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

Abstract

This provides a wireless communication terminal that communicates wirelessly with a base wireless communication terminal. [Solution] The wireless communication terminal includes a transceiver and a processor. The processor transmits low-latency traffic configured as traffic for low-latency transmission or a response to the low-latency traffic within a limited service period, and transmissions other than the transmission of the low-latency traffic and the transmission of responses to the low-latency traffic are restricted within the limited service period.

Description

Technical Field

[0001] The present invention relates to a wireless communication method using a limited traveling wave tube (TWT) and a wireless communication terminal using the same.

Background Art

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

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

[0004] Furthermore, IEEE 802.11n is a technical standard established to overcome the limitations in communication speed that had been pointed out as a vulnerability in wireless LANs. The purpose of IEEE 802.11n is to increase network speed and reliability and extend the operating range of wireless networks. Specifically, IEEE 802.11n supports high throughput (HT) with a data processing speed of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas at both the transmitter and receiver ends to minimize transmission errors and optimize data speed. In addition, this standard uses a coding method that transmits multiple duplicate copies to improve data reliability.

[0005] As the proliferation of wireless LANs accelerates and the applications using them diversify, there is a growing need for new wireless LAN systems that can support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n. Among these, IEEE 802.11ac supports a wide bandwidth (80MHz to 160MHz) at the 5GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5GHz band, early 11ac chipsets are expected to support operation in the 2.4GHz band for backward compatibility with older 2.4GHz band products. Theoretically, this standard allows for a minimum wireless LAN speed of 1Gbps and a maximum single-link speed of 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Another method for transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz band is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, making it suitable for streaming large amounts of data and high-bitrate video such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage of being difficult to pass through obstacles, limiting its use to devices in short-range spaces.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is nearing completion as a wireless LAN standard for 802.11ac and 802.11ad and beyond, to provide highly efficient and high-performance wireless LAN communication technology in high-density environments where access points (APs) and terminals are densely packed. In an 802.11ax-based wireless LAN environment, it is necessary to provide highly frequency-efficient communication indoors and outdoors in the presence of high-density stations and APs (Access Points), and various technologies have been developed to realize this.

[0007] Furthermore, in order to support new multimedia applications such as high-definition video and real-time games, development has begun on a new wireless LAN standard to increase the maximum transmission speed. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is being developed with the goal of supporting a maximum transmission rate of 30 Gbps in the 2.4 / 5 / 6 GHz band through wider bandwidth, increased spatial streams, and multiple AP coordination. [Overview of the project] [Problems that the invention aims to solve]

[0008] One embodiment of the present invention aims to provide a wireless communication method using multilink and a wireless communication terminal using the same. [Means for solving the problem]

[0009] A wireless communication terminal that communicates wirelessly with a base wireless communication terminal according to one embodiment of the present invention includes a transmitting / receiving unit and a processor. The processor transmits low-latency traffic configured as traffic for low-latency transmission or a response to the low-latency traffic within a limited service period. During this limited service period, the transmission of the low-latency traffic and transmissions other than the transmission of the low-latency traffic are restricted.

[0010] The processor may terminate the TXOP for sending traffic other than the low-latency traffic before the start of the restricted service period.

[0011] The processor may obtain a random integer within the competition window, perform channel access based on the obtained random integer, complete channel access before the start of the restricted service period, and, if it determines that frame exchange cannot be completed before the start of the restricted service period and abandons transmission, perform channel access again.

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

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

[0014] A quiet section is set corresponding to the restricted service period, and not all transmissions are permitted within the quiet section. The processor does not need to transmit the low-latency traffic or a response to the low-latency traffic within the restricted service period, ignoring the quiet section corresponding to the restricted service period, and does not need to transmit CF End frames within the restricted service period.

[0015] A quiet section is set corresponding to the restricted service period, and not all transmissions are permitted during the quiet section. In this case, the processor decides whether to ignore the quiet section based on the start time of the restricted service period and the start time of the quiet section, and if it decides to ignore the quiet section, it can ignore the quiet section corresponding to the restricted service period and transmit the low-latency traffic or a response to the low-latency traffic within the restricted service period.

[0016] The processor may ignore the quiet section if it satisfies the conditions determined based on the start of the restricted service period and the start of the quiet section, and may not perform any transmissions if it does not satisfy the conditions determined based on the start of the restricted service period and the start of the quiet section.

[0017] The conditions determined based on the start time of the restricted service period and the start time of the quiet section may be such that the start time of the quiet section and the start time of the restricted service period are within a predetermined time.

[0018] An embodiment of the present invention describes the operation method of a wireless communication terminal that communicates wirelessly with a base wireless communication terminal, which includes the step of transmitting low-latency traffic set as traffic for low-latency transmission or a response to said low-latency traffic within a limited service period. During this time, transmissions other than the transmission of said low-latency traffic and the transmission of responses to said low-latency traffic may be restricted within the limited service period.

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

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

[0021] The step of performing the channel access again may include the step of maintaining the size of the conflict window used for the completed channel access when the wireless communication terminal performs the channel access again.

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

[0023] A quiet section is set corresponding to the restricted service period, and not all transmissions are permitted within the quiet section. In this case, the step of transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period may include the step of transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period, ignoring the quiet section corresponding to the restricted service period; and the step of not transmitting a CF End frame within the restricted service period.

[0024] A quiet section is set corresponding to the restricted service period, and not all transmissions are permitted within the quiet section. In this case, the step of transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period may include the step of deciding whether or not to ignore the quiet section based on the start time of the restricted service period and the start time of the quiet section; and, if it is decided to ignore the quiet section, the step of transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period, ignoring the quiet section corresponding to the restricted service period.

[0025] The step of determining whether to ignore a quiet section based on the start of the restricted service period and the start of the quiet section may include: ignoring the quiet section if the conditions determined based on the start of the restricted service period and the start of the quiet section are met; and not making any transmissions if the conditions determined based on the start of the restricted service period and the start of the quiet section are not met.

[0026] The condition determined based on the start time of the restricted service period and the start time of the quiet period may be that the start time of the quiet period and the start time of the service period of the TWT are within a specified time in advance.

Effect of the Invention

[0027] One embodiment of the present invention provides a wireless communication method for providing a restricted TWT function and a wireless communication terminal using the same.

Brief Description of the Drawings

[0028] [Figure 1] FIG. shows a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. shows a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. shows a configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. shows a configuration of an access point according to an embodiment of the present invention. [Figure 5] FIG. schematically shows a process in which a STA sets a link with an AP. [Figure 6] FIG. shows a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] FIG. shows an example of PPDU (PLCP Protocol Data Unit) formats for different standard generations. [Figure 8] FIG. shows an example of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats according to an embodiment of the present invention and a method for instructing the same. [Figure 9] FIG. shows a multi-link device according to an embodiment of the present invention. [Figure 10]The embodiments of the present invention demonstrate that transmissions on different links occur simultaneously in multilink operation. [Figure 11] This illustrates the operation of a multilink device when the link is modified according to one embodiment of the present invention. [Figure 12] One embodiment of the present invention demonstrates that when one station of a non-STR multilink device is receiving, channel access for other stations of the non-STR multilink device is prohibited. [Figure 13] An embodiment of the present invention demonstrates the operation of releasing the channel access ban when it is confirmed that the intended recipient of the PPDU received by a station in a non-STR multilink device is not the station. [Figure 14] This example demonstrates that a station according to an embodiment of the present invention performs channel access after the channel access ban has been lifted. [Figure 15] This describes the operation of a station according to one embodiment of the present invention, which transmits after the channel access ban has been lifted. [Figure 16] An embodiment of the present invention demonstrates a transmission performed based on the status of a station in a non-STR multilink device. [Figure 17] This indicates a situation in which interference or collision may occur between links. [Figure 18] This example demonstrates that a multilink device according to an embodiment of the present invention abandons receiving a PPDU that is being received on the first link of a non-STR multilink pair and attempts to transmit a PPDU on the second link of the non-STR multilink pair. [Figure 19] This indicates a situation where a multilink device cannot exchange RTS / CTS frames in a non-STR multilink pair to transmit low-latency traffic. [Figure 20] This demonstrates that a multilink device according to an embodiment of the present invention determines whether or not to transmit traffic based on traffic priority before frame exchange. [Figure 21]The Frame Control field format of an RTS frame according to an embodiment of the present invention is shown. [Figure 22] The User Info field format of a MU-RTS frame according to an embodiment of the present invention is shown. [Figure 23] This indicates that a station that received an RTS frame requests the AP that sent the RTS frame according to an embodiment of the present invention to transfer the transmission opportunity. [Figure 24] An embodiment of the present invention illustrates the format of the Frame Control field in a CTS frame that includes a request for priority processing of low-latency traffic. [Figure 25] An embodiment of the present invention demonstrates a method for setting up a broadcast TWT between an AP and a station. [Figure 26] This embodiment of the present invention demonstrates that AP sets a quiet interval. [Figure 27] An embodiment of the present invention describes a method for setting a TXOP (Time-Controlled Operation) that takes into account a limited service period for a station. [Figure 28] This embodiment of the present invention demonstrates that a station performs the channel access procedure again, taking into account a limited service period. [Figure 29] An embodiment of the present invention demonstrates an operation in which an AP terminates a limited service period early. [Figure 30] This embodiment of the present invention demonstrates that a multilink device transmits over a non-SRT link pair. [Figure 31] This shows a frame replacement starting from a non-AP station multilink device to which the embodiments of the present invention are not applied. [Figure 32] This embodiment of the present invention demonstrates frame replacement starting from a non-AP station multilink device. [Figure 33] An embodiment of the present invention demonstrates that when a multilink device transmits a message requesting an immediate response on the first link of a non-STR link pair, it transmits a message on the second link that does not request an immediate response. [Figure 34] An embodiment of the present invention demonstrates the operation in which a multilink device performs UL OFDMA transmission on the first link of a non-STR link pair, while simultaneously transmitting on the second link. [Figure 35] An embodiment of the present invention shows a case in which a single link pair is determined to be either a non-STR link pair or an STR link pair depending on the transmission direction. [Modes for carrying out the invention]

[0029] The terminology used herein has been selected to the greatest extent possible from currently widely used general terms, taking into account the function of the present invention; however, this may differ depending on the intent, conventions, or emergence of new technologies of the articulate persons in the relevant field. In addition, in certain cases, the applicant has arbitrarily selected some terms, and in such cases, the meaning of these terms will be described in the relevant section of the invention description. Therefore, it should be made clear that the terms used herein are not merely names of terms, but should be interpreted based on the substantive meaning of the terms and the content of this specification as a whole.

[0030] Throughout the specification, when one component is described as being "connected" to another, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" with other components in between. Furthermore, when a component is described as "containing" a particular component, this means, unless otherwise stated, that it may contain other components rather than excluding them. In addition, limitations such as "greater than or equal to" or "less than or equal to" a specific critical value may be appropriately replaced by "greater than" or "less than" depending on the embodiment.

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

[0032] Figure 1 shows a wireless LAN system according to one embodiment of the present invention.

[0033] A wireless LAN system includes one or more Basic Service Sets (BSS), where a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

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

[0035] A Station (STA) is any device that includes Medium Access Control (MAC) and a Physical Layer interface to a wireless medium in accordance with the IEEE 802.11 standard, and in a broad sense includes not only non-AP stations but also all access points (APs). In this specification, "terminal" is used to refer to non-APs, APs, or both. A station for wireless communication includes a processor and a communication unit, and depending on the embodiment, further includes a user interface unit and a display unit, etc. The processor generates frames to be transmitted over the wireless network or processes frames received over the wireless network, and performs various other processing for controlling the station. The communication unit is functionally connected to the processor and sends and receives frames over the wireless network for the station. In this invention, "terminal" is used as a term that includes user equipment (UE).

[0036] An Access Point (AP) is an individual device that provides connectivity to a distribution system (DS) via a wireless medium for stations associated with it. In infrastructure BSS, communication between non-AP stations is generally conducted via APs, however, direct communication is possible between non-AP stations if a direct link is configured. In this invention, AP is used as a concept that includes PCP (Personal BSS Coordination Point), but in a broader sense, it includes all concepts such as central controllers, base stations (BS), node B, BTS (Base Transceiver System), or site controllers. In this invention, AP is also referred to as a base wireless communication terminal, but in a broader sense, base wireless communication terminal is used as a term that includes APs, base stations, eNBs (eNodeBs), and transmission points (TPs). Furthermore, base wireless communication terminals include various forms of wireless communication terminals that allocate and schedule communication medium resources in communication with multiple wireless communication terminals.

[0037] Multiple infrastructure BSSs are connected to each other via a distribution system DS. In this case, multiple BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0038] Figure 2 shows an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of Figure 2, redundant explanations are omitted for parts that are the same as or corresponding to the embodiment of Figure 1.

[0039] As shown in Figure 2, BSS3 is an independent BSS and does not include APs, so all stations (STA6, STA7) are not connected to APs. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to one another.

[0040] Figure 3 is a block diagram showing the configuration of station 100 according to one embodiment of the present invention. As shown, station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0041] First, the communication unit 120 transmits and receives wireless signals such as wireless LAN packets and may be incorporated into the station 100 or provided externally. According to one embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules of different frequency bands such as 2.4GHz, 5GHz, 6GHz, and 60GHz. According to one embodiment, the station 100 may include a communication module using a frequency band of 7.125GHz or higher and a communication module using a frequency band of 7.125GHz or lower. Each communication module can perform wireless communication with an AP or external station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the station 100, the communication unit 120 may operate only one communication module at a time or operate multiple communication modules together simultaneously. When the station 100 includes multiple communication modules, each communication module may be provided in an independent form, or the multiple modules may be integrated as a single chip. In embodiments of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0042] Next, the user interface 140 includes various forms of input / output means provided in the station 100. In other words, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. The user interface unit 140 also outputs based on instructions from the processor 110 using various output means.

[0043] Next, the display unit 150 outputs an image to the display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or user interfaces based on control instructions from the processor 110. The memory 160 stores control programs used by the station 100 and various data associated with them. Such control programs include connection programs necessary for the station 100 to connect with APs or external stations.

[0044] The processor 110 of the present invention executes various instructions or programs and processes data within the station 100. The processor 110 also controls each unit of the station 100 and controls the transmission and reception of data between units. According to an embodiment of the present invention, the processor 110 executes a program for connection with the AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information regarding the priority conditions of the station 100 contained in the communication setup message and requests a connection to the AP based on the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling a part of the station 100's configuration, such as the communication unit 120. In other words, the processor 110 may be a modem or a modulator and / or demodulator that modulates and demodulates the wireless signals transmitted and received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. A detailed embodiment relating to this will be described later.

[0045] The station 100 shown in Figure 3 is a block diagram according to one embodiment of the present invention, and the separately shown blocks represent logically distinguished elements of the device. Therefore, the above-described elements of the device are mounted on one chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated and implemented on a single chip, or they may be implemented on separate chips. Furthermore, in the embodiment of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0046] Figure 4 is a block diagram showing the configuration of AP200 according to one embodiment of the present invention. As shown, AP200 according to an embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In Figure 4, redundant explanations are omitted for parts of the AP200 configuration that are the same as or correspond to the configuration of station 100 in Figure 3.

[0047] Referring to Figure 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of Figure 3, the communication unit 220 of the AP 200 can also include a plurality of communication modules using different frequency bands. That is, the AP 200 according to an embodiment of the present invention can include two or more communication modules using different frequency bands, for example, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can communicate wirelessly with the station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the AP 200, the communication unit 220 can operate only one communication module at a time or operate multiple communication modules together simultaneously. In an embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0048] Next, the memory 260 stores the control program used by the AP200 and various data associated with it. Such a control program includes a connection program that manages station connections. The processor 210 controls each unit of the AP200 and controls the transmission and reception of data between units. According to one embodiment of the present invention, the processor 210 executes the program for connecting with stations stored in the memory 260 and transmits a communication setting message to one or more stations. In this case, the communication setting message includes information regarding the connection priority conditions of each station. The processor 210 also performs connection settings in response to connection requests from stations. According to one embodiment, the processor 210 is a modem or modulation / demodulation unit that modulates and demodulates the wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations of wireless signal transmission and reception of the AP200 according to the embodiment of the present invention. A detailed embodiment relating thereto will be described later.

[0049] Figure 5 is a schematic diagram illustrating the process by which STA establishes a link with AP.

[0050] Referring to Figure 5, the link between STA100 and AP200 is established through three main steps: scanning, authentication, and association. First, the scanning step is the step in which STA100 obtains connection information for the BSS operated by AP200. There are two methods for performing scanning: passive scanning, which obtains information using only the beacon message S101 that AP200 periodically transmits, and active scanning, in which STA100 transmits a probe request S103 to the AP, receives a probe response S105 from the AP, and obtains connection information.

[0051] In the scanning step, STA100, having successfully received wireless connection information, transmits an authentication request (S107a), receives an authentication response from AP200 (S107b), and performs the authentication step. After the authentication step is performed, STA100 transmits an association request (S109a), receives an association response from AP200 (S109b), and performs the association step. In this specification, "association" basically means wireless coupling, but the present invention is not limited to this, and in a broad sense, coupling includes both wireless and wired coupling.

[0052] On the other hand, an additional 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are performed. In Figure 5, Server 300 is a server that processes authentication between STA100 and the 802.1X-based system, and may be physically connected to AP200 or exist as a separate server.

[0053] Figure 6 shows the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0054] A terminal performing wireless LAN communication checks whether a channel is busy or not by performing carrier sensing before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to that channel. This process is called Clear Channel Assessment (CCA), and the level at which the detection of the signal is determined is called the CCA threshold. If a wireless signal above the CCA threshold is received by the terminal and the terminal is the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel, or if a wireless signal below the CCA threshold is detected, the channel is determined to be idle.

[0055] If a channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after a time period determined by the status of each terminal, such as an IFS (Inter Frame Space), AIFS (Arbitration IFS), PIFS (PCF IFS), etc. In this embodiment, the AIFS is used as a replacement for the conventional DIFS (DCF IFS). Each terminal waits, decreasing a slot time equal to a random number determined for that terminal during the interval of idle state of the channel, and the terminal that has exhausted all of its slot time attempts to access the channel. The period in which each terminal performs this backoff procedure is called the competition window period. At this time, the random number can be called the backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number acquired by the terminal. If a terminal senses that a channel is idle during the slot time, the terminal can decrease the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be allowed to access the channel. Therefore, terminal transmission may be permitted when the channel is idle during the AIFS time and the backoff counter slot time.

[0056] If a specific terminal successfully accesses the channel, it transmits data through the channel. However, if a terminal attempting access collides with another terminal, the colliding terminals are each assigned a new random number and perform a further backoff procedure. In one embodiment, the random number newly assigned to each terminal is determined within a range twice the range (competition window, CW) of the random number previously assigned to that terminal (2*CW). Meanwhile, each terminal attempts access again in the next competition window interval by performing a further backoff procedure, but this time, each terminal performs the backoff procedure from the slot time remaining in the previous competition window interval. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0057] <Examples of various PPDU formats>

[0058] Figure 7 shows examples of various standard generational PPDU (PLCP Protocol Data Unit) formats. More specifically, Figure 7(a) shows one example of a legacy PPDU format based on 802.11a / g, Figure 7(b) shows one example of an HE PPDU format based on 802.11ax, and Figure 7(c) shows one example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Figure 7(d) shows the detailed field configuration of L-SIG and RL-SIG commonly used in the aforementioned PPDU formats.

[0059] Referring to Figure 7(a), the legacy PPDU preamble includes L-STF (Legacy Short Training field), L-LTF (Legacy Long Training field), and L-SIG (Legacy Signal field). In embodiments of the present invention, the L-STF, L-LTF, and L-SIG can be referred to as the legacy preamble.

[0060] Referring to Figure 7(b), the HE PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as the HE preamble. The specific configuration of the HE preamble may be modified according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0061] Referring to Figure 7(c), the EHT PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used in only some of the EHT PPDU formats.

[0062] The L-SIG field included in the PPDU preamble is configured with 64 FFT OFDM and consists of a total of 64 subcarriers. Of these, 48 subcarriers, excluding the guard subcarrier, DC subcarrier, and pilot subcarrier, are used for L-SIG data transmission. Since BPSK and a Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information configuration of the L-SIG.

[0063] Referring to Figure 7(d), L-SIG includes the L_RATE field and the L_LENGTH field. The L_RATE field consists of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of a modulation scheme such as BPSK / QPSK / 16-QAM / 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. Combining the information from the L_RATE and L_LENGTH fields allows us to determine the total length of the PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0064] The L_LENGTH field is measured in bytes, with a total of 12 bits allocated, allowing for signaling up to 4095. In combination with the L_RATE field, it can indicate the length of the PPDU. In this case, legacy and non-legacy terminals can parse the L_LENGTH field in different ways.

[0065] First, the method by which a legacy or non-legacy terminal analyzes the length of the PPDU using the L_LENGTH field is as follows: When the L_RATE field is set to 6Mbps, 3 bytes (i.e., 24 bits) may be transmitted in 4us, which is the symbol duration of one 64FFT. Therefore, by adding the 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing this by the transmission amount of one symbol, which is 3 bytes, the number of 64FFT reference symbols after L-SIG is obtained. After multiplying the obtained number of symbols by 4us, which is the symbol duration of one symbol, and then adding 20us, which is the transmission time for L-STF, L-LTF, and L-SIG, the length of the PPDU, i.e., the reception time (RXTIME), is obtained. This can be expressed mathematically as shown in Equation 1 below.

[0066]

number

[0067] At this time,

number

[0068]

number

[0069] Here, TXTIME is the total transmission time that constitutes the PPDU, as shown in Equation 3 below. In this case, TX represents the transmission time of X.

[0070]

number

[0071] Referring to the above formula, the length of the PPDU is calculated based on the rounded-up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​L_LENGTH = {3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0072] Referring to Figure 7(e), the U-SIG (Universal SIG) field persists in EHT PPDUs and subsequent generations of wireless LAN PPDUs, playing a role in distinguishing which generation of PPDU it is, including 11be. The U-SIG is a 64FFT-based OFDM with two symbols, capable of transmitting a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits of CRC / tail, are broadly divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0073] The VI bit maintains its current bit configuration, allowing current 11be terminals to obtain information about a PPDU from its VI field even when subsequent generations of PPDUs are defined. To this end, the VI field consists of the PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits and is responsible for sequentially distinguishing 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink or downlink PPDU. The BSS color represents the BSS identifier defined in 11ax and has a value of 6 bits or more. The TXOP represents the Transmit Opportunity Duration, which was transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the PPDU, and it has a value of 7 bits or more.

[0074] The VD field may consist of the PPDU format as signaling information useful only for the 11be version of PPDU, fields that are common to any PPDU format such as BW, and fields that are defined differently depending on the PPDU format. The PPDU format is a divisor that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDU, etc. The BW field broadly signals five basic PPDU BW options of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz (BW that can be expressed in the form of a power of 20*2 can be called a basic BW), and various remaining PPDU BWs composed of preamble puncturing. In addition, after being signaled at 320 MHz, some 80 MHz may be punctured and then signaled. Furthermore, the punctured and deformed channel shape may be signaled directly in the BW field, or it may be signaled using both the BW field and fields appearing after the BW field (for example, fields within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0075] Fields located after the BW field vary depending on the form and format of the PPDU. MU PPDUs and SU PPDUs may be signaled in the same PPDU format. A field to distinguish between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. Both SU PPDUs and MU PPDUs include an EHT-SIG field, but some fields unnecessary for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or have a reduced size compared to the original fields included in the MU PPDU. For example, in the case of a SU PPDU, the common fields of the EHT-SIG may be omitted or replaced, or user-specific fields may be replaced or reduced to one, resulting in a different configuration.

[0076] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (e.g., the RA field) may be omitted depending on the value of the compression field.

[0077] If a portion of the EHT-SIG field of an SU PPDU is compressed, the information contained in the compressed field may be signaled together with the uncompressed field (e.g., a common field). In the case of MU PPDUs, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must know the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether or not the transmitted MU PPDU was sent to them. Therefore, the AP must transmit the EHT-SIG field with the above information included. To this end, the U-SIG field signals information for efficient transmission of the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the modulation method, MCS. The EHT-SIG field may include size and location information of the RU assigned to each user.

[0078] In the case of an SU PPDU, multiple RUs may be assigned to the STA, and these RUs may be consecutive or discontinuous. If the RUs assigned to the STA are not consecutive, the STA can efficiently receive the SU PPDU only if it recognizes the punctured RU in the middle. Therefore, the AP can transmit the SU PPDU including information about the punctured RUs among the RUs assigned to the STA (e.g., the puncturing pattern of the RUs). That is, in the case of an SU PPDU, the EHT-SIG field may contain a puncturing mode field that includes information on whether a puncturing mode was applied and the puncturing pattern shown in bitmap format or similar, and the puncturing mode field can signal the form of discontinuous channels appearing within the bandwidth.

[0079] The form of the signaled discontinuous channels is limited and, in combination with the value of the BW field, indicates the BW and discontinuous channel information of the SU PPDU. For example, in the case of an SU PPDU, since it is a PPDU transmitted to only one terminal, the STA can recognize the bandwidth allocated to it from the BW field included in the PPDU, and can recognize the punctured resources within the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU with the remaining resource units excluding the specific channel of the punctured resource unit. At this time, the multiple RUs allocated to the STA may consist of different frequency bands or tones.

[0080] The reason only restricted forms of discontinuous channel configurations are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed on each 20MHz subchannel, when puncturing is performed on a bandwidth with multiple 20MHz subchannels, such as 80, 160, and 320MHz, in the case of 320MHz, the usage status of the remaining 15 20MHz subchannels (excluding the primary channel) must be represented, and the discontinuous channel configuration (if a configuration where only the end 20MHz is punctured is also considered discontinuous) must be signaled. Using 15 bits to signal the discontinuous channel configuration for single-user transmission in this way can result in excessive signaling overhead when considering the low transmission speed of the signaling portion.

[0081] This invention proposes a method for signaling the discontinuous channel configuration of an SU PPDU and illustrates the discontinuous channel configuration determined by the proposed method. Furthermore, it proposes a method for signaling the primary 160MHz and secondary 160MHz puncturing configurations of an SU PPDU in a 320MHz BW configuration.

[0082] Furthermore, in one embodiment of the present invention, a method is proposed in which the configuration of the PPDU indicated by the preamble puncturing BW value differs depending on the signaled PPDU format in the PPDU format field. Assuming that the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, one symbol of EHT-SIG-A is further signaled after U-SIG, or it is not necessary to signal EHT-SIG-A from the beginning. Taking this into consideration, it is necessary to fully signal up to 11 puncturing modes using only the BW field of U-SIG. However, in the case of an EHT MU PPDU, EHT-SIG-B is further signaled after U-SIG, so up to 11 puncturing modes can be signaled in a different way than in an SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20MHz or 10MHz bandwidth. Detailed puncturing patterns for each PPDU type will be described in detail in Figures 11 and 12.

[0083] Figure 7(f) shows the format-specific fields of the VD field when EHT MU PPDU is indicated in the U-SIG PPDU format field. In the case of MU PPDU, SIG-B, which is a signaling field for simultaneous reception by multiple users, is required, and SIG-B may be transmitted after U-SIG without a separate SIG-A. For this purpose, U-SIG must signal information for decoding SIG-B. Such fields include SIG-B MCS, SIG-B DCM, Number of SIG-B Symbols, SIG-B Compression, and Number of EHT-LTF Symbols fields.

[0084] Figure 8 shows examples of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and methods for specifying them according to embodiments of the present invention.

[0085] Referring to Figure 8, a PPDU may consist of a preamble and a data portion, and one type of format, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether or not the PPDU format is an EHT PPDU may be indicated based on the PPDU format field included in the U-SIG field.

[0086] Figure 8(a) shows an example of the EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single-user (SU) transmission between an AP and a single STA, and may have an EHT-SIG-A field for additional signaling after the U-SIG field.

[0087] Figure 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. An EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used as a response to a trigger frame. Unlike an EHT SU PPDU, an EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0088] Figure 8(c) shows an example of the EHT MU PPDU format, which is an EHT PPDU for multiple users. An EHT MU PPDU is a PPDU used to send a PPDU to one or more STAs. In the EHT MU PPDU format, the HE-SIG-B field may be located after the U-SIG field.

[0089] Figure 8(d) shows an example of the EHT ER SU PPDU format used for single-user transmissions with STAs in an extended range. EHT ER SU PPDU may be used for single-user transmissions with STAs in a wider range than EHT SU PPDU described in Figure 8(a), and the U-SIG field may be repeatedly positioned on the time axis.

[0090] The EHT MU PPDU described in Figure 8(c) can be used by an AP to transmit downlink data to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive PPDUs transmitted from the AP. The EHT MU PPDU can transmit the AID information of the recipient and / or sender of the PPDU transmitted through the user-specific field of EHT-SIG-B to the STAs. Therefore, multiple terminals that receive the EHT MU PPDU can perform spatial reuse operations based on the AID information in the user-specific field included in the preamble of the received PPDU.

[0091] Specifically, the resource unit allocation (RA) field in the HE-SIG-B field included in the HE MU PPDU may contain information about the configuration of resource units (e.g., resource unit division configuration) within a specific bandwidth on the frequency axis (e.g., 20 MHz). That is, the RA field can instruct the STA on the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU in order to receive the PPDU. Information about the STA allocated (or specified) to each divided resource unit may be included in the user-specific field of EHT-SIG-B and transmitted to the STA. That is, the user-specific field may contain one or more user fields corresponding to each divided resource unit.

[0092] For example, among the multiple divided resource units, the user field corresponding to at least one resource unit used for data transmission may contain the recipient's or sender's AID, while the user fields corresponding to the remaining resource units not used for data transmission may contain a previously set Null STA ID.

[0093] For the sake of clarity, the terms frame or MAC frame may be used interchangeably with MPDU in this specification.

[0094] When a single wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be increased. In this case, a link is a physical path and may be configured as a single wireless medium that can be used to transmit an MSDU (MAC service data unit). For example, if the frequency band of one link is being used by another wireless communication device, the wireless communication device can continue to communicate using another link. In this way, the wireless communication device can make effective use of multiple channels. Furthermore, when the wireless communication device communicates simultaneously using multiple links, the overall throughput can be increased. However, existing wireless LANs are defined on the premise that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is necessary. Referring to Figures 9 to 26, the wireless communication method for a wireless communication device using multiple links will be explained. First, using Figure 9, a specific form of a wireless communication device using multiple links will be explained.

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

[0096] A multi-link device (MLD) may be defined for the wireless communication method using the multiple links described above. A multi-link device can represent a device having one or more affiliated stations. In specific embodiments, a multi-link device can represent a device having two or more affiliated stations. A multi-link device can also exchange multi-link elements. A multi-link element contains information about one or more stations or one or more links. A multi-link element may include the multi-link setup element described later. In this case, the multi-link device may be a logical entity. Specifically, a multi-link device can have multiple affiliated stations. A multi-link device can be called an MLLE (multi-link logical entity) or an MLE (multi-link entity). A multi-link device can have one medium access control service access point (SAP) up to logical link control (LLC). An MLD can also have one MAC data service.

[0097] Multiple stations included in a multilink system can operate on multiple links. Furthermore, multiple stations included in a multilink system can operate on multiple channels. Specifically, multiple stations included in a multilink system can operate on different links or different channels. For example, multiple stations included in a multilink system can operate on different channels of 2.4GHz, 5GHz, and 6GHz.

[0098] The operation of a multilink device can be called multilink operation, MLD operation, or multi-band operation. Furthermore, if the station paired with the multilink device is an AP (Application Platform), the multilink device can be called an AP MLD (Application Platform Multilink). Conversely, if the station paired with the multilink device is a non-AP station, the multilink device can be called a non-AP MLD (Application Platform Multilink).

[0099] Figure 9 illustrates the communication operation between a non-AP MLD and an AP-MLD. Specifically, the non-AP MLD and AP-MLD communicate using three links each. The AP MLD includes the first AP (AP1), the second AP (AP2), and the third AP (AP3). The non-AP MLD includes the first non-AP STA (non-AP STA1), the second non-AP STA (non-AP STA2), and the third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via the first link (Link1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via the second link (Link2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via the third link (Link3).

[0100] Multilink operation can include a multilink setup operation. Multilink setup corresponds to the association operation of single-link operation described above and must be performed before frame exchange in multilink. A multilink device can obtain the information necessary for multilink setup from a multi-link setup element. Specifically, the multi-link setup element can include capability information related to multilink. In this case, capability information can include information indicating whether one of the multiple devices included in the multilink device can transmit and the other devices can receive simultaneously. Capability information can also include information about the links available to each station included in the MLD. Capability information can also include information about the channels available to each station included in the MLD.

[0101] Multilink configuration may be established through negotiations between peer stations. Specifically, multilink configuration may be performed through communication between stations without communication with the AP. Furthermore, multilink configuration may be established through any one of the links. For example, even if links 1 through 3 are configured via a multilink, the multilink configuration may be performed through link 1.

[0102] Furthermore, a mapping between TIDs (traffic identifiers) and links may be configured. Specifically, frames corresponding to a specific TID value may be exchanged only through pre-specified links. The mapping between TIDs and links may be configured in a directional-based manner. For example, if multiple links are configured between a first multilink device and a second multilink device, the first multilink device may be configured to send frames with a first TID to multiple first links, and the second multilink device may be configured to send frames with a second TID to the first links. Additionally, a default setting may exist for the mapping between TIDs and links. Specifically, if there are no additional settings in the multilink configuration, the multilink device can exchange frames corresponding to TIDs on each link according to the default setting. In this case, the default setting may be such that all TIDs are exchanged on any one link.

[0103] Let's explain TID in detail. TID is an ID used to classify traffic and data to support QoS (Quality of Service). TID may be used and assigned at layers higher than the MAC layer. TID can also indicate traffic category (TC) and traffic stream (TS). There may be 16 distinct TID values. For example, a TID may be specified as one of the values ​​from 0 to 15. Different TID values ​​may be specified depending on the access policy, channel access, or medium access method. For example, when EDCA (enhanced distributed channel access) or HCAF (hybrid coordination function contention based channel access) is used, the TID value may be assigned in the range of 0 to 7. When EDCA is used, TID can indicate user priority (UP). In this case, UP may be specified by TC or TS. UP may be assigned at layers higher than MAC. Furthermore, when HCCA (HCF controlled channel access) or SPCA is used, the TID value may be assigned in the range of 8 to 15. When HCCA or SPCA is used, TID can represent TSID. Furthermore, when HEMM or SEMM is used, the TID value may be assigned in the range of 8 to 15. When HEMM or SEMM is used, TID can represent TSID.

[0104] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in EDCA channel contention. QoS stations can guarantee QoS using AC. AC can also 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. AC_BK, AC_BE, AC_VI, and AC_VO may also be classified into sub-ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. Similarly, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. UP or TID may also be mapped to AC. For example, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. Furthermore, the priority of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be in that order from highest to lowest. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priority may be in the order of AC_BK, AC_BE, AC_VI, and AC_VO, from highest to lowest. Furthermore, AC_BK, AC_BE, AC_VI, and AC_VO can each correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to these characteristics of TIDs, the mapping between TIDs and links can represent the mapping between ACs and links.Furthermore, the mapping between links and ACs can represent the mapping between TIDs and links.

[0105] As mentioned above, a TID may be mapped to each of multiple links. The mapping may specify which links can exchange traffic corresponding to a particular TID or AC. Additionally, TIDs or ACs that can be transmitted in different transmission directions within a link may be specified. As mentioned above, a default setting may exist for the mapping between TIDs and links. Specifically, in a multilink configuration where no additional settings are made, the multilink device can exchange frames corresponding to TIDs on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on any one link. At any given time, any TID or AC may always be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0106] When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to that link may be transmitted on that link. Therefore, when a link is mapped to a TID or AC, frames that do not correspond to a TID or AC not mapped to that link do not need to be transmitted on that link. When a link is mapped to a TID or AC, the ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK agreement may be determined based on the mapping between TIDs and links. Furthermore, in other specific embodiments, the mapping between TIDs and links may be determined based on a block ACK agreement. Specifically, a block ACK agreement may be set for a TID mapped to a particular link.

[0107] The aforementioned mapping of TIDs to links may ensure QoS. Specifically, a relatively small number of stations may be operational, or higher-priority ACs or TIDs may be mapped to links with good channel conditions. Furthermore, the aforementioned mapping of TIDs to links may enable stations to maintain a power-saving state for longer periods.

[0108] Figure 10 shows that, according to an embodiment of the present invention, transmissions on different links are performed simultaneously in multilink operation.

[0109] The implementation of multilink devices does not always support simultaneous operation on multiple links. For example, a multilink device may support simultaneous transmission on multiple links, simultaneous reception on multiple links, or transmission on one link while receiving on another. Reception or transmission on one link may affect reception or transmission on other links. Specifically, transmission on one link may act as interference on other links. Interference from one link of a multilink device affecting other links can be called internal leakage. Internal leakage tends to increase as the frequency spacing between links decreases. If internal leakage is not too large, transmission on one link can occur while transmission is occurring on other links. If internal leakage is large, transmission on one link cannot occur while transmission is occurring on other links. Thus, simultaneous operation of multiple links by a multilink device can be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, when a multilink device transmits on multiple links simultaneously, transmits on one link while receiving on another, or receives on multiple links simultaneously, this can be called STR (Simultaneous Transmission / Reception).

[0110] As mentioned earlier, multilink devices can support STR (Stroke Response) both fully and with limitations. Specifically, multilink devices can only support STR under certain conditions. For example, a multilink device may not be able to perform STR when operating as a single radio. Similarly, a multilink device may not be able to perform STR when operating as a single antenna. Furthermore, a multilink device may not be able to perform STR if internal leakage is detected to be above a predetermined level.

[0111] A station can exchange information with other stations regarding its STR capability. Specifically, a station can exchange information with other stations regarding whether there are limitations on its ability to transmit or receive on multiple links simultaneously. Specifically, information regarding limitations on the ability to transmit or receive on multiple links may indicate whether transmission or reception occurs simultaneously on multiple links, or whether transmission and reception occur simultaneously. Furthermore, information regarding limitations on the ability to transmit or receive on multiple links may be indicated in stages. Specifically, information regarding limitations on the ability to transmit or receive on multiple links may be information indicating stages indicating the magnitude of internal leakage. In a specific embodiment, information indicating stages indicating the magnitude of internal leakage may be information indicating stages indicating the magnitude of interference caused by internal leakage. In yet another specific embodiment, it may be information indicating stages indicating the frequency spacing between links that may affect internal leakage. Furthermore, information indicating stages indicating the magnitude of internal leakage may be information indicating the relationship between the frequency spacing between links and the magnitude of internal leakage in stages.

[0112] In Figure 10, the first station (STA1) and the second station (STA2) are affiliated to a single non-AP multilink device. Alternatively, the first AP (AP1) and the second AP (AP2) may also be affiliated to a single non-AP multilink device. A first link (link1) is established between the first AP (AP1) and the first station (STA1), and a second link (link2) is established between the second AP (AP2) and the second station (STA2). In Figure 10, the non-AP multilink device can perform STR (Signal Transmitting) to a limited extent. When the second station (STA2) transmits on the second link (Link2), reception by the first station (STA1) on the first link (Link1) may be interfered with by transmission on the second link (Link2). For example, in the following case, reception by the first station (STA1) on the first link (Link1) may be interfered with by transmission on the second link (Link2). On the second link (Link2), the second station (STA2) transmits the first data (Data1), and the first access point (AP1) transmits an acknowledgment (Ack for Data1) to the first station (STA1). On the second link (Link2), the second station (STA2) transmits the second data (Data2). At this time, the transmission timing of the second data (Data2) and the transmission timing of the acknowledgment (Ack for Data1) may overlap. In this case, the transmission to the second station (STA2) on the second link (Link2) may cause interference on the first link (Link1). Therefore, the first station (STA1) may not receive the acknowledgment (Ack for Data1) for the first data (Data1).

[0113] This section describes how a multilink device performs channel access. For multilink operations not specifically described, the channel access procedure shown in Figure 6 can be followed.

[0114] A multilink device can perform channel access independently from multiple links. In this case, the channel access may be backoff-based channel access. When the multilink device performs channel access independently from multiple links and the backoff counters reach 0 on multiple links, the multilink device can start transmitting on multiple links simultaneously. In a specific embodiment, when the backoff counter of any one of the links in the multilink reaches 0 and a predetermined condition is met, the multilink device can perform channel access on other links where the backoff counter has not reached 0, in addition to the link where the backoff counter reached 0. Specifically, when the backoff counter of any one of the links in the multilink reaches 0, the multilink device can sense energy on other links where the backoff counter has not reached 0. In this case, if no energy greater than a predetermined amount is sensed, the multilink device can perform channel access on the link where energy sensing was performed, in addition to the link where the backoff counter reached 0. This allows the multilink device to start transmitting on multiple links simultaneously. The size of the threshold used for energy sensing may be smaller than the size of the threshold used when deciding whether to decrease the backoff counter. Furthermore, when deciding whether to reduce the backoff counter, the multilink device can sense any form of signal, not just Wi-Fi signals. Also, in the energy sensing described above, the multilink device can sense any form of signal, not just Wi-Fi signals. Internal leakage may not be detected as a Wi-Fi signal. In such cases, the multilink device can detect the signal detected by internal leakage through energy sensing. Also, as mentioned above, the size of the threshold used for energy sensing can be smaller than the size of the threshold used when deciding whether or not to reduce the backoff counter. Therefore, even when transmission is taking place on one link, the multilink device can reduce the backoff counter on other links.

[0115] The degree of interference between links used by the multilink device may determine whether the stations operating on each link can operate independently. In this case, the degree of interference between links may be the magnitude of interference perceived by other stations of the multilink device when any one station of the multilink device transmits on any one link. If the transmission of the first station of the multilink device on the first link causes interference exceeding a predetermined magnitude to the second station of the multilink device operating on the second link, the operation of the second station may be restricted. Specifically, the reception or channel access of the second station may be restricted. When interference occurs, the second station may fail to decode the received signal due to the interference. Also, when interference occurs, the second station may determine that the channel is in use when using backoff for channel access.

[0116] Furthermore, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can operate independently. Specifically, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can independently access the channel. Also, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can independently transmit or receive. When interference below a predetermined magnitude occurs, the second station can successfully decode the received signal even in the presence of interference. Also, when interference below a predetermined magnitude occurs, the second station can determine that the channel is idle when using backoff for channel access.

[0117] The degree of interference between stations in a multilink system can vary not only depending on the interval between the frequency bands of the links on which the stations operate, but also on the hardware characteristics of the multilink system. For example, internal interference in a multilink system that includes high-RF (radio frequency) equipment may be less than internal interference in a multilink system that includes low-RF equipment. Therefore, the degree of interference between stations in a multilink system may be determined based on the characteristics of the multilink system.

[0118] Figure 10 shows that the magnitude of interference varies depending on the interval between the frequency bands of the links and the characteristics of the multilink device. In the embodiment shown in Figure 10, the first multilink device (MLD#1) includes a first station (STA1)-1 operating on the first link (Link1) and a second station (STA1)-2 operating on the second link (Link2). The second multilink device (MLD#2) includes a first station (STA2)-1 operating on the first link (Link1) and a second station (STA2)-2 operating on the second link (Link2). The frequency interval between the first link (Link1) and the second link (Link2) in which the first multilink device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) in which the second multilink device (MLD#2) operates. However, the magnitude of interference differs due to the difference between the characteristics of the first multilink device (MLD#1) and the characteristics of the second multilink device (MLD#2). Specifically, the magnitude of interference generated by the second multilink device (MLD#2) may be greater than the magnitude of interference generated by the first multilink device (MLD#1). Considering that the magnitude of interference may differ depending on the characteristics of the multilink devices, and that the availability of STR support may vary for each multilink device, it is necessary to exchange information regarding whether or not STR support is provided.

[0119] A multilink device can signal whether or not a station it includes provides STR support. Specifically, an AP multilink device and a non-AP multilink device can exchange whether or not an AP included in the AP multilink device provides STR support and whether or not a STA included in the non-AP multilink device provides STR support. In such an embodiment, an element indicating the presence or absence of STR support may be used. The element indicating the presence or absence of STR support may be called an STR support element. The STR support element can indicate, with one bit, whether or not a station in the multilink device that transmitted the STR support element provides STR support. Specifically, the STR support element can indicate, one bit at a time, whether or not each station included in the multilink device that transmitted the STR support element provides STR support. In this case, the bit value may be 1 when the station provides STR support, and 0 when the station does not provide STR support. If the multilink device that transmits the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support the STR, but the second station (STA2) does not, then the STR support element is 101 1b The STR support element may include a field containing a bit. It is assumed that stations operating in different frequency bands support each other, and the STR support element may omit signaling for the presence or absence of STR support between stations operating in different frequency bands. For example, suppose the first station (STA1) operates on the 2.4GHz first link, and the second station (STA2) and third station (STA3) operate on the 5GHz second and third links, respectively. In this case, the STR support element can indicate with one bit that STR support is provided between the second station (STA2) and the third station (STA3). The STR support element may also contain only one bit if there are two stations to which the STR support element signals.

[0120] In a specific embodiment, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz in a multilink device may always be considered a STR (Structured Link). Therefore, signaling for the presence or absence of a STR between the 2.4 GHz link and the 5 GHz or 6 GHz link may be omitted.

[0121] In the embodiments described above, what is described as the operation of a station in a multilink device may be replaced with the operation of the multilink device itself. Also, in the embodiments described above, the operation of the AP may be replaced with the operation of a non-AP station, and the operation of a non-AP station may be replaced with the operation of the AP. Therefore, the operation of the AP in a non-STR multilink device may be replaced with the operation of a non-AP station in a non-STR multilink device, and the operation of a non-AP station in an STR multilink device may be replaced with the operation of the AP in an STR multilink device. Furthermore, the operation of a non-AP station in a non-STR multilink device may be replaced with the operation of the AP in a non-STR multilink device, and the operation of the AP in an STR multilink device may be replaced with the operation of a non-AP station in an STR multilink device.

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

[0123] The STR support element may be replaced when the link frequency bandwidth is changed. As mentioned above, the presence or absence of STR support at a station may depend on the distance between the link frequency bandwidths, and the presence or absence of STR support at a station may change when the link frequency bandwidth is changed. When the link frequency bandwidth is changed, this may include at least one of the following: a change in the link center frequency, a change in the bandwidth of the frequency band, and a 20MHz main channel. The AP and the station can replace the STR support element by request and response. Furthermore, in other specific embodiments, the STR support element may be replaced without further request when the link frequency bandwidth is changed. Also, in the embodiments described above, when the link frequency bandwidth is changed, this may include a change in the station's operating channel.

[0124] If a station of a non-AP multilink device is unable to perform a STR (Stroke Response), the station may request a link change from the AP (Application Platform). Specifically, the station may request a change to at least one of the following: a change in the center frequency, a change in the bandwidth of the frequency band, and a change in the 20 MHz main channel. The link change request may be transmitted to the AP through the link to which the change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP through a link that is not to be changed. In this case, the link change request may include information indicating which link is to be changed. The information indicating the link may be a number that identifies the link. In such an embodiment, the link change may be a change in the operating channel within a single frequency band. The link change may also include information about how the link is changed. Specifically, the link change request may indicate moving the center frequency of the link to a higher frequency than the current center frequency, or moving the center frequency of the link to a lower frequency than the current center frequency. In yet another specific embodiment, the link change request may implicitly indicate a change to a frequency band that moves away from adjacent links. Furthermore, a link change request may indicate a reduction in link bandwidth. A link change request may also request a change in the location of the primary channel. Specifically, a link change request may indicate a change in the location of the primary channel to a channel in a lower or higher frequency band than the current primary channel location. An AP receiving a link change request may change the link in response to the request. In a specific embodiment, an AP receiving a link change request may also ignore it.

[0125] In the embodiment shown in Figure 11, the second station (STA2) and third station (STA3) of the non-AP multilink device are unable to support STR. The non-AP multilink device requests the AP multilink device to change the third link (Link3). Upon receiving the link change request, the AP multilink device changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can send a change request to the third AP (AP3). Furthermore, in other specific embodiments, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0126] When an AP changes links, it can broadcast information about the link change using a beacon frame. This link change information may include information about the link frequency. This information may include at least one of the following: changes to the link's center frequency, operating bandwidth, and primary channel. The link change information may also include information about the timing of the link change. Furthermore, the link change may be completed when the beacon containing the link change information is transmitted.

[0127] In Figure 11, the link on which the third station (STA3) operates is changed, and both the third station (STA3) and the second station (STA2) can support the STR. As mentioned earlier, the non-AP multilink device can transmit an STR support element to the AP multilink device and signal whether or not the STR support has been changed.

[0128] As mentioned above, link changes may not be permitted, or STR may not be supported even with a link change. Also, as shown in the embodiment in Figure 11, AP multilink devices may support STR, while non-AP multilink devices may not. This is because AP multilink devices generally use relatively high-RF equipment, while non-AP multilink devices generally use relatively low-RF equipment. Therefore, a method is needed for efficient communication between multilink devices even when one of the multilink devices does not support STR. In this case, STR can represent simultaneous transmission and reception. This is explained in Figure 12.

[0129] Figure 12 shows that, according to one embodiment of the present invention, when one station of the non-STR multilink device is receiving, channel access for other stations of the non-STR multilink device is prohibited.

[0130] When transmission occurs on one link of a non-STR multilink device and reception occurs on the other links, both reception and transmission may fail. To resolve this, channel access may be prohibited on the other links of the non-STR multilink device when reception occurs on one link. Specifically, when reception occurs on one link of the non-STR multilink device, backoff of channel access may be prohibited on the other links. This prevents transmission from starting on the other links of the non-STR multilink device when reception occurs on one link. In a specific embodiment, backoff of channel access may be prohibited on the other links of the non-STR multilink device when reception starts on one link. This may be set by a specific bit in memory, such as a channel access prohibition flag. The presence or absence of channel access prohibition may be shared by the memory inside the multilink device. Such an embodiment allows channel access prohibition to be implemented without separate frame exchange. For the sake of clarity, as used herein, channel access prohibition, unless otherwise specified, refers to prohibiting channel access or transmission in order to protect the transmission or reception of non-STR multilink equipment.

[0131] When channel access is prohibited, stations operating on the prohibited link cannot perform backoff procedures regardless of NAV and CCA results. Furthermore, when channel access is prohibited, stations operating on the prohibited link cannot transmit regardless of NAV and CCA results. However, even when channel access is prohibited, stations operating on the prohibited link can still receive. Additionally, a channel access prohibition on the second link due to reception on the first link may be lifted based on the completion of reception on the first link. Specifically, a channel access prohibition on the second link due to reception on the first link may be lifted when reception on the first link is completed. Furthermore, in other specific embodiments, a channel access prohibition on the second link due to reception on the first link may be lifted based on the point at which an ACK is sent after reception on the first link is completed. Specifically, a channel access prohibition on the second link due to reception on the first link may be lifted at the point at which an ACK is sent after reception on the first link is completed. In further specific embodiments, channel access prohibition on the second link due to reception on the first link may be lifted when the transmission of the ACK is completed after reception on the first link is complete. Also, immediately after the channel access prohibition is lifted, the station can immediately decrement the backoff counter without additional sensing. In this case, the additional sensing can represent sensing performed between DIFS (DCF Interframe Space). In yet another specific embodiment, immediately before the channel access prohibition is lifted, if the channel is idle for a predetermined time, the station can immediately decrement the backoff counter without additional sensing. In this case, the predetermined time may be one of PIFS (PCF Interframe Space), DIFS, SIFS (Short Interframe Space), and AIFS (Arbitration Interframe Space).

[0132] In the embodiment of FIG. 12, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) is receiving, in-device interference occurs. As described above, while the first station (STA1) operating on the first link (Link1) is receiving, channel access by the second station (STA2) on the second link (Link2) is prohibited. After the reception of the first station (STA1) on the first link (Link1) is completed, the channel access prohibition is released. Immediately after the channel access prohibition is released, the second station (STA2) can decrement the previous backoff counter value from 3 to 2 without additional sensing.

[0133] For the sake of expression convenience, in FIG. 12, Rx and Tx are represented using a single block (Tx solid line, Rx dotted line), and this single block may be understood to represent an operation including Tx / Ack reception and Rx / Ack transmission even without a separate Ack block being shown. This may be equally applicable to the drawings described later.

[0134] When it is confirmed that the intended recipient of the PPDU received by the station is not the station, the station may interrupt the reception of the PPDU. In such a case, the operation of releasing the channel access prohibition of the multi-link device becomes a problem. In this specification, the intended recipient is used in the same meaning as the destination station.

[0135] FIG. 13 shows the operation of releasing the channel access prohibition when it is confirmed that the intended recipient of the PPDU received by the station of the non-STR multi-link device according to an embodiment of the present invention is not the station.

[0136] If a station confirms that it is not the intended recipient of the PPDU it receives, it can lift the channel access ban. The station can determine whether it is the intended recipient of the PPDU based on the information indicating the recipient address in the PPDU's signaling field. In this case, the information indicating the recipient address in the PPDU's signaling field may be the value of the STA-ID field in the EHT-SIG field as described above. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field points to the station. The station can also determine whether it is the intended recipient of the PPDU based on the value of the RA field in the MAC frame contained in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame contained in the PPDU points to the station. In Figure 13, the non-STR multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The first station (STA1) receives the PPDU. The first station (STA1) determines that the intended recipient of the received PPDU is not the first station (STA1) and interrupts the reception of the PPDU. At this time, the first station (STA1) can lift the channel access ban on the second station (STA2). Even after the channel access ban on the second station (STA2) is lifted, channel access on the second station (STA2) may be delayed by the NAV set on the second station (STA2).

[0137] As shown in Figure 13, even after channel access restrictions are lifted, stations included in non-STR multilink devices often have fewer channel access opportunities than stations not included in multilink devices or stations included in STR multilink devices. Therefore, a method is needed to compensate for the channel access opportunities of stations included in non-STR multilink devices in order to ensure fair competition with other stations. For example, immediately after the channel access restriction is lifted, it may be permissible for a station whose channel access restriction has been lifted to reduce its backoff counter by 2 or more. This will be explained in Figure 14.

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

[0139] A station whose channel access ban has been lifted can reduce its backoff counter by 2 or more immediately after the ban is lifted. This is to ensure fairness in channel access opportunities among stations, as other stations performed the backoff procedure while the station's channel access was banned.

[0140] In further specific embodiments, a station whose channel access is prohibited can perform a channel access procedure to reduce the CCA (CSMA) and backoff counter while channel access is prohibited. In Figure 14, a non-STR multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). In Figure 14, channel access for the second station (STA2) is prohibited while the first station (STA1) is receiving. In Figure 14(a), while channel access for the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure to reduce the CCA (CSMA) and backoff counter. In Figure 14(a), while channel access for the second station (STA2) is prohibited, the channel on the second link (Link2) is idle, so the second station (STA2) reduces the backoff counter.

[0141] Furthermore, a station whose channel access is prohibited can delay transmission even if the backoff counter reaches 0 during the period when channel access is prohibited. In this case, the station can maintain the backoff counter value at 0. Also, even if the station delays transmission, the station can maintain the CW value as is. Therefore, this is differentiated from the station doubling the CW value because the channel it is accessing is busy. This is because the reason for the transmission delay is not that the channel was determined to be in use. In Figure 14(b), while channel access for the second station (STA2) is prohibited, the second station (STA2) can perform channel access procedures to reduce the CCA (CSMA) and backoff counter. In Figure 14(b), while channel access for the second station (STA2) is prohibited, the channel on the second link (Link2) is idle, so the second station (STA2) reduces the backoff counter. While channel access for Station 2 (STA2) is prohibited, Station 2's (STA2) backoff counter reaches 0. Station 2 (STA2) delays transmission and begins transmitting after the channel access prohibition is lifted.

[0142] As mentioned above, channel access prohibition may include prohibiting transmission to the second station when the first station of a non-STR multilink device is transmitting. Furthermore, channel access prohibition may also include prohibiting transmission by the second station when the first station of a non-STR multilink device is receiving.

[0143] In the embodiment described in Figure 14(b), if multiple stations have channel access prohibited, there is a high probability that the channel access prohibition will be lifted simultaneously for multiple stations, and multiple stations will attempt to transmit at the same time. Therefore, a method is needed to reduce the probability of transmission collisions. This will be explained in Figure 15.

[0144] Figure 15 shows the operation of a station according to one embodiment of the present invention, which transmits after the channel access ban is lifted.

[0145] As mentioned above, in a non-STR multilink device, transmission may occur on the first link while transmission is prohibited on the second link. If the transmission is completed on the first link, transmission on the second link may begin with RTS / CTS frame exchange. Therefore, when transmission occurs on the first link among the multiple links in which a non-STR multilink device operates, the non-STR multilink device can begin RTS / CTS frame exchange on the second link. After the channel access prohibition is lifted for a station whose transmission has been delayed due to channel access prohibition, the station can begin RTS / CTS (request to send / clear to send) frame exchange before starting the delayed transmission. At this time, if the station cannot receive a CTS frame, it may not be able to start the delayed transmission. In the embodiment shown in Figure 15(a), the station whose transmission has been delayed due to channel access prohibition sends an RTS frame before starting the delayed transmission. After the station receives a CTS frame as a response to the RTS frame, it starts the delayed transmission.

[0146] In another specific embodiment, after a station whose transmission has been delayed due to channel access prohibition has had its channel access prohibition lifted, the station can transmit a frame containing only a portion of the delayed transmission. In this case, after the station receives a response, such as an ACK, to the frame containing only a portion of the delayed transmission, the station can transmit the untransmitted portion of the delayed transmission. If the station does not receive a response to the frame containing only a portion of the delayed transmission, the station does not need to transmit the untransmitted portion of the delayed transmission. Thus, the reason why a station can start RTS / CTS exchange or transmit only a portion of the delayed transmission after channel access prohibition is lifted is because the probability of a collision in transmissions after channel access prohibition is higher than in general transmissions. Therefore, the above-described embodiment may be mandatory for transmissions made after channel access prohibition is lifted. In existing wireless LAN operations, RTS / CTS frames have been used to solve the hidden node problem and could be used based on the size of the transmitted data. In the above-described embodiment, the RTS / CTS frame is intended to prevent transmission collisions with stations attempting to perform delayed transmissions to protect the transmission or reception of non-STR multilink devices.

[0147] As mentioned above, when one station of a non-STR multilink device is receiving, transmission by other stations of the non-STR multilink device may be restricted. Also, when one station of a non-STR multilink device is transmitting, it may be difficult for other stations of the non-STR multilink device to accurately sense the channel status of the link on which the station is operating. Specifically, when the first station of a non-STR multilink device is transmitting, the second station of the non-STR multilink device may always determine that the channel status of the link on which the second station is operating is busy. For this reason, the second station may determine that the channel is in use due to internal interference, even when the channel on the link on which the second station is operating is idle. In this way, when a station cannot determine the channel status due to internal interference, or when one station of the non-STR multilink device is continuing to transmit, the other stations of the non-STR multilink device are said to be in a blind state. Due to the circumstances described above, a station in a blind state may find it difficult to attempt to transmit by performing a backoff procedure. Furthermore, stations in a blind state due to the aforementioned circumstances will likely have difficulty in initiating PPDU reception or successfully decoding it. Therefore, a transmission method that takes blind stations into consideration is necessary. This will be explained in Figure 16.

[0148] Figure 16 shows a transmission performed based on the status of a station in a non-STR multilink device according to an embodiment of the present invention.

[0149] A station attempting to transmit to a station in a non-STR multilink device can decide whether or not to transmit based on whether the non-STR multilink device station is blinded. In this case, the station attempting to transmit to a station in a non-STR multilink device may be a station included in an STR multilink device. Alternatively, the station attempting to transmit to a station in a non-STR multilink device may be an AP included in an AP multilink device, and the non-STR multilink device may be a non-AP multilink device. A station attempting to transmit to a station in a non-STR multilink device can determine whether or not the non-STR multilink device station is blinded. The station attempting to transmit can determine whether or not other stations in the multilink device that it includes are currently transmitting to the non-STR multilink device. If other stations in the multilink device that it includes are currently receiving from the non-STR multilink device, the station can determine that the non-STR multilink device station receiving the station's transmission is blinded. In the embodiment shown in Figure 16, the STR AP multilink device includes a first AP (AP1) operating on the first link (Link1) and a second AP (AP2) operating on the second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can inform the first AP (AP1) that it is receiving from the second station (STA2). Specifically, the second AP (AP2) can inform the first AP (AP1) that the entity transmitting to the second AP (AP2) is the second station (STA2). In yet another specific embodiment, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is currently transmitting.At this time, the first AP (AP1) can determine, based on the notification, that the first station (STA1) is in a blind state.

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

[0151] A station does not need to transmit to a station that is blind. This is because even if a station transmits to a blind station, there is a high probability that the blind station will not be able to disclose its reception or will not be able to decode the PPDU. In this case, the station can cancel the transmission to the blind station and transmit to another station.

[0152] When an STR multilink device transmits to a non-STR multilink device, the STR multilink device can transmit to the non-STR multilink device on multiple links. Specifically, when the STR multilink device transmits to a non-STR multilink device on the first link, the STR multilink device can start transmitting to the non-STR multilink device on the second link. At this time, the STR multilink device can determine the length of the transmission on the second link based on the fact that it is a transmission to a non-STR multilink device. Specifically, the STR multilink device can determine the length of the transmission to the non-STR multilink device on the second link based on the length of the transmission to the non-STR multilink device on the first link. In a specific embodiment, the STR multilink device can complete the transmission on the first link and the transmission on the second link simultaneously. This is to prevent transmission to other stations of the non-STR multilink device from occurring while a transmission to one of the non-STR multilink device stations is completed and that station is sending a response to the transmission, such as an ACK. In the embodiment described above, multiple stations of the non-STR multilink device can simultaneously send responses to transmissions to multiple stations.

[0153] STR multilink devices cannot determine the status of stations included in non-STR multilink devices in real time. Therefore, even if the STR multilink device operates as described in the embodiment in Figure 16, interference or transmission collisions may occur between links where non-STR multilink devices are operating. For example, in the embodiment in Figure 16, the first AP (AP1) may start transmitting to the first station (STA1) before the second station (STA2) recognizes that it is in the process of transmitting to the second AP (AP2). In this way, the probability of interference or collisions between links may be greater than the probability of interference or transmission collisions within a link. This will be explained in more detail in Figure 17.

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

[0155] A transmission collision may occur between links when the transmission from the second station of a non-STR station multilink device to the second AP of an STR AP multilink device begins simultaneously with the transmission from the first AP of an STR AP multilink device to the first station of a non-STR station multilink device. This is shown in Figure 17(a). As mentioned above, this can occur because the STR multilink device cannot determine the state of stations included in the non-STR multilink device in real time.

[0156] Furthermore, even if the transmission from the second station of a non-STR station multilink device to the second AP of an STR AP multilink device begins earlier than the transmission from the first AP of an STR AP multilink device to the first station of a non-STR station multilink device, a transmission collision can still occur between links. This is shown in Figure 17(b). This is because it may take time for the second AP (AP2) to inform the first AP (AP1) that the second station (STA2) is performing a transmission. Thus, transmission collisions can occur even between stations that start transmitting at different times, so the probability of interference or a transmission collision between devices may be greater than the probability of interference or a collision within a link. Also, the longer the time it takes for an AP of an STR multilink device to identify the sender of the PPDU it receives, the greater the probability of interference or a transmission collision between links may become. Therefore, a method to resolve this is necessary. When one of the stations of an STR multilink device is performing a reception, other stations of the STR multilink device do not need to access the channel. However, if channel access is prohibited in this way, the meaning of the STR function may be lost. Therefore, an operating method that does not prohibit channel access is required for the STR multilink device. This is explained in Figure 18.

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

[0158] Various services using wireless LANs are being implemented. In particular, with the increasing proliferation of wireless VR (virtual reality) devices, the need for low-latency service support is growing. Therefore, a wireless LAN operation method to support low-latency services is necessary. For the sake of explanation, traffic for low-latency services will be referred to as low-latency traffic. Low-latency traffic may be designated by stations. In this case, stations include APs. Specifically, which traffic is low-latency traffic may be designated at layers higher than the MAC layer. Alternatively, specific traffic may be designated as low-latency traffic. Furthermore, low-latency traffic may be traffic whose priority takes precedence over a predetermined priority. In this case, the priority may be determined based on AC (access category).

[0159] Low-latency service support must also be considered in the operation of the non-STR multilink device described above. This is because the transmission of low-latency traffic may be delayed due to the operating characteristics of the non-STR multilink device. For example, if the non-STR multilink device is receiving on the first link, transmission on the second link may be restricted in order to protect the transmission of PPDUs that are being sent on the first link. As a result, the transmission of low-latency traffic that should be transmitted on the second link may be delayed. A method to solve this problem is explained in Figure 18.

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

[0161] A multilink device can transmit low-latency traffic on the second link of a non-STR link pair even while receiving on the first link of the non-STR link pair. A non-STR link pair represents a pair of links where a non-STR multilink device cannot transmit on one of the two links while simultaneously receiving on the other. In this case, the multilink device gives up receiving on the first link. Specifically, even while receiving a PPDU on the first link of a non-STR link pair, the multilink device can attempt to transmit a PPDU containing low-latency traffic on the second link of the non-STR link pair. In this case, the multilink device may interrupt the reception of the PPDU on the first link.

[0162] Furthermore, if the traffic contained in a PPDU that the multilink device intends to transmit on the second link has a higher priority than the traffic contained in a PPDU that the multilink device receives on the first link, the non-STR multilink device may attempt to transmit a PPDU containing the higher-priority traffic on the second link of the non-STR link pair, even while receiving a PPDU on the first link of the non-STR link pair. In this case, the multilink device may interrupt the reception of the PPDU on the first link. In yet another specific embodiment, the multilink device may transmit on the second link and ignore the signal received on the first link.

[0163] In the embodiment described above, the condition under which the multilink device can interrupt reception is that the priority of the traffic included in the reception currently underway on the first link is lower than the priority of the traffic to be transmitted on the second link. Therefore, if the priority of the traffic included in the reception currently underway on the first link is higher than the priority of the traffic to be transmitted on the second link, the multilink device cannot interrupt reception on the first link.

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

[0165] In the embodiment shown in Figure 18, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-STR multilink device, the non-AP station multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on the first link (Link1). The second AP (AP2) and the second station (STA2) operate on the second link (Link2). In the AP multilink device, the first AP (AP1) receives the first PPDU from the second AP (AP2). At this time, if the first PPDU contains only traffic that is not low-latency traffic, and transmission of low-latency traffic is required on the second link (Link2), the AP multilink device may give up receiving the first PPDU on the first link (Link1) and attempt to transmit a second PPDU containing low-latency traffic on the second link (Link2). Alternatively, if the traffic priority of the second PPDU that the AP multilink device intends to transmit on the second link (Link2) is higher than the traffic priority of the first PPDU that the AP multilink device receives on the first link (Link1), the AP multilink device may interrupt the reception of the first PPDU on the first link (Link1) and attempt to transmit the second PPDU on the second link (Link2).

[0166] In such embodiments, the multilink device can adjust the traffic exchange priority according to the type or priority of the traffic. In the embodiments described above, the traffic priority may be set by a predetermined policy. Also, as mentioned above, the traffic priority may be specified at a layer higher than the MAC layer.

[0167] Figure 18 illustrates an example of preventing delays in low-latency traffic transmission at the PPDU reception stage, i.e., at the physical layer level. Figures 19 to 22 illustrate an example of preventing delays in low-latency traffic transmission at the frame exchange stage, i.e., at the MAC layer level.

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

[0169] When a multilink device performs frame exchange on one of the non-STR multilink pairs, transmission of low-latency traffic may be delayed on the remaining links of the non-STR multilink pair. In the embodiment shown in Figure 19, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-AP station multilink device, which is a non-STR multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on the first link (Link1). The first AP (AP1) sends an RTS frame to the first station (STA1). The first station (STA1) sends a CTS (clear to send) frame to the first AP (AP1) in response to the RTS (request to send) frame. Due to the RTS frame / CTS frame exchange sequence performed on the first link, frame exchange between the second AP (AP2) and the second station (STA2) is not possible on the second link (Link2). Furthermore, even after the RTS / CTS frame exchange is complete, transmission may be restricted on the second link (Link2) for a certain period of time, such as during MediumSyncDelay or NAVSyncDelay.

[0170] Furthermore, in existing wireless LAN operation, a station that receives an RTS frame must transmit a CTS frame. Therefore, even if the PPDU reception interruption example described in Figure 18 is applied when existing wireless LAN operation is applied as is, low-latency traffic may be delayed until after the RTS frame / CTS frame exchange.

[0171] Figure 20 shows that a multilink device according to an embodiment of the present invention determines whether or not to transmit traffic based on traffic priority before frame exchange.

[0172] A multilink device can interrupt frame exchange in a frame exchange sequence performed by one of the non-STR multilink pairs in order to transmit low-latency traffic. Specifically, the multilink device can transmit low-latency traffic without transmitting frames that would normally be transmitted in the frame exchange sequence. In a specific embodiment, the multilink device does not need to transmit response frames in the frame exchange sequence in order to transmit low-latency traffic. In such an embodiment, the multilink device can resume the frame exchange sequence after transmitting low-latency traffic.

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

[0174] Furthermore, the frames exchanged in the frame exchange sequence may include information regarding the priority of the traffic contained in the frames transmitted after the frame exchange sequence. In this case, the priority information may indicate whether or not the traffic contained in the frames transmitted after the frame exchange sequence is low-latency traffic. Alternatively, the priority information may be the TID (traffic identifier) ​​of the traffic contained in the frames transmitted after the frame exchange sequence. The priority information can also represent the priority of the traffic contained in the frames transmitted after the frame exchange sequence. In such an embodiment, the multilink device can receive a frame in a frame exchange sequence performed by one of the non-STR multilink pairs and decide whether or not to continue the frame exchange sequence based on the additional information in the received frame. For example, if the frame received by the multilink device indicates that no low-latency traffic will be transmitted after the frame exchange sequence, the multilink device can interrupt the frame exchange sequence. Alternatively, if the frame received by the multilink device indicates that low-latency traffic will be transmitted after the frame exchange sequence, the multilink device may continue the frame exchange sequence. In further specific embodiments, the multilink device may interrupt the frame exchange sequence if the frames received by the multilink device indicate that the priority of the traffic to be transmitted after the frame exchange sequence is lower than the priority of the traffic waiting to be transmitted on the remaining links of the non-STR multilink pair. Alternatively, the multilink device may continue the frame exchange sequence if the frames received by the multilink device indicate that the priority of the traffic to be transmitted after the frame exchange sequence is equal to or higher than the priority of the traffic waiting to be transmitted on the remaining links of the non-STR multilink pair. The specific format of the traffic priority information included in the frames transmitted after the frame exchange sequence is illustrated in Figures 21 and 22.

[0175] In the embodiment described above, the multilink device can determine whether or not to transmit a response frame for a received frame based on additional information in the received frame. Furthermore, the multilink device can determine the type of response frame for a received frame based on additional information in the received frame.

[0176] Furthermore, a station that fails to receive a response frame in the frame exchange sequence does not need to retransmit the frame. This is because if the station were to retransmit the frame, it could interfere with the transmission of low-latency traffic that would otherwise proceed in place of the frame exchange sequence. Specifically, a station that sent a frame to a non-STR multilink device does not need to retransmit the frame even if it fails to receive a response frame. Similarly, a station that sent a frame on one of the non-STR multilink pairs does not need to retransmit the frame even if it fails to receive a response frame. In yet another specific embodiment, a station that fails to receive a response frame in the frame exchange sequence can decide whether or not to retransmit the frame based on whether the link from which the frame was sent and the links corresponding to the non-STR multilink pair have reached the service period for low-latency traffic transmission. For example, if the link from which the frame was sent and the links corresponding to the non-STR multilink pair have reached the service period for low-latency traffic transmission, the station that sent the frame does not need to retransmit the frame. A station that failed to receive a response frame in the frame exchange sequence can decide whether or not to retransmit the frame based on whether the frame's receiver participated in service period negotiations for low-latency traffic transmission. For example, if the frame's receiver participates in service period negotiations for low-latency traffic transmission, the station that sent the frame does not need to retransmit it. In the above embodiment, the service period for low-latency traffic transmission may be a restricted (R)-TWT (target wakeup time) service period. R-TWT is explained in Figure 25.

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

[0178] AP1 failed to receive a CTS frame from Station1 (STA1), but does not retransmit an RTS frame to Station1 (STA1). AP1 also transmits an RTS frame to a station other than Station1 (STA1) via Link1.

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

[0180] As mentioned above, frames exchanged in a frame exchange sequence may include information regarding the priority of traffic contained in frames transmitted after the frame exchange sequence. Specifically, the initiating frame that starts the frame exchange may include information regarding traffic priority. Specifically, if the initiating frame is a control frame, the frame control field may include information regarding traffic priority. For example, the initiating frame may include a 1-bit field (Low latency indication) indicating whether the traffic contained in frames transmitted after the frame exchange sequence is low latency traffic. In this case, the 1-bit field may be included in the initiating frame instead of the More Data field. The initiating frame may also include a 4-bit field (TID Info) indicating the TID (traffic identifier) ​​of the traffic contained in frames transmitted after the frame exchange sequence. In yet another specific embodiment, the initiating frame may include a 4-bit field (Priority Info) indicating the priority of traffic transmitted after the frame exchange sequence. In this case, the 4-bit field may be included in the initiating frame instead of the To DS field, From DS field, More Fragments field, and Retry field. Furthermore, the initiation frame may include a 1-bit field (Traffic info Flag) indicating whether or not it contains information about the traffic priority of the frames transmitted after the frame exchange sequence. In this case, the 1-bit field may be included instead of the Protected Frame field. The More Data field, To DS field, From DS field, More Fragments field, Retry field, and Protected Frame field in the control frame do not convey any additional meaning.

[0181] Figure 21(a) shows the Frame Control field of an RTS frame that does not contain information regarding traffic prioritization. Figure 21(b) shows the Frame Control field of an RTS frame that includes information regarding traffic prioritization according to an embodiment of the present invention.

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

[0183] The format of the traffic priority information may be the same as that used in the embodiment described in Figure 21. Figure 22(a) shows the User Info field of a MU-RTS frame that does not contain traffic priority information. Figure 22(b) shows the User Info field of a MU-RTS frame that contains traffic priority information according to an embodiment of the present invention.

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

[0185] When applying existing wireless LAN operations, a multilink device must acquire a transmission opportunity to transmit low-latency traffic even after a frame exchange sequence interruption. Therefore, it must compete with other wireless communication devices, and in this process, the transmission of low-latency traffic may be delayed again. A low-latency traffic transmission method may be needed to prevent this. This is explained in Figures 23 and 24.

[0186] Figure 23 shows that a station that receives an RTS frame requests the AP that sent the RTS frame to transfer the transmission opportunity according to an embodiment of the present invention.

[0187] When a station that buffers low-latency traffic receives an initiation frame to start a frame exchange sequence, the station can insert a request for priority processing of the low-latency traffic into its response frame to the initiation frame and send the response frame. The station that sent the initiation frame can accept or reject the request for priority processing of the low-latency traffic. A station that receives a response frame containing a request for priority processing of the low-latency traffic can accept the request by sending a response frame. Alternatively, a station that receives a response frame containing a request for priority processing of the low-latency traffic can reject the request for priority processing of the low-latency traffic by performing a scheduled transmission after the frame exchange sequence.

[0188] For example, Station 1 receives an RTS frame from Station 2. If Station 1 has buffered low-latency traffic transmissions, Station 1 can insert a request for priority processing of the low-latency traffic into the CTS frame and send the CTS frame to Station 2. Station 2 receives the CTS frame containing the request for priority processing of the low-latency traffic. If Station 2 accepts the request for priority processing of the low-latency traffic, Station 2 sends a CTS frame to Station 1. Station 1 receives the CTS frame and sends a frame containing the low-latency traffic. If Station 2 rejects the request for priority processing of the low-latency traffic, Station 2 sends DL data to Station 1. In such an embodiment, the interval between frames may be SIFS.

[0189] In another specific embodiment, when a station that buffers low-latency traffic receives an initiation frame to start a frame exchange sequence, the station can send an initiation frame in response to the initiation frame, requesting priority processing of the low-latency traffic. In this case, the initiation frame sent in response to the initiation frame contains information about the characteristics of the low-latency traffic that the station buffers. For example, a first station receives an RTS frame from a second station. If the first station has buffered low-latency traffic transmissions, the first station can send an RTS frame to the second station. In this case, the Frame Control field of the RTS frame may contain information about the characteristics of the low-latency traffic that the station buffers. In this case, the information about the characteristics of the low-latency traffic may be indicated as in the embodiment described in Figure 21.

[0190] In the above embodiment, a station that receives a request for priority processing of low-latency traffic may not accept the request and may terminate the frame exchange sequence. For example, a station that receives an RTS frame as a response to an RTS frame, or a CTS frame containing a request for priority processing of low-latency traffic, does not need to transmit a DL data frame afterward. This is because it can be interpreted as signaling that the station does not want any further sequences following the frame exchange sequence for the request for priority processing of low-latency traffic.

[0191] Furthermore, a station transmitting an initiation frame may include information in the initiation frame regarding the characteristics of the traffic it intends to transmit after the frame exchange sequence. For example, a station transmitting an RTS frame in an RTS frame / CTS frame exchange sequence may include information in the RTS frame regarding the characteristics of the traffic to be transmitted after the RTS frame / CTS frame exchange sequence. The information regarding the traffic characteristics may be indicated as in the embodiment described in Figure 21. In such an embodiment, a station receiving the initiation frame can determine whether or not to request priority processing of low-latency traffic based on the information regarding the traffic characteristics contained in the initiation frame. For example, a first station may transmit an RTS frame to a second station that includes information regarding the characteristics of the traffic to be transmitted after the RTS frame / CST frame exchange. The second station can then determine whether or not to request priority processing of low-latency traffic from the first station based on the information regarding the characteristics of the traffic to be transmitted after the RTS frame / CST frame exchange. Specifically, the second station may request priority processing of low-latency traffic from the first station if the traffic to be transmitted after the RTS frame / CST frame exchange is not low-latency traffic. Furthermore, the second station does not need to request the first station to prioritize low-latency traffic if the traffic transmitted after the RTS frame / CST frame exchange is low-latency traffic. In other specific embodiments, the second station may request the first station to prioritize low-latency traffic if the priority of the traffic transmitted after the RTS frame / CST frame exchange is lower than the priority of the low-latency traffic stored in the second station's buffer. Also, the second station does not need to request the first station to prioritize low-latency traffic if the priority of the traffic transmitted after the RTS frame / CST frame exchange is equal to or higher than the priority of the low-latency traffic stored in the second station's buffer.

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

[0193] In the embodiment described above, when the transmission of low-latency traffic is completed and a TXOP configured for frame exchange remains, the station that transmitted the low-latency traffic can transmit a response frame to signal that the transmission of the low-latency traffic is complete. Specifically, a station that has requested priority processing of the low-latency traffic in the RTS frame / CTS frame exchange sequence and has completed the transmission of the low-latency traffic can transmit a CTS frame. At this time, the station can transmit the CTS frame using a format other than non-HT PPDU, such as HT PPDU, VHT PPDU, or EHT PPDU. In the specific embodiment, the format other than non-HT PPDU may be the EHT PPDU format. This is because the CTS frame is not transmitted with the intention of setting a NAV, but rather with the intention of indicating that the transmission of low-latency traffic is complete.

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

[0195] Figure 24 shows the format of the Frame Control field of a CTS frame containing a request for priority processing of low-latency traffic according to an embodiment of the present invention.

[0196] As mentioned above, the CTS frame may contain information regarding requests for priority processing of low-latency traffic.

[0197] A CTS frame may include a 1-bit field (Low latency indication) indicating a request for priority processing of low-latency traffic. A CTS frame may also include a 4-bit field (TID Info) indicating the TID (traffic identifier) ​​of the low-latency traffic frame. Furthermore, in other specific embodiments, a CTS frame may include a 4-bit field (Priority Info) indicating the priority of the low-latency traffic. A CTS frame may also include a 1-bit field (UL Request) indicating whether the station transmitting the CTS frame requests uplink transmission.

[0198] Scheduling for low-latency traffic transmission is explained in Figures 25 to 30. In conventional wireless LAN communication, EDCA (enhanced distributed channel access) is used to set channel access parameters for each AC, and the set channel access parameters are used to support traffic processing according to priority for each AC. However, existing EDCA provides channel access with a probabilistically high priority, and therefore has shortcomings in supporting the transmission of low-latency traffic. To compensate for this, it is possible to set a time interval in which low-latency traffic can be transmitted preferentially. For the sake of explanation, the time interval in which low-latency traffic is transmitted preferentially is called the restricted service period. Most services that require low-latency traffic transmission, such as VR / AR, require periodic traffic transmission, and therefore the effect of reducing the transmission delay of low-latency traffic by using the restricted service period is significant.

[0199] A restricted service period may be a time interval in which the transmission of low-latency traffic and the transmission of responses to low-latency traffic are preferentially permitted. Specifically, a restricted service period may be a time interval in which only the transmission of low-latency traffic and the transmission of responses to low-latency traffic are permitted. In yet another specific embodiment, a restricted service period may be a time interval in which the transmission of low-latency traffic and the transmission of responses to low-latency traffic have occurred, and the transmission of traffic other than low-latency traffic is permitted after the transmission of low-latency traffic and the transmission of responses to low-latency traffic have been completed.

[0200] First, we will explain how to set a restricted service period. The restricted service period may be set by the TWT of an existing WLAN. The TWT sets a service period through consultation between the AP and the station, and the AP and station transmit and receive data during the service period, while assisting in entering low-power mode outside of the service period. This will be explained in detail in Figure 25. For the sake of explanation, we will refer to the setting of a restricted service period by the TWT and the operation of the AP and station based on the said restricted service period as a restricted TWT.

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

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

[0203] In the embodiment shown in Figure 25, the first station (STA1) requests the AP to configure the TWT. The AP and the first station (STA1) configure the TWT parameters, such as the initial TBTT and the listen interval. This configures the broadcast TWT for the AP, the first station (STA1), and the second station (STA2). The AP uses a beacon frame to indicate the broadcast TWT service period. During the broadcast TWT service period, the AP can either send a DL (downlink) PPDU (physical layer protocol data unit) to the first station (STA1) and the second station (STA2), or send a trigger frame to the first station (STA1) and the second station (STA2) to trigger an UL (uplink) transmission. During the broadcast TWT service period, the first station (STA1) and the second station (STA2) wake up to receive the beacon frame. The first station (STA1) and the second station (STA2) obtain information about the TWT from the received beacon frame. The AP sends a trigger frame to the first station (STA1) and the second station (STA2). The first station (STA1) sends a PS-Poll frame to the AP, and the second station (STA2) sends a QoS Null frame to the AP. The AP receives the PS-Poll frame and QoS Null frame sent by the first station (STA1) and the second station (STA2) and determines that the first station (STA1) and the second station (STA2) are in an awake state. The AP sends a multi-STA Block ACK frame to the first station (STA1) and the second station (STA2). The AP sends a DL PPDU to the first station (STA1) and the second station (STA2).

[0204] The existing TWT service period does not restrict stations that do not participate in the TWT from accessing or transmitting channels. This is because the TWT is intended to help stations participating in the TWT enter a doze state. However, a restricted service period designed to prevent transmission delays of low-latency traffic must guarantee preferential transmission of low-latency traffic, and therefore, a method is needed to protect the restricted service period.

[0205] During a restricted service period, stations not participating in a restricted TWT may be restricted from accessing the channel. Specifically, stations not participating in a restricted TWT may not be able to access the channel during the restricted service period. If a station not participating in a restricted TWT completes channel access during the restricted service period, the station may restart the channel access procedure without transmitting. In this case, the station can restart the channel access procedure when the restricted service period ends. Furthermore, a station's channel access can represent an EDCA backoff procedure. Completion of channel access can represent the EDCA backoff procedure's backoff counter reaching 0. Also, when a station restarts the channel access procedure, the station may randomly obtain an integer within the CW used for the previous channel access and use the obtained integer as the backoff counter. That is, the station does not need to double the size of the CW used for the previous channel access. In this case, the CW may be maintained separately for each AC. Such channel access restrictions may only be applied to stations supporting a restricted TWT. Specifically, such channel access restrictions apply only to non-legacy (EHT) stations where the EHT Capabilities element's dot11RestrictedTWTOptionImplemented is set to true, and do not apply to non-legacy (EHT) stations where the EHT Capabilities element's dot11RestrictedTWTOptionImplemented is set to false. In this specification, non-legacy stations can represent EHT stations and stations after EHT stations. Legacy stations are stations before EHT stations and can represent non-HT stations, HT stations, VHT stations, and HE stations.

[0206] Furthermore, during the restricted service period, non-legacy stations may be configured with NAVs for traffic other than low-latency traffic. Specifically, as if NAVs were configured for traffic other than low-latency traffic, stations can suspend channel access procedures for transmitting traffic other than low-latency traffic. In such embodiments, the NAV may be independent of conventional NAVs (basic NAVs, Intra-BSS NAVs). In this case, non-legacy stations may be limited to stations supporting restricted TWTs. In yet another specific embodiment, non-legacy stations may be limited to stations participating in restricted TWTs.

[0207] The restricted service period may be included within the broadcast TWT service period. Furthermore, in other specific embodiments, the restricted service period may not be included within the broadcast TWT service period.

[0208] Furthermore, the restricted service period may be repeated at a frequency specified by the AP. That is, the AP can specify the repetition frequency of the restricted service period. This eliminates the need for the AP to send a TWT element of the beacon frame every time to set the restricted service period. In this case, the service period frequency may be set according to the characteristics of the low-latency service using low-latency traffic. For example, the frequency of a low-latency service period where low-latency traffic is generated every 50ms may be 50ms.

[0209] Furthermore, a Quiet Interval may be set for stations that do not support the restricted TWT. In conventional wireless LANs, the Quiet Interval is a section that supports channel sensing. When a Quiet Interval is set, all stations suspend transmission. This characteristic of the Quiet Interval can be used to protect the restricted service period. This is explained in Figure 26. In this case, stations that do not support the restricted TWT may be limited to legacy stations.

[0210] Figure 26 shows that AP sets a quiet interval according to an embodiment of the present invention.

[0211] APs operating a restricted TWT can send a Quiet element to set a quiet interval. During a quiet interval, stations suspend channel access. However, if channel access is restricted for stations participating in a restricted TWT, they will not be able to send low-latency traffic. Therefore, stations participating in a restricted TWT may ignore the quiet interval corresponding to the restricted service period. In this case, the quiet interval corresponding to the restricted service period represents the quiet interval set to protect the restricted service period of the restricted TWT. Specifically, stations participating in a restricted TWT can consider the quiet interval corresponding to the restricted service period as the restricted service period itself. APs operating a restricted TWT do not need to set the quiet interval to match the restricted service period. This is because in the Quiet element, the quiet interval is set in TU (time unit, 1024us) units, and the TWT is set in 256us units.

[0212] However, channel access in a quiet section other than one not set for a restricted service period may interfere with quiet sections not set for a restricted service period. Therefore, it is necessary to distinguish between quiet sections set for a restricted service period, i.e., quiet sections corresponding to a restricted service period. Consequently, stations participating in a restricted TWT may not be able to ignore quiet sections that do not correspond to a restricted service period. Stations cannot transmit at all in quiet sections that do not correspond to a restricted service period. Specifically, stations participating in a restricted TWT may not be able to ignore quiet sections that do not overlap with a restricted service period. In a specific example, stations participating in a restricted TWT cannot transmit at all in quiet sections that do not overlap with a restricted service period.

[0213] Furthermore, in the above embodiment, a station participating in a restricted TWT can be considered a quiet section corresponding to a restricted service period if the start time of the restricted service period and the start time of the quiet section are within a predetermined time. As mentioned above, APs operating a restricted TWT do not need to set the quiet section to coincide with the restricted service period.

[0214] In the embodiment shown in Figure 25, the AP transmits a beacon frame to set a quiet interval and a restricted service period. In Figure 25(a), the quiet interval is set to the same time interval as the restricted service period. Therefore, stations participating in the restricted TWT within the quiet interval will have channel access. In Figure 25(b), the quiet interval is set to a point earlier than the start of the restricted service period and a point later than the end of the restricted service period. In Figure 25(b), channel access is restricted for stations participating in the restricted TWT within a quiet interval that does not overlap with the restricted service period. Stations participating in the restricted TWT within a quiet interval that overlaps with the restricted service period will have channel access.

[0215] As mentioned earlier, channel access may be restricted during the restricted service period. This means that such restrictions may also apply to TXOP configurations. This is illustrated in Figure 27.

[0216] Figure 27 illustrates how a station configures a TXOP considering a limited service period according to an embodiment of the present invention.

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

[0218] In a specific example, when a station that is a TXOP holder transmits low-latency traffic, frame exchange may continue even after the restricted service period has begun.

[0219] This document describes specific methods for a station to terminate a TXOP before its limited service period.

[0220] A station can configure a TXOP based on a restricted service period. Specifically, a station can set the end of the TXOP to before the start of the restricted service period. In this case, the station can set the duration of the starting frame that initiates the frame exchange sequence to before the start of the restricted service period. For example, if a station successfully accesses the channel 3m before the start of the restricted service period, the station can set the TXOP to 3ms or earlier. Alternatively, a station may terminate the TXO by sending a CTS-to-Self frame. In this case, the station can send the CTS-to-Self frame at the base transmission rate, 6Mbps, because many legacy stations can receive frames when the station sends them at the base transmission rate.

[0221] In yet another specific embodiment, the station can transmit the CF-End frame before the start of the restricted service period. This allows the station to terminate the TXOP before the start of the restricted service period. In this case, the station can transmit the CF-End frame at the base transmission rate, 6 Mbps, because many legacy stations can receive the frame when the station transmits it at the base transmission rate.

[0222] Furthermore, a station that is not a TXOP holder can deactivate the NAV set before the restricted service period began at the start of the restricted service period. In this case, the station may be a station that supports restricted TWT. That is, the station may be a station that has set the value of the dot11RestrictedTWTOptionImplemented field to True. A station that is not a TXOP holder but does not support restricted TWT cannot deactivate the NAV set before the restricted service period began at the start of the restricted service period. However, if the station has completed frame exchange and the remaining duration of the TXOP is less than twice the sum of the time it takes to transmit the CF-End frame and the SIFS, the station does not need to transmit a CF-End frame. In this case, the station can be considered to have deactivated the TXOP at the start of the restricted service period. Specifically, the station can be considered to have deactivated the basic NAV at the start of the restricted service period.

[0223] In other specific embodiments, the stations may be limited to stations participating in a restricted TWT.

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

[0225] Conventional wireless LAN operation defines actions that may be transmitted beyond the TXOP limit as exceptions to the TXOP rule. For example, the retransmission of a single MPDU, the transmission of a single MSDU under a Block ack agreement (not included in an A-MSDU or an A-MPDU consisting of two or more MPDUs), and the transmission of control frames and QoS Null frames (not included in an A-MPDU consisting of two or more MPDUs) may be transmitted beyond the TXOP limit. If such exceptions are granted to restricted service periods, the transmission of low-latency traffic may be delayed. Such exceptions to the TXOP limit must not be applied in violation of restricted service periods.

[0226] If the end time of a TXOP and the start time of a restricted service period are within a predetermined time difference, the station can determine that the TXOP was acquired before the start of the restricted service period. The predetermined time difference may be 100us. Furthermore, in other specific embodiments, if the end time of a TXOP is within a restricted service period, the station can determine that the TXOP was acquired before the start of the restricted service period.

[0227] As mentioned above, stations may be required to complete frame replacement before the restricted service period. This means that stations are not permitted to initiate frame replacement if the completion of the frame replacement falls within the restricted service period. In this case, stations may perform fragmentation to complete the frame replacement before the start of the restricted service period.

[0228] Furthermore, if low-latency traffic is transmitted during frame exchange performed by a station that is a TXOP holder, the station may continue frame exchange even after the start of the low-latency service period.

[0229] Figure 28 illustrates the channel access procedure considering the limited service period.

[0230] Figure 28 shows that a station according to an embodiment of the present invention performs the channel access procedure again, taking into account a limited service period.

[0231] As mentioned above, even if a station completes channel access before the restricted service period, if the frame exchange is completed after the restricted service period has started, the station can restart the channel access procedure without transmitting. At this time, the station can obtain the backoff counter value again. At this time, the station can use the same CW size used in the previous channel access procedure. In other words, the station does not need to double the CW size used in the previous channel access procedure or initialize it to the minimum value that the CW can have. Also, the station does not need to increase the number of retries, such as the QSRC (QoS STA Retry Counter).

[0232] Furthermore, if a station completes channel access within a predetermined time frame from the start of a restricted service period, the station may restart the channel access procedure without transmitting.

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

[0234] Furthermore, as mentioned above, the station can operate in such a way that NAV is set for AC of traffic other than low-latency traffic. Therefore, the station can determine that the CCA result for transmitting AC of traffic other than low-latency traffic is not idle (busy).

[0235] In the embodiment shown in Figure 28, the AP transmits a beacon frame containing a TWT element to signal that a restricted service period is being set. The station's channel access backoff counter value reaches 0 before the restricted service period begins. The station determines that the completion of the frame exchange containing the traffic it intends to transmit occurs after the start of the service period. Therefore, the station obtains a backoff counter within the CW value used in the previous channel access procedure. The station then performs the channel access procedure again using the obtained backoff counter. At this time, the station does not increment the retransmission counter.

[0236] It is possible that all low-latency traffic transmissions are completed before the restricted service period ends. In such cases, restricting the transmission of traffic other than low-latency traffic due to the low-latency service period can be inefficient. Therefore, a method for terminating the restricted service period early may be necessary. This will be explained using the example shown in Figure 29.

[0237] Figure 29 shows the operation by which an AP terminates a limited service period early according to an embodiment of the present invention.

[0238] For an AP to terminate a restricted service period early, it must be able to determine that all low-latency traffic transmissions from stations participating in the restricted TWT have been completed. To this end, stations participating in the restricted TWT can signal whether or not to transmit additional low-latency traffic in the frames they transmit. Specifically, a station can signal to transmit additional low-latency traffic by setting the value of the More data subfield in the Frame Control field of the frame. In this case, if the value of the More data subfield in the Frame Control field of a frame transmitted during the restricted service period is 1, the More data subfield indicates that additional transmission of low-latency traffic is required, and does not need to indicate whether additional transmission of non-low-latency traffic is required. For example, if a station participating in the restricted TWT does not store low-latency traffic in the transmit buffer and only stores non-low-latency traffic, the station can set the value of the More data subfield in the Frame Control field of the frames it transmits during the restricted service period to 0. An AP may terminate a restricted service period early based on whether stations participating in a restricted TWT have a value of 0 in the More data subfield of the Frame Control field of a frame during the restricted service period. Specifically, if there is no low-latency traffic to send to the AP's transmit buffer and stations participating in a restricted TWT have a value of 0 in the More data subfield of the Frame Control field of a frame during the restricted service period, the AP may terminate the restricted service early.

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

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

[0241] As mentioned above, a quiet period may be set for the restricted service period to protect legacy wireless communication terminals from the restricted service period. In this case, the AP can send a CF-End frame to terminate the restricted service period. When the AP sends a CF-End frame, the quiet period set on the legacy station is also released.

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

[0243] When a quiet interval is set for a restricted service period, stations participating in the restricted TWT are not permitted to transmit CF-End frames within the restricted service period. In a specific embodiment, stations participating in the restricted TWT are not permitted to transmit CF-End frames in the quiet interval corresponding to the restricted service period. This is because if a station participating in the restricted TWT transmits a CF-End frame, the NAV set on the legacy station is deactivated. However, as mentioned above, if the CF-End frame is used to terminate the restricted service period early, the AP may transmit a CF-End frame within the restricted service period.

[0244] In the embodiment shown in Figure 29, the AP transmits a beacon frame containing a TWT element and a Quiet element. Stations supporting the restricted TWT determine that a restricted service period has been set, while stations not supporting the restricted TWT determine that a quiet section has been set. When the AP determines that all low-latency traffic has been transmitted within the restricted service period, it transmits a CF-End frame to terminate the restricted service period early and remove the quiet section set on legacy stations. At this time, stations supporting the restricted TWT determine that the channel access restrictions applied during the restricted service period have been removed. Specifically, as described above, if an embodiment in which NAV is set during the restricted service period is applied, stations supporting the restricted TWT can determine that the NAV for the restricted service period has been removed. Also, stations not supporting the restricted TWT that receive a CF-End frame remove the NAV.

[0245] The operation of the multilink device was explained using Figures 11 to 24. The channel access operation of the multilink device was explained using Figures 30 to 35.

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

[0247] Furthermore, if the second station is the TXOP holder, the second station can terminate the TXOP before it receives a specific frame on the first link. In this case, the method for terminating the TXOP may be the same as the embodiment of terminating the TXOP described in Figure 28. Specifically, the second station can set the termination of the TXOP to occur before it receives a specific frame on the first link. For example, if the specific frame is a DTIM, the second station can set the termination time of the TXOP based on the reception cycle of the DTIM. Also, the second station can transmit a CF-End frame before it receives a specific frame on the first link. Furthermore, the TXOP limit exception does not need to be applied to such embodiments.

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

[0249] Figure 30 shows that a multilink device transmits using a non-STR link pair according to an embodiment of the present invention.

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

[0251] A multilink device operating with non-STR multilink equipment can synchronize the transmission start times of non-STR multilink pairs. In this case, the transmission start time of a frame can represent the transmission start time of the PPDU containing the frame. To synchronize the transmission start times of non-STR link pairs, the multilink device can maintain a backoff value of 0 in the channel access procedure, thereby delaying transmission.

[0252] Furthermore, when transmission and reception occur consecutively on a non-STR multilink pair, the multilink device may synchronize the end time of transmission on the non-STR multilink pair. To this end, the multilink device may add padding bits or fields to the frame or PPDU being transmitted. The multilink device may also add a Packet Extension (PE). Additionally, when consecutive frame exchanges occur on a non-STR multilink pair, the multilink device may synchronize the start time of transmission on the non-STR multilink after the first frame exchange. In yet another specific embodiment, the multilink device may perform fragmentation to synchronize the end time of transmission.

[0253] If the TXOP start time is the same for multiple links, the TXOPs for frame transmission on each link may be synchronized. In this case, simultaneous transmission using multiple links may occur after the negotiation phase for simultaneous transmission on multiple links. In the negotiation phase for simultaneous transmission, the multilink device performing the transmission sends a request frame to acquire a TXOP for simultaneous transmission via synchronized transmission on multiple links, and the multilink device that receives the request frame can send a response frame at a SIFS (Short Interframe Space) interval with the request frame. In this case, the response frame may be sent simultaneously on one or more links that received the request frame. The request frame may be a control frame. For example, the request frame may be either an RTS frame or a MU (Multi-user)-RTS frame. In this case, the response frame may be a CTS frame. If a channel on any one link is occupied during channel contention for simultaneous transmission, the multilink device can wait to perform simultaneous transmission or transmit using only the links that include idle channels. The exchange of the request frame and response frame described above does not have to be performed simultaneously on multiple links. Furthermore, synchronized frame exchange may be defined as the synchronization of the start time of transmission of the PPDU containing the frame and the synchronization of the end time of transmission of the PPDU containing the frame.

[0254] When a multilink device transmits a frame requesting an immediate response on the first link of a non-STR link pair, the multilink device can synchronize the end of transmission on the first and second links of the non-STR link pair. In this case, an immediate response indicates that the interval between the received frame and the response frame is a predetermined interval. The predetermined interval may be SIFS. In other specific embodiments, the predetermined interval may be PIFS. Furthermore, when a multilink device transmits a frame that does not request an immediate response on the first link of a non-STR link pair, the multilink device does not need to synchronize the end of transmission on the first and second links of the non-STR link pair. In this case, the multilink device may also transmit a PPDU that does not request an immediate response on the second link, and is not permitted to transmit a PPDU that requests an immediate response.

[0255] In the embodiment described above, the synchronization of the transmission start time indicates that the difference between transmission start times is within a predetermined time. Similarly, the synchronization of the transmission end time indicates that the difference between transmission end times is within a predetermined time. In this case, the predetermined time may be the time required to prevent the channel state from being recognized as busy on other links when channel sensing and backoff operations are performed individually on each link. In a specific embodiment, the predetermined time may be the receive-transmit turnaround time (RxTxTurnaroundTime). For example, the predetermined time may be 8us or 4us.

[0256] These embodiments enable multilink devices to prevent transmission on one link from being interrupted on the other links in a non-STR link pair.

[0257] In the embodiment shown in Figure 30, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-STR multilink device, the non-AP station multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on the first link (Link1). The second AP (AP2) and the second station (STA2) operate on the second link (Link2). In Figure 30(a), the AP multilink device and the station multilink device perform synchronized transmission and synchronized reception. This prevents transmission from being interrupted on any one link of the non-STR multilink pair. In Figure 30(b), the first AP (AP1) transmits a DL PPDU on the first link (Link1) that does not require an immediate response. Since DL PPDUs that do not require an immediate response are sent on the first link (Link1), the second station (STA2) sends DL PPDUs that do not require an immediate response on the second link (Link2) without synchronizing them with the transmission on the first link.

[0258] Figure 30 shows an embodiment in which frame replacement begins with the AP multilink device, which is an STR multilink device, in a non-STR multilink pair. The embodiment described in Figure 30 may also be applied when frame replacement begins with the non-STR multilink device. This will be explained in Figures 31 to 32.

[0259] Figure 31 shows a frame replacement starting from a non-AP station multilink device to which an embodiment of the present invention is not applied. Figure 32 shows a frame replacement starting from a non-AP station multilink device according to an embodiment of the present invention.

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

[0261] Therefore, when a non-STR multilink device transmits a frame requesting an immediate response on the first link of a non-STR link pair, the non-STR multilink device may synchronize the end of transmission on the first and second links of the non-STR link pair. In this case, an immediate response indicates that the interval between the received frame and the response frame is a predetermined interval. The predetermined interval may be SIFS. In other specific embodiments, the predetermined interval may be PIFS. Also, when a non-STR multilink device transmits a frame that does not request an immediate response on the first link of a non-STR link pair, the non-STR multilink device does not need to synchronize the end of transmission on the first and second links of the non-STR link pair. In this case, the non-STR multilink device may also transmit a PPDU that does not request an immediate response on the second link, and is not permitted to transmit a PPDU that requests an immediate response.

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

[0263] Using FIGS. 33 to 35, the case where transmissions not synchronized in a non-STR link pair are allowed will be described.

[0264] FIG. 33 shows that when the multi-link device performs a transmission that requests an immediate response on the first link among non-STR link pairs according to an embodiment of the present invention, it performs a transmission that does not request an immediate response on the second link.

[0265] When the multi-link device transmits a frame that requests an immediate response on the first link among non-STR link pairs, the multi-link device can complete the transmission on the second link among the non-STR link pairs before the end point of the transmission on the first link and perform a transmission that does not request an immediate response. In such an embodiment, since no response frame is transmitted on the second link, it is possible to prevent the transmission of the multi-link device on the first link and the response frame to the transmission from being interfered by the transmission of the multi-link device on the second link. Also, when the transmission of the multi-link device on the second link does not complete before the end point of the transmission on the first link, the transmission of the response frame on the first link may be interfered by the transmission of the multi-link device on the second link. Therefore, the transmission of the multi-link device on the second link must complete before the transmission on the first link.

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

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

[0268] The magnitude of the inter-link influence may vary depending on the RU on which transmission is performed in the non-STR multi-link pair. Therefore, even when the multi-link device performs transmission on the first link of the first link and the second link which are non-STR multi-link pairs, transmission on the second link may be permitted depending on the positions of the RU of the first link on which the multi-link device performs transmission and the RU of the second link on which the multi-link device performs transmission. Specifically, when the multi-link device performs UL OFDMA transmission, transmission on the second link may be permitted depending on which RU performs UL OFDMA transmission. In yet another specific embodiment, transmission on the second link may be permitted depending on the magnitude of the bandwidth used when the multi-link device performs transmission on each link. At this time, the multi-link device can perform transmission using any one of bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 320 MHz.

[0269] In the embodiment shown in Figure 34, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-STR multilink device, a non-AP station multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on the first link (Link1). The second AP (AP2) and the second station (STA2) operate on the second link (Link2). The first station (STA1) participates in UL OFDMA transmission on the first link (Link1). At this time, the second station (STA2) performs uplink transmission if the positions of the RUs where the first station (STA1) performs UL OFDMA and the RUs where the second station (STA2) transmits satisfy a predetermined condition. At this time, the predetermined condition may be that the distance between the RUs is smaller than a predetermined distance. Furthermore, whether or not transmission on the second link is permitted may be determined by the direction of bandwidth expansion in which the transmission is performed.

[0270] The transmission direction may determine whether the link pair is a non-STR link pair or an STR link pair. This is explained in Figure 35.

[0271] Figure 35 shows an embodiment of the present invention in which a single link pair is determined to be either a non-STR link pair or an STR link pair depending on the transmission direction.

[0272] The first multilink device cannot transmit on the second link when receiving on the first link of the link pair, but can transmit on the first link when receiving on the second link. For example, the station's transmit power may be limited to a predetermined level in the 6GHz band. Therefore, when the first link is located in the 6GHz band, the first multilink device cannot transmit on the second link when receiving on the first link of the link pair, but can transmit on the first link when receiving on the second link. Therefore, depending on the transmission direction, it may be permissible for the end of transmission on the second link to be out of sync with the end of transmission on the first link while transmission is taking place on the first link. In this case, the multilink device may terminate transmission on the second link before transmission on the first link. For this purpose, the multilink device can perform fragmentation on traffic that it intends to transmit on the second link.

[0273] In the embodiment shown in Figure 35, the AP multilink device includes a first AP (AP1) and a second AP (AP2), and the non-STR multilink device, the non-AP station multilink device, includes a first station (STA1) and a second station (STA2). The first AP (AP1) and the first station (STA1) operate on the first link (Link1). The second AP (AP2) and the second station (STA2) operate on the second link (Link2). In this case, the non-AP station cannot transmit on the second link when receiving on the first link, which is located in the 6GHz band, but it can transmit on the first link (Link1) when receiving on the second link (Link2). While the first station (STA1) is performing an uplink transmission on the first link (Link1), the second station (STA2) begins an uplink transmission on the second link (Link2). At this time, the second station (STA1) completes its uplink transmission before the first station (STA1) completes its uplink transmission. Through this process, the uplink transmission is completed on both the first and second links, and the BA frame is successfully transmitted.

[0274] Although the present invention has been described using wireless LAN communication as an example, it is not limited to this and can be applied equally to other communication systems such as cellular communication. Furthermore, although the methods, apparatus, and systems of the present invention have been described in relation to specific embodiments, some or all of the components and operations of the present invention can be embodied by a computer system having a general-purpose hardware architecture.

[0275] The features, structures, and effects described in the examples above are included in at least one embodiment of the present invention, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, and effects exemplified in each embodiment can be combined or modified and implemented in other embodiments by a person with ordinary skill in the art to which the embodiment belongs. Therefore, it should be interpreted that such combinations and modifications are included within the scope of the present invention.

[0276] While the above description has focused on embodiments, these are merely illustrative and do not limit the present invention. Those with ordinary skill in the art to which the present invention pertains will understand that various modifications and applications not exemplified above are possible, without departing from the essential characteristics of these embodiments. For example, each component specifically shown in the embodiments can be modified. Furthermore, any differences related to such modifications and applications should be interpreted as being within the scope of the present invention as defined in the attached claims. [Explanation of symbols]

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

Claims

1. A wireless communication terminal that communicates wirelessly with a base wireless communication terminal, Transmitting and receiving unit; and Including the processor, The aforementioned processor, Within a limited service period, transmit low-latency traffic configured as traffic for low-latency transmission, or a response to said low-latency traffic. A wireless communication terminal in which the transmission of low-latency traffic and transmissions other than the transmission of low-latency traffic are restricted within the aforementioned restricted service period.

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

3. The aforementioned processor, Get a random integer within the competition window, Based on the random integer obtained, channel access is performed. The wireless communication terminal according to claim 1, which completes channel access before the start of the restricted service period and, if it determines that frame exchange cannot be completed before the start of the restricted service period and abandons transmission, performs channel access again.

4. The aforementioned processor, The wireless communication terminal according to claim 3, wherein when the wireless communication terminal performs the channel access again, it maintains the size of the conflict window used in the completed channel access.

5. The aforementioned processor, The wireless communication terminal according to claim 3, wherein when the wireless communication terminal performs the channel access again, it maintains the retransmission count of the completed channel access.

6. A quiet period is set corresponding to the aforementioned restricted service period, and no transmissions are permitted during the quiet period. The aforementioned processor, Ignoring the quiet interval corresponding to the restricted service period, the low-latency traffic or a response to the low-latency traffic is transmitted within the restricted service period. The wireless communication terminal according to claim 1, which does not transmit a CF End frame within the aforementioned limited service period.

7. A quiet period is set corresponding to the aforementioned restricted service period, and no transmissions are permitted during the quiet period. The aforementioned processor, Based on the start time of the restricted service period and the start time of the quiet section, a decision is made as to whether or not to ignore the quiet section. The wireless communication terminal according to claim 1, which, when it is decided to ignore the quiet section, ignores the quiet section corresponding to the restricted service period and transmits the low-latency traffic or a response to the low-latency traffic within the restricted service period.

8. The aforementioned processor, If the conditions determined based on the start of the restricted service period and the start of the quiet section are met, the quiet section will be ignored. The wireless communication terminal according to claim 7, which does not perform any transmissions if the conditions determined based on the start of the restricted service period and the start of the quiet interval are not met.

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

10. A method for operating a wireless communication terminal that communicates wirelessly with a base wireless communication terminal, Within a limited service period, the process includes sending low-latency traffic configured as traffic for low-latency transmission, or a response to said low-latency traffic. A method of operation in which, within the restricted service period, transmissions other than the transmission of low-latency traffic and the transmission of responses to the low-latency traffic are restricted.

11. The aforementioned operation method is, The operation method according to claim 10, further comprising the step of terminating a TXOP for the transmission of traffic other than the low-latency traffic before the start of the restricted service period.

12. The aforementioned operation method is, The stage of obtaining a random integer within the competition window; The step of performing channel access based on the random integer obtained above; and The operation method according to claim 10, further comprising the step of performing channel access again if channel access is completed before the start of the restricted service period and transmission is abandoned because it is determined that frame exchange cannot be completed before the start of the restricted service period.

13. The step of performing the aforementioned channel access again is: The operation method according to claim 12, further comprising the step of maintaining the size of the conflict window used for the completed channel access when the wireless communication terminal performs the channel access again.

14. The step of performing the aforementioned channel access again is: The operation method according to claim 12, further comprising the step of maintaining the retransmission count of the completed channel access when the wireless communication terminal performs the channel access again.

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

16. A quiet period is set corresponding to the aforementioned restricted service period, and no transmissions are permitted during the quiet period. The step of transmitting the low-latency traffic or a response to the low-latency traffic within the aforementioned limited service period is: A step of determining whether to ignore the quiet section based on the start time of the restricted service period and the start time of the quiet section; and The operation method according to claim 10, further comprising the step of transmitting the low-latency traffic or a response to the low-latency traffic within the restricted service period, ignoring the quiet interval corresponding to the restricted service period, if it is decided to ignore the quiet interval.

17. The step of determining whether to ignore the quiet section based on the start time of the restricted service period and the start time of the quiet section is: A stage in which the quiet interval is ignored if the conditions determined based on the start of the restricted service period and the start of the quiet interval are met; and The operation method according to claim 16, further comprising a step of not performing any transmissions if the conditions determined based on the start of the restricted service period and the start of the quiet interval are not met.

18. The operating method according to claim 17, wherein the condition determined based on the start time of the restricted service period and the start time of the quiet interval is that the start time of the quiet interval and the start time of the TWT service period are within a predetermined time.

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