Wireless communication terminal for wireless communication with a base wireless communication terminal and the method of operating this device.

Abstract

The invention relates to a wireless communication terminal that transmits wirelessly to a base wireless communication terminal. The wireless communication terminal comprises: a transceiver; and a processor. The processor transmits low-latency traffic configured as traffic for low-latency transmission during the limited service time, or response to low-latency traffic, and during the limited service time, transmissions except for the transmission of low-latency traffic and the transmission of response to low-latency traffic are limited.

Description

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

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

[0002] With the recent proliferation of mobile devices, wireless LAN (WLAN) technology, which can provide them with fast wireless Internet service, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly connect to the Internet at home, in businesses, or in specific service areas.

[0003] Since supporting the initial wireless LAN technology using the 2.4 GHz frequency, IEEE (Institute of Electrical and Electronics Engineers) 802.11 has been commercializing or developing various technology standards. First, IEEE 802.11b supports a communication speed of up to 11 Mbps while using the 2.4 GHz band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz band instead of the 2.4 GHz band, thereby reducing the impact of interference compared to the considerably crowded 2.4 GHz band. It also uses OFDM (orthogonal frequency division multiplexing) technology to increase the communication speed to up to 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication range than IEEE 802.11b. And IEEE 802.11g, like IEEE 802.11b, uses the 2.4GHz band to achieve a communication speed of up to 54Mbps and satisfies backward compatibility, which has garnered considerable attention. It is also superior to IEEE 802.11a in terms of communication distance.

[0004] And to overcome the limitations of communication speed, which has been pointed out as a vulnerability in wireless LAN, there is IEEE 802.11n, a technical standard established. IEEE 802.11n aims to increase the speed and reliability of networks and extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT) with data processing speeds of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. In addition, this standard can use a coding method that transmits multiple redundant copies to increase data reliability.

[0005] As wireless LAN becomes more widespread and applications diversify, the need for new wireless LAN systems that support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n has arisen. 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 for the 5GHz band, early 11ac chipsets will also support operation in the 2.4GHz band to ensure backward compatibility with existing 2.4GHz band products. Theoretically, according to this specification, multi-station wireless LAN speeds can reach at least 1Gbps and a maximum single-link speed of at least 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, such as wider radio frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256 QAM). In addition, there is IEEE 802.11ad, which transmits data using the 60 GHz band instead of the existing 2.4 GHz / 5 GHz. IEEE 802.11ad is a transmission standard that provides speeds of up to 7 Gbps using beamforming technology, making it suitable for streaming high-bitrate video such as large amounts of data or uncompressed HD video. However, the 60 GHz frequency band has a disadvantage in that it has difficulty passing through obstacles, so it can only be used between devices in short distances.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard, which follows 802.11ac and 802.11ad as a wireless LAN standard, is nearing completion to provide high-efficiency and high-performance wireless LAN communication technology in high-density environments with densely packed APs and terminals. In an 802.11ax-based wireless LAN environment, high-frequency efficient communication must be provided indoors and outdoors in the presence of high-density stations and APs (Access Points), and various technologies have been developed to achieve this.

[0007] Additionally, development of new wireless LAN standards has begun to increase maximum transmission speeds to support emerging multimedia applications such as high-definition video and real-time gaming. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is currently under development with the goal of supporting transmission rates of up to 30 Gbps in the 2.4 / 5 / 6 GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation.

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

[0009] In one embodiment of the present invention, a wireless communication terminal that wirelessly communicates with a base wireless communication terminal includes a transceiver; and a processor. The processor transmits low-latency traffic set as traffic for low-latency transmission within a limited service period or a response to the low-latency traffic. At this time, transmission of the low-latency traffic and transmissions other than the low-latency traffic are restricted within the limited service period.

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

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

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

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

[0014] A quiet interval corresponding to the limited service period may be set, and no transmission may be permitted during the quiet interval. The processor may ignore the quiet interval corresponding to the limited service period, transmit the low-latency traffic or a response to the low-latency traffic within the limited service period, and not transmit a CF End frame within the limited service period.

[0015] A quiet period corresponding to the limited service period may be set, and no transmission may be permitted during the quiet period. At this time, the processor may determine whether to ignore the quiet period based on the start time of the limited service period and the start time of the quiet period, and if it is determined to ignore the quiet period, the processor may ignore the quiet period corresponding to the limited service period and transmit the low-latency traffic or a response to the low-latency traffic within the limited service period.

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

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

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

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

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

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

[0023] A quiet period corresponding to the limited service period may be set, and no transmission may be permitted in the quiet period. At this time, the step of transmitting the low-delay traffic or a response to the low-delay traffic within the limited service period may include the step of transmitting the low-delay traffic or a response to the low-delay traffic within the limited service period by ignoring the quiet period corresponding to the limited service period; and the step of not transmitting a CF End frame within the limited service period.

[0024] A quiet period corresponding to the limited service period may be set, and no transmission may be permitted in the quiet period. At this time, the step of transmitting the low-delay traffic or a response to the low-delay traffic within the limited service period may include the step of determining whether to ignore the quiet period based on a start time of the limited service period and a start time of the quiet period; and, if it is determined to ignore the quiet period, the step of transmitting the low-delay traffic or a response to the low-delay traffic within the limited service period by ignoring the quiet period corresponding to the limited service period.

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

[0026] The condition determined based on the start time of the above limited service period and the start time of the quiet section may be that the start time of the above quiet section and the start time of the service period of the above TWT are within a pre-specified time.

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

[0028] Figure 1 illustrates a wireless LAN system according to one embodiment of the present invention.

[0029] Figure 2 illustrates a wireless LAN system according to another embodiment of the present invention.

[0030] Figure 3 shows the configuration of a station according to one embodiment of the present invention.

[0031] Figure 4 shows the configuration of an access point according to one embodiment of the present invention.

[0032] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0033] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0034] Figure 7 illustrates an example of various standard generation-specific PPDU (PLCP Protocol Data Unit) formats.

[0035] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and a method for indicating the same according to an embodiment of the present invention.

[0036] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0037] FIG. 10 shows that transmissions on different links are performed simultaneously in a multi-link operation according to an embodiment of the present invention.

[0038] FIG. 11 shows the operation of a multi-link device when a link is changed according to one embodiment of the present invention.

[0039] FIG. 12 shows that when one station of a non-STR multi-link device is performing reception according to one embodiment of the present invention, channel access of another station of the non-STR multi-link device is prohibited.

[0040] FIG. 13 illustrates an operation of releasing channel access prohibition when a station of a non-STR multi-link device determines that the intended recipient of a PPDU received by the station is not the station, according to an embodiment of the present invention.

[0041] FIG. 14 shows a station performing channel access after channel access prohibition is lifted according to an embodiment of the present invention.

[0042] FIG. 15 shows an operation of a station performing transmission after channel access prohibition is lifted according to one embodiment of the present invention.

[0043] FIG. 16 shows transmission performed based on the status of a station in a non-STR multi-link device according to an embodiment of the present invention.

[0044] Figure 17 shows a situation where interference or collision between links may occur.

[0045] FIG. 18 shows that a multi-link device according to an embodiment of the present invention gives up reception of a PPDU being received on a first link of a non-STR multi-link pair and attempts to transmit a PPDU on a second link of a non-STR multi-link pair.

[0046] Figure 19 shows a situation where a multi-link device cannot transmit low-latency traffic by exchanging RTS / CTS frames in a non-STR multi-link pair.

[0047] FIG. 20 shows a multi-link device according to an embodiment of the present invention that determines whether to transmit traffic based on the priority of the traffic before frame exchange.

[0048] Figure 21 shows the Frame Control field format of an RTS frame according to an embodiment of the present invention.

[0049] FIG. 22 shows the User Info field format of an MU-RTS frame according to an embodiment of the present invention.

[0050] FIG. 23 shows a station that has received an RTS frame requesting a transmission opportunity transfer to an AP that has transmitted the RTS frame according to an embodiment of the present invention.

[0051] FIG. 24 shows the format of a Frame Control field of a CTS frame including a request for priority processing of low-latency traffic according to an embodiment of the present invention.

[0052] FIG. 25 illustrates a method for setting up a broadcast TWT between an AP and a station according to an embodiment of the present invention.

[0053] FIG. 26 shows an AP setting a quiet interval according to an embodiment of the present invention.

[0054] FIG. 27 illustrates a method for setting a TXOP by considering a limited service period of a station according to an embodiment of the present invention.

[0055] FIG. 28 shows a station performing a channel access procedure again considering a limited service period according to an embodiment of the present invention.

[0056] FIG. 29 illustrates an operation of an AP terminating a limited service period early according to an embodiment of the present invention.

[0057] FIG. 30 shows a multi-link device performing transmission on a non-SRT link pair according to an embodiment of the present invention.

[0058] FIG. 31 shows frame exchange initiated from a non-AP station multi-link device to which an embodiment of the present invention is not applied.

[0059] FIG. 32 illustrates frame exchange initiated from a non-AP station multi-link device according to an embodiment of the present invention.

[0060] FIG. 33 shows a method in which a multi-link device performs a transmission requesting an immediate response on a first link of a non-STR link pair according to an embodiment of the present invention, while performing a transmission not requesting an immediate response on a second link.

[0061] FIG. 34 shows an operation of performing transmission on a second link when a multi-link device performs UL OFDMA transmission on a first link among a non-STR link pair according to an embodiment of the present invention.

[0062] FIG. 35 shows a case where a link pair is determined to be a non-STR link pair or a STR link pair depending on the transmission direction according to an embodiment of the present invention.

[0063] The terms used in this specification have been selected from widely used and current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, customs, or the emergence of new technologies. Furthermore, in certain cases, the applicant may arbitrarily select terms, in which case their meanings will be described in the description of the relevant invention. Therefore, it should be noted that the terms used in this specification should be interpreted based on their substantive meaning and the overall content of this specification, rather than simply their names.

[0064] Throughout the specification, when a component is said to be "connected" to another component, this includes not only the case where the component is "directly connected," but also the case where the component is "electrically connected" with another component intervening therebetween. Furthermore, when a component is said to "include" a particular component, this does not exclude the other component, but rather allows the inclusion of other components, unless specifically stated otherwise. Furthermore, the terms "more than" or "less than" with respect to a specific threshold may be appropriately replaced with "greater than" or "less than", respectively, depending on the embodiment.

[0065] Hereinafter, in the present invention, fields and subfields may be used interchangeably.

[0066] Figure 1 illustrates a wireless LAN system according to one embodiment of the present invention.

[0067] A wireless LAN system includes one or more Basic Service Sets (BSSs), which represent a collection of devices that have successfully synchronized and can communicate with each other. BSSs can generally be categorized as infrastructure BSSs and independent BSSs (IBSSs). Figure 1 illustrates an infrastructure BSS.

[0068] As illustrated in FIG. 1, the infrastructure BSS (BSS1, BSS2) includes one or more stations (STA1, STA2, STA3, STA4, STA5), an access point (AP-1, AP-2) that provides a distribution service, and a distribution system (DS) that connects multiple access points (AP-1, AP-2).

[0069] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium that complies with the IEEE 802.11 standard, and broadly includes both non-access point (AP) stations and access points (APs). In addition, the term "terminal" in this specification may refer to a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface unit and a display unit, depending on the embodiment. The processor may generate a frame to be transmitted through a wireless network or process a frame received through the wireless network, and may perform various other processes for controlling the station. In addition, the communication unit is functionally connected to the processor and transmits and receives frames through the wireless network for the station. In the present invention, a terminal may be used as a term that includes a user equipment (UE).

[0070] An Access Point (AP) is an entity that provides access to a distribution system (DS) via a wireless medium for stations associated with it. In an infrastructure BSS, communication between non-AP stations is in principle performed via the AP, but direct communication is also possible between non-AP stations when a direct link is established. Meanwhile, in the present invention, the AP is used as a concept including a Personal BSS Coordination Point (PCP), and in a broad sense, it can include concepts such as a centralized controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller. In the present invention, the AP may also be referred to as a base wireless communication terminal, and the base wireless communication terminal may be used as a term including, in a broad sense, an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal may include various types of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with multiple wireless communication terminals.

[0071] Multiple infrastructure BSSs can be interconnected via a distribution system (DS). Multiple BSSs connected via the distribution system are referred to as an Extended Service Set (ESS).

[0072] FIG. 2 illustrates an independent BSS, a wireless LAN system, according to another embodiment of the present invention. In the embodiment of FIG. 2, portions identical or corresponding to those in the embodiment of FIG. 1 will be omitted for duplicative description.

[0073] BSS3, illustrated in Figure 2, is an independent BSS and does not include an AP. Therefore, all stations (STA6, STA7) are not connected to an AP. An independent BSS does not allow access to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) can be directly connected to another.

[0074] FIG. 3 is a block diagram showing the configuration of a station (100) according to one embodiment of the present invention. As illustrated, the station (100) according to the embodiment of the present invention may include a processor (110), a communication unit (120), a user interface unit (140), a display unit (150), and a memory (160).

[0075] First, the communication unit (120) transmits and receives wireless signals such as wireless LAN packets, and may be built into or externally installed in the station (100). According to an embodiment, the communication unit (120) may include at least one communication module using different frequency bands. For example, the communication unit (120) may include communication modules of different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to one embodiment, the station (100) may include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (120) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the station (100). When the station (100) includes multiple communication modules, each communication module may be provided in an independent form, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit (120) may represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0076] Next, the user interface unit (140) includes various types of input / output means provided in the station (100). That is, the user interface unit (140) can receive user input using various input means, and the processor (110) can control the station (100) based on the received user input. In addition, the user interface unit (140) can perform output based on a command of the processor (110) using various output means.

[0077] Next, the display unit (150) outputs an image on the display screen. The display unit (150) can output various display objects, such as content executed by the processor (110) or a user interface based on the control commands of the processor (110). In addition, the memory (160) stores a control program used in the station (100) and various data corresponding thereto. Such a control program may include a connection program required for the station (100) to connect to an AP or an external station.

[0078] The processor (110) of the present invention can execute various commands or programs and process data within the station (100). In addition, the processor (110) can control each unit of the above-described station (100) and control data transmission and reception between the units. According to an embodiment of the present invention, the processor (110) can execute a program for connection to an AP stored in the memory (160) and receive a communication setup message transmitted by the AP. In addition, the processor (110) can read information on the priority conditions of the station (100) included in the communication setup message and request connection to the AP based on the information on the priority conditions of the station (100). The processor (110) of the present invention may refer to the main control unit of the station (100), and according to an embodiment, may refer to a control unit for individually controlling some components of the station (100), such as the communication unit (120). That is, the processor (110) may be a modem or modulator and / or demodulator that modulates and / or demodulates wireless signals transmitted and received from the communication unit (120). The processor (110) controls various operations of transmitting and receiving wireless signals of the station (100) according to an embodiment of the present invention. A specific embodiment thereof will be described later.

[0079] The station (100) illustrated in FIG. 3 is a block diagram according to one embodiment of the present invention, and the blocks shown separately are logically distinguished elements of the device. Accordingly, the elements of the above-described device may be mounted as one chip or as multiple chips depending on the design of the device. For example, the processor (110) and the communication unit (120) may be implemented by being integrated into one chip or may be implemented as separate chips. In addition, 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).

[0080] Fig. 4 is a block diagram illustrating the configuration of an AP (200) according to one embodiment of the present invention. As illustrated, the AP (200) according to the embodiment of the present invention may include a processor (210), a communication unit (220), and a memory (260). In Fig. 4, redundant descriptions of portions of the configuration of the AP (200) that are identical or corresponding to the configuration of the station (100) of Fig. 3 will be omitted.

[0081] Referring to FIG. 4, the AP (200) according to the present invention has a communication unit (220) for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit (220) of the AP (200) may also include a plurality of communication modules that utilize different frequency bands. That is, the AP (200) according to the embodiment of the present invention may include two or more communication modules for different frequency bands, such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP (200) may include a communication module that utilizes a frequency band of 7.125 GHz or higher and a communication module that utilizes a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with a station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (220) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the AP (200). In an embodiment of the present invention, the communication unit (220) may represent an RF communication module that processes an RF (Radio Frequency) signal.

[0082] Next, the memory (260) stores the control program used in the AP (200) and various data according to the control program. This control program may include a connection program that manages the connection of the station. In addition, the processor (210) controls each unit of the AP (200) and may control data transmission and reception between the units. According to an embodiment of the present invention, the processor (210) may execute a program for connection with a station stored in the memory (260) and transmit a communication setup message to one or more stations. At this time, the communication setup message may include information on the connection priority conditions of each station. In addition, the processor (210) performs connection setup according to a connection request from a station. According to one embodiment, the processor (210) may be a modem or a modulator and / or demodulator that modulates and demodulates a wireless signal transmitted and received from the communication unit (220). The processor (210) controls various operations of wireless signal transmission and reception of the AP (200) according to an embodiment of the present invention. Specific examples of this will be described later.

[0083] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0084] Referring to FIG. 5, the link between STA (100) and AP (200) is largely established through three stages: scanning, authentication, and association. First, the scanning stage is a stage in which STA (100) acquires access information of the BSS operated by AP (200). Methods for performing scanning include a passive scanning method in which information is acquired only by utilizing a beacon message (S101) periodically transmitted by AP (200), and an active scanning method in which STA (100) acquires access information by transmitting a probe request to AP (S103) and receiving a probe response from AP (S105).

[0085] The STA (100) that successfully receives wireless access information in the scanning step transmits an authentication request (S107a) and receives an authentication response from the AP (200) (S107b) to perform the authentication step. After the authentication step is performed, the STA (100) transmits an association request (S109a) and receives an association response from the AP (200) (S109b) to perform the association step. In this specification, association basically means wireless association, but the present invention is not limited thereto, and association in a broad sense may include both wireless association and wired association.

[0086] Meanwhile, an additional 802.1X-based authentication step (S111) and an IP address acquisition step (S113) via DHCP may be performed. In Fig. 5, the authentication server (300) is a server that processes STA (100) and 802.1X-based authentication, and may be physically connected to the AP (200) or may exist as a separate server.

[0087] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0088] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether the channel is busy. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to the channel. This process is called clear channel assessment (CCA), and the level that determines whether the signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by the terminal is intended for the terminal, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected on the channel or a wireless signal with a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0089] When the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an IFS (Inter Frame Space) time, such as AIFS (Arbitration IFS) or PIFS (PCF IFS), depending on the status of each terminal. In some embodiments, the AIFS may be used as a configuration to replace the existing DIFS (DCF IFS). Each terminal waits while decreasing the slot time by a random number determined for the terminal during the idle interval of the channel, and a terminal that has exhausted all slot times attempts to access the channel. The period during which each terminal performs the backoff procedure is called a contention window period. At this time, the random number may be referred to as a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal may decrease the backoff counter by 1. Additionally, if the backoff counter reaches 0, the terminal may be permitted to perform channel access on the corresponding channel. Accordingly, transmission by the terminal may be permitted if the channel is idle during the AIFS time and the slot time of the backoff counter.

[0090] If a specific terminal successfully accesses the channel, the terminal can transmit data through the channel. However, if the terminal attempting access collides with another terminal, the collided terminals are each assigned a new random number and perform a backoff procedure again. According to one embodiment, the random number newly assigned to each terminal may be determined within a range twice (2*CW) of the random number range (contention window, CW) previously assigned to the terminal. Meanwhile, each terminal performs the backoff procedure again in the next contention window period to attempt access, and at this time, each terminal performs the backoff procedure starting from the slot time remaining in the previous contention window period. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0091] <Various PPDU format examples>

[0092] Fig. 7 illustrates examples of various standard generation-specific PPDU (PLCP Protocol Data Unit) formats. More specifically, Fig. 7(a) illustrates an embodiment of a legacy PPDU format based on 802.11a / g, Fig. 7(b) illustrates an embodiment of a HE PPDU format based on 802.11ax, and Fig. 7(c) illustrates an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. In addition, Fig. 7(d) illustrates detailed field configurations of L-SIG and RL-SIG commonly used in the above PPDU formats.

[0093] Referring to FIG. 7(a), the preamble of a legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0094] Referring to FIG. 7(b), the preamble of the HE PPDU additionally includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF may be referred to as a 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.

[0095] Referring to FIG. 7(c), the preamble of the EHT PPDU additionally includes, in addition to the legacy preamble, an RL-SIG (Repeated Legacy Short Training field), a U-SIG (Universal Signal field), an EHT-SIG-A (Extremely High Throughput Signal A field), an EHT-SIG-A (Extremely High Throughput Signal B field), an EHT-STF (Extremely High Throughput Short Training field), and an EHT-LTF (Extremely High Throughput Long Training field). In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some of the EHT PPDU formats.

[0096] The L-SIG field included in the PPDU preamble applies 64FFT 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 L-SIG applies BPSK, Rate=1 / 2 Modulation and Coding Scheme (MCS), it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of L-SIG.

[0097] Referring to Fig. 7(d), L-SIG includes an L_RATE field and an 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 combine modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and inefficiencies such as 1 / 2, 2 / 3, and 3 / 4. Combining the information in the L_RATE field and the L_LENGTH field can indicate the total length of the corresponding PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0098] The L_LENGTH field is allocated in bytes, with a total of 12 bits, allowing for signaling up to 4095. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. At this time, legacy and non-legacy terminals may interpret the L_LENGTH field in different ways.

[0099] First, the method by which a legacy terminal or non-legacy terminal interprets the length of the PPDU using the L_LENGTH field is as follows. If the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4 us, which is the duration of one symbol of 64 FFT. Therefore, by adding 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of symbols based on 64 FFT after L-SIG is obtained. Multiplying the obtained number of symbols by 4 us, which is the duration of one symbol, and then adding 20 us required for transmission of L-STF, L-LTF, and L-SIG, the length of the PPDU, i.e., the reception time (RXTIME) is obtained. This can be expressed as a formula as shown in Mathematical Expression 1 below.

[0100]

[0101] At this time, represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU can be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as in Mathematical Expression 2 below.

[0102]

[0103] Here, TXTIME is the total transmission time that constitutes the corresponding PPDU, as shown in mathematical expression 3 below. In this case, TX represents the transmission time of X.

[0104]

[0105] Referring to the above formulas, the length of the PPDU is calculated based on the rounded value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0106] Referring to Fig. 7(e), the U-SIG (Universal SIG) field continues to exist in EHT PPDUs and subsequent generation wireless LAN PPDUs, and serves to distinguish which generation of PPDU it is, including 11be. U-SIG is an OFDM 2 symbol based on 64FFT and can convey a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits of CRC / Tail, are largely divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0107] The VI bit maintains its current bit configuration in the future so that even if a subsequent generation PPDU is defined, current 11be terminals can obtain information about the PPDU through the VI fields of the PPDU. To this end, the VI field consists of PHY version, UL / DL, BSS Color, TXOP, and Reserved fields. The PHY version field is 3 bits and sequentially distinguishes 11be and subsequent generation wireless LAN standards by version. For 11be, it has the value 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS Color means an identifier for each BSS defined in 11ax and has a value of 6 bits or more. TXOP means the Transmit Opportunity Duration transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP including the PPDU can be inferred without having to decode the MPDU, and has a value of 7 bits or more.

[0108] The VD field is signaling information that is only useful for 11be version PPDUs. It can be composed of fields that are commonly used in any PPDU format, such as PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a delimiter that distinguishes EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs. The BW field signals five basic PPDU BW options (a BW that can be expressed in the form of an exponential power of 20*2 can be called a basic BW) of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz, as well as various remaining PPDU BWs configured through Preamble Puncturing. In addition, after being signaled at 320 MHz, some 80 MHz can be signaled in a punctured form. Additionally, the punctured and modified channel shape can be signaled directly in the BW field, or can be signaled using the BW field together with a field appearing after the BW field (e.g., a field within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signaling is possible, so only 3 puncturing modes can be signaled at most. If the BW field is 4 bits, a total of 16 BW signaling is possible, so a maximum of 11 puncturing modes can be signaled.

[0109] The fields located after the BW field vary depending on the type and format of the PPDU. MU PPDUs and SU PPDUs can be signaled in the same PPDU format, and a field to distinguish between MU PPDUs and SU PPDUs can be located before the EHT-SIG field, and additional signaling can be performed for this. Both SU PPDUs and MU PPDUs include the EHT-SIG field, but some fields that are not necessary in the SU PPDU may be compressed. In this case, the information in the compressed fields may be omitted or may have a reduced size compared to the original fields included in the MU PPDU. For example, in the case of the SU PPDU, the common field of the EHT-SIG may be omitted or replaced, or the user-specific field may be replaced or reduced to one, etc., and may have a different configuration.

[0110] Alternatively, the SU PPDU may further include a compression field indicating whether compression is performed, and some fields (e.g., RA field, etc.) may be omitted depending on the value of the compression field.

[0111] If part of the EHT-SIG field of the SU PPDU is compressed, information to be included in the compressed field may be signaled together in an uncompressed field (e.g., a common field, etc.). In the case of the MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of signaled information may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is allocated, and whether the transmitted MU PPDU was transmitted to itself. Therefore, the AP must include and transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the MCS modulation method. The EHT-SIG field may include information on the size and location of the RU allocated to each user.

[0112] In the case of an SU PPDU, multiple RUs may be allocated to an STA, and the multiple RUs may or may not be consecutive. If the RUs allocated to the STA are not consecutive, the STA must recognize RUs that are punctured in the middle to efficiently receive the SU PPDU. Therefore, the AP may transmit information on punctured RUs among the RUs allocated to the STA in the SU PPDU (e.g., puncturing patterns of the RUs). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and a puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field may signal the type of a discontinuous channel that appears within the bandwidth.

[0113] The form of the signaled discontinuous channel is limited, and the BW and discontinuous channel information of the SU PPDU are indicated in combination with the value of the BW field. For example, in the case of the SU PPDU, since it is a PPDU transmitted to only a single terminal, the STA can recognize the bandwidth allocated to it through the BW field included in the PPDU, and can recognize the punctured resource among the allocated bandwidth through 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 in the remaining resource units except for a specific channel of the punctured resource unit. At this time, multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0114] The reason why only a limited number of discontinuous channel types are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed on a per-20 MHz subchannel basis, if puncturing is performed on a BW with multiple 20 MHz subchannels, such as 80, 160, and 320 MHz, the discontinuous channel type (if only the edge 20 MHz is punctured, it is also considered discontinuous) must be signaled by individually indicating whether the remaining 15 20 MHz subchannels, excluding the primary channel, are used. Dedicating 15 bits to signaling the discontinuous channel type of single-user transmission can result in excessive signaling overhead considering the low data rate of the signaling portion.

[0115] The present invention proposes a technique for signaling the discontinuous channel type of an SU PPDU, and illustrates the discontinuous channel type determined according to the proposed technique. In addition, the present invention proposes a technique for signaling the puncturing types of the Primary 160 MHz and Secondary 160 MHz in a 320 MHz BW configuration of an SU PPDU, respectively.

[0116] In addition, one embodiment of the present invention proposes a technique for differentiating the configuration of a PPDU indicated by preamble puncturing BW values ​​according to the PPDU Format signaled in the PPDU Format field. Assuming that the BW field is 4 bits long, in the case of an EHT SU PPDU or TB PPDU, since 1 symbol of EHT-SIG-A may be additionally signaled after the U-SIG or EHT-SIG-A may not be signaled at all, it is necessary to fully signal up to 11 puncturing modes only through the BW field of the U-SIG in consideration of this. However, in the case of an EHT MU PPDU, since EHT-SIG-B is additionally signaled after the U-SIG, up to 11 puncturing modes can be signaled in a different way from the SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20MHz or 10MHz band.

[0117] Figure 7(f) illustrates the configuration of the Format-specific field of the VD field when the PPDU Format field of the U-SIG indicates an EHT MU PPDU. In the case of the MU PPDU, the SIG-B signaling field for simultaneous reception by multiple users is essential, and SIG-B can be transmitted after the U-SIG without a separate SIG-A. To this end, the U-SIG must signal information for decoding SIG-B. These fields include the SIG-B MCS, SIG-B DCM, Number of SIG-B Symbols, SIG-B Compression, and Number of EHT-LTF Symbols fields.

[0118] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and a method for indicating the same according to an embodiment of the present invention.

[0119] Referring to FIG. 8, a PPDU can be composed of a preamble and a data portion, and the format of one type of EHT PPDU can be distinguished according to the U-SIG field included in the preamble. Specifically, whether the format of the PPDU is an EHT PPDU can be indicated based on the PPDU format field included in the U-SIG field.

[0120] Figure 8 (a) shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

[0121] Figure 8 (b) shows an example of the EHT Trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. The EHT Trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used for responding to the trigger frame. Unlike the EHT SU PPDU, the EHT PPDU does not have an EHT-SIG-A field located after the U-SIG field.

[0122] Figure 8 (c) illustrates an example of the EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit a PPDU to one or more STAs. The EHT MU PPDU format may include a HE-SIG-B field after the U-SIG field.

[0123] Fig. 8(d) illustrates an example of an EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU can be used for single-user transmission with STAs in a wider range than the EHT SU PPDU described in Fig. 8(a), and the U-SIG field can be repeatedly positioned on the time axis.

[0124] The EHT MU PPDU described in (c) of FIG. 8 can be used by an AP for downlink transmission to multiple STAs. At this time, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive the PPDU transmitted from the AP. The EHT MU PPDU can transmit AID information of the receiver and / or transmitter of the PPDU transmitted through the user specific field of EHT-SIG-B to the STA. Accordingly, multiple terminals receiving the EHT MU PPDU can perform a spatial reuse operation based on the AID information of the user specific field included in the preamble of the received PPDU.

[0125] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information about the configuration of resource units (e.g., the partitioning form of resource units) in a specific bandwidth (e.g., 20 MHz, etc.) of the frequency axis. That is, the RA field may indicate the configuration of resource units partitioned in the bandwidth for transmission of the HE MU PPDU for the STA to receive the PPDU. Information about the STA allocated (or designated) to each partitioned resource unit may be included in the user-specific field of the EHT-SIG-B and transmitted to the STA. That is, the user-specific field may include one or more user fields corresponding to each partitioned resource unit.

[0126] For example, among the multiple resource units that are divided, a user field corresponding to at least one resource unit used for data transmission may include an AID of a receiver or a sender, and a user field corresponding to the remaining resource unit(s) that are not used for data transmission may include a preset null STA ID.

[0127] For convenience of explanation, in this specification, frame or MAC frame may be used interchangeably with MPDU.

[0128]

[0129] When a single wireless communication device communicates using multiple links, its communication efficiency can be improved. A link can be defined as a physical path, a single wireless medium that can be used to transmit MAC service data units (MSDUs). For example, if the frequency band of one link is occupied by another wireless communication device, the wireless communication device can continue communicating via the other link. In this way, the wireless communication device can effectively utilize multiple channels. Furthermore, when a wireless communication device simultaneously communicates using multiple links, overall throughput can be increased. However, existing wireless LANs are defined on the assumption that a single wireless communication device uses a single link. Therefore, a wireless LAN operation method that utilizes multiple links is needed. A wireless communication method for a wireless communication device using multiple links will be described with reference to FIGS. 9 through 26. First, a specific form of a wireless communication device using multiple links will be described with reference to FIG. 9.

[0130] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0131] For the wireless communication method using multiple links described above, a multi-link device (MLD) may be defined. The multi-link device may represent a device having one or more affiliated stations. In a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. In addition, the multi-link device may exchange multi-link elements. The multi-link element includes information about one or more stations or one or more links. The multi-link element may include a multi-link setup element, which will be described later. In this case, the multi-link device may be a logical entity. Specifically, the multi-link device may have multiple affiliated stations. The multi-link device may be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one medium access control service access point (SAP) up to a logical link control (LLC). In addition, the MLD may have one MAC data service.

[0132] A plurality of stations included in a multi-link device can operate on multiple links. Furthermore, the plurality of stations included in the multi-link device can operate on multiple channels. Specifically, the plurality of stations included in the multi-link device can operate on multiple different links or multiple different channels. For example, the plurality of stations included in the multi-link device can operate on multiple different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0133] The operation of a multi-link device may be referred to as multi-link operation, MLD operation, or multi-band operation. Furthermore, if the station associated with the multi-link device is an AP, the multi-link device may be referred to as AP MLD. Furthermore, if the station associated with the multi-link device is a non-AP station, the multi-link device may be referred to as non-AP MLD.

[0134] Figure 9 shows the operation of a non-AP MLD and an AP-MLD communicating. Specifically, the non-AP MLD and the AP-MLD each communicate using three links. The AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). The non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via the first link (Link1). In addition, the second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via the second link (Link2). In addition, the third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via the third link (Link3).

[0135]

[0136] A multi-link operation may include a multi-link setup operation. The multi-link setup operation corresponds to the association operation of the single-link operation described above, and may need to be performed first for frame exchange in a multi-link. A multi-link device may obtain information necessary for multi-link setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multi-link. In this case, the capability information may include information indicating whether one of the multiple devices included in the multi-link device can perform transmission and another device can perform reception simultaneously. In addition, the capability information may include information regarding the links that each station included in the MLD can use. In addition, the capability information may include information regarding the channels that each station included in the MLD can use.

[0137] Multi-link configuration can be established through negotiation between peer stations. Specifically, multi-link configuration can be performed through communication between stations without communication with the AP. Furthermore, multi-link configuration can be established through any one link. For example, even if the first to third links are established through multi-link, multi-link configuration can be performed through the first link.

[0138] In addition, a mapping between a traffic identifier (TID) and a link can be established. Specifically, frames corresponding to a TID of a specific value can only be exchanged through a pre-designated link. The mapping between a TID and a link can be established on a directional basis. For example, when multiple links are established between a first multi-link device and a second multi-link device, the first multi-link device can be established to transmit a frame of the first TID to the first link of the multiple links, and the second multi-link device can be established to transmit a frame of the second TID to the first link. In addition, a default setting can exist for the mapping between a TID and a link. Specifically, if there is no additional setting in the multi-link setting, the multi-link device can exchange frames corresponding to the TID on each link according to the default setting. In this case, the default setting can be that all TIDs are exchanged on one link.

[0139] Here is a detailed explanation of TID. TID is an ID that classifies traffic and data to support QoS (quality of service). In addition, TID can be used or assigned in a layer higher than the MAC layer. In addition, TID can represent traffic category (TC) and traffic stream (TS). In addition, TID can be distinguished into 16. For example, TID can be assigned to any one of 0 to 15. The TID value used can be assigned differently depending on the access policy, channel access, or medium access method. For example, when enhanced distributed channel access (EDCA) or hybrid coordination function contention-based channel access (HCAF) is used, TID value can be assigned from 0 to 7. When EDCA is used, TID can represent user priority (UP). In this case, UP can be assigned according to TC or TS. UP can be assigned at a layer higher than MAC. In addition, when HCCA (HCF controlled channel access) or SPCA is used, the value of TID can be assigned from 8 to 15. When HCCA or SPCA is used, the TID can indicate the TSID. In addition, when HEMM or SEMM is used, the value of TID can be assigned from 8 to 15. When HEMM or SEMM is used, the TID can indicate the TSID.

[0140] UP and AC can be mapped. AC can be a label for providing QoS in EDCA. AC can be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in channel contention of EDCA. A QoS station can use AC to guarantee QoS. In addition, AC can include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO can represent background, best effort, video, and voice, respectively. In addition, AC_BK, AC_BE, AC_VI, and AC_VO can be classified into sub-ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. In addition, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. In addition, UP or TID can be mapped to AC. For example, 1, 2, 0, 3, 4, 5, 6, 7 of UP or TID can be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO respectively. In addition, 1, 2, 0, 3, 4, 5, 6, and 7 of UP or TID can be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate respectively. In addition, 1, 2, 0, 3, 4, 5, 6, and 7 of UP or TID can be in order of priority. That is, 1 can be in order of low priority and 7 can be in order of high priority. Therefore, AC_BK, AC_BE, AC_VI, AC_VO can be in order of priority.Additionally, 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.

[0141] As previously described, TIDs can be mapped to each of multiple links. The mapping may specify a link on which traffic corresponding to a specific TID or AC can be exchanged. Additionally, TIDs or ACs that can be transmitted in each transmission direction within the link may be specified. As previously described, there may be a default setting for the mapping between TIDs and links. Specifically, if there are no additional settings in the multi-link configuration, the multi-link device can exchange frames corresponding to the TIDs on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on a single link. At any given time, any TID or AC can be mapped to at least one link. Management frames and control frames can be transmitted on all links.

[0142] When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to the link can be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames that do not correspond to a TID or AC that is not mapped to the link cannot be transmitted on the link. When a link is mapped to a TID or AC, ACKs can also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK agreement can be determined based on the mapping between the TID and the link. In another specific embodiment, the mapping between the TID and the link can be determined based on the block ACK agreement. Specifically, a block ACK agreement can be established for a TID mapped to a specific link.

[0143] QoS can be guaranteed through the mapping between TIDs and links described above. Specifically, high-priority ACs or TIDs can be mapped to links with relatively few operating stations or with good channel conditions. Furthermore, the mapping between TIDs and links described above can allow stations to remain in power-saving mode for longer periods of time.

[0144]

[0145] FIG. 10 shows that transmissions on different links are performed simultaneously in a multi-link operation according to an embodiment of the present invention.

[0146] Depending on the implementation of the multi-link device, simultaneous operation may not be supported on multiple links. For example, a multi-link device may not support simultaneous transmission on multiple links, simultaneous reception on multiple links, or transmission on one link and reception on another. This is because reception or transmission on one link may affect reception or transmission on another link. Specifically, transmission on one link may interfere with the other link. Interference from one link of a multi-link device to another link is referred to as internal leakage. The smaller the frequency spacing between links, the greater the internal leakage. If the internal leakage is not too large, transmission on one link can be performed on the other link. If the internal leakage is large, transmission on one link cannot be performed on the other link. This simultaneous operation of a multi-link device on multiple links can be referred to as STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multi-link device that transmits simultaneously on multiple links, performs transmission on one link and simultaneously receives on another link, or performs reception on multiple links simultaneously can be called STR.

[0147] As mentioned above, a multi-link device may support STR, or may only support it in a limited manner. Specifically, a multi-link device may only support STR under certain conditions. For example, if a multi-link device operates with a single radio, the multi-link device may not be able to perform STR. Furthermore, if a multi-link device operates with a single antenna, the multi-link device may not be able to perform STR. Furthermore, if an internal leak exceeds a predetermined size, the multi-link device may not be able to perform STR.

[0148] A station can exchange information regarding its STR capabilities with other stations. Specifically, the station can exchange information with other stations regarding whether the station's ability to simultaneously transmit or receive on multiple links is restricted. Specifically, the information regarding whether the station's ability to transmit or receive on multiple links is restricted may indicate whether the multiple links can simultaneously transmit, receive, or transmit and receive simultaneously. Furthermore, the information regarding whether the ability to transmit or receive on multiple links is restricted may be step-by-step information. Specifically, the information regarding whether the ability to transmit or receive on multiple links is restricted may be information indicating a step indicating the magnitude of internal leakage. In a specific embodiment, the information indicating a step indicating the magnitude of internal leakage may be information indicating a step indicating the magnitude of interference caused by internal leakage. In another specific embodiment, the information indicating a step indicating a frequency spacing between links that may affect internal leakage may be information indicating a step indicating the relationship between the frequency spacing between links and the magnitude of internal leakage.

[0149] In FIG. 10, a first station (STA1) and a second station (STA2) are affiliated with a single non-AP multi-link device. In addition, a first AP (AP1) and a second AP (AP2) may be affiliated with a single non-AP multi-link device. A first link (link 1) is established between the first AP (AP1) and the first station (STA1), and a second link (link 2) is established between the second AP (AP2) and the second station (STA2). In FIG. 10, the non-AP multi-link device may perform STR in a limited manner. When the second station (STA2) transmits on the second link (Link 2), reception of the first station (STA1) on the first link (Link 1) may be interrupted by the transmission performed on the second link (Link 2). For example, in the following case, reception by a first station (STA1) on a first link (Link 1) may be interrupted by a transmission performed on a second link (Link 2). In the second link (Link 2), a second station (STA2) transmits first data (Data1), and a first AP (AP1) transmits a response (Ack for Data1) to the first station (STA1) for the first data (Data1). In the second link (Link2), the second station (STA2) transmits second data (Data2). At this time, the transmission timing of the second data (Data2) and the transmission timing of the response (Ack for Data1) to the first data (Data1) may overlap. At this time, interference may occur in the first link (Link1) due to the transmission to the second station (STA2) on the second link (Link2). Therefore, the first station (STA1) may not receive the response (Ack for Data1) to the first data (Data1).

[0150]

[0151] This section describes the operation of a multi-link device performing channel access. Multi-link operations without a specific description may follow the channel access procedure described in FIG. 6.

[0152] A multi-link device can independently perform channel access on multiple links. In this case, the channel access may be backoff-based channel access. If the multi-link device independently performs channel access on multiple links and the backoff counter reaches 0 on multiple links, the multi-link device can initiate transmission simultaneously on the multiple links. In a specific embodiment, if any of the backoff counters of the links of the multi-link reaches 0 and a predetermined condition is satisfied, the multi-link device can perform channel access not only on the link where the backoff counter reaches 0 but also on other links where the backoff counter does not reach 0. Specifically, if any of the backoff counters of the links of the multi-link reaches 0, the multi-link device can perform energy detection on other links where the backoff counter does not reach 0. In this case, if energy exceeding a predetermined amount is not detected, the multi-link device can perform channel access not only on the link where the backoff counter reaches 0 but also on the link where the energy detection was performed. This allows the multi-link device to initiate transmission simultaneously on multiple links. The threshold used for energy detection may be smaller than the threshold used to determine whether to decrease the backoff counter. Furthermore, when determining whether to decrease the backoff counter, the multi-link device can detect any type of signal, not just a wireless LAN signal. Furthermore, in the energy detection described above, the multi-link device can detect any type of signal, not just a wireless LAN signal. Internal leakage may not be detected as a wireless LAN signal. In this case, the multi-link device can sense the signal detected due to the internal leakage as energy detection. Furthermore, as described above, the threshold used for energy detection may be smaller than the threshold used to determine whether to decrease the backoff counter.Therefore, even if a transmission is being performed on one link, a multi-link device can decrement the backoff counter on the other link.

[0153] Depending on the degree of interference between the links used by the multi-link device, the multi-link device can determine whether the stations operating on each link can operate independently. In this case, the degree of interference between the links may be the magnitude of interference detected by another station of the multi-link device when one station of the multi-link device performs transmission on one link. If the transmission of the first station of the multi-link device on the first link causes interference greater than a predetermined magnitude to the second station of the multi-link 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. This is because when interference occurs, the second station may fail to decode the signal it receives due to the interference. Furthermore, when interference occurs, the second station may determine that the channel is busy when accessing the channel using backoff.

[0154] In addition, if the transmission of the first station of the multi-link device on the first link causes interference less than a predetermined size to the second station of the multi-link device operating on the second link, the first station and the second station can operate independently. Specifically, if the transmission of the first station of the multi-link device on the first link causes interference less than a predetermined size to the second station of the multi-link device operating on the second link, the first station and the second station can independently perform channel access. In addition, if the transmission of the first station of the multi-link device on the first link causes interference less than a predetermined size to the second station of the multi-link device operating on the second link, the first station and the second station can independently perform transmission or reception. This is because if interference less than a predetermined size occurs, the second station can successfully decode the signal it receives even if interference exists. In addition, if interference less than a predetermined size occurs, the second station can determine that the channel is idle when accessing the channel using backoff.

[0155] The degree of interference between stations in a multi-link device can vary not only depending on the frequency bands between the stations' operating links, but also on the hardware characteristics of the multi-link device. For example, the internal interference generated in a multi-link device that includes expensive RF (radio frequency) devices may be less than that generated in a multi-link device that includes inexpensive RF devices. Therefore, the degree of interference generated between stations in a multi-link device can be determined based on the characteristics of the multi-link device.

[0156] Fig. 10 shows that the size of interference that occurs varies depending on the spacing between frequency bands of links and the characteristics of the multi-link device. In the embodiment of Fig. 10, the first multi-link device (MLD#1) includes a first station (STA1-1) operating in a first link (Link1) and a second station (STA1-2) operating in a second link (Link2). The second multi-link device (MLD#2) includes a first station (STA2-1) operating in a first link (Link1) and a second station (STA2-2) operating in a second link (Link2). The frequency spacing between the first link (Link1) and the second link (Link2) on which the first multi-link device (MLD#1) operates and the frequency spacing between the first link (Link1) and the second link (Link2) on which the second multi-link device (MLD#2) operates are the same. However, the magnitude of interference generated is different due to the difference in the characteristics of the first multi-link device (MLD#1) and the second multi-link device (MLD#2). Specifically, the magnitude of interference generated by the second multi-link device (MLD#2) may be greater than that generated by the first multi-link device (MLD#1). Considering that the magnitude of interference generated may vary depending on the characteristics of the multi-link devices, and that STR support may vary depending on the multi-link devices, information regarding STR support needs to be exchanged.

[0157] A multi-link device can signal whether a station included in the multi-link device supports STR. Specifically, an AP multi-link device and a non-AP multi-link device can exchange whether an AP included in the AP multi-link device supports STR and whether an STA included in the non-AP multi-link device supports STR. In these embodiments, an element indicating whether STR is supported may be used. The element indicating whether STR is supported may be referred to as an STR support element. The STR support element may indicate whether a station of a multi-link device that has transmitted the STR support element supports STR through 1 bit. Specifically, the STR support element may indicate whether each station included in the multi-link device that transmits the STR support element supports STR for each bit. In this case, if the station supports STR, the value of the bit may be 1, and if the station does not support STR, the value of the bit may be 0. If a multi-link device that transmits an STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support STR and the second station (STA2) does not support STR, the STR support element is 101. 1b. Stations operating in different frequency bands are assumed to support STR, and the STR support element may omit signaling of STR support between stations operating in different frequency bands. For example, a first station (STA1) operates in a first link of 2.4 GHz, and a second station (STA2) and a third station (STA3) operate in a second link and a third link of 5 GHz, respectively. In this case, the STR support element may use 1 bit to indicate that STR is supported between the second station (STA2) and the third station (STA3). In addition, the STR support element may include only 1 bit when there are two stations signaled by the STR support element.

[0158] In a specific embodiment, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz among the links of a multi-link device can always be determined as STR. Accordingly, signaling regarding whether a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz are STR can be omitted.

[0159]

[0160] In the embodiments described above, the operations of the stations of the multi-link device can be replaced with the operations of the multi-link device. In addition, in the embodiments described above, the operations of the AP can be replaced with the operations of the non-AP stations, and the operations of the non-AP stations can be replaced with the operations of the AP. Accordingly, the operations of the AP of the non-STR multi-link device can be replaced with the operations of the non-AP stations of the non-STR multi-link device, and the operations of the non-AP stations of the STR multi-link device can be replaced with the operations of the AP of the STR multi-link device. In addition, the operations of the non-AP stations of the non-STR multi-link device can be replaced with the operations of the AP of the non-STR multi-link device, and the operations of the AP of the STR multi-link device can be replaced with the operations of the non-AP stations of the STR multi-link device.

[0161]

[0162] FIG. 11 shows the operation of a multi-link device when a link is changed according to one embodiment of the present invention.

[0163] When the frequency band of the link changes, the STR support element may be exchanged. As described above, whether a station supports STR may vary depending on the distance between the frequency bands of the link, and when the frequency band of the link changes, the station's STR support may also change. A change in the frequency band of the link may include at least one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a 20MHz main channel. The AP and the station may exchange the STR support element through a request and a response. In another specific embodiment, when the frequency band of the link changes, the STR support element may be exchanged without a separate request. Furthermore, in the embodiments described above, a change in the frequency band of the link may include a change in the operating channel of the station.

[0164] If a station of a non-AP multi-link device cannot perform STR, the station of the non-AP multi-link device may request a change of link to the AP. Specifically, the station of the non-AP multi-link device may request a change of at least one of a center frequency, a change of a bandwidth of a frequency band, and a change of a 20MHz main channel. The link change request may be transmitted to the AP via the link requesting the change. In another specific embodiment, the link change request may be transmitted to the AP via a link that does not request the change. In this case, the link change request may include information indicating the link requesting the change. The information indicating the link may be a number identifying the link. In these embodiments, the link change may be a change of an operating channel within a frequency band. In addition, the link change may include information on a method for changing the link. Specifically, the link change request may indicate whether the center frequency of the link is to be moved to a higher frequency than the current center frequency, or whether the center frequency of the link is to be moved to a lower frequency than the current center frequency. In another specific embodiment, a link change request may implicitly indicate a change to a frequency band further from an adjacent link. Furthermore, a link change request may indicate a reduction in the link's bandwidth. Furthermore, a link change request may 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 that receives a link change request may change the link in accordance with the link change request. Furthermore, in a specific embodiment, an AP that receives a link change request may ignore the link change request.

[0165] In the embodiment of FIG. 11, the second station (STA2) and the third station (STA3) of the non-AP multi-link device do not support STR. The non-AP multi-link device requests the AP multi-link device to change the third link (Link3). The AP multi-link device, which has received the link change request, changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can transmit a change request to the third AP (AP3). In another specific embodiment, a station that does not operate on the third link (link3) can transmit a change request to an AP that does not operate on the third link (link3).

[0166] When an AP changes a link, the AP can broadcast information about the link change via a beacon frame. The information about the link change may include information about the link's frequency. The information about the link's frequency may include at least one of the following: a center frequency, an operating bandwidth, or a change in the primary channel. Furthermore, the information about the link change may include information about the timing of the link change. Furthermore, the link change may be completed upon transmission of a beacon containing the information about the link change.

[0167] In Fig. 11, the link on which the third station (STA3) operates is changed, so that the third station (STA3) and the second station (STA2) can support STR. As described above, a non-AP multi-link device can signal whether it supports the changed STR by transmitting an STR support element to the AP multi-link device.

[0168]

[0169] The link change described above may not be allowed, or STR may not be supported even through a link change. In addition, as in the embodiment of FIG. 11, an AP multi-link device may support STR, but a non-AP multi-link device may not support STR. This is because it may be common for relatively expensive devices to be used in AP multi-link devices, and relatively inexpensive devices to be used in non-AP multi-link devices. Therefore, when communicating between multi-link devices, a method is needed that can perform efficient communication even when one of the multi-link devices does not support STR. In this case, STR may indicate that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

[0170] FIG. 12 shows that when one station of a non-STR multi-link device is performing reception according to one embodiment of the present invention, channel access of another station of the non-STR multi-link device is prohibited.

[0171] When transmission is performed on one link of a non-STR multi-link device and reception is performed on another link of the non-STR multi-link device, reception and transmission of the non-STR multi-link device may fail. To resolve this, when reception is performed on one link of the non-STR multi-link device, channel access may be prohibited on the other link of the non-STR multi-link device. Specifically, backoff of channel access may be prohibited on the other link of the non-STR multi-link device when reception is performed on one link of the non-STR multi-link device. This may prevent transmission from being initiated on the other link of the non-STR multi-link device when reception is performed on one link of the non-STR multi-link device. In a specific embodiment, backoff of channel access may be prohibited on the other link of the non-STR multi-link device when reception is initiated on one link of the non-STR multi-link device. This may be set via a specific bit of memory, such as a channel access prohibition flag. Whether or not channel access is prohibited may be shared via memory within the multi-link device. These embodiments allow channel access prohibition to be implemented without separate frame exchange. For convenience of explanation, the term "channel access prohibition" used herein refers to prohibiting channel access or transmission to protect transmission or reception of a non-STR multi-link device, unless otherwise specified.

[0172] When channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform a backoff procedure regardless of the NAV and CCA results. Furthermore, when channel access is prohibited, a station operating on a link where channel access is prohibited cannot transmit regardless of the NAV and CCA results. However, even if channel access is prohibited, a station operating on a link where channel access is prohibited can perform reception. Furthermore, the prohibition of channel access in a second link due to reception performed on a first link may be lifted based on the completion of reception on the first link. Specifically, the prohibition of channel access in a second link due to reception performed on the first link may be lifted when reception on the first link is completed. In another specific embodiment, the prohibition of channel access in a second link due to reception performed on the first link may be lifted based on the point in time when an ACK is transmitted after reception on the first link is completed. Specifically, the prohibition of channel access in a second link due to reception performed on the first link may be lifted when an ACK is transmitted after reception on the first link is completed. In another specific embodiment, the channel access prohibition on the second link due to reception performed on the first link may be lifted at the point in time when the ACK transmission is completed after reception on the first link is completed. In addition, immediately after the channel access prohibition is lifted, the station may immediately decrease the backoff counter without additional sensing. In this case, the additional sensing may refer to sensing performed during the DCF Interframe Space (DIFS). In another specific embodiment, if the channel is idle for a predetermined time immediately before the channel access prohibition is lifted, the station may immediately decrease the backoff counter without additional sensing.At this time, the pre-specified time can be any one of PIFS (PCF Interframe Space), DIFS, SIFS (Short Interframe Space), and AIFS (Arbitration Interframe Space).

[0173] In the embodiment of FIG. 12, a non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) performs reception, interference occurs within the device. As described above, while the first station (STA1) operating on the first link (Link1) performs reception, the channel access of the second station (STA2) operating 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 lifted. Immediately after the channel access prohibition is lifted, the second station (STA2) can decrease the previous backoff counter value by 1 from 3 to 2 without additional sensing.

[0174] For convenience of expression, the drawing utilized in Fig. 12 utilizes a single block (Tx solid line, Rx dotted line) when representing Rx and Tx, and even if the single block does not depict a separate Ack block, it can be understood that it represents an operation including Tx / Ack reception and Rx / Ack transmission. This can be equally applied to the drawings described later.

[0175]

[0176] If a station determines that the PPDU it is receiving is not intended for the station, the station may discontinue receiving the PPDU. In this case, the multi-link device's channel access prohibition release operation is problematic. In this specification, the "intended recipient" is used synonymously with the "destination station."

[0177] FIG. 13 illustrates an operation of releasing channel access prohibition when a station of a non-STR multi-link device determines that the intended recipient of a PPDU received by the station is not the station, according to an embodiment of the present invention.

[0178] If the station determines that the PPDU received by the station is not the intended recipient, the station may lift the channel access prohibition. The station may determine whether the station is the intended recipient of the PPDU based on information indicating the recipient address in the signaling field of the PPDU. At this time, the information indicating the recipient address in the signaling field of the PPDU may be the value of the STA-ID field of the EHT-SIG field described above. Specifically, the station may determine whether the STA-ID field of the EHT-SIG field indicates the station. In addition, the station may determine whether the station is the intended recipient of the PPDU based on the value of the RA field of the MAC frame included in the PPDU. Specifically, the station may determine whether the RA field of the MAC frame included in the PPDU indicates the station. In FIG. 13, a non-STR multi-link device includes a first station (STA1) operating in a first link (Link 1) and a second station (STA2) operating in a second link (Link 2). The first station (STA1) receives a PPDU. The first station (STA1) determines that the intended recipient of the received PPDU is not the first station (STA1) and stops receiving the PPDU. At this time, the first station (STA1) may lift the channel access prohibition on the second station (STA2). Even if the channel access prohibition on the second station (STA2) is lifted, the channel access of the second station (STA2) may be delayed depending on the NAV set for the second station (STA2).

[0179]

[0180] Even if the channel access ban is lifted, as shown in FIG. 13, stations included in a non-STR multi-link device may often not have channel access opportunities compared to stations not included in a multi-link device or stations included in an STR multi-link device. Therefore, a method for compensating for the channel access opportunities of stations included in a non-STR multi-link device may be necessary to ensure fair competition with other stations. For example, immediately after the channel access ban is lifted, a station whose channel access ban is lifted may be permitted to decrease its backoff counter by more than 2. This will be described with reference to FIG. 14.

[0181] FIG. 14 shows a station performing channel access after channel access prohibition is lifted according to an embodiment of the present invention.

[0182] A station whose channel access is lifted may decrement its backoff counter by at least 2 immediately after the channel access ban is lifted. This is to ensure fairness in channel access opportunities with other stations, as other stations performed backoff procedures while the station's channel access was barred.

[0183] In another specific embodiment, a station whose channel access is prohibited can perform a channel access procedure that reduces the CCA (CSMA) and backoff counter while the channel access is prohibited. In FIG. 14, a non-STR multi-link device includes a first station (STA1) operating on a first link (Link 1) and a second station (STA2) operating on a second link (Link 2). In FIG. 14, while the first station (STA1) performs reception, the channel access of the second station (STA2) is prohibited. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure that reduces the CCA (CSMA) and backoff counter. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, the channel of the second link (Link 2) is idle, so the second station (STA2) reduces the backoff counter.

[0184] In addition, a station whose channel access is prohibited can delay transmission without starting transmission even if the backoff counter reaches 0 while channel access is prohibited. At this time, the station can keep the value of the backoff counter as 0. In addition, even if the station delays transmission, the station can keep the value of the CW as it is. Therefore, this is different from the case where the station doubles the value of the CW because the channel the station is accessing is busy. This is because the reason for the delay in transmission is not because the channel is determined to be busy. In FIG. 14(b), while the channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure that decreases the CCA (CSMA) and the backoff counter. In FIG. 14(b), while the channel access of the second station (STA2) is prohibited, the channel of the second link (Link 2) is idle, so the second station (STA2) decreases the backoff counter. While channel access of the second station (STA2) is prohibited, the backoff counter of the second station (STA2) reaches 0. The second station (STA2) delays transmission and starts transmission after the channel access prohibition is lifted.

[0185] As described above, channel access prohibition may include prohibiting transmission to a second station when a first station of a non-STR multi-link device transmits. Furthermore, channel access prohibition may include prohibiting transmission to a second station when a first station of a non-STR multi-link device receives.

[0186]

[0187] As shown in Figure 14(b), in the embodiments where multiple stations are prohibited from channel access, there is a high probability that the channel access prohibition for multiple stations will be lifted simultaneously, and multiple stations will attempt to transmit simultaneously. Therefore, a method for reducing the probability of transmission collisions is needed. This is described in Figure 15.

[0188] FIG. 15 shows an operation of a station performing transmission after channel access prohibition is lifted according to one embodiment of the present invention.

[0189] As described above, when a transmission is performed on a first link among multiple links on which a non-STR multi-link device operates, transmission may be prohibited on a second link. When the transmission on the first link is completed, transmission on the second link may begin with an RTS / CTS frame exchange. Therefore, when a transmission is performed on the first link among multiple links on which a non-STR multi-link device operates, the non-STR multi-link device may begin an RTS / CTS frame exchange on the second link. After a station whose transmission has been delayed due to channel access prohibition is lifted from channel access prohibition, the station may begin an exchange of RTS / CTS (request to send / clear to send) frames before beginning the delayed transmission. At this time, if the station does not receive a CTS frame, the delayed transmission may not begin. In the embodiment of FIG. 15(a), a station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before beginning the delayed transmission. The station begins the delayed transmission after receiving a CTS frame in response to the RTS frame.

[0190] In another specific embodiment, after a station whose transmission has been delayed due to channel access prohibition is lifted, the station may transmit a frame containing only a portion of the delayed transmission. At this time, after the station receives a response, such as an ACK, to the frame containing only a portion of the delayed transmission, the station may 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 may not transmit the untransmitted portion of the delayed transmission. In this way, the station may initiate an RTS / CTS exchange or transmit only a portion of the delayed transmission after the channel access prohibition is lifted because the collision probability of transmissions after the channel access prohibition may be higher than that of general transmissions. Therefore, the embodiments described above may be mandatorily applied to transmissions performed after the channel access prohibition is lifted. In existing wireless LAN operations, the RTS / CTS frame was used to solve the hidden node problem and could be used based on the size of the transmitted data. In the embodiments described above, the RTS / CTS frame is intended to prevent transmission collisions with stations attempting to perform delayed transmissions to protect transmission or reception of a NON-STR multi-link device.

[0191]

[0192] As described above, when one station of a non-STR multi-link device performs reception, the transmission of other stations of the non-STR multi-link device may be restricted. Furthermore, when one station of a non-STR multi-link device performs transmission, it may be difficult for other stations of the non-STR multi-link device to accurately sense the channel status of the link on which the station operates. Specifically, when a first station of a non-STR multi-link device performs transmission, a second station of the non-STR multi-link device may always determine the channel status of the link on which the second station operates as busy. As a result, the second station may determine that the channel of the link on which the second station operates is busy due to interference within the device even when the channel is idle. In this way, when a station that cannot determine the channel status due to interference within the device or when one station of the non-STR multi-link device is continuously transmitting, the other stations of the non-STR multi-link device are referred to as being in a blind state. Due to the situations described above, a station in a blind state may have difficulty attempting transmission by performing a backoff procedure. Additionally, due to the aforementioned circumstances, a station in a blind state may have difficulty initiating PPDU reception or successfully decoding it. Therefore, a transmission method that takes blind stations into account is needed. This is described in Figure 16.

[0193] FIG. 16 shows transmission performed based on the status of a station in a non-STR multi-link device according to an embodiment of the present invention.

[0194] A station attempting to transmit to a station of a non-STR multi-link device can determine whether to transmit based on whether the station of the non-STR multi-link device is in a blind state. At this time, the station attempting to transmit to a station of the non-STR multi-link device may be a station included in the STR multi-link device. Additionally, the station attempting to transmit to a station of the non-STR multi-link device may be an AP included in an AP multi-link device, and the non-STR multi-link device may be a non-AP multi-link device. A station attempting to transmit to a station of the non-STR multi-link device can determine whether the station of the non-STR multi-link device is in a blind state as follows. A station attempting to transmit can determine whether another station of the multi-link device including the station is transmitting to the non-STR multi-link device. If another station of the multi-link device including the station is receiving from the non-STR multi-link device, the station can determine that the station of the non-STR multi-link device that will receive the station's transmission is in a blind state. In the embodiment of FIG. 16, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link 1) and a second AP (AP2) operating on a second link (Link 2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link 1) and a second station (STA2) operating on a second link (Link 2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can notify the first AP (AP1) that it is performing reception from the second station (STA2). Specifically, the second AP (AP2) can notify the first AP (AP1) that the subject of transmission to the second AP (AP2) is the second station (STA2).In another specific embodiment, a second AP (AP2) may notify a first AP (AP1) that a second station (STA2) is currently transmitting. At this time, the first AP (AP1) may determine that the first station (STA1) is in a blind state based on the notification.

[0195] Stations within a multi-link device can operate via a common MAC. Therefore, the information exchange between the first AP (AP1) and the second AP (AP2) described above may not be explicitly performed.

[0196] A station may not transmit to a station in the blind state. 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 initiate reception or decode the PPDU. In this case, the station may cancel the transmission to the blind station and transmit to another station.

[0197] When an STR multi-link device performs a transmission to a non-STR multi-link device, the STR multi-link device can perform the transmission to the non-STR multi-link device on multiple links. Specifically, when the STR multi-link device performs a transmission to the non-STR multi-link device on a first link, the STR multi-link device can initiate a transmission to the non-STR multi-link device on a second link. At this time, the STR multi-link device can determine the length of the transmission performed on the second link based on the transmission to the non-STR multi-link device. Specifically, the STR multi-link device can determine the length of the transmission to the non-STR multi-link device on the second link based on the length of the transmission to the non-STR multi-link device on the first link. In a specific embodiment, the STR multi-link device can terminate the transmission on the first link and the transmission on the second link simultaneously. This is to prevent transmission to any one of the stations of the non-STR multi-link device from being terminated first, and transmission to any other station of the non-STR multi-link device from being performed while any one of the stations of the non-STR multi-link device transmits a response to the transmission, e.g., an ACK. The embodiment described above allows multiple stations of a non-STR multi-link device to simultaneously transmit responses to transmissions to multiple stations.

[0198]

[0199] The STR multi-link device cannot determine the status of a station included in a non-STR multi-link device in real time. Therefore, even if the STR multi-link device operates according to the embodiments described with reference to FIG. 16, interference or transmission collisions may occur between links on which the non-STR multi-link device operates. For example, in the embodiment of FIG. 16, the first AP (AP1) may start transmitting to the first station (STA1) before the second station (STA2) recognizes that it is transmitting to the second AP (AP2). In this way, the probability of interference or collision occurring between links may be greater than the probability of interference or transmission collision occurring within a link. This will be described in more detail with reference to FIG. 17.

[0200] Figure 17 shows a situation where interference or collision between links may occur.

[0201] If a transmission from a second station of a non-STR station multi-link device to a second AP of a STR AP multi-link device starts simultaneously with a transmission from a first AP of the STR AP multi-link device to a first station of a non-STR station multi-link device, a transmission collision may occur between links. Fig. 17(a) illustrates this. This may occur because, as previously explained, the STR multi-link device cannot determine the status of a station included in a non-STR multi-link device in real time.

[0202] In addition, even if the transmission of the second station of the non-STR station multi-link device to the second AP of the STR AP multi-link device starts earlier than the transmission of the first AP of the STR AP multi-link device to the first station of the non-STR station multi-link device, a transmission collision may occur between the links. FIG. 17(b) illustrates this. This is because it may take time for the second AP (AP2) to inform the first AP (AP1) that the second station (STA2) is transmitting. Since transmission collisions may also occur between stations that start transmitting at different times, the probability of interference or transmission collisions occurring between them may be greater than the probability of interference or collisions occurring within a link. In addition, the probability of interference or transmission collisions occurring between links may increase as the time it takes for the AP of the STR multi-link device to identify the sender of the PPDU it receives increases. Therefore, a method to resolve this is needed. If one of the stations of the STR multi-link device is receiving, the channel access of other stations of the STR multi-link device may not be performed. However, if channel access is prohibited in this manner, the implementation of the STR function may lose its meaning. Therefore, an operating method other than prohibiting channel access for STR multi-link devices may be required. This is explained in Figure 18.

[0203] As described above, it may be important for a multi-link device to quickly determine the station performing the transmission to the multi-link device. The User field of the EHT-SIG of the EHT UL PPDU may indicate the identifier (STA-ID) of the station transmitting the EHT UL PPDU. Specifically, if the DL / UL field of the signaling field of the EHT PPDU indicates that the EHT PPDU is a UL PPDU, the User field of the EHT-SIG of the EHT PPDU may indicate the identifier of the station transmitting the EHT UL PPDU. A multi-link device receiving an EHT PPDU can identify the station transmitting the EHT PPDU based on the User field of the EHT-SIG of the EHT UL PPDU. Through this, the AP multi-link device can determine the station transmitting the EHT UL PPDU, and the AP multi-link device can determine the destination device of the transmission. Specifically, the AP multi-link device can determine whether the transmission being attempted is likely to fail due to an inter-link collision. Additionally, if there is a high probability that the transmission that the AP multi-link device is attempting to perform will fail, the AP multi-link device may delay the transmission that it is attempting to perform and perform another transmission.

[0204]

[0205] Various services are being implemented using wireless LAN. In particular, the need for low-latency service support is increasing, as the proliferation of wireless VR (virtual reality) devices increases. Therefore, a wireless LAN operation method that supports low-latency services is needed. For convenience of explanation, traffic for low-latency services is referred to as "low-latency traffic." Low-latency traffic can be designated by a station, including an access point (AP). Specifically, a layer above the MAC layer can designate which traffic is low-latency traffic. Furthermore, specific traffic can be designated as low-latency traffic. Furthermore, low-latency traffic can be traffic that has a priority that takes precedence over a pre-defined priority. In this case, the priority can be determined based on an access category (AC).

[0206] Even in the operation of the non-STR multi-link device described above, low-latency service support must be considered. This is because the transmission of low-latency traffic may be delayed due to the operating characteristics of the non-STR multi-link device. For example, if a non-STR multi-link device is receiving on the first link, transmission on the second link may be restricted to protect the transmission of PPDUs transmitted on the first link. Consequently, transmission of low-latency traffic that should be transmitted on the second link may be delayed. A method for resolving this issue is described in FIG. 18.

[0207] FIG. 18 shows that a multi-link device according to an embodiment of the present invention gives up reception of a PPDU being received on a first link of a non-STR multi-link pair and attempts to transmit a PPDU on a second link of a non-STR multi-link pair.

[0208] A multi-link device can transmit low-latency traffic on a second link of a non-STR link pair even if it is performing reception on a first link of a non-STR link pair. A non-STR link pair refers to a link pair in which a non-STR multi-link device can transmit on one of the two links and simultaneously cannot perform reception on the other link. At this time, the multi-link device gives up reception on the first link. Specifically, even if the multi-link device is receiving a PPDU on the first link of a non-STR link pair, it can attempt to transmit a PPDU including low-latency traffic on the second link of the non-STR link pair. At this time, the multi-link device can stop receiving the PPDU on the first link.

[0209] In addition, if the priority of the traffic included in the PPDU to be transmitted on the second link is higher than the priority of the traffic included in the PPDU received by the multi-link device on the first link, the non-STR multi-link device may attempt to transmit the PPDU including the high-priority traffic on the second link among the non-STR link pair even while receiving the PPDU on the first link among the non-STR link pair. At this time, the multi-link device may stop receiving the PPDU on the first link. In another specific embodiment, the multi-link device may perform transmission on the second link and ignore a signal received on the first link.

[0210] In the embodiments described above, the condition under which a multi-link device can stop reception is when the priority of traffic included in the ongoing reception on the first link is lower than the priority of traffic to be transmitted on the second link. Therefore, if the priority of traffic included in the ongoing reception on the first link is higher than the priority of traffic to be transmitted on the second link, the multi-link device cannot stop reception on the first link.

[0211] However, when low latency traffic is received through a specific link, channel access and transmission (including response) through other links that are non-STR related to the specific link may be restricted.

[0212] In the embodiment of FIG. 18, 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). The AP multi-link device receives a first PPDU from the second AP (AP2) through the first AP (AP1). At this time, if the first PPDU includes only non-low-latency traffic and low-latency traffic needs to be transmitted through the second link (Link 2), the AP multi-link device may give up receiving the first PPDU through the first link (Link 1) and attempt to transmit a second PPDU including low-latency traffic through the second link (Link 2). Alternatively, if the priority of the traffic included in the second PPDU to be transmitted on the second link (Link 2) is higher than the priority of the traffic included in the first PPDU received by the AP multi-link device on the first link (Link 1), the AP multi-link device may stop receiving the first PPDU on the first link (Link 1) and attempt to transmit the second PPDU on the second link (Link 2).

[0213] These embodiments allow multi-link devices to prioritize traffic exchange based on traffic type or priority. Furthermore, in the aforementioned embodiments, traffic priorities can be set according to predefined policies. Furthermore, as described above, traffic priorities can be assigned at layers higher than the MAC layer.

[0214]

[0215] An embodiment of preventing delay in transmission of low-latency traffic at the PPDU reception stage, i.e., the physical layer level, is described through FIG. 18. An embodiment of preventing delay in transmission of low-latency traffic at the frame exchange stage, i.e., the MAC layer level, is described through FIG. 19 to FIG. 22.

[0216] Figure 19 shows a situation where a multi-link device cannot transmit low-latency traffic by exchanging RTS / CTS frames in a non-STR multi-link pair.

[0217] When a multi-link device performs frame exchange on one of the non-STR multi-link pairs, transmission of low-latency traffic on the remaining link of the non-STR multi-link pair may be delayed. In the embodiment of FIG. 19, 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 the first link (Link 1). The first AP (AP1) transmits an RTS frame to the first station (STA1). The first station (STA1) transmits a CTS (clear to send) frame to the first AP (AP1) in response to the RTS (request to send) frame. Due to the RTS frame / CTS frame exchange sequence performed on the first link, frame exchange between the second AP (AP 2) and the second station (STA2) cannot be performed on the second link (Link2). In addition, even after the RTS frame / CTS frame exchange is completed, transmission may be restricted on the second link (Link2) for a certain period of time, such as MediumSyncDelay or NAVSyncDelay.

[0218] Additionally, in existing wireless LAN operations, a station that receives an RTS frame must transmit a CTS frame. Therefore, if existing wireless LAN operations are applied as is, even if the PPDU reception interruption example described in FIG. 18 is applied, low-latency traffic may be delayed until after the RTS frame / CTS frame exchange.

[0219] FIG. 20 shows a multi-link device according to an embodiment of the present invention that determines whether to transmit traffic based on the priority of the traffic before frame exchange.

[0220] A multi-link device may interrupt frame exchange in a frame exchange sequence performed on one of a non-STR multi-link pair for transmission of low-latency traffic. Specifically, the multi-link device may transmit low-latency traffic without transmitting a frame that should be transmitted in the frame exchange sequence. In a specific embodiment, the multi-link device may not transmit a response frame in the frame exchange sequence for transmission of low-latency traffic. In such embodiments, the multi-link device may resume the frame exchange sequence after transmitting the low-latency traffic.

[0221] Additionally, the frame exchange sequence may be a frame exchange sequence for setting up a network allocation vector (NAV). The frame exchange sequence for setting up a NAV may include at least one of an RTS (request to send) frame / CTS (clear to send) frame exchange sequence and an MU (multi-user)-RTS frame / CTS frame exchange sequence. Additionally, the interval between frames in the frame exchange sequence may be SIFS. In this case, a data frame exchange sequence may be excluded from the frame exchange sequence.

[0222] Additionally, frames exchanged in the frame exchange sequence may include information regarding the priority of traffic included in a frame to be transmitted after the frame exchange sequence. In this case, the information regarding the priority may be information indicating whether the traffic included in the frame to be transmitted after the frame exchange sequence is low-latency traffic. Additionally, the information regarding the priority may be a traffic identifier (TID) of traffic included in a frame to be transmitted after the frame exchange sequence. Additionally, the information regarding the priority may indicate the priority of traffic included in a frame to be transmitted after the frame exchange sequence. In these embodiments, the multi-link device may receive a frame in a frame exchange sequence performed in any one of the non-STR multi-link pairs, and determine whether to continue the frame exchange sequence based on additional information of the received frame. For example, if the frame received by the multi-link device indicates that low-latency traffic will not be transmitted after the frame exchange sequence, the multi-link device may abort the frame exchange sequence. Additionally, if the frame received by the multi-link device indicates that low-latency traffic will be transmitted after the frame exchange sequence, the multi-link device may continue the frame exchange sequence. In another specific embodiment, if the multi-link device receives a frame that has a priority of traffic to be transmitted after the frame exchange sequence that is lower than the priority of traffic waiting to be transmitted on the remaining links of the non-STR multi-link pair, the multi-link device may abort the frame exchange sequence. Furthermore, if the multi-link device receives a frame that has a priority of traffic to be transmitted after the frame exchange sequence that is equal to or higher than the priority of traffic waiting to be transmitted on the remaining links of the non-STR multi-link pair, the multi-link device may continue the frame exchange sequence.The specific format of information regarding the priority of traffic included in a frame to be transmitted after the frame exchange sequence is described with reference to FIGS. 21 and 22.

[0223] In the embodiments described above, the multi-link device may determine whether to transmit a response frame for the received frame based on additional information about the received frame. Furthermore, the multi-link device may determine the type of response frame for the received frame based on the additional information about the received frame.

[0224] In addition, a station that does not receive a response frame in the frame exchange sequence may not perform frame retransmission. This is because if the station performs frame retransmission, it may interfere with the transmission of low-latency traffic that is performed instead of the frame exchange sequence. Specifically, even if a station that transmitted a frame to a non-STR multi-link device does not receive a response frame, the station may not perform frame retransmission. Even if a station that transmitted a frame in any one of the non-STR multi-link pairs does not receive a response frame, the station may not perform frame retransmission. In another specific embodiment, a station that does not receive a response frame in the frame exchange sequence may determine whether to perform frame retransmission based on whether the link on which the frame was transmitted and the link corresponding to the non-STR multi-link pair have reached a service period for low-latency traffic transmission. For example, if the link on which the frame was transmitted and the link corresponding to the non-STR multi-link pair have reached a service period for low-latency traffic transmission, the station that transmitted the frame may not perform frame retransmission. A station that does not receive a response frame in a frame exchange sequence may determine whether to perform frame retransmission based on whether the receiver of the frame has participated in service period negotiation for low-latency traffic transmission. For example, if the receiver of the frame has participated in service period negotiation for low-latency traffic transmission, the station that transmitted the frame may not perform frame retransmission. In the above embodiments, the service period for low-latency traffic transmission may be a service period of restricted (R)-TWT (target wakeup time). R-TWT is described with reference to FIG. 25.

[0225] In the embodiment of FIG. 20, 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 in a first link (Link 1). The first AP (AP1) transmits an RTS frame to the first station (STA1). The first station (STA1) transmits a CTS (clear to send) frame to the first AP (AP1) in response to the RTS (request to send) frame. At this time, the RTS frame includes information regarding the priority of traffic to be transmitted after the RTS frame / CTS frame exchange. The information regarding the priority may indicate that traffic other than low-latency traffic is transmitted after the RTS frame / CTS frame exchange. Alternatively, information regarding priority may indicate that traffic with a lower priority than the priority of traffic waiting to be transmitted on the second link after the RTS frame / CTS frame exchange will be transmitted. In this case, the first station (STA1) does not transmit a CTS frame, and the second station (STA2) transmits low-latency traffic to the second AP (AP2).

[0226] Although the first AP (AP1) does not receive a CTS frame from the first station (STA1), it does not retransmit an RTS frame to the first station (STA1). In addition, the first AP (AP1) transmits an RTS frame to a station other than the first station (STA1) on the first link (Link 1).

[0227]

[0228] Fig. 21 shows the Frame Control field format of an RTS frame according to an embodiment of the present invention. In addition, Fig. 22 shows the User Info field format of an MU-RTS frame according to an embodiment of the present invention.

[0229] As described above, frames exchanged in a frame exchange sequence may include information regarding the priority of traffic included in a frame to be transmitted after the frame exchange sequence. Specifically, an initiating frame that initiates frame exchange may include information regarding the priority of traffic. Specifically, if the initiating frame is a control frame, the frame control field may include information regarding the priority of traffic. For example, the initiating frame may include a 1-bit field (Low latency indication) indicating whether traffic included in a frame to be 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. In addition, the initiating frame may include a 4-bit field (TID Info) indicating a TID (traffic identifier) ​​of traffic included in a frame to be transmitted after the frame exchange sequence. In another specific embodiment, the initiating frame may include a 4-bit field (Priority Info) indicating the priority of traffic to be transmitted after the frame exchange sequence. At this time, the 4-bit field may be included in the initiation frame instead of the To DS field, From DS field, More Fragments field, and Retry field. In addition, the initiation frame may include a 1-bit field (Traffic Info Flag) indicating whether the frame to be transmitted after the frame exchange sequence includes information about the priority of traffic included in the frame. At this time, the 1-bit field may be included instead of the Protected Frame field. This is because 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 additional meaning.

[0230] Figure 21(a) shows the Frame Control field of an RTS frame that does not include information regarding traffic priority. Additionally, Figure 21(b) shows the Frame Control field of an RTS frame that includes information regarding traffic priority according to an embodiment of the present invention.

[0231] The MU-RTS frame is a type of trigger frame. The trigger frame can trigger transmission of one or more stations. To this end, the trigger frame can include as many User Info fields as the number of stations that trigger transmission. Each User Info field indicates information signaled to each station that triggers transmission of the trigger frame. The User Info field of the MU-RTS frame can include information regarding the priority of traffic included in a frame to be transmitted after the MU-RTS frame / CTS frame exchange sequence. At this time, the User Info field of the MU-RTS frame can include information regarding the priority of traffic using a reserved field. Specifically, the User Info field can include information regarding the priority of traffic using a UL FEC Coding Type field, a UL HE-MCS field, a UL DCM field, an SS Allocation / RA-RU Information field, and a UL Target Receive Power field.

[0232] The format of information regarding traffic priority may be applied to the embodiments described through FIG. 21. FIG. 22(a) shows the User Info field of an MU-RTS frame that does not include information regarding traffic priority. Additionally, FIG. 22(b) shows the User Info field of an MU-RTS frame that includes information regarding traffic priority according to an embodiment of the present invention.

[0233] The MU-RTS frame / CTS frame exchange sequence can also be performed between one AP and multiple stations, so that the MU-RTS frame / CTS frame exchange sequence can continue even if the multi-link device does not transmit a CTS frame.

[0234]

[0235] When applying existing wireless LAN operations, multi-link devices must obtain transmission opportunities to transmit low-latency traffic even after the frame exchange sequence is interrupted. Consequently, they must compete with other wireless communication devices, which can further delay low-latency traffic transmission. To prevent this, a low-latency traffic transmission method may be required. This will be described in Figures 23 and 24.

[0236] FIG. 23 shows a station that has received an RTS frame requesting a transmission opportunity transfer to an AP that has transmitted the RTS frame according to an embodiment of the present invention.

[0237] When a station storing low-latency traffic in a buffer receives an initiation frame that initiates a frame exchange sequence, the station can insert a request for prioritizing low-latency traffic into a response frame to the initiation frame and transmit the response frame. The station that transmitted the initiation frame can accept or reject the request for prioritizing low-latency traffic. The station that received the response frame including the request for prioritizing low-latency traffic can accept the request for prioritizing low-latency traffic by transmitting the response frame. In addition, the station that received the response frame including the request for prioritizing low-latency traffic can reject the request for prioritizing low-latency traffic by performing a scheduled transmission after the frame exchange sequence.

[0238] For example, a first station receives an RTS frame from a second station. At this time, if the first station is storing low-latency traffic transmission in a buffer, the first station can insert a request for prioritizing the low-latency traffic into the CTS frame and transmit the CTS frame to the second station. The second station receives the CTS frame including the request for prioritizing the low-latency traffic. At this time, if the second station accepts the request for prioritizing the low-latency traffic, the second station transmits a CTS frame to the first station. At this time, the first station receives the CTS frame and transmits a frame including the low-latency traffic. If the second station rejects the request for prioritizing the low-latency traffic, the second station transmits DL data to the first station. In these embodiments, the interval between frames may be SIFS.

[0239] In another specific embodiment, when a station storing low-latency traffic in a buffer receives an initiation frame that initiates a frame exchange sequence, the station may transmit an initiation frame in response to the initiation frame to request priority processing of the low-latency traffic. At this time, the initiation frame transmitted in response to the initiation frame includes information regarding the characteristics of the low-latency traffic that the station stores in the buffer. For example, a first station receives an RTS frame from a second station. At this time, if the first station is storing low-latency traffic transmission in the buffer, the first station may transmit an RTS frame to the second station. At this time, the Frame Control field of the RTS frame may include information regarding the characteristics of the low-latency traffic that the station stores in the buffer. At this time, the information regarding the characteristics of the low-latency traffic may be indicated as in the embodiment described with reference to FIG. 21.

[0240] In the preceding embodiments, a station that receives a request for prioritization of low-latency traffic may not accept the request and may also terminate the frame exchange sequence. For example, a station that receives an RTS frame in response to an RTS frame or a CTS frame containing a request for prioritization of low-latency traffic may not transmit any subsequent DL data frames. This is because the subsequent sequence following the low-latency traffic prioritization request frame exchange sequence may be interpreted as unwanted signaling.

[0241] Additionally, a station transmitting an initiation frame may include in the initiation frame information regarding the characteristics of traffic to be transmitted after the frame exchange sequence. For example, a station transmitting an RTS frame in an RTS frame / CTS frame exchange sequence may include in the RTS frame information regarding the characteristics of traffic to be transmitted after the RTS frame / CTS frame exchange sequence. The information regarding the characteristics of the traffic may be indicated as in the embodiment described with reference to FIG. 21. In this embodiment, a station receiving an initiation frame may determine whether to request priority processing of low-latency traffic based on the information regarding the characteristics of the traffic included in the initiation frame. For example, a first station may transmit an RTS frame including information regarding the characteristics of traffic to be transmitted after an RTS frame / CST frame exchange to a second station. The second station may determine whether to request priority processing of low-latency traffic from the first station based on the information regarding the characteristics of traffic to be transmitted after the RTS frame / CST frame exchange. Specifically, if the traffic to be transmitted after the RTS frame / CST frame exchange is not low-latency traffic, the second station may request the first station to prioritize low-latency traffic. Furthermore, if the traffic to be transmitted after the RTS frame / CST frame exchange is low-latency traffic, the second station may not request the first station to prioritize low-latency traffic. In another specific embodiment, if the priority of the traffic to be transmitted after the RTS frame / CST frame exchange is lower than the priority of the low-latency traffic stored in the buffer of the second station, the second station may request the first station to prioritize low-latency traffic. Furthermore, if the priority of the traffic to be transmitted after the RTS frame / CST frame exchange is equal to or higher than the priority of the low-latency traffic stored in the buffer of the second station, the first station may not request the first station to prioritize low-latency traffic.

[0242] In the embodiment of FIG. 23, an AP transmits an RTS frame to a station. At this time, the RTS frame includes characteristics regarding traffic to be transmitted after the RTS frame / CTS frame exchange. Specifically, the RTS frame may indicate that the traffic to be transmitted after the RTS frame / CTS frame exchange is not low-latency traffic, and may indicate the priority of the traffic to be transmitted after the RTS frame / CTS frame exchange. Since the traffic to be transmitted after the RTS frame / CTS frame exchange is not low-latency traffic, the station transmits a CTS frame (CTS#1) requesting priority processing of low-latency traffic. At this time, the station sets the value of the duration field of the CTS frame (CTS#1) to a value obtained by subtracting the time required for CTS frame transmission (CTStime) and SIFS from the value of the duration field of the RTS frame. The AP receives the CTS frame (CTS#1) from the station. The AP accepts transmission of low-latency traffic by transmitting a CTS frame (CTS#2) to the station. 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 required for CST frame transmission (CTStime) and SIFS from the value of the duration field of the CTS frame (CTS#1).

[0243] In the embodiments described above, when the transmission of low-latency traffic is terminated and there is a remaining TXOP set for frame exchange, 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, the station that requests priority processing of the low-latency traffic in the RTS frame / CTS frame exchange sequence and completes the transmission of the low-latency traffic 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 a specific embodiment, the format other than non-HT PPDU may be the EHT PPDU format. This is because the CTS frame is not transmitted to set a NAV, but rather to indicate that the transmission of the low-latency traffic is complete.

[0244] In the embodiments described above regarding CTS frame / RTS frame transmission, transmitting to a station means setting the RA field of the CTS frame / RTS frame to the MAC address of the corresponding station.

[0245] FIG. 24 shows the format of a Frame Control field of a CTS frame including a request for priority processing of low-latency traffic according to an embodiment of the present invention.

[0246] As previously explained, the CTS frame may contain information regarding a request for priority handling of low-latency traffic.

[0247] The CTS frame may include a 1-bit field (Low Latency Indication) indicating a request for priority handling of low-latency traffic. Furthermore, the CTS frame may include a 4-bit field (TID Info) indicating the traffic identifier (TID) of the low-latency traffic. In another specific embodiment, the CTS frame may include a 4-bit field (Priority Info) indicating the priority of the low-latency traffic. Furthermore, the CTS frame may include a 1-bit field (UL Request) indicating whether the station transmitting the CTS frame requests uplink transmission.

[0248]

[0249] Scheduling for low-latency traffic transmission is explained with reference to FIGS. 25 to 30. In conventional wireless LAN communications, channel access parameters are set for each AC through EDCA (enhanced distributed channel access), and traffic is processed according to the priority of each AC using the set channel access parameters. However, since the existing EDCA provides channel access with a high priority based on probability, it is insufficient in supporting the transmission of low-latency traffic. To compensate for this, a time period during which low-latency traffic can be transmitted with priority can be set. For the convenience of explanation, the time period during which low-latency traffic is transmitted with priority is referred to as a limited service period. Since most services that require low-latency traffic transmission, such as VR / AR, require periodic traffic transmission, the limited service period has a significant effect in reducing transmission delay of low-latency traffic.

[0250] A limited service period may be a time period during which transmission of low-latency traffic and transmission of responses to low-latency traffic are given priority. Specifically, the limited service period may be a time period during which only transmission of low-latency traffic and transmission of responses to low-latency traffic are permitted. In another specific embodiment, the limited service period may be a time period during which transmission of low-latency traffic and transmission of responses to low-latency traffic are performed, and after the transmission of low-latency traffic and transmission of responses to low-latency traffic are completed, transmission of traffic other than low-latency traffic is permitted.

[0251] First, we describe how to set a limited service period. A limited service period can be set via TWT in existing WLANs. TWT establishes a service period through agreement between the AP and the station. It supports transmission and reception between the AP and the station during the service period and entry into low-power mode outside the service period. This is described in detail in Figure 25. For convenience of explanation, setting a limited service period via TWT and having the AP and station operate based on the limited service period is referred to as limited TWT.

[0252] FIG. 25 illustrates a method for setting up a broadcast TWT between an AP and a station according to an embodiment of the present invention.

[0253] In TWT, the service period can be set as follows. The AP requests the station associated with the AP to participate in TWT. The station can participate in broadcast TWT or negotiate an individual TWT with the AP. At this time, the AP can request the station to participate in TWT by setting the value of the TWT Required subfield of the HE Operation element to 1. In addition, the AP can transmit the Broadcast TWT element through a management frame, such as a beacon frame, to provide the station with information necessary for participation in broadcast TWT. At this time, the AP can signal that it supports broadcast TWT by setting dot11TWTOptionActivated to true and setting the Broadcast TWT Support field (of the element) of the HE Capabilities element to 1. The AP can set a limited service period similar to the service period of TWT.

[0254] In the embodiment of FIG. 25, the first station (STA1) requests the AP to set up TWT. The AP and the first station (STA1) set up TWT parameters, such as the initial TBTT and the listen interval. Accordingly, the AP and the first station (STA1) and the second station (STA2) set up a broadcast TWT. The AP indicates a broadcast TWT service period using a beacon frame. In the broadcast TWT service period, the AP can transmit a downlink (DL) physical layer protocol data unit (PPDU) to the first station (STA1) and the second station (STA2) or transmit a trigger frame to the first station (STA1) and the second station (STA2) to trigger an uplink (UL) transmission. In 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 TWT from the received beacon frame. The AP transmits a trigger frame to the first station (STA1) and the second station (STA2), the first station (STA1) transmits a PS-Poll frame to the AP, and the second station (STA2) transmits a QoS Null frame to the AP. The AP receives the PS-Poll frame and the QoS Null frame transmitted by the first station (STA1) and the second station (STA2), and determines that the first station (STA1) and the second station (STA2) are in an awake state. The AP transmits a multi-STA Block ACK frame to the first station (STA1) and the second station (STA2). The AP transmits a DL PPDU to the first station (STA1) and the second station (STA2).

[0255] Existing TWT service periods do not restrict non-TWT stations from accessing channels or transmitting. This is because TWT is intended to facilitate stations participating in TWT entering a doze state. However, limited service periods, intended to prevent transmission delays for low-latency traffic, must ensure priority transmission of low-latency traffic. Therefore, a method to protect limited service periods is needed.

[0256] During a limited service period, a station that does not participate in the limited TWT may be restricted from accessing the channel. Specifically, during the limited service period, a station that does not participate in the limited TWT may not be able to perform channel access. During the limited service period, if a station that does not participate in the limited TWT completes channel access, the station may restart the channel access procedure without performing transmission. At this time, the station may restart the channel access procedure when the limited service period ends. Furthermore, the station's channel access may indicate an EDCA backoff procedure. Completing the channel access may indicate that the backoff counter of the EDCA backoff procedure has reached zero. Furthermore, when the 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. In other words, the station may not double the size of the CW used for the previous channel access. At this time, the CW may be maintained for each AC. These channel access restrictions may only be applied to stations supporting restricted TWT. Specifically, these channel access restrictions may only be applied to non-legacy (EHT) stations for which the dot11RestrictedTWTOptionImplemented property of the EHT Capabilities element is set to true, and may not be applied to non-legacy (EHT) stations for which the dot11RestrictedTWTOptionImplemented property of the EHT Capabilities element is set to false. In this specification, a non-legacy station may refer to an EHT station and a station after an EHT station. In addition, a legacy station may refer to a station before an EHT station, such as a non-HT station, an HT station, a VHT station, and a HE station.

[0257] Additionally, during a limited service period, a NAV may be set for non-legacy stations for traffic other than low-latency traffic. Specifically, as if a NAV had been set for traffic other than low-latency traffic, the station may suspend channel access procedures for transmission of traffic other than low-latency traffic. In this embodiment, the NAV may be a NAV independent from a conventional NAV (basic NAV, intra-BSS NAV). In this case, non-legacy stations may be limited to stations that support limited TWT. In another specific embodiment, non-legacy stations may be limited to stations that participate in limited TWT.

[0258] The limited service period may be included within a broadcast TWT service period. In another specific embodiment, the limited service period may not be included within a broadcast TWT service period.

[0259] Additionally, the limited service period can be repeated periodically as specified by the AP. That is, the AP can specify the repetition frequency of the limited service period. This allows the AP to avoid transmitting the TWT element of the beacon frame every time to establish the limited service period. In this case, the service period period can be set according to the characteristics of the low-latency service in which low-latency traffic is used. For example, the period of a low-latency service period in which low-latency traffic is generated every 50 ms can be 50 ms.

[0260] Additionally, a quiet interval can be set for stations that do not support limited TWT. In conventional wireless LANs, a quiet interval is a period to support channel sensing. When a quiet interval is set, all stations stop transmitting. This quiet interval characteristic can be utilized to protect the limited service period. This is explained in detail in Figure 26. In this case, stations that do not support limited TWT can be limited to legacy stations.

[0261]

[0262] FIG. 26 shows an AP setting a quiet interval according to an embodiment of the present invention.

[0263] An AP operating a restricted TWT can establish a quiet period by transmitting a Quiet element. During the Quiet period, stations suspend channel access. However, if channel access of stations participating in the restricted TWT is restricted, low-latency traffic cannot be transmitted. Therefore, stations participating in the restricted TWT can ignore the Quiet period corresponding to the restricted service period. In this case, the Quiet period corresponding to the restricted service period represents a Quiet period established to protect the restricted service cycle of the restricted TWT. Specifically, stations participating in the restricted TWT can regard the Quiet period corresponding to the restricted service period as a restricted service period. An AP operating a restricted TWT may not set the Quiet period to match the restricted service period. This is because the Quiet period in the Quiet element is set in units of TU (time units, 1024us), while the TWT is set in units of 256us.

[0264] However, if channel access is performed in a quiet interval that is not set for a limited service period, it may interfere with a quiet interval that is not set for a limited service period. Therefore, it is necessary to distinguish between a quiet interval set for a limited service period, i.e., a quiet interval corresponding to a limited service period. Therefore, a station participating in a limited TWT may not be able to ignore a quiet interval that does not correspond to a limited service period. A station may not be able to perform any transmission in a quiet interval that does not correspond to a limited service period. Specifically, a station participating in a limited TWT may not be able to ignore a quiet interval that does not overlap with a limited service period. In a specific embodiment, a station participating in a limited TWT may not be able to perform any transmission in a quiet interval that does not overlap with a limited service period.

[0265] Additionally, in the above embodiments, a station participating in a limited TWT may consider a quiet interval corresponding to a limited service period if the start time of the limited service period and the start time of the quiet interval are within a predetermined time, and if the start time of the service period and the start time of the quiet interval are within a predetermined time. As described above, an AP operating a limited TWT may not set the quiet interval to match the limited service period.

[0266] In the embodiment of FIG. 25, the AP transmits a beacon frame to establish a quiet period and a restricted service period. In FIG. 25(a), the quiet period is set to the same time period as the restricted service period. Therefore, stations participating in the restricted TWT in the quiet period perform channel access. In FIG. 25(b), the quiet period is set to a time period starting from a time earlier than the start time of the restricted service period to a time later than the end time of the restricted service period. In FIG. 25(b), channel access of stations participating in the restricted TWT in the quiet period that does not overlap with the restricted service period is restricted. Stations participating in the restricted TWT in the quiet period that overlaps with the restricted service period perform channel access.

[0267]

[0268] As previously explained, channel access may be restricted during limited service periods. Accordingly, these restrictions may also apply to TXOP settings. This is explained in Figure 27.

[0269] FIG. 27 illustrates a method for setting a TXOP by considering a limited service period of a station according to an embodiment of the present invention.

[0270] A station that has acquired a TXOP before the start of a restricted service period, i.e., a TXOP holder, may need to terminate the TXOP before the start of the restricted service period. This is because if frame exchange of the TXOP holder continues even after the start of the restricted service period, transmission of low-latency traffic may be interrupted. In this case, the station may be a non-legacy station. In another specific embodiment, the station may be limited to stations that support restricted TWT. That is, this restriction may not be applied to stations that set the value of the dot11RestrictedTWTOptionImplemented field to false.

[0271] In a specific embodiment, if a station that is a TXOP holder transmits low-latency traffic, it may continue to exchange frames even after the limited service period begins.

[0272] Describes the specific method by which a station terminates a TXOP before the limited service period.

[0273] A station can set a TXOP based on a limited service period. Specifically, the station can set the TXOP end time to be before the start of the limited service period. At this time, the station can set the duration of the initiating frame that initiates the frame exchange sequence to be before the start of the limited service period. For example, if the station successfully accesses the channel 3 ms before the start of the limited service period, the station can set the TXOP to be 3 ms before. Additionally, the station can end the TXO by transmitting a CTS-to-Self frame. At this time, the station can transmit the CTS-to-Self frame at the default transmission rate, 6 Mbps. This is because many legacy stations can receive the frame when the station transmits the frame at the default transmission rate.

[0274] In another specific embodiment, a station may transmit a CF-End frame before the start of a limited service period. This allows the station to terminate a TXOP before the start of the limited service period. In this case, the station may transmit the CF-End frame at the default transmission rate of 6 Mbps. This is because when a station transmits a frame at the default transmission rate, many legacy stations may receive the frame.

[0275] In addition, a station that is not a TXOP holder may release the NAV set before the start of the restricted service period at the start of the restricted service period. At this time, the station may be a station that supports restricted TWT. That is, the station may be a station that sets the value of the dot11RestrictedTWTOptionImplemented field to True. A station that is not a TXOP holder but does not support restricted TWT may not release the NAV set before the start of the restricted service period at the start of the restricted service period. However, if the station completes the frame exchange and the remaining duration of the TXOP is less than twice the sum of the time required to transmit the CF-End frame and SIFS, the station may not transmit the CF-End frame. At this time, the station may consider the TXOP to be released at the start of the restricted service period. Specifically, the station may consider the basic NAV to be released at the start of the restricted service period.

[0276] In another specific embodiment, stations may be limited to those participating in a limited TWT.

[0277] In the embodiment of Fig. 27, the AP transmits a beacon frame including a TWT element to signal that a restricted service period is established. In the embodiment of Fig. 27(a), the station transmits an RTS frame to establish a TXOP. At this time, the station sets the value of the duration field of the RTS frame to before the restricted service period. The station performs a frame exchange with the AP and completes the frame exchange before the start of the restricted service period. At this time, the station transmits a CTS-to-Self frame last. In the embodiment of Fig. 27(b), the station transmits an RTS frame to establish a TXOP. At this time, the station sets the value of the duration field of the RTS frame without considering the restricted service period. The station performs a frame exchange with the AP and completes the frame exchange before the start of the restricted service period. At this time, the station releases the TXOP by transmitting a CF-end frame last.

[0278] In conventional wireless LAN operation, operations that can be transmitted beyond the TXOP limit are defined as exceptions to the TXOP rule. For example, retransmission of a single MPDU, transmission of a single MSDU (not included in an A-MSDU and an A-MPDU composed of two or more MPDUs) under a block ack agreement, transmission of control frames and QoS Null frames (not included in an A-MPDU composed of two or more MPDUs) can be transmitted beyond the TXOP limit. If such exceptions are recognized even for a limited service period, transmission of low-latency traffic may be delayed. Such exceptions to the TXOP limit cannot be applied because they violate the limited service period.

[0279] If the end time of a TXOP is within a predetermined time difference from the start time of the limited service period, the station may determine that the TXOP was acquired before the start of the limited service period. The predetermined time may be 100 microseconds. In another specific embodiment, if the end time of a TXOP is within the limited service period, the station may determine that the TXOP was acquired before the start of the limited service period.

[0280]

[0281] As previously explained, a station may need to complete frame exchanges before the limited service period begins. Accordingly, a station may not be permitted to initiate frame exchanges if the completion time of the frame exchange falls within the limited service period. In this case, the station can perform fragmentation to complete the frame exchange before the start of the limited service period.

[0282] Additionally, if a station that is a TXOP holder transmits low-latency traffic in a frame exchange performed by the station, the station may continue to exchange frames even after the low-latency service period begins.

[0283]

[0284] The channel access procedure considering the limited service period is described in Fig. 28.

[0285] FIG. 28 shows a station performing a channel access procedure again considering a limited service period according to an embodiment of the present invention.

[0286] As previously explained, even if a station completes channel access before the limited service period, if the frame exchange is completed after the start of the limited service period, the station may initiate the channel access procedure again without performing transmission. At this time, the station may reacquire the value of the backoff counter. At this time, the station may use the same size of the CW used in the previous channel access procedure. That is, the station may not double the size of the CW used in the previous channel access procedure, nor may it initialize it to the minimum value that the CW can have. In addition, the station may not increase the number of retries, such as the QSRC (QoS STA Retry Counter).

[0287] Additionally, if the time at which the station completes channel access is within a pre-specified time from the start of the limited service period, the station may initiate the channel access procedure again without performing transmission.

[0288] In the preceding embodiments, a station attempting to transmit low-latency traffic may initiate frame exchange after channel access is completed, even if the frame exchange completion time is after the start of a limited service period. This exception may only be permitted if the station attempting to transmit low-latency traffic is participating in a restricted TWT.

[0289] Additionally, as previously described, a station can operate as if an NAV is set for ACs for traffic other than low-latency traffic. Therefore, the station can determine that the CCA result for transmission of ACs for traffic other than low-latency traffic is not idle (BUSY).

[0290] In the embodiment of FIG. 28, the AP transmits a beacon frame containing a TWT element to signal that a limited service period is established. Before the limited service period begins, the backoff counter value of the station's channel access reaches 0. The station determines that the completion time of the frame exchange containing the traffic to be transmitted is after the start time of the service period. Therefore, the station acquires a backoff counter within the CW value used in the previous channel access procedure. The station performs the channel access procedure again using the acquired backoff counter. At this time, the station does not increment the retransmission counter.

[0291]

[0292] All low-latency traffic transmission may be completed before the limited service period ends. In such cases, limiting the transmission of non-low-latency traffic due to the low-latency service period may be inefficient. Therefore, a method for terminating the limited service period early may be necessary. This is described in the example of FIG. 29.

[0293] FIG. 29 illustrates an operation of an AP terminating a limited service period early according to an embodiment of the present invention.

[0294] In order for an AP to terminate a limited service period early, it must be able to determine that all low-latency traffic transmissions by a station participating in the limited TWT have been completed. To this end, a station participating in the limited TWT can signal whether to transmit additional low-latency traffic in the frame it transmits. Specifically, a station can signal that it will transmit additional low-latency traffic by setting the value of the More data subfield of the Frame Control field of the frame. In this case, if the value of the More data subfield of the Frame Control field of a frame transmitted in the limited service period is 1, the More data subfield indicates that additional low-latency traffic is required and may not indicate whether additional transmission of traffic other than low-latency traffic is required. For example, if a station participating in the limited TWT does not store low-latency traffic in its transmission buffer and only stores non-low-latency traffic, the station can set the value of the More data subfield of the Frame Control field of the frame it transmits in the limited service period to 0. An AP may prematurely terminate a restricted service period based on whether a station participating in a restricted TWT has a non-zero value in the More data subfield of the Frame Control field of a frame in the restricted service period. Specifically, if there is no low-latency traffic to transmit in the AP's transmit buffer and a station participating in a restricted TWT has a non-zero value in the More data subfield of the Frame Control field of a frame in the restricted service period, the AP may prematurely terminate the restricted service.

[0295] An AP can terminate a limited service period early by transmitting a pre-designated control frame. 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. Additionally, the AP can set the Individual / Group bit of the BSSID (TA) field of the CF-End frame to 1. In another specific embodiment, the AP can terminate a limited service period early by transmitting a pre-designated management frame.

[0296] A station that receives a pre-designated frame that terminates the limited service period within a limited service period can determine that the limited service period has ended. At this time, the station that received the pre-designated frame can resume channel access without the restrictions applied to the limited service period. As described above, the pre-designated frame may be a CF-End frame. At this time, if the value of the TA (BSSID) field of the CF-End frame received by the station within the limited service period is the MAC address of the AP to which the station is associated, the station can determine that the CF-End frame is the CF-End frame that terminates the limited service period.

[0297] As previously explained, a quiet interval can be set for the limited service period to protect the limited service period from legacy wireless communication terminals. At this time, the AP can transmit a CF-End frame to end the limited service period. This is because when the AP transmits a CF-End frame, it can also release the quiet interval set for the legacy station.

[0298] In the embodiments described above, the CF-End frame may have a Frame Control field whose Type is a control frame (Type value B3 B2 == 01) and whose Subtype is a CF-End frame (Subtype value B7 B6 B4 B4 == 1110).

[0299] When a quiet interval is set for a restricted service period, a station participating in the restricted TWT may not be permitted to transmit a CF-End frame within the restricted service period. In a specific embodiment, a station participating in the restricted TWT may not be permitted to transmit a CF-End frame in the quiet interval corresponding to the restricted service period. This is because when a station participating in the restricted TWT transmits a CF-End frame, the NAV set for the legacy station is released. However, if the CF-End frame is used to terminate the restricted service period early as described above, the AP may transmit the CF-End frame within the restricted service period.

[0300] In the embodiment of FIG. 29, the AP transmits a beacon frame including a TWT element and a Quiet element. A station supporting restricted TWT determines that a restricted service period is set, and a station not supporting restricted TWT determines that a quiet period is set. If the AP determines that transmission of all low-latency traffic within the restricted service period is completed, the AP transmits a CF-End frame to early end the restricted service period and releases the quiet period set for legacy stations. At this time, the station supporting restricted TWT determines that the channel access restriction applied during the restricted service period is removed. Specifically, if the embodiment in which the NAV is set during the restricted service period as described above is applied, the station supporting restricted TWT can determine that the NAV for the restricted service period is released. In addition, a station not supporting restricted TWT that receives the CF-End frame releases the NAV.

[0301]

[0302] The operation of the multi-link device is described through FIGS. 11 to 24. The channel access operation of the multi-link device is described through FIGS. 30 to 35.

[0303] When a first station of a non-STR multi-link device is scheduled to receive a specific frame on the first link, a second station of the non-STR multi-link device operating on the second link may not perform channel access or transmission at the time of receiving the specific frame on the first link. In this case, the specific frame may be a periodically transmitted frame. Specifically, the specific frame may be a DTIM frame.

[0304] In addition, if the second station is a TXOP holder, the second station may terminate the TXOP before receiving a specific frame from the first link. In this case, the method for terminating the TXOP may be applied to the embodiment of terminating the TXOP described through FIG. 28. Specifically, the second station may set the end of the TXOP before receiving a specific frame from the first link. For example, if the specific frame is a DTIM, the second station may set the end of the TXOP based on the reception cycle of the DTIM. In addition, the second station may transmit a CF-End frame before receiving a specific frame from the first link. In addition, the TXOP limit exception may not be applied to these embodiments.

[0305] Additionally, the second station may suspend channel access before receiving a specific frame from the first link. In this case, the channel access suspension embodiment described with reference to FIG. 28 may be applied. Specifically, if the time at which the second station completes channel access is insufficient to complete the frame exchange that the second station intends to perform, and the time at which the second station is scheduled to receive a specific frame from the first link differs by a significant amount, the second station may re-perform the channel access procedure. In this case, the second station may acquire a backoff counter using the same size of the CW used in the previous channel access procedure. Additionally, the second station may not increment the retransmission counter.

[0306]

[0307] FIG. 30 shows a multi-link device performing transmission on a non-STR link pair according to an embodiment of the present invention.

[0308] When a multi-link device transmits a frame on a first link of a non-STR link pair, the multi-link device may restrict frame transmission on a second link of the non-STR link pair for a certain period of time from the time of completion of frame transmission. At this time, the multi-link device may be a non-STR multi-link device. At this time, the certain period of time may be referred to as MediumSyncDelay. The restriction of the frame transmission operation may mean that the channel access procedure described above cannot be performed during the MediumSyncDelay. Specifically, the multi-link device may not perform a Distributed Coordination Function (DCF) or an Enhanced Distributed Channel Access Function (EDCAF) operation defined in IEEE 802.11 during the MediumSyncDelay on the second link. In another specific embodiment, when the multi-link device performs channel sensing during the MediumSyncDelay on the second link, the multi-link device may lower the energy level of a threshold, which is a criterion for a channel busy state. At this time, the multi-link device may set the energy level of the threshold to -82 dBm.

[0309] A multi-link device operating in a non-STR multi-link device can synchronize the start time of transmission in a non-STR multi-link pair. In this case, the transmission start time of a frame may indicate the transmission start time of a PPDU containing the frame. The multi-link device may delay transmission by keeping the backoff value set to 0 in the channel access procedure to synchronize the transmission start time in a non-STR link pair.

[0310] In addition, when reception is performed continuously after transmission in a non-STR multi-link pair, the multi-link device can synchronize the end time of transmission in the non-SRT multi-link pair. To this end, the multi-link device can add a bit or field for padding to the transmitted frame or PPDU. In addition, the multi-link device can add a packet extension (PE). In addition, when consecutive frame exchanges are performed in a non-STR multi-link pair, the multi-link device can synchronize the start time of transmission on the non-STR multi-link after the first frame exchange. In another specific embodiment, the multi-link device can synchronize the end time of transmission by performing fragmentation.

[0311] When the TXOP start time is the same in multiple links, the TXOP for frame transmission in each link can be synchronized. At this time, simultaneous transmission using multiple links can be performed after a negotiation step for simultaneous transmission in multiple links. In the negotiation step for simultaneous transmission, a multi-link device to perform transmission transmits a request frame for obtaining a TXOP for simultaneous transmission through synchronized transmission in multiple links, and a multi-link device that receives the request frame can transmit a response frame at an interval of SIFS (Short Interframe Space) from the request frame. At this time, the response frame can be transmitted simultaneously in one or more links that received the request frame. The request frame can be a control frame. For example, the request frame can be one of an RTS frame and an MU (Multi-user)-RTS frame. At this time, the response frame can be a CTS frame. If the channel of one link is occupied during channel contention for simultaneous transmission, the multi-link device can wait to perform a simultaneous transmission operation or perform transmission using only a link that includes an idle channel. The exchange of request and response frames described above may not be performed simultaneously across multiple links. Furthermore, synchronized frame exchange may involve synchronization between the start and end times of transmission of the PPDUs containing the frames.

[0312] When a multi-link device transmits a frame requesting an immediate response on a first link of a non-STR link pair, the multi-link device may synchronize the transmission end times on the first and second links of the non-STR link pair. At this time, the 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 another specific embodiment, the predetermined interval may be PIFS. In addition, when a multi-link device transmits a frame that does not request an immediate response on a first link of a non-STR link pair, the multi-link device may not synchronize the transmission end times on the first and second links of the non-STR link pair. At this time, the multi-link device may transmit a PPDU that does not request an immediate response on the second link as well, and transmission of a PPDU requesting an immediate response may not be permitted.

[0313] In the embodiments described above, synchronization of transmission start times may indicate that the difference between transmission start times is within a predetermined time period. Furthermore, synchronization of transmission end times may indicate that the difference between transmission end times is within a predetermined time period. In this case, the predetermined time period may be a time period during which, when performing channel sensing and backoff operations individually on links, the start of frame transmission on one link does not cause the other link to perceive the channel state as a busy state. In a specific embodiment, the predetermined time period may be the receive / transmit turnaround time (RxTxTurnaroundTime). For example, the predetermined time period may be 8 microseconds or 4 microseconds.

[0314] These embodiments enable a multi-link device to prevent transmission on one link in a non-STR link pair from preventing transmission on the other link.

[0315] In the embodiment of FIG. 30, 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). In FIG. 30(a), the AP multi-link device station multi-link device performs synchronized transmission and synchronized reception. This prevents transmission from being interrupted in either link in a non-STR multi-link pair. In FIG. 30(b), the first AP (AP1) transmits a DL PPDU that does not request an immediate response from the first link (Link 1). Since a DL PPDU that does not request an immediate response is transmitted on the first link (Link 1), the second station (STA2) transmits a DL PPDU that does not request an immediate response on the second link (Link2) without synchronizing with the transmission on the first link.

[0316] Figure 30 illustrates an embodiment in which frame exchange in a non-STR multi-link pair is initiated from an AP multi-link device, which is an STR multi-link device. The embodiment described with reference to Figure 30 can also be applied when frame exchange is initiated from a non-STR multi-link device. This will be described with reference to Figures 31 and 32.

[0317] Figure 31 illustrates frame exchange initiated from a non-AP station multi-link device that does not apply an embodiment of the present invention. Figure 32 illustrates frame exchange initiated from a non-AP station multi-link device according to an embodiment of the present invention.

[0318] In the embodiment of FIG. 31, 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). The termination times of transmissions by the first station (STA1) and the second station (STA2) are not synchronized. The transmission by the first station (STA1) ends before the transmission by the second station (STA2). Therefore, the transmission by the second station (STA2) continues while the first AP (AP1) transmits a BA frame to the first station (STA1). Therefore, the transmission by the first AP (AP1) fails.

[0319] Accordingly, when a non-STR multi-link device transmits a frame requesting an immediate response on the first link of a non-STR link pair, the non-STR multi-link device can synchronize the transmission end times on the first and second links of the non-STR link pair. At this time, the 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 another specific embodiment, the predetermined interval may be PIFS. In addition, when a non-STR multi-link device transmits a frame that does not request an immediate response on the first link of a non-STR link pair, the non-STR multi-link device may not synchronize the transmission end times on the first and second links of the non-STR link pair. At this time, the non-STR multi-link device may transmit a PPDU that does not request an immediate response on the second link as well, and transmitting a PPDU that requests an immediate response may not be permitted.

[0320] 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). The termination times 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 transmissions of the second AP (AP2) are successfully completed without interfering with each other.

[0321]

[0322] The cases where unsynchronized transmission is allowed in a non-STR link pair are described through FIGS. 33 to 35.

[0323] FIG. 33 shows a method in which a multi-link device performs a transmission requesting an immediate response on a first link of a non-STR link pair according to an embodiment of the present invention, while performing a transmission not requesting an immediate response on a second link.

[0324] When a multi-link device transmits a frame requesting an immediate response on a first link of a non-STR link pair, the multi-link device can perform a transmission that is completed before the end time of the transmission on the first link and does not request an immediate response on the second link of the non-STR link pair. In such an embodiment, since a response frame is not transmitted on the second link, it is possible to prevent transmission of the multi-link device on the first link and a response frame to the transmission from being interrupted by transmission of the multi-link device on the second link. In addition, if transmission of the multi-link device on the second link is not completed before the end time of the transmission on the first link, transmission of the response frame on the first link may be interrupted by transmission of the multi-link device on the second link. Therefore, transmission of the multi-link device on the second link must be completed before transmission on the first link.

[0325] 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). When the first station (STA1) performs an uplink transmission requesting an immediate response in the first link, the second station (STA2) performs an uplink transmission that is terminated before the transmission of the first station (STA1) is terminated and does not request an immediate response in the second link (Link 2). The uplink transmission of the first station (STA1) and the uplink transmission of the second station (STA2) are completed without interfering with each other.

[0326]

[0327] FIG. 34 shows an operation of performing transmission on a second link when a multi-link device performs UL OFDMA transmission on a first link among a non-STR link pair according to an embodiment of the present invention.

[0328] In a non-STR multi-link pair, the magnitude of the influence between links may vary depending on the RU through which transmission is performed. Therefore, even if a multi-link device performs transmission on the first link among the first and second links of a non-STR multi-link pair, transmission on the second link may be permitted depending on the positions of the RU of the first link through which the multi-link device performs transmission and the RU of the second link through 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 is used to perform the UL OFDMA transmission. In another specific embodiment, transmission on the second link may be permitted depending on which size of bandwidth the multi-link device uses to perform transmission on each link. In this case, the multi-link device may use any of a bandwidth of 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 320 MHz to perform transmission.

[0329] In the embodiment of FIG. 34, 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). The first station (STA1) participates in UL OFDMA transmission in the first link (Link 1). At this time, if the position of the RU where the first station (STA1) performs UL OFDMA satisfies a pre-specified condition, the second station (STA2) performs uplink transmission. At this time, the pre-specified condition may be that the interval between RUs is smaller than the pre-specified interval. Additionally, it can be determined whether transmission on the second link is allowed depending on the direction of expansion of the bandwidth in which transmission is performed.

[0330]

[0331] Depending on the transmission direction, a link pair can be determined to be a non-STR link pair or a STR link pair. This is explained in FIG. 35.

[0332] FIG. 35 shows a case where a link pair is determined to be a non-STR link pair or a STR link pair depending on the transmission direction according to an embodiment of the present invention.

[0333] When reception is performed on the first link of a link pair, the first multi-link device cannot transmit on the second link. However, when reception is performed on the second link, the first multi-link device can transmit on the first link. For example, the transmission power of a station in the 6 GHz band may be limited to a predetermined power or less. Therefore, when the first link is located in the 6 GHz band, the first multi-link device cannot transmit on the second link when reception is performed on the first link of a link pair. However, when reception is performed on the second link, the first multi-link device can transmit on the first link. Therefore, depending on the transmission direction, while transmission is performed on the first link, transmission in which the transmission end time of the first link and the transmission end time of the second link are not synchronized may be permitted. In this case, the multi-link device may terminate transmission on the second link before transmission on the first link. To this end, the multi-link device may fragment traffic to be transmitted on the second link.

[0334] In the embodiment of FIG. 35, 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 in a first link (Link 1). The second AP (AP2) and the second station (STA2) operate in a second link (Link 2). At this time, the non-AP station cannot perform transmission in the second link when reception is performed in the first link located in the 6 GHz band. However, when the non-AP station performs reception in the second link (Link 2), transmission can be performed in the first link (Link 1). While the first station (STA1) is performing uplink transmission in the first link (Link 1), the second station (STA2) starts uplink transmission in the second link (Link 2). At this time, the second station (STA1) completes the uplink transmission before the first station (STA1) completes the uplink transmission. Through this operation, the uplink transmission is completed on the first and second links, and the BA frame is also successfully transmitted.

[0335]

[0336] While the present invention has been described using wireless LAN communication as an example, it is not limited thereto and can be equally applied to other communication systems, such as cellular communication. Furthermore, while the methods, devices, and systems of the present invention have been described with reference to specific embodiments, some or all of the components and operations of the present invention can be implemented using a computer system with a general-purpose hardware architecture.

[0337] The features, structures, effects, etc. described in the embodiments 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, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments pertain. Therefore, the contents related to such combinations and modifications should be construed as being included within the scope of the present invention.

[0338] Although the above has been described focusing on embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiment. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

Claims

1. In a wireless communication terminal that communicates wirelessly with a base wireless communication terminal, Transmitter and receiver; and Contains a processor, The above processor Transmitting low-latency traffic set as traffic for low-latency transmission within a limited service period or a response to said low-latency traffic, Within the above limited service period, transmission of the above low-latency traffic and transmission other than the above low-latency traffic are restricted. Wireless communication terminal.

2. In paragraph 1, The above processor Terminate TXOP for transmission of traffic other than low-latency traffic before the start of the above limited service period. Wireless communication terminal.

3. In paragraph 1, The above processor Obtain a random integer within the competition window, Channel access is performed based on the random integer obtained above, If channel access is completed before the start of the above-mentioned limited service period and transmission is abandoned because it is determined that frame exchange cannot be completed before the start of the above-mentioned limited service period, channel access is performed again. Wireless communication terminal.

4. In paragraph 3, The above processor When the wireless communication terminal performs the channel access again, the size of the contention window used in the completed channel access is maintained as is. Wireless communication terminal.

5. In paragraph 3, The above processor When the wireless communication terminal performs the channel access again, the retransmission count of the completed channel access is maintained as is. Wireless communication terminal.

6. In paragraph 1, A quiet period corresponding to the above limited service period is set, and no transmission is permitted during the quiet period. The above processor Transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period by ignoring the quiet interval corresponding to the limited service period, Do not transmit CF End frame within the above limited service period. Wireless communication terminal.

7. In paragraph 1, A quiet period corresponding to the above limited service period is set, and no transmission is permitted during the quiet period. The above processor Decide whether to ignore the quiet period based on the start time of the above limited service period and the start time of the above quiet period, If it is decided to ignore the above quiet period, the quiet period corresponding to the limited service period is ignored and the low-latency traffic or the response to the low-latency traffic is transmitted within the limited service period. Wireless communication terminal.

8. In paragraph 7, The above processor If the conditions determined based on the start time of the above limited service period and the start time of the above quiet period are satisfied, the above quiet period is ignored, If the conditions determined based on the start time of the above limited service period and the start time of the above quiet period are not satisfied, no transmission is performed. Wireless communication terminal.

9. In paragraph 8, The condition judged based on the start time of the above limited service period and the start time of the quiet section is that the start time of the above quiet section and the start time of the above limited service period are within a pre-specified time. Wireless communication terminal.

10. In the operation method of a wireless communication terminal that wirelessly communicates with a base wireless communication terminal, Comprising a step of transmitting low-latency traffic set as traffic for low-latency transmission within a limited service period or a response to said low-latency traffic, Within the above limited service period, transmission is restricted except for transmission of the low-latency traffic and transmission of responses to the low-latency traffic. How it works.

11. In Article 10, The above method of operation is Further comprising a step of terminating a TXOP for transmission of traffic other than the low-latency traffic before the start of the limited service period. How it works.

12. In Article 10, The above method of operation is A step of obtaining a random integer within a competition window; A step of performing channel access based on the obtained random integer; and If it is determined that channel access is completed before the start of the limited service period and frame exchange is not completed before the start of the limited service period, and transmission is abandoned, a step of performing channel access again is included. How it works.

13. In Article 12, The steps to re-access the above channels are: When the wireless communication terminal performs the channel access again, the step of maintaining the size of the contention window used for the completed channel access as it is How it works.

14. In paragraph 12, The steps to re-access the above channels are: A step of maintaining the retransmission count of the completed channel access when the wireless communication terminal performs the channel access again. How it works.

15. In Article 10, A quiet period corresponding to the above limited service period is set, and no transmission is permitted during the quiet period. The step of transmitting the low-latency traffic or a response to the low-latency traffic within the above limited service period A step of transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period by ignoring the quiet interval corresponding to the limited service period; and Including a step of not transmitting a CF End frame within the above limited service period. How it works.

16. In Article 10, A quiet period corresponding to the above limited service period is set, and no transmission is permitted during the quiet period. The step of transmitting the low-latency traffic or a response to the low-latency traffic within the above limited service period A step of determining whether to ignore the quiet interval based on the start time of the limited service period and the start time of the quiet interval; and If it is decided to ignore the above quiet period, the step of ignoring the quiet period corresponding to the limited service period and transmitting the low-latency traffic or a response to the low-latency traffic within the limited service period is included. How it works.

17. In Article 16, The step of determining whether to ignore the quiet period based on the start time of the above limited service period and the start time of the above quiet period is A step of ignoring the quiet interval when a condition determined based on the start time of the limited service period and the start time of the quiet interval is satisfied; and A step of not performing any transmission if the condition determined based on the start time of the above limited service period and the start time of the above quiet period is not satisfied. How it works.

18. In Article 17, The condition judged based on the start time of the above limited service period and the start time of the quiet section is that the start time of the above quiet section and the start time of the service period of the above TWT are within a pre-specified time. How it works.

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