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

Abstract

A method for transmitting a frame by a multi-link device (MLD) in a wireless communication system is disclosed. The MLD may transmit a request frame for mapping between traffic identifiers (TIDs) and links, and the request frame may include first mapping information for establishing 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. The MLD may then receive a response frame in response to the request frame, and a previously established mapping relationship with a link may be maintained or a default mapping relationship may be applied to first remaining TIDs among the plurality of TIDs, excluding the at least one TID, and the first remaining TID may not be indicated as having a mapping relationship with a specific link by the first mapping information.

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 Art

[0002] Recently, with the spread of mobile devices, Wireless LAN (WLAN) technology that can provide fast wireless Internet services to them has been in the spotlight. WLAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, and embedded devices to be wirelessly connected to the Internet in homes, enterprises, or specific service-providing areas based on wireless communication technology at short distances.

[0003] Since IEEE (Institute of Electronics Engineers) 802.11 supported the initial WLAN technology using a 2.4 GHz frequency, various technology standards have been put into practical use or are under development. First, IEEE 802.11b uses a frequency in the 2.4 GHz band and supports a communication speed of up to 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses a frequency in the 5 GHz band instead of the 2.4 GHz band, thereby reducing the impact on interference compared to the rather congested 2.4 GHz band frequency, and using OFDM technology to improve the communication speed up to 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. And IEEE 802.11g uses a frequency in the 2.4 GHz band like IEEE 802.11b to implement a communication speed of up to 54 Mbps, satisfies backward compatibility, and has received considerable attention, but is also superior to IEEE 802.11a in terms of communication distance.

[0004] Then, there is IEEE 802.11n, which is a technical standard established to overcome the limitations regarding communication speed pointed out as vulnerabilities in Wi-Fi. The purpose of IEEE 802.11n is to increase the speed and reliability of the network and extend the operating distance of the wireless network. Specifically, IEEE 802.11n supports a high throughput (HT) with a maximum data processing speed of 540 Mbps or more, and is based on the MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitting and receiving ends to minimize transmission errors and optimize the data speed. In addition, this standard uses a coding method that transmits multiple copies of redundant transcripts to increase the reliability of the data.

[0005] As the popularity of wireless LANs has been activated and the applications using them have become diversified, there is an emerging need for a new wireless LAN system that supports a processing rate (Very High Throughput, VHT) higher than the data processing speed supported by IEEE 802.11n. Among them, IEEE 802.11ac supports a wide bandwidth (80 MHz to 160 MHz) at the 5 GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5 GHz band, it is considered that the initial 11ac chipset supports operation in the 2.4 GHz band for compatibility with conventional 2.4 GHz band products. Theoretically, according to this standard, the speed of a wireless LAN with multiple stations can be up to a minimum of 1 Gbps, and the maximum single-link speed can be up to a minimum of 500 Mbps. This is achieved by expanding the concepts of wireless interfaces accepted in 802.11n, such as a wider wireless frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Also, as a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz, there is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide a speed of up to 7 Gbps and is suitable for streaming high-bitrate videos such as large-capacity data and uncompressed HD videos. However, the 60 GHz frequency band has the disadvantage that it is difficult for obstacles to pass through and is only available between devices in a short-distance space.

[0006] On the other hand, as a wireless LAN standard after 802.11ac and 802.11ad, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is in the completion stage to provide high-efficiency and high-performance wireless LAN communication technology in a high-density environment where APs and terminals are concentrated. In an 802.11ax-based wireless LAN environment, it is necessary to provide high-frequency efficiency communication indoors / outdoors in the presence of a high density of stations and APs (Access Points), and various technologies for realizing this have been developed.

[0007] In addition, in order to support new multimedia applications such as high-quality videos and real-time games, a new Wi-Fi standard for increasing the maximum transmission speed has been started to be developed. In the 7th generation Wi-Fi standard, IEEE 802.11be (Extremely High Throughput, EHT), the standard development is in progress with the goal of supporting a maximum transmission rate of 30 Gbps by using a wider bandwidth, increased spatial streams, and multi-AP coordination in the 2.4 / 5 / 6 GHz bands.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

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

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

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

[0011] The technical problems to be achieved 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 knowledge in the technical field to which the present invention pertains from the following description.

MEANS FOR SOLVING THE PROBLEMS

[0012] A multi-link device (MLD) of a wireless communication system includes a communication module and a processor for controlling the communication module. The processor transmits a request frame for mapping between a traffic identifier (TID) and a link. The request frame includes first mapping information for setting 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. The processor receives a response frame as a response to the request frame. For the first remaining TIDs among the plurality of TIDs excluding the at least one TID, whether the previously set mapping relationship with the link is effectively maintained or the default mapping relationship is applied, and the first remaining TIDs are not instructed of the mapping relationship with a specific link by the first mapping information.

[0013] Also, in the present invention, one of the at least one link is mapped with one or more TIDs among the at least one TID.

[0014] Also, in the present invention, the default mapping relationship is a state where all TIDs are mapped with all links, and the default mapping relationship is applied when the first remaining TIDs were set with the default mapping relationship before transmission of the request frame.

[0015] Also, 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 for which the setting between the MLD and the other MLD that transmitted the request frame is completed.

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

[0017] Also, in the present invention, when the mapping relationship between the at least one TID among the plurality of TIDs and the at least one link is allowed, the response frame does not include second mapping information for other mapping relationships between the at least one TID among the plurality of TIDs and the at least one link.

[0018] Also, in the present invention, when the mapping relationship between the at least one TID among the plurality of TIDs and the at least one link is not allowed, 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 on the at least one link with the mapping relationship set between the at least one TID and the mapping relationship.

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

[0021] Also, in the present invention, the processor receives a frame including second mapping information for setting a mapping relationship between one or more TIDs among the plurality of TIDs and one or more links, and the second remaining TIDs excluding the one or more TIDs among the plurality of TIDs are indicated to have a preferred specific mapping relationship or no preferred mapping relationship.

[0022] Also, in the present invention, the preferred specific mapping relationship is an existing set mapping relationship or the basic mapping relationship.

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

[0024] The present invention also provides a method including transmitting a request frame for mapping between a traffic identifier (TID) and a link, where the request frame includes first mapping information for setting 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 with the at least one link is requested; and receiving a response frame as a response to the request frame. For the first remaining TIDs excluding the at least one TID among the plurality of TIDs, whether the previously set mapping relationship with the link is effectively maintained or a default mapping relationship is applied, and the first remaining TIDs are not indicated by the first mapping information to have a mapping relationship with a specific link.

Advantages of the Invention

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

[0026] According to an embodiment of the present invention, a multi-link device can perform TID-to-Link mapping.

[0027] According to an embodiment of the present invention, a multi-link device can perform QMF-to-Link mapping.

[0028] According to an embodiment of the present invention, when performing TID-to-Link mapping, a multi-link device can implicitly indicate a request / proposal link.

[0029] According to an embodiment of the present invention, the multi-link device can manage TID-to-Link mapping when the ML setup is changed.

[0030] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0031]

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Best Mode for Carrying Out the Invention

[0032] The terms used in this specification are selected as general terms that are currently widely used as much as possible in consideration of the functions in the present invention. However, this may vary depending on the intentions, conventions of those skilled in the relevant technical field, or the emergence of new technologies. Also, in certain cases, there are terms arbitrarily selected by the applicant. In such cases, the meaning will be described in the explanatory part of the corresponding invention. Therefore, it is clarified that the terms used in this specification are not merely the names of the terms, but should be interpreted based on the substantial meanings of the terms and the content throughout this specification.

[0033] Throughout the specification, if a certain configuration is said to be "connected" to another configuration, this includes not only the case where they are "directly connected", but also the case where they are "electrically connected" with other components interposed therebetween. Also, if a certain component "includes" a specific component, this means that it may further include other components rather than excluding other components, unless otherwise stated to the contrary. In addition, the limiting terms "above" or "below" based on a specific critical value may be appropriately replaced by "exceeding" or "less than" respectively according to the examples. Hereinafter, in the present invention, a field and a sub-field may be used in the same meaning.

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

[0035] The wireless LAN system includes one or more basic service sets (BSSs), where a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs). FIG. 1 shows an infrastructure BSS among them.

[0036] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1 and AP-2 that are stations providing a distribution service, and a distribution system DS that connects the plurality of 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 in accordance with the provisions of the IEEE 802.11 standard. In a broad sense, it includes not only non-access point non-AP stations but also all access points AP. Also, in this specification, the term "terminal" is used to refer to 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 unit, a display unit, etc. according to embodiments. The processor generates a frame to be transmitted via a wireless network, or processes a frame received via the wireless network, and performs various processes for controlling the station. And the communication unit is functionally connected to the processor and transmits and receives frames via a wireless network for the station. In the present invention, the term "terminal" is used to include a 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 stations associated with it. In an infrastructure BSS, communication between non-AP stations is generally carried out via the AP, but direct communication is possible between non-AP stations if a direct link is set up. On the other hand, in the present invention, an AP is used as a concept including a PCP (Personal BSS Coordination Point), but in a broad sense, it includes concepts such as a centralized controller, a base station (BS), a Node B, a BTS (Base Transceiver System), or a site controller. In the present invention, an AP is also referred to as a base wireless communication terminal, and the base wireless communication terminal is used as a term that includes all of an AP, a base station, an eNB (eNodeB), and a transmission point TP in a broad sense. Moreover, the base wireless communication terminal includes various forms of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with a plurality of wireless communication terminals.

[0039] A plurality of infrastructure BSSs are connected to each other via a distribution system DS. At this time, a plurality of BSSs connected via the distribution system are called an extended service set (ESS).

[0040] FIG. 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, parts that are the same as or corresponding to those in the embodiment of FIG. 1 are not described repeatedly.

[0041] Since the BSS3 shown in FIG. 2 is an independent BSS that does not include an AP, all stations (STA6, STA7) are not connected to the AP. An independent BSS does not allow connection to the distribution system and forms a self - contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0042] FIG. 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 an 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 wireless LAN packets and may be incorporated into or externally attached to the station 100. According to an embodiment, the communication unit 120 can include at least one communication module using different frequency bands. For example, the communication unit 120 can include communication modules for different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 can be provided with a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can perform wireless communication with an AP or an external station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 120 can operate only one communication module at a time or operate a plurality of communication modules together according to the performance and requirements of the station 100. When the station 100 includes a plurality of communication modules, each communication module may be provided in an independent form, or a plurality of modules may be integrated as one chip. In an embodiment of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0044] Next, the user interface 140 includes various forms 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 the instructions of the processor 110 using various output means.

[0045] Next, the display unit 150 outputs an image on the display screen. The display unit 150 outputs various display objects such as content performed by the processor 110 or a user interface based on the control instructions of the processor 110. Also, the memory 160 stores control programs used in the station 100 and various data thereby. Such control programs include connection programs necessary for the station 100 to connect to an AP or an external station.

[0046] The processor 110 of the present invention executes various instructions or programs and processes data within the station 100. Further, the processor 110 controls each unit of the station 100 described above 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 the AP stored in the memory 160 and receives a communication setting message transmitted by the AP. Further, the processor 110 reads information regarding the priority conditions of the station 100 included in the communication setting message and requests a connection regarding the AP based on the information regarding the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or may refer to a control unit for individually controlling some configurations of the station 100, for example, the communication unit 120, etc. according to an embodiment. That is, the processor 110 may be a modem, or a modulator and / or demodulator that modulates and demodulates the radio signals transmitted and received from the communication unit 120. The processor 110 controls various operations of radio signal transmission and reception of the station 100 according to an embodiment of the present invention. Detailed embodiments thereof 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 separately shown blocks are shown by logically distinguishing the elements of the device. Therefore, the above-described elements of the device are attached to one chip or a plurality of chips according to the design of the device. For example, the processor 110 and the communication unit 120 may be integrated and implemented on one chip, or may be implemented on separate chips. Further, in an embodiment of the present invention, some configurations of the station 100, for example, the user interface unit 140 and the display unit 150, etc. may be selectively provided in the station 100.

[0048] FIG. 4 is a block diagram showing the configuration of the AP200 according to an embodiment of the present invention. As shown, the AP200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, duplicate explanations for the same or corresponding parts of the configuration of the AP200 and the configuration of the station 100 in FIG. 3 are omitted.

[0049] Referring to FIG. 4, the AP200 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 AP200 can also include a plurality of communication modules using different frequency bands. That is, the AP200 according to the embodiment of the present invention can include two or more communication modules using different frequency bands, for example, any of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP200 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can perform wireless communication with a station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 220 can operate only one communication module at a time or operate a plurality of communication modules simultaneously according to the performance and requirements of the AP200. In the embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0050] Next, the memory 260 stores the control program used in the AP200 and various data thereby. Such a control program includes a connection program for managing the connection of the stations. Further, the processor 210 controls each unit of the AP200 and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 210 executes a program for connection to the station stored in the memory 260 and transmits a communication setting message for one or more stations. At this time, the communication setting message includes information regarding the connection priority condition of each station. Further, the processor 210 performs connection setting in response to a connection request from the station. According to one embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates a radio signal transmitted and received by the communication unit 220. The processor 210 controls various operations of the radio signal transmission and reception of the AP200 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0051] FIG. 5 is a diagram schematically showing a process in which a STA sets a link with an AP.

[0052] Referring to FIG. 5, the link between the STA100 and the AP200 is set through three major steps of scanning, authentication, and association. First, the scanning step is a step in which the STA100 obtains connection information of the BSS operated by the AP200. As a method for performing scanning, there are a passive scanning method of obtaining information by utilizing only the beacon message S101 periodically transmitted by the AP200, and an active scanning method in which the STA100 transmits a probe request to the AP at S103, receives a probe response from the AP at S105, and obtains connection information.

[0053] The STA100 that has successfully received the wireless connection information in the scanning step transmits an authentication request to S107a, receives an authentication response from the AP200 to S107b, and performs the authentication step. After the authentication step is performed, the STA100 transmits an association request to S109a, receives an association response from the AP200 to S109b, and performs the association step. In this specification, "association" basically means a wireless connection, but the present invention is not limited thereto, and the association in a broad sense includes all wireless connections and wired connections.

[0054] On the other hand, an additional 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are performed. In FIG. 5, the server 300 is a server that processes 802.1X-based authentication with the STA100, and may be physically connected to the AP200 or exist as a separate server.

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

[0056] A terminal performing wireless LAN communication checks whether a channel is in a busy state by performing carrier sensing before transmitting data. If a wireless signal with a certain intensity or higher is sensed, the corresponding channel is determined to be in a busy state, and the terminal delays access to the corresponding channel. Such a process is called Clear Channel Assessment (CCA), and the level for determining the presence or absence of sensing of the corresponding signal is called the CCA threshold. If a wireless signal equal to or higher than the CCA threshold received by the terminal has the terminal as the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is sensed from the corresponding channel or a wireless signal with an intensity lower than the CCA threshold is sensed, the channel is determined to be in an idle state.

[0057] If the channel is determined to be in an idle state, each terminal having data to transmit performs a backoff procedure after a time of IFS (Inter Frame Space) according to the situation of each terminal, for example, AIFS (Arbitration IFS), PIFS (PCF IFS), etc. According to an embodiment, the AIFS is used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while decreasing the slot time by the random number determined for the corresponding terminal during the interval of the idle state of the channel, and the terminal that has exhausted all the slot times attempts access to the corresponding channel. Thus, the section in which each terminal performs the backoff procedure is called a contention window section.

[0058] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if a terminal attempting access collides with another terminal, the colliding terminals are each assigned a new random number and perform a further backoff procedure. According to one embodiment, the new random number newly assigned to each terminal is determined within a range (2*CW) that is twice the range (contention window, CW) of the random number previously assigned to the corresponding terminal. On the other hand, each terminal attempts access by performing a further backoff procedure 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, each terminal performing wireless LAN communication can avoid mutual collisions with respect to a specific channel.

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

[0060] <Examples of various PPDU formats>

[0061] FIG. 7 shows an example of various standard-generation PPDU (PLCP Protocol Data Unit) formats. More specifically, FIG. 7(a) shows an embodiment of a legacy PPDU format based on 802.11a / g, FIG. 7(b) shows an embodiment of a HE PPDU format based on 802.11ax, and FIG. 7(c) shows an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Also, FIG. 7(d) shows the detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0062] Referring to FIG. 7(a), the preamble of the legacy PPDU includes an L-STF (Legacy Short Training field), an L-LTF (Legacy Long Training field), and an L-SIG (Legacy Signal field). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG can be referred to as a legacy preamble.

[0063] Referring to FIG. 7(b), the preamble of the HE PPDU further includes, in addition to the legacy preamble, an RL-SIG (Repeated Legacy Short Training field), an HE-SIG-A (High Efficiency Signal A field), an HE-SIG-B (High Efficiency Signal B field), an HE-STF (High Efficiency Short Training field), and an HE-LTF (High Efficiency Long Training field). 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 be deformed according to the HE PPDU format. For example, the 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 RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be deformed according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some formats of the EHT PPDU format.

[0065] The L-SIG field included in the preamble of the PPDU applies 64 FFT OFDM and is composed of a total of 64 subcarriers. Among these, 48 subcarriers excluding the guard subcarriers, DC subcarriers, and pilot subcarriers are used for data transmission of L-SIG. Since BPSK and MCS (Modulation and Coding Scheme) with a rate of 1 / 2 are applied to L-SIG, it can include a total of 24 bits of information. FIG. 7(d) shows the 24-bit information configuration of 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 value among the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and coding rates such as 1 / 2, 2 / 3, 3 / 4. Combining the information of the L_RATE field and the L_LENGTH field can indicate the total length of the PPDU. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

[0067] The unit of the L_LENGTH field is byte. A total of 12 bits are allocated and can signal up to 4095, and in combination with the L_RATE field, it can indicate the length of the corresponding PPDU. At this time, the legacy terminal and the non-legacy terminal can interpret the L_LENGTH field in different ways.

[0068] First, the method for a legacy terminal or a non-legacy terminal to interpret the length of the corresponding PPDU using the L_LENGTH field is as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted during the 4 us of one symbol duration of 64 FFT. Therefore, adding the 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of 64 FFT reference symbols after L-SIG is obtained. After multiplying the obtained number of symbols by 4 us, which is one symbol duration, and then adding the 20 us required for transmitting L-STF, L-LTF, and L-SIG, the length of the corresponding PPDU, that is, the reception time (RXTIME) is obtained. Expressed as a mathematical formula, it is as shown in Equation 1 below.

[0069]

Equation

[0070] At this time, [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 up to a maximum of 5.484 ms. The non-legacy terminal that transmits the PPDU must set the L_LENGTH field as shown in Equation 2 below.

[0071]

Number

[0072] Here, TXTIME is the total transmission time that constitutes the PPDU, as shown in Equation 3 below. At this time, TX represents the transmission time of X.

[0073]

Number

[0074] Referring to the above equations, the length of the PPDU is calculated based on the ceiling value of L_LENGTH / 3. Therefore, for any k value, three different values of L_LENGTH = {3k + 1, 3k + 2, 3(k + 1)} indicate the same PPDU length.

[0075] Referring to FIG. 7(e), the U-SIG (Universal SIG) field persists in EHT PPDUs and PPDUs of subsequent generations of wireless LANs and plays a role in distinguishing which generation of PPDU it is, including 11be. U-SIG is two symbols of 64FFT-based OFDM and can transmit a total of 52 bits of information. Of these, 43 bits excluding the 9-bit CRC / tail are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0076] The VI bit continues to maintain the current bit configuration later, and even if subsequent generations of PPDUs are defined, current 11be terminals can obtain information about the PPDU from the VI field of the PPDU. For this purpose, the VI field is composed of a PHY version, UL / DL, BSS color, TXOP, and Reserved field. The PHY version field is 3 bits and serves to sequentially version the 11be and subsequent generations of wireless LAN standards. 11be has a value of 000b. The UL / DL field differentiates whether the PPDU is an uplink / downlink PPDU. The BSS color means the BSS identifier defined in 11ax and has a value of 6 bits or more. The TXOP means the transmit opportunity duration that was transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP included in the PPDU can be inferred without decoding the MPDU, and it has a value of 7 bits or more.

[0077] The VD field may be composed of signaling information that is only useful for PPDUs in the 11be version, fields that are commonly used in any PPDU format, such as PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a discriminator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDUs, etc. The BW field mainly signals five basic PPDU BW options of 20, 40, 80, 160 (80 + 80), 320 (160 + 160) MHz (the BW that can be expressed in the form of 20 * 2 to the power of n can be called the basic BW), and various remaining PPDU BWs formed by preamble puncturing. Also, after being signaled at 320 MHz, some 80 MHz may be signaled in a punctured form. Also, the channel form that has been punctured and deformed may be directly signaled in the BW field, or may be signaled using both the BW field and fields that appear after the BW field (for example, fields within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so the puncturing mode can signal a maximum of 3. If the BW field is 4 bits, a total of 16 BW signalings are possible, so the puncturing mode can signal a maximum of 11.

[0078] The fields located after the BW field differ depending on the form and format of the PPDU. The MU PPDU and SU PPDU may be signaled in the same PPDU format. Before the EHT-SIG field, there may be a field for distinguishing between the MU PPDU and the SU PPDU, and additional signaling may be performed for that purpose. Both the SU PPDU and the MU PPDU contain the EHT-SIG field, but some fields that are unnecessary in the SU PPDU may be compressed. At this time, the information of the fields to which compression is applied may be omitted, or may have a size smaller than the size of the original fields included in the MU PPDU. For example, in the case of the SU PPDU, the common fields of the EHT-SIG may be omitted or replaced, the user-specific fields may be replaced, or it may have different configurations such as being reduced to one.

[0079] Alternatively, the SU PPDU can further include a compression field indicating whether it is compressed, and some fields (such as the RA field, etc.) may be omitted depending on the value of the compression field.

[0080] When a part of the EHT-SIG field of an SU PPDU is compressed, the information contained in the compressed field may be signaled together with uncompressed fields (such as common fields). 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 obligatorily after the U-SIG field, and the amount of information to be signaled may be variable. That is, since a plurality of MU PPDUs are transmitted to a plurality of STAs, each STA must recognize the position of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU is transmitted to itself. Therefore, the AP must transmit the EHT-SIG field including the above information. For this purpose, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols of the EHT-SIG field and / or the MCS which is the modulation method. The EHT-SIG field can include the size and position information of the RUs assigned to each user.

[0081] In the case of an SU PPDU, a plurality of RUs may be assigned to an STA, and the plurality of RUs may be consecutive or non-consecutive. When the RUs assigned to an STA are not consecutive, the STA can efficiently receive the SU PPDU only by recognizing the RUs punctured in the middle. Therefore, the AP can transmit the SU PPDU including the information of the punctured RUs among the RUs assigned to the STA (such as the RU puncturing pattern). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether the puncturing mode is applied and the puncturing pattern in a bitmap format or the like may be included in the EHT-SIG field, and the puncturing mode field can signal the form of the discontinuous channels appearing within the bandwidth.

[0082] The form of the discontinuous channel signaled is restricted and indicates the BW of the SU PPDU and the discontinuous channel information in combination with the value of the BW field. For example, in the case of an SU PPDU, which is a PPDU transmitted only to a single terminal, the STA can recognize the bandwidth assigned to itself from the BW field included in the PPDU, and can recognize the punctured resources among the assigned bandwidths from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU with the resource units other than the specific channels of the punctured resource units. At this time, the plurality of RUs assigned to the STA may be composed of different frequency bands or tones.

[0083] The reason why only the restricted form of the discontinuous channel form is signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing may be performed for each 20 MHz subchannel, when puncturing is performed for a BW having a plurality of 20 MHz subchannels such as 80, 160, and 320 MHz, in the case of 320 MHz, it is necessary to signal the form of the discontinuous channel (including the case where only the end 20 MHz is considered discontinuous) by expressing the use or non-use of each of the remaining 15 20 MHz subchannels excluding the primary channel. Using 15 bits to signal the discontinuous channel form of single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0084] The present invention proposes a method for signaling the discontinuous channel form of the SU PPDU and shows the discontinuous channel form determined by the proposed method. Further, a method for signaling the puncturing forms of the main (Primary) 160 MHz and the secondary (Secondary) 160 MHz in the 320 MHz BW configuration of the SU PPDU is proposed.

[0085] In addition, in one embodiment of the present invention, a method is proposed to vary the configuration of the PPDU according to the preamble puncturing BW value indicated by the PPDU format signaled in the PPDU format field. Assuming that the length of the BW field is 4 bits, in the case of an EHT SU PPDU or a TB PPDU, since it is possible to further signal 1 symbol of EHT-SIG-A after U-SIG or not signal EHT-SIG-A at all, considering this, it is necessary to signal all up to 11 puncturing modes using only the BW field of U-SIG. However, in the case of an EHT MU PPDU, since EHT-SIG-B is further signaled after U-SIG, up to 11 puncturing modes may be signaled in a different way from 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] FIG. 7(f) shows the configuration of the format-specific field of the VD field when indicated as an EHT MU PPDU in the PPDU format field of U-SIG. In the case of an MU PPDU, SIG-B, which is a signaling field for simultaneous reception by multiple users, is essential, and SIG-B may be transmitted without a separate SIG-A after U-SIG. Therefore, U-SIG must signal information for decoding SIG-B. Such fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, number of EHT-LTF symbols fields, etc.

[0087] FIG. 8 shows an example of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats according to an embodiment of the present invention and a method for indicating the same.

[0088] Referring to FIG. 8, the PPDU may be composed of a preamble and a data part, and the format of one type of EHT PPDU may be distinguished by the U-SIG field included in the preamble. Specifically, based on the PPDU format field included in the U-SIG field, whether the format of the PPDU is an EHT PPDU may be indicated.

[0089] FIG. 8(a) shows an example of the 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] FIG. 8(b) shows an example of the 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. Different from the EHT SU PPDU, the EHT-SIG-A field is not located after the U-SIG field in the EHT PPDU.

[0091] FIG. 8(c) shows an example of the EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit the PPDU to one or more STAs. The EHT MU PPDU format may have an HE-SIG-B field located after the U-SIG field.

[0092] (d) of FIG. 8 shows an example of the 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 a wider range of STAs than the EHT SU PPDU described in (a) of FIG. 8, and the U-SIG field may be repeatedly positioned on the time axis.

[0093] The EHT MU PPDU described in (c) of FIG. 8 can be used by the AP for downlink transmission to multiple STAs. At this time, 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 transmit the AID information of the recipient and / or transmitter of the PPDU transmitted through the user specific field of EHT-SIG-B to the STA. Therefore, multiple terminals that have received the EHT MU PPDU can perform a spatial reuse operation based on the AID information in 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 can include information regarding the configuration of resource units (e.g., the division form of resource units) in a specific bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field can indicate the configuration of resource units divided by the bandwidth for the transmission of the HE MU PPDU for the STA to receive the PPDU. The information of the STA assigned (or designated) to each divided resource unit may be included in the user specific field of EHT-SIG-B and transmitted to the STA. That is, the user specific field can include one or more user fields corresponding to each divided resource unit.

[0095] For example, among a plurality of divided resource units, the user field corresponding to at least one resource unit used for data transmission can include the AID of the recipient or the sender, and the user field corresponding to the remaining resource units not used for data transmission can include the already 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 with 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. At this time, the EHT SU PPDU and the EHT MU PPDU may be distinguished by 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 may be identified as an EHT MU PPDU when the number of STAs is set so that two or more STAs receive it. In other words, two or more PPDU formats shown in FIG. 8 can be indicated using the same subfield value.

[0097] Also, some of the fields or part of the information of the fields shown in FIG. 8 may be omitted, and the case where some of the fields or part of the information of the fields are omitted can be defined as the compression mode or the compressed mode.

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

[0099] Referring to FIG. 9, the concept of a device with one or more STAs affiliated may be defined. Further, according to an embodiment of the present invention as another example, a device with more than one (i.e., two or more) STAs affiliated may be defined. At this time, the device may be a logical concept. Therefore, a device with one or more or more than one STA of such a concept can be called a multi-link device (MLD), a multi-band device, or a multi-link logical entity (MLLE).

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

[0101] The STAs included in the MLD can operate on one or more links or channels. That is, the STAs included in the MLD can operate on a plurality of different channels. For example, the STAs included in the MLD can operate using channels in different frequency bands of 2.4 GHz, 5 GHz, and 6 GHz. Thereby, the MLD can obtain the gain in channel connection and improve the performance of the entire network. Existing wireless LANs operated on a single link, but MLD operation can use a plurality of links to obtain more channel connection opportunities or enable the STAs to operate efficiently on a plurality of links considering the channel situation.

[0102] Also, when the STA affiliated with the MLD is an AP, the MLD affiliated with the AP may be an AP MLD. On the other hand, when the STA affiliated with the MLD is a non-AP STA, the MLD affiliated with the non-AP may be a non-AP MLD.

[0103] Referring to FIG. 9, there may be an MLD including a plurality of STAs, and the plurality of STAs included in the MLD can operate on a plurality of links. In FIG. 9, the MLD including APs AP1, AP2, and AP3 can be referred to as an AP MLD, and the MLD including non-AP STAs non-AP STA1, non-AP STA2, and non-AP STA3 can be referred to as a non-AP MLD. The STAs included in the MLD can operate on Link 1 (Link1), Link 2 (Link2), Link 3 (Link3), or a part 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 the association performed in the single-link operation. A multi-link setup may precede in order to exchange frames over multiple links. 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 exponentially each time a new protocol version is introduced. In recent years, 802.11ax, which is in the final stage, is expected to support a data rate of up to approximately 10 Gbps. The improved Wi-Fi data rate has been achieved by the improvement of hardware performance, which enables the PHY protocol to support processing for a wider bandwidth (BW) and higher MCS, and by the availability of multiple antennas.

[0108] However, despite the exponentially increased data rate, Wi-Fi still has the problem of transmission delay. All communication systems, including Wi-Fi, support a finite data rate and thus induce a certain amount of transmission delay when transmitting traffic. However, the reason why Wi-Fi's transmission delay becomes a problem is that it has the characteristic of being unpredictable. In other words, in a communication system that utilizes dedicated communication resources (wired or wireless licensed bands), the delay time required to transmit traffic can be predicted based on the amount of traffic to be transmitted. However, in a communication system that utilizes an unlicensed band like Wi-Fi, an unpredictable transmission delay may occur when the medium is occupied by other devices. When such an unpredictable transmission delay occurs, traffic with a short lifetime, such as voice traffic, may lose its usability. In this case, even if Wi-Fi supports a high data rate, it is difficult to expect an improvement in the quality of service (QoS).

[0109] The IEEE 802.11 standardization organization has been continuously developing the MAC protocol to overcome the limitations of the unlicensed band as described above. EDCA (enhanced distributed channel access) introduced in 802.11e can be said to be one of the results. Hereinafter, for the convenience of explanation, the QoS AP is referred to as AP, the QoS STA as STA, and the QoS BSS as BSS. Therefore, when referring to the AP, it may be interpreted as referring to the QoS AP.

[0110] EDCA provides a mechanism for differentiating and managing traffic into four types of AC (access category) according to its characteristics. At this time, the four types of AC are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best effort), and AC_BK (AC Background). Each AC may have different CW (contention window), TXOP (transmit opportunity), and AIFSN parameters. Briefly speaking, EDCA is a mechanism for adjusting the transmission priority of traffic transmitted by utilizing each AC by differentiating the CW, TXOP, and AIFSN parameters for the four types of AC. For this purpose, EDCA can map the traffic to be served by the MAC (MSDU) to one of the four ACs according to the TC (traffic category) or TS (traffic stream). At this time, the traffic mapped to one of the four ACs by EDCA is managed separately in the four queues for each AC. At this time, the four queues may be logically separated queues without being physically separated.

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

[0112] AC_VI is an AC that can be used for traffic that is more resilient to transmission delay than voice traffic but still requires low-latency transmission and can handle a large amount of traffic such as video. AC_VI has CW and AIFSN parameter values that are larger than those of AC_VO but smaller than those of other ACs. Instead, the TXOP is about twice as long as that of AC_VI.

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

[0114] AC_BK is an AC that is similar to AC_BE in being traffic that is resilient to transmission delay, but can be used for traffic with a lower priority than BE traffic. AC_BK uses the same CW parameter value as AC_BE and a larger value for the AIFSN parameter value compared to AC_BE. Also, like AC_BE, AC_BK does not have a separate TXOP and cannot utilize the TXOP transmission sequence.

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

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

[0117]

Table 1

[0118] Also, the above four types of EDCA ACs 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 and different values can be utilized for each BSS.

[0119] When the EDCA mechanism is utilized, Wi - Fi traffic is stored in one of the four queues corresponding to the four ACs, and can be transmitted to the destination device only when the AC it belongs to succeeds in channel access due to competition for channel access with other ACs. At this time, the channel access operations between the EDCAs (EDCA functions) corresponding to the ACs may be performed by competition, and the access parameters (CW[AC], AIFSN[AC]) assigned to each AC in the competition may be used. The channel access competition operation performed by each AC is the same as that of DCF. At this time, if there is no traffic in the queue to be transmitted by a specific AC, that specific AC cannot be used for competition.

[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, it is highly likely that the traffic of AC_VO will be served with priority over the traffic of other ACs.

[0121] Also, 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 the PPDU including the traffic of other ACs other than the AC (primary AC) that won the competition.

[0122] In addition to the above-mentioned EDCA, 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 ensure 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 they 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 above-mentioned EDCA mechanism, 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 FIG. 9, the MLD operates one or more STAs that are operated on different links from each other. Therefore, each STA of the MLD may have a transmission queue that is independent of each other. At this time, the queues may be logically separated, which may be in line with the meaning that the MLD can be a logical concept.

[0126] From a principle similar to that in which EDCA strengthens the QoS service by separating and operating queues for each of the four ACs, the MLD can map the traffic it should serve to one of the STAs it operates, considering the nature of the traffic, in order to strengthen the QoS. In other words, similar to the EDCA mechanism mapping traffic to one of the four ACs, the MLD can map the traffic to one of the STAs it operates. At this time, the operation of the MLD mapping specific traffic to a specific STA may be understood as the MLD mapping the specific traffic to the link on which the specific STA operates. For easier understanding, FIG. 10 is used to explain how the MLD strengthens the QoS using a number of STAs (Links).

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

[0128] Referring to FIG. 10, (a) the AP MLD and (b) the Non-AP MLD are each an MLD that operates four STAs, namely AP1, AP2, AP3, and AP4, and Non-AP STA1, Non-AP STA2, Non-AP STA3, and Non-AP STA4. Each of the four STAs of both MLDs can be associated with each other.

[0129] If the AP MLD utilizes the queues of the four STAs (AP1, AP2, AP3, and AP4) it operates in a manner similar to the AC-specific queues of EDCA, as shown in Table 1, traffic that utilizes AC_BK can be mapped to the queue of AP1, traffic that utilizes AC_BE to AP2, traffic that utilizes AC_VI to AP3, and traffic that utilizes AC_VO to AP4, respectively. In this way, the traffic mapped to each STA may be served by the channel access procedure performed by each STA. Therefore, traffic with different ACs will not be affected by the transmission delay that occurs during the process of transmitting traffic with different ACs to each other. That is, the QoS enhancement effect obtained by the MLD separating the STAs mapped according to the nature of the traffic is similar to the EDCA granting transmission priority to traffic with a higher priority, but there is a difference in that traffic with different ACs can be prevented from being affected by each other's transmissions.

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

[0131] For example, when AP1, which is an STA of (a) AP MLD, operates in the 2.4 GHz band, the AP1 may have a maximum operating bandwidth of 40 MHz. When AP4, which is another STA of (a) AP MLD, operates in the 6 GHz band, the AP4 can utilize a maximum of 320 MHz of BW as the operating bandwidth. At this time, if the MLD has to map traffic with characteristics that require high throughput and low latency, it can attempt to enhance QoS by mapping the traffic to the AP4. In this way, by performing STA mapping considering the characteristics of the traffic to be served, the MLD can obtain the effect of differentiating, for each type of traffic, not only the transmission priority but also the amount of resources (hardware and frequency) that can be utilized when transmitting.

[0132] <TID (traffic identifier)-to-Link mapping>

[0133] From one embodiment described in FIG. 10, it was explained that the MLD can perform traffic mapping to the STA (link) it operates considering the characteristics of the traffic to be served for QoS enhancement. In one embodiment of FIG. 10, for comparison with EDCA, it was expressed that the traffic mapped to each AC is mapped to each STA. However, 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 exist. For example, signaling for indicating a TID corresponding to a frame may be included in the frame, and the signaling may be a TID subfield. More specifically, the signaling for indicating a TID may be included in the MAC header of the frame. For example, the signaling for indicating a 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. 802.11 indicates a TID according to a traffic type in a TID subfield existing in a QoS control field of a MAC frame in order to enhance QoS. At this time, the TID indicates UPs (user priorities) of an MSDU or a fragment or an A-MSDU included in a Frame body or a TSID (traffic stream identifier). The TID subfield is composed of a total of 4 bits and can indicate values from 0 to 15.

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

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

[0137] At this time, 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 an MSDU having a value of the TID subfield from 8 to 15 is indicated by the access policy which is another subfield of the TS Info field, and may be interpreted as indicating EDCA when the access policy subfield (bits 7, 8) of the TS Info field is indicated as (1, 0), and indicating HCCA when indicated as (1, 0) or (1, 1).

[0138] Also, when mapping the TID corresponding to the TS to a link, an Intra-Access Category Priority element may be indicated in the ADDTS request frame utilized when generating the TS, and the Alternate queue (AC queue) information utilized when transmitting the TS by User Priority and EDCA may be included in the Intra-Access Priority field existing in the element. In this case, the MLD can process the traffic having the TID corresponding to the TS in consideration of the UP and queue information indicated in the Intra-Access priority field.

[0139] Thus, since the TID has a meaning corresponding to the UPs of the traffic, it is possible to consider that the MLD maps the traffic of each TID to different STAs, similar to mapping the traffic corresponding to each AC to different STAs in one embodiment of FIG. 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 the MLDs communicating with each other.

[0140] That is, a specific MLD can signal its TID-to-Link mapping plan to other MLDs, and the MLD that receives the TID-to-Link mapping plan from the specific MLD may accept or reject the TID-to-Link mapping planned by the specific MLD. At this time, when there is no separate TID-to-Link mapping agreement between two MLDs that have established a connection with each other, each MLD may send traffic regardless of the TID of the traffic through all the links established with the peer MLD. This may be understood as all TIDs being mapped to all links, and may be an implicit agreement on the basic TID-to-Link mode between the two MLDs that first established the connection.

[0141] Detailed rules to be observed when performing TID-to-Link need not be defined. However, an MLD must map all TIDs to one or more links when performing TID-to-Link. According to an embodiment of the present invention, it is possible to transmit a frame for a TID mapped to a link over the link. Also, it is possible not to transmit a frame for a TID not mapped to the link over the link. Also, the mapping between a TID and a link may be made individually for each MLD. Also, the mapping between a TID and a link may be made individually for each transmission direction of the link. For example, the mapping between a TID and a link may exist for each of the upstream link and the downstream link. Also, in the present invention, TID-to-Link mapping may be used interchangeably with TID-to-Link, TID-to-Link mapping, mapping between a TID and a link, etc. Also, in the present invention, TID-to-Link mapping may also mean mapping between an AC and a link, or mapping between a user priority and a link, or mapping between a traffic class and a link, or mapping between a traffic stream and a link.

[0142] Also, the above-described TID-to-Link mapping may be agreed to be different between MLDs connected to each other. As an example, when MLD1 and MLD2 are connected through Link1 and Link2, MLD1 can map traffic with TID values of 0 to 3 to Link1, and MLD2 can map traffic with TID values of 4 to 7 to Link1.

[0143] Also, the signaling of the TID-to-Link mapping may be made implicitly. As an example, when MLD1 and MLD2 are connected through Link1 and Link2, MLD1 does not need to separately signal the link that maps the remaining TIDs while only mapping traffic with TID values of 0 to 3 to Link1. In this case, it may be understood that other traffic with TID values not equal to 0 to 3 is mapped to Link2. That is, TIDs not mapped to a specific link in the TID-to-Link mapping signaling may be interpreted as being mapped to other links not separately indicated in the TID-to-Link mapping signaling. At this time, the links not separately indicated may be interpreted as the links to which all TIDs are mapped.

[0144] Also, when two connected MLDs are first connected and when changes are required during operation, 1) when an MLD converts the STA of a specific link to Disassociation / Disable according to the operation policy (for purposes such as power saving), 2) when an MLD determines that it is difficult to guarantee QoS for the traffic mapped to a specific link, etc., the MLD can request the other MLD to change its TID-to-Link mapping settings.

[0145] In addition, a specific MLD can request the peer MLD to change the TID-to-Link mapping. As an example, when the traffic with TIDs 0 to 3 among the traffic sent by the AP MLD to the Non-AP MLD is mapped to Link1, the Non-AP MLD can request to change the mapping link of the traffic to another link (for example, Link2) instead of Link1.

[0146] Also, when a TID-to-Link mapping request made by a specific MLD is rejected by the peer MLD, the specific MLD may be restricted for a certain period of time from requesting the mapping of the same TID-to-Link configuration. This is to prevent repeated TID-to-Link mapping requests and rejections, and the time limit for restricting the same TID-to-Link request after rejection may be the time instructed by the AP.

[0147] That is, after a specific MLD requests the mapping of a link for a specific TID using the TID-to-Link mapping element of a request frame, if the peer 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 the request frame.

[0148] For this purpose, the AP MLD can signal the time information related to the TID-to-Link mapping request interval to the STAs in its BSS as BSS operation parameters. At this time, the restriction on the rejected TID-to-Link mapping may be applied separately for each rejected TID. In other words, when mapping requests for a plurality of TIDs and links proposed at once are rejected for a specific TID, the specific TID may be restricted from making a mapping request again for the rejected link.

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

[0150] In order to establish a TID-to-Link mapping rule between an AP MLD and a 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 that indicates which TID is mapped 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 is mapped.

[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 for.

[0153] Also, the TID-to-Link mapping element may include a TIDs info field. The TIDs info field may include information about the TID to be mapped. The TIDs info field may include information about the TID that the TID-to-Link mapping element including the TIDs info field maps to. For example, the TIDs info field may include information about the TID that is mapped to the 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 certain TID is mapped to a link, the bit corresponding to the certain TID can be set to a preset value (e.g., 1). Also, if a certain TID is not mapped to a link, the bit corresponding to the certain TID can be set to a preset value different from the preset value (e.g., 0).

[0154] The (a) AP MLD in FIG. 11 can plan to send the traffic (MSDU) with TIDs 0 to 3, where the TID is 0 to 3, among the traffic to be sent to the (b) Non-AP MLD, through AP1 operating on Link1.

[0155] Therefore, after the AP MLD indicates Link1 using the Link ID field of the (c) TID-to-Link mapping element, it can signal to the Non-AP MLD using the TIDs info field that TIDs 0 to 3 are mapped to Link1. At this time, it can be easily understood that the (c) TID-to-Link mapping element is an element format for illustration, and elements with other structures may be used for the same purpose.

[0156] After the Non-AP MLD confirms the per-TID transmission link planned by the AP MLD from the TID-to-Link mapping element, it can approve or reject it.

[0157] After the (b) Non-AP MLD in FIG. 12 confirmed the TID-to-Link mapping received from the (a) AP MLD, it can be understood that the situation is such that it agreed to map the traffic corresponding to TIDs 0 to 3 to Link1 and the traffic corresponding to TIDs 4 to 7 to Link2. At this time, the TID-to-Link mapping element transmitted by the AP MLD to the Non-AP MLD may each have a configuration including two Link IDs and a TIDs info subfield. At this time, each of the two Link ID subfields may indicate Link1 and Link2 respectively, and each of the two TIDs info subfields may be indicated with a value meaning 0 to 3 and a value meaning 4 to 7 respectively.

[0158] At this time, the TIDs info subfield may be configured with 8 bits, and each bit may be interpreted as corresponding to TID 0 to TID 7 respectively. That is, to indicate TIDs 0 to 3, the 8 bits of the TIDs info subfield may be shown as 1111 0000, and to indicate TIDs 4 to 7, the 8 bits of the TIDs info subfield may be shown as 0000 1111.

[0159] At this time, the TIDs info subfield may be configured with 8 bits, and each bit may be interpreted as corresponding to TID 0 to TID 15 respectively. That is, to indicate TIDs 0 to 3, the 16 bits of the TIDs info subfield may be shown as 1111 0000 0000 0000, and to indicate TIDs 4 to 7, the 16 bits of the TIDs info subfield may be shown as 0000 1111 0000 0000.

[0160] Alternatively, the TIDs Info subfield may internally consist of two subfields, and the two subfields may be Min TID and Max TID. At this time, the Min TID subfield indicates the lowest TID value among the TIDs mapped to the link, and the Max TID subfield can indicate the largest TID mapped to the link. At this time, the Min TID and MAX TID may each be indicated by 3 bits or 4 bits.

[0161] As an example of 3 bits, when the Min TID subfield of the TIDs Info subfield is shown as 000 and the Max TID subfield is shown as 011, the TID indicated by the TIDs Info subfield may be interpreted as 0 to 3. When the Min TID subfield is shown as 100 and the Max TID subfield is shown as 111, the TID indicated by the TIDs Info subfield may be interpreted as 4 to 7.

[0162] As an example of 4 bits, when the Min TID subfield of the TIDs Info subfield is shown as 0000 and the Max TID subfield is shown as 0011, the TID indicated by the TIDs Info subfield may be interpreted as 0 to 3. When the Min TID subfield is shown as 0100 and the Max TID subfield is shown as 0111, the TID indicated by the TIDs Info subfield may be interpreted as 4 to 7.

[0163] After the (a) AP MLD in FIG. 11 confirmed the TID-to-Link mapping received from the (b) Non-AP MLD, it can be understood that in the situation where it agreed to map the traffic corresponding to TIDs 0 to 3 to Link1 and the traffic corresponding to TIDs 0 to 7 to Link2.

[0164] At this time, the (b) Non-AP MLD only indicates that TIDs 0 to 3 are mapped to Link1 using the TID-to-Link mapping element, and does not need to separately indicate that TIDs 0 to 7 are mapped to Link2. In other words, the (b) Non-AP MLD does not separately indicate the TIDs mapped to Link2 in the TID-to-Link mapping element sent to the (a) AP MLD, and the (a) AP MLD can be implicitly interpreted as all TIDs being mapped to the unindicated Link2.

[0165] By utilizing the above-described TID-to-Link mapping, the MLD can map the traffic to be served to one or more STAs (Links) it operates based on the TID of the traffic. If there are two or more EDCA ACs corresponding to the TIDs mapped to a specific link, the QoS STA (of the MLD) operating on the specific link can serve the traffic of the mapped TIDs by differentiating the AC using the EDCA mechanism. That is, the MLD can map TIDs to each link by utilizing the TID-to-Link mapping, and each STA of the MLD can apply the EDCA mechanism to the traffic of the TIDs mapped to its own link.

[0166] As an example, when a specific MLD maps the traffic corresponding to AC_VO and the traffic corresponding to AC_BK to a specific link using the TID-to-Link mapping, the STA operating on the specific link can serve the traffic corresponding to AC_VO with a higher probability and priority than the traffic corresponding to AC_BK. At this time, if the 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 the traffic corresponding to AC_VO with priority over the traffic of AC_BK.

[0167] In this way, depending on the operation target, the MLD can enhance QoS or perform operations considering the performance characteristics of each link by adjusting and changing the TID mapped to each link, and the rules to be followed when performing TID-to-Link mapping do not need to be defined separately. This means that, unlike the EDCA mechanism that provides UP to AC rules, the MLD can freely utilize TID-to-Link mapping according to its operation policy. However, all TIDs must be mapped to at least one link, and the MLD shall not request the TID-to-Link mapping of a configuration where at least one TID is not mapped to any link from another MLD. Therefore, when the TID mapping for at least one link is not implicitly made, all TIDs need to be explicitly mapped to at least one link.

[0168] FIG. 12 shows an example of a TID-to-Link mapping method that can be established between the AP MLD and the Non-AP MLD.

[0169] FIG. 12(a) is an example in which both the AP MLD and the Non-AP MLD utilize the basic (Default) TID-to-Link mapping, considering the situation where the AP MLD and the Non-AP MLD operate AP1 and AP2, Non-AP STA1 and Non-AP STA2 on Link1 and Link2, respectively. In this case, when no separate TID-to-Link mapping request / approval is made after the AP MLD and the Non-AP perform MLD association, the basic TID-to-Link mapping state as considered in this example can be maintained.

[0170] Referring to Fig. 12(a), it can be confirmed that the AP MLD maps all the TSIDs to all the links in addition to the TID. Also, the TSID may be in the basic mapping state where it is mapped to all the links without performing another TID-to-Link mapping. At this time, if the MLD attempts to change the mapping form of the TSID to a non-basic mode (for example, mapping only TSID9 to Link2), the TSID-to-Link mapping can be performed in the same way 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, so a detailed description is omitted.

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

[0172] As described above, for the purpose of enhancing QoS, 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. This can be understood as similar to the conventional Wi-Fi using the EDCA mechanism to differentiate the AC according to the nature of the traffic, where the MLD utilizes each link as an AL (Access link) and differentiates the AL according to the nature of the traffic.

[0173] However, the traffic that the Wi-Fi MAC has to process includes not only the MSDU requested to be processed at the upper layer but also the management frame containing information for operating the BSS. Such a management frame does not have an individual TID, unlike each MSDU having a TID.

[0174] Therefore, the QoS STA needs to determine the AC to be utilized when transmitting the QoS management frame. The conventional 802.11 standard provides a basic QMF policy for QoS management frames, enabling the QoS STA to determine the AC to be utilized when transmitting the QoS management frame (hereinafter referred to as the management frame). At this time, the QMF policy may be changed by the QoS AP operating the QoS BSS. According to one embodiment, there may be an AC corresponding to the management frame.

[0175] Also, the AC corresponding to the management frame may be determined by the QMF policy. At this time, the AC corresponding to the management frame can be called the QMF connection category. Also, the type, subtype, or category value of the management frame, etc., can be determined based on the type, subtype, or category value corresponding to the management frame. Also, a service in which there is an AC corresponding to the management frame or a service that accesses the channel based on the AC based on the QMF policy when transmitting the management frame, etc., can be called a QMF service. Also, transmitting a frame based on the QMF policy may be limited to the case where both the STA transmitting the frame and the STA that is the recipient of the frame support QMF.

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

[0177]

Table 2

[0178] Referring to Table 2, for (Re)Association Request / Response, AC_VO is set as the basic AC. Therefore, when a QoS STA sends an Association Request or responds to an Association Response, it must utilize the CW and AIFSN parameters of AC_VO for transmission. On the other hand, for Timing Advertisement, the basic AC is set as AC_BE. Therefore, when a QoS STA sends the Timing Advertisement, it must utilize the CW and AIFSN parameters of AC_BE for transmission if the QoS AP does not separately change the QMF policy of the QoS BSS.

[0179] The reason for assigning different QMF connection categories according to the type of management frame in the basic QMF policy as described above is that among management frames, there are types of management frames with low processing urgency. This is to prevent delays in other traffic and management frame services during the process of processing such management frames with low urgency.

[0180] As described above, it is also necessary to differentiate ACs according to the information and roles included in management frames. Therefore, similar to differentiating ALs by TID using TID-to-Link mapping, MLD can map management frames to different links according to their types.

[0181] However, the basic QMF policy of MLD may be set so that all QMFs can utilize all ACs. In other words, for all subtypes of management frames in the basic QMF policy of MLD, the QMF access category may be set as AC_Any.

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

[0183] That is, the general frame is transmitted on the link mapped to the assigned TID. However, for the management frame, no TID may be assigned and the link to be transmitted may not be specified. In this case, since there is no assigned TID for the management frame, it may not be necessary to set 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 mapping>

[0185] As the easiest way to perform QMF-to-Link mapping, each management frame can be mapped to the link to which the traffic corresponding to the AC is mapped according to the QMF connection category given to each management frame (see Table 2). That is, it is possible to transmit the management frame based on the TID-to-Link mapping.

[0186] For example, when a certain AC (or TID) is mapped to a link and the AC (or TID) corresponding to the management frame is the said AC (or TID), it is possible to transmit the management frame over the said link. Also, when a certain AC (or TID) is not mapped to a link and the AC (or TID) corresponding to the management frame is the said AC (or TID), it may not be possible to transmit the management frame over the said link.

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

[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 a QMF that does not have a TID.

[0189] However, in the case of a specific QMF, it may contain information that needs to be exchanged between each STA of the MLD, rather than information exchanged at the MLD level like a general MSDU. In this case, if the MLD maps the specific QMF only to a specific link, there is a problem that STAs operating on links other than the specific link cannot transmit the specific QMF.

[0190] That is, in the case of QMF, there can be a QMF that has the characteristic of being transmissible over all links regardless of the type of AC given to the QMF. Therefore, the MLD can indicate a QMF that can be mapped to all links regardless of the given AC.

[0191] In other words, in the case of a management frame, since a specific TID cannot be assigned and there is no TID assignment, the mapping between the TID and the link does not need to be applied. Therefore, the management frame may be transmitted on all links regardless of the mapping between the TID and the link. At this time, the link on which the management frame is transmitted may be an enabled link on which the mapping between the TID and the link is set. At this time, the enabled link means a link on which a mapping relationship with at least one TID is set.

[0192] In this case, when the management frame is transmitted only through the enabled link, there may be a case where the management frame is not transmitted when there is no enabled link, except for the broadcast management frame transmitted regardless of the link. Therefore, in the case of a specific management frame, it can be transmitted even when 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 a TID-to-Link mapping, the MLD can indicate a QMF that can be mapped to all links regardless of the AC given by the QMF policy.

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

[0196] As shown in FIG. 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. Further, when the QMF Support field corresponding to a specific link is indicated as 1 (true), all types of QMFs may be mapped to the specific link regardless of the QMF policy of each QMF.

[0197] Also, a (QMF) management frame subtype may be indicated in the TID-to-Link mapping element. At this time, the QMF of the subtype corresponding to the value indicated by the management frame subtype field may be mapped to all links regardless of the given AC. As an example, when the Management Frame subtype field is indicated as 0101 (Probe Response), the Probe response frame may be mapped to all links regardless of the AC assigned (allocated / indicated) 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. Also, the TID-to-Link mapping element may include a (QMF) Management Frame subtype for indicating whether a management frame of a specific subtype can be mapped to all links. Or, there may be signaling indicating whether to base on the TID-to-Link mapping when transmitting QMF. That is, there may be signaling indicating whether the determination of whether to transmit based on the TID-to-Link mapping when transmitting QMF on a specific link.

[0199] That is, according to one embodiment, when the signaling indicates a preset value, it is possible to transmit the QMF regardless of the TID-to-Link mapping. That is, even if the AC corresponding to the QMF is not mapped to a link based on the TID-to-Link mapping, it is possible to transmit it on the link. As yet another embodiment, when the signaling indicates a preset value, it is possible to transmit the QMF based on the TID-to-Link mapping. That is, when the AC corresponding to the QMF is mapped to a link based on the TID-to-Link mapping, it is possible to transmit it on the link. Also, when the AC corresponding to the QMF is not mapped to a link based on the TID-to-Link mapping, it may 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 (transmit) 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 on a specific link, the corresponding Response-type QMF frame can respond through the specific link regardless of the AC. Also, when a Request-type QMF frame is received on a specific link, the corresponding Response-type QMF frame may be responded through the specific link regardless of the QMF-to-Link mapping.

[0201] FIG. 14 shows an embodiment of the operation of an MLD that has established a QMF policy using TID-to-Link mapping.

[0202] (a) of FIG. 14 is an illustration of a TID-to-Link mapping element that can be generated to perform TID-to-Link mapping for three links. At this time, if the MLD that generated the element utilizes more than four links and is associated with other MLDs, links not explicitly indicated by the Link ID field of the element may be interpreted by the receiving MLD as implicitly indicating that the basic TID-to-Link mapping is utilized.

[0203] At this time, when a specific MLD generates a TID-to-Link mapping element shown in (a) of FIG. 14 and the peer MLD accepts it, the specific MLD can transmit traffic and QMF frames in the manner shown in (b) of FIG. 14. For reference, (a_1), (a_2), and (a_3) in (a) of FIG. 14 represent sub-fields for Link1, Link2, and Link3 respectively, and (a_common) is inserted to represent sub-fields that are commonly applied to all links.

[0204] Referring to (b) of FIG. 14, the MLD can map and transmit traffic having TIDs 0 to 3 using Link1. At this time, the TIDs 0 to 3 may be TIDs corresponding to AC_BK (UP 1, 2) and AC_BE (UP 0, 3) among the ACs. At this time, referring to (a_1) in (a) of FIG. 14, the QMF Support of Link1 is indicated as 1 (true). Therefore, the MLD can transmit (map) all types (subtypes) of QMFs through Link1 regardless of the AC given to each QMF.

[0205] As shown in Fig. 14(b), the MLD can transmit (map) traffic having TIDs 0 to 3 identical to 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 through Link2. However, since the (QMF) management frame subtype field is indicated as 1111 by (a_common) in Fig. 16(a), the MLD can transmit (map) the QMF (1111) with the management frame subtype of 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) with the management frame subtype of 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 embodiments of the present invention, by performing TID-to-Link mapping, the MLD can map each TID to a different link to enhance QoS. An embodiment of the present invention described below provides a specific signaling method and negotiation progress method for TID-to-Link mapping performed between MLDs.

[0209] For reference, the drawings of each embodiment provided below may be shown in a form in which some Immediate Ack frames are omitted for the sake of concise representation. For example, a responding MLD that has received a TID-to-Link mapping request frame can transmit an Immediate Ack frame (responded after SIFS) as a response, which may be omitted for the sake of simplicity.

[0210] An MLD (AP MLD or non-AP MLD) that requests TID-to-Link mapping can request to map the indicated TID to the indicated link by using a TID-to-Link mapping element to indicate a specific TID and a specific link. At this time, the TID-to-Link mapping element may be used to indicate both a number of TID groups and a number of link groups.

[0211] As an example, a single TID-to-Link mapping element can indicate TID sets #1, #2, and #3 corresponding to Link sets #1, #2, and #3 respectively. At this time, when TID set #1 is indicated corresponding to Link set #1, it may be understood that an attempt is made to map the TIDs corresponding to TID set #1 to the links corresponding to Link set #1. At this time, the TID-to-Link mapping element including the desired TID and link information may be transmitted through (and included in) the TID-to-Link mapping request frame. At this time, the MLD that transmitted the TID-to-Link mapping request frame can be called the Initiating MLD or the Requesting MLD.

[0212] In this way, the MLD that received the TID-to-Link mapping element including the indication information for the TID and the link (in the TID-to-Link mapping request frame) can confirm the mapping information between the TID and the link desired by the MLD that transmitted the TID-to-Link mapping request frame. Then, the MLD that received the TID-to-Link mapping request frame may need to respond with a TID-to-Link mapping response frame in order to accept or reject the mapping between the TID and the link requested by the Initiating MLD. At this time, the MLD that received the response frame may be called the Responding MLD because it must respond with a TID-to-Link mapping response frame.

[0213] When the response MLD attempts to accept the TID-to-Link mapping requested from the start MLD, it may respond without including the TID-to-Link mapping element in the TID-to-Link mapping response frame it sends in response. That is, when the start MLD receives a TID-to-Link mapping response frame that does not contain a TID-to-Link mapping element as a response to the TID-to-Link mapping request frame it sent, it can recognize that the TID-to-Link mapping it requested has been accepted by the response MLD.

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

[0215] At this time, the said period of grace may be for managing the transmission queues of the STAs of each (connected) link included in each MLD. Further, after the TID-to-Link mapping negotiation is completed, each MLD may have a grace 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 grace period corresponding to the said certain period has passed, the two MLDs that have completed the TID-to-Link mapping must communicate according to the negotiated TID-to-Link mapping state. At this time, communicating according to the TID-to-Link mapping state means that only the traffic (frames, etc.) of the TIDs mapped to the link can be transmitted / received on a specific link.

[0216] On the one hand, when the responding MLD attempts to reject the TID-to-Link mapping requested by the initiating MLD, it can respond by including a TID-to-Link mapping element in the TID-to-Link mapping response frame to which it responds. At this time, the TID-to-Link mapping element included in the response frame can indicate a TID and a link different from those of the TID-to-Link mapping element included in the request frame. For example, in the TID-to-Link mapping element included in the request frame, TID 0 may be indicated as corresponding to Link1. At this time, if the responding MLD indicates TID 0 as corresponding to Link2 in the TID-to-Link mapping element included in the response frame, the initiating MLD that sent the request frame can recognize that its proposal to map TID 0 to Link1 has been rejected. Also, the initiating MLD can recognize that the responding MLD desires to map TID 0 to Link2 by confirming that TID 0 is indicated as corresponding to Link2 in the response frame responded to by the responding MLD.

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

[0218] Also, the response MLD may attempt to accept only a part of the TID-to-Link mappings instructed (requested) by the start MLD through the TID-to-Link mapping element. For example, by instructing the start MLD to correspond TID 0 to Link1, the start MLD can request to map TID 0 to Link1, and at the same time, by instructing to correspond TID1 to Link2, the start MLD can request to map TID1 to Link2. At this time, the response MLD may attempt to commit to only one of the two mapping requests (TID 0 to Link1, TID1 to Link2) requested by the start MLD. In this case, the response MLD can commit to the TID-Link mapping request related to the specific TID by instructing only the remaining TIDs excluding the specific TID that it attempts to commit in the TID-to-Link mapping element included in the response frame. In other words, when there is a TID-Link mapping that the response MLD attempts to commit among the TID-Link mapping list (field or sub-field) instructed by the start MLD (included in the TID-to-Link mapping element of the request frame), the response MLD can implicitly indicate the commitment by not indicating the TID (the TID that it attempts to commit) in the response frame. Therefore, when there is a TID that is not indicated (not counter-proposed) in the response frame of the response MLD among the TIDs instructed by the start MLD through the request frame, the start MLD can recognize (interpret) that the TID-Link mapping request for the TID has been committed.

[0219] By including the TID-to-Link mapping element in the Beacon frame and transmitting it, the AP MLD can help the non-AP STA (MLD) that receives the Beacon frame recognize its preferred TID-Link mapping state. In this case, when the non-AP STA MLD transmits an Association request frame to the said AP MLD, it can request TID-to-Link mapping negotiation with the TID-to-Link mapping element. At this time, the non-AP STA MLD may need to set the TID-to-Link mapping element included in the Association request frame it transmits in consideration of the preferred TID-Link mapping state of the AP indicated through the Beacon frame. At this time, the AP MLD that includes the TID-to-Link mapping element in the Beacon frame may be limited to the AP MLD that supports TID-to-Link mapping negotiation.

[0220] The TID-to-Link mapping element may be transmitted included in the (Re)Association request / response frame, or may be transmitted through the TID-to-Link mapping request / response frame. At this time, the TID-to-Link mapping element included in the two types of response frames may be included to propose the TID-Link mapping preferred by the MLD that transmitted the request frame. Or, an unsolicited response frame transmitted without receiving a request frame including the TID-to-Link mapping element may be transmitted to propose (indicate) the preferred TID-to-Link mapping state to the MLD that is the single destination device of the said frame.

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

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

[0223] That is, to indicate a set of links, an 8-bit Links info field may be used, and each bit of the Links info field may be used to indicate whether the TID indicated for the corresponding link corresponds to the respective 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 such that the TIDs Info field is indicated as 1111 0000 and the Links Info field is indicated as 1100 0000, it may be understood that TID 0 to TID 3 are proposed / anti-proposed to be mapped to Link1(0) to Link2(1).

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

[0225] That is, the TID-to-Link mapping element can indicate different TIDs and links in each TID-to-Link Mapping Info field through a number of TID-to-Link Mapping Info fields. However, within a single TID-to-Link mapping element, a specific TID is not 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 less than once) within the 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 the TID-to-Link mapping element, TID 0 may not be indicated in the remaining TID-to-Link Mapping Info fields included in the element. At this time, the indication of the TID 0 may mean that TID 0 is indicated alone, or a TID set including TID 0 (for example, TID 0 to TID 3) is indicated.

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

[0228] In Figure 15(a), 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. At this time, the information related to the length may be information related to the number of TID-to-Link Mapping Info fields (Figure 15(c)) included in the TID-to-Link Mapping Info field and the length (size) related information of each TID-to-Link Mapping Info field. That is, the information regarding the length may be information related to the number of one or more TIDs mapped to one or more links.

[0229] Referring to Figure 15(b), the TID-to-Link Mapping Control field may be configured to include a TID-to-Link Mapping Info size sub-field and a Link Bitmap size sub-field. The TID-to-Link Mapping Info size sub-field can 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 sub-field can 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 sub-field can indicate the size (such as 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 utilized to indicate the size of the Link Info subfield included in each TID-to-Link Mapping Info field. The reason the Link Bitmap size subfield is necessary is that, unlike the number of TIDs being fixed at 8 (TIDs 0 to 7), the number of Links in MLD can be variable. Therefore, the Link Bitmap size subfield can 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 composed of 4 bits and can 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 composed of 1 bit and can indicate one of the sizes of the already set Link Info subfields. For example, if the Link Bitmap size subfield is shown as 0, it may be indicated that the size of the Link Info subfield is 8 bits, and if the Link Bitmap size subfield is shown as 1, it may be indicated 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 proceed simultaneously for the DL and UL directions. That is, a single TID-to-Link mapping element may be simultaneously instructed with information for the DL TID-to-Link mapping and the UL TID-to-Link mapping negotiation. Considering this, the TID-to-Link Mapping Info field may include both a DL TID-to-Link Mapping Info field and a UL TID-to-Link Mapping Info field.

[0232] Also, the TID-to-Link Mapping Info size subfield may be composed of two types of TID-to-Link Mapping Info size subfields (a DL TID-to-Link Mapping Info size subfield and a 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, it may be unidirectional TID-to-Link mapping information applied to the transmission or reception direction of the MLD that transmitted the request frame including the TID-to-Link mapping element when information for DL and UL is not separately instructed in 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 the 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 may be mapped to Link1, and in the second of the second TID-to-Link Mapping Info fields, another set of TIDs including TID 0 may be mapped and indicated to Link2 again. In this case, the MLD (responding 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 responding 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 include the TID-to-Link mapping element.

[0234] <Proposing / Accepting / Rejecting (Counterproposing) Method for TID-to-Link Mapping Negotiation>

[0235] As described above, TID-to-Link mapping negotiation can be performed between MLDs using a TID-to-Link mapping element. The initiating MLD can indicate the TID-Link mapping it intends to propose (prefer) by utilizing the TID-to-Link mapping element included in a 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 determine whether to accept the TID-Link mapping indicated by the TID-to-Link mapping element. The responding MLD and the initiating MLD can utilize a TID-to-Link mapping request frame, a TID-to-Link mapping response frame, a TID-to-Link Mapping Teardown frame, etc. to conduct TID-to-Link mapping negotiation.

[0236] The TID-to-Link Mapping Req / Resp / Teardown frame may be a frame format corresponding to the TID-to-Link Mapping Action frame. That is, in the Category field of the Action field, a value indicating that it is a TID-to-Link Mapping Action frame is indicated, and the Action Details field may be indicated with 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 that remains reserved in 11ax (for example, 32). At this time, the TID-to-Link Mapping Req / Resp / Teardown frames may be distinguished by being indicated as 0, 1, and 2 respectively in the 1 octet immediately following the Category field. That is, when the Category field value of the Action frame is indicated as 32 and the octet immediately following the Category field indicates 0 (0000 0000), the Action frame may be a TID-to-Link mapping request frame.

[0237] If the response MLD attempts to reject all or part of the TID-Link mapping method proposed by the start MLD, the response MLD can reject the TID-Link mapping proposed by the start MLD by including a TID-to-Link mapping element in the response frame (TID-to-Link mapping response frame, (Re)Association response frame). That is, when the response frame is responded with a TID-to-Link mapping element included, it may be understood that the TID-to-Link mapping negotiation between the start MLD and the response MLD is not in a completed state. At this time, 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 response MLD counter-proposes to the start MLD. For example, if the start MLD proposes (indicates / requests) to map TID 0 to Link1 (through a request frame), and the response MLD indicates through the request frame that TID 0 corresponds (maps) to Link2, the start MLD can interpret that the response MLD has counter-proposed to map TID 0 to Link2.

[0238] Also, the response MLD can commit to the Link mapping requests for the remaining TIDs other than the indicated TIDs by indicating (counter-proposing) only some of the TID-Link mappings proposed (requested) by the start MLD through the response frame. In other words, the TID-Link mapping of the start MLD for the TIDs not indicated by the response MLD through the response frame may be understood to be committed by the response MLD. Therefore, after the start MLD indicates the Link mapping for a specific TID in the TID-to-Link mapping element of the request frame, when 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 committed by the response MLD.

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

[0240] That is, when the start MLD sends a request frame to set the mapping between the response MLD, the TID, and the link, the start MLD can implicitly instruct the response MLD of the mapping relationship for some of the TIDs among the plurality of TIDs for mapping with the link by not including the mapping information for some of the TIDs in the TID-to-Link mapping element of the request frame. In other words, when the mapping information for the mapping relationship between a specific TID and the link is missing from the request frame, the mapping relationship between the specific TID and the link may be implicitly indicated (or proposed).

[0241] At this time, the implicit proposal may be that 1) the previously set mapping relationship remains valid without being changed, or 2) the mapping relationship between the TID and the link may be a default mapping relationship.

[0242] At this time, the default 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 all TIDs not indicated in the TID-to-Link mapping element to all links. That is, when the starting MLD does not indicate a specific TID in the TID-to-Link mapping element included in the request frame, it may be (implicitly) indicated / requested that the specific TID be mapped to all links.

[0244] Alternatively, the implicit proposal may be a proposal to maintain the link mapping state already agreed upon for a TID for all TIDs not indicated in the TID-to-Link mapping element. That is, when the starting MLD does not indicate a specific TID in the TID-to-Link mapping element included in the request frame, it may be (implicitly) indicated / requested that the specific TID maintain the TID-Link mapping state already established before transmitting the request frame including the TID-to-Link mapping element.

[0245] That is, when the TID-Link mapping requested in the previously transmitted request frame has been committed for a specific TID, the starting MLD can effectively maintain the already committed link mapping state for the specific TID without changing it by not indicating information for the specific TID in the next request frame to be transmitted.

[0246] Alternatively, when there is already a completed negotiated TID-to-Link mapping mode (including the Default TID-to-Link mapping mode) and it is not desired to change the link mapping state for a specific TID, the starting MLD can maintain the link mapping state for the specific TID by not indicating information for the specific TID in the request frame.

[0247] At this time, the state in which there is a completed TID-to-Link mapping mode in the negotiation may be a state in which the basic TID-to-Link mapping mode is applied between both MLDs after the execution of the Association, or a state in which the most recent TID-to-Link mapping response frame transmitted / received between the MLDs does not include a TID-to-Link mapping element.

[0248] On the other hand, when the responding MLD attempts to accept all the TID-Link mappings (explicitly / implicitly) proposed by the initiating MLD, after receiving a TID-to-Link mapping request frame from 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. In other words, the responding MLD can accept the TID-to-Link mapping instructed (proposed) by the initiating MLD by not making a reverse proposal of the TID-Link mapping using the response frame. When the initiating MLD receives a TID-to-Link mapping response frame that does not include a TID-to-Link mapping element from the responding MLD, it can confirm that the TID-to-Link mapping negotiation has been completed. Also, it can be said that the TID-Link mapping committed by the responding MLD is applied starting from the point when the TID-to-Link mapping negotiation is completed.

[0249] The above-described method of proposing / committing / rejecting (counter-proposing) the TID-to-Link mapping negotiation may be applied to the TIDs for DL and UL respectively, or may be applied at once to all the TIDs of DL or UL. For example, when the starting MLD does not indicate the TID for DL through the TID-to-Link mapping element (when the DL TID-to-Link Mapping Info size is indicated as 0), the starting MLD may be implicitly proposing to maintain the TID-Link mapping state for DL in the already agreed state. Or, the starting MLD may not indicate the TID for DL to change the TID-to-Link mapping state for DL to the basic TID-to-Link mapping state.

[0250] That is, when only the TID for UL is indicated by the TID-to-Link mapping element included in the request frame by the starting MLD, the responding MLD may be interpreted as desiring that the starting MLD maintain the TID-to-Link mapping state for DL in the same state as before. Or, the responding MLD may be interpreted as requesting that the starting MLD change the TID-to-Link mapping state for DL to the basic TID-to-Link mapping state.

[0251] Similarly, when the responding MLD does not give an indication for all the TIDs of DL or UL in the response frame (when the DL or UL TID-to-Link Mapping Info size is 0), the unindicated DL or UL may be interpreted by the starting MLD as having all the proposed TID-to-Link mappings committed.

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

[0253] Also, when the TID-to-Link mapping state applied between both MLDs is released, that is, when switching to the basic TID-to-Link mapping mode, both MLDs must be able to process the traffic for all TIDs on all links within a certain period of time. For example, the MLD that has switched to the basic TID-to-Link mapping mode must maintain a state where it can perform a BA frame response (immediate BA) for all TIDs on all links after the certain period of time. At this time, all the TIDs may only mean the TIDs for which a BA session has been established between both MLDs. That is, when a mapping relationship is formed between a TID and a link, the MLD can send and receive a frame and the corresponding BA to the other MLD using the formed mapping relationship.

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

[0255] Referring to FIG. 16(a), the AP MLD and the non-AP MLD maintain the basic TID-to-Link mapping state. The AP MLD and the non-AP MLD are associated through two links (Link1 and Link2), and all TIDs (TID 0 to TID 7, or including TSID) are mapped to both of the two links.

[0256] To perform TID-to-Link mapping negotiation with the AP MLD, the Non-AP MLD can send a TID-to-Link mapping request frame to the AP MLD as shown in Fig. 16(b). At this time, in the request frame sent through STA1, the Non-AP MLD does not indicate the DL TID, but can indicate to map UL TIDs 0 to 3 to Link1 and UL TIDs 4 to 7 to Link2. At this time, to indicate mapping UL TIDs 0 to 3 to Link1, the Non-AP MLD may indicate TIDs 0 to 3 in the TID Info subfield of the first UL TID-to-Link Mapping Info field and indicate Link1 in the Link Info subfield of the UL TID-to-Link Mapping Info field. At this time, to indicate mapping UL TIDs 4 to 7 to Link2, the Non-AP MLD may indicate TIDs 4 to 7 in the TID Info subfield of the second UL TID-to-Link Mapping Info field and indicate Link2 in the Link Info subfield of the UL TID-to-Link Mapping Info field.

[0257] After receiving the TID-to-Link mapping request frame from STA1 of the non-AP MLD, the AP MLD can recognize through the TID-to-Link mapping element included in the received frame that the non-AP MLD desires to maintain the basic TID-to-Link mapping state for the DL TID, map UL TIDs 0 to 3 to Link1, and map UL TIDs 4 to 7 to Link2. When the AP MLD attempts 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 the TID-to-Link mapping element as shown in Fig. 16(b).

[0258] When a non-AP MLD receives a TID-to-Link mapping response frame that does not contain a TID-to-Link mapping element from an AP MLD, it can recognize that the TID-to-Link mapping negotiation has been completed. After that, a TID-to-Link mapping state as shown in Fig. 16(c) is applied between the AP MLD and the non-AP MLD. The non-AP MLD can only UL transmit traffic for TIDs 0 to 3 through Link1 and can only UL transmit traffic for TIDs 4 to 7 through Link2.

[0259] Fig. 17 shows an example in which the responding MLD selectively responds to some TIDs among the TID and link mappings indicated (or proposed) by the initiating MLD.

[0260] Referring to Fig. 17, the initiating MLD indicates (proposes) through the TID-to-Link Mapping Request frame #1 to map TIDs 0 to 3 to Link1 and TIDs 4 to 7 to Link2 through the TID-to-Link mapping element. At this time, the responding MLD may accept the proposal of the initiating MLD to map TIDs 0 to 3 to Link1, but may reject mapping TIDs 4 to 7 to Link2.

[0261] In this case, the responding MLD can send a TID-to-Link Mapping Response frame #1 containing a TID-to-Link mapping element to the initiating MLD as a response to the TID-to-Link Mapping Request frame #1 received from the initiating MLD. At this time, when configuring the TID-to-Link mapping element, the responding MLD can indicate (counter-propose) to map TIDs 4 to 5 to Link2 and TIDs 6 to 7 to Link3, thereby accepting the Link1 mapping for TIDs 0 to 3 and indicating rejection of the Link2 mapping for TIDs 4 to 7.

[0262] Upon receiving the response of the Response MLD to TID-to-Link Mapping Response frame #1, the Initiating MLD can reconfigure TID-to-Link Mapping Request frame #2 considering the TID-Link mapping state (TID 4 - 5 = Link2, TID 6 - 7 = Link3) indicated by the Response MLD through TID-to-Link Mapping Response frame #1. At this time, the Initiating MLD can send TID-to-Link Mapping Request frame #2 which instructs to map TID 4 - TID 5 to Link2 and TID 6 - TID 7 to Link3 in the TID-to-Link mapping element, considering the TID-Link mapping state proposed by the Response MLD in reverse. The Response MLD can end the TID-to-Link mapping negotiation procedure by responding with TID-to-Link Mapping Response frame #2 that does not contain the TID-to-Link mapping element in order to commit to the TID-Link mapping state indicated by TID-to-Link Mapping Request frame #2 received from the Initiating 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 committed through TID-to-Link Mapping Response frame #1 (TID 0 to 3 = Link1) and the TID-to-Link mapping state committed through TID-to-Link Mapping Response frame #2 (TID 4 to 5 = Link2, TID 6 to 7 = Link3) 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 indicated 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 indicated 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 indicated as true.

[0266] Also, even in the case of an MLD that supports TID-to-Link mapping negotiation, there may be a limit to the number of link sets that support TID-to-Link mapping for each MLD. For example, an MLD that can manage and differentiate TIDs in TID-to-Link mapping with 4 links may not be able to support TID-to-Link mapping negotiation for more than 4 links. Therefore, when the initiating MLD constructs a TID-to-Link mapping request frame for TID-to-Link mapping negotiation, it must construct the request frame considering the number of link sets supported by the responding MLD. Also, since the initiating MLD may attempt TID-to-Link mapping negotiation for both the DL / UL directions, when constructing the TID-to-Link mapping request frame, it must consider not only the number of link sets supported by the responding MLD but also the number of link sets it can support.

[0267] Similarly, after receiving a TID-to-Link mapping request frame from the initiating MLD, the responding MLD must also consider both the number of link sets it can support and the number of link sets supported by the initiating MLD when constructing a TID-to-Link mapping response frame to (inversely) propose a TID-Link mapping.

[0268] Therefore, in order to perform TID-to-Link mapping negotiation between MLDs, the number of link sets that can support each other must be recognized. For this purpose, 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 can indicate a value related to the maximum number of link sets that it 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 need to 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 need to indicate a value meaning four through the TID-to-Link Mapping Negotiation supported subfield.

[0269] In short, when each MLD proposes / counter-proposes the TID-Link mapping state to the peer MLD through the TID-to-Link mapping request / response frame it sends, it must perform the TID-Link mapping considering 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, the initiating MLD that sends the request frame shall not (explicitly / implicitly) indicate through the TID-to-Link mapping element of the request frame a number of link sets exceeding min(the number of link sets it supports, the number of link sets the responding MLD supports). Similarly, the responding MLD that sends the response frame shall not (explicitly / implicitly) indicate (counter-propose) through the TID-to-Link mapping element of the response frame a number of link sets exceeding min(the number of link sets it supports, the number of link sets the initiating MLD supports).

[0270] Also, when the TID-Link mapping for a specific TID is rejected (counter-proposed) by the responding MLD, the initiating MLD shall not request the same link mapping that was rejected again for a certain period of time. At this time, the certain period of time may be a value determined by a parameter indicated by the AP MLD. At this time, the certain period of time may be the time until an Unsolicited response frame is received from the responding MLD. At this time, the certain period of time may mean the Life time.

[0271] For example, after the starting MLD instructs (proposes / requests) to map TID 0 to Link1 through a TID-to-Link mapping request frame, if the responding MLD is instructed (counter-proposes) to map TID 0 to Link2, the starting MLD shall not request to map TID 0 to Link1 within a certain period of time (or a pre-set time or a time instructed by the AP MLD). This may be a restriction to prevent waste of frequency resources and network congestion due to repeated TID-to-Link mapping request / response frame exchanges. However, if the starting MLD has not had a proposal to map TID 0 to Link3 rejected, it can make a new request to map TID 0 to Link3 without following the proposal of the responding MLD.

[0272] <Concise TID-to-Link Mapping Negotiation Procedure>

[0273] In the above-described TID-to-Link mapping negotiation procedure, the starting MLD proposes a mapping for a TID and a link, and the responding MLD can accept or reject the mapping state proposed by the starting MLD. At this time, the responding MLD can accept only the proposals for some TIDs and reject the proposals for the remaining TIDs with respect to the TID-Link mapping state proposed by the starting MLD. At this time, the responding MLD can instruct (counter-propose) a preferred link mapping state for the TIDs for which the proposals are rejected. The point in time when the TID-to-Link mapping negotiation between the starting MLD and the responding MLD is completed is restricted to the time when the responding MLD responds with a TID-to-Link mapping response frame that does not contain a TID-to-Link mapping element.

[0274] When considering such a TID-to-Link mapping negotiation procedure, there is inefficiency in that the initiating MLD that receives a reverse proposal of the TID-Link mapping state from the responding MLD has to retransmit the TID-to-Link mapping request frame even if it tries to accept the (reverse) proposal of the responding MLD. That is, the initiating MLD has to retransmit the TID-to-Link mapping request frame that indicates the same TID-to-Link mapping state proposed in reverse by the TID-to-Link mapping element in order to accept the TID-Link mapping state proposed in reverse by the responding MLD. Similarly, the responding MLD receives from the initiating MLD the same TID-Link mapping proposal that it itself proposed in reverse, and completes the TID-to-Link mapping negotiation procedure by responding again with a TID-to-Link mapping response frame that does not contain the TID-to-Link mapping element. At this time, the exact time of completion of the correct TID-to-Link mapping negotiation procedure may be the time when an Ack response is made to the TID-to-Link mapping response frame.

[0275] Thus, even if the initiating MLD intends to follow the TID-Link mapping state proposed in reverse by the responding MLD, the TID-to-Link mapping negotiation procedure in which the initiating MLD has to retransmit the request frame and the responding MLD also has to respond with the response frame again can induce extra overhead in the retransmitted request frame and response frame.

[0276] Therefore, a TID-to-Link mapping negotiation procedure that allows the initiating MLD to accept the TID-Link mapping state (in reverse) proposed by the responding MLD in response to the initiating MLD may be considered. That is, after the initiating MLD sends a TID-to-Link mapping request frame, if the TID-to-Link mapping response frame responded by the responding MLD contains a TID-to-Link mapping element, the initiating MLD can accept the TID-Link mapping state indicated through the TID-to-Link mapping element. At this time, after receiving the TID-to-Link mapping response frame from the responding MLD, the initiating MLD can (implicitly) accept the (reverse) proposal of the responding MLD for the specific TID by not including a TID-to-Link mapping element in the TID-to-Link mapping request frame to be sent or by not indicating the specific TID with the TID-to-Link mapping element. Such a method for the initiating MLD to respond to the TID-to-Link mapping request frame is similar to the method for the responding MLD to respond to the TID-to-Link mapping response frame, so detailed description is omitted. At this time, the initiating MLD can also send a TID-to-Link mapping response frame (without including 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, when the initiating MLD sends 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, when the 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] Figure 18 shows the response method of the start MLD that accepts (receives) the TID-to-Link mapping proposed in reverse from the response MLD.

[0279] Referring to Figure 18, the start MLD sends a TID-to-Link Mapping Request frame #1 to the response MLD to start the TID-to-Link mapping negotiation procedure, and the response MLD can make a reverse proposal while rejecting the link mapping for TIDs 4 to 7 by responding with Response frame #1. At this time, the start MLD can decide to accept the TID-Link mapping state indicated by the response MLD through the TID-to-Link Mapping Request frame #1 and request the response MLD to complete the TID-to-Link mapping.

[0280] In Example 1 of Figure 18, after the start MLD receives the TID-to-Link Mapping Request frame #1, it can send a 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 sent by the start MLD may be an unsolicited response frame. At this time, the TID-to-Link Mapping Response frame #2 sent by the start MLD has a configuration that does not include the TID-to-Link mapping element, and the response MLD that receives the TID-to-Link Mapping Response frame #2 from the start MLD can recognize that the start MLD accepts the TID-Link mapping state it (reverse) proposed and desires to complete the TID-to-Link mapping procedure. Therefore, after receiving the TID-to-Link Mapping Request frame #2, the response MLD can complete the TID-to-Link mapping negotiation procedure with the start 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 include a TID-to-Link mapping element, and the responding 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 it (inversely) proposed and desires to complete the TID-to-Link mapping procedure. Therefore, after receiving TID-to-Link Mapping Request frame #2, the responding 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 include 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 responding MLD, and the request / response frames exchanged between the two MLDs may be individually addressed frames.

[0284] However, since the AP MLD has to perform TID-to-Link mapping negotiations with multiple non-AP MLDs in the BSS, performing individual TID-to-Link mapping negotiations with all non-AP MLDs can be a task that induces a lot of overhead. Therefore, the AP MLD can inform the non-AP MLDs of its preferred TID-Link mapping configuration by sending non-individually addressed TID-to-Link mapping response frames. When the AP MLD thus informs the non-AP MLDs of its preferred TID-Link mapping state, the non-AP MLD has the advantage that it can start the TID-to-Link mapping negotiation procedure in a state where it already knows the TID-Link mapping configuration preferred by the AP MLD, which is the responding MLD. That is, when the non-AP MLD sends a TID-to-Link mapping request frame as the starting MLD, it can operate already knowing the preference of the responding MLD, so the TID-to-Link mapping negotiation procedure may proceed more easily.

[0285] The Unsolicited TID-to-Link mapping response frame sent by the AP MLD may have a TID-to-Link mapping element configuration different from that of a general TID-to-Link mapping request / response frame. Further, the Unsolicited TID-to-Link mapping response frame sent by the AP MLD can indicate the same TID more than once through the TID-to-Link mapping element. For example, in a specific (DL / UL) TID-to-Link Mapping Info field included in the TID-to-Link mapping element, TIDs 0 to TID1 may be indicated as corresponding (Mapping) to Link1 to Link2, and in another (DL / UL) TID-to-Link Mapping Info field, TIDs 0 to TID4 may be indicated as corresponding to Link1 to Link3. Therefore, a non-AP MLD that receives an Unsolicited TID-to-Link mapping response frame from the AP MLD can make choices such as setting Link1 and / or Link2 for TIDs 0 to TID1 and setting Link3 for TIDs 3 to TID4 if it aims to differentiate the links for TIDs 0 to TID1 and TIDs 2 to TID3. That is, the AP MLD can help the non-AP MLD select a configured link starting from the association stage by including a TID-to-Link mapping element in the Beacon frame it sends. Further, the non-AP MLD can select and set a link according to its desired TID separation method by checking the TID-Link mapping state 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 the AP MLD and the TID-to-Link mapping negotiation process between the AP MLD and the non-AP MLD.

[0287] Referring to FIG. 19, the AP MLD can send an Unsolicited TID-to-Link mapping response frame. At this time, the Unsolicited TID-to-Link mapping response frame may be sent as a non-individually addressed frame. That is, the Unsolicited TID-to-Link mapping response frame sent by the AP MLD may be targeted at one or more non-AP MLDs.

[0288] As shown in FIG. 19, the AP MLD can instruct to map TIDs 0 to 3 to Link1, TIDs 4 to 5 to Link2, and TIDs 6 to 7 to Link3 through an Unsolicited TID-to-Link mapping request frame.

[0289] Upon receiving this, the non-AP MLD (initiating MLD) can, as in Sequence 1 of FIG. 19, commit to the TID-Link mapping indicated through the Unsolicited response frame to the AP MLD (responding MLD) by sending a TID-to-Link mapping request frame that does not contain a TID-to-Link mapping element, and can instruct to execute and complete the TID-to-Link mapping negotiation. After receiving the TID-to-Link mapping request frame that does not contain a TID-to-Link mapping, the AP MLD can respond by sending an Ack frame to indicate that the TID-to-Link mapping negotiation has been completed.

[0290] In Sequence 2, the non-AP MLD (initiating MLD) can confirm that, among the TID-Link mappings indicated by the AP MLD (responding MLD) through the Unsolicited TID-to-Link mapping response frame, there are two link mapping options for TIDs 4 to 7. 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 sending 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 for all TIDs for DL and UL may switch to the same state as if all were mapped to all links.

[0293] When considering the above-described TID-to-Link mapping negotiation method of the present invention, when the starting MLD configures that the TID-to-Link mapping request frame is the starting MLD, 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 example) and the Link Info subfield is indicated as 1111 1111 (8-bit example), the TID-to-Link mapping for the DL direction may be indicated as the basic mode.

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

[0295] Thus, even though it is possible to switch to the basic TID-to-Link mapping mode through the TID-to-Link mapping request frame and the TID-to-Link mapping response frame, the reason why the TID-to-Link Mapping Teardown frame is necessary may be that the TID-to-Link mapping agreement cancellation process is not done by agreement between both MLDs, but can be completed by the intention (will) of a specific MLD. That is, when a specific MLD among both MLDs attempts to operate in the basic TID-to-Link mapping mode, the other MLD may need to necessarily switch to the basic TID-to-Link mapping mode according to the request of the specific MLD. Therefore, if the specific MLD transmits a TID-to-Link Mapping Teardown frame, the other MLD cannot make a counter-proposal using the TID-to-Link mapping response frame and must agree to switch to the basic TID-to-Link mapping mode. At this time, the other MLD may need to respond with an Ack frame or a TID-to-Link mapping response frame that does not contain a TID-to-Link mapping element in order to convey the fact of the agreement.

[0296] At this time, after the specific MLD and the other MLD have agreed 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 period of time. That is, both MLDs that have switched to the basic TID-to-Link mapping mode through the TID-to-Link Mapping Teardown frame need to be operated (switched) to a state where they can perform transmission / reception and BA (BlockAck) responses for all TIDs on all links within a certain period of time. At this time, the certain period of time may be a time already set by the EHT standard or the BSS, or a time already agreed upon between both MLDs performing TID-to-Link mapping.

[0297] For operational purposes, the AP MLD can simultaneously (at once) release the TID-to-Link mapping modes negotiated with a number of Associated non-AP MLDs and attempt to switch to the basic TID-to-Link mapping mode. In this case, instead of sending a TID-to-Link Mapping Teardown frame individually to all Associated non-AP MLDs, the AP MLD can send a non-individually addressed TID-to-Link Mapping Teardown frame. At this time, after sending the DTIM Beacon frame, the AP MLD can send the TID-to-Link Mapping Teardown frame as a group addressed frame. After receiving the DTIM Beacon frame, during the process of receiving a group addressed frame, the Non-AP MLD can receive the TID-to-Link Mapping Teardown frame and 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 sending a response using an Ack or TID-to-Link mapping response frame. That is, a TID-to-Link Mapping Teardown frame sent by an 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 a 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 functionally equivalent element formats can also be configured in various ways.

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

[0302] Referring to FIG. 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, which is the same as the use of the fields included in other elements, and detailed description thereof is omitted.

[0303] The Link Mapping of TID 0 to 7 fields are each composed of 2 octets (16 bits), and each bit may correspond to the Link ID of each link. At this time, each bit of the Link Mapping of TID field corresponds to the link with a Link ID that is 1 smaller than the order of the bit. Further, the first bit of the Link Mapping of TID field corresponds to the link with a Link ID of 0 (1 - 1), the second bit of the Link Mapping of TID field corresponds to the link with a Link ID of 1 (2 - 1), and the tenth bit of the Link Mapping of TID field may correspond to the link with a Link ID of 9 (10 - 1).

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

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

[0306] The Direction sub-field indicates information related to the directionality of the information included in the TID-to-Link mapping element. More specifically, the Direction sub-field indicates whether the TID-to-Link mapping element is for UL direction TID-to-Link mapping, or for DL direction TID-to-Link mapping, or for TID-to-Link mapping for both UL / DL (bidirectional) directions. For example, it may be indicated that when the Direction sub-field is set to 0 / 1 / 2 respectively, the TID-to-Link mapping element includes DL / UL / Bi-directional direction TID-to-Link mapping information. At this time, another value 3 that can be indicated by the Direction sub-field (2 bits) may be reserved.

[0307] The Default Link Mapping sub-field may be a sub-field that indicates that the TID-to-Link mapping mode proposed through the TID-to-Link mapping element is the basic mode (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 basic mapping mode by setting the Default Link Mapping sub-field to 1.

[0308] That is, when 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, the TID-to-Link mapping in the DL direction may be proposed as the basic mode.

[0309] On the other hand, when 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, the TID-to-Link mapping in the UL direction may be proposed as the basic mode.

[0310] Alternatively, when 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, the TID-to-Link mapping in the Bidirectional (DL / UL) direction 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 or DL or Bidirectional direction. Therefore, the TID-to-Link mapping request frame and the (solicited or unsolicited) TID-to-Link mapping response frame may be transmitted including two or one TID-to-Link mapping element. However, for a TID-to-Link mapping (Request and Response) frame including two TID-to-Link mapping elements, the Direction sub-fields of the two TID-to-Link mapping elements (of the TID-to-Link Mapping Control field) may need to be set to 0 and 1 respectively. That is, it is not allowed that the Direction sub-fields of the two TID-to-Link mapping elements included in a single TID-to-Link mapping frame are both set to 0 or 1. Also, when a TID-to-Link mapping frame includes a TID-to-Link element with the Direction sub-field set to 2, no other TID-to-Link element is further included.

[0312] At this time, the meaning that the TID-to-Link mapping in the DL direction is in the basic mode may mean a state where all TIDs are mapped to all configured links for the DL direction. At this time, the meaning that the TID-to-Link mapping in the UL direction is in the basic mode may mean a state where all TIDs are mapped to all configured links for the UL direction. At this time, the meaning that the TID-to-Link mapping in the Bidirectional direction is in the basic mode may mean a state where all TIDs are mapped to all configured links for 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 in both the DL and UL directions between MLDs. On the other hand, the basic TID-to-Link mapping state for the DL direction or the UL direction may be defined separately.

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

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

[0316] However, the basic link mapping mode (Default Link Mapping mode) of the TID-to-Link Mapping Control field may be utilized not for establishing the basic mapping mode for each TID and each link, but for establishing the basic mapping mode in the minimum DL or UL direction.

[0317] Alternatively, the basic 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 basic mode. That is, the Default Link Mapping subfield may be indicated as 1 to switch to the basic TID-to-Link mapping mode for either the Bidirectional direction, and thus 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 is composed of 8 bits and can indicate whether the Link Mapping of TID field (for 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 Link Mapping of TID(i) subfield for TID i is included in the TID-to-Link mapping element. 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 TID-to-Link mapping element may be reserved and all bits may need to be set to 0.

[0319] For example, when the Link Mapping Presence Indicator subfield is indicated as 1100 1000, the TID-to-Link mapping element may include Link Mapping of TID subfields (i.e., Link Mapping of TID 0 subfield, Link Mapping of TID1 subfield, Link Mapping of TID 4 subfield) for TID 0, TID1, and TID 4 in sequence.

[0320] At this time, a specific TID (TID for the direction indicated by the Direction subfield) for which no separate Link Mapping of TID subfield is included in the TID-to-Link mapping element where the Default Link Mapping subfield is indicated as 0 may be implicitly indicated to maintain the current Link mapping state for the specific TID from the device that transmitted the TID-to-Link mapping element. That is, in the above-described embodiment, even if the Link mapping state for TID2 to TID 3 and TID 5 to TID 7 is negotiated by the request frame (including the TID-to-Link mapping element), the previous Link mapping state may be maintained without being changed.

[0321] That is, the TID-to-Link mapping Requesting MLD can request (propose) to maintain the link mapping state already established for the specific TID by sending a TID-to-Link mapping element that does not include the Link Mapping of TID subfield for the specific TID. At this time, 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). At this time, the TID-to-Link mapping Requesting MLD can mean the MLD that sends a TID-to-Link mapping request frame or a (Re)Association request frame including a TID-to-Link mapping element.

[0322] Also, the MLD (Responding MLD) that sends an Unsolicited TID-to-Link mapping response frame can indicate (counter-propose) to the peer MLD that it prefers to maintain the link mapping state already established for the 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, the MLD can send an Unsolicited TID-to-Link mapping response frame for indicating the mapping relationship between the TID and the link preferred by the MLD before a request frame for setting the mapping relationship between the TID and the link is sent from the peer MLD. At this time, when the MLD does not include mapping information related to the 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] At this time, the implicitly indicated mapping relationship may be: 1) effectively maintained without changing the existing mapping relationship, 2) there is no particularly preferred mapping relationship, or 3) one of the basic mapping relationships.

[0325] First, when it is implied that it is preferred to effectively maintain the existing mapping relationship without changing it by the MLD not including mapping information related to the mapping relationship in the Unsolicited TID-to-Link mapping response frame, if there is no separate Link mapping established for a specific TID, one or more TIDs may be interpreted by the peer MLD as having the basic mapping relationship (mapped to all configured links) being preferred. At this time, the Unsolicited TID-to-Link mapping response frame may be an Unsolicited TID-to-Link mapping response frame individually addressed by the responding MLD to the peer MLD (Requesting MLD).

[0326] Second, when it is implicitly indicated that there is no particularly preferred mapping relationship by the MLD not including mapping information related to the mapping relationship in the Unsolicited TID-to-Link mapping response frame, since the MLD has no particularly preferred mapping relationship, the MLD cannot reject the mapping relationship between the TID requested by the peer MLD through the request frame and the link and must accept it. That is, since there is no mapping relationship between the preferred TID and the link, when the mapping relationship between the TID and the link is requested by the peer MLD through the request frame, the MLD must accept it without rejecting it through the response frame.

[0327] Thirdly, when it is implied that the basic mapping relationship is preferred by the MLD not including mapping information related to the mapping relationship in the Unsolicited TID-to-Link mapping response frame, since it is indicated that the basic mapping state is preferred for the mapping relationship between one or more TIDs and the link, unlike the second case, the MLD can reject the mapping relationship requested through the response frame even if the mapping relationship between one or more TIDs and the link is requested through the request frame from the peer MLD.

[0328] However, when the peer MLD requests the same preferred mapping relationship indicated through the Unsolicited TID-to-Link mapping response frame sent from the MLD through the request frame, the MLD cannot reject the requested mapping relationship and must accept it. That is, when the requesting MLD, which is the peer MLD, sends a TID-to-Link mapping request frame including the same TID-to-Link mapping element as the TID-to-Link mapping element sent by the responding MLD, which is the MLD, the responding MLD may necessarily need to accept the proposed (or requested) TID-to-Link mapping.

[0329] The above method for interpreting the mapping relationship between the preferred TID and the link is applicable not only when the mapping relationship between the TID and the link preferred by the Unsolicited TID-to-Link mapping response frame is indicated through the mapping information, but also when the mapping relationship between the TID and the link preferred by the (Re)Association response frame or the TID-to-Link mapping response frame is indicated through the mapping information.

[0330] That is, when the mapping relationship between the TID requested through a request frame, such as an association request frame or a TID-to-Link mapping request frame, and a link 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 by any of the three methods described above.

[0331] Specifically, as described above, the MLD may be requested to set the mapping relationship between the TID and the link through the mapping information included in the TID-to-Link mapping element of a request frame (for example, an association request frame or a TID-to-Link mapping request frame, etc.) from the peer MLD. At this time, the MLD may allow or reject the mapping relationship between the TID requested through the request frame and the link. If the MLD rejects the mapping relationship between the TID requested through the request frame and the link, the MLD may reject the mapping relationship requested through the response frame (for example, a (Re)Association response frame or a TID-to-Link mapping response frame, etc.).

[0332] In this case, while rejecting the mapping relationship requested through the response frame, the MLD can include the mapping relationship between the TID preferred by the MLD and the link in the mapping information of the TID-to-Link mapping element and send it to the peer MLD through the response frame. At this time, when the mapping information for the preferred mapping relationship does not include the mapping relationship between the link and some or all of the TIDs, the mapping relationship between the non-included TID and the link may be implicitly indicated as described above. The implicitly indicated mapping relationship may be one of 1) effectively maintaining without changing the existing mapping relationship, 2) having no particularly preferred mapping relationship, or 3) the basic mapping relationship, and the specific interpretation method is as described above.

[0333] After that, the peer MLD can recognize the mapping relationship preferred by the MLD from the response frame and resend the request frame to the MLD based on it.

[0334] As yet another embodiment of the present invention, when the MLD rejects the mapping relationship between the requested TID and the link through the above response frame, if the MLD includes the mapping information for the mapping relationship between the TID preferred through the response frame and the link in the TID-to-Link mapping element, it can explicitly include the mapping relationship between the link and all TIDs. In this case, since the mapping relationship between the link and all TIDs is explicitly indicated through the mapping information, the implicit interpretation method for the mapping relationship between the TID and the link is not applicable.

[0335] As another example, the TID-to-Link mapping element may be configured to indicate the TID-to-Link mapping for a specific direction (UL or DL) as the default, and include the TID-to-Link mapping proposal / indication information for other directions not in the specific direction (DL direction when the specific direction is UL, UL direction when the specific direction is DL). Further, 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 function to request the DL direction TID-to-Link mapping as the default mapping in the TID-to-Link mapping request frame. At the same time, the specific TID-to-Link mapping element may have a configuration including one or more than one Link Mapping of TID fields in the TID-to-Link mapping element. At this time, the one or more than one Link Mapping of TID fields may be included to request the TID-to-Link mapping in the UL direction (the opposite direction of DL indicated as Direction).

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

[0337] <TID-to-Link Mapping Proposal Rule Considering Whether a Link is Set>

[0338] As described above, the requesting MLD (initiating MLD) sends a TID-to-Link mapping request frame to the responding MLD to establish the 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] When a TID-to-Link mapping is established / negotiated between two MLDs, when transmitting traffic corresponding to a specific TID, both of the said MLDs must perform the transmission only using the link to which the specific TID is mapped.

[0340] If, when establishing a TID-to-Link mapping between both MLDs, a specific TID is mapped only to a link not set between the two MLDs, a constraint that the specific TID must be transmitted only through the link not set is applied, and it may not be necessary to transmit. This means that the TID mapping for the link not set (Association) is not valid. Therefore, the MLD attempting to establish a TID-to-Link Mapping negotiation must attempt to map the TID only to the links set between each other.

[0341] Therefore, the MLD transmitting a TID-to-Link mapping request frame to the peer MLD must request a TID mapping only for the link set with the peer MLD. That is, no TID mapping request may be made for a link not set.

[0342] Therefore, when indicating the link to map for a specific TID, the requesting MLD must always set the bit corresponding to the ID of the link not set to 0 and perform a TID-to-Link mapping request.

[0343] Similarly, the MLD (responding MLD) indicating a preferred TID-to-Link mapping to the requesting MLD must always set the bit corresponding to the link not set to 0 and perform a TID-to-Link Mapping Response. That is, no TID mapping may be proposed for a link not set.

[0344] Therefore, when the response MLD proposes a link to map to a specific TID, it must always set the ID of the link that has not been configured and the corresponding bit to 0 and perform a (solicited or unsolicited) TID-to-Link Mapping response. At this time, the unsolicited TID-to-Link Mapping response can mean that a specific MLD sends a TID-to-Link mapping response frame to propose its preferred TID-to-Link mapping (preferred TID-to-Link Mapping suggestion) to the peer MLD.

[0345] In short, the MLD that sends the TID-to-Link mapping element must always set the bit of the Link ID corresponding to the link that has not been configured with the peer MLD (of the TID-to-Link mapping element) to 0. That is, the TID-to-Link mapping element transmitted and received between two MLDs must always have the Link ID of the link for which no configuration has been established between the two MLDs set to 0.

[0346] However, the MLD that includes the TID-to-Link mapping element in the (Re)Association request frame must request the TID mapping only for the link for which it requests configuration from the peer MLD. That is, the MLD that includes the TID-to-Link mapping element in the (Re)Association request frame must always set the bit of the Link ID corresponding to the link for which it has not requested configuration from the peer MLD (of the TID-to-Link mapping element) to 0.

[0347] Similarly, the MLD that transmits the TID-to-Link mapping element included in the (Re)Association response frame must indicate a preferred TID mapping only for the link that accepts the setting. That is, the MLD that transmits the TID-to-Link mapping element included in the (Re)Association response frame must always set to 0 the bits of the Link ID (of the TID-to-Link mapping element) corresponding to the link that does not accept the setting with the peer MLD.

[0348] At this time, since the maximum index of the Link ID for which a setting can be established between MLDs is limited to 14 at most (a maximum of 15 links are divided using Link ID 0 to Link ID 14), the 16th bit of the Link Mapping of TID field (that is, the bit corresponding to Link ID 15) must always be set to 0.

[0349] <Efficient Link Mapping of TID Field Configuration Method>

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

[0351] If, for example, the number of configured links between two MLDs performing TID-to-Link Mapping negotiation is only 2, 14 of the 16 bits of the Link Mapping TID field (13 bits corresponding to the Link ID of the unconfigured link + the 16th bit) may be bits that are always indicated as 0. Thus, if the bits that must be indicated as 0 are repeatedly indicated in the TID-to-Link mapping element, it leads to an overhead problem. Therefore, a more efficient Link Mapping of TID field configuration may be considered.

[0352] According to an 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 set between MLDs that transmit / receive the TID-to-Link mapping element.

[0353] For example, if the requesting MLD and the responding MLD are set 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 with a size of 3 bits.

[0354] According to an embodiment of the present invention, the 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 the link set between MLDs that transmit / receive the TID-to-Link mapping element. At this time, 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 the requesting MLD and the responding MLD are set through three Links (Link ID 0, Link ID 3, Link ID 10), the 3 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. That is, when the 3 bits of the Link Mapping of TID field for a specific TID are indicated as 010, the specific TID may be interpreted as being mapped / requested to the link corresponding to Link ID 3.

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

[0357] That is, the MLD that transmits / receives the TID-to-Link mapping element after performing the multi-link (re)setup determines the link corresponding to each bit of the Link Mapping of TID field in consideration of the ID of the link set with the peer MLD.

[0358] Also, when the variable-length Link Mapping of TID field is utilized 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. At this time, the Padding field may be included after the Link Mapping of TID field and have a size of less than one octet.

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

[0360] Referring to FIG. 21, the TID-to-Link mapping element may have a configuration 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 3-bit size, and if there are five links established, each Link Mapping of TID field may have a 5-bit size.

[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 of 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 in which ML configuration is performed through 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 a 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 a link with Link ID 3.

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

[0365] The AP MLD and the non-AP MLD can perform (re)configuration to change the configuration of the configured links. That is, the AP MLD and the non-AP MLD can perform reconfiguration to add a configured link or release the configuration of a configured link. At this time, the reconfiguration performed between the AP MLD and the non-AP MLD may be performed by (Re)Association request / response frame exchange. When reconfiguration is performed between two MLDs, TID mapping management related to the configured links added or removed through the reconfiguration must be involved. For the sake of convenience of explanation, in an embodiment of the present invention described later, no reference is made to the directionality (UL or DL) of the TID-to-Link mapping. However, since all TID-to-Link mappings have directionality, it may be understood that an explanation for a specific direction or both directions (Bidirectional) is provided even without a separate reference 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 added configured link applied when the (Re)Association request frame exchanged for reconfiguration does not include the TID-to-Link mapping element.

[0368] However, when a configured link is added through a (Re)Association request frame including a TID-to-Link mapping element, the added configured link may have a TID mapped based on the information indicated by the TID-to-Link mapping element. At this time, since the method for determining the link mapped to the added configured link is not different from the above-described TID-to-Link Mapping negotiation procedure, detailed description thereof is omitted.

[0369] Next, when a link configured through reconfiguration is removed (reset), the TID mapped to the removed link may be changed to the basic mapping state. Further, the TIDs mapped to the links whose configurations have been released through reconfiguration may be changed to a state where they are mapped to all configured links (excluding the released links) after reconfiguration (that is, the Default Link Mapping state of the TID). This may be a TID-to-Link mapping management method considered to prevent the specific TID from being changed to a state where it is not mapped to any configured link when the specific link is released through reconfiguration while the specific TID is mapped only to the specific link.

[0370] However, if the TID mapped to a specific link whose configuration has been released through reconfiguration is also mapped to other configured links (which are still in the configured state after reconfiguration), the specific TID may not need to switch to a state where it is mapped to all configured links even if the configuration of the specific link is released.

[0371] Also, when the (Re)Association request frame exchanged for reconfiguration includes a TID-to-Link mapping element, based on the information indicated by the TID-to-Link mapping element, the TID mapped to the link whose configuration has been released may be mapped to other configured links.

[0372] That is, after the MLD performs reconfiguration, if the specific TID is not explicitly mapped to any setting link, the specific TID may be changed (configured) to a state where it is mapped to all setting links (the default link mapping state of the TID).

[0373] Alternatively, the MLD can change (configure) the specific TID (the TID that is not mapped to any setting link) to a state where it is mapped to a specific setting link in accordance with a previously agreed-upon method. At this time, the previously agreed-upon method can be various methods, such as a method of changing the mapping to the setting link with the smallest Link ID index, or a method of changing the mapping to the most recently configured link (excluding the released link).

[0374] As an exception, when a specific link is additionally set through reconfiguration while another link is unset (i.e., when the number of set links does not change and only the Link ID of the set links is changed), the TID mapped to the link that has been unset may be automatically mapped to the link that is additionally set. This may be understood as a TID-to-Link Mapping transition that is only applicable when the (Re)Association request frame exchanged during the reconfiguration does not contain a TID-to-Link mapping element. At this time, when the link additionally set through reconfiguration is a number equal to or greater than 1, and the link whose setting is unset is also a number equal to or greater than 1, a similar TID-to-Link Mapping transition may be applicable. For example, when 2 set links are unset through reconfiguration and 1 link is added (set), the TID mapped to the 2 unset links may be automatically mapped to the 1 added link. As another example, when 1 set link is unset through reconfiguration and 2 links are added (set), the TID mapped to the 1 unset link may be automatically mapped to all of the 2 added links. As yet another example, when 2 set links are unset through reconfiguration and 2 links are added (set), the TID (the sum of the TIDs mapped to the 2 links) mapped to the 2 unset links may be automatically mapped to all of the 2 added links respectively.

[0375] Alternatively, in order to simplify the TID-to-Link mapping management, the MLD that has removed the setup link through reconfiguration must switch to the basic TID-to-Link mapping mode where all TIDs are mapped to all setup links (all TIDs to all setup Links). At this time, the condition for the MLD that has removed the link through the reconfiguration to switch to the basic TID-to-Link mapping mode may be limited to the case where the (Re)Association request frame exchanged for reconfiguration does not contain the TID-to-Link mapping element. That is, when a new TID-to-Link Mapping negotiation has not been executed (completed) together with the reconfiguration, the MLD that has had the link set through the reconfiguration removed must switch to the basic TID-to-Link mapping mode. At this time, the MLD switching to the basic TID-to-Link mapping mode may mean that the TID-to-Link mapping established between the MLDs is released (the negotiated TID-to-Link mapping is torn down). Alternatively, the MLD switching to the basic TID-to-Link mapping mode may mean considering that there is no negotiated TID-to-Link mapping existing for the MLD.

[0376] Therefore, when the (Re)Association request frame sent to remove the link set through reconfiguration does not contain the TID-to-Link mapping element, it can perform a function similar / identical to that of the (Re)Association request frame containing the Tear down element.

[0377] Alternatively, when two MLDs with negotiated TID-to-Link mapping (excluding the basic mode in this case) release the setup link through reconfiguration, they may be compelled to always conduct a new TID-to-Link Mapping negotiation through the (Re)Association request / response frame. That is, the requesting MLD attempting to release the setup link through reconfiguration with the MLD having the negotiated TID-to-Link mapping must always include the TID-to-Link mapping element in the (Re)Association request frame.

[0378] Also, the responding MLD (AP MLD) performing reconfiguration with the MLD having the negotiated TID-to-Link mapping must respond with a (Re)Association response frame that does not contain the TID-to-Link mapping element when accepting the reconfiguration to release the setup link. That is, the responding MLD (AP MLD) must always accept the TID-to-Link mapping request requested together when accepting the reconfiguration to release the setup link.

[0379] FIG. 22 shows an example of a method for managing the TID-to-Link mapping of two MLDs where a setup link is added through reconfiguration.

[0380] Referring to FIG. 22, the AP MLD and the non-AP MLD may perform ML configuration through Link1 and Link2. Also, the AP MLD and the non-AP MLD may be in a state where they have conducted a TID-to-Link Mapping negotiation that maps TID 0 to TID 3 to Link1 and TID 4 to TID 7 to Link2.

[0381] Both the AP MLD and the non-AP MLD may attempt to perform ML configuration through three links by additionally configuring Link3. To this end, the non-AP MLD may attempt to perform reconfiguration through (Re)Association request frames. When the additional configuration for Link3 from the AP MLD is approved (accepted), the AP MLD and the non-AP MLD are changed to the ML configuration state through Links 1 to 3.

[0382] Since Link3 was not a configured link when the AP MLD and the non-AP MLD performed TID-to-Link Mapping negotiation for Links 1 and 2, there is no established negotiated TID Mapping state. Therefore, the newly configured Link3 through reconfiguration is set to the basic TID mapping state (a state where 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 the (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 set to a state where it is not in the basic TID mapping state.

[0384] FIG. 23 shows an example of a method for managing the TID-to-Link mapping of two MLDs for a link whose configuration has been released by reconfiguration.

[0385] Referring to FIG. 23, the AP MLD and the Non-AP MLD are in a state where the ML setting is performed through the first three links. Also, the AP MLD and the Non-AP MLD perform TID-to-Link Mapping negotiation for Link1~Link3, and for both directions, Link1 maps TID 0~TID 2, Link2 maps TID 3~TID 4, and Link3 maps TID 5~TID 7. The Non-AP MLD may change the ML setting and send a (Re)Association request frame to the AP MLD to maintain only the links of Link1 and Link2 and release the configured link of Link3. After receiving the (Re)Association request frame, the AP MLD recognizes that the links for which the Association was requested are only Link1 and Link2, and can respond with a (Re)Association response frame, maintain the settings for Link1 and Link2, and approve to release the setting of Link3. In this case, the reconfiguration procedure of the AP MLD and the non-AP MLD is successfully completed, and the Link3 set between the AP MLD and the non-AP MLD may be released.

[0386] Thus, when the configured link is released between the AP MLD and the non-AP MLD, the TID mapped to the released link (Link3 in FIG. 23) may be changed to a state where it is not mapped to any configured link.

[0387] Therefore, the AP MLD and the non-AP MLD may automatically map the TID 5~TID 7 mapped to Link3 to the links for which the setting is maintained, as in (a) Case1 of FIG. 23. In the case of (a) Case1, even if Link3 is released (after the reconfiguration is completed), Link1 and Link2 remain the configured links as before, so the TID 5~TID 7 mapped to Link3 are automatically mapped to Link1 and Link2.

[0388] Alternatively, the AP MLD and the non-AP MLD may switch to the basic TID-to-Link mapping mode such that the negotiated TID-to-Link mapping is released when the reconfiguration procedure in which Link3 is released is completed, as in Case 2 of (b) in FIG. 23. That is, the two MLDs can perform TID-to-Link mapping management similar to that in which TID-to-Link Mapping Tear down frames are exchanged after reconfiguration.

[0389] FIG. 24 is a flowchart showing an example of a method for mapping a TID and a link according to the present invention.

[0390] Referring to FIG. 24, an MLD, which is a device with one or more logically associated STAs (affiliates), 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, the MLD can send a request frame for mapping between a traffic identifier (TID) and a link to the peer MLD (S24010). At this time, the request frame may include first mapping information for setting 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.

[0392] Before sending a request frame, MLD can receive a frame containing second mapping information for setting the mapping relationship for one or more of the plurality of TIDs and one or more links from the peer MLD. That is, MLD can receive an Unsolicited TID-to-Link mapping response frame containing second mapping information for the mapping relationship preferred for one or more of the one or more TIDs and one or more links from the peer MLD.

[0393] At this time, as described above, it may be implicitly indicated that for the second remaining TIDs excluding the one or more TIDs among the plurality of TIDs, there is no preferred specific mapping relationship or preferred mapping relationship.

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

[0395] After that, MLD can receive a response frame as a response to the request frame from the peer MLD (S24020).

[0396] At this time, for the first remaining TIDs excluding the at least one TID among the plurality of TIDs, whether the previously set mapping relationship with the link is effectively maintained or the basic mapping relationship is applied, the mapping relationship of the first remaining TIDs with a specific link may not be indicated by the first mapping information.

[0397] One of the at least one link may be mapped to one or more of the at least one TID, and the basic mapping relationship can mean a state where the TID is mapped to all links.

[0398] Further, the basic mapping relationship may be applied when the first remaining TID was set with the basic mapping relationship before the transmission of the request frame.

[0399] The request frame may further include transmission direction information indicating a transmission direction for the at least one TID, and the plurality of TIDs may be mapped only to the links for which the setting between the MLD and the peer MLD that transmitted the request frame is completed.

[0400] Also, the response frame can indicate whether the mapping relationship between the at least one TID among the plurality of TIDs and the at least one link is allowed.

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

[0402] At this time, as described with reference to FIGS. 10 to 16, the MLD can receive a management frame from a peer MLD, and the management frame may be transmitted only on the at least one link for which the mapping relationship with the at least one TID is set. Also, the management frame may be transmitted based on the assigned access category (AC), and may be transmitted on 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, since a specific TID is not assigned and there is no TID assignment, the mapping between the TID and the link does not need to be applied. Therefore, the management frame may be sent to all links regardless of the mapping between the TID and the link. At this time, the link to which the management frame is sent may be an enabled link for which the mapping between the TID and the link is set.

[0404] In this case, when the management frame is sent only through the enabled link, there may be a case where the management frame is not sent when there is no enabled link except for the broadcast management frame sent regardless of the link. Therefore, a specific management frame may be sent even when there is no enabled link.

[0405] The above description of the present invention is for illustrative purposes, and those of ordinary skill in the art to which the present invention pertains will be able to understand that it can be easily modified into other specific forms without changing the technical idea and essential features of the present invention. Therefore, the embodiments described above should be understood as being illustrative in every aspect and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, the components described as being distributed may also be implemented in a combined form.

[0406] The scope of the present invention is indicated by the claims described below rather than the above detailed description, and any changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

Description of Reference Numerals

[0407] 100 Station 110 Processor 120 Communication Unit 140 User Interface 150 Display Unit 160 Memory 200 AP 210 Processor 220 Communication Unit 260 Memory 300 Server

Claims

1. A non-access point multi-link device (non-APMLD) of a wireless communication system, comprising: a communication module; a processor configured to control the communication module, wherein the processor transmits a request frame including a traffic identifier (TID)-to-Link Mapping element to an AP MLD, wherein the TID-to-Link Mapping element includes: i) one or more Link Mapping Of TID fields; and ii) a link mapping existence subfield indicating whether each of the one or more Link Mapping Of TID fields exists; each of the one or more Link Mapping Of TID fields indicates a mapping between a corresponding TID among a plurality of TIDs and at least one link among a plurality of links; receives a response frame as a response to the request frame; when all of the at least one first link mapped to a first TID among the plurality of TIDs are deleted by deleting at least one AP belonging to the AP MLD, the first TID among the plurality of TIDs is mapped to all of the remaining valid links of the non-AP MLD except all of the at least one first link; before the at least one AP is deleted from the AP MLD, the first TID is mapped only to the at least one first link; configured as such; non-APMLD.

2. The non-APMLD according to Claim 1, wherein when at least one Link Mapping Of TID field corresponding to at least one TID does not exist within the TID-to-Link Mapping element, the most recent mapping between at least one TID among the plurality of TIDs and one or more links among the plurality of links remains unchanged and is effectively maintained. **Claim 3**: The non-APMLD according to claim 2, wherein when the mapping for the at least one TID fails to be successfully negotiated, the at least one TID is mapped to one or more valid links among the plurality of links. **Claim 4** The request frame further includes transmission direction information indicating a transmission direction for the plurality of TIDs. The non-APMLD according to claim 1, wherein the plurality of links are links for which the setup between the non-AP ML-D and the AP ML-D is completed. **Claim 5** The non-APMLD according to claim 1, wherein the response frame indicates whether the mapping indicated by the TID-to-Link Mapping element is approved. **Claim 6**: The non-APMLD according to claim 1, wherein the invalid link for the non-AP ML-D is used in the request frame and the response frame when i) the request frame is a probe request frame which is a management frame, ii) the response frame is a probe response frame which is a management frame, and iii) the invalid link for the non-AP ML-D exists. **Claim 7** The processor is configured to receive a management frame. The non-APMLD according to claim 1, wherein the management frame is transmitted only on one or more links mapped to the plurality of TIDs. **Claim 8** The non-APMLD according to claim 7, wherein the management frame is transmitted based on an assigned access category (AC). **Claim 9** A method for a non-access point multi-link device (non-APMLD) to transmit a frame in a wireless communication system, comprising: transmitting a request frame for mapping between a traffic identifier (TID) and a link, wherein the request frame includes a traffic identifier (TID)-to-Link Mapping element to an AP ML-D. The TID-to-Link Mapping element includes: i) one or more Link Mapping Of TID fields; and ii) a link mapping existence sub-field indicating whether each of the one or more Link Mapping Of TID fields exists. Each of the one or more Link Mapping Of TID fields represents a mapping between a corresponding TID among a plurality of TIDs and at least one link among a plurality of links. Receiving a response frame as a response to the request frame. When all of the at least one first link mapped to the first TID among the plurality of TIDs are deleted by deleting at least one AP belonging to the AP MLD, the first TID among the plurality of TIDs is mapped to all of the remaining valid links of the non-AP MLD except for all of the at least one first link among the plurality of links. The first TID is mapped only to the at least one first link before the at least one AP is deleted from the AP MLD. Method. **Claim 10**: The method according to claim 9, wherein the latest mapping between at least one TID among the plurality of TIDs and one or more links among the plurality of links remains unchanged and is effectively maintained when at least one Link Mapping Of TID field corresponding to the at least one TID does not exist within the TID-to-Link Mapping element. **Claim 11**: The method according to claim 10, wherein the at least one TID is mapped to one or more valid links among the plurality of links when the mapping for the at least one TID is not successfully negotiated. **Claim 12** The request frame further includes transmission direction information indicating a transmission direction for the plurality of TIDs. The method according to claim 9, wherein the plurality of links are links for which the setup between the non-AP MLD and the AP MLD is completed. **Claim 13** The method according to claim 9, wherein the response frame indicates whether the mapping indicated by the TID-to-Link Mapping element is approved. **Claim 14**: The method according to claim 9, wherein the invalid link for non-AP MLD is such that i) the request frame is a probe request frame which is a management frame, ii) the response frame is a probe response frame which is a management frame, and iii) when the invalid link for non-AP MLD exists, it is used for the request frame and the response frame. **Claim 15** The method according to claim 9, further comprising receiving a management frame, wherein the management frame is transmitted only on one or more links mapped to the plurality of TIDs. **Claim 16** The method according to claim 15, wherein the management frame is transmitted based on an assigned access category (AC).

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