Wireless communication method using restricted twt and wireless communication terminal using the same

Abstract

To provide a wireless communication terminal that wirelessly communicates with a base wireless communication terminal.SOLUTION: A wireless communication terminal includes a transceiver and a processor, the processor transmits low-latency traffic set as traffic for low-latency transmission or a response to the low-latency traffic within a restricted service period, and transmissions other than the transmission of the low-latency traffic and the transmission of the response to the low-latency traffic are restricted within the restricted service period.SELECTED DRAWING: Figure 26

Description

[Technical field]

[0001] The present invention relates to a wireless communication method using a restricted TWT 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, a wireless communication terminal for wirelessly communicating with a base wireless communication terminal includes a transceiver unit and a processor. The processor transmits low-latency traffic set as traffic for low-latency transmission or a response to the low-latency traffic within a restricted service period. In this case, transmission of the low-latency traffic and transmissions other than the low-latency traffic are restricted within the restricted service period.

[0010] The processor may terminate a TXOP for transmission of traffic other than the low latency traffic before the restricted service period begins.

[0011] The processor obtains a random integer within a contention window, performs channel access based on the obtained random integer, completes channel access before the start of the restricted service period, and, if it determines that frame exchange cannot be completed before the start of the restricted service period and gives up transmission, can perform channel access again.

[0012] The processor may maintain the size of the contention window used in the completed channel access when the wireless communication terminal performs the channel access again.

[0013] The processor may maintain a retransmission count of the completed channel access when the wireless communication terminal attempts the channel access again.

[0014] A quiet interval corresponding to the restricted service period may be set, and all transmissions may not be allowed during the quiet interval. The processor may ignore the quiet interval corresponding to the restricted service period, transmit the low-latency traffic or a response to the low-latency traffic during the restricted service period, and not transmit a CF End frame during the restricted service period.

[0015] A quiet interval corresponding to the restricted service period may be set, and all transmissions may not be permitted during the quiet interval. In this case, the processor may determine whether to ignore a quiet interval based on a start time of the restricted service period and a start time of the quiet interval, and when it is determined to ignore the quiet interval, may ignore the quiet interval corresponding to the restricted service period and transmit the low-latency traffic or a response to the low-latency traffic within the restricted service period.

[0016] The processor may ignore the quiet interval if a condition determined based on the start time of the limited service period and the start time of the quiet interval is met, and may not perform any transmission if a condition determined based on the start time of the limited service period and the start time of the quiet interval is not met.

[0017] The condition determined based on the start time of the limited service period and the start time of the quiet interval may be that the start time of the quiet interval and the start time of the limited service period are within a pre-specified time.

[0018] According to an embodiment of the present invention, a method for operating a wireless communication terminal wirelessly communicating with a base wireless communication terminal includes transmitting low-latency traffic set as traffic for low-latency transmission or a response to the low-latency traffic within a restricted service period, wherein transmissions other than the transmission of the low-latency traffic and the transmission of the response to the low-latency traffic may be restricted within the restricted service period.

[0019] The operating method may further include terminating a TXOP for transmission of traffic other than the low latency traffic before a start of the restricted service period.

[0020] The operating method may include the steps of: obtaining a random integer within a contention window; performing channel access based on the obtained random integer; and completing channel access before the start of the restricted service period and re-performing channel access if the transmission is abandoned because it is determined that frame exchange cannot be completed before the start of the restricted service period.

[0021] The step of resuming channel access may include maintaining a size of the contention window used in the completed channel access when the wireless communication terminal resuming the channel access.

[0022] The step of resuming channel access may include maintaining a retransmission count of the completed channel access when the wireless communication terminal resuming the channel access.

[0023] A quiet interval corresponding to the restricted service period may be set, and no transmission may be permitted during the quiet interval. In this case, transmitting the low-latency traffic or a response to the low-latency traffic during the restricted service period may include: ignoring the quiet interval corresponding to the restricted service period and transmitting the low-latency traffic or a response to the low-latency traffic during the restricted service period; and not transmitting a CF End frame during the restricted service period.

[0024] A quiet interval corresponding to the restricted service period may be set, and all transmissions may not be allowed in the quiet interval. In this case, the step of transmitting the low-latency traffic or the response to the low-latency traffic within the restricted service period may include the steps of: determining whether to ignore a quiet interval based on a start time of the restricted service period and a start time of the quiet interval; and, when it is determined to ignore the quiet interval, transmitting the low-latency traffic or the response to the low-latency traffic within the restricted service period while ignoring the quiet interval corresponding to the restricted service period.

[0025] The step of determining whether to ignore a quiet interval based on the start time of the restricted service period and the start time of the quiet interval may include: ignoring the quiet interval if a condition determined based on the start time of the restricted service period and the start time of the quiet interval is satisfied; and not performing any transmission if a condition determined based on the start time of the restricted service period and the start time of the quiet interval is not satisfied.

[0026] The condition determined based on the start time of the restricted service period and the start time of the quiet interval may be that the start time of the quiet interval and the start time of the service period of the TWT are within a pre-specified time. Effect of the Invention

[0027] An embodiment of the present invention provides a wireless communication method providing a limited TWT function and a wireless communication terminal using the same. [Brief description of the drawings]

[0028] [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] 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 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] 1 shows that, 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] 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] This shows a situation where interference or collision between links may occur. [Figure 18] This shows that a multi-link device according to an embodiment of the present invention gives up receiving a PPDU that is being received on a first link of a non-STR multi-link pair, and attempts to transmit a PPDU on a second link of the non-STR multi-link pair. [Figure 19] This indicates a situation in which a multilink device is unable to exchange RTS / CTS frames to transmit low latency traffic on a non-STR multilink pair. [Figure 20] 1 illustrates a multi-link device according to an embodiment of the present invention determining whether to transmit traffic based on traffic priority before frame exchange. [Figure 21]13 shows a Frame Control field format of an RTS frame according to an embodiment of the present invention. [Figure 22] 13 shows a User Info field format of an MU-RTS frame according to an embodiment of the present invention. [Figure 23] 4 shows that a station that receives an RTS frame requests the AP that transmitted the RTS frame to hand over a transmission opportunity according to an embodiment of the present invention. [Figure 24] 1 illustrates a format of a Frame Control field of a CTS frame including a request for priority processing of low-latency traffic according to an embodiment of the present invention. [Diagram 25] 1 illustrates a method for setting a broadcast TWT between an AP and a station according to an embodiment of the present invention. [Figure 26] 4 illustrates an example of an AP setting a quiet interval according to an embodiment of the present invention. [Figure 27] A method for a station to set a TXOP taking into account a limited service period according to an embodiment of the present invention will now be described. [Figure 28] 13 shows a station according to an embodiment of the present invention re-performing a channel access procedure taking into account a limited service period. [Figure 29] 13 illustrates an operation of an AP prematurely terminating a limited service period according to an embodiment of the present invention. [Diagram 30] 1 illustrates a multilink device transmitting on a non-SRT link pair according to an embodiment of the present invention. [Diagram 31] 13 shows a frame exchange initiated by a non-AP station multilink device to which an embodiment of the present invention is not applied. [Diagram 32] 1 illustrates a frame exchange initiated by a non-AP station multilink device according to an embodiment of the present invention. [Diagram 33] According to an embodiment of the present invention, when a multilink device performs a transmission requesting an immediate response on a first link of a non-STR link pair, the multilink device performs a transmission not requesting an immediate response on a second link. [Diagram 34] 10 illustrates an operation of transmitting on a second link when a multi-link device performs UL OFDMA transmission on a first link of a non-STR link pair according to an embodiment of the present invention. [Diagram 35] 10 shows a case where a link pair is determined to be a non-STR link pair or an STR link pair depending on the transmission direction according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] 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.

[0030] 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.

[0031] Hereinafter, in the present invention, the terms field and subfield may be used interchangeably.

[0032] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0033] 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.

[0034] As shown in FIG. 1, infrastructure BSS BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1, AP-2 which are stations providing a distribution service, and a distribution system DS which connects multiple access points AP-1, AP-2.

[0035] 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 to 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).

[0036] 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.

[0037] 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).

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 to 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.

[0045] 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 between 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.

[0046] 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.

[0047] 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.

[0048] 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 station connections. 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 wireless signals 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.

[0049] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] <Examples of various PPDU formats>

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066]

number

[0067] At this time,

number

[0068]

number

[0069] 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.

[0070]

number

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The present invention proposes a method for signaling the discontinuous channel type of the SU PPDU, illustrates the discontinuous channel type determined by the proposed method, and proposes a method for signaling the primary 160 MHz and secondary 160 MHz puncturing types in the 320 MHz BW configuration of the SU PPDU.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0094] 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.

[0095] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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).

[0100] 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.

[0101] 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.

[0102] 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 a 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] FIG. 10 illustrates simultaneous transmission of different links in a multi-link operation according to an embodiment of the present invention.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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).

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 support is provided needs to be exchanged.

[0119] 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.

[0120] 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.

[0121] In the above-mentioned embodiment, the operation of the station of the multilink device may be replaced by the operation of the multilink device. Also, in the above-mentioned embodiment, the operation of the AP may be replaced by the operation of the non-AP station, and the operation of the non-AP station may be replaced by the operation of the AP. Thus, the operation of the AP of the non-STR multilink device may be replaced by the operation of the non-AP station of the non-STR multilink device, and the operation of the non-AP station of the STR multilink device may be replaced by the operation of the AP of the STR multilink device. Also, the operation of the non-AP station of the non-STR multilink device may be replaced by the operation of the AP of the non-STR multilink device, and the operation of the AP of the STR multilink device may be replaced by the operation of the non-AP station of the STR multilink device.

[0122] FIG. 11 illustrates the operation of a multilink device when a link is changed according to one embodiment of the present invention.

[0123] 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.

[0124] 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.

[0125] 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).

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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 lifted 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 lifted, 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 lifted, 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).

[0132] 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.

[0133] 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.

[0134] 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.

[0135] FIG. 13 illustrates an operation of canceling channel access inhibition when it is determined 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.

[0136] 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).

[0137] 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.

[0138] FIG. 14 shows a station according to an embodiment of the present invention performing channel access after channel access prohibition is lifted.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] FIG. 15 illustrates an operation of a station according to an embodiment of the present invention performing transmission after channel access prohibition is lifted.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] FIG. 16 illustrates transmissions based on the state of stations in a non-STR multilink system according to an embodiment of the present invention.

[0149] 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.

[0150] Since the stations in the multi-link device can operate via a common MAC, the information exchange between the first AP (AP1) and the second AP (AP2) described above may not be performed explicitly.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] FIG. 17 illustrates a situation in which interference or collision between links may occur.

[0155] 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.

[0156] 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.

[0157] As mentioned above, it may be important for the multilink device to quickly determine the station that transmits to the multilink device. The User field of the EHT-SIG of the EHT UL PPDU may indicate the identifier (STA-ID) of the station that transmits the EHT UL PPDU. Specifically, when the DL / UL field of the signaling field of the EHT PPDU indicates that the EHT PPDU is a UL PPDU, the User field of the EHT-SIG of the EHT PPDU may indicate the identifier of the station that transmits the EHT UL PPDU. The multilink device that receives the EHT PPDU may identify the station that transmits the EHT PPDU based on the User field of the EHT-SIG of the EHT UL PPDU. In this way, the AP multilink device may determine the station that transmits the EHT UL PPDU, and the AP multilink device may determine the destination device of the transmission. Specifically, the AP multilink device may determine whether the transmission that is to be performed is likely to fail due to an inter-link collision. Furthermore, if there is a high possibility that a transmission that the AP multilink device is attempting to perform will fail, the AP multilink device can delay the transmission that it is attempting to perform and perform another transmission.

[0158] Various services using wireless LANs have been realized. In particular, the need for supporting low-latency services is increasing due to the widespread use of wireless virtual reality (VR) devices. Therefore, a wireless LAN operation method for supporting low-latency services is required. For convenience of explanation, traffic for low-latency services is referred to as low-latency traffic. The low-latency traffic may be designated by a station. In this case, the station includes an AP. Specifically, which traffic is low-latency traffic may be designated in a layer higher than the MAC layer. Also, specific traffic may be designated as low-latency traffic. Also, the low-latency traffic may be traffic whose priority level takes precedence over a pre-designated priority level. In this case, the priority level may be determined based on an access category (AC).

[0159] The operation of the non-STR multilink device described above must also take into consideration support for low latency services. This is because the transmission of low latency traffic may be delayed depending on the operating characteristics of the non-STR multilink device. For example, when receiving on the first link, the non-STR multilink device may restrict transmission on the second link to protect the transmission of the PPDU transmitted on the first link. As a result, the transmission of low latency traffic that should be transmitted on the second link may be delayed. A method for solving this problem will be described with reference to FIG. 18.

[0160] Figure 18 shows that a multi-link device in an embodiment of the present invention gives up receiving a PPDU that is being received on a first link of a non-STR multi-link pair and attempts to transmit a PPDU on a second link of the non-STR multi-link pair.

[0161] The multilink device may transmit low-latency traffic on the second link of the non-STR link pair even while receiving on the first link of the non-STR link pair. A non-STR link pair refers to a link pair in which the non-STR multilink device transmits on one of the two links and cannot simultaneously receive on the remaining link. In this case, the multilink device gives up receiving on the first link. Specifically, the multilink device may attempt to transmit a PPDU including low-latency traffic on the second link of the non-STR link pair even while receiving a PPDU on the first link of the non-STR link pair. In this case, the multilink device may suspend receiving PPDUs on the first link.

[0162] In addition, when the priority of traffic included in a PPDU to be transmitted on a second link is higher than the priority of traffic included in a PPDU received by the multilink device on a first link, the non-STR multilink device may attempt to transmit a PPDU including high priority traffic on a second link of the non-STR link pair even while receiving a PPDU on the first link of the non-STR link pair. In this case, the multilink device may suspend reception of the PPDU on the first link. In yet another specific embodiment, the multilink device may transmit on the second link and ignore signals received on the first link.

[0163] In the above embodiment, the condition under which the multilink device can suspend reception is when the priority of the traffic included in the ongoing reception on the first link is lower than the priority of the traffic to be transmitted on the second link. Therefore, when the priority of the traffic included in the ongoing reception on the first link is higher than the priority of the traffic to be transmitted on the second link, the multilink device cannot suspend reception on the first link.

[0164] However, when low latency traffic is received on a specific link, channel access and transmission (including responses) on other links having a non-STR relationship with the specific link may be restricted.

[0165] In the embodiment of FIG. 18, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). In the AP multilink device, the first AP (AP1) receives a first PPDU from the second AP (AP2). At this time, if the first PPDU contains only traffic that is not low-latency traffic and low-latency traffic needs to be transmitted on the second link (Link2), the AP multilink device can give up receiving the first PPDU on the first link (Link1) and attempt to transmit a second PPDU containing low-latency traffic on the second link (Link2). Alternatively, when the priority of the traffic contained in the second PPDU that the AP multi-link device intends to transmit on the second link (Link 2) is higher than the priority of the traffic contained in the first PPDU that the AP multi-link device receives on the first link (Link 1), the AP multi-link device can interrupt reception of the first PPDU on the first link (Link 1) and attempt to transmit the second PPDU on the second link (Link 2).

[0166] In this embodiment, the multilink device can adjust the priority of traffic exchanges according to the type or priority of the traffic. Also, in the above-mentioned embodiment, the priority of the traffic may be set according to a pre-specified policy. Also, as mentioned above, the priority of the traffic may be specified at a layer higher than the MAC layer.

[0167] An embodiment for preventing a delay in low latency traffic transmission at the PPDU reception stage, i.e., at the physical layer level, has been described with reference to Fig. 18. An embodiment for preventing a delay in low latency traffic transmission at the frame exchange stage, i.e., at the MAC layer level, will be described with reference to Figs. 19 to 22.

[0168] FIG. 19 illustrates a situation in which a multilink device cannot exchange RTS / CTS frames to transmit low latency traffic on a non-STR multilink pair.

[0169] When a multilink device exchanges frames on one of the non-STR multilink pairs, the transmission of low latency traffic may be delayed on the remaining links of the non-STR multilink pair. In the embodiment of FIG. 19, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The first AP (AP1) transmits an RTS frame to the first station (STA1). The first station (STA1) transmits a CTS (clear to send) frame to the first AP (AP1) in response to the RTS (request to send) frame. Due to the RTS frame / CTS frame exchange sequence performed on the first link, frame exchange between the second AP (AP2) and the second station (STA2) cannot be performed on the second link (Link2). Even after the RTS frame / CTS frame exchange is completed, transmission may be restricted on the second link (Link2) for a certain period of time, for example, MediumSyncDelay or NAVSyncDelay.

[0170] In addition, in the existing WLAN operation, a station that receives an RTS frame must transmit a CTS frame. Therefore, if the existing WLAN operation is applied as is, low latency traffic may be delayed until after the RTS frame / CTS frame exchange even if the PPDU reception interruption embodiment described in FIG. 18 is applied.

[0171] FIG. 20 shows that the multi-link device according to the embodiment of the present invention determines whether to transmit traffic based on the priority of the traffic before frame exchange.

[0172] The multilink device may interrupt a frame exchange sequence performed in one of the non-STR multilink pairs in order to transmit low-latency traffic. Specifically, the multilink device may transmit low-latency traffic without transmitting a frame that should be transmitted in the frame exchange sequence. In a specific embodiment, the multilink device may not transmit a response frame in the frame exchange sequence in order to transmit low-latency traffic. In such an embodiment, the multilink device may resume the frame exchange sequence after transmitting the low-latency traffic.

[0173] Also, the frame exchange sequence may be a frame exchange sequence for setting a network allocation vector (NAV). The frame exchange sequence for setting the NAV may include at least one of a request to send (RTS) frame / clear to send (CTS) frame exchange sequence and a multi user (MU)-RTS frame / CTS frame exchange sequence. Also, in the frame exchange sequence, the interval between frames may be SIFS. In this case, the data frame exchange sequence may be excluded from the frame exchange sequence.

[0174] Also, the frame exchanged in the frame exchange sequence may include information regarding the priority of the traffic included in the frame transmitted after the frame exchange sequence. In this case, the information regarding the priority may be information indicating whether the traffic included in the frame transmitted after the frame exchange sequence is low latency traffic. Also, the information regarding the priority may be a traffic identifier (TID) of the traffic included in the frame transmitted after the frame exchange sequence. Also, the information regarding the priority may indicate the priority of the traffic included in the frame transmitted after the frame exchange sequence. In such an embodiment, the multilink device may receive a frame in a frame exchange sequence performed in one of the non-STR multilink pairs, and determine whether to continue the frame exchange sequence based on additional information of the received frame. For example, if the frame received by the multilink device indicates that low latency traffic is not transmitted after the frame exchange sequence, the multilink device may abort the frame exchange sequence. Also, if the frame received by the multilink device indicates that low latency traffic is transmitted after the frame exchange sequence, the multilink device may continue the frame exchange sequence. In yet another specific embodiment, if a frame received by the multilink device indicates that the priority of the traffic to be transmitted after the frame exchange sequence is lower than the priority of the traffic waiting to be transmitted on the remaining links of the non-STR multilink pair, the multilink device may abort the frame exchange sequence. Also, if a frame received by the multilink device indicates that the priority of the traffic to be transmitted after the frame exchange sequence is equal to or higher than the priority of the traffic waiting to be transmitted on the remaining links of the non-STR multilink pair, the multilink device may continue the frame exchange sequence. A specific format of the information on the priority of the traffic included in the frame transmitted after the frame exchange sequence will be described in Figures 21 and 22.

[0175] In the above-described embodiment, the multilink device can determine whether to transmit a response frame for the received frame based on the additional information of the received frame. Also, the multilink device can determine the type of the response frame for the received frame based on the additional information of the received frame.

[0176] Also, a station that fails to receive a response frame in the frame exchange sequence may not retransmit the frame. This is because if the station retransmits the frame, it may disrupt the transmission of low-latency traffic that is performed instead of the frame exchange sequence. Specifically, even if a station that transmits a frame to a non-STR multilink device fails to receive a response frame, the station may not retransmit the frame. Even if a station that transmits a frame on one of the non-STR multilink pairs fails to receive a response frame, the station may not retransmit the frame. In yet another specific embodiment, a station that fails to receive a response frame in the frame exchange sequence may determine whether to retransmit the frame based on whether the link on which the frame was transmitted and the link corresponding to the non-STR multilink pair have reached a service period for low-latency traffic transmission. For example, if the link on which the frame was transmitted and the link corresponding to the non-STR multilink pair have reached a service period for low-latency traffic transmission, the station that transmitted the frame may not retransmit the frame. A station that fails to receive a response frame in a frame exchange sequence can determine whether to retransmit the frame based on whether the receiver of the frame participated in the service period negotiation for low-latency traffic transmission. For example, if the receiver of the frame participated in the service period negotiation for low-latency traffic transmission, the station that transmitted the frame may not retransmit the frame. In the above embodiment, the service period for low-latency traffic transmission may be a restricted (R)-TWT (target wakeup time) service period. R-TWT is described in FIG. 25.

[0177] In the embodiment of FIG. 20, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The first AP (AP1) transmits an RTS frame to the first station (STA1). The first station (STA1) transmits a CTS (clear to send) frame to the first AP (AP1) in response to the RTS (request to send) frame. At this time, the RTS frame includes information on the priority of traffic to be transmitted after the RTS frame / CTS frame exchange. The information on the priority may indicate that traffic that is not low latency traffic is transmitted after the RTS frame / CTS frame exchange. Or, the information on the priority may indicate that traffic having a lower priority than the priority of traffic waiting to be transmitted on the second link is transmitted after the RTS frame / CTS frame exchange. In such a case, the first station (STA1) does not transmit a CTS frame, and the second station (STA2) transmits low-latency traffic to the second AP (AP2).

[0178] The first AP (AP1) fails to receive a CTS frame from the first station (STA1), but does not retransmit an RTS frame to the first station (STA1). Also, the first AP (AP1) transmits an RTS frame to stations other than the first station (STA1) on the first link (Link1).

[0179] Fig. 21 shows a Frame Control field format of an RTS frame according to an embodiment of the present invention, and Fig. 22 shows a User Info field format of an MU-RTS frame according to an embodiment of the present invention.

[0180] As described above, a frame exchanged in a frame exchange sequence may include information regarding the priority of traffic included in a frame transmitted after the frame exchange sequence. Specifically, an initiating frame that initiates a frame exchange may include information regarding the priority of traffic. Specifically, when the initiating frame is a control frame, a frame control field may include information regarding the priority of traffic. For example, the initiating frame may include a 1-bit field (Low latency indication) indicating whether traffic included in a frame transmitted after the frame exchange sequence is low latency traffic or not. In this case, the 1-bit field may be included in the initiating frame instead of a More Data field. Also, the initiating frame may include a 4-bit field (TID Info) indicating a TID (traffic identifier) ​​of traffic included in a frame transmitted after the frame exchange sequence. In yet another specific embodiment, the initiating frame may include a 4-bit field (Priority Info) indicating the priority of traffic transmitted after the frame exchange sequence. In this case, the 4-bit field may be included in the initiating frame instead of a To DS field, a From DS field, a More Fragments field, and a Retry field. Also, the start frame may include a 1-bit field (Traffic info Flag) indicating whether or not information on the priority of traffic included in the frame transmitted after the frame exchange sequence is included. In this case, the 1-bit field may be included instead of the Protected Frame field. In the control frame, the More Data field, the To DS field, the From DS field, the More Fragments field, the Retry field, and the Protected Frame field do not convey additional meaning.

[0181] Figure 21(a) shows a Frame Control field of an RTS frame that does not include information about traffic priority, and Figure 21(b) shows a Frame Control field of an RTS frame that includes information about traffic priority according to an embodiment of the present invention.

[0182] The MU-RTS frame is a type of trigger frame. The trigger frame can trigger transmission of one or more stations. To this end, the trigger frame may include as many User Info fields as the number of stations that trigger transmission. Each User Info field indicates information to be signaled to each station that triggers transmission of the trigger frame. The User Info field of the MU-RTS frame may include information on the priority of traffic included in a frame transmitted after the MU-RTS frame / CTS frame exchange sequence. In this case, the User Info field of the MU-RTS frame may include information on the priority of traffic using a reserved field. Specifically, the User Info field may include information on the priority of traffic using a UL FEC Coding Type field, a UL HE-MCS field, a UL DCM field, a SS Allocation / RA-RU Information field, and a UL Target Receive Power field.

[0183] The format of the information on traffic priority may be the same as the embodiment described with reference to Fig. 21. Fig. 22(a) shows the User Info field of an MU-RTS frame that does not include information on traffic priority. Fig. 22(b) shows the User Info field of an MU-RTS frame that includes information on traffic priority according to an embodiment of the present invention.

[0184] Since the MU-RTS frame / CTS frame exchange sequence may occur between one AP and multiple stations, the MU-RTS frame / CTS frame exchange sequence may continue even if the multilink device does not transmit a CTS frame.

[0185] When applying the existing WLAN operation, the multilink device must obtain a transmission opportunity to transmit low latency traffic even after the frame exchange sequence is interrupted. Therefore, it must compete with other wireless communication devices, and in this process, the low latency traffic transmission may be delayed again. To prevent this, a low latency traffic transmission method may be required. This will be described with reference to FIG. 23 and FIG. 24.

[0186] FIG. 23 illustrates a process in which a station that has received an RTS frame requests an AP that has transmitted the RTS frame to hand over a transmission opportunity according to an embodiment of the present invention.

[0187] When a station that buffers low-latency traffic receives an initiation frame that starts a frame exchange sequence, the station can insert a request for priority processing of low-latency traffic into a response frame for the initiation frame and transmit the response frame. The station that transmitted the initiation frame can accept or reject the request for priority processing of low-latency traffic. A station that receives a response frame including a request for priority processing of low-latency traffic can transmit a response frame to accept the request for priority processing of low-latency traffic. Also, a station that receives a response frame including a request for priority processing of low-latency traffic can perform a scheduled transmission after the frame exchange sequence and reject the request for priority processing of low-latency traffic.

[0188] For example, a first station receives an RTS frame from a second station. At this time, if the first station has stored a low-latency traffic transmission in a buffer, the first station can insert a request for priority processing of the low-latency traffic into the CTS frame and transmit the CTS frame to the second station. The second station receives the CTS frame including the request for priority processing of the low-latency traffic. At this time, if the second station accepts the request for priority processing of the low-latency traffic, the second station transmits a CTS frame to the first station. At this time, the first station receives the CTS frame and transmits a frame including the low-latency traffic. If the second station rejects the request for priority processing of the low-latency traffic, the second station transmits DL data to the first station. In such an embodiment, the interval between frames may be SIFS.

[0189] In yet another specific embodiment, when a station that buffers low-latency traffic receives a start frame that starts a frame exchange sequence, the station may transmit a start frame in response to the start frame to request priority processing of the low-latency traffic. At this time, the start frame transmitted in response to the start frame includes information on characteristics of the low-latency traffic that the station buffers. For example, a first station receives an RTS frame from a second station. At this time, if the first station buffers low-latency traffic transmission, the first station may transmit an RTS frame to the second station. At this time, the Frame Control field of the RTS frame may include information on characteristics of the low-latency traffic that the station buffers. At this time, the information on characteristics of the low-latency traffic may be indicated as in the embodiment described in FIG. 21.

[0190] A station that receives a request for priority handling of low-latency traffic according to the above embodiment may not accept the request for priority handling of low-latency traffic and may terminate the frame exchange sequence. For example, a station that receives an RTS frame in response to an RTS frame or a CTS frame including a request for priority handling of low-latency traffic may not transmit any DL data frames thereafter, because the station may interpret the subsequent sequence after the frame exchange sequence for priority handling of low-latency traffic as undesired signaling.

[0191] Also, a station transmitting an initiation frame may include, in the initiation frame, information on the characteristics of the traffic to be transmitted after the frame exchange sequence. For example, a station transmitting an RTS frame in an RTS frame / CTS frame exchange sequence may include, in the RTS frame, information on the characteristics of the traffic to be transmitted after the RTS frame / CTS frame exchange sequence. The information on the characteristics of the traffic may be indicated as in the embodiment described in FIG. 21. In such an embodiment, a station receiving an initiation frame may determine whether to request priority processing of low-latency traffic based on the information on the characteristics of the traffic included in the initiation frame. For example, a first station may transmit, to a second station, an RTS frame including information on the characteristics of the traffic to be transmitted after the RTS frame / CST frame exchange. The second station may determine whether to request priority processing of low-latency traffic from the first station based on the information on the characteristics of the traffic to be transmitted after the RTS frame / CST frame exchange. Specifically, the second station may request priority processing of low-latency traffic from the first station when the traffic to be transmitted after the RTS frame / CST frame exchange is not low-latency traffic. Also, if traffic transmitted after the RTS frame / CST frame exchange is low-latency traffic, the second station may not request the first station to prioritize the low-latency traffic. In yet another specific embodiment, if the priority of the traffic transmitted after the RTS frame / CST frame exchange is lower than the priority of the low-latency traffic stored in the buffer of the second station, the second station may request the first station to prioritize the low-latency traffic. Also, if the priority of the traffic transmitted after the RTS frame / CST frame exchange is equal to or higher than the priority of the low-latency traffic stored in the buffer of the second station, the second station may not request the first station to prioritize the low-latency traffic.

[0192] In the embodiment of FIG. 23, the AP transmits an RTS frame to the station. At this time, the RTS frame includes characteristics related to the traffic transmitted after the RTS frame / CTS frame exchange. Specifically, the RTS frame indicates that the traffic transmitted after the RTS frame / CTS frame exchange is not low-latency traffic, and can indicate the priority of the traffic transmitted after the RTS frame / CTS frame exchange. Since the traffic transmitted after the RTS frame / CTS frame exchange is not low-latency traffic, the station transmits a CTS frame (CTS#1) requesting priority processing of the low-latency traffic. At this time, the station sets the value of the duration field of the CTS frame (CTS#1) to a value obtained by subtracting the time required for CST frame transmission (CTStime) and SIFS from the value of the duration field of the RTS frame. The AP receives the CTS frame (CTS#1) from the station. The AP transmits a CTS frame (CTS#2) to the station, accepting the transmission of low-latency traffic. At this time, the AP sets the value of the duration field of the CST frame (CTS#2) to the value obtained by subtracting the time it takes to transmit the CST frame (CTStime) and SIFS from the value of the duration field of the CTS frame (CTS#1).

[0193] In the above embodiment, when the transmission of the low-latency traffic is completed and a TXOP set for frame exchange remains, the station that transmitted the low-latency traffic may transmit a response frame to signal the completion of the transmission of the low-latency traffic. Specifically, a station that requests priority processing of the low-latency traffic in the RTS frame / CTS frame exchange sequence and completes the transmission of the low-latency traffic may transmit a CTS frame. At this time, the station may transmit the CTS frame using a format other than the non-HT PPDU, for example, an HT PPDU, a VHT PPDU, or an EHT PPDU. In a specific embodiment, the format other than the non-HT PPDU may be the EHT PPDU format. This is because the CTS frame is not transmitted with the intention of setting the NAV, but is transmitted with the intention of notifying the completion of the transmission of the low-latency traffic.

[0194] In the above-described embodiment, in relation to the transmission of a CTS frame / RTS frame, transmission to a certain station means setting the RA field of the CTS frame / RTS frame to the MAC address of that station.

[0195] FIG. 24 illustrates a format of a Frame Control field of a CTS frame including a request for priority processing of low latency traffic according to an embodiment of the present invention.

[0196] As previously mentioned, the CTS frame may contain information regarding priority handling requests for low latency traffic.

[0197] The CTS frame may include a 1-bit field (Low latency indication) indicating a priority processing request for low latency traffic. The CTS frame may also include a 4-bit field (TID Info) indicating a traffic identifier (TID) of the frame low latency traffic. In yet another specific embodiment, the CTS frame may include a 4-bit field (Priority Info) indicating a priority of the low latency traffic. The CTS frame may also include a 1-bit field (UL Request) indicating whether the station transmitting the CTS frame requests an uplink transmission.

[0198] Scheduling for low-latency traffic transmission will be described with reference to FIG. 25 to FIG. 30. In conventional wireless LAN communication, channel access parameters are set for each AC using enhanced distributed channel access (EDCA), and traffic is supported to be processed according to priority for each AC using the set channel access parameters. However, since the existing EDCA provides channel access with high priority in a probabilistic manner, it is insufficient in supporting low-latency traffic transmission. To compensate for this, a time period in which low-latency traffic can be preferentially transmitted can be set. For convenience of explanation, the time period in which low-latency traffic is preferentially transmitted is called a limited service period. Most services requiring low-latency traffic transmission, such as VR / AR, require periodic traffic transmission, and therefore the limited service period has a large effect of reducing the transmission delay of low-latency traffic.

[0199] The limited service period may be a time period in which the transmission of low latency traffic and the transmission of a response to the low latency traffic are preferentially permitted. Specifically, the limited service period may be a time period in which only the transmission of low latency traffic and the transmission of a response to the low latency traffic are permitted. In yet another specific embodiment, the limited service period may be a time period in which the transmission of low latency traffic and the transmission of a response to the low latency traffic are performed, and the transmission of traffic other than the low latency traffic is permitted after the transmission of the low latency traffic and the transmission of the response to the low latency traffic are completed.

[0200] First, a method for setting a restricted service period will be described. The restricted service period may be set by the TWT of an existing WLAN. The TWT sets a service period through negotiation between an AP and a station, and supports the AP and the station to transmit and receive during the service period and enter a low power mode during periods other than the service period. This will be described in detail with reference to FIG. 25. For ease of explanation, the operation of the AP and the station based on the restricted service period, in which the restricted service period is set by the TWT, is called a restricted TWT.

[0201] FIG. 25 illustrates a method for setting up a broadcast TWT between an AP and a station according to an embodiment of the present invention.

[0202] In the TWT, the service period may be set as follows: The AP requests stations associated with the AP to join the TWT. The stations can join the broadcast TWT or negotiate with the AP about an individual TWT. At this time, the AP can request stations to join the TWT by setting the value of the TWT Required subfield of the HE Operation element to 1. The AP can also transmit the broadcast TWT element in a management frame, for example a beacon frame, to convey information required for stations to join the broadcast TWT. At this time, the AP can signal that it supports broadcast TWT by setting dot11TWTOptionActivated to true and the Broadcast TWT Support field of the HE Capabilities element to 1. The AP can set the limited service period to be similar to the service period of the TWT.

[0203] In the embodiment of FIG. 25, the first station (STA1) requests the AP to set the TWT. The AP and the first station (STA1) set TWT parameters, such as an initial TBTT and a listen interval. As a result, the AP and the first and second stations (STA1 and STA2) are set to a broadcast TWT. The AP indicates a broadcast TWT service period using a beacon frame. During the broadcast TWT service period, the AP can transmit a downlink (DL) physical layer protocol data unit (PPDU) to the first and second stations (STA1 and STA2) or can trigger an uplink (UL) transmission by transmitting a trigger frame to the first and second stations (STA1 and STA2). During the broadcast TWT service period, the first and second stations (STA1 and STA2) wake up to receive a beacon frame. The first and second stations (STA1 and STA2) obtain information about the TWT from the received beacon frame. The AP transmits a trigger frame to the first station (STA1) and the second station (STA2), the first station (STA1) transmits a PS-Poll frame to the AP, and the second station (STA2) transmits a QoS Null frame to the AP. The AP receives the PS-Poll frame and the QoS Null frame transmitted by the first station (STA1) and the second station (STA2), and determines that the first station (STA1) and the second station (STA2) are in an awake state. The AP transmits a multi-STA Block ACK frame to the first station (STA1) and the second station (STA2). The AP transmits a DL PPDU to the first station (STA1) and the second station (STA2).

[0204] In the service period of the existing TWT, stations that do not participate in the TWT are not restricted from accessing the channel or transmitting because the TWT is intended to help stations participating in the TWT enter a doze state. However, the restricted service period to prevent transmission delays of low-latency traffic must guarantee the preferential transmission of low-latency traffic, and therefore a method for protecting the restricted service period is required.

[0205] During the restricted service period, a station that does not participate in the restricted TWT may be restricted from accessing the channel. Specifically, during the restricted service period, a station that does not participate in the restricted TWT may not be able to access the channel. When a station that does not participate in the restricted TWT completes channel access during the restricted service period, the station may restart the channel access procedure without transmitting. In this case, the station may restart the channel access procedure when the restricted service period ends. In addition, the channel access of the station may represent an EDCA backoff procedure. Completion of the channel access may represent a backoff counter of the EDCA backoff procedure reaching 0. In addition, when the station restarts the channel access procedure, the station may randomly obtain an integer within the CW used in the previous channel access and use the obtained integer for the backoff counter. That is, the station may not double the size of the CW used in the previous channel access. In this case, the CW may be maintained for each AC. Such channel access restriction may be applied only to stations that support the restricted TWT. Specifically, such channel access restriction is applied only to non-legacy (EHT) stations in which dot11RestrictedTWTOptionImplemented in the EHT Capabilities element is set to true, and may not be applied to non-legacy (EHT) stations in which dot11RestrictedTWTOptionImplemented in the EHT Capabilities element is set to false. In this specification, non-legacy stations may refer to EHT stations and stations after EHT stations. Also, legacy stations are stations before EHT stations, and may refer to non-HT stations, HT stations, VHT stations, and HE stations.

[0206] Also, during the restricted service period, a NAV may be set for a non-legacy station for traffic other than low-latency traffic. Specifically, as a NAV is set for traffic other than low-latency traffic, the station may discontinue channel access procedures for transmission of traffic other than low-latency traffic. In such an embodiment, the NAV may be a NAV independent of the conventional NAV (basic NAV, Intra-BSS NAV). In this case, the non-legacy station may be limited to stations that support the restricted TWT. In yet another specific embodiment, the non-legacy station may be limited to stations that participate in the restricted TWT.

[0207] The limited service period may be included within the broadcast TWT service period. In yet another specific embodiment, the limited service period may not be included within the broadcast TWT service period.

[0208] Also, the limited service period may be repeated at a period specified by the AP. That is, the AP may specify a period for repeating the limited service period. This eliminates the need for the AP to transmit a TWT element of a beacon frame every time to set the limited service period. In this case, the period of the service period may be set according to the characteristics of a low-latency service in which low-latency traffic is used. For example, the period of the low-latency service period in which low-latency traffic is generated every 50 ms may be 50 ms.

[0209] Also, a quiet interval may be set for stations that do not support the restricted TWT. In a conventional WLAN, the quiet interval is an interval for supporting channel sensing. When the quiet interval is set, all stations stop transmission. Using the characteristics of the quiet interval, the restricted service period can be protected. This will be described with reference to FIG. 26. In this case, stations that do not support the restricted TWT may be limited to legacy stations.

[0210] FIG. 26 illustrates how an AP sets a quiet interval according to an embodiment of the present invention.

[0211] An AP operating a restricted TWT may transmit a quiet element and set a quiet period. In the quiet period, the station suspends channel access. However, if the channel access of a station participating in the restricted TWT is also restricted, low latency traffic cannot be transmitted. Therefore, a station participating in the restricted TWT may ignore a quiet period corresponding to a restricted service period. In this case, the quiet period corresponding to a restricted service period represents a quiet period set to protect the restricted service period of the restricted TWT. Specifically, a station participating in the restricted TWT may regard a quiet period corresponding to a restricted service period as a restricted service period. An AP operating a restricted TWT may not set a quiet period to coincide with the restricted service period. This is because the quiet period is set in units of TU (time unit, 1024 us) in the quiet element and the TWT is set in units of 256 us.

[0212] However, when a channel access is performed in a quiet interval other than the quiet interval not set for the restricted service period, the quiet interval not set for the restricted service period may be disturbed. For this reason, it is necessary to distinguish the quiet interval set for the restricted service period, i.e., the quiet interval corresponding to the restricted service period. Therefore, a station participating in the restricted TWT may not be able to ignore the quiet interval not corresponding to the restricted service period. In the quiet interval not corresponding to the restricted service period, the station cannot perform all transmissions. Specifically, a station participating in the restricted TWT may not be able to ignore the quiet interval that does not overlap with the restricted service period. In a specific embodiment, a station participating in the restricted TWT may not be able to perform all transmissions in the quiet interval that does not overlap with the restricted service period.

[0213] In addition, in the above embodiment, a station participating in a restricted TWT may consider a quiet period corresponding to a restricted service period if the start time of the restricted service period and the start time of the quiet period are within a pre-specified time, and the start time of the service period and the start time of the quiet period are within a pre-specified time, because, as described above, an AP operating a restricted TWT does not need to set a quiet period to coincide with the restricted service period.

[0214] In the embodiment of FIG. 25, an AP transmits a beacon frame to set a quiet interval and a restricted service period. In FIG. 25(a), the quiet interval is set to the same time interval as the restricted service period. Therefore, a station participating in the restricted TWT in the quiet interval performs channel access. In FIG. 25(b), the quiet interval is set from a time earlier than the start time of the restricted service period to a time later than the end time of the restricted service period. In FIG. 25(b), channel access of a station participating in the restricted TWT in a quiet interval that does not overlap with the restricted service period is restricted. A station participating in the restricted TWT in a quiet interval that overlaps with the restricted service period performs channel access.

[0215] As mentioned above, channel access may be restricted during restricted service periods, and such restrictions may also be applied in relation to TXOP settings, as illustrated in FIG.

[0216] FIG. 27 illustrates a method for a station to set a TXOP taking into account a limited service period according to an embodiment of the present invention.

[0217] A station that has obtained a TXOP before the restricted service period begins, i.e., a station that is a TXOP holder, may need to terminate the TXOP before the restricted service period begins. This is because if the TXOP holder continues to exchange frames even after the restricted service period begins, it may interfere with the transmission of low-latency traffic. In this case, the station may be a non-legacy station. In yet another specific embodiment, the station may be limited to stations that support restricted TWT. That is, such restrictions may not be applied to stations for which the value of the dot11RestrictedTWTOptionImplemented field is set to false.

[0218] In an illustrative embodiment, if a station that is a TXOP holder is transmitting low latency traffic, it may continue exchanging frames after the limited service period has begun.

[0219] A specific method for a station to terminate a TXOP before a limited service period will now be described.

[0220] The station can set TXOP based on the limited service period. Specifically, the station can set the end point of TXOP to be before the start of the limited service period. At this time, the station can set the duration of the start frame that starts the frame exchange sequence to be before the start of the limited service period. For example, if the station succeeds in channel access 3m before the start of the limited service period, the station can set TXOP to be 3ms before. Also, the station may end TXO by transmitting a CTS-to-Self frame. At this time, the station can transmit the CTS-to-Self frame at the basic transmission rate of 6Mbps. This is because many legacy stations can receive frames when the station transmits frames at the basic transmission rate.

[0221] In yet another specific embodiment, the station can transmit a CF-End frame before the start of the limited service period, so that the station can end the TXOP before the start of the limited service period. In this case, the station can transmit the CF-End frame at a basic transmission rate of 6 Mbps, because many legacy stations can receive the frames when the station transmits the frames at the basic transmission rate.

[0222] Also, a station that is not a TXOP holder may release the NAV set before the start of the restricted service period at the start of the restricted service period. In this case, the station may be a station that supports restricted TWT. That is, the station may be a station that sets the value of the dot11RestrictedTWTOptionImplemented field to True. A station that is not a TXOP holder but does not support restricted TWT may not release the NAV set before the start of the restricted service period at the start of the restricted service period. However, when the station completes frame exchange and the remaining duration of the TXOP is less than twice the sum of the time required to transmit the CF-End frame and the SIFS, the station may not transmit the CF-End frame. In this case, the station may consider the TXOP to be released at the start of the restricted service period. Specifically, the station may consider the basic NAV to be released at the start of the restricted service period.

[0223] In yet another illustrative embodiment, stations may be limited to those that participate in a restricted TWT.

[0224] In the embodiment of FIG. 27, the AP transmits a beacon frame including a TWT element to signal that a limited service period is set. In the embodiment of FIG. 27(a), the station transmits an RTS frame to set a TXOP. At this time, the station sets the value of the Duration field of the RTS frame to "before the limited service period". The station exchanges frames with the AP and completes the frame exchange before the start of the limited service period. At this time, the station finally transmits a CTS-to-Self frame. In the embodiment of FIG. 27(b), the station transmits an RTS frame to set a TXOP. At this time, the station sets the value of the duration field of the RTS frame without considering the limited service period. The station exchanges frames with the AP and completes the frame exchange before the start of the limited service period. At this time, the station finally transmits a CF-end frame to release the TXOP.

[0225] In conventional WLAN operation, an exception to the TXOP rule defines an operation that may be transmitted beyond the TXOP limit. For example, retransmission of a single MPDU, transmission of a single MSDU under a Block ack agreement (not included in A-MSDU and A-MPDU consisting of two or more MPDUs), and transmission of a control frame and a QoS Null frame (not included in A-MPDU consisting of two or more MPDUs) may be transmitted beyond the TXOP limit. If such an exception is recognized even for a limited service period, the transmission of low latency traffic may be delayed. Such an exception to the TXOP limit must not be applied in violation of the limited service period.

[0226] If the end time of the TXOP and the start time of the restricted service period are within a pre-specified time difference, the station can determine that the TXOP is a TXOP obtained before the start of the restricted service period. The pre-specified time may be 100 us. In yet another specific embodiment, if the end time of the TXOP is within the restricted service period, the station can determine that the TXOP is a TXOP obtained before the start of the restricted service period.

[0227] As mentioned above, a station may need to complete a frame exchange before the restricted service period. Thus, a station may not be allowed to start a frame exchange if the completion time of the frame exchange is within the restricted service period. In this case, the station may perform fragmentation to complete the frame exchange before the start of the restricted service period.

[0228] Also, if low latency traffic is transmitted in a frame exchange performed by a station that is a TXOP holder, the station may continue the frame exchange even after the low latency service period begins.

[0229] A channel access procedure taking into account limited service periods is described in FIG.

[0230] FIG. 28 illustrates a station according to an embodiment of the present invention re-performing a channel access procedure taking into account a limited service period.

[0231] As described above, even if the station completes channel access before the restricted service period, if the frame exchange completion time is after the start of the restricted service period, the station can start the channel access procedure again without transmitting. At this time, the station can acquire the back-off counter value again. At this time, the station can use the size of the CW used in the previous channel access procedure as it is. That is, the station does not need to double the size of the CW used in the previous channel access procedure, and does not need to initialize it to the minimum value that the CW can have. In addition, the station does not need to increase the number of retries, for example, QSRC (QoS STA Retry Counter).

[0232] Also, if the station completes channel access within a pre-specified time from the start of the restricted service period, the station may initiate the channel access procedure again without transmitting.

[0233] In the above embodiment, a station that wishes to transmit low latency traffic may start frame exchange after completing channel access even if the frame exchange completion time is after the start of the restricted service period. Such an exception may be allowed only if the station that wishes to transmit low latency traffic is a station participating in the restricted TWT.

[0234] Also, as described above, the station can operate as if the NAV is set for the AC of traffic other than the low-latency traffic, and therefore the station can determine that the CCA result for the transmission of the AC of traffic other than the low-latency traffic is not idle (BUSY).

[0235] In the embodiment of FIG. 28, the AP transmits a beacon frame including a TWT element to signal that a limited service period is to be set. The station's channel access back-off counter value reaches 0 before the start of the limited service period. The station determines that the frame exchange including the traffic to be transmitted will be completed after the start of the service period. Therefore, the station obtains a back-off counter within the CW value used in the previous channel access procedure. The station performs the channel access procedure again using the obtained back-off counter. At this time, the station does not increment the retransmission counter.

[0236] It may happen that all low-latency traffic transmission is completed before the completion of the limited service period. In such a case, it may be inefficient for the low-latency service period to restrict the transmission of traffic other than the low-latency traffic. Therefore, a method for early termination of the limited service period may be required. This will be described using the example of FIG. 29.

[0237] FIG. 29 illustrates an operation of an AP prematurely terminating a limited service period according to an embodiment of the present invention.

[0238] In order for the AP to terminate the limited service period early, it must be able to determine that all low-latency traffic transmissions of stations participating in the limited TWT have been completed. To this end, stations participating in the limited TWT can signal whether or not they will transmit further low-latency traffic in the frames they transmit. Specifically, the station can signal further transmission of low-latency traffic by setting the value of the More data subfield of the Frame Control field of the frame. In this case, if the value of the More data subfield of the Frame Control field of the frame transmitted in the limited service period is 1, the More data subfield indicates that further transmission of low-latency traffic is required, and does not need to indicate whether further transmission of traffic other than the low-latency traffic is required. For example, if a station participating in the limited TWT does not store low-latency traffic in its transmit buffer and only stores traffic other than the low-latency traffic, the station can set the value of the More data subfield of the Frame Control field of the frame transmitted by the station in the limited service period to 0. The AP can terminate the limited service period early based on whether the station participating in the limited TWT has a frame in the limited service period with a value of 0 in the More data subfield of the Frame Control field. Specifically, the AP can terminate the limited service early if the AP's transmit buffer has no low latency traffic to transmit and the station participating in the limited TWT has a frame in the limited service period with a value of 0 in the More data subfield of the Frame Control field.

[0239] The AP can terminate the restricted service period early by transmitting a pre-specified control frame. In this case, the control frame may be a CF-End frame. In this case, the AP can set the BSSID (TA) field of the CF-End frame to the MAC address or BSSID of the AP. Also, the AP can set the Individual / Group bit of the BSSID (TA) field of the CF-End frame to 1. In yet another specific embodiment, the AP can terminate the restricted service period early by transmitting a pre-specified management frame.

[0240] When a station receives a frame that is pre-designated to end the restricted service period within the restricted service period, the station can determine that the restricted service period has ended. At this time, the station that receives the pre-designated frame can resume channel access without the restrictions that apply to the restricted service period. As described above, the pre-designated frame may be a CF-End frame. At this time, if the value of the TA (BSSID) field of the CF-End frame that the station receives during the restricted service period is the MAC address of the AP to which the station is associated, the station can determine that it is a CF-End frame that ends the restricted service period.

[0241] As described above, in order to protect the limited service period from the legacy wireless communication terminal, a quiet interval for the limited service period may be set. In this case, the AP can transmit a CF-End frame to end the limited service period. When the AP transmits the CF-End frame, the quiet interval set for the legacy station can also be cancelled.

[0242] In the above-described embodiment, the CF-End frame may have a Frame Control field with a Type of a control frame (Type value B3 B2==01) and a Subtype of a CF-End frame (Subtype value B7 B6 B4 B4==1110).

[0243] When a quiet period for a restricted service period is set, a station participating in the restricted TWT may not be allowed to transmit a CF-End frame within the restricted service period. In a specific embodiment, a station participating in the restricted TWT may not be allowed to transmit a CF-End frame in a quiet period corresponding to the restricted service period. This is because the NAV set for the legacy station is released when a station participating in the restricted TWT transmits a CF-End frame. However, as described above, if the CF-End frame is used to terminate the restricted service period early, the AP may transmit a CF-End frame within the restricted service period.

[0244] In the embodiment of FIG. 29, the AP transmits a beacon frame including a TWT element and a Quiet element. A station supporting the restricted TWT determines that a restricted service period has been set, and a station not supporting the restricted TWT determines that a quiet period has been set. When the AP determines that the transmission of all low latency traffic has been completed within the restricted service period, the AP transmits a CF-End frame to terminate the restricted service period early and release the quiet period set for the legacy station. At this time, a station supporting the restricted TWT determines that the channel access restriction applied during the restricted service period has been removed. Specifically, as described above, when the embodiment in which the NAV is set during the restricted service period is applied, a station supporting the restricted TWT can determine that the NAV for the restricted service period has been released. Also, a station not supporting the restricted TWT that receives the CF-End frame releases the NAV.

[0245] The operation of the multilink device has been described with reference to Figures 11 to 24. The channel access operation of the multilink device will be described with reference to Figures 30 to 35.

[0246] When a first station of a non-STR multi-link device is scheduled to receive a specific frame on the first link, a second station of the non-STR multi-link device operating on the second link at the time of receiving the specific frame on the first link may not perform channel access or transmission. In this case, the specific frame may be a frame that is periodically transmitted. Specifically, the specific frame may be a DTIM frame.

[0247] Also, when the second station is a TXOP holder, the second station can terminate the TXOP before the specific frame is received on the first link. In this case, the method of terminating the TXOP may be the embodiment of terminating the TXOP described in FIG. 28. Specifically, the second station can set the end of the TXOP to be before the specific frame is received on the first link. For example, when the specific frame is a DTIM, the second station can set the end of the TXOP based on the reception period of the DTIM. Also, the second station can transmit a CF-End frame before the specific frame is received on the first link. Also, the TXOP limit exception may not be applied to such an embodiment.

[0248] Also, the second station can abort the channel access before receiving the specific frame on the first link. In this case, the channel access abort embodiment described in FIG. 28 can be applied. Specifically, if the difference between the time when the second station completes the channel access and the time when the specific frame is scheduled to be received on the first link is insufficient to complete the frame exchange that the second station is about to perform, the second station can perform the channel access procedure again. In this case, the second station can obtain the backoff counter by using the same size of the CW used in the previous channel access procedure. Also, the second station does not need to increment the retransmission counter.

[0249] FIG. 30 illustrates a multilink device transmitting on a non-STR link pair according to an embodiment of the present invention.

[0250] When the multilink device transmits a frame on a first link of a non-STR link pair, the multilink device may be restricted from transmitting a frame on a second link of the non-STR link pair for a certain period of time from the completion of frame transmission. In this case, the multilink device may be a non-STR multilink device. In this case, the certain period of time may be called MediumSyncDelay. The restriction of the frame transmission operation may mean that the above-mentioned channel access procedure cannot be performed in the MediumSyncDelay. Specifically, the multilink device may be unable to perform a Distributed Coordination Function (DCF) or Enhanced Distributed Channel Access Function (EDCAF) operation defined in IEEE 802.11 during MediumSyncDelay on the second link. In yet another specific embodiment, when the multilink device performs channel sensing on the second link during MediumSyncDelay, the multilink device may lower a threshold energy level, which is a criterion for a channel occupancy (busy) state. In this case, the multilink device may set the threshold energy level to -82 dBm.

[0251] A multilink device operating as a non-STR multilink device can synchronize the start time of transmission on a non-STR multilink pair. At this time, the transmission start time of a frame can indicate the transmission start time of a PPDU including the frame. In order to synchronize the transmission start time on a non-STR link pair, the multilink device can maintain a backoff value of 0 in the channel access procedure and postpone transmission.

[0252] Also, when reception is performed consecutively after transmission on a non-STR multilink pair, the multilink device may synchronize the end of transmission on the non-SRT multilink pair. To this end, the multilink device may add a bit or field for padding to the frame or PPDU to be transmitted. The multilink device may also add a packet extension (PE). Also, when consecutive frame exchanges are performed on a non-STR multilink pair, the multilink device may synchronize the start of transmission on the non-STR multilink after the first frame exchange. In yet another specific embodiment, the multilink device may perform fragmentation to synchronize the end of transmission.

[0253] When the TXOP start time is the same in a plurality of links, the TXOP for frame transmission in each link may be synchronized. In this case, after a negotiation stage for simultaneous transmission in a plurality of links, simultaneous transmission using a plurality of links may be performed. In the negotiation stage for simultaneous transmission, a multilink device performing transmission transmits a request frame for acquiring a TXOP for simultaneous transmission in a synchronized transmission in a plurality of links, and a multilink device receiving the request frame may transmit a response frame at a SIFS (Short Interframe Space) interval from the request frame. In this case, the response frame may be transmitted simultaneously in one or more links receiving the request frame. The request frame may be a control frame. For example, the request frame may be one of an RTS frame and a MU (Multi-user)-RTS frame. In this case, the response frame may be a CTS frame. If a channel of any one link is occupied during channel contention for simultaneous transmission, the multilink device may wait to perform a simultaneous transmission operation, or may perform transmission using only a link including an idle channel. The exchange of the request frame and the response frame described above may not be performed simultaneously in a plurality of links. Furthermore, the synchronized frame exchange may be such that the transmission start time of the PPDU including the frame is synchronized, and the transmission end time of the PPDU including the frame is synchronized.

[0254] When the multilink device transmits a frame requesting an immediate response on the first link of the non-STR link pair, the multilink device may synchronize the end points of transmission on the first and second links of the non-STR link pair. In this case, the immediate response indicates that the interval between the received frame and the response frame is a pre-specified interval. The pre-specified interval may be SIFS. In another specific embodiment, the pre-specified interval may be PIFS. In addition, when the multilink device transmits a frame not requesting an immediate response on the first link of the non-STR link pair, the multilink device may not synchronize the end points of transmission on the first and second links of the non-STR link pair. In this case, the multilink device may transmit a PPDU not requesting an immediate response on the second link as well, and may not be allowed to transmit a PPDU requesting an immediate response.

[0255] In the above embodiment, the synchronization of the transmission start times may indicate that the difference between the transmission start times is within a pre-specified time. Also, the synchronization of the transmission end times may indicate that the difference between the transmission end times is within a pre-specified time. In this case, the pre-specified time may be a time for preventing the start of frame transmission on one link from recognizing the channel state of another link as a channel occupied (busy) state when channel sensing and backoff operations are performed individually on the links. In a specific embodiment, the pre-specified time may be a receive-transmit turnaround time (RxTxTurnaroundTime). For example, the pre-specified time may be 8us or 4us.

[0256] According to these embodiments, the multilink device can prevent transmission on one link of a non-STR link pair from preventing transmission on the other link.

[0257] In the embodiment of FIG. 30, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). In FIG. 30(a), the AP multilink device and the station multilink device perform synchronized transmission and synchronized reception. This prevents transmission from being interrupted on any one link of the non-STR multilink pair. In FIG. 30(b), the first AP (AP1) transmits a DL PPDU that does not request an immediate response on the first link (Link1). Since a DL PPDU not requesting an immediate response is transmitted on the first link (Link1), the second station (STA2) transmits a DL PPDU not requesting an immediate response on the second link (Link2) without synchronizing with the transmission of the first link.

[0258] In Fig. 30, an embodiment is shown in which frame exchange is initiated from the AP multilink device, which is the STR multilink device, in a non-STR multilink pair. The embodiment described in Fig. 30 may also be applied to the case in which frame exchange is initiated from the non-STR multilink device. This will be described with reference to Figs. 31 and 32.

[0259] Fig. 31 shows frame exchange initiated from a non-AP station multilink device to which an embodiment of the present invention is not applied, and Fig. 32 shows frame exchange initiated from a non-AP station multilink device according to an embodiment of the present invention.

[0260] In the embodiment of FIG. 31, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). The end points of transmission of the first station (STA1) and the second station (STA2) are not synchronized. The transmission of the first station (STA1) ends before the transmission of the second station (STA2). Therefore, the transmission of the second station (STA2) continues while the first AP (AP1) transmits a BA frame to the first station (STA1). As a result, the transmission of the first AP (AP1) fails.

[0261] Therefore, when a non-STR multilink device transmits a frame requesting an immediate response on a first link of a non-STR link pair, the non-STR multilink device may synchronize the end points of transmission on the first and second links of the non-STR link pair. In this case, the immediate response indicates that the interval between the received frame and the response frame is a pre-specified interval. The pre-specified interval may be SIFS. In yet another specific embodiment, the pre-specified interval may be PIFS. Also, when a non-STR multilink device transmits a frame not requesting an immediate response on a first link of a non-STR link pair, the non-STR multilink device may not synchronize the end points of transmission on the first and second links of the non-STR link pair. In this case, the non-STR multilink device may transmit a PPDU not requesting an immediate response on the second link as well, and may not be allowed to transmit a PPDU requesting an immediate response.

[0262] In the embodiment of FIG. 32, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). The end points of transmissions of the first station (STA1) and the second station (STA2) are synchronized. Therefore, the transmissions of the first AP (AP1) and the second AP (AP2) are successfully completed without interfering with each other.

[0263] A case where unsynchronized transmission is permitted in a non-STR link pair will be described with reference to FIGS.

[0264] FIG. 33 shows that, according to an embodiment of the present invention, when a multilink device transmits a transmission requesting an immediate response on a first link of a non-STR link pair, it transmits a transmission not requesting an immediate response on the second link.

[0265] When a multilink device transmits a frame requesting an immediate response on a first link of a non-STR link pair, the multilink device can perform a transmission on a second link of the non-STR link pair that is completed before the end of the transmission of the first link and does not request an immediate response. In such an embodiment, since a response frame is not transmitted on the second link, it is possible to prevent the multilink device's transmission on the first link and the response frame to the transmission from the multilink device from being interfered with by the multilink device's transmission on the second link. Also, if the multilink device's transmission on the second link is not completed before the end of the transmission of the first link, the transmission of the response frame on the first link may be interfered with by the multilink device's transmission on the second link. For this reason, the multilink device's transmission on the second link must be completed before the transmission of the first link.

[0266] In the embodiment of FIG. 33, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). When the first station (STA1) performs an uplink transmission requesting an immediate response on the first link, the second station (STA2) performs an uplink transmission that does not request an immediate response and ends before the transmission of the first station (STA1) ends on the second link (Link2). The uplink transmission of the first station (STA1) and the uplink transmission of the second station (STA2) are completed without interfering with each other.

[0267] FIG. 34 illustrates an operation of a multi-link device performing transmission on a second link when performing UL OFDMA transmission on a first link of a non-STR link pair according to an embodiment of the present invention.

[0268] The magnitude of the influence between the links may vary depending on the RU that transmits in the non-STR multilink pair. Therefore, even if the multilink device transmits in the first link of the first link and the second link of the non-STR multilink pair, the transmission in the second link may be permitted depending on the position of the RU of the first link that the multilink device transmits in and the RU of the second link that the multilink device transmits in. Specifically, when the multilink device performs UL OFDMA transmission, the transmission in the second link may be permitted depending on which RU performs UL OFDMA transmission. In yet another specific embodiment, the transmission in the second link may be permitted depending on the size of the bandwidth used when the multilink device transmits in each link. In this case, the multilink device can transmit using any of the bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 320 MHz.

[0269] In the embodiment of FIG. 34, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). The first station (STA1) participates in UL OFDMA transmission on the first link (Link1). At this time, if the RU on which the first station (STA1) performs UL OFDMA and the location of the RU on which the second station (STA2) performs transmission satisfy a pre-specified condition, the second station (STA2) performs uplink transmission. At this time, the pre-specified condition may be that the interval between the RUs is smaller than the pre-specified interval. In addition, whether transmission on the second link is permitted may be determined according to the expansion direction of the bandwidth in which transmission is performed.

[0270] The direction of transmission may determine whether a link pair is a non-STR link pair or an STR link pair, as will be described with reference to FIG.

[0271] FIG. 35 illustrates a case in which it is determined whether a link pair is a non-STR link pair or an STR link pair depending on the transmission direction according to an embodiment of the present invention.

[0272] The first multilink device cannot transmit on the second link when receiving on the first link of the link pair, but can transmit on the first link when receiving on the second link. For example, in the 6 GHz band, the transmission power of the station may be limited to a pre-specified power or less. Thus, when the first link is located in the 6 GHz band, the first multilink device cannot transmit on the second link when receiving on the first link of the link pair, but can transmit on the first link when receiving on the second link. Thus, while transmission is being performed on the first link depending on the transmission direction, transmission in the second link may be permitted in which the end time of the transmission of the first link is not synchronized with the end time of the transmission of the first link. In this case, the multilink device may end transmission on the second link before transmission on the first link. For this reason, the multilink device may perform fragmentation on the traffic to be transmitted on the second link.

[0273] In the embodiment of FIG. 35, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on a first link (Link1). The second AP (AP2) and the second station (STA2) operate on a second link (Link2). At this time, the non-AP station cannot transmit on the second link when receiving on the first link located in the 6 GHz band, but can transmit on the first link (Link1) when receiving on the second link (Link2). While the first station (STA1) is in the middle of transmitting uplink on the first link (Link1), the second station (STA2) starts transmitting uplink on the second link (Link2). At this time, the second station (STA1) completes its uplink transmission before the first station (STA1) completes its uplink transmission. Through these operations, upstream transmission is completed on the first and second links, and the BA frame is also successfully transmitted.

[0274] Although the present invention has been described above with reference to wireless LAN communication, the present invention is not limited thereto and can 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 a specific embodiment, some or all of the components and operations of the present invention can be embodied by a computer system having a general-purpose hardware architecture.

[0275] 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 only one embodiment. The features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by a person having ordinary skill in the art 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.

[0276] The above description focuses on the embodiments, but 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 embodiment. For example, each component specifically illustrated in the embodiments can be modified. Furthermore, differences related to such modifications and applications should be interpreted as being included in the scope of the present invention as defined in the appended claims. [Explanation of symbols]

[0277] 110 Processor 120 Communications Department 140 User Interface Section 150 display units 160 Memory 210 Processor 220 Communications Department 260 Memory

Claims

1. A wireless communication terminal that wirelessly communicates with a base wireless communication terminal, A transceiver unit; and A processor is included. The processor, Transmitting low-latency traffic designated as traffic for low-latency transmission or a response to the low-latency traffic within the limited service period; A wireless communication terminal in which transmission of the low latency traffic and transmissions other than the low latency traffic are restricted during the restricted service period.

2. The processor, The wireless communication terminal according to claim 1 , wherein a TXOP for transmitting traffic other than the low latency traffic is terminated before the restricted service period begins.

3. The processor, Get a random integer within the contention window, performing channel access based on the obtained random integer; 2. The wireless communication terminal according to claim 1, wherein, when channel access is completed before the start of the restricted service period and transmission is abandoned because it is determined that frame exchange cannot be completed before the start of the restricted service period, channel access is performed again.

4. The processor, 4. The wireless communication terminal according to claim 3, wherein when the wireless communication terminal performs the channel access again, the size of the contention window used in the completed channel access is maintained as it is.

5. The processor, 4. The wireless communication terminal of claim 3, wherein the wireless communication terminal maintains a retransmission count of the completed channel access when the wireless communication terminal performs the channel access again.

6. A quiet period corresponding to the restricted service period is set, and no transmission is permitted during the quiet period; The processor, Transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period while ignoring a quiet period corresponding to the limited service period; The wireless communication terminal according to claim 1 , wherein a CF End frame is not transmitted within the limited service period.

7. A quiet period corresponding to the restricted service period is set, and no transmission is permitted during the quiet period; The processor, determining whether to ignore a quiet interval based on a start time of the limited service period and a start time of the quiet interval; 2. The wireless communication terminal according to claim 1, wherein when it is determined to ignore the quiet interval, the wireless communication terminal ignores the quiet interval corresponding to the limited service period and transmits the low-latency traffic or a response to the low-latency traffic within the limited service period.

8. The processor, ignoring the quiet interval when a condition determined based on a start time of the limited service period and a start time of the quiet interval is satisfied; The wireless communication terminal according to claim 7 , wherein all transmissions are suspended when a condition determined based on a start time of the limited service period and a start time of the quiet interval is not satisfied.

9. 9. The wireless communication terminal according to claim 8, wherein the condition determined based on the start point of the limited service period and the start point of the quiet interval is that the start point of the quiet interval and the start point of the limited service period are within a pre-specified time.

10. 1. A method of operating a wireless communication terminal that wirelessly communicates with a base wireless communication terminal, comprising: transmitting low-latency traffic designated as traffic for low-latency transmission or a response to the low-latency traffic within a limited service period; An operating method in which transmissions other than the transmission of the low-latency traffic and transmission of a response to the low-latency traffic are restricted during the restricted service period.

11. The method of operation includes: The method of claim 10, further comprising terminating a TXOP for transmission of traffic other than the low latency traffic before the restricted service period begins.

12. The method of operation includes: obtaining a random integer within a contention window; performing channel access based on the obtained random integer; and 11. The method of claim 10, further comprising completing channel access before the start of the limited service period and reattempting channel access if the transmission is abandoned due to determining that frame exchange cannot be completed before the start of the limited service period.

13. The step of re-accessing the channel includes: The method of claim 12, further comprising the step of: maintaining a size of the contention window used in the completed channel access when the wireless communication terminal performs the channel access again.

14. The step of re-accessing the channel includes:

13. The method of claim 12, further comprising maintaining a retransmission count for the completed channel access when the wireless communication terminal attempts the channel access again.

15. A quiet period corresponding to the restricted service period is set, and no transmission is permitted during the quiet period; The step of transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period includes: transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period while ignoring a quiet interval corresponding to the restricted service period; and 11. The method of claim 10, comprising not transmitting a CF End frame within the limited service period.

16. A quiet period corresponding to the restricted service period is set, and no transmission is permitted during the quiet period; The step of transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period includes: determining whether to ignore a quiet interval based on a start time of the limited service period and a start time of the quiet interval; and The method of claim 10, further comprising: ignoring a quiet interval corresponding to the limited service period and transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period when it is determined to ignore the quiet interval.

17. determining whether to ignore a quiet interval based on a start time of the limited service period and a start time of the quiet interval, ignoring the quiet interval if a condition determined based on a start time of the limited service period and a start time of the quiet interval is satisfied; and 17. The method of claim 16, further comprising disabling all transmissions if a condition determined based on a start time of the limited service period and a start time of the quiet interval is not met.

18. 20. The method of claim 17, wherein the condition determined based on the start time of the restricted service period and the start time of the quiet interval is that the start time of the quiet interval and the start time of the service period of the TWT are within a pre-specified time.

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