STA that received the PPDU. The pre-configured format may include a TB PPDU.The TB PPDU may include an HE TB PPDU and an EHT TB PPDU. The TB PPDU may be a PPDU transmitted in response to a triggering frame. The triggering frame may include a trigger frame. The triggering frame may include a frame including triggering information. The triggering information may be included in a MAC header, for example, an A-control field. The triggering information or information included in the trigger frame may include the length of the response PPDU, the RU to be used in the response, the PHY configuration to be used in the response, the MAC configuration, etc. The intra-PPDU power saving operation may be an operation that can enter a doze state until the end of the received PPDU. As another example, if a STA determines that the intended recipient of a received PPDU or frame is not the STA, the STA may suspend reception or decoding of the PPDU or frame.

[0157] The operation based on the classified BSS may include an operation of setting (or updating) a NAV. According to an embodiment, a STA may operate one or more NAVs. Furthermore, when a STA receives a PPDU or a frame, the STA may set a NAV corresponding to the classified BSS based on the received PPDU or frame. For example, an intra-BSS NAV may be a NAV corresponding to an intra-BSS PPDU. Furthermore, a basic NAV may be a NAV corresponding to a PPDU that is not an intra-BSS PPDU. Alternatively, a basic NAV may be a NAV corresponding to an inter-BSS PPDU. Furthermore, when setting a NAV based on a received PPDU or a received frame, duration information included in the received PPDU or the received frame may be used. The duration information may include a TXOP. TXOP may refer to a value included in the TXOP field. The TXOP field may be included in the preamble of a PPDU. For example, the TXOP field may be included in the HE-SIG-A field of an HE PPDU. Alternatively, the TXOP field may be included in the U-SIG field of an EHT PPDU or a post-EHT standard PPDU. The duration information may also be included in the MAC header. For example, the duration information may be included in a Duration / ID field included in the MAC header.

[0158] The operation based on the classified BSS may include a spatial reuse operation. The operation based on the classified BSS may include a channel access operation. The spatial reuse operation may be a channel access operation. When a STA receives a PPDU or a frame, if a pre-set condition is met, the spatial reuse operation can be performed. The pre-set condition may include a condition that the received PPDU or the received frame corresponds to an inter-BSS. The pre-set condition may include a condition that the signal strength of the received PPDU or the received frame is lower than a threshold. For example, the threshold may be variable. The threshold may be a threshold for an OBSS PD-based spatial reuse operation. The threshold may be a value equal to or greater than the CCA threshold. The threshold may be a value based on the power to be transmitted. The spatial reuse operation may include an operation of transmitting a PPDU. The spatial reuse operation may include an operation of resetting a PHY. For example, resetting the PHY may be issuing a PHY-CCARESET.request primitive. Spatial reuse may include not setting a NAV based on a received PPDU or frame. If a STA performs spatial reuse, the STA may be able to transmit a PPDU while a received PPDU or frame is being transmitted or received.

[0159] Referring to FIG. 13, BSS A and BSS B may exist, and BSS A and BSS B may be different BSSs. BSS A and BSS B may correspond to inter-BSSs. That is, a PPDU or frame transmitted by a STA associated with BSS A in BSS B may be classified as an inter-BSS PPDU or an inter-BSS frame. STA1 and STA2 may belong to BSS A (or associated with the AP operating BSS A). STA3 and STA4 may belong to BSS B (or associated with the AP operating BSS B). Referring to FIG. 13, STA1 may transmit a PPDU. The PPDU transmitted by STA1 may include information about the BSS. For example, the information about the BSS may be information for classifying the BSSs described above. The PPDU transmitted by STA1 may include duration information.

[0160] STA2 receives the PPDU transmitted by STA1 and can classify the BSS for this PPDU. Since STA2 and STA1 belong to BSS A, the PPDU received by STA2 may be classified as an intra-BSS PPDU. Furthermore, the PPDU received by STA2 may be a UL PPDU or a PPDU for which the STA is not the intended recipient. Therefore, according to the above-described embodiment, STA2 can perform intra-PPDU power saving. Referring to FIG. 13, STA2 may enter a doze state until the end of the received PPDU. Furthermore, STA2 can set its NAV based on the Duration information included in the received PPDU. Since STA2 has classified the received PPDU as an intra-BSS PPDU, it can set its intra-BSS NAV.

[0161] STA3 receives the PPDU sent by STA1 and can classify the BSS for this PPDU. Also, since STA3 and STA1 belong to BSS B and BSS A, respectively, the PPDU received by STA3 can be classified as an inter-BSS PPDU. Also, STA3 can set the NAV based on the Duration information included in the received PPDU. Since STA3 has classified the received PPDU as an inter-BSS PPDU, it can set basic NAV.

[0162] STA4 receives the PPDU transmitted by STA1 and can classify the BSS for this PPDU. Furthermore, since STA4 and STA1 belong to BSS B and BSS A, respectively, the PPDU received by STA4 may be classified as an inter-BSS PPDU. Furthermore, the signal strength of the PPDU received by STA4 may be lower than a threshold. Therefore, since the PPDU received by STA4 is classified as an inter-BSS PPDU and the signal strength of the PPDU received by STA4 is lower than a threshold, STA4 can perform spatial reuse. Therefore, STA4 can perform channel access and backoff procedures and begin transmission. For example, STA4 may begin transmission before the PPDU transmitted by STA1 has finished.

[0163] FIG. 14 shows a wireless LAN function according to an embodiment of the present invention.

[0164] Referring to FIG. 14 , a WLAN of one standard may include the functions of a WLAN of another standard. Or, when a WLAN of one standard is used, it may be a WLAN of another standard. Here, WLAN can refer to an STA. Furthermore, WLAN can refer to an MLD including an STA. For example, a WLAN standard may include the standard functions of a previous generation and include additional functions. For example, an HT STA can also be an OFDM PHY STA. An HT STA can also perform additional functions in addition to the functions of an OFDM PHY STA. For example, a VHT STA can also be an HT STA. A VHT STA can also perform additional functions in addition to the functions of an HT STA. For example, an HE STA can also be a VHT STA. An HE STA can also perform additional functions in addition to the functions of a VHT STA. An EHT STA can also be an HE STA. An EHT STA can also perform additional functions in addition to the functions of an HE STA. There may also be standards subsequent to the EHT standard. In the present invention, the standard subsequent to the EHT standard can be called the NEXT standard, and the STA that complies with the NEXT standard can be called the NEXT STA. The NEXT STA can also be an EHT STA. In addition, the NEXT STA can perform additional functions in addition to the functions of the EHT STA.

[0165] Figure 14 is a diagram showing the relationship between STAs of each standard. Referring to Figure 14, an EHT STA can be an HE STA, a VHT STA, an HT STA, or an OFDM PHY STA. Also, a NEXT STA can be an EHT STA, an HE STA, a VHT STA, an HT STA, or an OFDM PHY STA.

[0166] FIG. 15 illustrates an uplink (UL) multi-user (MU) operation according to one embodiment of the present invention.

[0167] Referring to FIG. 15, an AP can instruct at least one STA to transmit a PPDU through a specific frame (e.g., a triggering frame), and at least one STA can simultaneously transmit PPDUs of the same or individual formats based on the specific frame transmitted from the AP.

[0168] Specifically, as shown in FIG. 15, a frame soliciting or triggering a multi-user (MU) transmission may be transmitted, and one or more STAs may transmit or respond to such a frame based on such a frame. In this case, when one or more STAs transmit a response to the frame, the one or more STAs may simultaneously respond immediately based on the frame, and the response to the frame may begin transmission SIFS after the end of the PPDU including the frame. For example, if the frame solicits an immediate response, one or more STAs may immediately transmit a response to the frame. A frame soliciting or triggering one or more STAs to transmit may be a trigger frame or a frame including information in its MAC header that solicits or triggers uplink transmission to one or more STAs. In this case, the frame may include information (e.g., a TRS control subfield) in its MAC header that triggers or solicits uplink transmission to only one STA.

[0169] For example, the information indicating or triggering an uplink transmission included in the MAC header may be a triggered response scheduling (TRS) or TRS control subfield included in an HT control field, a control subfield, or an A-control subfield.

[0170] A frame for instructing or triggering uplink transmission may be transmitted by an AP. If the frame for instructing or triggering uplink transmission is a trigger frame, a response thereto may be transmitted in a trigger-based PPDU (TB PPDU) format. In this case, the TB PPDDU may include the above-mentioned HE TB PPDU and EHT TB PPDU, as well as a NEXT TB PPDU that may be defined in the next standard.

[0171] The HE TB PPDU may consist of a preamble, data, and a packet extension (PE), and the preamble may include L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-STF, and HE-LTF in that order.

[0172] The EHT TB PPDU and NEXT TB PPDU may also be composed of a preamble, data, and PE, and the preambles of the EHT TB PPDU and NEXT TB PPDU may include L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, (EHT- / NEXT-)STF, and (EHT- / NEXT-)LTF in that order.

[0173] A frame that instructs or triggers one or more STAs to transmit a PPDU may include information necessary for one or more STAs to transmit a TB PPDU. For example, if a frame includes a type subfield of "01" (B3 B2) and a subtype subfield of "0010" (B7 B6 B5 B4), the frame including such type and subtype subfields may be a trigger frame, which is a control frame.

[0174] If multiple STAs are instructed or triggered to respond with a TB PPDU, and the formats of the PPDUs to which the multiple STAs respond are different from each other, a problem may occur in that the AP that instructed or triggered the response has difficulty receiving the response PPDUs transmitted from the multiple STAs. Alternatively, if the information contained in the preambles of the PPDUs to which the multiple STAs respond differs depending on the format, a problem may occur in that the AP that instructed or triggered the response has difficulty receiving the response PPDUs transmitted from the multiple STAs.

[0175] Therefore, to solve this problem, when multiple STAs respond to a frame from an AP, the format of the responding PPDU and / or the type of information included in the preamble of the PPDU may be set to be the same. For example, when multiple STAs transmit HE TB PPDUs in response to a frame from an AP, the AP may transmit information so that the information included in the L-STF, L-LTF, L-SIG, RL-SIG, and HE-SIG-A is the same, or a convention may be defined for the information included in the HE TB PPDU, so that the AP can successfully receive the preambles transmitted by the multiple STAs. However, if the HE TB PPDU, EHT TB PPDU, and NEXT TB PPDU are simultaneously transmitted in overlapping subbands, the TB PPDU formats may be different from each other, which may make it difficult for the AP to receive them.

[0176] According to an embodiment of the present invention, an HE STA can transmit an HE TB PPDU. An EHT STA can transmit an EHT TB PPDU or an HE TB PPDU. A NEXT STA can transmit a NEXT TB PPDU, an EHT TB PPDU, or an HE TB PPDU. This is because, as described in FIG. 10, a STA of a certain standard may include the functionality of a previous standard.

[0177] As shown in Figure 15, when an AP transmits a frame to schedule the transmission of a TB PPDU to an HE STA and an EHT STA, and uses the frame to instruct or trigger the transmission of a TB PPDU, there may be no precise instruction or protocol for the TB PPDU format. In this case, the HE STA transmits an HE TB PPDU in response to the frame, and the EHT STA may respond with an EHT TB PPDU or an HE TB PPDU. In this case, the AP may have difficulty receiving the TB PPDUs transmitted by these STAs. This may result in the AP being unable to successfully receive TB PPDUs from multiple STAs, resulting in the medium being occupied and reducing transmission opportunities for other STAs.

[0178] Hereinafter, in the present invention, instructing an STA can mean instructing a response from the STA, and the terms "trigger" and "instruct" may be used interchangeably.

[0179] Furthermore, the HE trigger frame, EHT trigger frame, and NEXT trigger frame may be trigger frames defined in the HE, EHT, and NEXT standards, respectively. Furthermore, in the present invention, the HE TRS, EHT TRS, and NEXT TRS may be TRSs defined in the HE, EHT, and NEXT standards, respectively.

[0180] FIG. 16 shows a trigger frame format according to an embodiment of the present invention.

[0181] Figure 16(a) shows the trigger frame format, and Figure 16(b) and (c) show the common info(information) field and the user info field, respectively, which are fields included in the trigger frame.

[0182] 16(a), as a trigger MAC header, the frame includes a Frame Control field, a Duration field, an Address field, and may include a Common Information field and a User Information List field. The Address field may include a Resource Allocation (RA) field and a Transmitter Address (TA) field.

[0183] The common information field may include information that is common to all STAs designated by the trigger frame. Figure 16(b) shows an example of the common information field.

[0184] The user information list field may contain zero or more user information fields, and the user information list field of a trigger frame other than a specific type of trigger frame may contain one or more user information fields. (c) of Figure 16 shows an example of a user information field.

[0185] The trigger frame may additionally include a padding field and a frame check sequence (FCS) field. The padding field may be used to increase the length of the frame to allow time for a STA receiving the trigger frame to prepare a response to the trigger frame, and may be optionally included in the trigger frame.

[0186] Referring to (b) of Figure 16, the common information field may include a trigger type subfield. The trigger type subfield may be used to identify a trigger frame variant. Alternatively, the type of trigger frame may be indicated based on the value of the trigger frame subfield. Furthermore, the information and length included in the trigger dependent common information subfield and the trigger dependent user information subfield shown in Figure 12 may be determined based on the trigger type subfield. For example, the trigger type subfield may be indicated by bits B0 to B3 of the common information field.

[0187] The common information field may include an Uplink (UL) length subfield. The UL length subfield may include information about the length of the TB PPDU, which is a response to the trigger frame, or may include information about the length of a frame responding to the trigger frame. The UL length subfield may also indicate the value included in the length subfield of the L-SIG of the TB PPDU responding to the trigger frame. Therefore, a STA that receives a trigger frame and responds with a TB PPDU can set the value of the length subfield included in the L-SIG of the TB PPDU based on the value of the UL length subfield included in the received trigger frame. Specifically, a STA that responds with a TB PPDU can set the length subfield included in the L-SIG of the TB PPDU to the value of the UL length subfield included in the received trigger frame. For example, a STA can transmit a TB PPDU by setting the length subfield included in the L-SIG of the TB PPDU based on the value of bits B4 to B15 of the common information field, which indicate the UL length subfield.

[0188] The common information field may further include an uplink bandwidth subfield (UL Bandwidth (BW) subfield). The UL BW subfield may indicate a BW value included in a signaling field (e.g., HE-SIG-A or U-SIG) of a TB PPDU responding to the trigger frame, and may indicate the maximum BW of a TB PPDU transmitted in response to the trigger frame. Therefore, the STA can set the BW value included in the signaling field of the TB PPDU based on the value of the UL BW subfield included in the trigger frame.

[0189] In addition, the common information field may further include information included in the signaling field of the TB PPDU, which is a response to the trigger frame. Therefore, after receiving the trigger frame, the STA can set the information included in the TB PPDU based on the information included in the trigger frame.

[0190] Referring to (c) of FIG. 16, the user information field may include an AID12 subfield. The AID12 subfield may be used to indicate the intended recipient of the user information field including the AID12 subfield or the function of the user information field. Therefore, the AID12 subfield may also serve to indicate the intended recipient of the trigger frame including the AID12 subfield or the function of the trigger frame. For example, if the value of the AID12 subfield is a pre-configured value, the user information field may indicate a Random Access Resource Unit (RA-RU). That is, the pre-configured value of the AID12 subfield may indicate that the user information field indicates an RA-RU. Specifically, if the value of the AID12 subfield is '0', the user information field may indicate an RA-RU for associated STAs. For example, if the value of the AID12 subfield is "0", the user information field can indicate an RA-RU for associated STAs, and if the value of the AID12 subfield is "2045", the user information field can indicate an RA-RU for unassociated STAs. STAs corresponding to the STA ID (e.g., AID (association ID)) indicated by the value of the AID12 subfield may be instructed to respond by a user information field including the AID12 subfield or a trigger frame including the AID subfield. For example, the AID12 subfield can indicate the AID or 12 LSBs of the AID. STAs corresponding to the value indicated by the AID12 subfield can transmit a TB PPDU in response to the received trigger frame. In this case, the value of the AID12 subfield may be in the range of "1" to "2007" (inclusive), and if the AID12 subfield is a previously set value (e.g., "2046"), the RU corresponding to the previously set value of the AID12 subfield may not be assigned to any STA.Also, if the AID subfield is already set to a value (for example, "4095"), the already set value may indicate that padding of the trigger frame begins.

[0191] Information in the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. For example, the Resource Unit (RU) Allocation subfield may indicate the size and location of the RU. In this case, the value of the RU Allocation subfield in the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. That is, the RU indicated by the RU Allocation subfield in the AID12 subfield may be the RU allocated to the STA indicated by the AID12 subfield.

[0192] The user information field may also indicate the coding method (UL FEC coding type), modulation method (UL HE-MCS, UL DCM), and power (UL Target RSSI) for generating the TB PPDU to be transmitted in response to the trigger frame.

[0193] FIG. 17 illustrates a method for indicating a triggered-based (TB) PPDU format according to one embodiment of the present invention.

[0194] Referring to FIG. 17, one STA can selectively transmit PPDUs of different formats based on instructions from a triggering frame instructing the transmission of the PPDU.

[0195] Specifically, an EHT STA can selectively transmit not only a legacy PPDU (e.g., an HE TB PPDU) but also an EHT TB PPDU, and a NEXT STA can selectively transmit an HE TB PPDU, an EHT TB PPDU, and / or a NEXT TB PPDU. In this case, STAs to which multiple standards are applied can be individually scheduled using one frame or one PPDU. This method can be advantageous because STAs to which multiple standards are applied share common resources in a WLAN. For example, an HE STA (an HE STA other than an EHT STA) can respond with an HE TB PPDU using one frame. That is, a non-AP STA can transmit a triggering frame to instruct EHT STAs as well as HE STAs to transmit an HE TB PPDU.

[0196] In addition, information for selecting the TB PPDU format may be included in a triggering frame, such as a trigger frame, a TRS, a PPDU including the trigger frame, or a PPDU including a TRS control subfield. That is, the AP STA includes information for selecting the TB PPDU format in a triggering frame and transmits it to at least one non-AP STA, and the non-AP STA can select the format of a PPDU to respond to based on the information included in the received triggering frame. The at least one non-AP STA can then transmit a PPDU to the AP based on the selected format.

[0197] Information on the format of the PPDU (TB PPDU format) which is a response to such a triggering frame may exist at the MAC level, and a trigger frame, which is one of the triggering frames, may be classified into an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame, and responses to each trigger frame may be classified into an HE TB PPDU, an EHT TB PPDU, and a NEXT TB PPDU.

[0198] In addition, classifying trigger frames into HE trigger frames, EHT trigger frames, and NEXT trigger frames may be equivalent to classifying TB PPDU formats, which are responses to trigger frames, into HE TB PPDU, EHT TB PPDU, and NEXT TB PPDU, respectively.

[0199] Whether the format of a trigger frame for distinguishing the format of a TB PPDU is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame may be identified based on a Frame Control field included in a MAC header. Specifically, the format of the trigger frame may be distinguished based on a Type subfield, a Subtype subfield, and / or a Control Frame Extension subfield. Furthermore, if the values ​​of the Type subfield, the Subtype subfield, and / or the Control Frame Extension subfield are pre-set values, the trigger frame may be identified as an HE trigger frame, and if the values ​​are other pre-set values, the trigger frame may be identified as an EHT trigger frame. Furthermore, if the values ​​of the Type subfield, the Subtype subfield, and / or the Control Frame Extension subfield are other pre-set values, the trigger frame may be identified as a NEXT trigger frame.

[0200] For example, if the Type subfield is 01 (B3 B2) and the Subtype subfield is 0010 (B7 B6 B5 B4), the format of the frame including the Type subfield and the Subtype subfield may be an HE trigger frame. In this case, it may be necessary to further use entries in the Type subfield (2 bits), the Subtype subfield (4 bits), and / or the Control Frame Extension subfield (4 bits), which are assigned limited numbers of bits, in the EHT standard and the NEXT standard.

[0201] Alternatively, whether the format of the trigger frame is an HE trigger frame or an EHT trigger frame may be identified based on the common information field included in the trigger frame. That is, the format of the PPDU transmitted in response to the trigger frame may be determined based on the value of a specific subfield (first subfield) included in the common information field. For example, a non-AP STA may select an HE TB PPDU or an EHT TB PPDU based on the value of the common information field and transmit it in the assigned RU. In this case, in addition to the common information field, a specific subfield (second subfield) of the user information field may also be used to identify the format of the PPDU.

[0202] That is, a variant for determining the format of a PPDU that is a response to the trigger frame may be determined based on the common information field of the trigger frame, and the format of the PPDU may be determined based on the determined variant. For example, if the variant for determining the PPDU format is determined to be the HE variant based on the common information field, the non-AP STA may respond with an HE TB PPDU, and if the variant for determining the PPDU format is determined to be the EHT variant based on the common information field, the non-AP STA may respond with an EHT TB PPDU.

[0203] In this case, the variant for determining the format of the PPDU may further use the user information field in addition to the common information field.

[0204] For example, a trigger frame may be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the trigger type subfield. For example, if the trigger type subfield value is a previously set value, the trigger frame may be an HE trigger frame. Also, if the trigger type subfield value is a previously set value, the trigger frame may be an EHT trigger frame. If the trigger type subfield value is a previously set value, the trigger frame may be a NEXT trigger frame.

[0205] For example, if the trigger type subfield value is 0 to 7, it is an HE trigger frame, and if it is not 0 to 7, it may be an EHT trigger frame or a NEXT trigger frame. The trigger type subfield indicates various trigger frame types, but in this case, there is a disadvantage that a limited trigger type subfield space must be used.

[0206] According to still another embodiment, a trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a UL length subfield of the trigger frame. For example, a trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a value obtained by modulating the UL length subfield value (remainder). That is, the value of the UL length subfield may be used to determine whether the format of a PPDU transmitted in response to a trigger frame is an HE PPDU or an EHT PPDU.

[0207] More specifically, the trigger frame can be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the value obtained by modulating the UL length subfield value modulo 3 (the remainder when the UL length subfield is divided by 3). For example, if the result of modulating the UL length subfield value modulo 3 is not 0, the trigger frame may be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 1, the trigger frame may be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 0, the trigger frame may not be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 0, the trigger frame may be an EHT trigger frame or a NEXT trigger frame.

[0208] That is, if the value modulo 3 of the UL length subfield of the trigger frame is not 0, the response to the trigger frame may be transmitted in an HE TB PPDU, and if the value modulo 3 of the UL length subfield is 1, the response to the trigger frame may be transmitted in an HE TB PPDU.

[0209] Also, when the value modulo 3 of the UL length subfield of the trigger frame is 0, the format of the PPDU transmitted in response to the trigger frame may be EHT TB PPDU.

[0210] Furthermore, an additional trigger frame classification method can be used in addition to this method to classify the HE trigger frame, EHT trigger frame, and NEXT trigger frame. For example, the classification method described in FIG. 16 can be used in addition to this method to classify the HE trigger frame, EHT trigger frame, and NEXT trigger frame.

[0211] According to one embodiment, the format of the trigger frame may be determined as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a User Info field of the trigger frame.

[0212] That is, similar to the above-described common information field, whether the format of the trigger frame is an HE trigger frame or an EHT trigger frame can be identified based on the user information field included in the trigger frame. That is, the format of the PPDU transmitted in response to the trigger frame may be determined based on the value of a specific subfield (second subfield) included in the user information field. For example, depending on the value of the user information field, a non-AP STA may select an HE TB PPDU or an EHT TB PPDU and transmit it in the assigned RU. In this case, in addition to the user information field, a specific subfield (first subfield) of the common information field may also be used to identify the format of the PPDU.

[0213] That is, a variant for determining the format of a PPDU that is a response to the trigger frame may be determined based on the user information field of the trigger frame, and the format of the PPDU may be determined based on the determined variant. For example, if the variant for determining the PPDU format is determined to be the HE variant based on the user information field, the non-AP STA may respond with an HE TB PPDU, and if the variant for determining the PPDU format is determined to be the EHT variant based on the user information field, the non-AP STA may respond with an EHT TB PPDU.

[0214] In this case, in addition to the user information field, a common information field may also be used as a variant for determining the format of the PPDU.

[0215] For example, a frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the AID12 subfield. According to one embodiment, a frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on whether or not it includes an AID12 subfield with a preset value. In this case, a question may arise as to whether a STA indicated by a certain user information field should continue to check the AID12 subfield present after the user information field to determine the trigger frame format. To solve this problem, a user information field including an AID12 subfield indicating which trigger frame it is may be located at the beginning of the user information list. In addition, to prevent HE STAs that cannot understand this signaling method from malfunctioning, a user information field including an AID12 subfield indicating which trigger frame it is may be located after the user information field corresponding to the HE STA.

[0216] In addition, since information on subfields other than the AID12 subfield included in the user information field may not be necessary for the TB PPDU response, subfields of the user information field including the AID12 subfield indicating which trigger frame it is may be omitted. That is, the length of the user information field may vary depending on the AID12 subfield. Referring to FIG. 17, the AID12 subfield may serve to indicate the format of the TB PPDU to be responded to. For example, if the AID12 subfield is a pre-set value, the response to the trigger frame including the AID12 subfield set to the pre-set value may be an EHT TB PPDU. For example, if the AID12 subfield value is 2047, the response to the trigger frame including the AID12 subfield may be an EHT TB PPDU. Furthermore, if the AID12 subfield is a pre-set value, the response to the trigger frame including the AID12 subfield set to the pre-set value may be a NEXT TB PPDU. For example, if the AID12 subfield value is 2048, the response to a trigger frame containing the AID12 subfield may be a NEXT TB PPDU.

[0217] According to another embodiment, when responding based on a user information field located at a pre-set position from the AID12 subfield of a pre-set value, the response can be made in a TB PPDU format corresponding to the pre-set value. For example, when responding based on a user information field located after the AID12 subfield of a pre-set value, the response can be made in a TB PPDU format corresponding to the pre-set value. If there are multiple values ​​indicating a TB PPDU format, when responding based on a user information field located after both the pre-set value 1 and the pre-set value 2, the response can be made in a TB PPDU format according to the pre-set priority between the TB PPDU format corresponding to the pre-set value 1 and the TB PPDU format corresponding to the pre-set value 2. Referring to FIG. 17, when responding based on a user information field located after the AID12 subfield set to 2047, the response can be made in an EHT TB PPDU. Also, when responding based on a user information field located after the AID12 subfield set to 2048, the response can be made in a NEXT TB PPDU. Also, when responding based on a user information field that exists after both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it can respond with a NEXT TB PPDU. Also, when responding based on a user information field that exists before both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it can respond with a HE TB PPDU.

[0218] In this embodiment, an example is given in which the AID12 subfield indicates the type of trigger frame, but the present invention is not limited to this, and it is also possible to indicate the type of trigger frame in other subfields of the user information field.

[0219] According to an embodiment, the trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a padding field of the trigger frame. For example, whether the trigger frame is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame can be determined based on whether the padding field includes a pre-set value indicating whether the trigger frame is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame.

[0220] According to an embodiment of the present invention, it is possible to distinguish between an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame by combining a plurality of trigger frame distinction methods described in the present invention. In addition, the contents described in the present invention regarding trigger frames are not limited to the above and can also be applied to TRS.

[0221] In yet another embodiment of the present invention, the AP may not be able to use a triggering frame to instruct transmission of both the EHT PPDU and the HE PPDU, i.e., the EHT AP cannot transmit a trigger frame instructing both the HE TB PPDU and the EHT TB PPDU, and can only instruct one PPDU format.

[0222] FIG. 18 illustrates UL MU operation according to yet another embodiment of the present invention.

[0223] As described above, in addition to the trigger frame, the transmission of a TB PPDU can also be indicated by a TRS. Also, the TRS may be included in the HT control field as described above. For example, when the HT control field includes an A-control field, it can include a TRS. The TRS can be conveyed by a TRS control subfield. The A-control field may be in the form of a series of control list fields. Also, the control list field may include a TRS.

[0224] In addition, a receiver of a frame including a TRS (indented receiver) can respond to the TRS. For example, a STA corresponding to an RA included in a frame including a TRS can respond to the TRS. The TRS may include information on the length of a PPDU or frame responding to the TRS (UL Data Symbols), the location and size of an RU used when responding to the TRS (RU Allocation), information on power when responding to the TRS (AP Tx Power, UL Target RSSI), information on a modulation method when responding to the TRS (UL HE-MCS), etc.

[0225] The embodiment of Fig. 18 may be a method for solving the problems described in Fig. 14 and Fig. 15. Also, as described above, the above-mentioned embodiment regarding the trigger frame can also be applied to the TRS. Also, the above-mentioned content can be omitted.

[0226] According to one embodiment of the present invention, in addition to the TRS defined in the HE standard (HE TRS), TRS defined in the EHT standard or the NEXT standard (EHT TRS and NEXT TRS, respectively) may also exist. Therefore, depending on whether the indicated TRS is the HE TRS, EHT TRS, or NEXT TRS, the TB PPDU responding to the TRS may be the HE TB PPDU, EHT TB PPDU, or NEXT TB PPDU, respectively. For example, the TRS defined by which standard can be determined by the Control ID subfield of the A-Control subfield. As an additional example, the TRS can be divided into two types: the HE TRS and a TRS other than the HE TRS.

[0227] Alternatively, for example, the TRS defined by which standard is used may be determined depending on whether the HT control field is an HE variant, an EHT variant, or a NEXT variant. Also, whether it is an HE variant, an EHT variant, or a NEXT variant may be determined depending on the value of the already set bits in the HT control field. For example, if B0 and B1 in the HT control field are 1, 1, it may be an HE variant. Also, whether it is an HE variant, an EHT variant, or a NEXT variant can be determined using B0 and B1 in the HT control field and an additional bit (e.g., B31).

[0228] According to one embodiment of the present invention, it is possible to determine the TB PPDU format in response to the TRS based on the PPDU format including the TRS. That is, when a PPDU instructing PPDU transmission includes a TRS control subfield, the PPDU format may be determined based on the format of the PPDU including the TRS control subfield. For example, when the format of the PPDU including the TRS control subfield is HE PPDU, the format of the indicated PPDU may be HE PPDU. However, when the format of the PPDU including the TRS control subfield is EHT PPDU, the format of the indicated PPDU may be EHT PPDU.

[0229] 18, when a TRS is transmitted in an HE PPDU, a TB PPDU responding to the TRS may be an HE TB PPDU. When a TRS is transmitted in an EHT PPDU, a TB PPDU responding to the TRS may be an EHT TB PPDU. When a TRS is transmitted in a NEXT PPDU, a TB PPDU responding to the TRS may be a NEXT TB PPDU.

[0230] According to an embodiment of the present invention, a subfield included in a TRS may be interpreted differently depending on the PPDU format in which the TRS is included. For example, when a TRS is included in an HE PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the HE MCS table. When a TRS is included in an EHT PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the EHT MCS table. When a TRS is included in a NEXT PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the NEXT MCS table. In addition, the RU Allocation subfield may also be interpreted differently depending on the PPDU format in which the TRS is included.

[0231] FIG. 19 shows a power management operation performed by a station according to an embodiment of the present invention.

[0232] According to an embodiment of the present invention, a station can operate in a power save mode (PS). At this time, a station operating in the power save mode may alternate between an awake state and a doze state. In the awake state, the station operates at full power. Also, in the awake state, the station can transmit and receive. In the power save state, the station's transmission and reception may be restricted. If a frame to be transmitted in the power save mode is buffered in the station, the station transitions to the awake state; otherwise, the station can operate in the power save state. In the power save mode, the station can frequently alternate between the awake state and the power save state. In the active mode, the station maintains a state in which it can always transmit and receive. That is, in the active mode, the station can always operate in the awake state.

[0233] When a station operates in a power-saving mode, the station may not be able to receive data. Therefore, the AP signals to the station that traffic to be transmitted is buffered, receives a response from the station, and then transmits data. For convenience of explanation, the signaling by the AP to the station that traffic to be transmitted is buffered is referred to as a traffic indication. Also, signaling for traffic indication is referred to as traffic indication signaling. Traffic indication between the AP and the station may be performed as follows. In this specification, traffic may include any one of a frame, a BU, an MSDU, and an MPDU.

[0234] When traffic to be transmitted to a station is buffered in an AP, the AP may transmit traffic indication signaling indicating that the traffic to be transmitted to the station has been buffered. In this specification, the traffic indication signaling may indicate that traffic has been buffered, and is not limited to traffic for a specific station, depending on the context. The traffic indication signaling may include at least one of a traffic indication map (TIM) element and a multi-link traffic element. The traffic indication signaling may be in a bitmap format. Specifically, the traffic indication signaling may indicate whether traffic corresponding to each bit of the bitmap has been buffered in the AP transmitting the bitmap. The traffic indication signaling may also indicate a recipient of the buffered traffic. For example, the traffic indication signaling may indicate that the buffered traffic corresponds to at least one of group addressed traffic, groupcast traffic, broadcast traffic, and individually addressed traffic. The bitmap can signal which group or station the traffic belongs to depending on the bit position of the bitmap. A station can determine whether traffic corresponding to a group to which the station belongs is buffered in the AP or whether traffic for the station is buffered in the AP depending on the bit position of the bitmap.

[0235] The traffic indication signaling may be transmitted based on a predetermined time point. Accordingly, a station in a power-saving state may switch from a power-saving state to an awake state based on the time point at which the traffic indication signaling is transmitted. The traffic indication signaling may be included in a beacon frame. Alternatively, the traffic indication signaling may be included in a TIM frame. Alternatively, the AP may periodically transmit the traffic indication signaling. Specifically, the AP may transmit the traffic indication signaling based on a target beacon transmission time (TBTT). However, if the channel is not idle (busy) at the TBTT, the AP may transmit the traffic indication signaling at a time point later than the TBTT. The station may remain awake at the TBTT and receive the traffic indication signaling. A beacon frame including the traffic indication signaling may not be transmitted exactly at the TBTT. Therefore, the station may remain awake for a certain period of time including the TBTT.

[0236] In the above embodiment, it has been described that the AP transmits the traffic indication signaling and the station receives it. In this case, the station may be a non-AP station. Also, the AP may be included in an AP multilink device, and the non-AP station may be included in a non-AP multilink device. Also, the traffic may refer to a bufferable unit (BU) or a buffered BU.

[0237] An AP can send a DTIM (delivery TIM) before sending group-addressed traffic or broadcast traffic. DTIM is a type of TIM that indicates whether group-addressed traffic and broadcast traffic have been buffered in the AP. A beacon frame that includes a DTIM can be called a DTIM beacon frame. If a station receives a DTIM that indicates that group traffic for a group that includes the station is to be transmitted, the station can send signaling to the AP indicating that it wants to receive the group traffic.

[0238] The station that receives the traffic indication signaling can transmit a signaling to induce (retrieve) transmission to the station. In this case, the signaling to induce (retrieve) transmission to the station can be at least one of a PS-Poll frame or a U-APSD trigger frame. The AP that receives the signaling to induce (retrieve) transmission to the station transmits buffered traffic to the station.

[0239] In FIG. 19, the first AP (AP1) includes a TIM in a beacon frame and transmits the beacon frame every TBTT. The TIM transmitted by the first AP (AP1) indicates that traffic for the first station (STA1) is buffered. The first station (STA1) transmits a PS-Poll frame and remains awake to receive traffic. The first AP (AP1) transmits the buffered traffic (Data to STA1) to the first station (STA1). The first station (STA1) may receive the buffered traffic and enter a power-saving state. The first station (STA1) may also remain awake when transmitting the next TIM.

[0240] Also, in FIG. 19, the first AP (AP1) transmits a DTIM every three beacon frames. Therefore, the DTIM interval is three beacon frames. At this time, the first station (STA1) operating in power save mode maintains an awake state every time a TIM is transmitted. After transmitting the DTIM beacon, the first AP (AP1) transmits broadcast traffic or group address traffic. If the DTIM indicates that the broadcast traffic or group address traffic to be received by the first station (STA1) is buffered, the first station (STA1) maintains an awake state to receive the broadcast traffic or group address traffic. This allows the first station (STA1) to stably receive broadcast traffic or group address traffic even in power save mode. With reference to FIG. 20, the format of a TIM element that can be included in traffic indication signaling will be described.

[0241] FIG. 20 shows the format of a TIM element according to an embodiment of the present invention.

[0242] The TIM element includes the TIM described above. The TIM element may include at least one of an Element ID subfield, a Length subfield, a DTIM Count subfield, a DTIM Period subfield, a Bitmap Control subfield, and a Partial Virtual Bitmap subfield. The Element ID subfield, the Length subfield, the DTIM Count subfield, the DTIM Period subfield, and the Bitmap Control subfield are each 1 octet, i.e., 8 bits in length. The Partial Virtual Bitmap subfield may have a variable length up to a maximum of 251 octets. The length of the Partial Virtual Bitmap subfield may be determined by the Bitmap Control field or the Bitmap Offset subfield of the Bitmap Control field.

[0243] The Element ID subfield indicates the ID of the element that contains it.

[0244] The Length subfield indicates the length of the element it is included in. Specifically, the Length subfield can indicate the length of the element excluding the Element ID subfield and the Length subfield.

[0245] The DTIM Count subfield indicates how many beacon frames are to be transmitted until the next DTIM. Specifically, the value of the DTIM Count subfield indicates how many beacon frames are to be transmitted until the next DTIM, including the beacon frame in which the DTIM Count subfield is included. For example, a value of 0 in the DTIM Count subfield may indicate that the DTIM Count subfield is included in the DTIM beacon.

[0246] The DTIM Period subfield indicates the number of beacon frames transmitted during the DTIM. If all TIMs are DTIMs, the value of the DTIM Period subfield is set to 1.

[0247] The Bitmap Control subfield may include a Traffic Indicator subfield and a Bitmap Offset subfield. The Traffic Indicator subfield may be a 1-bit field, and the Bitmap Offset subfield may be a 7-bit field. The Traffic Indicator subfield may indicate whether group address traffic is buffered. Specifically, if group address traffic is buffered, the AP may set the value of the Traffic Indicator subfield to 1. Group address traffic may be traffic whose receiver AID is 0. The Bitmap Offset subfield indicates the starting point of the bit corresponding to the Partial Virtual Bitmap in the Traffic indication virtual bitmap. The AID (association ID) corresponding to the Partial Virtual Bitmap is determined by the Bitmap Offset subfield.

[0248] Each bit in the Partial Virtual Bitmap field indicates whether traffic to be transmitted to a station with an AID corresponding to that bit is buffered in the AP transmitting the TIM. When the value of a bit in the Partial Virtual Bitmap field is 1, it indicates that traffic to be transmitted to a station with an AID corresponding to that bit is buffered in the AP transmitting the TIM. When the value of a bit in the Partial Virtual Bitmap field is 0, it indicates that traffic to be transmitted to a station with an AID corresponding to that bit is not buffered in the AP transmitting the TIM. Therefore, when the value of a bit in the Partial Virtual Bitmap field is 1, a station receiving a TIM can determine that traffic to be transmitted to a station with an AID corresponding to that bit is buffered in the AP transmitting the TIM. When the value of a bit in the Partial Virtual Bitmap field is 0, a station receiving a TIM can determine that traffic to be transmitted to a station with an AID corresponding to that bit is not buffered in the AP transmitting the TIM. Furthermore, a station that receives a TIM can determine that traffic to be sent to a station with an AID not specified by the Partial Virtual Bitmap is not buffered in the AP that sends the TIM.

[0249] The TIM element may include a Traffic indication virtual bitmap subfield. In this case, the bit number in the Traffic indication virtual bitmap subfield may indicate the AID of the station corresponding to the bit. Specifically, a bit numbered n in the Traffic indication virtual bitmap subfield indicates whether a frame transmitted to a station with AID n is buffered in the AP transmitting the TIM element. Specifically, when the bit number in the Traffic indication virtual bitmap subfield is N, the bit may indicate whether traffic transmitted to a station with AID N or a group with Group ID N is buffered in the AP transmitting the TIM element. The TIM may include a Partial Virtual Bitmap subfield instead of the Traffic indication virtual bitmap subfield. The Partial Virtual Bitmap subfield is the Traffic indication virtual bitmap subfield with consecutive bits set to 0 omitted. The Partial Virtual Bitmap subfield may be the Traffic indication virtual bitmap subfield with either the first consecutive bits or the last consecutive bits omitted from a set of consecutive bits set to 0. Specifically, the Partial Virtual Bitmap subfield may be bits from octet number N1 to N2 in the Traffic indication virtual bitmap subfield, where N1 may be the largest even number in the Traffic indication virtual bitmap subfield where bit numbers 1 to (N1*8-1) are all 0.N2 may be the smallest number in the Traffic indication virtual bitmap subfield where all bit numbers from (N2+1)*8 to 2007 are 0. This may be a method for configuring the Partial Virtual Bitmap subfield when multiple BSSID sets are not supported, i.e., when dot11MultiBSSIDImplemented is false. In this specification, the bit number n of a bitmap or subfield represents the (n+1)th bit of the bits of the bitmap or subfield.

[0250] When the values ​​of all bits in the Traffic indication virtual bitmap subfield except for the bit with bit number 0 are 0, the Partial Virtual Bitmap subfield has a length of 1 octet, and the values ​​of all bits in the Partial Virtual Bitmap subfield may be set to 0. In this case, the value of the Bitmap Offset field may be 0, and the value of the Length field may be set to 4.

[0251] Also, when all bits in the Traffic indication virtual bitmap subfield have a value of 0 and all bits in the Bitmap Control subfield have a value of 0, the TIM element may not include the Partial Virtual Bitmap field and the Bitmap Control field. In this case, the value of the Length field may be set to 2. In this way, when the Partial Virtual Bitmap field exists in the TIM, the Bitmap Control field may also exist.

[0252] Therefore, when multiple BSSID sets are supported, i.e., when dot11MultiBSSIDImplemented is True, a method for configuring the Partial Virtual Bitmap subfield may be performed according to the following embodiment. When multiple BSSID sets are used, a management frame transmitted from an AP corresponding to a transmitted BSSID may include information for a BSS corresponding to a nontransmitted BSSID. In this case, the management frame may include at least one of a beacon frame and a probe response frame. The TIM element of a beacon frame transmitted from a transmitted BSSID may indicate whether an AP corresponding to a nontransmitted BSSID included in a multiple BSSID set including the transmitted BSSID buffers the frame. Taking this into consideration, a method for configuring the Partial Virtual Bitmap subfield will be described.

[0253] If the maximum number of BSSIDs that a multiple BSSID set can have is n, bits from bitmap number 1 to bitmap number (2^n-1) in the Traffic indication virtual bitmap subfield can indicate whether a group address frame is buffered in the AP transmitting the TIM element. In this case, the group address frame may be a frame buffered in the AP corresponding to the nontransmitted BSSID. Therefore, the group address frame is a group address frame of the AP or BSS corresponding to the nontransmitted BSSID. Each of bits from bitmap number 1 to bitmap number (2^n-1) in the Traffic indication virtual bitmap subfield can indicate whether a frame is buffered in the AP corresponding to that bit. In this case, bits in the Traffic indication virtual bitmap subfield with bit numbers greater than (2^n-1) indicate whether a frame transmitted to a station with AID n is buffered in the AP transmitting the TIM element. Therefore, an AP does not need to assign AIDs from 1 to (2^n-1). In this embodiment, a bit corresponding to an inactive nontransmitted BSSID may be set to a reserved bit. In this case, the value of the reserved bit may be set to 0. The AP may also assign a number equal to or greater than 2^n as the AID of a station. In this case, the AP may assign any value from 2^n to 2007 as the AID of a station. The EHT AP may not assign 2007 as the AID. This range of values ​​that can be assigned as AIDs is called the AID space. Transmitted BSSIDs and nontransmitted BSSIDs may share one AID space. In a specific embodiment, the EHT AP may not assign 2007 as the AID of a station.

[0254] The maximum number of BSSIDs, n, that a multiple BSSID set may have may be signaled in the multiple BSSID element, where n may be the value indicated by the MaxBSSID Indicator of the multiple BSSID element.

[0255] The following describes how to configure the Partial virtual bitmap subfield. The method for configuring the Partial virtual bitmap subfield may vary depending on the multiple BSSID set-related capabilities of the AP transmitting the TIM element. A non-S1G AP can configure the Partial virtual bitmap subfield using Method A or Method B. An S1G AP can configure the Partial virtual bitmap subfield using Method C. A non-HT AP, HT AP, VHT AP, HE AP, or EHT AP may all be a non-S1G AP. An S1G AP refers to an AP that operates in a frequency band below 1 GHz, while a non-S1G AP refers to an AP that operates in a frequency band above 1 GHz.

[0256] First, we will explain method A. The subfield of the partial virtual bitmap may be composed of bits with octet numbers 0 to N2 in the Traffic indication virtual bitmap. N2 is the smallest number among the numbers that satisfy the condition that the values ​​of bits with bit numbers (N2+1)*8 to 2007 in the Traffic indication virtual bitmap are all 0. If there is no N2 that satisfies this condition, N2 is 250. In method A, the value of the Bitmap Offset field is 0. Also, the value of the Length field is N2+4.

[0257] Method B will be described. The subfield of the Partial virtual bitmap may be composed of bits from octet number 0 to (N0 - 1) of the Traffic indication virtual bitmap and bits from octet number N1 to N2 of the Traffic indication virtual bitmap. N0 may be the largest positive integer that satisfies (N0 * 8 - 2^n < 8). When N0 is odd, N1 may be the largest even number that satisfies N0 < N1 and that all the values of the bits from bit number N0 * 8 to (N1 * 8 - 1) are 0. When there is no value of N1 > N0, N1 may be N0. Also, N2 may be the smallest positive integer (integer) that satisfies that all the values of the bits from bit number (N2 + 1) * 8 to 2007 of the Traffic indication virtual bitmap are 0. When there is no N2 that satisfies this, N2 may be 250. In Method B, the value of the Bitmap Offset field is (N1 - N0) / 2. Also, the value of the Length field is (N0 + N2 - N1 + 4). When there is no buffered frame in any of the BSSs corresponding to the transmitted BSSID and the nontransmitted BSSID, the length of the Partial Virtual Bitmap subfield is 1 octet, and all the bit values of the Partial Virtual Bitmap subfield may be set to 0. At this time, the value of the Bitmap Offset field is 0. Also, the value of the Length field is 4.

[0258] If individually addressed frames are not buffered in any BSS corresponding to the transmitted or nontransmitted BSSID, and group addressed frames are buffered in one or more BSSs, the Partial virtual bitmap subfield may consist of bits from octet number 0 to (N0-1), where N0 is the largest positive integer such that (N0*8-2^n)<8.

[0259] It may be necessary for a multilink device to direct buffered traffic to each of the multiple links it operates on, as will be explained with reference to Figures 13-18.

[0260] FIG. 21 shows the format of a Multi-Link Traffic element according to an embodiment of the present invention.

[0261] APs operating in one multilink device can share an AID space. Specifically, one multilink device may have one AID space. In this case, when a buffered frame is indicated to an AP using the TIM element described in FIG. 20, a station may have difficulty determining which link the frame is buffered on. To solve this problem, a traffic indication signaling method is needed. Specifically, the multilink device can perform traffic indication signaling for each link. In a specific embodiment, the multilink device can perform traffic indication signaling for each station belonging to the multilink device. The TIM element transmitted by the multilink device can indicate whether there is a buffered frame on each multilink operated by the multilink device. In this case, the TIM element transmitted by the multilink device is called a Multi-Link Traffic element.

[0262] A multi-link device can transmit a Multi-Link Traffic element in a beacon frame or a TIM frame, and the Multi-Link Traffic element may be included in a frame that includes a TIM element.

[0263] In FIG. 21, the Multi-Link Traffic element may include an Element ID subfield, a Length subfield, an Element ID Extension subfield, a Multi-Link Traffic Control subfield, and a Per-Link Traffic Indication List subfield.

[0264] The Element ID subfield is a one-octet field that indicates the ID of the element that contains it.

[0265] The Length subfield is a one-octet field that indicates the length of the element it is included in. Specifically, the Length subfield can indicate the length of the element excluding the Element ID subfield and the Length subfield.

[0266] The Element ID Extension subfield is a one-octet field that indicates a value that, in combination with the value of the Element ID subfield in which it is included, identifies the element.

[0267] The Multi-Link Traffic Control subfield is a 1-octet field and includes a Bitmap Size subfield and an AID Offset subfield. The Bitmap Size subfield is a 4-bit subfield and indicates the size of the Per-Link Traffic Indication Bitmap subfield. If the value of Bitmap Size is M, the size of the Per-Link Traffic Indication Bitmap subfield may be M+1. A Bitmap Size value of 0 is a reserved value.

[0268] The AID Offset subfield is an 11-bit subfield that indicates the starting position of the bit in the Traffic Indication virtual bitmap indicated by the Per-Link Traffic Indication List or Per-Link Traffic Indication Bitmap subfield. Therefore, the AID (association ID) corresponding to the Per-Link Traffic Indication List or Per-Link Traffic Indication Bitmap subfield is determined by the AID Offset subfield. If the value of AID Offset is K, the Per-Link Traffic Indication List or Per-Link Traffic Indication Bitmap subfield indicates bit number K of the Traffic Indication virtual bitmap. Also, if the value of the AID Offset subfield is K, the smallest value of the AIDs corresponding to the Per-Link Traffic Indication List or Per-Link Traffic Indication Bitmap subfield is K. The Per-Link Traffic Indication List subfield is a variable-length field and may include one or more Per-Link Traffic Indication Bitmap subfields. When the value of the AID Offset subfield is K, each Per-Link Traffic Indication Bitmap subfield indicates the bit number of the Traffic indication virtual bitmap starting from bit number K. The number of Per-Link Traffic Indication Bitmap subfields included in the Per-Link Traffic Indication List subfield may be the number of bits set to 1 among the bits corresponding to the AID of the non-AP multilink device in the Partial Virtual Bitmap.The plurality of Per-Link Traffic Indication Bitmap subfields may be sorted by the AIDs corresponding to the Per-Link Traffic Indication Bitmap subfields in the Per-Link Traffic Indication List subfield. Specifically, the plurality of Per-Link Traffic Indication Bitmap subfields may be sorted in ascending order of the AIDs corresponding to the Per-Link Traffic Indication Bitmap subfields in the Per-Link Traffic Indication List subfield.

[0269] When the value of the Bitmap Size field is m, the size of the Per-Link Traffic Indication Bitmap subfield is m+1 bits. When the TID-to-link mapping negotiation is successful, the bit of the Per-Link Traffic Indication Bitmap subfield indicates whether traffic to be transmitted to a non-AP station operating on the link corresponding to that bit is buffered. Specifically, when the value of a bit of the Per-Link Traffic Indication Bitmap subfield is 1, the bit of the Per-Link Traffic Indication Bitmap subfield may indicate that traffic to be transmitted to a non-AP station operating on the link corresponding to that bit is buffered. When the value of a bit of the Per-Link Traffic Indication Bitmap subfield is 0, the bit of the Per-Link Traffic Indication Bitmap subfield may indicate that traffic to be transmitted to a non-AP station operating on the link corresponding to that bit is not buffered. When the TID-to-link mapping is the default mapping, a bit in the Per-Link Traffic Indication Bitmap subfield may indicate whether to recommend retrieving buffered traffic transmission on the link corresponding to the bit. Specifically, when the value of a bit in the Per-Link Traffic Indication Bitmap subfield is 1, the bit in the Per-Link Traffic Indication Bitmap subfield may indicate that it is recommended to request transmission of buffered traffic on the link corresponding to the bit. When the TID-to-link mapping of a link corresponds to the default mapping, uplink and downlink transmissions on the link may be performed without TID restrictions. In addition, the default mapping is applied to links for which TID-to-link mapping negotiation has not been successfully completed.Therefore, if the TID-to-link mapping negotiation is successful, it can indicate the case where the TID-to-link mapping negotiation is successful and not all TIDs are mapped to all links.

[0270] The bits in the Per-Link Traffic Indication Bitmap subfield are mapped to links according to their bit numbers. Specifically, a bit in the Per-Link Traffic Indication Bitmap subfield with bit number n may be mapped to a link with link ID n. The Per-Link Traffic Indication List subfield may also include a padding field. This allows the Per-Link Traffic Indication List subfield to have a length in octets. The padding field may have a length between 0 and 7 bits.

[0271] The AP multilink device can transmit a frame including both a Multi-Link Traffic element and a TIM element. In this case, the frame may be a beacon frame. With reference to FIG. 14, a method for the AP multilink device to signal traffic buffered in the AP multilink device using the Multi-Link Traffic element and the TIM element will be described.

[0272] FIG. 22 illustrates how the Partial Virtual Bitmap subfield of the Multi-Link Traffic element and the TIM element signal buffered traffic to an AP multi-link device according to an embodiment of the invention.

[0273] The bit corresponding to the non-AP multilink device in the Partial Virtual Bitmap subfield or Traffic indication virtual bitmap of the TIM element transmitted by the AP multilink device may be set to 1. In this case, the non-AP multilink device can parse the Multi-Link Traffic element. Based on the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device in the Multi-Link Traffic element, the non-AP multilink device can determine which link the non-AP multilink device recommends retrieving buffered traffic from or which link the non-AP multilink device buffered traffic on. As described in FIG. 21, if the TID-to-link mapping negotiation is successful, the non-AP multilink device can determine whether traffic to be transmitted to a station of the non-AP multilink device operating on the link corresponding to the bit is buffered based on the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device. In addition, when the TID-to-link mapping is the default mapping, the non-AP multilink device can indicate whether to recommend that the AP multilink device request transmission of buffered traffic on the link corresponding to the bit, based on the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device.

[0274] A non-AP multilink device may request the AP multilink device to transmit buffered traffic on links corresponding to bits set to 1 in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device. Specifically, if the TID-to-link mapping negotiation is successful, the non-AP multilink device may request the AP multilink device to transmit buffered traffic on links corresponding to bits set to 1 in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device. If the TID-to-link mapping is the default mapping, the non-AP multilink device may request the AP multilink device to transmit buffered traffic on one or more links, including the link corresponding to bits set to 1 in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multilink device. In such an embodiment, the non-AP multilink device may transmit a U-APSD trigger frame or a PS-Poll frame to request the AP multilink device to transmit buffered traffic. When a request for transmission of buffered traffic is received, the AP multilink device can transmit the buffered traffic to the non-AP multilink device, and when a request for transmission of buffered traffic is received, the AP multilink device can transmit a QoS Null frame in place of the buffered traffic.

[0275] In the embodiment of FIG. 22, a legacy station before EHT or a station whose TID-to-link mapping is set to the default mapping is assigned an AID value smaller than K. A non-AP station that has successfully negotiated TID-to-link mapping is assigned an AID value equal to or greater than K. In the Traffic Indication Virtual Bitmap of FIG. 22, all bits smaller than bit number (N-1)*8 are set to 0. Therefore, the AP multilink device does not buffer traffic for stations whose AID is smaller than (N-1)*8. At least one bit of bits corresponding to bit number (N-1)*8 or greater is set to 1. N-1 is an even number, and N*8 is the value k. Therefore, the Partial Virtual Bitmap subfield includes the Traffic Indication Virtual Bitmap starting from bit number (N-1)*8. In this case, the value of the Bitmap Offset subfield of the Partial Virtual Bitmap subfield is set to (N-1) / 2. In addition, the values ​​of the bits in the Partial Virtual Bitmap subfield that correspond to AIDs (N-1)*8, (N-1)*8+2, (N-1)*8+3, k, k+2, and k+3 are set to 1.

[0276] As described above, the AID Offset subfield of the Multi-Link Traffic element can indicate the AID of the multi-link device corresponding to the leading one of the Per-Link Traffic Indication Bitmap subfields of the Multi-Link Traffic element. In Figure 14, the value of the AID Offset subfield is set to K. The Multi-Link Traffic element includes a Per-Link Traffic Indication Bitmap subfield corresponding to the multi-link device indicated by the Partial Virtual Bitmap subfield as 1. In Figure 22, the Multi-Link Traffic element includes Per-Link Traffic Indication Bitmap subfields for stations or non-AP multi-link devices whose AIDs are k, k+2, and k+3. In this case, the Per-Link Traffic Indication Bitmap subfields are sorted in ascending order of AID.

[0277] The value of the Bitmap Size field of the Multi-Link Traffic element is 2. Therefore, the Per-Link Traffic Indication Bitmap subfield of the Multi-Link Traffic element includes 3 bits. In this case, the first bit (B0) of the Per-Link Traffic Indication Bitmap subfield is mapped to a link whose link ID is 0, the second bit (B1) is mapped to a link whose link ID is 1, and the third bit (B2) is mapped to a link whose link ID is 2.

[0278] As described above, default mapping is applied to the multilink device with AID value K, and TID-to-link mapping is successfully performed for the multilink devices with AID values ​​K+2 and K+3. Therefore, the Per-Link Traffic Indication Bitmap subfield corresponding to AID K indicates that a request for transmission of buffered traffic on the link with link ID 1 is recommended. Furthermore, the Per-Link Traffic Indication Bitmap subfield corresponding to AID K+2 indicates that the AP multilink device is buffering traffic on two links with link IDs 1 and 2. In this case, the traffic buffered on the link with link ID 1 and the traffic buffered on the link with link ID 2 may be the same or different. Furthermore, the Per-Link Traffic Indication Bitmap subfield corresponding to AID K+3 indicates that the AP multilink device is buffering traffic on the link with link ID 1.

[0279] However, it may not be guaranteed that the AIDs of non-AP multilink devices connected to the AP multilink device are assigned consecutively. Furthermore, AIDs of non-AP stations not included in the multilink device may be assigned between AIDs of non-AP multilink devices. In this case, it may be difficult for the non-AP multilink device to determine which AIDs belong to stations not included in the non-AP multilink device. Therefore, if the Multi-Link Traffic element does not include a Per-Link Traffic Bitmap subfield for stations not included in the non-AP multilink device, it may be difficult for the non-AP multilink device to parse the Per-Link Traffic Bitmap subfield. For example, in the embodiment of FIG. 14, AID K+1 is assigned to the non-AP multilink device, and the bit corresponding to AID K+1 in the Partial Virtual Bitmap subfield of the TIM element may have a value of 1. In this case, a non-AP multilink device with AID K+2 or K+3 cannot determine which of the three Per-Link Traffic Bitmap subfields is the Per-Link Traffic Bitmap subfield for that non-AP multilink device. Therefore, a method for configuring the Multi-Link Traffic element is required to resolve this issue. This will be explained with reference to FIG. 15.

[0280] FIG. 23 illustrates a method for configuring a Multi-Link Traffic element according to an embodiment of the present invention.

[0281] In an embodiment of the present invention, the AP multilink device may include a Per-Link Traffic Bitmap subfield for non-AP stations not included in the multilink device in the Multi-Link Traffic element. Specifically, the AP multilink device may include a Per-Link Traffic Bitmap subfield for non-AP stations in the Multi-Link Traffic element even if the non-AP station is not included in the multilink device, if the bit value of the Traffic Indication Bitmap subfield or Partial Virtual Bitmap subfield corresponding to the non-AP station is 1. Therefore, the AP multilink device may include a Per-Link Traffic Bitmap subfield for all stations corresponding to a bit of the Traffic Indication Bitmap subfield or a bit of the Partial Virtual Bitmap subfield set to 1 in the Multi-Link Traffic element. For convenience of explanation, a station corresponding to a bit of the Traffic Indication Bitmap subfield or a bit of the Partial Virtual Bitmap subfield set to 1 may be referred to as a station for which buffered traffic is indicated.

[0282] In this case, the AP multilink device can include a Per-Link Traffic Bitmap subfield for all stations to which buffered traffic is indicated in the Multi-Link Traffic element, regardless of whether the station to which buffered traffic is indicated belongs to the multilink device, whether it corresponds to a non-AP multilink device, or which AP or BSS it belongs to. The AP or BSS to which the station to which buffered traffic is indicated belongs can indicate whether the station to which buffered traffic is indicated belongs to a multiple BSSID set.

[0283] The AP multilink device can include the same number of Per-Link Traffic Bitmap subfields as the number of stations for which buffered traffic is indicated in the Multi-Link Traffic element. A method for the AP multilink device to set the Per-Link Traffic Bitmap subfields corresponding to stations that do not belong to the multilink device will be described.

[0284] The AP multilink device may set all bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device to 0. That is, the AP multilink device may set bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device to a reserved field. In yet another specific embodiment, the AP multilink device may set bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device to an arbitrary value. In yet another specific embodiment, the AP multilink device may set bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device to 1. In this case, the non-AP multilink device may ignore bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device. In yet another specific embodiment, the AP multilink device may set bit values ​​in the Per-Link Traffic Bitmap subfield corresponding to stations that do not belong to the multilink device to 1. In yet another specific embodiment, the AP multilink device can set the value of the bit in the Per-Link Traffic Bitmap subfield corresponding to the link on which a station not belonging to the multilink device operates to 1, and set the value of the remaining bits to 0.

[0285] In the embodiment of Figure 23, the settings of the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield may be the same as the settings of the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield in Figure 14. However, in the embodiment of Figure 23, AID k and AID k+3 correspond to non-AP multilink devices. AID k+2 corresponds to a station not included in the multilink device. The Per-Link Traffic Bitmap subfields corresponding to AID k and AID k+3 of the Multi-Link Traffic element are set as in the embodiment of Figure 14. Since AID k+2 is a station not included in the multilink device, all bits of the Per-Link Traffic Bitmap subfield corresponding to AID k+2 of the Multi-Link Traffic element are set to 0.

[0286] The AID Offset subfield of the Multi-Link Traffic element may indicate bits after all bits corresponding to the Group ID and group address frame in the Traffic indication virtual bitmap and Partial Virtual Bitmap subfield. In this case, the Group ID may include an AID value of 0. The Group ID may also include a bit number in the Traffic indication virtual bitmap corresponding to a multiple BSSID set, i.e., an AID corresponding to the bit number. The Group ID may also include a bit number in the Traffic indication virtual bitmap corresponding to a transmitted BSSID and a nontransmitted BSSID, i.e., an AID corresponding to the bit number. The Group ID may include values ​​corresponding to AID 0 to (2^n-1) when the maximum number of BSSIDs possible in a multiple BSSID set is 2^n. The AID Offset subfield may indicate values ​​after the value corresponding to AID 0 to (2^n-1) when a multiple BSSID set is used and the maximum number of BSSIDs possible in a multiple BSSID set is 2^n. The reason for setting the AID Offset field in this way is that the group address frame is not limited to being transmitted on a specific link, and therefore there is little point in signaling it for each link.

[0287] According to yet another embodiment of the present invention, even if the AID Offset subfield indicates a bit in the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield that is earlier than the bit indicating the Group ID, the Per-Link Traffic Indication Bitmap subfield corresponding to the Group ID may not be included in the Multi-Link Traffic element. Even if the AID Offset subfield indicates a bit in the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield that is earlier than the bit indicating the Group ID, the Multi-Link Traffic element may include only Per-Link Traffic Indication Bitmap subfields corresponding to individual stations among the stations for which buffered traffic is indicated. Specifically, when the maximum number of configurable BSSIDs in a multiple BSSID set is 2^n, the AID Offset subfield may indicate a bit in the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield that is earlier than the bit indicating the Group ID, corresponding to an AID that is (2^n-1) or less. In this case, the Multi-Link Traffic element may include only the Per-Link Traffic Indication Bitmap corresponding to the bits set to 1 among the bits of the Traffic indication virtual bitmap and the bits of the Partial Virtual Bitmap subfield corresponding to AID2^n.A station receiving the Multi-Link Traffic element can determine that the Multi-Link Traffic element contains only the Per-Link Traffic Indication Bitmap corresponding to the bits set to 1 among the bits of the Traffic indication virtual bitmap and the bits of the Partial Virtual Bitmap subfield corresponding to AID 2^n.

[0288] According to yet another embodiment of the present invention, regardless of whether the AID Offset subfield indicates bits before the bit indicating the Group ID in the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield, the Multi-Link Traffic element may include a Per-Link Traffic Indication Bitmap corresponding to all bits set to 1 after the bits indicated by the AID Offset subfield in the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfield. In this case, the AP multilink device may set the values ​​of the Per-Link Traffic Indication Bitmap fields corresponding to the bits of the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfields corresponding to the group address to a predetermined value. The predetermined value may be 0. In yet another specific embodiment, the AP multilink device may set the values ​​of the Per-Link Traffic Indication Bitmap fields corresponding to the bits of the Traffic indication virtual bitmap and the Partial Virtual Bitmap subfields corresponding to the group address to an arbitrary value. The AP multilink device can set the bits in the Per-Link Traffic Indication Bitmap field corresponding to the link on which the group address frame is transmitted to 1 and the remaining bits to 0 in the Traffic indication virtual bitmap and Partial Virtual Bitmap subfields corresponding to the group address.

[0289] Figure 24 shows a method for setting the Per-Link Traffic Bitmap subfield of the Multi-Link Traffic element when the link set in which an AP multi-link device operates is different from the link set in which a non-AP multi-link device communicating with the AP multi-link device operates, in accordance with an embodiment of the present invention.

[0290] The link set on which an AP multilink device operates may differ from the link set on which a non-AP multilink device that communicates with the AP multilink device operates. For example, the AP multilink device may communicate with a first non-AP multilink device via links 1 to 3, and the AP multilink device may communicate with a second non-AP multilink device via links 1 to 2. In this case, the method for setting the Per-Link Traffic Bitmap subfield of the Multi-Link Traffic element may become an issue.

[0291] Even if the link set in which the AP multilink device operates is different from the link set in which a non-AP multilink device communicating with the AP multilink device operates, the AP can set the size of all Per-Link Traffic Indication Bitmap subfields included in the Multi-Link Traffic element to be the same and set the links to which each bit in all Per-Link Traffic Indication Bitmap subfields maps to be the same. Specifically, the AP multilink device can set the number of bits in all Per-Link Traffic Indication Bitmap subfields included in the Multi-Link Traffic element to be greater than the number of links configured by the AP multilink device. This is because the link IDs configured by the AP multilink device may not start with 0 or the IDs of the multiple links may not be consecutive. For example, the AP multilink device can set the number of bits in all Per-Link Traffic Indication Bitmap subfields included in the Multi-Link Traffic element to the maximum number of links that the AP multilink device can configure. In yet another specific embodiment, the AP multilink device can set the number of bits of all Per-Link Traffic Indication Bitmap subfields included in the Multi-Link Traffic element to the value obtained by adding 1 to the maximum link ID value that the AP multilink device can set.

[0292] A problem may arise in how to set the value of a bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a link not established by the AP multilink device and a link not established by a non-AP multilink device corresponding to the Per-Link Traffic Indication Bitmap subfield. For convenience of explanation, a bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a link not established by the AP multilink device and a link not established by a non-AP multilink device corresponding to the Per-Link Traffic Indication Bitmap subfield is referred to as a no-link bit. The AP multilink device can set the value of the no-link bit to a pre-specified value. Therefore, the AP multilink device can set the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a link not established by the AP multilink device or a non-AP multilink device to a pre-specified value. In this case, the pre-specified value may be 0. In yet another specific embodiment, the AP multilink device can set the value of the no-link bit to an arbitrary value. In this case, a non-AP station can ignore the value of the no-link bit.

[0293] In addition, the value of a bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a disabled link may be set to reserved. Specifically, the value of a bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a disabled link may be set to 0. In this case, a disabled link may be a link in which uplink and downlink transmissions are stopped. Specifically, a disabled link may be a link in which uplink and downlink transmissions of individual address frames are stopped. In this case, non-AP stations can ignore the value of the no-disabled bit.

[0294] In the embodiment of FIG. 24, as shown in FIG. 24(a), the AP multilink device (AP MLD) operates on the first link (Link 0) to the third link (Link 2). The first multilink device (MLD1) and the AP multilink device (AP MLD) configure the first link (Link 0) to the third link (Link 2). The second multilink device (MLD2) and the AP multilink device (AP MLD) configure the first link (Link 0) to the second link (Link 1). The AP multilink device (AP MLD) sets the number of bits in the Per-Link Bitmap subfield of the Multi-Link Traffic element to 3 bits. The Multi-Link Traffic element transmitted by the AP multilink device (AP MLD) includes Per-Link Bitmap subfields corresponding to the first multilink device (MLD 1), the first station (STA 1), and the second multilink device (MLD 2). The AP multilink device (AP MLD) sets the value of the Per-Link Bitmap subfield corresponding to the first multilink device (MLD 1) according to the embodiment described in Figures 14 and 15. In addition, the AP multilink device (AP MLD) sets the value of the Per-Link Bitmap subfield corresponding to the first station (STA 1) according to the embodiment described in Figure 23. The AP multilink device (AP MLD) sets the values ​​of the first bit (B0) to the second bit (B1) of the Per-Link Bitmap subfield corresponding to the second multilink device (MLD 2) according to the embodiment described in Figures 22 and 23. In addition, the AP multilink device (AP MLD) sets the value of the third bit (B2) of the Per-Link Bitmap subfield corresponding to the second multilink device (MLD 2) to 0, which is a pre-specified value, as described above.

[0295] In the above embodiment, it has been described that the bit number of a bit in the Per-Link Traffic Indication Bitmap subfield is the same as the ID of the link corresponding to that bit. Depending on a specific embodiment, the bit number of a bit in the Per-Link Traffic Indication Bitmap subfield may not be the same as the ID of the link corresponding to that bit. The link IDs of the links set by the AP multilink device that transmitted the Per-Link Traffic Indication Bitmap subfield may be mapped to the bit numbers of the bits in the Per-Link Traffic Indication Bitmap subfield in ascending order. The AP multilink device may set a link with an ID of 1 and a link with an ID of 3, and the Per-Link Traffic Indication Bitmap subfield may be a 2-bit field. In this case, the first bit (B0) of the Per-Link Traffic Indication Bitmap subfield is mapped to the link with an ID of 1, and the second bit (B1) is mapped to the link with an ID of 3.

[0296] A method for setting up a multi-link will be described with reference to Fig. 25 to Fig. 29. First, a Multi-Link element will be described with reference to Fig. 25.

[0297] FIG. 25 illustrates signaling associated with the Multi-Link element and MediumSyncDelay according to one embodiment of the present invention.

[0298] A multilink device may perform multilink discovery and multilink setup using a multilink element. In this case, the multilink element may be included in a management frame. Specifically, the multilink element may be included in at least one of a beacon frame, a probe request frame, a probe response frame, an authentication frame, an association request frame, an association response frame, a reassociation request frame, and a reassociation response frame.

[0299] The Multi-Link element may include an Element ID subfield, a Length subfield, an Element ID Extension subfield, a Multi-Link Control subfield, a Common Info subfield, and a Link Info subfield. The Element ID subfield or the Element ID Extension subfield may indicate the ID of the element including the Element ID subfield or the Element ID Extension subfield. The Length subfield may indicate the length of the element including the Length subfield. The Multi-Link Control subfield may include a Type subfield and a Presence Bitmap subfield. The Type subfield may indicate the type of the Multi-Link element. The format of the Multi-Link element may be determined based on the type of the Multi-Link element. The Presence Bitmap subfield may indicate whether subfields that can be included in the Multi-Link element are included. For example, the Presence Bitmap subfield may indicate whether subfields that can be included in the Common Info subfield included in the Multi-Link element are included. Subfields indicating whether the Presence Bitmap subfield is included may include a multilink device MAC address subfield, a Link ID Info subfield, a BSS Parameters Change Count subfield, a Medium Synchronization Delay Information subfield, an EML Capabilities subfield, and an MLD Capabilities subfield. The Medium Synchronization Delay Information subfield may include MediumSyncDelay and related information.

[0300] The Common Info subfield may contain information about multiple links or all links. The Common Info subfield may contain information commonly required or commonly applied to multiple links or all links. The Link Info subfield may contain information about the link corresponding to the Link Info subfield.

[0301] The information related to MediumSyncDelay indicates a value set for the duration of MediumSyncDelay and may have a default value. In certain situations, a multilink device can initialize the duration of MediumSyncDelay to a basic value. Also, if a multilink device (non-AP multilink device) does not receive information related to MediumSyncDelay from a peer multilink device (AP multilink device), the multilink device can set the duration of MediumSyncDelay to a default value. If a multilink device (non-AP multilink device) receives information related to MediumSyncDelay from a peer multilink device (AP multilink device), it can set the duration of MediumSyncDelay to a value indicated by the received information related to MediumSyncDelay.

[0302] In FIG. 25, the Medium Synchronization Delay Information subfield may include a Medium Synchronization Duration subfield, a Medium Synchronization OFDM ED Threshold subfield, and a Medium Synchronization Maximum Number Of TXOPs subfield.

[0303] The Medium Synchronization Duration subfield may indicate MediumSyncDelay. That is, the Medium Synchronization Duration subfield may indicate a value to set the MediumSyncDelay timer. For example, the Medium Synchronization Duration subfield may be an 8-bit field. Also, the Medium Synchronization Duration subfield may indicate a duration in 32us units. That is, when the Medium Synchronization Duration subfield is set to A, the time indicated by the Medium Synchronization Duration subfield may be A*32us.

[0304] The Medium Synchronization OFDM ED Threshold subfield may indicate a CCA threshold when MediumSyncDelay is applied. The CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may be the CCA ED threshold. That is, the Medium Synchronization OFDM ED Threshold subfield may indicate dot11MSDOFDMEDthreshold. The Medium Synchronization OFDM ED Threshold subfield may be a 4-bit field. The CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may be the value of the Medium Synchronization OFDM ED Threshold subfield plus -72, and the unit of the CCA threshold may be dBm. Therefore, when the value of the Medium Synchronization OFDM ED Threshold subfield is 0 or greater, the CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may be -72 dBm or greater. Furthermore, the maximum value of the CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm. In this case, the value of the Medium Synchronization OFDM ED Threshold subfield may be set in the range of 0 to 10. At this time, values ​​11 to 15 may be reserved for the Medium Synchronization OFDM ED Threshold subfield. That is, the value of the Medium Synchronization OFDM ED Threshold subfield is set to 0 to 10, and at this time, the Medium Synchronization OFDM ED Threshold subfield can indicate that the CCA threshold is -72 dBm to -62 dBm.That is, if the value of the Medium Synchronization OFDM ED Threshold subfield is x, the Medium Synchronization OFDM ED Threshold subfield can indicate that the CCA threshold is (x-72 dBM).

[0305] The Medium Synchronization Maximum Number Of TXOPs subfield may indicate MSD_TXOP_MAX. That is, the Medium Synchronization Maximum Number Of TXOPs subfield may indicate the maximum number of transmission attempts a station may make while MediumSyncDelay is applied. The Medium Synchronization Maximum Number Of TXOPs subfield may be a 4-bit field. In a specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be MSD_TXOP_MAX. In yet another specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be (MSD_TXOP_MAX+1). In yet another specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be (MSD_TXOP_MAX-1). Such an embodiment may be applied when the value of the Medium Synchronization Maximum Number Of TXOPs subfield is not set to the maximum value. If the value of the Medium Synchronization Maximum Number Of TXOPs subfield is set to the maximum value, e.g., 15 if the Medium Synchronization Maximum Number Of TXOPs subfield is a 4-bit field, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate that a station is allowed to attempt transmission an unlimited number of times while MediumSyncDelay is applied.

[0306] FIG. 26 illustrates a multi-link setup process according to an embodiment of the present invention.

[0307] In Figure 26, the AP multilink device includes a first AP (AP 1), a second AP (AP 2), and a third AP (AP 3). The non-AP multilink device (non-AP MLD) includes a first non-AP station (STA 1), a second non-AP station (STA 2), and a third non-AP station (STA 3). The first AP (AP 1) and the first non-AP station (STA 1) operate on a first link (link 1). The second AP (AP 2) and the second non-AP station (STA 2) operate on a second link (link 2). The third AP (AP 3) operates on a third link (link 3).

[0308] The first AP (AP 1) can transmit a Reduced Neighbor Report element to signal the presence of an AP Multilink Device (AP MLD) and AP Multilink Device (AP MLD)-related parameters. The Reduced Neighbor Report element transmitted by the first AP (AP 1) can include information about the second AP (AP 2) or the third AP (AP 3). The Reduced Neighbor Report element can be included in a beacon frame or a probe response frame.

[0309] In addition, the first non-AP station (STA 1) that receives a frame including a Reduced Neighbor Report element can recognize the AP or AP multilink device indicated by the Reduced Neighbor Report element. In this case, the first non-AP station (STA 1) can transmit a probe request frame including a Multi-Link element to the first AP (AP 1) and request information about the AP multilink device (AP MLD) or the multilink on which the AP multilink device (AP MLD) operates from the first AP (AP 1). In this case, the Multi-Link element may include information about the non-AP multilink device or information about the AP included in the non-AP multilink device.

[0310] The first AP (AP 1) may transmit a probe response frame to the non-AP station (STA 1) in response to the probe request frame. In this case, the probe response frame may include a Multi-Link element. The Multi-Link element may include information about the AP multi-link device or information about the AP included in the AP multi-link device (AP MLD). Specifically, the Multi-Link element may include information requested by the first non-AP station (STA 1).

[0311] A first non-AP station (STA 1) may transmit an association request frame or a reassociation request frame to a first AP (AP 1). The association request frame and the reassociation request frame may include a Multi-Link element. In this case, the Multi-Link element may include information about the link for which the non-AP multi-link device is to perform multi-link setup. For example, in FIG. 25, the Multi-Link element may include information about a first link (link 1) and a second link (link 2).

[0312] The first AP (AP 1) may transmit an association response frame or a reassociation response frame to the first non-AP station (STA 1). In this case, the association response frame and the reassociation response frame may include a Multi-Link element. In this case, the Multi-Link element may include information about the link on which multi-link setup is to be performed. The link on which multi-link setup is to be performed may be determined based on the link on which the non-AP multi-link device is to perform multi-link setup. In FIG. 25, the Multi-Link element may include information about the first link (link 1) and the second link (link 2) on which the first non-AP station (STA 1) is to perform multi-link setup.

[0313] If the association response frame or reassociation response frame is successfully transmitted, it may be considered that the multi-link setup for the link indicated by the Multi-Link element included in the association response frame or reassociation response frame has been successfully performed.

[0314] FIG. 27 shows the format of a Reduced Neighbor Report element according to an embodiment of the present invention.

[0315] The Reduced Neighbor Report element described in FIG. 26 will now be further described.

[0316] The station or AP that transmits an element is called the reporting station or reporting AP. The station or AP that the element points to is called the reported station or reported AP. The station or AP that transmits a Reduced Neighbor Report element or a Multi-Link element is called the reporting station or reporting AP. The station or AP that the Reduced Neighbor Report element or a Multi-Link element points to is called the reported station or reported AP.

[0317] Referring to FIG. 27(a), the Reduced Neighbor Report element may include an Element ID subfield, a Length subfield, and one or more Neighbor AP Information subfields. The Element ID subfield may indicate the ID of an element. The Element ID subfield of the Reduced Neighbor Report element may indicate the ID of the Reduced Neighbor Report element. The Length subfield may indicate the size of the Reduced Neighbor Report element. For example, the Length subfield may indicate the length of the Reduced Neighbor Report element excluding the Element ID subfield and the Length subfield. That is, in the embodiment of FIG. 27(a), the Length subfield may indicate the length of the Neighbor AP Information subfield.

[0318] Each of the one or more Neighbor AP Information fields included in the Reduced Neighbor Report element may be the same as the Neighbor AP Information subfield shown in Figure 27(b). The Neighbor AP Information subfield may include a TBTT Information Header subfield, an Operating Class subfield, a Channel Number subfield, and a TBTT Information Set subfield.

[0319] The TBTT Information Header subfield may be a 2-octet field. The format of the TBTT Information Header subfield may be as shown in Figure 27(c). The TBTT Information Header subfield may include a TBTT Information Field Type subfield, a Filtered Neighbor AP subfield, a Reserved subfield, a TBTT Information Count subfield, and a TBTT Information Length subfield. The TBTT Information Field Type subfield may be a 2-bit field, the Filtered Neighbor AP subfield may be a 1-bit field, the Reserved subfield may be a 1-bit field, the TBTT Information Count subfield may be a 4-bit field, and the TBTT Information Length subfield may be an 8-bit field.

[0320] The TBTT Information Field Type subfield, together with the TBTT Information Length subfield, identifies the TBTT Information subfield. The value of the TBTT Information Field Type subfield is set to 0, and the TBTT Information Field Type subfield values ​​1, 2, and 3 may be reserved values.

[0321] If the Filtered Neighbor AP subfield is not included in a probe response frame transmitted by a TVHT AP, the Filtered Neighbor AP subfield is set to a reserved field. The Filtered Neighbor AP subfield is reserved except when a Reduced Neighbor Report element is carried in a probe response frame transmitted by a TVHT AP. If the Filtered Neighbor AP subfield is included in a probe response frame transmitted by a TVHT AP and all BSSs of the APs in the Filtered Neighbor AP subfield correspond to a specific SSID, the value of the Filtered Neighbor AP subfield may be set to 1. Otherwise, the value of the Filtered Neighbor AP subfield may be set to 0.

[0322] The TBTT Information Count subfield may indicate the number of TBTT Information subfields included in the Neighbor AP Information subfield including the TBTT Information Count subfield. For example, the TBTT Information Count subfield may be set to a value obtained by subtracting 1 from the number of TBTT Information subfields included in the Neighbor AP Information subfield including the TBTT Information Count subfield.

[0323] The TBTT Information Length subfield may indicate the length of each TBTT Information subfield included in the Neighbor AP Information subfield including the TBTT Information Length subfield. Also, the TBTT Information Length subfield may indicate the configuration of each TBTT Information subfield included in the Neighbor AP Information subfield including the TBTT Information Length subfield. In this case, the TBTT Information Length subfield may indicate the length and configuration of each TBTT Information subfield.

[0324] The TBTT Information Set subfield may include one or more TBTT Information subfields.

[0325] The TBTT Information subfield may be as shown in Figure 27(d). The TBTT Information subfield may include a Neighbor AP TBTT Offset subfield, a BSSID subfield, a Short SSID subfield, a BSS Parameters subfield, a 20MHz PSD subfield, and an MLD Parameters subfield. The size of each subfield may be as shown in Figure 27(d). In this case, the subfields included in the TBTT Information subfield may be selectively included.

[0326] The Neighbor AP TBTT Offset subfield indicates an offset of 1, obtained by rounding down the interval from the previous TBTT of the AP transmitting the Reduced Neighbor Report element to the next TBTT, to the nearest TU. If the value of the Neighbor AP TBTT Offset subfield is 254, it indicates that the offset is 254 TU or more. If the value of the Neighbor AP TBTT Offset subfield is 255, it indicates that the offset value is unknown.

[0327] The BSSID subfield may indicate the BSSID.

[0328] The Short SSID subfield may indicate an SSID, specifically, abbreviated SSID information.

[0329] The BSS Parameters subfield may indicate information about the BSS, which may include information about BSS operation.

[0330] The 20 MHz PSD subfield can indicate the maximum transmit power for the default category on the 20 MHz primary channel. In this case, the 20 MHz PSD subfield can indicate the maximum transmit power in dBm / MHz. The value of the 20 MHz PSD subfield is a signed integer, and a value of -128 in the 20 MHz PSD subfield is a reserved value. A value of 127 in the 20 MHz PSD subfield can indicate that there is no limit on the maximum transmit power for the default category. Also, when the value Y of the 20 MHz PSD subfield is between -127 and 126, the 20 MHz PSD subfield can indicate that the maximum transmit power for the default category on the 20 MHz primary channel is Y / 2 dBm / MHz.

[0331] The configuration of the TBTT Information field indicated by the value of the TBTT Information Length subfield may be as follows: If the value of the TBTT Information Length subfield is 1, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield. If the value of the TBTT Information Length subfield is 2, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield and the BSS Parameters subfield. If the value of the TBTT Information Length subfield is 4, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield and the MLD Parameters subfield. If the value of the TBTT Information Length subfield is 5, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield and the Short SSID subfield. If the value of the TBTT Information Length subfield is 6, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the Short SSID subfield, and the BSS Parameters subfield. If the value of the TBTT Information Length subfield is 7, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield and the BSSID subfield. If the value of the TBTT Information Length subfield is 8, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the BSSID subfield, and the BSS Parameters subfield.When the value of the TBTT Information Length subfield is 9, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the BSSID subfield, the BSS Parameters subfield, and the 20MHz PSD subfield. When the value of the TBTT Information Length subfield is 10, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the BSSID subfield, and the MLD Parameters subfield. When the value of the TBTT Information Length subfield is 11, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the BSSID subfield, and the Short SSID subfield. When the value of the TBTT Information Length subfield is 12, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, the BSSID subfield, the Short SSID subfield, and the BSS Parameters subfield. When the value of the TBTT Information Length subfield is 13, the TBTT Information subfield may include a Neighbor AP TBTT Offset subfield, a BSSID subfield, a Short SSID subfield, a BSS Parameters subfield, and a 20MHz PSD subfield. When the value of the TBTT Information Length subfield is 16, the TBTT Information subfield may include a Neighbor AP TBTT Offset subfield, a BSSID subfield, a Short SSID subfield, a BSS Parameters subfield, a 20MHz PSD subfield, and an MLD Parameters subfield.If the value of the TBTT Information Length subfield is 17 or greater, the TBTT Information subfield may include the Neighbor AP TBTT Offset subfield, BSSID subfield, Short SSID subfield, BSS Parameters subfield, 20MHz PSD subfield, and MLD Parameters subfield in the preceding 16 octets. The remaining subfields of the TBTT Information subfield not mentioned above may be designated as reserved. That is, if the TBTT Information Length subfield is 4, 10, 16, or 17 or greater, the MLD Parameters subfield may be included.

[0332] The MLD Parameter subfield may be as shown in Figure 27(e). The MLD Parameters subfield may include an MLD ID subfield, a Link ID subfield, a BSS Parameters Change Count subfield, and a Reserved subfield. The MLD ID subfield may be an 8-bit field. The Link ID subfield may be a 4-bit field. The BSS Parameters Change Count subfield may be 8 bits. The Reserved subfield may be a 4-bit field.

[0333] The MLD ID subfield can indicate the ID of a multilink device, for example, an AP multilink device. The MLD subfield can indicate the ID of a multilink device corresponding to the TBTT Information subfield containing the MLD ID subfield. A specific setting method for the MLD ID subfield can be as shown in Figure 28.

[0334] The Link ID subfield may indicate the ID of the link corresponding to the reported AP. If the reported AP does not belong to a multi-link device or the reporting AP does not have related information, the link ID may be set to 15.

[0335] The BSS Parameters Change Count subfield may indicate a value that is incremented when a significant update occurs in the beacon frame of the reported AP. The value of the BSS Parameters Change Count subfield may be initialized to 0. The value of the BSS Parameters Change Count subfield may be incremented by 1 when a significant update occurs in the AP or BSS corresponding to the BSS Parameters Change Count subfield. The significant update may include updating pre-specified parameters. The pre-specified parameters may include operation parameters. If the reported AP does not belong to a multilink device or the reporting AP does not have information about the multilink device to which the reported AP belongs, the value of the BSS Parameters Change Count subfield may be set to 255.

[0336] FIG. 28 illustrates a method for setting the ID of a multilink device according to an embodiment of the present invention.

[0337] The ID of the multilink device may be a value indicated by the MLD ID subfield described in FIG. 27. The MLD ID subfield may be 8 bits. The MLD ID subfield may indicate a value from 0 to 255. In an embodiment of the present invention, a reporting AP may represent an AP that sets and transmits the MLD ID subfield. A reported AP may represent an AP indicated by the MLD ID subfield or a TBTT Information subfield including the MLD ID subfield.

[0338] According to an embodiment of the present invention, the MLD ID subfield may be set as follows: The MLD ID subfield may indicate the ID of the AP multilink device to which the reported AP belongs. If the reported AP belongs to the AP multilink device to which the reporting AP belongs, the MLD ID subfield may be set to 0. If a nontransmitted BSSID belonging to the multiple BSSID set to which the reported AP belongs belongs to the multilink device set, the value of the MLD ID subfield may be set to the same value as the value of the BSSID Index field of the Multiple BSSID-Index element of the nontransmitted BSSID profile corresponding to the nontransmitted BSSID. If the reported AP is part of another AP multilink device and the frame including the MLD ID subfield does not include a Multiple BSSID element, the value of the MLD ID subfield may be set to a value greater than 0 and less than 255. Furthermore, if the reported AP is part of a multilink device with other APs and the frame including the MLD ID subfield includes a Multiple BSSID element, the value of the MLD ID subfield may be set to a value greater than 2^n-1 and less than 255, where n is the value of the MaxBSSID Indicator subfield of the Multiple BSSID element. If the reported AP is not part of a multilink device or the reported AP does not have information about the multilink device, the value of the MLD ID subfield may be set to 255. That is, if the reported AP belongs to the multilink device to which the reporting AP belongs, the value of the MLD ID subfield may be set to 0. Specifically, if the reported AP is not part of a multilink device or the reporting AP does not have information about whether the reported AP belongs to the multilink device, the value of the MLD ID subfield may be set to 255. That is, if the reported AP belongs to the multilink device to which the reporting AP belongs, the value of the MLD ID subfield may be set to 0.

[0339] In the embodiment of Figure 28, the reporting AP operates on the first link (link 1). The reporting AP belongs to the first multilink device, and the reporting AP transmits a Reduced Neighbor Report element and an MLD ID subfield. The first multilink device (MLD 1) operates on the first link (link 1), the second link (link 2), and the third link (link 3). In this case, the reporting AP sets the value of the MLD ID subfield corresponding to the AP operating on each of the second link (link 2) and the third link (link 3) to 0.

[0340] Alternatively, the reporting AP may transmit multiple BSSID elements along with the Reduced Neighbor Report element. In yet another specific embodiment, the reporting AP may not transmit multiple BSSID elements. In this case, if the reporting AP transmits multiple BSSID elements, it may indicate that the reporting AP belongs to a multiple BSSID set. Alternatively, if the reporting AP does not transmit multiple BSSID elements, it may indicate that the reporting AP does not belong to a multiple BSSID set.

[0341] According to an embodiment of the present invention, if the reported AP is included in the multiple BSSID set to which the reporting AP belongs, the value of the MLD ID subfield may be set to the BSSID index of the multiple BSSID set. Also, if the reported AP belongs to a multilink device to which an AP that belongs to the multiple BSSID set to which the reporting AP belongs, the value of the MLD ID subfield may be set to the BSSID index of the AP that belongs to the multiple BSSID set. If the reported AP belongs to a multilink device to which an AP with a nontransmitted BSSID that belongs to the multiple BSSID set to which the reported AP belongs, the value of the MLD ID subfield may be set to the BSSID index of the reported AP.

[0342] The multiple BSSID set to which the reporting AP belongs may include APs operating on the first link (link 1) and belonging to the second multilink device (MLD 2). The second multilink device (MLD 2) may include APs operating on the first link (link 1) and APs operating on the second link (link 2). The reporting AP can set the values ​​of the MLD ID subfields corresponding to the APs operating on the first link (link 1) belonging to the second multilink device (MLD 2) and the APs operating on the second link (link 2) belonging to the second multilink device (MLD 2) to the BSSID index of the reported AP. This is because the AP of the second multilink device (MLD 2) operating on the first link (link 1) and the AP of the second multilink device (MLD 2) operating on the second link (link 2) belong to the same multiple BSSID set as the reporting AP or belong to a multilink device included in the multiple BSSID set to which the reporting AP belongs.

[0343] When a reporting AP sends a multiple BSSID element, if the reported AP does not belong to the multilink device to which the reporting AP belongs, if the reported AP does not belong to the multiple BSSID set to which the reporting AP belongs, and if the reported AP does not belong to the multilink device to which an AP in the multiple BSSID set to which the reporting AP belongs belongs, the value of the MLD ID subfield may be set to a value greater than (2^n-1) and less than a pre-specified value.

[0344] Furthermore, when a reporting AP transmits a multiple BSSID element, if the reported AP does not belong to the multilink device to which the reporting AP belongs, if the reported AP does not belong to the multiple BSSID set to which the reporting AP belongs, and if the reported AP does not belong to the multilink device to which an AP in the multiple BSSID set to which the reporting AP belongs belongs, the value of the MLD ID subfield may be set to a value greater than (2^n-1) and less than a predetermined value. This may be limited to cases where the reported AP belongs to the MLD. The predetermined value may be the maximum value that the MLD ID subfield can indicate. The predetermined value may be 255. Furthermore, n may be the MaxBSSID Indicator value corresponding to the multiple BSSID set to which the reporting AP belongs.

[0345] 28, the third multilink device (MLD3) may include an AP operating on the first link (link 1) and an AP operating on the second link (link 2). The AP belonging to the third multilink device (MLD3) and operating on the first link (link 1) may not belong to the multiple BSSID set to which the reporting AP belongs. In this case, the values ​​of the MLD ID subfields for the AP belonging to the third multilink device (MLD3) and operating on the first link (link 1) and the AP belonging to the third multilink device (MLD3) and operating on the second link (link 2) may be set to values ​​greater than 2^n-1 and less than 255. This is because the AP belonging to the third multilink device (MLD 3) and operating on the first link (link 1) and the AP belonging to the third multilink device (MLD 3) and operating on the second link (link 2) do not belong to the multilink device to which the reporting AP belongs, and these two APs are not included in the multilink device to which the APs in the multiple BSSID set to which the reporting AP belongs belong.

[0346] If the reporting AP does not transmit multiple BSSID elements or if the reported AP does not belong to the same multi-link device as the reporting AP, the value of the MLD ID subfield may be set to a value greater than 0 and less than a pre-specified value. This may be limited to cases where the reported AP belongs to a multi-link device. The pre-specified value may be the maximum value that the MLD ID subfield can indicate. The pre-specified value may be 255.

[0347] Furthermore, if 1) the reported AP does not belong to a multilink device, 2) the reporting AP does not have information on whether the reported AP belongs to a multilink device, or 3) the reporting AP does not have information for setting the value of the MLD ID subfield, the reporting AP can set the value of the MLD ID subfield to a pre-specified value. In yet another specific embodiment, if 1) the reported AP does not belong to a multilink device, 2) the reporting AP does not have information on whether the reported AP belongs to a multilink device, or 3) the reporting AP does not have information for setting the value of the MLD ID subfield, the reporting AP can set the value of the MLD ID subfield to a pre-specified value or greater. The pre-specified value may be the maximum value that the MLD ID subfield can indicate. The pre-specified value may be 255.

[0348] In Figure 28, the fourth AP (AP4) operates on link 1 (link 1). In this case, the fourth AP (AP4) does not belong to any multilink device. Therefore, the reporting AP can set the value of the MLD ID subfield corresponding to the fourth AP (AP4) to 255.

[0349] A station can determine from which BSS a frame was transmitted based on the MAC address field in the MAC header of a received frame. Specifically, the station can determine whether the received frame was transmitted from the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station is associated based on the MAC address field in the MAC header of the received frame. In a specific embodiment, the station can determine whether the received frame was transmitted from the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station is associated based on the TA field in the MAC header of the received frame. In this case, if the TA field of the frame received by the station indicates the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs, the station can determine that the received frame was transmitted from the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs. If the TA field of a frame received by a station does not indicate the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs, the station can determine that the received frame was transmitted from the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs.

[0350] A station can determine to which AP a frame is transmitted based on the MAC address field in the MAC header of a received frame. In a specific embodiment, a station can determine whether a received frame is transmitted to the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the station is associated based on the RA field in the MAC header of the received frame. In this case, if the RA field of a frame received by the station indicates the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the station is associated, the station can determine that the received frame is transmitted to the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the station is associated. If the RA field of a frame received by the station does not indicate the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the station is associated, the station can determine that the received frame is transmitted to the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the station is associated.

[0351] A station can determine whether a frame is an inter-BSS frame based on the MAC address field in the MAC header of the received frame. The MAC address field may include at least one of an RA field, a TA field, and a BSSID field. If none of the RA field, TA field, and BSSID field of the frame received by the station indicates the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs, the station can determine the received frame as an inter-BSS frame. If at least one of the RA field, TA field, and BSSID field of the frame received by the station indicates the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to the multiple BSSID set to which the AP to which the station is associated belongs, the station can determine the received frame as an intra-BSS frame.

[0352] In such an embodiment, the BSSID may be used instead of the MAC address of the AP.

[0353] If the BSS color included in the preamble of the PPDU received by the station is the same as the BSS color of the BSS to which the station belongs and the preamble of the PPDU received by the station indicates that it is for downlink transmission, the station can determine that the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station belongs transmitted the received PPDU.If the BSS color included in the preamble of the PPDU received by the station is different from the BSS color of the BSS to which the station belongs or the preamble of the PPDU received by the station does not indicate that it is for downlink transmission, the station can determine that the AP to which the station is associated or an AP belonging to the multiple BSSID set to which the AP to which the station belongs did not transmit the received PPDU.

[0354] A multiple BSSID set may be a set of multiple BSSs for which information about the BSSs can be signaled in a single beacon frame or a single probe response frame. Specifically, a set of BSSIDs indicated by a single "multiple BSSID" element can be referred to as a "multiple BSSID set." Furthermore, a single TIM element included in a single beacon frame or a single TIM frame can indicate frames buffered for multiple BSSIDs included in the multiple BSSID set. Furthermore, a single beacon frame or a single probe response frame may include a "multiple BSSID" element. A "multiple BSSID" element can signal information about multiple BSSs. The BSSID of the BSS from which the single beacon frame or probe response frame is transmitted is referred to as the "transmitted BSSID." The remaining BSSIDs in a multiple BSSID set, excluding the transmitted BSSID, can be referred to as "nontransmitted BSSIDs." In addition, beacon frames or probe response frames may not be transmitted in a BSS corresponding to a nontransmitted BSSID.

[0355] As described above, the maximum number of BSSIDs that a multiple BSSID set can include may be 2^n. Here, n may be a value signaled in the Multiple BSSID element. For example, n may be a value indicated by the MaxBSSID Indicator included in the Multiple BSSID element. A station receiving the Multiple BSSID element can determine the MAC addresses or BSSIDs of APs included in the multiple BSSID set based on the received Multiple BSSID element. Furthermore, multiple BSSID indexes may be mapped to each BSSID included in the multiple BSSID set. Therefore, the BSSIDs included in the multiple BSSID set may be identified by the BSSID index. The maximum value of the MaxBSSID Indicator may be 8.

[0356] However, depending on the embodiment of the method for setting the MLD ID subfield described above, there may be cases where the value of the MLD ID subfield cannot be set.

[0357] In the above-described embodiment, if at least one of the pre-specified conditions is satisfied, the reporting AP may set the value of the MLD ID subfield to a pre-specified value. In another specific embodiment, if the pre-specified condition is satisfied, the reporting AP may set the value of the MLD ID subfield to a value equal to or greater than the pre-specified value. The pre-specified value may be the maximum value that the MLD ID subfield can indicate. In this case, the pre-specified value may be 255. The pre-specified condition may include at least one of: 1) the reported AP does not belong to a multilink device; 2) the reporting AP does not have information on whether the reported AP belongs to a multilink device; and 3) the reporting AP does not have information for setting the value of the MLD ID subfield. In addition, the pre-specified condition may include the reported AP not being included in a multilink device to which an AP of the multiple BSSID set to which the reporting AP belongs belongs when the value of the MaxBSSID Indicator field corresponding to the reporting AP is the maximum value. Such a condition may be that the reporting AP transmits multiple BSSID elements. The maximum value of the MaxBSSID Indicator field may be 8.

[0358] When a reporting AP sends a multiple BSSID element, if the reported AP is an AP included in a multiple BSSID set that includes the reporting AP, or if the reported AP belongs to a multilink device to which an AP in the multiple BSSID set that includes the reporting AP belongs, the MLD ID subfield can be set to the BSSID index of the AP included in the multiple BSSID set. If the value of the MaxBSSID Indicator subfield is 8, the maximum number of BSSIDs that the multiple BSSID set can include may be 2^8 = 256. Therefore, according to the above conditions, there may be no value greater than 2^n-1 and less than 255.

[0359] In addition, when the value of the MaxBSSID Indicator subfield corresponding to the reporting AP is the maximum value, the reporting AP may not be able to set the value of the MLD ID subfield even if the reported AP belongs to a multilink device to which an AP in the multiple BSSID set to which the reporting AP belongs belongs. For example, the reporting AP cannot indicate a multilink device whose BSSID index is 255. The MLD ID subfield value can be set to 255 according to the above-described embodiment. Therefore, when the value of the MLD ID subfield is 255, it is difficult to distinguish whether the 255 is set based on the BSSID index or a pre-specified value.

[0360] Therefore, the condition for setting the value of the MLD ID subfield to a predetermined value may further include that when the value of the MaxBSSID Indicator subfield corresponding to the reporting AP is the maximum value, the reported AP belongs to a multilink device to which an AP in the multiple BSSID set to which the reporting AP belongs belongs. In yet another specific embodiment, use of 255 as a BSSID index in a multiple BSSID set may not be allowed.

[0361] Furthermore, according to the above-described embodiment, the reporting AP may have difficulty in setting the value of the MLD ID subfield regardless of whether the reporting AP transmits multiple BSSID elements. For example, when the reporting AP indicates information for a large number of APs, the reporting AP may have difficulty in setting the value of the MLD ID subfield. Because the number of reported APs is greater than the number of configurable multilink device IDs, the reported AP may not be identified by the multilink device ID. For example, when the reporting AP transmits multiple BSSID elements and transmits information to more than (254-2^n+1) APs, the reported AP may not be identified by the limited range of multilink device IDs. When the reporting AP does not transmit multiple BSSID elements and transmits information to more than (254-1+1) APs, the reported AP may not be identified by the limited range of IDs. The conditions for setting the value of the MLD ID subfield to a pre-specified value may further include a case where the reported AP cannot be identified by an ID within a limited range.

[0362] To solve the above problem, the size of the MLD ID subfield can be set to more than 8 bits. In this case, the pre-specified value may be the maximum value that the MLD ID subfield can indicate. That is, if the size of the MLD ID subfield is N bits, the pre-specified value may be 2^N-1. For example, if the size of the MLD ID subfield is 9 bits, the pre-specified value may be 511. As another example, if the size of the MLD ID subfield is 16 bits, the pre-specified value may be 65535.

[0363] 29 and 30 illustrate a method for allocating AIDs to non-AP stations belonging to a multi-link device according to an embodiment of the present invention.

[0364] According to an embodiment of the present invention, one association ID (AID) may be assigned to a multilink device, that is, the AIDs of stations included in one multilink device may be the same.

[0365] AID allocation may be performed by an AP. For example, the AP may transmit the AID it has allocated to a non-AP STA. The non-AP STA can recognize that the AID received from the AP is the AID corresponding to the non-AP STA. A non-AP station that receives a subfield containing an AID value assigned to the non-AP station can recognize that the subfield containing the AID value assigned to the non-AP station indicates the non-AP station.

[0366] The AID assigned to a non-AP station may be included in the association response frame or reassociation response frame. If multilink setup is performed after the AP assigns an AID to a non-AP station, the AID assigned to the non-AP station may be the AID assigned to the multilink device to which the non-AP station belongs.

[0367] The AID or information related to the AID may be included in the preamble of the PPDU. In this case, the PPDU preamble may use the AID to indicate that the intended recipient of the PPDU is a non-AP station corresponding to the AID. The PPDU preamble may use the AID to indicate that the sender of the PPDU is a non-AP station corresponding to the AID. Also, as described above, the AID may be used to indicate traffic. A frame may use the AID to indicate that a station corresponding to the AID is the recipient of the frame. For example, a trigger frame may use the AID to indicate the station that the trigger frame will trigger.

[0368] An AID assigned to a multilink device may not be allowed to be assigned to other stations or other multilink devices. In a specific embodiment, an AID assigned to a multilink device may not be allowed to be assigned to stations or multilink devices that operate on links other than the link used by the multilink device.

[0369] In Figure 29, the first multilink device (MLD 1) operates on the first link (Link 1) and the second link (Link 2). The second multilink device (MLD 2) operates on the third link (Link 3) and the fourth link (Link 4). In this case, X is assigned as the AID of the first multilink device (MLD 1). Therefore, X is not permitted to be assigned as the AID of the second multilink device (MLD 2), and Y is assigned instead.

[0370] In a specific embodiment of the present invention, an AP multilink device can reallocate an AID previously assigned to one multilink device to another station or another multilink device. If a pre-specified condition is met, the AP multilink device can reallocate an AID previously assigned to one multilink device to another station or another multilink device. In this case, the pre-specified condition may include multilink devices or stations commonly assigned an AID operating on different links. That is, the pre-specified condition may include multilink devices or stations commonly assigned an AID operating on non-overlapping links. In this case, stations operating on a single link may not be permitted to have multiple multilink devices assigned the same AID. In yet another specific embodiment, multilink devices or stations commonly assigned an AID may operate on non-overlapping channels.

[0371] In Figure 30(a), the first multilink device (MLD 1) operates on the first link (Link 1) and the second link (Link 2). The AP multilink device assigns X as the AID of the station of the first multilink device (MLD 1). In this case, the AP multilink device can assign X as the AID of the first station (STA 1), which does not belong to the first multilink device (MLD 1) and operates on the third link (Link 3) rather than the first link (Link 1) and the second link (Link 2).

[0372] In such an embodiment, if a frame contains information about multiple links, a single AID assigned to multiple multilink devices or stations may cause confusion. To prevent this, information transmitted on any one link may apply to the station or multilink device operating on that link. For example, information transmitted on a first link may apply to a station or multilink with AID X operating on the first link, but may not apply to a station or multilink with AID X operating on a second link.

[0373] In Figure 30(b), beacon frames including TIMs are transmitted over both the first link (Link 1) and the second link (Link 2). At this time, the TIMs transmitted over both the first link (Link 1) and the second link (Link 2) indicate that traffic corresponding to AID X is buffered. The TIM transmitted over the first link (Link 1) indicates that traffic for the multi-link device (MLD 1) operating over the first link (Link 1) has been buffered, and the TIM transmitted over the second link (Link 2) indicates that traffic for the station (STA 1) operating over the second link (Link 2) has been buffered.

[0374] The TID-to-link mapping negotiation will be described with reference to FIGS.

[0375] FIG. 31 is a diagram illustrating TID-to-link mapping negotiation according to one embodiment of the present invention.

[0376] As described above, default mapping may be applied to a link for which no TID-to-link mapping is performed. Also, when the TID-to-link mapping is torn down for a link for which TID-to-link mapping negotiation has been completed, default mapping may be applied to the link again.

[0377] TID-to-link mapping negotiation may be performed using a TID-to-link mapping request and a TID-to-link mapping response. Specifically, a multilink device may request TID-to-link mapping by transmitting a frame including a TID-To-Link Mapping element. In this case, the frame may include an association request frame, a reassociation request frame, and a TID-to-link mapping request frame. Thus, a non-AP station or a non-AP multilink device may request TID-to-link mapping by transmitting an association request frame, a reassociation request frame, or a TID-to-link mapping request frame. An AP or an AP multilink device may request TID-to-link mapping by transmitting a TID-to-link mapping request frame. A multilink device that receives a TID-to-link mapping request may respond to TID-to-link mapping by transmitting a frame including a TID-To-Link Mapping element. In this case, the frame may include an association response frame, a reassociation response frame, and a TID-to-link mapping response frame. Therefore, an AP or AP multilink device can respond to a TID-to-link mapping request by transmitting an association response frame, a reassociation response frame, or a TID-to-link mapping request frame. A non-AP station or non-AP station multilink device can respond to a TID-to-link mapping request by transmitting a TID-to-link mapping response frame.

[0378] A multilink device can initiate TID-to-link mapping by transmitting a TID-to-link mapping request. At this time, the multilink device can request default mapping by transmitting a frame including a TID-to-link element. A multilink device that receives a TID-to-link mapping request can accept TID-to-link mapping by transmitting a TID-to-link mapping response to the TID-to-link mapping request. At this time, a multilink device that receives a TID-to-link mapping request can accept TID-to-link mapping by transmitting a frame that does not include a TID-to-link Mapping element. In yet another specific embodiment, a multilink device that receives a TID-to-link mapping request can accept TID-to-link mapping by transmitting a frame including a TID-to-link Mapping element having the same content as the TID-t122222222222222222 content received from a non-AP multilink device.

[0379] In addition, a multilink device that has received a TID-to-link mapping request may reject the TID-to-link mapping by transmitting a TID-to-link mapping response to the TID-to-link mapping request. In this case, a multilink device that has received a TID-to-link mapping request may reject the TID-to-link mapping by transmitting a frame that does not include a TID-to-link Mapping element. In yet another specific embodiment, a multilink device that has received a TID-to-link mapping request may reject the TID-to-link mapping by transmitting a frame that includes a TID-to-link Mapping element having content different from the content of the received TID-to-link Mapping element. If the TID-to-link mapping is rejected, a default mapping may be applied to the link.

[0380] In this embodiment, the frames transmitted by the multilink device for the TID-to-link mapping request and response may include at least one of an association request frame, an association response frame, a reassociation request frame, a reassociation response frame, a TID-to-link mapping request frame, and a TID-to-link mapping response frame, as described above. Specifically, a multilink device that receives a TID-to-link mapping request may transmit a TID-to-link mapping response frame in response to the TID-to-link mapping request. In this case, a multilink device that receives a TID-to-link mapping request may insert a status code into the TID-to-link mapping response frame to accept or reject the TID-to-link mapping request. Specifically, a multilink device that receives a TID-to-link mapping request may set the status code of the TID-to-link mapping response frame to SUCCESS and accept the TID-to-link mapping request. Furthermore, a multilink device that receives a TID-to-link mapping request can reject the TID-to-link mapping request by setting the status code of the TID-to-link mapping response frame to REJECT or DENIED_TID_TO_LINK_MAPPING. A multilink device that receives a TID-to-link mapping request can reject the TID-to-link mapping request by setting the status code of the TID-to-link mapping response frame to PREFERRED_TID_TO_LINK_MAPPING_SUGGESTED. In this case, a multilink device that receives a TID-to-link mapping request can propose a preferred TID-to-link mapping while rejecting the TID-to-link mapping request. A multilink device that receives a TID-to-link mapping request can reject the TID-to-link mapping request by transmitting a TID-to-link mapping rejection frame.

[0381] The TID-To-Link Mapping element included in the TID-to-link matching request indicates the TID-to-link mapping that is the target of the TID-to-link mapping request. Also, the TID-To-Link Mapping element sent when accepting a TID-to-link mapping can indicate the accepted TID-to-link mapping. Also, the TID-To-Link Mapping element sent when rejecting a TID-to-link mapping can indicate a newly proposed TID-to-link mapping.

[0382] If the TID-to-link mapping request is accepted, the TID-to-link mapping included in the TID-to-link mapping request is set to the link that is the target of the TID-to-link mapping. If the TID-to-link mapping request is rejected, a default mapping may be applied to the link that is the target of the TID-to-link mapping.

[0383] Furthermore, for TID-to-link mapping negotiation, the TID-to-link mapping request frame and the TID-to-link mapping response frame may include a dialogue token. The dialogue token maps the TID-to-link mapping request frame and the TID-to-link mapping response frame. Specifically, if the value of the dialogue token in the TID-to-link mapping request frame and the value of the dialogue token in the TID-to-link mapping response frame are the same, the TID-to-link mapping response frame may be transmitted in response to the TID-to-link mapping request frame. Therefore, when a multilink device that has received a TID-to-link mapping request frame transmits a TID-to-link mapping response frame, the multilink device can set the value of the dialogue token in the TID-to-link mapping request frame to the value of the dialogue token in the TID-to-link mapping request frame. When a multilink device does not receive a TID-to-link mapping request frame and transmits a TID-to-link mapping response frame, the multilink device can set the dialogue token value of the TID-to-link mapping response frame to a pre-specified value. In this case, the pre-specified value may be 0. That is, when a multilink device transmits an unsolicited TID-To-Link Mapping Response frame, the multilink device can set the dialogue token value of the TID-to-link mapping response frame to a pre-specified value. A field indicating a dialogue token in the TID-to-link mapping request frame and the TID-to-link mapping response frame may be a 1-octet field. The dialogue token value may have any one value from 0 to 255.

[0384] If the capabilities of a multilink device support TID-to-link mapping, the multilink device can perform TID-to-link mapping. Furthermore, the scope of TID-to-link mapping that the multilink device can perform may vary depending on the capabilities of the multilink device. For example, the number of TIDs that the multilink device can map to links or the number of applicable TID and link mapping combinations may vary depending on the capabilities of the multilink device. The capabilities of a multilink device may indicate whether the multilink device can map to link sets where all TIDs are the same. Furthermore, the capabilities of a multilink device may indicate how many link sets a TID can be mapped to.

[0385] In the embodiment of Figure 31, the AP multilink device (AP ML) includes a first AP (AP 1), a second AP (AP 2), and a third AP (AP 3). The non-AP multilink device (Non-AP MLD) includes a first non-AP station (Non-AP STA 1) and a second non-AP station (Non-AP STA 2). The non-AP multilink device (Non-AP MLD) transmits an association request frame including a TID-to-link Mapping element to the AP multilink device (AP ML). The AP multilink device (AP ML) transmits an association response frame including a TID-to-link Mapping element to the non-AP multilink device (Non-AP MLD) to accept or reject the TID-to-link mapping corresponding to the TID-to-link Mapping element. In addition, the non-AP multilink device (Non-AP MLD) can renegotiate the TID-to-link mapping by sending a TID-to-link mapping request frame to the AP multilink device (AP ML). At this time, the AP multilink device (AP ML) can accept or reject the TID-to-link mapping corresponding to the TID-to-link Mapping element by sending a TID-to-link mapping response frame to the non-AP multilink device (Non-AP MLD).

[0386] FIG. 32 illustrates a TID-to-link mapping negotiation in which an AP multilink device sends a TID-to-link mapping request according to an embodiment of the present invention.

[0387] The AP multilink device may transmit a TID-to-link mapping request using an association response frame, a reassociation response frame, and a TID-to-link mapping request frame. Specifically, the AP multilink device may initiate TID-to-link mapping negotiation using the association response frame, the reassociation response frame, and the TID-to-link mapping request frame. In this case, the AP multilink device may include a TID-to-link Mapping element in the association response frame, the reassociation response frame, and the TID-to-link mapping request frame. Specifically, the AP multilink device may include a TID-to-link Mapping element in the association response frame, the reassociation response frame, and the TID-to-link mapping request frame to initiate TID-to-link mapping negotiation. This is because the TID-to-link mapping request transmitted by a non-AP multilink device may be in a format that the AP multilink device does not desire, and the AP multilink device may not transmit the TID-to-link mapping request transmitted by the non-AP multilink device. In addition, an AP multilink device can grasp the overall network status more easily than a non-AP multilink device and determine an efficient TID-to-link mapping. Since the AP multilink device first transmits an association response frame or a reassociation response frame before completing the TID-to-link mapping negotiation, it can complete the multilink setup and reconfiguration. When a non-AP multilink device that receives a TID-to-link mapping request transmits a TID-to-link mapping response, the TID-to-link mapping negotiation is successfully completed.

[0388] The cases in which the AP multilink device can transmit a TID-to-link mapping request using an association response frame and a reassociation response frame may be limited. Specifically, if the association request frame does not request TID-to-link mapping, the AP multilink device can transmit a TID-to-link mapping request using the association response frame. If the association request frame does not include a TID-to-link Mapping element, the AP multilink device can determine that the association request frame does not request TID-to-link mapping. Also, if the reassociation request frame does not request TID-to-link mapping, the AP multilink device can transmit a TID-to-link mapping request using the reassociation response frame. If the reassociation request frame does not include a TID-to-link Mapping element, the AP multilink device can determine that the reassociation request frame does not request TID-to-link mapping. If the association request frame transmitted by the non-AP multilink device does not include a TID-to-link Mapping element, the non-AP multilink device can determine that the association response frame, which includes a TID-to-link Mapping element and is received in response to the association request frame, requests TID-to-link mapping. If the reassociation request frame transmitted by the non-AP multilink device does not include a TID-to-link Mapping element, the non-AP multilink device can determine that the reassociation response frame, which includes a TID-to-link Mapping element and is received in response to the reassociation request frame, requests TID-to-link mapping. This embodiment is because, if the association request frame includes a TID-to-link element and the association request frame includes a TID-to-link element, the non-AP multilink device may confuse the purpose of including the TID-to-link element in the association response frame. The same applies to the reassociation request frame.

[0389] In this embodiment, the AP multilink device may not determine that the TID-to-link mapping has been successfully completed until it receives a TID-to-link mapping response from the non-AP multilink device. Therefore, the AP multilink device may operate using default mapping until it receives a TID-to-link mapping response from the non-AP multilink device. Even if the AP multilink device receives an ACK for the association response frame or reassociation response frame, the AP multilink device may not determine that the TID-to-link mapping has been successfully completed.

[0390] A non-AP multilink device can respond to a TID-to-link mapping request transmitted by an AP multilink device using an association frame or a reassociation frame according to the above-described embodiment. However, the non-AP multilink device must clearly indicate that it is responding to a TID-to-link mapping request transmitted by an AP multilink device using an association frame or a reassociation frame. The non-AP multilink device can transmit a TID-to-link mapping response as a response frame to an association response frame requesting TID-to-link mapping or a reassociation response frame requesting TID-to-link mapping. In addition, the non-AP multilink device can set the dialogue token value of the TID TID-to-link mapping response to the same value as the dialogue token value included in the association response frame requesting TID-to-link mapping or the reassociation response frame requesting TID-to-link mapping. However, the association response frame requesting TID-to-link mapping and the reassociation response frame requesting TID-to-link mapping may not include a dialogue token.

[0391] Therefore, the TID-to-link Mapping element may include a response indication field indicating that the TID-to-link Mapping element is a response to the TID-to-link mapping request. In this case, the response indication field may be included in the TID-to-Link Mapping Control field. Specifically, the response indication field may be included in the reserved field of the reserved field of the TID-to-Link Mapping Control field. For example, the response indication field may be any one of the fourth bit (B3) to the eighth bit (B8) of the TID-to-Link Mapping Control field. A multilink device that receives the TID-to-link element can determine whether the TID-to-link Mapping element requests TID-to-link mapping based on the response indication field.

[0392] Because a non-AP multilink device transmits a TID-to-link mapping response frame in response to an association request frame or a reassociation request frame, the AP multilink device must distinguish which frame the TID-to-link mapping response frame is a response to. Specifically, when a non-AP multilink device transmits a TID-to-link mapping response frame in response to an association request frame or a reassociation request frame, the non-AP multilink device may set the value of the dialogue token in the TID-to-link mapping response frame to a random value. Also, if the value of the dialogue token in the TID-to-link mapping response frame is the same as the value of the dialogue token in the TID-to-link mapping request frame transmitted by the AP multilink device, the AP multilink device may determine that the TID-to-link mapping response frame is a response to the TID-to-link mapping request frame. Also, if the value of the dialogue token in the TID-to-link mapping response frame is different from the value of the dialogue token in the TID-to-link mapping request frame sent by the AP multilink device, the AP multilink device may determine that the TID-to-link mapping response frame is a response to an association request frame or a reassociation request frame.

[0393] In yet another specific embodiment, when the AP multilink device transmits a TID-to-link mapping request using an association response frame or a reassociation response frame, the value of the dialogue token of the TID-to-link mapping response frame transmitted as a response to the TID-to-link mapping request may be set to a predetermined value. In this case, the predetermined value may be 0, 1, or 255. When the AP multilink device transmits a TID-to-link mapping request using an association frame or a reassociation frame and receives a TID-to-link mapping response frame having a dialogue token value equal to the predetermined value, the AP multilink device may determine that the received TID-to-link mapping response frame is a response to the transmitted TID-to-link mapping request.

[0394] In yet another specific embodiment, when the AP multilink device transmits a TID-to-link mapping request using an association response frame or a reassociation response frame, the status code of the TID-to-link mapping response frame transmitted in response to the TID-to-link mapping request may be a predetermined value. In this case, the value of the predetermined status code may be different from the value of the status code of the TID-to-link mapping response frame transmitted in response to the TID-to-link mapping request transmitted by the multilink device using a frame other than an association frame or a reassociation frame. Thus, the AP multilink device can determine whether the received TID-to-link mapping response frame is a response to the TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame based on the status code of the received TID-to-link mapping response frame. Specifically, if the status code of the received TID-to-link mapping response frame is a pre-specified value, the AP multilink device can determine that the received TID-to-link mapping response frame is a response to a TID-to-link mapping request sent by the AP multilink device using an association response frame or a reassociation response frame.

[0395] In yet another specific embodiment, the AP multilink device may determine whether the received TID-to-link mapping response frame is a response to a TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame, based on the value of the Link Mapping field for the TID in the received TID-to-link mapping response frame. Specifically, if the value of the Link Mapping field for the TID in the received TID-to-link mapping response frame is the same as the value of the Link Mapping field for the TID in the TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame, the AP multilink device may determine that the received TID-to-link mapping response frame is a response to a TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame. Specifically, the received TID-to-link mapping response frame may include Link Mapping fields for multiple TIDs. In this case, if the values ​​of all Link Mapping fields included in the TID-to-link mapping response frame are the same as the values ​​of all Link Mapping fields of the TID-to-link mapping request transmitted by the AP multilink device using the association response frame or reassociation response frame, the AP multilink device can determine that the received TID-to-link mapping response frame is a response to the TID-to-link mapping request transmitted by the AP multilink device using the association response frame or reassociation response frame.If the value of the Link Mapping field for the TID of the TID-to-link mapping response frame received by the AP multilink device is different from the value of the Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multilink device using the association response frame or reassociation response frame, the AP multilink device does not need to transmit an ACK for the received TID-to-link mapping response frame.In addition, if the Link Mapping field for the TID of the TID-to-link mapping response frame received by the AP multilink device includes at least one value of the Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame, the AP multilink device does not need to transmit an ACK for the received TID-to-link mapping response frame. In addition, if the TID-to-link mapping response frame received by the AP multilink device does not include any Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame, or if the value of the Link Mapping field of the TID-to-link mapping response frame received by the multilink device is different from the value of the Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multilink device using an association response frame or a reassociation response frame, the AP multilink device does not need to transmit an ACK for the received TID-to-link mapping response frame. The above-described embodiment may also be applied when the TID-to-link mapping request is not transmitted using an association response frame or a reassociation response frame.

[0396] In the embodiment of Figure 32, the AP multilink device (AP ML) includes a first AP (AP 1), a second AP (AP 2), and a third AP (AP 3). The non-AP multilink device (Non-AP MLD) includes a first non-AP station (Non-AP STA 1) and a second non-AP station (Non-AP STA 2). The non-AP multilink device (Non-AP MLD) transmits an association request frame that does not include a TID-to-link Mapping element to the AP multilink device (AP ML). The AP multilink device (AP ML) transmits an association response frame that includes a TID-to-link Mapping element to the non-AP multilink device (Non-AP MLD) to request a TID-to-link mapping corresponding to the TID-to-link Mapping element. At this time, the non-AP multilink device (Non-AP MLD) transmits a TID-to-link mapping response frame to the AP multilink device (AP ML) to accept the TID-to-link mapping request.

[0397] FIG. 33 illustrates TID-to-link mapping negotiation when a link set requesting TID-to-link mapping is different from a link set established by a TID-to-link mapping response according to an embodiment of the present invention.

[0398] The link set for which the TID-to-link mapping is requested in the association request frame or reassociation request frame may be different from the link set for which the TID-to-link mapping is to be set in the association response frame or reassociation response frame. For example, the association request frame or reassociation request frame may request TID-to-link mapping for three links, and the association response frame or reassociation response frame may set TID-to-link mapping for two links. Also, different link sets may mean different link set configurations. Specifically, different link set configurations may mean different operating channels for the link sets. Also, different link sets may mean different link set configurations.

[0399] 31, when an AP multilink device receives an association request frame or a reassociation request frame including a TID-to-link Mapping element, the AP multilink device may establish a multilink by transmitting an association response frame or a reassociation response frame that does not include a TID-to-link Mapping element. However, as described above, the link set for which the TID-to-link mapping is requested in the association request frame or the reassociation request frame may differ from the link set for which the TID-to-link mapping is to be established in the association response frame or the reassociation response frame.

[0400] Therefore, in yet another embodiment of the present invention, if an AP multilink device receives an association request frame or reassociation request frame including a TID-to-link Mapping element and attempts to establish a link set different from the link set of the multilink that the association request frame or reassociation request frame is attempting to establish, the AP multilink device can transmit an association response frame or reassociation response frame that does not include a TID-to-link Mapping element. This allows the AP multilink device to reject the TID-to-link mapping. In this case, a default mapping may be applied to the AP multilink device and non-AP multilink devices.

[0401] When an AP multilink device receives an association request frame or reassociation request frame including a TID-to-link Mapping element and transmits an association response frame or reassociation response frame that sets a link set different from the link set of the multilink that the association request frame or reassociation request frame is attempting to establish, the AP multilink device may transmit an association response frame or reassociation response frame that does not include a TID-to-link Mapping element. Also, when a non-AP multilink device transmits an association request frame or reassociation request frame including a TID-to-link Mapping element and receives an association response frame or reassociation response frame that sets a link set different from the link set of the multilink that the association request frame or reassociation request frame is attempting to establish, the non-AP multilink device may determine that the TID-to-link mapping request has been rejected even if the received association response frame or reassociation response frame does not include a TID-to-link Mapping element. In this case, default mapping may be applied to the AP multilink device and the non-AP multilink device.

[0402] In yet another specific embodiment, when an AP multilink device receives an association request frame or a reassociation request frame including a TID-to-link Mapping element and attempts to establish a link set different from the link set of the multilink that the association request frame or the reassociation request frame attempts to establish, the AP multilink device may transmit an association response frame or a reassociation response frame including a TID-to-link Mapping element. In this case, the TID-To-Link Mapping element included in the association response frame or the reassociation response frame may indicate the TID-to-link mapping proposed by the AP multilink device. In this case, the operation of the non-AP multilink device may be the same as the embodiment described in FIG. 28.

[0403] In the above-described embodiment, for convenience of explanation, the operation of the multilink device has been described. However, the operation of the multilink device may also be performed by a station included in the multilink device.

[0404] FIG. 34 is a diagram illustrating an example of a TBTT information field format according to an embodiment of the present invention.

[0405] FIG. 34 is an additional explanation of the TBTT information field described in FIG. 27, and the contents described in FIG. 27 are equally applied to this embodiment, but will be omitted.

[0406] An AP or AP MLD can send a Reduced Neighbor Report (RNR) element, and a non-AP STA or non-AP MLD can receive the RNR element. The RNR element may include information about the AP or AP MLD or BSS. A non-AP STA or non-AP MLD can probe the AP or AP MLD based on the received RNR element. A non-AP STA or non-AP MLD can further request information from the AP or AP MLD based on the received RNR element. For example, a non-AP STA or non-AP MLD can send a probe request frame to the AP or AP MLD based on the received RNR element. Alternatively, a non-AP STA or non-AP MLD can perform (re)association or multi-link (re)setup based on the received RNR element. (Re)association or multi-link (re)setup can be performed by a non-AP STA or non-AP MLD sending a (Re)association Request frame.

[0407] The RNR element may include one or more Neighbor AP Information fields.

[0408] The neighbor AP information field may include a TBTT information set field.

[0409] The TBTT information set field may include one or more TBTT information fields, and the number of TBTT information fields included in the TBTT information set field may be indicated by a TBTT information count subfield included in the TBTT information set field.

[0410] The length of each TBTT information field included in the TBTT information set field included in the Neighbor AP Information field may be indicated by the TBTT Information Length subfield included in the Neighbor AP Information field, i.e., the length of the TBTT information field included in one Neighbor AP Information field may be the same.

[0411] The format and contents of the TBTT information field may be determined based on a TBTT information header field included in a neighbor AP information field including the TBTT information field. More specifically, the format and contents of the TBTT information field may be determined based on a TBTT information field type and a TBTT information field length indicated by a neighbor AP information field including the TBTT information field. The TBTT information field type may indicate a TBTT information field type subfield. Furthermore, the TBTT information field length may indicate a TBTT information length subfield. The neighbor AP information field includes one TBTT information field type subfield and one TBTT information length subfield. Therefore, the format and contents of the TBTT information field included in one neighbor AP information field may be the same.

[0412] Specifically, all TBTT information fields included in the neighbor AP information field may have the same format, length, and content, and the length may be indicated by a TBTT information length subfield. When the length of the TBTT information field is indicated by the TBTT information length subfield, the format and content of the TBTT information field may be determined depending on the length. For example, the content included may vary depending on the length of the TBTT information field.

[0413] In addition, the operation of the UE processing the TBTT information field may differ depending on the value of the TBTT information field type subfield and the value of the TBTT information length subfield included in the TBTT information header field of the neighbor AP information field. Specifically, the length of the TBTT information field processed by the UE may vary depending on whether the value of the TBTT information field type subfield, which indicates the type (or format) of the TBTT information field, is set to a first value (e.g., '0') or a second value (e.g., '1'). In addition, the length at which the TBTT information field is processed may take into account the value of the TBTT information length subfield. That is, when the value of the TBTT information field subfield is set to a first value or a second value, the value of the TBTT information length subfield is compared with a first threshold value (e.g., 16 octets), a second threshold value (e.g., 13 octets), and / or a third threshold value (e.g., 3 octets), and the terminal may process all, only a portion, or none of the TBTT information field. For example, when the value of the perceptible TBTT information field subfield is '0', if the length of the TBTT information field indicated by the TBTT information length subfield is equal to or less than the second threshold value, the terminal may ignore the TBTT information field of a received frame (e.g., a beacon frame or a probe response frame) without processing it in its entirety. However, if the value of the recognizable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is greater than the second threshold value and equal to or less than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first second octet value (e.g., 13 octets) and can ignore the remaining octets without processing them.However, if the value of the Recognizable TBTT Information Field subfield is '0' and the length of the TBTT information field indicated by the TBTT Information Length subfield is greater than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first octet value (e.g., 16 octets) and can ignore the remaining octets without processing them.

[0414] If the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is less than the third threshold value, the terminal may ignore the entire TBTT information field of a received frame (e.g., a beacon frame or a probe response frame, etc.) without processing it. However, if the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the third threshold value, the terminal may process the TBTT information field of the received frame up to the first three octet value (e.g., 3 octets) and ignore the remaining octets without processing them.

[0415] In yet another embodiment of the present invention, the TBTT information field may be processed only up to a specific threshold value depending on whether the value of the TBTT information length subfield includes the specific threshold value. That is, if the value of the TBTT information length subfield is smaller than the specific threshold value, the TBTT information field may not be processed. However, if the value of the TBTT information length subfield is greater than (equal to or greater than) the specific threshold value, the TBTT information field may also be processed up to the length (octets) corresponding to the specific threshold value. In this case, if the value of the TBTT information length field is between two threshold values ​​(e.g., greater than or equal to a second threshold value and less than the first threshold value), the TBTT information field may be processed up to the length corresponding to the second threshold value.

[0416] For example, when the value of the TBTT information field subfield is set to a first value or a second value, the UE may compare the value of the TBTT information length subfield with a first threshold value (e.g., 16 octets), a second threshold value (e.g., 13 octets), and / or a third threshold value (e.g., 3 octets) and process all, only a portion, or none of the TBTT information field. Specifically, when the value of the perceptible TBTT information field subfield is '0', if the length of the TBTT information field indicated by the TBTT information length subfield is less than the second threshold value, the UE may ignore the TBTT information field of a received frame (e.g., a beacon frame or a probe response frame) without processing it in its entirety. However, if the value of the recognizable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the second threshold value and less than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first 2nd octet value (e.g., 13 octets) and can ignore the remaining octets without processing them. However, if the value of the recognizable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the first threshold value, the terminal can process the TBTT information field of the received frame up to the first 1st octet value (e.g., 16 octets) and can ignore the remaining octets without processing them.

[0417] If the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is less than the third threshold value, the terminal may ignore the entire TBTT information field of a received frame (e.g., a beacon frame or a probe response frame, etc.) without processing it. However, if the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the third threshold value, the terminal may process the TBTT information field of the received frame up to the first three octet value (e.g., 3 octets) and ignore the remaining octets without processing them.

[0418] The TBTT information field type subfield may have a value of 0 to 3. An EHT STA can understand, recognize, and acknowledge the TBTT information field type subfield value when it is 0 or 1. An EHT STA may not be able to recognize the TBTT information field type subfield value when it is 2 or 3. An HE STA that is not an EHT STA or an STA of an earlier standard may understand, recognize, and acknowledge the TBTT information field type subfield value when it is 0, but may not be able to recognize the TBTT information field type subfield value when it is 1 to 3.

[0419] The TBTT information field configuration described in FIG. 27 may be an example when the TBTT information field type subfield value is 0. FIG. 34(a) shows the TBTT information field format described in FIG. 21. According to one embodiment, when the TBTT information field type subfield value is 0 and the TBTT information length subfield value is 1, 2, 5, 6, 7, 8, 9, 11, 12, 13, 16, or 17 or more, the corresponding TBTT information field content (subfields included in the TBTT information field) may be the same as that described in FIG. 27. Also, when the TBTT information field type subfield value is 0 and the TBTT information length subfield value is 0, 3, 4, 10, 14, or 15, the corresponding TBTT information field may not be defined (reserved). Also, when the TBTT information field type subfield value is 0, the corresponding TBTT information field may always include a Neighbor AP TBTT Offset subfield.

[0420] Figure 34(b) shows the TBTT information field format when the TBTT information field type subfield value is 1. When the TBTT information field type subfield value is 1, the corresponding TBTT information field may include an MLD Parameters field. For example, when the TBTT information field type subfield value is 1, the corresponding TBTT information field may always include an MLD Parameters field. Also, when the TBTT information field type subfield value is 1 and the TBTT information length subfield value is 3, the corresponding TBTT information field may include an MLD Parameters field.

[0421] In the present invention, a TBTT information field corresponding to a TBTT information field type subfield or a TBTT information length subfield may refer to a TBTT information field included in a neighbor AP information field including the TBTT information field type subfield or the TBTT information length subfield.

[0422] The MLD Parameters field may include the subfields described in Figure 21 and may further include an All Updates Included subfield in bit B20. The All Updates Included subfield may indicate whether or not the frame including the RNR element including the All Updates Included subfield includes all updated elements that change the value of the BSS Parameters Change Count subfield. If all are included, it may be set to 1, otherwise it may be set to 0.

[0423] According to an embodiment of the present invention, the multiple STAs may include STAs (i.e., APs) belonging to an AP MLD. For example, there may be cases where an AP MLD operates on an NSTR link pair. Such an AP MLD may be referred to as an NSTR AP MLD, an NSTR mobile AP MLD, or an NSTR soft AP MLD.

[0424] The NSTR mobile AP MLD can set up, assign, and designate primary and non-primary links. In addition, a non-AP MLD in a multi-link setup with the NSTR mobile AP MLD can receive information from the NSTR mobile AP MLD as to which link is the primary link and which is the non-primary link and determine this information. The NSTR mobile AP MLD may be able to transmit beacon frames, probe response frames, association response frames, and reassociation response frames only over the primary link. The NSTR mobile AP MLD may be unable to transmit beacon frames, probe response frames, association response frames, and reassociation response frames over non-primary links. In addition, a non-AP MLD in a multi-link setup (or attempting to do so) with the NSTR mobile AP MLD may be able to transmit probe request frames, association request frames, and reassociation request frames only over the primary link. A non-AP MLD that is associated with an NSTR mobile AP MLD or that has (or is attempting to) set up a multi-link may not be able to transmit probe request frames, association request frames, or reassociation request frames on a non-primary link.

[0425] In addition, NSTR mobile AP MLD or non-AP MLD combined with NSTR mobile AP MLD may require the use of a primary link to initiate a TXOP (start frame transmission) on a non-primary link. For example, to start PPDU transmission on a non-primary link, PPDU transmission must be started on the primary link simultaneously with the non-primary link. A backoff procedure may also exist to start PPDU transmission on the primary link and non-primary link simultaneously. For example, a link whose backoff counter has reached 0 can maintain a backoff counter value of 0, and a link with a backoff counter of 0 can start PPDU transmission when the backoff counter on another link reaches 0.

[0426] Furthermore, an AP MLD can indicate whether it is an NSTR mobile AP MLD or an AP MLD that is not an NSTR mobile AP MLD (AP MLD that operates on an STR link pair). For example, the Multi-Link element described in FIG. 20 may include the indication. More specifically, the MLD Capabilities field of the Common Info field included in the Multi-Link element may include the indication. Even more specifically, the B7 bit of the MLD Capabilities field may indicate the indication. The indication may be present when an AP MLD transmits a Multi-Link element. For example, when an NSTR mobile AP MLD transmits a Multi-Link element, the bit value may be set to 1. When an AP MLD that is not an NSTR mobile AP MLD transmits a Multi-Link element, the bit value may be set to 0. A non-AP MLD that receives the bit can determine whether a Multi-Link element including the bit is an NSTR mobile AP MLD based on the bit.

[0427] Furthermore, when an NSTR mobile AP MLD transmits an RNR element, it may include only the MLD Parameters subfield in the TBTT information field corresponding to the NSTR mobile AP MLD. Furthermore, when an AP MLD other than an NSTR mobile AP MLD transmits an RNR element, it may not necessarily include only the MLD Parameters subfield in the TBTT information field corresponding to the AP MLD. The RNR element may be included in a beacon frame, a probe response frame, an association response frame, or a reassociation response frame. Therefore, a non-AP MLD receiving a TBTT information field can determine whether the AP MLD corresponding to the TBTT information field is an NSTR mobile AP MLD depending on whether the TBTT information field includes only the MLD Parameters field. Whether the TBTT information field includes only the MLD Parameters subfield may be determined based on a field indicating the length or type of the TBTT information field. For example, the MLD Parameters subfield may have a preset length, e.g., 3 octets. Also, if the value indicating the length of the TBTT information field indicates the preset length, it can be determined that the TBTT information field includes only the MLD Parameters subfield and corresponds to the NSTR mobile AP MLD.

[0428] Alternatively, an AP or AP MLD (e.g., NSTR mobile AP MLD) may vary the setting of a neighbor AP information field for a corresponding link to indicate whether the link is a primary link or a non-primary link. For example, when the TBTT information field type subfield is set to a preset value, the neighbor AP information field including the TBTT information field type subfield or the TBTT information field corresponding to the TBTT information field type subfield may indicate whether the corresponding AP operates on a primary link or a non-primary link. More specifically, when the TBTT information field type subfield is set to a preset value, the neighbor AP information field including the TBTT information field type subfield or the TBTT information field corresponding to the TBTT information field type subfield may indicate that the corresponding AP operates on a non-primary link. The preset value may be 1.

[0429] Alternatively, if the TBTT information field includes an MLD Parameters field but does not include any of the Neighbor AP TBTT Offset subfield, BSSID subfield, Short SSID subfield, BSS Parameters subfield, and 20MHz PSD subfield, it may indicate whether the AP corresponding to the TBTT information field operates on a primary link or a non-primary link. More specifically, if the TBTT information field includes an MLD Parameters field but does not include any of the Neighbor AP TBTT Offset subfield, BSSID subfield, Short SSID subfield, BSS Parameters subfield, and 20MHz PSD subfield, it may indicate that the AP corresponding to the TBTT information field operates on a non-primary link.

[0430] Therefore, among APs belonging to the NSTR mobile AP MLD, an AP operating on a primary link may transmit a Neighbor AP Information field or a TBTT Information field corresponding to a non-primary link or an AP operating on a non-primary link. In this case, the value of the TBTT Information Field Type subfield included in the Neighbor AP Information field may be set to 1. Also, the TBTT Information field may include an MLD Parameters field, but may not include any of the Neighbor AP TBTT Offset subfield, BSSID subfield, Short SSID subfield, BSS Parameters subfield, and 20MHz PSD subfield.

[0431] In addition, among APs belonging to the NSTR mobile AP MLD, an AP operating on a primary link may transmit a neighbor AP information field or a TBTT information field corresponding to the primary link or the AP. In this case, the TBTT information field type subfield value included in the neighbor AP information field may be set to 0. In addition, the TBTT information field may include an MLD Parameters field.

[0432] A STA or non-AP MLD that receives the neighbor AP information field or TBTT information field set by the above-mentioned embodiment can determine whether the received neighbor AP information field or the received TBTT information field corresponds to an NSTR mobile AP MLD, an AP operating on a primary link, or an AP operating on a non-primary link.

[0433] FIG. 35 is a diagram illustrating the operation of receiving and analyzing a neighbor AP information field according to one embodiment of the present invention.

[0434] According to an embodiment of the present invention, when a STA receives a Neighbor AP Information field containing an unrecognized TBTT Information Field Type subfield value, it can ignore the Neighbor AP Information field or the rest of the RNR element containing the Neighbor AP Information field.

[0435] According to one embodiment of the present invention, an AP (reporting AP) included in the AP MLD can transmit a frame (e.g., a beacon frame or a probe response frame) including a Reduced Neighbor Report (RNR) element to STAs included in the non-AP MLD. The non-AP STA can obtain information about other APs (reported APs) included in the AP MLD based on the received RNR element, and can recognize the content and format of TBTT information related to the information about other APs based on the TBTT information field type subfield and the TBTT information length subfield included in the RNR element of the frame. In addition, the length that the non-AP STA can process the TBTT information field may vary based on the TBTT information length field depending on the value of the TBTT information field type subfield. In this case, the content (or information) of the TBTT information field that is not processed may be ignored.

[0436] The TBTT information field type subfield and the TBTT information length subfield may be included in a TBTT information header included in the neighbor AP information field of the RNR element.

[0437] The TBTT information length subfield may indicate the length (e.g., octets) of each of the TBTT information fields included in the TBTT information set, and may have a value of 1, 5, 7, or 11. However, this is merely an example, and the TBTT information length subfield may have a value other than 1, 5, 7, or 11. The TBTT information length subfield may also indicate the content of the TBTT information field.

[0438] When a STA receives a Neighbor AP Information field containing a recognized TBTT Information Field Type subfield value and an unrecognized TBTT Information Length subfield value, there may be a method that operates, such as a method based on Threshold 1 and Threshold 2, as described above.

[0439] For example, if the TBTT Information Length subfield is less than or equal to a threshold value of 1, the Neighbor AP Information field including the TBTT Information Length subfield can be ignored, and the following Neighbor AP Information field can be processed (decoded). (Operation 1)

[0440] If the TBTT information length subfield is greater than threshold 1, the first threshold 1 octet of each corresponding TBTT information field is processed so that the TBTT information length subfield value is threshold 1, and the remaining octets of each corresponding TBTT information field ((TBTT information length subfield value - threshold 1) octets) are ignored, and the following neighbor AP information field can be processed. This is an additional condition, and may be applicable in an embodiment where threshold 1 is less than threshold 2 and the TBTT information length subfield is less than threshold 2. (Operation 2)

[0441] If the TBTT information length subfield is greater than threshold 2, the first two threshold octets of each corresponding TBTT information field are processed so that the TBTT information length subfield value is threshold 2, and the remaining octets of each corresponding TBTT information field ((TBTT information length subfield value - threshold 2) octets) are ignored, and the following neighbor AP information field can be processed. (Operation 3)

[0442] According to one embodiment, critical value 1 may be 13, and critical value 2 may be 16.

[0443] In an additional embodiment, there may be a critical value 3 that is greater than critical value 2. In the embodiment previously described with respect to critical value 1 and critical value 2, there may be an embodiment in which critical value 1 and critical value 2 are changed to critical value 2 and critical value 3, respectively.

[0444] That is, possible operation methods may include operation 1, operation 2, and operation 3. A STA can perform operation 1 under the conditions described for operation 1. Also, a HE STA can perform operation 2 under the conditions described for operation 2. A non-HE STA can perform operation 1 or operation 2 under the conditions described for operation 2. An EHT STA can perform operation 3 under the conditions described for operation 3. A non-EHT STA can perform operation 1, operation 2, or operation 3 under the conditions described for operation 3.

[0445] In the described embodiment, the operation of processing only a critical value of the TBTT information field having an unknown TBTT information length subfield value and ignoring the rest may be for forward compatibility, or may be for the purpose of analyzing at least the possible amount even if it is defined that the TBTT information field contains information different from the information contained in the TBTT information field known to the STA.

[0446] Referring to FIG. 35, a STA may receive a Neighbor AP Information field including a recognized TBTT Information Field Type subfield value and an unrecognized TBTT Information Length subfield value. In this case, it may check whether the TBTT Information Length subfield value is less than or equal to 13. If true, it may ignore the Neighbor AP Information field. If false, it may check whether the TBTT Information Length subfield value is greater than 16. If false (the TBTT Information Length subfield value is greater than 13 but less than or equal to 16), it may process the first 13 octets of each TBTT information field included in the Neighbor AP Information field so that the TBTT Information Length subfield value is 13, and may ignore the remaining TBTT Information fields except for the first 13 octets. If true (the TBTT information length subfield value exceeds 16), the preceding 16 octets of each TBTT information field contained in the neighbor AP information field are processed so that the TBTT information length subfield value is 16, and the remaining TBTT information fields except for the preceding 16 octets can be ignored.

[0447] However, the design of the TBTT information field may increase the length of the TBTT information field in consideration of forward compatibility, but this may correspond to one TBTT information field type subfield value. That is, for other TBTT information field type subfield values, the length of the TBTT information field may not be defined to increase. Therefore, when an unrecognized TBTT information length subfield value is received, a problem occurs in analyzing the neighbor AP information field.

[0448] For example, as shown in Example 1 of FIG. 35, a Neighbor AP Information field may be received in which the TBTT Information Length subfield value is greater than 3 and less than or equal to 13. The TBTT Information Field Type subfield value included in the Neighbor AP Information field may be 1. In this case, the actually transmitted TBTT Information field may be as shown in Example 1 of FIG. 35. That is, it may include a 3-octet MLD Parameters field before it, followed by New Field 1. For example, the length of New Field 1 may be 3 octets. An EHT STA may recognize that the TBTT Information Field Type subfield value is 1, but may not recognize that the TBTT Information Length subfield value is greater than 3, and therefore may operate according to the embodiment described in FIG. 35. Therefore, since the TBTT Information Length subfield value is less than or equal to 13, the STA may ignore the Neighbor AP Information field. Therefore, the STA cannot obtain information from the MLD Parameters field that it can parse.

[0449] As shown in Example 2 of FIG. 35, a Neighbor AP Information field may be received in which the TBTT Information Length subfield value is greater than 16. The TBTT Information Field Type subfield value included in the Neighbor AP Information field may be 1. In this case, the actually transmitted TBTT information field may be as shown in Example 2 of FIG. 35. That is, it may be preceded by a 3-octet MLD Parameters field and followed by New Field 2. For example, the length of New Field 2 may be 14 octets. An EHT STA can recognize that the TBTT Information Field Type subfield value is 1, but cannot recognize that the TBTT Information Length subfield value is greater than 3, and therefore can operate according to the embodiment described in FIG. 35. Therefore, because the TBTT Information Length subfield value is greater than 16, the EHT STA can parse the preceding 16 octets of the TBTT information field included in the Neighbor AP Information field as if the TBTT Information Length subfield value were 16. However, when the TBTT information length subfield value is 16, the TBTT information field is the same as that shown in (Example 2) STA's interpretation in Figure 35, so the information actually composed of MLD Parameters and New field 2 will be incorrectly interpreted as (Example 2) STA's interpretation.

[0450] FIG. 36 is a diagram illustrating the operation of receiving and analyzing a neighbor AP information field according to one embodiment of the present invention.

[0451] The embodiment of Fig. 36 may be intended to solve the problem described in Fig. 35. Furthermore, in this embodiment, the above content may be omitted. Furthermore, in the present invention, any reference to or embodiments having such meanings as greater than or equal to (greater than or equal to), less than or equal to (smaller than or equal to), exceeding (greater than), or less than (smaller than) can be extended to embodiments in which the references are replaced with exceeding (greater than), less than (smaller than), greater than or equal to (greater than or equal to), or less than or equal to (smaller than or equal to), respectively.

[0452] According to an embodiment of the present invention, when a STA receives a Neighbor AP Information field containing an unrecognized TBTT Information Field Type subfield value, it can ignore the Neighbor AP Information field or the rest of the RNR element containing the Neighbor AP Information field.

[0453] That is, an AP (reporting AP) included in the AP MLA can transmit a frame (e.g., a beacon frame or a probe response frame) including an RNR element to non-AP STAs included in the non-AP MLD, and the non-AP STAs can acquire and discover information about other APs (reported APs) included in the AP MLD based on this. If the value of the TBTT information field type subfield included in the RNR element is an unrecognized (or unknown) value, the non-AP STA can ignore the remaining fields (or octets) of the RNR element without processing them. However, if the value of the TBTT information field type subfield included in the RNR element is a recognizable (or known) value, the non-AP STA can process up to a partial length (or up to a partial octet) or the entire TBTT information field included in the TBTT information set according to the value of the TBTT information length subfield, based on the value of the TBTT information field type subfield. In this case, the unprocessed portion can be ignored.

[0454] Specifically, the TBTT information fields included in the neighbor AP information field may all have the same format, length, and content, and the length may be indicated by a TBTT information length subfield. If the TBTT information length subfield indicates the length of the TBTT information field, the format and content of the TBTT information field may be determined according to the length. For example, the content included in the TBTT information field may vary depending on the length of the TBTT information field.

[0455] In addition, the UE's operation of processing the TBTT information field may differ depending on the values ​​of the TBTT information field type subfield and the TBTT information length subfield included in the TBTT information header field of the neighbor AP information field. Specifically, the length of the TBTT information field processed by the UE may differ depending on whether the value of the TBTT information field type subfield, which indicates the type (or format) of the TBTT information field, is set to a first value (e.g., '0') or a second value (e.g., '1'). Furthermore, the length of the TBTT information field processed may be determined taking into account the value of the TBTT information length subfield. That is, when the value of the TBTT information field subfield is set to the first value or the second value, the UE may process all, only a portion, or none of the TBTT information field by comparing the value of the TBTT information length subfield with a first threshold value (e.g., 16 octets), a second threshold value (e.g., 13 octets), and / or a third threshold value (e.g., 3 octets). For example, if the value of the perceivable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or less than the second threshold, the terminal can ignore the entire TBTT information field of a received frame (e.g., a beacon frame or a probe response frame, etc.) without processing it. However, if the value of the perceivable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is greater than the second threshold and equal to or less than the first threshold, the terminal can process the TBTT information field of the received frame up to the first second octet value (e.g., 13 octets) and ignore the remaining octets without processing them.However, if the value of the Recognizable TBTT Information Field subfield is '0' and the length of the TBTT information field indicated by the TBTT Information Length subfield is greater than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first octet value (e.g., 16 octets) and can ignore the remaining octets without processing them.

[0456] If the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is less than the third threshold value, the terminal may ignore the entire TBTT information field of a received frame (e.g., a beacon frame or a probe response frame, etc.) without processing it. However, if the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the third threshold value, the terminal may process the TBTT information field of the received frame up to the first three octet value (e.g., 3 octets) and ignore the remaining octets without processing them.

[0457] In yet another embodiment of the present invention, the TBTT information field may be processed only up to a specific threshold value depending on whether the value of the TBTT information length subfield includes the specific threshold value. That is, if the value of the TBTT information length subfield is smaller than the specific threshold value, the TBTT information field may be ignored without being processed. However, if the value of the TBTT information length subfield is greater than (equal to or greater than) the specific threshold value, the TBTT information field may be processed up to a length (octets) corresponding to the specific threshold value. In this case, if the value of the TBTT information length field is between two threshold values ​​(e.g., greater than or equal to a second threshold value and less than the first threshold value), the TBTT information field may be processed up to a length corresponding to the second threshold value.

[0458] For example, when the value of the TBTT information field subfield is set to a first value or a second value, the value of the TBTT information length subfield is compared with a first threshold value (e.g., 16 octets), a second threshold value (e.g., 13 octets), and / or a third threshold value (e.g., 3 octets), and the terminal may process all, only a portion, or none of the TBTT information field. Specifically, when the value of the perceptible TBTT information field subfield is '0', if the length of the TBTT information field indicated by the TBTT information length subfield is less than the second threshold value, the terminal may ignore the TBTT information field of a received frame (e.g., a beacon frame or a probe response frame) without processing it in its entirety. However, if the value of the recognizable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the second threshold value and less than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first 2nd octet value (e.g., 13 octets) and can ignore the remaining octets without processing them. However, if the value of the recognizable TBTT information field subfield is '0' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the first threshold value, the terminal can process the TBTT information field of the received frame up to the first 1st octet value (e.g., 16 octets) and can ignore the remaining octets without processing them.

[0459] If the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is less than the third threshold value, the terminal may ignore the entire TBTT information field of a received frame (e.g., a beacon frame or a probe response frame, etc.) without processing it. However, if the value of the perceivable TBTT information field subfield is '1' and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the third threshold value, the terminal may process the TBTT information field of the received frame up to the first three octet value (e.g., 3 octets) and ignore the remaining octets without processing them.

[0460] According to one embodiment of the present invention, a method may exist for an STA to operate when it receives a neighbor AP information field including a recognized TBTT information field type subfield value and an unrecognized TBTT information length subfield value. In this case, an operation may be performed based on the TBTT information field type subfield...

Claims

1. A multi-link device (MLD) including a plurality of stations each operating on a plurality of links, The processor Receive a frame from an AP (Access Point) of an AP MLD that includes a plurality of APs; The frame includes a Reduced Neighbor Report (RNR) element including one or more Neighbor AP information fields containing information related to other APs included in the AP MLD; The neighbor AP information field includes a TBTT (target beacon transmission time) information field type subfield, a TBTT information length field, and a TBTT information set field including one or more TBTT information fields; processing each of the one or more TBTT information fields based on the TBTT information type subfield and the TBTT information length field; When the value of the TBTT information type subfield is '0', each of the one or more TBTT information fields is processed only up to a first octet value or a second octet value by comparing the value of the TBTT information length field with a first threshold value and / or a second threshold value; When the value of the TBTT information type subfield is '1', each of the one or more TBTT information fields is processed only up to the third octet value by comparing the value of the TBTT information length field with a third threshold value, MLD.

2. the TBTT Information Field Type subfield is used to indicate the content and / or length of the one or more TBTT Information fields; The MLD of claim 1 , wherein the TBTT information length field indicates a length of each of the one or more TBTT information fields.

3. When the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is less than the first threshold value and equal to or greater than the second threshold value, each of the one or more TBTT information fields is processed only up to the second octet value; The MLD of claim 1 , wherein the second octet value is less than the first octet value.

4. The MLD according to claim 3 , wherein the remaining octets in each of the one or more TBTT information fields, excluding the second octet value, are not processed.

5. If the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is equal to or greater than the first threshold value, the one or more TBTT information fields are processed only up to the first octet value; The MLD of claim 1 , wherein the second octet value is less than the first octet value.

6. The MLD according to claim 5, wherein the remaining octets in each of the one or more TBTT information fields, except for the first octet value, are not processed.

7. The MLD of claim 1, wherein if the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is less than the second threshold value, the one or more TBTT information fields are not processed.

8. 2. The MLD of claim 1, wherein when the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is equal to or greater than the third threshold value, the one or more TBTT information fields are processed only up to the third octet value.

9. The MLD according to claim 8, wherein the remaining octets in each of the one or more TBTT information fields, except for up to the third octet value, are not processed.

10. 2. The MLD of claim 1, wherein if the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is less than the third threshold value, the one or more TBTT information fields are not processed.

11. Each of the one or more TBTT information fields includes a neighbor AP TBTT offset subfield; The MLD of claim 1 , wherein the neighbor AP TBTT offset subfield indicates an offset between a TBTT for the AP to transmit a beacon frame and a TBTT for another AP to transmit a beacon frame.

12. The MLD of claim 11, wherein when the other AP is included in the AP MLD, the offset value indicated by the neighbor AP TBTT offset subfield is set to a value other than a preset value associated with Unknown.

13. The MLD according to claim 12, wherein the preset value is "255".

14. 1. A method performed by a multi-link device (MLD) including a plurality of stations operating on a plurality of links in a wireless communication system, the method comprising: receiving a frame from an AP (Access Point) of an AP MLD including a plurality of APs, The frame includes a Reduced Neighbor Report (RNR) element including one or more Neighbor AP information fields containing information related to other APs included in the AP MLD; The neighbor AP information field includes a TBTT (target beacon transmission time) information field type subfield, a TBTT information length field, and a TBTT information set field including one or more TBTT information fields; processing each of the one or more TBTT information fields based on the TBTT information type subfield and the TBTT information length field; When the value of the TBTT information type subfield is '0', each of the one or more TBTT information fields is processed only up to a first octet value or a second octet value by comparing the value of the TBTT information length field with a first threshold value and / or a second threshold value; If the value of the TBTT information type subfield is '1', each of the one or more TBTT information fields is processed only up to a third octet value by comparing the value of the TBTT information length field with a third threshold value.

15. the TBTT Information Field Type subfield is used to indicate the content and / or length of the one or more TBTT Information fields; The method of claim 14 , wherein the TBTT information length field indicates a length of each of the one or more TBTT information fields.

16. When the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is less than the first threshold value and equal to or greater than the second threshold value, each of the one or more TBTT information fields is processed only up to the second octet value; The method of claim 14 , wherein the second octet value is less than the first octet value.

17. 17. The method of claim 16, wherein the remaining octets in each of the one or more TBTT information fields, up to but not including the second octet value, are not processed.

18. If the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is equal to or greater than the first threshold value, the one or more TBTT information fields are processed only up to the first octet value; The method of claim 14 , wherein the second octet value is less than the first octet value.

19. 20. The method of claim 18, wherein the remaining octets in each of the one or more TBTT information fields, up to but not including the first octet value, are not processed.

20. 15. The method of claim 14, wherein if the value of the TBTT information type subfield is '0' and the value of the TBTT information length field is less than the second threshold value, the one or more TBTT information fields are not processed.

21. 15. The method of claim 14, wherein when the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is equal to or greater than the third threshold value, the one or more TBTT information fields are processed only up to the third octet value.

22. 22. The method of claim 21, wherein the remaining octets in each of the one or more TBTT information fields, up to but not including the third octet value, are not processed.

23. 15. The method of claim 14, wherein if the value of the TBTT information type subfield is '1' and the value of the TBTT information length field is less than the third threshold value, the one or more TBTT information fields are not processed.

24. Each of the one or more TBTT information fields includes a neighbor AP TBTT offset subfield; The method of claim 14 , wherein the neighbor AP TBTT offset subfield indicates an offset between a TBTT for the AP to transmit a beacon frame and a TBTT for another AP to transmit a beacon frame.

25. 25. The method of claim 24, wherein if the other AP is included in the AP MLD, the offset value indicated by the neighbor AP TBTT offset subfield is set to a value other than a preset value associated with Unknown.

26. 26. The method of claim 25, wherein the preset value is "255."

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