Method and apparatus for power saving in a communication system supporting multiple links

Abstract

Disclosed are a method and apparatus for power saving in a communication system supporting multiple links. The operation method of a first STA included in a first apparatus includes the steps of: transmitting a first frame to a first AP included in a second apparatus, the first frame requesting to configure one or more TWT SPs for a plurality of links including a first link and a second link, the first link and the second link being in an NSTR relationship; and receiving a second frame including configuration information of the one or more TWT SPs from the first AP, wherein the one or more TWT SPs in the first link and the one or more TWT SPs in the second link are configured to be the same.

Description

Technical Field

[0001] This invention relates to a wireless local area network (WLAN) communication technology, and more specifically to a low-power operation technology in a communication system supporting multiple links. Background Technology

[0002] Recently, with the increasing distribution of mobile devices, wireless LAN technology, which provides fast wireless communication services for mobile devices, has attracted attention. Wireless LAN technology is a technology that uses wireless communication to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly access the internet.

[0003] The standard for wireless LAN technology is primarily standardized within the Institute of Electrical and Electronics Engineers (IEEE) as the IEEE 802.11 standard. With the development and widespread adoption of this wireless LAN technology, its applications have diversified, and there has been a demand for wireless LAN technologies supporting higher throughput. Therefore, the frequency bandwidth utilized in the IEEE 802.11ac standard (e.g., "maximum 160MHz bandwidth" or "80+80MHz bandwidth") has been expanded, and the number of supported spatial streams has also increased. The IEEE 802.11ac standard can be a Very High Throughput (VHT) wireless LAN technology, supporting throughput of 1 gigabit per second (Gbps) or higher. The IEEE 802.11ac standard can support downlink transmission across multiple stations by utilizing MIMO technology.

[0004] With the emergence of applications requiring higher throughput and real-time transmission, the IEEE 802.11be standard, an Extreme High Throughput (EHT) wireless LAN technology, is under development. The goal of the IEEE 802.11be standard is to support high throughput of 30Gbps. The IEEE 802.11be standard can support techniques to reduce transmission latency. Furthermore, the IEEE 802.11be standard can support extended frequency bandwidth (e.g., 320MHz bandwidth), multi-link transmission, and aggregation operations including multi-band operation, multiple access point (AP) transmission operation, and / or efficient retransmission operations (e.g., Hybrid Automatic Repeat Request (HARQ) operation).

[0005] However, since multilink operation is not defined in existing WLAN standards, detailed operations may need to be defined depending on the environment in which multilink operation is performed. In particular, methods to support low-power operation in multilink environments are needed.

[0006] On the other hand, the techniques described as the background of this invention are intended to improve the understanding of the background of this invention, and these techniques may include content that is not yet known to those skilled in the art to which this invention pertains. Summary of the Invention

[0007] Technical issues

[0008] The present invention aims to provide a method and apparatus for low-power operation in a communication system that supports multiple links.

[0009] Technical solution

[0010] According to a first exemplary embodiment of the present invention for achieving the above-described objective, the operation method of a first station (STA) included in a first device may include: sending a first frame to a first access point (AP) included in a second device, the first frame requesting the configuration of one or more Target Wake-up Time (TWT) Service Periods (SPs) for a multi-link system including a first link and a second link, the first link and the second link having a Non-Simultaneous Transmit and Receive (NSTR) relationship; and receiving a second frame from the first AP including configuration information for one or more TWT SPs, wherein one or more TWT SPs in the first link and one or more TWT SPs in the second link are configured to be identical.

[0011] The operation method may further include: performing a monitoring operation on the trigger frame within TWT SP#n of a first link in one or more TWT SPs; sending a response frame to the first AP within TWT SP#n of the first link in response to receiving the trigger frame from the first AP; and receiving a data frame from the first AP within TWT SP#n of the first link, where n is a natural number.

[0012] The operation method may further include receiving a beacon frame from a first AP in the first link, wherein when the beacon frame indicates the presence of data to be sent to a first STA, a monitoring operation of the trigger frame can be performed within TWT SP#n.

[0013] The operation method may further include: in response to the TWT SP#n of the first link being in a busy state, performing a monitoring operation on the trigger frame within TWT SP#n+1 after TWT SP#n in one or more TWT SPs of the first link.

[0014] When TWT SP#n or the time period before T0 from the start time of TWT SP#n is in an idle state, monitoring of the trigger frame can be performed.

[0015] The first STA's operating state can transition from sleep to wake-up at the start time of TWT SP#n or before said start time.

[0016] The response frame can be a power saving (PS) polling frame, an unscheduled-automatic power save delivery (U-APSD) frame, or a quality-of-service (QoS) empty frame.

[0017] The operating method may further include: sending an association request frame to a first AP in a first link, the association request frame including information indicating whether low-power operation is supported; and receiving an association response frame from the first AP in the first link in response to the association request frame.

[0018] The associated response frame may include an associated identifier (AID) configured for each device.

[0019] According to a second exemplary embodiment of the present invention for achieving the above-described objective, the operation method of the first device may include: configuring a target wake-up time (TWT) service period (SP) in a first link of a multi-link system using a second device; identifying the state of the multi-link system during a time period prior to T0 from the start time of the TWT SP; performing a monitoring operation on a trigger frame within the TWT SP of the second link in response to identifying that the second link of the multi-link system is in an idle state; sending a response frame to the second device within the TWT SP of the second link in response to receiving a trigger frame from the second device; and receiving a data frame from the second device within the TWT SP of the second link.

[0020] The configuration of the TWT SP may include: sending a multi-link (ML) TWT request frame to a first access point (AP) included in the second device in a first link; and receiving an MLTWT response frame from the first AP in the first link as a response to the ML TWT request frame, wherein the configuration information of the TWT SP is included in the ML TWT response frame.

[0021] The operation method may further include receiving a beacon frame from a first AP included in the second device in the first link, wherein when the beacon frame indicates the presence of data to be sent to a first STA included in the first device, a monitoring operation of the trigger frame can be performed within the TWT SP.

[0022] All STAs included in the first device can operate in a wake-up state during a period of time prior to T0, starting from the start time of TWT SP, and the operating state of STAs operating in links determined to be busy during the time period can be switched to a sleep state.

[0023] T0 can be set to the time within the sum of the distributed coordination function (DCF) inter-frame interval (DIFS) and the maximum value of the backoff counter.

[0024] According to a third exemplary embodiment of the present invention for achieving the above-described objectives, the operation method of the first device may include: configuring a Target Wake-up Time (TWT) service period (SP) in a first link of a multi-link system using a second device; identifying the state of the first link of the multi-link system during a first T1 period starting from the start time of the TWT SP; identifying the state of the second link of the multi-link system during a second T1 period starting from the end time of the first T1 period in response to identifying that the first link is busy; performing a monitoring operation on a trigger frame within the TWT SP of the second link in response to identifying that the second link is idle; sending a response frame to the second device within the TWT SP of the second link in response to receiving a trigger frame from the second device; and receiving a data frame from the second device within the TWT SP of the second link.

[0025] The length of the TWT SP can be increased to the first T1 time period.

[0026] In response to the first link's state changing from busy to idle during the first T1 period, the first link's state can be additionally identified during the T2 period.

[0027] The configuration of the TWT SP may include: sending a multi-link (ML) TWT request frame to a first AP included in the second device in a first link; and receiving an ML TWT response frame from the first AP in the first link as a response to the ML TWT request frame, wherein the configuration information of the TWT SP is included in the ML TWT response frame.

[0028] The operation method may further include receiving a beacon frame from a first AP included in the second device in the first link, wherein when the beacon frame indicates the presence of data to be sent to a first STA included in the first device, a monitoring operation of the trigger frame can be performed within the TWT SP.

[0029] T1 can be set to the time within the sum of the Distributed Coordination Function (DCF) Inter-Frame Interval (DIFS) and the maximum value of the backoff counter.

[0030] Beneficial effects

[0031] According to the present invention, in communication utilizing multiple links, data frame transmission and reception can be performed by triggering frame transmission of a single communication node (e.g., access point (AP), station (STA), multi-link device (MLD)) when communication is feasible. Therefore, communication errors can be prevented when simultaneous transmission and reception (STR) is not possible, and data can be transmitted quickly even when the communication node is performing low-power operation or when limited low-power operation is performed in a multi-link system. Attached Figure Description

[0032] Figure 1 This is a block diagram illustrating a first exemplary embodiment of a communication node constituting a wireless local area network system.

[0033] Figure 2 This is a conceptual diagram illustrating a first exemplary implementation of multiple links configured between MLDs.

[0034] Figure 3 This is a sequence diagram illustrating a first exemplary implementation of a negotiation process for multi-link operation in a wireless local area network system.

[0035] Figure 4 This is a timing diagram illustrating a first exemplary embodiment of a power-saving method in a wireless local area network system.

[0036] Figure 5a This is a timing diagram illustrating a second exemplary embodiment of a power-saving method in a wireless local area network system.

[0037] Figure 5b This is a timing diagram illustrating a third exemplary embodiment of a power-saving method in a wireless local area network system.

[0038] Figure 6 This is a timing diagram illustrating a fourth exemplary embodiment of a power-saving method in a wireless local area network system.

[0039] Figure 7 This is a timing diagram illustrating a fifth exemplary embodiment of a power-saving method in a wireless local area network system.

[0040] Figure 8 This is a timing diagram illustrating a sixth exemplary embodiment of a power-saving method in a wireless local area network system.

[0041] Figure 9 This is a timing diagram illustrating a first exemplary embodiment of the operation method of the T2 timer in a wireless local area network system. Detailed Implementation

[0042] Because the present invention can be modified in various ways and can take many forms, specific exemplary embodiments will be shown in the accompanying drawings and described in detail in the specific embodiments. However, it should be understood that the present invention is not intended to be limited to the specific exemplary embodiments, but rather, the present invention covers all modifications and alternatives that fall within the spirit and scope of the present invention.

[0043] Relational terms such as "first," "second," etc., may 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. For example, without departing from the scope of the invention, a first component may be named a second component, and a second component may similarly be named a first component. The term "and / or" refers to any one or a combination of a plurality of related and described items.

[0044] In an exemplary embodiment of the present invention, "at least one of A and B" may refer to "at least one of A or B" or "at least one combination of one or more of A and B". Furthermore, "one or more of A and B" may refer to "one or more of A or B" or "one or more combinations of one or more of A and B".

[0045] When it is said that a component is "connected" or "connected" to another component, it should be understood that the component is directly "connected" or "connected" to the other component, or that another component may be provided between them. Conversely, when it is said that a component is "directly connected" or "directly linked" to another component, it should be understood that no other component is provided between them.

[0046] The terminology used in this invention is for describing specific exemplary embodiments only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly specifies otherwise. In this invention, terms such as “comprising” 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.

[0047] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms commonly used in dictionaries and already in dictionaries should be interpreted as having the meaning corresponding to their contextual meaning in this field. In this specification, unless explicitly defined, terms are not necessarily to be interpreted as having a formal meaning.

[0048] The invention will now be described in detail with reference to the accompanying drawings. In describing the invention, for the purpose of providing a thorough understanding, the same reference numerals refer to the same elements throughout the description of the drawings, and repeated descriptions thereof will be omitted.

[0049] In the following description, a wireless communication system applying an exemplary embodiment of the present invention will be described. The wireless communication system applying an exemplary embodiment of the present invention is not limited to what is described below, and the exemplary embodiments of the present invention can be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network".

[0050] Figure 1 This is a block diagram illustrating a first exemplary embodiment of a communication node constituting a wireless local area network system.

[0051] like Figure 1 As shown, communication node 100 can be an access point, station, access point (AP) multi-link device (MLD), or non-AP MLD. An access point can refer to an AP, and a station can refer to a STA or a non-AP STA. The operating channel width supported by the access point can be 20 MHz, 80 MHz, 160 MHz, etc. The operating channel width supported by the station can be 20 MHz, 80 MHz, etc.

[0052] Communication node 100 may include at least one processor 110, memory 120, and multiple transceivers 130 connected to a network to perform communication. Transceivers 130 may be referred to as transceivers, radio frequency (RF) units, RF modules, etc. Furthermore, communication node 100 may further include input interface devices 140, output interface devices 150, storage devices 160, etc. Components included in communication node 100 can be connected to each other via bus 170 to communicate.

[0053] However, the various components included in communication node 100 can be connected via separate interfaces or a separate bus centered on processor 110 instead of the common bus 170. For example, processor 110 can be connected via a dedicated interface to at least one of memory 120, transceiver 130, input interface device 140, output interface device 150, and storage device 160.

[0054] Processor 110 can execute at least one instruction stored in at least one of memory 120 and storage device 160. Processor 110 may refer to a central processing unit (CPU), graphics processing unit (GPU), or dedicated processor that performs the methods according to exemplary embodiments of the present invention. Each of memory 120 and storage device 160 may be configured as at least one volatile storage medium and a non-volatile storage medium. For example, memory 120 may be configured with at least one read-only memory (ROM) and random access memory (RAM).

[0055] Figure 2 This is a conceptual diagram illustrating a first exemplary implementation of multiple links configured between MLDs.

[0056] like Figure 2 As shown, an MLD can have a Medium Access Control (MAC) address. In an exemplary embodiment, an MLD can refer to an AP MLD and / or a non-AP MLD. The MAC address of the MLD can be used in the multi-link establishment process between the non-AP MLD and the AP MLD. The MAC address of the AP MLD can be different from the MAC address of the non-AP MLD. APs associated with an AP MLD can have different MAC addresses, and stations (STAs) associated with non-AP MLDs can have different MAC addresses. Each AP with a different MAC address can be responsible for each of the multiple links supported by the AP MLD and can act as an independent AP.

[0057] Each STA with a different MAC address can be responsible for each of the multiple links supported by a non-AP MLD and can perform the function of an independent STA. A non-AP MLD can be referred to as a STA MLD. An MLD can support Simultaneous Transmit and Receive (STR) operations. In this case, the MLD can perform a transmit operation on link 1 and a receive operation on link 2. An MLD that supports STR operations can be referred to as a STR MLD (e.g., a STR AP MLD, a STR non-AP MLD). In exemplary embodiments, a link can refer to a channel or frequency band. A device that does not support STR operations can be referred to as a non-STR (NSTR) AP MLD or an NSTR non-AP MLD (or an NSTR STA MLD).

[0058] MLDs can transmit and receive frames across multiple links (i.e., multi-link) by utilizing discontinuous bandwidth extension schemes (e.g., 80MHz + 80MHz). Multi-link operation can include multi-band transmission. An AP MLD can include multiple APs, and these APs can operate on different links. Each of the multiple APs can perform the functions of a lower-level 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., the AP) can operate at a higher-level layer (or...) Figure 1 The processor 110 shown operates under the control of the processor. A non-AP MLD may include multiple STAs, and these STAs may operate on different links. Each of the multiple STAs may be referred to as a "communication node" or a "lower-level entity." A communication node (i.e., a STA) may operate at a higher-level layer (or...) Figure 1 It operates under the control of the processor 110 shown.

[0059] MLDs can perform communication across multiple frequency bands (i.e., multi-band). For example, an MLD can perform communication in the 2.4 GHz band using 80 MHz of bandwidth according to a channel extension scheme (e.g., a bandwidth extension scheme), and in the 5 GHz band using 160 MHz of bandwidth according to the same scheme. An MLD can also perform communication in the 5 GHz band using 160 MHz of bandwidth and in the 6 GHz band using 160 MHz of bandwidth. A frequency band (e.g., a channel) utilized by an MLD can be defined as a link. Alternatively, multiple links can be configured within a single frequency band utilized by an MLD. For example, an MLD can configure one link in the 2.4 GHz band and two links in the 6 GHz band. These links can be referred to as Link 1, Link 2, and Link 3. Alternatively, these links can be referred to as Link 1, Link 2, and Link 3. Link numbers can be set by the AP, and identifiers (IDs) can be assigned to each link.

[0060] A Multilink Provider (MLD) (e.g., an AP MLD and / or a non-AP MLD) can configure multilinks by performing an access procedure and / or negotiation procedure for multilink operation. In this case, the number of links and / or links utilized in the multilink operation can be configured. A non-AP MLD (e.g., a STA) can identify information about the frequency bands that can communicate with the AP MLD. During the negotiation process for multilink operation between the non-AP MLD and the AP MLD, the non-AP MLD can configure one or more links supported by the AP MLD for multilink operation. Stations that do not support multilink operation (e.g., IEEE 802.11a / b / g / n / ac / ax STAs) can connect to one or more links in the multilink operation supported by the AP MLD.

[0061] When the bandwidth spacing between multiple links is sufficient (e.g., the bandwidth spacing between link 1 and link 2 in the frequency domain), the MLD can perform STR operations. For example, the MLD can use link 1 to transmit Physical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU) 1 and can use link 2 to receive PPDU 2. On the other hand, if the MLD performs STR operations when the bandwidth spacing between multiple links is insufficient, in-device coexistence (IDC) interference, i.e., interference between multiple links, will occur. Therefore, link pairs with insufficient bandwidth spacing between multiple links can be non-STR link pairs, and the MLD can operate as a non-STR MLD (e.g., a non-STR non-AP (STA) MLD or a non-STR AP MLD) that cannot perform STR operations. The AP included in the non-STR AP MLD can be a soft AP. The exemplary embodiments described below can be performed by APs (e.g., APs included in a STR AP MLD) and soft APs (e.g., APs included in a non-STR AP MLD).

[0062] For example, multiple links, including Link 1, Link 2, and Link 3, can be configured between the AP MLD and the non-AP MLD 1. If the bandwidth spacing between Link 1 and Link 3 is sufficient, the AP MLD can perform STR operations using Link 1 and Link 3. That is, the AP MLD can transmit frames using Link 1 and receive frames using Link 3. If the bandwidth spacing between Link 1 and Link 2 is insufficient, Link 1 and Link 2 can be a non-STR link pair, and the AP MLD or STA MLD may not be able to perform STR operations using Link 1 and Link 2. If the bandwidth spacing between Link 2 and Link 3 is insufficient, the AP MLD or STA MLD may not be able to perform STR operations using Link 2 and Link 3.

[0063] On the other hand, in a wireless LAN system, a negotiation process for multi-link operation can be performed during the access process between the STA and the AP.

[0064] A device that supports multiple links (e.g., an AP or a STA) can be called a multi-link device (MLD). An AP that supports multiple links can be called an AP MLD, and a STA that supports multiple links can be called a non-AP MLD or a STA MLD. An AP MLD can have a physical address (e.g., a MAC address) for each link. An AP MLD can be implemented as if it were a separate AP responsible for each link. Multiple APs can be managed within a single AP MLD. Therefore, coordination between multiple APs belonging to the same AP MLD is possible. Similarly, a STA MLD can have a physical address (e.g., a MAC address) for each link. A STA MLD can be implemented as if it were a separate STA responsible for each link. Multiple STAs can be managed within a single STA MLD. Therefore, coordination between multiple STAs belonging to the same STA MLD is possible.

[0065] For example, AP1 of the AP MLD and STA1 of the STA MLD can each be responsible for the first link and can communicate using the first link. AP2 of the AP MLD and STA2 of the STA MLD can each be responsible for the second link and can communicate using the second link. STA2 can receive state change information from the first link in the second link. In this case, the STA MLD can collect information received from each link (e.g., state change information) and can control the operations performed by STA1 based on the collected information.

[0066] Figure 3 This is a sequence diagram illustrating a first exemplary implementation of a negotiation process for multi-link operation in a wireless local area network system.

[0067] like Figure 3 As shown, the access process between a STA and an AP in a basic service set (BSS) can generally be divided into a detection step to detect the AP, an authentication step to authenticate between the STA and the detected AP, and an association step to associate between the STA and the authenticated AP.

[0068] During the detection step, the STA can detect one or more APs using either a passive scanning scheme or an active scanning scheme. When using a passive scanning scheme, the STA can detect one or more APs by listening to beacons sent by one or more APs. When using an active scanning scheme, the STA can send probe request frames and can detect one or more APs by receiving probe response frames (responses to probe request frames) from one or more APs.

[0069] When one or more access points (APs) are detected, the STA can perform authentication steps with the detected APs. In this case, the STA can perform authentication steps with multiple APs. Authentication algorithms according to the IEEE 802.11 standard can be categorized into open system algorithms that exchange two authentication frames, shared key algorithms that exchange four authentication frames, etc.

[0070] The STA can send authentication request frames based on the authentication algorithm according to the IEEE 802.11 standard, and can complete authentication with the AP by receiving authentication response frames (which are responses to the authentication request frames) from the AP.

[0071] Once authentication with the AP is complete, the STA can perform the association steps with the AP. Specifically, the STA can select an AP from the APs for which it has already performed authentication steps, and can then perform the association steps with the selected AP. That is, the STA can send an association request frame to the selected AP, and can complete the association with the AP by receiving an association response frame (which is a response to the association request frame) from the selected AP.

[0072] On the other hand, multi-link operation can be supported in a wireless LAN system. A multi-link device (MLD) can include one or more STAs associated with the MLD. The MLD can be a logical entity. MLDs can be divided into AP MLDs and non-AP MLDs. Each STA associated with an AP MLD can be an AP, and each STA associated with a non-AP MLD can be a non-AP STA. To configure multi-link, a multi-link discovery process, a multi-link establishment process, etc., can be performed. The multi-link discovery process can be performed during the probe step between the STA and the AP. In this case, the multi-link information element (MLIE) can be included in the beacon frame, probe request frame, and / or probe response frame.

[0073] For example, to perform multi-link operation, during the probing step, an AP (e.g., an AP associated with an MLD) can exchange information with a STA (e.g., a non-AP STA associated with an MLD) indicating whether multi-link operation is available, as well as information about available links. During the multi-link operation negotiation process (e.g., the multi-link establishment process), the STA can send link information to be used for the multi-link operation. The multi-link operation negotiation process can be performed during the access process between the STA and the AP (e.g., the association step), and the information elements required for multi-link operation can be configured or changed via action frames during the negotiation process.

[0074] Furthermore, during the access process between the STA and the AP (e.g., the association step), the available links of the AP can be configured, and an identifier (ID) can be assigned to each link. Subsequently, during the negotiation and / or change process for multi-link operation, information indicating whether each link is active can be sent, and the link ID can be used to represent the information.

[0075] During the exchange of performance information elements (e.g., EHT performance information elements) between the STA and AP, information indicating whether multi-link operation is available can be sent and received. Performance information elements may include: information about supported frequency bands, information about supported links (e.g., the ID and / or number of supported links), information about links capable of simultaneous transmit and receive (STR) operations (e.g., information about the frequency band of the links, information about the spacing between links), etc. Furthermore, performance information elements may include information specifically indicating which links are capable of STR operations.

[0076] Figure 4 This is a timing diagram illustrating a first exemplary embodiment of a power-saving method in a wireless local area network system.

[0077] like Figure 4 As shown, multi-link communication can be performed between an AP MLD acting as the first MLD and a non-AP MLD (e.g., a STAMLD) acting as the second MLD, and low-power operation can be performed on each link to save power. Low-power operation can refer to power-saving operations. Low-power operation can refer to data transmission / reception operations scheduled by the AP MLD. Data transmission / reception operations scheduled by the AP MLD can be Target Wake-up Time (TWT) operations. The STAMLD can utilize one link to perform an association process with the AP MLD. Negotiation for low-power operation can be performed during the association process or the low-power operation negotiation process. For low-power operation negotiation, STA1 of the ST MLD can generate an association request frame including information indicating whether low-power operation is performed (or supported), and send the association request frame on the first link.

[0078] The information indicating whether to perform low-power operation can be the beacon frame monitoring interval. The beacon frame monitoring interval can be set in units of beacon intervals. When the beacon frame monitoring interval is set to 0, this means that low-power operation is not performed. When the beacon frame monitoring interval is set to a value other than 0, this means that low-power operation is performed.

[0079] AP1 of the AP MLD can receive an association request frame from STA1 on the first link. Based on the information included in the association request frame (e.g., information indicating whether low-power operation is to be performed), AP1 in the AP MLD can identify whether STA1 of the STA MLD is performing low-power operation. AP1 of the AP MLD can assign an association identifier (AID) to the STA MLD and can send an association response frame including the AID (e.g., 1111) on the first link. Since an AID can be assigned to each MLD, STA1 and STA2 included in the STA MLD can have the same AID. Furthermore, the association response frame can include information about the beacon interval. The beacon interval can be the beacon transmission period. The STA MLD (e.g., STA1 and / or STA2) can periodically wake up according to the beacon interval and perform monitoring operations on the beacon frames.

[0080] When the STA MLD (e.g., STA1 and / or STA2) supports low-power operation and the association process is complete, all links (e.g., STA1 and STA2 of the STA MLD) can operate in sleep mode. When the STA MLD (e.g., STA1 and / or STA2) supports low-power operation for sending and receiving scheduled data, a negotiation process can be performed within a TWT (e.g., triggering a TWT-enabled service period (SP) or a restricted TWT (rTWT)). TWT-related processes can be configured to execute only on specific links. For example, TWT or rTWT-related processes can be configured to execute only on the links where the TWT negotiation process is performed. During the TWT negotiation process, the links where the TWT or rTWT-related processes are performed can be specified. When TWT or rTWT is configured, the STA MLD and AP MLD can send and receive frames within a service period (SP), which is the time indicated by the TWT (e.g., the scheduled time). Furthermore, TWT or rTWT can be configured to trigger TWT activation, where the STA MLD can send data frames only via a trigger frame sent by the AP MLD. In an exemplary implementation, a link can be interpreted as an AP and / or STA utilizing that link. The operational state of one link in a multi-link system (e.g., a wake-up state or a sleep state) can change based on the beacon interval negotiated during the association process. For example, STA1 and STA2 of STA MLD can operate in a sleep state after the association process is completed, and the operational state of STA1 can change from a sleep state to a wake-up state based on the beacon interval negotiated during the association process. STA1 operating in the wake-up state can receive beacon frames from AP1 of APMLD by performing a beacon frame monitoring operation.

[0081] The STA MLD's STA1 can identify the value of the bit corresponding to the STA MLD in the bitmap of the traffic indication map (TIM) included in the beacon frame (e.g., AID = 1111). If the bit value is set to 0, this can mean that there are no data units (e.g., buffer units (BUs)) to be sent to the STA MLD in the AP MLD. If the bit value is set to 1, this can mean that there are data units to be sent to the STA MLD in the AP MLD. The AP MLD can specify the link to send the BU via the TIM or a separate frame. In this case, the STA MLD can send power-saving (PS) polling frames, unscheduled automatic power-saving delivery (U-APSD) frames, or quality of service (QoS) empty frames on one or more of the links specified as the links to send the BU.

[0082] When a transmission opportunity (TXOP) is configured for AP1 to send data frames to another communication node on the first link, or for another communication node to send data frames to AP1, the first link may be busy. Therefore, STA1 of the STA MLD may be unable to send PS polling frames (or U-APSD frames or QoS empty frames) on the first link. In this case, STA2 of the STA MLD can utilize the second link to send PS polling frames (or U-APSD frames or QoS empty frames). To receive beacon frames, STA1's operating state can change from sleep to wake-up, and when it is determined that the first link is busy, STA2's operating state can change from sleep to wake-up to send PS polling frames. Furthermore, when it is determined that the first link is busy, STA1's operating state can change from wake-up to sleep.

[0083] When the frequency bands of the first link and the second link are adjacent, STR operation may not be possible. That is, the relationship between the first and second links can be a non-STR link pair with a non-STR link relationship. In this case, even if a PS polling frame is transmitted in the second link, AP2 of AP MLD may not be able to send an ACK as an immediate response to the PS polling frame in the second link because the first link is busy. That is, when AP1 of AP MLD is performing a receive operation in the first link, it can receive the PS polling frame transmitted in the second link. When an ACK as an immediate response is sent, the receive operation in the first link can be stopped. Therefore, when AP1 of AP MLD is performing a transmit operation in the first link but does not send an ACK as an immediate response, the PS polling frame transmitted in the second link may not be received by AP2 of AP MLD. In this case, an ACK as an immediate response cannot be sent. When no ACK for the PS polling frame is received, STA2 of STA MLD can continuously retransmit the PS polling frame in the second link. When the busy state of the first link (e.g., TXOP) ends, AP2 of AP MLD can send ACK for the PS polling frame of STA2 in the second link through the second link.

[0084] Since a PS polling frame was received and an immediate response was sent normally on the second link, AP2 of the AP MLD can send a data frame on the second link, the data frame including data units stored in a buffer. STA2 of the STA MLD can receive data frames from AP2 on the second link and can send an ACK for the data frame on the second link. The data frame may include a Traffic Identifier (TID) field and additional data fields; the TID field can be set to 1, and the additional data fields can be set to 0.

[0085] When the first link is busy and there is inter-device interference, PS polling frames sent on the second link may interfere with the first link. Therefore, transmission errors may occur on the first link. When the first link is busy and the relationship between the first and second links is not a STR link relationship, STA1 of the STA MLD can send PS polling frames on the first link after the busy state ends. When a hidden node uses the first link, STA1 of the STA MLD can determine the state of the first link as idle rather than busy and can send PS polling frames on the first link. In this case, PS polling frames sent on the first link may cause transmission errors in another communication node (e.g., the hidden node).

[0086] Figure 5a This is a timing diagram illustrating a second exemplary embodiment of a power-saving method in a wireless local area network system.

[0087] like Figure 5a As shown, low-power operation can be a low-power operation used for transmitting and receiving scheduled data. When the STAMLD (e.g., STA1 and / or STA2) supports low-power operation for transmitting and receiving scheduled data, the low-power operation can be performed based on TWT (e.g., triggering TWT enable SP or rTWT). The STA MLD can perform a TWT negotiation procedure with the AP MLD to configure multi-link TWT. The TWT-related procedure can be configured to be performed only on specific links. For example, the TWT or rTWT-related procedure can be configured to be performed only on the link where the TWT negotiation procedure is performed. During the TWT negotiation procedure, the link where the TWT or rTWT-related procedure is performed can be specified. When TWT or rTWT is configured, the STA MLD and AP MLD can transmit and receive frames within an SP, which is the time indicated by the TWT (e.g., the scheduled time). Furthermore, TWT or rTWT can be configured to trigger TWT enable, where the STA MLD can transmit data frames only via a trigger frame sent by the AP MLD. When STAMLD supports low-power operation indicating the presence of a BU via TIM, TWT-related procedures can be performed together. The TWT negotiation process can be performed between a STA MLD and an AP MLD. For example, STA1 of STA MLD can perform a TWT negotiation process with AP1 of APMLD. During the TWT negotiation process, STA1 of STA MLD can send a Multi-Link (ML) TWT Request frame to AP1 in the first link. AP1 of AP MLD can receive the ML TWT Request frame from STA1 in the first link and can send an ML TWT Response frame in the first link as a response to the ML TWT Request frame. The ML TWT Response frame can include information about the ML TWT. The ML TWT Request frame can refer to a general TWT Request frame that includes multi-link related information (e.g., a link ID bitmap indicating the link running TWT or restricted TWT information). The ML TWT Response frame can refer to a general TWT Response frame that includes multi-link related information (e.g., a link ID bitmap indicating the link running TWT or restricted TWT information).

[0088] When the relationship between the first and second links is a non-STR link relationship (e.g., a non-STR link pair), or when the AP controls the STA's PS polling frame transmission due to many hidden nodes, the power management (PM) bit included in the ML TWT response frame can be set to 1. A PM bit set to 1 can indicate that communication between the STA and AP is not performed during periods other than the Service Period (SP). Alternatively, a PM bit set to 1 can indicate that data transmission needs to be terminated before the SP begins so that scheduled communication between the STA and AP can be performed within the SP.

[0089] When the relationship between the first and second links is a non-STR link relationship (e.g., a non-STR link pair), a non-STR communication terminal (e.g., a STA MLD or AP MLD) operating in the non-STR link pair can perform data transmission / reception operations (e.g., TWT operations) within a TWT SP or within an rTWT SP (e.g., rTWT operations). In this case, the AP MLD can match all TWT SPs of the first and second links, which are non-STR link pairs (e.g., making the start and / or end times of TWT SP#1 coincide with the start and / or end times of TWT SP#2). For example, the period of the TWT SP in the first link can be set to be equal to the period of the TWT SP in the second link, the start time of the TWT SP in the first link can be set to be equal to the start time of the TWT SP in the second link, and the end time of the TWT SP in the first link can be set to be equal to the end time of the TWT SP in the second link. That is, the TWT SP in the first link can be synchronized with the TWT SP in the second link.

[0090] Furthermore, during the ML TWT negotiation process, the TWT can be configured to trigger-enabled TWT, where the STA MLD can perform transmission within the TWT SP solely through the AP's trigger frame. Information regarding trigger-enabled TWT can be included in the ML TWT response frame, and trigger-enabled TWT can be configured in the first link. The link operating trigger-enabled TWT can be specified. When a trigger-enabled TWT SP is configured, the STA (e.g., STA1) can transmit frames (e.g., PS polling frames, U-APSD frames, or QoS empty frames) upon receiving a trigger frame from the AP (e.g., AP1) within the trigger-enabled TWT SP. The STA can request data transmission (e.g., BU transmission) by sending PS polling frames, U-APSD frames, or QoS empty frames. In low-power operation where the presence of a BU is indicated by a TIM, the AP MLD can send a trigger frame for the transmission of PS polling frames, U-APSD frames, and / or QoS empty frames, and the STA MLD can send PS polling frames, U-APSD (data frames), and / or QoS empty frames as response frames to the trigger frame.

[0091] When TWT is enabled via a trigger and PM is set to 1 in the first link, the operating state of STA1 in the STA MLD can transition from sleep to wake-up based on the beacon interval. STA1 operating in wake-up mode can receive beacon frames from AP1 in the AP MLD and can identify the TIM included in the beacon frame. Here, the AID of the STA MLD (e.g., STA1 and / or STA2) can be set to 1111.

[0092] Since the TWT SPs in the first and second links, which are non-STR link pairs, are synchronized, if the value of the bit corresponding to the STA MLD in the TIM bitmap is set to 1 (e.g., when there is a data unit (BU) in the AP MLD to be sent to the STA MLD), the operating state of all STAs in the STA MLD (e.g., the STA responsible for all links) or STAs in the links indicated by the TIM or individual frames can transition from a sleep state to a wake-up state at the same start time when the TWT SP is triggered in the first and second links, or before the start time when the TWT SP is triggered. During the synchronized triggering of the TWT SP in the first and second links, which are non-STR link pairs, all STAs operating in the wake-up state can send frames simply by receiving the trigger frame. Therefore, the corresponding STA can perform monitoring operations for receiving the trigger frame. Here, all STAs can include STA1 and STA2.

[0093] When the bitmap of the TIM included in the beacon frame indicates the presence of a data unit (e.g., BU) to be sent to the STA MLD, and the relationship between the first and second links is a non-STR link relationship (e.g., a non-STR link pair), and the first link is busy during the trigger-enabled TWT SP#1 synchronized between the first and second links (which are non-STR link pairs) due to AP1's transmit or receive operation, a receive operation including channel snooping can be omitted in the second link due to the non-STR link pair. Therefore, since the channel access procedure (e.g., backoff) cannot be performed, trigger frames can be omitted in the second link during the trigger-enabled TWT SP#1 synchronized between the first and second links (which are non-STR link pairs). When AP1 of the AP MLD performs a receive operation during the trigger-enabled TWT SP#1, trigger frames sent by AP2 of the AP MLD in the second link during the trigger-enabled TWT SP#1 synchronized between the first and second links may interfere with the receive operation of the first link. Therefore, trigger frames can be omitted from the second link during the trigger-enabled TWT SP#1. Therefore, STA1 and STA2 can remain silent, where no frame transmission is performed within the trigger-enabled TWT SP#1 synchronized in the first and second links. When the STA MLD performs transmit / receive operations in one link of a non-STR link pair, the transmit / receive operations in that one link may interfere with the transmit / receive operations in the other link of the non-STR link pair. During TWT configuration, the TWT or rTWT can be configured to operate in one link of a non-STR link pair (e.g., the first link). In this case, during the TWT or rTWT SP (e.g., trigger-enabled TWT SP#1) operating in one link of a non-STR link pair (e.g., the first link), the STA MLD can remain silent, where no transmission is performed in the other link of the link pair (e.g., the second link). STA1 and STA2 can wait until the next trigger-enabled TWT SP#2 to receive the trigger frame. When the first link is idle within trigger-enabled TWT SP#2, AP1 of the AP MLD can transmit the trigger frame through the first link within trigger-enabled TWT SP#2. STA1 of STA MLD can receive the trigger frame of AP1 via the first link within the trigger enabled TWT SP#2.

[0094] When TWT is triggered and enabled, upon receiving a trigger frame from AP1 within TWT SP#2, STA1 of the STA MLD can transmit frames (e.g., PS polling frames, U-APSD frames (data frames), and / or QoS empty frames) via the first link in response to the trigger frame. AP1 of the AP MLD can receive STA1's PS polling frames via the first link within TWT SP#2, send an ACK as an immediate response to the PS polling frames, and transmit data frames (e.g., data frames including BU) via the first link within TWT SP#2. Data frames can be transmitted after performing a channel access procedure (e.g., backoff) within TWT SP#2. Data frames can be configured to complete transmission within TWT SP#2. STA1 of the STA MLD can receive AP1's data frames via the first link within TWT SP#2.

[0095] In cases of TWTs other than those that trigger TWTs, or in cases of TWTs or rTWTs that do not require waiting for a trigger frame, refer to Figure 5a In the exemplary embodiment shown, STA1 of the STA MLD can receive control frames (e.g., RTS or MU-RTS) from AP1 within the TWT SP#2 trigger enable. When a control frame is received from AP1 within the TWT SP#2 trigger enable, STA1 of the STA MLD can transmit a control frame (e.g., a CTS frame) via the first link in response to the received control frame. AP1 of the AP MLD can receive a control frame as a response from STA1 via the first link within the TWT SP#2 trigger enable, and can transmit a data frame (e.g., a data frame including BU) after SIFS elapsed from the time the control frame was received. STA1 of the STA MLD can receive a data frame from AP1 via the first link within the TWT SP#2 trigger enable, and can transmit a receive response message (e.g., ACK or BA) as an immediate response after SIFS elapsed from the time the data frame was received.

[0096] When both links are available, a portion of a data unit (e.g., BU) can be included in data frame #1, which can be transmitted on the first link. The remaining portion of the data unit can be included in data frame #2, which can be transmitted on the second link. Therefore, data unit transmission can be performed quickly. The transmission time of frames sent by the AP MLD on the first and second links can be the same, and the reception time of frames received by the AP MLD on the first and second links can also be the same. Trigger frames transmitted on the first and second links can have the same length. The transmission time allocated to STA1 via the trigger frame transmitted on the first link can be the same as the transmission time allocated to STA2 via the trigger frame transmitted on the second link. That is, the transmission of frames sent by STA1 and STA2 needs to be completed simultaneously.

[0097] Figure 5b This is a timing diagram illustrating a third exemplary embodiment of a power-saving method in a wireless local area network system.

[0098] like Figure 5bAs shown, low-power operation can be a low-power operation used for transmitting and receiving scheduled data. When a STAMLD (e.g., STA1 and / or STA2) supports low-power operation for transmitting and receiving scheduled data, the low-power operation can be performed based on a TWT (e.g., triggering TWT enablement SP or rTWT). The STA MLD can perform a TWT negotiation procedure with the AP MLD to configure multi-link TWT. The TWT-related procedure can be configured to be performed only on specific links. For example, the TWT or rTWT-related procedure can be configured to be performed only on the link where the TWT negotiation procedure is performed. During the TWT negotiation procedure, the link where the TWT or rTWT-related procedure is performed can be specified. When TWT or rTWT is configured, the STA MLD and AP MLD can transmit and receive frames within an SP, which is a time indicated by the TWT (e.g., a scheduled time). Furthermore, TWT or rTWT can be configured to trigger TWT enablement, where the STA MLD can transmit data frames only via a trigger frame sent by the AP MLD. The TWT negotiation procedure can be performed between a STA MLD and an AP MLD. For example, STA1 of STA MLD can perform a TWT negotiation process with AP1 of AP MLD. During the TWT negotiation process, STA1 of STA MLD can send a Multi-Link (ML) TWT Request Frame to AP1 in the first link. AP1 of AP MLD can receive the ML TWT Request Frame from STA1 in the first link and can send an ML TWT Response Frame in the first link as a response to the ML TWT Request Frame. The ML TWT Response Frame can include information about the ML TWT. The ML TWT Request Frame can refer to a general TWT Request Frame that includes information related to the multi-link (e.g., a link ID bitmap indicating the link running TWT or restricted TWT information). The ML TWT Response Frame can refer to a general TWT Response Frame that includes information related to the multi-link (e.g., a link ID bitmap indicating the link running TWT or restricted TWT information).

[0099] When the relationship between the first and second links is a non-STR link relationship (e.g., a non-STR link pair), an ML TWT response frame including a non-STR operation support indicator can be transmitted. The non-STR operation support indicator can be a PM bit. A PM bit set to 1 indicates that non-STR communication between the STA and AP is performed within the SP. Therefore, a PM bit set to 1 indicates that data transmission in a multi-link system needs to end before the SP begins, so that scheduled communication between the STA and AP can be performed within the SP.

[0100] When the relationship between the first and second links is a non-STR link relationship (e.g., a non-STR link pair), a non-STR communication terminal (e.g., a STA MLD or AP MLD) operating in the non-STR link pair can perform data transmission / reception operations (e.g., TWT operations) within a TWT SP or within an rTWT SP (e.g., rTWT operations). In this case, the AP MLD can match all TWT SPs of the first and second links, which are non-STR link pairs (e.g., making the start and / or end times of TWT SP#1 coincide with the start and / or end times of TWT SP#2). For example, the period of the TWT SP in the first link can be set to be equal to the period of the TWT SP in the second link, the start time of the TWT SP in the first link can be set to be equal to the start time of the TWT SP in the second link, and the end time of the TWT SP in the first link can be set to be equal to the end time of the TWT SP in the second link. That is, the TWT SP in the first link can be synchronized with the TWT SP in the second link.

[0101] When a TWT or rTWT operation is performed on one link (e.g., the first link) of a non-STR link pair, the data transmission operation performed by the STA of the STAMLD (e.g., STA2) on the other link (e.g., the second link) of the non-STR link pair must be terminated before the start time of the TWT or rTWT SP on that link (e.g., the first link). Furthermore, during the TWT SP or rTWT SP on one link (e.g., the first link) of the non-STR link pair, the STA of the STA MLD (e.g., STA2) can remain silent, where no transmission operation is performed on the other link (e.g., the second link) of the non-STR link pair. The AP MLD can allocate or notify the STA operating on the second link via the TWT SP or rTWT SP that the STA of the AP MLD needs to terminate the data transmission operation and remain silent for a period of time.

[0102] Furthermore, during the ML TWT negotiation process, the TWT can be configured to trigger TWT activation, where the STA MLD can perform transmission within the TWT SP via a trigger frame from the AP. Additionally, when data transmission / reception is performed on one link (e.g., the first link) of a non-STR link pair during a TWT or rTWT SP, data transmission / reception can be suspended on the other link (e.g., the second link) of the same non-STR link pair during the same time period. Therefore, to enable the STA MLD to operate within a TWT or rTWT SP, the AP MLD can configure the STA MLD to trigger TWT or rTWT activation with the same SP in both the first and second links of a non-STR link pair.

[0103] In a non-STR link pair, the STA MLD operating as a non-STR STA MLD can negotiate with the AP MLD to run TWT or rTWT in the first link through the ML TWT negotiation process. Data frames can be configured to terminate data frame transmission in both the first and second links before the start time of the TWTSP in the first link. In the first link where TWT or rTWT is running, ACK or block ACK (BA), which is an immediate response to the data frame, can be transmitted before the start time of the TWT or rTWT SP. The second link can be a non-STR link pair with the first link, and TWT or rTWT may not be running in the second link. In this case, during the TWT or rTWT SP in the second link, AP2 can send an immediate response to STA2's data frame based on the transmission time of the trigger frame in the first link. Therefore, in the second link, STA2 can complete data transmission before the start time of the TWT or rTWT SP in the first link. That is, data frames can be configured to complete data transmission before the start time of the TWT or rTWT SP in the first link.

[0104] When the STA MLD is an eMLSR or eMLMR terminal, the end time of a data frame to be transmitted on the second link can be determined by considering the time required to switch a radio to the first link. Data transmission operations (e.g., data transmission operations including ACK or BA reception operations) can be performed so that the radio can switch to the first link before the start time of the SP. That is, the eMLSR or eMLMR terminal can receive frames received on the first link via multiple spatial streams by switching all radios (e.g., radios operating on the second link) to the first link operating at TWT or rTWT before the start time of the SP of the first link's TWT or rTWT.

[0105] In a non-STR link pair, the STA MLD operating as a non-STR STA MLD can negotiate to run a TWT or rTWT on the first link through the ML TWT negotiation process with the AP MLD. A TWT or rTWT with the same SP as the first link can be configured to run on the second link, which is another link in the non-STR link pair. In the case of a non-STR link pair, when a TWT or rTWT is configured on the first link, the TWT or rTWT on the second link can be implicitly configured. Even if the configuration-related parameters for the second link's TWT are not configured during the TWT configuration process, the TWT or rTWT on the second link can be implicitly configured.

[0106] Information about trigger-enabled TWT can be included in the ML TWT response frame, and trigger-enabled TWT can be configured in the first link. The link where trigger-enabled TWT is running can be specified. When a trigger-enabled TWT SP is configured, an STA (e.g., STA1) can send a frame (e.g., a data frame) upon receiving a trigger frame from an AP (e.g., AP1) within the trigger-enabled TWT SP. When trigger-enabled TWT is configured in the first link and PM is set to 1, the operating state of STA1 in the STA MLD can transition to a transmit / receive state for data scheduled with the AP MLD within the TWT or rTWT SP. All STAs operating in a non-STR manner within the TWT or rTWT SP and having a TWT or rTWT configuration can send a frame upon receiving a trigger frame. Therefore, the corresponding STA can perform monitoring operations for receiving trigger frames. That is, if no trigger frame is received, the STA can remain silent and not perform any transmission operations within the TWT or rTWT SP. If trigger-enabled TWT is configured in the TWT or rTWT SP of one link in a non-STR link pair, then a STA (e.g., STA2) of a STA MLD operating in the other link of the non-STR link pair can remain silent and not perform transmission operations in the second link during the same TWT or rTWT SP as the first link, even if no TWT or rTWT operation is configured for execution. Alternatively, it can be interpreted that trigger-enabled TWT is implicitly configured in the second link as in the first link, and STA2 of the STA MLD can perform data transmission upon receiving a trigger frame in the second link.

[0107] When a trigger frame is received from AP1, STA1 of the STA MLD can send a frame (e.g., a data frame) via the first link in response to the trigger frame within Trigger Enabled TWT SP#2. STA2 of the STA MLD, which has not yet received a trigger frame from AP2 on the second link, can remain silent during Trigger Enabled TWT SP#2. AP1 of the AP MLD can receive the data frame from STA1 via the first link within Trigger Enabled TWT SP#2 and can send an ACK as an immediate response to the data frame.

[0108] When both links of a non-STR link pair are available, trigger frames can be transmitted simultaneously on both the first and second links because synchronous transmission should be performed. The time points at which the transmission of the trigger frame is completed can be the same. The time allocated for the trigger frame in both the first and second links can be the same, and STA1 and STA2 can complete the transmission simultaneously. Each of AP1 and AP2 can send an immediate response (e.g., ACK or BA) after SIFS from the time the data frame is received. The sending and completion times of AP1's immediate response can be the same as those of AP2's immediate response. That is, the transmission of immediate responses on the first and second links can be synchronized.

[0109] Figure 6 This is a timing diagram illustrating a fourth exemplary embodiment of a power-saving method in a wireless local area network system.

[0110] like Figure 6 As shown, low-power operation can be performed based on TWT. The STA MLD can perform a TWT negotiation process with the AP MLD to configure multi-link TWT. The TWT negotiation process can be performed when the STA MLD supports low-power operation or low-power operation for transmitting and receiving scheduled data. The TWT negotiation process can be performed on one link in a multi-link system. For example, in the first link, STA1 of the STA MLD can perform a TWT negotiation process with AP1 of the AP MLD. During the TWT negotiation process, ML TWT request frames and ML TWT response frames can be exchanged, and TWT SP can be configured to be triggered through the TWT negotiation process.

[0111] STA1, operating in the first link where the TWT negotiation process has been performed, can perform monitoring operations for receiving beacon frames from AP1 based on the beacon interval (e.g., beacon transmission period). When a beacon frame is received from AP1 of AP MLD, STA1 of STA MLD can identify whether data to be sent to STA1 exists in AP1 by recognizing the TIM (e.g., bitmap) included in the beacon frame. When STA MLD's AID is 1111, and the bit corresponding to AID=1111 in the partial virtual bitmap of the TIM is set to 1, STA1 of STA MLD can operate in a wake-up state at the start time of the trigger-enabled TWT SP configured through the TWT negotiation process or at the start time of the trigger-enabled TWT SP indicated by the beacon frame (or before the start time), and can perform monitoring operations on the trigger frame within the trigger-enabled TWT SP.

[0112] When the available links during the TWT SP activation period are unknown, in order to monitor all links, the operational state of all STAs (e.g., STA1, STA2, and STA3) in the STA MLD can transition from a sleep state to an awake state before T0, starting from the start time of the TWT SP activation. All STAs (e.g., STA1, STA2, and STA3) in the STA MLD can perform monitoring operations during T0. T0 can be the time period for performing link monitoring, and each of the STAs (e.g., STA1, STA2, and STA3) in the STA MLD can identify whether the link is idle or busy during T0. T0 can be set to a time within [Distributed Coordination Function (DCF) Inter-Frame Interval (DIFS) + maximum value of the backoff counter]. The operational state of STAs (e.g., STA1 and STA2) operating in links that are busy during T0 can transition from an awake state to a sleep state after T0. Alternatively, T0 can be the start time of the TWT SP activation.

[0113] When the third link is idle during the Trigger Enable TWT SP, AP3 of AP MLD can send a trigger frame on the third link. STA3 of STA MLD can receive AP3's trigger frame via the third link during the Trigger Enable TWT SP. Upon receiving the trigger frame, STA3 of STA MLD can send PS polling frames, U-APSD frames, or QoS empty frames via the third link during the Trigger Enable TWT SP. AP3 of AP MLD can receive STA3's PS polling frames, U-APSD frames, or QoS empty frames via the third link during the Trigger Enable TWT SP. Upon receiving STA3's PS polling frames, U-APSD frames, or QoS empty frames, AP3 of AP MLD can determine that the third link is available. In this case, AP3 of AP MLD can send data frames (e.g., including BU data frames) via the third link during the Trigger Enable TWT SP. STA3 of STA MLD can receive AP3's data frames via the third link during the Trigger Enable TWT SP.

[0114] Alternatively, links that have already undergone the TWT negotiation process can be monitored up to T0 from the start time of triggering the TWT SP, and these links can be in a busy state. In this case, the STA responsible for other links can change its operating state from sleep to wake-up, and the corresponding STA can monitor the links within the TWT SP triggering period. If the links that have already undergone the TWT negotiation process are busy at the start time of triggering the TWT SP triggering period, the AP MLD can send a trigger frame through the link among the links available to the STA MLD that first successfully completed the channel access operation.

[0115] Figure 7 This is a timing diagram illustrating a fifth exemplary embodiment of a power-saving method in a wireless local area network system.

[0116] like Figure 7 As shown, low-power operation can be performed based on TWT. The STA MLD can perform a TWT negotiation process with the AP MLD to configure multi-link TWT. The TWT negotiation process can be performed on one link of the multi-link system. For example, in the first link, STA1 of the STA MLD can perform a TWT negotiation process with AP1 of the AP MLD. During the TWT negotiation process, MLTWT request frames and ML TWT response frames can be exchanged, and TWT SP can be configured to be triggered through the TWT negotiation process.

[0117] STA1, operating in the first link where the TWT negotiation process has been performed, can perform monitoring operations for receiving beacon frames from AP1 based on the beacon interval (e.g., beacon transmission period). When a beacon frame is received from AP1 of AP MLD, STA1 of STA MLD can identify whether data to be sent to STA1 exists in AP1 by recognizing the TIM (e.g., bitmap) included in the beacon frame. When STA MLD's AID is 1111, and the bit corresponding to AID=1111 in the partial virtual bitmap of the TIM is set to 1, STA1 of STA MLD can operate in a wake-up state at the start time of the trigger-enabled TWT SP configured through the TWT negotiation process or at the start time of the trigger-enabled TWT SP indicated by the beacon frame (or before the start time), and can perform monitoring operations on the trigger frame within the trigger-enabled TWT SP.

[0118] When the available links during the TWT SP activation period are unknown, STAMLD can sequentially monitor each link for a period T1 starting from the start time of the TWT SP activation activation. T1 can be set to a time within [DIFS + maximum value of the backoff counter]. T1 can be a time period. For example, if a link is busy during T1, STAMLD can monitor another link during the next T1 period. When the status of a link changes from busy to idle during T1, STAMLD can additionally perform monitoring operations on the corresponding link during T2. T2 can be set to a time within [DIFS + maximum value of the backoff counter]. If the status of the corresponding link changes from idle to busy during T2, STAMLD can perform monitoring operations on another link during T1.

[0119] The length of time required to trigger TWT SP activation can increase the time for performing link monitoring operations. When monitoring operations are performed on each of the first and second links during T1, the length of time required to trigger TWT SP activation can be increased by [T1+T1]. If a specific link is monitored during T2, the length of time required to trigger TWT SP activation can be further increased by T2.

[0120] When the third link is idle during a Triggered Enabled TWT SP, AP3 of AP MLD can send a trigger frame on the third link. STA3 of STA MLD can receive AP3's trigger frame via the third link during a Triggered Enabled TWT SP (e.g., an extended Triggered Enabled TWT SP). Upon receiving the trigger frame, STA3 of STA MLD can send PS polling frames, U-APSD frames, or QoS empty frames via the third link during a Triggered Enabled TWT SP (e.g., an extended Triggered Enabled TWT SP). AP3 of APMLD can receive STA3's PS polling frames, U-APSD frames, or QoS empty frames via the third link during a Triggered Enabled TWT SP (e.g., an extended Triggered Enabled TWT SP). Upon receiving STA3's PS polling frames, U-APSD frames, or QoS empty frames, AP3 of APMLD can determine that the third link is available. In this case, AP3 of AP MLD can send data frames (e.g., data frames including BU) via the third link during a Triggered Enabled TWT SP (e.g., an extended Triggered Enabled TWT SP). STAMLD's STA3 can receive AP3 data frames via a third link within a triggered TWT SP (e.g., an extended triggered TWT SP).

[0121] Figure 8 This is a timing diagram illustrating a sixth exemplary embodiment of a power-saving method in a wireless local area network system.

[0122] like Figure 8 As shown, low-power operation can be performed based on TWT. The STA MLD can perform a TWT negotiation process with the AP MLD to configure multi-link TWT. The TWT negotiation process can be performed on one link of the multi-link system. For example, in the first link, STA1 of the STA MLD can perform a TWT negotiation process with AP1 of the AP MLD. During the TWT negotiation process, MLTWT request frames and ML TWT response frames can be exchanged, and TWT SP can be configured to be triggered through the TWT negotiation process.

[0123] STA1, operating in the first link where the TWT negotiation process has been performed, can perform monitoring operations for receiving beacon frames from AP1 based on the beacon interval (e.g., beacon transmission period). When a beacon frame is received from AP1 of AP MLD, STA1 of STA MLD can identify whether data to be sent to STA1 exists in AP1 by recognizing the TIM (e.g., bitmap) included in the beacon frame. When STA MLD's AID is 1111, and the bit corresponding to AID=1111 in the partial virtual bitmap of the TIM is set to 1, STA1 of STA MLD can operate in a wake-up state at the start time of the trigger-enabled TWT SP configured through the TWT negotiation process or the start time of the trigger-enabled TWT SP indicated by the beacon frame (or before that start time), and can perform monitoring operations on the trigger frame within the trigger-enabled TWT SP.

[0124] When the available links during the TWT SP activation period are unknown, the STA MLD can monitor all links for a preset time starting from the start time of the TWT SP activation. When a trigger frame is received from the AP MLD within the preset time, the operating state of the STAs responsible for all links except the one that received the corresponding trigger frame can change from the wake-up state to the sleep state. For example, when a trigger frame is received in the first link, the operating states of STA2 and STA3 responsible for the second link, and STA3 responsible for the third link, can change from the wake-up state to the sleep state. That is, STA2 and STA3 can operate in a power-saving state.

[0125] The preset time can be T2 (e.g., the time corresponding to the T2 timer). When the link is in an idle state during the TWT SP trigger activation, the STA MLD (e.g., each STA) can start the T2 timer. When the link's state changes from idle to busy, the STA MLD (e.g., each STA) can stop the T2 timer. The state of STAs on links other than the link whose T2 timer expires first can be changed to a power-saving state. The operation method based on the T2 timer can be performed as follows.

[0126] Figure 9 This is a timing diagram illustrating a first exemplary embodiment of the operation method of the T2 timer in a wireless local area network system.

[0127] like Figure 9As shown, in the first link, STA1 can start timer T2 at the beginning of time period b (e.g., a time period in an idle state) and terminate (or stop) timer T2 at the beginning of time period c (e.g., a time period in a busy state). Since the state of the first link changes from busy to idle during time period d, STA1 can start timer T2 at the beginning of time period d (e.g., a time period in an idle state). If the idle state in the first link lasts for the time corresponding to timer T2, timer T2 can expire.

[0128] In the second link, STA2 can start timer T2 at the beginning of time period e (e.g., an idle period) and terminate timer T2 at the beginning of time period f (e.g., a busy period). Since the state of the first link changes from busy to idle during time period g, STA2 can start timer T2 at the beginning of time period g (e.g., an idle period). If the idle state of the second link continues for the time corresponding to timer T2, timer T2 can expire.

[0129] In the third link, STA3 can start timer T2 at the beginning of time period i (e.g., the idle period). If the idle state of the third link continues for the time corresponding to timer T2, timer T2 can expire.

[0130] Refer again Figure 8 The STA MLD can transition the STA to a power-saving state on all links except the one where the T2 timer expires, at the time when the T2 timer first expires. If a trigger frame is received while the T2 timer is running, the STA MLD can terminate the T2 timer. In this case, the T2 timer can be considered to have terminated normally. For example, if a trigger frame is received while the T2 timer is running on the first link, the T2 timer can be terminated. In this case, the STAs on all links except the first link can transition to a power-saving state.

[0131] Even if timer T2 is normally terminated due to receiving a trigger frame in the first link, the state of the STAs in links other than the first link may not transition to a power-saving state, depending on the information included in the trigger frame. That is, the state of the STAs in each of the second and third links may remain in a normal state (e.g., a wake-up state).

[0132] Even when a TIM is received, the STA may not know the TID of the data (e.g., BU) to be received from the AP. The TID can be determined through a link mapping, and the link to be received can be identified based on the determined TID. Therefore, the trigger frame can additionally include information indicating the TID of the data (e.g., BU). The STA can identify the TID indicated by the trigger frame and report the TID of the data (e.g., BU) to be received from the AP to the MLD. The MLD can receive the TID information from the STA and keep the STA responsible for mapping to the corresponding TID in a normal state. Based on this operation, data (e.g., BU) can be received from the AP through multiple links.

[0133] Exemplary embodiments of the present invention can be implemented as program instructions that are computer-executable and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, or combinations thereof. The program instructions recorded on the computer-readable medium may be specifically designed and configured for the present invention, or may be known and available to those skilled in the art of computer software.

[0134] Examples of computer-readable media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code produced by, for example, a compiler, and high-level language code executable by a computer using an interpreter. The aforementioned hardware devices may be configured to operate as at least one software module to perform exemplary embodiments of the present invention, and vice versa.

[0135] Although embodiments of the invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of the invention.

Claims

1. A method for operating a device supporting multiple links, the method comprising: The process of performing a restricted target wake-up time service period on the first link of a non-simultaneous transmit and receive link pair; Obtain transmission opportunities in the second link of a non-simultaneous transmission and reception link pair; Perform the first communication on the second link; as well as On the first link, terminate the first communication before the start of the restricted target wake-up time service period; On the first link, the second communication is performed during the restricted target wake-up time service period.

2. The method according to claim 1, wherein, The apparatus includes a first station for first link operation. The restricted target wake-up time service period is configured by the relevant access point used for the first station.

3. The method according to claim 1, wherein, The device includes a second station operating in the second link. During the time period corresponding to the restricted target wake-up time service period, the second station does not perform the second communication on the second link.

4. The method according to claim 1, wherein, The interval between the end time of the first communication and the start time of the restricted target wake-up time service period is 0.

5. The method according to claim 1, wherein, When the device supports Enhanced Multilink Single Radio or Enhanced Multilink Multiple Radio, The end time of the first communication is determined based on the time of switching to the second link.

6. The method according to claim 1, wherein, The device includes a second station operating in the second link. The second station configures another restricted target wake-up time service period.

7. The method according to claim 6, wherein, The restricted target wake-up time service period overlaps with another restricted target wake-up time service period.

8. An apparatus supporting multiple links, the apparatus comprising: The processor, configured to enable the first station: The process of performing a restricted target wake-up time service period on the first link of a non-simultaneous transmit and receive link pair; Obtain transmission opportunities in the second link of a non-simultaneous transmission and reception link pair; Perform the first communication on the second link; On the first link, the first communication is terminated before the start of the restricted target wake-up time service period. On the first link, the second communication is performed during the restricted target wake-up time service period.

9. The apparatus supporting multiple links according to claim 8, wherein, The device includes a second station operating in the second link. During the time period corresponding to the restricted target wake-up time service period, the second station does not perform the second communication on the second link.

10. The apparatus supporting multiple links according to claim 8, wherein, The interval between the end time of the first communication and the start time of the restricted target wake-up time service period is 0.

11. The apparatus supporting multiple links according to claim 8, wherein, When the device supports Enhanced Multilink Single Radio or Enhanced Multilink Multiple Radio, The end time of the first communication is determined based on the time of switching to the second link.

12. The apparatus supporting multiple links according to claim 8, wherein, The device further includes a second station operating in the second link. The second station configures another restricted target wake-up time service period.

13. The apparatus supporting multiple links according to claim 12, wherein, The restricted target wake-up time service period overlaps with another restricted target wake-up time service period.

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