Communication device, control method for the same, and program

Abstract

To appropriately determine the technical method for realizing a multi-AP cooperative configuration.SOLUTION: A communication device determines whether one or more other communication devices capable of performing cooperative communication by coordinating the use of a predetermined frequency band with the communication device can acquire channel state information from one or more communication partner devices performing the cooperative communication. On the basis of the result of the determination, the communication device selects a communication method for performing the cooperative communication from among multiple communication methods.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication control technique for a wireless LAN. [Background technology]

[0002] The IEEE 802.11 series of standards is known as a communication standard for wireless local area networks (WLANs). The IEEE 802.11ax standard uses OFDMA to achieve high peak throughput and improved communication speeds under congested conditions. OFDMA stands for Orthogonal Frequency-Division Multiple Access. To further improve throughput, a study group called IEEE 802.11 EHT (Extreme (or Extremely) High Throughput)) has been established within the IEEE as a successor to the IEEE 802.11ax standard. One of the measures to improve throughput that IEEE 802.11 EHT aims for is a multi-AP coordination configuration, in which multiple access points (APs) work together. In a multi-AP coordination configuration, multiple APs work together, enabling WLAN terminals to connect faster and more reliably than with a single AP. There are several technical methods for implementing a multi-AP coordination configuration.

[0003] Furthermore, Distributed MIMO (Multiple-Input Multiple-Output) (D-MIMO) communication has been proposed for wireless LAN environments that comply with the IEEE802.11 series of standards (Patent Document 1). D-MIMO is a technology in which multiple APs communicate with a single wireless LAN terminal at the same time using the same frequency channel, and can achieve high-speed communication by multiplexing the space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2018 / 263045 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, there are multiple techniques for implementing a multi-AP cooperative configuration. However, no proposal has been made so far as to how to determine the technique for implementing a multi-AP cooperative configuration based on the communication conditions between communication devices communicating in the multi-AP cooperative configuration.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to appropriately determine a technical method for realizing a multi-AP cooperative configuration. [Means for solving the problem]

[0007] A communication device according to one aspect of the present invention has the following features: the communication device includes first determination means for determining whether the communication device and one or more other communication devices capable of performing cooperative communication with the communication device by cooperatively using a predetermined frequency band together can acquire channel state information from one or more communication partner devices performing the cooperative communication, and selection means for selecting a communication method for performing the cooperative communication from a plurality of communication methods based on a result of determination by the first determination means. [Effects of the Invention]

[0008] It becomes possible to appropriately determine the technical method for realizing a multi-AP cooperative configuration. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a network configuration. [Figure 2] FIG. 2 is a diagram showing an example of the hardware configuration of an AP. [Figure 3] FIG. 2 is a diagram showing an example of the functional configuration of an AP. [Figure 4] 10 is a flowchart of a process executed by an AP. [Figure 5] 1A and 1B are schematic diagrams illustrating configurations according to several multi-AP cooperation methods. [Figure 6] 10 is a sequence chart illustrating channel status check and null steering configuration. [Figure 7] 1 is a sequence chart for explaining the JTX (D-MIMO) configuration. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] (Network configuration) FIG. 1 shows an example of the configuration of a wireless communication network according to this embodiment. The network of BSS (Basic Service Set) 1 (BSS1) managed by AP (Access Point) 102 is indicated by a two-dot chain circle 101. The network of BSS2 managed by AP 105 is indicated by a dotted circle 104. STAs (Station) 103 and 106, which are wireless LAN terminals, can maintain connections with multiple APs. APs 102 and 105 and STAs 103 and 106 are devices (EHT devices) that comply with the IEEE 802.11 EHT (Extremely High Throughput) standard. APs 102 and 105 support multi-AP coordination (have a multi-AP coordination function). APs with the multi-AP coordination function can coordinate with other APs to use a specified frequency band for cooperative communication. This allows connected wireless LAN terminals to achieve faster or more stable communication than with a single AP. Here, a stable state refers to any combination of a good signal-to-noise ratio, low interference, low latency, and low jitter. There are various technical methods (multi-AP cooperation methods) that realize the multi-AP cooperation function, as will be described later.

[0012] The backhaul 100 is a communication means for intercommunication between multiple APs managing networks of different BSSs. The backhaul 100 may be configured using a wired system such as Ethernet (registered trademark) or a telephone line, or may be configured using a wireless system such as LTE (Long-Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). Alternatively, the backhaul 100 may be configured using a wireless LAN conforming to the IEEE 802.11 series of standards. When the backhaul 100 is configured using such a wireless LAN, the wireless channel used between the APs 102 and 105 and the STAs 103 and 106 may be the same as or different from that used.

[0013] 1 is merely an example for explanation, and for example, a network including a large number of EHT devices and legacy devices (communication devices conforming to the IEEE802.11a / b / g / n / ax standards) in a wider area may be configured. Furthermore, the following discussion is not limited to the arrangement of each communication device shown in FIG. 1, and can be applied to the positional relationships of various communication devices.

[0014] (AP configuration) 2 is a block diagram showing the hardware configuration of AP 102. Note that AP 105 also has a hardware configuration similar to that of AP 102. AP 102 has, as an example of its hardware configuration, a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and one or more antennas 207.

[0015] The storage unit 201 is configured with memories such as ROM and RAM, and stores various information such as programs for performing various operations described below and communication parameters for wireless communication. Note that, in addition to memories such as ROM and RAM, 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 may also be used as the storage unit 201. Furthermore, the storage unit 201 may include multiple memories.

[0016] The control unit 202 is configured with, for example, a processor 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 controls the AP 102 by executing a program stored in the storage unit 201. The control unit 202 may control the AP 102 in cooperation with the program stored in the storage unit 201 and an OS (Operating System). The control unit 202 may also be configured with multiple processors, such as a multi-core processor, and control the AP 102. The control unit 202 also controls the function unit 203 to perform predetermined processes such as capturing images, printing, and projection. The function unit 203 is hardware that enables the AP 102 to perform predetermined processes (which may include capturing images, printing, and projection).

[0017] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user. Here, the output by the output unit 205 includes at least one of display on a screen, audio output by a speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be implemented by a single module, such as a touch panel.

[0018] The communication unit 206 controls wireless communication conforming to the IEEE 802.11 series of standards, wireless communication conforming to Wi-Fi (registered trademark), and IP (Internet Protocol) communication. Furthermore, the communication unit 206 controls one or more antennas 207 to transmit and receive radio signals for wireless communication. The one or more antennas 207 may be configured to enable D-MIMO (Distributed Multiple-Input Multiple-Output) communication as described below.

[0019] 3 is a block diagram showing an example of the functional configuration of AP 102. Note that AP 105 also has the same functional configuration as AP 102. As an example of its functional configuration, AP 102 has a wireless LAN control unit 301, a UI control unit 302, a selection unit 303, a single-AP configuration control unit 304, a JTX configuration control unit 305, a null steering configuration control unit 306, a Coordinated OFDMA configuration control unit 307, a Fractional Coordinated OFDMA configuration control unit 308, and a schedule adjustment configuration control unit 309.

[0020] The wireless LAN control unit 301 includes circuits for transmitting and receiving wireless signals to and from other wireless LAN devices (e.g., other APs or STAs) and programs for controlling these circuits. The wireless LAN control unit 301 performs wireless LAN communication control, such as frame generation and frame transmission, and reception of wireless frames from other wireless LAN devices, in accordance with the IEEE 802.11 standard series. The wireless LAN control unit 301 also has a function of analyzing received wireless frames and determining whether or not predetermined conditions are satisfied based on the information contained in the wireless frames.

[0021] The UI control unit 302 receives operations on the input unit 204 (Figure 2) by a user (not shown) of the AP 102, and controls the transmission of control signals corresponding to the operations to each component, as well as controls the output (including display, etc.) of the output unit 205 (Figure 2).

[0022] The selection unit 303 selects (determines) a communication method for the AP 102 according to the analysis / determination result by the wireless LAN control unit 301. Details of the operation of the selection unit 303 will be described later with reference to FIG. 4. When the selection unit 303 selects the Single-AP method, the Single-AP configuration control unit 304 performs communication control to realize a configuration according to that method. When the selection unit 303 selects the Joint Transmission (JTX) method, the JTX configuration control unit 305 performs communication control to realize a configuration according to that method. When the selection unit 303 selects the null steering method, the null steering configuration control unit 306 performs communication control to realize a configuration according to that method. When the selection unit 303 selects the Coordinated OFDMA method, the Coordinated OFDMA configuration control unit 307 performs communication control to realize a configuration according to that method. When the selection unit 303 selects the Fractional Coordinated OFDMA method, the Fractional Coordinated OFDMA configuration control unit 308 performs communication control to realize a configuration according to that method. The schedule adjustment configuration control unit 309 performs communication control to realize a configuration according to a schedule adjustment method when the selection unit 303 selects the method. The operations of the functional units of the single-AP configuration control unit 304, JTX configuration control unit 305, null steering configuration control unit 306, Coordinated OFDMA configuration control unit 307, Fractional Coordinated OFDMA configuration control unit 308, and schedule adjustment configuration control unit 309 will be described later.

[0023] (STA configuration) The hardware configuration of the STAs 103 and 106, which are communication counterpart devices of the APs 102 and 106, may be similar to the hardware configuration of the AP 102 described above (FIG. 2). That is, the STAs 103 and 106 may be configured to include a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and one or more antennas 207. Although the functional configuration of the STAs 103 and 106 is not shown, they may be configured to be able to communicate in accordance with a communication method selected by the AP 102.

[0024] (Processing flow) Next, the flow of processing executed by the AP configured as described above will be explained. Fig. 4 shows a flowchart of communication method selection processing executed by AP 102. The processing shown in Fig. 4 can be performed when AP 102 establishes the BSS1 network (circle 101 in Fig. 1) or at any timing while the BSS1 network is in operation. The flowchart shown in Fig. 4 can be realized by the control unit 202 of AP 102 executing a control program stored in the storage unit 201, and performing calculations and processing of information and control of each piece of hardware.

[0025] In S401, the wireless LAN control unit 301 of the AP 102 checks and searches for APs (neighboring APs) that exist in the vicinity of the AP 102. Here, a neighboring AP refers to an AP with which the AP 102 can communicate wirelessly or via a wired connection. The check and search procedures include a passive procedure in which a Beacon frame is received via wireless communication or a frame is received by broadcast / multicast via wired communication, and an active procedure in which an inquiry frame is sent. In the network configuration of FIG. 1, the AP 102 finds the AP 105 as a neighboring AP as a result of the check and search.

[0026] If no neighboring APs are found (No in S401), the process proceeds to S403. In S403, the selection unit 303 selects the Single-AP method and ends the process. The Single-AP configuration is a configuration in which an AP does not need to control other APs when operating and managing the BSS network. When the Single-AP configuration is selected, the Single-AP configuration control unit 304 of AP 102 performs control to independently manage the BSS1 network (circle 101 in FIG. 1) without the control of AP 105.

[0027] If a neighboring AP is found (Yes in S401), the process proceeds to S402. In S402, the wireless LAN control unit 301 determines whether the found neighboring AP supports multi-AP cooperative operation (whether the neighboring AP has a multi-AP cooperative function). The wireless LAN control unit 301 can determine whether the neighboring AP supports multi-AP cooperative operation based on an information element related to capabilities, etc., included in the frame received during the neighboring AP search operation in S401. As described above, in the network configuration of FIG. 1, APs 102 and 105 support multi-AP cooperative operation. If the neighboring AP does not support multi-AP cooperative operation (No in S402), the process proceeds to S403, where the selection unit 303 selects the single-AP method, and the process ends.

[0028] If the neighboring APs support multi-AP cooperative operation (Yes in S402), the process proceeds to S404. In S404, the wireless LAN control unit 301 determines whether the local AP (AP 102) and each neighboring AP can acquire CSI (Channel State Information) from all STAs connected to these APs. In the network configuration of FIG. 1, it determines whether AP 102 can acquire channel information with STA 106 in addition to STA 103, and whether AP 105 can acquire channel information with STA 103 in addition to STA 106. Note that CSI can be acquired by a sounding procedure using a null data packet (NDP) or a beamforming procedure. The information that can be acquired by this procedure is specified in the CSI Report field of the IEEE 802.11 standard as the signal-to-noise ratio (SNR) and the CSI matrix.

[0029] Here, an example of the conditions under which CSI can be acquired is described. The first condition is that a certain AP and all STAs connected to that AP and neighboring APs are within radio wave coverage. In addition to simple radio wave coverage, a condition that the RSSI (Received Signal Strength Indicator) or CQI (Channel Quality Indicator) is equal to or greater than a predetermined value may be added. The second condition is that a STA can transmit data to other neighboring APs while under the control of one AP. Here, "under the control" means that an association (connection) based on the IEEE 802.11 series of standards has been established. The function of simultaneously establishing connections with multiple APs in this way is called a multi-AP association function. Generally, an AP knows whether a STA supports multi-AP association by exchanging information elements related to the capabilities of the STA when connecting with it. Furthermore, APs supporting multi-AP cooperative operation can exchange information on whether each terminal supports multi-AP association. The conditions under which CSI can be acquired are not limited to the first and / or second conditions described above, and other conditions may also be used. For example, the condition is that implicit beamforming can be used. Implicit beamforming refers to performing beamforming without NDP sounding (assuming the channel state is the default). Implicit beamforming can be enabled, for example, when a user has configured a specific setting via input unit 204 (FIG. 2) or when the RSSI is good in communication with the communication partner device. When the conditions for using implicit beamforming are met (when implicit beamforming can be used), the AP can perform subsequent transmission processing assuming that the default channel state has been obtained without NDP sounding.

[0030] If it is determined in S404 that CSI of all STAs can be acquired (Yes in S404), the process proceeds to S405, otherwise (No in S404), the process proceeds to S408. If Yes in S404, a communication method using CSI is selected, and if No in S404, a communication method not using CSI is selected.

[0031] In S405, the wireless LAN control unit 301 checks the connection status between the AP 102 and the surrounding APs and determines whether a high-speed connection is possible. Here, a state where a high-speed connection is possible means that the AP and the surrounding APs can communicate independently without affecting communication between the AP and the STAs. A first example of a state that satisfies this condition is when the backhaul 100 for communication between the AP and the surrounding APs is a wired communication such as Ethernet (registered trademark) or xDSL (various digital subscriber lines), or a public wireless communication such as LTE (Long-Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). A second example of a state that satisfies this condition is when the AP and the surrounding APs are multiband or multichannel compatible (connected via multiband or multichannel). Here, multiband compatibility means that simultaneous communication is possible in multiple operating frequency bands of the wireless LAN. Therefore, for example, this includes communication using the 2.4 GHz band between the AP and the STAs and the 5 GHz or 6 GHz band between the AP and the surrounding APs. Multi-channel compatibility also means that a device can communicate simultaneously over multiple frequency channels of a wireless LAN. For example, in the 5 GHz band, communication between an AP and a STA can use four channels, W52 (36ch, 40ch, 44ch, 48ch), and communication between an AP and a neighboring AP can use 11 channels, W56 (100ch, 104ch, ..., 140ch).

[0032] If it is determined in S405 that a high-speed connection is possible (Yes in S405), the process proceeds to S406. In S406, the selection unit 303 selects the JTX (Joint Transmission) method as the method for multi-AP cooperative configuration, and ends the process. If it is determined in S405 that a high-speed connection is not possible (No in S405), the process proceeds to S407. In S407, the selection unit 303 selects the null steering method as the method for multi-AP cooperative configuration, and ends the process. Note that null steering is also sometimes referred to as forming a zero point of a beam.

[0033] If it is determined in S404 that CSI of all STAs cannot be acquired (No in S404), the process proceeds to S408. In S408, the wireless LAN control unit 301 determines whether or not it is possible to adjust the communication schedule using a predetermined frequency band in a time-division manner. The wireless LAN control unit 301 may determine whether or not it is possible to adjust the communication schedule based on information elements related to capabilities exchanged with neighboring APs. Alternatively, each AP in the system may be configured in advance to determine whether or not it is possible to adjust the communication schedule. If it is determined that it is possible to adjust the communication schedule (Yes in S408), the process proceeds to S409. In S409, the selection unit 303 selects the schedule adjustment method as the method for the multi-AP cooperative configuration, and ends the process.

[0034] If it is determined in S408 that the communication schedule cannot be adjusted (No in S408), the process proceeds to S410. In S410, the wireless LAN control unit 301 determines whether an interference-limited STA (terminal) exists. Here, an interference-limited STA refers to an STA that is affected by communications from an AP to which it is not connected (an STA that also belongs to a BBS network that overlaps with the BBS network to which it belongs). In the network configuration of FIG. 1, STA 103 and STA 106 are both interference-limited STAs. An unaffected STA is called a non-interference-limited STA. For example, in FIG. 1, if STA 106 is outside the BBS1 network (circle 101) and inside the BBS2 network (circle 104), it is a non-interference-limited STA. The wireless LAN control unit 301 can make the determination in S410 after receiving reports from each STA indicating that the location information and the strength / quality of received frames are above a predetermined level. For example, when a STA receives a frame from an AP (a network of another BSS) different from the AP to which it is connected (the network of the BSS to which it belongs) with strength / quality at or above a predetermined level, it can report that information to the AP to which it is connected. Furthermore, it is assumed that this information is shared between APs. The wireless LAN control unit 301 can make the determination in S410 by receiving this information. An example of strength / quality is RSSI (Received Signal Strength Indicator).

[0035] If it is determined that an interference-restricted STA exists (Yes in S410), the process proceeds to S411. In S411, the selection unit 303 selects the Coordinated OFDMA method as the method for the multi-AP cooperative configuration, and ends the process. If it is determined that an interference-restricted STA does not exist in S410 (No in S410), the process proceeds to S412. In S412, the selection unit 303 selects the Fractional Coordinated OFDMA method as the method for the multi-AP cooperative configuration, and ends the process.

[0036] Next, a configuration according to the multi-AP cooperation scheme selected by the selection unit 303 will be described. FIGS. 5(a) to 5(c) are schematic diagrams illustrating configurations according to several multi-AP cooperation schemes, showing (a) a Coordinated OFDMA configuration (S411), (b) a Fractional Coordinated OFDMA configuration (S412), and (c) a schedule adjustment configuration (S409). FIG. 5(d) will be described later. Note that, as a common notation in FIGS. 5(a) to 5(d), the horizontal axis represents time and the vertical axis represents frequency. Here, the absolute interval length on the time axis and the granularity / unit of time may vary depending on the use case of the multi-AP cooperation configuration. For example, the granularity / unit may be anything from microseconds, which is the IEEE 802.11 Time Unit (TU), to milliseconds or seconds, which are related to human sensitivity and operation, or even greater values ​​or units. Furthermore, the granularity / unit of the frequency axis is, for example, the Resource Unit (RU), which is the frequency band unit for OFDMA communications specified by IEEE 802.11ax. However, depending on the capabilities of the AP and STA, this granularity / unit may also be a band (frequency band) that can be used for multi-band communication or a channel that can be used for multi-channel communication. Also, the solid line rectangle indicates the time axis / frequency domain used by AP 102 (BSS1 network), and the dashed line rectangle indicates the time axis / frequency domain used by AP 105 (BSS2 network).

[0037] Fig. 5(a) is a schematic diagram of a Coordinated OFDMA configuration. This configuration is realized by the Coordinated OFDMA configuration control unit 307. In this configuration, RUs are clearly separated between multiple BSSs (APs and STAs). In other words, the RUs used for communication between AP 102 and STA 103, and AP 105 and STA 106 do not overlap. Note that the edge STA in Fig. 5(a) is synonymous with interference limited STA.

[0038] FIG. 5(b) is a schematic diagram of a fractional coordinated OFDMA configuration. This configuration is realized by the fractional coordinated OFDMA configuration control unit 308. In this configuration, the RUs used between multiple BSSs (APs and STAs) may overlap partially or completely. Note that in the figure, the two rectangles are shown offset for ease of understanding, but they may also overlap completely. In this way, fractional means that the frequency is not completely divided, that is, parts here and there (fractionally) are used like in OFDMA. Also, the center STA in FIG. 5(b) is synonymous with non-interference limited STA.

[0039] 5(c) is a schematic diagram of a schedule adjustment configuration. This configuration is realized by the schedule adjustment configuration control unit 309. In this configuration, the communication times of the BSS1 network (AP 102 and STA 103) and the BSS2 network (AP 105 and STA 106) are clearly separated. In other words, the BSS1 network and the BSS2 network use the same frequency band in a time-division manner. As mentioned above, the units of TU1 (Time Unit) and TU2 in the figure can be any time as long as they can be adjusted between APs.

[0040] According to the communication configurations shown in Figures 5(a) to (c), cooperation between multiple APs and STAs enables effective use of time or frequency resources (resource units, bands, channels), leading to efficient use of the wireless medium.

[0041] FIG. 6 is a sequence diagram for explaining the null steering configuration (S407). This configuration is realized by the null steering configuration control unit 306. In this method, first, each AP acquires CSI for communication with a STA. F601 is a procedure for checking the channel state between the AP 102 and the STA 103. As described above, as an example, the AP transmits an NDP, and the STA estimates the channel state in response to receiving the NDP and feeds back the channel information as CSI. Similarly, in F602, a channel state checking procedure is performed between the AP 105 and the STA 103, in F603, between the AP 102 and the STA 106, and in F604, between the AP 105 and the STA 106. In F605, the AP 102 and the AP 105 exchange and share information on the respective channel state checks. This information exchange enables multiple APs to simultaneously perform DL (downlink) MU (multi-user) operations from an AP to multiple STAs. In addition, when acquiring CSI, the status when the STA transmitted the CSI to the AP may also be checked. This information is used when multiple STAs perform UP (uplink) MU (multi-user) operations with the AP as multi-AP cooperative operations.

[0042] The null steering configuration is sometimes called Coordinated BF (BeamForming) or Coordinated BF and Nulling, since it directs the null point of the beam in beamforming.

[0043] Next, in F606, the AP 102 sends a null steering Trigger Frame (TF) to the AP 105. This TF is used to measure the timing of the next transmission operation. Here, it is assumed that the negotiation as to which of the AP 102 and the AP 105 will send this TF has been performed in the procedure of F605. After a Short Inter Frame Space (SIFS) has elapsed from F606, or after another predetermined time has elapsed, in 607, the AP 102 transmits a data frame addressed to the STA 103. This data frame becomes a null point of the beam at the STA 106, and therefore does not affect the reception operation of the STA 106. Similarly, in F608, the AP 105 transmits a data frame addressed to the STA 106. This data frame becomes a null point of the beam at the STA 103, and therefore does not affect the reception operation of the STA 103.

[0044] Communications according to this null steering configuration allow multiple APs and STAs to cooperate to use time or frequency resources (resource units, bands, channels) without division, leading to efficient use of the wireless medium.

[0045] FIG. 7 is a sequence diagram for explaining the JTX configuration (S406). Here, the JTX configuration refers to a configuration in which multiple APs transmit data to one STA. This configuration is realized by the JTX configuration control unit 305. One of the wireless technologies that realizes this JTX is D-MIMO. Here, D-MIMO is an abbreviation for Distributed MIMO or Distributed MU MIMO. This D-MIMO is a technology in which multiple access points communicate with one STA at the same time and on the same channel (or RU: Resource Unit in OFDMA), and realizes high-speed communication by multiplexing the space.

[0046] In this D-MIMO system, first, each AP acquires CSI for communication with the STA. This is the same as the processing from F601 to F604 in Figure 6, so a description will be omitted. Next, in F701, a master AP determination procedure is executed between AP102 and AP105. The master AP is an AP that controls the operation of D-MIMO and is also called an M-AP (Master Access Point). The S-AP (Slave AP) executes JTX under the control of the M-AP. In this example, AP102 is determined to be the master AP, and in F702, AP102 begins operating as the master AP. Furthermore, in F703, AP105 begins operating as the slave AP.

[0047] In F704, data is shared between AP 102 and AP 105 via the backhaul 100. This type of communication via the backhaul allows "communication between APs" and "communication between APs and STAs" to occur in parallel. In F705, AP 102 sends a JTX TF (Trigger Frame) to AP 105. This JTX TF triggers AP 105's transmission and specifies its timing. In F706, AP 102 transmits data to STA 106, and in F707, AP 105 transmits data to STA 106. The timings of F706 and F707 are synchronized. Similarly, in F708, AP 102 transmits data to STA 103, and in F709, AP 102 transmits data to STA 106. The timings of F708 and F709 are synchronized. This synchronization is achieved by the rule that transmission occurs after a Short Inter Frame Space (SIFS) has elapsed for the JTX TF. Note that this transmission timing synchronization specification may also include relative time other than absolute time or SIFS in the JTX TF. Communications that conform to this JTX configuration enable effective multiplexing of multiple APs and STAs in a single frequency band, enabling high-speed communications (high-throughput communications).

[0048] Note that the same data may be transmitted between F706 and F708, or between F707 and F709. By having multiple APs cooperate in this way, although it is redundant, it has the effect of improving the reliability and stability of communication.

[0049] <Variation 1> One example of JTX is when there is only one STA that is the target of cooperative operation of multiple APs. In the configuration of Figure 1, this corresponds to the case where AP102 and AP105 communicate with STA106 using D-MIMO. Referring to Figure 7, at F710, AP102 sends data to AP105 that will actually be transmitted by JTX. At F711, AP102 sends a JTX TF (Trigger Frame) to AP105. At F712, AP105 transmits data to STA106. At F713, AP102 transmits data to STA106. Here, the timing of F712 and F713 is synchronized for the same reason as above.

[0050] In this modification, the AP 102 does not need to know the channel state with the STA 103. Therefore, the determination in S404 of FIG. 4 may be based only on the conditions related to the AP 102 and the STA 106. Furthermore, this modification does not exclude the connection between the AP 102 and the STA 103. Since the AP 102 cooperates with the AP 105, it can communicate with the STA 103 when the AP 105 is not transmitting. This operation may be performed by the single-AP configuration control unit 304. Furthermore, the same data may be transmitted in F712 and F713. This cooperative operation of multiple APs produces the effect of improving the reliability and stability of communication, although it is redundant.

[0051] <Variation 2> Transmission power control (TPC) may be used in combination with the schedule adjustment configuration (S409) described in the above embodiment. FIG. 5(d) is a schematic diagram of a schedule adjustment method that also uses transmission power control. The solid rectangle in the figure indicates the area used by AP102 / BSS1, and the dashed line indicates the area used by AP105 / BSS2. The shaded area indicates the presence of TPC. In FIG. 5(d), AP102, which manages the BSS1 network, sets its transmission power to a normal value in TU1 and a value limited by TPC in TU2. AP105, which manages the BSS2 network, sets its transmission power to a value limited by TPC in TU1 and a normal value in TU2. Here, this transmission power control may be realized by applying spatial reuse (SR) technology introduced in IEEE 802.11ax.

[0052] As described above, the embodiment described above contributes to improving the efficiency of wireless medium usage, and the communication speed and stability of the entire system and individual communication devices.

[0053] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0054] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0055] 102, 105: AP (access point), 103, 106: STA (wireless LAN terminal)

Claims

1. A communication device, a first determination means for determining whether the communication device and one or more other communication devices capable of performing cooperative communication with the communication device by cooperatively using a predetermined frequency band can acquire channel state information from one or more communication partner devices performing the cooperative communication; a selection means for selecting a communication method for performing the cooperative communication from among a plurality of communication methods based on a result of the determination by the first determination means; A communication device comprising:

2. further comprising a second determination means for determining a connection state between the communication device and the one or more other communication devices; When the first determination means determines that the channel state information can be acquired, and the second determination means determines that the connection state is a state in which the communication device and the one or more other communication devices can communicate independently of communication with the one or more communication partner devices, 2. The communication device according to claim 1, wherein the selection means selects a JTX (Joint Transmission) method in which the communication device and the one or more other communication devices communicate with one other communication device by checking channel state information.

3. When the first determination means determines that the channel state information can be acquired, and the second determination means determines that the connection state is a state in which the communication device and the one or more other communication devices cannot communicate independently of communication with the one or more communication partner devices, 3. The communication device according to claim 2, wherein the selection means selects a null steering scheme in which the communication device and the one or more other communication devices each check channel state information for a different communication partner device and communicate with the other communication device.

4. The communication device described in claim 2 or 3, characterized in that when the communication device and the one or more other communication devices are connected via wired communication or public wireless communication, the second determination means determines that the communication device and the one or more other communication devices are in a state where they can communicate independently of communication with the communication partner device.

5. A communication device described in any one of claims 2 to 4, characterized in that when the communication device and the one or more other communication devices are connected via multi-band or multi-channel, the second determination means determines that the communication device and the one or more other communication devices are in a state where they can communicate independently of communication with the communication partner device.

6. The communication device and the one or more other communication devices further include a third determination means for determining whether or not a schedule adjustment for using the predetermined frequency band in a time-division manner is possible between the communication device and the one or more other communication devices; If the first determination means does not determine that the channel state information can be acquired and the third determination means determines that the schedule adjustment is possible, 6. The communication device according to claim 1, wherein the selection means selects a schedule adjustment method.

7. If the first determination means does not determine that the channel state information can be acquired and the third determination means determines that the schedule adjustment is possible, The communication device according to claim 6, characterized in that the selection means selects a schedule adjustment method that also uses transmission power control, in which the communication device and the one or more other communication devices are controlled to have different transmission powers and use the specified frequency band in a time-division manner.

8. a fourth determination means for determining whether or not there is a communication partner device that also belongs to another network that overlaps with the network to which the communication partner device belongs, among the one or more communication partner devices; If the first determination means does not determine that the channel state information can be acquired and the fourth determination means determines that the communication partner device exists, 8. The communication device according to claim 1, wherein the selection means selects a Coordinated OFDMA (Orthogonal Frequency Division Multiple Access) method in which the frequency band is divided and used between the communication device and the one or more other communication devices.

9. If the first determination means does not determine that the channel state information can be acquired and the fourth determination means determines that the communication partner device does not exist, 9. The communication device according to claim 8, wherein the selection means selects a Fractional Coordinated OFDMA system in which the frequency bands are used so as to overlap at least partially between the communication device and the one or more other communication devices.

10. The communication device and the one or more other communication devices are access points (APs) that comply with the IEEE 802.11 series of standards, and perform the cooperative communication using a multi-AP coordination configuration. The communication device according to any one of claims 1 to 9.

11. A method for controlling a communication device, comprising: a determination step of determining whether the communication device and one or more other communication devices capable of performing cooperative communication with the communication device by cooperatively using a predetermined frequency band can acquire channel state information from one or more communication partner devices performing the cooperative communication; a selection step of selecting a communication scheme for performing the cooperative communication from among a plurality of communication schemes based on a result of the determination step; A method for controlling a communication device, comprising:

12. A program for causing a computer to function as the communication device according to any one of claims 1 to 10.

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