Method and apparatus for low latency communication in wireless local area network supporting multiple links

Abstract

A method and an apparatus for low latency communication in a wireless local area network supporting multiple links are disclosed. The method of the first device comprises the steps of: identifying an SP set in the second link; and communicating with the second device in the first link before the start time of the SP, wherein the communication between the first device and the second device ends before the start time of the SP.

Description

Technical Field

[0001] The present invention relates to a wireless local area network (WLAN) communication technology, and more specifically, to a technology for channel access based on restricted target wake time (R-TWT) in a dense WLAN environment. Background Art

[0002] Recently, as the distribution of mobile devices expands, wireless local area network technology that can provide fast wireless communication services for mobile devices has attracted attention. Wireless local area network (WLAN) technology can be a technology that supports mobile devices such as smart phones, smart tablets, laptops, portable multimedia players, embedded devices, etc. to access the Internet wirelessly based on wireless communication technology.

[0003] The IEEE 802.11ac standard has expanded the bandwidth used (e.g., a maximum of 160 MHz bandwidth or 80+80 MHz bandwidth) and also increased the number of supported spatial streams. The IEEE 802.11ac standard may refer to a very high throughput (VHT) wireless local area network technology capable of supporting data rates exceeding 1 gigabit per second (Gbps). The IEEE 802.11ac standard may utilize MIMO technology to support downlink transmission to multiple stations.

[0004] With the emergence of applications requiring higher throughput and applications requiring real-time transmission, the IEEE 802.11be standard is being developed, which is an Extreme High Throughput (EHT) wireless LAN technology. The goal of the IEEE 802.11be standard may be to support a high throughput of 30 Gbps. The IEEE 802.11be standard may support technologies for reducing transmission delays. In addition, the IEEE 802.11be standard may support a more extended frequency bandwidth (e.g., 320 MHz bandwidth), multi-link transmission, and aggregation operations including multi-band operation, multi-access point (AP) transmission operation, and / or efficient retransmission operation (e.g., Hybrid Automatic Repeat Request (HARQ) operation).

[0005] Multiple links may be used in a wireless LAN, and specific operations may need to be defined for a wireless LAN that supports multiple links. For example, a restricted target wake time (R-TWT) operation may be defined for low-latency communication. The station (STA) performing the R-TWT operation may be a non-simultaneous transmit and receive (NSTR) STA and / or an enhanced multi-link single radio (EMLSR) STA. Although the NSTR STA or EMLSR STA performs communication with the AP in the R-TWT SP configured on the first link, it may not be possible to communicate on the second link. A method for communicating on the second link may be required so as not to affect the communication in the R-TWT SP configured on the first link.

[0006] On the other hand, the background technologies of the present invention are written to enhance understanding of the background of the present invention and may include contents that are not known to ordinary technicians in the field to which the present invention belongs. Summary of the invention

[0007] Technical issues

[0008] The present invention is directed to providing a method and apparatus for communication of an NSTR device or an EMLSR device in a wireless local area network supporting R-TWT operation.

[0009] Technical Solution

[0010] A method of a first device according to an exemplary embodiment of the present invention for achieving the above-mentioned purpose may include: identifying a service period (SP) configured on a second link; performing communication with a second device on the first link before a start time of the SP, wherein the communication between the first device and the second device ends before the start time of the SP.

[0011] Performing communication with the second device may include: sending a data frame to the second device on the first link; receiving a reception response frame for the data frame from the second device on the first link, wherein an end time of the reception response frame is before a start time of the SP.

[0012] Performing communication with the second device may include: receiving a data frame from the second device on the first link; sending a reception response frame for the data frame to the second device on the first link, wherein an end time of the reception response frame is before a start time of the SP.

[0013] The method may further include: when the medium synchronization delay timer is operated in the SP of the second link, sending the first frame to release the medium synchronization delay timer.

[0014] The first link and the second link may be a non-simultaneous transmit and receive (NSTR) link pair, and when communication between the first device and the second device is performed on the first link, transmission and reception operations on the second link may not be possible.

[0015] The communication between the first device and the second device may end before the offset from the start time of the SP.

[0016] When the first device is an enhanced multi-link single radio (EMLSR) device, communication between the first device and the second device may end before an EMLSR switching delay time from a start time of the SP.

[0017] When the first device is a station (STA) MLD, the second device may be an access point (AP) multi-link device (MLD), and when the first device is an AP MLD, the second device may be a STA MLD, the STAMLD may include a first STA operating on a first link and a second STA operating on a second link, and the AP MLD may include a first AP operating on the first link and a second AP operating on the second link.

[0018] According to an exemplary embodiment of the present invention for achieving the above-mentioned purpose, a first device may include a processor, which causes the first device to execute: identifying a service period (SP) configured on a second link; and performing communication with a second device on the first link before a start time of the SP, wherein the communication between the first device and the second device ends before the start time of the SP.

[0019] In executing communication with the second device, the processor may cause the first device to execute: sending a data frame to the second device on the first link; receiving a reception response frame for the data frame from the second device on the first link, wherein an end time of the reception response frame is before a start time of the SP.

[0020] In executing communication with the second device, the processor may cause the first device to execute: receiving a data frame from the second device on the first link; sending a reception response frame for the data frame to the second device on the first link, wherein an end time of the reception response frame is before a start time of the SP.

[0021] The processor may cause the first device to execute: when the medium synchronization delay timer is operated in the SP of the second link, sending the first frame to release the medium synchronization delay timer.

[0022] The first link and the second link may be a non-simultaneous transmit and receive (NSTR) link pair, and when communication between the first device and the second device is performed on the first link, transmission and reception operations on the second link may not be possible.

[0023] The communication between the first device and the second device may end before the offset from the start time of the SP.

[0024] When the first device is an enhanced multi-link single radio (EMLSR) device, communication between the first device and the second device may end before an EMLSR switching delay time from a start time of the SP.

[0025] When the first device is a station (STA) MLD, the second device may be an access point (AP) multi-link device (MLD), and when the first device is an AP MLD, the second device may be a STA MLD, the STAMLD may include a first STA operating on a first link and a second STA operating on a second link, and the AP MLD may include a first AP operating on the first link and a second AP operating on the second link.

[0026] Beneficial Effects

[0027] According to the present invention, when an R-TWT service period (SP) is configured on a second link, the first device may terminate the communication on the first link before the start time of the R-TWT SP of the second link. According to the above operation, the communication on the first link may not affect the communication in the R-TWT SP of the second link. Therefore, low-latency communication can be smoothly performed within the R-TWT SP. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a block diagram showing a first exemplary embodiment of a communication node constituting a wireless LAN system.

[0029] Figure 2 is a conceptual diagram showing a first exemplary embodiment of a plurality of links configured between multi-link devices (MLDs).

[0030] Figure 3 is a sequence diagram showing a first exemplary embodiment of a problem according to an NSTR state within an R-TWT SP in a wireless LAN supporting multi-links.

[0031] Figure 4a is a timing diagram illustrating a first exemplary embodiment for low-latency communication within an R-TWT SP.

[0032] Figure 4b is a timing diagram illustrating a second exemplary embodiment for low-latency communication within an R-TWT SP.

[0033] Figure 5a is a timing diagram illustrating a third exemplary embodiment for low-latency communication within an R-TWT SP.

[0034] Figure 5b is a timing diagram illustrating a fourth exemplary embodiment for low-delay communication within an R-TWT SP.

[0035] Figure 6 is a timing diagram illustrating a first exemplary embodiment of synchronous transmission in the NSTR state. DETAILED DESCRIPTION

[0036] Since the present invention can be variously modified and has various forms, specific exemplary embodiments will be shown in the drawings and described in detail in the specific embodiments. However, it should be understood that it is not intended to limit the present invention to specific exemplary embodiments. But on the contrary, the present invention covers all modifications and alternative forms that fall within the spirit and scope of the present invention.

[0037] Relational terms such as first, second, etc. can be used to describe various elements, but these elements should not be limited by the terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present invention, the first component can be named as the second component, and the second component can also be similarly named as the first component. The term "and / or" refers to any one or a combination of multiple related and described matters.

[0038] In an exemplary embodiment of the present invention, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B". In addition, "one or more of A and B" may mean "one or more of A or B" or "one or more combinations of one or more of A and B".

[0039] When it is mentioned that a certain component is "coupled" or "connected" to another component, it should be understood that the certain component is directly "coupled" or "connected" to the other component, or another component may be provided therebetween. Conversely, when it is mentioned that a certain component is "directly coupled" or "directly connected" to another component, it will be understood that no other component is provided therebetween.

[0040] The terms used in the present invention are only used to describe specific exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly stipulates otherwise. In the present invention, terms such as "including" or "having" are intended to indicate the presence of features, values, steps, operations, components, parts or combinations thereof described in the specification, but it should be understood that these terms do not exclude the presence or addition of one or more features, values, steps, operations, components, parts or combinations thereof.

[0041] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. Terms commonly used in dictionaries and already in dictionaries should be interpreted as having meanings that match the contextual meanings in the art. In this specification, unless explicitly defined, terms are not necessarily interpreted as having formal meanings.

[0042] Hereinafter, the form of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate a comprehensive understanding of the present invention, the same reference numerals refer to the same elements throughout the description of the accompanying drawings, and repeated description thereof will be omitted.

[0043] Hereinafter, a wireless communication system to which an exemplary embodiment according to the present invention is applied will be described. The wireless communication system to which an exemplary embodiment according to the present invention is applied is not limited to the contents described below, and the exemplary embodiment according to the present invention can be applied to various wireless communication systems. The wireless communication system can be referred to as a "wireless communication network".

[0044] In an exemplary embodiment, "configuration of an operation (e.g., a transmission operation)" may mean signaling "configuration information (e.g., information element, parameter) of an operation" and / or "information indicating execution of an operation". "Configuration of an information element (e.g., parameter)" may mean signaling an information element. "Configuration of a resource (e.g., a resource region)" may mean signaling setting information of a resource.

[0045] Figure 1 is a block diagram showing a first exemplary embodiment of a communication node constituting a wireless LAN system.

[0046] like Figure 1 As shown in , the communication node 100 may be an access point, a station (Station), an access point (AP) multi-link device (MLD) or a non-AP MLD. An access point may be referred to as an "AP", and a station may be referred to as a "STA" or a "non-AP STA". The operating channel width supported by the AP may be 20 megahertz (MHz), 80 MHz, 160 MHz, etc. The operating channel width supported by the STA may be 20 MHz, 80 MHz, etc.

[0047] The communication node 100 may include at least one processor 110, a memory 120, and a transceiver 130 connected to a network to perform communication. The transceiver 130 may be referred to as a transceiver, 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 various components included in the communication node 100 may be connected to communicate with each other via a bus 170.

[0048] 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.

[0049] The processor 110 may execute program instructions 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 that executes a method according to an exemplary embodiment of the present invention. The memory 120 and the storage device 160 may each 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).

[0050] Figure 2 is a conceptual diagram showing a first exemplary embodiment of multi-links configured between multi-link devices (MLDs).

[0051] like Figure 2 As shown in , the MLD may have a Medium Access Control (MAC) address. In an exemplary embodiment, the MLD may represent an AP MLD 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 APs associated with the AP MLD may have different MAC addresses, and the stations associated with the non-AP MLD may have different MAC addresses. Each of the APs with different MAC addresses within the AP MLD may be responsible for each link and may perform the role of an independent AP.

[0052] Each of the STAs with different MAC addresses within the non-AP MLD may be responsible for each link and may perform the role of an independent STA. The non-AP MLD may be referred to as a STA MLD. The MLD may support simultaneous transmit and receive (STR) operations. In this case, the MLD may perform a transmit operation in link 1 and may perform a receive operation in link 2. An MLD that supports STR operations may be referred to as a STR MLD (e.g., STR AP MLD, STR non-AP MLD). In an exemplary embodiment, a link may represent a channel or a frequency band. A device that does not support STR operations may be referred to as a non-STR (NSTR) AP MLD or an NSTR non-AP MLD (or an NSTR STA MLD).

[0053] MLD can send and receive frames in multiple links by utilizing a non-contiguous bandwidth extension scheme (e.g., 80MHz+80MHz). Multi-link operation can include multi-band transmission. AP MLD can include multiple APs, and the multiple APs can operate in different links. Each of the multiple APs can perform the functions of the lower MAC layer. Each of the multiple APs can be referred to as a "communication node" or a "lower-level entity". The communication node (i.e., AP) can be in the upper layer (or Figure 1 The non-AP MLD may include multiple STAs, and the multiple STAs may operate in different links. Each of the multiple STAs may be referred to as a "communication node" or a "lower-level entity". The communication node (i.e., STA) may be in the upper layer (or Figure 1 The processor 110 shown in FIG. 1 operates under the control of the processor 110.

[0054] MLD can perform communication in multiple frequency bands (i.e., multi-band). For example, MLD can perform communication using 80MHz bandwidth in the 2.4GHz band according to a channel extension scheme (e.g., bandwidth extension scheme), and perform communication using 160MHz bandwidth in the 5GHz band according to a channel extension scheme. MLD can perform communication using 160MHz bandwidth in the 5GHz band, and can perform communication using 160MHz bandwidth in the 6GHz band. A frequency band (e.g., a channel) utilized by MLD can be defined as a link. Alternatively, multiple links can be configured in a frequency band utilized by MLD. For example, MLD can configure one link in the 2.4GHz band and two links in the 6GHz band. Each link can be referred to as a first link, a second link, and a third link. Alternatively, each link can be referred to as link 1, link 2, link 3, etc. The link number can be set by the access point, and an identifier (ID) can be assigned to each link.

[0055] 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 number of links and / or links utilized in the multi-link may be configured. Non-AP MLD (e.g., STA) 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 configure one or more of the links supported by AP MLD for multi-link operation. A station that does not support multi-link operation (e.g., IEEE 802.11a / b / g / n / ac / ax STA) may be connected to one or more links of the multi-link supported by AP MLD.

[0056] When the frequency band spacing between multiple links (for example, the frequency band spacing between link 1 and link 2 in the frequency domain) is sufficient, the MLD can perform the STR operation. For example, the MLD may be able to send physical layer protocol data unit (PPDU) 1 using link 1 among the multiple links, and may receive PPDU 2 using link 2 among the multiple links. On the other hand, if the MLD performs the STR operation when the frequency band spacing between multiple links is insufficient, in-device coexistence (IDC) interference, that is, interference between multiple links, will occur. Therefore, when the frequency band spacing between multiple links is insufficient, the MLD may not be able to perform the STR operation. The link pair with the above-mentioned interference relationship may be a non-simultaneous transmit and receive (NSTR) limited link pair. Here, the MLD may be referred to as an "NSTR AP MLD" or an "NSTR non-AP MLD".

[0057] 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 frequency band interval between link 1 and link 3 is sufficient, the AP MLD may perform the STR operation using link 1 and link 3. That is, the AP MLD may send a frame using link 1 and receive a frame using link 3. When the frequency band interval between link 1 and link 2 is insufficient, the AP MLD may not be able to perform the STR operation using link 1 and link 2. When the frequency band interval between link 2 and link 3 is insufficient, the AP MLD may not be able to perform the STR operation using link 2 and link 3.

[0058] On the other hand, in a wireless local area network system, a negotiation process for multi-link operation may be performed in an access process between a station and an access point. A device (e.g., access point, station) supporting multiple links may be referred to as a "multi-link device (MLD)". An access point supporting multiple links may be referred to as an "AP MLD", and a station supporting multiple links may be referred to as a "non-AP MLD" or a "STA MLD". AP MLD may have a physical address (e.g., MAC address) for each link. APMLD may be implemented as if there is an AP responsible for each link alone. Multiple APs may be managed within one AP MLD. Therefore, coordination between multiple APs belonging to the same AP MLD is possible. STA MLD may have a physical address (e.g., MAC address) for each link. STA MLD may be implemented as if there is an STA responsible for each link alone. Multiple STAs may be managed within one STA MLD. Therefore, coordination between multiple STAs belonging to the same STA MLD is possible.

[0059] For example, AP1 of AP MLD and STA1 of STAMLD may each be responsible for the first link and perform communication using the first link. AP2 of AP MLD and STA2 of STA MLD may each be responsible for the second link and perform communication using the second link. STA2 may receive state change information for the first link on the second link. In this case, STAMLD may collect information (e.g., state change information) received on each link and control the operation performed by STA1 based on the collected information.

[0060] Hereinafter, a method for transmitting and receiving data in a wireless local area network system will be described. Even when describing a method (e.g., transmission or reception of a signal) performed at a first communication node among communication nodes, a corresponding second communication node may perform a method (e.g., reception or transmission of a signal) corresponding to the method performed at the first communication node. That is, when describing the operation of an STA, an AP corresponding thereto may perform an operation corresponding to the operation of the STA. Conversely, when describing the operation of an AP, an STA corresponding thereto may perform an operation corresponding to the operation of the AP.

[0061] In an exemplary embodiment, the operation of STA may be interpreted as the operation of STA MLD, the operation of STAMLD may be interpreted as the operation of STA, the operation of AP may be interpreted as the operation of AP MLD, and the operation of AP MLD may be interpreted as the operation of AP. The STA of STA MLD may refer to the STA to which STA MLD is attached, and the AP of AP MLD may refer to the AP to which AP MLD is attached. When STAMLD includes a first STA operating on a first link and a second STA operating on a second link, the operation of STAMLD on the first link may be interpreted as the operation of the first STA, and the operation of STAMLD on the second link may be interpreted as the operation of the second STA. When AP MLD includes a first AP operating on the first link and a second AP operating on the second link, the operation of AP MLD on the first link may be interpreted as the operation of the first AP, and the operation of AP MLD on the second link may be interpreted as the operation of the second AP. In an exemplary embodiment, the transmission time of a frame may refer to the transmission start time or the transmission end time, and the reception time of a frame may refer to the reception start time or the reception end time. The transmission time may be interpreted as corresponding to the reception time. The time point may be interpreted as the time, and the time may be interpreted as the time point.

[0062] AP MLD, AP, STAMLD and / or STA may perform restricted target wake time (R-TWT) operation for low-latency communication. In the present invention, R-TWT operation may be interpreted as TWT operation, and R-TWT service period (SP) may be interpreted as TWT SP. R-TWT SP and / or TWT SP may be simply expressed as "SP". For example, R-TWT SP1 may be referred to as a first SP, and R-TWT SP2 may be referred to as a second SP.

[0063] Figure 3 is a sequence diagram showing a first exemplary embodiment of a problem according to an NSTR state within an R-TWT SP in a wireless LAN supporting multi-links.

[0064] like Figure 3As shown, AP MLD1 may include AP1-1 operating on the first link and AP1-2 operating on the second link. STAMLD1 may include STA1-1 operating on the first link and STA1-2 operating on the second link. STAMLD1 may be an NSTR device. The first link and the second link may form an NSTR link pair. Therefore, STR operation may not be performed on the first link and the second link. AP MLD1 may be configured with an R-TWTSP for low-latency communication on the second link. Low-latency communication may be performed within the R-TWT SP. Normal communication may be performed in a period outside the R-TWT SP.

[0065] STA MLD1 can be configured to participate in communications within the R-TWT SP configured by AP MLD1. In other words, STAMLD1 can perform communications (e.g., low-latency communications) within the R-TWT SP configured by AP MLD1. STA MLD1 (e.g., STA1-2) can be a member of the R-TWT SP. STA1-1 of STA MLD1 can send a frame (e.g., a data frame) to AP1-1 or another communication node on the first link. The period during which the transmission operation of STA1-1 is performed on the first link may overlap (e.g., partially overlap or completely overlap) with the R-TWT SP on the second link. Due to the transmission operation of STA1-1 on the first link, a deaf (or blind) section may occur on the second link. In other words, due to the transmission operation of STA1-1, STA1-2 may not be able to perform channel sensing operations and / or frame reception operations. Blind sections may occur within the R-TWT SP. In the blind section within the R-TWT SP, channel access operations, channel sensing operations, frame transmission operations, and / or frame reception operations may not be performed. Therefore, STAMLD1 may not be able to perform low-latency communication within the R-TWT SP.

[0066] To address the above issues (e.g., to ensure low-latency communication), the communication on the first link may preferably end before the R-TWT SP of the second link. The EMLSR device (e.g., EMLSR AP, EMLSR STA) may terminate the communication before the R-TWT SP by additionally considering the switching delay (which is the time required for the link switching of the receiving radio). The switching delay may be the EMLSR switching delay.

[0067] Figure 4a is a timing diagram illustrating a first exemplary embodiment for low-latency communication within an R-TWT SP.

[0068] like Figure 4aAs shown, AP MLD1 may include AP1-1 operating on a first link and AP1-2 operating on a second link. STA MLD1 may include STA1-1 operating on a first link and STA1-2 operating on a second link. STA MLD1 may be an NSTR device. The first link and the second link may form an NSTR link pair. AP MLD1 may configure an R-TWT SP on the second link. STA MLD1 may identify the R-TWT SP configured by AP MLD1. AP MLD1 may generate a beacon frame including an R-TWT information element (e.g., R-TWT IE) to configure the R-TWT SP, and may send the beacon frame. STA MLD1 may receive the beacon frame of AP MLD1, and may identify the R-TWT SP indicated by the beacon frame. STA MLD1 (e.g., STA1-2) may be a member of the R-TWT SP of the second link. STA1-1 of STA MLD1 may terminate the transmission operation of the frame on the first link before the start time of the R-TWT SP or before the time before the offset from the start time of the R-TWT SP. In the present invention, the start time of the R-TWT SP may be interpreted as including the time before the offset from the start time of the R-TWT SP.

[0069] For example, STA1-1 can adjust the length of the frame so that the "sending operation of the frame (for example, the data frame) + the short inter frame space (SIFS) + the receiving operation of the receiving response frame" on the first link ends before the start time of the R-TWT SP of the second link. In the present invention, the receiving response frame can be an acknowledgment (ACK) frame or a block ACK (BA) frame. Accordingly, the blind segment caused by the communication on the first link can be terminated (for example, released, removed) before the start time of the R-TWT SP of the second link, and the low-latency communication of STA MLD1 within the R-TWTSP of the second link can be ensured.

[0070] Figure 4b is a timing diagram illustrating a second exemplary embodiment for low-latency communication within an R-TWT SP.

[0071] like Figure 4bAs shown, AP MLD1 may include AP1-1 operating on a first link and AP1-2 operating on a second link. STA MLD1 may include STA1-1 operating on a first link and STA1-2 operating on a second link. STAMLD1 may be an EMLSR device. An EMLSR device (e.g., EMLSR STA) may perform communication on one link. In other words, the EMLSR device may not be able to perform communication on multiple links at the same time. The listening operation of the EMLSR device may be performed on multiple links, but the EMLSR operation of the EMLSR device may be performed on one link. Therefore, when STA MLD1 performs communication on the first link, a blind section may occur on the second link. In other words, due to the communication operation of STA1-1, STA1-2 may not be able to perform a channel sensing operation and / or a frame reception operation. AP MLD1 may configure an R-TWT SP on the second link. STA MLD1 may identify the R-TWT SP configured by AP MLD1. AP MLD1 may generate a beacon frame including an R-TWT information element (e.g., R-TWT IE) to configure the R-TWT SP, and transmit the beacon frame. STA MLD1 may receive the beacon frame of AP MLD1 and identify the R-TWT SP indicated by the beacon frame. STA MLD1 (e.g., STA1-2) may be a member of the R-TWT SP of the second link.

[0072] STA1-1 of STA MLD1 may terminate the transmission operation of the frame on the first link before the time before the transition delay (e.g., EMLSR transition delay) from the start time of the R-TWT SP or before the time before [transition delay + offset] from the start time of the R-TWT SP. In the present invention, the time before the transition delay from the start time of the R-TWT SP may be interpreted as including the time before [transition delay + offset] from the start time of the R-TWT SP.

[0073] For example, STA1-1 can adjust the length of the frame so that the "sending operation of the frame (e.g., data frame) + SIFS + receiving operation of the receiving response frame + conversion delay" on the first link ends before the start time of the R-TWT SP of the second link. In the present invention, the receiving response frame can be an ACK frame or a BA frame. Therefore, the blind segment caused by the communication on the first link can be ended before the start time of the R-TWT SP of the second link, and the low-latency communication of STAMLD1 within the R-TWT SP of the second link can be ensured.

[0074] If a blind segment occurs due to the EMLSR operation or NSTR state of STA MLD1, and the blind segment is equal to or greater than the preset time, the MediumSyncDelay timer can operate even after the blind segment ends. The MediumSyncDelay timer can be called a medium synchronization delay timer, a synchronization timer, or a delay timer. In the period corresponding to the MediumSyncDelay timer, the sending operation of the communication node (e.g., MLD, AP, STA) may not be possible. The value of the MediumSyncDelay timer can be preset. If the MediumSyncDelay timer operates within the R-TWT SP, the low-power communication of the communication nodes within the R-TWT SP can be limited. In order to solve the above problem, AP MLD1 can release the MediumSyncDelay timer of STA MLD1 by sending any data frame, QoS empty frame and / or trigger frame within the R-TWT SP.

[0075] Figure 5a is a timing diagram illustrating a third exemplary embodiment for low-latency communication within an R-TWT SP.

[0076] like Figure 5a As shown, AP MLD1 may include AP1-1 operating on a first link and AP1-2 operating on a second link. STA MLD1 may include STA1-1 operating on a first link and STA1-2 operating on a second link. STAMLD1 may be an NSTR device. The first link and the second link may form an NSTR link pair. In other words, due to the transmission operation of STA1-1, STA1-2 may not be able to perform a channel sensing operation and / or a frame reception operation. AP MLD1 may configure an R-TWT SP on the second link. STA MLD1 may identify the R-TWT SP configured by AP MLD1. STA MLD1 (e.g., STA1-2) may be a member of the R-TWT SP on the second link. AP MLD1 may generate a beacon frame including an R-TWT information element (e.g., R-TWTIE) to configure the R-TWT SP, and transmit the beacon frame. STA MLD1 may receive the beacon frame of AP MLD1 and identify the R-TWT SP indicated by the beacon frame.

[0077] AP1-1 of AP MLD1 can terminate the sending operation of the frame on the first link before the start time of the R-TWT SP or before the time offset from the start time of the R-TWT SP. For example, AP1-1 can adjust the length of the frame so that the "sending operation of the frame (e.g., data frame) + SIFS + receiving operation of receiving the response frame" on the first link ends before the start time of the R-TWT SP of the second link. Accordingly, the blind segment caused by the communication on the first link can be terminated (e.g., released, removed) before the start time of the R-TWT SP of the second link, and low-latency communication of STA MLD1 within the R-TWT SP of the second link can be ensured.

[0078] Figure 5b is a timing diagram illustrating a fourth exemplary embodiment for low-delay communication within an R-TWT SP.

[0079] like Figure 5b As shown, AP MLD1 may include AP1-1 operating on the first link and AP1-2 operating on the second link. STA MLD1 may include STA1-1 operating on the first link and STA1-2 operating on the second link. STAMLD1 may be an EMLSR device. An EMLSR device (e.g., EMLSR STA) may perform communication on one link. In other words, the EMLSR device may not be able to perform communication on multiple links at the same time. The listening operation of the EMLSR device may be performed on multiple links, but the EMLSR operation of the EMLSR device may be performed on one link. Therefore, when communication between AP MLD1 and STA MLD1 is performed on the first link, a blind section may occur on the second link. AP MLD1 may configure the R-TWT SP on the second link. STA MLD1 may identify the R-TWT SP configured by AP MLD1. STA MLD1 (e.g., STA1-2) may be a member of the R-TWT SP on the second link. AP MLD1 may generate a beacon frame including an R-TWT information element (eg, R-TWT IE) to configure the R-TWT SP, and transmit the beacon frame. STA MLD1 may receive the beacon frame of AP MLD1 and identify the R-TWT SP indicated by the beacon frame.

[0080] AP1-1 of AP MLD1 can terminate the sending operation of the frame on the first link before the time before the conversion delay (e.g., EMLSR conversion delay) from the start time of the R-TWT SP or before the time before [conversion delay + offset] from the start time of the R-TWT SP. For example, AP1-1 can adjust the length of the frame so that the "sending operation of the frame (e.g., data frame) + SIFS + receiving operation of receiving response frame + conversion delay" on the first link ends before the start time of the R-TWT SP on the second link. Accordingly, the blind segment caused by the communication on the first link can be terminated before the start time of the R-TWT SP on the second link, and low-latency communication of STA MLD1 within the R-TWT SP of the second link can be ensured.

[0081] If a blind segment occurs due to the EMLSR operation or NSTR state of STA MLD1, and the blind segment is equal to or greater than the preset time, the MediumSyncDelay timer can operate even after the blind segment ends. The sending operation of the communication node (e.g., MLD, AP, STA) may not be performed in the period corresponding to the MediumSyncDelay timer. The value of the MediumSyncDelay timer can be preset. When the MediumSyncDelay timer operates within the R-TWT SP, the low-power communication of the communication nodes within the R-TWT SP can be restricted. In order to solve the above problem, AP MLD1 can release the MediumSyncDelay timer of STA MLD1 by sending any data frame, QoS empty frame and / or trigger frame within the R-TWT SP.

[0082] Figure 6 is a timing diagram illustrating a first exemplary embodiment of synchronous transmission in the NSTR state.

[0083] like Figure 6 As shown, AP MLD1 may include AP1-1 operating on a first link and AP1-2 operating on a second link. STA MLD1 may include STA1-1 operating on a first link and STA1-2 operating on a second link. STAMLD1 may be an NSTR device. The first link and the second link may form an NSTR link pair.

[0084] AP MLD may perform a backoff operation on the first link and the second link for synchronous transmission of frames. STAMLD may perform a backoff operation on the first link and the second link for synchronous transmission of frames. When performing synchronous transmission, the start time of the frames on the first link and the second link (e.g., the transmission start time) may be the same, and the end time of the frames on the first link and the second link (e.g., the transmission end time) may be the same. The backoff operation may be an enhanced distributed channel access function (EDCAF) operation according to an access category (AC). The AC may be as shown in Table 1 below.

[0085] [Table 1]

[0086]

[0087] AC_BK may indicate background data, AC_BE may indicate data transmitted in a best effort manner, AC_VI may indicate video data, and AC_VO may indicate voice data.

[0088] If the EDCAF backoff counter value on the first link is 0 and the backoff operation on the second link is not completed, AP1-1 may wait for the sending operation on the first link until the backoff operation on the second link is completed. In other words, AP1-1 may keep the EDCAF backoff counter value on the first link as 0 until the backoff operation on the second link is completed. The EDCAF backoff counter value of 0 may mean that the backoff operation is completed. The backoff operation being completed may mean that the EDCAF backoff counter value is 0.

[0089] Before the backoff operation on the second link is completed, the EDCAF backoff counter value for AC_BE on the first link may become 0, and the EDCAF backoff counter value for AC_VO on the first link may become 0. The EDCAF backoff counter values ​​for multiple ACs may become 0. If the backoff counter value on the second link becomes 0 (for example, if the backoff operation on the second link is successful), the AP MLD (for example, AP1-1) and / or the STA MLD (for example, STA1-1) may select an AC from the ACs (for example, AC_BE and AC_VO) for which the backoff operation on the first link is successful. The operation of selecting an AC on the first link may be performed even before the backoff operation on the second link is successful. On the first link, the AP MLD (for example, AP1-1) and / or the STA MLD (for example, STA1-1) may select AC_VO with a higher priority among AC_BE and AC_VO. The length of the AC_VO frame transmitted on the first link may be shorter than the length of the frame (for example, AC_VO frame) transmitted on the second link. In other words, synchronization of the AC_VO frame on the first link may not match synchronization of the AC_VO frame on the second link. The AC_VO frame may be a frame including data corresponding to AC_VO.

[0090] For synchronous transmission on the first link and the second link, the communication node (e.g., AP MLD1) may match the start and end times of the frame on the first link with the start and end times of the frame on the second link. In order to match the end times of the frames on the first link and the second link, the length of the frame on the first link may be adjusted. For example, AP MLD1 (e.g., AP1-1) may add padding bits to the frame on the first link. If the length of the frame on the first link is shorter than the length of the frame on the second link, AP MLD1 (e.g., AP1-1) may send additional frames on the first link to match the end times of the frames on the first link and the second link. For example, AP1-1 may send a data frame including an AC_VO frame and an AC_BE frame on the first link. The data frame including the AC_VO frame and the AC_BE frame may have an aggregated (A)-MPDU form. In this case, an AC_BE frame that is not selected by AP MLD1 (e.g., AP1-1) in the AC selection process may also be sent on the first link. When there are remaining transmission opportunities (TXOPs) for AC_VO, the operation of sending AC_VO frames and AC_BE frames may be performed. In other words, the maximum length of "AC_VO frame + AC_BE frame" may not exceed the TXOP limit of AC_VO. "AC_VO frame + AC_BE frame" whose length exceeds the TXOP limit of AC_VO may not be sent. The start and end times of the "AC_VO frame + AC_BE frame" on the first link may be the same as the start and end times of the AC_VO frame on the second link, respectively.

[0091] The operation of the method according to the exemplary embodiment of the present invention can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium may include a recording device of all types having data that can be read by a computer system. In addition, the computer-readable recording medium can store and execute programs or codes, which can be distributed in a computer system connected via a network and read by a computer in a distributed manner.

[0092] Computer readable recording media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM or flash memory. Program instructions may include not only machine language codes created by a compiler, but also high-level language codes that can be executed by a computer using an interpreter.

[0093] Although some aspects of the present invention have been described in the context of a device, these aspects can indicate the corresponding description according to the method, and a block or device can correspond to the step of the method or the feature of the step. Similarly, the aspects described in the context of the method can be expressed as the feature of a corresponding block or project or a corresponding device. Some or all steps of the method can be performed by (or utilizing) a hardware device such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, one or more of the most important steps of the method can be performed by such a device.

[0094] In some exemplary embodiments, a programmable logic device such as a field programmable gate array can be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, the field programmable gate array can be operated with a microprocessor to perform one of the methods described herein. Typically, the method is preferably performed by a specific hardware device.

[0095] The description of the present disclosure is merely exemplary in nature, and therefore variant forms that do not deviate from the essence of the present invention are intended to fall within the scope of the present invention. Such variant forms should not be regarded as deviations from the spirit and scope of the present invention. Therefore, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A method of a first device, comprising: identifying a service period (SP) configured on the second link; as well as performing communication with the second device on the first link before the start time of the SP, The communication between the first device and the second device ends before the start time of the SP.

2. The method according to claim 1, wherein: Performing communication with the second device includes: sending a data frame to the second device over the first link; and receiving a receive response frame for the data frame from the second device on the first link, The end time of receiving the response frame is before the start time of the SP.

3. The method according to claim 1, wherein: Performing communication with the second device includes: receiving a data frame from a second device over the first link; and sending a reception response frame for the data frame to the second device on the first link, The end time of receiving the response frame is before the start time of the SP.

4. The method according to claim 1, further comprising: When the medium synchronization delay timer is operated in the SP of the second link, the first frame is transmitted to release the medium synchronization delay timer.

5. The method according to claim 1, wherein: The first link and the second link are a non-simultaneous transmission and reception (NSTR) link pair, and when communication between the first device and the second device is performed on the first link, transmission and reception operations on the second link are disabled.

6. The method according to claim 1, wherein: The communication between the first device and the second device ends before the offset from the start time of the SP.

7. The method according to claim 1, wherein: When the first device is an enhanced multi-link single radio (EMLSR) device, the communication between the first device and the second device ends before the EMLSR switching delay time from the start time of the SP.

8. The method according to claim 1, wherein: When the first device is a station (STA) MLD, the second device is an access point (AP) multi-link device (MLD), and when the first device is an AP MLD, the second device is a STA MLD, the STA MLD includes a first STA operating on a first link and a second STA operating on a second link, and the AP MLD includes a first AP operating on the first link and a second AP operating on the second link.

9. A first device comprising a processor, wherein: The processor causes the first device to execute: identifying a service period (SP) configured on the second link; and performing communication with the second device on the first link before the start time of the SP, The communication between the first device and the second device ends before the start time of the SP.

10. The first device according to claim 9, wherein: When performing communication with the second device, the processor causes the first device to execute: sending a data frame to the second device over the first link; and receiving a reception response frame for the data frame from the second device at the first link, The end time of receiving the response frame is before the start time of the SP.

11. The first device according to claim 9, wherein: When performing communication with the second device, the processor causes the first device to execute: receiving a data frame from a second device over the first link; and sending a reception response frame for the data frame to the second device at the first link, The end time of receiving the response frame is before the start time of the SP.

12. The first device according to claim 9, wherein: The processor causes the first device to execute: when the medium synchronization delay timer is operated in the SP of the second link, sending a first frame to release the medium synchronization delay timer.

13. The first device according to claim 9, wherein: The first link and the second link are a non-simultaneous transmission and reception (NSTR) link pair, and when communication between the first device and the second device is performed on the first link, transmission and reception operations on the second link are disabled.

14. The first device according to claim 9, wherein: The communication between the first device and the second device ends before the offset from the start time of the SP.

15. The first device according to claim 9, wherein: When the first device is an enhanced multi-link single radio (EMLSR) device, the communication between the first device and the second device ends before the EMLSR switching delay time from the start time of the SP.

16. The first device according to claim 9, wherein: When the first device is a station (STA) MLD, the second device is an access point (AP) multi-link device (MLD), and when the first device is an AP MLD, the second device is a STA MLD, the STA MLD includes a first STA operating on a first link and a second STA operating on a second link, and the AP MLD includes a first AP operating on the first link and a second AP operating on the second link.

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