Communication device, communication method, and program

Abstract

This communication device, which functions as an access point conforming to the IEEE 802.11 series standards, receives, from one or more other communication devices functioning as access points, a radio frame including capability information indicating the preparation time required for preparing transmission of a signal to the communication device, determines, on the basis of the capability information, the padding length of a trigger frame for causing the one or more other communication devices to transmit the signal to the communication device, and transmits a trigger frame including padding of the determined length to the one or more other communication devices when data from the one or more other communication devices is to be received.

Description

Communication device, communication method, and program

[0001] The present invention relates to a control technique for communication between multiple access points.

[0002] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 series of standards is known as a communication standard for wireless LANs (Local Area Networks). The IEEE 802.11 series of standards includes standards such as IEEE 802.11a / b / g / n / ac / ax / be (see Patent Document 1). For the IEEE 802.11be standard and its successor standards, the introduction of technology that improves communication efficiency and throughput by cooperatively operating multiple access point devices (hereinafter sometimes referred to as "APs") is being considered. A communication technology in which multiple APs cooperate is called multi-AP communication. In this multi-AP communication, APs are classified into one Coordinator AP that manages all APs, and Coordinated APs that operate under the management of the Coordinator.

[0003] JP 2018-050133 A

[0004] It is assumed that the Coordinator AP, for example, controls the allocation of transmission opportunities (TXOPs) to the Coordinated APs for a predetermined period. Here, the Coordinator AP may require a certain amount of time to complete preparation for communication, depending on the content of the communication to be performed by the AP. For this reason, it is important for the Coordinator AP to set a TXOP for the Coordinated AP, taking into account the preparation period for communication.

[0005] The present invention provides a technique for improving the reliability of communications between multiple access points.

[0006] A communication device according to one aspect of the present invention is a communication device that functions as an access point compliant with the IEEE 802.11 series standard, and has: a receiving means for receiving a wireless frame from one or more other communication devices that function as access points, the wireless frame including capability information indicating the preparation time required to prepare for transmitting a signal to the communication device; a determining means for determining, based on the capability information, the length of padding in a trigger frame that causes the one or more other communication devices to transmit a signal to the communication device; and a transmitting means for transmitting the trigger frame including the padding of the determined length to the one or more other communication devices when data should be received from the one or more other communication devices.

[0007] According to the present invention, it is possible to improve the reliability of communication between a plurality of access points.

[0008] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals.

[0009] The accompanying drawings are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention, and together with the description are used to explain the principles of the present invention. Figure 1 is a diagram showing an example of the configuration of a wireless communication system. Figure 2 is a diagram showing an example of the hardware configuration of a communication device. Figure 3 is a diagram showing an example of the functional configuration of a communication device. Figure 4 is a diagram showing an example of information elements transmitted from a Coordinated AP. Figure 5 is a diagram showing an example of the configuration of a trigger frame. Figure 6 is a diagram showing an example of the flow of communication processing. Figure 7 is a diagram showing an example of the flow of communication processing. Figure 8 is a diagram showing an example of processing performed by a Coordinator AP. Figure 9 is a diagram showing an example of processing performed by a Coordinated AP.

[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] (Configuration of Wireless Communication System) FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. In one example, this wireless communication system is configured to perform wireless communication using a wireless local area network (wireless LAN) conforming to the IEEE 802.11 series of standards. IEEE stands for Institute of Electrical and Electronics Engineers. The following description assumes a wireless LAN conforming to the IEEE 802.11 series of standards, but is not limited to this. The method described below may also be applied to communications conforming to other wireless communication standards. In the example of FIG. 1, three access points (AP101-AP103) and four stations (STA122-STA124) are shown as communication devices performing wireless communication. In the following description, the access points may be referred to as APs or AP STAs, and the stations may be referred to as STAs or non-AP STAs. 1 is merely an example, and the wireless communication system is configured so that at least two APs share a transmission opportunity (TXOP) to communicate (cooperative communication). That is, the number of APs may be two, or may be four or more. Similarly, the number of STAs may be one to three, or may be five or more.

[0012] APs 101 to 103 are configured to operate in accordance with the successor standard to the IEEE 802.11be standard, which targets a maximum transmission speed of 46.08 Gbps (gigabits per second), and a standard targeting a maximum transmission speed of 90 to 100 Gbps or more. Similarly, STAs 121 to 124 may also be configured to operate in accordance with this successor standard. Hereinafter, this successor standard will be referred to as the IEEE 802.11bn standard or the UHR standard. Furthermore, a wireless frame transmitted and received under this successor standard will be referred to as a UHR PPDU. Note that UHR stands for Ultra High Reliability. Furthermore, PPDU stands for PLCP Protocol Data Unit, and PLCP stands for Physical Layer Convergence Protocol. The UHR standard's main features are support for highly reliable communication, low latency communication, and AP cooperation. The names IEEE 802.11bn standard and UHR standard are names given for convenience to successor standards having such features, and may be given different names when the standard is fully formulated. In other words, although the following explanation will be given using the names IEEE 802.11bn standard and UHR standard, the following discussion can also be applied to standards with different names, such as further successor standards to the UHR standard. In addition, APs 101 to 103 and STAs 121 to 124 can be configured to be able to communicate in accordance with any legacy standard other than the UHR standard, such as the IEEE 802.11a / b / g / n / ac / ax / be standard.

[0013] In the example of FIG. 1 , STA 121 and STA 122 participate in network 112 formed by AP 102, and STA 123 and STA 124 participate in network 113 formed by AP 103. AP 101 to AP 103 can perform MU (Multi-User) communication, which uses OFDMA (Orthogonal Frequency Division Multiple Access) technology to communicate with multiple STAs in parallel. In MU communication using OFDMA technology, one frequency channel is divided into multiple sub-channels called RUs (Resource Units). Each divided RU is then assigned as a resource to be used for communication with a different STA (or a group of STAs consisting of multiple STAs). This allows the AP and multiple STAs to communicate in parallel via a single frequency channel. In this case, when data is transmitted from the AP to one or more STAs, the AP transmits an MU (Multi User) PPDU in which the data is modulated using OFDMA. If all communication devices involved in the MU communication are compatible with the UHR standard, a UHR MU PPDU, which is an MU PPDU compliant with the UHR standard, may be transmitted to one or more STAs.

[0014] Furthermore, AP101 to AP103 and STA121 to STA124 may be configured to support wireless communication based on other communication standards, such as Bluetooth (registered trademark), NFC, or Bluetooth (registered trademark) Low Energy (LE). Here, NFC stands for Near Field Communication. AP101 to AP103 may also be configured to support wired communication using an Ethernet (registered trademark) cable or wired communication using optical fiber. AP101 to AP103 may be, for example, but are not limited to, a wireless LAN router or a personal computer (PC). Furthermore, STA121 to STA124 may be, for example, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, or a wearable device such as smart glasses. AP101 to AP103 and STA121 to STA124 may be information processing devices such as wireless chips that support at least one of transmission and reception of UHR PPDU.

[0015] In this embodiment, when AP101 to AP103 provide a network, each network has a different BSSID. BSSID stands for Basic Service Set Identifier and is an identifier for identifying an access point. Furthermore, each communication device, such as AP101 to AP103 and STA121 to STA124, can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 480 MHz, and 640 MHz.

[0016] In this embodiment, APs 101 to 103 are assumed to have an AP cooperation function that allows them to operate in coordination with other APs. Here, AP 101 is an AP that performs overall control for AP cooperation, and hereinafter, such an AP may be referred to as a Coordinator AP. Furthermore, APs 102 to 103 are APs that function as controlled devices controlled by the Coordinator AP, and hereinafter, such APs may be referred to as Coordinated APs. The roles of the Coordinator AP and the Coordinated AP may be dynamically changed. That is, after AP 101 functions as the Coordinator AP, AP 102 or AP 103 may function as the Coordinator AP and control AP 101, which functions as the Coordinated AP. Note that AP 101 provides network 111, AP 102 provides network 112, and AP 103 provides network 113. STA121 to STA124 are STAs that participate in a network provided by one of the APs.

[0017] AP 101 transmits a trigger frame to AP 102 and AP 103. The trigger frame is a mechanism introduced in IEEE 802.11ax and later standards, and is used to allow multiple STAs to receive a trigger frame transmitted from an AP and transmit frames in parallel. More specifically, when an STA receives a trigger frame intended for itself, it performs uplink (UL) communication using an assigned resource unit (RU) after the SIFS period has elapsed. Here, SIFS is Short IFS defined in the IEEE 802.11 series standards, and IFS is Inter-Frame Space. This mechanism enables efficient use of the wireless medium.

[0018] By using such a trigger frame mechanism, AP102 and AP103 can perform uplink (UL) communication in parallel at a timing based on the trigger frame from AP101. In this embodiment, "UL" in AP-to-AP communication refers to a link in the direction of transmitting data from the Coordinator AP (AP101) to the Coordinator AP (AP101). Here, AP102 and AP103 may need to prepare in advance for transmission using the assigned RU. For example, AP102 and AP103 may need to perform communication control, such as scheduling, in the network they formed, or processes for handling a relatively large amount of data, which may require a certain amount of time to complete preparation for UL communication. Therefore, it may be assumed that AP102 and AP103 are not ready for UL communication after a SIFS period has elapsed since receiving the trigger frame transmitted from AP101. Here, if AP 102 and AP 103 are not ready for UL communication when SIFS has elapsed since receiving the trigger frame from AP 101, they may wait until they are ready before transmitting a UL communication frame. However, in this case, a period longer than SIFS may occur between the end of the trigger frame transmitted from AP 101 and the beginning of the UL communication frame transmitted from AP 102 or AP 103. As a result, during that period, other communication devices may determine that the frequency channel is not in use and may begin transmitting frames. In this case, even though AP 101 has assigned a transmission opportunity (TXOP) to AP 102 and AP 103 using the trigger frame, it is expected that AP 102 and AP 103 will not be able to communicate during that TXOP.

[0019] In this embodiment, in consideration of these circumstances, the length of the trigger frame is increased so that AP 101 can start UL communication at the timing when AP 102 and AP 103 are ready for UL communication. That is, AP 101 can add padding to the trigger frame to adjust the length of the trigger frame and ensure that UL communication is performed after a SIFS period has elapsed from the end of the trigger frame. Here, if this padding is excessively long, communication efficiency decreases, while if the padding is short, communication between AP 102 and AP 103 may not be initiated SIFS after the end of the trigger frame. In consideration of these circumstances, in this embodiment, each AP is configured to perform control processing to set padding of an appropriate length. Below, the configuration of an AP that performs such processing, the flow of processing executed by the AP, and examples of control information used for such control will be described.

[0020] Note that, although the following description will be given assuming that AP 101 is a Coordinator AP and APs 102 and 103 are Coordinating APs, this is not limiting. That is, AP 102 or AP 103 may function as a Coordinator AP. Furthermore, for example, the roles of the Coordinator AP and the Coordinating AP may be dynamically changed. Furthermore, the following description will be given assuming that two APs (AP 102 and AP 103) perform UL communication in parallel. However, a similar procedure can be used when a single AP performs UL communication. When only one AP performs UL communication, padding is performed taking into account the preparation time for that UL communication, thereby preventing interruptions by other communication devices during the UL communication of that single AP. Furthermore, when multiple APs perform UL communication, padding is performed taking into account the preparation time of each AP, allowing multiple APs to communicate in parallel at a common timing while preventing interruptions from other communication devices.

[0021] (Device Configuration) An example configuration of a communication device (AP101 to AP103) functioning as an AP according to this embodiment will be described using Fig. 2. Fig. 2 shows an example hardware configuration of an AP. As shown in Fig. 2, the AP includes, as its hardware configuration, for example, 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 antennas 207 to 209.

[0022] The storage unit 201 includes one or more memories, such as a ROM or a RAM, and stores various information, such as computer programs for performing various operations described below and communication parameters for wireless communication. Note that ROM stands for Read Only Memory, and RAM stands for Random Access Memory. The storage unit 201 may include storage media such as a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, or a DVD, in addition to or instead of memories such as a ROM or a RAM. The storage unit 201 may also include a solid state drive (SSD). The storage unit 201 may also include multiple memories.

[0023] The control unit 202 is configured with one or more processors, such as a CPU or MPU, and controls the entire AP by executing a computer program stored in the storage unit 201, for example. The CPU stands for Central Processing Unit, and the MPU stands for Micro Processing Unit. The control unit 202 may be configured to perform processes such as generating data and signals to be transmitted in communication with other communication devices, in addition to overall control of the AP. The control unit 202 may be configured to execute processes such as overall control of the AP in cooperation with a computer program stored in the storage unit 201 and an OS (Operating System). The control unit 202 may also include multiple processors, such as a multi-core processor, and may execute processes such as overall control of the AP using the multiple processors. The control unit 202 may also be configured with an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

[0024] The control unit 202 also controls the functional unit 203 to perform predetermined processes such as capturing images, printing, and projection. The functional unit 203 is hardware that enables the AP to perform predetermined processes. For example, if the AP is a camera such as a digital still camera or a smartphone equipped with a camera, the functional unit 203 is an imaging unit that performs imaging processing of surrounding images. For example, if the AP is a printer, the functional unit 203 is a printing unit that performs printing processing on a sheet such as paper based on print data stored in the storage unit 201 or acquired from an external device via wireless communication or the like. For example, if the AP is a projector or smart glasses, the functional unit 203 is a projection unit that performs projection processing of image data or video data stored in the storage unit 201 or acquired from an external device via wireless communication or the like. In the case of smart glasses, the projection surface is the end user's retina, for example. The data processed by the functional unit 203 may be data stored in the storage unit 201 or data communicated with another AP or STA via the communication unit 206, which will be described later. Furthermore, the AP can also provide a network storage function such as NAS (Network Attached Storage). This function is provided to other communication devices as a web service such as a network storage service. For example, another communication device such as an STA connects to a network storage service provided by APs 101 to 103 using a protocol such as SMB, FTP, or WebDAV. The other communication device such as an STA can then upload files to the storage service or download files from the storage. Data communication for this upload or download can be performed using a wireless communication function that complies with the UHR standard, for example.

[0025] 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, for example, at least one of a display on a screen, an audio output from a speaker, and a vibration output. Note that both the input unit 204 and the output unit 205 may be implemented by a single module, such as a touch panel. Furthermore, the input unit 204 and the output unit 205 may each be built into the AP, or may be configured as an external device connected to the AP.

[0026] The communication unit 206 controls wireless communications compliant with the IEEE 802.11 series standards and Internet Protocol (IP) communications. The communication unit 206 cooperates with antennas 207 to 209 to transmit and receive UHR PPDUs, which are wireless frames conforming to the UHR standard, as well as PPDUs conforming to earlier standards. The antennas 207 to 209 are capable of transmitting and receiving signals in at least one of the following frequency bands: sub-GHz, 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, and 60 GHz. While three antennas 207 to 209 are shown in this embodiment, the number of antennas may be one or two, or four or more. In one example, a different antenna may be provided for each frequency band. Furthermore, if the AP has multiple antennas, it may have multiple communication units 206 corresponding to the multiple antennas, respectively. If the AP is compatible with the above-mentioned NFC standard or Bluetooth (registered trademark) standard, a communication unit 206 configured to control wireless communication in accordance with these communication standards may be provided.

[0027] FIG. 3 shows an example of the functional configuration of an AP. The AP has a frame processing unit 301, a padding processing unit 302, and a frame transmission / reception unit 303 as its functional configuration. These functions can be realized, for example, by the control unit 202 executing a program stored in the storage unit 201, or by a processing function unit in the communication unit 206. Note that FIG. 3 is a diagram illustrating the main functions of this embodiment, and other functions are omitted. Therefore, the AP can naturally have, for example, a control function for establishing a connection with an STA as a normal AP and for communication, as well as functions generally possessed by a communication device. Furthermore, multiple functional blocks in FIG. 3 may be integrated into a single functional block, or a single functional block may be divided into multiple functional blocks.

[0028] The frame processing unit 301 interprets various wireless frames received from the outside, notifies higher layer functions (not shown), and performs wireless communication control processing based on information obtained through the interpretation. Furthermore, when transmitting data to a communication partner device, the frame processing unit 301 generates a data frame containing the data. The frame processing unit 301 of the AP 101 may acquire capability information for determining padding from frames received from the APs 102 and 103. The frame processing unit 301 of the AP 101 may also generate a trigger frame including padding determined based on the acquired capability information. The frame processing unit 301 of the AP 101 may also generate a request frame to be transmitted to the APs 102 and 103 to request the above-mentioned capability information. The frame processing units 301 of the APs 102 and 103 may also generate notification frames including capability information for the AP 101 to determine padding. Furthermore, the frame processing unit 301 of APs 102 and 103 processes trigger frames and request frames including padding received from AP 101. The notification frames and request frames transmitted and received between APs may be management frames conforming to the IEEE 802.11 series standards, such as Probe Request, Probe Response, Beacon, and Action frames. When an Action frame is used, the value of its Category code may be set to a value indicating that the frame is used for transmitting and receiving information for determining the length of padding. However, this is merely an example, and any frame that is not a management frame may be used as the notification frame or request frame described above as long as it can be used to notify information for determining padding or to request such information.

[0029] The padding processing unit 302 of the AP 101 determines padding to be added to the trigger frame based on capability information included in a notification frame (e.g., a management frame) from the APs 102 and 103. The padding processing unit 302 of the APs 102 and 103 also notifies the frame processing unit 301 of capability information used to determine padding corresponding to the preparation time required to start UL communication, causing the frame processing unit 301 to generate a notification frame. The frame transmitting / receiving unit 303 cooperates with the antennas 207 and 209 to receive wireless frames such as UHR PPDUs transmitted from other external communication devices. The frame transmitting / receiving unit 303 also transmits wireless frames such as UHR PPDUs generated by the frame processing unit 301 to the other communication device (another AP or STA).

[0030] (Frame Configuration) Next, the configuration of a frame transmitted and received for cooperative communication between APs in this embodiment will be described with reference to FIGS. 4 and 5. FIG.

[0031] 4 shows an example of an information element used when a Coordinated AP (AP102-AP103) transmits capability information usable for determining padding to a Coordinator AP (AP101). This information element is stored in, for example, a management frame such as a Beacon, Probe Response, or Action frame, or in another wireless frame and transmitted. In this information element, an Element ID field 401 is a field in which information for identifying the type of information element is stored. Here, for example, information identifying that the information element is for storing a capability group of the UHR standard is stored in the Element ID field 401. A value indicating the length of this information element is stored in the Length field 402. The UHR MAC Capabilities field 403 stores, for example, capability information related to the MAC (medium access control) layer among the capabilities of the UHR standard. In one example, the UHR MAC Capabilities field 403 includes a Multi-AP TF MAC Padding Duration subfield 404. The Multi-AP TF MAC Padding Duration subfield 404 stores capability information indicating a preparation time required for the Coordinated AP to start UL communication (or capable of at least specifying the preparation time). Note that "Multi-AP TF MAC Padding Duration" is an example of the name of a subfield for storing capability information, and a subfield (or field) with a different name that stores similar information may be used. The Multi-AP TF MAC Padding Duration subfield 404 stores, for example, the information shown in Table 1.

[0032] Note that a subfield defined in a conventional standard may be used as the subfield in which the capability information regarding the preparation time is stored. For example, a Trigger Frame MAC Padding Duration subfield defined in the IEEE 802.11ax standard or later may be used as such a subfield, as shown in Table 2.

[0033] Here, the information shown in Table 2 can be used for both APs and STAs (non-AP STAs). That is, information such as that shown in Table 2 can be used in both the notification of capability information from a conventional STA and the notification of capability information from a Coordinated AP according to this embodiment. In one example, if information indicating that a frame containing this information element is used for transmitting capability information between APs is included, this information element can be interpreted as being for the AP. Furthermore, if a frame containing this information element is used for communication between an AP and a STA, this information element can be interpreted as being for the STA. Furthermore, as shown in Table 3, the number of bits in this subfield may be extended from 2 to 3 (allowing values ​​0 to 7 to be used) so that whether information indicating information for the STA or information for the AP is stored can be distinguished based on the content of the information. In the information elements in Table 3, the first bit of the three bits indicates whether the information is for the STA or the AP. That is, when the first bit is 0 (values ​​0 to 3), information for the STA is indicated, and when the first bit is 1 (values ​​4 to 7), information for the AP is indicated. However, this is merely an example, and information may be notified in any format, such as indicating whether the information is for the STA or the AP depending on the last bit.

[0034] In addition, in one example, the preparation time of an AP may vary greatly depending on, for example, the load caused by communication with the STA. Therefore, the number of bits of this information may be increased to expand the range of values ​​of the preparation time for the AP (0 to 16 μs (microseconds) in Tables 1 to 3). For example, the preparation time value may be indicated in eight stages using three bits, or the preparation time value may be indicated in 16 stages or more using four or more bits.

[0035] 5 shows an example of the format of a trigger frame that a Coordinator AP (AP 101) transmits to Coordinated APs (APs 102 and 103) when performing inter-AP cooperative communication. A Frame Control field 501 stores, for example, a value indicating that this frame is a trigger frame used in standards after the IEEE 802.11ax standard. A Common Info field 502 stores information that is commonly applied to multiple Coordinated APs that are the destinations of this trigger frame. This Common Info field 502 includes a Trigger Type field 503 and a Trigger Dependent Common Info field 504. The Trigger Type field 503 stores information for identifying the type of trigger frame. The Trigger Dependent Common Info field 504 stores information dependent on this trigger frame. Padding 505 is added to provide APs receiving this trigger frame with time to prepare for UL transmission. The length of padding 505 is determined based on, for example, the capability information (value of the Trigger Frame MAC Padding Duration subfield 404) notified from each AP. In one example, for each of one or more Coordinated APs targeted by the trigger frame, the length of padding 505 is determined to be the length corresponding to the longest value of the time length indicated by the received capability information. For example, if the capability information of AP 102 indicates 8 μs (microseconds) and the capability information of AP 103 indicates 16 μs, padding 505 with a length corresponding to the longer of these values, 16 μs, may be prepared. Note that this is just an example, and the length of Padding 505 may be determined based on other criteria. For example, for each of one or more Coordinated APs targeted by the trigger frame, the length corresponding to the shortest value of the time length indicated by the received capability information may be determined as the length of Padding 505. FCS 506 is a Frame Check Sequence.

[0036] (Processing Flow) Next, an example of the communication processing flow will be described. Fig. 6 shows an example of the communication processing flow when a Coordinated AP voluntarily provides capability information. Note that in the example of Fig. 6, two APs (AP 102 and AP 103) are shown as Coordinated APs, but the number of Coordinated APs may naturally be one or three or more.

[0037] The Coordinated APs (AP 102, AP 103) include capability information indicating the preparation time required to start UL communication in the Beacon frames and broadcast (transmit) the Beacon frames 601 to 602, respectively. Note that the example in FIG. 6 illustrates a case where capability information is notified using the Beacon frames 601 to 602, but this is not limiting. For example, the Coordinated AP may include capability information indicating the preparation time in an Action frame and transmit it voluntarily. At this time, the Coordinated AP may unicast the Action frame to the Coordinator AP. That is, the Coordinated AP may notify the Coordinator AP of the preparation time information in any format, such as broadcast, multicast, or unicast, using any frame that can be transmitted including information indicating the preparation time.

[0038] When the Coordinator AP (AP 101) receives Beacon frames 601-602, it analyzes the frames and checks capability information indicating the preparation time required for each AP to start UL communication. This allows AP 101 to determine the length of padding to be added to the trigger frame. After determining the length of padding to be added to the trigger frame based on the received information, AP 101 transmits a trigger frame 603 to APs 102-103, with padding 604 of that length added. APs 102-103 then perform reception processing for the trigger frame 603 with padding 604 added. Then, APs 102-103 transmit UL PPDUs 606-607 to AP 101 after a period of SIFS 605 has elapsed from the end of the trigger frame 603. 6, the Coordinator AP can adjust the length of the padding in the trigger frame based on the preparation time information voluntarily transmitted from the Coordinated AP. By adjusting the length of the padding in this way, the Coordinating AP can complete preparation for UL communication when a SIFS period has elapsed from the end of the trigger frame.

[0039] 7 shows an example of the flow of communication processing when a Coordinated AP receives a request frame from a Coordinator AP and notifies the Coordinator AP of its capability information in a response frame. While the example in FIG. 7 shows only one Coordinated AP (AP 102), it is understood that there may be two or more Coordinated APs. In other words, the number of Coordinated APs is arbitrary, whether the Coordinated AP transmits capability information spontaneously or in response to a request.

[0040] In Fig. 7 , the Coordinator AP (AP 101) transmits a predetermined request frame to request capability information used to determine the length of padding to be added to the trigger frame. In the example of Fig. 7 , AP 101 transmits a Probe Request frame 701 as this request frame. Upon receiving this request frame, AP 102 transmits a response frame including capability information indicating the preparation time required to start UL communication. In Fig. 7 , AP 102 transmits a Probe Response frame 702 as a response frame to the Probe Request frame 701. Note that AP 101 may transmit the Probe Request frame including request information indicating a request for capability information indicating the preparation time. Only when AP 102 receives a Probe Request frame including this request information, may AP 102 reply with a Probe Response frame including the capability information. However, this is just one example, and even if the AP 102 receives a Probe Request frame that does not include request information, the AP 102 may return a Probe Response frame that includes capability information. The Probe Request frame and Probe Response frame are examples of a request frame requesting capability information and a corresponding response frame, and frames other than these may also be used. For example, the AP 101 may transmit an Action frame to the AP 102 that includes information requesting preparation time information, and the AP 102 may notify the AP 102 of the preparation time information in a response frame to the Action frame.

[0041] When AP 101 receives Probe Response frame 702, it analyzes the frame and confirms capability information indicating the preparation time required for AP 102 to start UL communication. This allows AP 101 to determine the length of padding to be added to the trigger frame. After determining the length of padding to be added to the trigger frame based on the received information, AP 101 transmits trigger frame 703 to AP 102, with padding 704 of that length added. AP 102 then performs reception processing for trigger frame 703 with padding 704 added. Then, after a period of SIFS 705 has elapsed from the end of trigger frame 703, AP 102 transmits UL PPDU 706 to AP 101. 7 , the Coordinator AP requests the Coordinator AP for information about the preparation time and obtains the information through a response to the request. The Coordinator AP can then adjust the length of the padding in the trigger frame based on the preparation time information. By adjusting the length of the padding in this manner, the Coordinator AP can complete preparation for UL communication when a SIFS period has elapsed from the end of the trigger frame.

[0042] 6 and 7, the above example has been described by distinguishing between a case where the Coordinating AP spontaneously notifies the preparation time information and a case where the Coordinating AP notifies the preparation time information upon receiving a request, but the Coordinating AP may also perform both of these. That is, the Coordinating AP may spontaneously (e.g., periodically) notify the preparation time information, and may also (e.g., temporarily) notify the information upon receiving a request frame from the Coordinator AP.

[0043] Next, an example of the flow of processing executed by the Coordinator AP (AP 101) will be described with reference to Fig. 8. This processing can be realized by the control unit 202 executing a program stored in the storage unit 201. This processing may also be realized by, for example, a processor included in the communication unit 206. The AP 101 starts this processing, for example, in response to a decision to transmit a trigger frame for communication between APs.

[0044] The AP 101 receives a frame including capability information indicating the preparation time required to start UL communication (S803). The AP 101 may receive the frame, for example, by waiting for a frame voluntarily transmitted from another AP with which it is performing cooperative communication using a trigger frame. The AP 101 may also generate and transmit a request frame requesting information indicating the preparation time as needed (S801, S802) and receive a response frame to the request frame including the preparation time information. The AP 101 may use, for example, a Probe Request frame as the request frame. In one example, the request frame may include information elements such as those shown in FIG. 4. The AP 101 acquires the capability information included in the frame received in S803 (S804) and, based on the capability information, determines the length of padding to be added to the trigger frame (S805). For example, the AP 101 may determine the length of padding to be the length corresponding to the longest preparation time among the preparation times of each of one or more Coordinated APs targeted by the trigger frame. The AP 101 may also determine the length of padding based on information such as the number of STAs connected to the Coordinated AP targeted by the trigger frame. In one example, there may be a tendency for the preparation time to be longer as the load of the Coordinated AP increases. In such a case, the length of padding may be calculated based on the number of STAs connected to each AP in accordance with this tendency. For example, the preparation time indicated by the capability information may be set to the minimum time required to start UL communication, and the AP 101 may determine the length of time corresponding to the length of padding by adding a certain amount of time to that minimum time depending on the load. The AP 101 may also determine the length of padding based on, for example, the amount of traffic at the Coordinated AP.

[0045] In this way, the Coordinator AP can acquire capability information indicating the preparation time required for each Coordinating AP to start UL communication. Then, based on the acquired capability information, the Coordinator AP can determine the length of padding in the trigger frame to be transmitted to that Coordinating AP.

[0046] 9 shows an example of the flow of processing executed by the Coordinated APs (AP 102, AP 103). This processing can be realized by the control unit 202 executing a program stored in the storage unit 201. This processing may also be realized by a processor included in the communication unit 206, for example. APs 102 to 103 start this processing in response to a decision to transmit capability information indicating the preparation time required for UL communication. Note that, in the following description, AP 102 is assumed to be the entity executing the processing, but AP 103 also performs similar processing.

[0047] The AP 102 identifies (e.g., calculates) the preparation time required for UL communication in its own device and generates capability information indicating that preparation time (S901). The preparation time indicated here may be the minimum time required for UL communication. The AP 102 then generates a frame including the capability information and transmits it to the Coordinator AP (S902). For example, information such as that described with reference to any of Tables 1 to 3 above is included in this frame and transmitted. The AP 102 may also include in this frame and transmit information used to determine the length of padding, such as the number of currently connected STAs or information that can identify the communication load of the currently connected STAs. The Coordinator AP (AP 101) may also obtain information used to determine the length of padding, such as information indicating the load, from the Coordinator AP via a frame separate from the frame in which the capability information is transmitted. In one example, the Coordinator AP may notify the Coordinator AP of information about the connection type with the Coordinator AP. For example, a wired connection is expected to impose a lower processing load than a wireless connection. Therefore, the Coordinator AP may notify the Coordinator AP of information about the connection type, such as "wired connection" or "wireless connection."

[0048] In this way, the Coordinating AP can transmit to the Coordinator AP the capability information required to determine the length of padding to be added to the trigger frame. The Coordinating AP may start the process of FIG. 9 in response to receiving a request frame (e.g., a Probe Request frame or a predetermined Action frame) from the Coordinator AP. Even if the Coordinating AP does not receive a request frame, the Coordinating AP may decide to start transmitting capability information based on, for example, a user operation. The Coordinating AP may start transmitting capability information, for example, using a Beacon frame, when it starts functioning as an AP.

[0049] The present invention can also be realized by supplying a program that realizes one or more of the 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.The present invention can also be realized by a circuit (e.g., an ASIC) that realizes one or more of the functions.

[0050] 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.

[0051] This application claims priority based on Japanese Patent Application No. 2024-001499, filed January 9, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A communication device that functions as an access point compliant with the IEEE 802.11 series of standards, comprising: - receiving means for receiving a wireless frame including capability information indicating a preparation time required for preparing for signal transmission to the communication device from one or more other communication devices that function as access points; - determining means for determining the length of Padding in a trigger frame for causing the one or more other communication devices to transmit a signal to the communication device based on the capability information; - transmitting means for transmitting the trigger frame including the Padding of the determined length to the one or more other communication devices when data from the one or more other communication devices is to be received.

2. The communication device according to claim 1, wherein the receiving means acquires the capability information by receiving a management frame including the capability information from each of the one or more other communication devices.

3. The communication device according to claim 2, wherein the management frame is a Beacon frame or an Action frame spontaneously transmitted from each of the one or more other communication devices.

4. The management frame is a Probe Response frame or an Action frame, and the receiving means transmits a Probe Request frame including information indicating a request for the capability information to receive the Probe Response frame including the capability information from each of the one or more other communication devices, and transmits a first Action frame including information indicating a request for the capability information to receive a second Action frame including the capability information from each of the one or more other communication devices. The communication device according to claim 2 or 3.

5. The management frame is a Probe Response frame, and the receiving means receives the Probe Response frame in which each of the one or more other communication devices spontaneously includes the capability information when a Probe Request frame not including information indicating a request for the capability information is transmitted. The communication device according to claim 2 or 3.

6. The communication device according to any one of claims 1 to 5, wherein the information indicating the preparation time is stored in a Trigger Frame MAC Padding Duration subfield included in a field indicating the capability information in the wireless frame.

7. The communication device according to claim 6, wherein the Trigger Frame MAC Padding Duration subfield includes a bit indicating whether the preparation time indicated is for communication between an access point and another access point or for communication between an access point and a station.

8. The communication device according to any one of claims 1 to 5, wherein the information indicating the preparation time is stored in a subfield indicating the preparation time for communication between an access point and another access point, which is included in a field indicating the capability information in the wireless frame.

9. A communication device functioning as an access point compliant with the IEEE 802.11 series standards, comprising: a transmission means for transmitting a wireless frame including capability information indicating a preparation time required for preparing to transmit a signal to another communication device functioning as an access point; a reception means for receiving, from the other communication device, a trigger frame for causing the communication device to transmit a signal to the other communication device, the trigger frame including Padding having a length determined based on the capability information; and based on receiving the trigger frame, the transmission means transmits data to the other communication device. Communication device.

10. The communication device according to claim 9, wherein the transmission means transmits a management frame including the capability information to the other communication device.

11. The communication device according to claim 10, wherein the management frame is a Beacon frame or an Action frame, and the transmission means spontaneously transmits the management frame to the other communication device.

12. The management frame is a Probe Response frame or an Action frame, and the transmitting means transmits the Probe Response frame including the capability information to the other communication device when a Probe Request frame including information indicating a request for the capability information is received from the other communication device, and transmits a second Action frame including the capability information to the other communication device when a first Action frame including information indicating a request for the capability information is received from the other communication device. The communication device according to claim 10 or 11.

13. The management frame is a Probe Response frame, and the transmitting means transmits the Probe Response frame including the capability information spontaneously included therein to the other communication device when a Probe Request frame not including information indicating a request for the capability information is received from the other communication device. The communication device according to claim 10 or 11.

14. The information indicating the preparation time is stored in a Trigger Frame MAC Padding Duration subfield included in a field indicating the capability information in the wireless frame. The communication device according to any one of claims 9 to 13.

15. The Trigger Frame MAC Padding Duration subfield includes a bit indicating whether it indicates the preparation time related to communication between an access point and another access point or the preparation time related to communication between an access point and a station. The communication device according to claim 14.

16. The information indicating the preparation time is stored in a subfield indicating the preparation time related to communication between an access point and another access point, which is included in a field indicating the capability information in the wireless frame. The communication device according to any one of claims 9 to 13.

17. A communication method executed by a communication device functioning as an access point compliant with the IEEE 802.11 series standards, the method comprising: receiving a wireless frame including capability information indicating a preparation time required for preparation of signal transmission to the communication device from one or more other communication devices functioning as access points; determining a length of Padding in a trigger frame for causing the one or more other communication devices to transmit a signal to the communication device based on the capability information; and transmitting the trigger frame including the Padding having the determined length to the one or more other communication devices when receiving data from the one or more other communication devices.

18. A communication method executed by a communication device functioning as an access point compliant with the IEEE 802.11 series standards, the method comprising: transmitting a wireless frame including capability information indicating a preparation time required for preparation of signal transmission to another communication device functioning as an access point; receiving, from the other communication device, a trigger frame for causing the other communication device to transmit a signal to the communication device, the trigger frame including Padding having a length determined based on the capability information; and transmitting data to the other communication device based on receiving the trigger frame.

19. A program for causing a computer to function as each means included in the communication device according to any one of claims 1 to 16.

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