Wireless communication method using multilink and wireless communication terminal using the same

Abstract

To provide a wireless communication method using multilink and a wireless communication terminal using the same.SOLUTION: An AP multilink device includes a transmitting / receiving unit; and a processor. When transmitting on a second link to a non-AP multilink device that operates on a first link and the second link, which are non-STR (Simultaneous Transmit and Receive) links in which transmission is not supported on the other link when reception is performed on either one of the links, the processor determines whether to transmit on the second link to the non-AP multilink device based on whether the non-AP multilink device is transmitting on the first link.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] Recently, as the use of mobile devices has become more widespread, wireless LAN technology that can provide them with high-speed wireless Internet services has been attracting attention. Wireless LAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, embedded devices, etc. to wirelessly connect to the Internet at home, in business, or in specific service areas based on short-distance wireless communication technology.

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

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been pointed out as a weakness of wireless LAN. The purpose of IEEE 802.11n is to increase the speed and reliability of the network and to extend the operating distance of the wireless network. In detail, IEEE 802.11n supports a high throughput (HT) of up to 540Mbps or more in data processing speed, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas on both the transmitting and receiving ends to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As the use of wireless LANs becomes more widespread and applications using them become more diverse, the need for new wireless LAN systems to support data throughput rates (Very High Throughput, VHT) higher than those supported by IEEE 802.11n is emerging. Among them, IEEE 802.11ac supports wide bandwidth (80MHz~160MHz) at 5GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5GHz band, it is expected that initial 11ac chipsets will also support operation in the 2.4GHz band for backward compatibility with existing 2.4GHz band products. Theoretically, this standard allows multi-station wireless LAN speeds of at least 1Gbps and maximum single link speeds of at least 500Mbps. This is done by extending the air interface concepts accepted by 802.11n, such as wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high density modulation (up to 256QAM). Also, there is IEEE 802.11ad, a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, and is suitable for streaming large amounts of data and high bitrate videos such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage that it is difficult to pass through obstacles and can only be used between devices in close proximity.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard is being developed and is in the final stages as the WLAN standard after 802.11ac and 802.11ad to provide high-efficiency and high-performance WLAN communication technology in high-density environments where APs and terminals are densely packed. In an 802.11ax-based WLAN environment, it is necessary to provide high-frequency efficient communication indoors / outdoors in the presence of high density stations and APs (Access Points), and various technologies are being developed to realize this.

[0007] In addition, new WLAN standards have begun to be developed to increase maximum transmission speeds to support new multimedia applications such as high-definition video and real-time games. IEEE 802.11be (Extremely High Throughput, EHT), the 7th generation WLAN standard, is currently being developed with the goal of supporting transmission rates of up to 30Gbps in the 2.4 / 5 / 6GHz bands through wider bandwidth, increased spatial streams, and multiple AP cooperation. Summary of the Invention [Problem to be solved by the invention]

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

[0009] According to an embodiment of the present invention, an AP multilink device includes a transceiver unit and a processor, and when transmitting to a non-AP multilink device operating on a first link and a second link that are non-STR (simultaneous transmit and receive) links that do not support simultaneous reception of the non-AP multilink device on one link and transmission of the non-AP multilink device on another link, the processor can determine whether to transmit to the non-AP multilink device on the second link based on whether the non-AP multilink device is transmitting on the first link.

[0010] The processor may not transmit to the non-AP multi-link device on the second link if the non-AP multi-link device is transmitting on the first link.

[0011] When the non-STR multi-link device is transmitting on the first link, the processor can transmit on the second link to another device other than the non-AP multi-link device instead of transmitting to the non-AP multi-link device.

[0012] When transmitting to a device other than the non-AP multilink device on the second link, the processor can transmit traffic having the same priority or a higher priority than the traffic for transmission to the non-AP multilink device.

[0013] The processor can maintain the value of a contention window (CW) used for channel access for transmission to the non-AP multilink device in the second link and use it for channel access for transmission to the other device. In the channel access procedure of the AP multilink device, the multilink device obtains a random number within the CW and sets it as an initial value of a backoff counter, and when the channel is detected as idle during a slot time, the multilink device decrements the backoff counter by 1, and performs transmission when the backoff counter reaches 0.

[0014] The processor can perform transmissions whose ends are synchronized on the first link and the second link. In this case, the transmissions whose ends are synchronized on the first link and the second link may end with a time difference within a pre-specified time interval. The processor can receive a transmission subsequent to the synchronized transmission from at least one of the first link and the second link. In this case, an interval between the subsequent transmission and the synchronized transmission transmitted on the link on which the subsequent transmission was transmitted may be the sum of a SIFS and a time within a pre-specified time interval.

[0015] In a channel access procedure of the AP multilink device, the AP multilink device may obtain a random number in a CW and set it as an initial value of a backoff counter, decrement the backoff counter by 1 if the channel is sensed to be idle during a slot time, and perform transmission when the backoff counter reaches 0. When a channel access procedure is completed in the first link, the processor may perform transmission in the first link and the second link if the channel of the second link is idle for a first predetermined time.

[0016] The processor can, upon completion of a channel access procedure on the first link, begin transmitting on the first link and the second link within a second pre-specified time difference if the channel of the second link is idle for a pre-specified time.

[0017] A non-AP multilink device according to an embodiment of the present invention includes a transceiver unit and a processor. The non-AP multilink device operates on a first link and a second link, which are non-STR (simultaneous transmit and receive) links that do not support simultaneous reception of the non-AP multilink device on one link and transmission of the non-AP multilink device on the other link. The processor is capable of not transmitting on the second link while transmitting on the first link, and of starting a request to send / clear to send (RTS / CTS) frame exchange on the second link after completing transmission on the first link.

[0018] The processor can receive a transmission whose end is synchronized on the first link and the second link. In this case, the transmission whose end is synchronized on the first link and the second link may end with a time difference within a pre-specified time interval. The processor can transmit a transmission subsequent to the synchronized transmission on at least one of the first link and the second link. In this case, an interval between the subsequent transmission and the synchronized transmission transmitted on the link on which the subsequent transmission was transmitted may be a sum of a SIFS and a time within a pre-specified time interval.

[0019] When a change occurs to the frequency band of one of the links, information regarding whether STR is supported or not can be transmitted.

[0020] In a channel access procedure of the non-AP multilink device, the non-AP multilink device may obtain a random number within a contention window (CW) and set it as an initial value of a backoff counter, decrement the backoff counter by 1 if the channel is sensed to be idle during a slot time, and perform transmission when the backoff counter reaches 0. The processor may maintain the value of the backoff counter for the non-performed transmission as 0.

[0021] In the channel access procedure of the non-AP multilink device, the non-AP multilink device may obtain a random number in a CW and set it as an initial value of a backoff counter, decrement the backoff counter by 1 if the channel is detected as idle during a slot time, and perform transmission when the backoff counter reaches 0. In this case, when the channel access procedure is completed in the first link, the processor may perform transmission in the first link and the second link if the channel of the second link is idle for a first predetermined time.

[0022] The processor can, upon completion of a channel access procedure on the first link, begin transmitting on the first link and the second link within a second pre-specified time difference if the channel of the second link is idle for a pre-specified time.

[0023] An operating method of an AP multi-link device in one embodiment of the present invention includes, when transmitting on the second link to a non-AP multi-link device operating on a first link and a second link which are non-STR (simultaneous transmit and receive) links in which transmission is not supported on the other link when reception is performed on either link, determining whether to transmit to the non-AP multi-link device on the second link based on whether the non-AP multi-link device is transmitting on the first link.

[0024] The step of determining whether to transmit to the non-AP multi-link device over the second link based on whether transmission is in progress over the first link may include a step of not transmitting to the non-AP multi-link device over the second link if the non-AP multi-link device is transmitting over the first link.

[0025] The operating method may further include a step of transmitting to another device other than the non-AP multi-link device on the second link instead of transmitting to the non-AP multi-link device if the non-STR multi-link device is transmitting on the first link.

[0026] The step of transmitting to other devices other than the non-AP multilink device may further include the step of transmitting traffic having the same priority or higher priority as traffic for transmission to the non-AP multilink device when transmitting to other devices other than the non-AP multilink device on the second link.

[0027] The operating method may further include maintaining a value of a contention window (CW) used for channel access for transmission to the non-AP multilink device in the second link and using it for channel access for transmission to the other device. In the channel access procedure of the AP multilink device, the multilink device may obtain a random number within the CW and set it as an initial value of a backoff counter, decrement the backoff counter by 1 when the channel is detected as idle during a slot time, and perform transmission when the backoff counter reaches 0.

[0028] The method includes performing transmission in which the end of transmission is synchronized between the first link and the second link, and the transmission in which the end of transmission is synchronized between the first link and the second link is terminated with a time difference within a pre-specified time period; and

[0029] The method may further include receiving a transmission subsequent to the synchronized transmission from at least one of the first link and the second link, wherein an interval between the subsequent transmission and the synchronized transmission transmitted on the link on which the subsequent transmission was transmitted is the sum of a SIFS and a time within a pre-specified time interval.

[0030] In a channel access procedure of the AP multilink device, the AP multilink device may obtain a random number within a contention window (CW) and set it as an initial value of a backoff counter, decrement the backoff counter by 1 if a channel is detected as idle during a slot time, and perform transmission when the backoff counter reaches 0. The operating method may further include performing transmission on the first link and the second link if a channel of the second link is idle for a first predetermined time when the channel access procedure is completed on the first link.

[0031] The operating method may further include a step of starting transmission on the first link and the second link with a difference of a second predetermined time if a channel of the second link is idle for a predetermined time when a channel access procedure is completed on the first link. Effect of the Invention

[0032] An embodiment of the present invention provides a wireless communication method that efficiently uses multiple links and a wireless communication terminal that uses the same. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing the configuration of an access point according to an embodiment of the present invention. [Diagram 5] 1 is a diagram illustrating a process in which a STA sets up a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] 1 shows examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8(a)] 1 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and a method for indicating the same according to an embodiment of the present invention. [Figure 8(b)] 1 illustrates an example of various EHT PPDU formats and a method for indicating the same according to an embodiment of the present invention. [Figure 8(c)]1 illustrates an example of various EHT PPDU formats and a method for indicating the same according to an embodiment of the present invention. [Figure 8(d)] 1 illustrates an example of various EHT PPDU formats and a method for indicating the same according to an embodiment of the present invention. [Figure 9] 1 illustrates a multi-link device according to an embodiment of the present invention. [Figure 10] 1 illustrates a multi-link operation in which transmissions on different links are performed simultaneously according to an embodiment of the present invention. [Figure 11] 4 illustrates the operation of a multilink device when a link is changed according to one embodiment of the present invention. [Figure 12] According to one embodiment of the present invention, when any one station of a non-STR multilink device is receiving, channel access of other stations of the non-STR multilink device is prohibited. [Figure 13] 13 shows an operation of canceling channel access inhibition when it is confirmed that the intended recipient of a PPDU received by a station in a non-STR multilink device is not a station according to an embodiment of the present invention. [Figure 14] 13 shows a station according to an embodiment of the present invention performing channel access after channel access prohibition is lifted. [Figure 15(a)] 11 illustrates an operation of a station performing transmission after channel access prohibition is lifted according to an embodiment of the present invention. [Figure 15(b)] 11 illustrates an operation of a station performing transmission after channel access prohibition is lifted according to an embodiment of the present invention. [Figure 16] 13 illustrates transmissions based on the state of stations in a non-STR multilink device according to an embodiment of the present invention. [Figure 17(a)] This shows a situation where interference or collision between links may occur. [Figure 17(b)] This shows a situation where interference or collision between links may occur. [Figure 18(a)]1 illustrates an operation of an STR multilink device ceasing transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 18(b)] 1 illustrates an operation of an STR multilink device ceasing transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 19] 13 shows how the STR multilink device processes the value of CW when it recognizes a transmission collision between links according to an embodiment of the present invention. [Figure 20(a)] 13 illustrates an operation of an STR multilink device performing channel access again after stopping transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 20(b)] 13 illustrates an operation of an STR multilink device performing channel access again after stopping transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 20(c)] 13 illustrates an operation of an STR multilink device performing channel access again after stopping transmission to a non-STR multilink device according to an embodiment of the present invention. [Figure 21] 13 illustrates an operation of an STR multilink device transmitting a CTS-to-Self frame before transmitting to a non-STR multilink device according to an embodiment of the present invention. [Figure 22] 1 shows that multiple APs included in a STR multi-link device transmit to multiple stations included in one non-STR multi-link device according to an embodiment of the present invention. [Diagram 23] According to an embodiment of the present invention, a plurality of APs included in an STR multilink device perform a plurality of transmissions, the end of which is synchronized, to a plurality of stations included in a single non-STR multilink device. [Figure 24] 1 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention. [Diagram 25] 25 illustrates a hidden node problem that occurs in the RTS / CTS frame exchange procedure according to the embodiment described in FIG. 24. [Figure 26]1 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention. [Figure 27] 10 shows that a multilink device transmits a response to a control frame exceptionally even when channel access is prohibited according to an embodiment of the present invention. [Figure 28] Indicates that a transmission to a station on a non-STR multilink device should be retransmitted. [Figure 29] 13 shows that, according to an embodiment of the present invention, a control frame is transmitted on a link in which a station in which channel access is not prohibited operates, rather than on a link in which a station in which channel access is prohibited operates. [Diagram 30] 4 illustrates a multi-link device sending an ACK according to an embodiment of the present invention. [Figure 31(a)] 13 shows an element field indicating information regarding support for receiving or transmitting a sink PPDU according to an embodiment of the present invention. [Figure 31(b)] 13 shows an element field indicating information regarding support for receiving or transmitting a sink PPDU according to an embodiment of the present invention. [Diagram 32] 1 illustrates a non-STR multi-link device performing an inter-link TXOP power save mode operation according to an embodiment of the present invention. [Diagram 33] 1 illustrates that a station in a non-STR multilink device enters a power saving state while waiting to receive a sync PPDU according to an embodiment of the present invention. [Diagram 34] 10 illustrates a state in which a station in a non-STR multilink device enters a power saving state while waiting to receive a sync PPDU according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The terms used in this specification are selected as general terms that are currently widely used as much as possible in consideration of the functions of the present invention, but this may vary depending on the intentions, customs, or the emergence of new technologies of the engineers in the relevant technical field. In addition, in certain cases, the applicant may arbitrarily select terms, and in such cases, the meanings of the terms will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be interpreted not simply as terms, but based on the substantial meanings of the terms and the contents of this specification as a whole.

[0035] Throughout the specification, when a component is "connected" to another component, this includes not only when it is "directly connected" to another component, but also when it is "electrically connected" with another component in between. Furthermore, when a component "includes" a specific component, this means that it may further include the other component, not excluding the other component, unless otherwise specified to the contrary. In addition, limitations such as "greater than" or "less than" based on a specific critical value may be appropriately replaced with "more than" or "less than" depending on the embodiment.

[0036] Hereinafter, in the present invention, the terms field and subfield may be used interchangeably.

[0037] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0038] A wireless LAN system includes one or more Basic Service Sets (BSS), which are a set of devices that can successfully synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0039] As shown in FIG. 1, infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 which are stations providing a distribution service, and a distribution system DS which connects multiple access points AP-1 and AP-2.

[0040] A station (STA) is any device including a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard, and in a broad sense includes not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and further includes a user interface unit and a display unit, etc., depending on the embodiment. The processor generates frames to be transmitted through a wireless network, processes frames received through the wireless network, and performs various other processes for controlling the station. The communication unit is functionally connected to the processor and transmits and receives frames through the wireless network for the station. In the present invention, the term "terminal" is used to include a user equipment (UE).

[0041] An access point (AP) is an entity that provides a connection to a distribution system DS via a wireless medium for a station associated therewith. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP, but when a direct link is set up, direct communication is possible between non-AP stations. Meanwhile, in the present invention, AP is used as a concept including a personal BSS coordination point (PCP), but in a broad sense, AP includes all concepts such as a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller. In the present invention, AP is also referred to as a base wireless communication terminal, but in a broad sense, the base wireless communication terminal is used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point TP. In addition, the base wireless communication terminal includes various types of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with a plurality of wireless communication terminals.

[0042] A plurality of infrastructure BSSs are connected to each other via a distribution system DS. In this case, a plurality of BSSs connected to each other via the distribution system is called an Extended Service Set (ESS).

[0043] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention, in which the same or corresponding parts in the embodiment of FIG. 2 are the same as or correspond to the embodiment of FIG.

[0044] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so all stations (STA6, STA7) are not connected to an AP. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0045] 3 is a block diagram showing a configuration of a station 100 according to an embodiment of the present invention. As shown in the figure, 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.

[0046] First, the communication unit 120 transmits and receives wireless signals such as wireless LAN packets, and may be built into or externally provided in the station 100. According to an embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules of different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 may include a communication module using a frequency band of 7.125 GHz or more and a communication module using a frequency band of 7.125 GHz or less. Each communication module may 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 may operate only one communication module at a time or operate multiple communication modules simultaneously according to the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided in an independent form, or multiple modules may be integrated into one chip. In an embodiment of the present invention, the communication unit 120 may represent a radio frequency (RF) communication module that processes RF signals.

[0047] Next, the user interface 140 includes various types of input / output means provided in the station 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on a command from the processor 110 using various output means.

[0048] Then, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects such as a user interface based on the contents performed by the processor 110 or a control command of the processor 110. The memory 160 also stores control programs used by the station 100 and various data associated therewith. Such control programs include connection programs required for the station 100 to connect to an AP or an external station.

[0049] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information on the priority conditions of the station 100 included in the communication setup message and requests a connection to the AP based on the information on the priority conditions of the station 100. The processor 110 of the present invention may refer to a main control unit of the station 100, or may refer to a control unit for individually controlling some components of the station 100, for example, the communication unit 120, depending on the embodiment. That is, the processor 110 may be a modem that modulates and demodulates a wireless signal transmitted and received from the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations of transmitting and receiving wireless signals of the station 100 according to an embodiment of the present invention. A detailed embodiment of the present invention will be described later.

[0050] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks are used to logically distinguish the elements of the device. Thus, the above-mentioned device elements may be mounted on one chip or multiple chips depending on the design of the device. For example, the processor 110 and the communication unit 120 may be integrated and embodied on one chip, or may be embodied on separate chips. In addition, in an embodiment of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0051] 4 is a block diagram showing a configuration of an AP 200 according to an embodiment of the present invention. As shown in the figure, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, a duplicated description of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in FIG. 3 will be omitted.

[0052] Referring to FIG. 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 may also include a plurality of communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention may include two or more communication modules using different frequency bands, for example, any of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 may 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 may perform wireless communication with a station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 220 may operate only one communication module at a time or operate multiple communication modules simultaneously according to the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF communication module that processes RF (Radio Frequency) signals.

[0053] Next, the memory 260 stores control programs used in the AP 200 and various data associated therewith. Such control programs include a connection program for managing the connection of stations. Also, the processor 210 controls each unit of the AP 200 and controls transmission and reception of data between the units. According to an embodiment of the present invention, the processor 210 executes a program for connection with a station stored in the memory 260 and transmits a communication setting message to one or more stations. At this time, the communication setting message includes information regarding connection priority conditions of each station. Also, the processor 210 performs connection setting in response to a connection request of a station. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates a wireless signal transmitted and received from the communication unit 220. The processor 210 controls various operations of transmitting and receiving wireless signals of the AP 200 according to an embodiment of the present invention. A detailed embodiment thereof will be described later.

[0054] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0055] 5, the link between the STA 100 and the AP 200 is set up through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information of the BSS operated by the AP 200. There are two methods for performing scanning: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0056] The STA 100 that has successfully received wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200 (S107b), and performs an authentication step. After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs an association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited thereto, and association in a broad sense includes both wireless association and wired association.

[0057] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, the server 300 is a server that processes 802.1X-based authentication with the STA 100, and may be physically connected to the AP 200 or may exist as a separate server.

[0058] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0059] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether a channel is occupied or not. If a wireless signal of a certain strength or more is detected, the channel is determined to be occupied and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not the signal is detected is called the CCA threshold. If a wireless signal of a strength greater than the CCA threshold is received by the terminal and the terminal is the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal of a strength less than the CCA threshold is detected, the channel is determined to be idle.

[0060] If the channel is determined to be in an idle state, each terminal having data to transmit performs a backoff procedure after an IFS (Inter Frame Space) according to the status of each terminal, for example, an AIFS (Arbitration IFS) or a PIFS (PCF IFS). In some embodiments, the AIFS is used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while decreasing a slot time of a random number determined for the corresponding terminal during an interval of the idle state of the channel, and a terminal that has exhausted all the slot time attempts to access the corresponding channel. In this manner, a section in which each terminal performs a backoff procedure is called a contention window section. At this time, the random number can be called a backoff counter. That is, an initial value of the backoff counter is set by an integer that is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal can decrease the backoff counter by 1. Also, if the backoff counter reaches 0, the terminal may be allowed to perform channel access on the corresponding channel. Thus, a terminal may be allowed to transmit if the channel is idle during the AIFS time and the backoff counter slot time.

[0061] If a specific terminal succeeds in accessing the channel, the terminal transmits data through the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are assigned new random numbers and perform a backoff procedure again. According to one embodiment, the random numbers newly assigned to each terminal are determined within a range (2*CW) twice the range (contention window, CW) of the random numbers previously assigned to the terminal. Meanwhile, each terminal attempts access by performing a backoff procedure again in the next contention window period, and at this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this manner, each terminal performing wireless LAN communication can avoid collision with each other on a specific channel.

[0062] <Examples of various PPDU formats>

[0063] 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 detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0064] 7(a), the preamble of the legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0065] Referring to FIG. 7(b), the preamble of the HE PPDU further includes a RL-SIG (Repeated Legacy Short Training field), a HE-SIG-A (High Efficiency Signal A field), a HE-SIG-B (High Efficiency Signal B field), a HE-STF (High Efficiency Short Training field), and a 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 an HE preamble. The specific configuration of the HE preamble may be modified according to the HE PPDU format. For example, the HE-SIG-B may be used only in the HE MU PPDU format.

[0066] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes a RL-SIG (Repeated Legacy Short Training field), a U-SIG (Universal Signal field), an EHT-SIG-A (Extremely High Throughput Signal A field), an EHT-SIG-A (Extremely High Throughput Signal B field), an EHT-STF (Extremely High Throughput Short Training field), and an 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 called an EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some formats of the EHT PPDU format.

[0067] The L-SIG field included in the preamble of the PPDU is configured with a total of 64 subcarriers by applying 64 FFT OFDM. Of these, 48 subcarriers excluding the guard subcarriers, DC subcarriers, and pilot subcarriers are used for L-SIG data transmission. Since BPSK and Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information configuration of the L-SIG.

[0068] Referring to FIG. 7(d), the L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field is composed of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of a modulation method such as BPSK / QPSK / 16-QAM / 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. The total length of the PPDU can be indicated by combining the information in the L_RATE field and the L_LENGTH field. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

[0069] The unit of the L_LENGTH field is byte, and a total of 12 bits are allocated so that a maximum of 4095 can be signaled. The length of the corresponding PPDU can be indicated in combination with the L_RATE field. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0070] First, a method in which a legacy or non-legacy terminal analyzes the length of the PPDU using the L_LENGTH field is as follows. When the L_RATE field is set to 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted at 4 us, which is one symbol duration of 64 FFT. Therefore, the number of 64 FFT reference symbols after the L-SIG is obtained by adding 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing it by 3 bytes, which is the transmission amount of one symbol. The length of the PPDU, i.e., the reception time (RXTIME), is obtained by multiplying the obtained number of symbols by 4 us, which is one symbol duration, and adding 20 us for the transmission of the L-STF, L-LTF, and L-SIG. This can be expressed as the following Equation 1.

[0071]

number

[0072] At this time,

[0073]

number

[0074] represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU may be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as shown in Equation 2 below.

[0075]

number

[0076] Here, TXTIME is the total transmission time constituting the PPDU, and is expressed as the following Equation 3. In this case, TX represents the transmission time of X.

[0077]

number

[0078] Referring to the above formula, the length of the PPDU is calculated based on the rounded up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0079] Referring to FIG. 7(e), the U-SIG (Universal SIG) field remains in the EHT PPDU and the PPDU of the succeeding generation of WLAN, and plays a role in identifying which generation of PPDU it is, including 11be. The U-SIG is two symbols of 64FFT-based OFDM and can transmit a total of 52 bits of information. Of these, 43 bits excluding the CRC / tail 9 bits are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0080] The VI bit will maintain the current bit configuration, and even if a subsequent generation PPDU is defined, a current 11be terminal can obtain information about the PPDU from the VI field of the PPDU. To this end, the VI field is composed of PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits, and serves to sequentially distinguish 11be and subsequent generation WLAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the corresponding PPDU is an uplink / downlink PPDU. The BSS color means a BSS-specific identifier defined in 11ax, and has a value of 6 bits or more. The TXOP means a transmit opportunity duration that was transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP containing the corresponding PPDU can be inferred without decoding the MPDU, and has a value of 7 bits or more.

[0081] The VD field may be composed of fields commonly used in any PPDU format, such as PPDU format and BW, which are signaling information useful only for PPDUs of the 11be version, and fields defined differently for each PPDU format. The PPDU format is a division factor that distinguishes EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDU, etc. The BW field mainly signals five basic PPDU BW options of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz (BWs that can be expressed in the form of a power of 20*2 can be called basic BWs), and various remaining PPDU BWs formed by preamble puncturing. After being signaled at 320 MHz, some 80 MHz may be signaled in a punctured form. Also, the punctured and modified channel shape may be directly signaled in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (e.g., a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0082] The fields located after the BW field vary depending on the type and format of the PPDU. The MU PPDU and the SU PPDU may be signaled in the same PPDU format, and a field for distinguishing the MU PPDU from the SU PPDU may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. Both the SU PPDU and the MU PPDU include an EHT-SIG field, but some fields that are not necessary in the SU PPDU may be compressed. In this case, the information of the compressed field may be omitted or may have a reduced size compared to the size of the original field included in the MU PPDU. For example, in the case of the SU PPDU, the common field of the EHT-SIG may be omitted or replaced, or the user-specific field may be replaced or reduced to one, and may have a different configuration.

[0083] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (eg, the RA field, etc.) may be omitted depending on the value of the compression field.

[0084] When a part of the EHT-SIG field of the SU PPDU is compressed, the information included in the compressed field may be signaled together in an uncompressed field (e.g., a common field, etc.). In the case of the MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU was transmitted to itself. Therefore, the AP must transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols of the EHT-SIG field and / or MCS, which is a modulation method. The EHT-SIG field may include the size and location information of the RU assigned to each user.

[0085] In the case of a SU PPDU, a STA may be assigned multiple RUs, and the multiple RUs may be contiguous or discontinuous. If the RUs assigned to the STA are not contiguous, the STA can receive the SU PPDU efficiently only by recognizing the RUs punctured in between. Therefore, the AP can transmit the SU PPDU including information on the punctured RUs among the RUs assigned to the STA (e.g., the puncturing pattern of the RUs, etc.). That is, in the case of a SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and the puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field may signal the type of discontinuous channels that appear within the bandwidth.

[0086] The form of the signaled discontinuous channel is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, in the case of a SU PPDU, since it is a PPDU transmitted only to a single UE, the STA can recognize the bandwidth allocated to itself from the BW field included in the PPDU, and can recognize the punctured resources of the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the UE can receive the PPDU in the remaining resource units except for the specific channel of the punctured resource unit. In this case, the multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0087] The reason why only limited discontinuous channel types are signaled is to reduce the signaling overhead of SU PPDU. Since puncturing may be performed for each 20 MHz subchannel, if puncturing is performed for a BW having multiple 20 MHz subchannels such as 80, 160, and 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered as discontinuous) must be signaled by expressing whether or not the remaining 15 20 MHz subchannels except the primary channel are used. In this way, using 15 bits to signal discontinuous channel types for single user transmission may result in excessive signaling overhead when considering the low transmission speed of the signaling part.

[0088] The present invention proposes a method for signaling the discontinuous channel type of SU PPDU, and illustrates the discontinuous channel type determined by the proposed method. In addition, a method for signaling the puncturing types of primary 160 MHz and secondary 160 MHz in the 320 MHz BW configuration of SU PPDU is proposed. The discontinuous channel types allowed when the above discontinuous channel type definition method is applied and a method for signaling the discontinuous channel type with 3 bits are shown in Figures 17 to 19.

[0089] In addition, in one embodiment of the present invention, a method is proposed in which the configuration of the PPDU indicated by the preamble puncturing BW value is different depending on the PPDU format signaled in the PPDU format field. Assuming that the BW field is 4 bits, in the case of EHT SU PPDU or TB PPDU, one symbol of EHT-SIG-A is further signaled after U-SIG, or EHT-SIG-A does not need to be signaled from the beginning, so that up to 11 puncturing modes must be completely signaled using only the BW field of U-SIG in consideration of this. However, in the case of EHT MU PPDU, EHT-SIG-B is further signaled after U-SIG, so up to 11 puncturing modes can be signaled in a different manner from SU PPDU. In the case of EHT ER PPDU, the BW field is set to 1 bit, and it is possible to signal whether the PPDU uses a 20 MHz or 10 MHz band. Detailed puncturing patterns for each PPDU type will be described in detail below with reference to FIG. 11 and FIG. 12.

[0090] FIG. 7(f) shows the format-specific field configuration of the VD field when the PPDU format field of the U-SIG indicates EHT MU PPDU. In the case of MU PPDU, SIG-B, which is a signaling field for simultaneous reception by multiple users, is required, and SIG-B may be transmitted after U-SIG without a separate SIG-A. For this purpose, U-SIG must signal information for decoding SIG-B. Such fields include SIG-B MCS, SIG-B DCM, Number of SIG-B Symbols, SIG-B Compression, and Number of EHT-LTF Symbols.

[0091] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and a method for indicating the same according to an embodiment of the present invention.

[0092] 8, a PPDU may be composed of a preamble and a data portion, and the format of an EHT PPDU, which is one type, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is an EHT PPDU may be indicated based on a PPDU format field included in the U-SIG field.

[0093] 8(a) shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

[0094] 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. The EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame, and is an uplink PPDU used for responding to the trigger frame. Unlike the EHT SU PPDU, the EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0095] 8(c) shows an example of an EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit a PPDU to one or more STAs. In the EHT MU PPDU format, an HE-SIG-B field may be located after the U-SIG field.

[0096] Fig. 8(d) shows an example of an EHT ER SU PPDU format used for single-user transmission with an STA in an extended range. The EHT ER SU PPDU may be used for single-user transmission with a STA in a wider range than the EHT SU PPDU described in Fig. 8(a), and the U-SIG field may be repeatedly positioned on the time axis.

[0097] The EHT MU PPDU described in (c) of FIG. 8 can be used by the AP for downlink transmission to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive the PPDU transmitted from the AP. The EHT MU PPDU can convey AID information of the receiver and / or sender of the PPDU transmitted through the user specific field of the EHT-SIG-B to the STA. Therefore, multiple terminals receiving the EHT MU PPDU can perform spatial reuse based on the AID information of the user specific field included in the preamble of the received PPDU.

[0098] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information regarding a resource unit configuration (e.g., a resource unit division form) in a specific bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field may indicate a resource unit configuration divided by a bandwidth for transmitting the HE MU PPDU so that the STA receives the PPDU. Information on the STA allocated (or designated) to each divided resource unit may be included in a user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field may include one or more user fields corresponding to each divided resource unit.

[0099] For example, a user field corresponding to at least one resource unit used for data transmission among the multiple divided resource units may include the AID of a receiver or sender, and a user field corresponding to the remaining resource units not used for data transmission may include a null STA ID that has already been set.

[0100] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0101] When one wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be improved. In this case, the link is a physical path, and may be configured as one wireless medium that can be used to transmit MSDU (MAC service data unit). For example, when the frequency band of any one link is being used by another wireless communication device, the wireless communication device can continue to communicate using another link. In this way, the wireless communication device can effectively use multiple channels. Also, when the wireless communication device simultaneously communicates using multiple links, the overall throughput can be increased. However, the existing wireless LAN is specified on the premise that one wireless communication device uses one link. For this reason, a wireless LAN operation method for using multiple links is required. A wireless communication method of a wireless communication device using multiple links will be described with reference to Figs. 9 to 26. First, a specific form of a wireless communication device using multiple links will be described with reference to Fig. 9.

[0102] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0103] For the wireless communication method using the above-mentioned multiple links, a multi-link device (MLD) may be defined. The multi-link device may represent a device having one or more affiliated stations. According to a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. Also, the multi-link device may exchange a multi-link element. The multi-link element includes information on one or more stations or one or more links. The multi-link element may include a multi-link setup element, which will be described later. In this case, the multi-link device may be a logical entity. Specifically, the multi-link device may have multiple affiliated stations. The multi-link device may be called a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one MAC service access point (SAP) up to a logical link control (LLC). Also, the MLD may have one MAC data service.

[0104] The stations included in the multilink device can operate on multiple links. Also, the stations included in the multilink device can operate on multiple channels. Specifically, the stations included in the multilink device can operate on different links or different channels. For example, the stations included in the multilink device can operate on different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0105] The operation of the multilink device may be referred to as multilink operation, MLD operation, or multi-band operation. If a station associated with the multilink device is an AP, the multilink device may be referred to as AP MLD. If a station associated with the multilink device is a non-AP station, the multilink device may be referred to as non-AP MLD.

[0106] FIG. 9 shows the operation of communication between non-AP MLD and AP-MLD. Specifically, non-AP MLD and AP-MLD each communicate using three links. AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). Non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate through a first link (Link1). Also, the second AP (AP2) and the second non-AP STA (non-AP STA2) communicate through a second link (Link2). Also, the third AP (AP3) and the third non-AP STA (non-AP STA3) communicate through a third link (Link3).

[0107] The 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 must be preceded for frame exchange in the multi-link. The multi-link device may obtain information required for the multi-link setup from the multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multi-link. In this case, the capability information may include information indicating whether one of the multiple devices included in the multi-link device can transmit and the other devices can receive at the same time. In addition, the capability information may include information regarding links available to each station included in the MLD. In addition, the capability information may include information regarding channels available to each station included in the MLD.

[0108] The multilink setting may be set by negotiation between peer stations. Specifically, the multilink setting may be set by communication between stations without communication with the AP. The multilink setting may be set through any one of the links. For example, even if the first link to the third link are set through the multilink, the multilink setting may be set through the first link.

[0109] Also, a mapping between a traffic identifier (TID) and a link may be set. Specifically, a frame corresponding to a specific TID value may be exchanged only through a link designated in advance. The mapping between a TID and a link may be set on a directional-based basis. For example, when a plurality of links are set between a first multilink device and a second multilink device, the first multilink device may be set to transmit a frame of a first TID to the plurality of first links, and the second multilink device may be set to transmit a frame of a second TID to the first link. Also, a default setting may exist for the mapping between a TID and a link. Specifically, when there is no additional setting in the multilink setting, the multilink device may exchange frames corresponding to a TID in each link according to a default setting. In this case, the default setting may be that all TIDs are exchanged in any one link.

[0110] The TID will be specifically described. The TID is an ID for classifying traffic and data to support QoS (quality of service). The TID may be used and assigned in a layer higher than the MAC layer. The TID may indicate a traffic category (TC) or a traffic stream (TS). The TID may be classified into 16 types. For example, the TID may be designated as one of 0 to 15. The TID value to be used may be designated differently depending on an access policy, a channel access, or a medium access method. For example, when EDCA (enhanced distributed channel access) or HCAF (hybrid coordination function contention based channel access) is used, the TID value may be assigned in the range of 0 to 7. When EDCA is used, the TID may indicate a user priority (UP). In this case, the UP may be designated by the TC or the TS. The UP may be assigned in a layer higher than the MAC. Also, when HCCA (HCF controlled channel access) or SPCA is used, the TID may be assigned a value in the range of 8 to 15. When HCCA or SPCA is used, the TID may indicate a TSID. Also, when HEMM or SEMM is used, the TID may be assigned a value in the range of 8 to 15. When HEMM or SEMM is used, the TID may indicate a TSID.

[0111] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in channel contention in EDCA. QoS stations can guarantee QoS using AC. AC may include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may indicate background, best effort, video, and voice, respectively. AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower ACs. For example, AC_VI may be subdivided into AC_VI primary and AC_VI alternate. AC_VO may be subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to AC. For example, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may have a higher priority in that order. That is, 1 may have a lower priority, and 7 may have a higher priority. Therefore, the priority may be higher 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 ACI (AC index) 0, 1, 2, and 3, respectively. Due to the characteristics of such a TID, the mapping between a TID and a link may represent the mapping between an AC and a link.Additionally, the mapping between links and ACs can represent the mapping between TIDs and links.

[0112] As described above, a TID may be mapped to each of a plurality of links. The mapping may be a designation of a link through which traffic corresponding to a particular TID or AC may be exchanged. Also, a TID or AC that may be transmitted for each transmission direction within a link may be designated. As described above, there may be a default setting for mapping between a TID and a link. Specifically, if there is no additional setting in the multilink setting, the multilink device may exchange frames corresponding to the TID on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on any one link. At any given time, any TID or AC may be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0113] When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to the link may be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames not corresponding to the TID or AC not mapped to the link may not be transmitted on the link. When a link is mapped to a TID or AC, an ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a Block ACK agreement may be determined based on the mapping between the TID and the link. In yet another specific embodiment, the mapping between the TID and the link may be determined based on the Block ACK agreement. Specifically, a Block ACK agreement may be set for a TID mapped to a specific link.

[0114] The above-mentioned TID-to-link mapping may ensure QoS. Specifically, a high priority AC or TID may be mapped to a link where a relatively small number of stations are in operation or where channel conditions are good. The above-mentioned TID-to-link mapping may also allow stations to stay in a power saving state for a longer period of time.

[0115] FIG. 10 illustrates simultaneous transmission of different links in a multi-link operation according to an embodiment of the present invention.

[0116] Depending on the implementation of the multilink device, simultaneous operation in the multilink may not be supported. For example, the multilink device may support simultaneous transmission in multiple links, simultaneous reception in multiple links, or transmission in one link and reception in another link. Reception or transmission in one link may affect reception or transmission in another link. Specifically, transmission in one link may act as interference in another link. Interference from one link of a multilink device acting on another link may be called internal leakage. The smaller the frequency interval between the links, the larger the internal leakage may be. If the internal leakage is not too large, transmission can be performed in another link when transmission is performed in one link. If the internal leakage is large, transmission cannot be performed in another link when transmission is performed in one link. In this way, the simultaneous operation of the multilink device in multiple links may be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multilink device may transmit on multiple links simultaneously, transmit on one link while receiving on another link, or receive on multiple links simultaneously, all of which may be referred to as STR.

[0117] As mentioned above, the multilink device can support STR or can support it in a limited manner. Specifically, the multilink device can support STR only under certain conditions. For example, if the multilink device operates with a single radio, the multilink device may not be able to perform STR. Also, if the multilink device operates with a single antenna, the multilink device may not be able to perform STR. Also, if an internal leak is detected to be equal to or greater than a pre-specified magnitude, the multilink device may not be able to perform STR.

[0118] A station can exchange information on the STR capability of the station with other stations. Specifically, a station can exchange information on the presence or absence of a restriction on the capability of the station to simultaneously transmit on multiple links or simultaneously receive on multiple links with other stations. Specifically, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links can indicate whether the station transmits on multiple links simultaneously, receives on multiple links simultaneously, or transmits and receives simultaneously. In addition, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links may be information indicated in stages. Specifically, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links may be information indicating a stage indicating the magnitude of the internal leakage. In a specific embodiment, the information indicating a stage indicating the magnitude of the internal leakage may be information indicating a stage indicating the magnitude of interference generated by the internal leakage. In yet another specific embodiment, the information indicating a stage indicating a frequency interval between links that may affect the internal leakage may be information indicating a stage indicating the magnitude of the internal leakage. In addition, the information indicating a stage indicating the magnitude of the internal leakage may be information indicating a relationship between the frequency interval between the links and the magnitude of the internal leakage in stages.

[0119] In FIG. 10, a first station (STA1) and a second station (STA2) are affiliated to one non-AP multilink device. Also, a first AP (AP1) and a second AP (AP2) may be affiliated to one non-AP multilink device. A first link (link1) is established between the first AP (AP1) and the first station (STA1), and a second link (link2) is established between the second AP (AP2) and the second station (STA2). In FIG. 10, the non-AP multilink device may perform STR in a limited manner. When the second station (STA2) transmits through the second link (Link2), the first station (STA1)'s reception through the first link (Link1) may be interrupted by the transmission through the second link (Link2). For example, in the following case, the first station (STA1)'s reception through the first link (Link1) may be interrupted by the transmission through the second link (Link2). The second station (STA2) transmits the first data (Data1) via the second link (Link2), and the first AP (AP1) transmits a response (Ack for Data1) to the first station (STA1). The second station (STA2) transmits the second data (Data2) via the second link (Link2). At this time, the transmission time of the second data (Data2) and the transmission time of the response (Ack for Data1) to the first data (Data1) may overlap. At this time, the transmission to the second station (STA2) via the second link (Link2) may cause interference to the first link (Link1). As a result, the first station (STA1) may not be able to receive the response (Ack for Data1) to the first data (Data1).

[0120] The operation of the multilink device performing channel access will now be described. The multilink operation not specifically described can follow the channel access procedure described in FIG.

[0121] The multilink device may perform channel access independently from a plurality of links. In this case, the channel access may be a back-off based channel access. When the multilink device performs channel access independently from a plurality of links and the back-off counters reach 0 in the plurality of links, the multilink device may start transmission simultaneously from the plurality of links. In a specific embodiment, when any one of the back-off counters of the links of the multilink reaches 0 and a pre-specified condition is satisfied, the multilink device may perform channel access not only for the link whose back-off counter reaches 0 but also for other links whose back-off counters have not reached 0. Specifically, when any one of the back-off counters of the links of the multilink reaches 0, the multilink device may perform energy sensing in other links whose back-off counters have not reached 0. In this case, when energy equal to or greater than a pre-specified magnitude is not detected, the multilink device may perform channel access not only for the link whose back-off counter reaches 0 but also for the link whose energy sensing has been performed. In this way, the multilink device may start transmission simultaneously from the plurality of links. The threshold value used for energy sensing may be smaller than the threshold value used when determining whether to decrease the back-off counter. In addition, when determining whether to decrease the back-off counter, the multilink device can sense any type of signal, not just a WLAN signal. In addition, in the above-mentioned energy sensing, the multilink device can sense any type of signal, not just a WLAN signal. Internal leakage may not be detected as a WLAN signal. In such a case, the multilink device can sense a signal detected due to internal leakage by energy sensing. In addition, as described above, the threshold value used for energy sensing may be smaller than the threshold value used when determining whether to decrease the back-off counter. Therefore, even when transmission is being performed on one link, the multilink device can decrease the back-off counter on the other link.

[0122] Depending on the degree of interference between links used by the multilink apparatus, the multilink apparatus may determine whether stations operating on each link can operate independently. In this case, the degree of interference between links may be the magnitude of interference sensed by other stations of the multilink apparatus when any one station of the multilink apparatus transmits on any one link. When the transmission of a first station of the multilink apparatus on the first link causes interference of a predetermined magnitude or more to a second station of the multilink apparatus operating on the second link, the operation of the second station may be restricted. Specifically, the reception or channel access of the second station may be restricted. When interference occurs, the second station may fail to decode a signal received due to the interference. Also, when interference occurs, the second station may determine that the channel is in use when the second station accesses the channel using backoff.

[0123] In addition, when the transmission of the first station of the multilink device through the first link generates interference of less than a pre-specified magnitude in the second station of the multilink device operating through the second link, the first station and the second station can operate independently. Specifically, when the transmission of the first station of the multilink device through the first link generates interference of less than a pre-specified magnitude in the second station of the multilink device operating through the second link, the first station and the second station can perform channel access independently. In addition, when the transmission of the first station of the multilink device through the first link generates interference of less than a pre-specified magnitude in the second station of the multilink device operating through the second link, the first station and the second station can perform transmission or reception independently. When interference of less than a pre-specified magnitude occurs, the second station can successfully decode the received signal even in the presence of interference. In addition, when interference of less than a pre-specified magnitude occurs, the second station can determine that the channel is idle when the second station accesses the channel using backoff.

[0124] The degree of interference occurring between stations of a multilink device may vary depending on the interval between the frequency bands of the links on which the stations operate as well as the hardware characteristics of the multilink device. For example, the internal interference occurring in a multilink device including a high RF (radio frequency) device may be smaller than the internal interference occurring in a multilink device including a low RF device. Therefore, the degree of interference occurring between stations of a multilink device may be determined based on the characteristics of the multilink device.

[0125] FIG. 10 shows that the magnitude of interference generated varies depending on the interval between the frequency bands of the links and the characteristics of the multilink device. In the embodiment of FIG. 10, the first multilink device (MLD#1) includes a first station (STA1)-1 operating on the first link (Link1) and a second station (STA1)-2 operating on the second link (Link2). The second multilink device (MLD#2) includes a first station (STA2)-1 operating on the first link (Link1) and a second station (STA2)-2 operating on the second link (Link2). The frequency interval between the first link (Link1) and the second link (Link2) in which the first multilink device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) in which the second multilink device (MLD#2) operates. However, the magnitude of interference generated varies depending on the difference between the characteristics of the first multilink device (MLD#1) and the characteristics of the second multilink device (MLD#2). Specifically, the magnitude of interference generated in the second multilink device (MLD#2) may be greater than the magnitude of interference generated in the first multilink device (MLD#1). Considering that the magnitude of interference generated may differ depending on the characteristics of the multilink devices and that the presence or absence of STR support may differ depending on the multilink devices, information regarding whether STR is supported or not needs to be exchanged.

[0126] The multilink device may signal whether or not a station included in the multilink device supports STR. Specifically, the AP multilink device and the non-AP multilink device may exchange whether or not an AP included in the AP multilink device supports STR and whether or not an STA included in the non-AP multilink device supports STR. In this embodiment, an element indicating whether or not an STR is supported may be used. The element indicating whether or not an STR is supported may be called an STR support element. The STR support element may indicate whether or not an STR is supported by a station of the multilink device that transmits the STR support element by one bit. Specifically, the STR support element may indicate whether or not an STR is supported by each station included in the multilink device that transmits the STR support element by one bit. In this case, if the station supports STR, the bit value may be 1, and if the station does not support STR, the bit value may be 0. If the multilink device that transmitted the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support STR, and the second station (STA2) does not support STR, the STR support element is 101 1b It is assumed that stations operating in different frequency bands support STR, and the STR support element may omit signaling regarding the presence or absence of STR support between stations operating in different frequency bands. For example, a first station (STA1) operates in a first link of 2.4 GHz, and a second station (STA2) and a third station (STA3) operate in a second link of 5 GHz and a third link of 5 GHz, respectively. In this case, the STR support element may indicate with one bit that STR is supported between the second station (STA2) and the third station (STA3). Also, the STR support element may include only one bit when there are two stations to which the STR support element signals.

[0127] In a specific embodiment, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz among the links of the multi-link device may always be determined as an STR, and therefore, signaling regarding the presence or absence of an STR between the link located at 2.4 GHz and the link located at 5 GHz or 6 GHz may be omitted.

[0128] FIG. 11 illustrates the operation of a multilink device when a link is changed according to one embodiment of the present invention.

[0129] When the frequency band of the link is changed, the STR support element may be exchanged. As described above, the presence or absence of STR support of the station may change depending on the distance between the frequency bands of the link, and when the frequency band of the link is changed, the presence or absence of STR support of the station may change. When the frequency band of the link is changed, at least one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a 20 MHz main channel may be included. The AP and the station may exchange the STR support element by a request and a response. In still another specific embodiment, when the frequency band of the link is changed, the STR support element may be exchanged without a separate request. Also, in the above embodiment, when the frequency band of the link is changed, it may include a change in the operating channel of the station.

[0130] When a station of a non-AP multilink device cannot perform STR, the station of the non-AP multilink device can request a link change to the AP. Specifically, the station of the non-AP multilink device can request at least one change of the center frequency, the bandwidth of the frequency band, and the 20 MHz primary channel. The link change request may be transmitted to the AP through a link for which the change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP through a link for which the change is not requested. At this time, the link change request may include information indicating a link for which the change is requested. The information indicating a link may be a number identifying the link. In such an embodiment, the link change may be a change of an operating channel within one frequency band. Also, the link change may include information regarding a method of changing the link. Specifically, the link change request may indicate whether to move the center frequency of the link to a frequency higher than the current center frequency, or to move the center frequency of the link to a frequency lower than the current center frequency. In yet another specific embodiment, the link change request may implicitly indicate a change to a frequency band away from an adjacent link. The link change request may also indicate reducing the bandwidth of the link. The link change request may also request changing the position of the primary channel. Specifically, the link change request may indicate changing the position of the primary channel to a channel in a lower frequency band or a channel in a higher frequency band than the current position of the primary channel. The AP that receives the link change request may change the link in response to the link change request. In a specific embodiment, the AP that receives the link change request may ignore the link change request.

[0131] In the embodiment of FIG. 11, the second station (STA2) and the third station (STA3) of the non-AP multilink device are in a state in which STR cannot be supported. The non-AP multilink device requests the AP multilink device to change the third link (Link3). The AP multilink device, having received the link change request, changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can send a change request to the third AP (AP3). In yet another specific embodiment, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0132] When an AP changes a link, the AP may broadcast information about the link change using a beacon frame. In this case, the information about the link change may include information about a frequency of the link. The information about the frequency of the link may include at least one of a change in a center frequency, an operating bandwidth, and a main channel of the link. In addition, the information about the link change may include information about a time point of the link change. In addition, the link change may be completed when a beacon including information about the link change is transmitted.

[0133] In Figure 11, the link on which the third station (STA3) operates is changed, and the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multilink device can send an STR support element to the AP multilink device to signal the presence or absence of changed STR support.

[0134] The above-mentioned link change may not be allowed or the STR may not be supported even if the link change occurs. Also, as in the embodiment of FIG. 11, the AP multilink device may support the STR, but the non-AP multilink device may not support the STR. This is because a relatively high RF device is generally used in the AP multilink device and a relatively low RF device is generally used in the non-AP multilink device. Therefore, a method is required for efficient communication even when one of the multilink devices does not support the STR during communication between the multilink devices. In this case, the STR may indicate that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

[0135] FIG. 12 shows that when any one station of a non-STR multilink device is receiving, other stations of the non-STR multilink device are prohibited from accessing the channel according to one embodiment of the present invention.

[0136] When transmission is performed on one link of the non-STR multilink device and reception is performed on another link of the non-STR multilink device, reception and transmission of the non-STR multilink device may fail. To solve this, when reception is performed on one link of the non-STR multilink device, channel access may be prohibited on the other links of the non-STR multilink device. Specifically, when reception is performed on one link of the non-STR multilink device, backoff of channel access may be prohibited on the other links of the non-STR multilink device. This makes it possible to prevent transmission from starting on the other links of the non-STR multilink device when reception is performed on one link of the non-STR multilink device. In a specific embodiment, when reception starts on one link of the non-STR multilink device, backoff of channel access may be prohibited on the other links of the non-STR multilink device. This may be set by a specific bit of a memory such as a channel access prohibition flag. This may be shared by a memory inside the multilink device to determine whether or not channel access is prohibited. With this embodiment, channel access prohibition can be implemented without a separate frame exchange. For ease of explanation, unless otherwise specified, channel access prohibition as used in this specification refers to prohibiting channel access or transmission in order to protect the transmission or reception of non-STR multilink devices.

[0137] When channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform a back-off procedure regardless of the NAV and CCA results. Also, when channel access is prohibited, a station operating on a link where channel access is prohibited cannot transmit regardless of the NAV and CCA results. However, even if channel access is prohibited, a station operating on a link where channel access is prohibited can receive. Also, the channel access prohibition on the second link due to reception performed on the first link may be released based on the time when reception on the first link is completed. Specifically, the channel access prohibition on the second link due to reception performed on the first link may be released when reception on the first link is completed. In still another specific embodiment, the channel access prohibition on the second link due to reception performed on the first link may be released based on the time when an ACK is transmitted after reception on the first link is completed. Specifically, the channel access prohibition on the second link due to reception performed on the first link may be released based on the time when an ACK is transmitted after reception on the first link is completed. In yet another specific embodiment, the channel access prohibition in the second link due to reception in the first link may be released when the transmission of an ACK is completed after the reception is completed in the first link. Also, immediately after the channel access prohibition is released, the station may immediately decrement the back-off counter without additional sensing. In this case, the additional sensing may represent sensing performed during a DCF Interframe Space (DIFS). In yet another specific embodiment, if the channel is idle for a pre-specified time immediately before the channel access prohibition is released, the station may immediately decrement the back-off counter without additional sensing. In this case, the pre-specified time may be any one of a PCF Interframe Space (PIFS), a DIFS, a Short Interframe Space (SIFS), and an Arbitration Interframe Space (AIFS).

[0138] In the embodiment of FIG. 12, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) receives, interference within the device occurs. As described above, while the first station (STA1) operating on the first link (Link1) receives, the channel access of the second station (STA2) on the second link (Link2) is prohibited. After the first station (STA1) completes reception on the first link (Link1), the channel access prohibition is lifted. Immediately after the channel access prohibition is lifted, the second station (STA2) can reduce the previous backoff counter value by 1, from 3 to 2, without additional sensing.

[0139] For convenience of illustration, in Fig. 12, Rx and Tx are represented by a single block (Tx solid line, Rx dotted line), and the single block may be understood as representing an operation including Tx / Ack reception and Rx / Ack transmission even if a separate Ack block is not shown. This may be equally applied to the drawings described later.

[0140] If the station determines that the intended recipient of the PPDU is not the station, the station may discontinue receiving the PPDU. In such a case, the channel access unblocking operation of the multilink device becomes problematic. In this specification, the intended recipient is used synonymously with the destination station.

[0141] FIG. 13 illustrates an operation of canceling channel access inhibition when it is confirmed that the intended recipient of a PPDU received by a station in a non-STR multilink device is not a station according to an embodiment of the present invention.

[0142] When the station confirms that the intended recipient of the PPDU it receives is not the station, the station can release the channel access prohibition. The station can determine whether the station is the intended recipient of the PPDU based on information indicating the recipient address in the signaling field of the PPDU. In this case, the information indicating the recipient address in the signaling field of the PPDU may be the value of the STA-ID field of the EHT-SIG field described above. Specifically, the station can determine whether the STA-ID field of the EHT-SIG field indicates the station. Also, the station can determine whether the station is the intended recipient of the PPDU based on the value of the RA field of the MAC frame included in the PPDU. Specifically, the station can determine whether the RA field of the MAC frame included in the PPDU indicates the station. In FIG. 13, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first station (STA1) receives a PPDU. The first station (STA1) determines that it is not the intended recipient of the received PPDU and stops receiving the PPDU. At this time, the first station (STA1) can lift the channel access prohibition for the second station (STA2). Even if the channel access prohibition for the second station (STA2) is lifted, the channel access of the second station (STA2) may be delayed due to the NAV set for the second station (STA2).

[0143] As shown in FIG. 13, even if channel access prohibition is lifted, stations included in a non-STR multilink device may not have a channel access opportunity compared to stations not included in the multilink device or stations included in the STR multilink device. Therefore, a method for compensating for channel access opportunities of stations included in a non-STR multilink device is required for fair competition with other stations. For example, immediately after channel access prohibition is lifted, a station whose channel access prohibition has been lifted may be allowed to decrement its backoff counter by 2 or more. This will be described in FIG. 14.

[0144] FIG. 14 shows a station according to an embodiment of the present invention performing channel access after channel access prohibition is lifted.

[0145] A station whose channel access prohibition has been released can decrement its backoff counter by 2 or more immediately after the channel access prohibition is released. This is to ensure fairness in channel access opportunities between the station and other stations, since other stations have performed backoff procedures while the station's channel access was prohibited.

[0146] In yet another specific embodiment, a station whose channel access is prohibited can perform a channel access procedure of CCA (CSMA) and decrementing a back-off counter while channel access is prohibited. In FIG. 14, a non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). In FIG. 14, channel access of the second station (STA2) is prohibited while the first station (STA1) is receiving. In FIG. 14(a), while channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure of CCA (CSMA) and decrementing a back-off counter. In FIG. 14(a), while channel access of the second station (STA2) is prohibited, the second station (STA2) decrements a back-off counter because the channel of the second link (Link2) is idle.

[0147] Also, a station whose channel access is forbidden can delay transmission without starting transmission even if the back-off counter reaches 0 while channel access is forbidden. In this case, the station can maintain the back-off counter value at 0. Also, even if the station delays transmission, the station can maintain the CW value as it is. This is different from the station doubling the CW value because the channel to which the station accesses is busy. This is because the reason for delaying transmission is not because it is determined that the channel is busy. In FIG. 14(b), while the channel access of the second station (STA2) is forbidden, the second station (STA2) can perform a channel access procedure of CCA (CSMA) and decrementing the back-off counter. In FIG. 14(b), while the channel access of the second station (STA2) is forbidden, the channel of the second link (Link2) is idle, so the second station (STA2) decrements the back-off counter. While the channel access of the second station (STA2) is prohibited, the backoff counter of the second station (STA2) reaches 0. The second station (STA2) delays transmission and resumes transmission after the channel access prohibition is lifted.

[0148] As described above, the channel access prohibition can include prohibiting a second station from transmitting when a first station of a non-STR multilink device is transmitting, and can also include prohibiting a second station from transmitting when a first station of a non-STR multilink device is receiving.

[0149] In the embodiment illustrated in FIG. 14(b), when multiple stations are prohibited from channel access, the channel access prohibition of multiple stations is released at the same time, and multiple stations are likely to attempt transmission at the same time. Therefore, a method is required to reduce the probability of transmission collision. This will be explained in FIG. 15.

[0150] FIG. 15 illustrates an operation of a station according to an embodiment of the present invention performing transmission after channel access prohibition is lifted.

[0151] As described above, among the multiple links on which the non-STR multilink device operates, transmission may be performed on a first link and transmission may be prohibited on a second link. When the transmission on the first link is completed, transmission on the second link may be started by exchanging RTS / CTS frames. Thus, when transmission is performed on a first link among the multiple links on which the non-STR multilink device operates, the non-STR multilink device may start exchanging RTS / CTS frames on the second link. After the channel access prohibition of a station whose transmission has been delayed due to channel access prohibition is lifted, the station may start exchanging RTS / CTS (request to send / clear to send) frames before starting the delayed transmission. At this time, if the station cannot receive the CTS frame, it may not be able to start the delayed transmission. In the embodiment of FIG. 15(a), the station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before starting the delayed transmission. After the station receives a CTS frame in response to the RTS frame, it starts the delayed transmission.

[0152] In yet another specific embodiment, after the channel access prohibition of a station whose transmission has been delayed due to the channel access prohibition is lifted, the station can transmit a frame including only a part of the delayed transmission. In this case, after the station receives a response, for example, an ACK, to the frame including only a part of the delayed transmission, the station can transmit the part of the delayed transmission that has not been transmitted. If the station does not receive a response to the frame including only a part of the delayed transmission, the station may not transmit the part of the delayed transmission that has not been transmitted. In this way, the station starts an RTS / CTS exchange after the channel access prohibition is lifted or transmits only a part of the delayed transmission because the collision probability of the transmission after the channel access prohibition is higher than that of a general transmission. Therefore, the above-mentioned embodiment may be mandatory for the transmission performed after the channel access prohibition is lifted. In the existing WLAN operation, the RTS / CTS frame is used to solve the hidden node problem and can be used based on the size of the transmission data. In the above-mentioned embodiment, the RTS / CTS frame is used to prevent transmission collision with a station that is attempting to perform a delayed transmission in order to protect the transmission or reception of a non-STR multilink device.

[0153] As described above, when any one station of the non-STR multilink device receives, the transmission of the other station of the non-STR multilink device may be restricted. In addition, when any one station of the non-STR multilink device transmits, it may be difficult for the other station of the non-STR multilink device to accurately sense the channel state of the link on which the station operates. Specifically, when a first station of the non-STR multilink device transmits, a second station of the non-STR multilink device may always determine that the channel state of the link on which the second station operates is busy. Therefore, even if the channel of the link on which the second station operates is idle, the second station may determine that the channel is busy due to interference within the device. In this way, when a station that cannot determine the channel state due to interference within the device or any one station of the non-STR multilink device continues to transmit, it is said that the other station of the non-STR multilink device is in a blind state. Due to the above-mentioned situation, it may be difficult for a station that is in a blind state to perform a backoff procedure and attempt transmission. In addition, due to the above-mentioned circumstances, it may be difficult for stations in a blind state to start receiving or successfully decode the PPDU. Therefore, a transmission method that takes into account stations in a blind state is required. This will be described in FIG. 16.

[0154] FIG. 16 illustrates transmissions based on the state of stations in a non-STR multilink system according to an embodiment of the present invention.

[0155] A station that is about to transmit to a station of a non-STR multilink device can determine whether to transmit depending on whether the station of the non-STR multilink device is in a blind state. In this case, the station that is about to transmit to a station of a non-STR multilink device can be a station included in the STR multilink device. Also, the station that is about to transmit to a station of a non-STR multilink device can be an AP included in the AP multilink device, and the non-STR multilink device can be a non-AP multilink device. A station that is about to transmit to a station of a non-STR multilink device can determine whether the station of the non-STR multilink device is in a blind state. A station that is about to transmit can determine whether another station of the multilink device in which the station is included is transmitting to the non-STR multilink device. If another station of the multilink device in which the station is included is receiving from the non-STR multilink device, the station can determine that the station of the non-STR multilink device receiving the station's transmission is in a blind state. In the embodiment of FIG. 16, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can inform the first AP (AP1) that it is receiving from the second station (STA2). Specifically, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is the subject of transmission to the second AP (AP2). In yet another specific embodiment, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is currently transmitting.At this time, the first AP (AP1) can determine based on the notification that the first station (STA1) is in a blind state.

[0156] A station does not need to transmit to a station in a blind state. This is because, even if a station transmits to a station in a blind state, there is a high possibility that the station in the blind state will not be able to open reception or will not be able to decode the PPDU. In this case, the station can cancel transmission to the station in the blind state and transmit to another station.

[0157] When the STR multilink device transmits to the non-STR multilink device, the STR multilink device can transmit to the non-STR multilink device through multiple links. Specifically, when the STR multilink device transmits to the non-STR multilink device through the first link, the STR multilink device can start transmitting to the non-STR multilink device through the second link. At this time, the STR multilink device can determine the length of the transmission to be performed on the second link based on the transmission to the non-STR multilink device. Specifically, the STR multilink device can determine the length of the transmission to the non-STR multilink device through the second link based on the length of the transmission to the non-STR multilink device through the first link. In a specific embodiment, the STR multilink device can simultaneously end the transmission on the first link and the transmission on the second link. This is to prevent the transmission to one of the stations of the non-STR multilink device from being terminated first and the transmission to another station of the non-STR multilink device from being performed while one of the stations of the non-STR multilink device transmits a response to the transmission, for example, an ACK. According to the above embodiment, multiple stations of the non-STR multilink device can simultaneously transmit responses to the transmission to multiple stations.

[0158] An STR multilink device cannot determine the state of a station included in a non-STR multilink device in real time. Therefore, even if an STR multilink device operates according to the embodiment described in FIG. 16, interference or transmission collision may occur between the links on which the non-STR multilink device operates. For example, in the embodiment of FIG. 16, the first AP (AP1) may start transmitting to the first station (STA1) before recognizing that the second station (STA2) is transmitting to the second AP (AP2). In this way, the probability of interference or collision between links may be greater than the probability of interference or transmission collision within a link. This will be described in more detail in FIG. 17.

[0159] FIG. 17 illustrates a situation in which interference or collision between links may occur.

[0160] When a transmission of a second station of a non-STR station multilink device to a second AP of the STR AP multilink device begins at the same time as a transmission of a first AP of the STR AP multilink device to a first station of the non-STR station multilink device, a transmission collision may occur between the links. This is shown in Figure 17(a). As mentioned above, this may occur because the STR multilink device cannot determine the status of the stations included in the non-STR multilink device in real time.

[0161] In addition, even if the transmission of the second station of the non-STR station multilink device to the second AP of the STR AP multilink device starts earlier than the transmission of the first AP of the STR AP multilink device to the first station of the non-STR station multilink device, a transmission collision may occur between the links. This is shown in FIG. 17(b). This is because it may take time for the second AP (AP2) to inform the first AP (AP1) that the second station (STA2) is performing transmission. In this way, since a transmission collision occurs even between stations that start transmission at different times, the probability of occurrence of interference or transmission collision between devices may be higher than the probability of occurrence of interference or collision within a link. In addition, the probability of occurrence of interference or transmission collision between links may increase as the time for identifying the sender of the PPDU received by the AP of the STR multilink device is delayed. Therefore, a method for solving this is required. When one of the stations of the STR multilink device is performing reception, it is not necessary to perform channel access of the other stations of the STR multilink device. However, if channel access is prohibited in this way, the meaning of implementing the STR function may be lost. Therefore, a method of non-blocking channel access operation of the STR multilink device is required, which is illustrated in FIG.

[0162] FIG. 18 illustrates an operation of an STR multilink device stopping transmission to a non-STR multilink device according to an embodiment of the present invention.

[0163] When a station of the STR multilink device determines that the station of the non-STR multilink device is in a blind state while the station of the STR multilink device is transmitting to the station of the non-STR multilink device, the STR multilink device can suspend transmission to the station of the non-STR multilink device in the blind state. Specifically, the STR multilink device can determine whether the station of the non-STR multilink device is in a blind state based on a value indicated as STA(AID)-ID in the signaling field of the received PPDU or a TA (transmitting address) field of the MAC frame included in the received PPDU. In this case, the STA-ID may be a value indicating a station transmitting the UL PPDU in the UL PPDU. In a specific embodiment, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state when a value indicated as STA(AID)-ID in the signaling field of the received PPDU indicates a first station included in the non-STR multilink device. In addition, if the TA field of the MAC frame included in the received PPDU indicates a first station included in the non-STR multilink device, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state. The operation of a station after canceling transmission will be described first.

[0164] When a TXOP set for a station of a non-STR multilink device remains, the station that canceled the transmission to the station of the non-STR multilink device can attempt transmission to other stations other than the station of the non-STR multilink device. At this time, the station that canceled the transmission to the station of the non-STR multilink device can transmit to other stations other than the station of the non-STR multilink device without a separate back-off procedure. In a specific embodiment, after canceling the transmission to the station of the non-STR multilink device, if the channel is sensed as idle for a pre-specified time period without a separate back-off procedure, the station that canceled the transmission to the station of the non-STR multilink device can transmit to other stations other than the station of the non-STR multilink device. At this time, the pre-specified time period may be any one of SIFS, PDIF, and DIFS.

[0165] When a station that has cancelled a transmission to a station of a non-STR multilink device transmits to a station other than the station of the non-STR multilink device, the station that has cancelled a transmission to the station of the non-STR multilink device can transmit traffic having the same priority as the traffic of the cancelled transmission or traffic having a higher priority. This is because fairness is not achieved if traffic having a lower priority than the priority of the traffic used when accessing the channel for the cancelled transmission is transmitted. In the above embodiment, the station of the STR multilink device may be an AP.

[0166] A station that cancels transmission to a station in a non-STR multilink device can initialize the TXOP it has set. Specifically, a station that cancels transmission to a station in a non-STR multilink device can send a CF-End frame after canceling transmission. This allows other stations operating on the link scheduled for transmission to use the link.

[0167] In FIG. 18, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state while transmitting to the first station (STA1). Therefore, the first AP (AP1) suspends transmission to the first station (STA1). In FIG. 18(a), after suspending transmission to the first station (STA1), the first AP (AP1) transmits to stations other than the first station (STA1) as in the embodiment described above. In FIG. 18(b), after suspending transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame as in the embodiment described below.

[0168] When a station pauses transmission, it may not transmit the next fragment after transmitting the fragment that was in transmission. In yet another specific embodiment, the station may immediately stop transmitting the packet that was in transmission.

[0169] In the above embodiment, when the STR multilink device stops transmission to a station of the non-STR multilink device in the blind state and transmits to other stations other than the station of the non-STR multilink device in the blind state, it is necessary to inform the other stations that transmission to the other stations may be performed in order to ensure stable reception. A method for this will be described. For convenience of explanation, the other stations other than the station of the non-STR multilink device in the blind state will be called other stations.

[0170] A station of the STR multilink device can insert the address of another station into a MAC frame. Specifically, the station of the STR multilink device can insert the address of the intended recipient of the MAC frame into the RA (receiving address) of the MAC frame, and the address of the other station into a separate field. In yet another specific embodiment, the station of the device can insert the address of the other station into the EHT-SIG. Specifically, the station of the STR multilink device can insert the address of the intended recipient of the PPDU and the address of the other station into the User field of the signaling field of the PPDU. In this case, the address of the other station can be inserted after the address of the intended recipient of the PPDU in the User field of the signaling field of the PPDU.

[0171] In yet another specific embodiment, the station may monitor the reception of the PPDU for a pre-specified time even after it has determined that the station is not the intended recipient of the received PPDU. Specifically, the station may monitor whether the reception of the PPDU continues for a pre-specified time even after it has determined that the station is not the intended recipient of the received PPDU. This allows the station to determine whether the transmission of the PPDU is interrupted and the transmission to the station begins. In this embodiment, if it is determined that the transmission of the PPDU continues for a pre-specified time, the station may enter a doze state. If it is determined that the transmission of the PPDU does not continue for a pre-specified time, the station may remain in a wake-up state. At this time, if a new PPDU is received at the station, the station may decode the PPDU.

[0172] In yet another specific embodiment, a station transmitting a PPDU may insert information into the PPDU, signaling that the transmission of the PPDU may be interrupted. The information signaling that the transmission of the PPDU may be interrupted may be a 1-bit subfield. For example, if the value of the subfield signaling that the transmission of the PPDU may be interrupted is 1, a station receiving the PPDU may determine that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame. If the station determines that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame, the station may postpone entering the power saving state. Also, a station transmitting a PPDU may insert information into a reserved field of the PPDU, signaling that the transmission may be interrupted.

[0173] In this way, it is possible to prevent unnecessary occupation of the channel due to transmission cancellation or interruption.

[0174] When transmission is interrupted or postponed due to a transmission collision between links, the value of the CW used for channel access may be doubled, as in the case of a general transmission failure. When transmission is interrupted or postponed due to a transmission collision between links, unlike a general channel access failure or transmission failure, the value of the CW used for channel access may not be doubled. That is, the station can maintain the value of the CW used for channel access as it is. The purpose of doubling the value of the CW is to increase the range of possible values ​​of the backoff counter and reduce the probability of a transmission collision. If the station can clearly recognize the transmission collision between links, this need may be reduced. Also, when transmission is interrupted or postponed due to a transmission collision between links, the station may double the value of the CW, which may delay the transmission. However, when a transmission collision between links and an intra-link collision occur simultaneously, the station needs to double the value of the CW. This will be described with reference to FIG. 19.

[0175] FIG. 19 shows how the STR multilink device processes the value of CW when it recognizes a transmission collision between links according to an embodiment of the present invention.

[0176] When the station cancels a transmission due to a transmission performed in a non-STR multilink device as in the above-mentioned embodiment, the station can sense the channel state after canceling the transmission. When the channel is sensed not to be idle, the station can double the value of the CW. In this case, the doubling can be performed according to the embodiment described in FIG. 6. Also, when the channel is sensed to be idle, the station can maintain the value of the CW. This embodiment is for treating the channel as being idle differently from a successful transmission because the possibility of a transmission collision occurring in the link is low even if the channel is sensed to be idle. In yet another specific embodiment, when the channel is sensed to be idle, the station can set the value of the CW to the minimum value (CW_min) of the CW of the traffic. This embodiment is for treating the channel as being idle the same as a successful transmission because the possibility of a transmission collision occurring in the link is low. The station can apply the above-mentioned embodiment to the CW of the AC of the traffic included in the canceled transmission.

[0177] In addition, when the station cancels transmission according to the above-described embodiment, the station may not increment the Retry Counter, which may include at least one of a long retry counter and a short retry counter.

[0178] In the above embodiments, canceling a transmission may include at least one of interrupting the transmission and / or delaying the transmission before commencing the transmission.

[0179] If a station sends a CTS-to-Self frame before attempting to transmit and then cancels transmission, the station does not need to initiate an RTS / CTS frame exchange before attempting to transmit after canceling transmission because the NAV has already been set by the CTS-to-Self frame. Also, if the station cancels transmission and then attempts to transmit again, and there is still a TXOP remaining, the station can attempt to transmit without a backoff procedure.

[0180] In FIG. 19, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state while transmitting to the first station (STA1). Therefore, the first AP (AP1) stops transmitting to the first station (STA1). In FIG. 19(a), the first AP (AP1) determines that the channel of the first link (Link1) is idle. At this time, since there is no TXOP remaining, the first AP (AP1) accesses the channel by a backoff procedure. In Fig. 19(b), the first AP (AP1) determines that the channel of the first link (Link1) is not idle. At this time, since the TXOP remains, the first AP (AP1) attempts to transmit without a backoff procedure.

[0181] In the above embodiment, if the channel is detected as idle for a pre-specified time period without a separate back-off procedure after canceling transmission to a station of the non-STR multilink device, the station that canceled transmission to the station of the non-STR multilink device can transmit to other stations other than the station of the non-STR multilink device. At this time, the duration of the pre-specified time period may be an issue. A station that receives a PPDU of a canceled transmission may fail to decode the PPDU. At this time, if the channel is detected as idle for an extended interframe space (EIFS), the station that fails to decode the PPDU may start a back-off procedure. Therefore, it is an issue whether the pre-specified time period should be set to be longer than the EIFS or the same. This will be described with reference to FIG. 20.

[0182] FIG. 20 illustrates an operation of an STR multilink device performing channel access again after stopping transmission to a non-STR multilink device according to an embodiment of the present invention.

[0183] As shown in FIG. 20(a), the pre-specified time interval may be DIFS. This is in consideration of the fact that a station of an STR multilink device acquires a channel access opportunity through a contention procedure and loses the acquired channel access opportunity due to a transmission collision between links. In other words, since a station of an STR multilink device acquires a channel access opportunity through a contention procedure, priority is given to the station compared to other stations performing channel access. When EDCA is applied, DIFS may be replaced with AIFS[AC].

[0184] In yet another specific embodiment, as shown in Fig. 20(b), the pre-specified time interval may be EIFS, which is based on the consideration that the STR multilink device may consider that it has already exhausted its transmission opportunities and on the consideration of fairness with other stations.

[0185] In another specific embodiment, as shown in FIG. 20(c), when the signaling field of the PPDU signals that the transmission may be interrupted, the pre-specified time period may be DIFS. Also, when a station receiving the PPDU detects that the transmission of the PPDU is interrupted, the station may detect whether the channel is idle using DIFS instead of EIFS. In this case, when the channel is detected as idle using DIFS, the station may start a backoff procedure. This embodiment improves the performance of the entire network and ensures fairness between stations. When EDCA is applied, DIFS may be replaced with AIFS [AC].

[0186] As described above, the STR multilink device can recognize that a transmission collision between links may occur. Specifically, when the first station of the STR multilink device completes the backoff procedure, the second station of the STR multilink device may be receiving a PPDU. In this case, if the second station cannot complete decoding of the signaling field of the PPDU, the first station cannot recognize that a transmission collision between links has occurred, but can determine that there is a possibility. In this case, the first station can insert information indicating that transmission may be interrupted into the PPDU to be transmitted, as described above. In addition, the NSTR multilink device can transmit a CTS-to-Self frame before transmitting to the non-STR multilink device for stable and efficient transmission. This will be described with reference to FIG. 21.

[0187] FIG. 21 illustrates an operation in which an STR multilink device transmits a CTS-to-Self frame before transmitting to a non-STR multilink device according to an embodiment of the present invention.

[0188] A station of the STR multilink device can transmit a CTS-to-Self frame before transmitting to the non-STR multilink device. Specifically, if a second station of the STR multilink device attempts to transmit to the non-STR multilink device while a first station of the STR multilink device is receiving, the second station of the STR multilink device can transmit a CTS-to-Self frame before transmitting to the non-STR multilink device. This allows the second station to secure a TXOP for transmission to the non-STR multilink device. Also, the second station can determine whether a transmission to the first station is transmitted from the non-STR multilink device before transmitting to the non-STR multilink device. The second station can determine the destination station of the transmission depending on whether a transmission to the first station is transmitted from the non-STR multilink device. Specifically, if a transmission to the first station is not transmitted from the non-STR multilink device, the second station can transmit to the non-STR multilink device. When a transmission for a first station is transmitted from the non-STR multilink device, a second station can transmit to a station not included in the non-STR multilink device. For example, when the first station plans to transmit a SU-PPDU for a station in the non-STR multilink device, a MU-PPDU including data for a station in the non-STR multilink device, and a PPDU including a trigger frame that triggers a transmission of a station in the non-STR multilink device, the first station can cancel the planned transmission. At this time, the first station can attempt to transmit a SU-PPDU for a station other than the station in the non-STR multilink device, a MU-PPDU including no data for a station in the non-STR multilink device, and a PPDU including a trigger frame that does not trigger a transmission of a station in the non-STR multilink device.In this case, the first station can start transmission after a time greater than SIFS from the time of transmitting the CTS-to-Self frame. Specifically, the first station can start transmission after PIFS from the time of transmitting the CTS-to-Self frame. The station that transmitted the CTS-to-Self frame must start transmission after SIFS from the time of transmitting the CTS-to-Self frame. As in the above-mentioned embodiment, when canceling a planned transmission and attempting a new transmission, processing time is required for the STR multilink device, such as generating a new MPDU to be transmitted. For this reason, an exception to the regulation on the time interval between the CTS-to-Self frame and transmission may be applied. In such an embodiment, the second station cannot transmit beyond the TXOP acquired by the CTS-to-Self in principle.

[0189] In FIG. 21, the STR multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). Since the second AP (AP2) receives and the first AP (AP1) plans to transmit to a station in the non-STR multi-link device, the first AP (AP1) transmits a CTS-to-Self frame before the planned transmission. As described above, the first AP (AP1) determines the destination station for transmission based on the judgment of the station that transmitted the PPDU received by the second AP (AP2). Also, the first AP (AP1) transmits after SIFS or PIFS from the time of transmitting the CTS-to-Self frame.

[0190] The second station can send an RTS frame instead of a CTS-to-Self frame to start the RTS / CTS frame exchange procedure. This allows the second station to achieve a similar effect to sending a CTS-to-Self frame. In the case of an RTS / CTS frame exchange, the second station can only win the TXOP if the destination station is not in the blind state.

[0191] FIG. 22 illustrates a case in which multiple APs included in a STR multilink device transmit to multiple stations included in one non-STR multilink device according to an embodiment of the present invention.

[0192] Multiple stations included in one non-STR multilink device can receive simultaneously. This is because multiple stations receiving simultaneously causes relatively little interference. FIG. 22 shows multiple stations included in one non-STR multilink device receiving simultaneously. In this case, in the STR multilink device, multiple APs included in the STR multilink device can perform multiple transmissions with synchronized end of transmission to multiple stations included in one non-STR multilink device for stable operation of the non-STR multilink device. This will be described in FIG. 23.

[0193] FIG. 23 shows that, according to an embodiment of the present invention, multiple APs included in an STR multilink device perform multiple transmissions with synchronized end of transmission to multiple stations included in a single non-STR multilink device.

[0194] In non-STR links, when a multilink device transmits on one of the links, the multilink device can simplify the channel access procedure for transmissions on the other links. Specifically, when a first station of the multilink device completes a backoff channel access procedure on the first link, if the channel is idle for a pre-specified time period in the link of a second station of the STR multilink device, the second station of the STR multilink device can start transmitting on the second link.

[0195] In a specific embodiment, when one station of the STR multilink device transmits to one station of the non-STR multilink device, the channel access procedure of the other station of the STR multilink device can be simplified. Specifically, when the first station of the STR multilink device completes the back-off channel access procedure of the transmission to the first station of the non-STR multilink device, if the channel is idle in a pre-specified time interval in the link of the second station of the STR multilink device, the second station of the STR multilink device can start transmitting to the second station of the non-STR multilink device. In this case, the pre-specified time interval may be PIFS. This operation may be applied when the first station and the second station of the STR multilink device transmit to the stations included in one non-STR multilink device. In such an embodiment, the first station and the second station can start transmitting with a difference within a pre-specified time interval. The pre-specified time interval may be a slot time.

[0196] In addition, when a first station and a second station of an STR multilink device transmit to a station included in one non-STR multilink device, the end of transmission of the first station and the second station may be synchronized. In this case, the synchronization of the end of transmission of the first station and the second station may indicate that the transmission of the first station and the transmission of the second station end with a difference within a first pre-specified time interval. The first pre-specified time interval may indicate within a slot boundary or within a symbol boundary.

[0197] A plurality of stations of a non-STR multilink device that receives a synchronized transmission end can simultaneously transmit a subsequent transmission, for example, a response. In this case, the response can include an ACK. In a conventional wireless LAN, a subsequent transmission after a reception is transmitted SIFS after the reception. However, transmitting a subsequent transmission with a slight time difference for a plurality of transmissions that have been completed with a slight time difference may complicate the implementation compared to transmitting the subsequent transmissions simultaneously. Therefore, as described above, a plurality of stations of a non-STR multilink device that receives a synchronized transmission end can simultaneously transmit a subsequent transmission. In this case, the interval between the transmissions following at least one of the plurality of transmissions whose transmission ends are synchronized may be the sum of the SIFS and the time within a pre-specified time interval. Specifically, a transmission following a transmission that has been completed earlier among the plurality of transmissions whose transmission ends are synchronized may be transmitted at an interval obtained by adding the SIFS and the time within a pre-specified time interval from the transmission. In this case, the pre-specified time interval may be one of a slot time or a symbol length. In addition, the difference within a pre-specified time interval may be the difference between the end of the last transmission among multiple transmissions whose end is synchronized and the first transmission among multiple transmissions whose end is synchronized.

[0198] In yet another specific embodiment, when multiple transmissions end with a time difference within a first pre-specified time interval, multiple stations receiving the transmission may transmit synchronized subsequent transmissions. The multiple subsequent transmissions with synchronized transmission ends may represent multiple subsequent transmissions transmitted with a time difference within a second pre-specified time interval. Also, the difference within the second pre-specified time interval may be the difference between the end of the last completed transmission among the multiple synchronized transmissions and the first completed transmission among the multiple transmissions with synchronized transmission ends. In this case, the second pre-specified time interval may be smaller than the first pre-specified time interval. In this way, a PPDU with synchronized transmission ends may be called a sync PPDU.

[0199] In FIG. 23, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) and the second AP (AP2) synchronize the end of transmission to the first station (STA1) and the second station (STA2), respectively. That is, after the first station (STA1) ends transmission, the second station (STA2) ends transmission within a time period previously designated by the first station (STA1). The first station (STA1) and the second station (STA2) simultaneously transmit ACK. At this time, the first station (STA1) transmits an ACK after the difference between the end of transmission to the first station (STA1) (SIFS) and the end of transmission to the first station and the end of transmission to the second station (STA2).

[0200] Such an embodiment may be applied to transmissions where the ACK policy is not set to No ACK. In particular, it may also be applied when the ACK policy is not immediate response. In a particular embodiment, when multiple stations of a multilink device receive transmissions that are synchronized in their end of transmission, the multiple stations of the multilink device may simultaneously receive an ACK request and simultaneously transmit an ACK in response to the ACK request. Multiple stations of the multilink device that receive a transmission with an ACK policy set to a value other than No ACK within a pre-specified time period may begin ACKing simultaneously.

[0201] When a non-STR multilink device is present, the non-STR multilink device must be taken into consideration in the operation of transmitting an RTS / CTS frame and a CTS-to-Self frame to set a TXOP. This will be described with reference to Figures 24 to 29.

[0202] FIG. 24 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention.

[0203] Even if a non-STR multilink device exists, the RTS / CTS frame exchange procedure can follow the procedure defined in the existing wireless LAN. The RTS / CTS frame can be used to set the NAV of a station operating on another link. Specifically, a station that receives an RTS / CTS frame can transmit the frame to another station operating on a link other than the link on which the station operates and included in the multilink device in which the station is included.

[0204] However, as in the above embodiment, channel access or transmission may be restricted when a non-STR multilink device is present. This may result in failure to transmit RTS / CTS as shown in Fig. 24. That is, a station planning to transmit to a first station of a non-STR multilink device may not attempt to exchange RTS / CTS frames if a second station of the non-STR multilink device is receiving.

[0205] In FIG. 24, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the first AP (AP1) transmits an RTS frame to the first station (STA1), the second station (STA2) is prohibited from accessing the channel. The second AP (AP2) can determine that the second station (STA2) is prohibited from accessing the channel. Therefore, the second AP (AP2) does not attempt to exchange an RTS / CTS frame with the second station (STA2). In such an embodiment, a hidden node problem may occur. This will be described in FIG. 25.

[0206] FIG. 25 illustrates a hidden node problem that occurs in the RTS / CTS frame exchange procedure according to the embodiment described in FIG.

[0207] As described above, a station transmitting to a station in a non-STR multilink device may transmit without being able to exchange CTS / RTS. At this time, since TXOP is not set to other stations, other stations may attempt to transmit, causing stations in the non-STR multilink device to fail to transmit or receive. In the embodiment of FIG. 25, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). Due to the transmission of the first AP (AP1) to the first station (STA1), the second AP (AP2) was unable to transmit an RTS frame before transmission. Therefore, a TXOP for the transmission of the second AP (AP2) is not set to the station operating on the second link (Link2). Therefore, when the second AP (AP2) transmits to the second station (STA2), a station in another BSS (OBSS STA) transmits on the second link (Link2). As a result, the second station (STA2) fails to receive the transmission of the second AP (AP2). In order to solve this hidden node problem, the following embodiment may be applied.

[0208] In a specific embodiment, if any one station of the non-STR multilink device is receiving, the station may not be allowed to transmit to any station of the non-STR multilink device. In yet another specific embodiment, if a station transmits to a first station of the non-STR multilink device and a second station of the non-STR multilink device is receiving, the station may transmit simultaneously with transmitting to the second station. If a station transmits to a first station of the non-STR multilink device and a second station of the non-STR multilink device is receiving, the station may synchronize the end of transmission to the first station with the end of transmission to the second station. Specifically, if a station transmits to a first station of the non-STR multilink device and a second station of the non-STR multilink device is receiving, the station may end transmission to the first station simultaneously with transmission to the second station. In such an embodiment, transmission to the second station may be performed by another station of the multilink device including the station.

[0209] FIG. 26 illustrates multilink devices exchanging RTS / CTS frames according to an embodiment of the present invention.

[0210] In another embodiment of the present invention, when a second station of the multilink device is about to transmit an RTS frame to a fourth station of the non-STR multilink device while a first station of the multilink device is continuing to transmit to a third station of the non-STR multilink device, the first station may end transmission to the third station before the fourth station is about to transmit the RTS frame. This allows the fourth station to transmit a CTS frame to the second station. Thus, a TXOP tentative setting for frame exchange between the second station and the fourth station can be performed. However, it may be difficult for the first station to end transmission before the fourth station is about to transmit the RTS frame.

[0211] In yet another embodiment of the present invention, when a second station in the multilink device is about to transmit an RTS frame to a fourth station in the non-STR multilink device while a first station in the multilink device continues transmission to a third station in the non-STR multilink device, the second station can transmit the RTS frame to the fourth station in accordance with the end time of the first station's transmission to the third station. To this end, the second station can insert padding into the RTS frame. In this case, the RTS frame can be in an RTS frame format that allows the transmission length to be flexibly adjusted. For convenience of explanation, such an RTS frame format is called an ML (multilink)-RTS frame. The ML-RTS frame can include a pad field for padding. For example, the format of the ML-RTS frame can be the same as the RTS frame format shown in FIG. 26. Also, the first station can insert padding into the transmission to the third station in order to align the RTS frame with the end time of the transmission.

[0212] In the embodiment of FIG. 26, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second AP (AP2) transmits an ML-RTS frame to the second STA (STA2) in accordance with the end of the transmission of the first AP (AP1) to the first station (STA1). Then, when the first station (STA1) transmits an ACK to the first AP (AP1), the second station (STA2) transmits an ACK to the second AP (AP2). As a result, a TXOP for frame exchange between the second AP (AP2) and the second station (STA2) is set in the station operating on the channel of the second link.

[0213] In yet another specific embodiment, another frame for setting NAV may be replaced instead of the RTS / CTS frame. In the above-mentioned embodiment, an ACK request frame may be transmitted instead of the RTS frame. The ACK request frame may include duration information related to a transmission end point. In addition, a frame including an ACK transmitted in response to the ACK request may also include duration information. In this case, the duration information of the frame including an ACK may be set according to the duration information of the ACK request frame.

[0214] Although the above embodiment has been described for the exchange of RTS / CTS frames, it may also be used for the exchange of control frames other than RTS / CTS frames. In this case, the control frame exchange may include the exchange of PS-Poll frames and response frames to PS-Poll.

[0215] FIG. 27 shows that a multilink device transmits a response to a control frame exceptionally even when channel access is prohibited according to an embodiment of the present invention.

[0216] As described in the above embodiment, when a non-STR multilink device exists, some stations may be prohibited from accessing the channel. Even if a station's channel access is prohibited, the station can still send a response to a control frame. Specifically, even if a station's channel access is prohibited, the station can still send a CTS frame in response to an RTS frame.

[0217] In this way, when a response to a control frame is transmitted as an exception to channel access denial, the following embodiment may be applied: A first station transmits a response to a control frame as an exception to channel access denial. When the first station transmits the response to the control frame, a third station transmits to a second station included in the multilink device in which the first station is included. In this case, the third station can perform a retransmission to the first station. The third station can expect that the transmission to the second station will fail.

[0218] In the embodiment of FIG. 27, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP) transmits to the first station (STA1). The second AP (AP2) transmits an RTS frame to the second station (STA2). Since the first station (STA1) receives, the second station (STA2) is prohibited from accessing the channel. However, the second station (STA2) transmits a CTS frame to the second AP (AP2) as an exception to the channel access prohibition. The first AP (AP1) can determine that the first AP (AP1) is likely to fail to transmit due to the CTS frame transmission of the second station (STA2). Therefore, the first AP (AP1) performs a retransmission to the first station (STA1). The retransmission method is described in more detail in FIG.

[0219] FIG. 28 illustrates retransmission of a transmission to a station of a non-STR multilink device.

[0220] In the retransmission described in FIG. 27, only a part of the packets included in the initial transmission may be retransmitted. Specifically, the station performing the retransmission may retransmit only a part of the packets included in the initial transmission. The station performing the retransmission may determine some of the packets included in the initial transmission as packets to be retransmitted based on the time interval in which the station performing the retransmission received a CTS frame. Specifically, the station performing the retransmission may determine, among the packets included in the initial transmission, packets transmitted in a time interval including the time interval in which the station performing the retransmission received a CTS frame as packets to be retransmitted. In this case, the station performing the retransmission may retransmit packets transmitted in a time interval including the time interval in which the station performing the retransmission received a CTS frame based on a propagation delay. In yet another specific embodiment, the station performing the retransmission may retransmit all packets included in the initial transmission.

[0221] Also, a station performing retransmission can perform retransmission before receiving an ACK for a transmission. In this case, after performing retransmission, the station performing retransmission can receive a Block ACK indicating whether or not the initial transmission and the retransmission have been received. Therefore, the station performing retransmission can perform retransmission before a SIFS after the initial transmission. In yet another specific embodiment, a station that fails to receive due to a control frame transmitted as an exception to channel access prohibition can wait to receive the retransmission without transmitting an ACK.

[0222] In the embodiment of Fig. 28, the first AP (AP1) retransmits the fourth and fifth packets in consideration of the interval in which the second AP (AP2) receives the CTS frame and the transmission delay. After the retransmission, the first AP (AP1) receives an ACK including whether or not the retransmission was received.

[0223] FIG. 29 shows that a control frame is transmitted on a link in which a station in which channel access is not prohibited operates, rather than on a link in which a station in which channel access is prohibited operates, according to an embodiment of the present invention.

[0224] As in the embodiment described in FIG. 26, the end of transmission for multiple stations of a non-STR multilink device may be synchronized. However, this is difficult to implement because it may require adjusting an already generated MPDU or generating an MPDU again. Therefore, the multilink device may transmit a control frame through a link in which a station in which channel access is not prohibited operates, rather than a link in which a station in which channel access is prohibited operates. Specifically, the multilink device may transmit a control frame through a link in which a station in the non-STR multilink device is currently receiving from the multilink device. In this case, the control frame may be an RTS frame.

[0225] In the embodiment of FIG. 29, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) transmits to the first station (STA1). Even if the second AP (AP2) succeeds in the backoff procedure, the second AP (AP2) cannot transmit to the second station (STA2) because the first station (STA1) is receiving a transmission sent from the first AP (AP1). At this time, the second AP (AP2) requests the first AP (AP1) to transmit an RTS frame of which the second station (STA2) is the recipient. At this time, the first AP (AP1) may include an RTS frame in which the second station (STA2) is the recipient in the transmission being performed by the first AP (AP1). In yet another specific embodiment, after the first AP (AP1) finishes the transmission being performed by the first AP (AP1), the first AP (AP1) may transmit an RTS frame in which the second station (STA2) is the recipient through the first link (Link1) after SIFS from the transmission. The first station (STA1) receives the RTS frame in which the second station (STA2) is the recipient, and transmits the received RTS frame to the second station (STA2). The second station (STA2) performs CCA in the PIFS. If the channel is idle in the PIFS, the second station (STA2) transmits a CTS-to-Self frame. The first AP (AP1) may stop transmission to the first station (STA1) in a time period in which the second station (STA2) is expected to transmit a response to the RTS frame. Also, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can transmit an ACK for the received transmission. In yet another specific embodiment, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can also transmit a response to the RTS frame.29 is provided to facilitate understanding of the description, and may be used for transmitting control frames other than the RTS frame and the CTS-to-Self frame. Also, time intervals other than the PIFS may be used.

[0226] FIG. 30 illustrates a multi-link device sending an ACK according to an embodiment of the present invention.

[0227] A station in a multilink device can request a link to transmit an ACK to a station in a no-STR multilink device. Specifically, a station in a multilink device can request to transmit an ACK on a link other than the link on which the transmission was made. In the embodiment of FIG. 28, the first AP (AP1) of the STR multilink device transmits (Tx(#2)) to the first station (STA1) of the non-STR multilink device. At this time, the first AP (AP1) requests to transmit an ACK for the transmission (Tx(#2)) on the second link (Link2). This is because the transmission (Tx(#2)) of the first AP (AP1) is completed before the transmission of the second AP (AP2) to the second station (STA2), and it is determined that it is difficult to transmit an ACK for the transmission (Tx(#2)) of the first AP (AP1).

[0228] Also, for such ACK transmission, the station can set an implicit BAR and ACK policy so as not to send an immediate response to the transmission. In yet another specific embodiment, the station can set the ACK policy for the transmission to BlockAckReq. However, in order to send a Block ACK, a BlockAckReq must be sent, which may cause channel access burden and transmission delay. Therefore, a new ACK policy for the multilink device is needed.

[0229] A station in a multilink device can transmit both an ACK for a transmission received by the station and an ACK for a transmission received by another station included in the same multilink device. Such an ACK transmission can be called ML (multilink)-ACK. In addition, ML-ACK may be set as an ACK policy. In the embodiment of FIG. 30, the first AP (AP1) sets the ACK policy for transmission (Tx(#2)) to ML-ACK. After receiving the transmission (Tx(#2)), the first station (STA1) does not transmit an ACK to the first AP (AP1). The second station (STA2) completes reception of the transmission transmitted from the second AP (AP2) and transmits to the second AP (AP2) both an ACK for the transmission from the first AP (AP1) and an ACK for the transmission from the second AP (AP2). The non-STR multi-link device may include a third station (STA3) in addition to the first station (STA1) and the second station (STA2), and the STR multi-link device may include a third AP (AP3) in addition to the first AP (AP1) and the second AP (AP2). In this case, the ACK policy of the transmission from the second AP (AP2) to the second station (STA2) may also be set to ML-ACK. When the transmission from the third AP (AP3) to the third station (STA3) is completed later than the transmission from the second AP (AP2) to the second station (STA3), the third station (STA1) may transmit to the third AP (AP3) an ACK for the transmission from the first AP (AP1) to the first station (STA1), an ACK for the transmission from the second AP (AP2) to the second station (STA2), and an ACK for the transmission from the third AP (AP3) to the third station (STA3).

[0230] This embodiment can prevent interference between links that may occur due to ACK transmissions even if transmissions to stations of non-STR multilink devices are not completed simultaneously. In the above-mentioned embodiment, the ACK policy may be set to BlockAck instead of ML-ACK. In yet another specific embodiment, the ACK policy may be set to No Ack instead of ML-ACK.

[0231] While the multilink device transmits traffic, the number of links that acquire transmission opportunities may increase. In this case, the multilink device may transmit traffic that was intended to be transmitted on a link that acquired a transmission opportunity earlier on a link that acquired a transmission opportunity later. In this case, the NAV set on the link on which the multilink device acquired a transmission opportunity earlier may be set higher than the NAV required to transmit traffic. When the NAV is set higher than the NAV required to transmit traffic on the link on which the multilink device acquired a transmission opportunity earlier, the multilink device can reset the NAV by transmitting a CF-END frame after completing transmission on the link that acquired a transmission opportunity earlier.

[0232] The above-mentioned reception of the SYNC PPDU and signaling related to the reception of the SYNC PPDU will be described with reference to FIGS.

[0233] In order for the first station of the non-STR multilink device to receive the above-mentioned Sync PPDU, it must determine whether the second station, which has a non-STR relationship with the first station, starts receiving the Sync PPDU. In addition, the first station must continuously perform preamble detection (PD). Considering that the first station receiving the Sync PPDU is prohibited from channel access due to the reception of other stations of the non-STR multilink device, such an operation of the first station may be unreasonable. Therefore, the first station can enter a power saving state within a pre-specified condition. The Sync PPDU may be transmitted within an existing TXOP. Therefore, the performance gain obtained by receiving the Sync PPDU may be determined by the length of the remaining TXOP. Therefore, the first station can determine whether to give up receiving the Sync PPDU based on the length of the Sync PPDU. If the first station gives up receiving the Sync PPDU, the first station can enter a power saving state. Such a power saving operation can be called inter-link TXOP power save (PS). A station that has entered the power saving state in the inter-link TXOP PS can wake up from the power saving state to receive frames periodically transmitted from the AP, such as a beacon frame, a TIM frame, and a DTIM frame. Also, when the TXOP ends, for example, when a CF-END frame is transmitted, a station that has entered the power saving state in the inter-link TXOP PS can wake up from the power saving state.

[0234] The above-mentioned TXOP may be changed to a period indicated by the length field of the signaling field of the PPDU and the Duration field of the MAC frame. Specifically, in the above-mentioned embodiment, the station can determine the time occupied by the PPDU based on the period indicated by the length field and the Duration field of the MAC frame.

[0235] The non-AP multilink device may signal information regarding whether or not it supports sync PPDU reception and conditions for supporting sync PPDU to the AP multilink device. Also, the AP multilink device may signal whether or not it supports AP multilink device sync PPDU transmission to the non-AP multilink device. At this time, the multilink device may signal whether or not it supports sync PPDU for each multilink device. For example, the AP multilink device may signal whether or not it supports sync PPDU transmission for each AP multilink device. In still another specific embodiment, the multilink device may signal whether or not it supports sync PPDU for each station. Specifically, the AP multilink device may signal whether or not it supports sync PPDU transmission for each AP included in the AP multilink device. For example, an AP multilink device including a first AP, a second AP, and a third AP may indicate that the first AP supports sync PPDU transmission and that the second AP and the third AP do not support sync PPDU transmission.

[0236] If an AP multilink device associated with a non-AP multilink device signals that it does not support sync PPDU transmission, a station of the non-AP multilink device can enter the power saving state of the inter-link PS described above while other stations of the non-AP multilink device are receiving. This is because the AP multilink device associated with the non-AP multilink device cannot transmit sync PPDUs. In this case, the station of the non-AP multilink device can determine the length of time to maintain the power saving state based on the length of the PPDU received by other stations of the non-AP multilink device.

[0237] Whether or not the sync PPDU transmission or reception is supported may be determined by an operation policy in addition to hardware performance. Therefore, whether or not the sync PPDU transmission or reception is supported may be signaled by information on an operating mode in addition to information on performance. A method of signaling whether or not the sync PPDU transmission or reception is supported will be described in detail with reference to FIG. 31.

[0238] FIG. 31 illustrates an element field indicating information regarding support for receiving or transmitting a sync PPDU according to an embodiment of the present invention.

[0239] As described above, the information indicating whether or not Sync PPDU transmission is supported may be included in an element indicating the station's capabilities. For convenience of explanation, the element indicating the station's capabilities is called a Capability element. In addition, a field of information indicating whether or not Sync PPDU transmission is supported in the Capability element is called a Supporting Sync PPDU Tx subfield. In this case, the Capability element may be a Multi-Link element that indicates capabilities related to multi-link. In addition, the Capability element may be an EHT Capability element that indicates EHT-related capabilities. An example of a Capability element is shown in FIG. 31(a).

[0240] If the value of the Supporting Sync PPDU Tx subfield is 1, the Supporting Sync PPDU Tx may indicate that the station or multilink device indicated by the Supporting Sync PPDU Tx subfield supports the transmission of the sync PPDU. If the value of the Supporting Sync PPDU Tx subfield is 0, the Supporting Sync PPDU Tx may indicate that the station or multilink device indicated by the Supporting Sync PPDU Tx subfield does not support the transmission of the sync PPDU. In addition, if a station not included in the multilink device transmits a Capability element, the Supporting Sync PPDU Tx subfield may signal information that is not related to the presence or absence of support for sync PPDU transmission or may be used as a reserved field.

[0241] As described above, the information indicating whether or not the sync PPDU reception is supported may be included in an element indicating operation-related information of a station. For convenience of explanation, the element indicating operation-related information of a station is referred to as an Operation element. In addition, a field of information indicating whether or not the sync PPDU reception is supported in the Operation element is referred to as a Supporting Sync PPDU Rx Disable subfield. FIG. 31(b) shows an example of an Operation element. When the value of the Supporting Sync PPDU Rx Disabled subfield is 1, it may indicate that the station does not want to receive the sync PPDU. Specifically, when the value of the Supporting Sync PPDU Rx Disabled subfield is 1, the Supporting Sync PPDU Rx Disabled subfield may indicate that the station transmitting the Supporting Sync PPDU Rx Disabled subfield does not want to wait for the reception of the sync PPDU. In a multilink device that sets the value of the Supporting Sync PPDU Rx Disabled subfield to 1, the second station of the multilink device may not perform PD and CCA while the first station of the multilink device is receiving. An AP multilink device connected to a multilink device that has transmitted the Supporting Sync PPDU Rx Disabled subfield may not transmit PPDUs simultaneously to multiple stations of the multilink device that has transmitted the Supporting Sync PPDU Rx Disabled subfield. The PPDU may be a SU PPDU, a Full BW MU PPDU, or an OFDMA MU PPDU transmitted in any one of non-HT PPDU, HT PPDU, VHT PPDU, HE PPDU, and EHT PPDU formats. In this case, the AP multilink device may not transmit a frame requesting a response, for example, an immediate response.The frame requesting a response may include at least one of an RTS, a multi-user RTS (MU-RTS), a trigger frame, and a block ack request (BAR).

[0242] Also, the Operation element may include information related to the minimum length of a sync PPDU that can be received by the station or multilink device that transmitted the Operation element. In this case, a subfield indicating information related to the minimum length of a sync PPDU is called a Remaining TXOP Threshold subfield. The Remaining TXOP Threshold subfield may indicate time. Also, the Remaining TXOP Threshold subfield may indicate in us, ms, or symbol units. A multilink device connected to a multilink device that transmitted the Remaining TXOP Threshold subfield may not be allowed to transmit a sync PPDU that is shorter than the length indicated by the Remaining TXOP Threshold subfield to the multilink device or station that transmitted the Remaining TXOP Threshold subfield.

[0243] Also, when the Remaining TXOP Threshold subfield is set to a pre-specified value, it may indicate that the multilink device or station that transmitted the Remaining TXOP Threshold subfield does not support receiving a Sync PPDU. The pre-specified value may be a value indicating a time greater than the maximum time that the Remaining TXOP Threshold subfield can indicate. In yet another specific embodiment, the pre-specified value may be 0. When such an embodiment is applied, the Sync PPDU Rx Disable subfield may be omitted in the Operation element.

[0244] Also, in the above embodiment, it has been described that the Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield can be signaled by the Operation element. The Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield may be signaled by an element other than the Operation element or by signaling information. In Figures 32 to 34, an embodiment in which the inter-link TXOP power save mode is performed by the signaling described in Figure 31 will be described.

[0245] FIG. 32 illustrates an inter-link TXOP power save mode operation in a non-STR multi-link device according to an embodiment of the present invention.

[0246] When a non-STR multilink device signals that it does not support sync PPDU reception, a second station of the non-STR multilink device may enter a power saving state while a first station of the non-STR multilink device is performing reception. In this case, the second station may maintain the power saving state until the end of the TXOP indicated by the PPDU received by the first station. As described above, the second station may be in a state where the time at which the second station predicts reception of a frame periodically transmitted from the AP is before the end of the TXOP indicated by the PPDU received by the first station. In this case, the second station may wake up from the power saving state before the end of the TXOP indicated by the PPDU received by the first station. As described above, the frame periodically transmitted from the AP may include at least one of a beacon frame, a TIM frame, and a DTIM frame.

[0247] The second station can maintain the power saving state even after the end of the TXOP indicated by the PPDU received by the first station. Specifically, the second station can determine whether to maintain the power saving state even after the end of the TXOP indicated by the PPDU received by the first station, based on information received from the AP to which the second station is connected. At this time, the information received from the AP to which the second station is connected may be NAV-related information. Also, the information received from the AP to which the second station is connected may be operation information of the AP to which the first station is connected. When the NAV set by the second AP of the AP multilink device performing transmission to the second station of the non-AP multilink device has not expired, the first AP of the AP multilink device can transmit information on the expected end time of the transmission or reception of the first AP and the expected expiration time of the NAV to the first station of the non-AP multilink device that signaled that it does not want to receive the sync PPDU. If the NAV set by the second AP of the AP multilink device performing transmission to the second station of the non-AP multilink device has not expired, the second AP may transmit or receive a PPDU from any one of the stations. If the NAV set by the second AP of the AP multilink device performing transmission to the second station of the non-AP multilink device has not expired, the NAV may be set in the second AP by a PPDU not transmitted by the second station.

[0248] In the embodiment of FIG. 32, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multilink device signals that it does not want to receive a sync PPDU. The first AP (AP1) transmits to the first station (STA1). The second station (STA2) then maintains a power saving state until the end of the TXOP indicated by the PPDU transmitted by the first AP (AP1) to the first station (STA1).

[0249] FIG. 33 illustrates a station in a non-STR multilink device entering a power saving state while waiting to receive a sync PPDU according to an embodiment of the present invention.

[0250] A first station of a non-STR multilink device can enter a power saving state of an inter-link TXOP when the remaining duration of a TXOP indicated by a PPDU being received by the first station of the non-STR multilink device is equal to or shorter than the length indicated by the Remaining TXOP Threshold subfield transmitted by the non-STR multilink device. At this time, before entering the power saving state, a second station can receive a sync PPDU transmitted to the second station when the remaining duration of a TXOP indicated by a PPDU being received by the first station is greater than the length indicated by the Remaining TXOP Threshold subfield transmitted by the non-STR multilink device. At this time, the second station can receive the sync PPDU. To this end, the second station can perform PD to determine whether the intended recipient of the received PPDU is the second station. Specifically, the second station can determine whether the AID indicated by the signaling field of the PPDU or the RA of the MAC frame included in the PPDU indicates the second station.

[0251] In the embodiment of FIG. 33, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multilink device signals that it wishes to receive a sync PPDU. At this time, the non-STR non-AP multilink device also signals the minimum TXOP length "a" required to receive the sync PPDU. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sync PPDU. When the TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is equal to or shorter than "a", the second station (STA2) enters the inter-link TXOP power saving state.

[0252] FIG. 34 illustrates a station in a non-STR multilink device entering a power saving state while waiting to receive a sync PPDU according to yet another embodiment of the present invention.

[0253] When a station of a non-STR multilink device detects a PPDU other than a Sync PPDU from a BSS operated by an AP connected to the station of the non-STR multilink device while waiting to receive a Sync PPDU, the station of the non-STR multilink device can enter an inter-link TXOP power saving state. In this case, the station can determine that a PPDU that is not the intended recipient of the station is not a Sync PPDU. In addition, when a station detects a PPDU other than a Sync PPDU from a BSS operated by an AP connected to the station of the non-STR multilink device even if the minimum TXOP signaled by the station remains, the station of the non-STR multilink device can enter an inter-link TXOP power saving state.

[0254] In the embodiment of FIG. 34, the STR AP multilink device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multilink device signals that it wishes to receive a sync PPDU. At this time, the non-STR non-AP multilink device also signals the minimum TXOP length "a" required to receive the sync PPDU. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sync PPDU. The second station (STA2) detects that a PPDU other than the sync PPDU is transmitted from the BSS to which the second station belongs. Although the TXOP of the PPDU sent by the first AP (AP1) to the first station (STA1) is larger than "a", the second station (STA2) enters the inter-link TXOP power saving state.

[0255] Although the present invention has been described above with reference to wireless LAN communication, the present invention is not limited thereto and may be equally applied to other communication systems such as cellular communication, etc. Also, although the method, apparatus and system of the present invention have been described in relation to specific embodiments, some or all of the components and operations of the present invention may be embodied using a computer system having a general-purpose hardware architecture.

[0256] The features, structures, effects, etc. described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. The features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by a person having ordinary knowledge in the field to which the embodiment belongs. Therefore, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

[0257] Although the above description focuses on the embodiments, these are merely illustrative and do not limit the present invention. Those skilled in the art will understand that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present invention. For example, each component specifically illustrated in the embodiments can be modified and implemented. Differences related to such modifications and applications should be interpreted as being included in the scope of the present invention defined in the appended claims. [Explanation of symbols]

[0258] 100 Stations 110 Processor 120 Communications Department 140 User Interface Section 150 display units 160 Memory 200 AP 210 Processor 220 Communications Department 260 Memory 300 Servers

Claims

1. An AP multilink device, A transceiver unit; and A processor is included. The processor, determining whether to transmit to the non-AP multilink device on the second link based on whether the non-AP multilink device transmits on the first link when transmitting to the non-AP multilink device on the second link, wherein the non-AP multilink device operates on the first and second links corresponding to non-simultaneous transmit and receive (STR) links in which transmission of the non-AP multilink device on one of the first and second links is restricted to protect transmission or reception of the non-AP multilink device on the other of the first and second links; configured to: In a channel access procedure for the second link, the processor Obtaining a random number within a contention window (CW); setting the random number as an initial value of a backoff counter for the second link; decrementing the back-off counter by one if the channel is sensed as idle during a slot time, and if the back-off counter is not zero, transmission of the AP multilink device on the second link is not permitted; If the backoff counter is 0, not transmitting on the second link while the non-AP multilink device is transmitting on the first link; maintaining a value of the CW after the non-transmission, the value of the CW being adjusted based on whether channel access for traffic was successful; and further configured to: AP multilink device.

2. The AP multilink device of claim 1, wherein the processor is configured to transmit to a device other than the non-AP multilink device, instead of transmitting to the non-AP multilink device on the second link while the non-AP multilink device is transmitting on the first link.

3. The AP multilink device of claim 2, wherein the processor is configured to transmit traffic having the same or higher priority as the traffic of the transmission to the non-AP multilink device when transmitting to the other device other than the non-AP multilink device on the second link.

4. The processor, performing synchronized transmission on the first link and the second link, the synchronized transmission ending at a time difference within a pre-specified first time interval; receiving a transmission subsequent to the synchronized transmission on at least one of the first link and the second link, wherein an interval between the subsequent transmission and the synchronized transmission on the link on which the subsequent transmission occurred is a short inter-frame space (SIFS) plus a time within the pre-specified first time interval; The AP multilink device according to claim 1 , configured to:

5. The AP multi-link device of claim 1 , wherein the processor is configured to transmit on the first link and the second link if the back-off counter is zero and a channel of the first link is idle.

6. 6. The AP multilink device of claim 5, wherein the processor is configured to start transmitting on the first link and the second link at a difference within a second time that is pre-specified when the backoff counter is 0 and the channel of the first link is idle.

7. A non-AP multilink device, A transceiver unit; and A processor is included. the non-AP multi-link device is configured to operate on the first link and the second link corresponding to a non-simultaneous transmit and receive (STR) link in which transmission of the non-AP multi-link device on one of the first link and the second link is restricted to protect transmission or reception of the non-AP multi-link device on the other of the first link and the second link; The processor, Obtaining a random number within a contention window (CW); setting the random number as an initial value of a backoff counter for the second link; decrementing the back-off counter by one if the channel is sensed as idle during a slot time, and if the back-off counter is not zero, transmission of the non-AP multilink device on the second link is not permitted; and If the backoff counter is equal to 0, the non-AP multilink device does not transmit on the second link while receiving on the first link; maintaining a value of the CW after the non-transmission, the value of the CW being adjusted based on whether channel access for traffic was successful; configured to: Non-AP multi-link device.

8. The processor, receiving a synchronized transmission on the first link and the second link, the synchronized transmission ending at a time difference on the first link and the second link within a pre-specified first time interval; performing a transmission subsequent to the synchronized transmission on at least one of the first link and the second link, wherein an interval between the subsequent transmission and the synchronized transmission performed on the link on which the subsequent transmission was performed is a sum of a short inter-frame space (SIFS) and the pre-specified first time interval; The non-AP multilink device according to claim 7, configured to perform the following:

9. The non-AP multi-link device of claim 7 , wherein the processor is configured to transmit information regarding whether STR is supported when a frequency band of either the first link or the second link is changed.

10. 8. The non-AP multi-link device of claim 7, wherein the processor is configured to transmit on the first link and the second link when the backoff counter is zero and the channel of the first link is idle for a pre-specified first time.

11. A method of operating an AP multilink device, comprising: determining whether to transmit to the non-AP multilink device on the second link based on whether the non-AP multilink device transmits on the first link when transmitting to the non-AP multilink device on the second link, wherein the non-AP multilink device operates on the first and second links corresponding to non-simultaneous transmit and receive (STR) links in which the non-AP multilink device's transmission on one of the first and second links is limited to protect the non-AP multilink device's transmission or reception on the other of the first and second links; Obtaining a random number within a contention window (CW); setting the random number as an initial value of a backoff counter for the second link; decrementing the back-off counter by one if the channel is sensed as idle during a slot time, and if the back-off counter is not zero, transmission of the AP multilink device on the second link is not permitted; If the backoff counter is 0, not transmitting on the second link while the non-AP multilink device is transmitting on the first link; maintaining the value of the CW after the non-transmission, the CW being adjusted based on whether channel access for traffic was successful; A method comprising:

12. The method of claim 11, further comprising: while the non-AP multilink device is transmitting on the first link, the transmission to the non-AP multilink device is not performed on the second link, but instead transmission to another device other than the non-AP multilink device is performed.

13. The method of claim 12, wherein transmitting to another device other than the non-AP multilink device further includes transmitting traffic having the same or higher priority as traffic of the transmission to the non-AP multilink device when the transmission to the other device other than the non-AP multilink device is performed on the second link.

14. performing synchronized transmission on the first link and the second link, the synchronized transmission ending on the first link and the second link with a time difference within a first time interval that is specified in advance; receiving a transmission subsequent to the synchronized transmission from at least one of the first link and the second link, wherein an interval between the subsequent transmission and the synchronized transmission made on the link from which the subsequent transmission occurred is a sum of a short inter-frame space (SIFS) and the pre-specified first time interval; The method of claim 11 , comprising:

15. A method for operating a non-AP multilink device, comprising: The non-AP multi-link device is configured to operate on the first and second links corresponding to non-simultaneous transmit and receive (STR) links in which transmissions of the non-AP multi-link device on one of the first and second links are restricted to protect transmissions or receptions of the non-AP multi-link device on the other of the first and second links, and the method includes: Obtaining a random number within a contention window (CW); setting the random number as an initial value of a backoff counter for the second link; decrementing the back-off counter by one if the channel is sensed as idle during a slot time, and if the back-off counter is not zero, transmission of the non-AP multilink device on the second link is not permitted; and If the backoff counter is equal to 0, the non-AP multilink device does not transmit on the second link while receiving on the first link; maintaining a value of the CW after the non-transmission, the value of the CW being adjusted based on whether channel access for traffic was successful; A method comprising:

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