Method and wireless communication terminal for transmitting / receiving data in wireless communication system

Abstract

To provide a high-speed wireless LAN service for a new multimedia application.SOLUTION: Provided is a method by which a multi-link device (MLD) of a wireless communication system transmits a frame. The MLD transmits a request frame for mapping between a traffic identifier (TID) and a link, the request frame including: first mapping information for establishing a mapping relationship between at least one TID from among a plurality of TIDs and at least one link; and information related to the number of the at least one TID for which mapping with the at least one link is requested. Thereafter, the MLD receives a response frame in response to the request frame. First remaining TIDs that exclude the at least one TID from among the plurality of TIDs maintain, to be valid, a previously established mapping relationship with a link or a default mapping relationship is applied. For the first remaining TIDs, a mapping relationship with a specific link may not be indicated by the first mapping information.SELECTED DRAWING: Figure 24

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system, and more particularly to a wireless communication method and a wireless communication terminal for efficiently signaling uplink multi-user information in a wireless communication system. [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 implemented or is currently developing standards for a variety of technologies. First, IEEE 802.11b uses the 2.4 GHz band and supports communication speeds of up to 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz band instead of the 2.4 GHz band, reducing the impact of interference compared to the significantly more congested 2.4 GHz band, and uses OFDM technology to improve communication speeds to up to 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. IEEE 802.11g has attracted considerable attention because it uses the same 2.4GHz band as IEEE 802.11b, achieving a maximum communication speed of 54Mbps and satisfying 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) of up to 540 Mbps and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas on both the transmitting and receiving ends to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As WLAN adoption 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, there is IEEE 802.11ad, a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, making it suitable for streaming large amounts of data and high-bitrate video, such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage of being difficult to pass through obstacles and can only be used between devices in close proximity.

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

[0007] Additionally, development of a new WLAN standard 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 being developed with the goal of supporting transmission rates of up to 30Gbps in the 2.4 / 5 / 6GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation. Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, an object of the present invention is to provide an ultra-high speed wireless LAN service for new multimedia applications.

[0009] Another object of the present invention is to provide a method for mapping TIDs and links between multi-link devices, which are a collection of logical entities.

[0010] Another object of the present invention is to provide a method for implicitly determining a mapping relationship between TIDs when the mapping relationship is not indicated in the process of mapping between TIDs and links.

[0011] The technical problems to be solved in this specification are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0012] A multi-link device (MLD) of a wireless communication system includes a communication module; and a processor that controls the communication module, wherein the processor transmits a request frame for mapping between traffic identifiers (TIDs) and links, the request frame including first mapping information for setting up a mapping relationship between at least one TID among a plurality of TIDs and at least one link, and information related to the number of the at least one TID for which mapping is requested with the at least one link, and receives a response frame in response to the request frame, wherein a previously set mapping relationship with the link is effectively maintained for first remaining TIDs other than the at least one TID among the plurality of TIDs, or a default mapping relationship is applied, and a mapping relationship with a specific link is not indicated for the first remaining TIDs by the first mapping information.

[0013] In addition, in the present invention, one link of the at least one link is mapped to one or more TIDs of the at least one TID.

[0014] In addition, in the present invention, the basic mapping relationship is a state in which TIDs and all links are mapped, and the basic mapping relationship is applied when the first remaining TID is set to the basic mapping relationship before transmitting the request frame.

[0015] In addition, in the present invention, the request frame further includes transmission direction information indicating a transmission direction for the at least one TID, and the plurality of TIDs are mapped only between links whose setup has been completed between the MLD and the other MLD that sent the request frame.

[0016] In addition, in the present invention, the response frame indicates whether a mapping relationship between the at least one TID among the plurality of TIDs and the at least one link is permitted.

[0017] In addition, in the present invention, when a mapping relationship between at least one TID among the plurality of TIDs and the at least one link is permitted, the response frame does not include second mapping information for another mapping relationship between the at least one TID among the plurality of TIDs and the at least one link.

[0018] In addition, in the present invention, when a mapping relationship between at least one TID among the plurality of TIDs and at least one link is not permitted, the response frame further includes second mapping information indicating a mapping relationship different from the first mapping relationship for the at least one TID among the plurality of TIDs.

[0019] Also, in the present invention, the processor receives a management frame, and the management frame is transmitted only through the at least one link for which the mapping relationship between the at least one TID and the at least one link is set.

[0020] In addition, in the present invention, the management frame is transmitted based on an assigned access category (AC), and is transmitted over the at least one link regardless of the access category set for the at least one link.

[0021] In addition, in the present invention, the processor receives a frame including second mapping information for setting a mapping relationship for one or more TIDs among the plurality of TIDs and one or more links, and a second remaining TID other than the one or more TIDs among the plurality of TIDs is indicated as having a preferred specific mapping relationship or no preferred mapping relationship.

[0022] In addition, in the present invention, the preferred specific mapping relationship is a pre-established mapping relationship or the basic mapping relationship.

[0023] Also, in the present invention, if the specific mapping relationship is the basic mapping relationship or there is no preferred mapping relationship, the mapping relationship for the overlapping TIDs among the at least one TID and the second remaining TID is not indicated by the response frame.

[0024] The present invention also provides a method including the steps of: transmitting a request frame for mapping between traffic identifiers (TIDs) and links, the request frame including first mapping information for setting up a mapping relationship between at least one TID among a plurality of TIDs and at least one link, and information related to the number of the at least one TID for which mapping is requested with the at least one link; and receiving a response frame in response to the request frame, wherein a previously set mapping relationship with a link is effectively maintained for first remaining TIDs other than the at least one TID among the plurality of TIDs, or a default mapping relationship is applied, and a mapping relationship with a specific link is not indicated for the first remaining TIDs by the first mapping information. [Effects of the Invention]

[0025] According to one embodiment of the present invention, the QoS of a multi-link device can be enhanced.

[0026] According to one embodiment of the present invention, a multi-link device is capable of performing TID-to-Link mapping.

[0027] According to one embodiment of the present invention, the multilink device is capable of performing QMF-to-Link mapping.

[0028] According to one embodiment of the present invention, a multilink device can implicitly indicate a solicited / proposed link when performing TID-to-Link mapping.

[0029] According to one embodiment of the present invention, a multi-link device can manage TID-to-Link mapping during ML setup changes.

[0030] 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]

[0031] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an access point according to an embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a process in which a STA establishes a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] 1 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8] 1 illustrates various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 is a diagram illustrating a multi-link device according to an embodiment of the present invention. [Figure 10]1 is a diagram illustrating how an MLD in one embodiment of the present invention maps traffic to its own STA (Link). [Figure 11] FIG. 10 illustrates an example of a TID-to-Link mapping method established between AP MLD and Non-AP MLD. [Figure 12] 1 illustrates an embodiment of a TID-to-Link mapping method that can be established between AP MLD and Non-AP MLD. [Figure 13] FIG. 10 is a diagram showing an example of a TID-to-Link mapping element that indicates a QMF that can be transmitted regardless of the link. [Figure 14] FIG. 10 illustrates an example of the operation of an MLD that has established a QMF policy using TID-to-Link mapping. [Figure 15] FIG. 10 illustrates one embodiment of the format of a TID-to-Link mapping element. [Figure 16] A diagram showing a TID-to-Link mapping procedure according to one embodiment of the present invention. [Figure 17] FIG. 10 is a diagram showing an embodiment in which a responding MLD selectively responds to some TIDs during TID and link mapping instructed (or proposed) by an initiating MLD. [Figure 18] 10 is a diagram showing a response method of an initiating MLD that accepts a TID-to-Link mapping counter-proposed by a responding MLD. [Figure 19] FIG. 10 is a diagram illustrating an example of an unsolicited TID-to-Link Mapping Response frame transmitted from an AP MLD and a TID-to-Link mapping negotiation process between an AP MLD and a non-AP MLD. [Figure 20] FIG. 10 illustrates yet another embodiment of a TID-to-Link mapping element. [Figure 21]FIG. 10 illustrates an embodiment of a TID-to-Link mapping element that includes a variable-length TID Link Mapping of TID field. [Figure 22] FIG. 10 is a diagram illustrating an embodiment of a TID-to-Link mapping management method for two MLDs in which a setup link is added by resetting. [Figure 23] 10 is a diagram illustrating an embodiment of a method for managing TID-to-Link mapping of two MLDs for a link whose setting has been cancelled by reconfiguration. FIG. [Figure 24] 3 is a flowchart illustrating an example method for mapping TIDs and links according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] 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.

[0033] Throughout this specification, when a component is referred to as being "connected" to another component, this includes not only when the component is "directly connected" to the other component, but also when the component is "electrically connected" to the other component via another component therebetween. Furthermore, when a component is referred to as "comprising" a specific component, this does not mean that the component excludes the other component, but that the component may further include the other component, unless otherwise specified. Additionally, limitations such as "greater than" or "less than" based on a specific critical value may be appropriately substituted with "exceeds" or "less than," respectively, depending on the embodiment. Hereinafter, in the present invention, the terms "field" and "subfield" may be used interchangeably.

[0034] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0035] 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.

[0036] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 that are stations providing distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0037] 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).

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Next, the display unit 150 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. Such control programs include a connection program required for the station 100 to connect to an AP or an external station.

[0046] 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.

[0047] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in embodiments of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively included in the station 100.

[0048] 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.

[0049] 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.

[0050] The memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a connection program that manages station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. The communication setup message includes information regarding connection preferences for each station. The processor 210 also performs connection setup in response to a station connection request. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals by the AP 200 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0051] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0052] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information for the BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0053] 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.

[0054] 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.

[0055] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0056] A terminal performing WLAN communication performs carrier sensing to check whether a channel is occupied before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not a signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold is received by the terminal and the terminal is 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.

[0057] If the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an Inter Frame Space (IFS), such as an Arbitration IFS (AIFS) or a PCF IFS (PIFS), depending on the status of each terminal. In some embodiments, the AIFS is used as a configuration replacing the conventional DCF IFS (DIFS). Each terminal waits while decreasing a slot time by a random number determined for the corresponding terminal during the idle interval of the channel, and a terminal that has exhausted all slot times attempts to access the corresponding channel. The period during which each terminal performs the backoff procedure is called a contention window period.

[0058] 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.

[0059] Hereinafter, in the present invention, a terminal may be referred to as a non-AP STA, an AP STA, an AP, an STA, a receiving device, or a transmitting device, and the present invention is not limited thereto. Also, in the present invention, an AP STA may be referred to as an AP.

[0060] <Examples of various PPDU formats>

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The unit of the L_LENGTH field is 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.

[0068] First, a legacy or non-legacy terminal interprets 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 one symbol duration of the 64FFT. 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 64FFT reference symbols after the L-SIG is obtained. The obtained number of symbols is multiplied by 4 us, which is one symbol duration, 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.

[0069]

number

[0070] Here, [x] represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU may be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as shown in Equation 2 below.

[0071]

number

[0072] 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.

[0073]

number

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 in the same PPDU format, and a field for distinguishing between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. 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.

[0079] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (such as the RA field) may be omitted depending on the value of the compression field.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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, and 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] Two or more PPDUs shown in FIG. 8 can be indicated by a value indicating the same PPDU format. That is, two or more PPDUs can be indicated as the same PPDU format by the same value. For example, an EHT SU PPDU and an EHT MU PPDU can be indicated by the same value using the U-SIG PPDU format subfield. In this case, the EHT SU PPDU and the EHT MU PPDU can be distinguished depending on the number of STAs receiving the PPDU. For example, a PPDU received by only one STA may be identified as an EHT SU PPDU, and when the number of STAs is set so that two or more STAs can receive the PPDU, it may be identified as an EHT MU PPDU. In other words, two or more PPDU formats shown in FIG. 8 can be indicated using the same subfield value.

[0097] In addition, some of the fields or some information of the fields shown in Figure 8 may be omitted, and such a case where some of the fields or some information of the fields is omitted can be defined as a compression mode or a compressed mode.

[0098] FIG. 9 is a diagram illustrating a multi-link device according to an embodiment of the present invention.

[0099] Referring to FIG. 9, the concept of a device to which one or more STAs are affiliated may be defined. As another example, according to an embodiment of the present invention, a device to which more than one STA is affiliated (i.e., two or more) may be defined. In this case, the device may be a logical concept. Therefore, such a device to which one or more STAs are affiliated may be referred to as a multi-link device (MLD), a multi-band device, or a multi-link logical entity (MLLE).

[0100] Alternatively, the above conceptual device can be called a multi-link entity (MLE). Also, an MLD may have one MAC medium access control service access point (SAP) to a logical link control (LLC), and an MLD may have one MAC data service.

[0101] A STA included in an MLD can operate on one or more links or channels. That is, a STA included in an MLD can operate on multiple different channels. For example, a STA included in an MLD can operate using channels in different frequency bands, such as 2.4 GHz, 5 GHz, and 6 GHz. This allows MLD to obtain gains in channel access and improve overall network performance. While existing WLANs operate on a single link, MLD operation can use multiple links to obtain more channel access opportunities or allow STAs to operate efficiently on multiple links taking into account channel conditions.

[0102] Also, if the STA affiliated to the MLD is an AP, the MLD to which the AP is affiliated may be an AP MLD, whereas if the STA affiliated to the MLD is a non-AP STA, the MLD to which the non-AP is affiliated may be a non-AP MLD.

[0103] 9, an MLD including multiple STAs may exist, and the multiple STAs included in the MLD may operate on multiple links. In FIG. 9, an MLD including APs AP1, AP2, and AP3 may be referred to as an AP MLD, and an MLD including non-AP STAs non-AP STA1, non-AP STA2, and non-AP STA3 may be referred to as a non-AP MLD. STAs included in the MLD may operate on Link 1, Link 2, Link 3, or some of Links 1 to 3.

[0104] According to an embodiment of the present invention, the multi-link operation can include a multi-link setup operation. The multi-link setup operation may be an operation corresponding to an association performed in a single-link operation. A multi-link setup may precede frame exchange in a multi-link. The multi-link setup operation may be performed using a multi-link setup element. Here, the multi-link setup element can include capability information related to the multi-link, and the capability information can include information related to whether, when a STA included in the MLD receives a frame on one link, another STA included in the MLD can transmit a frame on another link. That is, the capability information can include information related to whether a STA (non-AP STA and / or AP (or, AP STA)) included in the MLD can transmit / receive frames simultaneously in different transmission directions on the links included in the MLD. Further, the capability information can further include information related to available links or operating channels. The multi-link setup may be set by negotiation between peer STAs, and the multi-link operation may be set on one link.

[0105] According to an embodiment of the present invention, a mapping relationship may exist between a TID and a link of the MLD. For example, when the TID and the link are mapped, the TID may be transmitted on the mapped link. The mapping between the TID and the link may be made based on the transmission direction. For example, the mapping may be made for each of the two directions between MLD1 and MLD2. Also, a default setting may exist for the mapping between the TID and the link. For example, the mapping between the TID and the link may basically be such that all TIDs are mapped to a certain link.

[0106] <Wi-Fi QoS (Quality of Service) Support>

[0107] The data rate of Wi-Fi (IEEE 802.11) has increased dramatically with each new protocol version, and 802.11ax, which is currently in the final stages of completion, is expected to support data rates up to approximately 10 Gbps. This increased Wi-Fi data rate can be attributed to improved hardware performance, which allows the PHY protocol to process wider bandwidths (BW) and higher MCS, and enables the use of multiple antennas.

[0108] However, despite this dramatically increased data rate, Wi-Fi still suffers from the problem of transmission delay. All communication systems, including Wi-Fi, support a finite data rate, which causes a certain amount of transmission delay when transmitting traffic. However, the reason why Wi-Fi transmission delay is a problem is that its transmission delay is unpredictable. In other words, in communication systems that use dedicated communication resources (wired or licensed wireless spectrum), the delay required to transmit traffic can be predicted based on the amount of traffic to be transmitted. However, in communication systems that use unlicensed spectrum, such as Wi-Fi, unpredictable transmission delays can occur when the medium is occupied by other devices. Such unpredictable transmission delays can reduce the usefulness of short-lifetime traffic, such as voice traffic. In this case, even if Wi-Fi supports a high data rate, it is difficult to expect improvements in quality of service (QoS).

[0109] The IEEE 802.11 standardization organization has been continuously developing MAC protocols to overcome the limitations of unlicensed bands as mentioned above, and the enhanced distributed channel access (EDCA) introduced in 802.11e is one of the results. For the sake of convenience, QoS AP will be referred to as AP, QoS STA as STA, and QoS BSS as BSS. Therefore, when referring to an AP, it can be interpreted as referring to a QoS AP.

[0110] EDCA provides a mechanism for differentiating and managing traffic into four access categories (ACs) according to their characteristics. The four ACs are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best Effort), and AC_BK (AC Background), and each AC may have different contention window (CW), transmit opportunity (TXOP), and AIFSN parameters. Simply put, EDCA is a mechanism for adjusting the transmission priority of traffic transmitted using each AC by differentiating the CW, TXOP, and AIFSN parameters for the four ACs. To this end, EDCA can map traffic (MSDUs) to be serviced by the MAC to one of the four ACs according to traffic category (TC) or traffic stream (TS). The traffic mapped to one of the four ACs by EDCA is managed in four queues, one for each AC. The four queues may not be physically separated but may be logically separated.

[0111] AC_VO is an AC that can be used for traffic that is vulnerable to transmission delays but does not have a large absolute volume of traffic like voice traffic, and has relatively small CW and AIFSN parameter values ​​to increase the probability of being served preferentially over traffic of other ACs. However, the TXOP parameter of AC_VO is limited to a value relatively smaller than the TXOP parameters of other ACs, ensuring a shorter transmission time than other ACs.

[0112] AC_VI is an AC that can be used for traffic such as video, which is more tolerant of transmission delays than voice traffic but still requires low-delay transmission and must handle large amounts of traffic. AC_VI has larger CW and AIFSN parameter values ​​than AC_VO but smaller than other ACs, and in return, its TXOP is about twice as long as AC_VI.

[0113] AC_BE is an AC that can be used for traffic that is tolerant to transmission delays, and most general traffic except for voice data and streaming video data may be classified as AC_BE. AC_BE uses larger values ​​for CW and AIFSN parameters than AC_VO and AC_VI. Also, AC_BE does not have a separate TXOP, so it cannot use the TXOP transmission sequence of receiving an ACK response after transmitting a PPDU and then transmitting another PPDU after SIFS.

[0114] AC_BK is an AC that can be used for traffic that is robust to transmission delays like AC_BE, but has a lower priority than BE traffic. AC_BK uses the same CW parameter value as AC_BE, but uses a larger AIFSN parameter value than AC_BE. Also, unlike AC_BE, AC_BK does not have a separate TXOP and cannot use a TXOP transmission sequence.

[0115] The four types of EDCA ACs mentioned above are mapped to 802.1D UP (user priority), and the EDCA AC is determined by the UP value of the traffic received via wire or the TID of the MSDU indicated by the upper layer. In this case, when the TID of the MSDU indicates a value from 0 to 7, the value indicated by the TID has a one-to-one correspondence with the UP.

[0116] The rules for mapping 802.1D UP and EDCA AC are shown in Table 1 below.

[0117] [Table 1]

[0118] In addition, the four types of EDCA ACs mentioned above have their respective basic (default) CW (CWmin, CWmax), AIFSN, and TXOP parameters defined in the standard, and the parameter values ​​of each AC can be changed by the AP so that different values ​​can be used for each BSS.

[0119] When using the EDCA mechanism, Wi-Fi traffic is stored in one of four queues corresponding to four ACs, and may be transmitted to a destination device only if the AC it belongs to successfully accesses the channel through contention with other ACs. Channel access operations between the EDCA functions (EDCAFs) corresponding to the ACs may be performed by contention, and access parameters (CW[AC], AIFSN[AC]) assigned to each AC may be used in the contention. The channel access contention operations performed by each AC are the same as those performed by DCF. If there is no traffic in the queue to be transmitted by a particular AC, the particular AC is unavailable for contention.

[0120] However, as described above, since the CW and AIFSN parameter values utilized by each AC are different from each other, the AC_VO having the smallest CW and AIFSN parameters has a high probability of successfully accessing the channel in channel access competition with other ACs. Therefore, there is a high possibility that the traffic of AC_VO will be served preferentially over the traffic of other ACs.

[0121] In addition, when an (internal) collision occurs between each AC in the EDCA mechanism, the AC with a higher priority (see Table 1) is used, and internal competition rules such as increasing the CW of other ACs that induced the collision are defined, as well as rules for constructing PPDUs including the traffic of other ACs other than the AC (primary AC) that won the competition.

[0122] In addition to the EDCA described above, the 802.11 MAC protocol defines an HCCA (HCF controlled channel access) mechanism for QoS management. This HCCA mechanism provides a function similar to a kind of centralized / hybrid coordinator that is utilized to guarantee the TS (Traffic Stream) QoS of applications (such as voice and video) to be served periodically. In addition, there are SPCA (Service Period Channel Access) and a mechanism for dynamic allocation of service period, but these can only be utilized by DMG STAs, and it can be said that the aforementioned EDCA is the most representative Wi-Fi QoS MAC protocol.

[0123] <QoS (quality-of-service) MLD operation>

[0124] When considering the operation of the EDCA mechanism described above, it can be understood that the purpose of applying different CW and AIFSN parameters to each AC by EDCA is to mediate the transmission priority considering the nature of the traffic.

[0125] Considering the structure of the MLD described in Figure 9, the MLD operates one or more STAs that operate on different links, and therefore each STA of the MLD may have an independent transmission queue. In this case, the queues may be logically separated, which may be in line with the fact that the MLD may be a logical concept.

[0126] Based on a similar principle to the EDCA mechanism that enhances QoS service by operating separate queues for each of the four ACs, the MLD can map traffic to be served by itself to one of the STAs it operates, taking into account the characteristics of the traffic, in order to enhance QoS. In other words, similar to the EDCA mechanism that maps traffic to one of the four ACs, the MLD can map traffic to one of the STAs it operates. In this case, the operation of the MLD mapping specific traffic to a specific STA can be understood as the MLD mapping the specific traffic to a link on which the specific STA operates. For easier understanding, a method for the MLD to enhance QoS using multiple STAs (links) will be described with reference to FIG. 10.

[0127] FIG. 10 shows an example of a method by which an MLD according to an embodiment of the present invention maps traffic to its own STA (Link).

[0128] Referring to Figure 10, (a) AP MLD and (b) Non-AP MLD are MLDs that operate four STAs, AP1, AP2, AP3, and AP4, and Non-AP STA1, Non-AP STA2, Non-AP STA3, and Non-AP STA4, respectively, and the four STAs in each MLD can associate with each other.

[0129] If AP MLD uses the queues of its four STAs (AP1, AP2, AP3, and AP4) in a manner similar to the AC-specific queues of EDCA, it can map traffic using AC_BK to the queue of AP1, traffic using AC_BE to AP2, traffic using AC_VI to AP3, and traffic using AC_VO to AP4, as shown in Table 1. In this way, traffic mapped to each STA can be served according to the channel access procedure performed by each STA, and therefore traffic for different ACs is not affected by transmission delays that occur during the transmission of traffic for different ACs. In other words, the QoS enhancement effect achieved by MLD by separating STAs to be mapped according to traffic characteristics is similar to EDCA's granting transmission priority to high-priority traffic, but differs in that traffic for different ACs can be prevented from being affected by each other's transmissions.

[0130] Meanwhile, since the channel quality and load conditions of the link on which each STA of the MLD operates may differ from each other, and the PHY performance and operating bandwidth of each STA may differ from each other, the BW and MCS of the PPDU containing the specific traffic may change depending on which STA the MLD maps the specific traffic to.

[0131] For example, if AP1, a STA of the (a)AP MLD, operates in the 2.4 GHz band, AP1 may have an operating bandwidth of up to 40 MHz. If AP4, another STA of the (a)AP MLD, operates in the 6 GHz band, AP4 may use a maximum BW of 320 MHz as its operating bandwidth. In this case, if the MLD needs to map traffic that requires high throughput and low latency, it can attempt to enhance QoS by mapping the traffic to AP4. In this way, by performing STA mapping that takes into account the characteristics of the traffic it serves, the MLD can achieve the effect of differentiating not only transmission priority but also the amount of resources (hardware and frequency) available for transmission by traffic.

[0132] <TID(traffic identifier)-to-Linkマッピング>

[0133] In the embodiment described in Figure 10, it has been explained that the MLD can map traffic to the STA (link) it operates, taking into account the characteristics of the traffic it should serve, in order to enhance QoS. In the embodiment of Figure 10, for comparison with EDCA, it is expressed that traffic mapped to each AC is mapped to each STA, but when the MLD maps traffic to the STA (link), it can attempt mapping by TID for higher resolution.

[0134] According to an embodiment of the present invention, a TID corresponding to a frame may be present. For example, signaling for indicating the TID corresponding to the frame may be included in the frame, and the signaling may be a TID subfield. More specifically, the signaling for indicating the TID may be included in the MAC header of the frame. For example, the signaling for indicating the TID may be included in a QoS Control field. For example, the type of the frame may be a data frame or a QoS data frame. To enhance QoS, 802.11 indicates a TID according to the traffic type in the TID subfield in the QoS Control field of the MAC frame. In this case, the TID indicates the user priorities (UPs) or traffic stream identifier (TSID) of an MSDU, fragment, or A-MSDU included in the frame body. The TID subfield consists of a total of 4 bits and can represent values ​​from 0 to 15.

[0135] When the TID subfield is indicated as a value between 0 and 7, the value indicated in the TID subfield is the value for the UP of the MSDU included in the frame body, and should be processed in the MAC entity using EDCA as the access policy and the AC parameters corresponding to the UP.

[0136] When the TID subfield is indicated as a value between 8 and 15, the value indicated in the TID subfield is the value for the TSID of the MSDU included in the frame body, and the MSDU must be processed by the MAC entity according to the UP indicated in the User Priority subfield in the TS Info field of the TSPEC and must comply with the values ​​indicated in other parameters of the TSPEC.

[0137] In this case, the UP of the TSID traffic may be confirmed from the User Priority field of TCLAS instead of TSPEC. Also, the access policy applied to the MSDU whose TID subfield has a value from 8 to 15 is indicated by the Access Policy, which is another subfield of the TS Info field. The Access Policy subfield (bits 7 and 8) of the TS Info field may be interpreted as indicating EDCA when indicated as (1,0), and as indicating HCCA when indicated as (1,0) or (1,1).

[0138] In addition, when mapping a TID corresponding to a TS to a link, an Intra-Access Category Priority element may be indicated in the ADDTS request frame used to generate the TS, and an Intra-Access Priority field in the element may include User Priority and Alternate Queue (AC Queue) information used to transmit the TS via EDCA. In this case, the MLD can process traffic having a TID corresponding to the TS taking into account the UP and queue information indicated in the Intra-Access Priority field.

[0139] In this way, since the TID has a meaning corresponding to the UPs of traffic, it can be considered that the MLD maps the traffic of each TID to a different STA, similar to the mapping of traffic corresponding to each AC to a different STA in one embodiment of Figure 10. This may be conceptually understood as TID-to-STA mapping or TID-to-Link mapping, and in order to perform the TID-to-Link mapping, an agreement may be required between MLDs communicating with each other.

[0140] That is, a specific MLD can signal its own TID-to-Link mapping plan to other MLDs, and an MLD that receives the TID-to-Link mapping plan from the specific MLD can accept or reject the TID-to-Link mapping planned by the specific MLD. In this case, if no separate TID-to-Link mapping agreement is made between two MLDs that have established a connection with each other, each MLD can transmit traffic through all links that have established a connection with the other MLD, regardless of the traffic's TID. This can be understood as all TIDs being mapped to all links, and may be the basic TID-to-Link mode implicitly agreed upon between the two MLDs that first established a connection.

[0141] Detailed rules to be followed when performing TID-to-Link mapping need not be defined. However, when performing TID-to-Link mapping, the MLD must map all TIDs to one or more links. According to an embodiment of the present invention, frames for TIDs mapped to a link can be transmitted over the link. Furthermore, frames for TIDs not mapped to a link can be not transmitted over the link. Furthermore, mapping between TIDs and links can be performed separately for each MLD. Furthermore, mapping between TIDs and links can be performed separately for each link transmission direction. For example, mapping between TIDs and links can exist for both uplinks and downlinks. Furthermore, in the present invention, TID-to-Link mapping can be used interchangeably with TID-to-Link, TID-to-Link mapping, TID-to-Link mapping, etc. Furthermore, in the present invention, TID-to-Link mapping can refer to mapping between ACs and links, mapping between user priorities and links, mapping between traffic classes and links, or mapping between traffic streams and links.

[0142] Furthermore, the above-mentioned TID-to-Link mapping may be agreed upon differently between the interconnected MLDs. As an example, when MLD1 and MLD2 are connected via Link1 and Link2, MLD1 may map traffic having TID values ​​of 0 to 3 to Link1, and MLD2 may map traffic having TID values ​​of 4 to 7 to Link1.

[0143] Alternatively, signaling of TID-to-Link mapping may be performed implicitly. As an example, when MLD1 and MLD2 are connected via Link1 and Link2, MLD1 may map only traffic having TID values ​​0 to 3 to Link1, and may not separately signal links to which the remaining TIDs are mapped. In this case, other traffic having TID values ​​other than 0 to 3 may be understood to be mapped to Link2. That is, a TID that is not mapped to a specific link in the TID-to-Link mapping signaling may be interpreted as being mapped to another link that is not separately indicated in the TID-to-Link mapping signaling. In this case, the link that is not separately indicated may be interpreted as a link to which all TIDs are mapped.

[0144] In addition, two linked MLDs can request the other MLD to change its TID-to-Link mapping settings when the MLD connection is first established, or when changes are required during operation, such as: 1) when an MLD disassociates / disables the STA of a specific link according to its operational policy (for purposes such as power saving), or 2) when an MLD determines that it is difficult to guarantee QoS for traffic mapped to a specific link.

[0145] In addition, a specific MLD can request the peer MLD to change the TID-to-Link mapping. For example, when an AP MLD maps traffic with TIDs 0 to 3 among traffic sent to a Non-AP MLD to Link 1, the Non-AP MLD can request that the mapping link for the traffic be changed from Link 1 to another link (e.g., Link 2).

[0146] In addition, if a TID-to-Link mapping request made by a specific MLD is rejected by a peer MLD, the specific MLD may be restricted from requesting mapping of the same TID-to-Link configuration for a certain period of time. This is to prevent repeated TID-to-Link mapping requests and rejections, and the period of time during which the same TID-to-Link request is restricted after a rejection may be a period of time designated by the AP.

[0147] That is, if a specific MLD requests mapping of a link for a specific TID using a TID-to-Link mapping element in a request frame and the other MLD rejects the mapping relationship requested by the request frame, the specific MLD may be restricted for a certain period of time from requesting the rejected mapping relationship again using a request frame.

[0148] To this end, the AP MLD can signal time information related to the TID-to-Link Mapping request interval to the STAs of its own BSS in the BSS operation parameters. In this case, the restriction on the rejected TID-to-Link mapping may be applied to each rejected TID. In other words, if a request for mapping multiple TIDs and links proposed at one time is rejected for a specific TID, the AP MLD may be restricted from requesting mapping of the specific TID again for the rejected link.

[0149] FIG. 11 shows an embodiment of a TID-to-Link mapping method established between AP MLD and Non-AP MLD.

[0150] To establish TID-to-Link mapping rules between AP MLD and non-AP MLD, it is necessary to explicitly indicate which TID is mapped to which link.

[0151] According to an embodiment of the present invention, there may be signaling indicating which TID to map to which link. For example, the signaling may be a TID-to-Link mapping element. The TID-to-Link mapping element may include a Link ID field. The Link ID field may include a value indicating the link to which the TID-to-Link mapping element including the Link ID field maps.

[0152] Alternatively, the Link ID field may include a value indicating which link the TIDs info field corresponding to the Link ID field indicates information about.

[0153] The TID-to-Link mapping element may also include a TIDs info field. The TIDs info field may include information about the TIDs to be mapped. The TIDs info field may include information about the TIDs to which the TID-to-Link mapping element including the TIDs info field maps. For example, the TIDs info field may include information about the TIDs to be mapped to a link indicated by the Link ID included in the TID-to-Link mapping element including the TIDs info field. For example, the TIDs info field may include one or more bits corresponding to each TID value. If a TID is mapped to a link, the bit corresponding to the TID may be set to a pre-defined value (e.g., 1). If a TID is not mapped to a link, the bit corresponding to the TID may be set to a pre-defined value (e.g., 0) different from the pre-defined value.

[0154] In FIG. 11, (a) AP MLD can plan to transmit traffic 0, 1, 2, and 3 with TIDs 0 to 3, among traffic (MSDUs) to be transmitted to (b) Non-AP MLD, through AP1 operated on Link1.

[0155] To this end, the AP MLD can indicate Link 1 using the Link ID field of the (c) TID-to-Link mapping element, and then use the TIDs info field to signal to the Non-AP MLD that TIDs 0 to 3 are mapped to Link 1. Here, the (c) TID-to-Link mapping element is an element format for illustrative purposes, and it can be easily understood that elements of other structures may be used for the same purpose.

[0156] The Non-AP MLD can confirm the transmission link for each TID planned by the AP MLD from the TID-to-Link mapping element and then approve or reject it.

[0157] 12(b) shows a situation in which, after confirming the TID-to-Link mapping received from the AP MLD (a), the Non-AP MLD agrees to map traffic corresponding to TIDs 0 to 3 to Link1 and traffic corresponding to TIDs 4 to 7 to Link2. In this case, each TID-to-Link mapping element transmitted from the AP MLD to the Non-AP MLD may include two Link IDs and two TIDs info subfields. In this case, each of the two Link ID subfields may indicate Link1 and Link2, respectively, and each of the two TIDs info subfields may indicate a value indicating 0 to 3 and a value indicating 4 to 7, respectively.

[0158] In this case, the TIDs info subfield is composed of 8 bits, and each bit may be interpreted as corresponding to TID 0 to TID 7. That is, to indicate TIDs 0 to 3, the 8 bits of the TIDs info subfield may be represented as 1111 0000, and to indicate TIDs 4 to 7, the 8 bits of the TIDs info subfield may be represented as 0000 1111.

[0159] In this case, the TIDs info subfield is composed of 8 bits, and each bit may be interpreted as corresponding to TID 0 to TID 15. That is, to indicate TIDs 0 to 3, the 16 bits of the TIDs info subfield may be represented as 1111 0000 0000 0000, and to indicate TIDs 4 to 7, the 16 bits of the TIDs info subfield may be represented as 0000 1111 0000 0000.

[0160] Alternatively, the TIDs Info subfield may be internally composed of two subfields, Min TID and Max TID. In this case, the Min TID subfield indicates the lowest TID value among the TIDs mapped to the link, and the Max TID subfield indicates the highest TID value among the TIDs mapped to the link. In this case, the Min TID and Max TID may be represented by 3 bits or 4 bits, respectively.

[0161] As a 3-bit embodiment, if the Min TID subfield of the TIDs Info subfield is indicated as 000 and the Max TID subfield is indicated as 011, the TID indicated by the TIDs Info subfield may be interpreted as 0 to 3, and if the Min TID subfield is indicated as 100 and the Max TID subfield is indicated as 111, the TID indicated by the TIDs Info subfield may be interpreted as 4 to 7.

[0162] As a 4-bit embodiment, if the Min TID subfield of the TIDs Info subfield is indicated as 0000 and the Max TID subfield is indicated as 0011, the TID indicated by the TIDs Info subfield may be interpreted as 0 to 3, and if the Min TID subfield is indicated as 0100 and the Max TID subfield is indicated as 0111, the TID indicated by the TIDs Info subfield may be interpreted as 4 to 7.

[0163] In Figure 11, (a) AP MLD confirms the TID-to-Link mapping received from (b) Non-AP MLD, and then agrees to map traffic corresponding to TIDs 0 to 3 to Link 1 and traffic corresponding to TIDs 0 to 7 to Link 2.

[0164] In this case, the (b) Non-AP MLD uses the TID-to-Link mapping element to indicate only that TIDs 0 to 3 are to be mapped to Link 1, and does not need to separately indicate that TIDs 0 to 7 are to be mapped to Link 2. In other words, the (b) Non-AP MLD does not separately indicate the TIDs to be mapped to Link 2 in the TID-to-Link mapping element that it sends to the (a) AP MLD, and the (a) AP MLD can be implicitly interpreted as meaning that all TIDs are mapped to the uninstructed Link 2.

[0165] By utilizing the above-described TID-to-link mapping, an MLD can map traffic to be served to one or more STAs (links) operated by the MLD according to the TID of the traffic. If a TID mapped to a specific link corresponds to two or more EDCA ACs, a QoS STA (in the MLD) operated on the specific link can service the traffic of the mapped TID by differentiating the ACs using the EDCA mechanism. That is, the MLD can map a TID to each link using the TID-to-link mapping, and each STA of the MLD can apply the EDCA mechanism to the traffic of the TID mapped to its own link.

[0166] For example, if a specific MLD maps traffic corresponding to AC_VO and traffic corresponding to AC_BK to a specific link using TID-to-Link mapping, a STA operating on the specific link can serve traffic corresponding to AC_VO with higher priority than traffic corresponding to AC_BK. In this case, if a STA operating on the specific link sets the sum of the CWmax and AIFSN parameters of AC_VO to be smaller than the AIFSN of AC_BK, the STA operating on the specific link can always serve traffic corresponding to AC_VO with higher priority than traffic corresponding to AC_BK.

[0167] In this way, an MLD can enhance QoS or take into account the performance characteristics of each link by adjusting and changing the TIDs mapped to each link according to operational goals. There is no need to define separate rules for TID-to-link mapping. This means that, unlike the EDCA mechanism that provides UP to AC rules, an MLD can freely use TID-to-link mapping according to its operational policy. However, every TID must be mapped to at least one link, and an MLD must not request TID-to-link mapping from another MLD in which at least one TID is not mapped to any link. Therefore, if TID mapping to at least one link is not implicit, every TID must be explicitly mapped to at least one link.

[0168] FIG. 12 illustrates one embodiment of a TID-to-Link mapping method that can be established between AP MLD and Non-AP MLD.

[0169] 12(a) shows an embodiment in which both AP MLD and Non-AP MLD use default TID-to-link mapping, where AP MLD and Non-AP MLD operate AP1 and AP2, and Non-AP STA1 and Non-AP STA2, respectively, on Link1 and Link2. In this case, if the AP MLD and Non-AP do not request / approve a separate TID-to-link mapping after MLD association, the default TID-to-link mapping state considered in this embodiment can be maintained.

[0170] Referring to (a) of FIG. 12, it can be confirmed that the AP MLD maps all the TSIDs to all the links in addition to the TIDs. Also, the TSIDs may be in the basic mapping state where they are mapped to all the links unless another TID-to-Link mapping is performed. At this time, if the MLD attempts to change the mapping form of the TSID to a non-basic mode (for example, map only TSID9 to Link2), the TSID-to-Link mapping can be performed in the same manner as the TID-to-Link. The specific method of the TSID-to-Link mapping can be easily understood by considering the TID-to-Link method, and thus, a detailed description is omitted.

[0171] <QMF (quality-of-service management frame) policy>

[0172] As described above, the MLD can perform service link differentiation considering the nature of the traffic to be served by the MAC by utilizing the TID-to-Link mapping for the purpose of enhancing QoS. This can be understood as being similar to the way that conventional Wi-Fi utilizes the EDCA mechanism to differentiate the ACs according to the nature of the traffic, where the MLD utilizes each link as an AL (Access link) and differentiates the ALs according to the nature of the traffic.

[0173] However, the traffic to be processed by the Wi-Fi MAC includes, in addition to the MSDUs requested to be processed at the upper layer, management frames containing information for operating the BSS. Such management frames do not have individual TIDs, unlike each MSDU having a TID.

[0174] Therefore, the QoS STA needs to determine the AC to use when transmitting the QoS management frame. The conventional 802.11 standard provides a basic QMF policy for the QoS management frame, allowing the QoS STA to determine the AC to use when transmitting the QoS management frame (hereinafter referred to as a management frame). In this case, the QMF policy may be changed by the QoS AP operating the QoS BSS. According to an embodiment, an AC corresponding to the management frame may exist.

[0175] In addition, the AC corresponding to the management frame may be determined according to a QMF policy. In this case, the AC corresponding to the management frame may be referred to as a QMF connection category. In addition, the type of management frame or the QMF AC may be determined based on the type, subtype, or category value corresponding to the management frame. In addition, a service in which an AC corresponding to the management frame exists or a service that accesses a channel based on an AC based on a QMF policy when transmitting a management frame may be referred to as a QMF service. In addition, frame transmission based on a QMF policy may be limited to cases where both the STA transmitting the frame and the STA receiving the frame support QMF.

[0176] Table 2 below shows some examples of default QMF policies.

[0177] [Table 2]

[0178] Referring to Table 2, for (Re)Association Request / Response, AC_VO is set as the basic AC, and therefore, when a QoS STA sends an Association Request or responds to an Association Response, it must use the CW and AIFSN parameters of AC_VO to transmit the Association Request or the Association Response. On the other hand, for Timing Advertisement, the basic AC is set as AC_BE, and therefore, unless the QoS AP has otherwise changed the QMF policy of the QoS BSS, the QoS STA must use the CW and AIFSN parameters of AC_BE to transmit the Timing Advertisement.

[0179] The reason why different QMF connection categories are assigned depending on the type of management frame in the basic QMF policy is that even though they are all management frames, there are types of management frames that are not urgently required for processing, and this is to prevent delays in the service of other traffic and management frames in the process of processing these less urgent management frames.

[0180] As mentioned above, management frames also need to differentiate ACs based on the information and role they contain, and therefore MLD can map management frames to different links based on their type, similar to how ALs are differentiated by TID using TID-to-Link mapping.

[0181] However, the basic QMF policy of the MLD may be set to allow all QMFs to utilize all ACs, i.e., the basic QMF policy of the MLD may be set to set the QMF access category to AC_Any for all subtypes of management frames.

[0182] According to one embodiment of the present invention, when the QMF service is enabled, a management frame can be transmitted based on a connection category corresponding to the management frame. However, the connection category may be limited to a channel connection. According to an embodiment of the present invention, when the QMF service is enabled, a management frame is transmitted based on a connection category corresponding to the management frame, but can be transmitted over any link regardless of the TID-to-Link mapping. For example, even if an AC corresponding to a management frame is not mapped to a link based on the TID-to-Link mapping, the management frame can be transmitted over the link.

[0183] That is, a general frame is transmitted on a link mapped to an assigned TID. However, a management frame may not be assigned a TID and the link to be transmitted may not be specified. In this case, since the management frame does not have an assigned TID, it may not be necessary to set up a mapping relationship between the TID and the link. Therefore, the management frame may be transmitted regardless of the mapping between the TID and the link.

[0184] <QMF(quality-of-service management frame)-to-Linkマッピング>

[0185] The easiest way to perform QMF-to-Link mapping is to map each management frame to the link to which the traffic corresponding to the AC is mapped, based on the QMF connection category (see Table 2) assigned to each management frame. In other words, it is possible to transmit management frames based on TID-to-Link mapping.

[0186] For example, if a certain AC (or TID) is mapped to a link and the AC (or TID) corresponding to the management frame is the AC (or TID), the management frame can be transmitted on the link. On the other hand, if a certain AC (or TID) is not mapped to a link and the AC (or TID) corresponding to the management frame is the AC (or TID), the management frame may not be transmitted on the link.

[0187] Furthermore, if a specific MLD maps a TID indicating traffic corresponding to AC_VO to a specific link, an Association Req / Resp management frame with a QMF connection category assigned to AC_VO may be mapped to the specific link. A QoS STA can change the AC used when processing each management frame without following the basic QMF policy. Therefore, by changing the AC assigned to each management frame, the QoS STA can freely change the link to which each management frame is mapped.

[0188] In this way, the MLD can perform QMF-to-Link mapping for each QMF in a manner similar to TID-to-Link mapping, even for QMFs that do not have TIDs.

[0189] However, in the case of a specific QMF, unlike a general MSDU, information that is exchanged at the MLD level may be included, but information that needs to be exchanged between STAs in the MLD. In this case, if the MLD maps the specific QMF only to a specific link, STAs operating on links other than the specific link may not be able to transmit the specific QMF.

[0190] That is, in the case of a QMF, there may be a QMF that has the property that it should be able to be transmitted on all links regardless of the type of AC assigned to the QMF, and therefore the MLD can indicate a QMF that can be mapped to all links regardless of the AC assigned to the QMF.

[0191] In other words, in the case of a management frame, a specific TID is not assigned, and therefore, mapping between TID and link does not need to be applied. Therefore, a management frame may be transmitted over all links regardless of mapping between TID and link. In this case, the link over which the management frame is transmitted may be an enabled link in which mapping between TID and link is set. In this case, an enabled link means a link in which a mapping relationship with at least one TID is set.

[0192] In this case, if management frames are transmitted only through an enabled link, a management frame may not be transmitted if there is no enabled link, except for broadcast management frames that are transmitted regardless of the link. Therefore, a specific management frame may be transmitted even if there is no enabled link.

[0193] FIG. 13 shows an example of a TID-to-Link mapping element that indicates a QMF that can be transmitted regardless of the link.

[0194] Referring to FIG. 13, when performing TID-to-Link mapping, the MLD can designate a QMF that can map to all links regardless of the AC assigned in the QMF policy.

[0195] Specifically, information related to a management frame subtype may be indicated in the TID-to-Link mapping element, and management frames of the indicated subtype may be mapped to all links regardless of the AC (or TID) assigned to the management frame.

[0196] As shown in Figure 13, the TID-to-Link mapping element may have a QMF Support field corresponding to each Link ID. The QMF Support field indicates whether all types of QMFs can be mapped to the link indicated by the corresponding Link ID field. Furthermore, if the QMF Support field corresponding to a specific link is indicated as 1 (true), all types of QMFs can be mapped to the specific link regardless of the QMF policy of each QMF.

[0197] The TID-to-Link mapping element may also indicate a (QMF) management frame subtype. In this case, a QMF of a subtype corresponding to the value indicated by the Management Frame Subtype field may be mapped to all links regardless of the assigned AC. For example, if the Management Frame Subtype field indicates 0101 (Probe Response), a Probe Response frame may be mapped to all links regardless of the AC assigned (assigned / instructed) by the QMF policy.

[0198] That is, the TID-to-Link mapping element may include a QMF Support field for indicating whether all QMFs can be mapped to each link. The TID-to-Link mapping element may also include a (QMF) Management Frame subtype for indicating whether a management frame of a specific subtype can be mapped to all links. Alternatively, there may be signaling indicating whether the TID-to-Link mapping is used when transmitting a QMF. That is, there may be signaling indicating whether the TID-to-Link mapping is used when transmitting a QMF on a specific link.

[0199] That is, according to one embodiment, if the signaling indicates a pre-set value, the QMF can be transmitted regardless of the TID-to-Link mapping. That is, even if an AC corresponding to the QMF is not mapped to a link based on the TID-to-Link mapping, the QMF can be transmitted on the link. As another embodiment, if the signaling indicates a pre-set value, the QMF can be transmitted based on the TID-to-Link mapping. That is, if an AC corresponding to the QMF is mapped to a link based on the TID-to-Link mapping, the QMF can be transmitted on the link. Also, if an AC corresponding to the QMF is not mapped to a link based on the TID-to-Link mapping, the QMF need not be transmitted on the link.

[0200] However, when the MLD receives a QMF that solicits a response, such as a Probe Request / Response, through a specific link, it can respond (send) a Response QMF frame through the specific link regardless of the MLD's QMF-to-Link mapping policy. That is, when a Request-type QMF frame is received through a specific link, a Response-type QMF frame in response to it can be sent through the specific link regardless of the AC. Also, when a Request-type QMF frame is received through a specific link, a Response-type QMF frame in response to it can be sent through the specific link regardless of the QMF-to-Link mapping.

[0201] FIG. 14 illustrates one embodiment of the operation of an MLD that establishes a QMF policy using TID-to-Link mapping.

[0202] 14(a) shows an example of a TID-to-Link mapping element that may be generated to perform TID-to-Link mapping for three links. In this case, if the MLD that generated the element is using more than four links and is associated with other MLDs, any links not explicitly indicated by the Link ID field of the element may be interpreted by the receiving MLD as an implicit indication that basic TID-to-Link mapping is to be used.

[0203] In this case, if a specific MLD generates a TID-to-Link mapping element as shown in Figure 14(a) and the peer MLD accepts it, the specific MLD can transmit traffic and QMF frames in the manner as shown in Figure 14(b). For reference, (a_1), (a_2), and (a_3) in Figure 14(a) represent subfields for Link1, Link2, and Link3, respectively, and (a_common) is inserted to represent a subfield that is commonly applied to all links.

[0204] Referring to (b) of Figure 14, the MLD can map and transmit traffic having TIDs 0 to 3 using Link 1, where TIDs 0 to 3 may be TIDs corresponding to AC_BK (UP 1, 2) and AC_BE (UP 0, 3) among ACs. Referring to (a_1) of (a) of Figure 14, QMF Support of Link 1 is indicated as 1 (true), so the MLD can transmit (map) all types (subtypes) of QMFs through Link 1 regardless of the ACs assigned to each QMF.

[0205] As shown in (b) of FIG. 14, the MLD can transmit (map) traffic having the same TIDs 0 to 3 as Link1 through Link2. However, since the QMF support field corresponding to Link2 (see (a_2) in FIG. 16(a)) is indicated as 0, only the QMF given the same AC as the TID mapped to Link2 can be mapped and transmitted to Link2. However, since the (QMF) management frame subtype field (1111 is indicated by (a_common) in FIG. 16(a)), the MLD can transmit (map) the QMF (1111) whose management frame subtype is 1111 through Link2. At this time, in order for the STA of Link2 to transmit the QMF (1111), it may be necessary to attempt channel access by applying the AC given to the QMF (indicated by the QMF policy).

[0206] Traffic having TIDs 4 to 7 may be transmitted (mapped) to Link3 of the MLD. At this time, the TIDs 4 to 7 may be traffic mapped to AC_VI and AC_VO. At this time, since the QMF support field corresponding to Link3 (see (a_3) in FIG. 16(a)) is indicated as 0, the MLD can only transmit or map the QMF given AC_VI / AC_VO through Link3. However, since 1111 is indicated in the (QMF) management frame subtype field, the MLD can transmit (map) the QMF (1111) whose management frame subtype is 1111 through Link3. At this time, in order for the STA of Link3 to transmit the QMF (1111), it may be necessary to attempt channel access by applying the AC given to the QMF (indicated by the QMF policy).

[0207] <TID (traffic identifier)-to-Link mapping negotiation>

[0208] According to the above-described embodiment of the present invention, the MLD can map each TID to a different link by performing TID-to-Link mapping, thereby enhancing QoS. An embodiment of the present invention, which will be described later, provides a specific signaling method and negotiation method for TID-to-Link mapping between MLDs.

[0209] For reference, in the drawings of the embodiments provided below, some Immediate Ack frames may be omitted for simplicity. For example, a responding MLD that receives a TID-to-Link Mapping Request frame may send an Immediate Ack frame (responded after SIFS) in response, which may be omitted for simplicity.

[0210] An MLD (AP MLD or non-AP MLD) requesting TID-to-Link mapping can request that the designated TID be mapped to the designated link by indicating a specific TID and a specific link using a TID-to-Link mapping element. In this case, the TID-to-Link mapping element can be used to indicate multiple TID groups and multiple link groups.

[0211] For example, a single TID-to-Link mapping element may indicate TID sets #1, #2, and #3 corresponding to Link sets #1, #2, and #3, respectively. In this case, when TID set #1 is indicated corresponding to Link set #1, it may be understood that an attempt is made to map a TID corresponding to TID set #1 to a link corresponding to Link set #1. In this case, a TID-to-Link mapping element including information on the TID and link for which the mapping is desired may be transmitted via a TID-to-Link Mapping Request frame (included in the TID-to-Link Mapping Request frame). In this case, the MLD that transmitted the TID-to-Link Mapping Request frame may be referred to as an initiating MLD or a requesting MLD.

[0212] In this way, an MLD that receives a TID-to-Link mapping element (TID-to-Link Mapping Request frame) including instruction information for the TID and link can confirm the TID-to-Link mapping information desired by the MLD that sent the TID-to-Link Mapping Request frame. The MLD that receives the TID-to-Link Mapping Request frame may then need to respond with a TID-to-Link Mapping Response frame to accept / adopt or refuse / reject / denied the mapping between the TID and link requested by the initiating MLD. In this case, the MLD that receives the Request frame may be called the Responding MLD because it must respond with a TID-to-Link Mapping Response frame.

[0213] When a responding MLD wishes to accept the TID-to-Link mapping requested by the initiating MLD, it may respond without including a TID-to-Link mapping element in its TID-to-Link mapping response frame. That is, when the TID-to-Link mapping response frame received in response to the TID-to-Link mapping request frame sent by the initiator MLD does not include a TID-to-Link mapping element, the initiator MLD can recognize that the TID-to-Link mapping requested by the responding MLD has been accepted by the responding MLD.

[0214] That is, when the transmission / reception of a response frame that does not include a TID-to-Link mapping element is completed, it may be understood that a new TID-to-Link mapping negotiation is completed between the two MLDs that transmitted / received the response frame. At this time, the two MLDs may be given a certain delay before communicating using the newly negotiated TID-to-Link mapping.

[0215] In this case, the certain time period may be used to manage the transmission queues of the STAs of each link included (connected) in each MLD. Furthermore, after the TID-to-Link mapping negotiation is completed, each MLD may have a certain time period to manage the transmission queues of the STAs corresponding to each link according to the negotiated TID-to-Link mapping state. That is, after the certain time period has elapsed, the two MLDs that have completed the TID-to-Link mapping must communicate according to the negotiated TID-to-Link mapping state. In this case, communicating according to the TID-to-Link mapping state means that only traffic (e.g., frames) of the TID mapped to a specific link can be transmitted / received.

[0216] On the other hand, when a responding MLD wishes to reject the TID-to-Link mapping requested by the initiator MLD, it can respond by including a TID-to-Link mapping element in its TID-to-Link mapping response frame. In this case, the TID-to-Link mapping element included in the response frame can indicate a different TID and link than the TID-to-Link mapping element included in the request frame. For example, the TID-to-Link mapping element included in the request frame may indicate that TID 0 corresponds to Link 1. If the responding MLD indicates that TID 0 corresponds to Link 2 in the TID-to-Link mapping element included in the response frame, the initiator MLD that sent the request frame can recognize that its proposal to map TID 0 to Link 1 has been rejected. Furthermore, the initiator MLD can recognize that the responding MLD desires to map TID 0 to Link 2 by confirming that TID 0 corresponds to Link 2 in the response frame returned from the responding MLD.

[0217] That is, when an initiating MLD receives a response frame including a TID-to-Link mapping element from a responding MLD, the initiating MLD may need to indicate the same TID-to-Link mapping information indicated in the received response frame when constructing a request frame to be later (re)sent to the responding MLD.

[0218] In addition, the responding MLD may accept only some of the TID-to-Link mappings indicated (requested) by the initiating MLD through the TID-to-Link mapping element. For example, the initiating MLD may request that TID 0 be mapped to Link 1 by indicating that TID 0 corresponds to Link 1, and may simultaneously request that TID 1 be mapped to Link 2 by indicating that TID 1 corresponds to Link 2. In this case, the responding MLD may accept only one of the two mapping requests (TID 0 to Link 1, TID 1 to Link 2) requested by the initiating MLD. In this case, the responding MLD may accept the TID-Link mapping request associated with a specific TID by indicating only the remaining TIDs excluding the specific TID it wishes to accept in the TID-to-Link mapping element included in the response frame. In other words, if there is a TID-Link mapping that the responding MLD wishes to accept among the TID-Link mapping list (field or subfield) indicated by the initiating MLD (included in the TID-to-Link mapping element of the request frame), the responding MLD can implicitly indicate acceptance by not indicating the TID (the TID to be accepted) in the response frame. Therefore, if there is a TID among the TIDs indicated by the initiating MLD through its request frame that is not indicated (not counter-proposed) in the response frame of the responding MLD, the initiating MLD can recognize (interpret) that the TID-Link mapping request for that TID has been accepted.

[0219] The AP MLD can help a non-AP STA (MLD) that receives a Beacon frame recognize its preferred TID-to-Link mapping state by including a TID-to-Link mapping element in the Beacon frame and transmitting it. In this case, the non-AP STA MLD can request TID-to-Link mapping negotiation using the TID-to-Link mapping element when transmitting an Association Request frame to the AP MLD. In this case, the non-AP STA MLD may need to set the TID-to-Link mapping element to be included in the Association Request frame it transmits, taking into account the AP's preferred TID-to-Link mapping state indicated through the Beacon frame. In this case, the AP MLD that includes the TID-to-Link mapping element in the Beacon frame may be limited to AP MLDs that support TID-to-Link mapping negotiation.

[0220] The TID-to-Link mapping element may be transmitted by being included in a (Re)association request / response frame, or may be transmitted through a TID-to-Link mapping request / response frame. In this case, the TID-to-Link mapping element included in the two types of response frames may be included to propose a preferred TID-Link mapping to the MLD that transmitted the request frame. Alternatively, a response frame (unsolicited response frame) transmitted without receiving a request frame containing a TID-to-Link mapping element may be transmitted to propose (instruct) a preferred TID-to-Link mapping state to the MLD that is the single-purpose device of the frame.

[0221] FIG. 15 shows an example of the format of a TID-to-Link mapping element.

[0222] The TID-to-Link mapping element must indicate a TID-Link pair and may include a subfield indicating a TID and a subfield indicating a link. The subfields indicating a TID and a link may be used to indicate a single TID and a link, or may be used to indicate a TID set and a link set. The method of indicating a TID and a link, or a TID set and a link set, may be similar to the TID indication method using the 8-bit TIDs info field described in the embodiment of FIG. 11.

[0223] That is, an 8-bit Links info field may be used to indicate a link set, and each bit of the Links info field may be used to indicate whether the indicated TID corresponds to the link corresponding to each index. For example, when a pair of the TIDs Info field and the Links Info field included in the TID-to-Link mapping element is indicated as 1111 0000 and 1100 0000, the pair may be understood as proposing / counterproposing that TID 0 to TID 3 be mapped to Link1(0) to Link2(1).

[0224] Referring to (a) of FIG. 15, a TID-to-Link mapping element may have a configuration including multiple TID-to-Link Mapping Info fields (see (c) of FIG. 15). This means that mapping for multiple TID and Link pairs can be proposed / counter-proposed through a single TID-to-Link mapping element. That is, a TID-to-Link mapping element may include mapping information indicating each mapping relationship to indicate mapping between one or more TIDs and one or more links. In this case, multiple TIDs may be mapped to one link.

[0225] That is, a TID-to-Link mapping element can indicate different TIDs and links in each TID-to-Link Mapping Info field through multiple TID-to-Link Mapping Info fields, but within a single TID-to-Link mapping element, a specific TID cannot be indicated in more than one TID-to-Link Mapping Info field.

[0226] In other words, there may be a restriction that each TID should be indicated only once (or at most once) within a TID-to-Link mapping element. For example, if TID 0 is indicated in the TID Info subfield of the first TID-to-Link Mapping Info field of a TID-to-Link mapping element, TID 0 may not be indicated in the remaining TID-to-Link Mapping Info fields included in the element. In this case, indicating TID 0 may mean that TID 0 is indicated alone, or that a TID set including TID 0 (e.g., TID 0 to TID 3) is indicated.

[0227] As shown in Figure 15, the format of the TID-to-Link mapping element may vary depending on the number of TID-to-Link Mapping Info fields included. Therefore, the TID-to-Link mapping element may be configured to include a field for indicating information related to its length.

[0228] In (a) of Figure 15, the TID-to-Link Mapping Control field is indicated before the TID-to-Link Mapping Info field and can indicate information related to the length of the TID-to-Link Mapping Info field. In this case, the information related to the length may be information related to the number of TID-to-Link Mapping Info fields ((c) of Figure 15) included in the TID-to-Link Mapping Info field and the length (size) of each TID-to-Link Mapping Info field. In other words, the information on the length may be information related to the number of one or more TIDs mapped to one or more links.

[0229] 15(b), the TID-to-Link Mapping Control field may include a TID-to-Link Mapping Info size subfield and a Link Bitmap size subfield. The TID-to-Link Mapping Info size subfield may indicate information related to the length of the TID-to-Link Mapping Info field included in the TID-to-Link mapping element. For example, the TID-to-Link Mapping Info size subfield may indicate the number of TID-to-Link Mapping Info fields included in the TID-to-Link mapping element. Alternatively, the TID-to-Link Mapping Info size subfield may indicate the size (e.g., in octets) of the TID-to-Link Mapping Info field included in the TID-to-Link mapping element.

[0230] The Link Bitmap size subfield may be used to indicate the size of the Link Info subfield included in each TID-to-Link Mapping Info field. The Link Bitmap size subfield is necessary because, unlike the fixed number of TIDs (TID 0 to TID 7), the number of Links in an MLD may be variable. Therefore, the Link Bitmap size subfield may indicate a value related to the size of the Link Info subfield included in the TID-to-Link Mapping Info field. For example, the Link Bitmap size subfield may be configured with 4 bits and may indicate that the Link Info subfield has a size of 1 bit (Link Bitmap size = 0000) to 16 bits (Link Bitmap size = 1111). Alternatively, the Link Bitmap size subfield may be configured with 1 bit and may indicate one of the previously set Link Info subfield sizes. For example, a Link Bitmap size subfield of 0 may indicate that the size of the Link Info subfield is 8 bits, and a Link Bitmap size subfield of 1 may indicate that the size of the Link Info subfield is 16 bits.

[0231] Also, as described above, the TID-to-Link mapping negotiation may be performed independently for the DL and UL directions (see FIG. 11). Therefore, the TID-to-Link mapping negotiation performed between MLDs using the TID-to-Link mapping element may be performed simultaneously for the DL and UL directions. That is, a single TID-to-Link mapping element may indicate information for both DL TID-to-Link mapping and UL TID-to-Link mapping negotiation. In consideration of this, the TID-to-Link Mapping Info field may include both the DL TID-to-Link Mapping Info field and the UL TID-to-Link Mapping Info field.

[0232] Also, the TID-to-Link Mapping Info size subfield may be configured with two types of TID-to-Link Mapping Info size subfields (DL TID-to-Link Mapping Info size subfield and UL TID-to-Link Mapping Info size subfield) to indicate information related to the size of the DL TID-to-Link Mapping Info field and the size of the UL TID-to-Link Mapping Info field, respectively. However, if information for DL ​​and UL is not separately indicated in the TID-to-Link mapping element, it may be unidirectional TID-to-Link mapping information applied to the transmitting or receiving direction of the MLD that transmitted the request frame including the TID-to-Link mapping element.

[0233] On the one hand, each TID may be indicated more than once within the TID-to-Link mapping element. For example, in the first of two TID-to-Link Mapping Info fields included in the TID-to-Link mapping element of a request frame, a set of TIDs including TID 0 is mapped to Link1, and in the second of the second TID-to-Link Mapping Info field, another set of TIDs including TID 0 may be mapped and indicated to Link2 again. In this case, the MLD (response MLD) that receives this can interpret that TID 0 is mapped to both Link1 indicated through the first TID-to-Link Mapping Info field and Link2 indicated through the second TID-to-Link Mapping Info field. Therefore, in this case, the response MLD can complete the TID-to-Link mapping negotiation by mapping TID 0 to both Link1 and Link2 by responding with a response frame that does not contain a TID-to-Link mapping element.

[0234] <Proposal / Commitment / Rejection (Counterproposal) Method for TID-to-Link Mapping Negotiation>

[0235] As mentioned above, TID-to-Link mapping negotiation can be performed between MLDs using the TID-to-Link mapping element. The initiating MLD can indicate the TID-Link mapping it wishes to propose (prefer) using the TID-to-Link mapping element included in the request frame (TID-to-Link Mapping Request frame or (Re)Association Request frame). After receiving the request frame from the initiating MLD, the responding MLD can decide whether to accept the TID-Link mapping indicated in the TID-to-Link mapping element. The responding MLD and the initiating MLD can use the TID-to-Link Mapping Request frame, TID-to-Link Mapping Response frame, TID-to-Link Mapping Teardown frame, etc. to negotiate the TID-to-Link mapping.

[0236] The TID-to-Link Mapping Req / Resp / Teardown frames may have a frame format corresponding to the TID-to-Link Mapping Action frame. That is, the Category field of the Action field may indicate a value indicating that it is a TID-to-Link Mapping Action frame, and the Action Details field may indicate a value for distinguishing the TID-to-Link Mapping Request frame, the TID-to-Link Mapping Response frame, and the TID-to-Link Mapping Teardown frame. For example, the TID-to-Link Mapping Action frame may be indicated by a Category value in the range of 32 to 125 (e.g., 32), which is reserved in 11ax. In this case, the TID-to-Link Mapping Req / Resp / Teardown frames may be distinguished by being indicated as 0, 1, or 2, respectively, in the octet immediately following the Category field. That is, if the Category field value of an Action frame is designated as 32 and the octet immediately following the Category field is designated as 0 (0000 0000), the Action frame may be a TID-to-Link mapping request frame.

[0237] If the responding MLD wishes to reject all or part of the TID-Link mapping method proposed by the initiator MLD, the responding MLD can reject the TID-Link mapping proposed by the initiator MLD by including a TID-to-Link mapping element in a response frame (TID-to-Link Mapping Response Frame, (Re)Association Response Frame). In other words, if a response frame includes a TID-to-Link mapping element, it can be understood that the TID-to-Link mapping negotiation between the initiator MLD and the responding MLD is not completed. In this case, the TID-to-Link Mapping Info field included in the TID-to-Link mapping element of the response frame can indicate the TID-Link mapping information that the responding MLD counter-proposes to the initiator MLD. For example, if an initiating MLD proposes (instructs / requests) to map TID 0 to Link 1 (through a request frame) and a responding MLD indicates TID 0 as corresponding (mapping) to Link 2 through a request frame, the initiating MLD can interpret this as the responding MLD (reverse) proposing to map TID 0 to Link 2.

[0238] In addition, the responding MLD can indicate (counter-propose) only some of the TID-Link mappings proposed (requested) by the initiator MLD through a response frame, and then accept the Link mapping requests (indicated (proposed) through the request frame) for the remaining TIDs other than the indicated TIDs. In other words, the TID-Link mappings of the initiator MLD for TIDs that the responding MLD has not indicated through a response frame can be considered as having been accepted by the responding MLD. Therefore, if the initiator MLD indicates Link mapping for a specific TID in the TID-to-Link mapping element of the request frame and then the specific TID is not indicated in the TID-to-Link mapping element of the response frame, it should be interpreted that the Link mapping request proposed for the specific TID has been accepted by the responding MLD.

[0239] As described above, the responding MLD can implicitly accept the mapping relationship between TIDs and links requested (or proposed) by the initiating MLD through the request frame by not including mapping information related to the mapping relationship for TIDs in the TID-to-Link mapping element included in the response frame. Similarly, the initiating MLD can implicitly propose mapping relationships between some TIDs and links to the responding MLD by not including mapping information for the mapping relationship for some TIDs in the TID-to-Link mapping element included in the request frame.

[0240] That is, when an initiator MLD transmits a request frame to a responder MLD to set up a mapping between a TID and a link, the initiator MLD may implicitly indicate to the responder MLD the mapping relationship for the remaining TIDs by not including mapping information for some of the TIDs among multiple TIDs for mapping with links in the TID-to-Link mapping element of the request frame. In other words, when mapping information for the mapping relationship between a specific TID and a link is missing from the request frame, the mapping relationship between the specific TID and the link may be implicitly indicated (or suggested).

[0241] In this case, the implicit proposal may be that 1) the previously established mapping relationship remains valid without change, or 2) the mapping relationship between the TID and the link is a default mapping relationship.

[0242] In this case, the basic mapping relationship may be a mapping relationship in which all links are mapped to one TID.

[0243] Specifically, the implicit proposal may be a proposal to map a TID not indicated in the TID-to-Link mapping element to all links, i.e., if the initiator MLD does not indicate a specific TID in the TID-to-Link mapping element included in the request frame, the specific TID may be (implicitly) indicated / requested to be mapped to all links.

[0244] Alternatively, the implicit proposal may be a proposal to maintain a link mapping state that has already been previously negotiated for a TID that is not indicated in the TID-to-Link mapping element. That is, if the initiator MLD does not indicate a specific TID in the TID-to-Link mapping element included in the request frame, the specific TID may (implicitly) indicate / request to maintain a TID-Link mapping state that was already established before transmitting the request frame including the TID-to-Link mapping element.

[0245] That is, if the TID-Link mapping requested in a previously transmitted request frame is approved for a specific TID, the initiator MLD may attempt to maintain the already approved link mapping status for the specific TID validly without changing it by not indicating information for the specific TID in the next transmitted request frame.

[0246] Alternatively, if there is a TID-to-Link mapping mode (including Default TID-to-Link mapping mode) that has already been negotiated and it is not desired to change the link mapping state for a specific TID, the initiator MLD may attempt to maintain the link mapping state for the specific TID by not indicating information for the specific TID in the request frame.

[0247] In this case, the state in which the negotiated TID-to-Link mapping mode exists may be a state in which the basic TID-to-Link mapping mode is applied between both MLDs after association is performed, or a state in which the most recent TID-to-Link mapping response frame sent / received between the MLDs does not include a TID-to-Link mapping element.

[0248] On the other hand, if the responding MLD wishes to accept all TID-Link mappings proposed (explicitly / implicitly) by the initiating MLD, the responding MLD can respond with a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element after receiving a TID-to-Link Mapping Request frame from the initiating MLD. In other words, the responding MLD can accept the TID-to-Link mappings instructed (proposed) by the initiating MLD by not counter-proposing TID-to-Link mappings using the Response frame. The initiating MLD can confirm that the TID-to-Link mapping negotiation is complete when it receives a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element from the responding MLD. In addition, it can be said that the TID-to-Link mappings accepted by the responding MLD are applied from the point in time when the TID-to-Link mapping negotiation is completed.

[0249] The above-described proposal / accept / reject (counterproposal) method of TID-to-Link mapping negotiation may be applied to TIDs for DL ​​and UL separately, or may be applied to all TIDs for DL ​​or UL at once. For example, if the initiator MLD does not indicate a TID for DL ​​through the TID-to-Link mapping element (if the DL TID-to-Link Mapping Info size is indicated as 0), the initiator MLD may have implicitly proposed to maintain the TID-Link mapping state for DL ​​as the already negotiated state. Alternatively, the initiator MLD may not indicate a TID for DL ​​in order to change the TID-to-Link mapping state for DL ​​to the basic TID-to-Link mapping state.

[0250] That is, if only the TID for the UL is specified in the TID-to-Link mapping element included in the request frame by the initiator MLD, the responding MLD can interpret this as meaning that the initiator MLD wants to maintain the existing TID-to-Link mapping state for the DL, or that the responding MLD has requested that the initiator MLD change the TID-to-Link mapping state for the DL to the basic TID-to-Link mapping state.

[0251] Similarly, if the responding MLD does not specify all TIDs for DL ​​or UL in the response frame (if the DL or UL TID-to-Link Mapping Info size is 0), the unspecified DL or UL may be interpreted by the initiating MLD as accepting all TID-to-Link mappings proposed by the initiating MLD.

[0252] In this way, when the TID-to-Link mapping negotiation procedure between the initiating MLD and the responding MLD is completed, both MLDs must perform link operation according to the negotiated TID-to-Link mapping state within a certain period of time. In other words, when the TID-to-Link mapping negotiation procedure is completed, both MLDs can process only traffic corresponding to the TID mapped to the link and direction (DL / UL) when transmitting.

[0253] In addition, when the TID-to-Link mapping state operated between the two MLDs is terminated, i.e., when the MLDs switch to the basic TID-to-Link mapping mode, both MLDs must be able to process traffic for all TIDs on all links within a certain period of time. For example, an MLD that switches to the basic TID-to-Link mapping mode must maintain a state in which it can send BA frame responses (immediate BA) for all TIDs on all links after the certain period of time. In this case, "all TIDs" may refer to only TIDs for which BA sessions have been established between the two MLDs. In other words, when a mapping relationship between a TID and a link is established, an MLD can send / receive frames and corresponding BAs to / from the other MLD using the established mapping relationship.

[0254] FIG. 16 shows a TID-to-Link mapping procedure according to one embodiment of the present invention.

[0255] 16(a), the AP MLD and non-AP MLD maintain a basic TID-to-Link mapping state. The AP MLD and non-AP MLD are associated through two links (Link 1 and Link 2), and all TIDs (including TID 0 to TID 7 or TSID) are mapped to the two links.

[0256] In order to negotiate TID-to-Link mapping with the AP MLD, the Non-AP MLD may transmit a TID-to-Link Mapping Request frame to the AP MLD as shown in (b) of Figure 16. In this case, the Non-AP MLD may not specify a DL TID in the request frame transmitted through STA1, but may instead specify that UL TID 0 to TID 3 are to be mapped to Link 1 and that UL TID 4 to TID 7 are to be mapped to Link 2. In this case, to specify that TID 0 to TID 3 are to be mapped to Link 1, the Non-AP MLD may specify TID 0 to TID 3 in the TID Info subfield of the first UL TID-to-Link Mapping Info field and specify Link 1 in the Link Info subfield of the UL TID-to-Link Mapping Info field. In this case, to indicate that TID 4 to TID 7 are mapped to Link 2, the Non-AP MLD may indicate TID 4 to TID 7 in the TID Info subfield of the second UL TID-to-Link Mapping Info field, and may indicate Link 2 in the Link Info subfield of the UL TID-to-Link Mapping Info field.

[0257] After receiving a TID-to-Link Mapping Request frame from STA1 of the non-AP MLD, the AP MLD can recognize from the TID-to-Link mapping element included in the received frame that the non-AP MLD wants to maintain the basic TID-to-Link mapping state for DL ​​TIDs, map UL TIDs 0 to 3 to Link 1, and map UL TIDs 4 to 7 to Link 2. When the AP MLD wants to accept the TID-to-Link mapping instructed (requested) by the non-AP MLD, it can respond with a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element, as shown in Figure 16(b).

[0258] When a non-AP MLD receives a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element from the AP MLD, the non-AP MLD recognizes that the TID-to-Link mapping negotiation has been completed. The TID-to-Link mapping state shown in Figure 16(c) is then applied between the AP MLD and the non-AP MLD, and the non-AP MLD can transmit UL traffic for TID 0 to TID 3 only through Link 1, and can transmit UL traffic for TID 4 to TID 7 only through Link 2.

[0259] FIG. 17 shows an embodiment in which a responding MLD selectively responds to some TIDs among the TIDs and link mappings instructed (or proposed) by an initiating MLD.

[0260] 17, the initiator MLD instructs (proposes) through the TID-to-Link mapping element via TID-to-Link Mapping Request frame #1 that it will map TID 0 to TID 3 to Link 1 and TID 4 to TID 7 to Link 2. At this time, the responding MLD may accept the initiator MLD's proposal to map TID 0 to TID 3 to Link 1, but may reject mapping TID 4 to TID 7 to Link 2.

[0261] In this case, the responding MLD can transmit a TID-to-Link Mapping Response frame #1 including a TID-to-Link mapping element to the initiator MLD as a response to the TID-to-Link Mapping Request frame #1 received from the initiator MLD. At this time, when configuring the TID-to-Link mapping element, the responding MLD can instruct (counter-proposal) that TID 4 to TID 5 be mapped to Link 2 and TID 6 to TID 7 to be mapped to Link 3, thereby accepting the Link 1 mapping for TID 0 to TID 3 and rejecting the Link 2 mapping for TID 4 to TID 7.

[0262] Upon receiving the TID-to-Link Mapping Response frame #1 from the responding MLD, the initiator MLD can reconstruct the TID-to-Link Mapping Request frame #2 taking into consideration the TID-Link mapping state (TIDs 4-5 = Link 2, TIDs 6-7 = Link 3) indicated by the responding MLD through the TID-to-Link Mapping Response frame #1. At this time, the initiator MLD can transmit the TID-to-Link Mapping Request frame #2 instructing that TIDs 4-5 be mapped to Link 2 and TIDs 6-7 be mapped to Link 3 in the TID-to-Link mapping element, taking into consideration the TID-Link mapping state counter-proposed by the responding MLD. The responding MLD can terminate the TID-to-Link mapping negotiation procedure by responding with the TID-to-Link Mapping Response frame #2 that does not include a TID-to-Link mapping element in order to accept the TID-Link mapping state indicated in the TID-to-Link Mapping Request frame #2 received from the initiator MLD.

[0263] At this time, the TID-to-Link mapping state established (negotiated) between the start MLD and the response MLD may be a state in which the TID-Link mapping state (TID 0 to 3 = Link1) committed through TID-to-Link Mapping Response frame #1 and the TID-to-Link mapping state (TID 4 to 5 = Link2, TID 6 to 7 = Link3) committed through TID-to-Link Mapping Response frame #2 are integrated. If the start MLD re-instructs (proposes) a specific TID committed through TID-to-Link Mapping Request frame #1 (link mapping for the specific TID) in TID-to-Link Mapping Request frame #2, the link mapping state of the specific TID finally established (negotiated) through TID-to-Link Mapping Response frame #2 that does not contain a TID-to-Link mapping element may be the link mapping state of the specific TID instructed in TID-to-Link Mapping Request frame #2.

[0264] <Restrictions on TID-to-Link Mapping Negotiation>

[0265] MLD may or may not support TID-to-Link mapping negotiation depending on the Capability. For example, an MLD for which dot11TIDtoLinkMappingActivated is not instructed as true may be an MLD that does not support TID-to-Link mapping negotiation. Therefore, the start MLD may need to confirm whether the response MLD supports TID-to-Link mapping negotiation before starting the TID-to-Link mapping negotiation. That is, the start MLD must send a TID-to-Link mapping request frame only to an MLD for which dot11TIDtoLinkMappingActivated is instructed as true.

[0266] Furthermore, even in an MLD that supports TID-to-Link mapping negotiation, there may be a limit on the number of link sets that support TID-to-Link mapping for each MLD. For example, an MLD that can manage four links by differentiating TIDs in TID-to-Link mapping may not be able to support TID-to-Link mapping negotiation for more than four links. Therefore, when an initiating MLD constructs a TID-to-Link mapping request frame for TID-to-Link mapping negotiation, the request frame must be constructed taking into account the number of link sets supported by the responding MLD. Furthermore, because the initiating MLD may attempt TID-to-Link mapping negotiation for both DL and UL directions, the initiating MLD must consider the number of link sets that it can support as well as the number of link sets supported by the responding MLD when constructing a TID-to-Link mapping request frame.

[0267] Similarly, when a responding MLD receives a TID-to-Link mapping request frame from an initiating MLD and then transmits a TID-to-Link mapping response frame to (reverse) propose TID-Link mapping, the responding MLD must construct the response frame taking into account both the number of link sets it can support and the number of link sets the initiating MLD can support.

[0268] Therefore, in order to negotiate TID-to-Link mapping between MLDs, the MLDs must mutually recognize the number of link sets they can support. To this end, the TID-to-Link Mapping Negotiation Supported subfield may be indicated in the EHT MAC Capabilities Information field. The TID-to-Link Mapping Negotiation Supported subfield may indicate a value associated with the maximum number of link sets that the MLD can manage through TID-to-Link mapping negotiation. If a specific MLD does not support TID-to-Link mapping negotiation at all (dot11TIDtoLinkMappingActivated=false), the specific MLD may indicate 0 in the TID-to-Link Mapping Negotiation Supported subfield. On the other hand, an MLD that can manage four link sets using TID-to-Link mapping may indicate a value indicating four in the TID-to-Link Mapping Negotiation supported subfield.

[0269] In other words, when each MLD proposes / counter-proposes TID-Link mapping status to a peer MLD through a TID-to-Link Mapping Request / Response frame it transmits, it must perform TID-Link mapping taking into account the maximum number of link sets it can support and the maximum number of link sets of the peer MLD confirmed through the TID-to-Link Mapping supported subfield. That is, an initiator MLD that transmits a request frame must not (explicitly / implicitly) indicate a number of link sets exceeding min (the number of link sets it supports, the number of link sets supported by the responding MLD) through the TID-to-Link mapping element of the request frame. Similarly, a responding MLD that transmits a response frame must not (explicitly / implicitly) indicate (counter-propose) a number of link sets exceeding min (the number of link sets it supports, the number of link sets supported by the initiator MLD) through the TID-to-Link mapping element of the response frame.

[0270] In addition, if a TID-Link mapping for a specific TID is rejected (counter-proposed) by a responding MLD, the initiator MLD must not re-request the same link mapping that was rejected for a certain period of time. In this case, the certain period of time may be a value determined by a parameter indicated by the AP MLD. In this case, the certain period of time may be the time until an Unsolicited response frame is received from the responding MLD. In this case, the certain period of time may refer to a Lifetime.

[0271] For example, if an initiator MLD proposes (proposes / requests) to map TID 0 to Link 1 through a TID-to-Link Mapping Request frame and then receives a counterproposal from a responder MLD to map TID 0 to Link 2, the initiator MLD must not make a request to map TID 0 to Link 1 for a certain period of time (or a pre-set period of time or a period of time specified by the AP MLD). This restriction may be intended to prevent frequency resource waste and network congestion due to repeated exchanges of TID-to-Link Mapping Request / Response frames. However, if the initiator MLD's proposal to map TID 0 to Link 3 has never been rejected, the initiator MLD may make a new request to map TID 0 to Link 3 without following the responder MLD's proposal.

[0272]

[0273] In the TID-to-Link mapping negotiation procedure described above, the initiating MLD proposes a mapping for a TID and a link, and the responding MLD can accept or reject the mapping state proposed by the initiating MLD. The responding MLD can accept only some of the TIDs proposed by the initiating MLD and reject the remaining TIDs. The responding MLD can indicate (counter-propose) its preferred link mapping state for the TIDs whose proposals it rejects. The completion of the TID-to-Link mapping negotiation between the initiating MLD and the responding MLD is limited to when the responding MLD responds with a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element.

[0274] Considering this TID-to-Link mapping negotiation procedure, an inefficiency exists in that an initiator MLD that has received a counter-proposed TID-Link mapping state from a responder MLD must retransmit a TID-to-Link Mapping Request frame to accept the responder MLD's (counter)proposal. That is, to accept the counter-proposed TID-Link mapping state from the responder MLD, the initiator MLD must retransmit a TID-to-Link Mapping Request frame that indicates the same counter-proposed TID-to-Link mapping state in the TID-to-Link mapping element. Similarly, the responder MLD completes the TID-to-Link mapping negotiation procedure by receiving the same TID-Link mapping proposal from the initiator MLD and responding with a TID-to-Link Mapping Response frame that does not include a TID-to-Link mapping element. In this case, the exact completion point of the TID-to-Link mapping negotiation procedure may be the point at which an Ack response is sent to the TID-to-Link Mapping Response frame.

[0275] In this way, even if the initiating MLD is willing to follow the TID-to-Link mapping state counter-proposed by the responding MLD, the initiating MLD must re-send a request frame and the responding MLD must re-send a response frame, and the re-sent request and response frames may result in a TID-to-Link mapping negotiation procedure that induces additional overhead.

[0276] Therefore, a TID-to-Link mapping negotiation procedure may be considered in which the initiator MLD accepts the TID-Link mapping state (counter)proposed by the responder MLD. That is, after the initiator MLD transmits a TID-to-Link mapping request frame, if the responder MLD responds with a TID-to-Link mapping response frame containing a TID-to-Link mapping element, the initiator MLD can accept the TID-Link mapping state indicated by the TID-to-Link mapping element. In this case, after receiving a TID-to-Link mapping response frame from the responder MLD, the initiator MLD can (implicitly) accept the responder MLD's (counter)proposition for the specific TID by not including a TID-to-Link mapping element in the TID-to-Link mapping request frame it transmits or by not indicating a specific TID in the TID-to-Link mapping element. Since the initiator MLD's method of responding to a TID-to-Link mapping request frame is similar to the responder MLD's method of responding to a TID-to-Link mapping response frame, a detailed description thereof will be omitted. In this case, the initiating MLD can also send a TID-to-Link mapping response frame (without a TID-to-Link mapping element) instead of a TID-to-Link mapping request frame and accept the TID-Link mapping state proposed by the responding MLD.

[0277] However, if the initiator MLD transmits a TID-to-Link mapping request frame that does not include a TID-to-Link mapping element, the TID-to-Link mapping negotiation procedure may be completed when the responding MLD responds with an Ack frame to the TID-to-Link mapping request frame. That is, if a TID-to-Link mapping request frame is received without including a TID-to-Link mapping element, the responding MLD can complete the TID-to-Link mapping negotiation procedure by responding with an Ack frame.

[0278] FIG. 18 shows a response method of an initiating MLD that accepts a TID-to-Link mapping proposed in return by a responding MLD.

[0279] 18, the initiator MLD transmits a TID-to-Link Mapping Request frame #1 to the responder MLD to start the TID-to-Link mapping negotiation procedure, and the responder MLD can make a counter-proposal by rejecting link mapping for TID 4 to TID 7 by responding with a Response frame #1. At this time, the initiator MLD can decide to accept the TID-Link mapping status indicated by the responder MLD through the TID-to-Link Mapping Request frame #1 and request the responder MLD to complete the TID-to-Link mapping.

[0280] In Example 1 of FIG. 18, after the initiator MLD receives TID-to-Link Mapping Request frame #1, it can transmit TID-to-Link Mapping Response frame #2 to complete the TID-to-Link mapping procedure. Strictly speaking, the TID-to-Link Mapping Response frame #2 transmitted by the initiator MLD may be an unsolicited response frame. In this case, the TID-to-Link Mapping Response frame #2 transmitted by the initiator MLD does not include a TID-to-Link mapping element. The responding MLD that receives the TID-to-Link Mapping Response frame #2 from the initiator MLD can recognize that the initiator MLD accepts the TID-Link mapping state it (counter)proposed and wishes to complete the TID-to-Link mapping procedure. Therefore, after receiving the TID-to-Link Mapping Request frame #2, the responding MLD can complete the TID-to-Link mapping negotiation procedure with the initiator MLD by responding with an Ack frame.

[0281] In Example 2 of FIG. 18, after the starting MLD receives TID-to-Link Mapping Request frame #1, it can send TID-to-Link Mapping Request frame #2 to complete the TID-to-Link mapping procedure. At this time, TID-to-Link Mapping Request frame #2 sent by the starting MLD has a configuration that does not contain a TID-to-Link mapping element. The response MLD that receives TID-to-Link Mapping Request frame #2 from the starting MLD can recognize that the starting MLD commits to the TID-Link mapping state proposed by itself (in reverse) and desires to complete the TID-to-Link mapping procedure. Therefore, after receiving TID-to-Link Mapping Request frame #2, the response MLD can complete the TID-to-Link mapping negotiation procedure with the starting MLD by responding with an Ack frame or a TID-to-Link mapping response frame that does not contain a TID-to-Link mapping element.

[0282] <Unsolicited TID-to-Link Mapping Response Frame Utilization>

[0283] Generally, the TID-to-Link mapping negotiation procedure performed between MLDs starts with a TID-to-Link mapping request frame sent by the starting MLD. Such a general TID-to-Link mapping negotiation is carried out between the starting MLD and the response MLD, and the request / response frames exchanged between the two MLDs may be individually addressed frames.

[0284] However, because the AP MLD must negotiate TID-to-Link mapping with multiple non-AP MLDs in the BSS, negotiating TID-to-Link mapping individually with all non-AP MLDs can incur significant overhead. Therefore, the AP MLD can inform the non-AP MLD of its preferred TID-to-Link mapping configuration by sending a non-individually addressed TID-to-Link Mapping Response frame. When the AP MLD informs the non-AP MLD of its preferred TID-to-Link mapping status, the non-AP MLD can advantageously begin the TID-to-Link mapping negotiation procedure knowing the TID-to-Link mapping configuration preferred by the responding AP MLD. In other words, the non-AP MLD can operate as the initiating MLD by already knowing the responding MLD's preference when it sends a TID-to-Link Mapping Request frame, which may facilitate the TID-to-Link mapping negotiation procedure.

[0285] The Unsolicited TID-to-Link Mapping Response frame transmitted by the AP MLD may have a different TID-to-Link mapping element configuration than a general TID-to-Link Mapping Request / Response frame. Furthermore, the Unsolicited TID-to-Link Mapping Response frame transmitted by the AP MLD may indicate the same TID more than once through the TID-to-Link mapping element. For example, a specific (DL / UL) TID-to-Link Mapping Info field included in the TID-to-Link mapping element may indicate TID0 to TID1 corresponding to Link1 to Link2, and another (DL / UL) TID-to-Link Mapping Info field may indicate TID0 to TID4 corresponding to Link1 to Link3. Therefore, if a non-AP MLD receives an Unsolicited TID-to-Link Mapping Response frame from the AP MLD and aims to differentiate between links TID 0-TID 1 and TID 2-TID 3, it can select Link 1 and / or Link 2 for TID 0-TID 1 and Link 3 for TID 3-TID 4. That is, the AP MLD can help the non-AP MLD select links to be established starting from the association stage by including a TID-to-Link mapping element in its Beacon frame. Furthermore, the non-AP MLD can select and establish links according to its desired TID separation method by checking the TID-Link mapping status preferred by the AP MLD through the Beacon frame.

[0286] FIG. 19 shows an example of an unsolicited TID-to-Link Mapping Response frame sent from an AP MLD and a TID-to-Link mapping negotiation process between an AP MLD and a non-AP MLD.

[0287] 19, the AP MLD may transmit an Unsolicited TID-to-Link Mapping Response frame. In this case, the Unsolicited TID-to-Link Mapping Response frame may be transmitted as a non-individually addressed frame. That is, the Unsolicited TID-to-Link Mapping Response frame transmitted by the AP MLD may be targeted at one or more non-AP MLDs.

[0288] As shown in FIG. 19, AP MLD can instruct to map TID 0 to TID 3 to Link 1, TID 4 to TID 5 to Link 2, and TID 6 to TID 7 to Link 3 through an Unsolicited TID-to-Link Mapping Request frame.

[0289] The non-AP MLD (initiating MLD) that receives this can instruct the AP MLD (responding MLD) to accept the TID-to-Link mapping indicated in the Unsolicited Response frame and attempt to perform and complete the TID-to-Link mapping negotiation by transmitting a TID-to-Link Mapping Request frame that does not include a TID-to-Link mapping element, as shown in Sequence 1 of Figure 19. After receiving a TID-to-Link Mapping Request frame that does not include a TID-to-Link mapping element, the AP MLD can respond that the TID-to-Link mapping negotiation has been completed by responding with an Ack frame.

[0290] In Sequence 2, the non-AP MLD (starting MLD) can confirm that for the TID-Link mapping of TIDs 4 to 7 among the TID-Link mappings indicated by the AP MLD (response MLD) through the Unsolicited TID-to-Link mapping response frame, there are two link mapping options. At this time, the non-AP MLD can select the option of mapping TIDs 4 to 7 to Link2 to Link3 and send a TID-to-Link mapping request frame to the AP MLD. At this time, since the non-AP MLD does not indicate TIDs 0 to 3 in the TID-to-Link mapping element of the request frame, it may be interpreted that the non-AP MLD has accepted the link mapping proposal of the AP MLD for TIDs 0 to 3 (indicated through the Unsolicited TID-to-Link mapping response frame).

[0291] <Release of TID-to-Link Mapping>

[0292] The TID-to-Link mapping agreement made between two MLDs may be released by one of the two MLDs sending a TID-to-Link Mapping Teardown frame and the other MLD making an Ack response. When the TID-to-Link mapping agreement made between two MLDs through the TID-to-Link Mapping Teardown frame is released, both MLDs may need to operate in the basic TID-to-Link mapping mode. That is, the traffic of all TIDs for DL and UL may switch to the same state as if all were mapped to all links.

[0293] Considering the TID-to-Link mapping negotiation method of the present invention described above, when the initiating MLD configures a TID-to-Link mapping request frame, it can be seen that it is also possible to switch to the basic TID-to-Link mapping mode by indicating all TIDs and all links in the TID-to-Link Mapping Info field of the TID-to-Link mapping element. More specifically, in the DL TID-to-Link Mapping Info field included in the TID-to-Link mapping element, when the TID Info subfield is indicated as 1111 1111 (8-bit embodiment) and the Link Info subfield is indicated as 1111 1111 (8-bit embodiment), the TID-to-Link mapping for the DL direction may be indicated as the basic mode.

[0294] Alternatively, as in the above-described embodiment of the present invention, if the DL TID-to-Link Mapping Info size subfield of the TID-to-Link mapping element is set to 0, the MLD receiving this can recognize that the peer MLD has indicated (proposed) the basic TID-to-Link mapping mode for the DL direction. Therefore, if the initiator MLD indicates both the DL TID-to-Link Mapping Info size subfield and the UL TID-to-Link Mapping Info size subfield in a TID-to-Link mapping request frame as 0, the responding MLD can recognize that the initiator MLD has indicated (proposed) the basic TID-to-Link mapping mode. Similarly, if the responding MLD indicates both the DL / UL TID-to-Link Mapping Info size fields in a TID-to-Link mapping response frame as 0, the initiator MLD can recognize that the responding MLD has indicated (counterproposed) the basic TID-to-Link mapping mode.

[0295] Although switching to the basic TID-to-Link mapping mode is possible through the TID-to-Link Mapping Request frame and the TID-to-Link Mapping Response frame, the TID-to-Link Mapping Teardown frame is necessary because the TID-to-Link mapping negotiation termination process may be completed by the intention of a specific MLD, rather than through negotiation between the two MLDs. That is, if one of the two MLDs wishes to operate in the basic TID-to-Link mapping mode, the other MLD may be required to switch to the basic TID-to-Link mapping mode at the request of the specific MLD. Therefore, if a specific MLD transmits a TID-to-Link Mapping Teardown frame, the other MLD cannot make a counterproposal using a TID-to-Link Mapping Response frame and must agree to switch to the basic TID-to-Link mapping mode. In this case, the other MLD may need to respond with an Ack frame or a TID-to-Link Mapping Response frame without a TID-to-Link mapping element to convey its agreement.

[0296] In this case, after the specific MLD and the peer MLD agree to change to the basic TID-to-Link mapping mode, they may need to operate each link in the basic TID-to-Link mapping mode within a certain time. That is, both MLDs that have switched to the basic TID-to-Link mapping mode through the TID-to-Link Mapping Teardown frame must operate (switch) to a state in which they can perform transmission / reception and BA (BlockAck) responses for all TIDs on all links within a certain time. In this case, the certain time may be a time previously set by the EHT standard or BSS, or a time previously agreed upon between both MLDs performing TID-to-Link mapping.

[0297] For operational purposes, an AP MLD can simultaneously (at once) terminate the TID-to-Link mapping mode negotiated with multiple associated non-AP MLDs and switch to the basic TID-to-Link mapping mode. In this case, instead of individually sending TID-to-Link Mapping Teardown frames to all associated non-AP MLDs, the AP MLD can send a non-individually addressed TID-to-Link Mapping Teardown frame. In this case, the AP MLD can send a TID-to-Link Mapping Teardown frame in a group-addressed frame after sending a DTIM Beacon frame. When a non-AP MLD receives a TID-to-Link Mapping Teardown frame in the process of receiving a group-addressed frame after receiving a DTIM Beacon frame, it can recognize that the TID-to-Link mapping mode negotiated with the AP MLD has switched to the basic TID-to-Link mapping mode.

[0298] At this time, a non-AP MLD that has received a TID-to-Link Mapping Teardown frame in a group-addressed frame using a DTIM Beacon frame may need to switch to the basic TID-to-Link mapping mode without responding with an Ack or a TID-to-Link mapping response frame. That is, the TID-to-Link Mapping Teardown frame sent by the AP MLD to a number of non-AP MLDs may be immediately applied without confirmation (such as Ack and TID-to-Link Mapping Response) from the responding MLD (non-AP MLD). This is because the TID-to-Link Mapping Teardown frame sent after DTIM is considered to be well received by the responding MLD even without a separate response.

[0299] <Other embodiments of the TID-to-Link mapping element>

[0300] The TID-to-Link mapping element is a simple element having a function of indicating a TID-Link pair, and thus various formats may be considered. In one embodiment of FIG. 15 described above, a TID-to-Link mapping element format having a structure capable of mapping one or more TID sets to one or more link sets is considered, and other element formats that are functionally the same can also be configured in various ways.

[0301] FIG. 20 shows still other embodiments of the TID-to-Link mapping element.

[0302] 20(a), the TID-to-Link mapping element may be composed of fields of Element ID, Length, Element ID Extension, TID-to-Link Mapping Control, and Link Mapping of TID 0 to 7. The Element ID, Length, and Element ID Extension fields indicate information indicating that the element is a TID-to-Link mapping element and information related to the length of the element, and are used in the same way as the fields included in other elements, so detailed description thereof will be omitted.

[0303] Each of the Link Mapping of TID 0 to 7 fields consists of two octets (16 bits), and each bit can correspond to the Link ID of each link. In this case, each bit of the Link Mapping of TID field corresponds to the link with the Link ID that is one less than the bit order. More specifically, the first bit of the Link Mapping of TID field can correspond to the link with Link ID 0 (1-1), the second bit of the Link Mapping of TID field can correspond to the link with Link ID 1 (2-1), and the tenth bit of the Link Mapping of TID field can correspond to the link with Link ID 9 (10-1).

[0304] That is, if the Link Mapping of TID'n' field in the TID-to-Link mapping element of the TID-to-Link mapping request frame is indicated as 1100 0000 0000 0000, it may be requested that TID'n' be mapped to the link corresponding to Link ID 0 to Link 1.

[0305] Referring to (b) of FIG. 20, the TID-to-Link Mapping Control field may have a configuration including Direction, Default Link Mapping, and Link Mapping Presence Indicator subfields.

[0306] The Direction subfield indicates information related to the directionality of the information contained in the TID-to-Link mapping element. More specifically, the Direction subfield indicates whether the TID-to-Link mapping element is for UL direction TID-to-Link mapping, DL direction TID-to-Link mapping, or bidirectional (UL / DL) TID-to-Link mapping. For example, the Direction subfield may be set to 0, 1, or 2, respectively, to indicate that the TID-to-Link mapping element contains DL / UL / bidirectional TID-to-Link mapping information, respectively. In this case, the other value 3 that can be indicated in the Direction subfield (2 bits) may be reserved.

[0307] The Default Link Mapping subfield may be a subfield that indicates that the TID-to-Link mapping mode proposed through the TID-to-Link mapping element is the default mode (all TIDs are mapped to all configured links). For example, a device that transmits a TID-to-Link mapping element can propose (counter-propose) the default mapping mode by setting the Default Link Mapping subfield to 1.

[0308] That is, if the Default Link Mapping subfield of the TID-to-Link mapping element, which is indicated as DL direction information through the Direction subfield, is indicated as 1, DL direction TID-to-Link mapping may be proposed as the basic mode.

[0309] On the other hand, if the Default Link Mapping subfield of the TID-to-Link mapping element, which is indicated as UL direction information through the Direction subfield, is indicated as 1, UL direction TID-to-Link mapping may be proposed as the basic mode.

[0310] Alternatively, if the Default Link Mapping subfield of the TID-to-Link mapping element, which is indicated as bidirectional direction information through the Direction subfield, is indicated as 1, bidirectional (DL / UL) TID-to-Link mapping may be proposed as the basic mode.

[0311] As described above, the TID-to-Link mapping element may include TID-to-Link mapping information for the UL, DL, or bidirectional direction. Therefore, a TID-to-Link mapping request frame and a (solicited or unsolicited) TID-to-Link mapping response frame may include one or two TID-to-Link mapping elements and be transmitted. However, a TID-to-Link mapping (Request and Response) frame including two TID-to-Link mapping elements may require the Direction subfields (in the TID-to-Link Mapping Control field) of the two TID-to-Link mapping elements to be set to 0 and 1, respectively. That is, it is not permitted for the Direction subfields of two TID-to-Link mapping elements included in a single TID-to-Link mapping frame to both be set to 0 or 1. Also, if a TID-to-Link mapping frame includes a TID-to-Link element with the Direction subfield set to 2, no other TID-to-Link elements may be included.

[0312] In this case, the meaning of the DL direction TID-to-Link mapping being in basic mode may mean a state in which all TIDs are mapped to all established links in the DL direction. In this case, the meaning of the UL direction TID-to-Link mapping being in basic mode may mean a state in which all TIDs are mapped to all established links in the UL direction. In this case, the meaning of the bidirectional direction TID-to-Link mapping being in basic mode may mean a state in which all TIDs are mapped to all established links in both the DL and UL directions.

[0313] Thus, the basic TID-to-Link mapping mode means that all TIDs are mapped to all configured links for both the DL and UL directions during MLD, but the basic TID-to-Link mapping state for the DL or UL direction may be defined separately.

[0314] Furthermore, a basic TID-to-link mapping state may be defined for each TID and link. More specifically, a state in which a specific TID is mapped to all configured links may be understood as a state in which the specific TID is in the basic (TID-to-link) mapping state. Similarly, a state in which all TIDs are mapped to a specific link may be understood as a state in which the specific link is in the basic (TID-to-link) mapping state.

[0315] For example, if a specific TID in the DL direction is in the basic mapping mode (state), it may mean that traffic of the specific TID to be transmitted in the DL direction is mapped (transmittable) to all established links. As another example, if a specific link in the UL direction is in the basic mapping mode (state), it may mean that all traffic in the UL direction is mapped to the specific link.

[0316] However, the Default Link Mapping mode in the TID-to-Link Mapping Control field may be used to establish the default mapping mode for the minimum DL or UL direction, rather than for each TID and each link.

[0317] Alternatively, the default link mapping mode of the TID-to-Link Mapping Control field may be utilized to switch the TID-to-Link mapping mode between two MLDs to the default mode. That is, the Default Link Mapping subfield may be set to 1 to switch to the default TID-to-Link mapping mode for either bidirectional direction. Therefore, the Default Link Mapping subfield can be set to 1 only when the Direction subfield is set to 2.

[0318] The Link Mapping Presence Indicator subfield consists of 8 bits and can indicate whether the Link Mapping of TID field (of the TID-to-Link mapping element) for each TID is included in the TID-to-Link mapping element. More specifically, when the i-th bit of the Link Mapping Presence Indicator subfield is indicated as 1, it means that the TID-to-Link mapping element includes the Link Mapping of TID(i) subfield for TID i. When the Default Link Mapping subfield of the TID-to-Link mapping element is set to 1, the Link Mapping Presence Indicator subfield included in the corresponding TID-to-Link mapping element may be reserved, and all bits may need to be set to 0.

[0319] For example, if the Link Mapping Presence Indicator subfield is indicated as 1100 1000, the TID-to-Link mapping element may include Link Mapping of TID subfields for TID 0, TID 1, and TID 4, in that order (i.e., Link Mapping of TID 0 subfield, Link Mapping of TID 1 subfield, and Link Mapping of TID 4 subfield).

[0320] In this case, a specific TID (TID for the direction indicated in the Direction subfield) for which a separate Link Mapping of TID subfield is not included in a TID-to-Link mapping element for which the Default Link Mapping subfield is indicated as 0 may be implicitly instructed by the device that transmitted the TID-to-Link mapping element to maintain the current link mapping state for the specific TID. That is, in the above-described embodiment, the link mapping states for TID2 to TID3 and TID5 to TID7 may be maintained unchanged even if negotiation is performed by the TID-to-Link mapping element (a request frame including the TID-to-Link mapping element).

[0321] That is, a TID-to-Link Mapping Requesting MLD can request (suggest) that the link mapping state already established for a specific TID be maintained by transmitting a TID-to-Link mapping element that does not include a Link Mapping of TID subfield for the specific TID. In this case, if there is no separate link mapping established for the specific TID, the specific TID may be maintained in the Default Link Mapping state (mapped to all configured links). In this case, the TID-to-Link Mapping Requesting MLD can refer to an MLD that transmits a TID-to-Link Mapping Request frame or a (Re)Association Request frame that includes a TID-to-Link Mapping element.

[0322] In addition, an MLD (Responding MLD) sending an Unsolicited TID-to-Link Mapping Response Frame can indicate (counter-proposal) to the peer MLD that it prefers to maintain the link mapping state already established for a specific TID by sending a TID-to-Link mapping element that does not include the Link Mapping of TID field for the specific TID.

[0323] That is, before a request frame for establishing a mapping relationship between TIDs and links is transmitted from a peer MLD, the MLD can transmit an Unsolicited TID-to-Link Mapping Response frame to indicate a mapping relationship between TIDs and links that is preferred by the MLD. In this case, if the MLD does not include mapping information related to a mapping relationship between one or more TIDs and one or more links in the Unsolicited TID-to-Link Mapping Response frame, the preferred mapping relationship between one or more TIDs and one or more TIDs may be implicitly indicated.

[0324] In this case, the implicitly indicated mapping relationship may be 1) an existing mapping relationship that remains valid without being changed, 2) no particularly preferred mapping relationship, or 3) one of the basic mapping relationships.

[0325] First, if an MLD does not include mapping information related to a mapping relationship in an Unsolicited TID-to-Link Mapping Response frame, implying that it prefers to keep the existing mapping relationship valid without changing it, and if there is no separate link mapping established for a specific TID, one or more TIDs may be interpreted by a peer MLD as preferring the basic mapping relationship (mapped to all established links). In this case, the Unsolicited TID-to-Link Mapping Response frame may be an Unsolicited TID-to-Link Mapping Response frame sent (individually addressed) by a responding MLD to a target device by a peer MLD (Requesting MLD, peer MLD).

[0326] Second, if an MLD implicitly indicates that it has no preferred mapping relationship by not including mapping information related to the mapping relationship in the Unsolicited TID-to-Link Mapping Response frame, the MLD cannot reject the TID-to-link mapping relationship requested by the peer MLD through a request frame because it has no preferred mapping relationship. In other words, if an MLD requests a TID-to-link mapping relationship through a request frame from the peer MLD because it has no preferred TID-to-link mapping relationship, the MLD must accept it through a response frame rather than reject it.

[0327] Third, when an MLD implies a preference for the basic mapping relationship by not including mapping information related to the mapping relationship in an Unsolicited TID-to-Link Mapping Response frame, it indicates that the basic mapping state is preferred in the mapping relationship between one or more TIDs and links. Therefore, unlike the second case, an MLD can reject the mapping relationship requested through a response frame even if a peer MLD requests a mapping relationship between one or more TIDs and links through a request frame.

[0328] However, if a peer MLD requests, through a request frame, the same preferred mapping relationship indicated through the Unsolicited TID-to-Link Mapping Response frame sent by the MLD, the MLD cannot reject the requested mapping relationship and must accept it. In other words, if the peer MLD, the requesting MLD, sends a TID-to-Link Mapping Request frame containing the same TID-to-Link mapping element as the TID-to-Link mapping element sent by the responding MLD, the responding MLD must accept the proposed (or requested) TID-to-Link mapping.

[0329] The above method of interpreting the mapping relationship between preferred TIDs and links may be applied not only to the case where the mapping relationship between preferred TIDs and links is indicated through mapping information in an Unsolicited TID-to-Link Mapping Response frame, but also to the case where the mapping relationship between preferred TIDs and links is indicated through mapping information in a (Re)Association Response frame or a TID-to-Link Mapping Response frame.

[0330] That is, when the mapping relationship between the TID and the link requested through a request frame, such as an association request frame or a TID-to-Link mapping request frame, is not allowed and is rejected or counter-proposed by a (Re)Association response frame or a TID-to-Link mapping response frame, the mapping relationship between the preferred TID and the link indicated by the (Re)Association response frame or the TID-to-Link mapping response frame may be interpreted in any of the three ways described above.

[0331] Specifically, as described above, an MLD may be requested by a peer MLD to establish a mapping relationship between a TID and a link through mapping information included in a TID-to-Link mapping element of a request frame (e.g., an association request frame or a TID-to-Link mapping request frame). In this case, the MLD may accept or reject the mapping relationship between a TID and a link requested through the request frame. If the MLD rejects the mapping relationship between a TID and a link requested through the request frame, the MLD may reject the requested mapping relationship through a response frame (e.g., a (Re)Association Response frame or a TID-to-Link Mapping Response frame).

[0332] In this case, the MLD may reject the mapping relationship requested in the response frame and include its preferred mapping relationship between TIDs and links in the mapping information of the TID-to-Link mapping element and transmit it to the peer MLD in the response frame. In this case, if the mapping information for the preferred mapping relationship does not include mapping relationships between links for some or all TIDs, the mapping relationship between the TIDs and links that is not included may be implicitly indicated as described above. The implicitly indicated mapping relationship may be one of 1) maintaining the existing mapping relationship valid without changing it, 2) no preferred mapping relationship, or 3) a basic mapping relationship, and the specific interpretation method is as described above.

[0333] The peer MLD can then learn the mapping relationship preferred by the MLD from the response frame and can send a request frame to the MLD again based on that.

[0334] In yet another embodiment of the present invention, if the MLD rejects the requested mapping relationship between TIDs and links through the response frame, the MLD may explicitly include the mapping relationship between all TIDs and links when including mapping information for the mapping relationship between preferred TIDs and links in the TID-to-Link mapping element through the response frame. In this case, since the mapping relationship between all TIDs and links is explicitly indicated through the mapping information, the implicit interpretation method for the mapping relationship between TIDs and links does not apply.

[0335] As another embodiment, the TID-to-Link mapping element may indicate TID-to-Link mapping for a specific direction (UL or DL) as default, and may include TID-to-Link mapping proposal / indication information for a direction other than the specific direction (DL direction if the specific direction is UL, or UL direction if the specific direction is DL). Furthermore, when the Direction subfield of a specific TID-to-Link mapping element is indicated as 0 (DL direction) and the Default Link Mapping subfield is indicated as 1, the specific TID-to-Link mapping element may be included in a TID-to-Link Mapping Request frame to request DL direction TID-to-Link mapping as default mapping. At the same time, the specific TID-to-Link mapping element may have a configuration including one or more Link Mapping of TID fields in the TID-to-Link mapping element, and in this case, the one or more Link Mapping of TID fields may be included to request TID-to-Link mapping in the UL direction (the opposite direction of the DL indicated as Direction).

[0336] That is, when a TID-to-Link mapping element that requests / indicates TID-to-Link mapping for a specific direction as a default mapping includes a Link Mapping of TID field, the Link Mapping of TID field may include information requesting TID-to-Link mapping for the direction opposite to the direction for which the default mapping is requested. In this case, the Link Mapping Presence Indicator subfield of the TID-to-Link mapping element may indicate information regarding which TID the Link Mapping of TID field (one or more) for the opposite direction is information about. That is, in this case, the Link Mapping Presence Indicator subfield does not have to be reserved even if TID-to-Link mapping for a specific direction is requested / indicated as a default. Therefore, when the Default Link Mapping subfield is indicated as 1 in the received TID-to-Link mapping element, if none of the Link Mapping Presence Indicator subfields of the TID-to-Link mapping element are 0, the MLD can recognize that the Link Mapping of TID field for the direction opposite to the direction indicated through the Direction subfield is indicated.

[0337] <TID-to-Link Mapping Proposal Rules Considering Whether Links Are Established or Not>

[0338] As described above, the requesting MLD (initiating MLD) sends a TID-to-Link mapping request frame to the responding MLD (responding MLD) to establish a TID-to-Link mapping, and the responding MLD can respond with a TID-to-Link mapping response frame to accept the TID-to-Link mapping proposed by the requesting STA.

[0339] Once a TID-to-Link mapping is established / negotiated between two MLDs, when transmitting traffic corresponding to a specific TID, both MLDs must transmit only using the link to which the specific TID is mapped.

[0340] If a specific TID is mapped only to a link that is not established between the two MLDs when establishing a TID-to-Link Mapping between them, the specific TID may not be transmitted due to the constraint that it must be transmitted only through the unassociated link. This means that TID mapping for unassociated links is not valid, and therefore, MLDs attempting to establish a TID-to-Link Mapping negotiation must attempt to map TIDs only to links that are established between them.

[0341] Therefore, an MLD that sends a TID-to-Link Mapping Request frame to a peer MLD must request TID mapping only for links that have been established with the peer MLD, i.e., it must not request any TID mapping for links that have not been established.

[0342] Therefore, when the requesting MLD requests a link to be mapped to a specific TID, it must always set the bits corresponding to the IDs of unconfigured links to 0 when making a TID-to-Link mapping request.

[0343] Similarly, an MLD suggesting a preferred TID-to-Link mapping to a requesting MLD (a responding MLD) MUST always set the bits corresponding to unconfigured links to 0 in its TID-to-Link Mapping Response, i.e., it MUST NOT suggest any TID mappings for unconfigured links.

[0344] Therefore, when a responding MLD proposes a link to be mapped to a specific TID, it must send a TID-to-Link Mapping response by always setting the bit corresponding to the ID of the unconfigured link to 0 (solicited or unsolicited). In this case, the unsolicited TID-to-Link Mapping response can mean that a specific MLD sends a TID-to-Link Mapping response frame to the other MLD to propose its preferred TID-to-Link mapping (preferred TID-to-Link Mapping suggestion).

[0345] In other words, an MLD that sends a TID-to-Link mapping element must always set the Link ID bit (in the TID-to-Link mapping element) corresponding to a link that has not been established with the other MLD to 0. In other words, in the TID-to-Link mapping element sent / received between two MLDs, the Link ID of a link that has not been established between the two MLDs must always be set to 0.

[0346] However, an MLD that includes a TID-to-Link mapping element in a (Re)Association Request frame must request TID mapping only for the links for which it is requesting the other MLD to set up. In other words, an MLD that includes a TID-to-Link mapping element in a (Re)Association Request frame must always set to 0 the Link ID bits (in the TID-to-Link mapping element) corresponding to links for which it is not requesting the other MLD to set up.

[0347] Similarly, an MLD sending a TID-to-Link mapping element in a (Re)Association Response frame MUST suggest preferred TID mappings only for links for which it accepts the configuration. That is, an MLD sending a TID-to-Link mapping element in a (Re)Association Response frame MUST always set to 0 the Link ID bits (in the TID-to-Link mapping element) that correspond to the peer MLD and links for which it does not accept the configuration.

[0348] In this case, the maximum index of the Link ID that can be established between MLDs is limited to 14 (a maximum of 15 links can be distinguished using Link ID 0 to Link ID 14), so the 16th bit of the Link Mapping of TID field (i.e., the bit that should correspond to Link ID 15) must always be set to 0.

[0349] <How to configure efficient Link Mapping of TID fields>

[0350] Referring to the above-described embodiment of the present invention, the TID-to-Link mapping element transmitted / received between MLDs may have a configuration in which some of the bits of the Link Mapping of TID field are always designated as 0.

[0351] If there are only two configured links between two MLDs performing TID-to-Link Mapping negotiation, 14 bits (13 bits corresponding to the Link IDs of unconfigured links + the 16th bit) out of the 16 bits of the Link Mapping TID field may always be designated as 0. If bits that must be designated as 0 are repeatedly designated in the TID-to-Link mapping element, it may cause overhead problems, and therefore a more efficient Link Mapping of TID field configuration should be considered.

[0352] According to one embodiment of the present invention, the size of each Link Mapping of TID field included in the TID-to-Link mapping element may be determined based on the number of links established between the MLDs that send / receive the TID-to-Link mapping element.

[0353] For example, if a requesting MLD and a responding MLD are established through three links, the TID-to-Link mapping element transmitted / received by the requesting MLD and the responding MLD may include a Link Mapping of TID field having a size of 3 bits.

[0354] According to an embodiment of the present invention, a link (Link ID) corresponding to each bit of the Link Mapping of TID field included in the TID-to-Link mapping element may be determined based on the ID of a link established between the MLDs transmitting / receiving the TID-to-Link mapping element. In this case, the links corresponding to the Link Mapping of TID field may correspond to each bit in ascending order of Link ID.

[0355] For example, if a requesting MLD and a responding MLD are established through three links (Link ID 0, Link ID 3, Link ID 10), the three bits of the Link Mapping of TID field of the TID-to-Link mapping element transmitted / received by the requesting MLD and the responding MLD may correspond to Link ID 0, Link ID 3, and Link ID 10, respectively. In other words, if the three bits of the Link Mapping of TID field for a specific TID are indicated as 010, it may be interpreted that the specific TID has been requested / instructed to be mapped to the link corresponding to Link ID 3.

[0356] That is, after performing multi-link (re)setup, the MLD that sends / receives the TID-to-Link mapping element determines (selects and recognizes) the size of the Link Mapping of TID field based on the number of links established with the peer MLD.

[0357] In other words, after multiple link (re)configuration, the MLD that sends / receives the TID-to-Link mapping element determines the link to which each bit in the Link Mapping of TID field corresponds, taking into account the ID of the link configured with the peer MLD.

[0358] Furthermore, when a variable-length Link Mapping of TID field is used according to an embodiment of the present invention, a padding field for maintaining the length of the TID-to-Link mapping element in multiple-octet units may be included in the TID-to-Link mapping element. In this case, the padding field may be included after the Link Mapping of TID field and may have a size of less than one octet.

[0359] FIG. 21 shows an example of a TID-to-Link mapping element that includes a variable length TID Link Mapping of TID field.

[0360] Referring to FIG. 21, the TID-to-Link mapping element may have a structure including a variable-length Link Mapping of TID field and a Padding field.

[0361] The size of the Link Mapping of TID field is determined based on the number of links established between the MLDs that transmit / receive the TID-to-Link mapping element (frame containing the TID-to-Link mapping element). That is, if there are three links established between the MLDs that transmit / receive the TID-to-Link mapping element, each Link Mapping of TID field may have a size of 3 bits, and if there are five links established, each Link Mapping of TID field may have a size of 5 bits.

[0362] If the Link Mapping of TID field has a size of 3 bits and the Link Mapping of TID fields for three TIDs are included in the TID-to-Link mapping element, the size of the Link Mapping of TID field may have a total size of 9 bits. In this case, a Padding field with a size of 7 bits is included in the TID-to-Link mapping element, and the size of the Link Mapping of TID field + the size of the Padding field may be 2 octets.

[0363] Also, each bit in the Link Mapping of TID field corresponds to a configured link. For example, in a TID-to-Link mapping element transmitted and received between two MLDs configured with Link ID 0, Link ID 3, and Link ID 7, the Link Mapping of TID field may have a 3-bit size, with the first bit of each Link Mapping of TID field corresponding to Link ID 0, the second bit corresponding to Link ID 3, and the third bit corresponding to Link ID 7. That is, when the bit corresponding to Link ID 3 in the Link Mapping of TID field for a specific TID (Link Mapping of TID 'specific TID' field) is indicated as 1, it may be requested (proposed) that the specific TID be mapped to the link with Link ID 3.

[0364] <TID-to-Link Mapping Management after (Re)configuration>

[0365] The AP MLD and non-AP MLD can change the configuration of established links through (re)configuration. That is, the AP MLD and non-AP MLD can add established links or remove established links through reconfiguration. In this case, reconfiguration between the AP MLD and non-AP MLD can be performed by exchanging (Re)Association Request / Response frames. When reconfiguration is performed between two MLDs, TID mapping management related to the established links added or removed through reconfiguration must be accompanied. For convenience of explanation, the following embodiment of the present invention does not refer to the directionality (UL or DL) of TID-to-Link mapping. However, since all TID-to-Link mappings are directional, it may be understood that a description of either a specific direction or both directions (bidirectional) is provided even if no separate reference is made to the TID-to-Link mapping direction.

[0366] First, when a configured link is added by reconfiguration, the added configured link may be set to a state in which all TIDs are mapped (basic TID mapping state of the link).

[0367] This may be the TID mapping state of the additionally established link that is applied when the (Re)Association Request frame exchanged for re-establishment does not include a TID-to-Link mapping element.

[0368] However, when an establishment link is added through a (Re)Association Request frame including a TID-to-Link mapping element, the TID of the added establishment link may be mapped based on the information indicated by the TID-to-Link mapping element. In this case, the method of determining the link to be mapped to the added establishment link is the same as the above-mentioned TID-to-Link Mapping negotiation procedure, and therefore, detailed description thereof will be omitted.

[0369] Next, when a link that was established through reconfiguration is removed (deconfigured), the TID that was mapped to the removed link may be changed to a default mapping state. Furthermore, the TID that was mapped to a link that was deconfigured through reconfiguration may be changed to a state where it is mapped to all established links (excluding the deconfigured link) after reconfiguration (i.e., the TID's Default Link Mapping state). This may be a TID-to-Link mapping management method that is considered to prevent a situation where a specific TID is mapped only to a specific link and the specific link is deconfigured through reconfiguration, causing the specific TID to be changed to a state where it is not mapped to any established link.

[0370] However, if a TID that was mapped to a specific link that has been released through reconfiguration is also mapped to other configured links (which remain configured after reconfiguration), even if the configuration of the specific link is released, the specific TID does not have to be switched to a state where it is mapped to all configured links.

[0371] In addition, if the (Re)Association Request frame exchanged for re-establishment includes a TID-to-Link mapping element, the TID that was mapped to the de-established link may be mapped to another established link based on the information indicated in the TID-to-Link mapping element.

[0372] That is, if a specific TID is not explicitly mapped to any configured link after the MLD has performed reconfiguration, the specific TID may be changed (set) to a state where it is mapped to all configured links (TID's Default Link Mapping state).

[0373] Alternatively, the MLD can change (set) the specific TID (a TID that is not mapped to any configured link) to a specific configured link by a pre-committed method. In this case, the pre-committed method can be a method of changing the mapping to the configured link with the smallest Link ID index, or a method of changing the mapping to the most recently configured link (excluding released links).

[0374] As an exception, if a specific link is additionally established through reconfiguration while other links are deconfigured (i.e., the number of established links remains unchanged, and only the Link IDs of the established links are changed), the TID that was mapped to the deconfigured link may be automatically mapped to the newly established link. This may be understood as a TID-to-Link Mapping transition that is applied exclusively when the (Re)Association Request frame exchanged during the reconfiguration does not include a TID-to-Link mapping element. In this case, a similar TID-to-Link Mapping transition may be applied when the number of links additionally established through reconfiguration is one or more than one, and the number of links deconfigured is one or more than one. For example, if two established links are deconfigured and one link is added (established) through reconfiguration, the TIDs that were mapped to the two deconfigured links may be automatically mapped to the added link. As another example, when one configured link is released and two links are added (configured) through reconfiguration, the TID that was mapped to the released configured link may be automatically mapped to both of the two added links. As yet another example, when two configured links are released and two links are added (configured) through reconfiguration, the TID that was mapped to the two released configured links (the sum of the TIDs that were mapped to the two links) may be automatically mapped to both of the added links.

[0375] Alternatively, to simplify TID-to-Link mapping management, an MLD that has removed a setup link through reconfiguration must switch to the basic TID-to-Link mapping mode (all TIDs to all setup Links) in which all TIDs are mapped to all setup links. The condition for an MLD that has removed a link through reconfiguration to switch to the basic TID-to-Link mapping mode may be limited to when the (Re)Association Request frame exchanged for reconfiguration does not include a TID-to-Link mapping element. That is, if a new TID-to-Link Mapping negotiation has not been performed (completed) along with the reconfiguration, an MLD that has removed a link that was set up through reconfiguration must switch to the basic TID-to-Link mapping mode. Switching an MLD to the basic TID-to-Link mapping mode may mean that the TID-to-Link mapping established between the MLDs is torn down (the negotiated TID-to-Link mapping is torn down). Alternatively, the MLD may switch to the basic TID-to-Link mapping mode as the MLD considers that no negotiated TID-to-Link mapping exists.

[0376] Therefore, if a (Re)Association Request frame sent to remove a link that was established through reconfiguration does not include a TID-to-Link mapping element, it can perform a function similar / identical to a (Re)Association Request frame that includes a Tear down element.

[0377] Alternatively, when two MLDs with negotiated TID-to-Link mappings (excluding basic mode in this case) want to release the established link through reconfiguration, they may be forced to negotiate a new TID-to-Link Mapping through a (Re)Association Request / Response frame. That is, the MLD with the negotiated TID-to-Link mapping and the requesting MLD that wants to release the established link through reconfiguration must include a TID-to-Link Mapping element in the (Re)Association Request frame.

[0378] In addition, when a responding MLD (AP MLD) that performs reconfiguration with an MLD that has a negotiated TID-to-Link mapping accepts a reconfiguration that releases the established link, it must respond with a (Re)Association Response frame that does not include a TID-to-Link mapping element. In other words, when a responding MLD (AP MLD) accepts a reconfiguration that releases the established link, it must also accept the requested TID-to-Link mapping request.

[0379] FIG. 22 shows an embodiment of a method for managing TID-to-Link mapping between two MLDs to which a setup link is added through resetting.

[0380] 22, the AP MLD and non-AP MLD may perform ML setup via Link 1 and Link 2. In addition, the AP MLD and non-AP MLD may be in a state where they have performed TID-to-Link Mapping negotiation to map TID 0 to TID 3 to Link 1 and TID 4 to TID 7 to Link 2.

[0381] AP MLD and non-AP MLD may attempt to set up ML through three links by adding Link 3, and for this purpose, non-AP MLD may attempt to re-establish via a (Re)Association Request frame. If the addition of Link 3 from AP MLD is accepted, AP MLD and non-AP MLD change to a ML establishment state through Links 1 to 3.

[0382] Link 3 was not a configured link when AP MLD and non-AP MLD performed TID-to-Link Mapping negotiation for Link 1 and Link 2, so there is no negotiated TID Mapping state already established. Therefore, Link 3, newly configured through reconfiguration, is set to the basic TID mapping state (all TIDs are mapped) for both directions (UL and DL, bidirectional).

[0383] If the Non-AP MLD includes a TID-to-Link mapping element in a (Re)Association Request frame for reconfiguration, and the included TID-to-Link mapping element requests a separate TID-to-Link mapping for Link3, Link3 may be configured to a state other than the basic TID mapping state.

[0384] FIG. 23 shows an embodiment of a method for managing TID-to-Link mapping of two MLDs for a link whose setting has been cancelled by reconfiguration.

[0385] Referring to Figure 23, the AP MLD and Non-AP MLD are in a state where ML configuration has been performed through the initial three links. The AP MLD and Non-AP MLD have also performed TID-to-Link Mapping negotiation for Link1 to Link3, with Link1 being mapped with TID 0 to TID 2, Link2 being mapped with TID 3 to TID 4, and Link3 being mapped with TID 5 to TID 7 in both directions (bidirectional). The Non-AP MLD may change the ML configuration and transmit a (Re)Association Request frame to the AP MLD to maintain only Link1 and Link2 and release the established link for Link3. After receiving the (Re)Association Request frame, the AP MLD recognizes that only Link1 and Link2 have requested association and can respond with a (Re)Association Response frame, approving the maintenance of the Link1 and Link2 settings and the release of Link3 settings. In this case, the reconfiguration procedure of the AP MLD and non-AP MLD is completed successfully, and Link3 that was set up between the AP MLD and non-AP MLD may be deconfigured.

[0386] In this way, when a configured link between an AP MLD and a non-AP MLD is released, the TID that was mapped to the released link (Link 3 in Figure 23) may be changed to a state where it is not mapped to any configured link.

[0387] Therefore, AP MLD and non-AP MLD may automatically map TID 5 to TID 7 that were mapped to Link 3 to the link whose configuration is maintained, as in (a) Case 1 of Figure 23. In (a) Case 1, even if Link 3 is released (even after reconfiguration is completed), Link 1 and Link 2 are still maintained as configured links, so TID 5 to TID 7 that were mapped to Link 3 are automatically mapped to Link 1 and Link 2.

[0388] Alternatively, the AP MLD and non-AP MLD may switch to the basic TID-to-Link mapping mode so that the negotiated TID-to-Link mapping is released when the reconfiguration procedure is completed and Link 3 is released, as in Case 2 of (b) of Figure 23. That is, the two MLDs can perform TID-to-Link mapping management similar to the exchange of TID-to-Link Mapping Tear down frames after reconfiguration.

[0389] FIG. 24 is a flow chart illustrating an exemplary method for mapping TIDs and links according to the present invention.

[0390] 24, an MLD, which is a device to which one or more STAs, which are logical entities, are affiliated, can map one or more TIDs and one or more links with a peer MLD. Hereinafter, the MLD may be an AP MLD or a non-AP MLD.

[0391] Specifically, an MLD may transmit a request frame for mapping between traffic identifiers (TIDs) and links to a peer MLD (S24010). At this time, the request frame may include first mapping information for setting up a mapping relationship between at least one TID and at least one link among a plurality of TIDs, and information related to the number of the at least one TID for which mapping is requested with the at least one link.

[0392] Before transmitting a request frame, an MLD can receive a frame including second mapping information for setting a mapping relationship between one or more TIDs among a plurality of TIDs and one or more links from a peer MLD. That is, an MLD can receive an Unsolicited TID-to-Link Mapping Response frame including second mapping information for a preferred mapping relationship between one or more TIDs and one or more links from a peer MLD.

[0393] In this case, as described above, the second remaining TIDs among the plurality of TIDs, excluding the one or more TIDs, may be implicitly indicated as having a preferred specific mapping relationship or no preferred mapping relationship.

[0394] The preferred specific mapping relationship is an existing configured mapping relationship or the basic mapping relationship, and if the specific mapping relationship is the basic mapping relationship or there is no preferred mapping relationship, the mapping relationship for overlapping TIDs among the at least one TID and the second remaining TID may not be indicated by the response frame.

[0395] Thereafter, the MLD can receive a response frame from the other MLD in response to the request frame (S24020).

[0396] In this case, for the first remaining TIDs, excluding the at least one TID among the plurality of TIDs, the previously established mapping relationship with the link is effectively maintained or a default mapping relationship is applied, and the first remaining TID may not be indicated as having a mapping relationship with a specific link by the first mapping information.

[0397] One link among the at least one link may be mapped to one or more TIDs among the at least one TID, and the basic mapping relationship may mean a state in which a TID and all links are mapped.

[0398] Also, the basic mapping relationship may be applied if the first remaining TID has been set to the basic mapping relationship before the transmission of the request frame.

[0399] The request frame may further include transmission direction information indicating the transmission direction for the at least one TID, and multiple TIDs may be mapped only between links that have been set up between the MLD and the other MLD that sent the request frame.

[0400] The response frame may also indicate whether a mapping relationship between the at least one TID among the plurality of TIDs and the at least one link is acceptable.

[0401] Furthermore, if the mapping relationship between at least one TID among the plurality of TIDs and the at least one link is permitted, the response frame may not include second mapping information for another mapping relationship between at least one TID among the plurality of TIDs and the at least one link, and if the mapping relationship between at least one TID among the plurality of TIDs and the at least one link is not permitted, the response frame may further include second mapping information indicating a mapping relationship different from the first mapping relationship for at least one TID among the plurality of TIDs.

[0402] In this case, as described in Figures 10 to 16, an MLD can receive a management frame from a partner MLD, and the management frame may be transmitted only through the at least one link for which the at least one TID and the mapping relationship are set. Also, the management frame may be transmitted based on an assigned access category (AC), and may be transmitted through the at least one link regardless of the access category set for the at least one link.

[0403] In the case of a management frame, a specific TID is not assigned, and therefore, mapping between TID and link does not need to be applied. Therefore, the management frame may be transmitted to all links regardless of the mapping between TID and link. In this case, the link through which the management frame is transmitted may be an enabled link for which mapping between TID and link is set.

[0404] In this case, if management frames are transmitted only through enabled links, a management frame may not be transmitted if there is no enabled link, except for broadcast management frames that are transmitted regardless of the link. Therefore, a specific management frame may be transmitted even if there is no enabled link.

[0405] The above description of the present invention is for illustrative purposes only, and those skilled in the art will appreciate that the present invention may be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative and not restrictive in all respects. For example, each component described as a single component may be implemented in a distributed form, and similarly, each component described as a distributed component may be implemented in a combined form.

[0406] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and all modifications and variations derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention. [Explanation of symbols]

[0407] 100 Stations 110 processors 120 Communications Department 140 User Interface 150 display units 160 memory 200 AP 210 processors 220 Communications Department 260 memory 300 servers

Claims

1. A non-access point multi-link device (non-AP MLD) of a wireless communication system, the non-AP MLD comprising: a communication module; a processor configured to control the communication module; The processor: sending a request frame to the AP MLD, the request frame including a traffic identifier (TID)-to-Link Mapping element associated with a corresponding TID among the plurality of TIDs and at least one link among the plurality of links; receiving a response frame in response to the request frame; a first TID among the plurality of TIDs is mapped to all remaining valid links of the non-AP MLD, except for all of the at least one first link among the plurality of links, when all of the at least one first link mapped to the first TID among the plurality of TIDs is deleted by deleting at least one AP belonging to the AP MLD; the first TID is mapped only to the at least one first link before the at least one AP is removed from the AP MLD; The response frame indicates whether the mapping indicated by the TID-to-Link Mapping element is approved or not. It is configured as follows: MLD.

2. 2. The MLD of claim 1, wherein the TID-to-Link Mapping element includes: i) one or more Link Mapping Of TID fields; and ii) a Link Mapping Present subfield indicating whether each of the one or more Link Mapping Of TID fields is present.

3. 3. The MLD of claim 2, wherein each of the one or more Link Mapping Of TID fields indicates a mapping between a corresponding TID of a plurality of TIDs and at least one link of a plurality of links.

4. 2. The MLD of claim 1, wherein a current mapping between at least one TID of the plurality of TIDs and one or more links of the plurality of links is kept unchanged and valid if at least one Link Mapping Of TID field corresponding to the at least one TID is not present in the TID-to-Link Mapping element.

5. The MLD of claim 4 , wherein the at least one TID is mapped to one or more valid links of a plurality of links if mapping for the at least one TID is not successfully negotiated.

6. The request frame further includes transmission direction information indicating a transmission direction for the plurality of TIDs, The MLD according to claim 1 , wherein the plurality of links are links whose setup has been completed between the non-AP MLD and the AP MLD.

7. The MLD of claim 1, wherein the invalid link for the non-AP MLD is used for the request frame and the response frame when i) the request frame is a probe request frame which is a management frame, and ii) the response frame is a probe response frame which is a management frame.

8. the processor is configured to receive a management frame; The MLD of claim 1 , wherein the management frame is transmitted only on one or more links mapped to the plurality of TIDs.

9. The MLD according to claim 8 , wherein the management frame is transmitted based on an allocated access category (AC).

10. 1. A method for a non-access point multi-link device (non-AP MLD) to transmit a frame in a wireless communication system, the method comprising: transmitting a request frame to the AP MLD, the request frame including a traffic identifier (TID)-to-Link Mapping element associated with a corresponding TID among the plurality of TIDs and at least one link among the plurality of links; receiving a response frame in response to the request frame; a first TID among the plurality of TIDs is mapped to all remaining valid links of the non-AP MLD, except for all of the at least one first link among the plurality of links, when all of the at least one first link mapped to the first TID among the plurality of TIDs is deleted by deleting at least one AP belonging to the AP MLD; the first TID is mapped only to the at least one first link before the at least one AP is removed from the AP MLD; The response frame indicates whether the mapping indicated by the TID-to-Link Mapping element is approved or not.

11. 11. The method of claim 10, wherein the TID-to-Link Mapping element includes: i) one or more Link Mapping Of TID fields; and ii) a Link Mapping Present subfield indicating whether each of the one or more Link Mapping Of TID fields is present.

12. 12. The method of claim 11, wherein each of the one or more Link Mapping Of TID fields indicates a mapping between a corresponding TID of a plurality of TIDs and at least one link of a plurality of links.

13. 11. The method of claim 10, wherein a current mapping between at least one TID of the plurality of TIDs and one or more links of the plurality of links remains unchanged and valid if at least one Link Mapping Of TID field corresponding to the at least one TID is not present in the TID-to-Link Mapping element.

14. 14. The method of claim 13, wherein the at least one TID is mapped to one or more valid links of a plurality of links if a mapping for the at least one TID is not successfully negotiated.

15. The request frame further includes transmission direction information indicating a transmission direction for the plurality of TIDs, The method of claim 10 , wherein the plurality of links are links that have been set up between the non-AP MLD and the AP MLD.

16. The method of claim 10, wherein the invalid link for the non-AP MLD is used for the request frame and the response frame when i) the request frame is a probe request frame that is a management frame, and ii) the response frame is a probe response frame that is a management frame.

17. The method comprises: The method further includes receiving a management frame; The method of claim 10 , wherein the management frames are transmitted only on one or more links that are mapped to the plurality of TIDs.

18. The method of claim 17, wherein the management frames are transmitted based on an assigned Access Category (AC).

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