Method and apparatus for joint communication of multiple aps in a wireless local area network system

Abstract

The operation method of an access point (AP) for joint communication of a plurality of APs in a wireless local area network system includes the steps of: negotiating with other APs for joint transmission; transmitting information for joint transmission based on the negotiation result; and transmitting a frame based on the negotiation result, wherein the negotiation includes a frequency for joint transmission, and the frame is transmitted using the frequency for joint transmission.

Description

Technical Field

[0001] This invention relates to wireless local area network (WLAN) systems, and more specifically, to a method and apparatus for cooperative communication among multiple access points (APs) in a WLAN system. Background Technology

[0002] Recently, with the widespread adoption of mobile devices, wireless LAN technology, which provides fast wireless communication services to 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, embedded devices, etc.) to wirelessly access the internet.

[0003] The standards for wireless LAN technology were primarily developed by the Institute of Electrical and Electronics Engineers (IEEE) as the IEEE 802.11 standard. As wireless LAN technology has developed and become more widespread, its applications have diversified, creating a demand for wireless LAN technologies that support higher reliability.

[0004] With the emergence of applications requiring higher reliability, the IEEE 802.11bn standard is being developed as an Ultra High Reliability (UHR) wireless LAN technology in single Basic Service Set (BSS) and / or redundant BSS environments. The IEEE 802.11bn standard aims to support higher data transmission rates, improved latency performance, and lower data error rates. Furthermore, the IEEE 802.11bn standard supports low-power operation and peer-to-peer communication.

[0005] In a wireless local area network (WLAN), a method may be needed for multiple access points (APs) to perform cooperative communication. Multiple APs can establish a cooperative communication schedule and change their operating frequencies to perform cooperative communication. However, if an AP operates while changing its operating frequency, communication between WLAN terminals connected to the AP may become impossible, thus reducing communication efficiency and increasing latency. In other words, the reliability of the WLAN network cannot be guaranteed.

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

[0007] Technical issues This invention provides a method and apparatus for performing joint transmission among multiple access points (APs) in a wireless local area network system.

[0008] This invention provides a method and apparatus for multiple access points (APs) in a wireless local area network (WLAN) system to perform negotiation in order to perform joint transmission.

[0009] This invention provides a method and apparatus for scheduling multiple access points (APs) in a wireless local area network (WLAN) system to perform joint transmission.

[0010] This invention provides a method and apparatus for setting transmission prohibition periods for stations (STAs) that do not participate in joint transmission in a wireless local area network system.

[0011] This invention provides a method and apparatus for enabling STAs that do not participate in joint transmission to communicate directly with each other in a wireless local area network system.

[0012] This invention provides a method and apparatus for performing media synchronization in a wireless local area network system after the termination of joint transmission.

[0013] The technical objectives to be achieved in this invention are not limited to those described above, and those skilled in the art who apply the technical configuration of this invention may consider other technical objectives not mentioned in the embodiments of this invention described below.

[0014] Technical solution A method for operating an access point (AP) in a wireless local area network system may include: negotiating with at least one other AP for joint transmission; sending information for joint transmission based on the result of the negotiation; and sending frames based on the result of the negotiation. The result of the negotiation includes a frequency for joint transmission, and the frames are sent using the frequency for joint transmission.

[0015] A method for an operator station (STA) in a wireless local area network system may include: receiving information for joint transmission from a connected access point (AP); and performing at least one of a transmission prohibition operation, a frame reception operation, or a direct communication operation during a joint transmission period based on the information for joint transmission. The information for joint transmission includes at least one information regarding the joint transmission period or information regarding the frequency used for joint transmission.

[0016] An access point (AP) in a wireless local area network (WLAN) system may include a transceiver and a processor connected to the transceiver. The processor may be configured to: negotiate with at least one other AP for joint transmission; send information for joint transmission based on the negotiation result; and send frames based on the negotiation result. The negotiation result includes a frequency for joint transmission, and the frames are sent using the frequency for joint transmission.

[0017] A station (STA) in a wireless local area network (WLAN) system may include a transceiver and a processor connected to the transceiver. The processor may be configured to: receive information for joint transmission from a connected access point (AP); and, based on the information for joint transmission, perform at least one of the following operations during a joint transmission period: a transmission prohibition operation, a frame reception operation, or a direct communication operation. The information for joint transmission includes at least one information regarding the joint transmission period or information regarding the frequency used for joint transmission.

[0018] Beneficial effects According to the present invention, scheduling for cooperative communication can be performed at a specific frequency.

[0019] According to the present invention, a direct communication period can be established for a station (STA) that is a wireless local area network terminal connected to an access point (AP).

[0020] According to the present invention, even when it is impossible to communicate with the AP, the STA can perform direct communication, thereby improving transmission efficiency.

[0021] The effects obtained in this invention are not limited to those described above, and those skilled in the art who apply the technical configuration of this invention can clearly deduce and understand other effects not mentioned above from the following description of the embodiments of this invention. That is, those skilled in the art can also deduce from the embodiments of this invention effects that were not conceived when implementing the configurations described in this invention. Attached Figure Description

[0022] Figure 1 This is a block diagram illustrating a first embodiment of a communication node constituting a wireless local area network system.

[0023] Figure 2 A first implementation scheme of the multi-AP joint transmission method is shown.

[0024] Figure 3 A second implementation scheme of the multi-AP joint transmission method is shown.

[0025] Figure 4 A third implementation scheme of the multi-AP joint transmission method is shown.

[0026] Figure 5A first implementation of a multi-AP frequency-changing communication method is shown.

[0027] Figure 6 This is a flowchart of the negotiation and communication process for joint transmission according to an embodiment of the present invention.

[0028] Figure 7 This is a flowchart of a communication process for joint transmission according to an embodiment of the present invention. Detailed Implementation

[0029] This invention can have various modifications and embodiments, and specific embodiments are shown in the accompanying drawings and described in detail in the specific description. However, this is not intended to limit the invention to the specific embodiments, but should be understood to include all modified embodiments, equivalent embodiments, or alternative embodiments that are included within the spirit and technical scope of the invention.

[0030] The terms "first," "second," etc., can be used to describe various components, but components should not be limited by the terms. Terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component. Terms and / or include combinations of multiple related descriptive terms or any one of multiple related descriptive terms.

[0031] When a component is claimed to be "connected to / attached to another component" or "connected to" another component, it should be understood that this component is directly connected to the other component or connected to the other component through any other component in between. On the other hand, when a component is claimed to be "directly connected to" or "directly coupled to" another component, it should be understood that there are no other components between these two components.

[0032] The terminology used in this invention is for describing particular embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, singular expressions include plural expressions. In this invention, terms such as “comprising” or “having” are intended to specify the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in this specification, but should be understood not to preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0033] Unless otherwise defined, all terms used herein (including technical or scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in general dictionaries shall be interpreted as having the same meaning as they have in the context of the relevant art, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0034] Preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings. In describing the invention, for ease of overall understanding, the same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components are omitted.

[0035] The following describes a wireless communication system applying embodiments of the present invention. The wireless communication system applying embodiments of the present invention is not limited to the following description, and the 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".

[0036] Figure 1 A block diagram of a communication node in a wireless local area network system is shown.

[0037] refer to Figure 1 Communication node 100 can be an access point, station, AP multi-link device (MLD), or non-AP MLD. STA can be a non-AP STA. The operating channel width supported by the AP can be 20 MHz, 80 MHz, or 160 MHz. The operating channel width supported by the STA can be 20 MHz or 80 MHz.

[0038] Communication node 100 may include at least one processor 110, memory 120, and at least one transmitting / receiving device 130, which is connected to a network and performs communication. Transmitting / receiving device 130 may also be referred to as a transceiver, radio frequency (RF) unit, or RF module. Additionally, communication node 100 may further include an input interface device 140, an output interface device 150, and a storage device 160. Components included in communication node 100 can be connected via bus 170 and perform communication between components.

[0039] However, each component included in communication node 100 may be connected via a separate interface or bus around processor 110 instead of via common bus 170. For example, processor 110 may be connected via a dedicated interface to at least one of memory 120, transmitting / receiving device 130, input interface device 140, output interface device 150, and storage device 160.

[0040] Processor 110 can execute program instructions stored in at least one of memory 120 and storage device 160. Processor 110 can be a central processing unit (CPU), graphics processing unit (GPU), or dedicated processor that performs methods according to embodiments of the present invention. Memory 120 and storage device 160 can each be configured as at least one volatile storage medium and at least one non-volatile storage medium. For example, memory 120 can be configured as at least one read-only memory (ROM) and random access memory (RAM).

[0041] Figure 2 A first implementation scheme of the multi-AP joint transmission method is shown.

[0042] refer to Figure 2AP 1 201 operates on the first link, AP 2 203 on the second link, and AP 3 205 on the third link. Here, "link" can refer to a specific operating frequency of the wireless LAN network. The operating frequencies of the first to third links can be different or the same. When the operating frequencies of AP 1 201 to AP 3 205 are the same, the overlapping basic service set (OBSS) of AP 1 201 is the basic service set (BSS) of AP 2 203 and AP 3 205, the OBSS of AP 2 203 is the BSS of AP 1 201 and AP 3 205, and the OBSS of AP 3 205 is the BSS of AP 1 201 and AP 2 203. AP 1 201 to AP 3 205 can synchronize their time synchronization functions (TSFs). In other words, AP 1 201 to AP 3 205 simultaneously have the same TSF value. TSF synchronization can be used to synchronize the joint transmission scheduling (e.g., restricted target wake time (R-TWT) SP) of AP 1 201 to AP 3 205 with each other. Additionally, when AP 1 201 to AP 3 205 operate at the same frequency, TSF synchronization can be used to synchronize the joint transmission scheduling (e.g., R-TWT SP) of OBSS with each other. AP 1 201 to AP 3 205 can perform scheduling negotiation 210 for joint transmission. Scheduling negotiation 210 for joint transmission can be a subchannel selective transmission (SST) target wake time (TWT) negotiation, a TWT negotiation of other types besides SST, or a transmission period negotiation. SST TWT negotiation is an agreement to establish that communication will take place on another channel during the TWT period. SST TWT negotiation can be an agreement to establish, for example, that AP 2 203, operating in the second link, and AP 3 205, operating in the third link, operate in the first link within a TWT SP. As a result of the scheduling negotiation 210 for joint transmission, AP 1 201 to AP 3 205 can establish a joint transmission period. The joint transmission period can be a TWT service period (SP). AP 1 201 can be the master AP that dominates the joint transmission scheduling negotiation 210, and AP 1 201 to AP 3 205 perform communication at the operating frequency of AP 1 201 (i.e., the first link or the first channel) during the joint transmission period.In other words, AP 2 203 and AP 3 205 must change their operating frequency (i.e., link or channel). Since AP 1 201 to AP 3 205 have synchronized TSFs, the start point of the joint transmission period of AP 1 201 to AP 3 205 can be the same, and AP 1 201 to AP 3 205 can know exactly when the joint transmission period begins.

[0043] APs 1 201 through AP 3 205 may send frames 221, 223, and 225 indicating the joint transmission period before its commencement. Frames 221, 223, and 225 indicating the joint transmission period can be of various forms. For example, frames 221, 223, and 225 may be beacon frames. Frames 221, 223, and 225 indicating the joint transmission period may include information indicating the joint transmission period (e.g., TWT information, TWT elements) and information indicating the frequency (e.g., link ID, channel number, information that may indicate a specific operating frequency). Frames 223 and 225 indicating the joint transmission period sent by APs 2 203 and 3 205 may further include information indicating that transmissions by STAs connected to APs 2 203 and 3 205 are prohibited during the joint transmission period (e.g., information indicating the prohibited transmission period, silence elements). Alternatively, information indicating prohibited transmissions during the joint transmission period may be included along with information indicating the joint transmission period (e.g., TWT information, TWT elements). The information indicating prohibited transmissions indicates a transmission prohibition period, which indicates a period during which the AP is unavailable and transmissions from the STA to the AP are prohibited. Frames indicating the joint transmission period may include TWT information (e.g., information indicating an R-TWT SP) indicating that transmissions must be terminated (e.g., transmission opportunity (TXOP) must be terminated) before the joint transmission period (e.g., TWT SP, R-TWT SP, SP). That is, information indicating the joint transmission period and frequency may indicate an R-TWT SP. Channel switching delay may be included in the transmission prohibition period; the channel switching delay is the time it takes for the AP to change to a frequency used for joint transmission. The channel switching delay can be applied to both the time point when changing from the operating frequency to the frequency used for joint transmission and the time point when changing from the frequency used for joint transmission back to the current operating frequency. The channel switching delay can differ between APs. APs can perform multi-AP joint transmissions from the same time point after the channel switching delay. If the channel handover delays of the APs are different, the lengths of the transmission prohibition periods can be different. For example, if the channel handover delay of AP 2 203 is longer than that of AP 1 201, and the channel handover delay of AP 3 205 is longer than that of AP 2 203, then considering the AP's channel handover delays, the length of the transmission prohibition period for AP 3 205 can be the longest, the length of the transmission prohibition period for AP 1 201 can be the shortest, and the length of the transmission prohibition period for AP 2 203 can be longer than the length of the transmission prohibition period for AP 1 201 but shorter than the length of the transmission prohibition period for AP 3 205. For example, the channel handover delay can be a predetermined value known to all STAs in the BSS.Alternatively, the AP may omit the channel handover delay from the transmission prohibition period. The STA may receive frames indicating the joint transmission period, and upon receiving a transmission prohibition indication included in frames 223 and 225 indicating the joint transmission period, the STA may calculate and identify the time prior to the AP's channel handover delay from the indicated time when the AP becomes unavailable. The STA will not perform any transmissions to the AP from the calculated time. Upon receiving a frame indicating the joint transmission period, the STA may terminate transmissions (e.g., terminate TXOP) before the start of the transmission prohibition period. When AP1 201 through AP3 205 operate at the same frequency, and a STA receives frames 223 and 225 from the OBSS (i.e., when the STA is connected to AP1 201, for AP2 203 and AP3 205; when the STA is connected to AP2 203, for AP1 201 and AP3 205; and when the STA is connected to AP3 205, for AP1 201 and AP2 203), indicating a joint transmission period, transmission can be terminated before the start of the transmission prohibition period included in frames 223 and 225 of the OBSS indicating the joint transmission period. Frames 223 and 225 indicating the joint transmission period sent by AP2 203 and AP3 205 may further include information indicating the operating frequencies of the STAs connected to AP2 203 and AP3 205 that wish to participate in the joint transmission period (e.g., link ID, channel number, information that can indicate a specific operating frequency). At the start of a joint transmission period, AP 2203 and AP 3 205 can operate at a frequency indicating joint transmission (e.g., on the first link), and AP 1 201 through AP3 205 use the frequency for joint transmission to perform cooperative communication. STAs connected to AP 2 203 and AP 3 205 that wish to participate in the joint transmission period can operate at the frequency for joint transmission (e.g., on the first link) at the start of the joint transmission period. STAs wishing to participate in the joint transmission period may need to perform a negotiation process with AP 2 203 and AP 3 205, and this negotiation process can be a TWT negotiation (e.g., broadcast TWT negotiation, individual TWT negotiation) process. Among STAs connected to AP 2203 and AP 3 205, STAs not participating in the joint transmission period do not send frames to the corresponding APs during the joint transmission period by indicating a transmission-prohibited message sent by AP 2 203 and AP 3 205. For example, a STA that does not participate in the joint transmission period may assume that there is no data (e.g., data packets, MSDU, MPDU) destined for AP 2 203 and AP 3 205.The STA's failure to transmit frames during the joint transmission period can be caused by network allocation vectors (NAVs) 251 and 253. For example, STAs connected to AP 2 203 and AP 3 205 can set NAVs 251 and 253 to the length of the joint transmission period based on information indicating prohibited transmission, and refrain from frame transmission during the set NAVs 251 and 253 by treating the channel as busy. Since AP 2 203 and AP 3 205 operate at a different operating frequency than their original operating frequency during the joint transmission period (e.g., in the first link), and do not perform receive operations (i.e., receive operations including channel detection operations, such as clear channel assessment (CCA)) at a different operating frequency before the joint transmission period, medium synchronization may be lost. Additionally, if the joint transmission period is longer than a certain length, changing back to the original operating frequency after the joint transmission period may result in loss of medium synchronization. Therefore, AP 2 203 and AP 3 205 must set the MediumSyncDelay timer immediately after commencing operation at the frequency used for commencing (e.g., the first link) at the start of the commencing transmission period. This timer is for restoring medium synchronization and can restrict frame transmission while the MediumSyncDelay timer is operating. Restricting frame transmission while the MediumSyncDelay timer is operating can mean that if the channel energy is below a certain level before transmitting a data frame, an RTS frame must be transmitted or an Idle Channel Assessment (CCA) operation must be performed without transmitting the frame. The MediumSyncDelay timer is released when the frame is received normally (e.g., the MPDU is received normally without errors) and successfully decoded. AP 1 201 does not change its operating frequency and can transmit frames immediately during the commencing transmission period. Accordingly, AP 1201 can transmit an "initial frame" (e.g., trigger frame 230) at the start of the commencing transmission period to release the MediumSyncDelay timers of AP 2 203 and AP 3 205 and restore medium synchronization. The initial frame includes not only the trigger frame, but also all types of frames that AP 2 203 and AP 3 205 can decode and correctly set the NAV. During the joint transmission frequency (i.e., the joint transmission period of the first link), AP 1 201 to AP 3 205 perform joint transmission.For example, AP 1 201 through AP 3 205 can transmit frame 240 to the STA in the first link by performing coordinated orthogonal frequency division multiple access (CO-OFDMA) or coordinated spatial reuse (CO-SR) operations. At the end of the joint transmission period, AP 2 203 and AP 3 205 operate again in the second and third links.

[0044] Figure 3 A second implementation scheme of the multi-AP joint transmission method is shown.

[0045] refer to Figure 3AP 1 301 operates on the first link, AP 2 303 on the second link, and AP 3305 on the third link. Here, a link can refer to a specific operating frequency of the wireless LAN. The operating frequencies of the first to third links can be different or the same. When the operating frequencies of AP 1 301 to AP 3 305 are the same, the OBSS of AP 1 301 is the BSS of AP 2 303 and AP 3 305, the OBSS of AP 2 303 is the BSS of AP 1 301 and AP 3 305, and the OBSS of AP 3 305 is the BSS of AP 1 301 and AP 2 303. AP 1 301 to AP 3 305 can synchronize their Time Synchronization Function (TSF). That is, AP 1 301 to AP 3 303 simultaneously have the same TSF value. TSF synchronization can be used to synchronize the joint transmission schedules (e.g., R-TWT SP) of AP 1 301 to AP 3 305 with each other. Additionally, when AP 1 301 to AP 3 305 operate at the same frequency, TSF synchronization can be used to synchronize the joint transmission schedules (e.g., R-TWT SP) of OBSS with each other. AP 1 301 to AP 3 305 can perform a scheduling negotiation 310 for joint transmission. The scheduling negotiation 310 for joint transmission can be a Sub-Channel Selective Transmission (SST) Target Wake-Up Time (TWT) negotiation, a TWT negotiation of other types besides SST, or a transmission period negotiation. An SST TWT negotiation is an agreement to establish that communication will take place on another channel during the TWT period. An SST TWT negotiation can be an agreement to establish, for example, that AP 2 303, operating in a second link, and AP 3 305, operating in a third link, operate in the first link within a TWT SP. As a result of the scheduling negotiation 310 for joint transmission, AP 1 301 to AP 3 305 can establish a joint transmission period. The joint transmission period can be a TWT (Service Time Hour) (SP). AP 1 301 can be the master AP leading the joint transmission scheduling negotiation 310, and AP 1 301 to AP 3 305 perform communication at AP 1 301's operating frequency (i.e., the first link or the first channel) during the joint transmission period. That is, AP 2 303 and AP 3 305 must change their operating frequencies (i.e., the link or the channel). Because AP 1 301 to AP 3 305 have synchronized TSFs, the start point of their joint transmission periods can be the same, and AP 1 301 to AP 3 305 can know precisely when the joint transmission period begins.

[0046] APs 1 301 to AP 3 305 may send frames 321, 323, and 325 indicating the joint transmission period before the start of the joint transmission period. Frames 321, 323, and 325 indicating the joint transmission period may be of various forms, such as beacon frames. Frames 321, 323, and 325 indicating the joint transmission period may include information indicating the joint transmission period (e.g., TWT information, TWT elements) and information indicating the frequency (e.g., link ID, channel number, information that may indicate a specific operating frequency). Frames 323 and 325 indicating the joint transmission period sent by APs 2 303 and 3 305 may further include information indicating that STAs connected to APs 2 303 and 3 305 will perform direct communication (e.g., communication between STAs without AP intervention) 350 during the joint transmission period (e.g., information about the period during which direct communication can be performed, and information about the STAs that can participate in direct communication). In this embodiment, the information indicating the performance of direct communication 350 is referred to as a direct communication indication. Direct communication indications may be included along with information indicating a joint transmission period (i.e., TWT elements, TWT information). The direct communication indication indicates that the AP performs direct communication 350 during an unavailable period, during which transmissions from the STA to the AP are prohibited. Frames 321, 323, and 325 indicating the joint transmission period may include TWT information (e.g., information indicating R-TWTSP) that must be terminated before the joint transmission period (e.g., the transmission opportunity (TXOP) must be terminated). That is, information indicating the joint transmission period and frequency may indicate R-TWTSP. The period during which direct communication is performed during a period when the AP is unavailable may be referred to as the direct communication period. Channel switching delay may be included in the direct communication period; this channel switching delay is the time taken for the AP to change to a frequency using joint transmission. The channel switching delay can be applied to both the point in time when changing from the operating frequency to the frequency used for joint transmission and the point in time when changing from the frequency used for joint transmission back to the current operating frequency. Channel switching delays can vary between access points (APs), and APs can perform joint transmission from the same point in time after the channel switching delay. If the channel switching delays of the APs are different, the length of the transmission prohibition period can also be different.For example, if the channel handover delay of AP 2 303 is longer than that of AP 1 301, and the channel handover delay of AP 3 305 is longer than that of AP 2 303, then considering the channel handover delays of the APs, the length of the transmission prohibition period for AP 3 305 can be the longest, the length of the transmission prohibition period for AP 1 301 can be the shortest, and the length of the transmission prohibition period for AP 2 303 can be longer than the length of the transmission prohibition period for AP 1 301 but shorter than the length of the transmission prohibition period for AP 3 305. The channel handover delay can be a predetermined value known to all STAs in the BSS. Alternatively, the AP may not include the channel handover delay in the direct communication period. The STA can receive frames 323 and 325 indicating the joint transmission period, and when it receives a direct communication indication included in a frame indicating the joint transmission period, the STA can calculate and identify the time prior to the AP's channel handover delay from the indicated time when the AP becomes unavailable. The STA does not perform any transmissions to the AP from the calculated time. When a STA receives frames 321, 323, and 325 indicating a joint transmission period, the STA may terminate transmission (e.g., terminate TXOP) before the start of a transmission prohibition period. When APs 1 301 to AP 3 305 operate at the same frequency, and the STA receives frames 323 and 325 from the OBSS indicating a joint transmission period (i.e., AP 2 303 and AP 3 305 when the STA is connected to AP 1 301, AP 1 301 and AP 3 305 when the STA is connected to AP 2 303, and AP 1 301 and AP 2 303 when the STA is connected to AP 3 305), the STA may terminate transmission before the start of the direct communication period contained in frames 323 and 325 of the OBSS indicating a joint transmission period. Additionally, frames 323 and 325, sent from AP 2 303 and AP 3 305 indicating a joint transmission period, may further include an indicator indicating that transmission is prohibited during periods when the APs are unavailable (e.g., information indicating a prohibited transmission period, a silence element). The indicator indicating that transmission is prohibited during periods when the APs are unavailable refers to information indicating that the STA sets a NAV during these periods. During periods when the APs are unavailable, an STA that recognizes a direct communication indication and wants to perform direct communication 350 may ignore the indicator indicating prohibited transmission (e.g., not setting a NAV) and perform direct communication 350 (e.g., performing a channel access operation, performing a frame transmission). STAs that do not perform direct communication 350 or do not recognize a direct communication indication set a NAV during periods when the APs are unavailable due to the transmission prohibition indicator and do not perform a channel access operation or frame transmission operation. During periods when the APs are unavailable, the STA performs direct communication 350, which is communication without going through the AP.Frames 323 and 325, sent by AP 2 303 and AP 3 305 indicating a joint transmission period, may further include information (e.g., link ID, channel number, information indicating a specific operating frequency) indicating the operating frequency of STAs connected to AP 2 303 and AP 3 305 that wish to participate in the joint transmission period. At the start of the joint transmission period, AP 2 303 and AP 3 305 may operate in the first link, and AP 1 301 through AP 3 305 perform cooperative communication. Among the STAs connected to AP 2 303 and AP 3 305, STAs wishing to participate in the joint transmission period may operate at the frequency indicating joint transmission (e.g., in the first link) at the start of the joint transmission period. STAs wishing to participate in the joint transmission period may need to perform a negotiation process with AP 2 303 and AP 3 305, and this negotiation process may be a TWT negotiation process (e.g., broadcast TWT negotiation, individual TWT negotiation). Among STAs connected to AP 2 303 and AP 3 305, STAs not participating in the joint transmission period perform communication (e.g., direct communication, peer-to-peer communication) using their original operating frequencies during the joint transmission period by instructing AP 2 303 and AP 3 305 to perform direct communication 350. STAs not participating in the joint transmission period do not send frames to AP 2 303 and AP 3 305 during the joint transmission period. When the joint transmission period and the direct communication period terminate, STAs not participating in the joint transmission period must select a new backoff counter (e.g., EDCA backoff counter). STAs not participating in the joint transmission period can assume that there is no data (e.g., data packets, MSDUs, MPDUs) destined for AP 2 303 and AP 3 305 in their queues during the joint transmission period. Because AP 2303 and AP 3305 operate at an operating frequency different from the original operating frequency during the joint transmission period (e.g., in the first link), and do not perform receive operations (i.e., receive operations including channel detection operations (e.g., free channel assessment (CCA)) at a different operating frequency before the joint transmission period, medium synchronization may be lost. Additionally, if the joint transmission period is longer than a certain length, changing to the original operating frequency after the joint transmission period may result in the loss of medium synchronization. Therefore, AP 2303 and AP 3305 must set a MediumSyncDelay timer immediately after starting operation at the frequency used for joint transmission (e.g., the first link) at the start time of the joint transmission period. This timer is for restoring medium synchronization and can limit frame transmission while the MediumSyncDelay timer is operating.Restricting frame transmission during MediumSyncDelay timer operation can mean that an RTS frame must be sent before a frame is sent, or that an Idle Channel Assessment (CCA) operation must be performed if no frame is sent. The MediumSyncDelay timer is released when a frame is received normally (e.g., the MPDU is received normally without errors) and successfully decoded. AP 1 301 does not change its operating frequency and can send frames immediately within the joint transmission period. Therefore, AP 1 301 can send an "initial frame" (e.g., trigger frame 330) at the beginning of the joint transmission period to release the MediumSyncDelay timers of AP 2 303 and AP 3 305 and restore media synchronization. The initial frame includes not only the trigger frame but also all types of frames that AP 2 303 and AP 3 305 can decode and correctly set the NAV for. During the joint transmission frequency (i.e., the joint transmission period of the first link), AP 1 301 through AP 3 305 perform joint transmission. For example, AP 1 301 through AP 3 305 can perform Cooperative Orthogonal Frequency Division Multiple Access (CO-OFDMA) or Cooperative Spatial Multiplexing (CO-SR) operations to send frame 340 to the STA in the first link. At the end of the joint transmission period, AP 2 303 and AP 3 305 again operate in the second and third links.

[0047] Figure 4 A third implementation scheme of the multi-AP joint transmission method is shown.

[0048] refer to Figure 4AP 1 401 operates on the first link, AP 2 403 on the second link, and AP 3 405 on the third link. A link can refer to a specific operating frequency of the wireless LAN. The operating frequencies of the first to third links can be different or the same. When AP 1 401 to AP 3 405 operate on the same frequency, the OBSS of AP 1 401 is the BSS of AP 2 403 and AP 3 405, the OBSS of AP 2 403 is the BSS of AP 1 401 and AP 3 405, and the OBSS of AP 3 405 is the BSS of AP 1 401 and AP 2 403. AP 1 401 to AP 3 405 can synchronize their Time Synchronization Function (TSF). That is, AP 1 401 to AP 3 405 simultaneously have the same TSF value. TSF synchronization can be used to synchronize the joint transmission schedules (e.g., R-TWT SP) of AP 1 401 to AP 3 405 with each other. Additionally, when AP 1 401 to AP 3 405 operate at the same frequency, TSF synchronization can be used to synchronize the joint transmission schedules (e.g., R-TWT SP) of OBSS with each other. AP 1 401 to AP 3 405 can perform a scheduling negotiation 410 for joint transmission. The scheduling negotiation 410 for joint transmission can be a Sub-Channel Selective Transmission (SST) Target Wake-up Time (TWT) negotiation, a TWT negotiation of other types besides SST, or a transmission period negotiation. An SST TWT negotiation is an agreement to establish that communication will take place on another channel during the TWT period. An SST TWT negotiation can be an agreement to establish, for example, that AP 2 403, operating in a second link, and AP 3 405, operating in a third link, operate in the first link within a TWT SP. As a result of the scheduling negotiation 410 for joint transmission, AP 1 401 to AP 3 405 can establish a joint transmission period. The joint transmission period can be a TWT (Service Hour) (SP). AP 1 401 can be the master AP leading the joint transmission scheduling negotiation 410, and AP 1 401 to AP 3 405 perform communication at the operating frequency of AP 1 401 (i.e., the first link or the first channel) during the joint transmission period. That is, AP 2 403 and AP 3 405 must change their operating frequencies (i.e., the link or the channel). Because AP 1 401 to AP 3 405 have synchronized TSFs, the start point of their joint transmission periods can be the same, and AP 1 401 to AP 3 405 can know precisely when the joint transmission period begins.

[0049] APs 1 401 through AP 3 405 may send frames 421, 423, and 425 indicating the joint transmission period before its commencement. Frames 421, 423, and 425 indicating the joint transmission period can be of various forms. For example, frames 421, 423, and 425 may be beacon frames. Frames 421, 423, and 425 indicating the joint transmission period may include information indicating the joint transmission period (e.g., TWT information, TWT elements) and information indicating the frequency (e.g., link ID, channel number, information that can indicate a specific operating frequency). Frames 423 and 425 indicating the joint transmission period sent by APs 2 403 and 3 405 may further include information indicating the operating frequencies of STAs connected to APs 2 403 and 3 405 that wish to participate in the joint transmission period (e.g., link ID, channel number, information that can indicate a specific operating frequency). Before the start of a joint transmission period, AP 2 403 and AP 3 405 may send frame 430 indicating the execution of direct communication (e.g., the operation of performing communication between STAs without sending data to the AP). Frame 430 indicating the execution of direct communication may indicate the period of direct communication (i.e., the direct communication period) and the STAs that may perform communication during the direct communication period. Alternatively, the indication of the execution of direct communication may be included in information indicating a joint transmission period. For example, a TWT element may indicate that the STAs are performing direct communication. In this embodiment, the indication of the execution of direct communication included in frame 430 indicating the execution of direct communication or in information indicating a joint transmission period is called a direct communication indication. The direct communication indication indicates that the AP is performing direct communication during an unavailable period and that transmissions to the AP may be prohibited during the corresponding period. Frames 421, 423, and 425 indicating a joint transmission period may include TWT information (e.g., information indicating an R-TWT SP) that must be terminated before the joint transmission period (e.g., TWT SP, R-TWT SP, SP). In other words, information indicating the joint transmission period and frequency can indicate the R-TWT SP. The period during which direct communication is performed when the AP is unavailable can be called the direct communication period. Channel switching delay can be included in the direct communication period; this channel switching delay is the time it takes for an AP to change to a frequency using joint transmission. The channel switching delay can be applied to both the time point when changing from the operating frequency to the frequency used for joint transmission and the time point when changing from the frequency used for joint transmission back to the current operating frequency. Channel switching delays can differ between APs, and APs can perform multi-AP joint transmission from the same time following the channel switching delay. If the channel switching delays of the APs are different, the length of the transmission-inactive period can be different.For example, if the channel handover delay of AP 2 403 is longer than that of AP 1 401, and the channel handover delay of AP 3 405 is longer than that of AP 2 403, then considering the AP's channel handover delay, the length of the transmission prohibition period for AP 3 405 can be the longest, the length of the transmission prohibition period for AP 1 401 can be the shortest, and the length of the transmission prohibition period for AP 2 403 can be longer than that of AP 1 401 but shorter than that of AP 3 405. The channel handover delay can be a predetermined value known to all STAs in the BSS. Alternatively, the AP may not include the channel handover delay in the direct communication period. STAs can receive frames 423 and 425 indicating the joint transmission period, and when a direct communication indication is received in a frame indicating the joint transmission period, the STA can calculate and identify the point in time prior to the AP's channel handover delay from the indicated time, and can refrain from transmitting to the AP from that time. Upon receiving frames 423 and 425 indicating a joint transmission period, the STA may terminate transmission (e.g., terminate TXOP) before the start of the transmission prohibition period. When APs 1 401 to AP 3 405 operate at the same frequency, and the STA receives frames 423 and 425 from the OBSS indicating a joint transmission period (i.e., AP 2 403 and AP 3 405 when the STA is connected to AP 1 401, AP 1 401 and AP 3 405 when the STA is connected to AP 2 403, and AP 1 401 and AP 2 403 when the STA is connected to AP 3 405), the STA may terminate transmission before the start of the direct communication period contained in frames 423 and 425 of the OBSS indicating the joint transmission period. During periods when the APs are unavailable, the STA performs direct communication, which is communication without access to the APs. Frame 430, indicating the execution of direct communication, can be a multi-user-request-to-send (MU-RTS) TXOP sharing (TXS) trigger frame, or any other type of frame that can indicate a direct communication period. Frame 430 can set the direct communication period to be the same as or longer than the joint transmission period. When the joint transmission period begins, AP 2 403 and AP 3 405 can operate at a frequency indicating joint transmission (e.g., in the first link), and AP1 401 through AP 3 405 use the frequency for joint transmission to perform cooperative communication. STAs connected to AP 2 403 and AP 3 405 that wish to participate in the joint transmission period can operate at the frequency for joint transmission (e.g., in the first link) at the start of the joint transmission period.STAs wishing to participate in the joint transmission period may need to perform a negotiation process with AP 2 403 and AP 3 405, and this negotiation process can be a TWT negotiation (e.g., broadcast TWT negotiation, individual TWT negotiation) process. STAs connected to AP 2 403 and AP 3 405 that do not participate in the joint transmission period perform direct communication by sending frames from AP 2 403 and AP 3 405 instructing them to perform direct communication. When the joint transmission period and the direct communication period terminate, STAs that did not participate in the joint transmission period must select a new backoff counter (e.g., EDCA backoff counter). STAs that do not participate in the joint transmission period can assume that there is no data (e.g., data packets, MSDUs, MPDUs) destined for AP 2 403 and AP 3 405 in their queues during the joint transmission period. STAs that do not participate in the joint transmission period do not send frames to AP 2 403 and AP 3 405 during the joint transmission period. Because AP 2 403 and AP 3 405 operate at an operating frequency different from the original operating frequency (e.g., the first link) during the joint transmission period, and do not perform receive operations (i.e., receive operations including channel sensing operations (e.g., free channel assessment (CCA)) at a different operating frequency before the joint transmission period, medium synchronization may be lost. Additionally, if the joint transmission period is longer than a certain length, changing to the original operating frequency after the joint transmission period may result in the loss of medium synchronization. Therefore, AP 2 403 and AP 3 405 must set a MediumSyncDelay timer immediately after starting operation at the frequency used for joint transmission (e.g., the first link) at the start time of the joint transmission period. This timer is for restoring medium synchronization and can restrict frame transmission while the MediumSyncDelay timer is operating. Restricting frame transmission while the MediumSyncDelay timer is operating can mean that an RTS frame must be sent when the channel energy is below a certain level before sending a data frame, or that an Free Channel Assessment (CCA) operation is performed without sending the frame. When a frame is received normally (e.g., the MPDU is received normally without errors) and successfully decoded, the MediumSyncDelay timer is released. AP 1 401 does not change its operating frequency and can immediately send frames within the joint transmission period. Therefore, AP 1 401 can send an "initial frame" (e.g., trigger frame 440) at the beginning of the joint transmission period to release the MediumSyncDelay timers of AP 2 403 and AP 3 405 and restore media synchronization. The initial frame includes not only the trigger frame but also all types of frames that AP 2 403 and AP 3 405 can decode and correctly set the NAV for.During the joint transmission frequency (i.e., the joint transmission period of the first link), AP 1 401 to AP 3 405 perform joint transmission. For example, AP 1 401 to AP 3 405 can send frame 450 to the STA in the first link by performing Cooperative Orthogonal Frequency Division Multiple Access (CO-OFDMA) operation or Cooperative Spatial Multiplexing (CO-SR) operation. At the end of the joint transmission period, AP 2 403 and AP 3 405 operate again in the second and third links. Because AP 2 403 and AP 3 405 operate in the first link during the joint transmission period, AP 2 403 and AP 3 405 lose medium synchronization in the second and third links, which are the original operating frequencies, and the MediumSyncDelay timer must be set, which is a timer used to restore medium synchronization. Due to the setting of the MediumSyncDelay timer, the frame transmission operation of AP 2 403 and AP 3 405 can be restricted. A STA capable of performing direct communication, as indicated in the frame sent by AP 2 403 and AP 3 405, simultaneously transmits frame 470 at a specific time point after the end of the joint transmission period (e.g., the end time of the joint transmission period, or a predetermined time point before the end of the direct communication period). The simultaneously transmitted frame 470 can be a frame used to restore media synchronization. The simultaneously transmitted frame 470 by the STA can be a simultaneous clear to send (S-CTS) frame. When the simultaneously transmitted frame 470 by the STA is an S-CTS frame, the SCRAMBLER_INITIAL_VALUE included in the TXVECTOR parameter present in the PHY preamble of the S-CTS frame is equal to the SCRAMBLER_INITIAL_VALUE of the RXVECTOR parameter obtained from the PHY preamble of the received MU-RTS TXS trigger frame. Alternatively, frame 430, sent by AP 2 403 and AP 3 405 indicating direct communication, can instruct one of the STAs connected to AP 2 403 and AP 3 405 (e.g., indicating a specific AID, indicating a specific MAC address). Each STA instructed by AP 2 403 and AP 3 405 performs direct communication during the direct communication period and, after the joint transmission period ends, sends a frame (e.g., a CTS frame, a QoS empty frame) to AP 2 403 and AP 3 405 to release the MediumSyncDelay timer of AP 2 403 and AP 3 405 and restore media synchronization. The frame used to restore media synchronization can be frame 470, sent simultaneously. Using frame transmission operations, AP 2 403 and AP 3 405 can restore media synchronization and release the MediumSyncDelay timer.For frame transmissions that cancel the MediumSyncDelay timer of AP 2 403 and AP 3 405, the end point of the direct communication period can be later than the end point of the combined transmission period. For example, the end point of the direct communication period can be later than the combined transmission period by at least a certain frame length (e.g., CTS frame, QoS empty frame).

[0050] Figure 5 A first implementation of a multi-AP frequency-changing communication method is shown.

[0051] refer to Figure 5AP 1 501 to AP 3 505 operate at the same operating frequency. AP 1 501 to AP 3 505 can exchange TWT (e.g., individual TWT, broadcast TWT, restricted TWT) schedules set within each AP. As a result of exchanging TWT schedules, AP 1 501 to AP 3 505 can know each other's TWT schedules (e.g., TWT SPs). The TWT schedules of AP 1 501 to AP 3 505 can overlap in time. For example, TWT SP #1, TWT SP #2, and TWT SP #3, as part of the TWT schedules of AP 1 501 to AP 3 505, can completely or partially overlap in time. AP 1 501 to AP 3 505 perform a negotiation 510 procedure to separate the frequencies of TWT schedule operations and negotiate with each other the frequencies to be used in the overlapping TWT schedules. As a result of negotiation 510, AP 1 501 to AP 3 505 can use different frequencies in the overlapping TWT schedules. For example, it is possible to negotiate that TWT SP #1, which is scheduled as AP 1 501, uses channel 1; it is possible to negotiate that TWT SP #2, which is scheduled as AP 2 503, uses channel 2; and it is possible to negotiate that TWT SP #3, which is scheduled as AP 3 505, uses channel 3. APs 1501 through AP 3505 can send frames indicating frequencies to be used in TWT scheduling (e.g., frames 521, 523, and 525 including SST TWT information, TWT information, and TWT elements). Frames 521, 523, and 525 indicating frequencies to be used in TWT scheduling can change existing TWT scheduling or set new TWT scheduling. The communication frequencies of the TWT scheduling indicated by frames 521, 523, and 525 sent by APs 1501 through AP 3505 can indicate frequencies negotiated by APs 1501 through AP 3505. TWT SP #1 of AP 1501 is executed on channel 1, TWT SP #2 of AP 2503 is executed on channel 2, and TWT SP #3 of AP 3505 is executed on channel 3. The 505's TWT scheduling is frequency-separated, allowing TWT operations to be performed without mutual interference.

[0052] The negotiation and communication process for joint transmission will be described below. This negotiation and communication process can be performed by multiple APs and STAs connected to each AP. The multiple APs can be APs communicating with the STAs using the same frequency. Alternatively, the multiple APs can be APs communicating with the STAs using different frequencies. Joint transmission can refer to the operation of multiple APs sending data or frames using the same frequency or link.

[0053] Figure 6 This is a flowchart of the negotiation and communication process for joint transmission according to an embodiment of the present invention. Figure 6 The illustrated process is executed by one of multiple APs. The AP in this invention can be a master AP. The master AP (e.g., Figure 2 AP 1 201) can be the AP that plays a leading role in the negotiation. Alternatively, the AP of the present invention can be an AP other than the main AP (e.g., Figure 2 AP 2203).

[0054] refer to Figure 6 In step S601, the AP performs negotiation with at least one other AP (e.g., Figure 2 (Scheduling negotiation 210 for joint transmission). An AP can negotiate with other APs to perform joint transmission. Negotiation can be performed to schedule joint transmission periods. Here, a joint transmission period refers to the time period during which joint transmission is performed. For example, negotiation can include SSTTWT negotiation, non-SST TWT negotiation, or transmission period negotiation. During the negotiation process, the AP can synchronize TSF to synchronize joint transmission scheduling or joint transmission periods.

[0055] In step S603, the AP sends information for cooperation based on the negotiation result. The AP can send information for cooperation to the STA. The information for cooperation can be generated based on the negotiation result. The information for cooperation can be generated by a beacon frame (e.g., Figure 2 The information for cooperation is carried in a frame 221 that indicates the joint transmission period. Information for cooperation includes information about the joint transmission period, information about the frequency, transmission prohibition indications, or information about direct communication. Alternatively, information about direct communication may be carried in a different frame than the information for cooperation (e.g., Figure 4 The frame 430, indicating the execution of direct communication, carries the information. For example, information regarding the joint transmission period includes at least one TWT information, channel switching delay, or TWT element. Information regarding the frequency includes at least one, such as link ID, channel number, or frequency information. A transmission prohibition indication may include at least one information regarding the transmission prohibition period or information regarding the STA that prohibits transmission. Information regarding direct communication includes at least one information regarding whether direct communication is being performed, the period during which direct communication is being performed, or the STAs participating in the direct communication.

[0056] In step S605, the AP performs a joint transmission. The joint transmission can be a frame sent to the STA (e.g., ...). Figure 2The operation of frame 240). Joint transmission may include the transmission of frames based on CO-OFDMA operation or CO-SR operation. In order to perform joint transmission, the AP changes the operating frequency or operating link based on information used for cooperation. The master AP may send an initial frame to another AP (e.g., frame 240). Figure 2 The initial frame 230 is used to perform joint transmission. Joint transmission can be performed during the joint transmission period. During the joint transmission period, the AP can send frames based on information used for cooperation. Frames can be sent to STAs participating in the joint transmission. STAs participating in the joint transmission can be STAs that have performed negotiation procedures with the AP. The negotiation procedures between the AP and STAs can be performed by APs other than the master AP. The negotiation procedures between the AP and STAs can be performed before the joint transmission period.

[0057] Figure 7 This is a flowchart of a communication process for joint transmission according to an embodiment of the present invention. Figure 7 The process executed by STA is shown. Figure 7 The STA can be a STA connected to an AP. For example, the STA of this invention can be a STA connected to a main AP (e.g., Figure 2 AP 1 201) or APs other than the main AP (e.g., Figure 2 AP 2 203) STA.

[0058] refer to Figure 7 In step S701, the STA receives information for collaboration. This information can be based on negotiation between APs (e.g., ...). Figure 2 Information generated during the scheduling negotiation (210) for joint transmission. Information used for cooperation includes information about the joint transmission period, information about the frequency, transmission prohibition indications, or information about direct communication. At least some of the information used for cooperation may be carried by at least one frame. For example, the information used for cooperation may be carried by a beacon frame (e.g., Figure 2 The information for cooperation can be carried by beacon frames and MU-RTS frames (e.g., frame 221, which indicates the joint transmission period). As another example, information for cooperation can be carried by beacon frames and MU-RTS frames (e.g., Figure 4 The information is carried in a frame (430) indicating direct communication. For example, in information used for cooperation, information about direct communication can be carried by a MU-RTS frame, and the remaining information can be carried by a beacon frame. For example, information about the joint transmission period includes at least one TWT information, channel switching delay, or TWT element. Information about the frequency includes at least one, such as link ID, channel number, or frequency information. Transmission prohibition indication may include at least one information about the transmission prohibition period or the STA that prohibits transmission. Information about direct communication includes at least one information about whether direct communication is performed, the period during which direct communication is performed, or the STAs participating in direct communication.

[0059] In step S703, the STA can set a transmission prohibition period based on information used for cooperation (e.g., Figure 3 (NAV 251 in the original text). A transmission prohibition period refers to a period during which frame transmission to the AP is prohibited. For example, a transmission prohibition period may include an NAV or a silent period. The transmission prohibition period may be set based on a transmission prohibition indication included in the information used for cooperation. Alternatively, the STA may set the transmission prohibition period based on information about the joint transmission period and channel handover delay. The STA may terminate frame transmission before the transmission prohibition period. For example, the STA may terminate frame transmission by terminating the TXOP before the transmission prohibition period. If the information used for cooperation includes information about direct communication, the STA may additionally set a direct communication period (e.g., ...). Figure 3 The direct communication period (350 periods) is the time during which the STA can send frames without going through the AP. When a direct communication period is set, a transmission prohibition period does not need to be set. In other words, a direct communication period can be set instead of a transmission prohibition period.

[0060] In step S705, the STA can send frames based on information used for cooperation. When an STA has established a direct communication period, it can send frames to another STA. An STA can send frames to another STA during a direct communication period. If an STA has not yet established a direct communication period, it can send frames after the joint transmission period ends. After the joint transmission period ends, STAs that have established a direct communication period and STAs that have not yet established a direct communication period can send frames (e.g., ...). Figure 4 The STA simultaneously sends frame 470 to release the timer used to restore media synchronization of the AP. For example, the STA can send an S-CTS frame or a QoS empty frame to the connected AP.

[0061] The operation of the method according to an 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 can include all types of recording means for storing data readable by a computer system. Furthermore, the computer-readable recording medium can store and execute programs or code that can be distributed across computer systems connected via a network and read in a distributed manner by a computer.

[0062] Additionally, 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 code created by a compiler, but also high-level language code that can be executed by a computer using an interpreter.

[0063] Although the invention has been described above with reference to preferred embodiments thereof, those skilled in the art will understand that various modifications and variations may be made to the invention without departing from the scope and spirit of the invention as defined by the appended claims.

[0064] Industrial applicability This invention can be applied to devices and recording media in wireless local area network systems.

Claims

1. A method for operating an access point (AP) in a wireless local area network system, comprising: Negotiate with at least one other AP for joint transmission; Based on the negotiation results, information for joint transmission is sent; as well as Frames are sent based on the negotiation results. The result of the negotiation includes the frequency used for joint transmission, and Frames are sent using frequencies used for joint transmission.

2. The method according to claim 1, wherein, The information used for joint transmission includes at least one of the following: information about the joint transmission period, information about the frequency used for joint transmission, information about the transmission prohibition period, or information about direct communication indication.

3. The method according to claim 1, in, The transmission of the frame further includes changing the operating frequency to a frequency used for joint transmission, and Frames are sent during the joint transmission period set through negotiation.

4. The method according to claim 3, wherein, The joint transmission period includes TWT service period (SP), restricted TWT (R-TWT) SP, or SP.

5. The method of claim 1, further comprising synchronizing the Time Synchronization Function (TSF) for joint transmission.

6. The method according to claim 1, wherein, Frames are transmitted based on Cooperative Orthogonal Frequency Division Multiple Access (CO-OFDMA) or Cooperative Spatial Reuse (CO-SR).

7. The method according to claim 1, wherein, The frame includes an initial frame for restoring media synchronization to other APs.

8. The method of claim 1, further comprising negotiating with participating stations (STAs) to conduct joint transmission.

9. The method according to claim 1, wherein, The negotiation includes at least one of the following: Subchannel Selective Transmission (SST) Target Wake-Up Time (TWT) negotiation, TWT negotiation other than SST, or Transmission Period negotiation.

10. A method for operating a station (STA) in a wireless local area network system, comprising: Receive information for combined transmission from the connected AP; as well as Based on the information used for joint transmission, at least one of the following operations is performed during the joint transmission period: transmission prohibition operation, frame reception operation, or direct communication operation. The information used for joint transmission includes at least one of information about the joint transmission period or information about the frequency used for joint transmission.

11. The method according to claim 10, wherein, The transmission prohibition operation includes setting a transmission prohibition period that includes a joint transmission period and ignoring frames scheduled to be sent to the connected AP during the transmission prohibition period.

12. The method according to claim 10, wherein, The frame receiving operation includes receiving frames using a frequency used for joint transmission during a joint transmission period.

13. The method according to claim 10, wherein, The direct communication operation includes the operation of communicating with another STA during a joint transmission period.

14. The method of claim 10, wherein, The information used for joint transmission includes at least one of the following: information about the joint transmission period, information about the frequency used for joint transmission, information about the transmission prohibition period, or information about direct communication indication.

15. The method of claim 10, further comprising sending a frame for media synchronization of the connected AP to the connected AP after the end of the joint transmission period.

16. The method of claim 10, further comprising negotiating with the connected AP to receive frames.

17. An access point (AP) in a wireless local area network system, comprising: transceiver; and The processor, which is connected to the transceiver, The processor is configured as follows: Negotiate with at least one other AP for joint transmission; Based on the negotiation results, information for joint transmission is sent; and Frames are sent based on the negotiation results. The result of the negotiation includes the frequency used for joint transmission, and Frames are sent using frequencies used for joint transmission.

18. A station (STA) in a wireless local area network system, comprising: transceiver; and The processor, which is connected to the transceiver, The processor is configured as follows: Receive information for combined transmission from the connected AP; and Based on the information used for joint transmission, at least one of the following operations is performed during the joint transmission period: transmission prohibition operation, frame reception operation, or direct communication operation. The information used for joint transmission includes at least one of information about the joint transmission period or information about the frequency used for joint transmission.

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