Wireless communication method using multi-links and wireless communication terminal using the same

Abstract

To provide a wireless communication method using multi-link and a wireless communication terminal using the same.SOLUTION: A station is disclosed that communicates with a single radio multi-link device that includes multiple stations each operating on multiple links but does not support the multiple stations transmitting or receiving simultaneously. The station includes a transmitting / receiving unit and a processor. The processor transmits a control frame to a first station of the single radio multi-link device using the transmitting / receiving unit, receives a response to the control frame from the first station of the single radio multi-link device, and initiates a null data packet (NDP) sounding sequence for the first station of the single radio multi-link device.SELECTED DRAWING: Figure 35

Description

Technical Field

[0001] The present invention relates to a wireless communication method using multi-links and a wireless communication terminal using the same.

Background Art

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

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

[0004] And, as a technical standard established to overcome the limitations regarding communication speed pointed out as vulnerabilities in Wi-Fi, there is IEEE 802.11n. IEEE 802.11n aims to increase the speed and reliability of the network and extend the operating distance of the wireless network. Specifically, IEEE 802.11n supports a high throughput (HT) with a maximum data processing speed of 540 Mbps or more, and is based on the MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitting and receiving ends to minimize transmission errors and optimize the data speed. Also, this standard uses a coding method that transmits multiple copies of the data to increase the reliability of the data.

[0005] As the popularity of wireless LANs has been activated and the applications using them have diversified, there is a growing need for a new wireless LAN system that supports a processing rate (Very High Throughput, VHT) higher than the data processing speed supported by IEEE 802.11n. Among them, IEEE 802.11ac supports a wide bandwidth (80 MHz to 160 MHz) at 5 GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5 GHz band, the initial 11ac chipset is considered to support operation in the 2.4 GHz band for backward compatibility with conventional 2.4 GHz band products. Theoretically, according to this standard, the speed of a multi-station wireless LAN can be up to 1 Gbps at minimum and the maximum single-link speed can be up to 500 Mbps at minimum. This is achieved by expanding the concepts of wireless interfaces adopted in 802.11n, such as a wider wireless frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Also, as a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz bands, there is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide a speed of up to 7 Gbps and is suitable for streaming high-bitrate videos such as large-capacity data and uncompressed HD videos. However, the 60 GHz frequency band has the disadvantage that it is difficult for obstacles to pass through and it can only be used between devices in a short-distance space.

[0006] On the other hand, as a wireless LAN standard after 802.11ac and 802.11ad, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is in the completion stage to provide high-efficiency and high-performance wireless LAN communication technology in a high-density environment where APs and terminals are concentrated. In an 802.11ax-based wireless LAN environment, it is necessary to provide high-frequency efficiency communication indoors / outdoors in the presence of a high density of stations and APs (Access Points), and various technologies for realizing this have been developed.

[0007] In addition, in order to support new multimedia applications such as high-quality videos and real-time games, a new Wi-Fi standard for increasing the maximum transmission speed has been started to be developed. In the 7th generation Wi-Fi standard IEEE 802.11be (Extremely High Throughput, EHT), the standard development is in progress with the goal of supporting a maximum transmission rate of 30 Gbps by using a wider bandwidth, increased spatial streams, and multi-AP coordination in the 2.4 / 5 / 6 GHz bands.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

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

MEANS FOR SOLVING THE PROBLEMS

[0009] A station communicating with a single radio multi-link device that includes a plurality of stations each operating on a plurality of links but does not support the plurality of stations transmitting or receiving simultaneously includes a transceiver and a processor. The processor transmits a control frame to a first station of the single radio multi-link device using the transceiver, receives a response to the control frame from the first station of the single radio multi-link device, and starts an NDP (null data packet) sounding sequence for the first station of the single radio multi-link device.

[0010] The control frame may be a MU-RTS frame.

[0011] The control frame may be a trigger frame of a type different from the MU-RTS frame.

[0012] The processor can transmit the control frame in a pre-specified PPDU (physical layer protocol data unit) format.

[0013] The pre-specified PPDU format may be at least one of a non-HT format or an HT format.

[0014] The processor can transmit the control frame at a data rate equal to or lower than a pre-specified data rate.

[0015] When the first station of the single radio multi-link device is transmitting or receiving, the processor does not have to transmit to the second station of the single radio multi-link device.

[0016] In addition to during the frame exchange sequence of the first station, the processor does not have to transmit to the second station of the single radio multi-link device for a certain period of time after the frame exchange sequence of the first station is completed.

[0017] During the frame exchange sequence of the first station, the use of multiple RF chains is supported on the link where the frame exchange sequence of the first station is performed, and the certain period of time may be determined based on the RF chain change time of the single radio multi-link device.

[0018] When the single radio multi-link device supports the use of multiple RF chains on the first link and does not support the use of RF chains on the second link but supports the use of RF chains on the second link, restrictions on channel access may be applied for a pre-specified period of time before channel access on the second link is performed.

[0019] The pre-specified time may be a pre-specified time applied when restrictions on channel access are necessary due to a time when channel monitoring is impossible.

[0020] The pre-specified time may be NAVSyncdelay.

[0021] When the single radio multi-link device supports the use of multiple RF chains on the first link and does not support the use of RF chains on the second link, the last frame exchange in the frame exchange sequence performed on the first link may be performed using SISO (single input single output) (1x1).

[0022] Embodiments of the present invention include multiple stations operating on multiple links respectively, but a single radio multi-link device that does not assist multiple stations in transmitting or receiving simultaneously includes a transceiver and a processor. When the link on which the RF chain of the single radio multi-link device operates is changed from the first link to the second link and the link on which the RF chain operates is changed back from the second link to the first link, before performing channel access on the first link, channel access is delayed for a pre-specified time.

[0023] The pre-specified time may be a pre-specified time applied when restrictions on channel access are necessary due to a time when channel monitoring is impossible.

[0024] The pre-specified time may be NAVSyncdelay.

[0025] When the processor determines that the single radio multi-link device supports the use of multiple RF chains on a first link and does not support the use of RF chains on a second link, it can transmit the last frame using SISO (single input single output) (1x1) in the frame exchange sequence performed on the first link.

[0026] A method for operating a station that communicates with a single radio multi-link device that includes multiple stations each operating on a plurality of links according to an embodiment of the present invention, but does not assist the multiple stations in transmitting or receiving simultaneously, includes transmitting a control frame to a first station of the single radio multi-link device; receiving a response to the control frame from the first station of the single radio multi-link device; and starting a NDP (null data packet) sounding sequence for the first station of the single radio multi-link device.

[0027] The control frame may be a MU-RTS frame.

[0028] The control frame may be a trigger frame of a type different from the MU-RTS frame.

Advantages of the Invention

[0029] An embodiment of the present invention provides a wireless communication method for efficiently using multi-link and a wireless communication terminal using the same.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0072] The terms used in this specification are selected as generally common terms that are currently widely used as much as possible in consideration of the functions in the present invention. However, this may vary depending on the intentions, conventions of those skilled in the relevant technical field, or the emergence of new technologies. In addition, in certain cases, there are terms arbitrarily selected by the applicant. In such cases, the meaning is described in the explanatory part of the corresponding invention. Therefore, it is clarified that the terms used in this specification are not merely the names of the terms, but should be interpreted based on the substantial meaning of the terms and the content throughout this specification.

[0073] Throughout the specification, if a certain configuration is "connected" to another configuration, this includes not only the case where it is "directly connected", but also the case where it is "electrically connected" with other components interposed therebetween. Also, if a certain component "includes" a specific component, this means that it can further include other components rather than excluding other components, unless otherwise stated to the contrary. In addition, the limiting terms "above" or "below" based on a specific critical value can be appropriately replaced by "exceeding" or "less than" respectively according to the embodiments.

[0074] Hereinafter, in the present invention, a field and a subfield may be used with the same meaning.

[0075] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0076] The wireless LAN system includes one or more Basic Service Sets (BSSs), and a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and Independent BSSs (IBSSs). FIG. 1 shows an infrastructure BSS among them.

[0077] As shown in FIG. 1, infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1 and AP-2 that are stations providing a distribution service, and a distribution system DS that connects the plurality of access points AP-1 and AP-2.

[0078] A station (STA) is any device that includes a Medium Access Control (MAC) according to the provisions of the IEEE 802.11 standard and a physical layer interface for a wireless medium, and in a broad sense includes not only non-access point non-AP stations but also all access points AP. Also, in this specification, the term "terminal" is used to refer to either a non-AP 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, a display unit, etc. according to an embodiment. The processor generates a frame to be transmitted via a wireless network, or processes a frame received via the wireless network, and performs various processes for controlling the station. And the communication unit is functionally connected to the processor and transmits and receives frames via the wireless network for the station. In the present invention, the term "terminal" is used to include a user equipment (UE).

[0079] An access point (AP) is an entity that provides a connection to a distribution system DS via a wireless medium for stations associated with itself. In an infrastructure BSS, in principle, communication between non-AP stations is carried out via the AP, but direct communication is possible between non-AP stations if a direct link is set up. On the other hand, in the present invention, the AP is used as a concept including a PCP (Personal BSS Coordination Point), but in a broad sense, it includes concepts such as a centralized controller, a base station (BS), a Node B, a BTS (Base Transceiver System), or a site controller. In the present invention, the AP is also referred to as a base wireless communication terminal, and the base wireless communication terminal is used as a term that includes, in a broad sense, an AP, a base station, an eNB (eNodeB), and a transmission point TP. Moreover, the base wireless communication terminal includes various forms of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with a plurality of wireless communication terminals.

[0080] A plurality of infrastructure BSSs are connected to each other via a distribution system DS. At this time, a plurality of BSSs connected via the distribution system are called an extended service set (ESS).

[0081] FIG. 2 is a diagram showing an independent BSS which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, parts that are the same as or corresponding to the embodiment of FIG. 1 are not described repeatedly.

[0082] Since the BSS3 shown in FIG. 2 is an independent BSS and does not include an AP, all stations (STA6, STA7) are not connected to the AP. An independent BSS does not allow connection to a distribution system and forms a self - contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0083] FIG. 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention. As shown, the station 100 according to an embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0084] First, the communication unit 120 transmits and receives wireless signals such as wireless LAN packets, and may be incorporated into or externally attached to the station 100. According to an embodiment, the communication unit 120 can include at least one communication module using different frequency bands. For example, the communication unit 120 can include communication modules for different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 can be provided with a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can perform wireless communication with an AP or an external station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 120 can operate only one communication module at a time or operate a plurality of communication modules together according to the performance and requirements of the station 100. When the station 100 includes a plurality of communication modules, each communication module may be provided in an independent form, or a plurality of modules may be integrated as one chip. In an embodiment of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0085] Next, the user interface 140 includes various forms of input / output means provided in the station 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on the instructions of the processor 110 using various output means.

[0086] Next, the display unit 150 outputs an image on the display screen. The display unit 150 outputs various display objects such as content performed by the processor 110 or a user interface based on the control instructions of the processor 110. Also, the memory 160 stores control programs used in the station 100 and various data thereby. Such control programs include connection programs necessary for the station 100 to connect to an AP or an external station.

[0087] The processor 110 of the present invention executes various instructions or programs and processes data within the station 100. Further, the processor 110 controls each unit of the station 100 described above and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection to the AP stored in the memory 160 and receives a communication setting message transmitted by the AP. Further, the processor 110 reads information regarding the priority conditions of the station 100 included in the communication setting message and requests a connection regarding the AP based on the information regarding the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or may refer to a control unit for individually controlling a part of the configuration of the station 100, for example, the communication unit 120, etc., according to an embodiment. That is, the processor 110 may be a modem, or a modulator and / or demodulator, that modulates and demodulates the radio signal transmitted and received from the communication unit 120. The processor 110 controls various operations of radio signal transmission and reception of the station 100 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0088] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separately shown blocks logically distinguish the elements of the device. Therefore, the above-described elements of the device may be attached to one chip or a plurality of chips according to the design of the device. For example, the processor 110 and the communication unit 120 may be integrated and implemented on one chip, or may be implemented on separate chips. Further, in an embodiment of the present invention, some configurations of the station 100, for example, the user interface unit 140 and the display unit 150, etc., may be selectively provided in the station 100.

[0089] FIG. 4 is a block diagram showing the configuration of AP200 according to an embodiment of the present invention. As shown in the figure, AP200 according to an embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, redundant descriptions are omitted for the parts of the configuration of AP200 that are the same as or corresponding to the configuration of station 100 in FIG. 3.

[0090] Referring to FIG. 4, AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 can also include a plurality of communication modules using different frequency bands. That is, AP 200 according to an embodiment of the present invention can include two or more communication modules using different frequency bands, for example, any of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, AP 200 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can perform wireless communication with a station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 220 can operate only one communication module at a time or operate a plurality of communication modules simultaneously according to the performance and requirements of AP 200. In an embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0091] Next, the memory 260 stores the control program used in the AP200 and various data thereby. Such control programs include a connection program for managing the connection of stations. Further, the processor 210 controls each unit of the AP200 and controls the transmission and reception of data between units. According to an embodiment of the present invention, the processor 210 executes a program for connection to the station stored in the memory 260 and transmits a communication setting message for one or more stations. At this time, the communication setting message includes information regarding the connection priority conditions of each station. Further, the processor 210 performs connection setting in response to a connection request from the station. According to one embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates the radio signal transmitted and received from the communication unit 220. The processor 210 controls various operations of radio signal transmission and reception of the AP200 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0092] FIG. 5 is a diagram schematically showing a process in which a STA sets a link with an AP.

[0093] Referring to FIG. 5, the link between the STA100 and the AP200 is set through three major steps: scanning, authentication, and association. First, the scanning step is a step in which the STA100 obtains connection information of the BSS operated by the AP200. As a method for performing scanning, there are a passive scanning method of obtaining information by utilizing only the beacon message S101 periodically transmitted by the AP200, and an active scanning method in which the STA100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and obtains connection information.

[0094] The STA100 that has successfully received the wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP200 (S107b), and performs an authentication step. After the authentication step is performed, the STA100 transmits an association request (S109a), receives an association response from the AP200 (S109b), and performs an association step. In this specification, "association" basically means a wireless connection, but the present invention is not limited thereto, and in a broad sense, "association" includes all wireless connections and wired connections.

[0095] On the other hand, an additional 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are performed. In FIG. 5, the server 300 is a server that processes 802.1X-based authentication with the STA100, and may be physically connected to the AP200 or exist as a separate server.

[0096] FIG. 6 is a diagram showing the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0097] A terminal performing wireless LAN communication checks whether a channel is busy by performing carrier sensing before transmitting data. If a wireless signal with a certain intensity or higher is detected, the corresponding channel is determined to be in the busy state, and the terminal delays access to the corresponding channel. Such a process is called Clear Channel Assessment (CCA), and the level for determining the presence or absence of signal detection is called the CCA threshold. If a wireless signal equal to or higher than the CCA threshold received by the terminal has the terminal as the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the corresponding channel or a wireless signal with an intensity lower than the CCA threshold is detected, the channel is determined to be in the idle state.

[0098] If the channel is determined to be in the idle state, each terminal having data to transmit performs a backoff procedure after a time of IFS (Inter Frame Space) according to the situation of each terminal, for example, AIFS (Arbitration IFS), PIFS (PCF IFS), etc. According to an embodiment, the AIFS is used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while decreasing the slot time by the random number determined for the corresponding terminal during the interval of the idle state of the channel, and the terminal that has exhausted all the slot times attempts access to the corresponding channel. Thus, the section in which each terminal performs the backoff procedure is called a contention window section. At this time, the random number can be called a backoff counter. That is, the initial value of the backoff counter is set by the integer that is the random number obtained by the terminal. When the terminal senses that the channel is idle during the slot time, the terminal can decrement the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be permitted to perform channel access on the corresponding channel. Therefore, the transmission of the terminal may be permitted when the channel is idle during the AIFS time and the slot time of the backoff counter.

[0099] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if a terminal that attempts access collides with other terminals, the collided terminals are each assigned a new random number and further perform a backoff procedure. According to one embodiment, the newly assigned random number for each terminal is determined within a range (2*CW) that is twice the range (competition window, CW) of the random number previously assigned to the corresponding terminal. On the other hand, each terminal performs a further backoff procedure in the next competition window interval to attempt access. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous competition window interval. In this way, each terminal performing wireless LAN communication can avoid mutual collisions with respect to a specific channel.

[0100] <Examples of various PPDU formats>

[0101] FIG. 7 shows an example of various standard-generation PPDU (PLCP Protocol Data Unit) formats. More specifically, FIG. 7(a) shows an example of a legacy PPDU format based on 802.11a / g, FIG. 7(b) shows an example of a HE PPDU format based on 802.11ax, and FIG. 7(c) shows an example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Further, FIG. 7(d) shows the detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0102] Referring to FIG. 7(a), the preamble of the legacy PPDU includes L-STF (Legacy Short Training field), L-LTF (Legacy Long Training field), and L-SIG (Legacy Signal field). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG can be referred to as a legacy preamble.

[0103] Referring to FIG. 7(b), the preamble of the HE PPDU further includes, in addition to the legacy preamble, 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 an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as the HE preamble. The specific configuration of the HE preamble may be deformed according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0104] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes, in addition to the legacy preamble, RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field). In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be deformed 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.

[0105] The L-SIG field included in the preamble of the PPDU applies 64 FFT OFDM and is composed of a total of 64 subcarriers. Among these, 48 subcarriers excluding the guard subcarriers, DC subcarriers, and pilot subcarriers are used for transmitting L-SIG data. Since BPSK and MCS (Modulation and Coding Scheme) with a rate of 1 / 2 are applied to L-SIG, it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information composition of L-SIG.

[0106] Referring to Figure 7(d), L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field is composed of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one value among the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and coding rates such as 1 / 2, 2 / 3, 3 / 4. Combining the information of the L_RATE field and the L_LENGTH field can indicate the total length of the PPDU. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

[0107] The unit of the L_LENGTH field is byte. A total of 12 bits are allocated and it can signal up to 4095. Combining with the L_RATE field can indicate the length of the PPDU. At this time, legacy terminals and non-legacy terminals can analyze the L_LENGTH field in different ways.

[0108] First, the method by which a legacy terminal or a non-legacy terminal analyzes the length of the PPDU using the L_LENGTH field is as follows. When the L_RATE field is set to 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted in a symbol duration of 4 us, which is one symbol duration of 64 FFT. Therefore, by adding 3 bytes corresponding to the SVC field and the 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 64 FFT reference symbols after L-SIG is obtained. After multiplying the obtained number of symbols by 4 us, which is one symbol duration, and then adding 20 us required for the transmission of L-STF, L-LTF, and L-SIG, the length of the PPDU, that is, the reception time (RXTIME) is obtained. Expressing this as a mathematical formula, it is as shown in Equation 1 below.

[0109]

Number

[0110] At this time,

Number

[0111]

Number

[0112] Here, TXTIME is the total transmission time for configuring the PPDU and is as shown in Equation 3 below. At this time, TX represents the transmission time of X.

[0113]

Number

[0114] Referring to the above formula, the length of the PPDU is calculated based on the ceiling value of L_LENGTH / 3. Therefore, for any k value, three different values of L_LENGTH = {3k + 1, 3k + 2, 3(k + 1)} indicate the same PPDU length.

[0115] Referring to FIG. 7(e), the U-SIG (Universal SIG) field persists in the EHT PPDU and subsequent generations of wireless LAN PPDUs and serves to distinguish which generation of PPDU it is, including 11be. U-SIG is two symbols of 64FFT-based OFDM and can transmit a total of 52 bits of information. Of these, 43 bits excluding the CRC / Tail 9 bits are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0116] The VI bits continue to maintain the current bit configuration in the future, and even if subsequent generations of PPDUs are defined, current 11be terminals can obtain information about the PPDU from the VI field of the PPDU. For this purpose, the VI field is composed of a PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits and serves to sequentially distinguish the 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS color means the BSS identifier defined in 11ax and has a value of 6 bits or more. TXOP means the transmit opportunity duration transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP included in the PPDU can be inferred without decoding the MPDU and has a value of 7 bits or more.

[0117] The VD field may be composed of signaling information that is only useful for PPDUs in the 11be version, 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 discriminator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDUs, etc. The BW field mainly signals five basic PPDU BW options of 20, 40, 80, 160 (80 + 80), 320 (160 + 160) MHz (BW that can be expressed in the form of 20 * 2 to the power of n can be called the basic BW), and various remaining PPDU BWs formed by preamble puncturing. Also, after being signaled at 320 MHz, some 80 MHz may be signaled in a punctured form. Also, the channel form that has been punctured and deformed may be directly signaled in the BW field, or may be signaled using both the BW field and fields that appear after the BW field (for example, fields within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so the puncturing mode can signal a maximum of 3. If the BW field is 4 bits, a total of 16 BW signalings are possible, so the puncturing mode can signal a maximum of 11.

[0118] The fields located after the BW field vary depending on the form and format of the PPDU. The MU PPDU and the SU PPDU may be signaled in the same PPDU format. Before the EHT-SIG field, a field for distinguishing between the MU PPDU and the SU PPDU may be located, and additional signaling may be performed for that purpose. Both the SU PPDU and the MU PPDU contain the EHT-SIG field, but some fields that are unnecessary in the SU PPDU may be compressed. At this time, the information of the fields to which compression is applied may be omitted or may have a size smaller than the size of the original fields included in the MU PPDU. For example, in the case of the SU PPDU, the common fields of the EHT-SIG may be omitted or replaced, the user-specific fields may be replaced, or it may have different configurations such as being reduced to one.

[0119] Alternatively, the SU PPDU may further include a compression field indicating whether it is compressed, and some fields (e.g., the RA field, etc.) may be omitted depending on the value of the compression field.

[0120] When a part of the EHT-SIG field of an SU PPDU is compressed, the information contained in the compressed field may be signaled together with uncompressed fields (e.g., common fields, etc.). In the case of an MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted obligatorily after the U-SIG field, and the amount of information to be signaled may be variable. That is, since a plurality of MU PPDUs are transmitted to a plurality of STAs, each STA must recognize the position of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU is transmitted to itself. Therefore, the AP must transmit the EHT-SIG field including the above information. For this purpose, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols of the EHT-SIG field and / or the MCS which is the modulation method. The EHT-SIG field can include the size and position information of the RUs assigned to each user.

[0121] In the case of an SU PPDU, a plurality of RUs may be assigned to an STA, and the plurality of RUs may be consecutive or non-consecutive. If the RUs assigned to the STA are not consecutive, the STA can efficiently receive the SU PPDU only by recognizing the RUs punctured in the middle. Therefore, the AP can transmit the SU PPDU including information on the punctured RUs among the RUs assigned to the STA (e.g., the RU puncturing pattern, etc.). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether the puncturing mode is applied and the puncturing pattern in a bitmap format or the like may be included in the EHT-SIG field, and the puncturing mode field can signal the form of the discontinuous channels appearing within the bandwidth.

[0122] The form of the discontinuous channel signaled is restricted and indicates the BW of the SU PPDU and the discontinuous channel information in combination with the value of the BW field. For example, in the case of an SU PPDU, which is a PPDU transmitted only to a single terminal, the STA can recognize the bandwidth assigned to itself from the BW field included in the PPDU, and can recognize the punctured resources among the assigned bandwidths from the puncturing mode field of the U-SIG field or the EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU with the resource units other than the specific channels of the punctured resource units. At this time, the plurality of RUs assigned to the STA may be composed of different frequency bands or tones from each other.

[0123] The reason why only the restricted form of the discontinuous channel form is signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing may be performed for each 20 MHz subchannel, when puncturing is performed for a BW having a plurality of 20 MHz subchannels such as 80, 160, and 320 MHz, in the case of 320 MHz, the availability of each of the remaining 15 20 MHz subchannels excluding the primary channel has to be expressed to signal the discontinuous channel form (including the form in which only the end 20 MHz is punctured as discontinuous). Using 15 bits to signal the discontinuous channel form of single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0124] The present invention proposes a method for signaling the discontinuous channel form of the SU PPDU and illustrates the discontinuous channel form determined by the proposed method. In addition, a method for signaling the puncturing forms of the primary 160 MHz and the secondary 160 MHz in the 320 MHz BW configuration of the SU PPDU is proposed.

[0125] Also, in one embodiment of the present invention, a method is proposed in which the configuration of the PPDU indicated by the preamble puncturing BW value is varied according to the signalized PPDU format in the PPDU format field. Assuming that the BW field is 4 bits, in the case of an EHT SU PPDU or a TB PPDU, since it is not necessary to further signal 1 symbol of EHT-SIG-A after U-SIG or to signal EHT-SIG-A from the beginning, considering this, it is necessary to completely signal up to 11 puncturing modes using only the BW field of U-SIG. However, in the case of an EHT MU PPDU, since EHT-SIG-B is further signalized after 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 is set to 1 bit, and it is possible to signal whether the PPDU uses a 20 MHz or 10 MHz band. The detailed puncturing patterns for each PPDU type will be described in detail later with reference to FIGS. 11 and 12.

[0126] FIG. 7(f) shows the configuration of the format-specific field of the VD field when indicated as an EHT MU PPDU in the PPDU format field of U-SIG. In the case of an MU PPDU, SIG-B, which is a signaling field for simultaneous reception of multiple users, is essential, and SIG-B may be transmitted without a separate SIG-A after U-SIG. Therefore, U-SIG must signal information for decoding SIG-B. Such fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, number of EHT-LTF symbols fields, etc.

[0127] FIG. 8 shows an example of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats according to embodiments of the present invention and a method for instructing the same.

[0128] Referring to FIG. 8, the PPDU may be composed of a preamble and a data part, and the format of one type of EHT PPDU may be distinguished by the U-SIG field included in the preamble. Specifically, based on the PPDU format field included in the U-SIG field, whether the format of the PPDU is an EHT PPDU may be indicated.

[0129] FIG. 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.

[0130] FIG. 8(b) shows an example of an EHT trigger-based PPDU format that 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 a response to the trigger frame. Different from the EHT SU PPDU, the EHT-SIG-A field is not located after the U-SIG field in the EHT PPDU.

[0131] FIG. 8(c) shows an example of an EHT MU PPDU format that is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit the PPDU to one or more STAs. The EHT MU PPDU format may have an HE-SIG-B field located after the U-SIG field.

[0132] (d) of FIG. 8 shows an example of the EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission with a wider range of STAs than the EHT SU PPDU described in (a) of FIG. 8, and the U-SIG field may be repeatedly positioned on the time axis.

[0133] The EHT MU PPDU described in (c) of FIG. 8 can be used by the AP for downlink transmission to multiple STAs. At this time, the EHT MU PPDU can include scheduling information so that multiple STAs can receive the PPDU transmitted from the AP simultaneously. The EHT MU PPDU can convey the AID information of the receiver and / or transmitter of the PPDU transmitted through the user specific field of the EHT-SIG-B to the STA. Therefore, multiple terminals that receive the EHT MU PPDU can perform a spatial reuse operation based on the AID information in the user specific field included in the preamble of the received PPDU.

[0134] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU can include information regarding the configuration of resource units (e.g., the division form of resource units) in a specific bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field can indicate the configuration of resource units divided by the bandwidth for the transmission of the HE MU PPDU for the STA to receive the PPDU. The information of the STA assigned (or designated) to each divided 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 can include one or more user fields corresponding to each divided resource unit.

[0135] For example, among a plurality of divided resource units, a user field corresponding to at least one resource unit used for data transmission may include the AID of the recipient or the sender, and a user field corresponding to the remaining resource units not used for data transmission may include a pre-set Null STA ID.

[0136] For the sake of convenience of explanation, in this specification, a frame or a MAC frame may be used in the same meaning as an MPDU.

[0137] When a wireless communication device communicates using a plurality of links, the communication efficiency of the wireless communication device can be improved. At this time, a link is a physical path and may be configured as one wireless medium available for transmitting an MSDU (MAC service data unit). For example, when the frequency band of any one link is in use by another wireless communication device, the wireless communication device can continue to communicate on another link. In this way, the wireless communication device can usefully use a plurality of channels. Also, when the wireless communication device communicates simultaneously using a plurality of links, the overall throughput can be increased. However, existing wireless LANs are defined on the premise that one wireless communication device uses one link. For this reason, a wireless LAN operation method for using a plurality of links is required. With reference to FIGS. 9 to 26, a wireless communication method of a wireless communication device using a plurality of links will be described. First, with reference to FIG. 9, a specific form of a wireless communication device using a plurality of links will be described.

[0138] FIG. 9 shows a multi-link device according to an embodiment of the present invention.

[0139] A multi-link device (MLD) may be defined for the wireless communication method using the plurality of links described above. The multi-link device can represent a device having one or more affiliated stations. According to a specific embodiment, the multi-link device can represent a device having two or more affiliated stations. Also, the multi-link device can exchange multi-link elements. The multi-link element includes information regarding one or more stations or one or more links. The multi-link element can include a multi-link setup element described later. At this time, the multi-link device may be a logical entity. Specifically, the multi-link device can have a plurality of affiliated stations. The multi-link device can be called an MLLE (multi-link logical entity) or an MLE (multi-link entity). The multi-link device can have one MAC service access point (medium access control service access point, SAP) up to the logical link control (LLC). Also, the MLD can have one MAC data service.

[0140] The plurality of stations included in the multi-link device can operate on a plurality of links. Also, the plurality of stations included in the multi-link device can operate on a plurality of channels. Specifically, the plurality of stations included in the multi-link device can operate on different plural links or different plural channels. For example, the plurality of stations included in the multi-link device can operate on different plural channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0141] The operation of the multi-link device can be referred to as multi-link operation, MLD operation, or multi-band operation. Also, when the station associated with the multi-link device is an AP, the multi-link device can be called an AP MLD. Further, when the station associated with the multi-link device is a non-AP station, the multi-link device can be called a non-AP MLD.

[0142] FIG. 9 shows the operation in which the non-AP MLD and the AP-MLD communicate. Specifically, the non-AP MLD and the AP-MLD communicate using three links each. The AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). The non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate through a first link (Link1). Also, the second AP (AP2) and the second non-AP STA (non-AP STA2) communicate through a second link (Link2). Also, the third AP (AP3) and the third non-AP STA (non-AP STA3) communicate through a third link (Link3).

[0143] Multi-link operation can include a multi-link setup operation. The multi-link setup corresponds to the association operation of the single-link operation described above and needs to precede frame exchange in a multi-link. A multi-link device can obtain information necessary for multi-link setup from a multi-link setup element. Specifically, the multi-link setup element can include capability information related to the multi-link. At this time, the capability information can include information indicating whether any one of a plurality of devices included in the multi-link device can perform transmission while another device can perform reception. Also, the capability information can include information regarding links available to each station included in the MLD. Further, the capability information can include information regarding channels available to each station included in the MLD.

[0144] The multi-link setup may be set by negotiation between peer stations. Specifically, the multi-link setup may be performed by communication between stations without communication with the AP. Also, the multi-link setup may be set through any one link. For example, even when the first to third links are set through a multi-link, the multi-link setup may be performed through the first link.

[0145] Also, a mapping between a TID (traffic identifier) and a link may be set. Specifically, frames corresponding to a specific value of the TID may be exchanged only through a pre-specified link. The mapping between the TID and the link may be set in a direction-based manner. For example, when a plurality of links are set between a first multi-link device and a second multi-link device, the first multi-link device may be set to transmit frames of a first TID to a plurality of first links, and the second multi-link device may be set to transmit frames of a second TID to the first link. Also, a basic setting may exist for the mapping between the TID and the link. Specifically, when 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 basic (default) setting. At this time, the basic setting may be such that all TIDs are exchanged on any one link.

[0146] Specifically describe the TID. The TID is an ID for classifying traffic and data to support QoS (Quality of Service). Also, the TID may be allocated and used in a layer higher than the MAC layer. Also, the TID can indicate a traffic category (TC) and a traffic stream (TS). Also, the TID may be distinguished into 16 types. For example, the TID may be specified as any one of 0 to 15. It may be specified so that the TID values used are different depending on the access policy, channel access, or medium access method. For example, when EDCA (Enhanced Distributed Channel Access) or HCAF (Hybrid Coordination Function Contention Based Channel Access) is used, the value of the TID may be allocated in the range of 0 to 7. When EDCA is used, the TID can indicate the user priority (UP). At this time, the UP may be specified by the TC or TS. The UP may be allocated in a layer higher than the MAC layer. Also, when HCCA (HCF Controlled Channel Access) or SPCA is used, the value of the TID may be allocated in the range of 8 to 15. When HCCA or SPCA is used, the TID can indicate the TSID. Also, when HEMM or SEMM is used, the value of the TID may be allocated in the range of 8 to 15. When HEMM or SEMM is used, the TID can indicate the TSID.

[0147] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. The EDCA parameter or EDCA parameter set is a parameter used in the channel contention of EDCA. The QoS station can guarantee QoS using AC. Also, AC can include AC_BK, AC_BE, AC_VI, and AC_VO. Each of AC_BK, AC_BE, AC_VI, and AC_VO can indicate background, best effort, video, and voice. Also, AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. Also, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. Also, UP or TID may be mapped to AC. For example, each of 1, 2, 0, 3, 4, 5, 6, 7 in UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO. Also, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be in descending order of priority. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priority may increase in the order of AC_BK, AC_BE, AC_VI, AC_VO. Also, each of AC_BK, AC_BE, AC_VI, and AC_VO may correspond to each of ACI (AC index) 0, 1, 2, 3. Due to the characteristics of such TID, the mapping between TID and the link can represent the mapping between AC and the link.Also, the mapping between the link and the AC can represent the mapping between the TID and the link.

[0148] As described above, a TID may be mapped to each of a plurality of links. The mapping may be such that a link through which traffic corresponding to a specific TID or AC can be exchanged is specified. Also, the TID or AC that can be transmitted in the link may be specified separately for each transmission direction within the link. As described above, there may be a basic setting for the mapping between the TID and the link. Specifically, when 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 basic (default) setting. At this time, the basic setting may be such that all TIDs are exchanged on any one link. At all times, at a certain point in time, any TID or AC may be mapped to at least one link. The management frame and the control frame may be transmitted on all links.

[0149] When a link is mapped to a TID or AC, only the data frame corresponding to the TID or AC mapped to the link may be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames not corresponding to the TID or AC not mapped to the link need not be transmitted on the link. When a link is mapped to a TID or AC, the ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, the block ACK agreement may be determined based on the mapping between the TID and the link. In still other specific embodiments, the mapping between the TID and the link may be determined based on the block ACK agreement. Specifically, a block ACK agreement may be set for the TID mapped to a specific link.

[0150] By the mapping of the TID and the link described above, QoS may be guaranteed. Specifically, a relatively small number of stations may operate, or a high-priority AC or TID may be mapped to a link with a good channel state. Also, by the mapping of the TID and the link described above, a station can be made to maintain a power-saving state for a longer time.

[0151] FIG. 10 shows that, according to an embodiment of the present invention, transmissions on different links are simultaneously performed in multi-link operation.

[0152] Depending on the implementation of the multi-link device, simultaneous operation on multiple links may not be supported. For example, the multi-link device may be supported in simultaneously transmitting on multiple links, simultaneously receiving on multiple links, or transmitting on one link while receiving on another link. Reception or transmission performed on any one link may affect reception or transmission performed on another link. Specifically, transmission on one link may act as interference to another link. The interference that one link of a multi-link device exerts on another link can be called internal leakage. The smaller the frequency interval between links, the greater the internal leakage may be. If the internal leakage is not too large, transmission can be performed on another link when transmission is performed on any one link. If the internal leakage is large, transmission cannot be performed on another link when transmission is performed on any one link. Thus, the multi-link device performing simultaneous operation on multiple links can be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, the multi-link device simultaneously transmitting on multiple links, transmitting on one link while receiving on another link, or simultaneously receiving on multiple links can be called STR.

[0153] As mentioned above, the multi-link device can support STR or support it in a limited way. Specifically, the multi-link device can support STR only under specific conditions. For example, when the multi-link device operates with a single radio, the multi-link device may not be able to perform STR. Also, when the multi-link device operates with a single antenna, the multi-link device may not be able to perform STR. Further, when internal leakage is detected to be greater than a specified magnitude, the multi-link device may not be able to perform STR.

[0154] A station can exchange information regarding the station's STR capabilities with other stations. Specifically, the station can exchange information with other stations regarding the presence or absence of limitations on the ability of the station to transmit simultaneously over multiple links or receive simultaneously over multiple links. Specifically, the information regarding the presence or absence of limitations on the ability to transmit or receive over multiple links can indicate whether transmission occurs simultaneously over multiple links, reception occurs simultaneously over multiple links, or both transmission and reception occur simultaneously. Also, the information regarding the presence or absence of limitations on the ability to transmit or receive over multiple links can be information that is indicated in stages. Specifically, the information regarding the presence or absence of limitations on the ability to transmit or receive over multiple links can be information that indicates a stage indicating the magnitude of internal leakage. In a specific embodiment, the information indicating a stage indicating the magnitude of internal leakage can be information that indicates a stage indicating the magnitude of interference caused by internal leakage. In yet another specific embodiment, it can be information that indicates a stage indicating the frequency spacing between links that can affect internal leakage. Also, the information indicating a stage indicating the magnitude of internal leakage can be information that indicates in stages the relationship between the frequency spacing between links and the magnitude of internal leakage.

[0155] In FIG. 10, the first station (STA1) and the second station (STA2) are affiliated with one non-AP multi-link device. Also, the first AP (AP1) and the second AP (AP2) may be affiliated with one non-AP multi-link device. A first link (link1) is set between the first AP (AP1) and the first station (STA1), and a second link (link2) is set between the second AP (AP2) and the second station (STA2). In FIG. 10, the non-AP multi-link device can perform STR in a limited manner. When the second station (STA2) transmits on the second link (Link2), the reception of the first station (STA1) on the first link (Link1) may be interfered with by the transmission performed on the second link (Link2). For example, in the following cases, the reception of the first station (STA1) on the first link (Link1) may be interfered with by the transmission performed on the second link (Link2). The second station (STA2) transmits the first data (Data1) on the second link (Link2), and the first AP (AP1) transmits an acknowledgment for the first data (Ack for Data1) to the first station (STA1). The second station (STA2) transmits the second data (Data2) on the second link (Link2). At this time, the transmission time of the second data (Data2) and the transmission time of the acknowledgment for the first data (Ack for Data1) may overlap. At this time, interference may occur on the first link (Link1) due to the transmission to the second station (STA2) on the second link (Link2). For this reason, the first station (STA1) may not be able to receive the acknowledgment for the first data (Ack for Data1).

[0156] The operation of the multi-link device for channel access will be described. The multi-link operations without specific descriptions can follow the channel access procedure described in FIG. 6.

[0157] A multi-link device can perform channel access independently from a plurality of links. At this time, the channel access may be backoff-based channel access. When the multi-link device performs channel access independently from a plurality of links and the backoff counters reach 0 in the plurality of links, the multi-link device can start transmissions simultaneously on the plurality of links. In a specific embodiment, when any one of the backoff counters of the multi-links reaches 0 and satisfies a specified condition, the multi-link device can perform channel access not only on the link where the backoff counter has reached 0 but also on other links where the backoff counters have not reached 0. Specifically, when any one of the backoff counters of the multi-links reaches 0, the multi-link device can perform energy sensing on other links where the backoff counters have not reached 0. At this time, when no energy greater than a specified magnitude is sensed, the multi-link device can perform channel access not only on the link where the backoff counter has reached 0 but also on the link where energy sensing has been performed. Thereby, the multi-link device can start transmissions simultaneously on the plurality of links. The magnitude of the threshold used for energy sensing may be smaller than the magnitude of the threshold used when determining whether to decrement the backoff counter. Also, when determining whether to decrement the backoff counter, the multi-link device can sense not only wireless LAN signals but also signals in any form. Also, in the above-described energy sensing, the multi-link device can sense not only wireless LAN signals but also signals in any form. Internal leakage may not be sensed as a wireless LAN signal. In such a case, the multi-link device can sense the signal sensed by internal leakage by energy sensing. Also, as described above, the magnitude of the threshold used for energy sensing may be smaller than the magnitude of the threshold used when determining whether to decrement the backoff counter. Therefore, even while a transmission is being performed on any one link, the multi-link device can decrement the backoff counter on other links.

[0158] Depending on the degree of interference between the links used by the multi-link device, it may be determined whether the stations operating on each link can operate independently. At this time, the degree of interference between the links may be the magnitude of the interference sensed by other stations of the multi-link device when any one station of the multi-link device performs transmission on any one link. When the transmission on the first link of the first station of the multi-link device causes interference greater than a specified magnitude in advance 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. When interference occurs, the second station may fail to decode the signal received due to the interference. Also, when interference occurs, when the second station uses backoff for channel access, the second station may determine that the channel is in use.

[0159] Also, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at the second station of the multi-link device operating on the second link, the first station and the second station can operate independently. Specifically, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at 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. Also, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at 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. When interference less than the specified magnitude occurs, the second station can succeed in decoding the received signal even when interference exists. Also, when interference less than the specified magnitude occurs, when the second station uses backoff for channel access, the second station can determine that the channel is idle.

[0160] The degree of interference occurring between stations of a multi-link device may vary not only depending on the interval between the frequency bands of the links on which the stations operate, but also depending on the hardware characteristics of the multi-link device. For example, the internal interference occurring in a multi-link device including a high RF (radio frequency) device may be smaller than the internal interference occurring in a multi-link device including a low RF device. Therefore, the degree of interference occurring between stations of a multi-link device may be determined based on the characteristics of the multi-link device.

[0161] FIG. 10 shows that the interference magnitude varies depending on the interval between the frequency bands of the 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 on the first link (Link1) and a second station (STA1)-2 operating on the second link (Link2). The second multi-link device (MLD#2) includes a first station (STA2)-1 operating on the first link (Link1) and a second station (STA2)-2 operating on the second link (Link2). The frequency interval between the first link (Link1) and the second link (Link2) on which the first multi-link device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) on which the second multi-link device (MLD#2) operates. However, the interference magnitudes generated due to the difference between the characteristics of the first multi-link device (MLD#1) and the second multi-link device (MLD#2) are different. Specifically, the interference magnitude generated by the second multi-link device (MLD#2) may be larger than the interference magnitude generated by the first multi-link device (MLD#1). Thus, considering that the interference magnitudes generated by the characteristics of the multi-link device may be different and the presence or absence of STR support may be different for each multi-link device, it is necessary to exchange information regarding whether STR is supported or not.

[0162] The multi-link device can signal the presence or absence of STR support for the stations included in the multi-link device. Specifically, the AP multi-link device and the non-AP multi-link device can exchange the presence or absence of AP STR support included in the AP multi-link device and the presence or absence of STA STR support included in the non-AP multi-link device. In such an embodiment, an element indicating the presence or absence of STR support may be used. The element indicating the presence or absence of STR support can be called an STR support element. The STR support element can indicate, by 1 bit, the presence or absence of STR support for the stations of the multi-link device that transmitted the STR support element. Specifically, the STR support element can indicate, for each station included in the multi-link device that transmits the STR support element, the presence or absence of STR support for each station by 1 bit. At this time, when a station supports STR, the value of the bit may be 1, and when a station does not support STR, the value of the bit may be 0. When the multi-link device that transmitted the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support STR, and the second station (STA2) does not support STR, the STR support element may have 101 1b and can include a field having. Stations operating in different frequency bands are assumed to support STR, and the STR support element may omit signaling for the presence or absence of STR support between stations operating in different frequency bands. For example, the first station (STA1) operates on a first link at 2.4 GHz, and each of the second station (STA2) and the third station (STA3) operates on a second link and a third link at 5 GHz. At this time, the STR support element can indicate by 1 bit that STR is supported between the second station (STA2) and the third station (STA3). Also, the STR support element can include only 1 bit when there are 2 stations for which the STR support element signals.

[0163] 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 may always be determined as STR. Therefore, signaling may be omitted for the presence or absence of STR of the link located at 2.4 GHz and the link located at 5 GHz or 6 GHz.

[0164] FIG. 11 shows the operation of a multi-link device when a link is changed according to an embodiment of the present invention.

[0165] When the frequency band of a link is changed, the STR support element may be exchanged. As described above, the presence or absence of STR support of a station may change depending on the distance between the frequency bands of the links, and when the frequency band of a link is changed, the presence or absence of STR support of the station may change. When the frequency band of a link is changed, it may include at least any one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a 20 MHz primary channel. The AP and the station can exchange the STR support element by request and response. In still other specific embodiments, when the frequency band of a link is changed, the STR support element may be exchanged without a separate request. Also, in the above-described embodiments, when the frequency band of a link is changed, it may include a change in the operating channel of the station.

[0166] When the station of the non-AP multi-link device cannot perform STR, the station of the non-AP multi-link device can request the AP to change the link. Specifically, the station of the non-AP multi-link device can request at least one of a change in the center frequency, a change in the bandwidth of the frequency band, and a change in at least one of the 20 MHz primary channels. The link change request may be transmitted to the AP through the link for which the change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP through the link for which no change is requested. At this time, the link change request may include information indicating the link for which the change is requested. The information indicating the link may be a number for identifying the link. In such an embodiment, the change of the link may be that the operating channel is changed within one frequency band. Also, the change of the link may include information regarding the method of changing the link. Specifically, the link change request can indicate whether to move the center frequency of the link to a frequency higher than the current center frequency or to move the center frequency of the link to a frequency lower than the current center frequency. In yet another specific embodiment, the link change request can implicitly indicate a change to a frequency band that moves away from an adjacent link. Also, the link change request can indicate reducing the bandwidth of the link. Also, the link change request can request a change in the position of the primary channel. Specifically, the link change request can indicate changing the position of the primary channel to a channel in a lower frequency band or a higher frequency band than the position of the current primary channel. The AP that has received the link change request can change the link according to the link change request. Also, in a specific embodiment, the AP that has received the link change request can ignore the link change request.

[0167] In the embodiment of FIG. 11, the second station (STA2) and the third station (STA3) of the non-AP multi-link device are in a state where they cannot 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 that receives the link change request changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can send a change request to the third AP (AP3). In still other specific embodiments, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0168] When the AP changes the link, the AP can broadcast information regarding the link change using a beacon frame. At this time, the information regarding the link change can include information regarding the frequency of the link. The information regarding the frequency of the link can include at least any one of the center frequency of the link, the operating bandwidth, and the change of the primary channel. Also, the information regarding the link change can include information regarding the time point of the link change. Also, the link change may be completed when the beacon is transmitted including the information regarding the link change.

[0169] In FIG. 11, the link on which the third station (STA3) operates is changed, and the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multi-link device can send an STR support element to the AP multi-link device and signal the presence or absence of the changed STR support.

[0170] The above link change may not be allowed, or STR may not be supported even by the link change. Also, as in the embodiment of FIG. 11, the AP multi-link device supports STR, but the non-AP multi-link device may not support STR. This is because relatively high RF devices are generally used for the AP multi-link device and relatively low RF devices are used for the non-AP multi-link device. Therefore, when communicating between multi-link devices, a method that enables efficient communication is required even when any one of the multi-link devices does not support STR. At this time, STR can represent that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

[0171] FIG. 12 shows that when any one of the stations of the non-STR multi-link device is receiving according to an embodiment of the present invention, channel access of other stations of the non-STR multi-link device is prohibited.

[0172] When transmission is performed on any 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 solve this problem, when reception is performed on any one link of the non-STR multi-link device, channel access may be prohibited on another link of the non-STR multi-link device. Specifically, when reception is performed on any one link of the non-STR multi-link device, backoff of channel access may be prohibited on another link of the non-STR multi-link device. Thereby, when reception is performed on any one link of the non-STR multi-link device, it is possible to prevent transmission from starting on another link of the non-STR multi-link device. In a specific embodiment, when reception starts on any one link of the non-STR multi-link device, backoff of channel access may be prohibited on another link of the non-STR multi-link device. This may be set by a specific bit of memory such as a channel access prohibition flag. The presence or absence of channel access prohibition may be shared by the memory inside the multi-link device. According to such an embodiment, channel access prohibition can be implemented without separate frame exchange. For convenience of explanation, the channel access prohibition used in this specification represents prohibiting channel access or transmission to protect transmission or reception of the non-STR multi-link device unless otherwise specified.

[0173] When channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform the backoff procedure regardless of the NAV and CCA results. Also, when channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform transmission 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. Also, the prohibition of channel access on the second link due to reception on the first link may be released based on the completion of reception on the first link. Specifically, the prohibition of channel access on the second link due to reception on the first link may be released when the reception on the first link is completed. In yet another specific embodiment, the prohibition of channel access on the second link due to reception on the first link may be released based on the time when an ACK is transmitted after the reception on the first link is completed. Specifically, the prohibition of channel access on the second link due to reception on the first link may be released at the time when an ACK is transmitted after the reception on the first link is completed. In yet another specific embodiment, in a specific embodiment, the prohibition of channel access on the second link due to reception on the first link may be released at the time when the transmission of the ACK is completed after the reception on the first link is completed. Also, immediately after the channel access prohibition is released, the station can immediately decrement the backoff counter without additional sensing. At this time, the additional sensing can represent the sensing performed during the DIFS (DCF Interframe Space). In yet another specific embodiment, immediately before the channel access prohibition is released, if the channel is idle for a pre-specified time, the station can immediately decrement the backoff counter without additional sensing. At this time, the pre-specified time may be any one of PIFS (PCF Interframe Sapce), DIFS, SIFS (Short Interframe Sapce), and AIFS (Arbitration Interframe Space).

[0174] In the embodiment of FIG. 12, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) is receiving, in-device interference occurs. As described above, while the first station (STA1) operating on the first link (Link1) is receiving, channel access by the second station (STA2) on the second link (Link2) is prohibited. After the reception of the first station (STA1) on the first link (Link1) is completed, the channel access prohibition is released. Immediately after the channel access prohibition is released, the second station (STA2) can decrement the previous backoff counter value from 3 to 2 without additional sensing.

[0175] For the sake of expression convenience, in FIG. 12, Rx and Tx are represented using a single block (Tx solid line, Rx dotted line), and it may be understood that the single block represents an operation including Tx / Ack reception and Rx / Ack transmission even if a separate Ack block is not shown. This may be equally applied to the drawings described later.

[0176] When it is confirmed that the intended recipient of the PPDU received by the station is not the station, the station may interrupt the reception of the PPDU. In such a case, the operation of releasing the channel access prohibition of the multi-link device becomes a problem. In this specification, the intended recipient is used in the same sense as the destination station.

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

[0178] When the station confirms that the intended receiver of the PPDU received by the station is not the station, the station can lift the channel access prohibition. The station can determine whether the station is the intended receiver of the PPDU based on the information indicating the receiver address in the signaling field of the PPDU. At this time, the information indicating the receiver address in the signaling field of the PPDU may be the value of the STA-ID field in the EHT-SIG field described above. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field indicates the station. Also, the station can determine whether the station is the intended receiver of the PPDU based on the value of the RA field in the MAC frame included in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame included in the PPDU indicates the station. In FIG. 13, the non-STR multi-link device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The first station (STA1) receives the PPDU. The first station (STA1) determines that the intended receiver of the received PPDU is not the first station (STA1) and interrupts the reception of the PPDU. At this time, the first station (STA1) can lift the channel access prohibition of the second station (STA2). Even if the channel access prohibition of the second station (STA2) is lifted, the channel access of the second station (STA2) may be delayed by the NAV set for the second station (STA2).

[0179] As shown in FIG. 13, even when the channel access prohibition is lifted, stations included in non-STR multi-link devices often may not have a channel access opportunity compared to stations not included in the multi-link device or stations included in the STR multi-link device. Therefore, a method for compensating the channel access opportunity of stations included in non-STR multi-link devices is required for fair competition with other stations. For example, immediately after the channel access prohibition is lifted, it may be allowed to decrement the backoff counter by two or more when the station whose channel access prohibition is lifted decrements the backoff counter. This will be described with reference to FIG. 14.

[0180] FIG. 14 shows that a station according to an embodiment of the present invention performs channel access after the channel access prohibition is lifted.

[0181] The station whose channel access prohibition is lifted can decrement the backoff counter by two or more immediately after the channel access prohibition is lifted. This is to equalize the fairness of the channel access opportunity with other stations because other stations perform the backoff procedure while the channel access of the station is prohibited.

[0182] In still other specific embodiments, a station with channel access prohibited can perform channel access procedures that reduce CCA (CSMA) and the backoff counter while the channel access is prohibited. In FIG. 14, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). In FIG. 14, the channel access of the second station (STA2) is prohibited while the first station (STA1) is receiving. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, the second station (STA2) can perform channel access procedures that reduce CCA (CSMA) and the backoff counter. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, since the channel of the second link (Link2) is idle, the second station (STA2) reduces the backoff counter.

[0183] Also, a station whose channel access is prohibited can delay transmission without starting transmission even if the backoff counter reaches 0 while the channel access is prohibited. At this time, the station can maintain the value of the backoff counter at 0. Also, even if the station delays transmission, the station can maintain the value of CW as it is. Therefore, since the channel accessed by the station is busy, it is differentiated from the case where the station doubles the value of CW. This is because the reason for the transmission delay is not when it is determined that the channel is 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 reduces CCA (CSMA) and the backoff counter. In FIG. 14(b), while the channel access of the second station (STA2) is prohibited, since the channel of the second link (Link2) is idle, the second station (STA2) reduces the backoff counter. While the channel access of the second station (STA2) is prohibited, the backoff counter of the second station (STA2) reaches 0. The second station (STA2) delays transmission and starts transmission after the channel access prohibition is released.

[0184] As described above, the channel access prohibition can include prohibiting transmission to the second station when the first station of the non-STR multi-link device performs transmission. Also, the channel access prohibition can include prohibiting the transmission of the second station when the first station of the non-STR multi-link device performs reception.

[0185] In the embodiment described in FIG. 14(b), when there are a plurality of stations whose channel access is prohibited, the channel access prohibitions of the plurality of stations are released simultaneously, and there is a high possibility that the plurality of stations will attempt to transmit simultaneously. Therefore, a method for reducing the transmission collision probability is required. This will be described with reference to FIG. 15.

[0186] FIG. 15 shows the operation of a station according to an embodiment of the present invention when transmission is performed after the channel access prohibition is released.

[0187] As described above, among the plurality of links in which the non-STR multi-link device operates, transmission may be performed on the first link and prohibited on the second link. When the transmission on the first link is completed, the transmission on the second link may start by RTS / CTS frame exchange. Therefore, when transmission is performed on the first link among the plurality of links in which the non-STR multi-link device operates, the non-STR multi-link device can start RTS / CTS frame exchange on the second link. After the channel access prohibition of the station whose transmission has been delayed due to the channel access prohibition is released, the station can start the exchange of RTS (request to send) / CTS (clear to send) frames before starting the delayed transmission. At this time, if the station cannot receive the CTS frame, it may not be able to start the delayed transmission. In the embodiment of FIG. 15(a), the station whose transmission has been delayed due to the channel access prohibition transmits an RTS frame before starting the delayed transmission. After the station receives a CTS frame as a response to the RTS frame, it starts the delayed transmission.

[0188] In yet another specific embodiment, after the channel access prohibition of a station whose transmission has been delayed due to the channel access prohibition is lifted, the station can transmit a frame including only a part of the delayed transmission. At this time, after the station receives a response, for example, an ACK, for the frame including only a part of the delayed transmission, the station can transmit the untransmitted part of the delayed transmission. If the station cannot receive a response for the frame including only a part of the delayed transmission, the station does not have to transmit the untransmitted part of the delayed transmission. Thus, the fact that the station starts an RTS / CTS exchange or transmits only a part of the delayed transmission after the channel access prohibition is lifted is because the collision probability of the transmission after the channel access prohibition is higher than that of a general transmission. Therefore, the above-described embodiments may be obligatorily applied to the transmission performed after the channel access prohibition is lifted. In the existing wireless LAN operation, 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 above-described embodiments, the RTS / CTS frame is for preventing a transmission collision with a station that attempts to perform a delayed transmission in order to protect the transmission or reception of the non-STR multi-link device.

[0189] As described above, when any one station of the non-STR multi-link device performs reception, the transmission of other stations of the non-STR multi-link device may be restricted. Also, when any one station of the 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 state of the link on which the station operates. Specifically, when the first station of the non-STR multi-link device performs transmission, the second station of the non-STR multi-link device may always determine that the channel state of the link on which the second station operates is busy. For this reason, even when the channel of the link on which the second station operates is idle, the second station may determine that the channel is in use due to in-device interference. Thus, when the transmission of any one station of the non-STR multi-link device or a station that cannot determine the channel state due to in-device interference is ongoing, the other stations of the non-STR multi-link device are in a blind state. A station in a blind state due to the above-described situation may have difficulty performing a backoff procedure to attempt transmission. Also, a station in a blind state due to the above-described situation may have difficulty starting to receive a PPDU or successfully decoding it. For this reason, a transmission method that takes into account stations in a blind state is necessary. This will be described with reference to FIG. 16.

[0190] FIG. 16 shows transmission performed based on the state of stations in a non-STR multi-link device according to an embodiment of the present invention.

[0191] 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. Also, the station attempting to transmit to a station of the non-STR multi-link device is an AP included in the AP multi-link device, and the non-STR multi-link device may be a non-AP multi-link device. The station attempting to transmit to a station of the non-STR multi-link device can determine based on whether the station of the non-STR multi-link device is in a blind state. The transmitting station can determine whether other stations of the multi-link device containing the station are currently transmitting to the non-STR multi-link device. When other stations of the multi-link device containing the station are currently receiving from the non-STR multi-link device, the station can determine that the station of the non-STR multi-link device receiving the station's transmission is in a blind state. In the embodiment of FIG. 16, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can notify the first AP (AP1) that it is currently receiving from the second station (STA2). Specifically, the second AP (AP2) can notify the first AP (AP1) that the entity transmitting to the second AP (AP2) is the second station (STA2). In yet another specific embodiment, the second AP (AP2) can notify the first AP (AP1) that the second station (STA2) is currently transmitting.At this time, based on the notification, the first AP (AP1) can determine that the first station (STA1) is in a blind state.

[0192] Since the stations in the multi-link device can operate via a common MAC, the information exchange between the first AP (AP1) and the second AP (AP2) described above may not be explicitly performed.

[0193] A station does not have to transmit to a station in a blind state. This is because even if a transmission is made to a station in a blind state, it is highly likely that the station in the blind state cannot disclose reception or cannot decode the PPDU. At this time, the station can cancel the transmission to the station in the blind state and perform a transmission to another station.

[0194] When the STR multi-link device sends data to the non-STR multi-link device, the STR multi-link device can send data to the non-STR multi-link device over multiple links. Specifically, when the STR multi-link device sends data to the non-STR multi-link device over the first link, the STR multi-link device can start sending data to the non-STR multi-link device over the second link. At this time, based on the data transmission to the non-STR multi-link device, the STR multi-link device can determine the length of the data transmission over the second link. Specifically, the STR multi-link device can determine the length of the data transmission over the second link based on the length of the data transmission over the first link to the non-STR multi-link device. In a specific embodiment, the STR multi-link device can end the data transmission over the first link and the data transmission over the second link simultaneously. This is to prevent the occurrence of data transmission to any other station of the non-STR multi-link device while any one of the stations of the non-STR multi-link device sends a response to the data transmission, such as an ACK, after the data transmission to one of the stations of the non-STR multi-link device ends first. According to the above-described embodiment, multiple stations of the non-STR multi-link device can send responses to the data transmission to multiple stations simultaneously.

[0195] The STR multi-link device cannot determine the state of the stations included in the non-STR multi-link device in real time. Therefore, even if the STR multi-link device operates according to the embodiment described in FIG. 16, interference or data transmission collision may occur between the links on which the non-STR multi-link device operates. For example, in the embodiment of FIG. 16, before recognizing that the second station (STA2) is executing data transmission to the second AP (AP2), the first AP (AP1) may start data transmission to the first station (STA1). Thus, the probability of interference or collision between links may be greater than the probability of interference or data transmission collision within a link. This will be described more specifically with reference to FIG. 17.

[0196] FIG. 17 shows a situation where interference or collision between links may occur.

[0197] When the transmission from the second station of the non-STR station multi-link device to the second AP of the STR AP multi-link device starts simultaneously with the transmission from 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. This is shown in FIG. 17(a). As described above, this may occur because the STR multi-link device cannot determine the state of the stations included in the non-STR multi-link device in real time.

[0198] Also, even when the transmission from 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 from 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. This is shown in FIG. 17(b). This is because it may take time for the second AP (AP2) to notify the first AP (AP1) that the second station (STA2) is in the middle of transmission. Thus, since transmission collisions occur even between stations that start transmission at different times, the probability of interference or transmission collision between devices may be greater than the probability of in-link interference or collision. Also, the probability of interference or transmission collision between links may increase as the time for the AP of the STR multi-link device to identify the transmitter of the PPDU it receives is delayed. Therefore, a method for solving this is necessary. When one of the stations of the STR multi-link device is in the middle of reception, the other stations of the STR multi-link device do not need to perform channel access. However, when channel access is prohibited in this way, the meaning of implementing the STR function may disappear. For this reason, an operation method that does not prohibit channel access for the STR multi-link device is necessary. This will be described with reference to FIG. 18.

[0199] As described above, it may be important for a multi-link device to quickly determine the station that transmits to the multi-link device. The User field of the EHT-SIG of the EHT UL PPDU can indicate the identifier (STA-ID) of the station that transmits the EHT UL PPDU. Specifically, when the DL / UL field of the signaling field of the EHT PPDU indicates that the EHT PPDU is a UL PPDU, the User field of the EHT-SIG of the EHT PPDU can indicate the identifier of the station that transmits the EHT UL PPDU. The multi-link device that receives the EHT PPDU can identify the station that transmits the EHT PPDU based on the User field of the EHT-SIG of the EHT UL PPDU. Thereby, the AP multi-link device can determine the station that transmits 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 it intends to execute is likely to fail due to an inter-link collision. Also, when there is a high possibility that the transmission the AP multi-link device intends to execute will fail, the AP multi-link device can delay the transmission it intends to execute and perform other transmissions.

[0200] FIG. 18 shows the operation in which the STR multi-link device aborts the transmission to the non-STR multi-link device according to an embodiment of the present invention.

[0201] When the station of the STR multi-link device determines that the station of the non-STR multi-link device is in a blind state during transmission to the station of the non-STR multi-link device, the STR multi-link device can interrupt the transmission to the station of the non-STR multi-link device in the blind state. Specifically, the STR multi-link device can determine whether the station of the non-STR multi-link device is in a blind state based on the value indicated by the signaling field of the received PPDU as STA(AID)-ID or the TA (transmitting address) field of the MAC frame included in the received PPDU. At this time, the STA-ID may be a value indicating the station that transmits the UL PPDU in the UL PPDU. In a specific embodiment, when the value indicated by the signaling field of the received PPDU as STA(AID)-ID indicates the first station included in the non-STR multi-link device, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in a blind state. Also, when the TA field of the MAC frame included in the received PPDU indicates the first station included in the non-STR multi-link device, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in a blind state. First, the operation of the station after canceling the transmission will be described.

[0202] When there is a remaining TXOP set for a station of the non-STR multi-link device, a station that has canceled the transmission to the station of the non-STR multi-link device can attempt to transmit to other stations other than the station of the non-STR multi-link device. At this time, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit to other stations other than the station of the non-STR multi-link device without a separate backoff procedure. In a specific embodiment, after canceling the transmission to the station of the non-STR multi-link device, when the channel is sensed as idle in a pre-specified time interval without a separate backoff procedure, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit to other stations other than the station of the non-STR multi-link device. At this time, the pre-specified time interval may be any one of SIFS, PDIF, and DIFS.

[0203] When a station that has canceled the transmission to the station of the non-STR multi-link device transmits to other stations other than the station of the non-STR multi-link device, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit traffic having the same priority as the traffic of the canceled transmission or traffic having a higher priority. This is because it is not in line with fairness to transmit traffic corresponding to a priority lower than the priority of the traffic used when accessing the channel for the canceled transmission. In the above-described embodiment, the station of the STR multi-link device may be an AP.

[0204] A station that cancels the transmission to a station of a non-STR multi-link device can initialize the set TXOP. Specifically, a station that cancels the transmission to a station of a non-STR multi-link device can transmit a CF-End frame after the cancellation. Thereby, other stations operating on the link scheduled for transmission can use the link.

[0205] In FIG. 18, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state while executing the transmission to the first station (STA1). Therefore, the first AP (AP1) interrupts the transmission to the first station (STA1). In FIG. 18(a), after interrupting the transmission to the first station (STA1), the first AP (AP1) performs transmission to other stations other than the first station (STA1) as in the embodiment described above. In FIG. 18(b), after interrupting the transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame as in the embodiment described later.

[0206] When a station interrupts transmission, after transmitting the fragment that was being transmitted, it does not have to transmit the next fragment. In yet another specific embodiment, the station may immediately abort the transmission of the packet that was being transmitted.

[0207] In the foregoing embodiments, when the STR multi-link device interrupts transmission to the station of the non-STR multi-link device in the blind state and performs transmission to other stations other than the station of the non-STR multi-link device in the blind state, for stable reception, it is necessary to notify other stations that transmission to other stations can be performed. A method therefor will be described. For the sake of convenience of explanation, stations other than the station of the non-STR multi-link device in the blind state are referred to as other stations.

[0208] The station of the STR multi-link device can insert the address of other stations into the MAC frame. Specifically, the station of the STR multi-link device can insert the address of the intended recipient of the MAC frame into the RA (receiving address) of the MAC frame and insert the address of other stations into a separate field. In yet another specific embodiment, the station of the device can insert the address of other stations into the EHT-SIG. Specifically, the station of the STR multi-link device can insert the address of the intended recipient of the PPDU and the address of other stations into the User field of the signaling field of the PPDU. At this time, the address of other stations may be inserted after the address of the intended recipient of the PPDU in the User field of the signaling field of the PPDU.

[0209] In yet another specific embodiment, even after the station recognizes that the intended recipient of the received PPDU is not the station, the station can monitor the reception of the PPDU for a specified time. Specifically, even after the station recognizes that the intended recipient of the received PPDU is not the station, the station can monitor whether the reception of the PPDU continues for a specified time. Thereby, the station can determine whether the transmission of the PPDU is interrupted and whether the transmission to the station starts. In such an embodiment, when it is determined that the transmission of the PPDU continues for the specified time, the station can enter the doze state. When it is determined that the transmission of the PPDU does not continue for the specified time, the station can maintain the wake-up state. At this time, when a new PPDU is received by the station, the station can decode the PPDU.

[0210] In yet another specific embodiment, the station transmitting the PPDU can insert information indicating that the transmission of the PPDU can be interrupted into the PPDU. The information indicating that the transmission of the PPDU can be interrupted may be a 1-bit subfield. For example, when the value of the subfield indicating that the transmission of the PPDU can be interrupted is 1, the station receiving the PPDU can determine that the transmission of the PPDU can be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame. When the station determines that the transmission of the PPDU can be interrupted before the time indicated by the Length field of the signaling field of the PPDU and the Duration field of the MAC frame, the station can defer entering the power-saving state. Also, the station transmitting the PPDU can insert information indicating that the transmission can be interrupted into the reserved field of the PPDU.

[0211] In this way, by canceling or interrupting the transmission, it is possible to prevent unnecessary occupation of the channel.

[0212] When the transmission is interrupted or postponed due to a transmission collision between links, similar to a general transmission failure, the value of CW used for channel access may be doubled. When the transmission is interrupted or postponed due to a transmission collision between links, different from a general channel access failure or transmission failure, the value of CW used for channel access does not have to be doubled (doubling). That is, the station can maintain the value of CW used for channel access as it is. Doubling the value of CW is to increase the range of numbers that can be the value of the backoff counter and reduce the probability of transmission collision. If the station can clearly recognize that it is a transmission collision between links, such a need may decrease. Also, when the transmission is interrupted or postponed due to a transmission collision between links, doubling the value of CW by the station may delay the transmission. However, when a transmission collision between links and an in-link collision occur simultaneously, the station needs to double the value of CW. This will be described with reference to FIG. 19.

[0213] FIG. 19 shows the processing of the value of CW when the STR multi-link device recognizes a transmission collision between links according to an embodiment of the present invention.

[0214] When the transmission is cancelled by the transmission performed by the non-STR multi-link device as in the above-described embodiment, the station can sense the channel state after cancelling the transmission. When it is sensed that the channel is not idle, the station can double the value of CW. At this time, the doubling can follow the embodiment described in FIG. 6. Also, when it is sensed that the channel is idle, the station can maintain the value of CW. Such an embodiment is for handling differently from the case of successful transmission because even when it is sensed that the channel is idle, the possibility of transmission collision in the link is low. Specifically, when the AP of the AP multi-link device fails to transmit to the station of the non-STR multi-link device, the AP of the AP multi-link device can obtain a back-off counter within CW without increasing CW. At this time, when the non-STR multi-link device of the AP multi-link device fails to transmit to the first station and the second station of the non-STR multi-link device performs transmission, the AP of the AP multi-link device can obtain a back-off counter within CW without increasing CW. As described above, the AP multi-link device can determine whether or not the second station of the non-STR multi-link device performs transmission based on the transmission station of the PPDU indicated by the signaling field of the PPDU or the station indicated by the TA field of the MAC frame included in the PPDU. When EDCA is applied in the above-described embodiment, the procedures regarding CW adjustment and back-off counter generation may be performed separately for each AC.

[0215] In still other specific embodiments, the STR multi-link device can determine whether the transmission of the PPDU has failed based on whether it has received a response to the PPDU. At this time, the STR multi-link device does not need to consider whether the station receiving the PPDU is included in a non-STR multi-link device. For example, even if the first station receiving the PPDU is included in a non-STR multi-link device and the second station of the non-STR multi-link device fails to send a response to the PPDU due to the second station performing transmission, the STR multi-link device can determine that the transmission of the PPDU has failed. Also, when the transmission of the PPDU by the STR multi-link device fails, the STR multi-link device can increase the value of the CW to the next larger value among the values that the CW value can have. At this time, when the value of the CW is the maximum value, the STR multi-link device may keep the value of the CW the same.

[0216] In still other specific embodiments, when the channel is sensed to be idle, the station can set the value of the CW to the minimum value (CW_min) of the CW for traffic. Such an embodiment is for handling in the same way as when transmission is successful because when the channel is sensed to be idle, the possibility of transmission collisions occurring within the link is low. The station can apply the foregoing embodiments to the CW of the AC of the traffic included in the canceled transmission.

[0217] Also, when the station cancels the transmission according to the foregoing embodiments, it does not need to increase the Retry Counter. At this time, the Retry Counter can include at least one of a long retry counter and a short retry counter.

[0218] In the previous embodiments, canceling the transmission can include at least either interrupting the transmission or delaying the transmission before starting the transmission.

[0219] If a station cancels transmission after sending a CTS-to-Self frame and before attempting to send, the station does not have to start an RTS / CTS frame exchange before attempting to send after the cancellation. This is because the NAV has already been set by the CTS-to-Self frame. Also, if there is a remaining TXOP when the station attempts to send again after canceling transmission, the station can attempt to send without a backoff procedure.

[0220] In FIG. 19, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state while executing transmission to the first station (STA1). Therefore, the first AP (AP1) interrupts the transmission to the first station (STA1). In FIG. 19(a), the first AP (AP1) determines that the channel of the first link (Link1) is idle. At this time, since there is no remaining TXOP, the first AP (AP1) accesses the channel by a backoff procedure. In FIG. 19(b), the first AP (AP1) determines that the channel of the first link (Link1) is not idle. At this time, since there is a remaining TXOP, the first AP (AP1) attempts to send without a backoff procedure.

[0221] In the foregoing embodiments, after canceling the transmission to the station of the non-STR multi-link device, if the channel is sensed to be idle in a specified time interval without a separate backoff procedure, the station that canceled the transmission to the station of the non-STR multi-link device can transmit to stations other than the station of the non-STR multi-link device. At this time, the duration of the specified time interval can be a problem. The station that received the canceled transmission PPDU may fail to decode the PPDU. At this time, if the channel is sensed to be idle for an EIFS (extended interframe space), the station that failed to decode the PPDU can start the backoff procedure. Therefore, the problem is whether to set the specified time interval longer than or the same as the EIFS. This will be described with reference to FIG. 20.

[0222] FIG. 20 shows the operation of the STR multi-link device to re-access the channel after canceling the transmission to the non-STR multi-link device according to an embodiment of the present invention.

[0223] As shown in FIG. 20(a), the specified time interval may be DIFS. This is considered in view of the fact that the station of the STR multi-link device obtained the channel access opportunity through the contention procedure and lost the channel access opportunity obtained due to the transmission collision between the links. That is, since the station of the STR multi-link device obtained the channel access opportunity through the contention procedure, it gives priority compared to other stations performing channel access. When EDCA is applied, DIFS may be replaced by AIFS[AC].

[0224] In yet another specific embodiment, as shown in FIG. 20(b), the pre-specified time interval may be EIFS. This is because the STR multi-link device can be considered to have already exhausted its transmission opportunity, and fairness with other stations is taken into account.

[0225] In yet another specific embodiment, as shown in FIG. 20(c), when signaling that transmission can be interrupted in the signaling field of the PPDU, the pre-specified time interval may be DIFS. Also, when a station that has received a PPDU senses that the transmission of the PPDU has been interrupted, the station can sense whether the channel is idle using DIFS instead of EIFS. At this time, if it is sensed that the channel is idle using DIFS, the station can start the backoff procedure. Such an embodiment can improve the performance of the entire network and also ensure fairness among stations. When EDCA is applied, DIFS may be replaced by AIFS[AC].

[0226] As described above, the STR multi-link device can recognize that transmission collisions can occur between links. Specifically, when the first station of the STR multi-link device completes the backoff procedure, the second station of the STR multi-link device may be receiving a PPDU. At this time, if the second station cannot complete the decoding of the signaling field of the PPDU, the first station cannot recognize that a transmission collision has occurred between links, but can determine that there is a possibility. At this time, as described above, the first station can insert information indicating that transmission can be interrupted into the PPDU to be transmitted. Also, the NSTR multi-link device can transmit a CTS-to-Self frame before transmitting to a non-STR multi-link device for stable and efficient transmission. This will be described with reference to FIG. 21.

[0227] FIG. 21 shows an operation in which the STR multi-link device according to an embodiment of the present invention transmits a CTS-to-Self frame before transmitting to the non-STR multi-link device.

[0228] The station of the STR multi-link device can transmit a CTS-to-Self frame before transmitting to a non-STR multi-link device. Specifically, when the second station of the STR multi-link device attempts to transmit to a non-STR multi-link device while the first station of the STR multi-link device is receiving, the second station of the STR multi-link device can transmit a CTS-to-Self frame before transmitting to the non-STR multi-link device. Thereby, the second station can secure a TXOP for transmitting to the non-STR multi-link device. Also, before transmitting to the non-STR multi-link device, the second station can determine whether a transmission to the first station will be transmitted from the non-STR multi-link device. The second station can determine the destination station of the transmission based on whether a transmission to the first station is transmitted from the non-STR multi-link device. Specifically, when a transmission to the first station is not transmitted from the non-STR multi-link device, the second station can transmit to the non-STR multi-link device. When a transmission to the first station is transmitted from the non-STR multi-link device, the second station can transmit to a station not included in the non-STR multi-link device. For example, when the first station plans to transmit a PPDU including an SU-PPDU to a station of the non-STR multi-link device, a MU-PPDU including data to a station of the non-STR multi-link device, or a PPDU including a trigger frame that triggers the transmission of a station of the non-STR multi-link device, the first station can cancel the planned transmission. At this time, the first station can attempt to transmit a PPDU including an SU-PPDU to a station other than the station of the non-STR multi-link device, a MU-PPDU not including data to a station of the non-STR multi-link device, or a PPDU including a trigger frame that does not trigger the transmission of a station of the non-STR multi-link device.At this time, the first station can start transmitting after a time greater than the SIFS since transmitting the CTS-to-Self frame. Specifically, the first station can start transmitting after the PIFS since transmitting the CTS-to-Self frame. The station that transmits the CTS-to-Self frame must start transmitting after the SIFS since transmitting the CTS-to-Self frame. As in the above-described embodiments, when canceling the scheduled transmission and attempting a new transmission, processing time of the STR multi-link device is required, such as generating the MPDU to be newly transmitted. Therefore, an exception to the rule regarding the time interval between the CTS-to-Self frame and the transmission may be applied. In such an embodiment, in principle, the second station cannot transmit beyond the TXOP acquired by the CTS-to-Self.

[0229] In FIG. 21, the STR multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). Since the second AP (AP2) receives and the first AP (AP1) plans to transmit to a station of a non-STR multi-link device, the first AP (AP1) transmits a CTS-to-Self frame before the planned transmission. As described above, the first AP (AP1) determines the destination station for transmission based on a determination for the station that transmits the PPDU received by the second AP (AP2). Also, the first AP (AP1) performs transmission after the SIFS or PIFS since transmitting the CTS-to-Self frame.

[0230] The second station can transmit an RTS frame instead of transmitting the CTS-to-Self frame and start the RTS / CTS frame exchange procedure. Thereby, the second station can obtain an effect similar to transmitting the CTS-to-Self frame. In the case of the RTS / CTS frame exchange, the second station can acquire the TXOP only when the destination station for transmission is not in a blind state.

[0231] Figure 22 shows that multiple APs included in the STR multi-link device according to an embodiment of the present invention transmit to multiple stations included in one non-STR multi-link device.

[0232] Multiple stations included in one non-STR multi-link device can receive simultaneously. This is because multiple stations receiving simultaneously causes relatively little interference. Figure 22 shows that multiple stations included in one non-STR multi-link device can receive simultaneously. At this time, for the stable operation of the non-STR multi-link device, multiple APs included in the STR multi-link device can perform multiple transmissions with synchronized transmission endings to multiple stations included in one non-STR multi-link device. This will be described with reference to Figure 23.

[0233] Figure 23 shows that multiple APs included in the STR multi-link device according to an embodiment of the present invention perform multiple transmissions with synchronized transmission endings to multiple stations included in one non-STR multi-link device.

[0234] In a non-STR link, when a multi-link device transmits on any one link, the multi-link device can simplify the channel access procedure for transmissions on other links. Specifically, when the first station of the multi-link device completes the backoff channel access procedure on the first link, if the channel is idle within a pre-specified time interval within the link of the second station of the STR multi-link device, the second station of the STR multi-link device can start transmitting on the second link.

[0235] In a specific embodiment, when one station of the STR multi-link device performs transmission to one station of the non-STR multi-link device, the channel access procedure of other stations of the STR multi-link device can be simplified. Specifically, when the first station of the STR multi-link device completes the back-off channel access procedure for transmission to the first station of the non-STR multi-link device, if the channel is idle within a specified time interval in advance within the link of the second station of the STR multi-link device, the second station of the STR multi-link device can start transmission to the second station of the non-STR multi-link device. At this time, the specified time interval may be PIFS. Such an operation may be applied when the first station and the second station of the STR multi-link device perform transmission to the stations included in one non-STR multi-link device. In such an embodiment, the first station and the second station can start transmission with a difference within the specified time interval. The specified time interval may be the slot time.

[0236] Also, when the first station and the second station of the STR multi-link device perform transmission to the stations included in one non-STR multi-link device, the transmission end of the first station and the second station may be synchronized. At this time, the synchronization of the transmission end of the first station and the second station can represent that the transmission of the first station and the transmission of the second station end with a difference within the first specified time interval. Within the first specified time interval, it can represent within the slot boundary or within the symbol boundary.

[0237] Multiple stations of a non-STR multi-link device that have received synchronized transmission end can, simultaneously, transmit subsequent transmissions, for example, responses. At this time, the response can include an ACK. In a conventional wireless LAN, a subsequent transmission after reception is transmitted after SIFS from the reception. However, for multiple transmissions that ended with a slight time difference, transmitting subsequent transmissions with a slight time difference may complicate the implementation compared to transmitting subsequent transmissions simultaneously. Therefore, as described above, multiple stations of a non-STR multi-link device that have received synchronized transmission end can, simultaneously, transmit subsequent transmissions. At this time, the interval between a transmission and a subsequent transmission following at least any one of the multiple transmissions whose transmission ends are synchronized may be the sum of SIFS and a time within a specified time interval in advance. Specifically, among the multiple transmissions whose transmission ends are synchronized, a transmission following the transmission that ended first may be transmitted at an interval obtained by adding SIFS and a time within a specified time interval in advance to the transmission. At this time, the specified time interval in advance may be one of a slot time or a symbol length. Also, the difference within the specified time interval in advance may be the difference between the end of the last-ended transmission among the multiple transmissions whose transmission ends are synchronized and the transmission that ended first among the multiple transmissions whose transmission ends are synchronized.

[0238] In yet another specific embodiment, when multiple transmissions end with a time difference within a first specified time interval in advance, multiple stations that have received a transmission can transmit synchronized subsequent transmissions. Multiple subsequent transmissions whose transmission ends are synchronized can represent multiple subsequent transmissions transmitted with a time difference within a second specified time interval in advance. Also, the difference within the second specified time interval in advance may be the difference between the end of the last-ended transmission among the multiple transmissions whose transmission ends are synchronized and the transmission that ended first among the multiple transmissions whose transmission ends are synchronized. At this time, the second specified time interval in advance may be smaller than the first specified time interval in advance. In this way, a PPDU whose transmission end is synchronized can be called a sync PPDU.

[0239] In FIG. 23, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) and the second AP (AP2) synchronize the end of transmission to the first station (STA1) and the second station (STA2), respectively. That is, after the first station (STA1) finishes transmitting, the second station (STA2) finishes transmitting within a specified time interval from the first station (STA1). The first station (STA1) and the second station (STA2) transmit ACKs simultaneously. At this time, the first station (STA1) transmits an ACK after the SIFS and after the difference between the end of transmission to the first station and the end of transmission to the second station (STA2).

[0240] Such an embodiment may be applied to transmissions for which the ACK policy is not set to No ACK. Specifically, it may also be applied when the ACK policy is not an immediate response. In a specific embodiment, when multiple stations of a multi-link device receive transmissions for which the end of transmission is synchronized, the multiple stations of the multi-link device can receive ACK requests simultaneously and transmit ACKs simultaneously in response to the ACK requests. Multiple stations of a multi-link device that receive a transmission for which the ACK policy is set to a value other than No ACK within a specified time can start transmitting ACKs simultaneously.

[0241] When a non-STR multi-link device exists, the non-STR multi-link device needs to be considered in the operation of transmitting RTS / CTS frames and CTS-to-Self frames to set a TXOP. This will be described with reference to FIGS. 24 to 29.

[0242] FIG. 24 shows that the multi-link device exchanges RTS / CTS frames according to an embodiment of the present invention.

[0243] Even when there is a non-STR multi-link device, the RTS / CTS frame exchange procedure can follow the procedure defined in the existing wireless LAN. The RTS / CTS frame may be used to set the NAV of stations operating on other links. Specifically, a station that receives an RTS / CTS frame can operate on a link other than the link on which the station operates and transmit it to other stations included in the multi-link device that includes the station.

[0244] However, as in the above-described embodiment, channel access or transmission may be restricted when there is a non-STR multi-link device. For this reason, it may not be possible to transmit RTS / CTS as shown in FIG. 24. That is, a station planning to transmit to the first station of the non-STR multi-link device does not have to attempt RTS / CTS frame exchange when the second station of the non-STR multi-link device is receiving.

[0245] In FIG. 24, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the first AP (AP1) transmits an RTS frame to the first station (STA1), channel access of the second station (STA2) is prohibited. The second AP (AP2) can determine that channel access of the second station (STA2) is prohibited. For this reason, the second AP (AP2) does not attempt RTS / CTS frame exchange with the second station (STA2). A hidden node problem may occur in such an embodiment. This will be described with reference to FIG. 25.

[0246] FIG. 25 shows the hidden node problem that occurs in the RTS / CTS frame exchange procedure according to the embodiment described in FIG. 24.

[0247] A station that transmits to a station of a non-STR multi-link device may, as described above, transmit without being able to perform CTS / RTS exchange. At this time, since a TXOP is not set for other stations, other stations may attempt to transmit, and the station of the non-STR multi-link device may fail in transmission and reception. In the embodiment of FIG. 25, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). Due to the transmission from the first AP (AP1) to the first station (STA1), the second AP (AP2) was unable to transmit an RTS frame before transmission. Therefore, a TXOP for the transmission of the second AP (AP2) is not set for the stations operating on the second link (Link2). For this reason, when the second AP (AP2) performs transmission to the second station (STA2), a station of another BSS (OBSS STA) performs transmission on the second link (Link2). As a result, the second station (STA2) fails to receive the transmission of the second AP (AP2). The following embodiments may be applied to solve such a hidden node problem.

[0248] In a specific embodiment, when any one station of the non-STR multi-link device is performing reception, the station may not be allowed to transmit to any station of the non-STR multi-link device. Further, in another specific embodiment, when the station transmits to the first station of the non-STR multi-link device, if the second station of the non-STR multi-link device is performing reception, the station may transmit simultaneously with the transmission to the second station. When the station transmits to the first station of the non-STR multi-link device and the second station of the non-STR multi-link device is performing reception, the station may synchronize the end of the transmission to the first station with the end of the transmission to the second station. Specifically, when the station transmits to the first station of the non-STR multi-link device and the second station of the non-STR multi-link device is performing reception, the station may end the transmission to the first station simultaneously with the transmission to the second station. In such an embodiment, the transmission to the second station may be performed by other stations of the multi-link device including the station.

[0249] FIG. 26 shows the multi-link device exchanging RTS / CTS frames according to an embodiment of the present invention.

[0250] In still another embodiment of the present invention, while the first station of the multi-link device continues to transmit to the third station of the non-STR multi-link device, if the second station of the multi-link device attempts to transmit an RTS frame to the fourth station of the non-STR multi-link device, the first station may end the transmission to the third station before the fourth station attempts to transmit the RTS frame. Thereby, the fourth station can transmit a CTS frame to the second station. Accordingly, TXOP reservation for frame exchange between the second station and the fourth station can be made. However, it may be difficult for the first station to end the transmission before the fourth station attempts to transmit the RTS frame.

[0251] In still another embodiment of the present invention, while the first station of the multi-link device continues to transmit to the third station of the non-STR multi-link device, if the second station of the multi-link device attempts to transmit an RTS frame to the fourth station of the non-STR multi-link device, the second station can transmit the RTS frame to the fourth station in accordance with the end point of the transmission of the first station to the third station. For that purpose, the second station can insert padding into the RTS frame. At this time, the RTS frame may be an RTS frame format capable of flexibly adjusting the transmission length. For convenience of explanation, such an RTS frame format is referred to as an ML (multilink)-RTS frame. The ML-RTS frame can include a pad field for padding. For example, the format of the ML-RTS frame may be the same as the RTS frame format described in FIG. 26. Also, the first station can insert padding into the transmission to the third station in order to match the RTS frame and the end point of the transmission.

[0252] In the embodiment of FIG. 26, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second AP (AP2) transmits an ML-RTS frame to the second STA (STA2) in accordance with the time point when transmission to the first station (STA1) of the first AP (AP1) ends. Thereafter, when the first station (STA1) transmits an ACK to the first AP (AP1), the second station (STA2) transmits an ACK to the second AP (AP2). Thereby, a TXOP for frame exchange between the second AP (AP2) and the second station (STA2) is set for a station operating on the channel of the second link.

[0253] In still other specific embodiments, other frames for setting NAV may be exchanged instead of the RTS / CTS frame. In the embodiments described above, an ACK request frame may be transmitted instead of the RTS frame. The ACK request frame can include duration information related to the end time of transmission. Also, a frame including an ACK transmitted in response to the ACK request can also include duration information. At this time, the duration information of the frame including the ACK may be set by the duration information of the ACK request frame.

[0254] The embodiments described above have been described as for RTS / CTS frame exchange, but may also be used for control frame exchange other than the RTS / CTS frame. At this time, the control frame exchange can include the exchange of PS-Poll frames and response frames to PS-Poll.

[0255] FIG. 27 shows that, according to an embodiment of the present invention, a multi-link device exceptionally transmits a response to a control frame even when channel access is prohibited.

[0256] As described in the foregoing embodiments, when there is a non-STR multi-link device, channel access of some stations may be prohibited. Even if the channel access of a station is prohibited, the station can send a response to a control frame. Specifically, even if the channel access of a station is prohibited, the station can send a CTS frame as a response to an RTS frame.

[0257] Thus, when a response to a control frame is sent as an exception to channel access prohibition, the following embodiments may be applicable. A first station sends a response to a control frame as an exception to channel access prohibition. When the first station sends a response to a control frame, a third station sends to a second station included in the multi-link device including the first station. In such a case, the third station can retransmit to the first station. It can be expected that the transmission to the second station by the third station will fail.

[0258] In the embodiment of FIG. 27, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP) performs transmission to the first station (STA1). The second AP (AP2) transmits an RTS frame to the second station (STA2). Since the first station (STA1) performs reception, channel access of the second station (STA2) is prohibited. However, the second station (STA2) transmits a CTS frame to the second AP (AP2) as an exception to the channel access prohibition. The first AP (AP1) can determine that there is a high possibility of failure in the transmission of the first AP (AP1) due to the transmission of the CTS frame by the second station (STA2). Therefore, the first AP (AP1) performs retransmission to the first station (STA1). The retransmission method will be described in more detail with reference to FIG. 28.

[0259] FIG. 28 shows retransmission of transmission to a station of a non-STR multi-link device.

[0260] In the retransmission described with reference to FIG. 27, only some of the packets included in the first transmission may be retransmitted. Specifically, the station performing the retransmission can retransmit only some of the packets included in the first transmission. The station performing the retransmission can determine the packets to be retransmitted from among the packets included in the first transmission based on the time interval during which the station performing the retransmission received the CTS frame. Specifically, the station performing the retransmission can determine, as the packets to be retransmitted, the packets transmitted during the time interval including the time interval during which the station performing the retransmission received the CTS frame among the packets included in the first transmission. At this time, the station performing the retransmission can retransmit the packets transmitted during the time interval including the time interval during which the station performing the retransmission received the CTS frame based on the propagation delay. In yet another specific embodiment, the station performing the retransmission can retransmit all of the packets included in the first transmission.

[0261] Also, the station performing the retransmission can perform the retransmission before receiving an ACK for the transmission. At this time, the station performing the retransmission can receive a Block ACK indicating the presence or absence of reception for the first transmission and the retransmission after performing the retransmission. Therefore, the station performing the retransmission can perform the retransmission after the first transmission and before the SIFS. In yet another specific embodiment, a station that has failed to receive due to a control frame transmitted as an exception to the channel access prohibition can wait for reception of the retransmission without transmitting an ACK.

[0262] In the embodiment of FIG. 28, the first AP (AP1) retransmits the fourth and fifth packets in consideration of the section in which the second AP (AP2) receives the CTS frame and the transmission delay. After the retransmission, the first AP (AP1) receives an ACK including the presence or absence of reception of the retransmission.

[0263] FIG. 29 shows that a control frame is transmitted on a link where a station whose channel access is not prohibited operates, rather than on a link where a station whose channel access is prohibited operates according to an embodiment of the present invention.

[0264] As in the embodiment described with reference to FIG. 26, the transmission termination to a plurality of stations of a non-STR multi-link device may be synchronized. However, this may involve adjusting the already generated MPDU or generating the MPDU again, which is difficult to implement. Therefore, the multi-link device may transmit a control frame on a link where a station whose channel access is not prohibited operates, rather than on a link where a station whose channel access is prohibited operates. Specifically, the multi-link device can transmit a control frame through a link that is currently receiving from the multi-link device among the stations of the non-STR multi-link device. At this time, the control frame may be an RTS frame.

[0265] In the embodiment of FIG. 29, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The first AP (AP1) transmits to the first station (STA1). Even if the second AP (AP2) succeeds in the backoff procedure, since the first station (STA1) is receiving the transmission sent from the first AP (AP1), the second AP (AP2) cannot transmit to the second station (STA2). At this time, the second AP (AP2) requests the first AP (AP1) to transmit an RTS frame with the second station (STA2) as the recipient. At this time, the first AP (AP1) can include an RTS frame with the second station (STA2) as the recipient in the transmission that the first AP (AP1) is performing. In still another specific embodiment, after the first AP (AP1) finishes the transmission that the first AP (AP1) is performing, the first AP (AP1) can transmit an RTS frame with the second station (STA2) as the recipient through the first link (Link1) after a SIFS from the said transmission. The first station (STA1) receives an RTS frame with the second station (STA2) as the recipient and transmits the received RTS frame to the second station (STA2). The second station (STA2) performs CCA with PIFS. When the channel is idle with PIFS, the second station (STA2) transmits a CTS-to-Self frame. The first AP (AP1) may abort the transmission to the first station (STA1) in a time interval when it is expected that the second station (STA2) will transmit a response to the RTS frame. Also, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can transmit an ACK for the received transmission. In still another specific embodiment, while the second station (STA2) is transmitting a response to the RTS frame, the first station (STA1) can transmit a response to the RTS frame together.FIG. 29 is for helping understanding of the description and may also be used for transmission of control frames other than RTS frames and CTS-to-Self frames. Also, other time intervals other than PIFS may be used.

[0266] FIG. 30 shows that a multi-link device transmits an ACK according to an embodiment of the present invention.

[0267] A station of a multi-link device can request a link to transmit an ACK to a station of a no-STR multi-link device. Specifically, a station of a multi-link device can request to transmit an ACK on a link other than the link on which transmission has been performed. In the embodiment of FIG. 28, the first AP (AP1) of the STR multi-link device performs transmission (Tx(#2)) to the first station (STA1) of the non-STR multi-link device. At this time, the first AP (AP1) requests to transmit an ACK for the transmission (Tx(#2)) on the second link (Link2). This is because the transmission (Tx(#2)) of the first AP (AP1) ends earlier than the transmission to the second station (STA2) of the second AP (AP2), and it is determined that it is difficult to transmit an ACK for the transmission (Tx(#2)) of the first AP (AP1).

[0268] Also, for such ACK transmission, a station can set an implicit BAR and ACK policy so as not to transmit an immediate response to the transmission. In still other specific embodiments, a station can set the ACK policy for the transmission to BlockAckReq. However, in order to transmit a Block ACK, BlockAckReq must be transmitted, and channel access burden and transmission delay may occur. For this reason, a new ACK policy for a multi-link device is required.

[0269] One station of the multi-link device can transmit both the ACK for the transmission received by the station and the ACK for the transmission received by other stations included in the same multi-link device. Such ACK transmission can be referred to as ML (multilink)-ACK. Also, ML-ACK may be set as the ACK policy. In the embodiment of FIG. 30, the first AP (AP1) sets the ACK policy for the transmission (Tx(#2)) to ML-ACK. After receiving the transmission (Tx(#2)), the first station (STA1) does not transmit an ACK to the first AP (AP1). The second station (STA2) completes receiving the transmission sent from the second AP (AP2), and transmits both the ACK for the transmission from the first AP (AP1) and the ACK for the transmission from the second AP (AP2) to the second AP (AP2). The non-STR multi-link device may include a third station (STA3) in addition to the first station (STA1) and the second station (STA2), and the STR multi-link device may include a third AP (AP3) in addition to the first AP (AP1) and the second AP (AP2). At this time, the ACK policy for the transmission to the second station (STA2) from the second AP (AP2) may also be set to ML-ACK. When the transmission to the third station (STA3) from the third AP (AP3) is completed later than the transmission to the second station (STA3) from the second AP (AP2), the third station (STA1) can transmit the ACK for the transmission from the first AP (AP1) to the first station (STA1), the ACK for the transmission from the second AP (AP2) to the second station (STA2), and the ACK for the transmission from the third AP (AP3) to the third station (STA3) to the third AP (AP3).

[0270] According to such an embodiment, even if the transmissions to the stations of the non-STR multi-link device are not completed simultaneously, it is possible to prevent interference between links that may occur due to ACK transmission. In the above-described embodiment, the ACK policy may be set to BlockAck instead of ML-ACK. In still other specific embodiments, the ACK policy may be set to No Ack instead of ML-ACK.

[0271] The number of links that the multi-link device has obtained a transmission opportunity while transmitting traffic may increase. At this time, the multi-link device may transmit the traffic that it tried to transmit on the link that obtained the transmission opportunity earlier on the link that obtained the transmission opportunity later. At this time, the NAV set on the link that the multi-link device obtained the transmission opportunity earlier may be set larger than the NAV required to transmit the traffic. When the NAV set on the link that the multi-link device obtained the transmission opportunity earlier is set larger than the NAV required to transmit the traffic on that link, the multi-link device can transmit a CF-END frame after completing the transmission on the link that obtained the transmission opportunity earlier to reset the NAV.

[0272] The reception of the sink PPDU and the signaling related to the reception of the sink PPDU described above will be described with reference to FIGS. 31 to 34.

[0273] In order for the first station of the non-STR multi-link device to receive the aforementioned sink PPDU, it is necessary to determine whether or not the second station, which is in a non-STR relationship with the first station, starts receiving the sink PPDU. Also, the first station must continuously perform PD (preamble detection). Considering that the channel access of the first station receiving the sink PPDU is prohibited by the reception execution of other stations of the non-STR multi-link device, such an operation of the first station may be unreasonable. Therefore, the first station can enter the power-saving state within the specified conditions in advance. The sink PPDU may be transmitted within the existing TXOP that has been set. Therefore, the performance gain obtained by receiving the sink PPDU may be determined by the remaining length of the TXOP. Therefore, the first station can determine whether or not to abandon the reception of the sink PPDU based on the length of the sink PPDU. When the first station abandons the reception of the sink PPDU, the first station can enter the power-saving state. Such a power-saving operation can be referred to as inter-link TXOP PS (power save). A station that has entered the power-saving state in inter-link TXOP PS can wake up from the power-saving state in order to receive frames periodically transmitted from the AP, such as beacon frames, TIM frames, and DTIM frames. Also, when the TXOP ends, for example, when a CF-END frame is transmitted, a station that has entered the power-saving state in inter-link TXOP PS can wake up from the power-saving state.

[0274] The aforementioned TXOP may be changed to the period indicated by the length field of the signaling field of the PPDU and the Duration field of the MAC frame. Specifically, in the aforementioned embodiment, the station can determine the time occupied by the PPDU based on the period indicated by the length field and the Duration field of the MAC frame.

[0275] The non-AP multi-link device can signal the AP multi-link device with information regarding the presence or absence of sink PPDU reception support and the sink PPDU support conditions. Also, the AP multi-link device can signal the non-AP multi-link device with information regarding the presence or absence of transmission support for the AP multi-link device sink PPDU. At this time, the multi-link device can signal the presence or absence of sink PPDU support for each multi-link device. For example, the AP multi-link device can signal the presence or absence of sink PPDU transmission support for each AP multi-link device. In yet another specific embodiment, the multi-link device can signal the presence or absence of sink PPDU support for each station. Specifically, the AP multi-link device can signal the presence or absence of sink PPDU transmission support for each AP included in the AP multi-link device. For example, an AP multi-link device including a first AP, a second AP, and a third AP can indicate that the first AP supports sink PPDU transmission, while the second AP and the third AP do not support sink PPDU transmission.

[0276] When signaling that the AP multi-link device associated with the non-AP multi-link device does not support sink PPDU transmission, the stations of the non-AP multi-link device can enter the power-saving state of the aforementioned inter-link PS while other stations of the non-AP multi-link device are receiving. This is because the AP multi-link device associated with the non-AP multi-link device cannot transmit the sink PPDU. At this time, the stations of the non-AP multi-link device can determine the length of time to maintain the power-saving state based on the length of the PPDU received by other stations of the non-AP multi-link device.

[0277] The presence or absence of the transmission support or reception support for the sink PPDU described above may be determined by the operation policy in addition to the hardware performance. Therefore, the presence or absence of the transmission support or reception support for the sink PPDU may be signaled by information regarding the operating mode in addition to the information regarding the performance. The signaling method for the transmission support or reception support for the sink PPDU will be specifically described with reference to FIG. 31.

[0278] FIG. 31 shows an element field for instructing information regarding the sink PPDU reception support or transmission support according to an embodiment of the present invention.

[0279] As described above, the information indicating the presence or absence of the sink PPDU transmission support may be included in an element that indicates the capabilities of the station. For the sake of convenience of explanation, the element that indicates the capabilities of the station is referred to as the Capability element. Also, the field of the information indicating the presence or absence of the sink PPDU transmission support in the Capability element is referred to as the Supporting Sync PPDU Tx subfield. At this time, the Capability element may be a Multi-Link element that is an element indicating the capabilities regarding multi-link. Also, the Capability element may be an EHT Capability element that is an element indicating the EHT-related capabilities. FIG. 31(a) shows an example of the Capability element.

[0280] When the value of the Supporting Sync PPDU Tx subfield is 1, Supporting Sync PPDU Tx can indicate that the station or multi-link device indicated by the Supporting Sync PPDU Tx subfield supports the transmission of the Sync PPDU. When the value of the Supporting Sync PPDU Tx subfield is 0, Supporting Sync PPDU Tx can indicate that the station or multi-link device indicated by the Supporting Sync PPDU Tx subfield does not support the transmission of the Sync PPDU. Also, when a station not included in the multi-link device transmits a Capability element, the Supporting Sync PPDU Tx subfield may signal information not related to the presence or absence of Sync PPDU transmission support or be used as a reserved field.

[0281] As described above, the information indicating the presence or absence of sink PPDU reception support may be included in an element that indicates operation-related information of a station. For convenience of explanation, an element that indicates operation-related information of a station is referred to as an Operation element. Also, a field of the information indicating the presence or absence of sink PPDU reception support in the Operation element is referred to as a Supporting Sync PPDU Rx Disable subfield. FIG. 31(b) shows an example of the Operation element. When the value of the Supporting Sync PPDU Rx Disabled subfield is 1, it can indicate that reception of a sink PPDU is not desired. Specifically, when the value of the Supporting Sync PPDU Rx Disabled subfield is 1, the Supporting Sync PPDU Rx Disabled subfield can indicate that a station that transmits the Supporting Sync PPDU Rx Disabled subfield does not desire to wait for reception of a sink PPDU. A multi-link device that sets the value of the Supporting Sync PPDU Rx Disabled subfield to 1 may not require a second station of the multi-link device to perform PD and CCA while a first station of the multi-link device is performing reception. An AP multi-link device connected to the multi-link device that transmitted the Supporting Sync PPDU Rx Disabled subfield does not transmit a PPDU to a plurality of stations of the multi-link device that transmitted the Supporting Sync PPDU Rx Disabled subfield at the same time. The PPDU may be a SU PPDU, a Full BW MU PPDU, or an OFDMA MU PPDU transmitted in any one of the non-HT PPDU, HT PPDU, VHT PPDU, HE PPDU, and EHT PPDU formats. At this time, the AP multi-link device shall not transmit a frame that requests a response, for example, an immediate response.The frame requesting a response can include at least one of RTS, MU-RTS (Multi-User RTS), trigger frame, and BAR (Block Ack Request).

[0282] Also, the Operation element can include information related to the minimum length of the sink PPDU that can be received by the station or multi-link device that transmitted the Operation element. At this time, the subfield indicating the information related to the minimum length of the sink PPDU is referred to as the Remaining TXOP Threshold subfield. The Remaining TXOP Threshold subfield can indicate time. Also, the Remaining TXOP Threshold subfield can be indicated in units of us, ms, or symbols. A multi-link device connected to the multi-link device that transmitted the Remaining TXOP Threshold subfield is not allowed to transmit a sink PPDU shorter than the length indicated by the Remaining TXOP Threshold subfield to the multi-link device or station that transmitted the Remaining TXOP Threshold subfield.

[0283] Also, when the Remaining TXOP Threshold subfield is set to a pre-specified value, it can indicate that the multi-link device or station that transmitted the Remaining TXOP Threshold subfield does not assist in receiving the sink PPDU. The pre-specified value can be a value indicating a time greater than the maximum time that the Remaining TXOP Threshold subfield can indicate. In yet another specific embodiment, the pre-specified value can be 0. When such an embodiment is applied, the Sync PPDU Rx Disable subfield in the Operation element can be omitted.

[0284] Also, in the above-described embodiments, it has been explained that the Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield can be signaled by the Operation element. The Sync PPDU Rx Disable subfield and the Remaining TXOP Threshold subfield may be signaled by an element other than the Operation element or signaling information. In FIGS. 32 to 34, embodiments in which the inter-link TXOP power-saving mode is performed by the signaling described in FIG. 31 will be described.

[0285] FIG. 32 shows that a non-STR multi-link device performs an inter-link TXOP power-saving mode operation according to an embodiment of the present invention.

[0286] When it is signaled that the non-STR multi-link device does not support sink PPDU reception, when the first station of the non-STR multi-link device is performing reception, the second station of the non-STR multi-link device can enter the power-saving state. At this time, the second station can maintain the power-saving state until the end point of the TXOP indicated by the PPDU received by the first station. As described above, the second station may be a case where the time when reception of a frame periodically transmitted from the AP is predicted is before the end point of the TXOP indicated by the PPDU received by the first station. At this time, the second station can wake up from the power-saving state before the end point of the TXOP indicated by the PPDU received by the first station. As described above, the frame periodically transmitted from the AP may include at least one of a beacon frame, a TIM frame, and a DTIM frame.

[0287] The second station can maintain the power-saving state even after the end of the TXOP indicated by the PPDU received by the first station. Specifically, the second station can determine whether to maintain the power-saving state even after the end of the TXOP indicated by the PPDU received by the first station based on the information received from the AP to which the second station is connected. At this time, the information received from the AP to which the second station is connected may be NAV-related information. Further, the information received from the AP to which the second station is connected may be the operation information of the AP to which the first station is connected. When the NAV set by the second AP of the AP multi-link device that is transmitting to the second station of the non-AP multi-link device has not expired, the first station of the non-AP multi-link device that has signaled that the first AP does not desire to receive the sink PPDU can transmit information regarding the expected end time of the transmission or reception of the first AP and the expected expiration time of the NAV. When the NAV set by the second AP of the AP multi-link device that is transmitting to the second station of the non-AP multi-link device has not expired, it can include the second AP transmitting or receiving a PPDU from any one of the stations. When the NAV set by the second AP of the AP multi-link device that is transmitting to the second station of the non-AP multi-link device has not expired, it can include that the NAV was set for the second AP by the PPDU not transmitted by the second station.

[0288] In the embodiment of FIG. 32, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multi-link device signals that it does not desire to receive a sink PPDU. The first AP (AP1) transmits to the first station (STA1). At this time, the second station (STA2) maintains a power-saving state until the end of the TXOP indicated by the PPDU transmitted by the first AP (AP1) to the first station (STA1).

[0289] FIG. 33 shows that, according to an embodiment of the present invention, the station of the non-STR multi-link device enters a power-saving state while waiting to receive a sink PPDU.

[0290] The first station of the non-STR multi-link device can enter the power-saving state of the inter-link TXOP when the remaining duration of the TXOP indicated by the PPDU being received by the first station of the non-STR multi-link device is equal to or shorter than the length indicated by the Remaining TXOP Threshold subfield transmitted by the non-STR multi-link device. At this time, before entering the power-saving state, that is, when the remaining duration of the TXOP indicated by the PPDU being received by the first station is greater than the length indicated by the Remaining TXOP Threshold subfield transmitted by the non-STR multi-link device, the second station can receive the sink PPDU transmitted to the second station. At this time, the second station can receive the sink PPDU. Therefore, the second station performs PD and can determine whether the intended recipient of the received PPDU is the second station. Specifically, the second station can determine whether the AID indicated by the signaling field of the PPDU or the RA of the MAC frame included in the PPDU indicates the second station.

[0291] In the embodiment of FIG. 33, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multi-link device signals a desire to receive a sink PPDU. At this time, the non-STR non-AP multi-link device also signals the length of the minimum TXOP, "a", required for sink PPDU reception. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sink PPDU. When the TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is the same as or shorter than "a", the second station (STA2) enters the inter-link TXOP power-saving state.

[0292] FIG. 34 shows that, according to yet another embodiment of the present invention, a station of a non-STR multi-link device enters a power-saving state while waiting to receive a sink PPDU.

[0293] While waiting to receive a sink PPDU, if a station of a non-STR multi-link device senses the transmission of a PPDU other than the sink PPDU from a BSS operated by an AP connected to the station of the non-STR multi-link device, the station of the non-STR multi-link device can enter the inter-link TXOP power-saving state. At this time, the station can determine that a PPDU whose intended recipient is not the station is not a sink PPDU. Also, even if the minimum TXOP signaled by the station remains, if the station of the non-STR multi-link device senses the transmission of a PPDU other than the sink PPDU from a BSS operated by an AP connected to the station of the non-STR multi-link device, the station of the non-STR multi-link device can enter the inter-link TXOP power-saving state.

[0294] In the embodiment of FIG. 34, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The non-STR non-AP multi-link device signals a desire to receive a sink PPDU. At this time, the non-STR non-AP multi-link device also signals the length of the minimum TXOP, "a", required for sink PPDU reception. The first AP (AP1) transmits to the first station (STA1), and the second station (STA2) waits to receive the sink PPDU. The second station (STA2) senses that a PPDU other than the sink PPDU is transmitted from the BSS to which the second station belongs. Although the TXOP of the PPDU transmitted by the first AP (AP1) to the first station (STA1) is greater than "a", the second station (STA2) enters the inter-link TXOP power saving state.

[0295] <Multi-Link Single Radio Multi-Link Device Service Procedure>

[0296] As described above, the multi-link device can operate adaptively in consideration of the fact that the second station becomes blind when the first station of the non-STR multi-link device transmits. Specifically, when the multi-link device determines that the station of the non-STR multi-link device is in a blind state, the multi-link device may interrupt transmission to the station of the non-STR multi-link device. Also, the station of the non-STR multi-link device may enter a power saving state (doze state) based on the operation of other stations of the non-STR multi-link device, for example, transmission and reception. Thereby, problems that may occur when the operation of one station of the non-STR multi-link device restricts the operation of other stations can be solved.

[0297] As described above, due to in-device interference, separate stations included in the non-STR multi-link device cannot perform reception and transmission simultaneously. Also, due to hardware configuration constraints of the non-STR multi-link device, separate stations included in the non-STR multi-link device cannot perform reception and transmission simultaneously. Specifically, when the first station of the non-STR multi-link device performs transmission or reception, the use of the transceiver by the second station of the non-STR multi-link device may be restricted. For example, the non-STR multi-link device can support only one PPDU processing. At this time, when the first station of the non-STR multi-device performs transmission or reception, the second station of the non-STR multi-device cannot perform transmission or reception. A multi-link device that includes a plurality of stations operating on a plurality of links respectively or does not support a plurality of stations transmitting or receiving simultaneously is called a single-radio multi-link device. Therefore, when any one station of the single-radio multi-link device performs transmission and reception, other stations of the single-radio multi-link device cannot perform transmission and reception. The multi-link device operating as a single-radio multi-link device may follow the hardware constraints or operation mode definition as described above. Therefore, in this specification, the single-radio multi-link device can refer to a multi-link device in which the operation of the stations is restricted by hardware constraints, as well as a multi-link device in which the operation of the stations is restricted by the definition of the operation mode. Therefore, the single-radio multi-link device in this specification can include a multi-link device that supports a plurality of stations of the multi-link device transmitting or receiving simultaneously, but does not support a plurality of stations of the multi-link device transmitting or receiving simultaneously under specific conditions. At this time, the specific conditions can include a specific time point.

[0298] The above-described embodiments regarding the operation of the non-STR multi-link device are also applicable to the operation of a single-radio multi-link device. Further, the above-described embodiments regarding the operation of the station that communicates with the non-STR multi-link station are also applicable to the operation of the station that communicates with the station of the single-radio multi-link device. For example, when it is determined that the station fails to transmit to the single-radio multi-link device on the first link by transmission or reception of the single-radio multi-link device on the second link, the station does not have to increase the CW of the channel access performed on the first link. Specifically, the station can apply the embodiment described with reference to FIG. 14. At this time, the method for determining that the station fails to transmit to the single-radio multi-link device on the first link by transmission or reception of the single-radio multi-link device on the second link may be similar to the method for determining whether the station fails to transmit to the non-STR multi-link station due to the operation limitation of the non-STR multi-link device.

[0299] FIG. 35 shows the connection between the single-radio multi-link device and the AP multi-link device according to an embodiment of the present invention.

[0300] In this specification, the PHY backend generally refers to a digital processor of a physical layer including a processor that encodes and decodes a PPDU. Further, the PHY frontend generally refers to an analog baseband circuit including an RF chain.

[0301] A plurality of stations of the single-radio multi-link device operate on different links from each other. The plurality of stations may share the PHY backend. At this time, when any one of the stations transmits a PPDU, the PHY backend is used for encoding the PPDU. Therefore, at this time, the remaining stations of the plurality of stations cannot use the PHY backend. Therefore, the single-radio multi-link device includes a plurality of stations that operate on different links from each other, but can transmit or receive only on one link at a time.

[0302] However, a single radio multi-link device can perform channel access on multiple links. Specifically, a single radio multi-link device can perform monitoring on multiple links. Therefore, a single radio multi-link device can perform channel access on multiple links. At this time, the monitoring can include channel sensing. Also, the channel sensing can include at least one of CCA (clear channel assessment) and PD (preamble detection). Thereby, the single radio multi-link device can reduce the channel access delay. Specifically, even if the first station of the single radio multi-link device cannot perform channel access due to the channel occupancy of other wireless communication devices performed on the first link, the second station of the single radio multi-link device can perform a backoff procedure on the second link.

[0303] To support such an embodiment, the PHY front end of the single radio multi-link device can support channel monitoring independently from the PHY back end. Also, the PHY front end of the single radio multi-link device can support decoding for the preamble of the PPDU independently from the PHY back end for PD. Also, the PHY front end of the single radio multi-link device can support receiving frames transmitted by a low MCS independently from the PHY back end. At this time, the frames transmitted by a low MCS can include at least one of an RTS frame and a MU-RTS frame. Therefore, the PHY front end can include a MAC processor. Also, according to such an embodiment, the processing power of the PHY back end can be intensively utilized for encoding and decoding data frames.

[0304] In the embodiment of FIG. 35, the AP multi-link device includes a first AP (AP1) and a second AP (AP2). The single radio multi-link device includes a first non-AP station (Non-AP STA1) and a second non-AP station (Non-AP STA2). The first AP (AP1) is connected to the first non-AP station (Non-AP STA1) via a first link Link1, and the second AP (AP2) is connected to the second non-AP station (Non-AP STA2) via a second link Link2. As in the above-described embodiment, each of the first Non-AP station (Non-AP STA1) and the second Non-AP station (Non-AP STA2) independently performs channel access using a PHY front end.

[0305] The single radio multi-link device can use the RF chains of stations that do not participate in transmission or reception for MIMO transmission. Specifically, when the first station of the single radio multi-link device obtains a channel access opportunity, the first station can perform MIMO transmission using, in addition to the RF chain used by the first station, the RF chain used by the second station of the single radio multi-link device. This will be described with reference to FIG. 36.

[0306] FIG. 36 shows that the single radio multi-link device according to an embodiment of the present invention performs MIMO transmission.

[0307] In the embodiment of FIG. 36, the first station STA1 of the single-radio multi-link device operates on the first link Link1, and the second station STA2 of the single-radio multi-link device operates on the second link Link2. The first station STA1 performs channel access on the first link Link1, and the second station STA2 performs channel access on the second link Link2. When the first station STA1 succeeds in channel access on the first link Link1, the first station STA1 uses, in addition to the RF chain used for channel access on the first link Link1, the RF chain used by the second station STA2 for channel access on the second link Link2 to perform 2x2 MIMO transmission on the first link Link1.

[0308] Thus, when the RF chain operating on the first link is changed to operate on the second link, the single radio multi-link device cannot perform monitoring and channel access on the first link. Also, when the RF chain operates on the second link again, the single radio multi-link device can perform channel access on the second link after waiting for a specified time. At this time, channel access of the single radio multi-link device on the second link may be restricted at the specified time from the completion of the RF change. Specifically, the single radio multi-link device can perform channel access on the second link after waiting for a specified time from the completion of the RF change. At this time, the channel access can include a backoff procedure. Also, the specified time may be a specified time applied when channel access needs to be restricted due to a time when channel monitoring is impossible. Specifically, the specified time may be NAVSyncdelay. Specifically, the single radio multi-link device can perform a backoff procedure after waiting for NAVSyncdelay. This is because there is a high probability that the transmission of other wireless communication terminals operating on the second link cannot be detected during the period when the single radio multi-link device cannot perform channel monitoring. Also, when the link on which the RF chain operates is changed, a delay time may be required for the RF chain to start operating. Therefore, the single radio multi-link device can perform channel access considering the delay time of the RF chain change. This will be described with reference to FIG. 37. Also, for convenience of explanation, changing the RF chain operating on any one link to operate on another link is referred to as an RF chain change. Also, the link change can refer to the change of the RF chain supported by the link. Specifically, when the use of a plurality of RF chains is supported on the first link but the use of one RF chain is supported, or when the use of one RF chain is not supported on the second link but the use of one RF chain is supported, it can be referred to as an RF chain change.

[0309] A station communicating using a single radio multi-link device and MIMO may be a station of the multi-link device. Specifically, a station communicating using a single radio multi-link device and MIMO may be an AP included in the multi-link device. Unless otherwise specified in this specification, a station communicating using a single radio multi-link device and MIMO may be a station included in the multi-link device. At this time, the station included in the multi-link device may be an AP. Also, what is described as the operation of the station of the multi-link device in this specification may represent the operation of the multi-link device.

[0310] FIG. 37 shows the operation of a single radio multi-link device according to an embodiment of the present invention to perform channel access considering the delay time of RF chain change.

[0311] The single radio multi-link device can change the RF chain before the time when it is expected to succeed in channel access. Specifically, the single radio multi-link device can change the RF chain by a time set based on the delay time of RF chain change from the time when it is expected to succeed in channel access. For example, the single radio multi-link device can change the RF chain at a time earlier by the delay time of RF chain change from the time when it is expected to succeed in channel access.

[0312] In the embodiment of FIG. 37, the first station STA1 of the single-radio multi-link device operates on the first link Link1, and the second station STA2 of the single-radio multi-link device operates on the second link Link2. The first station STA1 performs channel access on the first link Link1, and the second station STA2 performs channel access on the second link Link2. When the first station STA1 successfully performs channel access on the first link Link1, in addition to the RF chain used for channel access on the first link Link1, the first station STA1 also uses the RF chain used by the second station STA2 for channel access on the second link Link2 to perform 2x2 MIMO transmission on the first link Link1. In the embodiment of FIG. 37(a), the single-radio multi-link device changes the RF chain at a time point earlier by the RF chain switching delay from the time point (Expected Tx time) when successful channel access is expected.

[0313] In still other specific embodiments, when starting transmission after the single-radio multi-link device changes the RF chain, the single-radio multi-link device can start the RTS frame / CTS frame exchange. In still other specific embodiments, when starting transmission after the single-radio multi-link device changes the RF chain, the single-radio multi-link device can transmit a CTS-to-Self frame. Also, the single-radio multi-link device can transmit a frame having a relatively short length instead of the CTS-to-Self frame. By such embodiments, the single-radio multi-link device can obtain the time taken until the RF chain change is completed. Also, different from the above-described embodiments, such embodiments do not cause problems even when channel access cannot be successfully performed at the predicted time point.

[0314] In the embodiment of FIG. 37(b), the single-radio multi-link device starts transmission by RTS frame / CTS frame exchange on the first link Link1.

[0315] FIG. 38 shows the Capability element and the Operation element used by the single radio multi-link device according to an embodiment of the present invention.

[0316] As described with reference to FIGS. 36 and 37, the single radio multi-link device can change the RF chain to perform transmission or reception. In addition, the single radio multi-link device can perform transmission or reception without changing the RF chain. The single radio multi-link device can select whether to change the RF chain.

[0317] The single radio multi-link device can indicate whether to also use the RF chains of other links when performing MIMO communication on the link in the MIMO Rx support subfield of the Operation element. For example, when the single radio multi-link device sets the value of the MIMO Rx support subfield of the Operation element to 1, the MIMO Rx support subfield can indicate that MIMO reception is performed using the number of spatial streams less than or equal to the value of the Max Rx spatial stream subfield of the Operation element. At this time, the station that performs MIMO transmission on the single radio multi-link device must perform MIMO transmission using the number of spatial streams less than or equal to the value of the Max Rx spatial stream subfield of the Operation element. In a specific embodiment, the format of the Operation element may be as shown in FIG. 38(a).

[0318] In addition, a single-radio multi-link device can signal the time taken for RF chain switching in a Capability element. At this time, the switching latency subfield of the Capability element can indicate the time taken for RF chain switching. A station that performs MIMO transmission on a single-radio multi-link device must perform MIMO transmission considering the time taken for RF chain switching. Specifically, a station that performs MIMO transmission on a single-radio multi-link device can start MIMO transmission after the time taken for RF chain switching has elapsed since the first transmission to the single-radio multi-link device. In a specific embodiment, the format of the Capability element may be as shown in Fig. 38(a).

[0319] When a single-radio multi-link device performs transmission or reception on a first link, it may not be allowed for a station attempting to transmit to the single-radio multi-link device to perform transmission on a link other than the first link. This is because the single-radio multi-link device cannot receive on a link other than the first link while transmission or reception is being performed on the first link. Specifically, in addition to when a frame is being exchanged on the first link, it may not be allowed for a station attempting to transmit to the single-radio multi-link device to perform transmission on a link other than the first link until a certain time has elapsed since the single-radio multi-link device has completed the frame exchange sequence. Specifically, the completion of the frame exchange sequence may be determined based on the reception or transmission of the last frame of the frame exchange sequence. At this time, the frame exchange sequence may be performed on a link where the use of multiple RF chains is possible. Specifically, the frame exchange sequence may be performed using MIMO. The certain time may be determined based on the time taken for RF chain switching. Specifically, the certain time may be the time taken for RF chain switching.

[0320] Also, in the frame exchange sequence immediately after the RF chain change, a station attempting to transmit to a single radio multi-link device can determine the format of the PPDU to be transmitted first (initial) in the frame exchange sequence based on the time taken for the RF chain change of the single radio multi-link device. Also, in the first frame exchange sequence starting after the RF chain change, a station attempting to transmit to a single radio multi-link device can determine the length of the padding used for PPDU transmission to be transmitted first (initial) in the frame exchange sequence based on the time taken for the RF chain change of the single radio multi-link device. At this time, the padding may be either physical layer padding or MAC layer padding. Specifically, the station can set the padding of the packet transmitted to a single radio multi-link device with a relatively short RF chain change time shorter than the padding of the packet transmitted to a single radio multi-link device with a relatively long RF chain change time.

[0321] FIG. 39 shows a single radio multi-link device according to an embodiment of the present invention transmitting a PPDU using MIMO.

[0322] A station attempting to perform MIMO transmission to a single radio multi-link device can start RTS frame / CTS frame exchange at the start of transmission after changing the RF chain. At this time, the RTS frame can secure the time for the RF chain to change and then protect the frame exchange. If it is determined that the RF chain change has not been completed even after the RTS frame / CTS frame exchange, the station attempting to perform MIMO transmission to the single radio multi-link device does not have to perform MIMO transmission. At this time, the station attempting to perform MIMO transmission to the single radio multi-link device can perform transmission using a single spatial stream.

[0323] When a single-radio multi-link device transmits or receives on any one link, the single-radio multi-link device cannot transmit or receive on a link different from that link. Therefore, when a single-radio multi-link device transmits or receives on any one link, a station operating on a link different from that link can be regarded as being in a blind state. Therefore, when a single-radio multi-link device transmits or receives on any one link, an AP attempting to transmit to the single-radio multi-link device does not have to transmit to a station operating on a link different from that link. At this time, the AP attempting to transmit to the single-radio multi-link device may interrupt the transmission being performed to a station operating on a link different from that link.

[0324] When a single-radio multi-link device transmits or receives on any one link, an AP that has transmitted to or interrupted transmission to a station of the single-radio multi-link device does not have to increase the CW of the backoff procedure used for channel access for transmission. Then, when the single-radio multi-link device attempts to transmit to the station again, it can take a backoff counter within the previously used CW. Thus, a station that has transmitted to or interrupted transmission to a station of the single-radio multi-link device does not have to increase the CW of the backoff procedure used for channel access for transmission when it meets a specified condition in advance. The specified condition may be that, according to the above-described embodiment, the station determines that any one of the stations of the single multi-link device has transmitted or received. Specifically, when the station determines that a station that has transmitted a PPDU received by another station of the multi-link device including the station is included in the single multi-link device, the station can determine that any one of the stations of the single multi-link device has transmitted. At this time, the station can determine the station that transmits the PPDU based on the identifier of the station that transmits the PPDU indicated by the signaling field of the PPDU. At this time, the station can determine which station of the single multi-link device the STA-ID in the User field of the HE PPDU indicates. Also, the station can determine which station of the single multi-link device the STA-ID in the User field of the EHT PPDU indicates. Also, the station can determine which station of the single multi-link device the TA field of the MAC frame included in the PPDU indicates. The MAC frame may be any one of an MSDU, an MPDU, and an A-MPDU. This may be similar to the embodiment applied to the transmission to the non-STR multi-link device described in FIG. 19 above. Also, when it is a channel access procedure to which EDCA is applied, the above-described CW can indicate the CW of the AC used for channel access.

[0325] Also, when the transmission to another station of the single radio multi-link device fails due to the transmission or reception of any one station of the single radio multi-link device, the station that has performed the transmission to another station of the single radio multi-link device does not have to increase the Retry counter. At this time, the Retry counter can include at least one of the Long retry counter and the Short retry counter.

[0326] Also, when a station transmits a MU PPDU to a plurality of stations including the stations of the single radio multi-link device, the embodiments regarding maintaining the size of the aforementioned CW may not be applicable. Specifically, when a station transmits a MU PPDU to a plurality of stations including the stations of the single radio multi-link device but fails to receive a response from any of the plurality of stations, the station that has transmitted the MU PPDU can increase the size of the CW. At this time, the station that has transmitted the MU PPDU can increase the CW value to the next larger value among the values that the CW value can have. When the CW value is the maximum value, the station that has transmitted the MU PPDU may keep the CW value the same.

[0327] In the embodiment of FIG. 39, the single radio multi-link device includes a first station STA1 operating on a first link Link1 and a second station STA2 operating on a second link Link2. When the station attempts to transmit using MIMO on the first link Link1 and successfully accesses the channel on the first link Link1, the first station STA1 transmits an RTS frame. The first station STA1 transmits a CTS frame as a response to the RTS frame. After the RF chain change of the single radio multi-link device is completed, a PPDU is received using 2x2 MIMO. After the first station STA1 receives the PPDU, the single radio multi-link device changes the RF chain, and the second station STA2 starts channel access on the second link Link2 after waiting for NAVSyncdelay from the time the RF chain is changed.

[0328] <NDP (null data packet) transmission procedure for a single radio multi-link device>

[0329] As described above, the single radio multi-link device can perform MIMO by changing the link on which the RF chain operates. When the link on which the RF chain operates is changed, learning of the RF characteristics on the changed link is required before MIMO communication.

[0330] Since learning of the channel characteristics of the RF chain has not been performed, closed-loop beamforming technology may not be available. Therefore, channel estimation may be required. Specifically, a single radio multi-link device can perform channel estimation using the NDP sounding protocol. In an explicit NDP sounding sequence, the beamformer transmits the NDP after transmitting the NDPA (NDP announcement). At this time, the interval between the NDPA and the NDP is the SIFS. When the station that has received the NDPA is instructed by the STA User Info list field of the NDPA, the station transmits the CSI (channel state information) feedback measured when receiving the NDP to the beamformer after receiving the NDP.

[0331] At this time, before the NDP sounding protocol is performed, RTS frame / CTS frame exchange may be performed. Specifically, a single radio multi-link device and a station attempting to start the NDP sounding protocol can transmit an RTS frame before transmitting an NDPA frame. For the convenience of explanation, a single radio multi-link device and a station attempting to start the NDP sounding protocol are referred to as the NDP sounding protocol start station. According to the foregoing embodiments, the NDP sounding protocol start station can protect the NDP sounding sequence. Also, thereby, the time taken for RF chain switching can be ensured. Also, the NDP sounding protocol start station can perform a MU-RTS frame / CTS frame exchange procedure instead of the RTS frame / CTS frame exchange procedure. Also, the NDP sounding protocol start station can perform an exchange of a trigger frame different from the MU-RTS frame and a response to the trigger frame instead of the MU-RTS frame / CTS frame exchange procedure. Also, in such an embodiment, the NDP sounding protocol start station can transmit a MU-RTS frame, a trigger frame of a type different from the MU-RTS frame, and an NDPA frame in a specified PPDU format. Specifically, the specified PPDU format may be at least one of a non-HT format or an HT format. Also, the NDP sounding protocol start station can transmit a MU-RTS frame, a trigger frame of a type different from the MU-RTS frame, and an NDPA frame at a data rate equal to or lower than a specified data rate.

[0332] The NDP sounding protocol starting station can adjust the length of the NDP sounding sequence based on the time required for RF chain changes. When the NDP sounding protocol starting station exchanges an NDP sounding sequence with a single radio multi-link device having a relatively short RF chain change time, compared to when it exchanges an NDP sounding sequence with a single radio multi-link device having a relatively long RF chain change time, a longer NDP sounding sequence can be used. At this time, the NDP sounding protocol starting station can adjust the length of the NDP sounding sequence by omitting a part of the NDP sounding sequence. Also, the NDP sounding protocol starting station can adjust the length of the NDP sounding sequence by adjusting the padding of the frames exchanged in the NDP sounding sequence. Also, the NDP sounding protocol starting station can adjust the length of the NDP sounding sequence by transmitting additional frames in the NDP sounding sequence. At this time, the padding may be physical layer padding. Also, the padding may be MAC layer padding. Therefore, in the embodiments described below, the padding may be N physical layer padding or MAC layer padding.

[0333] Also, when the NDP sounding protocol starting station performs the NDP sounding protocol with a plurality of single radio multi-link devices, the NDP sounding protocol starting station can adjust the length of the NDP sounding sequence based on the longest time required for RF chain changes among the plurality of single radio multi-link devices. The method for adjusting the length of the NDP sounding sequence will be described with reference to FIGS. 40 to 42.

[0334] FIG. 40 shows that a station and a single radio multi-link device according to an embodiment of the present invention perform an NDP sounding process.

[0335] As described above, the NDP sounding protocol starting station can adjust the length of the NDP sounding sequence by adjusting the padding of the frames exchanged in the NDP sounding sequence. When the NDP sounding sequence includes RTS frame / CTS frame exchange, the NDP sounding protocol starting station can insert padding into the RTS frame to adjust the length of the NDP sounding sequence. Specifically, when the NDP sounding protocol starting station determines that the RF chain change is not completed even after the RTS frame / CTS frame exchange, the NDP sounding protocol starting station can insert padding into the RTS frame.

[0336] In yet another specific embodiment, when the NDP sounding protocol starting station determines that the RF chain change is not completed even after the RTS frame / CTS frame exchange, the NDP sounding protocol starting station can transmit a MU-RTS frame instead of the RTS frame. At this time, the NDP sounding protocol starting station can insert padding into the MU-RTS frame.

[0337] In the above-described embodiment, the NDP sounding protocol start station can determine whether the RF chain change is completed even after the RTS frame / CTS frame exchange based on whether the RF chain change is completed after the time obtained by adding 2 X SIFS to the length of the CTS frame has elapsed since the reception completion time of the RTS frame of the single radio multi-link device. Also, the RTS reception completion time may be one of the transmission start time of the PPDU including the RTS frame, the time when the physical layer header of the PPDU including the RTS frame is transmitted, the transmission completion time of the PPDU including the RTS frame, and the transmission completion time of the RTS frame or the A-MPDU including the RTS frame. Further, in the above embodiment in which the MU-RTS frame is used instead of the RTS frame, the MU-RTS frame may be applied instead of the RTS frame. FIG. 40(a) shows that the NDPA frame, the NDP frame, and the feedback frame are exchanged after the RTS frame / CTS frame exchange according to the above-described embodiment. At this time, the NDP sounding protocol start station performs MIMO transmission based on the received feedback frame.

[0338] Also, the NDP sounding protocol starting station may omit the transmission of NDPA frames in the NDP sounding sequence. At this time, the NDP sounding protocol starting station and the single radio multi-link device can negotiate to perform the NDP sounding protocol without transmitting NDPA frames. Therefore, the station of the single radio multi-link device can wait for NDP reception without receiving NAPA frames. Specifically, the station of the single radio multi-link device can signal, using the Capability element, that it can receive NDP without receiving NDPA frames. In a specific embodiment, the station of the single radio multi-link device can set the NDPA compression support subfield of the Capability element to 1 to signal that it can receive NDP frames without receiving NDPA frames. Also, the station of the radio multi-link device can set the NDPA compression support subfield of the Capability element to 0 to signal that it cannot receive NDP frames without receiving NDPA frames. The NDP sounding protocol starting station can determine whether to omit the transmission of NDPA frames. At this time, the NDP sounding protocol starting station can omit the transmission of NDPA frames in the NDP sounding sequence for the single radio multi-link device that has received that it can receive NDP frames without receiving NDPA frames. Also, the embodiment of omitting the transmission of NDPA frames from the NDP sounding sequence in this way is applicable only when the NDP sounding protocol starting station transmits NDP to one station. At this time, when the NDP sounding protocol starting station transmits NDP to multiple stations, the transmission of NDPA frames cannot be omitted. FIG. 40(b) shows that, according to the above-described embodiment, NDP frames and feedback frames are exchanged without NDPA frames after the RTS frame / CTS frame exchange.At this time, the NDP sounding protocol start station performs MIMO transmission based on the received feedback frame.

[0339] In the above-described embodiments, since the control frame exchange is included before the NDPA frame, the NDP frame, and the feedback frame are exchanged in the NDP sounding sequence, excessive overhead may occur. Also, excessive overhead may occur even if the NDPA transmission is omitted. An implicit feedback beamforming sounding sequence may be performed to reduce the excessive overhead. This will be described with reference to FIG. 41.

[0340] FIG. 41 shows that a station and a single radio multi-link device according to an embodiment of the present invention perform a feedback beamforming sounding sequence.

[0341] The frame exchange start station that starts the frame exchange can also omit the NDP frame transmission and the feedback frame transmission in addition to the NDPA frame transmission. At this time, however, the frame exchange start station can measure the channel state while receiving a PPDU including a response to a control frame, for example, an RTS frame, a MU-RTS frame, or a trigger frame of a type different from the MU-RTS frame. The frame exchange start station can obtain a steering matrix to be used for MIMO transmission based on the measured channel state. Specifically, the frame exchange start station can obtain a steering matrix based on the measured channel state. The frame exchange start station can perform MIMO transmission using the obtained steering matrix.

[0342] In such an embodiment, the frame exchange start station can insert padding into the control frame based on the time taken for the RF chain change, as described above. Specifically, the frame exchange start station can insert padding into the control frame based on a value obtained by subtracting the SIFS from the time taken for the RF chain change.

[0343] Also, the frame exchange start station can transmit a QoS data frame instead of the control frame. At this time, the single radio multi-link device can transmit an Ack frame or a Block Ack frame as a response to the QoS data frame.

[0344] Also, in the above-described embodiment, the frame exchange start station can set the TRQ (training request) bit of the control frame and the QoS data frame to 1.

[0345] Also, in the above-described embodiment, even for a control frame that can set a plurality of stations as recipients, such as a MU-RTS frame, one station may be set as the recipient of the control frame.

[0346] In the embodiment of FIG. 41(a), the frame exchange start station sets the TRQ field to 1 and transmits a MU-RTS frame. The frame exchange start station transmits a PPDU including the MU-RTS frame, and the frame exchange start station measures the channel state while receiving a PPDU including a CTS frame that is a response to the MU-RTS frame. The frame exchange start station obtains a steering matrix based on the acquired channel state, and performs MIMO transmission using the acquired steering matrix. In the embodiment of FIG. 41(b), the frame exchange start station transmits an RTS frame instead of the MU-RTS frame. This may be the case where the time required for RF chain change is shorter than SIFS. Thereafter, the frame exchange start station and the station of the single radio multi-link device operate in the same manner as in the embodiment of FIG. 41(a). However, in the embodiment of FIG. 41(b), the station of the single radio multi-link device transmits a BA frame in SISO (single input single output).

[0347] In the frame exchange sequence performed immediately after the RF chain change, the last frame exchange may be performed in SISO (single input single output) (1x1). Specifically, the station of the single radio multi-link device can transmit the last frame of the frame exchange sequence performed immediately after the RF chain change in SISO (1x1). Also, when there are no frames for MIMO transmission or reception remaining in the frame exchange sequence performed immediately after changing the RF chain, the station of the single radio multi-link device can change the RF chain. Specifically, the station of the single radio multi-link device can start changing the RF chain before transmitting the last frame of the frame exchange sequence performed immediately after changing the RF chain.

[0348] FIG. 42 shows that the station and the single radio multi-link device according to the embodiment of the present invention perform an NDP sounding process.

[0349] The NDP sounding protocol start station can determine the MIMO transmission start time based on the time required for the RF chain change of a single radio multi-link device. Specifically, the NDP sounding protocol start station can delay the MIMO transmission start time until the RF chain change of the single radio multi-link device is completed. For example, when the RF chain change is not completed during the exchange of a response frame for a control frame / control frame, such as an RTS frame / CTS frame or a MU-RTS frame / CTS frame, the NDP sounding protocol start station can delay the MIMO transmission start time. Specifically, the NDP sounding protocol start station can transmit the first PPDU transmitted after the response to the control frame / control frame using SISO.

[0350] Thus, when the RF chain change is not completed, the MIMO transmission of the NDP sounding protocol start station may not be permitted. Also, the above-mentioned explicit and implicit NDP sounding protocols may not be permitted before the RF chain change is completed.

[0351] In addition, the NDP sounding protocol start station can determine whether the RF chain change is completed during the exchange of the response frame for the control frame / control frame based on the time required for the RF chain change indicated by the Capability element transmitted by the single radio multi-link device.

[0352] When a single-radio multi-link device performs transmission using SISO, a station that performs a frame exchange sequence on a link that supports the use of multiple RF chains can transmit the remaining frames in the frame exchange sequence using SISO. For the sake of convenience of explanation, in the description related to this embodiment, a station that performs a frame exchange sequence on a link that supports the use of multiple RF chains is referred to as a frame exchange sequence execution station. That is, when a single-radio multi-link device performs transmission using SISO, it is not necessary to allow the frame exchange sequence execution station to transmit the remaining frames in the frame exchange sequence using MIMO. Specifically, when a single-radio multi-link device transmits an ACK for the transmission of the frame exchange sequence execution station using SISO, the frame exchange sequence execution station can transmit the remaining frames in the frame exchange sequence using SISO. At this time, the ACK can include an ACK frame and a BA frame. Therefore, when a single-radio multi-link device transmits an ACK for the transmission of the frame exchange sequence execution station using SISO, the frame exchange sequence execution station cannot transmit the remaining frames in the frame exchange sequence using MIMO.

[0353] In the embodiments of FIGS. 42(a) and 42(b), the RF chain change of the single-radio multi-link device was not completed during the RTS frame and CTS frame exchange. Therefore, in the embodiment of FIG. 42(a), SISO is also used until the PPDU and BA frame transmissions after the RTS frame and CTS frame exchange. When the NDP sounding protocol start station receives an ACK frame, it determines that the RF chain change has been completed. At this time, the NDP sounding protocol start station starts the sounding protocol using MIMO (2x2).

[0354] Also, in the embodiment of FIG. 42(b), SISO is used even after the RTS frame and CTS frame are exchanged until the PPDU is transmitted. Since the RF chain change is completed after the PPDU is received, the first station STA1 of the single radio multi-link device transmits the BA frame using MIMO (2x2). Since the first station STA1 of the single radio multi-link device transmits the BA frame using MIMO (2x2), the NDP sounding protocol start station determines that MIMO (2x2) transmission is allowed. Therefore, after receiving the BA frame transmitted using MIMO (2x2), the NDP sounding protocol start station transmits the PPDU using MIMO (2x2).

[0355] Although the present invention has been described by taking up wireless LAN communication as described above, the present invention is not limited to this, and can be equally applied to other communication systems such as cellular communication. Also, although the method, apparatus, and system of the present invention have been described in relation to specific embodiments, some or all of the components and operations of the present invention can be implemented by a computer system having a general-purpose hardware architecture.

[0356] 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 only one embodiment. Note that the features, structures, effects, etc. exemplified in each embodiment can be combined or modified for other embodiments by those having ordinary knowledge in the field to which the embodiment belongs. Therefore, the content related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

[0357] Although the embodiments have been mainly described above, these are merely illustrative and do not limit the present invention. Those having ordinary knowledge in the field to which the present invention pertains will understand that various modifications and applications not exemplified above are possible without departing from the essential characteristics of this embodiment. For example, each component specifically shown in the embodiment can be modified. Also, differences related to such modifications and applications should be interpreted as being included in the scope of the present invention defined by the appended claims.

Explanation of Signs

[0358] 100 Station 110 Processor 120 Communication Unit 140 User Interface Unit 140 User Interface 150 Display Unit 160 Memory 210 Processor 220 Communication Unit 260 Memory 300 Server

Claims

Claim 1: A station communicating with a single radio multi-link device, the single radio multi-link device including a plurality of stations each operating on a respective one of a plurality of links and operating in a pre-specified operating mode, wherein when the single radio multi-link device operates, the single radio multi-link device does not assist in transmitting or receiving for one of the plurality of stations on one of the plurality of links while another station among the plurality of stations performs frame exchange on another one of the plurality of links, the station comprising: a transceiver; and a processor, wherein the processor is configured to: not transmit to a second station of the single radio multi-link device during a first pre-specified time interval starting from when a frame exchange sequence of a first station of the single radio multi-link device is not only in progress but also completed, and be configured to transmit a control frame to the second station of the single radio multi-link device after the first pre-specified time interval, wherein completion of the frame exchange sequence is determined based on reception or transmission of a last frame of the frame exchange sequence, wherein the first pre-specified time interval is applied based on a radio frequency (RF) chain change time of the single radio multi-link device, wherein the RF chain change time is a time interval including a delay required to start a monitoring operation of the RF chain after the change of the RF chain. A station. Claim 2: The station according to claim 1, wherein the processor transmits the control frame in a pre-specified physical layer protocol data unit (PPDU) format. Claim 3: The station according to claim 2, wherein the pre-specified PPDU format is a non-HT format. Claim 4: The station according to claim 1, wherein the processor transmits the control frame at a data rate below a pre-specified data rate. **Claim 5**: The station according to claim 1, wherein when the single radio multi-link device supports the use of a plurality of RF chains in a first link and does not support the use of RF chains in a second link, the last frame exchange in the frame exchange sequence performed in the first link is performed using SISO (single input single output) (1x1). **Claim 6**: A single radio multi-link device including a plurality of stations each operating on a plurality of links, wherein when the single radio multi-link device operates in a pre-specified operation mode, the single radio multi-link device does not support the transmission or reception of one of the plurality of stations on one of the plurality of links while another station among the plurality of stations performs frame exchange on another link of the plurality of links, a transceiver; and including a processor, wherein the processor delays channel access for a pre-specified time interval before performing channel access on the first link when the link on which the RF chain of the single radio multi-link device operates is changed from a first link to a second link and the link on which the RF chain operates is changed back from the second link to the first link, is configured to receive a control frame, wherein the pre-specified time interval is applied based on the radio frequency (RF) chain change time of the single radio multi-link device, wherein the RF chain change time is a time interval including a delay required to start a monitoring operation of the RF chain after the change of the RF chain, a single radio multi-link device. **Claim 7**: The single radio multi-link device according to claim 6, wherein the control frame is transmitted in a pre-specified PPDU (physical layer protocol data unit) format. **Claim 8**: The single radio multi-link device according to claim 7, wherein the pre-specified PPDU format is a non-HT format. **Claim 9**: The single radio multi-link device according to claim 6, wherein the control frame is transmitted at a data rate below a pre-specified data rate.

10. When the single radio multi-link device supports the use of multiple RF chains in the first link and does not support the use of RF chains in the second link, the processor transmits the last frame in the frame exchange sequence performed in the first link using SISO (single input single output) (1x1). The single radio multi-link device according to Claim 6.

11. An operating method of a station communicating with a single radio multi-link device including multiple stations operating on multiple links respectively. When the single radio multi-link device operates in a pre-specified operating mode, the single radio multi-link device does not assist in the transmission or reception of one of the multiple stations in one of the multiple links while other stations among the multiple stations perform frame exchange in other links of the multiple links. The method includes: Not only performing the frame exchange sequence of the first station of the single radio multi-link device, but also not transmitting to the second station of the single radio multi-link device even in a pre-specified first time interval from when the frame exchange sequence of the first station is completed; After the pre-specified first time interval, transmitting a control frame to the second station of the single radio multi-link device; The completion of the frame exchange sequence is determined based on the reception or transmission of the last frame of the frame exchange sequence; The pre-specified first time interval is applied based on the RF chain change time of the single radio multi-link device; The RF chain change time is a time interval including the delay required to start the monitoring operation of the RF chain after the change of the RF chain. Method.

12. The step of transmitting the control frame includes transmitting the control frame in a pre-specified PPDU (physical layer protocol data unit) format. The method according to Claim 11.

13. The pre-specified PPDU format is a non-HT format. The method according to Claim 12.

14. The method according to claim 11, wherein the step of transmitting the control frame includes transmitting the control frame at a data rate equal to or lower than a pre-specified data rate.

15. The method according to claim 11, wherein, when the single radio multi-link device supports the use of a plurality of RF chains in a first link and does not support the use of RF chains in a second link, the last frame exchange in the frame exchange sequence performed in the first link is performed using SISO (single input single output) (1x1).

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