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

Abstract

In a wireless communication system, a non-AP multi-link device (MLD) including a plurality of stations operating on a plurality of links respectively can receive a frame from an AP MLD including a plurality of APs (Access Points) operating on each of the plurality of links, and can perform processing of each of one or more TBTT information fields based on a TBTT information type subfield and the TBTT information length field included in the frame.

Description

Technical Field

[0001] The present invention relates to a wireless communication method using multi-links and a wireless communication terminal using the same.

Background Art

[0002] Recently, as the popularity of mobile devices has expanded, wireless LAN (Local Area Network) technology that can provide fast wireless Internet services to them has been in the spotlight. Wireless LAN 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 at home, in enterprises, or in specific service-providing areas based on wireless communication technology at short distances.

[0003] Since IEEE (Institute of Electrical and Electronics Engineers) 802.11 supported the initial wireless LAN 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 maximum communication speed of 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 uses OFDM (Orthogonal Frequency Division Multiplexing) technology to improve the communication speed up to a maximum of 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance compared to IEEE 802.11b. And IEEE 802.11g uses the same 2.4 GHz band frequency as IEEE 802.11b to achieve a maximum communication speed of 54 Mbps and satisfies backward compatibility, attracting considerable attention, but it is also superior to IEEE 802.11a in terms of communication distance.

[0004] And there is IEEE 802.11n, 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. Also, this standard uses a coding method that transmits multiple copies of overlapping 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 5 GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5 GHz band, the initial 11ac chipset is considered to support operation in the 2.4 GHz band for backward 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 1 Gbps at minimum and the maximum single-link speed can be up to 500 Mbps at minimum. 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 it can only be used 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 have been developed to implement this.

[0007] In order to support new multimedia applications such as high-quality videos and real-time games, a new Wi-Fi standard has been developed to increase the maximum transmission speed. The 7th generation Wi-Fi standard, IEEE 802.11be (Extremely High Throughput, EHT), aims to support a maximum transmission rate of up to 30 Gbps through wider bandwidth, increased spatial streams, and multi-AP cooperation in the 2.4 / 5 / 6 GHz bands. Technologies such as 320 MHz bandwidth, multi-link operation, multi-AP (Multi-Access Point) operation, and hybrid automatic repeat request (HARQ) have been proposed in IEEE 802.11be.

Summary of the Invention

Problems to be Solved by the Invention

[0008] An embodiment of the present invention aims to provide a wireless communication method using multi-link and a wireless communication terminal using the same.

[0009] The technical problems to be solved in the specification are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary knowledge in the technical field to which the present invention pertains from the following description.

Means for Solving the Problems

[0010] A multi-link device (MLD) including a plurality of stations each operating on a plurality of links according to the present invention, the multi-link device includes a transceiver and a processor, the processor receives a frame from an AP of an AP MLD including a plurality of APs (Access points), the frame includes a RNR (Reduced Neighbor Report) element including one or more neighbor AP information fields (Neighbor AP information field) including information related to other APs included in the AP MLD, the neighbor AP information field includes a TBTT (target beacon transmission time) information field type sub-field, a TBTT information length field, and a TBTT information set field (TBTT information set field) including one or more TBTT information fields, performs processing of each of the one or more TBTT information fields based on the TBTT information type sub-field and the TBTT information length field, when the value of the TBTT information type sub-field is "0", each of the one or more TBTT information fields compares the value of the TBTT information length field with a first threshold value and / or a second threshold value, and is processed only up to a first octet value or a second octet value, when the value of the TBTT information type sub-field is "1", each of the one or more TBTT information fields compares the value of the TBTT information length field with a third threshold value, and is processed only up to a third octet value.

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

[0012] In the present invention, when the value of the TBTT information type subfield is "0", the value of the TBTT information length field is less than the first critical value, and is equal to or greater than the second critical value, each of the one or more TBTT information fields is processed only up to the second octet value, and the second octet value is smaller than the first octet value.

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

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

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

[0016] In the present invention, when the value of the TBTT information type subfield is "0", and the value of the TBTT information length field is less than the second critical value, the one or more TBTT information fields are not processed.

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

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

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

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

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

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

[0023] Also, the present invention provides a method including: receiving, from an AP of an AP MLD including a plurality of APs (Access points), a frame, where the frame includes an RNR (Reduced Neighbor Report) element including one or more neighbor AP information fields (Neighbor AP information field) including information related to other APs included in the AP MLD, and the neighbor AP information field includes a TBTT (target beacon transmission time) information field type sub-field, a TBTT information length field, and a TBTT information set field (TBTT information set field) including one or more TBTT information fields; and processing each of the one or more TBTT information fields based on the TBTT information type sub-field and the TBTT information length field, where when the value of the TBTT information type sub-field is "0", each of the one or more TBTT information fields compares the value of the TBTT information length field with a first threshold value and / or a second threshold value, and is processed only up to a first octet value or a second octet value, and when the value of the TBTT information type sub-field is "1", each of the one or more TBTT information fields compares the value of the TBTT information length field with a third threshold value, and is processed only up to a third octet value.

Advantages of the Invention

[0024] One embodiment of the present invention provides a wireless communication method that efficiently uses multi-link and a wireless communication terminal using the same.

[0025] 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 of ordinary skill in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

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[0027] The terms used in this specification are generally selected as widely used general terms as possible considering their functions in the present invention, but these may vary depending on the intentions, conventions of those skilled in the relevant technical field, or the emergence of new technologies. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in such cases, the meaning thereof is described in the corresponding invention description part. Therefore, it is clarified that the terms used in this specification should not be merely the names of the terms, but should be interpreted based on the substantial meanings of the terms and the content throughout this specification.

[0028] Throughout the specification, if a certain configuration is said to be "connected" to another configuration, this includes not only the case where it is "directly connected", but also the case where it is "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 threshold value can be appropriately replaced by "exceeding" or "less than" respectively according to the embodiments.

[0029] Hereinafter, in the present invention, a field and a subfield may be used with the same meaning.

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

[0031] The wireless LAN system includes one or more basic service sets (BSS), and a BSS indicates a set of devices that have successfully synchronized and can communicate with each other. Generally, a BSS is classified into an infrastructure BSS and an independent BSS (IBSS), and FIG. 1 shows the infrastructure BSS among them.

[0032] As shown in FIG. 1, 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.

[0033] A station (STA) is any device that includes a Medium Access Control (MAC) conforming to the provisions of the IEEE 802.11 standard and a physical layer interface for a wireless medium, and in a broad sense 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 in some embodiments further includes a user interface unit, a display unit, etc. 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).

[0034] An access point (AP) is an entity that provides a connection to a distribution system DS via a wireless medium for stations associated with itself. In an infrastructure BSS, in principle, communication between non-AP stations is carried out via the AP. However, if a direct link is set up, direct communication is also possible between non-AP stations. On the other hand, in the present invention, the AP is used as a concept including a PCP (Personal BSS Coordination Point). 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, the AP is also referred to as a base wireless communication terminal. The base wireless communication terminal is used as a term that includes, in a broad sense, an AP, a base station, an eNB (eNodeB), and a transmission point TP. 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.

[0035] 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).

[0036] 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 the embodiment of FIG. 1 are not redundantly described.

[0037] Since the BSS3 shown in FIG. 2 is an independent BSS and does not include an AP, all stations (STA6, STA7) are not connected to the AP. An independent BSS is not allowed to connect to the distribution system and forms a self - contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0038] FIG. 3 is a block diagram showing the configuration of the station 100 according to an embodiment of the present invention. As shown, the station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0039] First, the communication unit 120 transmits and receives wireless signals such as 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 one 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.

[0040] 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.

[0041] 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.

[0042] The processor 110 of the present invention executes various instructions or programs and processes the data inside 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 a part of the configuration 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 signal transmitted and received from the communication unit 120. The processor 110 controls various operations of the radio signal transmission and reception of the station 100 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0043] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separately shown blocks logically distinguish 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, a part of the configuration 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.

[0044] FIG. 4 is a block diagram showing the configuration of AP200 according to an embodiment of the present invention. As shown, 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 descriptions of the parts of the configuration of AP200 that are the same as or corresponding to the configuration of station 100 in FIG. 3 are omitted.

[0045] Referring to FIG. 4, AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 can also include a plurality of communication modules using different frequency bands. That is, AP 200 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, AP 200 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 AP 200. 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.

[0046] 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 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 a 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 conditions of each station. Further, the processor 210 performs connection setting in response to a connection request from a 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 radio signal transmission and reception of the AP200 according to an embodiment of the present invention. A detailed embodiment thereof will be described later.

[0047] FIG. 5 is a diagram schematically showing a process in which a STA sets a link with an AP.

[0048] Referring to FIG. 5, the link between the STA100 and the AP200 is set through three major steps: scanning, authentication, and association. First, the scanning step is a step in which the STA100 acquires connection information of a BSS operated by the AP200. As a method for performing scanning, there are a passive scanning method of acquiring information by using 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 acquires connection information.

[0049] If STA100 successfully receives wireless connection information in the scanning step, it transmits an authentication request (S107a), receives an authentication response from AP200 (S107b), and performs an authentication step. After the authentication step is performed, STA100 transmits an association request (S109a), receives an association response from AP200 (S109b), and performs an association step. In this specification, "association" basically means a wireless connection, but the present invention is not limited thereto, and "association" in a broad sense includes all wireless connections and wired connections.

[0050] 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, server 300 is a server that processes 802.1X-based authentication with STA100, and may be physically connected to AP200 or exist as a separate server.

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

[0052] A terminal performing wireless LAN communication checks whether the channel is busy by performing carrier sensing before transmitting data. If a wireless signal with a certain intensity or higher is detected, the corresponding channel is determined to be in the 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 detection 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 detected from the corresponding channel or a wireless signal with an intensity smaller than the CCA threshold is detected, the channel is determined to be in the idle state.

[0053] When the channel is determined to be in the 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 may be used as a configuration replacing the existing DIFS (DCF IFS). Each terminal waits while decreasing the slot time by the random number determined for the terminal during the interval of the idle state of the channel, and the terminal that has used up the slot time attempts access to the channel. The section in which each terminal performs the backoff procedure in this way is called a contention window section. At this time, the random number may be used as a backoff counter. That is, the initial value of the backoff counter is set by the integer that is the random number obtained by the terminal. When the terminal senses that the channel is idle during the slot time, the terminal can decrement the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be allowed to perform channel access on the channel. Therefore, the transmission of the terminal may be allowed when the channel is idle during the AIFS time and the slot time of the backoff counter.

[0054] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if a terminal attempting access collides with other terminals, the collided terminals are each assigned a new random number and further perform a backoff procedure. According to one embodiment, the newly assigned random number for 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 performs a further backoff procedure in the next contention window period to attempt access. 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.

[0055] <Examples of various PPDU formats>

[0056] FIG. 7 shows an example of various standard-generation PPDU (PLCP Protocol Data Unit) formats. More specifically, FIG. 7(a) shows an example of a legacy PPDU format based on 802.11a / g, FIG. 7(b) shows an example of a HE PPDU format based on 802.11ax, and FIG. 7(c) shows an example 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.

[0057] 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.

[0058] Referring to FIG. 7(b), the preamble of the HE PPDU further includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as the HE preamble. The specific configuration of the HE preamble may be deformed according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0059] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes 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 of the EHT PPDU formats.

[0060] 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 transmitting L-SIG data. Since BPSK and MCS (Modulation and Coding Scheme) with Rate = 1 / 2 are applied to L-SIG, it can contain a total of 24 bits of information. Fig. 7(d) shows the 24-bit information composition of L-SIG.

[0061] Referring to Fig. 7(d), 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 corresponding PPDU. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

[0062] The unit of the L_LENGTH field is bytes. 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, legacy terminals and non-legacy terminals can analyze the L_LENGTH field in different ways.

[0063] First, the method by which a legacy terminal or a non-legacy terminal analyzes the length of a 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 4 us, which is the symbol duration of 64 FFT. Therefore, by adding 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 the symbol duration of one symbol, and then adding 20 us required for the transmission of L-STF, L-LTF, and L-SIG, the length of the corresponding PPDU, i.e., the reception time (RXTIME), is obtained. Expressing this in a mathematical formula is as shown in Equation 1 below.

[0064]

Number

[0065] At this time,

Number

[0066]

Number

[0067] Here, TXTIME is the total transmission time for the PPDU and is as shown in Equation 3 below. At this time, TX represents the transmission time of X.

[0068]

Number

[0069] Referring to the above formula, the length of the PPDU is calculated based on the 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.

[0070] Referring to FIG. 7(e), the U-SIG (Universal SIG) field persists in EHT PPDUs and PPDUs of subsequent generations of wireless LANs and serves to distinguish 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 this, 43 bits excluding the CRC / Tail 9 bits are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0071] The VI bits continue to maintain the current bit configuration in the future, 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 fields. The PHY version field is 3 bits and serves to sequentially distinguish the 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS color means the BSS identifier defined in 11ax and has a value of 6 bits or more. TXOP means the transmit opportunity duration 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 has a value of 7 bits or more.

[0072] The VD field may be composed of signaling information that is only useful for the 11be version of the PPDU, fields that are commonly used in any PPDU format such as the PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a discriminator that differentiates between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDUs, etc. The BW field generally 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 a power of 20 * 2 can be called the basic BW), and various remaining PPDU BWs constituted 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.

[0073] The fields located after the BW field vary depending on the form and format of the PPDU. The MU PPDU and the SU PPDU may be signaled in the same PPDU format. Before the EHT-SIG field, a field for distinguishing between the MU PPDU and the SU PPDU may be located, and additional signaling may be performed for that purpose. Both the SU PPDU and the MU PPDU include 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.

[0074] 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.

[0075] 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 an uncompressed field (e.g., a common field, etc.). 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 RU assigned to each user.

[0076] 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 information on the punctured RUs among the RUs assigned to the STA (e.g., the RU puncturing pattern, etc.). 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, etc. 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.

[0077] The form of the discontinuous channel signaled is restricted, and it 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.

[0078] 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 (when the form in which only the end 20 MHz is punctured is also regarded as discontinuous) by expressing the availability 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.

[0079] The present invention proposes a method for signaling the discontinuous channel form of an 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.

[0080] Also, 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] (d) of FIG. 8 shows an example of the EHT ER SU PPDU format used for single-user transmission to STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission to a wider range of STAs than the EHT SU PPDU described in (a) of FIG. 8, and the U-SIG field may be repeatedly located on the time axis.

[0088] 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 receive the PPDU transmitted from the AP simultaneously. 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 the EHT-SIG-B to the STAs. 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.

[0089] 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 STAs to receive the PPDU. The information of the STAs assigned (or designated) to each divided resource unit may be included in the user specific field of the EHT-SIG-B and transmitted to the STAs. That is, the user specific field can include one or more user fields corresponding to each divided resource unit.

[0090] 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.

[0091] For the sake of convenience of explanation, in this specification, a frame or a MAC frame may be used in the same meaning as an MPDU.

[0092] When a wireless communication device communicates using a plurality of links, the communication efficiency of the wireless communication device can be improved. At this time, a link is a physical path and may be composed of one wireless medium that can be used to transmit an MSDU (MAC service data unit). For example, when the frequency band of any one link is in use by another wireless communication device, the wireless communication device can continue to communicate using another link. In this way, the wireless communication device can usefully use a plurality of channels. Also, when the wireless communication device communicates simultaneously using a plurality of links, the overall throughput can be increased. However, existing wireless LANs are defined on the premise that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using a plurality of links is required. With reference to FIGS. 9 to 26, a wireless communication method of a wireless communication device using a plurality of links will be described. First, with reference to FIG. 9, a specific form of a wireless communication device using a plurality of links will be described.

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

[0094] A multi-link device (MLD) may be defined for the wireless communication method using the plurality of links described above. The multi-link device may refer to a device having one or more affiliated stations. According to a specific embodiment, the multi-link device may refer to a device having two or more affiliated stations. Also, the multi-link device can exchange multi-link elements. The multi-link element includes information regarding one or more stations or one or more links. The multi-link element may include a multi-link setup element described later. At this time, the multi-link device may be a logical entity. Specifically, the multi-link device may have a plurality of affiliated stations. The multi-link device can be called an MLLE (multi-link logical entity) or an MLE (multi-link entity). The multi-link device may have one MAC service access point (medium access control service access point, SAP) up to the logical link control (LLC). Also, the MLD may have one MAC data service.

[0095] The plurality of stations included in the multi-link device can operate on a plurality of links. Also, the plurality of stations included in the multi-link device can operate on a plurality of channels. Specifically, the plurality of stations included in the multi-link device can operate on a plurality of different links or a plurality of different channels from each other. For example, the plurality of stations included in the multi-link device can operate on a plurality of different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0096] The operation of the multi-link device can be referred to as multi-link operation, MLD operation, or multi-band operation. Also, when the station associated with the multi-link device is an AP, the multi-link device can be called an AP MLD. Further, when the station associated with the multi-link device is a non-AP station, the multi-link device can be called a non-AP MLD.

[0097] FIG. 9 shows the operation in which the non-AP MLD communicates with the AP-MLD. Specifically, the non-AP MLD and the AP-MLD communicate using three links each. The AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). The non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) communicates with the first non-AP STA (non-AP STA1) via a first link (Link 1). Also, the second AP (AP2) communicates with the second non-AP STA (non-AP STA2) via a second link (Link 2). Also, the third AP (AP3) communicates with the third non-AP STA (non-AP STA3) via a third link (Link 3).

[0098] Multi-link operation may include a multi-link setup operation. The multi-link setup corresponds to the association operation of the single-link operation described above and may be what should be done first for frame exchange in multi-link. A multi-link device can obtain information necessary for multi-link setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information related to multi-link. At this time, the capability information may include information indicating whether any one of a plurality of devices included in the multi-link device can transmit and at the same time other devices can receive. Also, the capability information may include information regarding the links available for each station included in the MLD. Also, the capability information may include information regarding the channels available for each station included in the MLD.

[0099] The multi-link setup may be set by negotiation between peer stations. Specifically, the multi-link setup may be performed by communication between stations without communication with an AP. Also, the multi-link setup may be set on any one link. For example, even when the first to third links are set by multi-link, the multi-link setup may be performed on the first link.

[0100] Also, a mapping between a TID (traffic identifier) and a link may be set. Specifically, frames corresponding to a specific value of the TID may be exchanged only on a pre-specified link. The mapping between the TID and the link may be set in a directional-based manner. For example, when a plurality of links are set between a first multi-link device and a second multi-link device, the first multi-link device may be set to transmit frames of a first TID on the plurality of links, and the second multi-link device may be set to transmit frames of a second TID on a first link. Also, a basic setting may exist for the mapping between the TID and the link. Specifically, when there is no additional setting in the multi-link setting, the multi-link device can exchange frames corresponding to the TID on each link according to a default setting. At this time, the basic setting may be that all TIDs are exchanged on any one link.

[0101] Specifically describe the TID. The TID is an ID for classifying traffic and data to support QoS (quality of service). Also, the TID may be used or assigned at a layer higher than the MAC layer. Also, the TID may represent a traffic category (TC) or a traffic stream (TS). Also, the TID may be distinguished into 16. For example, the TID may be specified as any one of 0 to 15. According to the access policy, channel access, or medium access method, the TID values used may be specified separately. For example, when EDCA (enhanced distributed channel access) or HCAF (hybrid coordination function contention based channel access) is used, the value of the TID may be assigned in the range of 0 to 7. When EDCA is used, the TID may represent the user priority (UP). At this time, the UP may be specified by the TC or TS. The UP may be assigned at a layer higher than the MAC. Also, when HCCA (HCF controlled channel access) or SPCA is used, the value of the TID may be assigned in the range of 8 to 15. When HCCA or SPCA is used, the TID may represent the TSID. Also, when HEMM or SEMM is used, the value of the TID may be assigned in the range of 8 to 15. When HEMM or SEMM is used, the TID may represent the TSID.

[0102] UP and AC may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. The EDCA parameter or EDCA parameter set is a parameter used in the channel contention of EDCA. The QoS station can guarantee QoS using AC. Also, AC may include AC_BK, AC_BE, AC_VI, and AC_VO. Each of AC_BK, AC_BE, AC_VI, and AC_VO may represent background, best effort, video, and voice. Also, AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. Also, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. Also, UP or TID may be mapped to AC. For example, each of 1, 2, 0, 3, 4, 5, 6, 7 of UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO. Also, each of 1, 2, 0, 3, 4, 5, 6, and 7 of UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate. Also, 1, 2, 0, 3, 4, 5, 6, and 7 of UP or TID may be in descending order of priority. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priorities of AC_BK, AC_BE, AC_VI, and AC_VO may be in descending order. Also, each of AC_BK, AC_BE, AC_VI, and AC_VO may correspond to each of ACI (AC index) 0, 1, 2, 3. Due to such characteristics of TID, the mapping between TID and the link may represent the mapping between AC and the link. Also, the mapping between the link and AC may represent the mapping between TID and the link.

[0103] As described above, a TID may be mapped to each of a plurality of links. The mapping may be such that a link through which traffic corresponding to a specific TID or AC can be exchanged is designated. Also, a TID or AC that can be transmitted in the transmission direction within the link may be designated. As described above, there may be a basic setting for the mapping between the TID and the link. Specifically, when there is no additional setting in the multi-link setting, the multi-link device can exchange frames corresponding to the TID on each link according to the basic (default) setting. At this time, the basic setting may be that all TIDs are exchanged on any one link. At any time, any TID or AC may always be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0104] When a link is mapped to a TID or AC, only a data frame corresponding to the TID or AC mapped to the link on that link may be transmitted. Therefore, when a link is mapped to a TID or AC, a frame that is mapped to the link but does not correspond to the TID or AC is not transmitted on that link. When a link is mapped to a TID or AC, an ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK agreement may be determined based on the mapping between the TID and the link. In still other specific embodiments, the mapping between the TID and the link may be determined based on the block ACK agreement. Specifically, a block ACK agreement may be set for a TID mapped to a specific link.

[0105] By the mapping between the TID and the link described above, QoS may be guaranteed. Specifically, a relatively small number of stations may operate or a link with a good channel state may have a high-priority AC or TID mapped thereto. Also, by the mapping between the TID and the link described above, a station can be made to maintain a power-saving state for a longer period of time.

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

[0107] Referring to FIG. 10, there may be a mapping relationship between a TID and a link as described in FIG. 9. Also, in the present invention, the mapping relationship between a TID and a link can be referred to as TID-to-link mapping, TID-to-link mapping, TID mapping, link mapping, etc. The TID may be a traffic identifier. Also, the TID may be an ID (identifier) for classifying traffic, data, etc. to support QoS (quality of service).

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

[0109] In addition, a mapping relationship may exist between the UP and access categories (ACs). The AC may be a label for providing QoS in EDCA or a label indicating a set of EDCA parameters. The EDCA parameters or the set of EDCA parameters may be those used for channel bonding. The AC may be used in a QoS STA.

[0110] The value of the AC may be set to one of AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may indicate background, best effort, video, and voice, respectively. In addition, AC_BK, AC_BE, AC_VI, and AC_VO can be subdivided. For example, AC_VI may be subdivided into AC_VI primary and AC_VI alternate. Also, AC_VO may be subdivided into AC_VO primary and AC_VO alternate. Also, the UP value or the TID value may be mapped to the AC value. For example, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO, respectively. Or, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate, respectively. Also, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be in order of higher priority. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priorities may increase in the order of AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO may correspond to ACIs (AC indices) 0, 1, 2, 3, respectively.

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

[0112] According to an embodiment of the present invention, there may be a TID mapped to each link of a multi-link. For example, there may be a mapping for which link among a plurality of links allows transmission and reception of a specific TID or a specific AC. Also, such a mapping may be defined individually for each direction of both directions of the link. Also, as described above, there may be a basic (default) setting for the mapping between TID and link. For example, basically, all TIDs may be mapped to a certain link. Also, according to an embodiment, at a specific time, a certain TID or a certain AC may be mapped to at least one link. Also, a management frame or a control frame may be transmitted on all links.

[0113] In the present invention, a data frame corresponding to a TID or an AC mapped to any direction of a link may be transmitted. Also, a data frame corresponding to a TID or an AC not mapped to any direction of a link may not be transmitted.

[0114] According to an embodiment, the TID-to-link mapping may also be applied to an acknowledgment. For example, a block ack agreement may be based on the TID-to-link mapping. Or, the TID-to-link mapping may be based on a block ack agreement. For example, it is possible that there is a block ack agreement for a TID mapped by the TID-to-link.

[0115] It is possible to provide QoS services by performing TID-to-link mapping. For example, by mapping a high-priority AC and TID to a link with good channel conditions or few STAs, it is possible to quickly transmit data for the AC and TID. Or, by performing TID-to-link mapping, it is possible to help the STA of a specific link save power (or enter the doze state).

[0116] Referring to FIG. 10, there may be an AP MLD including AP1 and AP2. Also, there may be a Non-AP MLD including STA1 and STA2. Also, there may be two links, Link1 and Link2, in the AP MLD. AP1 and STA1 may be associated via Link1, and AP2 and STA2 may be associated via Link2.

[0117] Therefore, Link1 may include a link for transmitting from AP1 to STA1 and / or a link for transmitting from STA1 to AP1, and Link2 may include a link for transmitting from AP2 to STA2 and / or a link for transmitting from STA2 to AP2. At this time, each link may have a TID and / or an AC mapped thereto.

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

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

[0120] The operation of MLD to transmit or receive simultaneously (STR; simultaneous transmit and receive; simultaneous transmission and reception) may be restricted, which may be related to the frequency interval between a plurality of links operating in a multi-link.

[0121] Therefore, according to an embodiment of the present invention, when the interval between links is m MHz, it is restricted to transmit or receive simultaneously, and when the interval between links is n MHz for n greater than m, it may not be restricted to transmit or receive simultaneously. This embodiment may be for solving the problem that it is restricted to transmit or receive simultaneously, and redundant explanations may be omitted. Also, this embodiment can be applied to an MLD that does not support STR.

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

[0123] Also, according to an embodiment of the present invention, it is possible to limit performing transmission or channel connection during a period based on period information shared between links. The method of limiting transmission or channel connection may include setting the NAV. Alternatively, the NAV can be reset to resume transmission or channel connection. At this time, the NAV may be an intra-BSS NAV. The intra-BSS NAV may be a NAV set by an intra-BSS frame (or PPDU). That is, an STA belonging to the MLD can set the NAV based on a frame (or PPDU) directed to another STA belonging to the MLD.

[0124] According to an embodiment of the present invention, an inter-link NAV may exist. The inter-link NAV may be a NAV used by STAs of a plurality of links belonging to a certain MLD when operating in a multi-link. For example, transmission on link 2 may not be required based on the inter-link NAV set based on the period information received on link 1. Also, the inter-link NAV can exist or be used for an MLD that cannot perform STR. For example, when the inter-link NAV is set, the MLD that set the inter-link NAV does not have to perform transmission or channel connection on a plurality of links (or all links used by the MLD).

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

[0126] When using the inter-link NAV separately, it may have advantages in situations where the NAV setting is updated compared to the case of not using the inter-link NAV. For example, a situation may occur where it is possible to reset the NAV set by other links. For example, although the inter-link NAV is set based on a certain frame (or PPDU), it may be determined that the frame (or PPDU) is not directed to the same MLD, and it may be possible to reset the set inter-link NAV. Suppose there is an MLD operating on Link 1 and Link 2. The NAV for Link 1 may be set based on the frame received on Link 1. Subsequently, the NAV of Link 1 may be updated based on the frame of Link 2. And when it is no longer necessary to maintain the NAV by Link 2, if the NAV of Link 1 is reset, there is a problem of losing the NAV information set based on the frame received on Link 1. If the inter-link NAV is used together with the NAV for each link, even if the inter-link NAV is reset, the NAV for each link is maintained, and the above problem can be solved.

[0127] Although the setting of the NAV has been taken up in the embodiments of the present invention, the embodiments of the present invention are not limited to this, and are also applicable to instructing to interrupt the channel connection in the physical layer or instructing the channel state to be busy. Also, it is not limited to resetting the NAV, and it is also applicable to instructing to continue the channel connection in the physical layer or instructing the channel state to be idle. At this time, primitives exchanged between the physical layer and the MAC layer may be used. Or, primitives exchanged between one STA of the MLD and other STAs may be used. Or, primitives exchanged between one MAC layer of the MLD and other MAC layers may be used.

[0128] According to an embodiment of the present invention, when a STA belonging to an MLD starts receiving a PPDU, other STAs belonging to the MLD may have to stop channel connection. As described above, the channel connection may be stopped based on the received period information. However, due to the position of the field including the period information or the time required for decoding, etc., there may be a time from when the PPDU starts to be received until the period information is obtained. Therefore, accessing the channel and starting transmission during this time may lead to the above-mentioned problems. Thus, according to an embodiment of the present invention, a STA of an MLD can interrupt the channel connection from the time when other STAs of the MLD start receiving. Also, when it is confirmed that a frame received after other STAs of the MLD start receiving is not directed to the other STAs, the channel connection can be started again.

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

[0130] FIG. 12 is a specific implementation of the description regarding the specific method of the embodiment described in FIG. 11, and duplicate descriptions may be omitted.

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

[0132] According to an embodiment of the present invention, when STA1 starts receiving a frame, STA2 may interrupt the channel connection. Also, when STA1 obtains duration information from the L-SIG, STA2 may maintain the state of interrupting the channel connection. At this time, the state in which STA2 interrupts the channel connection can be determined until the end of the frame received by STA1. Also, when STA1 cannot surely decode the L-SIG (when it is an invalid L-SIG), STA2 can resume the channel connection.

[0133] In addition, STA1 can receive the TXOP duration and the BSS color from the U-SIG of the frame it receives. If the received BSS color indicates that it is intra-BSS or the BSS color is the BSS color corresponding to STA1, the channel connection can be interrupted. As an example, the period during which the channel connection is interrupted at this time may be until the end of the received frame. In this case, after the received frame ends, there is an advantage that the channel connection can be started earlier. As another example, the period during which the channel connection is interrupted at this time may be the TXOP duration. In this case, the period of the channel connection interrupted based on the L-SIG may be updated. In this case, there is an advantage that the sequence following the received frame can be better protected.

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

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

[0136] In addition, although the case of receiving the U-SIG has been described, the same embodiment can also be applied when receiving the HE PPDU or when receiving the HE-SIG-A. For example, the HE-SIG-A may include the TXOP duration and the BSS color, and thus, the operations as described above can be performed.

[0137] In addition, STA1 may receive a STA-ID from the EHT-SIG of the frame it receives. If the received STA-ID is an indicator that STA1 should receive, for example, when the STA-ID indicates STA1, indicates the group to which STA1 belongs, or indicates broadcast, STA2 can maintain the state of interrupting the channel connection.

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

[0139] In addition, although the case of receiving the EHT-SIG has been described, the same embodiment can also be applied when receiving a HE PPDU or when receiving a HE-SIG-B. For example, the HE-SIG-B may include a STA-ID, and thus, the operations as described above can be performed.

[0140] In addition, STA1 may receive the MAC header of the frame it receives. If the RA (receiver address) or DA (destination address) included in the received MAC header indicates the value that STA1 should receive, for example, when the RA or DA indicates STA1, indicates the group to which STA1 belongs, or indicates broadcast, STA2 can maintain the state of interrupting the channel connection. At this time, the period of interrupting the channel access can be obtained based on the period information included in the received MAC header. More specifically, the period of interrupting the channel access can be obtained based on the period information indicated by the Duration / ID field included in the received MAC header.

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

[0142] The channel connection interruption and resumption described in FIG. 12 may operate in the order of decoding as the frame (or PPDU) is received and sequentially decoded at STA1. The decoding order may be based on the PPDU format, frame format, etc. For example, it can be decoded in the order of L-SIG, U-SIG, EHT-SIG, MAC header (in the case of EHT PPDU). Or, it can be decoded in the order of L-SIG, HE-SIG-A, MAC header (in the case of HE SU PPDU, HE TB PPDU). Or, it can be decoded in the order of L-SIG, HE-SIG-A, HE-SIG-B, MAC header (in the case of HE MU PPDU). Or, it can be decoded in the order of L-SIG, MAC header (in the case of 11a / g PPDU).

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

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

[0145] According to an embodiment of the present invention, a STA can classify (or determine) a BSS based on a received frame or a received PPDU. Classifying a BSS may include an operation of classifying whether a received frame or a received PPDU corresponds to the BSS to which the STA that classifies belongs. Or, classifying a BSS can mean an operation of classifying whether a received frame or a received PPDU is transmitted from the BSS to which the STA that classifies belongs. Further, classifying a BSS may include an operation of classifying whether a received frame or a received PPDU corresponds to a BSS to which the STA that classifies does not belong. Or, classifying a BSS can mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the STA that classifies does not belong. Also, classifying a BSS may include an operation of classifying to which BSS a received frame or a received PPDU belongs. Or, classifying a BSS can mean an operation of classifying from which BSS a received frame or a received PPDU is transmitted. According to an embodiment of the present invention, the BSS to which the STA that classifies belongs can be called an intra-BSS. Or, the BSS including the BSS to which the STA that classifies belongs can be called an intra-BSS. Also, a BSS that is not an intra-BSS can be called an inter-BSS. Or, a BSS that is not an intra-BSS may be an inter-BSS or a BSS that is not classified. Or, an inter-BSS may include a BSS that is not classified. Also, a BSS to which the STA that classifies does not belong can be called an inter-BSS.

[0146] According to one embodiment, when it is determined that the received frame or the received PPDU belongs to an intra-BSS or is transmitted from an intra-BSS, the received frame or the received PPDU can be referred to as an intra-BSS frame and an intra-BSS PPDU, respectively. Also, when it is determined that the received frame or the received PPDU belongs to an inter-BSS or is transmitted from an inter-BSS, the received frame or the received PPDU can be referred to as an inter-BSS frame and an inter-BSS PPDU, respectively. Further, a PPDU including an intra-BSS frame may be an intra-BSS PPDU. Also, a PPDU including an inter-BSS frame may be an inter-BSS PPDU.

[0147] According to one embodiment of the present invention, a BSS can be classified based on one or more BSS classification conditions. For example, the BSS can be classified according to whether at least one of the one or more BSS classification conditions is satisfied.

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

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

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

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

[0152] Also, when the Partial AID field of the received PPDU indicates a part of the BSS color, if the received Partial AID field value is the same as the part of the BSS color corresponding to the received STA, the received PPDU can be classified as an intra-BSS PPDU. At this time, a part of the BSS color can be the 4 LSBs of the BSS color. According to another embodiment, the Partial AID field can indicate a part of the BSSID. For example, when the Group ID field included in the VHT-SIG-A field of the VHT PPDU is a preset value (for example, when the Group ID field is set to 0), the Partial AID field can indicate a part of the BSSID. According to one embodiment, when the Partial AID field of the received PPDU indicates a part of the BSSID, if the received Partial AID field value is different from the part of the BSSID corresponding to the received STA, the received PPDU can be classified as an inter-BSS PPDU. Also, when the Partial AID field of the received PPDU indicates a part of the BSSID, if the received Partial AID field value is the same as the part of the BSSID corresponding to the received STA, the received PPDU can be classified as an intra-BSS PPDU. At this time, a part of the BSSID can be the 9 MSBs of the BSSID. Also, the Partial AID field value may be included in the TXVECTOR parameter PARTIAL_AID or the RXVECTOR parameter PARTIAL_AID. Also, the Group ID field value may be included in the TXVECTOR parameter GROUP_ID or the RXVECTOR parameter GROUP_ID.

[0153] The BSS classification condition may include a condition for the AP to receive a PPDU of a previously set condition. For example, the PPDU of the previously set condition may include a downlink PPDU. According to one embodiment, the downlink PPDU may include a VHT MU PPDU. Also, the downlink PPDU may include a PPDU in which the signaling indicating uplink or downlink is set to a previously set value. The signaling indicating uplink or downlink may be included in the signaling field of the HE PPDU. Or, the signaling indicating uplink or downlink may be included in the U-SIG. The U-SIG may be included in the preamble of the EHT PPDU or a PPDU after the EHT standard.

[0154] Also, there may be a case where it cannot be classified into an intra-BSS PPDU or an inter-BSS PPDU. For example, when neither the condition for classifying into the intra-BSS PPDU described above nor the condition for classifying into the inter-BSS PPDU is satisfied, it cannot be classified into the intra-BSS PPDU or the inter-BSS PPDU.

[0155] Also, when classifying the BSS, if the classification results by a plurality of conditions do not match, it is possible to determine the final result according to the previously set conditions. For example, when the result by the condition based on the BSS color and the result by the condition based on the MAC address do not match, the result by the condition based on the MAC address may be prioritized, or the result by the condition based on the MAC address may be determined as the final result. Or, when both the condition for classifying into the intra-BSS PPDU and the condition for classifying into the inter-BSS PPDU are satisfied, it can be classified into the intra-BSS PPDU.

[0156] According to an embodiment of the present invention, the STA can perform operations based on the classified BSS. The operations based on the classified BSS may include intra-PPDU power save operations. The intra-PPDU power save operation may be a power save operation based on the received PPDU. It is possible to perform the intra-PPDU power save operation when the already set conditions are satisfied. The already set conditions may include the conditions for classifying the received PPDU as an intra-BSS PPDU. Also, the already set conditions may include the condition that the intended receiver of the received PPDU is not the STA that received the PPDU. For example, when the ID or address included in the PPDU does not correspond to the STA that received the PPDU, the intended receiver of the PPDU may not be the STA that received the PPDU. The ID may be included in the preamble of the PPDU. For example, the ID may be the STA_ID included in the preamble of the PPDU. Also, the STA_ID may be included in the HE MU PPDU or EHT PPDU. Also, the address may be the MAC address described above. Also, when the signaling indicating whether the received PPDU is an uplink or a downlink indicates an uplink, the intended receiver of the PPDU may not be the STA that received the PPDU. Also, when the settings of the received PPDU are set to those not supported by the STA that received the PPDU, the intended receiver of the PPDU may not be the STA that received the PPDU. The settings of the received PPDU may include the MCS of the PPDU, the number of spatial streams, the channel width, etc. Also, when the settings of the received PPDU are not supported by the STA that received the PPDU, a PHY-RXEND.indication(UnsupportedRate) primitive may be received. Also, when the received PPDU is in the already set format, the intended receiver of the PPDU may not be the STA that received the PPDU. The already set format may include the TB PPDU.The TB PPDU may include a HE TB PPDU and an EHT TB PPDU. Also, the TB PPDU may be a PPDU transmitted as a response to a triggering frame. The triggering frame may include a trigger frame. The triggering frame may include a frame containing triggering information. The triggering information may be included in the MAC header, for example, the A-control field. Also, the triggering information or the information included in the trigger frame may include the length of the responding PPDU, the RU used during response, the PHY configuration used during response, the MAC configuration, etc. The intra-PPDU power-saving operation may be an operation that can enter the doze state until the end of the received PPDU. As yet another example, when it is determined that the intended recipient of the PPDU or frame received by the STA is not the STA, the reception or decoding of the PPDU or frame can be interrupted.

[0157] Operations based on the classified BSS may include operations to set (or update) the NAV. According to one embodiment, a STA can operate one or more NAVs. Also, when a STA receives a PPDU or a frame, it is possible to set the NAV corresponding to the BSS classified based on the received PPDU or the received frame. For example, the intra-BSS NAV may be the NAV corresponding to the intra-BSS PPDU. Also, the basic NAV may be the NAV corresponding to a PPDU that is not an intra-BSS PPDU. Or, the basic NAV may be the NAV corresponding to an inter-BSS PPDU. Also, when setting the NAV based on the received PPDU or the received frame, it is possible to use the duration information included in the received PPDU or the received frame. The duration information may include a TXOP. The TXOP can mean the value included in the TXOP field. The TXOP field may be included in the preamble of the PPDU. For example, the TXOP field may be included in the HE-SIG-A field of the HE PPDU. Or, the TXOP field may be included in the U-SIG field of the EHT PPDU or a PPDU of a standard after EHT. Also, the duration information may be included in the MAC header. For example, the duration information may be included in the Duration / ID field included in the MAC header.

[0158] Operations based on the classified BSS may include spatial reuse operations. Also, operations based on the classified BSS may include channel connection operations. The spatial reuse operation may be a channel connection operation. When a STA receives a PPDU or a frame, if the already set conditions are satisfied, it is possible to perform a spatial reuse operation. The already set conditions may include conditions where the received PPDU or the received frame corresponds to an inter-BSS. Also, the already set conditions may include conditions where the signal strength of the received PPDU or the received frame is smaller than a threshold. For example, the threshold may be variable. Also, the threshold may be a threshold for OBSS PD-based Spatial reuse operations. Also, the threshold may be a value equal to or greater than the CCA threshold. Also, the threshold may be a value based on the power to be transmitted. The spatial reuse operation may include an operation of transmitting a PPDU. Also, the spatial reuse operation may include an operation of resetting the PHY. For example, the operation of resetting the PHY may be an operation of issuing a PHY-CCARESET.request primitive. Also, the spatial reuse operation may include an operation of not setting the NAV based on the received PPDU or the received frame. If, when a STA performs a spatial reuse operation, it may be possible for the STA to transmit a PPDU while the received PPDU or the received frame is being transmitted or received.

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

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

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

[0162] STA4 can receive the PPDU transmitted by STA1 and classify the BSS for this PPDU. Also, since STA4 and STA1 belong to BSS B and BSS A respectively, the PPDU received by STA4 may be classified as an inter-BSS PPDU. Also, the signal strength of the PPDU received by STA4 may be smaller than the threshold value. Therefore, since the PPDU received by STA4 is classified as an inter-BSS PPDU and the signal strength of the PPDU received by STA4 is smaller than the threshold value, STA4 can perform a spatial reuse operation. Therefore, STA4 can perform a channel connection and a backoff procedure and start transmission. For example, it may be possible for STA4 to start transmission when the PPDU transmitted by STA1 has not ended.

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

[0164] Referring to FIG. 14, a certain standard wireless LAN may include the functions of other standard wireless LANs. Or, when it is a certain standard wireless LAN, it may be another standard wireless LAN. Here, the wireless LAN can mean an STA. Further, here, the wireless LAN may mean an MLD including an STA. For example, the wireless LAN standard may include the functions of previous generation standards and additional functions. For example, an HT STA can also be an OFDM PHY STA. Also, in addition to the functions of an OFDM PHY STA, an HT STA can perform additional functions. For example, a VHT STA can also be an HT STA. Also, in addition to the functions of an HT STA, a VHT STA can perform additional functions. For example, an HE STA can also be a VHT STA. Also, in addition to the functions of a VHT STA, an HE STA can perform additional functions. Also, an EHT STA can also be an HE STA. Also, in addition to the functions of an HE STA, an EHT STA can perform additional functions. Also, there may be standards after the EHT standard. In the present invention, the standard after the EHT standard can be called the NEXT standard, and the STA conforming to the NEXT standard can be called the NEXT STA. The NEXT STA can also be an EHT STA. Also, in addition to the functions of an EHT STA, the NEXT STA can perform additional functions.

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

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

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

[0168] Specifically, as shown in FIG. 15, a frame that instructs or triggers multi-user (MU) transmission may be transmitted, and based on such a frame, one or more STAs can transmit or respond to such a frame. At this time, when one or more STAs transmit a response to the frame, based on the frame, one or more STAs can simultaneously and immediately respond, and the response to the frame may start to be transmitted after SIFS from the end of the PPDU containing the frame. For example, when the frame instructs an immediate response, one or more STAs can immediately transmit a response to the frame. A frame that instructs or triggers transmission to one or more STAs may be a trigger frame or a frame that includes information in the MAC header that instructs or triggers uplink transmission to one or more STAs. At this time, the frame may include information (e.g., a TRS control subfield) in the MAC header that triggers or instructs uplink transmission to only one STA.

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

[0170] Frames for instructing or triggering uplink transmission may be transmitted by the AP. When the frame for instructing or triggering uplink transmission is a trigger frame, the response thereto may be transmitted in a trigger-based PPDU (TB PPDU) format. At this time, the TB PPDDU may include, in addition to the HE TB PPDU and EHT TB PPDU described above, a NEXT TB PPDU that may be defined by the following standard.

[0171] The HE TB PPDU may be composed of a preamble, data, and a packet extension (PE). The preamble may sequentially include L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-STF, and HE-LTF.

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

[0173] Frames for instructing or triggering the transmission of a PPDU to one or more STAs may include information necessary for one or more STAs to transmit a TB PPDU. For example, when the type subfield included in the frame is "01" (B3 B2) and the subtype subfield is "0010" (B7 B6 B5 B4), a frame including such type and subtype subfields may be a trigger frame that is a control frame.

[0174] If, when responses to a TB PPDU are indicated or triggered for a plurality of STAs, the formats of the PPDUs to be responded to by the plurality of STAs are different from each other, there may arise a problem that it is difficult for the AP that indicated or triggered the responses to receive the PPDUs that are the responses transmitted from the plurality of STAs. Or, if the information included in the preambles of the PPDUs to be responded to by the plurality of STAs is different from each other depending on the format, there may arise a problem that it is difficult for the AP that indicated or triggered the responses to receive the PPDUs that are the responses transmitted from the plurality of STAs.

[0175] Therefore, in order to solve such problems, when a plurality of STAs respond to an AP's frame, the format of the PPDU to be responded to and / or the type of information included in the preamble of the PPDU may be set to be the same. For example, when a plurality of STAs transmit a HE TB PPDU as a response to an AP's frame, the AP may transmit information so that the information included in the L-STF, L-LTF, L-SIG, RL-SIG, and HE-SIG-A is the same so that the preamble transmitted by the plurality of STAs can be successfully received by the AP, or an agreement may be defined for the information included in the HE TB PPDU. However, if the TB PPDU formats are different from each other when HE TB PPDUs, EHT TB PPDUs, and NEXT TB PPDUs are simultaneously transmitted in an overlapping subband, there may arise a problem that it is difficult for the AP to receive them.

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

[0177] As shown in FIG. 15, when AP transmits a frame for scheduling the transmission of a TB PPDU to a HE STA and an EHT STA, and instructs or triggers the transmission of the TB PPDU using the frame, there may be no exact instruction or protocol for the TB PPDU format. In this case, the HE STA transmits a HE TB PPDU as a response to the frame, and the EHT STA can respond with an EHT TB PPDU or a HE TB PPDU. In this case, the AP may have difficulty receiving the TB PPDUs transmitted by these STAs. The AP may not be able to successfully receive TB PPDUs from multiple STAs. Even though the transmission was not successful, the medium may be occupied, resulting in a problem where the transmission opportunities of other STAs are reduced.

[0178] Hereinafter, in the present invention, instructing an STA may mean instructing a response from the STA, and trigger and instruct may be used with the same meaning.

[0179] Also, the HE trigger frame, the EHT trigger frame, and the NEXT trigger frame may each be a trigger frame defined by the HE, EHT, and NEXT standards, respectively. Also, in the present invention, the HE TRS, the EHT TRS, and the NEXT TRS may each be a TRS defined by the HE, EHT, and NEXT standards, respectively.

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

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

[0182] Referring to FIG. 16(a), as a trigger MAC header, the frame includes a Frame Control field, a Duration field, and an Address field, and may include a common information field and a user information list field. The Address field may include a Resource Allocation (RA) field and a transmitter address (TA) field.

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

[0184] The user information list field may include zero or more user information fields. The user information list field of a trigger frame, excluding a specific type of trigger frame, may include one or more user information fields. FIG. 16(c) shows an example of the user information field.

[0185] Additionally, the trigger frame may further include a Padding field and a Frame Check Sequence (FCS) field. The Padding field may be used to increase the length of the frame to ensure that the STA receiving the trigger frame has enough time to prepare a response to the trigger frame, and may be selectively included in the trigger frame.

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

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

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

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

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

[0191] The information of the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. For example, the Resource Unit (RU) Allocation subfield can indicate the size and location of the RU, etc. At this time, the value of the RU allocation subfield of the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. That is, the RU indicated by the RU allocation subfield of the AID12 subfield may be the RU allocated to the STA indicated by the AUD12 subfield.

[0192] Also, the user information field can indicate the coding method (UL FEC coding type), modulation method (UL HE-MCS, UL DCM), and power (UL Target RSSI), etc. for generating the TB PPDU transmitted as a response to the trigger frame.

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

[0194] Referring to FIG. 17, one STA can selectively transmit PPDUs in different formats based on being indicated by a triggering frame that indicates the transmission of the PPDU.

[0195] Specifically, the EHT STA can selectively transmit not only legacy PPDUs (e.g., HE TB PPDUs), but also EHT TB PPDUs, and the NEXT STA can selectively transmit HE TB PPDUs, EHT TB PPDUs, and / or NEXT TB PPDUs. In this case, STAs to which multiple standards are respectively applied in one frame or one PPDU can be individually scheduled. Since multiple standards are applied to the common resources used by STAs in the wireless LAN together, such a method can be an advantage. For example, HE STAs (HE STAs other than EHT STAs) and EHT STAs can be made to respond with HE TB PPDUs using one frame. That is, the non-AP STA can transmit a triggering frame and instruct the transmission of HE TB PPDUs not only to HE STAs but also to EHT STAs.

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

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

[0198] Also, distinguishing the trigger frame into an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame may have the same meaning as distinguishing the TB PPDU format, which is a response to the trigger frame, into an HE TB PPDU, an EHT TB PPDU, and a NEXT TB PPDU, respectively.

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

[0200] For example, when the Type subfield is 01 (B3 B2) and the Subtype subfield is 0010 (B7 B6 B5 B4), the format of the frame including the Type subfield and the Subtype subfield may be an HE trigger frame. In this case, entries of the Type subfield (2 bits), the Subtype subfield (4 bits), and / or the Control Frame Extension subfield (4 bits) with limited number of bits may need to be further used in the EHT standard and the NEXT standard.

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

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

[0203] At this time, for the variant for determining the format of the PPDU, in addition to the common information field, the user information field may also be further used.

[0204] For example, the trigger frame may be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the trigger type subfield. For example, when the trigger type subfield value is a preset value, the trigger frame may be an HE trigger frame. Also, when the trigger type subfield value is a preset value, the trigger frame may be an EHT trigger frame. When the trigger type subfield value is a preset value, the trigger frame may be a NEXT trigger frame.

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

[0206] According to yet another embodiment, based on the UL length subfield of the trigger frame, it can be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. For example, based on the value obtained by performing a mod (remainder) operation on the UL length subfield value, it can be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. That is, using the value of the UL length subfield, it may be determined whether the format of the PPDU transmitted as a response to the trigger frame is an HE PPDU or an EHT PPDU.

[0207] More specifically, based on the value obtained by performing a modulo (remainder) 3 operation on the UL length subfield value (the remainder when the UL length subfield is divided by 3), it is possible to distinguish whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. For example, when the result of modulo 3 operation on the UL length subfield value is not 0, the trigger frame may be a HE trigger frame. Or, when the result of modulo 3 operation on the UL length subfield value is 1, the trigger frame may be a HE trigger frame. Or, when the result of modulo 3 operation on the UL length subfield value is 0, the trigger frame may not be a HE trigger frame. Or, when the result of modulo 3 operation on the UL length subfield value is 0, the trigger frame may be an EHT trigger frame or a NEXT trigger frame.

[0208] That is, when the value obtained by performing a modulo 3 operation on the value of the UL length subfield of the trigger frame is not 0, the response to the trigger frame may be transmitted as a HE TB PPDU, and when the value obtained by performing a modulo 3 operation on the value of the UL length subfield is 1, the response to the trigger frame may be transmitted as a HE TB PPDU.

[0209] Also, when the value obtained by performing a modulo 3 operation on the value of the UL length subfield of the trigger frame is 0, the format of the PPDU transmitted as a response to the trigger frame may be an EHT TB PPDU.

[0210] In addition, it is possible to distinguish HE trigger frames, EHT trigger frames, and NEXT trigger frames by using such a method together with an additional trigger frame classification method. For example, it is possible to distinguish HE trigger frames, EHT trigger frames, and NEXT trigger frames by using the classification method described in FIG. 16 together.

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

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

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

[0214] At this time, for the variant for determining the format of the PPDU, in addition to the user information field, the common information field may be further used.

[0215] For example, based on the AID12 subfield, it may be classified as a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. According to one embodiment, whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame may be classified according to whether it includes the AID12 subfield of a preset value. Also, in this case, it may be a problem whether the STA indicated by a certain user information field should continuously check the AID12 subfield existing after the user information field to determine the trigger frame format. To solve such a problem, the user information field including the AID12 subfield indicating which trigger frame it is may be present in front of the user information list. Also, to prevent a HE STA that cannot understand such a signaling method from malfunctioning, it is possible that there is a user information field including the AID12 subfield indicating which trigger frame it is after the user information field corresponding to the HE STA.

[0216] Also, at this time, since the information of other sub-fields other than the AID12 sub-field included in the user information field may not be necessary for the TB PPDU response, the sub-field of the user information field including the AID12 sub-field indicating which trigger frame it is can be omitted. That is, the length of the user information field may vary based on the AID12 sub-field. Referring to FIG. 17, the AID12 sub-field can play a role in indicating the response TB PPDU format. For example, when the AID12 sub-field has a preset value, the response to the trigger frame including the AID12 sub-field set to the preset value may be an EHT TB PPDU. For example, when the AID12 sub-field value is 2047, the response to the trigger frame including the AID12 sub-field may be an EHT TB PPDU. Also, when the AID12 sub-field has a preset value, the response to the trigger frame including the AID12 sub-field set to the preset value may be a NEXT TB PPDU. For example, when the AID12 sub-field value is 2048, the response to the trigger frame including the AID12 sub-field may be a NEXT TB PPDU.

[0217] According to still other embodiments, when responding based on the user information field existing at the already set position from the AID12 subfield of the already set value, it is possible to respond in the TB PPDU format corresponding to the already set value. For example, when responding based on the user information field existing after the AID12 subfield of the already set value, it is possible to respond in the TB PPDU format corresponding to the already set value. If there are multiple values indicating the TB PPDU format, when responding based on the user information field existing after both the already set value 1 and the already set value 2, among the TB PPDU format corresponding to the already set value 1 and the TB PPDU format corresponding to the already set value 2, it is possible to respond in the TB PPDU format according to the already set priority order. Referring to FIG. 17, when responding based on the user information field existing after the AID12 subfield set to 2047, it is possible to respond with an EHT TB PPDU. Also, when responding based on the user information field existing after the AID12 subfield set to 2048, it is possible to respond with a NEXT TB PPDU. Also, when responding based on the user information field existing after both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it is possible to respond with a NEXT TB PPDU. Also, when responding based on the user information field existing before both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it is possible to respond with a HE TB PPDU.

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

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

[0220] According to an embodiment of the present invention, it is possible to classify HE trigger frames, EHT trigger frames, and NEXT trigger frames by combining a plurality of trigger frame classification methods described in the present invention. In addition, the content described in the present invention regarding trigger frames is not limited to the above, and is also applicable to TRS.

[0221] As still another example of the present invention, the AP may not be able to simultaneously instruct the transmission of the EHT PPDU and the HE PPDU using a trigger frame. That is, the EHT AP cannot transmit a trigger frame that simultaneously instructs the HE TB PPDU and the EHT TB PPDU, and can only instruct one PPDU format.

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

[0223] As described above, in addition to the trigger frame, the transmission of the TB PPDU can also be instructed by the TRS. Further, the TRS may be included in the HT control field as described above. For example, when the HT control field includes an A-control field, it is possible to include the TRS. The TRS can be transmitted by the TRS control subfield. The A-control field may be in a form in which the control list field continues continuously. Further, the control list field may include the TRS.

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

[0225] The embodiment of FIG. 18 can be a method for solving the problems described in FIGS. 14 to 15. Also, as described above, the embodiments regarding the above trigger frame are also applicable to the TRS. Also, the above-described content can be omitted.

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

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

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

[0229] Referring to FIG. 18, when the TRS is transmitted by a HE PPDU, the TB PPDU that responds to the TRS may be a HE TB PPDU. Also, when the TRS is transmitted by an EHT PPDU, the TB PPDU that responds to the TRS may be an EHT TB PPDU. Also, when the TRS is transmitted by a NEXT PPDU, the TB PPDU that responds to the TRS may be a NEXT TB PPDU.

[0230] According to an embodiment of the present invention, based on a PPDU format including a TRS, subfields included in the TRS can be analyzed differently. For example, when the TRS is included in a HE PPDU, the UL HE-MCS subfield (or the subfield related to MCS) included in the TRS can indicate a value corresponding to the HE MCS table. When the TRS is included in an EHT PPDU, the UL HE-MCS subfield (or the subfield related to MCS) included in the TRS can indicate a value corresponding to the EHT MCS table. When the TRS is included in a NEXT PPDU, the UL HE-MCS subfield (or the subfield related to MCS) included in the TRS can indicate a value corresponding to the NEXT MCS table. Also, the RU Allocation subfield may be analyzed differently based on the PPDU format including the TRS.

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

[0232] According to an embodiment of the present invention, a station can operate in a power save (PS) mode. At this time, a station operating in the power save mode may move back and forth between an awake state and a doze state. In the awake state, the station operates with the overall power. Also, in the awake state, the station can transmit and receive. In the doze state, the station's transmission and reception may be restricted. When a frame to be transmitted in the power save mode is buffered in the station, the station can transition to the awake state, and in other cases, it can operate in the doze state. In the power save mode, the station can frequently move back and forth between the awake state and the doze state. In the active mode, the station always maintains a state where it can transmit and receive. That is, in the active mode, the station can always operate in the awake state.

[0233] When the station operates in the power-saving mode in this way, the station in the power-saving state may not be able to receive. Therefore, the AP signals that the traffic to be sent to the station is buffered, and can receive a response thereto from the station and then perform the transmission. For the convenience of explanation, signaling that the traffic sent by the AP to the station is buffered is called traffic cindication. Also, the signaling for traffic cindication is called traffic indication signaling. The traffic indication between the AP and the station may be performed as follows. In this specification, the traffic may include any one of a frame, a BU, an MSDU, and an MPDU.

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

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

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

[0237] The AP can send a DTIM (delivery TIM) before sending group address traffic or broadcast traffic. The DTIM is a type of TIM that indicates whether group address traffic and broadcast traffic are buffered at the AP. A beacon frame containing the DTIM can be called a DTIM beacon frame. When the received DTIM at the station indicates that group traffic for the group including the station is to be sent, the station can send signaling to the AP indicating that it will receive the group traffic.

[0238] A station that has received traffic indication signaling can send signaling to induce (retrieve) transmissions to the station. At this time, the signaling to induce (retrieve) transmissions to the station may be at least one of a PS-Poll frame or a U-APSD trigger frame. The AP that has received the signaling to induce (retrieve) transmissions to the station sends the buffered traffic to the station.

[0239] In FIG. 19, the first AP (AP1) includes a TIM in the beacon frame and sends the beacon frame every TBTT. The TIM sent by the first AP (AP1) indicates that traffic for the first station (STA1) is buffered. The first station (STA1) sends a PS-Poll frame and maintains an awake state to receive the traffic. The first AP (AP1) sends the buffered traffic (Data to STA1) to the first station (STA1). The first station (STA1) may receive the buffered traffic and enter a power-saving state. Also, the first station (STA1) may maintain an awake state at the next TIM transmission.

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

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

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

[0243] The Element ID subfield indicates the ID of the element in which the Element ID subfield is included.

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

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

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

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

[0248] Each bit of the Partial Virtual Bitmap field indicates whether the traffic sent to the station with the AID corresponding to each bit is buffered at the AP that transmits the TIM. When the value of a bit in the Partial Virtual Bitmap field is 1, it can indicate that the traffic sent to the station with the AID corresponding to the bit in the Partial Virtual Bitmap field is buffered at the AP that transmits the TIM. When the value of a bit in the Partial Virtual Bitmap field is 0, it can indicate that the traffic sent to the station with the AID corresponding to the bit in the Partial Virtual Bitmap field is not buffered at the AP that transmits the TIM. Therefore, when the value of a bit in the Partial Virtual Bitmap field is 1, the station that receives the TIM can determine that the traffic sent to the station with the AID corresponding to the bit in the Partial Virtual Bitmap field is buffered at the AP that transmits the TIM. When the value of a bit in the Partial Virtual Bitmap field is 0, the station that receives the TIM can determine that the traffic sent to the station with the AID corresponding to the bit in the Partial Virtual Bitmap field is not buffered at the AP that transmits the TIM. Also, the station that receives the TIM can determine that the traffic sent to the station with an AID not indicated by the Partial Virtual Bitmap is not buffered at the AP that transmits the TIM.

[0249] The TIM element may include a Traffic indication virtual bitmap subfield. At this time, the number of bits in the Traffic indication virtual bitmap subfield can indicate the AID of the station corresponding to the bit. Specifically, a bit with the bit number n in the Traffic indication virtual bitmap subfield indicates whether a frame to be transmitted to a station with AID n is buffered in the AP that transmits the TIM element. Specifically, when the bit number of a bit in the Traffic indication virtual bitmap subfield is N, the bit can indicate whether traffic to be transmitted to a station with AID N or a group with Group ID N is buffered in the AP that transmitted the TIM. The TIM may include a Partial Virtual Bitmap subfield instead of the Traffic indication virtual bitmap subfield. The Partial Virtual Bitmap subfield is obtained by omitting consecutive bits with a value of 0 in the Traffic indication virtual bitmap subfield. The Partial Virtual Bitmap subfield may be one in which the first consecutive bits or the last consecutive bits of a set of consecutive bits with a value of 0 in the Traffic indication virtual bitmap subfield are omitted. Specifically, the Partial Virtual Bitmap subfield may be the bits from octet number N1 to N2 in the Traffic indication virtual bitmap subfield. N1 may be the largest even number such that all bits from bit number 1 to (N1 * 8 - 1) are 0 in the Traffic indication virtual bitmap subfield.N2 may be the smallest number such that all bits from bit number (N2 + 1)*8 to 2007 are 0 in the Traffic indication virtual bitmap subfield. This may be a way to configure the Partial Virtual Bitmap subfield when multiple BSSID sets are not supported, i.e., when dot11MultiBSSIDImplemented is false. In this specification, the bit number n of a bitmap or subfield represents the (n + 1)-th bit among the bits of the bitmap or subfield.

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

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

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

[0253] When the maximum number of BSSIDs that a multiple BSSID set can have is n, the bits from bitmap number 1 to bitmap number (2^n - 1) in the Traffic indication virtual bitmap subfield can indicate whether frames are buffered at the AP that transmits the TIM element for a group address frame. At this time, the group address frame may be a frame buffered at the AP corresponding to the nontransmitted BSSID. Therefore, the group address frame is a group address frame of the AP or BSS corresponding to the nontransmitted BSSID. Each of the bits from bitmap number 1 to bitmap number (2^n - 1) in the Traffic indication virtual bitmap subfield can indicate whether a frame is buffered at the AP corresponding to each bit. At this time, the bits in the Traffic indication virtual bitmap subfield whose bitmap number is greater than (2^n - 1) indicate whether frames transmitted to the station with AID n are buffered at the AP that transmits the TIM element. Therefore, the AP does not have to allocate numbers from 1 to (2^n - 1) as AIDs. In such an embodiment, the bits corresponding to the inactive nontransmitted BSSIDs may be set as reserved bits. At this time, the value of the reserved bits may be set to 0. Also, the AP can allocate a number equal to or greater than 2^n as the AID of the station. At this time, the AP can allocate any value from 2^n to 2007 as the AID of the station. The EHT AP does not have to allocate 2007 as the AID. The range that can be allocated as the AID is called the AID space. The transmitted BSSID and the nontransmitted BSSID can share one AID space. In a specific embodiment, the EHT AP does not have to allocate 2007 as the AID of the station.

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

[0255] The method of configuring the sub-fields of the Partial virtual bitmap will be described. The method of configuring the sub-fields of the Partial virtual bitmap may vary depending on the multiple BSSID set related functions of the AP that transmits the TIM element. Non-S1G APs can configure the sub-fields of the Partial virtual bitmap by Method A or Method B. Also, S1G APs can configure the sub-fields of the Partial virtual bitmap by Method C. Any of non-HT APs, HT APs, VHT APs, HE APs, and EHT APs may be non-S1G APs. S1G AP refers to an AP that operates in a frequency band of 1 GHz or less, and non-S1G AP refers to an AP that operates in a frequency band greater than 1 GHz.

[0256] First, Method A will be described. The sub-fields of the Partial virtual bitmap may be composed of bits from octet number 0 to N2 of the Traffic indication virtual bitmap. N2 is the smallest number among the numbers that satisfy the condition that the values of the bits from (N2 + 1)*8 to 2007 in the Traffic indication virtual bitmap are all 0. If there is no N2 that satisfies this condition, N2 is 250. In Method A, the value of the Bitmap Offset field is 0. Also, the value of the Length field is N2 + 4.

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

[0258] When there is no individually addressed frame buffered in any of the BSSs corresponding to the transmitted BSSID and the non-transmitted BSSID, and there is a group addressed frame buffered in one or more BSSs, the subfield of the Partial virtual bitmap may be composed of bits from octet number 0 to (N0 - 1). N0 is the largest positive integer that satisfies (N0 * 8 - 2^n) < 8.

[0259] It may be necessary to indicate the traffic buffered in each of the multi-links in which the multi-link device operates. This will be described with reference to FIGS. 13 to 18.

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

[0261] APs operating in one multi-link device can share the AID space. Specifically, one multi-link device may have one AID space. At this time, when indicating the frame buffered in the AP by the TIM element described in FIG. 20, it may be difficult for the station to determine which link the frame is buffered in. A traffic indication signaling method for solving this problem is required. Specifically, the multi-link device can perform traffic indication signaling for each link. In a specific embodiment, the multi-link device can perform traffic indication signaling for each of the stations belonging to the multi-link device. The TIM element transmitted by the multi-link device can indicate whether there is a frame buffered in each of the multi-links in which the multi-link device operates. At this time, the TIM element transmitted by the multi-link device is called a Multi-Link Traffic element.

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

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

[0264] The Element ID subfield is a 1-octet field and indicates the ID of the element that includes the Element ID subfield.

[0265] The Length subfield is a 1-octet field and indicates the length of the element that includes the Length subfield. Specifically, the Length subfield can indicate the length of the element excluding the Element ID subfield and the Length subfield from the element.

[0266] The Element ID Extension subfield is a 1-octet field and indicates a value that combines with the value of the Element ID subfield that includes the Element ID Extension subfield to identify the element.

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

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

[0269] When the value of the Bitmap Size field is m, the size of the Per-Link Traffic Indication Bitmap subfield is m + 1 bits. When the TID-to-link mapping negotiation is successfully performed, the bits of the Per-Link Traffic Indication Bitmap subfield indicate whether the traffic sent to the non-AP station operating on the link corresponding to the bit is buffered. Specifically, when the value of the bit of the Per-Link Traffic Indication Bitmap subfield is 1, the bit of the Per-Link Traffic Indication Bitmap subfield can indicate that the traffic sent to the non-AP station operating on the link corresponding to the bit is buffered. When the value of the bit of the Per-Link Traffic Indication Bitmap subfield is 0, the bit of the Per-Link Traffic Indication Bitmap subfield can indicate that the traffic sent to the non-AP station operating on the link corresponding to the bit is not buffered. When the TID-to-link mapping is the default mapping, the bits of the Per-Link Traffic Indication Bitmap subfield can indicate whether to recommend requesting (retrieving) the transmission of the traffic buffered on the link corresponding to the bit. Specifically, when the value of the bit of the Per-Link Traffic Indication Bitmap subfield is 1, the bit of the Per-Link Traffic Indication Bitmap subfield can indicate that it is recommended to request the transmission of the traffic buffered on the link corresponding to the bit. When the TID-to-link mapping of a certain link corresponds to the default mapping, the uplink transmission and downlink transmission performed on the link may be performed without TID restriction. Also, the default mapping is applied to the links where the TID-to-link mapping negotiation has not been successfully performed.Therefore, if the TID-to-link mapping negotiation is successfully conducted, it can indicate the case where the TID-to-link mapping negotiation is successfully conducted and all TIDs are not mapped to all links.

[0270] The bits of the Per-Link Traffic Indication Bitmap subfield are mapped to a link by the bit number of the bit. Specifically, the bit corresponding to the bit number n in the Per-Link Traffic Indication Bitmap subfield may be mapped to the link with the link ID n. Also, the Per-Link Traffic Indication List subfield may include a padding field. Thereby, the Per-Link Traffic Indication List subfield may have a length in octet units. The padding field may have a length between 0 bits and 7 bits.

[0271] The AP multi-link device can transmit a frame including both the Multi-Link Traffic element and the TIM element. At this time, the frame may be a beacon frame. Referring to FIG. 14, a method for the AP multi-link device to signal the traffic buffered in the AP multi-link device using the Multi-Link Traffic element and the TIM element will be described.

[0272] FIG. 22 shows a method for the Partial Virtual Bitmap subfield of the Multi-Link Traffic element and the TIM element according to an embodiment of the present invention to signal the traffic buffered in the AP multi-link device.

[0273] The bit corresponding to the non-AP multi-link device in the Partial Virtual Bitmap subfield of the TIM element or the Traffic indication virtual bitmap transmitted by the AP multi-link device may be set to 1. At this time, the non-AP multi-link device can parse the Multi-Link Traffic element. The non-AP multi-link device recommends whether to request the retrieval of the traffic buffered on which link by the non-AP multi-link device, or can determine on which link the traffic is buffered by the non-AP multi-link device, based on the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device in the Multi-Link Traffic element. As described in FIG. 21, when the TID-to-link mapping negotiation is successfully performed, the non-AP multi-link device can determine whether the traffic transmitted to the station of the non-AP multi-link device operating on the link corresponding to the bit is buffered, based on the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device. Also, when the TID-to-link mapping is the default mapping, the non-AP multi-link device can indicate whether to recommend that the AP multi-link device request the transmission of the traffic buffered on the link corresponding to the bit, based on the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device.

[0274] The non-AP multi-link device can request the AP multi-link device to transmit the traffic buffered on the link corresponding to the bit set to 1 among the bits of the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device. Specifically, when the TID-to-link mapping negotiation is successfully performed, the non-AP multi-link device can request the AP multi-link device to transmit the traffic buffered on the link corresponding to the bit set to 1 among the bits of the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device. When the TID-to-link mapping is the default mapping, the non-AP multi-link device can request the AP multi-link device to transmit the traffic buffered on one or more links including the link corresponding to the bit set to 1 among the bits of the Per-Link Traffic Indication Bitmap subfield corresponding to the non-AP multi-link device. In such an embodiment, the non-AP multi-link device can send a U-APSD trigger frame or a PS-Poll frame to request the AP multi-link device to transmit the buffered traffic. When receiving a request for transmitting the buffered traffic, the AP multi-link device can transmit the buffered traffic to the non-AP multi-link device. Also, when receiving a request for transmitting the buffered traffic, the AP multi-link device can transmit a QoS Null frame instead of the buffered traffic.

[0275] In the embodiment of FIG. 22, a legacy station before EHT or a station with TID-to-link mapping set to the default mapping was assigned a value smaller than K as the AID value. A non-AP station for which negotiation regarding TID-to-link mapping was successfully performed was assigned a value equal to or greater than K as the AID value. In the Traffic indication virtual bitmap of FIG. 22, all bits smaller than the bit number (N - 1)*8 are set to 0. Therefore, the AP multi-link device does not buffer traffic for stations with an AID smaller than (N - 1)*8. At least one of the bits corresponding to bits with a bit number of (N - 1)*8 or more is set to 1. N - 1 is an even number, and the N*8 value is the k value. Therefore, the Partial Virtual Bitmap subfield starts from and includes the bit number (N - 1)*8 of the Traffic indication virtual bitmap. At this time, the value of the Bitmap Offset subfield of the Partial Virtual Bitmap subfield is set to (N - 1) / 2. Also, among the bits of the Partial Virtual Bitmap subfield, the bits corresponding to AIDs of (N - 1)*8, (N - 1)*8 + 2, (N - 1)*8 + 3, k, k + 2, and k + 3 are set to 1.

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

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

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

[0279] However, it may not be guaranteed that the AIDs of non-AP multi-link devices connected to the AP multi-link device are continuously assigned. Also, the AID between the AIDs of non-AP multi-link devices may be assigned to the AID of a non-AP station not included in the multi-link device. At this time, it is difficult for the non-AP multi-link device to determine which AID belongs to a station not included in the non-AP multi-link device. Therefore, when the Multi-Link Traffic element does not include the Per-Link Traffic Bitmap subfield for stations not included in the non-AP multi-link device, the non-AP multi-link device may have difficulty parsing the Per-Link Traffic Bitmap subfield. For example, in the embodiment of FIG. 14, AID K+1 is assigned to a non-AP multi-link device, and the value of the bit corresponding to AID K+1 in the Partial Virtual Bitmap subfield of the TIM element may be 1. At this time, the non-AP multi-link device with AID K+2 or K+3 cannot determine which of the three Per-Link Traffic Bitmap subfields is the Per-Link Traffic Bitmap subfield for the non-AP multi-link device. Therefore, a method for setting the Multi-Link Traffic element to solve this problem is required. This will be described through FIG. 15.

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

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

[0282] At this time, regardless of whether the station indicated by the buffered traffic belongs to a station belonging to the multi-link device, corresponds to a non-AP multi-link device, or to which AP or BSS it belongs, the AP multi-link device can include, in the Multi-Link Traffic element, a Per-Link Traffic Bitmap subfield for all stations indicated by the buffered traffic. Which AP or BSS the station indicated by the buffered traffic belongs to can indicate whether the station indicated by the buffered traffic belongs to a multiple BSSID set.

[0283] The AP multi-link device can include, in the Multi-Link Traffic element, the Per-Link Traffic Bitmap sub-fields as many as the number of stations to which the buffered traffic is directed. A method for setting the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device by the AP multi-link device will be described.

[0284] The AP multi-link device can set all the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device to 0. That is, the AP multi-link device can set the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device to the reserved field. In yet another specific embodiment, the AP multi-link device can set the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device to an arbitrary value. In yet another specific embodiment, the AP multi-link device can set the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device to 1. At this time, the non-AP multi-link device can ignore the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device. In yet another specific embodiment, the AP multi-link device can set the bit values of the Per-Link Traffic Bitmap sub-field corresponding to a station that does not belong to the multi-link device to 1. In yet another specific embodiment, the AP multi-link device can set the bit values corresponding to the link on which the station that does not belong to the multi-link device operates among the bits of the Per-Link Traffic Bitmap sub-field to 1 and set the values of the remaining bits to 0.

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

[0286] The AID Offset subfield of the Multi-Link Traffic element can indicate the bits after all the bits corresponding to the Group ID and the group address frame in the bits of the Traffic indication virtual bitmap and the bits of the Partial Virtual Bitmap subfield. At this time, the Group Id may include those with an AID value of 0. Also, the Group ID may include the bit numbers of the Traffic indication virtual bitmap corresponding to the multiple BSSID sets, that is, the AIDs corresponding to the bit numbers. Also, the Group ID may include the bit numbers of the Traffic indication virtual bitmap corresponding to the transmitted BSSID and the nontransmitted BSSID, that is, the AIDs corresponding to the bit numbers. When the maximum number of possible BSSIDs in the multiple BSSID sets is 2^n, the Group ID may include values corresponding to AIDs 0 to (2^n - 1). The AID Offset subfield can indicate the values after the values corresponding to AIDs 0 to (2^n - 1) when the multiple BSSID sets are used and the maximum number of possible BSSIDs in the multiple BSSID sets is 2^n. Such a setting of the AID Offset field is because the group address frame is not limited to being transmitted on a specific link, so it doesn't make much sense to signal link by link.

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

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

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

[0290] The link set in which the AP multi-link device operates may be different from the link set in which the non-AP multi-link device communicating with the AP multi-link device operates. For example, the AP multi-link device may communicate with the first non-AP multi-link device over the first to third links, and the AP multi-link device may communicate with the second non-AP multi-link device over the first and second links. At this time, the method of setting the Per-Link Traffic Bitmap subfield of the Multi-Link Traffic element may become a problem.

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

[0292] Problems may arise with the method of setting the values of the bits in the Per-Link Traffic Indication Bitmap subfield corresponding to links not set by the AP multi-link device and links not set by the non-AP multi-link device corresponding to the Per-Link Traffic Indication Bitmap subfield. For the sake of convenience of explanation, the bits in the Per-Link Traffic Indication Bitmap subfield corresponding to links not set by the AP multi-link device and links not set by the non-AP multi-link device corresponding to the Per-Link Traffic Indication Bitmap subfield are referred to as no-link bits. The AP multi-link device can set the value of the no-link bit to a pre-specified value. Therefore, the AP multi-link device can set the bits in the Per-Link Traffic Indication Bitmap subfield corresponding to links not set by the AP multi-link device or the non-AP multi-link device to a pre-specified value. At this time, the pre-specified value may be 0. In still other specific embodiments, the AP multi-link device can set the value of the no-link bit to any value. At this time, the non-AP station can ignore the value of the no-link bit.

[0293] Also, the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a disabled link may be set to reserved. Specifically, the value of the bit in the Per-Link Traffic Indication Bitmap subfield corresponding to a disabled link may be set to 0. At this time, the disabled link may be a link where uplink and downlink transmissions are aborted on that link. Specifically, the disabled link may be a link where uplink and downlink transmissions of the individual address frame are aborted. At this time, the non-AP station can ignore the value of the no-disabled bit.

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

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

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

[0297] FIG. 25 shows signaling related to the Multi-Link element and MediumSyncDelay according to an embodiment of the present invention.

[0298] The multi-link device can perform multi-link discovery and multi-link setup using multi-link elements. At this time, the multi-link elements may be included in the management frame. Specifically, the multi-link elements may be included in at least any one of a beacon frame, a probe request frame, a probe response frame, an authentication frame, an association request frame, an association response frame, a reassociation request frame, and a reassociation response frame.

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

[0300] The Common Info subfield may include information regarding multiple links or all links. The Common Info subfield may include information that is commonly required or commonly applied to multiple links or all links. The Link Info subfield may include information regarding the link corresponding to the Link Info subfield.

[0301] The information associated with MediumSyncDelay represents the value set for the duration of MediumSyncDelay and may have a default value. In certain situations, the multi-link device can initialize the duration of MediumSyncDelay to a base value. Also, when the multi-link device (non-AP multi-link device) fails to receive the information associated with MediumSyncDelay from the peer multi-link device (AP multi-link device), the multi-link device can set the duration of MediumSyncDelay to the default value. When the multi-link device (non-AP multi-link device) receives the information associated with MediumSyncDelay from the peer multi-link device (AP multi-link device), the duration of MediumSyncDelay can be set to the value indicated by the received information associated with MediumSyncDelay.

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

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

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

[0305] The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX. That is, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate the maximum number of transmission attempts that a station can make to transmit while the MediumSyncDelay is applied. The Medium Synchronization Maximum Number Of TXOPs subfield may be a 4-bit field. In a specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be MSD_TXOP_MAX. In yet another specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be (MSD_TXOP_MAX + 1). In yet another specific embodiment, the value of the Medium Synchronization Maximum Number Of TXOPs subfield may be (MSD_TXOP_MAX - 1). Such embodiments may be applicable when the value of the Medium Synchronization Maximum Number Of TXOPs subfield is not set to the maximum value. If the value of the Medium Synchronization Maximum Number Of TXOPs subfield is set to the maximum value, for example, 15 when the Medium Synchronization Maximum Number Of TXOPs subfield is a 4-bit field, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate that the station is allowed to attempt transmission without limitation on the number of transmission attempts while the MediumSyncDelay is applied.

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

[0307] In Figure 26, the AP multi-link device includes a first AP (AP 1), a second AP (AP 2), and a third AP (AP 3). The non-AP multi-link device (non-AP MLD) includes a first non-AP station (STA 1), a second non-AP station (STA 2), and a third non-AP station (STA 3). The first AP (AP 1) and the first non-AP station (STA 1) operate on a first link (link1). Also, the second AP (AP 2) and the second non-AP station (STA 2) operate on a second link (link2). Also, the third AP (AP 3) operates on a third link (link3).

[0308] The first AP (AP 1) can send a Reduced Neighbor Report element and signal the presence of the AP multi-link device (AP MLD) and AP multi-link device (AP MLD)-related parameters. The Reduced Neighbor Report element sent by the first AP (AP 1) may include information about the second AP (AP 2) or the third AP (AP 3). The Reduced Neighbor Report element may be included in a beacon frame or a probe response frame.

[0309] Also, the first non-AP station (STA 1) that receives a frame including the Reduced Neighbor Report element can recognize the AP or AP multi-link device indicated by the Reduced Neighbor Report element. At this time, the first non-AP station (STA 1) sends a probe request frame including a Multi-Link element to the first AP (AP 1), and can request the first AP (AP 1) for information about the AP multi-link device (AP MLD) or the multi-link on which the AP multi-link device (AP MLD) operates. At this time, the Multi-Link element may include information about the non-AP multi-link device or information about the AP included in the non-AP multi-link device.

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

[0311] The first non-AP station (STA 1) can send an association request frame or a reassociation request frame to the first AP (AP 1). The association request frame and the reassociation request frame may include a Multi-Link element. At this time, the Multi-Link element may include information about the link that the non-AP multi-link device intends to perform a multi-link setup on. For example, in FIG. 25, the Multi-Link element may include information about the first link (link1) and the second link (link2).

[0312] The first AP (AP 1) can send an association response frame or a reassociation response frame to the first non-AP station (STA 1). At this time, the association response frame and the reassociation response frame may include a Multi-Link element. At this time, the Multi-Link element may include information about the link on which the multi-link setup is performed. The link on which the multi-link setup is performed may be determined based on the link that the non-AP multi-link device intends to perform a multi-link setup on. In FIG. 25, the Multi-Link element may include information about the first link (link1) and the second link (link2) that the first non-AP station (STA 1) intends to perform a multi-link setup on.

[0313] When a combined response frame or a recombined response frame is successfully transmitted, it may be regarded that the multi-link setting for the link indicated by the Multi-Link element included in the combined response frame or the recombined response frame has been successfully performed.

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

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

[0316] The station or AP that transmits the element is called the reporting station and the reporting AP. Also, the station or AP indicated by the element is called the reported station or the reported AP. The station or AP that transmits the Reduced Neighbor Report element or the Multi-Link element is called the reporting station and the reporting AP. The station or AP indicated by the Reduced Neighbor Report element or the Multi-Link element is called the reported station and the reported AP.

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

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

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

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

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

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

[0323] The TBTT Information Length subfield can indicate the length of each TBTT Information subfield included in the Neighbor AP Information subfield that includes the TBTT Information Length subfield. Also, the TBTT Information Length subfield can indicate the configuration of each TBTT Information subfield included in the Neighbor AP Information subfield that includes the TBTT Information Length subfield. At this time, the TBTT Information Length subfield can indicate the length and configuration of each TBTT Information subfield.

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

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

[0326] The Neighbor AP TBTT Offset subfield can indicate the offset obtained by truncating to the nearest TU the interval from the immediately preceding TBTT to the next TBTT of the AP that transmits the Reduced Neighbor Report. When the value of the Neighbor AP TBTT Offset subfield is 254, it can indicate that the offset is 254 TUs or greater. When the value of the Neighbor AP TBTT Offset subfield is 255, it can indicate that the offset value is unknown.

[0327] The BSSID subfield can indicate the BSSID.

[0328] The Short SSID subfield can indicate the SSID. Specifically, the Short SSID subfield can indicate the reduced SSID information.

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

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

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

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

[0333] The MLD ID subfield can indicate the ID of a multi-link device, such as an AP multi-link device. The MLD subfield can indicate the ID of the multi-link device corresponding to the TBTT Information subfield including the MLD ID subfield. The specific setting method of the MLD ID subfield may be as shown in Fig. 28.

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

[0335] The BSS Parameters Change Count subfield can indicate a value that increases when an important update occurs in the beacon frame of the reported AP. The value of the BSS Parameters Change Count subfield may be initialized to 0. The value of the BSS Parameters Change Count subfield may increase by 1 when an important update occurs in the AP or BSS corresponding to the BSS Parameters Change Count subfield. An important update may include that a pre-specified parameter is updated. The pre-specified parameter may include an operation parameter. If the reported AP does not belong to a multi-link device or the reporting AP does not have information about the multi-link device to which the reported AP belongs, the value of the BSS Parameters Change Count subfield may be set to 255.

[0336] FIG. 28 shows a method for setting the ID of a multi-link device according to an embodiment of the present invention.

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

[0338] According to an embodiment of the present invention, the MLD ID subfield may be set as follows. The MLD ID subfield can indicate the ID of the AP multi-link device to which the reported AP belongs. When the reported AP belongs to the AP multi-link device to which the reporting AP belongs, the MLD ID subfield may be set to 0. When the nontransmitted BSSID belonging to the multiple BSSID set to which the reported AP belongs belongs to the multi-link device set, the value of the MLD ID subfield may be set to the same value as the value of the BSSID Index field of the Multiple BSSID-Index element of the nontransmitted BSSID propyl corresponding to the nontransmitted BSSID. When the reported AP is part of another AP multi-link device and the frame containing the MLD ID subfield does not contain a Multiple BSSID element, the value of the MLD ID subfield may be set to a value greater than 0 and less than 255. Also, when the reported AP is part of another AP multi-link device and the frame containing the MLD ID subfield contains a Multiple BSSID element, the value of the MLD ID subfield may be set to a value greater than 2^n - 1 and less than 255. At this time, n is the value of the MaxBSSID Indicator subfield of the Multiple BSSID element. When the reported AP is not part of a multi-link device or the reported AP does not have information about the multi-link device, the value of the MLD ID subfield may be set to 255. That is, when the reported AP belongs to the multi-link device to which the reporting AP belongs, the value of the MLD ID subfield may be set to 0. Specifically, when the reported AP is not part of a multi-link device or the reporting AP does not have information regarding whether the reported AP belongs to a multi-link device, the value of the MLD ID subfield may be set to 255. That is, when the reported AP belongs to the multi-link device to which the reporting AP belongs, the value of the MLD ID subfield may be set to 0.

[0339] In the embodiment of FIG. 28, the reporting AP operates on the first link (link1). The reporting AP belongs to the first multi-link device, and the reporting AP transmits a Reduced Neighbor Report element and an MLD ID subfield. Also, the first multi-link device (MLD 1) operates on the first link (link 1), the second link (link 2), and the third link (link 3). At this time, the reporting AP sets the value of the MLD ID subfield corresponding to the AP operating on each of the second link (link 2) and the third link (link 3) to 0.

[0340] Also, the reporting AP can transmit a multiple BSSID element together with the Reduced Neighbor Report element. In still other specific embodiments, the reporting AP does not have to transmit a multiple BSSID element. At this time, when the reporting AP transmits a multiple BSSID element, it may be the case where the reporting AP belongs to a multiple BSSID set. Also, when the reporting AP does not transmit a multiple BSSID element, it may be the case where the reporting AP does not belong to a multiple BSSID set.

[0341] According to an embodiment of the present invention, when the reported AP is included in a multiple BSSID set to which the reporting AP belongs, the value of the MLD ID subfield may be set to the BSSID index of the multiple BSSID set. Further, when the reported AP belongs to a multi-link device to which an AP belonging to a multiple BSSID set to which the reporting AP belongs belongs, the value of the MLD ID subfield may be set to the BSSID index of the AP belonging to the multiple BSSID set. When the reported AP belongs to a multi-link device to which an AP of a nontransmitted BSSID belonging to a multiple BSSID set to which the reported AP belongs belongs, the value of the MLD ID subfield may be set to the BSSID index of the reported AP.

[0342] The multiple BSSID set to which the reporting AP belongs may operate on a first link (link 1) and include an AP belonging to a second multi-link device (MLD 2). The second multi-link device (MLD 2) may include an AP operating on the first link (link 1) and an AP operating on a second link (link 2). The value of the MLD ID subfield corresponding to the AP operating on the first link (link 1) belonging to the second multi-link device (MLD 2) and the AP operating on the second link (link 2) belonging to the second multi-link device (MLD 2) can be set to the BSSID index of the reported AP. This is because the AP of the second multi-link device (MLD 2) operating on the first link (link 1) and the AP of the second multi-link device (MLD 2) operating on the second link (link 2) belong to the same multiple BSSID set as the reporting AP or belong to a multi-link device included in the multiple BSSID set to which the reporting AP belongs.

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

[0344] Also, when the reporting AP sends a multiple BSSID element, if the reported AP does not belong to the multi-link device to which the reporting AP belongs, the reported AP does not belong to the multiple BSSID set to which the reporting AP belongs, and the reported AP does not belong to the multi-link device to which the APs in the multiple BSSID set to which the reporting AP belongs belong, the value of the MLD ID subfield may be set to a value greater than (2^n - 1) and less than a pre-specified value. Also, this may be limited to the case where the reported AP belongs to the MLD. The pre-set value may be the maximum value that the MLD ID subfield can indicate. The pre-set value may be 255. Also, n may be the MaxBSSID Indicator value corresponding to the multiple BSSID set that includes the reporting AP.

[0345] In FIG. 28, the third multi-link device (MLD3) may include an AP operating on the first link (link 1) and an AP operating on the second link (ink2). Further, the AP operating on the first link (link 1) and belonging to the third multi-link device (MLD3) may not belong to the multiple BSSID sets to which the reporting AP belongs. At this time, the value of the MLD ID sub-field for the AP operating on the first link (link 1) and belonging to the third multi-link device (MLD3) and the AP operating on the second link (link 2) and belonging to the 3 multi-link device (MLD3) may be set to a value greater than 2^n - 1 and less than 255. This is because the AP operating on the first link (link 1) and belonging to the third multi-link device (MLD 3) and the AP operating on the second link (link 2) and belonging to the third multi-link device (MLD 3) do not belong to the multi-link device to which the reporting AP belongs, and neither of these two APs is included in the multi-link device to which the AP of the multiple BSSID sets to which the reporting AP belongs belongs.

[0346] When the reporting AP does not transmit a multiple BSSID element and the reported AP does not belong to the multi-link device to which the reporting AP belongs, the value of the MLD ID sub-field may be set to a value greater than 0 and less than a pre-specified value. Also, this may be limited to the case where the reported AP belongs to a multi-link device. Also, the pre-specified value may be the maximum value that the MLD ID sub-field can indicate. The pre-specified value may be 255.

[0347] Also, when 1) the reported AP does not belong to a multi-link device, 2) the reporting AP does not have information regarding whether the reported AP belongs to a multi-link device, or 3) the reporting AP does not have information for setting the value of the MLD ID subfield described above, the reporting AP can set the value of the MLD ID subfield to a pre-specified value. In yet another specific embodiment, when 1) the reported AP does not belong to a multi-link device, 2) the reporting AP does not have information regarding whether the reported AP belongs to a multi-link device, or 3) the reporting AP does not have information for setting the value of the MLD ID subfield described above, the reporting AP can set the value of the MLD ID subfield to a value equal to or greater than the pre-specified value. The pre-specified value may be the maximum value that the MLD ID subfield can indicate. The pre-specified value may be 255.

[0348] In FIG. 28, the fourth AP (AP4) operates on the first link (link 1). At this time, the fourth AP (AP 4) does not belong to any multi-link device. Therefore, the reporting AP can set the value of the MLD ID subfield corresponding to the fourth AP (AP 4) to 255.

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

[0350] The station can determine to which AP the frame is transmitted based on the MAC address field of the MAC header of the received frame. In a specific embodiment, the station can determine whether the received frame is transmitted to the AP to which the station is associated or an AP belonging to multiple BSSIDs to which the AP to which the station is associated belongs, based on the RA field of the MAC header of the received frame. At this time, when the RA field of the frame received by the station indicates the MAC address of the AP to which the station is associated or the MAC address of an AP belonging to a set of multiple BSSIDs to which the AP to which the station is associated belongs, the station can determine that the received frame is transmitted to the AP to which the station is associated or an AP belonging to a set of multiple BSSIDs to which the AP to which the station is associated belongs. When the RA field of the frame received by the station does not indicate the MAC address of the AP to which the station is associated and the MAC address of an AP belonging to a set of multiple BSSIDs to which the AP to which the station is associated belongs, the station can determine that the received frame is transmitted to the AP to which the station is associated and an AP belonging to a set of multiple BSSIDs to which the AP to which the station is associated belongs.

[0351] The station can determine whether the received frame is an Inter-BSS frame based on the MAC address field in the MAC header of the received frame. The MAC address field may include at least one of the RA field, TA field, and BSSID field. When none of the RA field, TA field, and BSSID field of the frame received by the station indicate the MAC address of the AP to which the station is associated and the MAC address of the AP belonging to the multiple BSSID sets to which the AP to which the station is associated belongs, the station can determine that the received frame is an Inter-BSS frame. When at least one of the RA field, TA field, and BSSID field of the frame received by the station indicates the MAC address of the AP to which the station is associated and the MAC address of the AP belonging to the multiple BSSID sets to which the AP to which the station is associated belongs, the station can determine that the received frame is an Intra-BSS frame.

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

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

[0354] A multiple BSSID set may be a plurality of BSS sets in which information regarding a BSS can be signaled in one (single) beacon frame or one (single) probe response frame. Specifically, a set of BSSIDs indicated by one multiple BSSID element can be referred to as a multiple BSSID set. Also, one TIM element included in one beacon frame or one TIM frame can indicate frames buffered for a plurality of BSSIDs included in a multiple BSSID set. Further, one (single) beacon frame or one (single) probe response frame may include a multiple BSSID element. A multiple BSSID element can signal information regarding a plurality of BSSs. The BSSID of the BSS in which the aforementioned one beacon frame or probe response frame was transmitted is referred to as the transmitted BSSID. The remaining BSSIDs other than the transmitted BSSID in a multiple BSSID set can be referred to as nontransmitted BSSIDs. Also, a beacon frame or a probe response frame may not be transmitted in a BSS corresponding to a nontransmitted BSSID.

[0355] As described above, the maximum number of BSSIDs that a multiple BSSID set can include may be 2^n. At this time, n may be a value signaled by a Multiple BSSID element. For example, n may be a value indicated by a MaxBSSID Indicator included in the Multiple BSSID element. A station that receives a Multiple BSSID element can determine the MAC address or BSSID of an AP included in the multiple BSSID set based on the received Multiple BSSID element. Also, each of a plurality of BSSID indexes may be mapped to each of the BSSIDs included in the multiple BSSID set. Therefore, the BSSIDs included in the multiple BSSID set may be identified by the BSSID indexes. The maximum value of the MaxBSSID Indicator may be 8.

[0356] However, there may be cases where the value of the MLD ID subfield cannot be set according to the embodiments regarding the method for setting the MLD ID subfield described above.

[0357] In the foregoing embodiments, when at least any one of the pre-specified conditions is satisfied, the reporting AP can set the value of the MLD ID sub-field to a pre-specified value. Further, in other specific embodiments, when the pre-specified conditions are satisfied, the reporting AP can set the value of the MLD ID sub-field to be greater than or equal to the pre-specified value. The pre-specified value may be the maximum value that the MLD ID sub-field can indicate. At this time, the pre-specified value may be 255. The pre-specified conditions may include at least one of 1) the reported AP does not belong to a multi-link device, 2) the reporting AP does not have information regarding whether the reported AP belongs to a multi-link device, and 3) the reporting AP does not have information for setting the value of the foregoing MLD ID sub-field. Also, the pre-specified conditions may include that when the value of the MaxBSSID Indicator field corresponding to the reporting AP is the maximum value, the reported AP is not included in the multi-link device to which the APs belonging to the multiple BSSID set to which the reporting AP belongs belong. Such a condition may be that the reporting AP transmits a multiple BSSID element. The maximum value of the MaxBSSID Indicator field may be 8.

[0358] When the reporting AP transmits a multiple BSSID element, if the reported AP is an AP included in the multiple BSSID set including the reporting AP, or if the reported AP belongs to the multi-link device to which the APs belonging to the multiple BSSID set including the reporting AP belong, the MLD ID sub-field can be set to the BSSID index of the AP included in the multiple BSSID set. When the value of the MaxBSSID Indicator sub-field is 8, the maximum number of BSSIDs that the multiple BSSID set can include may be 2^8 = 256. Therefore, there may not be a value greater than 2^n - 1 and less than 255 according to the foregoing conditions.

[0359] Also, when the value of the MaxBSSID Indicator subfield corresponding to the reporting AP is the maximum value, even if the reported AP belongs to a multi-link device to which the APs in the multiple BSSID sets to which the reporting AP belongs belong, the reporting AP may not be able to set the value of the MLD ID subfield. For example, the reporting AP cannot indicate a multi-link device with a BSSID index of 255. According to the above-described embodiments, the value of the MLD ID subfield can be set to 255. Therefore, when the value of the MLD ID subfield is 255, it is difficult to distinguish whether it is 255 set based on the BSSID index or 255 set based on a pre-specified value.

[0360] Therefore, the condition for setting the value of the MLD ID subfield to a pre-specified value may further include that when the value of the MaxBSSID Indicator subfield corresponding to the reporting AP is the maximum value, the reported AP belongs to a multi-link device to which the APs in the multiple BSSID sets to which the reporting AP belongs belong. In still other specific embodiments, it may not be allowed to use 255 as the BSSID index in the multiple BSSID sets.

[0361] Also, according to the above-described embodiments, it may be difficult for the reporting AP to set the value of the MLD ID subfield regardless of whether the reporting AP transmits a multiple BSSID element. For example, when the reporting AP instructs information for a large number of APs, it may be difficult for the reporting AP to set the value of the MLD ID subfield. Since the number of reported APs is larger than the number of multi-link device IDs that can be set, the reported APs may not be identifiable by the multi-link device IDs. For example, when the reporting AP transmits a multiple BSSID element and the reporting AP transmits information for more than (254 - 2^n + 1) APs, the reported APs may not be identifiable by the multi-link device IDs within a limited range. When the reporting AP does not transmit a multiple BSSID element and the reporting AP transmits information for more than (254 - 1 + 1) APs, the reported APs may not be identifiable by the IDs within a limited range. The condition for setting the value of the MLD ID subfield to a pre-specified value may further include the case where the reported APs cannot be identified by the IDs within a limited range.

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

[0363] FIGs. 29 and 30 show a method of assigning an AID to a non-AP station belonging to a multi-link device according to an embodiment of the present invention.

[0364] According to an embodiment of the present invention, one AID (association ID) may be assigned to a multi-link device. That is, the AIDs of the stations included in one multi-link device may be the same as each other.

[0365] The AID assignment may be performed by an AP. For example, the AID assigned by the AP can be sent to a non-AP STA. The non-AP STA can recognize that the AID received from the AP corresponds to itself. A non-AP station that has received a subfield including the AID value assigned to the non-AP station can recognize that the subfield including the AID value assigned to the non-AP station indicates the non-AP station.

[0366] The AID assigned to the non-AP station may be included in an association response frame or a re-association response frame. When multi-link configuration is performed after the AP assigns an AID to the non-AP station, the AID assigned to the non-AP station may be the one assigned to the multi-link device to which the non-AP station belongs.

[0367] The AID or information related to the AID may be included in the preamble of the PPDU. At this time, the PPDU preamble can use the AID to indicate that the intended recipient of the PPDU is a non-AP station corresponding to the AID. The PPDU preamble can use the AID to indicate that the sender of the PPDU is a non-AP station corresponding to the AID. Also, as described above, the AID may be used for traffic indication. The frame can use the AID to indicate that the station corresponding to the AID is the recipient of the frame. For example, the trigger frame can use the AID to indicate the station triggered by the trigger frame.

[0368] The AID assigned to a multi-link device may not be allowed to be assigned to other stations or other multi-link devices. In a specific embodiment, the AID assigned to a multi-link device may not be allowed to be assigned to a station or multi-link device that operates on a link other than the link on which the multi-link device operates.

[0369] In FIG. 29, the first multi-link device (MLD 1) operates on the first link (Link 1) and the second link (Link 2). Also, the second multi-link device (MLD 2) operates on the third link (Link 3) and the fourth link (Link 4). At this time, X is assigned as the AID of the first multi-link device (MLD 1). Therefore, it is not allowed to assign X as the AID of the second multi-link device (MLD 2), and Y is assigned.

[0370] In a specific embodiment of the present invention, the AP multi-link device can re-assign the AID assigned to any one multi-link device to other stations or other multi-link devices. When the specified conditions are met, the AP multi-link device can re-assign the AID assigned to any one multi-link device to other stations or other multi-link devices. At this time, the specified conditions may include that the multi-link devices or stations to which one AID is commonly assigned operate on different links. That is, the specified conditions may include that the multi-link devices or stations to which one AID is commonly assigned operate on non-overlapping links. At this time, it may not be allowed for stations operating on one link and multiple multi-link devices to be assigned one AID. In yet another specific embodiment, the specified conditions may include that the multi-link devices or stations to which one AID is commonly assigned operate on non-overlapping channels.

[0371] In FIG. 30(a), the first multi-link device (MLD 1) operates with the first link (Link 1) and the second link (Link 2). The AP multi-link device assigns X as the AID of the station of the first multi-link device (MLD 1). At this time, the AP multi-link device does not belong to the first multi-link device (MLD 1), and X can be assigned as the AID of the first station (STA 1) that operates on the third link (Link 3) instead of the first link (Link 1) and the second link (Link 2).

[0372] In such an embodiment, when a frame contains information related to multiple links, one AID assigned to multiple multi-link devices or stations may cause confusion. To prevent this, the information transmitted on any one link may be applicable to the station or multi-link device operating on that link. For example, the information transmitted on the first link may be applicable to the station or multi-link with AID X operating on the first link, and not necessarily applicable to the station or multi-link with AID X operating on the second link.

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

[0374] With reference to FIGS. 31 to 33, the TID-to-link mapping negotiation will be described.

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

[0376] As described above, a default mapping may be applied to a link for which TID-to-link mapping is not performed. Also, when TID-to-link mapping is torn down for a link for which TID-to-link mapping negotiation has been completed, the default mapping may be applied to the link again.

[0377] TID-to-link mapping negotiation may be performed by a TID-to-link mapping request and a TID-to-link mapping response. Specifically, the multi-link device can send a frame including a TID-To-Link Mapping element to make a TID-to-link mapping request. At this time, the frame may include an association request frame, a re-association request frame, and a TID-to-link mapping request frame. Therefore, a non-AP station or a non-AP multi-link device can request TID-to-link mapping by sending an association request frame, a re-association request frame, or a TID-to-link mapping request frame. An AP or an AP multi-link device can request TID-to-link mapping by sending a TID-to-link mapping request frame. The multi-link device that has received the TID-to-link mapping request can send a frame including a TID-To-Link Mapping element to make a TID-to-link mapping response. At this time, the frame may include an association response frame, a re-association response frame, and a TID-to-link mapping response frame. Therefore, an AP or an AP multi-link device can respond to a TID-to-link mapping request by sending an association response frame, a re-association response frame, or a TID-to-link mapping request frame. A non-AP station or a non-AP multi-link device of the station can respond to a TID-to-link mapping request by sending a TID-to-link mapping response frame.

[0378] The multi-link device can start the TID-to-link mapping by sending a TID-to-link mapping request. At this time, the multi-link device can request the default mapping by sending a frame containing a TID-to-link element. The multi-link device that has received the TID-to-link mapping request can accept the TID-to-link mapping by sending a TID-to-link mapping response to the TID-to-link mapping request. At this time, the multi-link device that has received the TID-to-link mapping request can accept the TID-to-link mapping by sending a frame that does not contain a TID-to-link Mapping element. In yet another specific embodiment, the multi-link device that has received the TID-to-link mapping request can accept the TID-to-link mapping by sending a frame containing a TID-to-link Mapping element having the same content as the TID-t12222222222222222222 content received from the non-AP multi-link device.

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

[0380] In such an embodiment, the frame transmitted by the multi-link device for TID-to-link mapping requests and responses may include at least any one of the binding request frame, binding response frame, re-binding request frame, re-binding response frame, TID-to-link mapping request frame, and TID-to-link mapping response frame as described above. Specifically, a multi-link device that receives a TID-to-link mapping request can transmit a TID-to-link mapping response frame in response to the TID-to-link mapping request. At this time, the multi-link device that has received the TID-to-link mapping request can insert a status code into the TID-to-link mapping response frame to accept or reject the TID-to-link mapping request. Specifically, the multi-link device that has received the TID-to-link mapping request can set the status code of the TID-to-link mapping response frame to SUCCESS to accept the TID-to-link mapping request. Also, the multi-link device that has received the TID-to-link mapping request can set the status code of the TID-to-link mapping response frame to REJECT or DENIED_TID_TO_LINK_MAPPING to reject the TID-to-link mapping request. Also, the multi-link device that has received the TID-to-link mapping request can set the status code of the TID-to-link mapping response frame to PREFERRED_TID_TO_LINK_MAPPING_SUGGESTED to reject the TID-to-link mapping request. At this time, the multi-link device that has received the TID-to-link mapping request can propose a preferred TID-to-link mapping while rejecting the TID-to-link mapping request. Also, the multi-link device that has received the TID-to-link mapping request can transmit a TID-To-Link mapping rejection frame to reject the TID-to-link mapping request.

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

[0382] When the TID-to-link mapping request is accepted, the TID-to-link mapping included in the TID-to-link mapping request is set for the link that is the subject of the TID-to-link mapping. Also, when the TID-to-link mapping request is rejected, a default mapping may be applied to the link that is the subject of the TID-to-link mapping.

[0383] Also, for TID-to-link mapping negotiation, the TID-to-link mapping request frame and the TID-to-link mapping response frame may include a Dialog Token. The Dialog Token maps the TID-to-link mapping request frame and the TID-to-link mapping response frame. Specifically, when the value of the Dialog Token in the TID-to-link mapping request frame is the same as the value of the Dialog Token in the TID-to-link mapping response frame, the TID-to-link mapping response frame may be sent as a response to the TID-to-link mapping request frame. Therefore, when the multi-link device that has received the TID-to-link mapping request frame sends a TID-to-link mapping response frame, the multi-link device can set it to the value of the Dialog Token of the TID-to-link mapping request frame. When the multi-link device has not received the TID-to-link mapping request frame and sends a TID-to-link mapping response frame, the multi-link device can set the Dialog Token value of the TID-to-link mapping response frame to a pre-specified value. At this time, the pre-specified value may be 0. That is, when the multi-link device sends an unsolicited TID-To-Link Mapping Response frame, the multi-link device can set the Dialog Token value of the TID-to-link mapping response frame to a pre-specified value. The field indicating the Dialog Token in the TID-to-link mapping request frame and the TID-to-link mapping response frame may be a 1-octet field. The value of the Dialog Token may have any one value from 0 to 255.

[0384] When the capabilities of a multi-link device assist in TID-to-link mapping, the multi-link device can perform TID-to-link mapping. Also, depending on the capabilities of the multi-link device, the range within which the multi-link device can progress with TID-to-link mapping may vary. For example, depending on the capabilities of the multi-link device, the number of TIDs that the multi-link device can map to a link or the number of combinations of applicable TIDs and link mappings may be different. The capabilities of the multi-link device can indicate whether the multi-link device can map to a link set where all TIDs are the same. Also, the capabilities of the multi-link device can indicate to how many link sets the multi-link device can map the TIDs.

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

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

[0387] The AP multi-link device can send a TID-to-link mapping request using a connection response frame, a reconnection response frame, and a TID-to-link mapping request frame. Specifically, the AP multi-link device can initiate TID-to-link mapping negotiation using a connection response frame, a reconnection response frame, and a TID-to-link mapping request frame. At this time, the AP multi-link device can include a TID-to-link Mapping element in the connection response frame, the reconnection response frame, and the TID-to-link mapping request frame. Specifically, the AP multi-link device can include a TID-to-link Mapping element in the connection response frame, the reconnection response frame, and the TID-to-link mapping request frame to initiate TID-to-link mapping negotiation. This is because the TID-to-link mapping request sent by the non-AP multi-link device may be in a form that the AP multi-link device does not desire, and the AP multi-link device may not send the TID-to-link mapping request sent by the non-AP multi-link device. Also, the AP multi-link device can more easily grasp the overall network situation compared to the non-AP multi-link device and can determine an efficient TID-to-link mapping. At this time, since the AP multi-link device first sends a connection response frame or a reconnection response frame before completing the TID-to-link mapping negotiation, multi-link setting and re-setting can be completed. When the non-AP multi-link device that has received the TID-to-link mapping request sends a TID-to-link mapping response, the TID-to-link mapping negotiation is successfully completed.

[0388] The AP multi-link device may be restricted if it can send a TID-to-link mapping request using a join response frame and a rejoin response frame. Specifically, when the join request frame does not request a TID-to-link mapping, the AP multi-link device can send a TID-to-link mapping request using the join response frame. When the join request frame does not contain a TID-to-link Mapping element, the AP multi-link device can determine that the join request frame does not request a TID-to-link mapping. Also, when the rejoin request frame does not request a TID-to-link mapping, the AP multi-link device can send a TID-to-link mapping request using the rejoin response frame. When the rejoin request frame does not contain a TID-to-link Mapping element, the AP multi-link device can determine that the rejoin request frame does not request a TID-to-link mapping. When the join request frame sent by the non-AP multi-link device does not contain a TID-to-link Mapping element, the non-AP multi-link device can receive it in response to the join request frame and determine that the join response frame containing the TID-to-link Mapping element requests a TID-to-link mapping. When the rejoin request frame sent by the non-AP multi-link device does not contain a TID-to-link Mapping element, the non-AP multi-link device can receive it in response to the rejoin request frame and determine that the rejoin response frame containing the TID-to-link Mapping element requests a TID-to-link mapping. Such an embodiment is because when the join request frame contains a TID-to-link element and the join request frame contains a TID-to-link element, the non-AP multi-link device may confuse the intention that the TID-to-link element of the join response frame is included. This is the same in the case of the rejoin request frame.

[0389] Also, in such an embodiment, the AP multi-link device does not have to determine that the TID-to-link mapping has been successfully completed until it receives a TID-to-link mapping response from the non-AP multi-link device. Therefore, the AP multi-link device may operate by default mapping until it receives a TID-to-link mapping response from the non-AP multi-link device. Also, even if the AP multi-link device receives an ACK for the association response frame or the re-association response frame, the AP multi-link device does not have to determine that the TID-to-link mapping has been successfully completed.

[0390] The non-AP multi-link device can respond to the TID-to-link mapping request sent by the AP multi-link device using the association frame or the re-association frame according to the foregoing embodiment. However, it is necessary to clearly indicate that the non-AP multi-link device responds to the TID-to-link mapping request sent by the AP multi-link device using the association frame or the re-association frame. The non-AP multi-link device can send a TID-to-link mapping response in a response frame for the association response frame requesting TID-to-link mapping or the re-association response frame requesting TID-to-link mapping. Also, the non-AP multi-link device can set the dialog token value of the TID TID-to-link mapping response to be the same as the dialog token value included in the association response frame requesting TID-to-link mapping or the re-association response frame requesting TID-to-link mapping. However, the association response frame requesting TID-to-link mapping and the re-association response frame requesting TID-to-link mapping do not have to include a dialog token.

[0391] Therefore, the TID-to-link Mapping element may include a response indication field that indicates that it is a response to a TID-to-link mapping request. At this time, the response indication field may be included in the TID-to-Link Mapping Control field described above. Specifically, the response indication field may be included in the reserved field of the reserved field of the TID-to-Link Mapping Control field described above. For example, the response indication field may be any one bit of the 4th bit (B3) to the 8th bit (B8) of the TID-to-Link Mapping Control field. The multi-link device that has received the TID-to-link element can determine whether the TID-to-link Mapping element requests a TID-to-link mapping based on the response indication field.

[0392] Since the non-AP multi-link device sends a TID-to-link mapping response frame as a response to a join request frame or a rejoin request frame, the AP multi-link device needs to distinguish which frame the TID-to-link mapping response frame is a response to. Specifically, when the non-AP multi-link device sends a TID-to-link mapping response frame as a response to a join request frame or a rejoin request frame, the non-AP multi-link device can set the value of the dialog token of the TID-to-link mapping response frame to a random value. Also, when the value of the dialog token of the TID-to-link mapping response frame is the same as the value of the dialog token of the TID-to-link mapping request frame sent by the AP multi-link device, the AP multi-link device may consider that the TID-to-link mapping response frame is a response to the TID-to-link mapping request frame. Further, when the value of the dialog token of the TID-to-link mapping response frame is different from the value of the dialog token of the TID-to-link mapping request frame sent by the AP multi-link device, the AP multi-link device may consider that the TID-to-link mapping response frame is a response to a join request frame or a rejoin request frame.

[0393] In yet another specific example, when the AP multi-link device sends a TID-to-link mapping request using a binding response frame or a re-binding response frame, the value of the dialog token of the TID-to-link mapping response frame sent as a response to the TID-to-link mapping request may be set to a preset value. At this time, the preset value may be 0, 1, or 255. When the AP multi-link device sends a TID-to-link mapping request using a binding frame or a re-binding frame and receives a TID-to-link mapping response frame whose preset value has the value of the dialog token, the AP multi-link device can determine that the received TID-to-link mapping response frame is a response to the sent TID-to-link mapping request.

[0394] In yet another specific example, when the AP multi-link device sends a TID-to-link mapping request using a bonding response frame or a re-bonding response frame, the status code of the TID-to-link mapping response frame sent as a response to the TID-to-link mapping request may be a pre-specified value. At this time, the pre-specified value of the status code may be different from the value of the status code of the TID-to-link mapping response frame sent as a response to the TID-to-link mapping request sent by the multi-link device using a frame other than the bonding frame and the re-bonding frame. Thereby, the AP multi-link device can determine whether the received TID-to-link mapping response frame is a response to the TID-to-link mapping request sent by the AP multi-link device using a bonding response frame or a re-bonding response frame based on the status code of the received TID-to-link mapping response frame. Specifically, when the status code of the received TID-to-link mapping response frame is the pre-specified value, the AP multi-link device can determine that the received TID-to-link mapping response frame is a response to the TID-to-link mapping request sent by the AP multi-link device using a bonding response frame or a re-bonding response frame.

[0395] In yet another specific embodiment, the AP multi-link device can determine whether the received TID-to-link mapping response frame is a response to the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame, based on the value of the Link Mapping field for the TID in the received TID-to-link mapping response frame. Specifically, when the value of the Link Mapping field for the TID in the received TID-to-link mapping response frame is the same as the value of the Link Mapping field for the TID in the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame, the AP multi-link device can determine that the received TID-to-link mapping response frame is a response to the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame. Specifically, the received TID-to-link mapping response frame may include Link Mapping fields for a plurality of TIDs. At this time, when the values of all the Link Mapping fields included in the TID-to-link mapping response frame are the same as the values of all the Link Mapping fields in the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame, the AP multi-link device can determine that the received TID-to-link mapping response frame is a response to the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame. When the value of the Link Mapping field for the TID in the TID-to-link mapping response frame received by the AP multi-link device is different from the value of the Link Mapping field for the TID in the TID-to-link mapping request sent by the AP multi-link device using the binding response frame or the re-binding response frame, the AP multi-link device does not have to send an ACK for the received TID-to-link mapping response frame.Also, when the Link Mapping field for the TID of the TID-to-link mapping response frame received by the AP multi-link device includes at least one of the values of the Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multi-link device using the association response frame or the re-association response frame, the AP multi-link device does not have to transmit an ACK for the received TID-to-link mapping response frame. Further, when the TID-to-link mapping response frame received by the AP multi-link device does not include even one Link Mapping field for the TID of the TID-to-link mapping request transmitted by the AP multi-link device using the association response frame or the re-association response frame, or when the value of the Link Mapping field of the TID-to-link mapping response frame received by the multi-link device is different from the value of the Link Mapping field for the TID of the TID-to-link mapping request transmitted using the association response frame or the re-association response frame, the AP multi-link device does not have to transmit an ACK for the received TID-to-link mapping response frame. The above-described embodiments may also be applied when the TID-to-link mapping request is not transmitted using the association response frame or the re-association response frame.

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

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

[0398] The link set that requests TID-to-link mapping in the association request frame or re-association request frame may be different from the link set that attempts to set the TID-to-link mapping in the association response frame or re-association response frame. For example, the TID-to-link mapping can be requested for three links in the association request frame or re-association request frame, and the TID-to-link mapping can be set for two links in the association response frame or re-association response frame. Also, the link sets being different may include the link sets being configured differently from each other. Specifically, the link sets being configured differently from each other may include the operating channels of the link sets being different from each other. Also, the link sets being different may include the link sets being composed differently from each other.

[0399] In some embodiments of FIG. 31, when the AP multi-link device receives an association request frame or re-association request frame that includes a TID-to-link Mapping element, the AP multi-link device can send an association response frame or re-association response frame that does not include the TID-to-link Mapping element to set up the multi-link. However, as described above, the link set that requests the TID-to-link mapping in the association request frame or re-association request frame may be different from the link set that attempts to set the TID-to-link mapping in the association response frame or re-association response frame.

[0400] Therefore, in yet another embodiment of the present invention, when an AP multi-link device receives an association request frame or a re-association request frame including a TID-to-link Mapping element, and the association request frame or the re-association request frame attempts to set a link set different from the link set of the multi-link to be set, the AP multi-link device can transmit an association response frame or a re-association response frame not including the TID-to-link Mapping element. Thereby, the AP multi-link device can reject the TID-to-link mapping. At this time, the default mapping may be applied to the AP multi-link device and the non-AP multi-link device.

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

[0402] In yet another specific embodiment, when the AP multi-link device receives a binding request frame or a re-binding request frame including a TID-to-link Mapping element and attempts to set a link set different from the link set of the multi-link that the binding request frame or the re-binding request frame attempts to set, the AP multi-link device can send a binding response frame or a re-binding response frame including a TID-to-link Mapping element. At this time, the TID-To-Link Mapping element included in the binding response frame or the re-binding response frame can indicate the TID-to-link mapping proposed by the AP multi-link device. At this time, the operation of the non-AP multi-link device may be the same as that of the embodiment described in FIG. 28.

[0403] In the foregoing embodiments, for the sake of convenience of explanation, the operation of the multi-link device has been described as such. However, the operation of the multi-link device may also be performed by a station included in the multi-link device.

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

[0405] FIG. 34 is an additional explanation of the TBTT information field described in FIG. 27. The content described in FIG. 27 is equally applicable to this embodiment and will be omitted.

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

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

[0408] The Neighbor AP Information field may include a TBTT Information Set field.

[0409] The TBTT Information Set field may include one or more TBTT information fields. The number of TBTT information fields included in the TBTT Information Set field can be indicated by the TBTT Information Count subfield included in the TBTT Information Set field.

[0410] The length of each TBTT information field included in the TBTT information set field included in the neighboring AP information field may be indicated by the TBTT Information Length subfield included in the neighboring AP information field. That is, the lengths of the TBTT information fields included in one neighboring AP information field may be the same.

[0411] The format and contents of the TBTT information field may be determined based on the TBTT Information Header field included in the neighboring AP information field that includes the TBTT information field. More specifically, the format and contents of the TBTT information field may be determined based on the TBTT information field type and the TBTT information field length indicated by the neighboring AP information field that includes the TBTT information field. The TBTT information field type may be indicated by the TBTT information field type subfield. Also, the TBTT information field length may be indicated by the TBTT information length subfield. The neighboring AP information field includes one TBTT information field type subfield and one TBTT information length subfield. Therefore, the format and contents of the TBTT information fields included in one neighboring AP information field may be the same.

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

[0413] Also, based on the value of the TBTT information field type sub-field and the value of the TBTT information length sub-field included in the TBTT information header field of the adjacent AP information field, the operation of the terminal to process the TBTT information field may be different. Specifically, depending on whether the value of the TBTT information field type sub-field indicating the type (or format) of the TBTT information field is set to a first value (e.g., "0") or a second value (e.g., "1"), the length of the TBTT information field processed by the terminal may change. Additionally, the length by which the TBTT information field is further processed may take into account the value of the TBTT information length sub-field. That is, when the value of the TBTT information field sub-field is set to the first value or the second value, the value of the TBTT information length sub-field is compared with a first critical value (e.g., 16 octets), a second critical value (e.g., 13 octets), and / or a third critical value (e.g., 3 octets), and the terminal may process only all or part of the TBTT information field, or may not process all of it. For example, when the value of the recognizable TBTT information field sub-field is "0" and the length of the TBTT information field indicated by the TBTT information length sub-field is equal to or less than the second critical value, the terminal can ignore the received frame (e.g., beacon frame or probe response frame, etc.) without processing all of the TBTT information field. However, when the value of the recognizable TBTT information field sub-field is "0" and the length of the TBTT information field indicated by the TBTT information length sub-field is greater than the second critical value and equal to or less than the first critical value, the terminal can process the TBTT information field of the received frame up to the first second octet value (e.g., 13 octets) and ignore the remaining octets without further processing.However, when the value of the recognizable TBTT information field sub-field is "0" and the length of the TBTT information field indicated by the TBTT information length sub-field is greater than the first critical value, the terminal can process the TBTT information field of the received frame up to the first first octet value (for example, 16 octets) and ignore the remaining octets without processing them.

[0414] If, when the value of the recognizable TBTT information field sub-field is "1" and the length of the TBTT information field indicated by the TBTT information length sub-field is less than the third critical value, the terminal can ignore the received frame (for example, beacon frame or probe response frame, etc.) without processing all of the TBTT information field. However, when the value of the recognizable TBTT information field sub-field is "1" and the length of the TBTT information field indicated by the TBTT information length sub-field is equal to or greater than the third critical value, the terminal can process the TBTT information field of the received frame up to the first third octet value (for example, 3 octets) and ignore the remaining octets without processing them.

[0415] As still another embodiment of the present invention, the TBTT information field may be processed only up to a specific critical value depending on whether the value of the TBTT information length sub-field includes the specific critical value. That is, when the value of the TBTT information length sub-field is less than the specific critical value, the TBTT information field may not be processed. However, when the value of the TBTT information length sub-field is equal to or greater than the specific critical value (the same or greater), the TBTT information field may also be processed up to the length (octets) corresponding to the specific critical value. At this time, when the value of the TBTT information length field is a value between two critical values (for example, equal to or greater than the second critical value and less than the first critical value), the TBTT information field may be processed up to the length corresponding to the second critical value.

[0416] For example, when the value of the TBTT information field subfield is set to the first value or the second value, the value of the TBTT information length subfield is compared with a first threshold value (for example, 16 octets), a second threshold value (for example, 13 octets), and / or a third threshold value (for example, 3 octets), and the terminal may process only all or part of the TBTT information field, or may not process all of it. Specifically, when the value of the recognizable TBTT information field subfield is "0", if the length of the TBTT information field indicated by the TBTT information length subfield is less than the second threshold value, the terminal can ignore the received frame (for example, beacon frame or probe response frame, etc.) without processing all of the TBTT information field of the received frame. However, when the value of the recognizable TBTT information field subfield is "0", if the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the second threshold value and less than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first second octet value (for example, 13 octets), and can ignore the remaining octets without processing. However, when the value of the recognizable TBTT information field subfield is "0", if the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the first threshold value, the terminal processes the TBTT information field of the received frame up to the first first octet value (for example, 16 octets), and can ignore the remaining octets without processing.

[0417] If the value of the recognizable TBTT information field subfield is "1" and the length of the TBTT information field indicated by the TBTT information length subfield is less than the third critical value, the terminal can ignore the received frame (e.g., beacon frame or probe response frame, etc.) without processing all of the TBTT information field. However, if the value of the recognizable TBTT information field subfield is "1" and the length of the TBTT information field indicated by the TBTT information length subfield is equal to or greater than the third critical value, the terminal can process the TBTT information field of the received frame up to the first third octet value (e.g., 3 octets) and ignore the remaining octets without processing.

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

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

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

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

[0422] The MLD Parameters field may include the subfields described in FIG. 21, and may further include the All Updates Included subfield in the bit at the B20 position. The All Updates Included subfield can indicate whether a frame including an RNR element including the All Updates Included subfield includes all updated elements that change the value of the BSS Parameters Change Count subfield. It may be set to 1 if all are included, and 0 otherwise.

[0423] According to an embodiment of the present invention, the plurality of STAs may include a STA belonging to the AP MLD (i.e., the AP). For example, there may be a case where the AP MLD operates in an NSTR link pair. Such an AP MLD can be referred to as an NSTR AP MLD or an NSTR mobile AP MLD or an NSTR soft AP MLD.

[0424] The NSTR mobile AP MLD can set, allocate, and designate primary and non-primary links. Also, the non-AP MLD that is multi-linked with the NSTR mobile AP MLD can receive information from the NSTR mobile AP MLD about which link is the primary link and which link is the non-primary link, and then make a judgment. The NSTR mobile AP MLD may be able to transmit beacon frames, probe response frames, association response frames, and re-association response frames only on the primary link. The NSTR mobile AP MLD may be unable to transmit beacon frames, probe response frames, association response frames, and re-association response frames on the non-primary link. Also, the non-AP MLD that is (or attempts to be) multi-linked with the NSTR mobile AP MLD may be able to transmit probe request frames, association request frames, and re-association request frames only on the primary link. The non-AP MLD that is associated with or (attempts to be) multi-linked with the NSTR mobile AP MLD may be unable to transmit probe request frames, association request frames, and re-association request frames on the non-primary link.

[0425] In addition, the NSTR mobile AP MLD or the non-AP MLD combined with the NSTR mobile AP MLD may sometimes have to use the primary link together to start a TXOP (start frame transmission) on a non-primary link. For example, to start transmitting a PPDU on a non-primary link, it may be necessary to start transmitting the PPDU on the primary link simultaneously with the non-primary link. Also, there may be a backoff procedure for starting PPDU transmission simultaneously on the primary link and the non-primary link. For example, a link that has reached a backoff counter of 0 can maintain a backoff counter value of 0, and a link with a backoff counter of 0 can start transmitting a PPDU when the backoff counter reaches 0 on other links.

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

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

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

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

[0430] Therefore, among the APs belonging to the NSTR mobile AP MLD that operate on the primary link, the AP can send the neighbor AP information field or the TBTT information field corresponding to the non-primary link or the AP operating on the non-primary link. At this time, the TBTT information field type sub-field value included in the neighbor AP information field may be set to 1. Further, the TBTT information field may include the MLD Parameters field, and does not necessarily include all of the Neighbor AP TBTT Offset sub-field, BSSID sub-field, Short SSID sub-field, BSS Parameters sub-field, and 20MHz PSD sub-field.

[0431] Also, among the APs belonging to the NSTR mobile AP MLD that operate on the primary link, the AP can send the primary link or the neighbor AP information field or the TBTT information field corresponding to the AP. At this time, the TBTT information field type sub-field value included in the neighbor AP information field may be set to 0. Further, the TBTT information field may include the MLD Parameters field.

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

[0433] FIG. 35 is a diagram showing the neighbor AP information field reception and analysis operation according to an embodiment of the present invention.

[0434] According to an embodiment of the present invention, when an STA receives a neighboring AP information field including an unrecognized (not recognizable, unknown) TBTT information field type subfield value, the neighboring AP information field or the rest of the RNR element including the neighboring AP information field can be ignored.

[0435] According to an embodiment of the present invention, an AP (reporting AP) included in an AP MLD can transmit a frame (e.g., a beacon frame or a probe response frame) including an RNR (Reduced Neighbor Report) element to an STA included in a non-AP MLD. A non-AP STA can obtain information on other APs (reported APs) included in the AP MLD based on the received RNR element. At this time, based on the TBTT information field type subfield and the TBTT information length subfield included in the RNR element of the frame, the content and format of the TBTT information related to the information of other APs can be recognized. Also, the non-AP STA may change the length that can process the TBTT information field based on the TBTT information length field according to the value of the TBTT information field type subfield. At this time, the content (or information) of the TBTT information field that is not processed may be ignored.

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

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

[0438] There may be a way of operating when the STA receives an adjacent AP information field including a recognized (recognizable, known) TBTT information field type subfield value and an unrecognized TBTT information length subfield value. For example, there may be a method based on threshold value 1 and threshold value 2, such as the method described above.

[0439] For example, when the TBTT information length subfield is less than or equal to threshold value 1, the adjacent AP information field including the TBTT information length subfield can be ignored, and the subsequent adjacent AP information fields can be processed (decoded). (Operation 1)

[0440] When the TBTT information length subfield is greater than threshold value 1, the first threshold value 1 octets of each corresponding TBTT information field are processed so that the TBTT information length subfield value is threshold value 1, and the remaining octets of each corresponding TBTT information field ((TBTT information length subfield value - threshold value 1) octets) are ignored, and the subsequent adjacent AP information fields can be processed. Also, this is an additional condition, and it may be an applicable example when threshold value 1 is less than threshold value 2 and the TBTT information length subfield is less than threshold value 2. (Operation 2)

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

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

[0443] As an additional example, there may be a threshold value 3 that is greater than the threshold value 2. In the example described above for the threshold value 1 and the threshold value 2, there may be an example in which the threshold value 1 and the threshold value 2 are changed to the threshold value 2 and the threshold value 3, respectively.

[0444] That is, as possible operating methods, there may be operation 1, operation 2, and operation 3. The STA can perform operation 1 according to the conditions described for operation 1. Also, the HE STA can perform operation 2 according to the conditions described for operation 2. The Non-HE STA can perform operation 1 or operation 2 according to the conditions described for operation 2. The EHT STA can perform operation 3 according to the conditions described for operation 3. The Non-EHT STA can perform operation 1 or operation 2 or operation 3 according to the conditions described for operation 3.

[0445] In the described example, the operation of processing only the threshold value portion of the TBTT information field having an unknown TBTT information length subfield value and ignoring the rest may be for forward compatibility. Even if it is defined that the TBTT information field contains information different from the information contained in the TBTT information field known to the STA, it may be for parsing as much as possible.

[0446] Referring to FIG. 35, the STA can receive an adjacent AP information field including a recognized TBTT information field type sub-field value and an unrecognized TBTT information length sub-field value. In such a case, it can be confirmed whether the TBTT information length sub-field value is 13 or less. If true, the adjacent AP information field can be ignored. If false, it can be confirmed whether the TBTT information length sub-field value exceeds 16. If false (if the TBTT information length sub-field value is more than 13 and 16 or less), the first 13 octets of each TBTT information field included in the adjacent AP information field can be processed such that the TBTT information length sub-field value is 13, and the remaining TBTT information fields excluding the first 13 octets can be ignored. If true (if the TBTT information length sub-field value exceeds 16), the first 16 octets of each TBTT information field included in the adjacent AP information field can be processed such that the TBTT information length sub-field value is 16, and the remaining TBTT information fields excluding the first 16 octets can be ignored.

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

[0448] For example, as shown in Example 1 of FIG. 35, it may receive an adjacent AP information field in which the TBTT information length subfield value is greater than 3 and less than or equal to 13. Also, the TBTT information field type subfield value included in the adjacent AP information field may be 1. In such a case, the actually transmitted TBTT information field may be as shown in Example 1 of FIG. 35. That is, it may include a 3-octet MLD Parameters field in front, followed by New Field 1. Also, for example, the length of New Field 1 may be 3 octets. Since the EHT STA can recognize that the TBTT information field type subfield value is 1 but cannot recognize that the TBTT information length subfield value is greater than 3, it may operate according to the embodiments described in FIG. 35. Therefore, since the TBTT information length subfield value is less than or equal to 13, the adjacent AP information field can be ignored. Therefore, the STA cannot obtain information from the analyzable MLD Parameters field.

[0449] As shown in Example 2 of FIG. 35, it may be possible to receive an adjacent AP information field in which the TBTT information length subfield value is greater than 16. Also, the TBTT information field type subfield value included in the adjacent AP information field may be 1. In such a case, the actually transmitted TBTT information field may be as shown in Example 2 of FIG. 35. That is, it may include a 3-octet MLD Parameters field in front, followed by New Field 2. Also, for example, the length of New Field 2 may be 14 octets. Since the EHT STA can recognize that the TBTT information field type subfield value is 1 and cannot recognize that the TBTT information length subfield value is greater than 3, it can operate according to the embodiment described in FIG. 35. Therefore, since the TBTT information length subfield value is greater than 16, the first 16 octets before the TBTT information field included in the adjacent AP information field can be analyzed so that the TBTT information length subfield value is 16. However, since the TBTT information field when the TBTT information length subfield value is 16 is the same as that shown in the (Example 2) STA’s interpretation of FIG. 35, the information actually composed of MLD Parameters and New Field 2 will be misinterpreted as in the (Example 2) STA’s interpretation.

[0450] FIG. 36 is a diagram showing the operation of receiving and analyzing an adjacent AP information field according to an embodiment of the present invention.

[0451] The embodiment of FIG. 36 may be for solving the problems described in FIG. 35. Also, the above-mentioned content may be omitted in this embodiment. Also, in the present invention, embodiments referring to greater than or equal to, less than or equal to, greater than, less than, etc., or having such meanings can be extended to embodiments replaced with greater than, less than, greater than or equal to, less than or equal to, respectively.

[0452] According to an embodiment of the present invention, when an STA receives a neighboring AP information field including an unrecognized (unrecognizable, unknown) TBTT information field type subfield value, the neighboring AP information field or the rest of the RNR element including the neighboring AP information field can be ignored.

[0453] That is, an AP (reporting AP) included in an AP MLD can send a frame (such as a beacon frame or a probe response frame) including an RNR element to a non-AP STA included in a non-AP MLD, and the non-AP STA can, based on this, obtain and discover information about other APs (reported APs) included in the AP MLD. At this time, when the value of the TBTT information field type subfield included in the aforementioned RNR element is an unrecognizable (or unknown) value, the non-AP STA can ignore the remaining fields (or octets) of the RNR element without processing. However, when the value of the TBTT information field type subfield included in the RNR element is a recognizable (or known) value, the non-AP STA can process, based on the value of the TBTT information field type subfield, up to the length of a part of the TBTT information fields included in the TBTT information set (or up to a part of the octets) or all of them according to the value of the TBTT information length subfield. At this time, the unprocessed part may be ignored.

[0454] Specifically, all the TBTT information fields included in the neighboring AP information field may be the same in terms of format, length, content, etc., and the length may be indicated by the TBTT information length subfield. When the length of the TBTT information...

Claims

1. A multi-link device (MLD) including a plurality of stations each operating on a plurality of links, wherein a processor receives a frame from an AP of an AP MLD including a plurality of APs, the frame including a reduced neighbor report (RNR) element including one or more neighbor AP information fields containing information related to other APs included in the AP MLD, the neighbor AP information field including a TBTT (target beacon transmission time) information field type subfield, a TBTT information length field, and a TBTT information set field including one or more TBTT information fields, performs processing of each of the one or more TBTT information fields based on the TBTT information field type subfield and the TBTT information length field, when the value of the TBTT information field type subfield is "0", each of the one or more TBTT information fields compares the value of the TBTT information length field with a first threshold value and / or a second threshold value, and is processed only up to a first octet value or a second octet value, when the value of the TBTT information field type subfield is "1", each of the one or more TBTT information fields compares the value of the TBTT information length field with a third threshold value and is processed only up to a third octet value, the MLD.

2. The TBTT information field type subfield is used to indicate the content and / or length of the one or more TBTT information fields, the TBTT information length field indicating the length of each of the one or more TBTT information fields, the MLD according to Claim 1.

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

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

5. When the value of the TBT T information type subfield is "0" and the value of the TBT T information length field is equal to or greater than the first critical value, the one or more TBT T information fields are processed only up to the first octet value. The MLD according to claim 1, wherein the second octet value is smaller than the first octet value.

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

7. The MLD according to claim 1, wherein when the value of the TBT T information type subfield is "0" and the value of the TBT T information length field is smaller than the second critical value, the one or more TBT T information fields are not processed.

8. The MLD according to claim 1, wherein when the value of the TBT T information type subfield is "1" and the value of the TBT T information length field is equal to or greater than the third critical value, the one or more TBT T information fields are processed only up to the third octet value.

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

10. The MLD according to claim 1, wherein when the value of the TBT T information type subfield is "1" and the value of the TBT T information length field is smaller than the third critical value, the one or more TBT T information fields are not processed.

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

12. When the other AP is included in the AP MLD, the offset value indicated by the neighboring AP TBT T offset subfield is set to a value other than a preset value associated with Unknown, the MLD according to claim 11.

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

14. A method performed by a multi-link device (Multi-Link Device: MLD) including a plurality of stations each operating on a plurality of links in a wireless communication system, the method comprising: Receiving a frame from an AP of an AP MLD including a plurality of APs (Access points), The frame includes an RNR (Reduced Neighbor Report) element including one or more neighbor AP information fields (Neighbor AP information field) including information related to other APs included in the AP MLD, The neighbor AP information field includes a TBT T (target beacon transmission time) information field type subfield, a TBT T information length field, and a TBT T information setting field ((TBT T information set field) including one or more TBT T information fields), Processing each of the one or more TBT T information fields based on the TBT T information type subfield and the TBT T information length field, When the value of the TBT T information type subfield is "0", each of the one or more TBT T information fields compares the value of the TBT T information length field with a first threshold value and / or a second threshold value, and is processed only up to a first octet value or a second octet value, When the value of the TBT T information type subfield is "1", each of the one or more TBT T information fields compares the value of the TBT T information length field with a third threshold value and is processed only up to a third octet value.

15. The TBT T information field type subfield is used to indicate the content and / or length of the one or more TBT T information fields. The method according to claim 14, wherein the TTBT information length field indicates the length of each of the one or more TTBT information fields. **Claim 16** When the value of the TTBT information type subfield is "0", the value of the TTBT information length field is less than the first critical value, and is equal to or greater than the second critical value, each of the one or more TTBT information fields is processed only up to the second octet value, The method according to claim 14, wherein the second octet value is less than the first octet value. **Claim 17** The method according to claim 16, wherein in each of the one or more TTBT information fields, the remaining octets up to the second octet value are not processed. **Claim 18** When the value of the TTBT information type subfield is "0", and the value of the TTBT information length field is equal to or greater than the first critical value, the one or more TTBT information fields are processed only up to the first octet value, The method according to claim 14, wherein the second octet value is less than the first octet value. **Claim 19** The method according to claim 18, wherein in each of the one or more TTBT information fields, the remaining octets up to the first octet value are not processed. **Claim 20** The method according to claim 14, wherein when the value of the TTBT information type subfield is "0" and the value of the TTBT information length field is less than the second critical value, the one or more TTBT information fields are not processed. **Claim 21** The method according to claim 14, wherein when the value of the TTBT information type subfield is "1" and the value of the TTBT information length field is equal to or greater than the third critical value, the one or more TTBT information fields are processed only up to the third octet value. **Claim 22** The method according to claim 21, wherein in each of the one or more TTBT information fields, the remaining octets up to the third octet value are not processed. **Claim 23** The method according to claim 14, wherein when the value of the TTBT information type subfield is "1" and the value of the TTBT information length field is less than the third critical value, the one or more TTBT information fields are not processed.

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

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

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

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