Access point device, communication method, communication system, and program

Abstract

To prevent deterioration in frequency utilization efficiency due to carrier sense.SOLUTION: Based on control that avoids interference between communication of a communication device and communication of other communication device that is executable by the communication device and other communication device, the communication device determines whether or not a partner device needs to perform carrier sense when data held by the partner device being connected to the communication device is transmitted to the communication device, and transmits, to the partner device, a frame that includes information indicating determination results and instructs the partner device to transmit data.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a technique for improving frequency utilization efficiency.

Background Art

[0002] As a communication standard related to Wireless Local Area Network (Wireless LAN), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard is known. In the IEEE 802.11ax standard, which is the latest standard in the IEEE 802.11 standard series, by using OFDMA (Orthogonal Frequency Division Multiple Access), in addition to high peak throughput, improvement in communication speed under congested situations is realized.

[0003] Currently, for further throughput improvement, as a successor standard to IEEE 802.11ax, a Task Group for formulating the IEEE 802.11be standard has been formed. And in this Task Group, a Multi-AP Coordination configuration in which a plurality of APs (Access Points) communicate in cooperation has been proposed. In this configuration, the OFDMA communication introduced from IEEE 802.11ax is performed through coordination between two or more APs (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In wireless LANs, interference is avoided when a communication device transmitting a signal performs carrier sensing on the channel to which it is to transmit the signal, confirming that no other communication devices are using that channel before transmitting the signal. This carrier sensing is performed even when the placement of communication devices has been determined to prevent other surrounding communication devices from using that channel. As a result, carrier sensing is performed unnecessarily even in environments where no interference occurs, and communication is not possible during that time, which can degrade frequency utilization efficiency.

[0006] This invention provides a technology to prevent the degradation of frequency utilization efficiency due to carrier sensing. [Means for solving the problem]

[0007] An access point device according to one aspect of the present invention is an access point device that performs wireless communication compliant with the IEEE 802.11 series, and comprises: negotiation means for negotiating between the access point device and the other access point device in order to avoid interference between the communication of the access point device and the communication of the other access point device by using different time domain resources for the communication of the access point device and the communication of the other access point device; receiving means for receiving a first trigger frame from the other access point device after the negotiation has been performed, which includes identification information of the access point device and information indicating the time to be allocated to the access point device; and generating means for generating a second trigger frame in which 0 is stored in the CS Required Bit based on the receipt of the first trigger frame. , receiving The system includes a transmission control means that controls the transmission of a second trigger frame, in which the CS Required Bit contains 0, to the other device during the time allocated to the access point device indicated by the transmitted first trigger frame. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and as a result of the sounding process, it is determined that interference avoidance control in the power domain between communication in the access point device and communication in the other access point device is possible, the transmission control means controls to transmit a trigger frame with 0 stored in the CS Required Bit to the other device. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and as a result of the sounding process, it is determined that interference avoidance control in the power domain is not possible, the transmission control means controls to transmit a trigger frame with 1 stored in the CS Required Bit to the other device. do. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the degradation of frequency utilization efficiency due to carrier sensing. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an example configuration of a wireless communication system. [Figure 2] This figure shows an example of the hardware configuration of a communication device. [Figure 3] This figure shows an example of the functional configuration of an access point. [Figure 4] This figure shows an example of the station's functional configuration. [Figure 5] This diagram shows an example of the communication flow in a wireless communication system. [Figure 6] This diagram illustrates an example of interference avoidance adjustments. [Figure 7A] This diagram shows an example of the processing flow performed by a communication device. [Figure 7B] This diagram shows an example of the processing flow performed by a communication device. [Figure 8] This diagram illustrates the structure of the MAC frame format. [Figure 9] This is a diagram illustrating the structure of the HT Control field format. [Figure 10A] This is a diagram illustrating the structure of a trigger frame. [Figure 10B] This is a diagram illustrating the structure of a trigger frame. [Figure 11] This diagram shows an example of the communication flow in a wireless communication system. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] (System Configuration) Using Figure 1, an example configuration of the wireless communication system according to this embodiment will be described. This wireless communication system is a wireless communication system in which access points (APs) each constitute a network and communicate with connected stations (STAs) using, for example, a wireless LAN compliant with the IEEE 802.11 standard series. Although only two APs (AP101, AP106) are shown in Figure 1, there may naturally be three or more APs, or there may be just one AP. Two or more APs can communicate with each other via the backhaul network 100. Also, although four STAs (STA102, STA103, STA107, and STA108) are shown in Figure 1, there may be more STAs than this, or there may be three or fewer STAs. Note that STA102 and STA103 are connected to AP101 and are assumed to be the communication partners of AP101. Also, STA107 and STA108 are connected to AP106 and are assumed to be the communication partners of AP106. Furthermore, AP and STA merely indicate that they are operating as a wireless LAN base station and terminal, respectively; they could be any communication device capable of operating as both an AP and an STA.

[0012] The backhaul network 100 can be composed of, for example, a wired communication line such as Ethernet (registered trademark) or a telephone line, but is not limited thereto. For example, the backhaul network 100 may be composed of a wireless communication line, or may be composed of a combination of a wireless communication line and a wired communication line. The wireless communication line can be, for example, a wireless communication line by a cellular communication network such as LTE (Long Term Evolution) or the 5th generation (5G). Also, the wireless communication line may be a wireless communication line based on other wireless communication standards such as WiMAX (Worldwide Interoperability for Microwave Access) or the IEEE802.11 standard series. When the backhaul network 100 compliant with the IEEE802.11 standard series is configured, a wireless channel different from the wireless channel used between the AP and the STA may be used, or the same wireless channel may be used. The backhaul network 100 can be used to interconnect the BSS (Basic Service Set) of the AP and other networks when the AP constructs a DS (Distribution System).

[0013] AP101 configures and manages a first network (first BSS) that provides communication services to STAs existing in area 104. Also, AP106 configures and manages a second network (second BSS) that provides communication services to STAs existing in area 109. Note that area 105 indicates a range within which the communication of the first BSS is not affected by interference from APs or STAs belonging to other BSSs (e.g., the second BSS). Also, area 110 indicates a range within which the communication of the second BSS is not affected by interference from APs or STAs belonging to other BSSs (e.g., the first BSS). On the other hand, the area in area 104 that is not included in area 105 is an area where communication of the first BSS is possible, but is affected by interference from the communication of APs or STAs belonging to other BSSs, or may interfere with the communication of those APs or STAs. Similarly, the area in area 109 that is not included in area 110 is an area where communication of the second BSS is possible, but is affected by interference from the communication of APs or STAs belonging to other BSSs, or may interfere with the communication of those APs or STAs.

[0014] In this embodiment, both AP101 and AP106 are assumed to have a Multi-AP Coordination configuration function. The Multi-AP Coordination function is a function that provides communication to the connected STAs in cooperation with other APs, and provides communication that is faster or has a better communication environment than communication by only one AP. That is, with the Multi-AP Coordination function, compared to the case of providing communication with only one AP, it is possible to improve any of the indicators indicating the communication environment, such as a high signal-to-noise ratio, a small amount of interference, a small communication delay, and a small jitter.

[0015] There are several communication methods that utilize the Multi-AP Coordination function. One such method is JTX (Joint Transmission) using D-MIMO (Distributed Multiple Input Multiple Output). D-MIMO is a MIMO that transmits and receives signals in parallel using geographically distributed antennas (APs). By transmitting signals in parallel from multiple APs using JTX with D-MIMO, the downlink (DL) throughput at the STA can be improved. Another such communication method is null steering, which adjusts antenna weights based on information indicating the state of the transmission path between the AP and the STA so that signals do not reach the STA during a particular communication. Coordinated OFDMA and Fractional Coordinated OFDMA are also such communication methods. These will be discussed later. In the following, Coordinated OFDMA will be referred to as "C-OFDMA" and Fractional Coordinated OFDMA as "FC-OFDMA". Also, when there is no particular distinction between C-OFDMA and FC-OFDMA, they may simply be referred to as C-OFDMA. If the Multi-AP Coordination configuration function is not executed, AP101 will manage only the first BSS, and AP106 will manage only the second BSS. Here, "management" primarily refers to the allocation of OFDMA resources and the management of the timing of that communication.

[0016] In this embodiment, the AP notifies the STA that carrier sensing is not necessary in an environment where interference is not expected to occur. For example, AP101 can create an environment where STA102 and STA103 do not need to perform carrier sensing by coordinating with AP106 using the Multi-AP Coordination function to prevent mutual interference. In this case, AP101 sends information to STA102 and STA103 indicating that carrier sensing is not necessary, and STA102 and STA103 send uplink (UL) signals to AP101 without performing carrier sensing. The uplink is the link used to send signals from a terminal to a base station (i.e., from STA to AP). On the other hand, the link used to send signals from AP to STA is called the downlink (DL). Similarly, AP106 also sends information to STA107 and STA108 indicating that carrier sensing is not necessary, and STA107 and STA108 send UL signals to AP101 without performing carrier sensing. According to this, in environments where interference can be avoided in advance through coordinated operation between APs, it becomes possible to prevent STAs from performing unnecessary carrier sensing and to prevent the degradation of frequency utilization efficiency due to such unnecessary carrier sensing. Furthermore, an AP can notify the STA that carrier sensing is unnecessary even if it is known that there are no other BSSs nearby. For example, in a limited area, if only one AP is provided and the network is configured so that the communication of other APs does not interfere with the communication of that one AP, there is no need to consider the effects of interference. In this case, for example, by pre-configuring the AP, the AP can notify the connected STA that carrier sensing is unnecessary even if coordinated operation with other APs is not performed. Furthermore, the AP may recognize that it is an environment where interference cannot occur by, for example, confirming that there are no other APs nearby via the backhaul network 100, or by obtaining information such as other surrounding APs having stopped communicating.

[0017] (Device configuration) Next, an example of the hardware configuration of a communication device (AP and STA) will be described using Figure 2. As an example of its hardware configuration, the communication device includes a storage unit 201, a control unit 202, a functional unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0018] The storage unit 201 is composed of one or more memories, including both ROM and RAM, or either one of them, and stores various information such as programs for performing various operations described later, and communication parameters for wireless communication. ROM is an acronym for Read Only Memory, and RAM is an acronym for Random Access Memory. In addition to ROM, RAM, and other memories, the storage unit 201 may also use storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs. Furthermore, the storage unit 201 may be composed of multiple memory or other storage devices.

[0019] The control unit 202 is composed of, for example, one or more processors such as a CPU or MPU, an ASIC (Application-Specific Integrated Circuit), a DSP (Digital Signal Processor), or an FPGA (Field-Programmable Gate Array). Here, CPU is an acronym for Central Processing Unit, and MPU is an acronym for Micro Processing Unit. The control unit 202 may also be a multi-core processor. The control unit 202 controls the entire device by executing a program stored in the memory unit 201. The control unit 202 may also control the entire device in cooperation with the OS (Operating System) and the program stored in the memory unit 201.

[0020] Furthermore, the control unit 202 controls the functional unit 203 to perform predetermined processes such as imaging, printing, and projection. The functional unit 203 is hardware that enables the device to perform predetermined processes. For example, if the device is a camera, the functional unit 203 is the imaging unit and performs imaging processing. Also, for example, if the device is a printer, the functional unit 203 is the printing unit and performs printing processing. Also, for example, if the device is a projector, the functional unit 203 is the projection unit and performs projection processing. The data processed by the functional unit 203 may be data stored in the storage unit 201, or data communicated with other APs or STAs via the communication unit 206, which will be described later. The functional unit 203 may also include processing circuits for realizing AP functions or STA functions, and may be configured to perform processing as a wireless LAN AP or STA compliant with the IEEE 802.11 standard series based on the control of the control unit 202.

[0021] The input unit 204 receives various operations from the user. The output unit 205 provides various outputs to the user. Here, the output from the output unit 205 includes at least one of the following: display on the screen, audio output from a speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be implemented in a single module, such as a touch panel.

[0022] The communication unit 206 controls wireless communication compliant with the IEEE 802.11 standard series and IP communication. The communication unit 206 is a so-called wireless chip and may include one or more processors and memory itself. In this embodiment, the communication unit 206 can perform processing compliant with at least the IEEE 802.11be standard. The communication unit 206 also controls the antenna 207 to transmit and receive wireless signals for wireless communication. The AP and STA communicate content such as image data, document data, and video data with other communication devices via the communication unit 206. The antenna 207 is, for example, an antenna capable of transmitting and receiving at least one of the sub-GHz band, 2.4GHz band, 5GHz band, and 6GHz band. The frequency bands (and their combinations) that the antenna 207 can handle are not particularly limited. The antenna 207 may be a single antenna or a set of two or more antennas for MIMO (Multi-Input and Multi-Output) transmission and reception. Furthermore, the antenna 207 may include two or more antennas (two or more sets) each capable of operating in different frequency bands. The communication unit 206 has a Multi-AP Coordination function. In Figure 2, one communication unit 206 and one antenna 207 are shown, but multiple combinations of these may be provided. Also, one or more antennas 207 may be shared by multiple communication units 206.

[0023] Next, using Figure 3, an example of the functional configuration of APs (AP101 and AP106) will be described. An AP includes, for example, a wireless LAN control unit 301, a UI control unit 302, a memory control unit 303, a cooperative operation method selection unit 304, and a Single-AP configuration control unit 305. Furthermore, an AP also includes a JTX configuration control unit 306, a null steering configuration control unit 307, a C-OFDMA configuration control unit 308, an FC-OFDMA configuration control unit 309, and a schedule adjustment configuration control unit 310. These functions can be realized, for example, by the control unit 202 executing a program stored in the memory unit 201 (in one example, by the control unit 202 controlling the communication unit 206).

[0024] The wireless LAN control unit 301 controls the transmission and reception of wireless signals with other communication devices (e.g., other APs and STAs) in accordance with wireless LAN standards. Specifically, the wireless LAN control unit 301 performs wireless LAN communication control, such as generating and transmitting wireless frames containing control information and data to be transmitted, and receiving wireless frames from other communication devices, in accordance with the IEEE 802.11 standard series. The UI control unit 302 detects operations on the user interface (UI), such as touch panels and buttons, by a user of the AP (not shown), and processes the detected operations by converting them into data usable within the AP. The UI control unit 302 also has functions to present information to the user, such as displaying images and outputting sound. The memory control unit 303 controls the storage of information related to the processing performed by the AP in the memory unit 201, and controls the reading of data stored in the memory unit 201. The cooperative operation method selection unit 304 selects the Multi-AP Coordination function to be used based on whether or not other APs exist within a predetermined range where cooperative operation is possible, information on the capabilities of other APs, and information indicating the connection status between other APs and the STA. The Single-AP configuration control unit 305 performs control when the Multi-AP Coordinate function is not operated, that is, when an AP communicates with the STA alone.

[0025] The JTX configuration control unit 306, null steering configuration control unit 307, C-OFDMA configuration control unit 308, and FC-OFDMA configuration control unit 309 are functional units for executing their respective Multi-AP Coordinate functions. Specifically, the JTX configuration control unit 306 performs control for executing JTX using D-MIMO, for example, and the null steering configuration control unit 307 performs control for executing null steering. The C-OFDMA configuration control unit 308 and FC-OFDMA configuration control unit 309 perform control for executing C-OFDMA and FC-OFDMA, respectively. The schedule adjustment configuration control unit 310 schedules the operation of the Multi-AP Coordinated function.

[0026] Figure 4 shows an example of the functional configuration of STA (STA102, STA103, STA107, STA108). STA includes, for example, a wireless LAN control unit 401, a UI control unit 402, a memory control unit 403, and a carrier sense control unit 404. These functions can be realized, for example, by the control unit 202 executing a program stored in the memory unit 201 (in one example, by the control unit 202 controlling the communication unit 206). The wireless LAN control unit 401, UI control unit 402, and memory control unit 403 are the same as the corresponding functional units of the AP (wireless LAN control unit 301, UI control unit 302, memory control unit 303). The carrier sense control unit 404 determines whether carrier sensing is necessary for a wireless frame received from the AP, and controls whether or not to perform carrier sensing based on the result of that determination. For example, if the carrier sense control unit 404 determines that carrier sensing is unnecessary, it can control the wireless LAN control unit 401 to transmit the UL wireless frame without performing carrier sensing. Furthermore, the carrier sense control unit 404 can, for example, control the wireless LAN control unit 401 to perform carrier sense before transmitting the UL wireless frame if it determines that carrier sense is necessary.

[0027] (Process flow) Next, the communication processing flow in this embodiment will be described. Figure 5 shows an example of the communication flow performed in a wireless communication system. First, a connection is established between AP101 and STA102 and STA103 (S501, S502). During this connection establishment process, AP and STA exchange Management frames containing information elements (IE) that indicate each other's capability information and operational information. The Management frame is, for example, one of Beacon, Probe Request / Response, Association Request / Response, or Authentication Request / Response. Also, AP101 sets an Association ID for each of STA102 and STA103 during the connection process. This ID is used as the STA ID to identify each STA in the TF (Trigger Frame) described later.

[0028] IEs (Indicators of Capability) that show capability and operational information have been increasing in number in line with the progress of standardization in the IEEE 802.11 series. For example, in the IEEE 802.11n standard, this IE is the HT Capability element, and in the IEEE 802.11ac standard, it is the VHT Capability element. This IE indicates, for example, whether or not support for BQR (Bandwidth Query Report) is possible in the IEEE 802.11ax standard. This is indicated by one bit in the "BQR Support" subfield included in HE MAC Capabilities. By setting this bit to "1", the AP indicates that it can receive BQRs from terminals, and by setting this bit to "1", the STA indicates that it can generate BQRs and notify the AP. Furthermore, whether or not support for Multi-AP, which was introduced in the IEEE 802.11be standard, is possible is indicated by the EHT Capabilities element.

[0029] AP101, while connected to STA102 and STA103, sends a BSRP (BSR Poll) TF to these STAs to request a BSR (Buffer Status Report) (S503). Then, STA102 and STA103 send a BSR indicating the amount of data accumulating in the transmit buffer to AP101 according to the BSRP TF (S504). Subsequently, AP101 sends a BQRP (BQR Poll) TF to STA102 and STA103 to report a BQR indicating channel availability (S505). Then, STA102 and STA103 send a BQR to AP102 according to this BQRP TF (S506). The same process from S501 to S506 described below is also performed between AP106 and STA107 and STA108.

[0030] Subsequently, AP101 performs the Multi-AP configuration setup procedure with AP106 (S507). This procedure includes negotiation to determine which AP, AP101 or AP106, will operate as the Master AP (and which AP will operate as the Slave AP). The Master AP is the AP that controls the entire Multi-AP configuration and operates to determine which RUs and timings each AP should use. The Master AP may also be called the Coordinator AP or Sharing AP. Similarly, the Slave AP may be called the Coordinated AP or Shared AP. In this example, it is assumed that AP101 has been determined to operate as the Master AP.

[0031] AP101 and AP106 perform interference avoidance adjustment processing after the setup procedure for the Multi-AP configuration (S508). This adjustment is explained using Figures 6(A) to 6(C).

[0032] In Figures 6(A) to 6(C), the horizontal axis represents time, and the vertical axis represents frequency. Note that Figures 6(A) to 6(C) show frequency and time in a schematic manner, and do not specifically limit the duration and units of time, nor the frequency bandwidth and units of frequency. The duration and units of time may vary depending on the use case of the Multi-AP Coordination configuration. For example, from the IEEE 802.11 standard series' TU (Time Unit, 1024 microseconds), milliseconds, seconds, or even larger numbers or units related to human sensitivity and operation may be used as duration and units of time. Furthermore, the frequency bandwidth and units of frequency may, for example, be the OFDMA RU (Resource Unit) as defined in the IEEE 802.11ax standard. However, this is not limited to this; for example, depending on the capabilities of the AP and STA and the use case, multi-band or multi-channel 20MHz units of channels may be used as units of frequency. In Figures 6(A) to 6(C), the solid rectangles indicate the time and frequency resources used by AP101 (the first BSS), and the dashed rectangles indicate the time and frequency resources used by AP106 (the second BSS).

[0033] Furthermore, to explain the operation of C-OFDMA or FC-OFDMA, we introduce the concept of interference-limited terminals. Interference-limited terminals, also called interference-limited STAs, refer to STAs that are affected by communications in BSSs to which they do not belong. In the configuration of Figure 1, SAT103 and STA108 are interference-limited terminals. STAs that are not affected by communications from other BSSs are called non-interference-limited terminals (non-interference-limited STAs). In Figure 1, STA102 and STA107 are non-interference-limited terminals. Note that interference-limited terminals are sometimes called edge terminals (edge ​​STAs), and non-interference-limited terminals are sometimes called center terminals (center STAs).

[0034] Figure 6(A) is a diagram illustrating the C-OFDMA method. In the C-OFDMA method, available frequency resources (RUs) are clearly separated among multiple BSSs (APs and STAs). That is, adjustments are made so that the RUs used in the first communication between AP101 and STA102 and STA103 do not overlap in the frequency domain with the RUs used in the second communication between AP106 and STA107 and STA108. In this way, C-OFDMA separates the available frequency resources at each BSS so that they do not overlap, thus preventing interference between communications between BSSs. In other words, when C-OFDMA is used, it is possible to prevent interference between communications between AP101 and STA102 and STA103 and communications between AP106 and STA107 and STA108.

[0035] Next, FC-OFDMA will be explained using Figure 6(B). In FC-OFDMA, it is permissible for the RUs used by multiple BSSs to overlap in the frequency domain. The overlapping frequency domain can be used, for example, for communication of STAs located near APs, thereby preventing interference between BSSs. For example, AP101 can receive radio frames even if STA102 transmits them at low power. It is also assumed that such radio frames will not reach AP106, STA107, and STA108 with sufficient power. Similarly, it is assumed that radio frames transmitted by STA107 at low power will not reach AP101, STA102, and STA103 with sufficient power. Therefore, for example, even if STA102 uses the same frequency resources as AP106, STA107, and STA108, the probability of causing interference that would prevent communication from those other communication devices is low. Similarly, for example, even if STA107 uses the same frequency resources as AP101, STA102, and STA103, the probability of it causing interference that would prevent communication from those other communication devices is low. Therefore, even if the frequency resources allocated to the communication of these STAs are the same as those allocated to other BSSs, the effects of interference can be sufficiently suppressed. Furthermore, FC-OFDMA can be said to be a power axis interference avoidance method in that even if the same frequency and time resources are used by multiple BSSs, it is only subjected to interference at a power level that is sufficiently low compared to the power of the signals within the BSS. Note that Figure 6(B) shows an example in which the entire frequency resources are shared by the first and second BSSs, but only a portion of the frequency resources may be shared.

[0036] Figure 6(C) shows an example of resource division in the time domain. The first BSS and the second BSS are coordinated to use different time resources. As a result, while the first BSS is communicating, the second BSS is not communicating, and while the second BSS is communicating, the first BSS is not communicating, thus preventing interference between these BSSs.

[0037] As described above, in one example, the type of interference avoidance is determined, which domains of frequency, power, or time are used to avoid (suppress) interference. Note that these are just examples, and interference avoidance may be performed in other domains (e.g., codes or space). At this point, if necessary, processing for interference avoidance control is performed among the communication devices (AP101, STA102, STA103, AP106, STA107, STA108). For example, if the determined type of interference avoidance is FC-OFDMA, processing is performed to determine "how frames from APs were received by other APs and STAs" and "how frames from STAs were received by each AP". In one example, a predetermined wireless frame transmitted by an AP is measured by other APs and STAs, and the STA notifies the connected AP of the measurement result. For example, a predetermined wireless frame transmitted by AP101 is measured by STA102 and STA103, AP106, STA107, and STA108. Then, STA102 and STA103 report their measurement results to AP101, and STA107 and STA108 report their measurement results to AP102. Similarly, AP101, STA102 and STA103, and STA107 and STA108 measure a predetermined radio frame transmitted by AP106. Then, STA102 and STA103 report their measurement results to AP101, and STA107 and STA108 report their measurement results to AP102. This identifies "how frames from APs were received by other APs and STAs." In this way, a kind of sounding process is performed in power-based interference avoidance control such as FC-OFDMA. AP101 and AP106 can share these identified results and use them in subsequent interference avoidance processing. Similarly, each AP can measure frames from each STA and share the results. This allows us to determine whether each STA is located at the edge (boundary) of the communication area or near the AP (near the center of the communication area). STAs located at the edge of the communication area may be treated as edge terminals, while STAs located near the center of the communication area may be treated as central terminals.Subsequently, AP101, as the Master AP, transmits a Multi-AP TF to AP106 (S509). The Multi-AP TF will be described later. Here, it is assumed that AP101 has decided to perform interference avoidance control in the frequency domain with AP106. At this time, the Multi-AP TF transmitted by AP101 includes information indicating that interference avoidance control should be performed in the frequency domain, and information indicating the frequency resources available to AP106.

[0038] Then, AP101 transmits a Basic TF to STA102 and STA103 (S510), and AP106 transmits a Basic TF to STA107 and STA108 (S511). At this time, AP101 determines, for example, which frequency resources to allocate to STA102 and STA103 from among the second frequency resources that are different from the first frequency resource allocated to AP106 in the Multi-AP TF. AP106 also determines which frequency resources to allocate to STA107 and STA108 from among the first frequency resources specified in the Multi-AP TF. AP101 and AP106 set the CS Required bit in the Common field of the Basic TF according to the result of the interference avoidance adjustment process in S508. This bit indicates whether the STAs that will transmit wireless frames by the TF need to perform carrier sensing. For example, if the CS Required bit is "0", it indicates that carrier sensing is not required. For example, AP101 and AP106 send a Basic TF with this bit set to "0" if they have been able to adjust for interference avoidance. For example, as described above, by using the second frequency resource for signal transmission to AP101 and the first frequency resource for signal transmission to AP106, an environment where they do not interfere with each other can be obtained. Therefore, AP101 and AP106 can notify the STA that carrier sensing is not required by setting the CS Required bit in the TF.

[0039] When STA102 and STA103 receive a Basic TF from AP101, they send a TB PPDU (Trigger Based Physical Layer Protocol Data Unit) to AP101 (S512). Similarly, when STA107 and STA108 receive a Basic TF from AP106, they send a TB PPDU to AP106 (S513). The TB PPDU transmits the data that each STA should send to the AP. Subsequently, AP101 sends a Multi-STA BA (Block Ack) to STA102 and STA103 (S514), and AP106 sends a Multi-STA BA to STA107 and STA108 (S515). If AP106 fails to receive data from either STA107 or STA108, it may prompt the source of that data to retransmit it (not shown). Here, AP106 may prompt data retransmission by sending a NACK or not sending an ACK when the HARQ (Hybrid Automatic Repeat reQuest) procedure is employed. Alternatively, AP106 may prompt data retransmission by sending a BlockAck with no BlockAck Bitmap set.

[0040] Next, the processing flow executed by the AP (AP101 or AP106) will be described in detail using Figures 7A and 7B. The processing shown in Figures 7A and 7B is realized, for example, by the AP's control unit 202 executing a program stored in the memory unit 201. At least a part of the following processing may be realized by dedicated hardware. It is assumed that the AP has completed various settings, such as settings related to the operation of the BSS, enabling / disabling Multi-AP operation related to this embodiment, and setting the transmission conditions for the TF. It is also assumed that AP101 has established a connection with STA102 and STA103 (the association procedure has been completed). Similarly, it is assumed that AP106 has established a connection with STA107 and STA108. In the association procedure, the AP understands the capabilities of the STA. The capabilities of the STA include an item called "Absolute transmit power accuracy," which indicates the accuracy of transmit power adjustment. The device class is classified by this value. A device with an absolute transmission power accuracy of ±3dB is classified as a Class A device. On the other hand, a device with an absolute transmission power accuracy of ±9dB is classified as a Class B device. This information can be used, for example, to determine whether interference avoidance control in the power domain is possible.

[0041] First, the AP sends a TF to the connected STA to inquire about the communication characteristics (S701), and in response to that TF, receives communication characteristic information from each STA (S702). The communication characteristics here refer to information indicating the characteristics of the traffic, and in one example, a BSR is used. The BSR is included in the Control subfield of the MAC (Medium Access Control) frame, described later, and is used to notify the amount of data for each access category held in the STA's transmit buffer. Alternatively, the inquiry about communication characteristics may be a TSPEC (traffic specification) inquiry. The TSPEC can specify the maximum and minimum Service Interval, Service Start Time, minimum Data Rate, Burst Size, etc. The Service Interval is information that can identify the time between two service periods that are not interposed by other service periods. The Service Start Time is information that can identify the time when the first service period of a service begins. The Data Rate refers to the communication speed, and the Burst Size indicates the burst size of the data being transmitted.

[0042] The AP determines, for example, whether to initiate UL communication based on the communication characteristics acquired in S702 (S703). In particular, the AP determines whether to instruct the STA to transmit data via TF. That is, if there is no need to instruct the STA to transmit data via TF, the AP may determine not to initiate UL communication. The AP may determine to initiate UL communication if, for example, multiple STAs hold the data to be transmitted. Also, even if only one STA holds the data to be transmitted, the AP will determine to initiate UL communication if it is necessary to instruct that STA to transmit the data via TF. If the AP determines to initiate UL communication (YES in S703), it moves the process to S704; if it determines not to initiate UL communication (NO in S703), it moves the process to S726.

[0043] In S704, AP101 sends a TF (BQRP TF) to each STA to query for the BQR, and then receives the BQR from each STA in response (S705). The BQR is notified using the Control subfield of the MAC frame, as described later, and is used to notify information indicating whether the channel operated by the BSS is available or unavailable in 20MHz units. In other words, the BQR indicates, in as little as one bit, whether a 20MHz sub-frequency band included in the channel operated by the BSS is available or unavailable (busy or not available). For example, in the IEEE 802.11be standard, the maximum frequency bandwidth that the BSS can operate is 320MHz, so the length of the BQR can be 16 bits (2 octets) or more. The STA may, but is not limited to, determine the availability of each sub-frequency band based on the state when it receives the BQRP TF. For example, STA may determine the availability of each sub-frequency band based on the percentage of busy or unavailable periods between the last reception of a BQRP TF and the current reception of a BQRP TF.

[0044] The AP determines, based on the received BQR, whether all of the channels in operation are available (S706). If all of the channels in operation are available (YES in S706), the AP proceeds to S713. In this case, it is assumed that there are no other BSSs interfering with the BSS formed by the AP. On the other hand, if at least some of the channels in operation are unavailable (NO in S706), the AP then determines whether the unavailable (busy or not available) channels are being used by the wireless LAN (S707). The AP makes this determination, for example, by receiving notification of the wireless LAN signal detection result from the STA, or by detecting signals from other BSSs itself, or based on information about other nearby APs that it has previously recognized. The AP may, for example, in S705, use the BQR supplemental information notification procedure to receive notification of the wireless LAN signal detection result from the STA. Supplemental information may indicate the BSS information (e.g., information associating BSSID with channel) used by a channel when the channel status in 20MHz units is busy. This information may be communicated using the content of new Action Frames or Data Frames in the IEEE 802.11 standard.

[0045] If an unavailable channel is being used by another BSS in the wireless LAN (YES in S707), the AP determines whether it can communicate with that BSS's AP in a Multi-AP configuration (S708). If the AP determines that it can communicate with the other AP using the channel in a Multi-AP configuration (YES in S708), it performs a Multi-AP setup process with that AP (S709). In the Multi-AP setup process, the AP searches for other APs that can cooperate in a Multi-AP configuration and determines the Master AP and Slave AP. The AP may, for example, search for other APs that can cooperate in a Multi-AP configuration by receiving a Beacon that contains information indicating that it has Multi-AP capability or is operating in a Multi-AP configuration. Alternatively, the AP may identify other APs that can cooperate in a Multi-AP configuration by confirming configuration information by the user. On the other hand, if the unavailable channel is not being used by another BSS in the wireless LAN (NO in S707), or if communication with other APs using the channel is not possible in a Multi-AP configuration (NO in S708), the AP proceeds to S715. In other words, if the AP cannot make adjustments, the process proceeds to S715. At this point, the AP may prompt the user to change the channel being used to another channel and proceed to S720.

[0046] Once an AP completes the Multi-AP setup, it exchanges information with other APs that make up the Multi-AP that indicates the types of adjustable controls (S710). This information, such as that shown in Figures 6(A) to 6(C), may indicate which domains of frequency, time, and power in OFDMA communication are available for interference avoidance control.

[0047] Interference avoidance control in the frequency domain can be determined by whether it is necessary to avoid a specific channel during communication, or whether communication is possible on any channel. If communication is possible on any channel, it is determined that interference avoidance control in the frequency domain is possible; however, if it is necessary to avoid a specific channel, it is determined that interference avoidance control in the frequency domain is not possible. For example, on a channel where radar is present, channel switching after radar detection and monitoring for a specified period are necessary. If the communication characteristics of the STA cannot accommodate such processing, it becomes necessary to avoid using that channel. In such cases, it is determined that adjustment in the frequency domain is not possible.

[0048] Time-domain interference avoidance control is determined based on the periodicity and acceptable delay of the communication. For example, if performing interference avoidance control in the time domain results in a period during which communication is impossible, and the STA's communication characteristics cannot tolerate this, then it is determined that time-domain adjustment is not possible.

[0049] Interference avoidance control in the power domain can be determined based on the device class of the AP and STA. The AP specifies the STA's transmit power by sending a TF with the value of UL Target receiver power set in the User Info field. On the other hand, for interference avoidance through multi-AP communication, the acceptable interference level is notified to other BSSs, and the transmit power of multiple BSSs performing multi-AP communication is controlled by each other. Therefore, the AP specifies the received power value that should be achieved by its own device without interfering with other BSSs as the UL Target receiver power. It is assumed that the range of transmit power values ​​that satisfy these conditions has a certain width. If this width is less than 9 dB, and a Class B STA is used, the transmit power of that STA may fall outside the range that satisfies the conditions due to errors in its transmit power. As a result, the AP may not meet the received power conditions, or the interference power to other BSSs may exceed the acceptable value. Therefore, in such cases, it may be determined that interference avoidance control in the power domain cannot be performed. Furthermore, since "UL Target receiver power" can be specified for each STA, by changing the STA targeted for UL MU communication to a Class A STA, interference avoidance control in the power domain can be enabled.

[0050] In S710, the AP determines whether there is a control type that can be commonly used with other APs that have exchanged information on the types of interference avoidance control that can be effectively implemented in a Multi-AP configuration. If the AP determines that both its device and the other APs can perform interference avoidance control in the frequency domain or the time domain (YES in S711), it determines the adjustment type and shares the determined adjustment type among the APs (S712). Note that if control is possible in multiple types, such as both the frequency domain and the time domain, or a combination of at least one of the frequency domain and the time domain and the power domain, the AP may decide to perform interference avoidance control in any combination. Then, the AP sets the "CS Required bit" in the TF transmitted in the processing described later to "0" (S713). This "CS Required bit" is a bit that indicates whether carrier sense is required or not, with "0" indicating that carrier sense is not required and "1" indicating that carrier sense is required. Here, interference avoidance control can be performed between BSSs in either the frequency or time domain, and to notify the STA that carrier sensing is not required, a TF with this bit set to "0" is sent to the STA.

[0051] On the other hand, if the AP does not have interference avoidance control in the frequency domain or the time domain (NO in S711) that can be performed in common with its own device and other APs, it determines whether interference avoidance control in the power domain is possible (S714). If the AP determines that interference avoidance control in the power domain is possible (YES in S714), it decides to use interference avoidance control in the power domain (S712) and sets the "CS Required bit" in the TF to "0" (S713). On the other hand, if the AP determines that interference avoidance control in the power domain is not possible (YES in S714), it sets the "CS Required bit" in the TF to "1" (S715). In other words, if it is determined that interference avoidance control cannot be performed between BSSs, the STA is notified that carrier sensing should be performed and a signal should be transmitted. Note that the determination in S714 may be performed simultaneously with S711. However, as mentioned above, a certain type of sounding process is necessary to determine whether or not interference avoidance control by power is possible. Therefore, the sounding process can be performed in parallel with the determination in S711, and the determination in S714 can be performed after the determination in S711, as shown in Figure 7A. Furthermore, interference avoidance control in the power domain may not be able to adequately avoid interference compared to interference avoidance control in the frequency domain or time domain, as it may change abruptly due to changes in the communication environment, etc. Therefore, if interference avoidance control in the frequency domain or time domain can be performed, those interference avoidance controls should be used, and as shown in Figure 7A, the applicability of interference avoidance control in the power domain may be determined only when those interference avoidance controls are not possible. In addition, the sounding process may be performed in advance so that the determination in S714 can also be performed at the time of processing S711. In this case, if the AP can perform interference avoidance control between BSSs in some form, it will proceed to processing S712, and if it cannot perform such interference avoidance control, it will move the processing to S715.

[0052] In addition, while the examples in Figures 7A and 7B describe cases where carrier sensing is deemed unnecessary when interference avoidance control is performed in the frequency domain, time domain, or power domain, the AP is not limited to these examples. For example, the AP may determine that carrier sensing is unnecessary when interference avoidance control is performed in the frequency domain or time domain, and that carrier sensing is necessary when interference avoidance control is performed only in the power domain. In other words, the AP may determine whether carrier sensing is necessary based on whether the type of interference avoidance control that can be performed is of a predetermined type.

[0053] Subsequently, if the AP is the Master-AP in a Multi-AP configuration (YES in S716), it transmits a Multi-AP TF (S717); otherwise, it receives a Multi-AP TF (S718) if it is not the Master-AP (NO in S716). The Multi-AP TF is an extension of the TF in the IEEE 802.11ax standard and is used to allocate OFDMA RUs or channels in 20MHz units to APs rather than STAs. The frame structure of the Multi-AP TF will be described later using Figures 10A and 10B.

[0054] The AP then determines the allocation of RUs for UL communication to the STA within the range of RUs or channels specified in the Multi-AP TF (S719), and sends a TF for UL communication to that STA (S720). The Common field of the TF sent here is set to the value of the "CS Required bit" set in S714 or S715 above. The value of the UL Length in this TF is determined based on the Duration value specified in the Multi-AP TF. When the AP assigns RUs to one or more STAs and instructs them to transmit signals using the TF sent in S720, it receives a TB PPDU transmitted from those STAs using the instructed RUs (S721). The AP then sends an acknowledgment (ACK) to the STA that sent the TB PPDU (S722). At this time, if the value of the "CS Required bit" is "0", the STA can recognize that carrier sensing is not necessary. On the other hand, if the value of the "CS Required bit" is "1", the STA can recognize that carrier sensing should be performed.

[0055] Subsequently, the AP determines whether to continue the UL communication (S723). If the AP decides to continue the UL communication (YES in S723), it determines whether to query the channel status (S724). The AP may decide to query the channel status based on at least one of the following conditions: the AP itself has detected a change in the radio medium, a predetermined amount of time has elapsed since the last BQR query, or an unsolicited BQR has been received from the STA. An unsolicited BQR is a BQR that is voluntarily transmitted by an STA that has not received a BQRP TF from the AP. The STA may include the BQR in the Control subfield of the MAC frame described below when transmitting. The MAC frame may be included in the TB PPDU transmitted by the STA in S721, or in the radio frame during communication transmitted without a TF via EDCA (Enhanced Distributed Channel Access). The STA may also notify the AP of the BSR using the unsolicited method without a TF.

[0056] If the AP determines that a channel status query is necessary (YES in S724), it returns to processing S704. On the other hand, if the AP determines that a channel status query is not necessary (NO in S724), it determines whether to maintain the type of interference avoidance control (for example, determined in S712) (S725). Then, if the AP decides to maintain the type of interference avoidance control (YES in S725), it returns to processing S716; if it decides not to maintain it (NO in S725), it returns to processing S709. The AP may decide not to maintain the type of interference avoidance control in response to changes in the status of BSS formed by other APs in a Multi-AP configuration or by its own device, or the activation of a different BSS. This allows the AP to perform the Multi-AP setup again and re-select the appropriate type of interference avoidance control.

[0057] On the other hand, if the AP decides not to continue UL communication (YES in S723), it decides whether or not to perform DL communication (S726). If the AP decides to perform DL communication (YES in S726), it sends a PPDU to one or more STAs. The AP may use a MU (Multi-User) PPDU when sending data to multiple STAs simultaneously, and a SU (Single-User) PPDU when sending data to a single STA. The AP may also perform MIMO sounding or BQR queries to the STA as needed during DL communication. After sending the PPDU, the AP receives an acknowledgment (ACK) from the STA to which the PPDU is sent (S728). The AP may resend the data to the STA if it detects a reception failure at the STA (not shown). The AP may detect a reception failure, for example, by receiving a NACK when the HARQ (Hybrid Automatic Repeat reQuest) procedure is used, or by not receiving an ACK. Alternatively, the AP may detect a reception failure based on receiving a BlockAck for which the BlockAck Bitmap is not set. The AP then returns processing to S726 and decides whether to continue DL communication.

[0058] If the AP decides not to perform DL communication, for example, if there is no data destined for STA (NO in S726), it determines whether to change the AP's operation (S729). For example, the AP determines whether it has received a user operation to change settings such as enabling / disabling Multi-AP operation. The AP may also transfer processing to S729 if it receives a user operation to change settings at any stage while the above processing is being performed. In other words, in the above example, the determination in S729 is made after the completion of a series of communications including UL communication and DL communication, but the AP may immediately transfer processing to S729 if a setting change occurs during these communications. If the AP determines to change its operation (YES in S729), it changes the operation setting (S730) and terminates processing. If other settings are changed while the Multi-AP operation setting remains enabled, the AP may return processing to S701 after changing the operation setting. If the AP determines not to change its operation (NO in S729), it returns processing to S701 while maintaining the current settings.

[0059] Thus, in this embodiment, for example, if an AP can avoid interference between BSSs in advance through a Multi-AP configuration with other APs, it can notify the STA that carrier sensing is unnecessary. Also, the AP can explicitly notify the STA that carrier sensing is necessary in environments where carrier sensing should be performed. In this embodiment, an example of setting the value of "CS Required bit" based on whether interference between APs can be adjusted is described, but it is not limited to this. For example, an AP may be configured to always set "CS Required bit" to "0" if a setting is made to indicate that the BSS formed by its own device should take precedence. That is, regardless of whether adjustment with other APs is possible, the AP may notify the STA that carrier sensing is unnecessary for the BSS formed by its own device. Alternatively, the AP may always set "CS Required bit" to "1" to indicate that carrier sensing is necessary. These can be set, for example, by user operation of the AP. Furthermore, the "CS Required bit" may be set independently of the interference avoidance control described above. It may also be indicated that carrier sense is required when the "CS Required bit" is "0", and not required when the "CS Required bit" is "1".

[0060] (Frame configuration) Next, using Figures 8(A) to 8(C), we will explain the structure of the MAC (Media Access Control) frame 800 of the IEEE 802.11 standard and the IE (Information Element), which is an element of its Frame Body 810.

[0061] Figure 8(A) shows an example of the overall structure of a MAC frame 800. In a MAC frame 800, Frame Control 801 is a field related to the control of the entire frame and has a length of 2 octets (16 bits). Details of Frame Control 801 are described later using Figure 8(B) and include subfields. Duration / ID 802 has a length of 2 octets, and when the MSB (Most Significant Bits: B15) is "1", the remaining 15 bits indicate the frame length, TXOP, etc., in the range of 0 to 32767 microseconds. Address 803 is a field with a length of 6 octets, and depending on the type of MAC frame (Type 822), addresses such as BSSID, source, and destination are set. Address 804, Address 805, and Address 807 are similar fields, but are set as needed depending on the number of addresses to be indicated. Sequence Control 806 is a field with a length of 2 octets that is set as needed to store information such as the sequence number of the data.

[0062] QoS Control808 is a field set to 2 octets in length as needed to store information such as BSRs (Buffer Status Reports) from standards prior to IEEE 802.11ax. When a BSR from a standard prior to IEEE 802.11ax is stored, that BSR is represented by two pieces of information. The first piece of information is a 4-bit TID (Traffic Identifier). In the case of the EDCA access scheme, the value from 0 to 7 indicated by this TID represents one of the four access categories: AC_VO (Voice), AC_VI (Video), AC_BE (Best Effort), or AC_BK (Background). The second piece of information is an 8-bit Queue size. The Queue size is expressed in units of 256 octets and indicates the amount of data accumulating in the transmit buffer.

[0063] HT Control809 is a field that is set to a length of 4 octets as needed. In the IEEE 802.11ax standard, setting the first bit to "0" indicates that it is an HT (High Throughput: IEEE 802.11n) frame. Setting the first two bits to 10 indicates that it is a VHT (Very High Throughput: IEEE 802.11ac) frame. Furthermore, setting the first two bits to 11 indicates that it is an HE (High Efficiency: IEEE 802.11ax) frame. It is currently undecided whether such a definition will be made for EHT (Extremely High Throughput: IEEE 802.11be) frames.

[0064] Frame Body 810 is a field where the data to be transmitted is stored, and its length is variable according to the data length. An IE (Internet Error Correction) as shown in Figure 8(C) may be stored as part of Frame Body 810. FCS811 is the Frame Check Sequence, where bits for error detection are stored.

[0065] Next, we will outline the contents of Frame Control 801 using Figure 8(B). Protocol Version 821 is a 2-bit subfield indicating the protocol version, and is set to "0" for IEEE 802.11 frames. Type 822 is a 2-bit subfield indicating the frame type, showing whether the frame is a Management, Control, or Data frame. Subtype 823 is a 4-bit subfield that stores information further classifying the Management, Control, and Data types. To DS 824 is a 1-bit subfield indicating whether the frame's destination is a DS (Distribution System). From DS 825 is a 1-bit subfield indicating whether the frame's source is a DS. More Fragment 826 is a 1-bit subfield indicating whether the frame is part of a fragment. Retry 827 is a 1-bit subfield indicating whether it is a retransmission of previously transmitted data. Power Management 828 is a 1-bit subfield indicating whether the STA is in power saving mode. More Data829 is a 1-bit subfield indicating whether there is any further data to be transmitted after the data transmitted in the current frame. Protected Frame830 is a 1-bit subfield indicating whether the frame is protected by encryption. +HTC831 is a 1-bit subfield indicating whether it contains, for example, HT Control809.

[0066] Next, the structure of the IE included in Frame Body 810 will be outlined using Figure 8(C). Here, in particular, the structure of the EHT Capabilities element will be shown. Element ID 841 stores the identifier of the IE. The value for EHT in IEEE 802.11be follows the value for the HE Capabilities element in IEEE 802.11ax, and is set to, for example, 255. Length 842 indicates the length of this information element. Element ID Extension 843 stores the identifier of the IE, which is set as needed. For example, in this embodiment, new values ​​are defined for the EHT Capabilities element related to capability information and the EHT Operation element related to operation information. These values ​​are then stored in Element ID Extension 843.

[0067] EHT MAC Capabilities Information 844 stores information about the capabilities of the MAC layer. EHT PHY Capabilities Information 845 stores information about the capabilities of the physical layer (PHY). Supported EHT-MCS And NSS Set 846 stores values ​​indicating the supported modulation and coding schemes (MCS) and spatial stream count (NSS). PPE (Physical layer Packet Extension) Thresholds 847 is optional information.

[0068] Figure 9 outlines the configuration of HT Control 809. The length of HT Control 809 is 4 octets = 32 bits. Variant 901 is the type of information. The type of information is determined by two bits (bits 902 and 903). In this embodiment, HE (High Efficiency: IEEE802.11ax) and EHT (Extremely High Throughput: IEEE802.11be) correspond to the same bit sequence "11". Note that the definition for EHT is yet to be determined. A-Control 904 is a 30-bit field when the type is HE or EHT. A-Control 904 includes Control List 905 and Padding 906. Control ID 907 indicates the type of Control List 905, and Control Information 908 indicates the content corresponding to that type. For example, in the BSR of S702 in this embodiment, "3" is stored as Control ID 907, and 26 bits of information are stored as Control Information 908. Furthermore, the BQR of S705 stores "5" as the Control ID 907 and 10 or 16 bits of information as the Control Information 908. This 10 or 16 bits of information indicates the channel status for every 20 MHz. Note that this is just an example, and the channel status may be indicated using more than 16 bits of information. The channel status may be indicated by a single bit, for example, whether it is available (idle) or unavailable (busy, etc.). Further details about the unavailable status may also be provided.

[0069] Figures 10A and 10B outline the configuration of the Trigger Frame (TF1000). The TF is a frame introduced in the IEEE 802.11ax standard, and it is a frame that indicates the activation timing and wireless channel information to be used, which is necessary for multiple STAs (Users) to send frames to APs in parallel.

[0070] Frame Control1001 is a field common to the IEEE 802.11 standard series, and contains a value indicating, for example, that it is an IEEE 802.11be Trigger Frame. The length of this field is 2 octets. Duration1002 is a field indicating the duration of this frame, and its length is 2 octets. RA1003 is a field indicating the receiver address, and its length is 6 octets. TA1004 is a field indicating the transmitter address, and its length is 6 octets. Common Info1005 is a field indicating information common to multiple terminals that are destinations of this TF, and its length is 8 octets or more. Details of Common Info1005 will be described later. Per User Info1006 is a field indicating individual information for each destination of this TF, and a separate field is provided for each destination. The length of each Per User Info1006 is 5 octets or more. Padding1007 is a field that provides a time buffer to the group of terminals that receive this TF. The AP determines this time buffer based on the MinTrigProcTime of each STA. Generally, the padding used corresponds to the maximum value of the MinTrigProcTime of each of the group of STAs that are the destination of the TF. FCS1008 is the Frame Check Sequence, and it stores bits for error detection.

[0071] Common Info1005 includes Trigger Type1011, Length1012, and Trigger Type dependent1013, as shown in (B). Trigger Type1011 is a 4-bit subfield, the details of which are shown, for example, in (C). In this embodiment, as an example, a new value of Trigger Type1011, "8", is provided for Multi-AP TFs. This allows other APs that receive a TF1000 with a Trigger Type1011 value of "8" to recognize that this TF is a Multi-AP TF. Length1012 stores the length corresponding to the type specified in Trigger Type1011. Trigger Type dependent1013 is a description corresponding to the type specified in Trigger Type1011.

[0072] (D) shows the details of Trigger Type dependent1013 when Trigger Type1011 is set to "8" and TF is a Multi-AP TF. Type 1031 stores information indicating the type of interference avoidance control to be used in the Multi-AP configuration. Type 1031 can be represented as 3 bits, each indicating whether or not interference avoidance control in the frequency domain, time domain, and power domain is used. For example, bit 0 indicates whether or not interference avoidance control in the frequency domain is used, bit 1 indicates whether or not interference avoidance control in the time domain is used, and bit 2 indicates whether or not interference avoidance control in the power domain is used. For example, bit sequence "101" indicates that interference avoidance control is performed in the frequency domain and power domain. Bit sequence "011" indicates that interference avoidance control is performed in the time domain and power domain. Bit sequence "111" indicates that interference avoidance control is performed in all three domains: frequency domain, time domain, and power domain. Note that this is just one example, and any bit sequence that can represent all possible combinations may be used, and a range of bits corresponding to that bit sequence may be provided as type 1031. Channel / RU1032 is a single bit of information indicating whether frequency division is performed on a 20MHz channel or on a RU unit basis.

[0073] (E) shows exemplary details of Per User Info 1006 when Trigger Type 1011 is set to "8" and the TF is a Multi-AP TF. BSSID 1041 is a 48-bit field that uniquely identifies the AP to which the Multi-AP TF is sent. For example, if AP 101 sends a Multi-AP TF to AP 106, the identification information of AP 106 is stored in BSSID 1041. Start Time 1042 is a 64-bit field that indicates the start time at which the BSS can use the channel or RU. This start time may be expressed as relative time from the transmission time of the Multi-AP TF, or as absolute time. Duration 1043 is a 32-bit field that indicates the time at which the BSS can use the channel or RU. Note that Length 1012 may be ignored in the case of a Multi-AP TF. Channel / RU Allocation 1044 is a field that stores information indicating the allocation of frequency resources by channel or RU in 20MHz units. The details of RU allocation for IEEE 802.11be are yet to be determined, but in one example it is similar to IEEE 802.11ax, and Channel / RU Allocation 1044 can have a length of 9 bits or more. TPC Parameter 1045 sets the constraint value for transmit power control to STA when interference avoidance control in the power domain is used.

[0074] In this way, a new Multi-AP TF is defined, which allows APs to share and communicate the interference avoidance control to be performed. Specifically, for example, when performing interference avoidance control in the frequency domain, an AP sends a Multi-AP TF to another AP with the bit corresponding to the frequency domain in type 1031 set to "1". At this time, the frequency resources available to the AP receiving the Multi-AP are indicated by Channel / RU Allocation 1044. The frequency resources are specified in 20MHz units if Channel is specified by Channel / RU 1032, and in RU units if RU is specified. This notifies other APs that interference avoidance control in the frequency domain can be performed. Similarly, for example, when performing interference avoidance control in the time domain, an AP sends a Multi-AP TF to another AP with the bit corresponding to the time domain in type 1031 set to "1". At this time, the time resources available to the AP receiving the Multi-AP are indicated by Start Time 1042 and Duration 1043. This notifies other APs that interference avoidance control in the time domain can be performed. Furthermore, for example, when performing interference avoidance control in the power domain, the AP sends a Multi-AP TF to other APs with the bit corresponding to the power domain in type 1031 set to "1". Then, TPC Parameter 1045 notifies the AP of information indicating a limit on the transmission power to prevent the transmission signal of the STA connected to the AP to which the Multi-AP TF was sent from interfering with the AP from which the TF was sent.

[0075] In the explanation above using Figure 5, an example of performing interference avoidance control in the frequency domain was described. Here, we will describe an example of performing interference avoidance control in the power domain. In this case, in the Multi-AP TF of S509, AP101 notifies AP106 of the fact that interference avoidance control in the power domain will be performed and information regarding the limiting of the transmit power. This information regarding the limiting of the transmit power may, for example, indicate the maximum transmit power that all STAs connected to AP106 (e.g., STA107 and STA108) must satisfy. Then, in S510, AP101 sends a TF to STA102 and STA103 that includes information specifying the limiting of the transmit power of STA102 and STA103 so that interference to AP106 is sufficiently suppressed. Also, in S511, AP106 sends a TF to STA107 and STA108 that includes information specifying the limiting of the transmit power of STA107 and STA108 based on the information stored in TPC Parameter 1045 from AP101. The transmission power limit for STA is set by "UL Target receive power" included in Per User Info1006 in Basic TF. This ensures, for example, that UL communication from STA102 and STA103 to AP101 does not interfere with AP106, and that UL communication from STA107 and STA108 to AP106 does not interfere with AP101. As a result, an environment can be created that does not require carrier sensing by STA. For this reason, in Basic TF in S510 and S511, "CS Required bit" can be set to "0" to omit carrier sensing by STA and prevent degradation of frequency utilization efficiency due to carrier sensing.

[0076] Furthermore, a maximum transmit power value may be specified for specific STAs. For example, STA102 and STA107 are located close to the connected AP, so suppressing their transmit power will have little impact on communication. For this reason, a Basic TF may be sent specifying these STAs and instructing them to reduce their transmit power. It is also possible to perform interference avoidance control in both the frequency domain and the time domain. In this case, for example, STA102 and STA107 may use the same frequency resource to perform UL communication with low transmit power, while STA103 and STA108 may be assigned different frequency resources. This also ensures that UL communication from STA102 and STA103 to AP101 does not interfere with AP106, and that UL communication from STA107 and STA108 to AP106 does not interfere with AP101.

[0077] Next, an example of performing interference avoidance control in the time domain will be explained using Figure 11. Note that the processing up to S507 is the same as in Figure 5, so the explanation will be omitted. In this process, AP101 performs interference avoidance coordination with AP106 and decides to set up interference avoidance control in the time domain (S1101). AP101 then determines the time resources to be used by AP101 (the first BSS) and AP106 (the second BSS). AP101 then sets the value indicating the time domain to type 1031 and sends a Multi-AP TF to AP106 specifying the time at which the UL communication of the second BSS should take place, indicated by Start Time 1042 and Duration 1043 (S1102). Note that the timing at which the UL communication of the first BSS starts may be set to a time when SIFS (Short Inter Frame Space) has elapsed after the transmission of the Multi-AP TF. Furthermore, the UL communication of the second BSS may be set to occur after the Multi-AP TF has been transmitted, the SIFS, communication duration, and ACK transmission period have elapsed, and then the SIFS has elapsed again.

[0078] Then, AP101 sends a Basic TF to STA102 and STA103 at the start of UL communication for the first BSS (S1103). At this time, since no communication is expected to occur in the second BSS and no interference is anticipated, a Basic TF with the CS Required bit set to "0" is sent. As a result, STA102 and STA103 recognize that they will not perform carrier sensing. Then, STA102 and STA103 send a TB PPDU to AP101 according to the TF (S1104), and AP101 sends an ACK to STA102 and STA103 (S1105). Meanwhile, AP106 waits for the Start Time 1042 specified in the Multi-AP TF after the transmission of the TF in S1102, and then sends a Basic TF to STA107 and STA108 (S1106). At this time, since no communication is expected to occur in the first BSS and no interference is anticipated, a Basic TF with the CS Required bit set to "0" is sent. As a result, STA107 and STA108 recognize that they will not perform carrier sensing. Then, STA107 and STA108 send a TB PPDU to AP106 in accordance with the TF (S1107), and AP106 sends an ACK to STA107 and STA108 (S1108).

[0079] In the example shown in Figure 11, the first BSS communicates first, followed by the second BSS; however, the reverse is also possible. That is, the second BSS may communicate first. Furthermore, communication may be performed by either the first or second BSS without using Basic TF. That is, UL communication using EDCA may be performed. DL communication may also be performed. This is because adjustments are made to prevent other BSSs from communicating during the set period.

[0080] As described above, the AP can prevent degradation of frequency utilization efficiency due to carrier sensing by only performing carrier sensing by the STA when necessary (especially when operating in a Multi-AP configuration). Furthermore, by eliminating unnecessary carrier sensing, the processing load on the STA is reduced, and its power consumption can be lowered.

[0081] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0082] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0083] 301: Wireless LAN control unit, 304: Cooperative operation method selection unit

Claims

1. An access point device that performs wireless communication compliant with the IEEE 802.11 series, To avoid interference between the communication of the access point device and the communication of the other access point device by using resources in different time domains for the communication of the access point device and the communication of the other access point device, a negotiation means for negotiating between the access point device and the other access point device, After the aforementioned negotiation is performed, a receiving means receives a first trigger frame from the other access point device, which includes identification information of the access point device and information indicating the time allocated to the access point device. A generation means that generates a second trigger frame in which 0 is stored in the CS Required Bit based on the receipt of the first trigger frame, A transmission control means controls the transmission of the second trigger frame, in which 0 is stored in the CS Required Bit, to the other device during the time allocated to the access point device indicated by the received first trigger frame, It has, If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and if, as a result of the sounding process, it is determined that interference avoidance control in the power domain between communication in the access point device and communication in the other access point device is possible, the transmission control means controls the transmission of a trigger frame with 0 stored in the CS Required Bit to the other device. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and if, as a result of the sounding process, it is determined that interference avoidance control in the power domain is not possible, the transmission control means controls the other device to transmit a trigger frame with 1 stored in the CS Required Bit.

2. The access point device according to claim 1, wherein the other access point device is an access point device that cooperates with the access point device, and based on the result of the negotiation with the other access point device, adjustments are made to the communication parameters to use different time domain resources for communication in the access point device and communication in the other access point device.

3. The access point device according to claim 2, characterized in that the adjustment of the communication parameters includes adjusting the communication parameters relating to the period during which communication should be performed.

4. A communication method that performs wireless communication compliant with the IEEE 802.11 series, A negotiation step is performed between the access point device and the other access point device in order to avoid interference between the communication of the access point device and the communication of the other access point device by using resources in different time domains for the communication of the access point device and the communication of the other access point device. The access point device receives, after the negotiation has taken place, a first trigger frame from the other access point device, which includes identification information of the access point device and information indicating the time allocated to the access point device. The access point device generates a second trigger frame in which 0 is stored in the CS Required Bit, based on the receipt of the first trigger frame. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device can be performed using resources in different time domains, the access point device is controlled to transmit the second trigger frame, in which 0 is stored in the CS Required Bit, to the other device during the time allocated to the access point device indicated by the received first trigger frame. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and as a result of the sounding process, it is determined that interference avoidance control in the power domain between communication in the access point device and communication in the other access point device is possible, the CS Required Bit is... A transmission control step which controls the system to send a trigger frame with 0 stored in the Bit to the other device, and if, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and if, as a result of the sounding process, it is determined that interference avoidance control in the power domain is not possible, then controls the system to send a trigger frame with 1 stored in the CS Required Bit to the other device. A communication method characterized by having the following features.

5. A communication system comprising at least an access point device and a station device that perform wireless communication compliant with the IEEE 802.11 series, The aforementioned access point device is To avoid interference between the communication of the access point device and the communication of the other access point device by using resources in different time domains for the communication of the access point device and the communication of the other access point device, a negotiation means for negotiating between the access point device and the other access point device, After the aforementioned negotiation is performed, a receiving means receives a first trigger frame from the other access point device, which includes identification information of the access point device and information indicating the time allocated to the access point device. A generation means that generates a second trigger frame in which 0 is stored in the CS Required Bit based on the receipt of the first trigger frame, A transmission control means controls the transmission of the second trigger frame, in which 0 is stored in the CS Required Bit, to the station device during the time allocated to the access point device indicated by the received first trigger frame, It has, The station device has a second transmission control means that, after receiving the second trigger frame in which 0 is stored in the CS Required Bit, controls the station device to transmit uplink data to the access point device without performing carrier sensing. If, as a result of the negotiation, it is determined that communication in the access point device and communication in the other access point device cannot be performed using resources in different time domains, and if, as a result of the sounding process, it is determined that interference avoidance control in the power domain between communication in the access point device and communication in the other access point device is possible, the transmission control means controls the transmission of a trigger frame with 0 stored in the CS Required Bit to the station device. A communication system characterized in that, if, as a result of the negotiation, it is determined that communication at the access point device and communication at the other access point device cannot be performed using resources in different time domains, and if, as a result of the sounding process, it is determined that interference avoidance control in the power domain is not possible, the transmission control means controls the transmission control means to transmit a trigger frame with 1 stored in the CS Required Bit to the station device.

6. A program for causing a computer to function as an access point device according to any one of claims 1 to 3.

Images