Method and apparatus for supporting STR in multi-link wireless LAN

Abstract

Disclosed are a method and an apparatus for supporting STR in a wireless LAN of multiple links. An operation method of a first communication node comprises the steps of: transmitting a first frame to a second communication node through a first link of a plurality of links; receiving a response frame for the first frame from the second communication node over the first link; checking a channel occupancy time in a second link of the plurality of links based on the first information included in the response frame; and performing a listening operation in a preset section after the end of the channel occupation time in the second link.

Description

[0001] This application is a divisional application of a patent application with an application date of January 6, 2021, an application number of 202180008523.9, and an invention name of “Method and device for STR in a wireless LAN supporting multi-links”. Technical Field

[0002] The present disclosure relates to a communication technology in a wireless LAN, and more particularly, to a communication technology for simultaneous transmission and reception (STR) in a wireless LAN supporting multi-links. Background Art

[0003] Recently, with the popularity of mobile devices, wireless local area network (LAN) technology that can provide fast wireless communication services to mobile devices has attracted attention. Wireless LAN technology can be a technology that supports mobile devices (e.g., smart phones, smart tablets, laptops, portable multimedia players, embedded devices, etc.) to wirelessly access the Internet based on wireless communication technology.

[0004] Wireless LAN technology is being standardized in the Institute of Electrical and Electronics Engineers (IEEE) 802.11. The initial version of the IEEE 802.11 standard can support communication speeds of 1 to 2 megabits per second (Mbps). Thereafter, standardization is carried out in the direction of improving the initial version. The IEEE 802.11a standard can support communication speeds of up to 54 Mbps using orthogonal frequency division multiplexing (OFDM) technology in the 5 GHz band. The IEEE 802.11b standard can support communication speeds of up to 11 Mbps using direct sequence spread spectrum (DSSS) technology in the 2.4 GHz band.

[0005] Due to the demand for improving communication speed, the IEEE 802.11n standard was developed to support high throughput (HT). OFDM technology can be supported in the IEEE 802.11n standard, and the operating frequency band of the IEEE 802.11n can be a 2.4 GHz band and a 5 GHz band. The IEEE 802.11n standard can provide an improved maximum communication speed by using channel bandwidth extension technology and multiple input multiple output (MIMO) technology. When four spatial streams and a 40 MHz bandwidth are used in the IEEE 802.11n standard, the maximum communication speed can be 600 Mbps.

[0006] As applications utilizing the above-mentioned wireless LAN technology diversify, there is a demand for wireless LAN technology that supports higher throughput. Therefore, in the IEEE 802.11ac standard that supports very high throughput (VHT), the bandwidth used has been expanded (for example, up to 160 MHz or 80+80 MHz), and the number of supportable spatial streams has been increased. The IEEE 802.11ac standard can provide communication speeds of 1 Gigabit per second (Gbps) or higher. Downlink communication for multiple base stations can be supported by using the MIMO technology in the IEEE 802.11ac standard.

[0007] As the demand for wireless LAN technology further increases, the IEEE 802.11ax standard was developed to improve spectrum efficiency in dense environments. The IEEE 802.11ax standard may support multi-user (MU) orthogonal frequency division multiple access (OFDMA) technology, and may perform uplink communication using MU MIMO / OFDMA technology.

[0008] With the emergence of applications requiring higher throughput and applications requiring real-time transmission, the IEEE 802.11be standard has been developed to support extremely high throughput (EHT). In the IEEE 802.11be standard, the target communication speed may be 30 Gbps, and operations for reducing frame transmission delays may be supported. In addition, the IEEE 802.11be standard may support extended bandwidth (e.g., 320 MHz bandwidth), multi-link operation using multiple frequency bands, aggregation operation, transmission operation of multiple access points (APs), efficient retransmission operation (e.g., hybrid automatic repeat request (HARQ) operation), etc.

[0009] However, it is necessary to define detailed operations regarding the multilink operation. Specifically, when frequency bands (eg, links, channels) performing the multilink operation are adjacent, a simultaneous transmission and reception (STR) operation using the multilink may not be performed due to interference between the adjacent frequency bands.

[0010] Furthermore, the prior art of the present disclosure has been described to enhance understanding of the background of the present disclosure and may include contents beyond the prior art that is known to one of ordinary skill in the art to which the present disclosure belongs. Summary of the invention

[0011] Technical issues

[0012] An object of the present disclosure to solve the above-mentioned problems is to provide a method and apparatus for supporting simultaneous transmission and reception (STR) in a wireless LAN system supporting multi-links.

[0013] Technical Solution

[0014] According to the first exemplary embodiment of the present disclosure, an operating method of a first device for achieving the purpose may include: sending a first frame using a first link in a multi-link; identifying a channel state in a second link in the multi-link at the end of sending the first frame; and when the channel state in the second link is an idle state, performing a carrier sensing operation in a first time period according to a first timer, wherein a sending operation in the first link and a receiving operation in the second link are not performed at the same time.

[0015] The transmission end time point of the first frame may be identified by a value of a duration field included in a header of the first frame.

[0016] When the first frame is transmitted, the virtual carrier sensing operation in the second link may not be performed.

[0017] The operation method may further include: when the channel state in the second link is a busy state, performing a carrier sensing operation in a second time period according to a second timer after the busy state ends.

[0018] Each of the first time period and the second time period may be longer than a short interframe space (SIFS), a point coordination function (PCF) interframe space (PIFS), a distributed interframe space (DIFS), or an arbitration interframe space (AIFS).

[0019] The operation method may further include: receiving a second frame including transmission time point information from a second device through one of the multiple links, wherein the transmission time point information indicates a time point at which transmission in the second link is possible.

[0020] The operation method may further include sending a third frame using the second link at a time point indicated by the transmission time point information.

[0021] According to the first exemplary embodiment of the present disclosure, a first device for achieving the purpose may include a processor; a first node, which performs communication in a first link in a multi-link under the control of the processor; a second node, which performs communication in a second link in the multi-link under the control of the processor; a memory, which electronically communicates with the processor; and instructions, which are stored in the memory, wherein, when executed by the processor, the instructions cause the first device to perform: using the first link in the multi-link to send a first frame; identifying a channel state in a second link in the multi-link at the end of sending the first frame; and when the channel state in the second link is an idle state, performing a carrier sensing operation in a first time period according to a first timer, wherein the sending operation in the first link and the receiving operation in the second link are not performed at the same time.

[0022] The transmission end time point of the first frame may be identified by a value of a duration field included in a header of the first frame.

[0023] When the first frame is transmitted, the virtual carrier sensing operation in the second link may not be performed.

[0024] The instructions may further cause the first device to execute: when the channel state in the second link is a busy state, performing a carrier sensing operation in a second time period according to a second timer after the busy state ends.

[0025] Each of the first time period and the second time period may be longer than a short interframe space (SIFS), a point coordination function (PCF) interframe space (PIFS), a distributed interframe space (DIFS), or an arbitration interframe space (AIFS).

[0026] The instructions may further cause the first device to execute: receiving a second frame including transmission time point information from the second device through one of the multiple links, wherein the transmission time point information indicates a time point at which transmission in the second link is feasible.

[0027] The instructions may further cause the first device to execute: transmitting the third frame using the second link at a time point indicated by the transmission time point information.

[0028] Beneficial Effects

[0029] When links (e.g., frequency bands, channels) are adjacent to each other in a WLAN system supporting multiple links, a simultaneous transmission and reception (STR) operation may not be performed due to interference. For example, when a transmission operation is performed in link 1, a virtual sensing operation based on a preamble and / or an operation for setting a network allocation vector (NAV) based on a duration field included in a frame may not be performed in link 2 adjacent to link 1.

[0030] In order to solve the above problem, the base station may perform a channel access operation after an extended interframe space (EIFS) from the end time point of the busy state in link 2. Alternatively, the base station may receive information about a channel use time (e.g., a frequency band use time, a link use time) of link 2 from an access point or another base station in link 1. In this case, the base station may perform a channel access operation in link 2 after an arbitration interframe space (AIFS) from the end time point of the channel use time.

[0031] Therefore, the fairness of the transmission operation using the existing link can be maintained in the WLAN supporting multi-link, and the time inefficiency of the channel access operation with respect to the multi-link operation can be minimized. Therefore, the communication performance in the WLAN system can be improved. The exemplary embodiments according to the present disclosure can be applied to various communication systems (e.g., WLAN system, cellular communication system). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1is a block diagram showing a first exemplary embodiment of a communication node constituting a wireless LAN system.

[0033] Figure 2 is a conceptual diagram showing a first exemplary embodiment of multi-links configured between MLDs.

[0034] Figure 3 is a sequence diagram showing a first exemplary embodiment of a negotiation procedure for a multi-link operation in a wireless LAN system.

[0035] Figure 4 is a sequence diagram showing a first exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0036] Figure 5 is a sequence diagram showing a second exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0037] Figure 6a is a sequence diagram showing a third exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0038] Figure 6b is a sequence diagram showing a fourth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0039] Figure 7a is a sequence diagram showing a fifth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0040] Figure 7b is a sequence diagram showing a sixth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0041] Figure 8 is a sequence diagram showing a seventh exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0042] Figure 9a is a sequence diagram showing an eighth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0043] Figure 9b is a timing chart illustrating a ninth exemplary embodiment of a communication method using multi-links in a wireless LAN system.

[0044] Fig.10a is a sequence diagram showing a tenth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0045] Fig.10b is a timing chart illustrating an eleventh exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0046] Fig.11 is a block diagram showing a first exemplary embodiment of a BA frame including channel use time information in a wireless LAN system. DETAILED DESCRIPTION

[0047] Although the present disclosure is susceptible to various modifications and alternative forms, specific embodiments are shown and described in detail by way of example in the accompanying drawings. However, it should be understood that this description is not intended to limit the present disclosure to specific embodiments, but on the contrary, the present disclosure will cover all modifications, equivalents and substitutes falling within the spirit and scope of the present disclosure.

[0048] Although the terms "first", "second", etc. may be used herein with reference to various elements, these elements should not be construed as being limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and a second element may be referred to as a first element, without departing from the scope of the present disclosure. The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0049] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intermediate elements. On the contrary, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intermediate elements.

[0050] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present disclosure. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. It will be further understood that the terms "include", "comprise", "include" and / or "comprises" when used herein specify the presence of stated features, integers, steps, operations, elements, parts and / or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or combinations thereof.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such in this article.

[0052] Hereinafter, preferred exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In describing the present disclosure, in order to facilitate overall understanding, the same reference numerals refer to the same elements throughout the description of the accompanying drawings, and their repeated description will be omitted.

[0053] Hereinafter, a wireless communication network to which an exemplary embodiment according to the present disclosure is applied will be described. The wireless communication network to which an exemplary embodiment according to the present disclosure is applied is not limited to the contents described below, and the exemplary embodiment according to the present disclosure can be applied to various wireless communication networks.

[0054] Figure 1 is a block diagram showing a first exemplary embodiment of a communication node constituting a wireless LAN system.

[0055] refer to Figure 1 , the communication node 100 may be an access point, a base station, an access point (AP) multi-link device (MLD), or a non-AP MLD. An access point may refer to an AP, and a base station may refer to a STA or a non-AP STA. An operating channel width supported by an access point may be 20 megahertz (MHz), 80 MHz, 160 MHz, etc. An operating channel width supported by a base station may be 20 MHz, 80 MHz, etc.

[0056] The communication node 100 may include at least one processor 110 connected to a network to perform communication, a memory 120, and a transceiver 130. The transceiver 130 may be referred to as a transceiver device, a radio frequency (RF) unit, an RF module, etc. In addition, the communication node 100 may further include an input interface device 140, an output interface device 150, a storage device 160, etc. The components included in the communication node 100 may be connected to communicate with each other through a bus 170.

[0057] However, the respective components included in the communication node 100 may be connected through a separate interface or a separate bus centered around the processor 110 instead of the common bus 170. For example, the processor 110 may be connected to at least one of the memory 120, the transceiver 130, the input interface device 140, the output interface device 150, and the storage device 160 through a dedicated interface.

[0058] The processor 110 may execute at least one instruction stored in at least one of the memory 120 and the storage device 160. The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which a method according to an exemplary embodiment of the present invention is executed. Each of the memory 120 and the storage device 160 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 120 may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0059] Figure 2 is a conceptual diagram showing a first exemplary embodiment of multi-links configured between MLDs.

[0060] refer to Figure 2 , the MLD may have one media access control (MAC) address. In an exemplary embodiment, the MLD may refer to an APMLD and / or a non-AP MLD. The MAC address of the MLD may be used in a multi-link establishment process between a non-AP MLD and an AP MLD. The MAC address of the AP MLD may be different from the MAC address of the non-AP MLD. The access point(s) belonging to the AP MLD may have different MAC addresses, and the base station(s) belonging to the non-AP MLD may have different MAC addresses. Each of the access points with different MAC addresses within the AP MLD may be responsible for each link and may be used as an independent AP. Similarly, each base station with different MAC addresses within the non-AP MLD may be responsible for each link and may be used as an independent STA. The non-AP MLD may also be referred to as a STAMLD. The MLD may support simultaneous transmission and reception (STR) operations. In this case, the MLD may perform a transmission operation in link 1 and a reception operation in link 2. An MLD supporting STR operations may be referred to as an STR MLD (e.g., STR AP MLD, STR non-AP MLD). In an exemplary embodiment, a link may refer to a channel or a frequency band. A device that does not support STR operation may be referred to as a non-STR (NSTR) AP MLD or an NSTR non-AP MLD (or NSTR STA MLD).

[0061] MLD can send and receive frames in multiple links by using a non-contiguous bandwidth extension scheme (e.g., 80MHz+80MHz). Multi-link operation may include multi-band transmission. AP MLD may include multiple APs, and the multiple APs may operate in different links. Non-AP MLD may include multiple base stations, and the multiple base stations may operate in different links.

[0062] MLD can perform communication in multiple frequency bands. For example, MLD can use 80MHz bandwidth to perform communication in 2.4GHz frequency band according to a channel extension scheme (e.g., bandwidth extension scheme), and use 160MHz bandwidth to perform communication in 5GHz frequency band according to the channel extension scheme. MLD can use 160MHz bandwidth in 5GHz frequency band and use 160MHz bandwidth in 6GHz frequency band to perform communication. A frequency band (e.g., a channel) used by MLD can be defined as a link. Optionally, multiple links can be configured in a frequency band used by MLD. For example, MLD can configure one link in 2.4GHz frequency band and configure two links in 6GHz frequency band.

[0063] MLD (e.g., AP MLD and / or non-AP MLD) may configure multi-link by performing an access procedure and / or a negotiation procedure for multi-link operation. In this case, the links and / or the number of links to be used among the multi-links may be configured. Non-AP MLD (e.g., base station) may identify information about a frequency band capable of communicating with AP MLD. In the negotiation process for multi-link operation between non-AP MLD and AP MLD, non-AP MLD may be configured to use one or more links among the links supported by AP MLD for multi-link operation. Base stations that do not support multi-link operation (e.g., IEEE 802.11a / b / g / n / ac / ax base stations) may be connected to one or more links among the links supported by AP MLD.

[0064] If the band gap between the multilinks (e.g., the band gap between link 1 and link 2 in the frequency domain) is sufficient, the MLD may perform the STR operation. For example, the MLD may send a physical layer convergence procedure (PLCP) protocol data unit (PPDU) 1 by using link 1 in the multilinks, and may receive PPDU 2 by using link 2 in the multilinks. On the other hand, if the MLD performs the STR operation when the band gap between the multilinks is insufficient, in-device coexistence (IDC) interference (i.e., interference between the multilinks) may occur. Therefore, if the band gap between the multilinks is insufficient, the MLD may not be able to perform the STR operation. That is, the MLD may be an NSTR AP MLD or an NSTR non-AP MLD.

[0065] For example, a multi-link including link 1, link 2, and link 3 may be configured between the AP MLD and the non-AP MLD 1. When the band gap between link 1 and link 3 is sufficient, the AP MLD may perform the STR operation by using link 1 and link 3. That is, the AP MLD may send a frame using link 1 and may receive a frame using link 3. If the band gap between link 1 and link 2 is insufficient, the AP MLD may not be able to perform the STR operation by using link 1 and link 2. If the band gap between link 2 and link 3 is insufficient, the AP MLD may not be able to perform the STR operation by using link 2 and link 3.

[0066] Furthermore, a negotiation process for a multi-link operation may be performed in an access process between a base station and an access point in a wireless LAN system.

[0067] Figure 3 is a sequence diagram showing a first exemplary embodiment of a negotiation procedure for a multi-link operation in a wireless LAN system.

[0068] refer to Figure 3, an access process between a base station and an access point in an infrastructure basic service set (BSS) may include a detection step of detecting an access point, an authentication step between the base station and the detected access point, and an association step between the base station and the authenticated access point.

[0069] In the detection step, the base station may detect one or more access points using a passive scanning scheme or an active scanning scheme. When using the passive scanning scheme, the base station may detect one or more access points by listening to beacon frames transmitted by one or more access points. When using the active scanning scheme, the base station may transmit a probe request frame, and may detect one or more access points by receiving a probe response frame as a response to the probe request frame from one or more access points.

[0070] When one or more access points are detected, the base station may perform an authentication procedure with the detected access points. In this case, the base station may perform an authentication procedure with multiple access points. The authentication algorithm according to the IEEE 802.11 specification may be classified into an open system algorithm that exchanges two authentication frames, a shared key algorithm that exchanges four authentication frames, and the like.

[0071] The base station may complete authentication by transmitting an authentication request frame based on an authentication algorithm according to the IEEE 802.11 specification, and receiving an authentication response frame as a response to the authentication request frame from the access point.

[0072] When the authentication with the access point is completed, the base station may perform an association procedure with the access point. In this case, the base station may select one of the access points with which the authentication procedure is performed by itself, and may perform an association procedure with the selected access point. That is, the base station may transmit an association request frame to the selected access point, and complete the association procedure with the selected access point by receiving an association response frame as a response to the association request frame from the selected access point.

[0073] In addition, multi-link operation can be supported in the WLAN system. MLD may include one or more STAs belonging to the MLD. MLD may be a logical entity. MLD may be classified into AP MLD and non-AP MLD. Each STA belonging to the AP MLD may be an AP, and each STA associated with the non-AP MLD may be a non-AP STA. In order to configure multi-link, a multi-link discovery process, a multi-link establishment process, etc. may be performed. The multi-link discovery process may be performed in a detection step between a base station and an access point. In this case, a multi-link (ML) information element (IE) may be included in a beacon frame, a detection request frame, and / or a detection response frame.

[0074] For example, in order to perform a multi-link operation, information indicating whether a multi-link operation can be performed between an access point (e.g., an AP belonging to an MLD) and a base station (e.g., a non-AP STA belonging to an MLD) and information about available links may be exchanged in a detection step. In a negotiation process (e.g., a multi-link establishment process) for a multi-link operation, an access point and / or a base station may send information about a link to be used for the multi-link operation. A negotiation process for a multi-link operation may be performed in an access process (e.g., an association process) between a base station and an access point, and information elements required for the multi-link operation may be configured and changed through an action frame in the negotiation process.

[0075] In addition, in an access process (e.g., an association step) between a base station and an access point, available links of the access point may be configured, and an identifier (ID) may be assigned to each link. Thereafter, in a negotiation process and / or a change process for a multi-link operation, information indicating whether each link is activated may be transmitted, and the link ID may be used to represent the information.

[0076] Information indicating whether a multi-link operation can be performed may be sent and received during the exchange of capability information elements (e.g., extremely high throughput (EHT) capability information elements) between a base station and an access point. The capability information element may include information about supported frequency bands, information about supported links (e.g., IDs and / or numbers of supported links), information about links capable of STR operation (e.g., information about frequency bands of links, information about intervals between links), etc. In addition, the capability information element may include information indicating links capable of STR operation alone.

[0077] Figure 4 is a sequence diagram showing a first exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0078] refer to Figure 4 , a transmission / reception operation using multiple links (hereinafter referred to as a "multi-link operation") may be independently performed in each link (e.g., link 1 and link 2). This operation may be referred to as an "independent transmission scheme", and the STR operation may be performed based on the independent transmission scheme. Here, link 1 may refer to Figure 2 The link 1 shown in FIG. 1 and the link 2 may refer to Figure 2 2. MLD (eg, AP MLD or STA MLD) may operate in multiple links and may include an AP or STA responsible for each link. STA1 included in STAMLD may be responsible for link 1, and STA2 included in STA MLD may be responsible for link 2.

[0079] When links (e.g., frequency bands or channels used by links) have sufficient spacing, an independent transmission scheme may be used so as not to interfere with base stations using multiple links. In an exemplary embodiment, a base station may refer to an AP, a STA (i.e., a non-AP STA), an APMLD, or a STAMLD (i.e., a non-AP MLD). When an independent transmission scheme is used, a lower layer (e.g., a physical (PHY) layer and / or a MAC layer) may independently perform a channel access operation in each link (e.g., Link 1 and Link 2) to transmit a frame (e.g., a PDU) obtained from a higher layer. When a transmission opportunity (TXOP) is obtained through a channel access operation, the lower layer may transmit a frame in the corresponding TXOP.

[0080] The channel access operation may be a carrier sensing operation performed during an arbitration interframe space (AIFS) according to data included in a frame (e.g., an access category (AC) of data). The carrier sensing operation may also be referred to as a "channel sensing operation." When it is determined through the carrier sensing operation that a channel (e.g., a link) is in a busy state or when the transmission of a data frame is completed, the channel access operation may include a carrier sensing operation during the AIFS and a fallback operation.

[0081] The carrier sensing operation may be classified into a physical carrier sensing (i.e., PHY layer carrier sensing) operation and a virtual carrier sensing operation. The PHY layer carrier sensing operation may be an energy detection (ED) operation for detecting the received power in an operating channel (e.g., an operating link). The virtual carrier sensing operation may include a setting operation based on the value of the length field included in the preamble of a frame (e.g., PPDU or MPDU) received from another base station, and a network allocation vector (NAV) setting operation based on the value of the duration field included in the MAC header and / or the value of the TXOP field included in the preamble of a frame received from another base station. NAV may be an indicator indicating the transmission time of a transmission not initiated by a base station setting NAV (i.e., the transmission time of a transmission initiated by another base station). The transmission time may be independent of the result of PHY layer channel sensing. The NAV setting operation may be an operation to set a period (e.g., a busy period) during which frame transmission is prohibited by using the value of the duration field included in the MAC header of a frame sent by a terminal inside and / or outside a basic service set (BSS). When the virtual carrier sensing is successful and the NAV is set, a period corresponding to the NAV may be determined as a busy period without performing actual carrier sensing.

[0082] When an independent transmission scheme is used, transmission times of frames in links (eg, link 1 and link 2) may not be consistent. Since a channel access operation is performed independently in each link, the links can be used efficiently.

[0083] Figure 5is a sequence diagram showing a second exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0084] refer to Figure 5 , when the interval between links (e.g., frequency bands used by the links) is insufficient, interference may occur between the links. When a transmission operation is performed in one link, a reception operation may not be performed in another link due to interference caused by the transmission operation. For example, a base station (e.g., MLD) may use two links, and link 1 and link 2 may operate in a 5 GHz frequency band. If the interval between link 1 and link 2 is insufficient, when the base station performs a transmission operation in link 1, a reception operation in link 2 may not be feasible. Here, link 1 may refer to Figure 2 The link 1 shown in FIG. 1 and the link 2 may refer to Figure 2 2. MLD (e.g., AP MLD or STAMLD) may operate in multiple links and may include an AP or STA responsible for each link. STA1 included in STA MLD may be responsible for link 1, and STA2 included in STA MLD may be responsible for link 2.

[0085] In order to solve the above problem, the base station may send frames in link 1 and link 2 at the same time. This operation may be referred to as a "simultaneous transmission scheme", and the STR operation may be performed based on the simultaneous transmission scheme. When the simultaneous transmission scheme is used, the transmission start time point and the transmission end time point of the frame sent in the link may be set identically. That is, the lengths of the frames sent simultaneously in the link may be the same. In order to support the simultaneous transmission scheme, when the lengths of the frames to be sent in the link are different, padding bits may be added to a specific frame to match the lengths of the frames.

[0086] When the simultaneous transmission scheme is used and one of the two links (eg, link 2) is busy, the base station may transmit frames in the other link (eg, link 1). Alternatively, the base station may perform a channel access operation (eg, a backoff operation).

[0087] When a simultaneous transmission scheme is used, the receiving base station may receive frames simultaneously in multiple links. Therefore, the frame reception operation can be simplified. The frame transmitted according to the simultaneous transmission scheme may include information about the link used for the simultaneous transmission scheme (e.g., link ID). The information about the link may be configured as a bitmap. In this case, the bitmap may be included in the EHT signal (SIG) field, and the specific bits included in the bitmap may indicate whether the link associated with the specific bit is used for the simultaneous transmission scheme. The EHT SIG field may be a field defined in the IEEE 802.11be specification and may be included in the preamble of a frame (e.g., PPDU). Optionally, the EHT control field included in the frame may indicate information about the link used for the simultaneous transmission scheme.

[0088] Figure 6a is a timing chart showing a third exemplary embodiment of a communication method using multi-link in a wireless LAN system, Figure 6b is a sequence diagram showing a fourth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0089] refer to Figure 6a and Figure 6b , interference between adjacent channels (e.g., adjacent links) may be large. Since the transmission power of a frame sent in one link (e.g., link 1) causes interference when one STA performs a transmission operation (e.g., a transmission operation of PPDU1) in the one link, virtual carrier sensing may not be performed in another link (e.g., link 2). Since virtual carrier sensing is not performed, NAV (e.g., a period in which a channel in which a frame cannot be sent is in a busy state) may not be set. In addition, although a physical carrier sensing operation is feasible, the MLD may not be able to distinguish whether the transmission power is the transmission power of a frame sent in another link or the transmission power sensed on a frame sent by another STA that does not belong to the MLD.

[0090] The above period during which a frame is transmitted in one link while sensing is not correctly performed in another link may be referred to as a blind period. After the transmission of the frame in link 1 is completed, the state of link 2 may be classified as Figure 6a The status and Figure 6b The status shown. Figure 6a In the exemplary embodiment shown, since the frame header is not decoded and only the transmission power is detected as a result of the carrier sensing operation after the blind period, the link state (eg, channel state) may be determined to be a busy state. Figure 6b In the illustrated exemplary embodiment, since no transmission power is detected as a result of a carrier sensing operation after the blind period, the link state (eg, channel state) may be determined to be an idle state.

[0091] If through Figure 6b If the carrier sensing operation shown determines that the channel is in an idle state, the base station can perform a channel access operation after an extended interframe space (EIFS). EIFS can be longer than short IFS (SIFS), point coordination function (PCF) IFS (PIFS), distributed IFS (DIFS), and arbitration IFS (AIFS). EIFS can be a waiting time for protecting the transmission of hidden nodes. EIFS can also be called a "hidden node protection timer" or a "medium synchronization delay timer."

[0092] When the interference between adjacent links is large, the virtual carrier sensing operation may not be performed on one link, while the transmission operation may be performed on the other link. In this case, a PHY layer carrier sensing operation may be performed instead of a virtual carrier sensing operation. Even if the channel of link 2 is determined to be in a busy state when the transmission operation in link 1 is ended by performing a PHY layer carrier sensing operation in link 2 while the transmission operation is being performed in link 1, the base station may not know the channel occupation time (e.g., channel use time) of link 2. In this case, the base station may wait during the EIFS from the end time point of the channel busy state of link 2. For example, the base station may perform additional channel sensing operations during the EIFS. The channel busy state (e.g., channel use time) may indicate the time when a channel (e.g., link) is occupied by another base station or access point.

[0093] When the interference between adjacent channels is very high, the channel sensing operation may be performed during the above-mentioned EIFS. For example, when the interference caused by the transmission operation in link 1 is large, that is, during the blind period, the PHY layer carrier sensing operation in link 2 may not be feasible. In a link where the carrier sensing operation (e.g., the PHY layer carrier sensing operation) cannot be performed, the channel access operation may not be performed.

[0094] In addition, even in the blind period when the above-mentioned channel access operation is not performed, the NAV time configured by the virtual carrier sensing operation performed before the blind period may be reduced. The normal reduction of the NAV time may mean that a successful virtual channel sensing is performed during the blind period, because the channel state is determined to be in a busy state even if the actual carrier sensing is not performed during the set NAV period.

[0095] After completing a transmission operation in one link (e.g., link 1), the base station may perform a channel access operation to transmit a frame in another link (e.g., link 2). When a transmission operation (e.g., a transmission operation started in a blind period) is being performed by another base station in link 2, since the base station detects transmission of a frame transmitted by another base station after completing the transmission operation in one link, the base station may not decode the preamble and / or MAC header transmitted in the blind period. That is, the base station may not be able to perform virtual carrier sensing in the blind period.

[0096] Therefore, a frame decoding error may occur in the base station. That is, only the channel busy state can be determined by physical carrier sensing, and due to the frame transmission of another base station, the base station can perform a carrier sensing operation during the EIFS from the end time point of the busy state (e.g., the busy state caused by the physical carrier sensing operation) to perform a channel access operation in link 2. If the channel is in an idle state during the EIFS, the base station can perform a fallback operation after the EIFS. When the fallback operation is completed, the base station can send a frame in link 2. EIFS can be longer than SIFS, PIFS, DIFS, and AIFS. EIFS can be a waiting time for protecting the transmission of hidden nodes.

[0097] In addition, when frame transmission is completed in one link, a carrier sensing operation may be performed in another link. Even when the channel is determined to be in an idle state due to the carrier sensing operation in another link, the base station may wait during the EIFS period before performing a channel access operation. This is because other base stations may occupy the channel by sending frames during a time when the base station cannot access the channel (e.g., a blind period).

[0098] After completing frame transmission in link 1, the base station can identify data transmission related information (e.g., channel occupancy time or the time when the channel is busy) of a link (e.g., link 2) based on data transmission related information obtained from link 2 or another link (e.g., link 1 or link 3) which is the current link, the data transmission related information including a period when a virtual carrier sensing operation is not feasible (e.g., a blind period).

[0099] When the data transmission related information is the channel occupancy time, the operation of the base station may be the same as the operation of setting the NAV by virtual carrier sensing when the channel occupancy time information is received. The channel occupancy time information may be used as information about a point in time when the base station can send data. Since the base station can send data after the channel occupancy time ends in link 2, the base station can perform a channel access operation based on AIFS instead of EIFS, which is a normal channel access operation. Information about the channel occupancy time (e.g., channel usage time, channel busy time) for link 2 may be received in any link to which an independent transmission scheme cannot be applied.

[0100] Optionally, since the link to be used has been negotiated between the access point and the base station, the access point may send data transmission related information (e.g., channel occupancy time) for another link in the negotiated link. The link to be used may be one of the multiple links negotiated between the MLDs. During the negotiation process of the link to be used, the base station may send information requesting the provision of data transmission related information and information indicating the type of data transmission related information requested to the access point. Sending information requesting the provision of data transmission related information to the access point means that there is data to be sent. Data transmission related information may be information for determining a possible transmission time point based on a channel state in order to send data. The type of data transmission related information (e.g., a frame including data transmission related information) may be a trigger frame sent at a possible data transmission time point, or a frame notifying a channel usage time and / or a channel busy time to notify a possible data transmission time point.

[0101] The operation of transmitting information on the channel occupation time of another link through the used link and the operation of accessing a channel in another link may be performed as follows.

[0102] Figure 7a is a timing chart showing a fifth exemplary embodiment of a communication method using multi-link in a wireless LAN system, Figure 7b is a sequence diagram showing a sixth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0103] refer to Figure 7a and Figure 7b , when the interference between adjacent channels (e.g., adjacent links) is large, and while a transmission operation (e.g., a transmission operation of PPDU1) is performed in one link (e.g., link 1), a channel usage time (e.g., channel occupancy time) for another link (e.g., link 2) is identified, the base station may perform a carrier sensing operation during the AIFS after the identified channel usage time. When the interference between adjacent channels is large, although a transmission operation (e.g., a transmission operation of PPDU1) is performed in one link (e.g., link 1), a reception operation may not be performed in another link (e.g., link 2). That is, a virtual carrier sensing operation may not be performed in another link. If the channel is in an idle state during the AIFS, the base station may perform a fallback operation after the AIFS. When the fallback operation is completed, the base station may send a data frame (e.g., PPDU2).

[0104] When the transmission operation in link 1 and the reception operation in link 2 cannot be performed simultaneously, the base station can identify information about the link (e.g., link 2) in which the virtual carrier sensing operation cannot be performed based on the frame received in another link (e.g., link 1), and can perform communication using the identified information. Since the negotiation on the use of multiple links between the access point and the base station is completed, the base station can identify whether the virtual carrier sensing operation cannot be performed in the link in which the independent transmission scheme cannot be used. That is, the base station can identify whether simultaneous transmission and reception are not possible in all links or a specific link pair.

[0105] For example, if it is agreed between the access point and the base station to use link 1 and link 2, and transmission and reception cannot be performed simultaneously in link 1 and link 2, the access point can determine that the base station cannot perform a virtual carrier sensing operation in link 2 while receiving a frame from the base station in link 1. That is, the period in which the virtual carrier sensing operation cannot be performed due to another link can be referred to as a blind period. In this case, the access point, rather than the base station, can identify the value of the duration field included in the header of the frame received from another base station in link 2 by performing a virtual carrier sensing operation during the blind period of link 2. The value of the duration field can be "transmission time of the frame + SIFS + reception time of ACK". Since the transmission time can be interpreted as the channel use time, the channel use time can be confirmed.

[0106] The access point may receive a frame (e.g., PPDU1) from the base station in link 1, generate a block ACK (BA) frame for the received frame, and transmit the generated BA frame to the base station in link 1. The BA frame may include information about the channel usage time of link 2 (e.g., the channel usage time or NAV value identified by the virtual carrier sensing operation performed by the access point). The channel usage time may be the value of the duration field included in the header of the frame received by the virtual carrier sensing operation in link 2. In an exemplary embodiment, an ACK frame may be used instead of the BA frame. The BA frame or the ACK frame may be a response frame for the frame (e.g., PPDU1). When the use of three or more links is negotiated, the information about the channel usage time may be included in the frame transmitted in the third link.

[0107] The base station may receive a BA frame in response to a frame (e.g., a data frame) from the access point in link 1, and may identify information about the channel use time in link 2 included in the BA frame. Here, the base station may set a NAV for the channel use time indicated by the BA frame in link 2. Since the base station knows the channel use time of link 2, the base station may perform a carrier sense operation (e.g., a channel sense operation) during the AIFS after the channel use time in link 2 ends. When the channel (e.g., the channel in link 2) is in an idle state during the AIFS, the base station may perform a fallback operation (e.g., a channel access operation) after the AIFS. When the fallback operation is completed, the base station may send a frame (e.g., PPDU2) in link 2.

[0108] Optionally, the BA frame may include information indicating that link 2 is not used (for example, the channel use time information is set to 0). In this case, the base station receiving the BA frame in link 1 may perform a carrier sense operation in link 2 during the AIFS from the end of reception of the BA frame. When it is determined through the carrier sense operation that the channel is in an idle state, the base station may perform a channel access operation (for example, a fallback operation) in link 2 after the AIFS. When the fallback operation is completed, the base station may send a frame (for example, PPDU2) in link 2.

[0109] On the other hand, the base station may communicate with another base station using multiple links. For example, base station 1 may send a frame (e.g., a data frame) to base station 2 in link 1. In link 1, base station 2 may receive a frame from base station 1 and may send a BA frame (e.g., a response frame) for the frame to base station 1. Here, the BA frame may include information indicating the channel usage time of link 2.

[0110] That is, when base station 1 cannot simultaneously perform frame sending operations in link 1 and frame receiving operations in link 2, base station 2 that receives data frames in link 1 may send a BA frame including information on the channel usage time of frames in link 2 (for example, frames sent in a blind area period) to base station 1 in link 1.

[0111] A separate frame may be used instead of a BA frame to inform a base station that does not support simultaneous transmission and reception about information about the channel use time. An access point or base station may generate a separate frame including information about the channel use time of a specific link, and may send the generated separate frame. The information about the channel use time may be data transmission related information. The information about the channel use time may refer to information about a time point at which the base station may send data in link 2 after a blind period. The frame including information about the time point may be a trigger frame sent at a transmission possible time point or a frame indicating the channel use time or a channel busy time. The operation may be performed as follows.

[0112] Figure 8is a sequence diagram showing a seventh exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0113] refer to Figure 8 , when the interference between adjacent channels (e.g., adjacent links) is large, and when information about the channel use time (e.g., channel occupancy time) of another link (e.g., link 2) is obtained while performing a transmission operation (e.g., a transmission operation of PPDU1) in one link (e.g., link 1), the base station may perform a carrier sensing operation (e.g., channel sensing operation) in link 2 during the AIFS after the channel use time ends. When the interference between adjacent channels is large, a transmission operation (e.g., a transmission operation of PPDU1) cannot be performed in another link (e.g., link 2) while performing a transmission operation (e.g., a transmission operation of PPDU1) in one link (e.g., link 1). That is, a virtual carrier sensing operation may not be performed in another link. If the channel is in an idle state during the AIFS, the base station may perform a fallback operation after the AIFS. When the fallback operation is completed, the base station may send a data frame (e.g., PPDU2) in link 2.

[0114] When the transmission operation in link 1 and the reception operation in link 2 cannot be performed at the same time, the base station can identify information about the link (e.g., link 2) in which the virtual carrier sensing operation cannot be performed through a frame received in another link (e.g., link 1), and perform communication using the identified information. For example, if the use of link 1 and link 2 is negotiated between the access point and the base station, and simultaneous transmission and reception in link 1 and link 2 are not feasible, since the base station does not support an independent transmission scheme (i.e., the base station does not support simultaneous transmission and reception), the access point can determine that there is a blind period, during which the virtual carrier sensing operation of the corresponding base station cannot be performed in link 2 while transmission is performed in link 1.

[0115] When the base station 1 performs a transmission operation of a frame (e.g., PPDU1) in link 1, and the base station 2 (or access point) receiving the frame knows information of the link used by the base station 1, the base station 2 (or access point) may notify the base station 1 of information about the link occupied in the blind period (e.g., information about the channel use time of the link 2), wherein the virtual carrier sensing operation cannot be performed when the frame (e.g., PPDU1) is transmitted in link 1 in the blind period. For example, if the use of link 1 and link 2 is negotiated between the access point and the base station, and simultaneous transmission and reception in link 1 and link 2 are not feasible, the access point may know that the base station cannot perform a virtual sensing operation in link 2 while transmitting the frame in link 1.

[0116] In this case, the access point (or another base station) can identify the channel usage time (e.g., channel occupancy time) by performing a virtual carrier sensing operation in link 2 during a blind period in which the base station cannot perform virtual carrier sensing, and transmit information about the channel usage time of link 2 to the base station in link 1. The virtual carrier sensing operation in link 2 can be performed by the access point (or another base station) instead of the base station.

[0117] Therefore, after transmitting a BA frame (e.g., a response frame) to a frame (e.g., PPDU1) received from the base station to the base station, the access point may transmit an arbitrary frame (hereinafter referred to as an "indication frame") to the base station in link 1, the arbitrary frame including information about the channel usage time of link 2 (e.g., the channel usage time or NAV value identified by the virtual carrier sensing operation of the access point). The indication frame may be transmitted after a specific time (e.g., a short interframe space (SIFS) or a point coordination function (PCF) interframe space (PIFS)) from the transmission end time point of the BA frame. The information about the channel usage time of link 2 may be a Clear To Send (CTS) frame (e.g., an EHT (E)-CTS frame), a separate frame including an EHT control field, or a trigger frame. The CTS frame, the separate frame, or the trigger frame may be used as the indication frame.

[0118] On the other hand, when base station 1 that does not support the simultaneous transmission / reception scheme transmits a frame in link 1 in the multilink, "transmission time of the BA frame for the corresponding frame + a specific time (e.g., SIFS or PIFS) + transmission time of the indication frame" may be set as an additional TXOP. That is, in consideration of the above-mentioned additional TXOP, the existing TXOP for transmitting a data frame (e.g., PPDU1) may be extended to an extended TXOP. The extended TXOP may be set by base station 1, base station 2, and / or an access point. The TXOP may be set to a duration field value included in the header of the transmitted frame.

[0119] For example, base station 1 may configure an extended TXOP and may notify base station 2 or an access point of information about the extended TXOP. Information about the extended TXOP may be included in a data frame (e.g., PPDU1) associated with the extended TXOP. Base station 2 or an access point may identify information about the extended TXOP by receiving a data frame from base station 1. When confirming that the existing TXOP has been extended, base station 2 or an access point may determine that the transmission of an indication frame is requested. The indication frame may be data transmission related information. Therefore, base station 1 requesting to send an indication frame may mean that base station 1 wants to send additional data present in a buffer in addition to the data frame sent in link 1. If the additional data in addition to the frame sent in link 1 does not exist in the buffer of base station 1, the indication frame may not be requested. This operation may mean that the TXOP is not extended and the indication frame may not be requested.

[0120] Whether the extended TXOP has been configured can be identified based on the value of the length field included in the preamble of the data frame (e.g., PPDU1) and the value of the duration field included in the MAC header. When the value of the duration field included in the MAC header>(the value of the length field included in the preamble+SIFS+the transmission time of the BA frame), the base station 2 or the access point can determine that the base station 1 has requested to send the indication frame. That is, the base station 2 or the access point can determine that the extended TXOP has been configured by the base station 1.

[0121] When confirming that the extended TXOP has been configured based on the information included in the data frame, the base station 2 or the access point may send an indication frame to the base station 1 after sending the BA frame for the corresponding data frame. Optionally, when the link 2 is in an idle state, the base station 2 or the access point may omit the sending of the indication frame. Information indicating whether to send the indication frame may be included in the "More Data" field of the MAC header of the BA frame. The bits in the "More Data" field may indicate whether there is a frame (e.g., a packet) to be sent additionally after the current frame is sent. When the bit of the "More Data" field included in the BA frame is set to a first value, this may indicate that the indication frame is sent after the BA frame is sent. When the bit of the "More Data" field included in the BA frame is set to a second value, this may indicate that the indication frame is not sent after the BA frame is sent. The bit set to the second value (e.g., the "More Data" bit) may indicate that the link 2 is in an idle state. Optionally, the omission of the sending of the indication frame may be indicated by setting the value of the duration field included in the MAC header of the BA frame to only the transmission time of the current BA frame.

[0122] Base station 1 may receive a BA frame for a data frame, and may identify a value of a "more data" field (e.g., a "more data" bit) and / or a value of a duration field included in the BA frame. When the bit of the "more data" field is set to a first value or when the value of the duration field is set to the end time of the extended TXOP, base station 1 may perform a reception operation of the indication frame. On the other hand, when the bit of the "more data" field is set to a second value or when the value of the duration field is set only to the transmission time of the current BA frame, base station 1 may not perform a reception operation of the indication frame. In this case, base station 1 may determine that link 2 is in an idle state.

[0123] In another exemplary embodiment, the existing TXOP may be configured by base station 1, and the additional TXOP may be configured by base station 2 or an access point. For example, base station 2 or an access point may receive a data frame (e.g., PPDU1) from base station 1, and may generate a BA frame for the data frame. When sending an indication frame, the value of the duration field included in the MAC header of the BA frame may be set in consideration of the transmission time of the indication frame. The value of the duration field included in the BA frame may be set to (transmission time of the BA frame + a specific time (e.g., SIFS or PIFS) + transmission time of the indication frame). Base station 2 or an access point may send a BA frame including a duration field indicating an additional TXOP to base station 1 in link 1.

[0124] The base station 1 may receive the BA frame and may identify the value of the duration field included in the MAC header of the BA frame. When the value of the duration field indicates an extended TXOP, the base station 1 may perform a reception operation of the indicated frame. On the other hand, when the value of the duration field does not indicate an extended TXOP, the base station 1 may not perform a reception operation of the indicated frame. According to the above operation, other base stations may be prevented from transmitting frames according to the channel contention process in the additional TXOP.

[0125] Upon receiving the indication frame, the base station 1 may perform a carrier sense operation in the link 2 during the AIFS from the end time point of the channel use time indicated by the indication frame. Here, the base station 1 may set the NAV according to the channel use time in the link 2. When the channel is idle during the AIFS, the base station 1 may perform a backoff operation in the link 2 after the AIFS. When the backoff operation is completed, the base station 1 may send a data frame (e.g., PPDU2) in the link 2.

[0126] When the indication frame indicates that link 2 is in an idle state (for example, when the channel use time is set to 0 or when the indication frame is indicated as not being transmitted), if the channel is in an idle state during the AIFS from the reception time point of the indication frame (for example, the receiving endpoint), the base station 1 may perform a fallback operation in link 2. That is, since the end time of the frame detected by the carrier sense operation after the blind period in link 2 can be identified by the received indication frame, a normal channel access process can be performed from the receiving endpoint indicated by the indication frame. When the fallback operation is completed, the base station 1 may send a data frame (for example, PPDU2) in link 2. Optionally, when omitting the transmission of the indication frame and not sending the indication frame means an idle state, if the channel is in an idle state during the AIFS from the reception time point of the BA frame (for example, the receiving endpoint), the base station 1 may perform a fallback operation in link 2. That is, when the idle state is determined in link 2 by the carrier sense operation after the blind period, it can be determined as an actual idle state in which no hidden node exists. In this case, a normal channel access process can be performed after the blind period. When the backoff operation is completed, base station 1 may send a data frame (eg, PPDU2) in link 2.

[0127] Figure 9a is a timing chart showing an eighth exemplary embodiment of a communication method using multi-link in a wireless LAN system, Figure 9b is a sequence diagram showing a ninth exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0128] refer to Figure 9a and Figure 9b , when the interference between adjacent channels (e.g., adjacent links) is large, and when information about the channel use time (e.g., channel occupancy time) of another link (e.g., link 2) is obtained during the blind period while performing a transmission operation (e.g., transmission operation of PPDU1) in one link (e.g., link 1), the base station may perform a normal channel access operation after the channel use time ends. That is, the base station may perform a carrier sense operation during the AIFS period.

[0129] When the interference between adjacent channels is large, although a transmission operation (e.g., a transmission operation of PPDU1) is performed in one link (e.g., link 1), a reception operation may not be performed in another link (e.g., link 2). That is, a virtual carrier sensing operation may not be performed in another link. If the channel is idle during the AIFS, the base station may perform a fallback operation after the AIFS. When the fallback operation is completed, the base station may transmit a data frame (e.g., PPDU2).

[0130] The use of link 1, link 2, and link 3 may be negotiated in a negotiation process for multi-link operation between an access point and a base station. In this case, the access point may send a separate frame (hereinafter referred to as an "indication frame") including information about the channel use time of link 2 to the base station in link 3. For example, the base station may not support a simultaneous transmission / reception scheme in link 1 and link 2. That is, link 1 and link 2 may be a link pair that cannot be transmitted and received at the same time. In this case, the access point may know that there is a blind period in which the base station cannot simultaneously perform a transmission operation in link 1 and a carrier sensing operation in link 2. Therefore, the access point may identify the channel use time (e.g., channel occupancy time) by performing a virtual carrier sensing operation in link 2 during the blind period. The access point may send an indication frame including information about the channel use time of link 2 (e.g., the channel use time or NAV identified by the virtual carrier sensing operation of the access point) in link 3. The indication frame may be a CTS frame (e.g., an E-CTS frame), a separate frame including an EHT control field, or a trigger frame.

[0131] Since link 1 and link 3 are not a link pair that cannot transmit and receive at the same time, the base station can receive an indication frame in link 3 while performing a transmission operation in link 1. The base station can identify the channel usage time of link 2 indicated by the indication frame. The base station can set the NAV in link 2 by using the channel usage time. The base station can perform normal channel access in link 2 from the end of the channel usage time (i.e., from the end of the NAV). The base station can perform a carrier sense operation during the AIFS from the end of the NAV, and when the channel is in an idle state during the AIFS, it can perform a channel access operation (e.g., a fallback operation) after the AIFS. When the fallback operation is completed, the base station can send a data frame (e.g., PPDU2) in link 2.

[0132] On the other hand, when the channel of link 2 is in a busy state when the base station performs a transmission operation (e.g., during a blind period), and the end point of the busy state of link 2 is after the transmission end point of the data frame (e.g., PPDU1) in link 1, it may be necessary for the access point to use link 3 to notify the end time point of the channel use time for link 2 (e.g., busy state end time point information). When the above operation is negotiated between the access point and the base station, the channel of link 3 is in an idle state at the transmission endpoint of link 1, and no information about the channel use time of link 2 is received from the access point, the base station can determine that the channel of link 2 is in an idle state. Therefore, the base station can perform a carrier sense operation in link 2 during the AIFS period from the transmission endpoint of link 1 (e.g., after the blind period). When the channel is in an idle state during the AIFS, the base station can perform a channel access operation (e.g., a fallback operation) after the AIFS. When the fallback operation is completed, the base station can send a data frame (e.g., PPDU2) in link 2.

[0133] In addition, when a base station that does not support a simultaneous transmission / reception scheme in multi-links obtains information about a channel use time of another link, the base station may perform a simultaneous transmission operation in multi-links based on the following procedure.

[0134] Fig.10a is a timing chart showing a tenth exemplary embodiment of a communication method using multi-link in a wireless LAN system, Fig.10b is a sequence diagram showing an eleventh exemplary embodiment of a communication method using multi-link in a wireless LAN system.

[0135] refer to Fig.10a and Fig.10b , when the interference between adjacent channels (e.g., adjacent links) is large, and when information about the channel usage time of another link (e.g., link 2) is obtained while performing a transmission operation (e.g., a transmission operation of PPDU1) in one link (e.g., link 1), a simultaneous transmission operation may be performed based on the channel usage time. When the interference between adjacent channels is large, although a transmission operation (e.g., a transmission operation of PPDU1) is performed in one link (e.g., link 1), a reception operation may not be performed in another link (e.g., link 2). That is, a virtual carrier sensing operation may not be performed in another link. Base station 1 may receive an indication frame (e.g., a CTS frame) including information about the channel usage time of link 2 in link 1. Base station 1 that cannot support a simultaneous transmission / reception scheme in multiple links may perform simultaneous transmission operations in multiple links (e.g., link 1 and link 2) based on the channel usage time indicated by the indication frame.

[0136] For example, when base station 1 does not support the simultaneous transmission / reception scheme in link 1 and link 2 and transmits a frame (eg, PPDU1) in link 1, access point or base station 2 may Figure 7a , Figure 7b , Figure 8 , Figure 9a and / or Figure 9b The method described in notifies the base station 1 of the information on the channel use time of the link 2. In this case, the base station 1 can recognize the information on the channel use time of the link 2, and determine that the channel of the link 2 is busy until the channel use time ends.

[0137] When the transmission operation ends in link 1, base station 1 may perform a channel access operation to transmit another frame (e.g., PPDU2). In this case, if the channel of link 2 is determined to be in an idle state, base station 1 may use link 1 and link 2 to perform simultaneous transmission operations. If it is desired to extend the transmission operation to link 1 and link 2 (e.g., when both link 1 and link 2 are to be used to perform simultaneous transmission), if the channel of link 2 is in an idle state during "T1-T2", base station 1 may transmit a frame (e.g., PPDU2) by using link 1 and link 2 simultaneously, regardless of EIFS. The length of "T1-T2" may be PIFS, AIFS, or the execution time of a channel access operation for transmitting PPDU2 in link 1. T2 may be the start time point or the end time point of the channel access operation for transmitting PPDU2 in link 1. T1 may be the length of "T2"-(the length of "T1-T2").

[0138] On the other hand, when the above Figure 7a , Figure 7b , Figure 8 , Figure 9a and / or Figure 9b When the end point of the channel use time indicated by the method shown in is after T1, the base station 1 may use only the link 1 to send the data frame (eg, PPDU2).

[0139] Fig.11 is a block diagram showing a first exemplary embodiment of a BA frame including channel use time information in a wireless LAN system.

[0140] refer to Fig.11 , BA frame (for example, Figure 7a and / or Figure 7b The BA frame shown in ) may include information about the channel use time of a specific link, an identifier (e.g., link ID) of a link to which the channel use time information is applied, and / or information indicating that the channel use time information is included in the corresponding BA frame. The information indicating that the channel use time information is included in the BA frame may be configured as follows.

[0141] - Scheme 1: By adding a value of 1 to 8 μs to the Duration field of the BA frame, it may be indicated that the channel use time information is included in the BA frame.

[0142] - Scheme 2: The BA control field of the BA frame may include information indicating that the channel use time information is included in the BA frame and / or a link ID indicating a link related to the channel use time information (eg, a link to which the channel use time information is applied).

[0143] When using scheme 1, the value added to the duration field may be a link ID indicating a link associated with the channel use time information. Alternatively, if the BA frame does not indicate a link associated with the channel use time information, the link associated with the channel use time information may be a link that cannot be transmitted simultaneously, which is identified by a communication node (e.g., a base station or an access point) that sends and receives the corresponding BA frame.

[0144] When the information included in the BA frame indicates that the channel usage time information is included in the corresponding BA frame, the communication node may generate a BA frame that also includes a field indicating the channel usage time information. The channel usage time indicated by the BA frame may start from the transmission time point (e.g., the transmission start point or the transmission end point) of the corresponding BA frame. The channel usage time may be set in μs. That is, the channel usage time may indicate a period (e.g., duration) of using the channel. Optionally, the channel usage time information included in the BA frame may indicate an end time point of the channel usage time.

[0145] In addition, the BA frame including the channel usage time information may have the form of an existing BA frame. The duration field of the BA frame may be used to indicate the remaining channel usage time of another link (e.g., the remaining channel occupancy time). For example, in the duration field, bits 14 and 15 may be set to "1", and the remaining bits may be set to indicate a value between 8192 and 16383. In this case, the remaining channel usage time of the other link may be expressed as "(the value indicated by bits 0 to 13 in the duration field - 8191) × 4μs". For example, if the value indicated by bits 0 to 13 in the duration field is 8192, the remaining channel usage time may be 4μs from the transmission time point of the BA frame. When the value indicated by bits 0 to 13 in the duration field is 16383, the remaining channel usage time may be 32768μs from the transmission time point of the BA frame.

[0146] When a BA frame for a data frame is received, the base station may analyze the duration field included in the BA frame based on the above scheme to identify the channel use time (e.g., remaining channel use time) of the link for which the carrier sense operation is not feasible. That is, the base station may determine that the channel (e.g., link) is busy during the channel use time indicated by the BA frame. When the BA control field of the BA frame includes a link ID indicating a link related to the channel use time, the base station may determine that the channel is in a busy state in the link indicated by the BA control field during the channel use time identified based on the duration field.

[0147] In another exemplary embodiment, in order to indicate the channel use time of another link (e.g., the remaining channel use time), a value smaller than the length of one time slot (e.g., 9 μs) may be used. For example, when the length of one time slot is 9 μs, 1 to 8 may be used to indicate the channel use time. When the maximum possible transmission time or the negotiated possible transmission time for one PPDU is T tx When T tx / 8 The corresponding time value. For example, when T tx is 100μs, T tx / 8 It can be 12.5. When the channel use time (e.g., the remaining channel use time) is 5 μs, the value of the duration field can be set to "the transmission time of the frame (e.g., the value of the existing duration field) + 1". When the channel use time (e.g., the remaining channel use time) is 26 μs, the value of the duration field can be set to "the transmission time of the frame (e.g., the value of the existing duration field) + 3".

[0148] When receiving a BA frame for a data frame, the base station can identify the channel use time (e.g., the remaining channel use time) by interpreting the value of the duration field included in the BA frame based on the above scheme. When the channel use time ends, the base station can determine that the channel (e.g., link) is in an idle state, and can perform a channel access operation in the corresponding channel.

[0149] In another exemplary embodiment, the duration field of the BA frame may indicate the additional waiting time (e.g., the time for performing additional carrier sensing operations) of the base station after determining that the channel is in an idle state through a channel access operation (e.g., a fallback operation). If the BA frame does not indicate the additional waiting time, since the base station performs the channel access operation after waiting for the EIFS after the busy state ends, it is preferred to set T tx Set to a more favorable value compared to EIFS to reduce unnecessary waiting time. For example, T tx Can be set to "T tx =EIFS", and the value calculated by the above scheme can be added to the duration field of the BA frame.

[0150] When the above method is used, the time for determining the channel state may be longer than AIFS and shorter than EIFS. When a BA frame for a data frame is received, the base station may identify the time by interpreting the remainder obtained by dividing the value of the duration field included in the BA frame by 9, and may additionally wait for an identifier time starting from the time point when the channel is determined to be idle. When the channel is in an idle state during the identified time (e.g., the waiting time), the base station may perform a channel access operation (e.g., a fallback operation).

[0151] Figure 8 , Figure 9a , Figure 9b , Fig.10a and / or Fig.10b The indication frame shown in can be configured the same as or similar to the above-mentioned BA frame. For example, the indication frame can include the channel use time information of a specific link, the ID of the link to which the channel use time information is applied, and / or information indicating that the channel use time information is included in the corresponding indication frame.

[0152] The exemplary embodiments of the present disclosure may be implemented as program instructions that can be executed by various computers and recorded on computer-readable media. The computer-readable medium may include program instructions, data files, data structures, or a combination thereof. The program instructions recorded on the computer-readable medium may be specifically designed and configured for the present disclosure, or may be known and available to those skilled in the art of computer software.

[0153] Examples of computer-readable media may include hardware devices, such as ROM, RAM, and flash memory, which are specifically configured to store and execute program instructions. Examples of program instructions include machine codes made by, for example, a compiler, and high-level language codes that can be executed by a computer using an interpreter. The above exemplary hardware devices may be configured to operate as at least one software module to perform embodiments of the present disclosure, and vice versa.

[0154] Although the embodiments of the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope of the disclosure.

Claims

1. A method for a first device supporting multi-link, comprising: Sending a first frame to a second device on a first link in the multilink; performing a carrier sense operation in a first time period according to a first timer on a second link in the multi-link after a blind period; as well as initiating an operation for transmission on the second link after the first time period, The sending operation on the first link and the receiving operation on the second link are not performed simultaneously, and the blind period occurs on the second link due to sending the first frame on the first link.

2. The method according to claim 1, further comprising: determining the blind period on the second link, The blind zone period is determined as a period during which the carrier sensing operation is not feasible.

3. The method according to claim 1, further comprising: A second frame is received from the second device on one of the multiple links in a period corresponding to the first time period of the second link.

4. The method according to claim 1, further comprising: A second frame is received from the second device on one of the multiple links after a period corresponding to the first time period of the second link.

5. The method according to claim 3, wherein: The second frame includes information indicating a transmission time on the second link, and the transmission time indicates a time when transmission on the second link is possible.

6. The method according to claim 5, further comprising: A third frame is sent on the second link at a time indicated by the transmission time.

7. The method according to claim 1, wherein: The operation for transmitting is a fallback operation.

8. The method according to claim 1, wherein: While the first frame is being transmitted, a virtual carrier sensing operation with frames transmitted by the second device is not performed on the second link.

9. The method according to claim 8, wherein: The virtual carrier sensing operation is an operation for configuring a network allocation vector NAV which is a time period during which the first device does not transmit.

10. The method according to claim 1, wherein: The first time period is longer than a short interframe space SIFS, a point coordination function PCF interframe space PIFS, a distributed interframe space DIFS or an arbitration interframe space AIFS.

11. A first device supporting multi-link, comprising: at least one processor, The at least one processor causes the first device to perform the following operations: Sending a first frame to a second device on a first link in the multilink; performing a carrier sensing operation in a first time period according to a first timer after a blind period on a second link in the multi-link; and initiating an operation for transmission on the second link after the first time period, The sending operation on the first link and the receiving operation on the second link are not performed simultaneously, and the blind period occurs on the second link due to sending the first frame on the first link.

12. The first device according to claim 11, wherein: The at least one processor further causes the first device to: determining the blind period on the second link, The blind zone period is determined as a period during which the carrier sensing operation is not feasible.

13. The first device according to claim 11, wherein: The at least one processor further causes the first device to: A second frame is received from the second device on one of the multiple links in a period corresponding to the first time period of the second link.

14. The first device according to claim 11, wherein: The at least one processor further causes the first device to: A second frame is received from the second device on one of the multiple links after a period corresponding to the first time period of the second link.

15. The first device according to claim 13, wherein: The second frame includes information indicating a transmission time on the second link, and the transmission time indicates a time when transmission on the second link is possible.

16. The first device according to claim 15, wherein: The at least one processor further causes the first device to: A third frame is sent on the second link at a time indicated by the transmission time.

17. The first device according to claim 11, wherein: The operation for transmitting is a fallback operation.

18. The first device according to claim 11, wherein: While the first frame is being transmitted, a virtual carrier sensing operation with frames transmitted by the second device is not performed on the second link.

19. The first device according to claim 18, wherein: The virtual carrier sensing operation is an operation for configuring a network allocation vector NAV which is a time period during which the first device does not transmit.

20. The first device according to claim 11, wherein The first time period is longer than a short interframe space SIFS, a point coordination function PCF interframe space PIFS, a distributed interframe space DIFS or an arbitration interframe space AIFS.

Images