Wireless communication method using multiple links and wireless communication terminal using the method

Abstract

A station for communicating with a single-radio multi-link device that includes multiple stations each operating on a respective one of a plurality of links, but does not support simultaneous transmission or reception by multiple stations. The station includes a transceiver and a processor. The processor uses the transceiver to transmit a control frame to a first station of the single-radio multi-link device, receive a response to the control frame from the first station of the single-radio multi-link device, and initiate a null data packet (NDP) sounding sequence for the first station of the single-radio multi-link device.

Description

Technical Field

[0001] The present invention relates to a wireless communication method using multiple links and a wireless communication terminal using the method. Background Art

[0002] In recent years, with the expansion of the supply of mobile devices, wireless local area network (Wireless LAN) technology that can provide fast wireless Internet services to mobile devices has received attention. The Wireless LAN technology allows mobile devices including smart phones, smart tablets, laptop computers, portable multimedia players, embedded devices, etc. to wirelessly access the Internet in a home or company or special service providing area based on short-range wireless communication technology.

[0003] Since the initial Wireless LAN technology that supports the use of a frequency of 2.4 GHz, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 has commercialized or developed various technical standards. First, IEEE 802.11b supports a maximum communication speed of 11 Mbps when using a frequency in the 2.4 GHz band. Compared with the significantly congested frequency in the 2.4 GHz band, IEEE 802.11a, which was commercialized after IEEE 802.11b, uses a frequency in the 5 GHz band instead of the 2.4 GHz band to reduce the influence of interference, and by using OFDM technology, increases the communication speed to a maximum of 54 Mbps. However, the disadvantage of IEEE 802.11a is that the communication distance is shorter than that of IEEE 802.11b. In addition, similar to IEEE 802.11b, IEEE 802.11g uses a frequency in the 2.4 GHz band to achieve a maximum communication speed of 54 Mbps and satisfies backward compatibility, which has attracted significant attention. Further, in terms of communication distance, it is superior to IEEE 802.11a.

[0004] In addition, as a technical standard established to overcome the limitations of communication speed pointed out as a weakness in wireless LANs, IEEE 802.11n has been provided. IEEE 802.11n aims to increase the speed and reliability of the network and extend the working distance of the wireless network. More specifically, IEEE 802.11n supports High Throughput (HT), where the data processing speed is 540 Mbps or higher at maximum, and further, is based on Multiple Inputs Multiple Outputs (MIMO) technology, where multiple antennas are used on both sides of the transmitting unit and the receiving unit to minimize transmission errors and optimize data speed. In addition, this standard can use an encoding scheme that transmits multiple copies of a repeat to increase data reliability.

[0005] With the activation of the supply of wireless LANs, and further, with the diversification of applications using wireless LANs, the demand for a new wireless LAN system that supports a throughput (Very High Throughput, VHT) higher than the data processing speed supported by IEEE 802.11n has received attention. Among them, IEEE 802.11ac supports a wide bandwidth (80 to 160 MHz) in the 5 GHz frequency band. The IEEE 802.11ac standard is defined only in the 5 GHz band, but the initial 11ac chipset even supports operation in the 2.4 GHz band for backward compatibility with existing 2.4 GHz band products. Theoretically, according to this standard, the wireless LAN speed of multiple stations can be made to reach at least 1 Gbps, and the maximum single-link speed can be made to reach at least 500 Mbps. This is achieved by expanding the concept of the wireless interface accepted by 802.11n, such as a wider wireless frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). In addition, as a scheme for transmitting data by using the 60 GHz band instead of the existing 2.4 GHz / 5 GHz, IEEE 802.11ad has been provided. IEEE 802.11ad is a transmission standard that provides a speed of up to 7 Gbps by using beamforming technology and is suitable for high-bitrate moving image streams, such as large-scale data or uncompressed HD video. However, since the 60 GHz band has difficulty passing through obstacles, its disadvantage is that the 60 GHz band can only be used among devices in a short-distance space.

[0006] As a wireless LAN standard following 802.11ac and 802.11ad, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard for providing efficient and high-performance wireless LAN communication technology in high-density environments of APs and terminals is in the development completion stage. In a wireless LAN environment based on 802.11ax, in the presence of high-density stations and access points (APs), communication with high-frequency efficiency should be provided indoors / outdoors, and various technologies for implementing such communication have been developed.

[0007] To support new multimedia applications such as high-definition video and real-time games, a new wireless LAN standard has been started to develop to increase the maximum transmission rate. In IEEE 802.11be Extremely High Throughput (EHT), which is the 7th generation wireless LAN standard, the standard is being developed with the aim of supporting a transmission rate of up to 30 Gbps in the 2.4 / 5 / 6 GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation, etc. Summary of the Invention

[0008] Technical Problem

[0009] An embodiment of the present invention is used to provide a wireless communication method using multiple links and a wireless communication terminal using this method.

[0010] Technical Solution

[0011] According to an embodiment of the present invention, a station communicating with a single-radio multi-link device, the single-radio multi-link device includes multiple stations operating on multiple links respectively, but does not support simultaneous transmission or reception of the multiple stations, the station includes: a transceiver; and a processor. The processor uses the transceiver to transmit a control frame to a first station of the single-radio multi-link device, receives a response to the control frame from the first station of the single-radio multi-link device, and starts a null data packet (NDP) sounding sequence for the first station of the single-radio multi-link device.

[0012] The control frame may be a MU-RTS frame.

[0013] The control frame may be a trigger frame of a different type from the MU-RTS frame.

[0014] The processor may transmit the control frame in a predetermined physical layer protocol data unit (PPDU) format.

[0015] The predetermined PPDU format may be at least one of a non - non - HT format or an HT format.

[0016] The processor may transmit the control frame at a rate below a predetermined data rate.

[0017] When the first station of the single - radio multi - link device is performing transmission or reception, the processor does not perform transmission to the second station of the single - radio multi - link device.

[0018] Not only during the execution of the frame exchange sequence of the first station but also during a certain period of time starting from the completion of the frame exchange sequence of the first station, the processor may not perform transmission to the second station of the single - radio multi - link device.

[0019] During the execution of the frame exchange sequence of the first station, multiple RF chains are supported for use in the link of the frame exchange sequence of the first station, and the certain period of time may be determined based on the RF chain change time of the single - radio multi - link device.

[0020] When the single - radio multi - link device supports the use of multiple RF chains in a first link and changes from not supporting the use of RF chains in a second link to supporting the use of RF chains in the second link, the processor may apply a restriction on channel access during a predetermined period of time before performing channel access in the second link.

[0021] The predetermined period of time may be the predetermined period of time applied when a restriction on channel access is required due to the time when channel monitoring is not possible.

[0022] The predetermined period of time may be NAVSyncdelay.

[0023] When the single - radio multi - link device supports the use of multiple RF chains in a first link and does not support the use of RF chains in a second link, single - input single output (SISO) (1x1) may be used to perform the final frame exchange in the frame exchange sequence executed in the first link.

[0024] According to an embodiment of the present invention, a single - radio multi - link device including multiple stations operating on multiple links respectively but not supporting simultaneous transmission or reception of the multiple stations includes: a transceiver; and a processor. When the link of the operating RF chain of the single - radio multi - link device changes from a first link to a second link and then changes from the second link back to the first link again, the processor delays performing channel access during a predetermined period of time before performing channel access in the first link.

[0025] The predetermined time may be a predetermined time applied when there is a need to restrict channel access due to a time when channel monitoring cannot be performed.

[0026] The predetermined time may be NAVSyncdelay.

[0027] When the single radio multi-link device supports the use of multiple RF chains in the first link and does not support the use of RF chains in the second link, in the frame exchange sequence executed by the processor in the first link, single input single output (SISO) (1x1) may be used to transmit the last frame.

[0028] According to an embodiment of the present invention, an operation method of a station communicating with a single radio multi-link device including multiple stations operating separately on multiple links but not supporting simultaneous transmission or reception of the multiple stations includes the following steps: transmitting a control frame to a first station of the single radio multi-link device; receiving a response to the control frame from the first station of the single radio multi-link device; and starting a null data packet (NDP) sounding sequence for the first station of the single radio multi-link device.

[0029] The control frame may be a MU-RTS frame.

[0030] The control frame may be a trigger frame of a type different from the MU-RTS frame.

[0031] Advantageous Effects

[0032] An embodiment of the present invention provides a wireless communication method for efficiently using multiple links and a wireless communication terminal using the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Illustrates a wireless LAN system according to an embodiment of the present invention.

[0034] Figure 2 Illustrates a wireless LAN system according to another embodiment of the present invention.

[0035] Figure 3 Illustrates the configuration of a station according to an embodiment of the present invention.

[0036] Figure 4 Illustrates the configuration of an access point according to an embodiment of the present invention.

[0037] Figure 5 Schematically illustrates the process of a station and an access point setting up a link.

[0038] Figure 6Illustrates the Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) method used in wireless LAN communication.

[0039] Figure 7 Illustrates an example of the format of a Physical Layer Protocol Data Unit (PPDU) for each of various standard generations.

[0040] Figure 8 Illustrates examples of various Extremely High Throughput (EHT) Physical Layer Protocol Data Unit (PPDU) formats and a method for indicating the format according to an embodiment of the present invention.

[0041] Figure 9 Illustrates a multi-link device according to an embodiment of the present invention.

[0042] Figure 10 Illustrates simultaneous transmission of different links in multi-link operation according to an embodiment of the present invention.

[0043] Figure 11 Illustrates the operation of a multi-link device when a link changes according to an embodiment of the present invention.

[0044] Figure 12 Illustrates prohibiting channel access of another station of a non-STR multi-link device when a station of the non-STR multi-link device performs reception according to an embodiment of the present invention.

[0045] Figure 13 Illustrates the operation of releasing the channel access prohibition when the expected receiver of a PPDU received by a station of a non-STR multi-link device is not that station.

[0046] Figure 14 Illustrates the station performing channel access after releasing the channel access prohibition according to an embodiment of the present invention.

[0047] Figure 15 Illustrates the operation of the station performing transmission after releasing the channel access prohibition according to an embodiment of the present invention.

[0048] Figure 16 Illustrates transmission performed based on the state of a station within a non-STR multi-link device according to an embodiment of the present invention.

[0049] Figure 17 Illustrates a situation where interference or conflict may occur between links.

[0050] Figure 18 Illustrates the operation of a STR multi-link device stopping transmission to a non-STR multi-link device according to an embodiment of the present invention.

[0051] Figure 19Illustrates the processing of the CW value when the STR multi-link device identifies a transmission conflict between links according to an embodiment of the present invention.

[0052] Figure 20 Illustrates the operation of the STR multi-link device to stop transmitting to the non-STR multi-link device and then perform channel access again according to an embodiment of the present invention.

[0053] Figure 21 Illustrates the operation of the STR multi-link device to send a CTS-to-Self frame before transmitting to the non-STR multi-link device according to an embodiment of the present invention.

[0054] Figure 22 Illustrates the transmission by multiple APs included in the STR multi-link device to multiple stations included in one non-STR multi-link device according to an embodiment of the present invention.

[0055] Figure 23 Illustrates multiple transmissions by multiple APs included in the STR multi-link device to multiple stations included in one non-STR multi-link device, where the transmission ends of the multiple transmissions are synchronized according to an embodiment of the present invention.

[0056] Figure 24 Illustrates the exchange of RTS / CTS frames by the multi-link device according to an embodiment of the present invention.

[0057] Figure 25 Illustrates according to the reference Figure 24 Describes the hidden node problem that occurs during the RTS / CTS frame exchange according to an embodiment of the present invention.

[0058] Figure 26 Illustrates the exchange of RTS / CTS frames by the multi-link device according to an embodiment of the present invention.

[0059] Figure 27 Illustrates that even in the case of prohibited channel access, the multi-link device exceptionally sends a response to the control frame according to an embodiment of the present invention.

[0060] Figure 28 Illustrates the retransmission of the transmission to the station of the non-STR multi-link device.

[0061] Figure 29 Illustrates that according to an embodiment of the present invention, the control frame is transmitted through the link where the channel access of the station is not prohibited rather than the link where the channel access of the station is prohibited.

[0062] Figure 30 Illustrates the sending of ACK by the multi-link device according to an embodiment of the present invention.

[0063] Figure 31 Illustrates an element field indicating information regarding supporting synchronous PPDU reception or transmission according to an embodiment of the present invention.

[0064] Figure 32 Illustrates the operation of an inter-link TXOP power saving mode performed by a non-STR multi-link device according to an embodiment of the present invention.

[0065] Figure 33 Illustrates that a station of a non-STR multi-link device enters the sleep state from the standby state of synchronous PPDU reception according to an embodiment of the present invention.

[0066] Figure 34 Illustrates that a station of a non-STR multi-link device enters the sleep state from the standby state of synchronous PPDU reception according to another embodiment of the present invention.

[0067] Figure 35 Illustrates the connection between a single-radio multi-link device and an AP multi-link device according to an embodiment of the present invention.

[0068] Figure 36 Illustrates that a single-radio multi-link device performs MIMO transmission according to an embodiment of the present invention.

[0069] Figure 37 Illustrates the operation of a single-radio multi-link device performing channel access considering the delay time of radiofrequency (RF) chain change according to an embodiment of the present invention.

[0070] Figure 38 Illustrates the Capability element and Operation element used by a single-radio multi-link device according to an embodiment of the present invention.

[0071] Figure 39 Illustrates that a single-radio multi-link device uses MIMO to send a PPDU according to an embodiment of the present invention.

[0072] Figure 40 Illustrates that a station and a single-radio multi-link device perform an NDP sounding process according to an embodiment of the present invention.

[0073] Figure 41 Illustrates that a station and a single-radio multi-link device perform a feedback beamforming sounding sequence according to an embodiment of the present invention.

[0074] Figure 42 Illustrates that a station and a single-radio multi-link device perform an NDP sounding process according to an embodiment of the present invention. Detailed Description

[0075] By considering the functions of the present invention, the terms used in this specification adopt the general terms widely used currently. However, the terms may change according to the intentions of those skilled in the art, habits, and the emergence of new technologies. In addition, in special cases, there are terms selected by the applicant, and in such cases, their meanings will be described in the corresponding description part of the present invention. Therefore, it should be understood that the terms used in this specification should be analyzed not only based on the name of the term, but also based on the substantial meaning of the term and the content of the entire specification.

[0076] Throughout the specification, when it is stated that one element is "coupled" to another element, the element may be "directly coupled" to the other element or "electrically coupled" to the other element via a third element. In addition, unless there is a clear contrary statement, the word "comprising" will be understood to implicitly include the stated elements, but not exclude any other elements. In addition, limitations such as "or more" or "or less" based on a specific threshold may be appropriately replaced by "greater than" or "less than" respectively.

[0077] Hereinafter, in the present invention, fields and sub - fields may be used interchangeably.

[0078] Figure 1 The figure illustrates a wireless LAN system according to an embodiment of the present invention.

[0079] The wireless LAN system includes one or more basic service sets (BSSs), and a BSS represents a set of devices that have successfully synchronized with each other to communicate with each other. Generally, a BSS can be divided into an infrastructure BSS and an independent BSS (IBSS), and Figure 1 The infrastructure BSS between them is shown.

[0080] As Figure 1 shown, the infrastructure BSSs (BSS1 and BSS2) include one or more stations (STA1, STA2, STA3, STA4, and STA5), access points (AP - 1 and AP - 2) that are stations providing distribution services, and a distribution system (DS) that connects multiple access points (AP - 1 and AP - 2).

[0081] A station (STA) is any device that includes a Medium Access Control (MAC) compliant with the provisions of the IEEE 802.11 standard and a Physical Layer interface for a wireless medium, and broadly includes both non-access point (non-AP) stations and access points (APs). In addition, in this specification, the term "terminal" is a term that can be used to refer to either a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a communication unit, and according to an embodiment, may further include a user interface unit and a display unit. The processor may generate frames to be transmitted via a wireless network, or process frames received via a wireless network, and in addition, perform various processes for controlling the station. In addition, the communication unit is functionally connected to the processor and transmits and receives frames via the wireless network for the station. According to the present invention, a terminal may be used as a term including a user equipment (UE).

[0082] An access point (AP) is an entity that provides access to a distributed system (DS) via a wireless medium for associated stations. In an infrastructure BSS, communication among non-AP stations is in principle performed via the AP, but when a direct link is configured, direct communication among non-AP stations is even allowed. At the same time, in the present invention, the AP is used as a concept including a Personal BSS Coordination Point (PCP), and broadly may include 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, the AP may also be referred to as a base station wireless communication terminal. The base station wireless communication terminal may be broadly used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, in communication with multiple wireless communication terminals, the base station wireless communication terminal may include various types of wireless communication terminals that allocate communication medium resources and perform scheduling.

[0083] Multiple infrastructure BSSs may be interconnected via a distributed system (DS). In this case, the multiple BSSs connected via the distributed system are called an Extended Service Set (ESS).

[0084] Figure 2 FIG. illustrates a stand-alone BSS according to another embodiment of the present invention, which is a wireless LAN system. InFigure 2 In the embodiments of Figure 1 identical to or corresponding to Figure 1 the parts of the embodiments will not be described repeatedly.

[0085] Since BSS3 illustrated in Figure 2 is an independent BSS and does not include an AP, all stations STA6 and STA7 are not connected to the AP. The independent BSS is not allowed to access the distributed system and forms a self - contained network. In the independent BSS, the corresponding stations STA6 and STA7 can be directly connected to each other.

[0086] Figure 3 is a block diagram illustrating the configuration of a station 100 according to an embodiment of the present invention. As shown, the station 100 according to an embodiment of the present invention may include a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0087] First, the communication unit 120 transmits and receives wireless signals, such as wireless LAN packets, etc., and may be embedded in the station 100 or provided as a peripheral device. 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 having 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 higher, and a communication module using a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit 120 may operate only one communication module at a time or operate multiple communication modules together simultaneously according to the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be implemented 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 an RF communication module for processing radio frequency (RF) signals.

[0088] Second, the user interface unit 140 includes various types of input / output devices provided in the station 100. That is, the user interface unit 140 may receive user input by using various input means, and the processor 110 may control the station 100 based on the received user input. In addition, the user interface unit 140 may perform output based on the command of the processor 110 by using various output means.

[0089] Next, the display unit 150 outputs an image on the display screen. The display unit 150 can output various display objects, such as content executed by the processor 110 or a user interface based on the control commands of the processor 110, etc. In addition, the memory 160 stores control programs and various data used in the station 100. The control program may include an access program required for the station 100 to access the AP or an external station.

[0090] The processor 110 of the present invention can execute various commands or programs and process data in the station 100. In addition, the processor 110 can control each unit of the station 100 and control data transmission / reception among the units. According to an embodiment of the present invention, the processor 110 can execute a program for accessing the AP stored in the memory 160 and receive a communication configuration message sent by the AP. In addition, the processor 110 can read information about the priority conditions of the station 100 included in the communication configuration message and request access to the AP based on the information about the priority conditions of the station 100. The processor 110 of the present invention can represent the main control unit of the station 100, and according to an embodiment, the processor 110 can represent a control unit for separately controlling certain components (such as the communication unit 120, etc.) of the station 100. That is, the processor 110 can be a modem or a modulator and / or demodulator for modulating a wireless signal sent to the communication unit 120 and demodulating a wireless signal received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission / reception of the station 100 according to an embodiment of the present invention. Its detailed embodiments will be described below.

[0091] In Figure 3 FIG. 1, the station 100 illustrated is a block diagram according to an embodiment of the present invention, where the separate blocks are illustrated as elements of logically distinct devices. Therefore, the elements of the device can be installed in a single chip or multiple chips according to the design of the device. For example, the processor 110 and the communication unit 120 can be integrated and implemented as a single chip or implemented as separate chips. In addition, in an embodiment of the present invention, certain components of the station 100, such as the user interface unit 140 and the display unit 150, etc., can be selectively provided in the station 100.

[0092] Figure 4 FIG. 2 is a block diagram illustrating the configuration of an AP 200 according to an embodiment of the present invention. As illustrated in Figure 4 FIG. 2, the AP 200 according to an embodiment of the present invention may include a processor 210, a communication unit 220, and a memory 260. In Figure 4 FIG. 2, among the configurations of the AP 200, the same as or corresponding to Figure 3 the configuration of the station 100 inFigure 3 Redundant descriptions of parts of the configuration of station 100 will be omitted.

[0093] Refer to Figure 4 , according to the present invention, the AP 200 includes a communication unit 220 that operates a BSS in at least one frequency band. As described in the embodiment of Figure 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 an embodiment of the present invention may include two or more communication modules in different frequency bands (e.g., 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz) together. 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 according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit 220 may operate only one communication module at a time or operate a plurality of communication modules together simultaneously according to the performance and requirements of the AP 200. In an embodiment of the present invention, the communication unit 220 may represent a radio frequency (RF) communication module for processing RF signals.

[0094] Next, the memory 260 stores control programs and various data used in the AP 200. The control program may include an access program for managing access of stations. In addition, the processor 210 may control each unit of the AP 200 and control data transmission / reception among the units. According to an embodiment of the present invention, the processor 210 may execute a program for accessing stations stored in the memory 260 and send a communication configuration message for one or more stations. In this case, the communication configuration message may include information about access priority conditions of each station. In addition, the processor 210 performs access configuration according to an access request of a station. According to an embodiment, the processor 210 may be a modem or a modulator and / or demodulator for modulating a wireless signal transmitted to the communication unit 220 and demodulating a wireless signal received from the communication unit 220. The processor 210 controls various operations such as wireless signal transmission / reception of the AP 200 according to an embodiment of the present invention. Its detailed embodiments will be described below.

[0095] Figure 5 is a diagram schematically illustrating a process of configuring a link between a station and an access point.

[0096] Refer to Figure 5, Broadly speaking, the link between STA100 and AP 200 is set up through three steps: scanning, authentication, and association. First, the scanning step is the step where STA 100 obtains access information of the BSS operated by AP 200. The methods for performing scanning include the passive scanning method, where AP 200 obtains information by using beacon messages (S101) sent periodically, and the active scanning method, where STA 100 sends a probe request to AP (S103) and obtains access information by receiving a probe response from AP (S105).

[0097] The STA 100 that has successfully received wireless access information in the scanning step performs the authentication step by sending an authentication request (S107a) and receiving an authentication response from AP 200 (S107b). After performing the authentication step, STA100 performs the association step by sending an association request (S109a) and receiving an association response from AP 200 (S109b). In this specification, association basically refers to wireless association. However, the present invention is not limited thereto, and association can broadly include both wireless association and wired association.

[0098] Meanwhile, the 802.1X-based authentication step (S111) and the IP address acquisition step via DHCP (S113) can be additionally performed. In Figure 5 this case, the authentication server 300 is a server that processes 802.1X-based authentication for STA 100, and can exist physically associated with AP 200 or as a separate server.

[0099] Figure 6 is a diagram showing the Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0100] A terminal performing wireless LAN communication checks whether a channel is in a busy state by performing carrier sensing before transmitting data. When a wireless signal with a predetermined intensity or greater intensity is sensed, the corresponding channel is determined to be in a busy state and the terminal delays access to the corresponding channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether the corresponding signal is sensed is called the CCA threshold. When a wireless signal received by the terminal with a CCA threshold or higher indicates the corresponding terminal as a receiver, the terminal processes the received wireless signal. Meanwhile, when no wireless signal is detected in the corresponding channel or a wireless signal with an intensity less than the CCA threshold is detected, the channel is determined to be in an idle state.

[0101] When it is determined that the channel is idle, each terminal having data to transmit performs a backoff process after an Inter Frame Space (IFS) time (e.g., Arbitration IFS (AIFS), PCF IFS (PIFS), etc.) depending on the situation of each terminal. According to this embodiment, AIFS can be used as a component to replace the existing DCF IFS (DIFS). Each terminal waits while reducing the slot time as long as a random number determined by the corresponding terminal during an interval of the idle state of the channel, and the terminal that completely exhausts the slot time attempts to access the corresponding channel. Thus, the interval during which each terminal performs the backoff process is called the contention window interval. In this case, the random number is called the backoff counter. That is, the initial value of the backoff counter can be set by an integer of a random number obtained as a UE. In the case where the UE detects that the channel is idle during the slot time, the UE can decrement the backoff counter by 1. Additionally, in the case where the backoff counter reaches 0, the UE can be allowed to perform channel access in the corresponding channel. Therefore, in the case where the channel is idle during the AIFS time and the slot time of the backoff counter, the UE can be allowed to transmit.

[0102] When a special terminal successfully accesses a channel, the corresponding terminal can send data through the channel. However, when a terminal attempting to access conflicts with another terminal, the conflicting terminals are each assigned a new random number to perform the backoff process again. According to an embodiment, the newly assigned random number for each terminal can be determined within a range (2*CW), which is twice the range (contention window CW) of the random number previously assigned to the corresponding terminal. At the same time, each terminal attempts to access by performing the backoff process again in the next contention window interval, and in this case, each terminal starts the backoff process from the remaining slot time in the previous contention window interval. By this method, each terminal performing wireless LAN communication can avoid mutual conflicts on the special channel.

[0103] <Examples of various PPDU formats>

[0104] Figure 7 The figure shows examples of the formats of physical layer protocol data units (PPDUs) for each of various standards generations. More specifically, Figure 7 (a) of shows an embodiment of a legacy PPDU format based on 802.11a / g, Figure 7 (b) of shows an embodiment of a HE PPDU format based on 802.11ax, and Figure 7 (c) of shows an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Figure 7 (d) of shows the detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU format.

[0105] Referring to Figure 7 (a) of, 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, L-STF, L-LTF, and L-SIG can be referred to as the legacy preamble.

[0106] Referring to Figure 7For (b), the preamble of the HE PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a High Efficiency Signal A field (HE-SIG-A), a High Efficiency Signal B field (HE-SIG-B), a High Efficiency Short Training field (HE-STF), and a High Efficiency Long Training field (HE-LTF) in the traditional preamble. In an embodiment of the present invention, RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF may be referred to as the HE preamble. The detailed configuration of the HE preamble can be modified according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0107] Referring to Figure 7 For (c), the EHT PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a Universal Signal field (U-SIG), an Extremely High Throughput Signal A field (EHT-SIG-A), an Extremely High Throughput Signal B field (EHT-SIG-B), an Extremely High Throughput Short Training field (EHT-STF), and an Extremely High Throughput Long Training field (EHT-LTF) in the traditional preamble. In an embodiment of the present invention, RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as the EHT preamble. The specific configuration of the non-traditional preamble can be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in a part of the EHT PPDU format.

[0108] 64-FFT OFDM is applied to the L-SIG field included in the preamble of the PPDU, and the L-SIG field includes a total of 64 subcarriers. Among the 64 subcarriers, 48 subcarriers other than the guard subcarriers, the DC subcarrier, and the pilot subcarriers are used for the transmission of L-SIG data. BPSK and a modulation and coding scheme (MCS) with a code rate of 1 / 2 are applied to the L-SIG, so the L-SIG can include a total of 24 bits of information. Figure 7 The (d) of Figure 7 illustrates the configuration of the 24-bit information of the L-SIG.

[0109] Referring to Figure 7 the (d) of Figure 7 , the L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field includes 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one value among the transmission rates of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps obtained by combining modulation schemes such as BPSK / QPSK / 16-QAM / 64-QAM with code rates such as 1 / 2, 2 / 3, 3 / 4, etc. The total length of the corresponding PPDU can be indicated by combining the information of the L_RATE field and the information of the L_LENGTH field. In the non-traditional PPDU format, the L_RATE field is configured as the minimum rate of 6 Mbps.

[0110] The unit of the L_LENGTH field can be allocated a total of 12 bits in bytes, can signal up to 4095, and can indicate the length of the corresponding PPDU by combination with the L_RATE field. In this case, traditional terminals and non-traditional terminals can use different methods to interpret the L_LENGTH field.

[0111] First, the method for a traditional terminal or a non-traditional terminal to use the L_LENGTH field to analyze the length of the corresponding PPDU is as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4 μs, which is the symbol duration of 64 FFT. Therefore, 3 bytes corresponding to the SVC field and the tail field are added to the value of the L_LENGTH field, and the added value is divided by 3 bytes, which is the transmission amount of one symbol, to obtain the number of 64-FFT-based symbols after the L-SIG. The obtained number of symbols is multiplied by 4 μs (i.e., the length of one symbol), and then 20 μs, which is the time required for the transmission of the L-STF, L-LTF, and L-SIG, is added to obtain the length of the corresponding PPDU, that is, the reception time RXTIME. This can be represented by Equation 1 below.

[0112] [Equation 1]

[0113]

[0114] In this case, represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU can be set to up to 5.484 ms. The non - traditional terminal that sends the PPDU should set the L_LENGTH field as shown in Equation 2 below.

[0115] [Equation 2]

[0116]

[0117] Here, TXTIME is the total transmission time of the corresponding PPDU and is represented by Equation 3 below. In this case, TX represents the transmission time of X.

[0118] [Equation 3]

[0119] TXTIME (us)=T L-STF +T L-LTF +T L-SIG +T RL-SIG +T U-SIG +(T EHT-SIG-A )+(T EHT-SIG-B )+T EHT-STF +N EHT-LTF ·T EHT-LTF +T DATA

[0120] Referring to the above equation, the length of the PPDU is calculated based on the ceiling value of L_LENGTH / 3. Therefore, for a random value k, the three different values of L_LENGTH = {3k + 1, 3k + 2, 3(k + 1)} indicate the same PPDU length.

[0121] Referring to Figure 7 (e) of, the Universal SIG (U - SIG) field continues to exist in the EHT PPDU and the next - generation wireless LAN PPDU and is used to distinguish which generation the PPDU belongs to, including 11be. The U - SIG is a 64 - FFT - based OFDM 2 - symbol and can transmit a total of 52 bits of information. Among the 52 bits, 43 bits, excluding the 9 bits of CRC / tail, are mainly divided into a Version Independent (VI) field and a Version Dependent (VD) field.

[0122] The VI bit enables the current bit configuration to be maintained subsequently, so that even if the next generation of PPDUs is defined, current 11be terminals can obtain information about the PPDU through the VI field of the PPDU. To this end, the VI field includes a PHY version, UL / DL, BSS color, TXOP, and a reserved field. The PHY version field is 3 bits and is used to sequentially distinguish 11be and the subsequent generation of wireless LAN standards by version. The value of 11be is 000b. The UL / DL field identifies whether the PPDU is an uplink / downlink PPDU. The BSS color indicates the identifier of each BSS defined in 11ax and has a value of 6 bits or higher. The TXOP indicates the Transmit Opportunity Duration sent in the MAC header. By adding the TXOP to the PHY header, the length of the TXOP included in the PPDU can be inferred without having to decode the MPDU, and the TXOP has a value of 7 bits or higher.

[0123] The VD field is signaling information useful only for 11be version PPDUs and can include fields commonly used in any PPDU format such as PPDU format and BW, as well as fields defined differently for each PPDU format. The PPDU format is a classifier that classifies EHT single user (SU), EHT multiple user (MU), EHT trigger-based (TB), EHT extended range (ER) PPDUs, etc. The BW field signals the five basic PPDU BW options of 20, 40, 80, 160 (80 + 80), and 320 (160 + 160) MHz (the BW that can be expressed in the form of an exponential power of 20 * 2 is called the basic BW), as well as various remaining PPDU BWs configured via preamble puncturing. After signaling at 320 MHz, it can be signaled in the form of some 80 MHz being punctured. The punctured and modified channel type can be signaled directly in the BW field, or the BW field can be used in combination with a field that appears after the BW field (e.g., a field within the EHT-SIG field) to signal the punctured and modified channel type. If the BW field is configured as 3 bits, a total of 8 BWs can be signaled, and thus at most 3 puncturing patterns can be signaled. If the BW field is configured as 4 bits, a total of 16 BWs can be signaled, and thus at most 11 puncturing patterns can be signaled.

[0124] The fields following the BW field vary according to the type and format of the PPDU. The MU PPDU and the SU PPDU can be signaled in the same PPDU format. The field for distinguishing the MU PPDU and the SU PPDU can be located before the EHT-SIG field, and additional signaling can be performed therefor. Both the SU PPDU and the MU PPDU include the EHT-SIG field, but some fields that are not required in the SU PPDU can be compressed. The information of the fields to which compression is applied can be omitted or can have a size smaller than the size of the original fields included in the MU PPDU. For example, in the case of the SU PPDU, there can be different configurations in which common fields of the EHT-SIG are omitted or replaced, or user-specific fields are replaced, reduced to one, etc.

[0125] Alternatively, the SU PPDU can also include a compression field indicating whether compression is performed, and partial fields (e.g., the RA field, etc.) can be omitted according to the value of the compression field.

[0126] If a part of the EHT-SIG field of the SU PPDU is compressed, the information to be included in the compression field can also be signaled in the uncompressed fields (e.g., common fields, etc.). The MU PPDU corresponds to the PPDU format for simultaneous reception by multiple users, and thus it is required to send the EHT-SIG field after the U-SIG field, and the amount of information transmitted can vary. That is, since multiple MU PPDUs are sent to multiple STAs, each STA should identify the location of the RU to which the MU PPDU is sent, the STA to which the RU is respectively allocated, and whether the transmitted MU PPDU has been sent to the STA itself. Therefore, the AP should send this information by including the above information in the EHT-SIG field. For this purpose, the information for efficiently transmitting the EHT-SIG field is signaled in the U-SIG field, and this can correspond to the MCS as the modulation method and / or the number of symbols in the EHT-SIG field. The EHT-SIG field can include information about the size and location of the RU allocated to each user.

[0127] In the case of a SU PPDU, multiple RUs can be allocated to a STA, and the multiple RUs can be contiguous or non - contiguous. If the RUs allocated to the STA are non - contiguous, the STA shall identify the intervening punctured RUs in order to effectively receive the SUPPDU. Accordingly, the AP can send a SU PPDU that includes information about the punctured RUs in the RUs allocated to the STA (e.g., the puncturing pattern of the RUs, etc.). That is, in the case of a SU PPDU, a puncturing pattern field can be included in the EHT - SIG field, and the puncturing pattern field includes information indicating the puncturing pattern and whether the puncturing pattern is applied in the form of a bitmap, etc., and the puncturing pattern field can signal the type of non - contiguous channel that appears within the bandwidth.

[0128] The signaled non - contiguous channel types are limited and indicate the BW of the SUPPDU and the non - contiguous channel information in combination with the value of the BW field. For example, a SU PPDU is a PPDU sent only to a single terminal, so the STA can identify the bandwidth allocated to itself through the BW field included in the PPDU, and the SU PPDU can identify the punctured resources in the allocated bandwidth through the puncturing pattern field of the U - SIG field or EHT - SIG field included in the PPDU. In this case, the terminal can receive the PPDU in the remaining resource units after excluding the special channels of the punctured resource units. The multiple RUs allocated to the STA can be configured by different frequency bands or tones.

[0129] To reduce the signaling overhead of the SU PPDU, only a limited number of non - contiguous channel types are signaled. Puncturing can be performed for each 20MHz sub - channel, so if puncturing is performed on a BW with multiple 20MHz sub - channels (such as 80, 160, and 320MHz), in the case of 320MHz, the non - contiguous channel (even puncturing of only the edge 20MHz is considered non - contiguous) type should be signaled by indicating whether each of the remaining 15 20MHz sub - channels after excluding the primary channel is used. In this way, considering the low transmission rate of the signaling part, allocating 15 bits to signal the non - contiguous channel type for single - user transmission may act as an excessive signaling overhead.

[0130] The present invention proposes a technique for signaling the non - contiguous channel type of a SU PPDU and illustrates the non - contiguous channel type determined according to the proposed technique. The present invention also proposes a technique for signaling each of the puncturing types of the primary 160MHz and secondary 160MHz in the 320MHz BW configuration of the SU PPDU.

[0131] In addition, in an embodiment of the present invention, a technique is proposed for differently configuring a PPDU indicated by a preamble puncturing BW value according to a PPDU format signaled in a PPDU format field. Assuming that the BW field is 4 bits, and in the case of an EHT-SU PPDU or a TB PPDU, an EHT-SIG-A of 1 symbol can be additionally signaled after the U-SIG, or the EHT-SIG-A may not be signaled at all. Therefore, considering this, it is necessary to signal up to 11 puncturing patterns entirely via the BW field of the U-SIG only. However, in the case of an EHT-MU PPDU, an EHT-SIG-B is additionally signaled after the U-SIG, so that up to 11 puncturing patterns can be signaled in a different method from that of the SU PPDU. In the case of an EHT-ER PPDU, the BW field can be configured as 1 bit to signal whether the EHT-ER PPDU is a PPDU using a 20 MHz band or a 10 MHz band.

[0132] Figure 7 FIG. (f) illustrates the configuration of a format-specific field of the VD field when an EHT-MU PPDU is indicated in the PPDU format field of the U-SIG. In the case of an MU PPDU, a SIG-B, which is a signaling field for simultaneous reception by multiple users, is necessarily required, and the SIG-B can be transmitted after the U-SIG without a separate SIG-A. For this purpose, information for decoding the SIG-B should be signaled in the U-SIG. These fields include the SIG-B MCS, SIG-B DCM, the number of SIG-B symbols, SIG-B compression, and the number of EHT-LTF symbol fields, etc.

[0133] Figure 8 FIG. illustrates examples of various Extremely High Throughput (EHT) physical layer protocol data unit (PPDU) formats according to an embodiment of the present invention and methods for indicating the formats.

[0134] Referring to Figure 8 , the PPDU may include a preamble and a data part, and the EHT PPDU format as a PPDU type can be classified according to the U-SIG field included in the preamble. Specifically, based on the PPDU format field included in the U-SIG field, it can be indicated whether the format of the PPDU is an EHT PPDU.

[0135] Figure 8(a) shows an example of the EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU for single-user (SU) transmission between an AP and a single STA, and the EHT-SIG-A field for additional signaling can be located after the U-SIG field.

[0136] Figure 8 (b) shows an example of the EHT trigger-based PPDU format corresponding to the 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 for the response to the trigger frame. Different from the EHT SU PPDU, in the EHT PPDU, the EHT-SIG-A field is not located after the U-SIG field.

[0137] Figure 8 (c) shows an example of the EHT MU PPDU format corresponding to the EHT PPDU for multiple users. The EHT MU PPDU is a PPDU for transmitting a PPDU to one or more STAs. In the EHT MU PPDU format, the HE-SIG-B field can be located after the U-SIG field.

[0138] Figure 8 (d) shows an example of the EHT ER SU PPDU format, which is used for single-user transmission with an STA within an extended range. Compared with the EHT SU PPDU described in Figure 8 (a), the EHT ER SU PPDU can be used for single-user transmission with a wider range of STAs, and on the time axis, the U-SIG field can be repeatedly located.

[0139] Figure 8 (c) The EHT MU PPDU described can be used by the AP to perform downlink transmission towards multiple STAs. Here, 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 pass the AID information of the receiver and / or transmitter of the transmitted PPDU to the STAs through the user specific field of the EHT-SIG-B. Therefore, multiple terminals that receive the EHT MU PPDU can perform spatial reuse operations based on the AID information of the user specific field included in the preamble of the received PPDU.

[0140] Specifically, the resource unit allocation (RA) field included in the HE-SIG-B field in the HE MU PPDU may include information on the configuration of resource units (e.g., the form of division of resource units) in a special bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field may indicate the configuration of resource units divided in the bandwidth used for the transmission of the HE MU PPDU so that the STA can receive the PPDU. Information on the STA assigned (or designated) to each divided resource unit may be included in the user-specific field of the EHT-SIG-B to be sent to the STA. That is, the user-specific field may include one or more user fields corresponding to the respective divided resource units.

[0141] For example, the user field corresponding to at least one resource unit used for data transmission among the divided multiple resource units may include the AID of the recipient or transmitter, and the user field corresponding to the remaining resource units not used for data transmission may include a pre-configured Null STA ID.

[0142] For ease of explanation, in this specification, frames or MAC frames may be used interchangeably with MPDUs.

[0143] When a wireless communication device communicates by using multiple links, the communication efficiency of the wireless communication device can be improved. In this case, a link may be a physical path and may be composed of a wireless medium that can be used to deliver a MAC service data unit (MSDU). For example, in the case where the frequency band of one link in the links is used by another wireless communication device, the wireless communication device can continue to perform communication through another link. In this way, the wireless communication device can usefully use multiple channels. In addition, when the wireless communication device simultaneously performs communication by using multiple links, the total throughput can be increased. However, in existing wireless LANs, it has been stipulated that one wireless communication device uses one link. Therefore, a WLAN operation method for using multiple links is needed. It will be described by Figures 9 to 26 describing the wireless communication method of a wireless communication device using multiple links. First, it will be described by Figure 9 describing the specific form of a wireless communication device using multiple links.

[0144] Figure 9 is a diagram showing a multi-link device according to an embodiment of the present invention.

[0145] A multi-link device (MLD) can be defined for a wireless communication method using the multiple links. The multi-link device can represent a device having one or more subordinate stations. According to a specific embodiment, the multi-link device can represent a device having two or more subordinate stations. In addition, the multi-link device can exchange multi-link elements. The multi-link elements include information about one or more stations or one or more links. The multi-link elements can include multi-link setup elements, which will be described later. In this case, the multi-link device can be a logical entity. Specifically, the multi-link device can have multiple subordinate stations. The multi-link device can be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device can have one media access control (MAC) service access point (SAP) up to the logical link control (LLC). The MLD can also have one MAC data service.

[0146] The multiple stations included in the multi-link device can operate on multiple links. In addition, the multiple stations included in the multi-link device can operate on multiple channels. Specifically, the multiple stations included in the multi-link device can operate on multiple different links or on multiple different channels. For example, the multiple stations included in the multi-link device can operate on multiple different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0147] The operation of the multi-link device can be referred to as multi-link operation, MLD operation, or multi-band operation. In addition, when the station attached to the multi-link device is an AP, the multi-link device can be referred to as an AP MLD. In addition, when the station attached to the multi-link device is a non-AP station, the multi-link device can be referred to as a non-AP MLD.

[0148] Figure 9 The operation of non-AP MLD and AP-MLD communication is illustrated. Specifically, the non-AP MLD and the AP-MLD communicate using three links respectively. The AP MLD includes a first AP AP1, a second AP AP2, and a third AP AP3. The non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP AP1 and the first non-AP STA (non-AP STA1) communicate through the first link Link1. In addition, the second AP AP2 and the second non-AP STA (non-AP STA2) communicate through the second link Link2. In addition, the third AP AP3 and the third non-AP STA (non-AP STA3) communicate through the third link Link3.

[0149] Multi-link operation may include multi-link setup operation. The multi-link setup may correspond to an associated operation of the single-link operation and may be performed first in the multi-link for frame exchange. A multi-link device may obtain information required for multi-link setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information associated with the multi-link. In this case, the capability information may include information indicating whether any one of a plurality of devices included in the multi-link device performs transmission and at the same time another device may perform reception. In addition, the capability information may include information about the links available for each station included in the MLD. In addition, the capability information may include information about the channels available for each station included in the MLD.

[0150] The multi-link setup may be set through negotiation between peer stations. Specifically, the multi-link setup may be performed through communication between stations without communicating with the AP. In addition, the multi-link setup may be set through any one of the links. For example, even if the first to third links are set through the multi-link, the multi-link setup may be performed through the first link.

[0151] In addition, a mapping between a traffic identifier (TID) and the links may be set. Specifically, frames corresponding to a TID with a special value may be exchanged only through a predetermined link. The mapping between the TID and the links may be set based on the direction. For example, when multiple links are set between a first multi-link device and a second multi-link device, the first multi-link device may be set to transmit frames of a first TID to a plurality of first links, while the second multi-link device may be set to transmit frames of a second TID to the first link. In addition, there may be a default setting for the mapping between the TID and the links. Specifically, in the case where there is no additional setting in the multi-link setup, the multi-link device may exchange frames corresponding to the TID at each link according to the default setting. In this case, the default setting may be to exchange all TIDs in any one of the links.

[0152] The TID will be described in detail. The TID is an ID used to classify services and data to support Quality of Service (QoS). In addition, the TID can be used or assigned in a layer higher than the MAC layer. In addition, the TID can indicate a Traffic Class (TC) or a Traffic Stream (TS). In addition, the TID can be classified into 16 types. For example, the TID can be specified as one of the values in the range from 0 to 15. The TID value to be used can be specified differently according to the access policy and the channel access or medium access method. For example, in the case of using Enhanced Distributed Channel Access (EDCA) or Hybrid Coordination Function Controlled Channel Access (HCAF), values in the range from 0 to 7 can be assigned to the TID. In the case of using EDCA, the TID can indicate the User Priority (UP). In this instance, the UP can be specified based on the TC or TS. The UP can be assigned in a layer higher than the MAC. In addition, in the case of using HCF Controlled Channel Access (HCCA) or SPCA, values in the range from 8 to 15 can be assigned to the TID. In the case of using HCCA or SPCA, the TID can indicate the TSID. In addition, in the case of using HEMM or SEMM, values in the range from 8 to 15 can be assigned to the TID. In the case of using HEMM or SEMM, the TID can indicate the TSID.

[0153] It is possible to map UP and AC. AC can be a label used to provide QoS in EDCA. AC can be a label used to indicate an EDCA parameter set. The EDCA parameters or the EDCA parameter set can be parameters for EDCA channel contention. The QoS station can use AC to guarantee QoS. In addition, AC can include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO can indicate background, best effort, video, and voice respectively. In addition, each of AC_BK, AC_BE, AC_VI, and AC_VO can be classified as a subordinate AC. For example, AC_VI can be subdivided into AC_VI primary and AC_VI secondary. In addition, AC_VO can be subdivided into AC_VO primary and AC_VO secondary. In addition, UP or TID can be mapped to AC. For example, UP or TID with values 1, 2, 0, 3, 4, 5, 6, and 7 can be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO respectively. In addition, UP or TID with values 1, 2, 0, 3, 4, 5, 6, and 7 can be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI secondary, AC_VI primary, AC_VO primary, and AC_VO secondary respectively. In addition, UP or TID with values 1, 2, 0, 3, 4, 5, 6, and 7 can have high priorities sequentially. That is, 1 indicates a low priority, while 7 indicates a high priority. Therefore, AC_BK, AC_BE, AC_VI, and AC_VO can have high priorities sequentially. In addition, AC_BK, AC_BE, AC_VI, and AC_VO can correspond to AC indices (ACIs) 0, 1, 2, and 3 respectively. Due to these characteristics of TID, the mapping between TID and the link can indicate the mapping between AC and the link. In addition, the mapping between the link and AC can indicate the mapping between TID and the link.

[0154] As described above, TID can be mapped to each of multiple links. The mapping can specify the link capable of exchanging traffic corresponding to a predetermined TID or AC. In addition, the TID or AC that can be transmitted for each transmission direction in the link can be specified. As described above, there can be a default configuration for the mapping between TID and the link. Specifically, in the case where there is no additional configuration for the multi-link configuration, the multi-link device can exchange frames corresponding to TID in each link according to the default configuration. In this instance, the default configuration can exchange all TIDs in any one link. Any TID or AC at any point in time can always be mapped to at least any one link. Management frames and control frames can be transmitted in all links.

[0155] In the case where a link is mapped to a TID or an AC, data frames corresponding only to the TID or AC mapped to the corresponding link can be transmitted in the corresponding link. Therefore, in the case where a link is mapped to a TID or an AC, frames not corresponding to the TID or AC mapped to the corresponding link cannot be transmitted in the corresponding link. In the case where a link is mapped to a TID or an AC, ACKs can also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK protocol can be determined based on the mapping between the TID and the link. According to another embodiment, the mapping between the TID and the link can be determined based on the block ACK protocol. In particular, a block ACK protocol can be set for the TID mapped to a predetermined link.

[0156] QoS can be guaranteed via the mapping between the TID and the link. Specifically, an AC or TID with a high priority can be mapped to a link operated by a relatively small number of stations or a link with good channel conditions. In addition, via the mapping between the TID and the link, a station can be enabled to maintain a power-saving state for a long period of time.

[0157] Figure 10 Illustrated is the simultaneous execution of transmissions on different links in multi-link operation according to an embodiment of the present disclosure.

[0158] Depending on the implementation of the multi-link device, simultaneous operation may not be supported in multi-links. For example, simultaneous transmission in multi-links, simultaneous reception in multi-links, or transmission in one link and reception in another link may not be supported. This is because reception or transmission performed in one link may affect reception or transmission performed in another link. Specifically, transmission in one link may act as interference to another link. The interference imposed by one multi-link device from one link to another link can be referred to as internal leakage. As the frequency separation between links is small, the internal leakage may become large. When the internal leakage is not very large, transmission can be performed in another link while transmission is being performed in one link. When the internal leakage is large, transmission cannot be performed in another link while transmission is being performed in one link. As described above, the simultaneous execution of operations by a multi-link device in multiple links can be referred to as simultaneous transmission and reception or simultaneous transmit and receive (STR). For example, simultaneous transmission by a multi-link device in multiple links, simultaneous transmission in one link and reception in another link, or simultaneous reception in multiple links can be referred to as STR.

[0159] As described above, a multi-link device may support STR or only support STR restrictively. Specifically, the multi-link device supports STR under special conditions. For example, when the multi-link device operates as a single-radio device, the multi-link device may not perform STR. Further, when the multi-link device operates as a single antenna, the STR of the multi-link device may not be performed. When an internal leakage with a size greater than or equal to a predetermined size is detected, the multi-link device may not perform STR.

[0160] A station may exchange information about the STR capability of the station with another station. Specifically, the station may exchange information with another station about the ability to restrict simultaneous transmission or simultaneous reception on multiple links. Specifically, the information about the ability to restrict transmission or reception on multiple links may indicate whether simultaneous transmission, simultaneous reception, or simultaneous transmission and reception can be performed on multiple links. The information about the ability to restrict transmission or reception on multiple links may be information indicated for each step. Specifically, the information about the ability to restrict transmission or reception on multiple links may be information indicating a step representing the size of the internal leakage. In a detailed embodiment, the information indicating a step representing the size of the internal leakage may be information indicating a step representing the size of the interference caused by the internal leakage. In another detailed embodiment, the information may be information indicating a step representing the frequency interval between links that may affect the internal leakage. The information indicating a step representing the size of the internal leakage may be information indicating the relationship between the frequency interval between links and the size of the internal leakage.

[0161] In Figure 10 , the first station (STA1) and the second station (STA2) are attached to a non-AP multi-link device. The first AP (AP1) and the second AP (AP2) may be attached to a non-AP multi-link device. A first link (link1) is configured between the first AP (AP1) and the first station (STA1), and a second link (link2) is configured between the second AP (AP2) and the second station (STA2). In Figure 10Among them, non-AP multi-link devices can perform STR restrictively. When the second station (STA2) performs transmission in the second link (link2), the reception of the first station (STA1) in the first link (link1) may be interfered by the transmission performed in the second link (link2). For example, in the following situation, the reception of the first station (STA1) in the first link (link1) may be interrupted by the transmission performed in the second link (link2). The second station (STA2) transmits the first data (data1) in the second link (link2), and the first AP (AP1) transmits a response to the first data (ack for data1) to the first station (STA1). The second station (STA2) transmits the second data (data2) in the second link (link2). At the same time, the transmission time point of the second data (data2) may overlap with the transmission time point of the response to the first data (ack for data1). The first link (link1) may be interfered by the transmission to the second station (STA2) in the second link (link1). Therefore, the first station (STA1) may not receive the response to the first data (Ack for Data1).

[0162] The operations of multi-link devices performing channel access are described. The operations of multi-links not described in detail can follow the channel access described in the reference Figure 6 described.

[0163] A multi-link device can independently perform channel access in multiple links. At this time, the channel access can be contention-based channel access. When the multi-link device independently performs channel access in multiple links and the backoff counters in the multiple links reach 0, the multi-link device can simultaneously perform transmissions in the multiple links. In a detailed embodiment, when one of the backoff counters of the multi-links reaches 0 and a predetermined condition is satisfied, the multi-link device can not only perform channel access in the link where the backoff counter reaches 0, but also perform channel access in another link where the backoff counter does not reach 0. Specifically, when one of the backoff counters of the multi-links reaches 0, the multi-link device can detect the energy in another link where the backoff counter does not reach 0. At this time, when no energy of a predetermined size or larger is detected, the multi-link device can not only perform channel access in the link where the backoff counter reaches 0, but also perform channel access in the link where the energy is detected. Accordingly, the multi-link device can simultaneously perform transmissions in multiple links. The size of the threshold for energy detection can be smaller than the size of the threshold for determining whether to decrement the backoff counter. In addition, when determining whether to decrement the backoff counter, the multi-link device can detect any type of signal as well as WLAN signals. In energy detection, the multi-link device can detect any type of signal as well as WLAN signals. The WLAN signal may not be able to detect internal leakage. In this case, the multi-link device can sense the signal detected due to internal leakage through energy detection. In addition, as described above, the size of the threshold for energy detection can be smaller than the size of the threshold for determining whether to decrement the backoff counter. Accordingly, even when performing a transmission in one link, the multi-link device can decrement the backoff counter in another link.

[0164] According to the degree of interference between the links used by the multi-link device, the multi-link device can determine whether the stations operating in each link can operate independently. At this time, the degree of interference between the links can be the size of the interference detected by another station of the multi-link device when one station performs a transmission in one link. When the transmission made by the first station of the multi-link device in the first link brings interference of a predetermined size or larger to the second station of the multi-link device operating in 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. This is because when interference occurs, the second station may not be able to decode the received signal due to the interference. In addition, this is because when interference occurs, when the second station performs channel access using backoff, the second station may determine that the channel is in use.

[0165] When the transmission of the first station of a multi-link device in the first link causes interference of a size less than a predetermined size to the second station of the multi-link device operating in the second link, the first station and the second station can operate independently. Specifically, when the transmission of the first station of a multi-link device in the first link causes interference of a size less than a predetermined size to the second station of the multi-link device operating in the second link, the first station and the second station can independently perform channel access. In addition, when the transmission of the first station of a multi-link device causes interference of a size less than a predetermined size to the second station of the multi-link device operating in the second link, the first station and the second station can independently perform transmission or reception. This is because when interference of a size less than a predetermined size is generated, even if the interference exists, the second station can successfully decode the received signal. In addition, this is because when interference of a size less than a predetermined size is generated, when the second station performs channel access using backoff, the second station can determine that the channel is idle.

[0166] The degree of interference generated between stations of a multi-link device can vary depending on the hardware characteristics of the multi-link device and the interval between the frequency bands of the links in which these stations operate. For example, the internal interference generated in a multi-link device including expensive radio frequency (RF) devices can be less than the internal interference generated in a multi-link device including inexpensive RF devices. Accordingly, the degree of interference generated between stations of a multi-link device can be determined based on the characteristics of the multi-link device.

[0167] Figure 10 The figure illustrates that the size of the generated interference varies according to the interval between the frequency bands of the links and the characteristics of the multi-link device. In Figure 10In an embodiment, the first multi-link device (MLD#1) includes a first station (STA1-1) operating in a first link (link1) and a second station (STA1-2) operating in a second link (link2). The second multi-link device (MLD#2) includes a first station (STA2-1) operating in the first link (link1) and a second station (STA2-2) operating in the second link (link2). The frequency interval between the first link (link1) and the second link (link2) in which the first multi-link 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 multi-link device (MLD#2) operates. However, due to the difference between the characteristics of the first multi-link device (MLD#1) and the characteristics of the second multi-link device (MLD#2), the magnitude of the generated interference may be different. Specifically, the magnitude of the interference generated in the first multi-link device (MLD#1) may be greater than the magnitude of the interference generated in the second multi-link device (MLD#2). As described above, the magnitude of the generated interference may vary depending on the characteristics of the multi-link device, and when it is considered that whether STR is supported is different for each multi-link device, it may be necessary to exchange information on whether STR is supported.

[0168] A multi-link device may signal information about whether STR is supported by stations included in the multi-link device. Specifically, an AP multi-link device and a non-AP multi-link device may exchange information about whether STR is supported by the AP included in the AP multi-link device and whether STR is supported by the STA included in the non-AP multi-link device. In such an embodiment, an element indicating whether STR is supported may be used. The element indicating whether STR is supported may be referred to as an STR support element. The STR support element may indicate, by 1 bit, whether STR is supported by the stations included in the multi-link device that transmits the STR support element. Specifically, the STR support element may indicate, by 1 bit, whether STR is supported by each station included in the multi-link device that transmits the STR support element. At this time, when a station supports STR, the value of the bit may be 1, and when the station does not support STR, the value of the bit may be 0. When the multi-link device that transmits the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), the first station (STA1) and the third station (STA3) support STR, and the second station (STA2) does not support STR, the STR support element may include a field having 1011b. Assume that stations operating in different frequency bands support STR, and the STR support element may omit signaling indicating whether STR is supported between stations operating in different frequency bands. For example, the first station (STA1) operates in a first link at 2.4 GHz, while the second station (STA2) and the third station (STA3) operate in a second link and a third link at 5 GHz, respectively. The STR support element may indicate support for STR between the second station (STA2) and the third station (STA3) by using 1 bit. In addition, when the number of stations signaled by the STR support element is 2, the STR support element may include only 1 bit.

[0169] In a detailed 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 a multi-link device may always be determined as STR. Accordingly, signaling for STR for a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz may be omitted.

[0170] Figure 11 Illustrated is the operation of a multi-link device according to an embodiment of the present disclosure when a link changes.

[0171] When the frequency band of a link changes, the STR support element can be changed. As described above, this is because whether the STR is supported by a station can vary according to the distance between the frequency bands of the link, and when the frequency band of the link changes, whether the STR is supported by the station can change. The change in the frequency band of the link can include at least one of a change in the center frequency, a change in the bandwidth of the frequency band, and the primary channel of 200 MHz. The AP and the station can exchange the STR support element through requests and responses. In another detailed embodiment, when the frequency band of the link changes, the STR support element can be exchanged without any separate request. Additionally, in the said embodiment, the change in the frequency band of the link can include a change in the operating channel of the station.

[0172] When a station of a non-AP multi-link device cannot perform STR, the station of the non-AP multi-link device can request the AP to change the link. Specifically, the station of the non-AP multi-link device can make a request to change at least one of the center frequency, the bandwidth of the frequency band, and the primary channel of 20 MHz. The link change request can be transmitted to the AP through the link whose change is requested. In another detailed embodiment, the link change request can be transmitted to the AP through a link that is not requested to be changed. At this time, the link change request can include information indicating the link whose change is requested. The information indicating the link can be a number for identifying the link. In such an embodiment, the change in the link can be a change in the operating channel within a frequency band. Additionally, the change in the link can include information about the method of changing the link. Specifically, the link change request can 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 another detailed embodiment, the link change request can implicitly indicate a change to a frequency band far from an adjacent link. Additionally, the link change request can indicate a reduction in bandwidth. The link change request can be a request for changing the position of the primary channel. Specifically, the link change request can indicate a change in the position of the primary channel to a channel in a frequency band lower than the position of the primary channel or to a channel in a frequency band higher than the position of the primary channel. The AP receiving the link change request can change the link according to the link change request. Additionally, in a detailed embodiment, the AP receiving the link change request can ignore the link change request.

[0173] In Figure 11In the embodiment, the second station (STA2) and the third station (STA3) of the non-AP multi-link device do not support STR. The non-AP multi-link device sends a request to change the third link (link3) to the AP multi-link device. The AP multi-link device that receives the link change request changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating in the third link (link3) to be changed can transmit a change request to the third AP (AP3). In another detailed embodiment, a station not operating in the third link (link3) can transmit a change request to an AP not operating in the third link (link3).

[0174] When the AP changes the link, the AP can broadcast information about the link change through a beacon frame. At this time, the information about the link change may include information about the link frequency. The information about the link frequency may include at least one of a change in the operating bandwidth and the primary channel. In addition, the information about the link change may include information about the link change time point. In addition, when transmitting a beacon including information about the link change, the link change can be completed.

[0175] In Figure 11 the link in which the third station (STA3) operates is changed, and thus the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multi-link device can transmit an STR support element concurrent signal notification indicating information about a change in support for STR to the AP multi-link device.

[0176] Link change may not be allowed, or STR may not be supported through link change. As Figure 11 shown in the embodiment, the AP multi-link device can support STR, but the non-AP multi-link device may not support STR. This is because it is common to use relatively expensive devices for the AP multi-link device and relatively inexpensive devices for the non-AP multi-link device. Accordingly, in communication between multi-link devices, even when one multi-link device does not support STR, a method for performing efficient communication is required. At this time, STR can indicate simultaneous transmission and reception. This will be described with reference to Figure 12 to describe.

[0177] Figure 12 Illustrates restricting channel access of another station of a non-STR multi-link device when receiving by one station of the non-STR multi-link device according to an embodiment of the present disclosure.

[0178] When transmitting a non-STR multi-link device on one link and receiving a non-STR multi-link device on another link, the reception and transmission of the non-STR multi-link device may fail. To solve this problem, when receiving a non-STR multi-link device on one link, the channel access of the non-STR multi-link device on the other link can be restricted. Specifically, when receiving a non-STR multi-link device on one link, the backoff of the channel access of the non-STR multi-link device on the other link can be restricted. Accordingly, when receiving a non-STR multi-link device on one link, the non-STR multi-link device can be prevented from starting transmission on the other link. In a detailed embodiment, when the reception of the non-STR multi-link device starts on one link, the backoff of the channel access of the non-STR multi-link device on the other link can be restricted. It can be configured through special bits in the memory (such as the channel access restriction flag). Whether to restrict channel access can be shared through the memory in the multi-link device. Through such an embodiment, channel access restriction can be achieved without separate frame exchange. For ease of description, the channel access restriction used in this specification indicates the restriction on channel access or transmission to protect the transmission or reception of the non-STR multi-link device, unless there is a separate description.

[0179] When channel access is restricted, a station operating on a link with restricted channel access cannot perform a backoff procedure, regardless of the NAV and CCA results. Additionally, when channel access is restricted, a station operating on a link with restricted channel access cannot perform a transmission, regardless of the NAV and CCA results. However, even when channel access is restricted, a station operating on a link with restricted channel access can perform a reception. Further, the channel access restriction in a second link due to a reception performed in a first link can be released based on the time point when the reception in the first link is completed. Specifically, when the reception in the first link is completed, the channel access restriction in the second link due to the reception performed in the first link can be released. In another detailed embodiment, the channel access restriction in the second link due to a reception performed in the first link can be released based on the time point when an ACK is transmitted after the reception in the first link is completed. Specifically, the channel access restriction in the second link due to the reception performed in the first link can be released at the time point when an ACK is transmitted after the reception in the first link is completed. In another detailed embodiment, the channel access restriction in the second link due to a reception performed in the first link can be released at the time point when the ACK transmission is completed after the reception in the first link is completed. Further, after the channel access restriction is released, the station can immediately decrement the backoff counter without additional sensing. Here, the additional sensing can indicate the sensing performed during the DCF interframe space (DIFS). In another detailed embodiment, when the channel is just idle for a predetermined time before the channel access restriction is released, the station can immediately decrement the backoff counter without additional sensing. Here, the predetermined time can be one of the PCF interframe space (PIFS), the short interframe space (SIFS), and the arbitration interframe space (AIFS).

[0180] In Figure 12 In an embodiment, 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 first station (STA1) performs a reception and the second station (STA2) performs a transmission on the second link (link2), in-device interference is generated. As described above, when the first station (STA1) operating on the first link (link1) performs a reception, the channel access of the second station (STA2) operating on the second link (link2) is restricted. After the reception of the first station (STA1) on the first link (link1) is completed, the channel access restriction is released. Right after the channel access restriction is released, the second station (STA2) can decrement the value of the previous backoff counter from 3 to 2 without additional sensing.

[0181] For ease of expression, in Figure 12In the accompanying drawings used, a single block (Tx solid line, Rx dashed line) is used to represent Rx and Tx, and it can be understood that this single block represents operations including Tx / Ack reception and Rx / Ack transmission, even though no separate Ack block is shown. This can be equivalently applied to the following drawings.

[0182] When a station recognizes that the received PPDU is not the intended receiver of the station, the station may stop receiving the PPDU. In this case, the operation of releasing the channel access prohibition by the multi-link device is problematic. The intended receiver in this specification is used to have the same meaning as the destination station.

[0183] Figure 13 The operation of releasing the channel access prohibition when it is recognized that the intended receiver of the PDDU received by a station of a non-STR multi-link device is not the station according to an embodiment of the present disclosure is illustrated.

[0184] When a station recognizes that the received PPDU is not the intended receiver of the station, the station may release the channel access prohibition. The station may determine whether the station is the intended receiver of the PPDU based on the information of the receiver address in the signaling field indicating the PPDU. At this time, the information of the receiver address in the signaling field indicating the PPDU may be the value of the STA-ID field in the EHT-SIG field. Specifically, the station may determine whether the STA-ID field in the EHT-SIG field indicates the station. In addition, the station may determine whether the station is the intended receiver of the PPDU based on the value of the RA field of the MAC frame included in the PPDU. Specifically, the station may determine whether the RA field of the MAC frame included in the PPDU indicates the station. In Figure 13 it, the non-STR multi-link device includes a first station (STA1) operating in a first link (link1) and a second station (STA2) operating in a second link (link2). The first station (STA1) receives the PPDU. The first station (STA1) determines that the intended receiver of the received PPDU is not the first station (STA1) and stops receiving the PPDU. At this time, the first station (STA1) may release the channel access prohibition of the second station (STA2). Even if the channel access prohibition of the second station (STA2) is released, the channel access of the second station (STA2) may be delayed according to the NAV configured in the second station (STA2).

[0185] As Figure 13As shown, even after the channel access prohibition is released, stations included in non-STR multi-link devices may have fewer channel access opportunities more frequently than stations not included in multi-link devices or stations included in STR multi-link devices. Therefore, in order to compete fairly with other stations, a method for ensuring the channel access opportunities of stations included in non-STR multi-link devices may be required. For example, after the channel access prohibition is released, a station whose channel access has been prohibited may be allowed to decrement the backoff counter by 2 or more. This will be described with reference to Figure 14 Description.

[0186] Figure 14 FIG. illustrates channel access performed by a station after releasing a channel access prohibition according to an embodiment of the present disclosure.

[0187] After releasing the channel access prohibition, a station that has had its channel access prohibition released may decrement the backoff counter by 2 or more. This is to balance the channel access opportunities with other stations because other stations perform the backoff process while the channel access of this station is prohibited.

[0188] In another detailed embodiment, a station whose channel access has been prohibited may perform a channel access process of decrementing CCA (CSMA) and the backoff counter when the channel access is prohibited. In Figure 14 this, the non-STR multi-link device includes a first station (STA1) operating in a first link (link1) and a second station (STA2) operating in a second link (link2). In Figure 14 this, the channel access of the second station (STA2) is prohibited when the first station (STA1) performs reception. In Figure 14 in (a) of Figure 14 when the channel access of the second station (STA2) is prohibited, the second station (STA2) may perform a channel access process of decrementing CCA (CSMA) and the backoff counter. In

[0189] In (a) of Figure 14 this, since the channel of the second link (link2) is idle when the channel access of the second station (STA2) is prohibited, the second station (STA2) decrements the backoff counter. Figure 14In (b), since the channel of the second link (link2) is idle when the channel access of the second station (STA2) is prohibited, the second station (STA2) decreases the backoff counter. When 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 the transmission and starts the transmission after the release of the channel access prohibition.

[0190] As described above, the channel access prohibition may include prohibiting the transmission of the second station when the first station of the non-STR multi-link device performs a transmission. In addition, the channel access prohibition may include prohibiting the transmission of the second station when the first station of the non-STR multi-link device performs a reception.

[0191] When in Figure 14 In the embodiment of (b), when the number of stations whose channel access is prohibited is multiple, the probability of simultaneously releasing the channel access prohibition of multiple stations and the simultaneous transmission of multiple stations is high. Therefore, a method for reducing the transmission collision probability is needed. This will be described with reference to Figure 15 for description.

[0192] Figure 15 The figure illustrates the operation of a station performing a transmission after releasing the channel access prohibition according to an embodiment of the present disclosure.

[0193] As described above, a transmission is performed in the first link among the multiple links of the non-STR multi-link device operation, so the transmission in the second link can be prohibited. When the corresponding transmission is completed in the first link, the transmission in the second link can start through RTS / CTS frame exchange. Therefore, when a transmission is performed in the first link among the multiple links of the non-STR multi-link device operation, the non-STR multi-link device can start the RTS / CTS frame exchange in the second link. After releasing the channel access prohibition of the station whose transmission is delayed due to the channel access prohibition, the station can start the request to send (RTS) / clear to send (CTS) frame exchange before starting the delayed transmission. At this time, when the station does not receive the CTS frame, the delayed transmission may not start. In Figure 15 (a) In the embodiment, the station whose transmission is delayed due to the channel access prohibition transmits an RTS frame before starting the delayed transmission. The station starts the delayed transmission after receiving the CTS frame in response to the RTS frame.

[0194] In another detailed embodiment, after the channel access prohibition of a station whose transmission has been delayed due to the channel access prohibition is released, the station may transmit a frame including only some of the delayed transmissions. At this time, after receiving a response (e.g., ACK) to the frame including only some of the delayed transmissions, the station may transmit the remaining part of the delayed transmissions that have not been transmitted. When the station does not receive a response to the frame including only some of the delayed transmissions, the station may not transmit the remaining part of the delayed transmissions that have not been transmitted. As described above, after the channel access prohibition is released, the station starts the RTS / CTS exchange or transmits only some of the delayed transmissions because the collision probability of the transmissions after the channel access prohibition may be higher than that of general transmissions. Therefore, the embodiment can be compulsorily applied to the transmissions performed after the channel access prohibition is released. In traditional WLAN operations, RTS / CTS frames are used to solve the hidden node problem and can be used based on the size of the transmitted data. In the embodiment, the RTS / CTS frames are used to prevent transmission collisions with the stations performing delayed transmissions in order to protect the transmissions or receptions of non-STR multi-link devices.

[0195] As described above, when one station of a non-STR multi-link device performs reception, the transmission of another station of the non-STR multi-link device may be restricted. In addition, when one station of a non-STR multi-link device performs transmission, it may be difficult to accurately sense the channel state of the link on which another station of the non-STR multi-link device operates. Specifically, when the first station of a non-STR multi-link device performs transmission, the second station of the non-STR multi-link device may determine that the channel state of the link on which the second station operates is always busy. Therefore, even if the channel of the link on which the second station operates is idle, due to in-device interference, the second station may determine that the channel is busy. As described above, when a station cannot determine its channel state due to in-device interference or when one station of a non-STR multi-link device continuously performs transmission, another station of the non-STR multi-link device is in a blind state. Due to this situation, it may be difficult for the station in the blind state to attempt transmission through the backoff process. In addition, due to this situation, it may be difficult for the station in the blind state to start receiving a PPDU or to successfully decode it. Therefore, a method for performing transmission considering the station in the blind state is needed. This will be described with reference to Figure 16 this.

[0196] Figure 16 illustrates the transmission performed based on the state of stations within a non-STR multi-link device according to an embodiment of the present disclosure.

[0197] A station that wants to perform a transmission to a station of a non-STR multi-link device can determine whether to perform the transmission based on whether the station of the non-STR multi-link device is in a blind state. At this time, the station that wants to perform a transmission to a station of a non-STR multi-link device can be a station included in an STR multi-link device. In addition, the station that wants to perform a transmission to a station of a non-STR multi-link device can be an AP included in an AP multi-link device, and the non-STR multi-link device can be a non-AP multi-link device. The station that wants to perform a transmission to a station of a non-STR multi-link device can determine whether the station of the non-STR multi-link device is in a blind state based on the following description. The station that wants to perform the transmission can determine whether another station of the multi-link device including the station is performing a transmission to the corresponding non-STR multi-link device. When another station of the multi-link device including the station is performing a reception from the corresponding non-STR multi-link device, the station can determine that the station of the non-STR multi-link device that is to receive the transmission of the station is in a blind state. In Figure 16 In an embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). Therefore, the second AP (AP2) can notify the first AP (AP1) that it is performing a reception from the second station (STA2). Specifically, the second AP (AP2) can notify the first AP (AP1) that the transmission entity to the second AP (AP2) is the second station (STA2). In another detailed embodiment, the second AP (AP2) can notify the first AP (AP1) that the second station (STA2) is currently performing a transmission. At this time, the first AP (AP1) can determine that the first station (STA1) is in a blind state based on this notification.

[0198] Stations in a multi-link device can operate through a common MAC. Therefore, the information exchange between the first AP (AP1) and the second AP (AP2) described above may not be explicitly performed.

[0199] The station may not perform a transmission to a station in a blind state. This is because even if a transmission is performed to a station in a blind state, it is very likely that the station in a blind state cannot start receiving or the station in a blind state cannot decode the PPDU. At this time, the station can cancel the transmission to the station in a blind state and can perform a transmission to another station.

[0200] When the STR multi-link device performs a transmission to a non-STR multi-link device, the STR multi-link device can perform the transmission to the non-STR multi-link device over multiple links. Specifically, when the STR multi-link device performs a transmission to a non-STR multi-link device over the first link, the STR multi-link device can start a transmission to the non-STR multi-link device over the second link. At this time, the STR multi-link device can determine the length of the transmission performed over the second link based on the transmission corresponding to the transmission to the non-STR multi-link device. Specifically, the STR multi-link device can determine the length of the transmission to the non-STR multi-link device over the second link based on the length of the transmission to the non-STR multi-link device over the first link. In a detailed embodiment, the STR multi-link device can end the transmissions over the first link and the second link simultaneously. This is to prevent a transmission to another station of the non-STR multi-link device when one of the stations of the non-STR multi-link device transmits a response (e.g., ACK) after the transmission to one of the stations of the non-STR multi-link device ends first. Through the above embodiment, multiple stations of the non-STR multi-link device can transmit responses to the transmission to multiple stations simultaneously.

[0201] The STR multi-link device cannot determine the status of the stations included in the non-STR multi-link device in real time. Therefore, even if the STR multi-link device operates according to the embodiments described in the reference Figure 16 interference or transmission conflicts may occur between the links in which the non-STR multi-link device operates. For example, in Figure 16 the embodiment, the first AP (AP1) may start a transmission to the first station (STA1) before identifying that the second station (STA2) is performing a transmission to the second AP (AP2). As described above, the probability of interference or conflict between links may be higher than the probability of interference or transmission conflict within a link. This will be described in more detail with reference to Figure 17

[0202] Figure 17 illustrates a situation where interference or conflict between links occurs.

[0203] When the transmission from the second station of the non-STR multi-link device to the second AP of the STR AP multi-link device and the transmission from the first AP of the STR AP multi-link device to the first station of the non-STR multi-link device start simultaneously, transmission conflicts may occur between the links. Figure 17 (a) illustrates this situation. This is because, as described above, the STR multi-link device cannot determine the status of the stations included in the non-STR multi-link device in real time.

[0204] ​In addition, even when the transmission from the second station of the non-STR multi-link device to the second AP of the STR AP multi-link device starts earlier than the transmission from the first AP of the STR-AP multi-link device to the first station of the non-STR multi-link device, transmission conflicts may occur between the links. Figure 17 (b) illustrates this situation. This is because the second AP (AP2) needs time to notify the first AP (AP1) that the second station (STA2) is performing transmission. As described above, since transmission conflicts occur between stations that start transmission at different time points, the probability of inter-link interference or transmission conflict may be higher than the probability of intra-link interference or conflict. In addition, since the time taken to identify the transmitter of the PPDU received by the AP of the STR multi-link device is delayed, the probability of interference or transmission conflict between the links may be even higher. Therefore, a method to solve this problem is needed. When one station of the STR multi-link device performs reception, another station of the STR multi-link device may not perform channel access. However, when channel access is prohibited, the significance of implementing the STR function may be lost. Therefore, an operation method other than prohibiting channel access for the STR multi-link device is needed. This will be described with reference to Figure 18 this.

[0205] As described above, it is important to quickly determine the station that transmits from the multi-link device to the multi-link device. The user field of the EHT-SIG of the EHT UL PPDU can display 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 can show the identifier of the station that transmits the EHT UL PPDU. The multi-link device that receives the EHT PPDU can identify the station that transmits the EHT PPDU based on the user field of the EHT-SIG of the EHT UL PPDU. Thus, the AP multi-link device can determine the station that transmits the EHT ULPPDU, and the AP multi-link device can determine the transmission destination device. Specifically, the AP multi-link device can determine the level of the probability that the transmission to be performed due to an inter-link conflict will fail. In addition, if the probability that the transmission to be performed by the AP multi-link device will fail is high, the AP multi-link device can delay the transmission to be performed and perform another transmission.

[0206] Figure 18 Illustrated is the operation of the STR multi-link device according to an embodiment of the present disclosure to stop transmission to the non-STR multi-link device.

[0207] When a station of an STR multi-link device determines that a station of a non-STR multi-link device is in a blind state during transmission to the station of the non-STR multi-link device, the STR multi-link device may stop transmitting to the station of the non-STR multi-link device in the blind state. Specifically, the STR multi-link device may determine whether a station of the non-STR multi-link device is in a blind state based on a value indicated by the STA(AID)-ID in the signaling field of the received PPDU or the transmission address (TA) field of the MAC frame included in the received PPDU. At this time, the STA-ID may be a value indicating the station transmitting the UL PPDU. In a detailed embodiment, when the value indicated by the STA(AID)-ID in the signaling field of the received PPDU indicates a first station included in the non-STR multi-link device, the STR multi-link device may determine that a second station included in the non-STR multi-link device is in a blind state. In addition, when the TA field of the MAC frame included in the received PPDU indicates a first station included in the non-STR multi-link device, the STR multi-link device may determine that a second station included in the non-STR multi-link device is in a blind state. Specifically, when the station of the PPDU indicated by the signaling field of the transmitted PPDU is the first station or the TA field of the MAC frame included in the PPDU is the first station, the STR multi-link device may determine that the second station included in the non-STR multi-link device is in a blind state. In this way, the STR multi-link device may determine that another station of the non-STR multi-link device is in a blind state by confirming transmission by any one of the stations in the non-STR multi-link device. First, the operation of the station after canceling the transmission is described.

[0208] When leaving the TXOP configured in the station of the non-STR multi-link device, the station that cancels the transmission to the station of the non-STR multi-link device may attempt to transmit to a station different from the station of the non-STR multi-link device. At this time, the station that cancels the transmission to the station of the non-STR multi-link device may perform transmission to a station different from the station of the non-STR multi-link device without a separate backoff process. In a detailed embodiment, when the channel is detected to be idle during a predetermined time interval without a separate backoff process after canceling the transmission to the station of the non-STR multi-link device, the station that cancels the transmission to the station of the non-STR multi-link device may perform transmission to a station different from the station of the non-STR multi-link device. At this time, the predetermined time interval may be one of SIFS, PDIF, and DIFS.

[0209] When performing transmission to a station different from the station of the non-STR multi-link device, the station that cancels the transmission to the station of the non-STR multi-link device may transmit traffic with a priority equal to or higher than the priority of the traffic of the canceled transmission. This is because the transmission of traffic with a priority lower than the channel access for the canceled transmission is unbalanced. In the embodiment, the station of the STR multi-link device may be an AP.

[0210] A station that cancels the transmission to a station of a non-STR multi-link device may initialize the configured TXOP. Specifically, a station that cancels the transmission to a station of a non-STR multi-link device may transmit a CF-End frame after canceling the transmission. It may allow another station operating in the link where the transmission is scheduled to use the link.

[0211] In Figure 18 , the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR non-AP multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state during the transmission to the first station (STA1). Accordingly, the first AP (AP1) stops the transmission to the first station (STA1). In Figure 18 (a), after stopping the transmission to the first station (STA1), the first AP (AP1) performs a transmission to a station different from the first station (STA1), as described in the first-described embodiment. In Figure 18 (b), after stopping the transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame, as described in the embodiment described later.

[0212] When a station stops transmitting, the station may transmit the fragment being transmitted and then may not transmit the subsequent fragments. In a detailed embodiment, the station may immediately stop the transmission of the packet being transmitted.

[0213] In the embodiment, when canceling the transmission to a station of a non-STR multi-link device in a blind state and performing a transmission to a station different from the station of the non-STR multi-link device, it is required that the STR multi-link device notify another station that a transmission to another station can be performed for stable reception. A method thereof is described. For ease of description, a station different from the station of the non-STR multi-link device in a blind state is referred to as a different station.

[0214] Stations of an STR multi-link device can insert the addresses of different stations into a MAC frame. Specifically, a station of an STR multi-link device can insert the address of the intended receiver of the MAC frame into the Receiver Address (RA) of the MAC frame, and insert the addresses of different stations into separate fields. In a detailed embodiment, a station of the device can insert the addresses of different stations into an EHT-SIG. Specifically, a station of an STR multi-link device can insert the address of the intended receiver of the PPDU and the addresses of different stations into the user field of the signaling field of the PPDU. At this time, the addresses of different stations can be inserted after the address of the intended receiver of the PPDU in the user field of the signaling field of the PPDU.

[0215] In another detailed embodiment, a station can monitor the reception of a PPDU during a predetermined time period after identifying that the intended receiver of the PPDU is not the station. Specifically, the station can monitor whether the reception of the PPDU continues for a predetermined time after identifying that the intended receiver of the received PPDU is not the station. Thus, the station can determine whether to stop the transmission of the PPDU and start the transmission to the station. In an embodiment, when it is determined that the PPDU transmission continues for a predetermined time, the station can enter a sleep state. When it is determined that the PPDU transmission does not continue for a predetermined time, the station can remain in a wake state. At this time, when the station receives a new PPDU, the station can decode the PPDU.

[0216] In another detailed embodiment, a station transmitting a PPDU can insert information signaling that the PPDU transmission can be stopped into the PPDU. The information signaling that the PPDU transmission can be stopped can be a 1-bit subfield. For example, when the value of the subfield signaling that the PPDU transmission can be stopped is 1, the station receiving the PPDU can determine that the PPDU transmission can be stopped before the time point indicated by the length field of the signaling field of the PPDU and the duration field of the MAC frame. When the station determines that the PPDU transmission can be stopped before the time point indicated by the length field of the signaling field of the PPDU and the duration field of the MAC frame, the station can postpone entering the sleep state. In addition, a station transmitting a PPDU can insert information signaling that the transmission can be stopped into the reserved field of the PPDU.

[0217] As described above, unnecessary channel occupancy can be prevented through transmission cancellation or transmission stop.

[0218] When the transmission is stopped or delayed due to a transmission conflict between links, the value of CW for channel access can be doubled as in the case of a general transmission failure. When the transmission is stopped or delayed due to a transmission conflict between links, the value of CW for channel access may not be doubled as in the case of a general transmission failure. That is, the station can maintain the value of CW for channel access. Doubling the value of CW is to reduce the probability of transmission conflicts by increasing the numerical range that can be the value of the backoff counter. This requirement may be lower when the station can clearly identify a transmission conflict between links. In addition, when the transmission is stopped or delayed due to a transmission conflict between links, doubling the value of CW by the station may cause transmission delays. However, when both an inter-link transmission conflict and an intra-link conflict occur simultaneously, the station needs to double the value of CW. This will be described with reference to Figure 19 for description.

[0219] Figure 19 illustrates the processing of the value of CW when an STR multi-link device identifies a transmission conflict between links according to an embodiment of the present disclosure.

[0220] As described in the embodiment, when a station cancels a transmission due to a transmission performed by a non-STR multi-link device, the station can sense the channel state after canceling the transmission. When it senses that the channel is not idle, the station can double the value of CW. At this time, the doubling can follow the embodiment described with reference to Figure 6 for description. In addition, when it senses that the channel is idle, the station can maintain the value of CW. This embodiment is used because even though the channel is sensed to be idle, the possibility of an intra-link transmission conflict is still very low, so this situation is treated differently from a successful transmission. Specifically, when the AP of an AP multi-link device fails to transmit to a station of a non-STR multi-link device, the AP of the AP multi-link device can obtain the backoff counter within CW without increasing CW. At this time, if the non-STR multi-link device of the AP multi-link device fails to transmit to the first station and the second station of the non-STR multi-link device performs a transmission, the AP of the AP multi-link device can obtain the backoff counter in CW without increasing CW. As described above, in an AP multi-link device, based on the transmission station of the PPDU indicated by the signaling field of the PPDU or the station indicated by the TA field of the MAC frame included in the PPDU, it can be determined whether the second station of the non-STR multi-link device performs a transmission. When EDCA is applied in the above embodiment, the process of CW adjustment and backoff counter generation can be performed by each AC.

[0221] In another specific embodiment, the STR multi-link device may determine whether the transmission of the PPDU has failed based on whether a response to the PPDU is received. At this time, the STR multi-link device may not consider whether the station receiving the PPDU is included in a non-STR multi-link device. For example, even if the first station receiving the PPDU is included in a non-STR multi-link device and the second station of the non-STR multi-link device performs a transmission such that the first station cannot transmit a response to the PPDU, the STR multi-link device may determine that the transmission of the PPDU has failed. In addition, when the transmission of the PPDU by the STR multi-link device fails, the STR multi-link device may increase the value of CW to the next larger value among the possible values of the CW value. At this time, when the value of CW is the maximum value, the STR multi-link device may keep the value of CW the same.

[0222] In another detailed embodiment, when the channel is sensed to be idle, the station may configure the value of CW to the minimum value (CW_min) of CW. This embodiment is used because the possibility of a transmission conflict within the link is low when the channel is sensed to be idle, and thus this situation is treated the same as a transmission success. The station may apply this embodiment to the CW of the AC of the traffic included in the cancelled transmission.

[0223] In addition, when a transmission is cancelled according to the embodiment, the station may not increase the retry counter. At this time, the retry counter may include at least one of a long retry counter and a short retry counter.

[0224] In this embodiment, cancelling the transmission may include at least one of stopping the transmission or delaying the transmission before starting the transmission.

[0225] When the station cancels the transmission after transmitting a CTS-to-Self frame before attempting to transmit, the station may not start an RTS / CTS frame exchange before attempting to transmit after cancelling the transmission. This is because the NAV is configured by the CTS-to-Self frame. In addition, when the station leaves the TXOP when attempting to transmit again after cancelling the transmission, the station may attempt to transmit without any backoff process.

[0226] In Figure 19Among them, the STR multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second station (STA2) is performing a transmission to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state during the transmission to the first station (STA1). Therefore, the first AP (AP1) stops the transmission to the first station (STA1). In Figure 19 (a), the first AP (AP1) determines that the channel of the first link (link1) is idle. At this time, since there is no remaining TXOP, the first AP (AP1) accesses the channel through a backoff process. In Figure 19 (b), the first AP (AP1) determines that the channel of the first link (link1) is not idle. At this time, since there is a remaining TXOP, the first AP (AP1) attempts to transmit without a backoff process.

[0227] In the embodiment, when the channel is detected to be idle during a predetermined time interval without a separate backoff process after canceling the transmission to the station of the non-STR multi-link device, the station that cancels the transmission to the station of the non-STR multi-link device may perform a transmission to a station different from the station of the non-STR multi-link device. At this time, the duration of the predetermined time interval may be problematic. The station that receives the PPDU whose transmission is canceled may not be able to decode the PPDU. At this time, when it senses that the channel is idle within the Extended Inter-Frame Space (EIFS), the station that cannot decode the PPDU may start a backoff process. Therefore, it is a problem whether the predetermined time interval is configured to be longer than or equal to EIFS. This will be described with reference to Figure 20 for description.

[0228] Figure 20 Illustrates the operation of the STR multi-link device according to an embodiment of the present disclosure to perform channel access again after stopping the transmission to the non-STR multi-link device.

[0229] As Figure 20 shown in (a) of, the predetermined time interval may be DIFS. This assumes that the station of the STR multi-link device obtains the channel access opportunity through a contention process and loses the obtained channel access opportunity due to a transmission conflict between links. That is, since the station of the STR multi-link device obtains the channel access opportunity through a contention process, a higher priority for performing channel access is provided to this station. When EDCA is applied, AIFS[AC] can be used instead of DIFS.

[0230] In another detailed embodiment, the predetermined time interval can be the EIFS as shown in (b) of Figure 20 . It is considered that the STR multi-link device can be considered to have exhausted its transmission opportunities and to consider the balance with other stations.

[0231] In another detailed embodiment, as shown in (c) of Figure 20 , when signaling information indicating that transmission can be stopped in the signaling field of the PPDU, the predetermined time interval can be the DIFS. In addition, when the station receiving the PPDU detects the stop of the PPDU transmission, the station can sense whether the channel is idle during the DIFS instead of the EIFS. At this time, if the channel is sensed to be idle during the DIFS, the corresponding station can start the backoff process. Through this embodiment, the performance of the entire network can be improved and the balance between stations can be ensured. When applying EDCA, the AIFS[AC] can be used instead of the DIFS.

[0232] As described above, the STR multi-link device can identify that transmission conflicts may occur between links. Specifically, when the first station of the STR multi-link device completes the backoff process, the second station of the STR multi-link device may be receiving the PPDU. At this time, when the second station has not completed the decoding of the signaling field of the PPDU, the first station can determine that the transmission conflict between links cannot be identified but there is a possibility. At this time, the first station can insert information indicating that the transmission can be stopped into the transmitted PPDU, as described above. In addition, for stable and efficient transmission, the NSTR multi-link device can transmit a CTS-to-Self frame before transmitting to a non-STR multi-link device. This will be described with reference to Figure 21 .

[0233] Figure 21 Illustrates the operation of the STR multi-link device transmitting a CTS-to-Self frame before transmitting to a non-STR multi-link device according to an embodiment of the present disclosure.

[0234] Stations of an STR multi-link device may transmit CTS-to-Self frames before transmitting to a non-STR multi-link device. Specifically, when reception is performed at a first station of an STR multi-link device and a second station of the STR multi-link device attempts to transmit to a non-STR multi-link device, the second station of the STR multi-link device may transmit a CTS-to-Self frame before transmitting to the non-STR multi-link device. Thus, the second station can ensure a TXOP for transmission to the non-STR multi-link device. In addition, before performing transmission to a non-STR multi-link device, the second station may determine whether transmission to the first station is performed from the corresponding non-STR multi-link device. The second station may determine the destination station of the transmission based on whether transmission to the first station is performed from the corresponding non-STR multi-link device. Specifically, when transmission to the first station is not performed from the corresponding non-STR multi-link device, the second station may perform transmission to the corresponding non-STR multi-link device. When transmission to the first station is performed from the corresponding non-STR multi-link device, the second station may perform transmission to a station not included in the corresponding non-STR multi-link device. For example, when the first station plans to transmit an SU-PPDU for a station of a non-STR multi-link device, an MU-PPDU including data for a station of a non-STR multi-link device, or a PPDU including a trigger frame for triggering transmission of a station of a non-STR multi-link device, the first station may cancel the planned transmission. At this time, the first station may attempt to transmit an SU-PPDU for a station that is not a station of a non-STR multi-link device, an MU-PPDU not including data for a station of a non-STR multi-link device, or a PPDU including a trigger frame that does not trigger transmission of a station of a non-STR multi-link device. At this time, the first station may start transmission after a time longer than the SIFS from the transmission of the CTS-to-Self frame. Specifically, the first station may start transmission after the PIFS from the transmission of the CTS-to-Self frame. The station transmitting the CTS-to-Self frame should start transmission after the SIFS from the transmission of the CTS-to-Self frame. When canceling a planned transmission and attempting a new transmission as described in the embodiment, processing time of the STR multi-link device for generating an MPDU to be newly transmitted is required. Thus, an exception may be applied to the rule for the time interval between the CTS-to-self frame and the transmission. In the embodiment, the second station exceeded the TXOP obtained by the CTS-to-self and thus, in principle, cannot perform transmission.

[0235] In Figure 21In this case, the STR multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). Since the second AP (AP2) performs reception and the first AP (AP1) schedules a transmission to a station of a non-STR multi-link device, the first AP (AP1) transmits a CTS-to-Self frame before the scheduled transmission. As described above, the first AP (AP1) determines the destination station of the transmission based on the determination of the station that transmits the PPDU received by the second AP (AP2). In addition, the first AP (AP1) performs the transmission after a SIFS or PIFS from the transmission of the CTS-to-Self frame.

[0236] The second station can start the RTS / CTS frame exchange process by transmitting an RTS frame instead of transmitting a CTS-to-Self frame. Therefore, the second station can obtain an effect similar to the transmission of a CTS-to-Self frame. In the case of RTS / CTS frame exchange, the second station can obtain a TXOP only when the destination station of the transmission is not in a blind state.

[0237] Figure 22 The figure illustrates transmissions from multiple APs included in an STR multi-link device to multiple stations included in a non-STR multi-link device according to an embodiment of the present disclosure.

[0238] Multiple stations included in a non-STR multi-link device can perform reception simultaneously. This is because simultaneous reception by multiple stations may cause only minor interference. Figure 22 The figure illustrates simultaneous reception performed by multiple stations included in a non-STR multi-link device. At this time, for the stable operation of the non-STR multi-link device, multiple APs included in the STR multi-link device can perform multiple transmissions whose transmission ends are synchronized with multiple stations included in a non-STR multi-link device. This will be described with reference to Figure 23 be described.

[0239] Figure 23 The figure illustrates multiple transmissions whose transmission ends are synchronized from multiple APs included in an STR multi-link device to multiple stations included in a non-STR multi-link device according to an embodiment of the present disclosure.

[0240] When a multi-link device performs a transmission in one of the non-STR links, the multi-link device can simplify the channel access process for the transmission performed in the other link. Specifically, when the first station of the multi-link device completes the backoff channel access process in the first link, if the channel is idle during a predetermined time interval within the link of the second station of the STR multi-link device, the second station of the STR multi-link device can start the transmission in the second link.

[0241] In a detailed embodiment, when a station of an STR multi-link device performs a transmission to a station of a non-STR multi-link device, the channel access process of another station of the STR multi-link device can be simplified. Specifically, when the first station of the STR multi-link device completes the backoff channel access process for the transmission to the first station of the non-STR multi-link device, if the channel is idle during a predetermined time interval within the link of the second station of the STR multi-link device, the second station of the STR multi-link device can start the transmission to the second station of the non-STR multi-link device. At this time, the predetermined time interval can be PIFS. Such an operation can be applied when the first station and the second station of the STR multi-link device perform a transmission to a station included in a non-STR multi-link device. In the embodiment, the first station and the second station can start the transmission with a difference within the predetermined time interval. The predetermined time interval can be the slot time.

[0242] In addition, when the first station and the second station of the STR multi-link device perform a transmission to a station included in a non-STR multi-link device, the transmission ends of the first station and the second station can be synchronized. At this time, the synchronization of the transmission ends of the first station and the second station can indicate that the end of the first station and the end of the second station have a difference within a first predetermined time interval. The first predetermined time interval can indicate the inside of the slot boundary or the symbol boundary.

[0243] Multiple stations of the non-STR multi-link device that receive the synchronized transmission ends can simultaneously perform subsequent transmissions (such as responses). At this time, the response can include ACK. In a conventional WLAN, the subsequent transmission after reception is performed after SIFS from the reception. However, for multiple transmissions that end with a tiny time difference, performing subsequent transmissions with a tiny time difference can make the implementation more complex compared to simultaneously performing subsequent transmissions. Therefore, as described above, multiple stations of the non-STR multi-link device that receive the synchronized transmission ends can simultaneously perform subsequent transmissions. At this time, the interval between transmissions following at least one of the multiple transmissions whose transmission ends are synchronized can be the sum of SIFS and the time within the predetermined time interval. Specifically, the transmission after the first-ended transmission among the multiple transmissions whose transmission ends are synchronized can be performed at an interval obtained by adding SIFS and the time within the predetermined time interval from the transmission. At this time, the predetermined time interval can be one of the slot time or the symbol length. In addition, the difference within the predetermined time interval can be the difference between the end of the last-ended transmission among the multiple transmissions whose transmission ends are synchronized and the first-ended transmission among the multiple transmissions whose transmission ends are synchronized.

[0244] In another detailed embodiment, when multiple transmissions end with a time difference within a first predetermined time interval, multiple stations receiving the transmissions may perform synchronized subsequent transmissions. Multiple subsequent transmissions whose transmission ends are synchronized may indicate multiple subsequent transmissions performed with a time difference within a second predetermined time interval. In addition, the difference within the second predetermined time interval may be the difference between the end of the last-ended transmission among multiple synchronized transmissions and the end of the first-ended transmission among multiple transmissions whose transmission ends are synchronized. At this time, the second predetermined time interval may be less than the first predetermined time interval. A PPDU whose transmission end is synchronized may be referred to as a sync PPDU.

[0245] In Figure 23 , 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 multi-link device includes a first station (STA1) operating on the first link (link1) and a second station (STA2) operating on the second link (link2). Each of the first AP (AP1) and the second AP (AP2) synchronizes the transmission ends to the first station (STA1) and the second station (STA2). That is, after the first station (STA1) ends its transmission, the second station (STA2) ends its transmission within a predetermined time interval from the first station (STA1). The first station (STA1) and the second station (STA2) transmit ACKs simultaneously. At this time, the first station (STA1) transmits an ACK after the SIFS starting from the end of the transmission to the first station (STA1) and the difference between the end of the transmission of the first station and the end of the transmission to the second station (STA2).

[0246] The embodiment may be applied to transmissions for which the ACK policy is not configured as No ACK. Specifically, the ACK policy may be applied to cases other than immediate response. In a detailed embodiment, when multiple stations of a multi-link device receive a transmission whose transmission ends are synchronized, the multiple stations of the multi-link device may receive an ACK request simultaneously and transmit an ACK according to the ACK request. Multiple stations of a multi-link device that receive a transmission within a predetermined time for which the ACK policy is configured with a value other than No ACK may start ACKs simultaneously.

[0247] When there is a non-STR multi-link device, the non-STR multi-link device should be considered during the operation of configuring TXOP by transmitting RTS / CTS frames and CTS-to-Self frames. This will be described with reference to Figures 24 to 29 which will be described.

[0248] Figure 24 illustrates the exchange of RTS / CTS frames by a multi-link device according to an embodiment of the present disclosure.

[0249] Even when there are non-STR multi-link devices, the RTS / CTS frame exchange process can follow the process defined in a conventional WLAN. The RTS / CTS frames can be used to configure the NAV of stations operating on another link. Specifically, a station receiving an RTS / CTS frame can operate on a link different from the link in which the corresponding station operates, and pass the RTS / CTS frame to another station included in the multi-link device that includes the corresponding station.

[0250] However, as described in the above embodiments, when there are non-STR multi-link devices, channel access or transmission may be restricted. Thus, as Figure 24 shown, RTS / CTS may not be transmitted. That is, if the second station of the non-STR multi-link device is performing reception, a station scheduling a transmission to the first station of the non-STR multi-link device may not attempt an RTS / CTS frame exchange.

[0251] In Figure 24 therein, 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 multi-link device includes a first station (STA1) operating on the first link (link1) and a second station (STA2) operating on the second link (link2). When the first AP (AP1) transmits an RTS frame to the first station (STA1), the channel access of the second station (STA2) is prohibited. The second AP (AP2) can determine that the channel access of the second station (STA2) is prohibited. Thus, the second AP (AP2) does not attempt an RTS / CTS frame exchange with the second station (STA2). In this embodiment, a hidden node problem may occur. This will be described with reference to Figure 25 which follows.

[0252] Figure 25 illustrates a hidden node problem that occurs during the RTS / CTS frame exchange process according to the embodiment described with reference to Figure 24 which follows.

[0253] A station performing a transmission to a station of a non-STR multi-link device can perform the transmission without a CTS / RTS exchange as described above. At this time, since a TXOP is not configured in another station, the other station may attempt a transmission, and thus the station of the non-STR multi-link device may not be able to receive the transmission. In Figure 25In an embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). Due to the transmission from the first AP (AP1) to the first station (STA1), the second AP (AP2) cannot transmit an RTS frame before transmission. Therefore, a TXOP for the transmission of the second AP (AP2) is not configured in the stations operating in the second link (link2). Thus, when the second AP (AP2) performs a transmission to the second station (STA2), a station of another BSS (OBSS STA) performs a transmission in the second link (link2). Accordingly, the second station (STA2) cannot receive the transmission of the second AP (AP2). To solve the hidden node problem, the following embodiments can be applied.

[0254] In a detailed embodiment, when a station of a non-STR multi-link device performs a reception, the station is not allowed to perform a transmission to any station of the non-STR multi-link device. In another detailed embodiment, when a second station of the non-STR multi-link device performs a reception while a station performs a transmission to the first station of the non-STR multi-link device, the station can perform a transmission and a transmission to the second station simultaneously. When a second station of the non-STR multi-link device performs a reception while a station performs a transmission to the first station of the non-STR multi-link device, the station can synchronize the end of the transmission to the first station and the end of the transmission to the second station. Specifically, when a second station of the non-STR multi-link device performs a reception while a station performs a transmission to the first station of the non-STR multi-link device, the station can end the transmission to the first station and the transmission to the second station simultaneously. In an embodiment, the transmission to the second station can be performed by another station of the multi-link device including the station.

[0255] Figure 26 Illustrated is an RTS / CTS frame exchange performed by a multi-link device according to an embodiment of the present disclosure.

[0256] In another embodiment of the present disclosure, when a first station of a multi-link device continues to perform a transmission to a third station of a non-STR multi-link device and a second station of the multi-link device transmits an RTS frame to a fourth station of the non-STR multi-link device, the first station can end the transmission to the third station before the time point when the fourth station transmits the RTS frame. Accordingly, the fourth station can transmit a CTS frame to the second station. Therefore, a TXOP for frame exchange between the second station and the fourth station can be configured. However, it may be difficult to achieve the end of the transmission before the time point when the first station transmits an RTS frame to the fourth station.

[0257] In another embodiment of the present disclosure, when the first station of the multi-link device continues to perform the transmission to the third station of the non-STR multi-link device, and the second station of the multi-link device transmits an RTS frame to the fourth station of the non-STR multi-link device, the second station may transmit the RTS frame to the fourth station at the time when the transmission from the first station to the third station ends. For this purpose, the second station may insert padding into the RTS frame. At this time, the RTS frame may be an RTS frame format for flexibly controlling the transmission length. For ease of description, the RTS frame format is referred to as a multi-link (ML)-RTS frame. The ML-RTS frame may include a padding field for padding. For example, the ML-RTS frame format may be the same as the Figure 26 RTS frame format shown. In addition, the first station may insert padding into the transmission to the third station in a timely manner to conform to the transmission end of the RTS frame.

[0258] In Figure 26 the embodiment, the STR AP multi-link device includes a first AP (AP1) operating in the first link (link1) and a second AP (AP2) operating in the second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The second AP (AP2) transmits an ML-RTS frame to the second STA (STA2) in a timely manner when the transmission from the first station (STA1) to the first AP (AP1) ends. Thereafter, when the first station (STA1) transmits an ACK to the first AP (AP1), the second station (STA2) transmits an ACK to the second AP (AP2). Therefore, a TXOP for frame exchange between the second AP (AP2) and the second station (STA2) is configured among the stations operating in the channel of the second link.

[0259] In another detailed embodiment, instead of the RTS / CTS frame, another frame for configuring the NAV may be exchanged. In this embodiment, an ACK request frame may be transmitted instead of the RTS frame. The ACK request frame may include duration information related to the transmission end time point. In addition, the frame including the ACK transmitted in response to the ACK request may also include duration information. At this time, the duration information of the frame including the ACK may be configured according to the duration information of the ACK request frame.

[0260] The embodiments have been described for RTS / CTS frame exchange, but they may also be used for controlling frame exchange as well as the RTS / CTS frame. At this time, the control frame exchange may include the exchange between the PS-Poll frame and the response frame of the PS-Poll.

[0261] Figure 27Illustrated is an exceptional transmission of a response to a control frame by a multi-link device in a case where channel access is prohibited according to an embodiment of the present disclosure.

[0262] As described in the embodiment, when there is a non-STR multi-link device, channel access of some stations may be prohibited. Even if the channel access of a station is prohibited, the station may transmit a response to a control frame. Specifically, even if the channel access of a station is prohibited, the station may transmit a CTS frame in response to an RTS frame.

[0263] As described above, when transmitting a response to a control frame as an exception to channel access prohibition, the following embodiment may be applied. A first station transmits a response to a control frame as an exception to channel access prohibition. When the first station transmits a response to a control frame, a third station performs a transmission to a second station included in a multi-link device including the first station. In this case, the third station may perform a retransmission to the first station. This is because the third station can anticipate a transmission failure of the second station.

[0264] In Figure 27 's embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The first AP (AP) performs a transmission to the first station (STA1). The second AP (AP2) transmits an RTS frame to the second station (STA2). Since the first station (STA1) performs reception, channel access of the second station (STA2) is prohibited. However, the second station (STA2) transmits a CTS frame to the second AP (AP2) as an exception to channel access prohibition. The first AP (AP1) may determine that there is a high possibility of a transmission failure of the first AP (AP1) due to the second station (STA2) transmitting a CTS frame. Therefore, the first AP (AP1) performs a retransmission to the first station (STA1). The retransmission method will be described in more detail with reference to Figure 28 More specifically, the retransmission method will be described.

[0265] Figure 28 Illustrated is a retransmission of a transmission to a station of a non-STR multi-link device.

[0266] In reference Figure 27In the described retransmission, only some of the packets included in the initial transmission may be retransmitted. Specifically, the station performing the retransmission may retransmit only some of the packets included in the initial transmission. The station performing the retransmission may determine some of the packets included in the initial transmission as the packets to be retransmitted based on the time interval during which the station performing the retransmission receives the CTS frame. Specifically, the station performing the retransmission may determine, as the packets to be retransmitted, the packets among the packets included in the initial transmission that are transmitted during the time interval including the time interval during which the station performing the retransmission receives the CTS frame. At this time, the station performing the retransmission may retransmit the packets transmitted during the time interval including the time interval during which the station performing the retransmission receives the CTS frame based on the propagation delay. In another detailed embodiment, the station performing the retransmission may retransmit all of the packets included in the initial transmission.

[0267] In addition, the station performing the retransmission may perform the retransmission before receiving the ACK for transmission. At this time, the station performing the retransmission may receive, after the retransmission, a block ACK indicating whether the initial transmission and the retransmission have been received. To this end, the station performing the retransmission may perform the retransmission before the SIFS after the initial transmission. In another detailed embodiment, a station that has failed to receive due to a control frame transmitted as an exception to the channel access prohibition may hold off receiving the retransmission without transmitting an ACK.

[0268] In Figure 28 the embodiment, considering the interval at which the second AP (AP2) receives the CTS frame and the transmission delay, the first AP (AP1) retransmits the fourth and fifth packets. The first AP (AP1) receives, after the retransmission, an ACK including whether the retransmission has been received.

[0269] Figure 29 FIG. illustrates the transmission of a control frame through a link in which a station whose channel access is not prohibited operates according to an embodiment of the present disclosure, rather than through a link in which a station whose channel access is prohibited operates.

[0270] As Figure 26 described in the embodiment shown in, the end of the transmission to multiple stations of a non-STR multi-link device may be synchronized. However, this requires controlling the already generated MPDU or regenerating the MPDU again, and may therefore cause implementation difficulties. Accordingly, the multi-link device may transmit a control frame through a link in which a station whose channel access is not prohibited operates, rather than through a link in which a station whose channel access is prohibited operates. Specifically, the multi-link device may transmit a control frame through a link that is currently performing reception from the multi-link device among the stations of the non-STR multi-link device. At this time, the control frame may be an RTS frame.

[0271] In Figure 29In an embodiment, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The first AP (AP1) performs a transmission to the first station (STA1). Even if the second AP (AP2) successfully performs a backoff process, since the first station (STA1) is receiving a transmission from the first AP (AP1), the second AP (AP2) cannot perform a transmission to the second station (STA2). At this time, the second AP (AP2) requests the first AP (AP1) to transmit an RTS frame with the second station (STA2) as the receiver. The first AP (AP1) may insert an RTS frame with the second station (STA2) as the receiver into the transmission performed by the first AP (AP1). In another detailed embodiment, after the first AP (AP1) finishes the transmission being performed by the first AP (AP1), the first AP (AP1) may transmit an RTS frame with the second station (STA2) as the receiver in the first link (link1) after the SIFS of the corresponding transmission. The first station (STA1) receives the RTS frame with the second station (STA2) as the receiver and passes the received RTS frame to the second station (STA2). The second station (STA2) performs a CCA during the PIFS. When the channel is idle during the PIFS, the second station (STA2) transmits a CTS-to-Self frame. During the time interval when the second station (STA2) is expected to transmit a response to the RTS frame, the first AP (AP1) may stop the transmission to the first station (STA1). In addition, when the second station (STA2) transmits a response to the RTS frame, the first station (STA1) may transmit an ACK for the received transmission. In another detailed embodiment, the first station (STA1) may also transmit a response to the RTS frame when the second station (STA2) transmits a response to the RTS frame. Figure 29 This is for helping understanding the description and can be used to control the transmission of frames as well as RTS frames and CTS-to-Self frames. In addition, another time interval other than the PIFS may be used.

[0272] Figure 30 It illustrates the transmission of an ACK by a multi-link device according to an embodiment of the present disclosure.

[0273] A station of the multi-link device may make a request for a link to transmit an ACK to a station of the non-STR multi-link device. Specifically, the station of the multi-link device may make a request to transmit an ACK in a link different from the link in which the transmission has been performed. Figure 28In an embodiment, the first AP (AP1) of the STR multi-link device performs a transmission (TX(#2)) to the first station (STA1) of the non-STR multi-link device. At this time, the first AP (AP1) makes a request to transmit an ACK for the transmission (TX(#2)) via the second link (link2). This is because since the transmission (TX(#2)) of the first AP (AP1) ends earlier than the transmission of the second AP (AP2) to the second station (STA2), it is determined that it is difficult to transmit the ACK for the transmission (TX(#2)) of the first AP (AP1).

[0274] In addition, for ACK transmission, a station may configure the ACK policy as an implicit BAR so as not to transmit an immediate response to the transmission. In another detailed embodiment, a station may configure the ACK policy for transmission as BlockAckReq. However, in order to transmit a block ACK, BlockAckReq should be transmitted and thus may generate a channel access burden and a transmission delay. Therefore, a new ACK policy for multi-link devices may be required.

[0275] A station of a multi-link device may also transmit an ACK for a transmission received by another station included in the multi-link device, and the ACK is the same as the ACK for the transmission received by the station. This ACK transmission may be referred to as multi-link (ML)-ACK. In addition, ML-ACK may be configured as an ACK policy. In Figure 30 the embodiment, the first AP (AP1) configures ML-ACK as the ACK policy for the transmission (TX(#2)). The first station (STA1) does not transmit an ACK to the first AP (AP1) after receiving the transmission (TX(#2)). The second station (STA2) completes the reception of the transmission from the second AP (AP2) and transmits the ACKs for the transmissions from the first AP (AP1) and from the second AP (AP2) together. The non-STR multi-link device may include not only the first station (STA1) and the second station (STA2), but also a third station (STA3), and the STR multi-link device may include not only the first AP (AP1) and the second AP (AP2) but also a third AP (AP3). At this time, ML-ACK may be configured as the ACK policy for the transmission from the second AP (AP2) to the second station (STA2). When the transmission from the third AP (AP3) to the third station (STA3) is completed later than the transmission from the second AP (AP2) to the second station (STA3), the third station (STA3) may transmit the ACK for the transmission from the first AP (AP1) to the first station (STA1), the ACK from the second AP (AP2) to the second station (STA2), and the ACK for the transmission from the third AP (AP3) to the third station (STA3) to the third AP (AP3).

[0276] With these embodiments, even if the transmission to the stations of the non-STR multi-link device is not completed simultaneously, interference between links that may be generated due to ACK transmission can be prevented. In the embodiments, the ACK policy may be configured as BlockACK instead of ML-ACK. In another detailed embodiment, the ACK policy may be configured as No ACK instead of ML-ACK.

[0277] When the multi-link device performs service transmission, the number of links obtaining the transmission opportunity may increase. At this time, the multi-link device may transmit the service through the link that obtains the transmission opportunity later, and the service is scheduled by the multi-link device to be transmitted through the link that obtains the transmission opportunity first. At this time, the NAV configured in the link where the multi-link device obtains the transmission opportunity first may be configured to be greater than the NAV required for transmitting the service. When the NAV is configured to be greater than the NAV required for transmitting the service in the link where the multi-link device obtains the transmission opportunity first, the multi-link device may transmit a CF-END frame after completing the transmission in the link that obtains the transmission opportunity first, so as to reset the NAV.

[0278] Reference Figures 31 to 34 Describe the reception of the synchronization PPDU and the signaling related to the reception of the synchronization PPDU.

[0279] To receive the synchronization PPDU, the first station of the non-STR multi-link device should determine whether the second station having a non-STR relationship with the first station starts to receive the synchronization PPDU. In addition, the first station should continuously perform preamble detection (PD). When it is considered that the channel access of the first station receiving the synchronization PPDU is prohibited by the reception of another station of the non-STR multi-link device, such an operation of the first station may be unreasonable. Therefore, the first station may enter the sleep state under a predetermined condition. The synchronization PPDU may be transmitted within a conventionally configured TXOP. Therefore, the performance gain that can be obtained by receiving the synchronization PPDU can be determined according to the length of the remaining TXOP. Therefore, the first station may determine whether to abandon receiving the synchronization PPDU based on the length of the synchronization PPDU. When the first station abandons receiving the synchronization PPDU, the first station may enter the sleep state. Such a power saving operation may be referred to as inter-link TXOP power saving (PS). In the inter-link TXOP PS, the station that enters the sleep state may wake up from the sleep state to receive frames periodically transmitted from the AP, for example, beacon frames, TIM frames, and DTIM frames. In addition, when the TXOP ends, for example, when a CF-END frame is transmitted, the station that enters the sleep state in the inter-link TXOP PS may wake up from the sleep state.

[0280] The TXOP can be changed to a period indicated by a length field of a signaling field of a PPDU or a duration field of a MAC frame. Specifically, in the embodiment, a station can determine the occupancy time of a PPDU based on a period indicated by a length field or a duration field of a MAC frame.

[0281] A non-AP multi-link device can signal information to an AP multi-link device regarding whether a synchronized PPDU is received and the synchronized PPDU support condition. In addition, the AP multi-link device can signal information to the non-AP multi-link device regarding whether the AP multi-link device supports PPDU transmission. At this time, the multi-link device can signal information regarding whether synchronized PPDU is supported for each multi-link device. For example, the AP multi-link device can signal information regarding whether synchronized PPDU transmission is supported for each AP multi-link device. In another detailed embodiment, the multi-link device can signal information regarding whether synchronized PPDU is supported for each station. Specifically, the AP multi-link device can signal information regarding whether synchronized PPDU transmission is supported for each AP included in the AP multi-link device. For example, an AP multi-link device including a first AP, a second AP, and a third AP can indicate that the first AP supports synchronized PPDU transmission, while the second AP and the third AP do not support synchronized PPDU transmission.

[0282] When information indicating that the AP multi-link device associated with the non-AP multi-link device does not support synchronized PPDU transmission is indicated, a station of the non-AP multi-link device can enter the inter-link PS sleep state while another station of the non-AP multi-link device performs reception. This is because the AP multi-link device associated with the non-AP multi-link device cannot transmit a synchronized PPDU. At this time, the station of the non-AP multi-link device can determine the length of time to maintain the sleep state based on the length of the PPDU received by another station of the non-AP multi-link device.

[0283] Whether to support synchronized PPDU transmission or reception can be determined according to an operation policy and hardware performance. Therefore, whether synchronized PPDU transmission or reception is supported can be signaled not only through information about performance but also through information about an operation mode. A method of signaling support for synchronized PPDU transmission or reception will be described in detail with reference to Figure 31 A method of signaling support for synchronized PPDU transmission or reception will be described in detail.

[0284] Figure 31 An element field indicating information regarding support for synchronized PPDU reception or transmission according to an embodiment of the present disclosure is illustrated.

[0285] As described above, the information indicating whether synchronous PPDU transmission is supported may be included in an element indicating the capabilities of the station. For ease of description, the element indicating the capabilities of the station is referred to as the capabilities element. In addition, in the capabilities element, the field of the information indicating whether synchronous PPDU transmission is supported is referred to as the support synchronous PPDU Tx subfield. At this time, the capabilities element may be a multi-link element, which is an element indicating the capabilities of a multi-link. In addition, the capabilities element may be an EHT capabilities element indicating the capabilities related to EHT. Figure 31 (a) illustrates an example of a capabilities element.

[0286] When the value of the support synchronous PPDU Tx subfield is 1, support synchronous PPDU Tx may indicate that the station or multi-link device indicated by the support synchronous PPDU Tx subfield supports synchronous PPDU transmission. When the value of the support synchronous PPDU Tx subfield is 0, support synchronous PPDU Tx may indicate that the station or multi-link device indicated by the support synchronous PPDU Tx subfield does not support synchronous PPDU transmission. In addition, when a station not included in a multi-link device transmits a capabilities element, the support synchronous PPDU Tx subfield may signal information that is not information unrelated to whether synchronous PPDU transmission is supported, or may be used as a reserved field.

[0287] As described above, the information indicating whether synchronous PPDU reception is supported may be included in an element indicating the information related to the operation of the station. For ease of description, the element indicating the information related to the operation of the station is referred to as the operation element. In addition, in the operation element, the information field indicating whether synchronous PPDU reception is supported is referred to as the support synchronous PPDU Rx disable subfield. Figure 31(b) illustrates an example of an operation element. When the value of the support synchronous PPDU Rx disable subfield is 1, it can indicate that synchronous PPDU reception is not supported. Specifically, when the value of the support synchronous PPDU Rx disable subfield is 1, the support synchronous PPDU Rx disable subfield can indicate that a station transmitting the support synchronous PPDU Rx disable subfield does not wish to pending reception of synchronous PPDUs. In the case where a multi-link device configures the value of the support synchronous PPDU Rx disable subfield to 1, when the first station of the multi-link device performs reception, the second station of the multi-link device may not perform PD and CCA. The AP multi-link device associated with the multi-link device transmitting the support synchronous PPDU Rx disable subfield does not transmit PPDUs to multiple stations of the multi-link device transmitting the support synchronous PPDU Rx disable subfield at the same time. The PPDU can be an SU PPDU, a full-BW MU PPDU, or an OFDMA MU PPDU transmitted in one of the non-HT PPDU format, HT PPDU format, VHT PPDU format, HE PPDU format, and EHT PPDU format. At this time, the AP multi-link device should not transmit frames requesting responses (e.g., immediate responses). Frames requesting responses can include at least one of RTS, multi-user (MU)-RTS, trigger frames, and block Ack requests (BAR).

[0288] In addition, the operation element can include information related to the minimum length of the synchronous PPDU that can be received by the station or multi-link device transmitting the operation element. At this time, the subfield indicating the information related to the minimum length of the synchronous PPDU is called the remaining TXOP threshold subfield. The remaining TXOP threshold subfield can indicate time. In addition, the remaining TXOP threshold subfield can be expressed in units of us, ms, or symbols. A multi-link device associated with the multi-link device transmitting the remaining TXOP threshold subfield may not be allowed to transmit a synchronous PPDU shorter than the length indicated by the remaining TXOP threshold subfield to the multi-link device or station transmitting the remaining TXOP threshold subfield.

[0289] In addition, when the remaining TXOP threshold subfield is configured to a predetermined value, it can indicate that the multi-link device or station transmitting the remaining TXOP threshold subfield does not support synchronous PPDU reception. The predetermined value can be a value indicating a time longer than the maximum time that can be represented by the remaining TXOP threshold subfield. In another detailed embodiment, the predetermined value can be 0. When applying the embodiment, the synchronous PPDU Rx disable subfield can be omitted in the operation field.

[0290] In addition, in the above-described embodiments, the synchronization PPDU Rx disable subfield and the remaining TXOP threshold subfield that can be signaled by an action element have been described. The synchronization PPDU Rx disable subfield and the remaining TXOP threshold subfield can be signaled by an element other than the action element or signaling information. Refer to Figures 32 to 34 describes embodiments for implementing an inter-link TXOP power saving mode according to the signaling described in the reference Figure 31 An example is provided.

[0291] Figure 32 FIG. illustrates the operation of an inter-link TXOP power saving mode performed by a non-STR multi-link device according to an embodiment of the present disclosure.

[0292] When information indicating that a non-STR multi-link device does not support synchronous PPDU reception is signaled, the second station of the non-STR multi-link device can enter a sleep state while the first station of the non-STR multi-link device performs reception. At this time, the second station can remain in the sleep state until the end time point of the TXOP indicated by the PPDU received by the first station. As described above, the time point at which the second station expects to receive a frame periodically transmitted from the AP can be before the end time point of the TXOP indicated by the PPDU received by the first station. At this time, the second station can wake up from the sleep state before the end time point of the TXOP indicated by the PPDU received by the first station. As described above, the frame periodically transmitted from the AP can include at least one of a beacon frame, a TIM frame, and a DTIM frame.

[0293] Even after the time point when the TXOP indicated by the PPDU received by the first station ends, the second station can remain in the sleep state. Specifically, based on the information received from the AP associated with the second station, even after the time point when the TXOP indicated by the PPDU received by the first station ends, the second station can remain in the sleep state. At this time, the information received from the AP associated with the second station can be NAV-related information. In addition, the information received from the AP associated with the second station can be the operation information of the AP associated with the first station. When the NAV configured by the second AP of the AP multi-link device that performs transmission to the second station of the non-AP multi-link device has not expired, the first AP of the AP multi-link device can transmit to the first station of the non-AP multi-link device information about the expected time point of transmission or reception of the first AP and the expected time point of NAV expiration, and the first station of the non-AP multi-link device signals information indicating that the first AP of the AP multi-link device does not want to receive the synchronization PPDU. When the NAV configured by the second AP of the AP multi-link device that performs transmission to the second station of the non-AP multi-link device does not expire, it can include the reception or transmission of the PPDU by the second AP from a station. When the NAV configured by the second AP of the AP multi-link device that performs transmission to the second station of the non-AP multi-link device does not expire, it can include configuring the NAV in the second AP by the PPDU not transmitted by the second station.

[0294] In Figure 32 In an embodiment of, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating that it does not expect to receive the synchronization PPDU. The first AP (AP1) performs transmission to the first station (STA1). At this time, the second station (STA2) maintains the sleep state until the time point when the TXOP indicated by the PPDU transmitted by the first AP (AP1) to the first station (STA1) ends.

[0295] Figure 33 The figure illustrates that the station of the non-STR multi-link device according to an embodiment of the present disclosure receives the standby of the synchronization PPDU and enters the sleep state.

[0296] When the remaining duration of the TXOP indicated by the PPDU received by the first station of the non-STR multi-link device is shorter than or equal to the length indicated by the remaining TXOP threshold subfield transmitted by the non-STR multi-link device, the first station of the non-STR multi-link device may enter the sleep state of the inter-link TXOP. At this time, when the remaining duration of the TXOP indicated by the PPDU being received by the first station is longer than the length indicated by the remaining TXOP threshold subfield transmitted by the non-STR multi-link device, the second station may receive the synchronization PPDU transmitted to the second station before entering the sleep state. At this time, the second station may receive the synchronization PPDU. To this end, the second station may perform PD and determine whether the intended receiver of the received PPDU is the second station. Specifically, the second station may determine whether the AID indicated by the signaling field of the PPDU or the RA of the MAC frame included in the PPDU indicates the second station.

[0297] In Figure 33 the embodiment of, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating a desire to receive a synchronization PPDU. At this time, the non-AP multi-link device also signals 'a', which is the minimum length of the TXOP required for synchronization PPDU reception. The first AP (AP1) performs transmission to the first station (STA1), while the second station (STA2) awaits receipt of the synchronization PPDU. When the TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is equal to or shorter than 'a', the second station (STA2) enters the inter-link TXOP power saving state.

[0298] Figure 34 Illustrated is that a station of a non-STR multi-link device according to another embodiment of the present disclosure enters the sleep state from standby for receiving a synchronization PPDU.

[0299] When a station of a non-STR multi-link device is pending reception of a synchronous PPDU and a transmission of a PPDU that is not a synchronous PPDU is detected in a BSS operated by an AP associated with the station of the non-STR multi-link device, the station of the non-STR multi-link device may enter the inter-link TXOP power save state. At this time, the station may determine that the PPDU having a non-expected receiver of the station is not a synchronous PPDU. In addition, when a transmission of a PPDU that is not a synchronous PPDU is detected in a BSS operated by an AP associated with the station of the non-STR multi-link device while in a sleep state, the station of the non-STR multi-link device may enter the inter-link TXOP power save state even if leaving the minimum TXOP signaled by the station.

[0300] In Figure 34 the embodiment of, the STR AP multi-link device includes a first AP (AP1) operating in a first link (link1) and a second AP (AP2) operating in a second link (link2). The non-STR multi-link device includes a first station (STA1) operating in the first link (link1) and a second station (STA2) operating in the second link (link2). The non-STR non-AP multi-link device signals information indicating an expectation to receive a synchronous PPDU. At this time, the non-AP multi-link device also signals "a", which is the minimum length of the TXOP required for synchronous PPDU reception. The first AP (AP1) performs a transmission to the first station (STA1), and the second station (STA2) is pending reception of the synchronous PPDU. The second station (STA2) detects a transmission of a PPDU that is not a synchronous PPDU in the BSS to which the second station belongs. The TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is greater than 'a', but the second station (STA2) enters the inter-link TXOP power save state.

[0301] <Multi-Link Single Radio Multi-Link Device Service Process>

[0302] As described above, considering that the multi-link device can operate adaptively when the transmission of the first station of the non-STR multi-link device makes the second station in a blind state. Specifically, when the multi-link device determines that the station of the non-STR multi-link device is in a blind state, the multi-link device may stop transmitting to the station of the non-STR multi-link device. In addition, the station of the non-STR multi-link device may enter a doze state based on the operations of other stations of the non-STR multi-link device, such as transmission and reception. Thus, problems that may occur when the operation of any one station of the non-STR multi-link device limits the operation of another station can be solved.

[0303] As described above, in a non-STR multi-link device, different stations included in the non-STR multi-link device cannot perform reception and transmission simultaneously due to interference within the device. In addition, due to limitations in the hardware configuration of the non-STR multi-link device, different stations included in the non-STR multi-link device cannot perform reception and transmission simultaneously. Specifically, when the first station of the non-STR multi-link device is transmitting or receiving, it may limit the second station of the non-STR multi-link device from using the transceiver. For example, the non-STR multi-link device may only support one PPDU process. In this case, when the first station of the non-STR multi-link device is transmitting or receiving, the second station of the non-STR multi-device cannot transmit or receive. In this way, a multi-link device that includes multiple stations operating independently but does not support simultaneous transmission or reception of multiple stations is called a single-radio multi-link device. Therefore, when any one station of the single-radio multi-link device is transmitting / receiving, other stations of the single-radio multi-link device cannot transmit / receive. The operation of the multi-link device as a single-radio multi-link device can be based on the hardware constraints or operation mode definitions described above. Therefore, in this specification, a single-radio multi-link device can refer to a multi-link device that restricts the operation of stations due to hardware constraints and a multi-link device that restricts the operation of stations according to the definition of the operation mode. Therefore, the single-radio multi-link device in this specification includes a multi-link device that supports simultaneous transmission or reception of multiple stations of the multi-link device but, under special conditions, does not support simultaneous transmission or reception of multiple stations of the multi-link device. In this case, the special conditions can include special time points.

[0304] Embodiments regarding the operation of the above-described non-STR multi-link device can also be applied to the operation of a single-radio multi-link device. In addition, embodiments regarding the operation of a station that exchanges data with a station of a non-STR multi-link can also be applied to the operation of a station that exchanges data with a station of a single-radio multi-link device. For example, when it is determined that a transmission from a station to a single-radio multi-link device on a first link fails due to a transmission or reception by the single-radio multi-link device on a second link, the station may not increase the CW for channel access performed on the first link. Specifically, the station can apply the embodiments described by Figure 14 At this time, the method for determining that a transmission from a station to a single-radio multi-link device on a first link fails due to a transmission or reception by the single-radio multi-link device on a second link can be similar to the method for determining whether a transmission from a station to a station of a non-STR multi-link fails due to operation restrictions of the non-STR multi-link device.

[0305] Figure 35 Illustrates the connection between a single-radio multi-link device and an AP multi-link device according to an embodiment of the present disclosure.

[0306] In this specification, the PHY backend is collectively referred to as the digital processor of the physical layer, which includes a processor for encoding and decoding PPDUs. In addition, the PHY frontend is collectively referred to as the analog baseband circuit including the RF chain.

[0307] Multiple stations of a single radio multi-link device operate on different links. Multiple stations can share a PHY backend. In this case, when any one of the stations transmits a PPDU, the PHY backend is used for encoding the PPDU. Therefore, at this time, the remaining stations among the multiple stations cannot use the PHY backend. Therefore, a single radio multi-link device includes multiple stations operating on different links, but can only transmit or receive on one link at a time.

[0308] However, a single radio multi-link device can perform channel access on multiple links. Specifically, a single radio multi-link device can monitor multiple links. Therefore, a single radio multi-link device can perform channel access on multiple links. In this case, the monitoring can include channel sensing. In addition, the channel sensing can include at least one of clear channel assessment (CCA) and preamble detection (PD). Thereby, a single radio multi-link device can reduce the channel access delay. Specifically, even if the first station of the single radio multi-link device cannot perform channel access due to channel occupancy by other wireless communication devices on the first link, the second station of the single radio multi-link device will perform a backoff process on the second link.

[0309] To support these embodiments, the PHY frontend of a single radio multi-link device can independently support channel monitoring from the PHY backend. In addition, the PHY frontend of a single radio multi-link device can independently support decoding of the preamble of a PPDU from the PHY backend for PD. In addition, the PHY frontend of a single radio multi-link device can independently support reception of frames transmitted through a low MCS from the PHY backend. In this case, the frames transmitted through a low MCS can include at least one of an RTS frame and a MU-RTS frame. Therefore, the PHY frontend can include a MAC processor. In addition, through these embodiments, the processing capacity of the PHY backend can be concentrated on encoding and decoding data frames.

[0310] In Figure 35In an embodiment, the AP multi-link device includes a first AP (AP1) and a second AP (AP2). The single-radio multi-link device includes a first non-AP station (Non-AP STA1) and a second non-AP station (Non-AP STA2). The first AP (AP1) is connected to the first non-AP station (Non-AP STA1) on a first link (Link1), and the second AP (AP2) is connected to the second non-AP station (Non-AP STA2) on a second link (Link1). In the embodiment as described above, the first non-AP station (Non-AP STA1) and the second non-AP station (Non-AP STA2) each independently perform channel access using a PHY front end.

[0311] The single-radio multi-link device may use the RF chains of stations that do not participate in transmission or reception for MIMO transmission. Specifically, when the first station of the single-radio multi-link device obtains a channel access opportunity, the first station performs MIMO transmission using not only the RF chain used by the first station but also the RF chain used by the second station of the single-radio multi-link device. This is illustrated by Figure 36 as follows.

[0312] Figure 36 FIG. illustrates a single-radio multi-link device performing MIMO transmission according to an embodiment of the present disclosure.

[0313] In Figure 36 an embodiment, the first station (STA1) of the single-radio multi-link device operates on a first link (Link 1), and the second station (STA2) of the single-radio multi-link device operates on a second link. The first station (STA1) performs channel access on the first link (Link 1), and the second station (STA2) performs channel access on the second link (Link 2). When the first station (STA1) successfully accesses the channel on the first link (Link 1), the first station (STA1) performs 2x2 MIMO transmission on the first link (Link 1) using not only the RF chain used for channel access in the first link (Link 1) but also the RF chain used by the second station (STA2) for channel access in the second link (Link 2).

[0314] Thus, when the RF chain operating on the first link changes to operate on the second link, the single-radio multi-link device cannot monitor and access the channel on the first link. In addition, when the corresponding RF chain operates on the second link again, the single-radio multi-link device can access the channel on the second link after a certain period of time on hold. At this time, from the completion of the RF change until the predetermined time period, the channel access of the single-radio multi-link device on the second link is restricted. Specifically, from after the completion of the RF change until after a certain period of time on hold, the single-radio multi-link device can access the channel on the second link. At this time, the channel access may include a backoff process. In addition, the predetermined time period may be a predetermined time applicable when channel access needs to be restricted due to the time when channel monitoring cannot be performed. Specifically, this predetermined time may be NAVSyncdelay. Specifically, the single-radio multi-link device can perform the backoff process after waiting for the same time as NAVSyncdelay. This is because the probability that the single-radio multi-link device cannot detect the transmission of other wireless communication terminals operating on the second link due to the period when channel monitoring is not performed is high. In addition, when the link on which the RF chain operates changes, a delay time for starting the RF chain operation may be required. Therefore, the single-radio multi-link device can consider the delay time of the RF chain change for channel access. For this, it will be described through Figure 37 In addition, for ease of explanation, the action of changing the RF chain operating on any one link to operate on another link is referred to as the change of the RF chain. In addition, the change of the link can be shown as the change of the RF chain supported by the link. Specifically, the situation where multiple RF chains are supported for use on the first link and then one RF chain is supported for use, or where one RF chain is not supported for use on the second link and then one RF chain is supported for use, can be referred to as the change of the RF chain.

[0315] The station communicating with the single-radio multi-link device using MIMO can be a station of the multi-link device. Specifically, the station communicating with the single-radio multi-link device using MIMO can be an AP included in the multi-link device. Without special instructions in this specification, the station communicating with the single-radio multi-link device using MIMO can be a station included in the multi-link device. In this case, the station included in the multi-link device can be an AP. In addition, the operation of the station of the multi-link device described in this specification can be expressed as the operation of the multi-link device.

[0316] Figure 37 The figure illustrates the operation of a single-radio multi-link device performing channel access considering the delay time of the RF chain change according to an embodiment of the present disclosure.

[0317] A single-radio multi-link device may change the RF chain before the time point at which expected channel access is successful. Specifically, the single-radio multi-link device may change the RF chain before the time from the time point at which expected channel access is successful to the delay time set based on the RF chain change. For example, the single-radio multi-link device may change the RF chain at an earlier time point from the time point at which expected channel access is successful to the delay time of the RF chain change.

[0318] In Figure 37 an embodiment, the first station (STA1) of the single-radio multi-link device operates on the first link (Link 1), and the second station (STA2) of the single-radio multi-link device operates on the second link. The first station (STA1) performs channel access on the first link (Link1), and the second station (STA2) performs channel access on the second link (Link 2). When the first station (STA1) succeeds in channel access on the first link (Link 1), the first station (STA1) not only uses the RF chain for channel access on the first link (Link 1) but also uses the RF chain used by the second station (STA2) for channel access on the second link (Link 2) to perform 2x2 MIMO transmission on the first link (Link 1). In Figure 37 an (a) embodiment, the single-radio multi-link device changes the RF chain at an earlier time from the time point of expected channel access success (Expected Tx time) to the RF chain change delay time (RF chain switchingdelay).

[0319] In another specific embodiment, when the single-radio multi-link device starts transmitting after changing the RF chain, the single-radio multi-link device may start exchanging RTS frames / CTS frames. In another specific embodiment, when the single-radio multi-link device starts transmitting after changing the RF chain, the single-radio multi-link device may transmit a CTS-to-Self frame. In addition, the single-radio multi-link device may transmit a frame with a relatively short length instead of a CTS-to-Self frame. Through these embodiments, the single-radio multi-link device can obtain the time required until the RF chain change is completed. In addition, these embodiments are different from the previously described embodiments, and no problems will occur even if channel access is not successful at the predicted time point.

[0320] In Figure 37 a (b) embodiment, the single-radio multi-link device starts transmitting by exchanging RTS frames / CTS frames on the first link (Link 1).

[0321] Figure 38Illustrated are the Capability elements and Operation elements used by a single radio multi-link device according to an embodiment of the present disclosure.

[0322] A single radio multi-link device, such as Figures 36 to 37 shown, can perform transmission or reception by changing the RF chain. In addition, a single radio multi-link device can perform transmission or reception without changing the RF chain. A single radio multi-link device can choose whether to change the RF chain.

[0323] A single radio multi-link device can indicate in the MIMO Rx support subfield of the Operation element whether to use the RF chain of another link when performing MIMO communication in the corresponding link. For example, when a single radio multi-link device sets the value of the MIMO Rx support subfield of the Operation element to 1, the MIMO Rx support subfield indicates that MIMO reception can be performed using a number of spatial streams equal to or less than the value of the Max Rx spatial stream subfield of the Operation element. At this time, a station that performs MIMO transmission to the single radio multi-link device performs MIMO transmission using a number of spatial streams equal to or less than the value of the Max Rx spatial stream subfield of the Operation element. In a specific embodiment, the format of the Operation element can be as Figure 38 shown in (a) of

[0324] In addition, a single radio multi-link device can signal in the Capability element the time required for RF chain change. At this time, the switching delay subfield of the Capability element can indicate the time required for RF chain change. A station that performs MIMO transmission to the single radio multi-link device must consider the time required for RF chain change when performing MIMO transmission. Specifically, a station that performs MIMO transmission to the single radio multi-link device can start MIMO transmission after the time required for the single radio multi-link device to change the RF chain from the initial transmission. In a specific embodiment, the format of the Capability element can be as Figure 38 shown in (a) of

[0325] When a single-radio multi-link device performs transmission or reception on a first link, a station that is to transmit to the single-radio multi-link device may not be allowed to transmit on a link other than the first link. This is because the single-radio multi-link device cannot perform reception on a link other than the first link during the period of performing transmission or reception on the first link. Specifically, not only during the period of performing frame exchange in the first link, but also until a predetermined time has elapsed since the completion of the frame exchange sequence by the single-radio multi-link device, a station that is to transmit to the single-radio multi-link device may not be allowed to transmit on a link other than the first link. Specifically, the completion of the frame exchange sequence can be determined based on the reception or transmission of the last frame of the frame exchange sequence. At this time, the frame exchange sequence can be performed on a link where multiple RF chains are available. Specifically, MIMO can be used to perform the frame exchange sequence. The predetermined time can be determined based on the time required for the RF chain to change. Specifically, the predetermined time can be the time required for the RF chain to change.

[0326] In addition, a station that is to transmit to the single-radio multi-link device in the frame exchange sequence after the RF chain change can determine the format of the PPDU for the initial transmission in the frame exchange sequence based on the time required for the RF chain change of the single-radio multi-link device. In addition, in the first frame exchange sequence started after the RF chain change, a station that is to transmit to the single-radio multi-link device can determine the padding length required for the initial transmission of the PPDU in the frame exchange sequence based on the time required for the RF chain change of the single-radio multi-link device. In this case, the padding can be one of physical layer padding or MAC layer padding. Specifically, compared to the padding of a packet transmitted to a single-radio multi-link device with a relatively large time required for RF chain change, a station can set the padding of a packet transmitted to a single-radio multi-link device with a relatively short time required for RF chain change to be shorter.

[0327] Figure 39 The figure illustrates a single-radio multi-link device transmitting a PPDU using MIMO according to an embodiment of the present disclosure.

[0328] A station that is to perform MIMO transmission to the single-radio multi-link device can start the RTS frame / CTS frame exchange at the start of transmission after changing the RF chain. At this time, the RTS frame can ensure the time for the RF chain change and protect the subsequent frame exchange. If it is determined that the RF chain change has not been completed even after the RTS frame / CTS frame exchange, the station that is to perform MIMO transmission to the single-radio multi-link device may not perform MIMO transmission. At this time, the station that is to perform MIMO transmission to the single-radio multi-link device can perform transmission using a single spatial stream.

[0329] When a single-radio multi-link device performs transmission or reception on any one link, the single-radio multi-link device cannot perform transmission or reception on other links different from the corresponding link. Therefore, when a single-radio multi-link device performs transmission or reception on any one link, stations operating on links different from the corresponding link can be regarded as in a blind state. Therefore, when a single-radio multi-link device performs transmission or reception on any one link, the AP to transmit to the single-radio multi-link device may not transmit to stations operating on links different from the corresponding link. At this time, the AP to transmit to the single-radio multi-link device can stop transmitting to stations operating on links different from the corresponding link.

[0330] When a single-radio multi-link device performs transmission or reception on any one link, the AP that transmits to or stops transmitting to the station of the single-radio multi-link device may not increase the CW for the backoff process of transmission channel access. Thereafter, when the single-radio multi-link device attempts to transmit to the corresponding station again, it can obtain a backoff counter in the previously used CW. Thus, when the station that transmits to or stops transmitting to the station of the single-radio multi-link device meets a predetermined condition, it may not increase the CW for the backoff process of channel access. The predetermined condition can determine which station among the stations of a single multi-link device performs transmission or reception according to the above embodiments. Specifically, when the station that transmits the PPDU received by other stations including the station of the multi-link device is determined to be included in a single multi-link device, the station can determine that any one of the stations of the single multi-link device performs transmission. In this case, the station can determine the station that transmits the PPDU based on the identifier of the station of the PPDU indicated by the signaling field of the transmitted PPDU. At this time, the station can determine which one of the stations of the single multi-link device is indicated by the STA-ID in the user field of the HE PPDU. In addition, the station can determine which one of the stations of the single multi-link device is indicated by the STA-ID in the user field of the EHT PPDU. In addition, the station can determine which one of the stations of the single multi-link device is indicated by the TA field of the MAC frame included in the PPDU. The MAC frame can be any one of MSDU, MPDU, and A-MPDU. This is similar to the embodiments of the transmission applicable to non-STR multi-link devices described above. In addition, in the case of the channel access process applicable to EDCA, the above CW can indicate the CW of the AC for channel access. Figure 19 This is similar to the embodiments of the transmission applicable to non-STR multi-link devices described above. In addition, in the case of the channel access process applicable to EDCA, the above CW can indicate the CW of the AC for channel access.

[0331] In addition, when a transmission or reception by any one station of a single-radio multi-link device causes a transmission failure of other stations of the single-radio multi-link device, the station that performs the transmission to other stations of the single-radio multi-link device may not increment the retry counter. In this case, the retry counter may include at least one of a Long retry counter and a Short retry counter.

[0332] In addition, when a station transmits a MU PPDU to multiple stations including a station of a single-radio multi-link device, the embodiments regarding maintaining the size of the CW described above may not be applicable. Specifically, when a station transmits a MU PPDU to multiple stations including a station of a single-radio multi-link device and does not receive a response from any of the multiple stations, the station that transmits the MU PPDU may increment the size of the CW. At this time, the station that transmits the MU PPDU may increment the value of the CW to the second-largest value among the values that the CW value can have. When the value of the CW is the maximum value, the station that transmits the MU PPDU may maintain the value of the CW at the same value.

[0333] In Figure 39 In the embodiment, the single-radio multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link 2). In order to transmit to the first station (STA1) using MIMO, the station has a successful channel access on the first link (Link1) and transmits an RTS frame to the first station (STA1). The first station (STA1) transmits a CTS frame in response to the RTS frame. After the RF chain change of the single-radio multi-link device is completed, the PPDU is received using 2x2 MIMO. After the first station (STA1) receives the PPDU, the single-radio multi-link device changes the RF chain, and the second station (STA2) starts channel access on the second link (Link 2) after the same amount of time as the NAV Sync delay with the RF chain change pending.

[0334] <Null data packet transmission process for a single-radio multi-link device>

[0335] As described above, a single-radio multi-link device may perform MIMO by changing the link on which the RF chain operates. When the link on which the RF chain operates changes, it is necessary to learn the RF characteristics of the changed link before MIMO communication.

[0336] Since the channel characteristics of the RF-chain have not yet been formed, it may not be possible to use closed-loop multi-antenna technology (beamforming). Therefore, channel estimation may be required. Specifically, a single radio multi-link device can perform channel estimation using the NDP sounding protocol. In an explicit NDP sounding sequence, the beamformer transmits the NDP after transmitting the NDP announcement (NDPA). At this time, the interval between the NDPA and the NDP is the SIFS. A station that receives the NDPA, if the STA user information list field of the NDPA indicates the station, then the station will feedback the channel state information (CSI) measured when receiving the NDP after receiving the NDP to the beamformer.

[0337] At this time, before performing the NDP sounding protocol, an RTS frame / CTS frame exchange can be performed. Specifically, a single radio multi-link device and a station that is about to start the NDP sounding protocol can transmit an RTS frame before transmitting the NDPA frame. For the convenience of explanation, the single radio multi-link device and the station that is about to start the NDP sounding protocol are referred to as the NDP sounding protocol initiating station. Through the above embodiments, the NDP sounding protocol initiating station can protect the NDP sounding sequence. In addition, thereby, the time required to change the RF chain can be ensured. In addition, the NDP sounding protocol initiating station can perform the exchange process of the MU-RTS frame / CTS frame to replace the RTS frame / CTS frame exchange process. In addition, the NDP sounding protocol initiating station can perform the exchange of a trigger frame of a different type from the MU-RTS frame and a response to the trigger frame to replace the MU-RTS frame / CTS frame exchange process. In addition, in this embodiment, the NDP sounding protocol initiating station can transmit the MU-RTS frame, a trigger frame of a different type from the MU-RTS frame, and the NDPA frame in a predetermined PPDU format. Specifically, the predetermined PPDU format can be at least one of a non-HT format and an HT format. In addition, the NDP sounding protocol initiating station can transmit the MU-RTS frame, a trigger frame of a different type from the MU-RTS frame, and the NDPA frame at a predetermined data rate or a lower data rate.

[0338] The NDP probe protocol initiator can adjust the length of the NDP probe sequence based on the time required for RF chain change. When the NDP probe protocol initiator exchanges the NDP probe sequence with a single-radio multi-link device with a longer time required for RF chain change compared to exchanging the NDP probe sequence with a single-radio multi-link device with a shorter time required for RF chain change, a longer NDP probe sequence can be used. At this time, the NDP probe protocol initiator can omit a part of the NDP probe sequence to adjust the length of the NDP probe sequence. In addition, the NDP probe protocol initiator can adjust the length of the NDP probe sequence by adjusting the padding of the frames exchanged in the NDP probe sequence. In addition, the NDP probe protocol initiator can transmit additional frames in the NDP probe sequence to adjust the length of the NDP probe sequence. At this time, the padding can be physical layer padding. In addition, the padding can be MAC layer padding. Therefore, in the embodiments described later, the padding can be physical layer padding or MAC layer padding.

[0339] In addition, when the NDP probe protocol initiator executes the NDP probe protocol with multiple single-radio multi-link devices, the NDP probe protocol initiator can adjust the length of the NDP probe sequence based on the longest time required for RF chain change among the multiple single-radio multi-link devices. It will be described through Figures 40 to 42 a method for adjusting the length of the NDP probe sequence.

[0340] Figure 40 FIG. illustrates the NDP probe process performed by a station and a single-radio multi-link device according to an embodiment of the present disclosure.

[0341] As described above, the NDP probe protocol initiator can adjust the length of the NDP probe sequence by adjusting the padding of the frames exchanged in the NDP probe sequence. If the NDP probe sequence includes RTS frame / CTS frame exchange, the NDP probe protocol initiator can adjust the length of the NDP probe sequence by inserting padding into the RTS frame. Specifically, when the NDP probe protocol initiator determines that the RF chain change cannot be completed even after the RTS frame / CTS frame exchange, the NDP probe protocol initiator can insert padding into the RTS frame.

[0342] In another specific embodiment, if the NDP probe protocol initiator determines that the RF chain change cannot be completed even after the RTS frame / CTS frame exchange, the NDP probe protocol initiator can transmit a MU-RTS frame instead of the RTS frame. In this case, the NDP probe protocol initiator can insert padding into the MU-RTS frame.

[0343] In the above embodiments, after the time elapsed from the time point when the NDP probe protocol initiating station receives the RTS frame from the single radio multi-link device until the time of the length of the CTS frame plus 2X SIFS, the result of whether the RF chain change is completed is used to determine whether the RF chain change is not completed after the RTS frame / CTS frame exchange. In addition, the RTS reception completion time point may be one of the transmission start time point of the PPDU including the RTS frame, the physical layer header transmission completion time point of the PPDU of the RTS frame, the transmission completion time point of the PPDU including the RTS frame, the transmission completion time point of the RTS frame or the A-MPDU including the RTS frame. In addition, in the above embodiments where the MU-RTS frame is used instead of the RTS frame, the MU-RTS frame may be applied instead of the RTS frame. Figure 40 The (a) of Figure 40 shows the exchange of NDPA frames, NDP frames and feedback frames after the RTS frame / CTS frame exchange according to the above embodiments. At this time, the NDP probe protocol initiating station performs MIMO transmission based on the received feedback frame.

[0344] In addition, the NDP probe protocol initiating station may omit the NDPA frame transmission in the NDP probe sequence. At this time, the NDP probe protocol initiating station and the single radio multi-link device may negotiate to execute the NDP probe protocol without the transmission of the NDPA frame. Therefore, the station of the single radio multi-link device may wait for the NDP reception without receiving the NAPA frame. Specifically, the station of the single radio multi-link device may use the capability element to signal the reception of the NDP without receiving the NDPA frame. In a specific embodiment, the station of the single radio multi-link device may signal the reception of the NDP frame by setting the NDPA compression support subfield of the capability element to 1 and without receiving the NDPA frame. In addition, the station of the radio multi-link device may signal the inability to receive the NDP frame by setting the NDPA compression support subfield of the capability element to 0 and without receiving the NDPA frame. The NDP probe protocol initiating station may determine whether to omit the NDPA frame transmission. In this case, the NDP probe protocol initiating station may omit the NDPA frame transmission for performing the NDP probe sequence for the single radio multi-link device that can receive the NDP frame without receiving the NDPA frame. In addition, the above embodiments of omitting the NDPA frame transmission in the NDP probe sequence are only applicable to the case where the NDP probe protocol initiating station transmits the NDP to one station. In this case, when the NDP probe protocol initiating station transmits the NDP to multiple stations, the transmission of the NDPA frame cannot be omitted. Figure 40 The (b) of Figure 40 shows the case of exchanging NDP frames and feedback frames without NDPA frame exchange after the RTS frame / CTS frame exchange according to the above embodiments. At this time, the NDP probe protocol initiating station performs MIMO transmission based on the received feedback frame.

[0345] In the above embodiments, since the NDP detection sequence includes the NDPA frame, the NDP frame, and the control frame exchange before the feedback frame exchange, excessive overhead may occur. In addition, even if the NDPA transmission is omitted, excessive overhead may still be generated. To reduce the excessive overhead, an implicit feedback beamforming detection sequence may be performed. This will be described by Figure 41 the following.

[0346] Figure 41 FIG. illustrates a station and a single radio multi-link device performing a feedback beamforming detection sequence according to an embodiment of the present disclosure.

[0347] The frame exchange initiating station that initiates the frame exchange can not only omit the NDPA frame transmission, but also omit the NDP frame transmission and the feedback frame transmission. At this time, only the frame exchange initiating station can receive control frames, such as RTS frames, MU-RTS frames, PPDUs including responses to trigger frames of a different type from the MU-RTS frame, and can measure the channel state. The frame exchange initiating station can obtain a steering matrix for MIMO transmission based on the measured channel state. Specifically, the frame exchange initiating station can obtain the steering matrix based on the measured channel state. The frame exchange initiating station can perform MIMO transmission using the obtained steering matrix.

[0348] In these embodiments, the frame exchange initiating station can insert padding into the control frame based on the time required for RF chain change as described above. Specifically, the frame exchange initiating station can insert padding into the control frame based on the value obtained by subtracting the SIFS from the time required for RF chain change.

[0349] In addition, the frame exchange initiating station can transmit a QoS data frame instead of the control frame. At this time, as a response to the QoS data frame, the single radio multi-link device can transmit an Ack frame or a Block Ack frame.

[0350] In addition, in the above embodiments, the frame exchange initiating station can set the bits of the training request (TRQ) of the control frame and the QoS data frame to 1.

[0351] In addition, in the above embodiments, for a control frame such as the MU-RTS frame, even in a control frame that can set multiple stations as receivers, the receiver of the control frame can be set to one station.

[0352] In Figure 41In the embodiment of (a), the frame exchange initiating station sets the TRQ field to 1 and transmits a MU-RTS frame. The frame exchange initiating station transmits a PPDU including the MU-RTS frame, and the frame exchange initiating station receives a PPDU including a CTS frame as a response to the MU-RTS frame and measures the channel state. The frame exchange initiating station obtains a steering matrix based on the obtained channel state and performs MIMO transmission using the obtained steering matrix. In Figure 41 In the embodiment of (b), the frame exchange initiating station transmits an RTS frame instead of the MU-RTS frame. This may be the case where the time required for the RF chain is shorter than the SIFS. Thereafter, the frame exchange initiating station and the stations of the single radio multi-link device operate Figure 41 in the same manner as in the embodiment of (a). However, in Figure 41 the embodiment of (b), the station of the single radio multi-link device transmits a BA frame through single input single output (SISO).

[0353] In the frame exchange sequence immediately executed after changing the RF chain, the last frame exchange can be performed through SISO (1x1). Specifically, the station of the single radio multi-link device can transmit the last frame of the frame exchange sequence immediately executed after changing the RF chain in SISO (1x1). In addition, when there is MIMO transmission or no frame to receive in the frame exchange sequence immediately executed after changing the RF chain, the station of the single radio multi-link device can change the RF chain. Specifically, the station of the single radio multi-link device can start changing the RF chain before transmitting the last frame of the frame exchange sequence immediately executed after changing the RF chain.

[0354] Figure 42 The figure illustrates a station and a single radio multi-link device performing an NDP sounding process according to an embodiment of the present disclosure.

[0355] The NDP sounding protocol initiating station can determine the MIMO transmission start time point based on the time required for the RF chain change of the single radio multi-link device. Specifically, the NDP sounding protocol initiating station can delay the MIMO transmission start time point until the time point when the RF chain change of the single radio multi-link device is completed. For example, if the RF chain change is not completed during the execution of a control frame / response frame to the control frame, such as an RTS frame / CTS frame or a MU-RTS frame / CTS frame exchange, the NDP sounding protocol initiating station can delay the MIMO transmission start time point. Specifically, the NDP sounding protocol initiating station can use the first PPDU transmitted after transmitting the control frame / response to the control frame through SISO.

[0356] Thus, when the RF chain change is not completed, MIMO transmission of the NDP probe protocol initiating station may not be allowed. In addition, the above explicit and implicit NDP probe protocols may also not be allowed before the RF chain change is completed.

[0357] In addition, the NDP probe protocol initiating station can determine whether the RF chain change is completed during the exchange of control frames / response frames to control frames based on the time required for the RF chain change indicated by the capability element of the single radio multi-link device transmission.

[0358] When the single radio multi-link device uses SISO transmission, the station that executes the frame exchange sequence in the link that supports the use of multiple RF chains can use SISO to transmit the remaining frames in the corresponding frame exchange sequence. For ease of explanation, in the description related to this embodiment, the station that executes the frame exchange sequence in the link that supports the use of multiple RF chains is referred to as the frame exchange sequence execution station. That is, when the single radio multi-link device uses SISO for transmission, the frame exchange sequence execution station may not be allowed to use MIMO to transmit the remaining frames in the corresponding frame exchange sequence. Specifically, when the single radio multi-link device uses SISO to execute the ACK for the transmission to the frame exchange sequence execution station, the frame exchange sequence execution station can use SISO to transmit the remaining frames in the corresponding frame exchange sequence. In this case, the ACK can include an ACK frame and a BA frame. Therefore, when the single radio multi-link device uses SISO to transmit the ACK to the frame exchange sequence execution station, the frame exchange sequence execution station cannot use MIMO to transmit the remaining frames in the corresponding frame exchange sequence.

[0359] In Figure 42 In the embodiments of (a) and 42(b), even during the exchange of the RTS frame and the CTS frame, the RF chain change of the single radio multi-link device is not completed. Therefore, in Figure 42 In the embodiment of (a), after the RTS frame and the CTS frame are exchanged, even the transmission of the PPDU and the BA frame is also performed using SISO. When the NDP probe protocol initiating station receives the ACK frame, it determines that the RF chain change is completed. At this time, the NDP probe protocol initiating station initiates the probe protocol using MIMO (2x2).

[0360] In addition, in Figure 42In the embodiment of (b), after the RTS frame and the CTS frame are exchanged, even the transmission of the PPDU is performed using SISO. Since the RF chain change is completed after receiving the PPDU, the first station (STA1) of the single radio multi-link device uses MIMO (2x2) to transmit the BA frame. Since the first station (STA1) of the single radio multi-link device uses MIMO (2x2) to transmit the BA frame, the NDP probe protocol initiating station determines that MIMO (2x2) transmission is allowed. Therefore, after the NDP probe protocol initiating station receives the BA frame transmitted using MIMO (2x2), the NDP probe protocol initiating station uses MIMO (2x2) to transmit the PPDU.

[0361] As described above, the present invention has been illustrated by taking wireless LAN communication as an example, but the present invention is not limited thereto and can be similarly applied to other communication systems such as cellular communication. Further, although the methods, apparatuses, and systems of the present invention have been illustrated by specific embodiments. However, some or all of the constituent elements and operations of the present invention can be implemented using a computer system having a general hardware architecture.

[0362] The features, structures, effects, etc. described in the above embodiments are included in at least one embodiment of the present invention and are not limited to one embodiment. Further, the features, structures, effects, etc. described in each embodiment can be combined or modified by those skilled in the art of the embodiments with respect to other embodiments. Therefore, the content related to these combinations and changes should be construed as being included within the scope of the present invention.

[0363] Although the above has been described in conjunction with embodiments, these are only examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will know that various modifications and applications not illustrated above can be made without departing from the essential features of the present embodiment. For example, each component specifically shown in the embodiment can be modified and implemented. And the differences related to these modifications and applications should be construed as being included within the scope of the present invention defined by the appended claims.

Claims

1. An access point AP multi-link device, including a first AP and a second AP, and communicating with a single-radio non-AP multi-link device including a first non-AP station and a second non-AP station, wherein, The first AP and the first non-AP station operate on a first link, and the second AP and the second non-AP station operate on a second link. When the single-radio non-AP multi-link device operates in a predetermined operation mode, when the other of the first non-AP station and the second non-AP station performs frame exchange, the single-radio non-AP multi-link device does not support the transmission or reception of one of the first non-AP station and the second non-AP station. The AP multi-link device includes: A transceiver; and A processor, wherein the processor is configured to not perform transmission to the second non-AP station not only when performing the frame exchange sequence of the first non-AP station but also for a first predetermined time interval starting from the completion of the frame exchange sequence of the first non-AP station, and after the first predetermined time interval, perform transmission to the second non-AP station of the single-radio non-AP multi-link device, wherein the completion of the frame exchange sequence is determined based on the reception or transmission of the last frame of the frame exchange sequence, wherein the first predetermined time interval is applied based on the radio frequency (RF) chain switching time interval of the single-radio non-AP multi-link device, wherein the RF chain switching time interval is a time interval including the delay required to start the operation of the RF chain after switching the RF chain, and wherein the element including the delay required to start the operation of the RF chain after switching the RF chain is signaled by the single-radio non-AP multi-link device.

2. The AP multi-link device according to claim 1, wherein, The processor sends a control frame to the first non-AP station of the single-radio non-AP multi-link device, receives a response to the control frame from the first non-AP station of the single-radio non-AP multi-link device; and starts an empty data packet (NDP) sounding sequence for the first non-AP station of the single-radio non-AP multi-link device, wherein the control frame is a MU-RTS frame.

3. The AP multi-link device according to claim 2, wherein, The processor sends the control frame in a predetermined physical layer protocol data unit (PPDU) format.

4. The AP multi-link device according to claim 3, wherein The predetermined PPDU format is a non-high throughput (HT) format.

5. The AP multi-link device according to claim 2, wherein, The processor sends the control frame at a data rate equal to or lower than a predetermined data rate.

6. A single-radio non-access point AP multi-link device includes a first non-AP station and a second non-AP station, and communicates with an AP multi-link device including a first AP and a second AP, wherein, The first non-AP station and the first AP operate on a first link, and the second non-AP station and the second AP operate on a second link. When the single-radio non-AP multi-link device operates in a predetermined operation mode, when the other of the first non-AP station and the second non-AP station performs frame exchange, the single-radio non-AP multi-link device does not support the transmission or reception of one of the first non-AP station and the second non-AP station. The single-radio non-AP multi-link device includes: A transceiver; and A processor, Wherein, the processor is configured to: when the link of the radio frequency (RF) chain on which the single-radio non-AP multi-link device operates switches from the first link to the second link, and when the link of the RF chain on which the RF chain operates switches from the second link back to the first link, delay channel access for a predetermined time interval before performing transmission to the first AP on the first link. Wherein, the first predetermined time interval is applied based on the RF chain switching time interval of the single-radio non-AP multi-link device, and wherein, the RF chain switching time interval is a time interval including the delay required to start the operation of the RF chain after switching the RF chain.

7. A method for operating an access point (AP) multi-link device, the AP multi-link device including a first AP and a second AP and communicating with a single-radio non-AP multi-link device including a first non-AP station and a second non-AP station, wherein, The first AP and the first non-AP station operate on the first link, and the second AP and the second non-AP station operate on the second link. Wherein, when the single-radio non-AP multi-link device operates in a predetermined operation mode, when the other of the first non-AP station and the second non-AP station performs frame exchange, the single-radio non-AP multi-link device does not support the transmission or reception of one of the first non-AP station and the second non-AP station. The method includes: Not performing transmission to the second non-AP station not only when performing the frame exchange sequence of the first non-AP station but also for a first predetermined time interval starting from the completion of the frame exchange sequence of the first non-AP station. After the first predetermined time interval, perform transmission to the second non-AP station of the single-radio non-AP multi-link device. Wherein, the completion of the frame exchange sequence is determined based on the reception or transmission of the last frame of the frame exchange sequence. Wherein, the first predetermined time interval is applied based on the RF chain switching time interval of the single-radio non-AP multi-link device. Wherein, the RF chain switching time interval is a time interval including the delay required to start the operation of the RF chain after switching the RF chain, and wherein, the element including the delay required to start the operation of the RF chain after switching the RF chain is signaled by the single-radio non-AP multi-link device.

8. The method according to claim 7, the method further includes: Sending a control frame to the first non-AP station of the single-radio non-AP multi-link device. Receiving a response to the control frame from the first non-AP station of the single-radio non-AP multi-link device; And Starting an empty data packet (NDP) sounding sequence for the first non-AP station of the single-radio non-AP multi-link device. Wherein, the control frame is a MU-RTS frame.

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